1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
2 "http://www.w3.org/TR/html4/strict.dtd">
5 <title>LLVM Assembly Language Reference Manual</title>
6 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
7 <meta name="author" content="Chris Lattner">
8 <meta name="description"
9 content="LLVM Assembly Language Reference Manual.">
10 <link rel="stylesheet" href="llvm.css" type="text/css">
15 <div class="doc_title"> LLVM Language Reference Manual </div>
17 <li><a href="#abstract">Abstract</a></li>
18 <li><a href="#introduction">Introduction</a></li>
19 <li><a href="#identifiers">Identifiers</a></li>
20 <li><a href="#highlevel">High Level Structure</a>
22 <li><a href="#modulestructure">Module Structure</a></li>
23 <li><a href="#linkage">Linkage Types</a>
25 <li><a href="#linkage_private">'<tt>private</tt>' Linkage</a></li>
26 <li><a href="#linkage_linker_private">'<tt>linker_private</tt>' Linkage</a></li>
27 <li><a href="#linkage_linker_private_weak">'<tt>linker_private_weak</tt>' Linkage</a></li>
28 <li><a href="#linkage_linker_private_weak_def_auto">'<tt>linker_private_weak_def_auto</tt>' Linkage</a></li>
29 <li><a href="#linkage_internal">'<tt>internal</tt>' Linkage</a></li>
30 <li><a href="#linkage_available_externally">'<tt>available_externally</tt>' Linkage</a></li>
31 <li><a href="#linkage_linkonce">'<tt>linkonce</tt>' Linkage</a></li>
32 <li><a href="#linkage_common">'<tt>common</tt>' Linkage</a></li>
33 <li><a href="#linkage_weak">'<tt>weak</tt>' Linkage</a></li>
34 <li><a href="#linkage_appending">'<tt>appending</tt>' Linkage</a></li>
35 <li><a href="#linkage_externweak">'<tt>extern_weak</tt>' Linkage</a></li>
36 <li><a href="#linkage_linkonce_odr">'<tt>linkonce_odr</tt>' Linkage</a></li>
37 <li><a href="#linkage_weak">'<tt>weak_odr</tt>' Linkage</a></li>
38 <li><a href="#linkage_external">'<tt>externally visible</tt>' Linkage</a></li>
39 <li><a href="#linkage_dllimport">'<tt>dllimport</tt>' Linkage</a></li>
40 <li><a href="#linkage_dllexport">'<tt>dllexport</tt>' Linkage</a></li>
43 <li><a href="#callingconv">Calling Conventions</a></li>
44 <li><a href="#namedtypes">Named Types</a></li>
45 <li><a href="#globalvars">Global Variables</a></li>
46 <li><a href="#functionstructure">Functions</a></li>
47 <li><a href="#aliasstructure">Aliases</a></li>
48 <li><a href="#namedmetadatastructure">Named Metadata</a></li>
49 <li><a href="#paramattrs">Parameter Attributes</a></li>
50 <li><a href="#fnattrs">Function Attributes</a></li>
51 <li><a href="#gc">Garbage Collector Names</a></li>
52 <li><a href="#moduleasm">Module-Level Inline Assembly</a></li>
53 <li><a href="#datalayout">Data Layout</a></li>
54 <li><a href="#pointeraliasing">Pointer Aliasing Rules</a></li>
55 <li><a href="#volatile">Volatile Memory Accesses</a></li>
58 <li><a href="#typesystem">Type System</a>
60 <li><a href="#t_classifications">Type Classifications</a></li>
61 <li><a href="#t_primitive">Primitive Types</a>
63 <li><a href="#t_integer">Integer Type</a></li>
64 <li><a href="#t_floating">Floating Point Types</a></li>
65 <li><a href="#t_x86mmx">X86mmx Type</a></li>
66 <li><a href="#t_void">Void Type</a></li>
67 <li><a href="#t_label">Label Type</a></li>
68 <li><a href="#t_metadata">Metadata Type</a></li>
71 <li><a href="#t_derived">Derived Types</a>
73 <li><a href="#t_aggregate">Aggregate Types</a>
75 <li><a href="#t_array">Array Type</a></li>
76 <li><a href="#t_struct">Structure Type</a></li>
77 <li><a href="#t_pstruct">Packed Structure Type</a></li>
78 <li><a href="#t_vector">Vector Type</a></li>
81 <li><a href="#t_function">Function Type</a></li>
82 <li><a href="#t_pointer">Pointer Type</a></li>
83 <li><a href="#t_opaque">Opaque Type</a></li>
86 <li><a href="#t_uprefs">Type Up-references</a></li>
89 <li><a href="#constants">Constants</a>
91 <li><a href="#simpleconstants">Simple Constants</a></li>
92 <li><a href="#complexconstants">Complex Constants</a></li>
93 <li><a href="#globalconstants">Global Variable and Function Addresses</a></li>
94 <li><a href="#undefvalues">Undefined Values</a></li>
95 <li><a href="#trapvalues">Trap Values</a></li>
96 <li><a href="#blockaddress">Addresses of Basic Blocks</a></li>
97 <li><a href="#constantexprs">Constant Expressions</a></li>
100 <li><a href="#othervalues">Other Values</a>
102 <li><a href="#inlineasm">Inline Assembler Expressions</a></li>
103 <li><a href="#metadata">Metadata Nodes and Metadata Strings</a></li>
106 <li><a href="#intrinsic_globals">Intrinsic Global Variables</a>
108 <li><a href="#intg_used">The '<tt>llvm.used</tt>' Global Variable</a></li>
109 <li><a href="#intg_compiler_used">The '<tt>llvm.compiler.used</tt>'
110 Global Variable</a></li>
111 <li><a href="#intg_global_ctors">The '<tt>llvm.global_ctors</tt>'
112 Global Variable</a></li>
113 <li><a href="#intg_global_dtors">The '<tt>llvm.global_dtors</tt>'
114 Global Variable</a></li>
117 <li><a href="#instref">Instruction Reference</a>
119 <li><a href="#terminators">Terminator Instructions</a>
121 <li><a href="#i_ret">'<tt>ret</tt>' Instruction</a></li>
122 <li><a href="#i_br">'<tt>br</tt>' Instruction</a></li>
123 <li><a href="#i_switch">'<tt>switch</tt>' Instruction</a></li>
124 <li><a href="#i_indirectbr">'<tt>indirectbr</tt>' Instruction</a></li>
125 <li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a></li>
126 <li><a href="#i_unwind">'<tt>unwind</tt>' Instruction</a></li>
127 <li><a href="#i_unreachable">'<tt>unreachable</tt>' Instruction</a></li>
130 <li><a href="#binaryops">Binary Operations</a>
132 <li><a href="#i_add">'<tt>add</tt>' Instruction</a></li>
133 <li><a href="#i_fadd">'<tt>fadd</tt>' Instruction</a></li>
134 <li><a href="#i_sub">'<tt>sub</tt>' Instruction</a></li>
135 <li><a href="#i_fsub">'<tt>fsub</tt>' Instruction</a></li>
136 <li><a href="#i_mul">'<tt>mul</tt>' Instruction</a></li>
137 <li><a href="#i_fmul">'<tt>fmul</tt>' Instruction</a></li>
138 <li><a href="#i_udiv">'<tt>udiv</tt>' Instruction</a></li>
139 <li><a href="#i_sdiv">'<tt>sdiv</tt>' Instruction</a></li>
140 <li><a href="#i_fdiv">'<tt>fdiv</tt>' Instruction</a></li>
141 <li><a href="#i_urem">'<tt>urem</tt>' Instruction</a></li>
142 <li><a href="#i_srem">'<tt>srem</tt>' Instruction</a></li>
143 <li><a href="#i_frem">'<tt>frem</tt>' Instruction</a></li>
146 <li><a href="#bitwiseops">Bitwise Binary Operations</a>
148 <li><a href="#i_shl">'<tt>shl</tt>' Instruction</a></li>
149 <li><a href="#i_lshr">'<tt>lshr</tt>' Instruction</a></li>
150 <li><a href="#i_ashr">'<tt>ashr</tt>' Instruction</a></li>
151 <li><a href="#i_and">'<tt>and</tt>' Instruction</a></li>
152 <li><a href="#i_or">'<tt>or</tt>' Instruction</a></li>
153 <li><a href="#i_xor">'<tt>xor</tt>' Instruction</a></li>
156 <li><a href="#vectorops">Vector Operations</a>
158 <li><a href="#i_extractelement">'<tt>extractelement</tt>' Instruction</a></li>
159 <li><a href="#i_insertelement">'<tt>insertelement</tt>' Instruction</a></li>
160 <li><a href="#i_shufflevector">'<tt>shufflevector</tt>' Instruction</a></li>
163 <li><a href="#aggregateops">Aggregate Operations</a>
165 <li><a href="#i_extractvalue">'<tt>extractvalue</tt>' Instruction</a></li>
166 <li><a href="#i_insertvalue">'<tt>insertvalue</tt>' Instruction</a></li>
169 <li><a href="#memoryops">Memory Access and Addressing Operations</a>
171 <li><a href="#i_alloca">'<tt>alloca</tt>' Instruction</a></li>
172 <li><a href="#i_load">'<tt>load</tt>' Instruction</a></li>
173 <li><a href="#i_store">'<tt>store</tt>' Instruction</a></li>
174 <li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a></li>
177 <li><a href="#convertops">Conversion Operations</a>
179 <li><a href="#i_trunc">'<tt>trunc .. to</tt>' Instruction</a></li>
180 <li><a href="#i_zext">'<tt>zext .. to</tt>' Instruction</a></li>
181 <li><a href="#i_sext">'<tt>sext .. to</tt>' Instruction</a></li>
182 <li><a href="#i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a></li>
183 <li><a href="#i_fpext">'<tt>fpext .. to</tt>' Instruction</a></li>
184 <li><a href="#i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a></li>
185 <li><a href="#i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a></li>
186 <li><a href="#i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a></li>
187 <li><a href="#i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a></li>
188 <li><a href="#i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a></li>
189 <li><a href="#i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a></li>
190 <li><a href="#i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a></li>
193 <li><a href="#otherops">Other Operations</a>
195 <li><a href="#i_icmp">'<tt>icmp</tt>' Instruction</a></li>
196 <li><a href="#i_fcmp">'<tt>fcmp</tt>' Instruction</a></li>
197 <li><a href="#i_phi">'<tt>phi</tt>' Instruction</a></li>
198 <li><a href="#i_select">'<tt>select</tt>' Instruction</a></li>
199 <li><a href="#i_call">'<tt>call</tt>' Instruction</a></li>
200 <li><a href="#i_va_arg">'<tt>va_arg</tt>' Instruction</a></li>
205 <li><a href="#intrinsics">Intrinsic Functions</a>
207 <li><a href="#int_varargs">Variable Argument Handling Intrinsics</a>
209 <li><a href="#int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a></li>
210 <li><a href="#int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a></li>
211 <li><a href="#int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a></li>
214 <li><a href="#int_gc">Accurate Garbage Collection Intrinsics</a>
216 <li><a href="#int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a></li>
217 <li><a href="#int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a></li>
218 <li><a href="#int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a></li>
221 <li><a href="#int_codegen">Code Generator Intrinsics</a>
223 <li><a href="#int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a></li>
224 <li><a href="#int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li>
225 <li><a href="#int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a></li>
226 <li><a href="#int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a></li>
227 <li><a href="#int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a></li>
228 <li><a href="#int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a></li>
229 <li><a href="#int_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a></li>
232 <li><a href="#int_libc">Standard C Library Intrinsics</a>
234 <li><a href="#int_memcpy">'<tt>llvm.memcpy.*</tt>' Intrinsic</a></li>
235 <li><a href="#int_memmove">'<tt>llvm.memmove.*</tt>' Intrinsic</a></li>
236 <li><a href="#int_memset">'<tt>llvm.memset.*</tt>' Intrinsic</a></li>
237 <li><a href="#int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a></li>
238 <li><a href="#int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a></li>
239 <li><a href="#int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a></li>
240 <li><a href="#int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a></li>
241 <li><a href="#int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a></li>
244 <li><a href="#int_manip">Bit Manipulation Intrinsics</a>
246 <li><a href="#int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a></li>
247 <li><a href="#int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic </a></li>
248 <li><a href="#int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic </a></li>
249 <li><a href="#int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic </a></li>
252 <li><a href="#int_overflow">Arithmetic with Overflow Intrinsics</a>
254 <li><a href="#int_sadd_overflow">'<tt>llvm.sadd.with.overflow.*</tt> Intrinsics</a></li>
255 <li><a href="#int_uadd_overflow">'<tt>llvm.uadd.with.overflow.*</tt> Intrinsics</a></li>
256 <li><a href="#int_ssub_overflow">'<tt>llvm.ssub.with.overflow.*</tt> Intrinsics</a></li>
257 <li><a href="#int_usub_overflow">'<tt>llvm.usub.with.overflow.*</tt> Intrinsics</a></li>
258 <li><a href="#int_smul_overflow">'<tt>llvm.smul.with.overflow.*</tt> Intrinsics</a></li>
259 <li><a href="#int_umul_overflow">'<tt>llvm.umul.with.overflow.*</tt> Intrinsics</a></li>
262 <li><a href="#int_fp16">Half Precision Floating Point Intrinsics</a>
264 <li><a href="#int_convert_to_fp16">'<tt>llvm.convert.to.fp16</tt>' Intrinsic</a></li>
265 <li><a href="#int_convert_from_fp16">'<tt>llvm.convert.from.fp16</tt>' Intrinsic</a></li>
268 <li><a href="#int_debugger">Debugger intrinsics</a></li>
269 <li><a href="#int_eh">Exception Handling intrinsics</a></li>
270 <li><a href="#int_trampoline">Trampoline Intrinsic</a>
272 <li><a href="#int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a></li>
275 <li><a href="#int_atomics">Atomic intrinsics</a>
277 <li><a href="#int_memory_barrier"><tt>llvm.memory_barrier</tt></a></li>
278 <li><a href="#int_atomic_cmp_swap"><tt>llvm.atomic.cmp.swap</tt></a></li>
279 <li><a href="#int_atomic_swap"><tt>llvm.atomic.swap</tt></a></li>
280 <li><a href="#int_atomic_load_add"><tt>llvm.atomic.load.add</tt></a></li>
281 <li><a href="#int_atomic_load_sub"><tt>llvm.atomic.load.sub</tt></a></li>
282 <li><a href="#int_atomic_load_and"><tt>llvm.atomic.load.and</tt></a></li>
283 <li><a href="#int_atomic_load_nand"><tt>llvm.atomic.load.nand</tt></a></li>
284 <li><a href="#int_atomic_load_or"><tt>llvm.atomic.load.or</tt></a></li>
285 <li><a href="#int_atomic_load_xor"><tt>llvm.atomic.load.xor</tt></a></li>
286 <li><a href="#int_atomic_load_max"><tt>llvm.atomic.load.max</tt></a></li>
287 <li><a href="#int_atomic_load_min"><tt>llvm.atomic.load.min</tt></a></li>
288 <li><a href="#int_atomic_load_umax"><tt>llvm.atomic.load.umax</tt></a></li>
289 <li><a href="#int_atomic_load_umin"><tt>llvm.atomic.load.umin</tt></a></li>
292 <li><a href="#int_memorymarkers">Memory Use Markers</a>
294 <li><a href="#int_lifetime_start"><tt>llvm.lifetime.start</tt></a></li>
295 <li><a href="#int_lifetime_end"><tt>llvm.lifetime.end</tt></a></li>
296 <li><a href="#int_invariant_start"><tt>llvm.invariant.start</tt></a></li>
297 <li><a href="#int_invariant_end"><tt>llvm.invariant.end</tt></a></li>
300 <li><a href="#int_general">General intrinsics</a>
302 <li><a href="#int_var_annotation">
303 '<tt>llvm.var.annotation</tt>' Intrinsic</a></li>
304 <li><a href="#int_annotation">
305 '<tt>llvm.annotation.*</tt>' Intrinsic</a></li>
306 <li><a href="#int_trap">
307 '<tt>llvm.trap</tt>' Intrinsic</a></li>
308 <li><a href="#int_stackprotector">
309 '<tt>llvm.stackprotector</tt>' Intrinsic</a></li>
310 <li><a href="#int_objectsize">
311 '<tt>llvm.objectsize</tt>' Intrinsic</a></li>
318 <div class="doc_author">
319 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>
320 and <a href="mailto:vadve@cs.uiuc.edu">Vikram Adve</a></p>
323 <!-- *********************************************************************** -->
324 <div class="doc_section"> <a name="abstract">Abstract </a></div>
325 <!-- *********************************************************************** -->
327 <div class="doc_text">
329 <p>This document is a reference manual for the LLVM assembly language. LLVM is
330 a Static Single Assignment (SSA) based representation that provides type
331 safety, low-level operations, flexibility, and the capability of representing
332 'all' high-level languages cleanly. It is the common code representation
333 used throughout all phases of the LLVM compilation strategy.</p>
337 <!-- *********************************************************************** -->
338 <div class="doc_section"> <a name="introduction">Introduction</a> </div>
339 <!-- *********************************************************************** -->
341 <div class="doc_text">
343 <p>The LLVM code representation is designed to be used in three different forms:
344 as an in-memory compiler IR, as an on-disk bitcode representation (suitable
345 for fast loading by a Just-In-Time compiler), and as a human readable
346 assembly language representation. This allows LLVM to provide a powerful
347 intermediate representation for efficient compiler transformations and
348 analysis, while providing a natural means to debug and visualize the
349 transformations. The three different forms of LLVM are all equivalent. This
350 document describes the human readable representation and notation.</p>
352 <p>The LLVM representation aims to be light-weight and low-level while being
353 expressive, typed, and extensible at the same time. It aims to be a
354 "universal IR" of sorts, by being at a low enough level that high-level ideas
355 may be cleanly mapped to it (similar to how microprocessors are "universal
356 IR's", allowing many source languages to be mapped to them). By providing
357 type information, LLVM can be used as the target of optimizations: for
358 example, through pointer analysis, it can be proven that a C automatic
359 variable is never accessed outside of the current function, allowing it to
360 be promoted to a simple SSA value instead of a memory location.</p>
364 <!-- _______________________________________________________________________ -->
365 <div class="doc_subsubsection"> <a name="wellformed">Well-Formedness</a> </div>
367 <div class="doc_text">
369 <p>It is important to note that this document describes 'well formed' LLVM
370 assembly language. There is a difference between what the parser accepts and
371 what is considered 'well formed'. For example, the following instruction is
372 syntactically okay, but not well formed:</p>
374 <pre class="doc_code">
375 %x = <a href="#i_add">add</a> i32 1, %x
378 <p>because the definition of <tt>%x</tt> does not dominate all of its uses. The
379 LLVM infrastructure provides a verification pass that may be used to verify
380 that an LLVM module is well formed. This pass is automatically run by the
381 parser after parsing input assembly and by the optimizer before it outputs
382 bitcode. The violations pointed out by the verifier pass indicate bugs in
383 transformation passes or input to the parser.</p>
387 <!-- Describe the typesetting conventions here. -->
389 <!-- *********************************************************************** -->
390 <div class="doc_section"> <a name="identifiers">Identifiers</a> </div>
391 <!-- *********************************************************************** -->
393 <div class="doc_text">
395 <p>LLVM identifiers come in two basic types: global and local. Global
396 identifiers (functions, global variables) begin with the <tt>'@'</tt>
397 character. Local identifiers (register names, types) begin with
398 the <tt>'%'</tt> character. Additionally, there are three different formats
399 for identifiers, for different purposes:</p>
402 <li>Named values are represented as a string of characters with their prefix.
403 For example, <tt>%foo</tt>, <tt>@DivisionByZero</tt>,
404 <tt>%a.really.long.identifier</tt>. The actual regular expression used is
405 '<tt>[%@][a-zA-Z$._][a-zA-Z$._0-9]*</tt>'. Identifiers which require
406 other characters in their names can be surrounded with quotes. Special
407 characters may be escaped using <tt>"\xx"</tt> where <tt>xx</tt> is the
408 ASCII code for the character in hexadecimal. In this way, any character
409 can be used in a name value, even quotes themselves.</li>
411 <li>Unnamed values are represented as an unsigned numeric value with their
412 prefix. For example, <tt>%12</tt>, <tt>@2</tt>, <tt>%44</tt>.</li>
414 <li>Constants, which are described in a <a href="#constants">section about
415 constants</a>, below.</li>
418 <p>LLVM requires that values start with a prefix for two reasons: Compilers
419 don't need to worry about name clashes with reserved words, and the set of
420 reserved words may be expanded in the future without penalty. Additionally,
421 unnamed identifiers allow a compiler to quickly come up with a temporary
422 variable without having to avoid symbol table conflicts.</p>
424 <p>Reserved words in LLVM are very similar to reserved words in other
425 languages. There are keywords for different opcodes
426 ('<tt><a href="#i_add">add</a></tt>',
427 '<tt><a href="#i_bitcast">bitcast</a></tt>',
428 '<tt><a href="#i_ret">ret</a></tt>', etc...), for primitive type names
429 ('<tt><a href="#t_void">void</a></tt>',
430 '<tt><a href="#t_primitive">i32</a></tt>', etc...), and others. These
431 reserved words cannot conflict with variable names, because none of them
432 start with a prefix character (<tt>'%'</tt> or <tt>'@'</tt>).</p>
434 <p>Here is an example of LLVM code to multiply the integer variable
435 '<tt>%X</tt>' by 8:</p>
439 <pre class="doc_code">
440 %result = <a href="#i_mul">mul</a> i32 %X, 8
443 <p>After strength reduction:</p>
445 <pre class="doc_code">
446 %result = <a href="#i_shl">shl</a> i32 %X, i8 3
449 <p>And the hard way:</p>
451 <pre class="doc_code">
452 %0 = <a href="#i_add">add</a> i32 %X, %X <i>; yields {i32}:%0</i>
453 %1 = <a href="#i_add">add</a> i32 %0, %0 <i>; yields {i32}:%1</i>
454 %result = <a href="#i_add">add</a> i32 %1, %1
457 <p>This last way of multiplying <tt>%X</tt> by 8 illustrates several important
458 lexical features of LLVM:</p>
461 <li>Comments are delimited with a '<tt>;</tt>' and go until the end of
464 <li>Unnamed temporaries are created when the result of a computation is not
465 assigned to a named value.</li>
467 <li>Unnamed temporaries are numbered sequentially</li>
470 <p>It also shows a convention that we follow in this document. When
471 demonstrating instructions, we will follow an instruction with a comment that
472 defines the type and name of value produced. Comments are shown in italic
477 <!-- *********************************************************************** -->
478 <div class="doc_section"> <a name="highlevel">High Level Structure</a> </div>
479 <!-- *********************************************************************** -->
481 <!-- ======================================================================= -->
482 <div class="doc_subsection"> <a name="modulestructure">Module Structure</a>
485 <div class="doc_text">
487 <p>LLVM programs are composed of "Module"s, each of which is a translation unit
488 of the input programs. Each module consists of functions, global variables,
489 and symbol table entries. Modules may be combined together with the LLVM
490 linker, which merges function (and global variable) definitions, resolves
491 forward declarations, and merges symbol table entries. Here is an example of
492 the "hello world" module:</p>
494 <pre class="doc_code">
495 <i>; Declare the string constant as a global constant.</i>
496 <a href="#identifiers">@.LC0</a> = <a href="#linkage_internal">internal</a> <a href="#globalvars">constant</a> <a href="#t_array">[13 x i8]</a> c"hello world\0A\00" <i>; [13 x i8]*</i>
498 <i>; External declaration of the puts function</i>
499 <a href="#functionstructure">declare</a> i32 @puts(i8*) <i>; i32 (i8*)* </i>
501 <i>; Definition of main function</i>
502 define i32 @main() { <i>; i32()* </i>
503 <i>; Convert [13 x i8]* to i8 *...</i>
504 %cast210 = <a href="#i_getelementptr">getelementptr</a> [13 x i8]* @.LC0, i64 0, i64 0 <i>; i8*</i>
506 <i>; Call puts function to write out the string to stdout.</i>
507 <a href="#i_call">call</a> i32 @puts(i8* %cast210) <i>; i32</i>
508 <a href="#i_ret">ret</a> i32 0
511 <i>; Named metadata</i>
512 !1 = metadata !{i32 41}
516 <p>This example is made up of a <a href="#globalvars">global variable</a> named
517 "<tt>.LC0</tt>", an external declaration of the "<tt>puts</tt>" function,
518 a <a href="#functionstructure">function definition</a> for
519 "<tt>main</tt>" and <a href="#namedmetadatastructure">named metadata</a>
522 <p>In general, a module is made up of a list of global values, where both
523 functions and global variables are global values. Global values are
524 represented by a pointer to a memory location (in this case, a pointer to an
525 array of char, and a pointer to a function), and have one of the
526 following <a href="#linkage">linkage types</a>.</p>
530 <!-- ======================================================================= -->
531 <div class="doc_subsection">
532 <a name="linkage">Linkage Types</a>
535 <div class="doc_text">
537 <p>All Global Variables and Functions have one of the following types of
541 <dt><tt><b><a name="linkage_private">private</a></b></tt></dt>
542 <dd>Global values with "<tt>private</tt>" linkage are only directly accessible
543 by objects in the current module. In particular, linking code into a
544 module with an private global value may cause the private to be renamed as
545 necessary to avoid collisions. Because the symbol is private to the
546 module, all references can be updated. This doesn't show up in any symbol
547 table in the object file.</dd>
549 <dt><tt><b><a name="linkage_linker_private">linker_private</a></b></tt></dt>
550 <dd>Similar to <tt>private</tt>, but the symbol is passed through the
551 assembler and evaluated by the linker. Unlike normal strong symbols, they
552 are removed by the linker from the final linked image (executable or
553 dynamic library).</dd>
555 <dt><tt><b><a name="linkage_linker_private_weak">linker_private_weak</a></b></tt></dt>
556 <dd>Similar to "<tt>linker_private</tt>", but the symbol is weak. Note that
557 <tt>linker_private_weak</tt> symbols are subject to coalescing by the
558 linker. The symbols are removed by the linker from the final linked image
559 (executable or dynamic library).</dd>
561 <dt><tt><b><a name="linkage_linker_private_weak_def_auto">linker_private_weak_def_auto</a></b></tt></dt>
562 <dd>Similar to "<tt>linker_private_weak</tt>", but it's known that the address
563 of the object is not taken. For instance, functions that had an inline
564 definition, but the compiler decided not to inline it. Note,
565 unlike <tt>linker_private</tt> and <tt>linker_private_weak</tt>,
566 <tt>linker_private_weak_def_auto</tt> may have only <tt>default</tt>
567 visibility. The symbols are removed by the linker from the final linked
568 image (executable or dynamic library).</dd>
570 <dt><tt><b><a name="linkage_internal">internal</a></b></tt></dt>
571 <dd>Similar to private, but the value shows as a local symbol
572 (<tt>STB_LOCAL</tt> in the case of ELF) in the object file. This
573 corresponds to the notion of the '<tt>static</tt>' keyword in C.</dd>
575 <dt><tt><b><a name="linkage_available_externally">available_externally</a></b></tt></dt>
576 <dd>Globals with "<tt>available_externally</tt>" linkage are never emitted
577 into the object file corresponding to the LLVM module. They exist to
578 allow inlining and other optimizations to take place given knowledge of
579 the definition of the global, which is known to be somewhere outside the
580 module. Globals with <tt>available_externally</tt> linkage are allowed to
581 be discarded at will, and are otherwise the same as <tt>linkonce_odr</tt>.
582 This linkage type is only allowed on definitions, not declarations.</dd>
584 <dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt></dt>
585 <dd>Globals with "<tt>linkonce</tt>" linkage are merged with other globals of
586 the same name when linkage occurs. This can be used to implement
587 some forms of inline functions, templates, or other code which must be
588 generated in each translation unit that uses it, but where the body may
589 be overridden with a more definitive definition later. Unreferenced
590 <tt>linkonce</tt> globals are allowed to be discarded. Note that
591 <tt>linkonce</tt> linkage does not actually allow the optimizer to
592 inline the body of this function into callers because it doesn't know if
593 this definition of the function is the definitive definition within the
594 program or whether it will be overridden by a stronger definition.
595 To enable inlining and other optimizations, use "<tt>linkonce_odr</tt>"
598 <dt><tt><b><a name="linkage_weak">weak</a></b></tt></dt>
599 <dd>"<tt>weak</tt>" linkage has the same merging semantics as
600 <tt>linkonce</tt> linkage, except that unreferenced globals with
601 <tt>weak</tt> linkage may not be discarded. This is used for globals that
602 are declared "weak" in C source code.</dd>
604 <dt><tt><b><a name="linkage_common">common</a></b></tt></dt>
605 <dd>"<tt>common</tt>" linkage is most similar to "<tt>weak</tt>" linkage, but
606 they are used for tentative definitions in C, such as "<tt>int X;</tt>" at
608 Symbols with "<tt>common</tt>" linkage are merged in the same way as
609 <tt>weak symbols</tt>, and they may not be deleted if unreferenced.
610 <tt>common</tt> symbols may not have an explicit section,
611 must have a zero initializer, and may not be marked '<a
612 href="#globalvars"><tt>constant</tt></a>'. Functions and aliases may not
613 have common linkage.</dd>
616 <dt><tt><b><a name="linkage_appending">appending</a></b></tt></dt>
617 <dd>"<tt>appending</tt>" linkage may only be applied to global variables of
618 pointer to array type. When two global variables with appending linkage
619 are linked together, the two global arrays are appended together. This is
620 the LLVM, typesafe, equivalent of having the system linker append together
621 "sections" with identical names when .o files are linked.</dd>
623 <dt><tt><b><a name="linkage_externweak">extern_weak</a></b></tt></dt>
624 <dd>The semantics of this linkage follow the ELF object file model: the symbol
625 is weak until linked, if not linked, the symbol becomes null instead of
626 being an undefined reference.</dd>
628 <dt><tt><b><a name="linkage_linkonce_odr">linkonce_odr</a></b></tt></dt>
629 <dt><tt><b><a name="linkage_weak_odr">weak_odr</a></b></tt></dt>
630 <dd>Some languages allow differing globals to be merged, such as two functions
631 with different semantics. Other languages, such as <tt>C++</tt>, ensure
632 that only equivalent globals are ever merged (the "one definition rule"
633 — "ODR"). Such languages can use the <tt>linkonce_odr</tt>
634 and <tt>weak_odr</tt> linkage types to indicate that the global will only
635 be merged with equivalent globals. These linkage types are otherwise the
636 same as their non-<tt>odr</tt> versions.</dd>
638 <dt><tt><b><a name="linkage_external">externally visible</a></b></tt>:</dt>
639 <dd>If none of the above identifiers are used, the global is externally
640 visible, meaning that it participates in linkage and can be used to
641 resolve external symbol references.</dd>
644 <p>The next two types of linkage are targeted for Microsoft Windows platform
645 only. They are designed to support importing (exporting) symbols from (to)
646 DLLs (Dynamic Link Libraries).</p>
649 <dt><tt><b><a name="linkage_dllimport">dllimport</a></b></tt></dt>
650 <dd>"<tt>dllimport</tt>" linkage causes the compiler to reference a function
651 or variable via a global pointer to a pointer that is set up by the DLL
652 exporting the symbol. On Microsoft Windows targets, the pointer name is
653 formed by combining <code>__imp_</code> and the function or variable
656 <dt><tt><b><a name="linkage_dllexport">dllexport</a></b></tt></dt>
657 <dd>"<tt>dllexport</tt>" linkage causes the compiler to provide a global
658 pointer to a pointer in a DLL, so that it can be referenced with the
659 <tt>dllimport</tt> attribute. On Microsoft Windows targets, the pointer
660 name is formed by combining <code>__imp_</code> and the function or
664 <p>For example, since the "<tt>.LC0</tt>" variable is defined to be internal, if
665 another module defined a "<tt>.LC0</tt>" variable and was linked with this
666 one, one of the two would be renamed, preventing a collision. Since
667 "<tt>main</tt>" and "<tt>puts</tt>" are external (i.e., lacking any linkage
668 declarations), they are accessible outside of the current module.</p>
670 <p>It is illegal for a function <i>declaration</i> to have any linkage type
671 other than "externally visible", <tt>dllimport</tt>
672 or <tt>extern_weak</tt>.</p>
674 <p>Aliases can have only <tt>external</tt>, <tt>internal</tt>, <tt>weak</tt>
675 or <tt>weak_odr</tt> linkages.</p>
679 <!-- ======================================================================= -->
680 <div class="doc_subsection">
681 <a name="callingconv">Calling Conventions</a>
684 <div class="doc_text">
686 <p>LLVM <a href="#functionstructure">functions</a>, <a href="#i_call">calls</a>
687 and <a href="#i_invoke">invokes</a> can all have an optional calling
688 convention specified for the call. The calling convention of any pair of
689 dynamic caller/callee must match, or the behavior of the program is
690 undefined. The following calling conventions are supported by LLVM, and more
691 may be added in the future:</p>
694 <dt><b>"<tt>ccc</tt>" - The C calling convention</b>:</dt>
695 <dd>This calling convention (the default if no other calling convention is
696 specified) matches the target C calling conventions. This calling
697 convention supports varargs function calls and tolerates some mismatch in
698 the declared prototype and implemented declaration of the function (as
701 <dt><b>"<tt>fastcc</tt>" - The fast calling convention</b>:</dt>
702 <dd>This calling convention attempts to make calls as fast as possible
703 (e.g. by passing things in registers). This calling convention allows the
704 target to use whatever tricks it wants to produce fast code for the
705 target, without having to conform to an externally specified ABI
706 (Application Binary Interface).
707 <a href="CodeGenerator.html#tailcallopt">Tail calls can only be optimized
708 when this or the GHC convention is used.</a> This calling convention
709 does not support varargs and requires the prototype of all callees to
710 exactly match the prototype of the function definition.</dd>
712 <dt><b>"<tt>coldcc</tt>" - The cold calling convention</b>:</dt>
713 <dd>This calling convention attempts to make code in the caller as efficient
714 as possible under the assumption that the call is not commonly executed.
715 As such, these calls often preserve all registers so that the call does
716 not break any live ranges in the caller side. This calling convention
717 does not support varargs and requires the prototype of all callees to
718 exactly match the prototype of the function definition.</dd>
720 <dt><b>"<tt>cc <em>10</em></tt>" - GHC convention</b>:</dt>
721 <dd>This calling convention has been implemented specifically for use by the
722 <a href="http://www.haskell.org/ghc">Glasgow Haskell Compiler (GHC)</a>.
723 It passes everything in registers, going to extremes to achieve this by
724 disabling callee save registers. This calling convention should not be
725 used lightly but only for specific situations such as an alternative to
726 the <em>register pinning</em> performance technique often used when
727 implementing functional programming languages.At the moment only X86
728 supports this convention and it has the following limitations:
730 <li>On <em>X86-32</em> only supports up to 4 bit type parameters. No
731 floating point types are supported.</li>
732 <li>On <em>X86-64</em> only supports up to 10 bit type parameters and
733 6 floating point parameters.</li>
735 This calling convention supports
736 <a href="CodeGenerator.html#tailcallopt">tail call optimization</a> but
737 requires both the caller and callee are using it.
740 <dt><b>"<tt>cc <<em>n</em>></tt>" - Numbered convention</b>:</dt>
741 <dd>Any calling convention may be specified by number, allowing
742 target-specific calling conventions to be used. Target specific calling
743 conventions start at 64.</dd>
746 <p>More calling conventions can be added/defined on an as-needed basis, to
747 support Pascal conventions or any other well-known target-independent
752 <!-- ======================================================================= -->
753 <div class="doc_subsection">
754 <a name="visibility">Visibility Styles</a>
757 <div class="doc_text">
759 <p>All Global Variables and Functions have one of the following visibility
763 <dt><b>"<tt>default</tt>" - Default style</b>:</dt>
764 <dd>On targets that use the ELF object file format, default visibility means
765 that the declaration is visible to other modules and, in shared libraries,
766 means that the declared entity may be overridden. On Darwin, default
767 visibility means that the declaration is visible to other modules. Default
768 visibility corresponds to "external linkage" in the language.</dd>
770 <dt><b>"<tt>hidden</tt>" - Hidden style</b>:</dt>
771 <dd>Two declarations of an object with hidden visibility refer to the same
772 object if they are in the same shared object. Usually, hidden visibility
773 indicates that the symbol will not be placed into the dynamic symbol
774 table, so no other module (executable or shared library) can reference it
777 <dt><b>"<tt>protected</tt>" - Protected style</b>:</dt>
778 <dd>On ELF, protected visibility indicates that the symbol will be placed in
779 the dynamic symbol table, but that references within the defining module
780 will bind to the local symbol. That is, the symbol cannot be overridden by
786 <!-- ======================================================================= -->
787 <div class="doc_subsection">
788 <a name="namedtypes">Named Types</a>
791 <div class="doc_text">
793 <p>LLVM IR allows you to specify name aliases for certain types. This can make
794 it easier to read the IR and make the IR more condensed (particularly when
795 recursive types are involved). An example of a name specification is:</p>
797 <pre class="doc_code">
798 %mytype = type { %mytype*, i32 }
801 <p>You may give a name to any <a href="#typesystem">type</a> except
802 "<a href="#t_void">void</a>". Type name aliases may be used anywhere a type
803 is expected with the syntax "%mytype".</p>
805 <p>Note that type names are aliases for the structural type that they indicate,
806 and that you can therefore specify multiple names for the same type. This
807 often leads to confusing behavior when dumping out a .ll file. Since LLVM IR
808 uses structural typing, the name is not part of the type. When printing out
809 LLVM IR, the printer will pick <em>one name</em> to render all types of a
810 particular shape. This means that if you have code where two different
811 source types end up having the same LLVM type, that the dumper will sometimes
812 print the "wrong" or unexpected type. This is an important design point and
813 isn't going to change.</p>
817 <!-- ======================================================================= -->
818 <div class="doc_subsection">
819 <a name="globalvars">Global Variables</a>
822 <div class="doc_text">
824 <p>Global variables define regions of memory allocated at compilation time
825 instead of run-time. Global variables may optionally be initialized, may
826 have an explicit section to be placed in, and may have an optional explicit
827 alignment specified. A variable may be defined as "thread_local", which
828 means that it will not be shared by threads (each thread will have a
829 separated copy of the variable). A variable may be defined as a global
830 "constant," which indicates that the contents of the variable
831 will <b>never</b> be modified (enabling better optimization, allowing the
832 global data to be placed in the read-only section of an executable, etc).
833 Note that variables that need runtime initialization cannot be marked
834 "constant" as there is a store to the variable.</p>
836 <p>LLVM explicitly allows <em>declarations</em> of global variables to be marked
837 constant, even if the final definition of the global is not. This capability
838 can be used to enable slightly better optimization of the program, but
839 requires the language definition to guarantee that optimizations based on the
840 'constantness' are valid for the translation units that do not include the
843 <p>As SSA values, global variables define pointer values that are in scope
844 (i.e. they dominate) all basic blocks in the program. Global variables
845 always define a pointer to their "content" type because they describe a
846 region of memory, and all memory objects in LLVM are accessed through
849 <p>A global variable may be declared to reside in a target-specific numbered
850 address space. For targets that support them, address spaces may affect how
851 optimizations are performed and/or what target instructions are used to
852 access the variable. The default address space is zero. The address space
853 qualifier must precede any other attributes.</p>
855 <p>LLVM allows an explicit section to be specified for globals. If the target
856 supports it, it will emit globals to the section specified.</p>
858 <p>An explicit alignment may be specified for a global, which must be a power
859 of 2. If not present, or if the alignment is set to zero, the alignment of
860 the global is set by the target to whatever it feels convenient. If an
861 explicit alignment is specified, the global is forced to have exactly that
862 alignment. Targets and optimizers are not allowed to over-align the global
863 if the global has an assigned section. In this case, the extra alignment
864 could be observable: for example, code could assume that the globals are
865 densely packed in their section and try to iterate over them as an array,
866 alignment padding would break this iteration.</p>
868 <p>For example, the following defines a global in a numbered address space with
869 an initializer, section, and alignment:</p>
871 <pre class="doc_code">
872 @G = addrspace(5) constant float 1.0, section "foo", align 4
878 <!-- ======================================================================= -->
879 <div class="doc_subsection">
880 <a name="functionstructure">Functions</a>
883 <div class="doc_text">
885 <p>LLVM function definitions consist of the "<tt>define</tt>" keyword, an
886 optional <a href="#linkage">linkage type</a>, an optional
887 <a href="#visibility">visibility style</a>, an optional
888 <a href="#callingconv">calling convention</a>, a return type, an optional
889 <a href="#paramattrs">parameter attribute</a> for the return type, a function
890 name, a (possibly empty) argument list (each with optional
891 <a href="#paramattrs">parameter attributes</a>), optional
892 <a href="#fnattrs">function attributes</a>, an optional section, an optional
893 alignment, an optional <a href="#gc">garbage collector name</a>, an opening
894 curly brace, a list of basic blocks, and a closing curly brace.</p>
896 <p>LLVM function declarations consist of the "<tt>declare</tt>" keyword, an
897 optional <a href="#linkage">linkage type</a>, an optional
898 <a href="#visibility">visibility style</a>, an optional
899 <a href="#callingconv">calling convention</a>, a return type, an optional
900 <a href="#paramattrs">parameter attribute</a> for the return type, a function
901 name, a possibly empty list of arguments, an optional alignment, and an
902 optional <a href="#gc">garbage collector name</a>.</p>
904 <p>A function definition contains a list of basic blocks, forming the CFG
905 (Control Flow Graph) for the function. Each basic block may optionally start
906 with a label (giving the basic block a symbol table entry), contains a list
907 of instructions, and ends with a <a href="#terminators">terminator</a>
908 instruction (such as a branch or function return).</p>
910 <p>The first basic block in a function is special in two ways: it is immediately
911 executed on entrance to the function, and it is not allowed to have
912 predecessor basic blocks (i.e. there can not be any branches to the entry
913 block of a function). Because the block can have no predecessors, it also
914 cannot have any <a href="#i_phi">PHI nodes</a>.</p>
916 <p>LLVM allows an explicit section to be specified for functions. If the target
917 supports it, it will emit functions to the section specified.</p>
919 <p>An explicit alignment may be specified for a function. If not present, or if
920 the alignment is set to zero, the alignment of the function is set by the
921 target to whatever it feels convenient. If an explicit alignment is
922 specified, the function is forced to have at least that much alignment. All
923 alignments must be a power of 2.</p>
926 <pre class="doc_code">
927 define [<a href="#linkage">linkage</a>] [<a href="#visibility">visibility</a>]
928 [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>]
929 <ResultType> @<FunctionName> ([argument list])
930 [<a href="#fnattrs">fn Attrs</a>] [section "name"] [align N]
931 [<a href="#gc">gc</a>] { ... }
936 <!-- ======================================================================= -->
937 <div class="doc_subsection">
938 <a name="aliasstructure">Aliases</a>
941 <div class="doc_text">
943 <p>Aliases act as "second name" for the aliasee value (which can be either
944 function, global variable, another alias or bitcast of global value). Aliases
945 may have an optional <a href="#linkage">linkage type</a>, and an
946 optional <a href="#visibility">visibility style</a>.</p>
949 <pre class="doc_code">
950 @<Name> = alias [Linkage] [Visibility] <AliaseeTy> @<Aliasee>
955 <!-- ======================================================================= -->
956 <div class="doc_subsection">
957 <a name="namedmetadatastructure">Named Metadata</a>
960 <div class="doc_text">
962 <p>Named metadata is a collection of metadata. <a href="#metadata">Metadata
963 nodes</a> (but not metadata strings) are the only valid operands for
964 a named metadata.</p>
967 <pre class="doc_code">
968 ; Some unnamed metadata nodes, which are referenced by the named metadata.
969 !0 = metadata !{metadata !"zero"}
970 !1 = metadata !{metadata !"one"}
971 !2 = metadata !{metadata !"two"}
973 !name = !{!0, !1, !2}
978 <!-- ======================================================================= -->
979 <div class="doc_subsection"><a name="paramattrs">Parameter Attributes</a></div>
981 <div class="doc_text">
983 <p>The return type and each parameter of a function type may have a set of
984 <i>parameter attributes</i> associated with them. Parameter attributes are
985 used to communicate additional information about the result or parameters of
986 a function. Parameter attributes are considered to be part of the function,
987 not of the function type, so functions with different parameter attributes
988 can have the same function type.</p>
990 <p>Parameter attributes are simple keywords that follow the type specified. If
991 multiple parameter attributes are needed, they are space separated. For
994 <pre class="doc_code">
995 declare i32 @printf(i8* noalias nocapture, ...)
996 declare i32 @atoi(i8 zeroext)
997 declare signext i8 @returns_signed_char()
1000 <p>Note that any attributes for the function result (<tt>nounwind</tt>,
1001 <tt>readonly</tt>) come immediately after the argument list.</p>
1003 <p>Currently, only the following parameter attributes are defined:</p>
1006 <dt><tt><b>zeroext</b></tt></dt>
1007 <dd>This indicates to the code generator that the parameter or return value
1008 should be zero-extended to a 32-bit value by the caller (for a parameter)
1009 or the callee (for a return value).</dd>
1011 <dt><tt><b>signext</b></tt></dt>
1012 <dd>This indicates to the code generator that the parameter or return value
1013 should be sign-extended to a 32-bit value by the caller (for a parameter)
1014 or the callee (for a return value).</dd>
1016 <dt><tt><b>inreg</b></tt></dt>
1017 <dd>This indicates that this parameter or return value should be treated in a
1018 special target-dependent fashion during while emitting code for a function
1019 call or return (usually, by putting it in a register as opposed to memory,
1020 though some targets use it to distinguish between two different kinds of
1021 registers). Use of this attribute is target-specific.</dd>
1023 <dt><tt><b><a name="byval">byval</a></b></tt></dt>
1024 <dd>This indicates that the pointer parameter should really be passed by value
1025 to the function. The attribute implies that a hidden copy of the pointee
1026 is made between the caller and the callee, so the callee is unable to
1027 modify the value in the callee. This attribute is only valid on LLVM
1028 pointer arguments. It is generally used to pass structs and arrays by
1029 value, but is also valid on pointers to scalars. The copy is considered
1030 to belong to the caller not the callee (for example,
1031 <tt><a href="#readonly">readonly</a></tt> functions should not write to
1032 <tt>byval</tt> parameters). This is not a valid attribute for return
1033 values. The byval attribute also supports specifying an alignment with
1034 the align attribute. This has a target-specific effect on the code
1035 generator that usually indicates a desired alignment for the synthesized
1038 <dt><tt><b><a name="sret">sret</a></b></tt></dt>
1039 <dd>This indicates that the pointer parameter specifies the address of a
1040 structure that is the return value of the function in the source program.
1041 This pointer must be guaranteed by the caller to be valid: loads and
1042 stores to the structure may be assumed by the callee to not to trap. This
1043 may only be applied to the first parameter. This is not a valid attribute
1044 for return values. </dd>
1046 <dt><tt><b><a name="noalias">noalias</a></b></tt></dt>
1047 <dd>This indicates that pointer values
1048 <a href="#pointeraliasing"><i>based</i></a> on the argument or return
1049 value do not alias pointer values which are not <i>based</i> on it,
1050 ignoring certain "irrelevant" dependencies.
1051 For a call to the parent function, dependencies between memory
1052 references from before or after the call and from those during the call
1053 are "irrelevant" to the <tt>noalias</tt> keyword for the arguments and
1054 return value used in that call.
1055 The caller shares the responsibility with the callee for ensuring that
1056 these requirements are met.
1057 For further details, please see the discussion of the NoAlias response in
1058 <a href="AliasAnalysis.html#MustMayNo">alias analysis</a>.<br>
1060 Note that this definition of <tt>noalias</tt> is intentionally
1061 similar to the definition of <tt>restrict</tt> in C99 for function
1062 arguments, though it is slightly weaker.
1064 For function return values, C99's <tt>restrict</tt> is not meaningful,
1065 while LLVM's <tt>noalias</tt> is.
1068 <dt><tt><b><a name="nocapture">nocapture</a></b></tt></dt>
1069 <dd>This indicates that the callee does not make any copies of the pointer
1070 that outlive the callee itself. This is not a valid attribute for return
1073 <dt><tt><b><a name="nest">nest</a></b></tt></dt>
1074 <dd>This indicates that the pointer parameter can be excised using the
1075 <a href="#int_trampoline">trampoline intrinsics</a>. This is not a valid
1076 attribute for return values.</dd>
1081 <!-- ======================================================================= -->
1082 <div class="doc_subsection">
1083 <a name="gc">Garbage Collector Names</a>
1086 <div class="doc_text">
1088 <p>Each function may specify a garbage collector name, which is simply a
1091 <pre class="doc_code">
1092 define void @f() gc "name" { ... }
1095 <p>The compiler declares the supported values of <i>name</i>. Specifying a
1096 collector which will cause the compiler to alter its output in order to
1097 support the named garbage collection algorithm.</p>
1101 <!-- ======================================================================= -->
1102 <div class="doc_subsection">
1103 <a name="fnattrs">Function Attributes</a>
1106 <div class="doc_text">
1108 <p>Function attributes are set to communicate additional information about a
1109 function. Function attributes are considered to be part of the function, not
1110 of the function type, so functions with different parameter attributes can
1111 have the same function type.</p>
1113 <p>Function attributes are simple keywords that follow the type specified. If
1114 multiple attributes are needed, they are space separated. For example:</p>
1116 <pre class="doc_code">
1117 define void @f() noinline { ... }
1118 define void @f() alwaysinline { ... }
1119 define void @f() alwaysinline optsize { ... }
1120 define void @f() optsize { ... }
1124 <dt><tt><b>alignstack(<<em>n</em>>)</b></tt></dt>
1125 <dd>This attribute indicates that, when emitting the prologue and epilogue,
1126 the backend should forcibly align the stack pointer. Specify the
1127 desired alignment, which must be a power of two, in parentheses.
1129 <dt><tt><b>alwaysinline</b></tt></dt>
1130 <dd>This attribute indicates that the inliner should attempt to inline this
1131 function into callers whenever possible, ignoring any active inlining size
1132 threshold for this caller.</dd>
1134 <dt><tt><b>hotpatch</b></tt></dt>
1135 <dd>This attribute indicates that the function should be 'hotpatchable',
1136 meaning the function can be patched even while it is loaded into memory.
1137 On x86, the function prologue will contain a two-byte no-op sequence;
1138 this is the same sequence used in the system DLLs in Microsoft Windows
1139 XP Service Pack 2 and higher.</dd>
1141 <dt><tt><b>inlinehint</b></tt></dt>
1142 <dd>This attribute indicates that the source code contained a hint that inlining
1143 this function is desirable (such as the "inline" keyword in C/C++). It
1144 is just a hint; it imposes no requirements on the inliner.</dd>
1146 <dt><tt><b>naked</b></tt></dt>
1147 <dd>This attribute disables prologue / epilogue emission for the function.
1148 This can have very system-specific consequences.</dd>
1150 <dt><tt><b>noimplicitfloat</b></tt></dt>
1151 <dd>This attributes disables implicit floating point instructions.</dd>
1153 <dt><tt><b>noinline</b></tt></dt>
1154 <dd>This attribute indicates that the inliner should never inline this
1155 function in any situation. This attribute may not be used together with
1156 the <tt>alwaysinline</tt> attribute.</dd>
1158 <dt><tt><b>noredzone</b></tt></dt>
1159 <dd>This attribute indicates that the code generator should not use a red
1160 zone, even if the target-specific ABI normally permits it.</dd>
1162 <dt><tt><b>noreturn</b></tt></dt>
1163 <dd>This function attribute indicates that the function never returns
1164 normally. This produces undefined behavior at runtime if the function
1165 ever does dynamically return.</dd>
1167 <dt><tt><b>nounwind</b></tt></dt>
1168 <dd>This function attribute indicates that the function never returns with an
1169 unwind or exceptional control flow. If the function does unwind, its
1170 runtime behavior is undefined.</dd>
1172 <dt><tt><b>optsize</b></tt></dt>
1173 <dd>This attribute suggests that optimization passes and code generator passes
1174 make choices that keep the code size of this function low, and otherwise
1175 do optimizations specifically to reduce code size.</dd>
1177 <dt><tt><b>readnone</b></tt></dt>
1178 <dd>This attribute indicates that the function computes its result (or decides
1179 to unwind an exception) based strictly on its arguments, without
1180 dereferencing any pointer arguments or otherwise accessing any mutable
1181 state (e.g. memory, control registers, etc) visible to caller functions.
1182 It does not write through any pointer arguments
1183 (including <tt><a href="#byval">byval</a></tt> arguments) and never
1184 changes any state visible to callers. This means that it cannot unwind
1185 exceptions by calling the <tt>C++</tt> exception throwing methods, but
1186 could use the <tt>unwind</tt> instruction.</dd>
1188 <dt><tt><b><a name="readonly">readonly</a></b></tt></dt>
1189 <dd>This attribute indicates that the function does not write through any
1190 pointer arguments (including <tt><a href="#byval">byval</a></tt>
1191 arguments) or otherwise modify any state (e.g. memory, control registers,
1192 etc) visible to caller functions. It may dereference pointer arguments
1193 and read state that may be set in the caller. A readonly function always
1194 returns the same value (or unwinds an exception identically) when called
1195 with the same set of arguments and global state. It cannot unwind an
1196 exception by calling the <tt>C++</tt> exception throwing methods, but may
1197 use the <tt>unwind</tt> instruction.</dd>
1199 <dt><tt><b><a name="ssp">ssp</a></b></tt></dt>
1200 <dd>This attribute indicates that the function should emit a stack smashing
1201 protector. It is in the form of a "canary"—a random value placed on
1202 the stack before the local variables that's checked upon return from the
1203 function to see if it has been overwritten. A heuristic is used to
1204 determine if a function needs stack protectors or not.<br>
1206 If a function that has an <tt>ssp</tt> attribute is inlined into a
1207 function that doesn't have an <tt>ssp</tt> attribute, then the resulting
1208 function will have an <tt>ssp</tt> attribute.</dd>
1210 <dt><tt><b>sspreq</b></tt></dt>
1211 <dd>This attribute indicates that the function should <em>always</em> emit a
1212 stack smashing protector. This overrides
1213 the <tt><a href="#ssp">ssp</a></tt> function attribute.<br>
1215 If a function that has an <tt>sspreq</tt> attribute is inlined into a
1216 function that doesn't have an <tt>sspreq</tt> attribute or which has
1217 an <tt>ssp</tt> attribute, then the resulting function will have
1218 an <tt>sspreq</tt> attribute.</dd>
1223 <!-- ======================================================================= -->
1224 <div class="doc_subsection">
1225 <a name="moduleasm">Module-Level Inline Assembly</a>
1228 <div class="doc_text">
1230 <p>Modules may contain "module-level inline asm" blocks, which corresponds to
1231 the GCC "file scope inline asm" blocks. These blocks are internally
1232 concatenated by LLVM and treated as a single unit, but may be separated in
1233 the <tt>.ll</tt> file if desired. The syntax is very simple:</p>
1235 <pre class="doc_code">
1236 module asm "inline asm code goes here"
1237 module asm "more can go here"
1240 <p>The strings can contain any character by escaping non-printable characters.
1241 The escape sequence used is simply "\xx" where "xx" is the two digit hex code
1244 <p>The inline asm code is simply printed to the machine code .s file when
1245 assembly code is generated.</p>
1249 <!-- ======================================================================= -->
1250 <div class="doc_subsection">
1251 <a name="datalayout">Data Layout</a>
1254 <div class="doc_text">
1256 <p>A module may specify a target specific data layout string that specifies how
1257 data is to be laid out in memory. The syntax for the data layout is
1260 <pre class="doc_code">
1261 target datalayout = "<i>layout specification</i>"
1264 <p>The <i>layout specification</i> consists of a list of specifications
1265 separated by the minus sign character ('-'). Each specification starts with
1266 a letter and may include other information after the letter to define some
1267 aspect of the data layout. The specifications accepted are as follows:</p>
1271 <dd>Specifies that the target lays out data in big-endian form. That is, the
1272 bits with the most significance have the lowest address location.</dd>
1275 <dd>Specifies that the target lays out data in little-endian form. That is,
1276 the bits with the least significance have the lowest address
1279 <dt><tt>p:<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
1280 <dd>This specifies the <i>size</i> of a pointer and its <i>abi</i> and
1281 <i>preferred</i> alignments. All sizes are in bits. Specifying
1282 the <i>pref</i> alignment is optional. If omitted, the
1283 preceding <tt>:</tt> should be omitted too.</dd>
1285 <dt><tt>i<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
1286 <dd>This specifies the alignment for an integer type of a given bit
1287 <i>size</i>. The value of <i>size</i> must be in the range [1,2^23).</dd>
1289 <dt><tt>v<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
1290 <dd>This specifies the alignment for a vector type of a given bit
1293 <dt><tt>f<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
1294 <dd>This specifies the alignment for a floating point type of a given bit
1295 <i>size</i>. Only values of <i>size</i> that are supported by the target
1296 will work. 32 (float) and 64 (double) are supported on all targets;
1297 80 or 128 (different flavors of long double) are also supported on some
1300 <dt><tt>a<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
1301 <dd>This specifies the alignment for an aggregate type of a given bit
1304 <dt><tt>s<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
1305 <dd>This specifies the alignment for a stack object of a given bit
1308 <dt><tt>n<i>size1</i>:<i>size2</i>:<i>size3</i>...</tt></dt>
1309 <dd>This specifies a set of native integer widths for the target CPU
1310 in bits. For example, it might contain "n32" for 32-bit PowerPC,
1311 "n32:64" for PowerPC 64, or "n8:16:32:64" for X86-64. Elements of
1312 this set are considered to support most general arithmetic
1313 operations efficiently.</dd>
1316 <p>When constructing the data layout for a given target, LLVM starts with a
1317 default set of specifications which are then (possibly) overridden by the
1318 specifications in the <tt>datalayout</tt> keyword. The default specifications
1319 are given in this list:</p>
1322 <li><tt>E</tt> - big endian</li>
1323 <li><tt>p:64:64:64</tt> - 64-bit pointers with 64-bit alignment</li>
1324 <li><tt>i1:8:8</tt> - i1 is 8-bit (byte) aligned</li>
1325 <li><tt>i8:8:8</tt> - i8 is 8-bit (byte) aligned</li>
1326 <li><tt>i16:16:16</tt> - i16 is 16-bit aligned</li>
1327 <li><tt>i32:32:32</tt> - i32 is 32-bit aligned</li>
1328 <li><tt>i64:32:64</tt> - i64 has ABI alignment of 32-bits but preferred
1329 alignment of 64-bits</li>
1330 <li><tt>f32:32:32</tt> - float is 32-bit aligned</li>
1331 <li><tt>f64:64:64</tt> - double is 64-bit aligned</li>
1332 <li><tt>v64:64:64</tt> - 64-bit vector is 64-bit aligned</li>
1333 <li><tt>v128:128:128</tt> - 128-bit vector is 128-bit aligned</li>
1334 <li><tt>a0:0:1</tt> - aggregates are 8-bit aligned</li>
1335 <li><tt>s0:64:64</tt> - stack objects are 64-bit aligned</li>
1338 <p>When LLVM is determining the alignment for a given type, it uses the
1339 following rules:</p>
1342 <li>If the type sought is an exact match for one of the specifications, that
1343 specification is used.</li>
1345 <li>If no match is found, and the type sought is an integer type, then the
1346 smallest integer type that is larger than the bitwidth of the sought type
1347 is used. If none of the specifications are larger than the bitwidth then
1348 the the largest integer type is used. For example, given the default
1349 specifications above, the i7 type will use the alignment of i8 (next
1350 largest) while both i65 and i256 will use the alignment of i64 (largest
1353 <li>If no match is found, and the type sought is a vector type, then the
1354 largest vector type that is smaller than the sought vector type will be
1355 used as a fall back. This happens because <128 x double> can be
1356 implemented in terms of 64 <2 x double>, for example.</li>
1361 <!-- ======================================================================= -->
1362 <div class="doc_subsection">
1363 <a name="pointeraliasing">Pointer Aliasing Rules</a>
1366 <div class="doc_text">
1368 <p>Any memory access must be done through a pointer value associated
1369 with an address range of the memory access, otherwise the behavior
1370 is undefined. Pointer values are associated with address ranges
1371 according to the following rules:</p>
1374 <li>A pointer value is associated with the addresses associated with
1375 any value it is <i>based</i> on.
1376 <li>An address of a global variable is associated with the address
1377 range of the variable's storage.</li>
1378 <li>The result value of an allocation instruction is associated with
1379 the address range of the allocated storage.</li>
1380 <li>A null pointer in the default address-space is associated with
1382 <li>An integer constant other than zero or a pointer value returned
1383 from a function not defined within LLVM may be associated with address
1384 ranges allocated through mechanisms other than those provided by
1385 LLVM. Such ranges shall not overlap with any ranges of addresses
1386 allocated by mechanisms provided by LLVM.</li>
1389 <p>A pointer value is <i>based</i> on another pointer value according
1390 to the following rules:</p>
1393 <li>A pointer value formed from a
1394 <tt><a href="#i_getelementptr">getelementptr</a></tt> operation
1395 is <i>based</i> on the first operand of the <tt>getelementptr</tt>.</li>
1396 <li>The result value of a
1397 <tt><a href="#i_bitcast">bitcast</a></tt> is <i>based</i> on the operand
1398 of the <tt>bitcast</tt>.</li>
1399 <li>A pointer value formed by an
1400 <tt><a href="#i_inttoptr">inttoptr</a></tt> is <i>based</i> on all
1401 pointer values that contribute (directly or indirectly) to the
1402 computation of the pointer's value.</li>
1403 <li>The "<i>based</i> on" relationship is transitive.</li>
1406 <p>Note that this definition of <i>"based"</i> is intentionally
1407 similar to the definition of <i>"based"</i> in C99, though it is
1408 slightly weaker.</p>
1410 <p>LLVM IR does not associate types with memory. The result type of a
1411 <tt><a href="#i_load">load</a></tt> merely indicates the size and
1412 alignment of the memory from which to load, as well as the
1413 interpretation of the value. The first operand type of a
1414 <tt><a href="#i_store">store</a></tt> similarly only indicates the size
1415 and alignment of the store.</p>
1417 <p>Consequently, type-based alias analysis, aka TBAA, aka
1418 <tt>-fstrict-aliasing</tt>, is not applicable to general unadorned
1419 LLVM IR. <a href="#metadata">Metadata</a> may be used to encode
1420 additional information which specialized optimization passes may use
1421 to implement type-based alias analysis.</p>
1425 <!-- ======================================================================= -->
1426 <div class="doc_subsection">
1427 <a name="volatile">Volatile Memory Accesses</a>
1430 <div class="doc_text">
1432 <p>Certain memory accesses, such as <a href="#i_load"><tt>load</tt></a>s, <a
1433 href="#i_store"><tt>store</tt></a>s, and <a
1434 href="#int_memcpy"><tt>llvm.memcpy</tt></a>s may be marked <tt>volatile</tt>.
1435 The optimizers must not change the number of volatile operations or change their
1436 order of execution relative to other volatile operations. The optimizers
1437 <i>may</i> change the order of volatile operations relative to non-volatile
1438 operations. This is not Java's "volatile" and has no cross-thread
1439 synchronization behavior.</p>
1443 <!-- *********************************************************************** -->
1444 <div class="doc_section"> <a name="typesystem">Type System</a> </div>
1445 <!-- *********************************************************************** -->
1447 <div class="doc_text">
1449 <p>The LLVM type system is one of the most important features of the
1450 intermediate representation. Being typed enables a number of optimizations
1451 to be performed on the intermediate representation directly, without having
1452 to do extra analyses on the side before the transformation. A strong type
1453 system makes it easier to read the generated code and enables novel analyses
1454 and transformations that are not feasible to perform on normal three address
1455 code representations.</p>
1459 <!-- ======================================================================= -->
1460 <div class="doc_subsection"> <a name="t_classifications">Type
1461 Classifications</a> </div>
1463 <div class="doc_text">
1465 <p>The types fall into a few useful classifications:</p>
1467 <table border="1" cellspacing="0" cellpadding="4">
1469 <tr><th>Classification</th><th>Types</th></tr>
1471 <td><a href="#t_integer">integer</a></td>
1472 <td><tt>i1, i2, i3, ... i8, ... i16, ... i32, ... i64, ... </tt></td>
1475 <td><a href="#t_floating">floating point</a></td>
1476 <td><tt>float, double, x86_fp80, fp128, ppc_fp128</tt></td>
1479 <td><a name="t_firstclass">first class</a></td>
1480 <td><a href="#t_integer">integer</a>,
1481 <a href="#t_floating">floating point</a>,
1482 <a href="#t_pointer">pointer</a>,
1483 <a href="#t_vector">vector</a>,
1484 <a href="#t_struct">structure</a>,
1485 <a href="#t_array">array</a>,
1486 <a href="#t_label">label</a>,
1487 <a href="#t_metadata">metadata</a>.
1491 <td><a href="#t_primitive">primitive</a></td>
1492 <td><a href="#t_label">label</a>,
1493 <a href="#t_void">void</a>,
1494 <a href="#t_floating">floating point</a>,
1495 <a href="#t_x86mmx">x86mmx</a>,
1496 <a href="#t_metadata">metadata</a>.</td>
1499 <td><a href="#t_derived">derived</a></td>
1500 <td><a href="#t_array">array</a>,
1501 <a href="#t_function">function</a>,
1502 <a href="#t_pointer">pointer</a>,
1503 <a href="#t_struct">structure</a>,
1504 <a href="#t_pstruct">packed structure</a>,
1505 <a href="#t_vector">vector</a>,
1506 <a href="#t_opaque">opaque</a>.
1512 <p>The <a href="#t_firstclass">first class</a> types are perhaps the most
1513 important. Values of these types are the only ones which can be produced by
1518 <!-- ======================================================================= -->
1519 <div class="doc_subsection"> <a name="t_primitive">Primitive Types</a> </div>
1521 <div class="doc_text">
1523 <p>The primitive types are the fundamental building blocks of the LLVM
1528 <!-- _______________________________________________________________________ -->
1529 <div class="doc_subsubsection"> <a name="t_integer">Integer Type</a> </div>
1531 <div class="doc_text">
1534 <p>The integer type is a very simple type that simply specifies an arbitrary
1535 bit width for the integer type desired. Any bit width from 1 bit to
1536 2<sup>23</sup>-1 (about 8 million) can be specified.</p>
1543 <p>The number of bits the integer will occupy is specified by the <tt>N</tt>
1547 <table class="layout">
1549 <td class="left"><tt>i1</tt></td>
1550 <td class="left">a single-bit integer.</td>
1553 <td class="left"><tt>i32</tt></td>
1554 <td class="left">a 32-bit integer.</td>
1557 <td class="left"><tt>i1942652</tt></td>
1558 <td class="left">a really big integer of over 1 million bits.</td>
1564 <!-- _______________________________________________________________________ -->
1565 <div class="doc_subsubsection"> <a name="t_floating">Floating Point Types</a> </div>
1567 <div class="doc_text">
1571 <tr><th>Type</th><th>Description</th></tr>
1572 <tr><td><tt>float</tt></td><td>32-bit floating point value</td></tr>
1573 <tr><td><tt>double</tt></td><td>64-bit floating point value</td></tr>
1574 <tr><td><tt>fp128</tt></td><td>128-bit floating point value (112-bit mantissa)</td></tr>
1575 <tr><td><tt>x86_fp80</tt></td><td>80-bit floating point value (X87)</td></tr>
1576 <tr><td><tt>ppc_fp128</tt></td><td>128-bit floating point value (two 64-bits)</td></tr>
1582 <!-- _______________________________________________________________________ -->
1583 <div class="doc_subsubsection"> <a name="t_x86mmx">X86mmx Type</a> </div>
1585 <div class="doc_text">
1588 <p>The x86mmx type represents a value held in an MMX register on an x86 machine. The operations allowed on it are quite limited: parameters and return values, load and store, and bitcast. User-specified MMX instructions are represented as intrinsic or asm calls with arguments and/or results of this type. There are no arrays, vectors or constants of this type.</p>
1597 <!-- _______________________________________________________________________ -->
1598 <div class="doc_subsubsection"> <a name="t_void">Void Type</a> </div>
1600 <div class="doc_text">
1603 <p>The void type does not represent any value and has no size.</p>
1612 <!-- _______________________________________________________________________ -->
1613 <div class="doc_subsubsection"> <a name="t_label">Label Type</a> </div>
1615 <div class="doc_text">
1618 <p>The label type represents code labels.</p>
1627 <!-- _______________________________________________________________________ -->
1628 <div class="doc_subsubsection"> <a name="t_metadata">Metadata Type</a> </div>
1630 <div class="doc_text">
1633 <p>The metadata type represents embedded metadata. No derived types may be
1634 created from metadata except for <a href="#t_function">function</a>
1645 <!-- ======================================================================= -->
1646 <div class="doc_subsection"> <a name="t_derived">Derived Types</a> </div>
1648 <div class="doc_text">
1650 <p>The real power in LLVM comes from the derived types in the system. This is
1651 what allows a programmer to represent arrays, functions, pointers, and other
1652 useful types. Each of these types contain one or more element types which
1653 may be a primitive type, or another derived type. For example, it is
1654 possible to have a two dimensional array, using an array as the element type
1655 of another array.</p>
1660 <!-- _______________________________________________________________________ -->
1661 <div class="doc_subsubsection"> <a name="t_aggregate">Aggregate Types</a> </div>
1663 <div class="doc_text">
1665 <p>Aggregate Types are a subset of derived types that can contain multiple
1666 member types. <a href="#t_array">Arrays</a>,
1667 <a href="#t_struct">structs</a>, and <a href="#t_vector">vectors</a> are
1668 aggregate types.</p>
1672 <!-- _______________________________________________________________________ -->
1673 <div class="doc_subsubsection"> <a name="t_array">Array Type</a> </div>
1675 <div class="doc_text">
1678 <p>The array type is a very simple derived type that arranges elements
1679 sequentially in memory. The array type requires a size (number of elements)
1680 and an underlying data type.</p>
1684 [<# elements> x <elementtype>]
1687 <p>The number of elements is a constant integer value; <tt>elementtype</tt> may
1688 be any type with a size.</p>
1691 <table class="layout">
1693 <td class="left"><tt>[40 x i32]</tt></td>
1694 <td class="left">Array of 40 32-bit integer values.</td>
1697 <td class="left"><tt>[41 x i32]</tt></td>
1698 <td class="left">Array of 41 32-bit integer values.</td>
1701 <td class="left"><tt>[4 x i8]</tt></td>
1702 <td class="left">Array of 4 8-bit integer values.</td>
1705 <p>Here are some examples of multidimensional arrays:</p>
1706 <table class="layout">
1708 <td class="left"><tt>[3 x [4 x i32]]</tt></td>
1709 <td class="left">3x4 array of 32-bit integer values.</td>
1712 <td class="left"><tt>[12 x [10 x float]]</tt></td>
1713 <td class="left">12x10 array of single precision floating point values.</td>
1716 <td class="left"><tt>[2 x [3 x [4 x i16]]]</tt></td>
1717 <td class="left">2x3x4 array of 16-bit integer values.</td>
1721 <p>There is no restriction on indexing beyond the end of the array implied by
1722 a static type (though there are restrictions on indexing beyond the bounds
1723 of an allocated object in some cases). This means that single-dimension
1724 'variable sized array' addressing can be implemented in LLVM with a zero
1725 length array type. An implementation of 'pascal style arrays' in LLVM could
1726 use the type "<tt>{ i32, [0 x float]}</tt>", for example.</p>
1730 <!-- _______________________________________________________________________ -->
1731 <div class="doc_subsubsection"> <a name="t_function">Function Type</a> </div>
1733 <div class="doc_text">
1736 <p>The function type can be thought of as a function signature. It consists of
1737 a return type and a list of formal parameter types. The return type of a
1738 function type is a first class type or a void type.</p>
1742 <returntype> (<parameter list>)
1745 <p>...where '<tt><parameter list></tt>' is a comma-separated list of type
1746 specifiers. Optionally, the parameter list may include a type <tt>...</tt>,
1747 which indicates that the function takes a variable number of arguments.
1748 Variable argument functions can access their arguments with
1749 the <a href="#int_varargs">variable argument handling intrinsic</a>
1750 functions. '<tt><returntype></tt>' is any type except
1751 <a href="#t_label">label</a>.</p>
1754 <table class="layout">
1756 <td class="left"><tt>i32 (i32)</tt></td>
1757 <td class="left">function taking an <tt>i32</tt>, returning an <tt>i32</tt>
1759 </tr><tr class="layout">
1760 <td class="left"><tt>float (i16, i32 *) *
1762 <td class="left"><a href="#t_pointer">Pointer</a> to a function that takes
1763 an <tt>i16</tt> and a <a href="#t_pointer">pointer</a> to <tt>i32</tt>,
1764 returning <tt>float</tt>.
1766 </tr><tr class="layout">
1767 <td class="left"><tt>i32 (i8*, ...)</tt></td>
1768 <td class="left">A vararg function that takes at least one
1769 <a href="#t_pointer">pointer</a> to <tt>i8 </tt> (char in C),
1770 which returns an integer. This is the signature for <tt>printf</tt> in
1773 </tr><tr class="layout">
1774 <td class="left"><tt>{i32, i32} (i32)</tt></td>
1775 <td class="left">A function taking an <tt>i32</tt>, returning a
1776 <a href="#t_struct">structure</a> containing two <tt>i32</tt> values
1783 <!-- _______________________________________________________________________ -->
1784 <div class="doc_subsubsection"> <a name="t_struct">Structure Type</a> </div>
1786 <div class="doc_text">
1789 <p>The structure type is used to represent a collection of data members together
1790 in memory. The packing of the field types is defined to match the ABI of the
1791 underlying processor. The elements of a structure may be any type that has a
1794 <p>Structures in memory are accessed using '<tt><a href="#i_load">load</a></tt>'
1795 and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a field
1796 with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction.
1797 Structures in registers are accessed using the
1798 '<tt><a href="#i_extractvalue">extractvalue</a></tt>' and
1799 '<tt><a href="#i_insertvalue">insertvalue</a></tt>' instructions.</p>
1802 { <type list> }
1806 <table class="layout">
1808 <td class="left"><tt>{ i32, i32, i32 }</tt></td>
1809 <td class="left">A triple of three <tt>i32</tt> values</td>
1810 </tr><tr class="layout">
1811 <td class="left"><tt>{ float, i32 (i32) * }</tt></td>
1812 <td class="left">A pair, where the first element is a <tt>float</tt> and the
1813 second element is a <a href="#t_pointer">pointer</a> to a
1814 <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
1815 an <tt>i32</tt>.</td>
1821 <!-- _______________________________________________________________________ -->
1822 <div class="doc_subsubsection"> <a name="t_pstruct">Packed Structure Type</a>
1825 <div class="doc_text">
1828 <p>The packed structure type is used to represent a collection of data members
1829 together in memory. There is no padding between fields. Further, the
1830 alignment of a packed structure is 1 byte. The elements of a packed
1831 structure may be any type that has a size.</p>
1833 <p>Structures are accessed using '<tt><a href="#i_load">load</a></tt> and
1834 '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a field with
1835 the '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction.</p>
1839 < { <type list> } >
1843 <table class="layout">
1845 <td class="left"><tt>< { i32, i32, i32 } ></tt></td>
1846 <td class="left">A triple of three <tt>i32</tt> values</td>
1847 </tr><tr class="layout">
1849 <tt>< { float, i32 (i32)* } ></tt></td>
1850 <td class="left">A pair, where the first element is a <tt>float</tt> and the
1851 second element is a <a href="#t_pointer">pointer</a> to a
1852 <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
1853 an <tt>i32</tt>.</td>
1859 <!-- _______________________________________________________________________ -->
1860 <div class="doc_subsubsection"> <a name="t_pointer">Pointer Type</a> </div>
1862 <div class="doc_text">
1865 <p>The pointer type is used to specify memory locations.
1866 Pointers are commonly used to reference objects in memory.</p>
1868 <p>Pointer types may have an optional address space attribute defining the
1869 numbered address space where the pointed-to object resides. The default
1870 address space is number zero. The semantics of non-zero address
1871 spaces are target-specific.</p>
1873 <p>Note that LLVM does not permit pointers to void (<tt>void*</tt>) nor does it
1874 permit pointers to labels (<tt>label*</tt>). Use <tt>i8*</tt> instead.</p>
1882 <table class="layout">
1884 <td class="left"><tt>[4 x i32]*</tt></td>
1885 <td class="left">A <a href="#t_pointer">pointer</a> to <a
1886 href="#t_array">array</a> of four <tt>i32</tt> values.</td>
1889 <td class="left"><tt>i32 (i32*) *</tt></td>
1890 <td class="left"> A <a href="#t_pointer">pointer</a> to a <a
1891 href="#t_function">function</a> that takes an <tt>i32*</tt>, returning an
1895 <td class="left"><tt>i32 addrspace(5)*</tt></td>
1896 <td class="left">A <a href="#t_pointer">pointer</a> to an <tt>i32</tt> value
1897 that resides in address space #5.</td>
1903 <!-- _______________________________________________________________________ -->
1904 <div class="doc_subsubsection"> <a name="t_vector">Vector Type</a> </div>
1906 <div class="doc_text">
1909 <p>A vector type is a simple derived type that represents a vector of elements.
1910 Vector types are used when multiple primitive data are operated in parallel
1911 using a single instruction (SIMD). A vector type requires a size (number of
1912 elements) and an underlying primitive data type. Vector types are considered
1913 <a href="#t_firstclass">first class</a>.</p>
1917 < <# elements> x <elementtype> >
1920 <p>The number of elements is a constant integer value larger than 0; elementtype
1921 may be any integer or floating point type. Vectors of size zero are not
1922 allowed, and pointers are not allowed as the element type.</p>
1925 <table class="layout">
1927 <td class="left"><tt><4 x i32></tt></td>
1928 <td class="left">Vector of 4 32-bit integer values.</td>
1931 <td class="left"><tt><8 x float></tt></td>
1932 <td class="left">Vector of 8 32-bit floating-point values.</td>
1935 <td class="left"><tt><2 x i64></tt></td>
1936 <td class="left">Vector of 2 64-bit integer values.</td>
1942 <!-- _______________________________________________________________________ -->
1943 <div class="doc_subsubsection"> <a name="t_opaque">Opaque Type</a> </div>
1944 <div class="doc_text">
1947 <p>Opaque types are used to represent unknown types in the system. This
1948 corresponds (for example) to the C notion of a forward declared structure
1949 type. In LLVM, opaque types can eventually be resolved to any type (not just
1950 a structure type).</p>
1958 <table class="layout">
1960 <td class="left"><tt>opaque</tt></td>
1961 <td class="left">An opaque type.</td>
1967 <!-- ======================================================================= -->
1968 <div class="doc_subsection">
1969 <a name="t_uprefs">Type Up-references</a>
1972 <div class="doc_text">
1975 <p>An "up reference" allows you to refer to a lexically enclosing type without
1976 requiring it to have a name. For instance, a structure declaration may
1977 contain a pointer to any of the types it is lexically a member of. Example
1978 of up references (with their equivalent as named type declarations)
1982 { \2 * } %x = type { %x* }
1983 { \2 }* %y = type { %y }*
1987 <p>An up reference is needed by the asmprinter for printing out cyclic types
1988 when there is no declared name for a type in the cycle. Because the
1989 asmprinter does not want to print out an infinite type string, it needs a
1990 syntax to handle recursive types that have no names (all names are optional
1998 <p>The level is the count of the lexical type that is being referred to.</p>
2001 <table class="layout">
2003 <td class="left"><tt>\1*</tt></td>
2004 <td class="left">Self-referential pointer.</td>
2007 <td class="left"><tt>{ { \3*, i8 }, i32 }</tt></td>
2008 <td class="left">Recursive structure where the upref refers to the out-most
2015 <!-- *********************************************************************** -->
2016 <div class="doc_section"> <a name="constants">Constants</a> </div>
2017 <!-- *********************************************************************** -->
2019 <div class="doc_text">
2021 <p>LLVM has several different basic types of constants. This section describes
2022 them all and their syntax.</p>
2026 <!-- ======================================================================= -->
2027 <div class="doc_subsection"><a name="simpleconstants">Simple Constants</a></div>
2029 <div class="doc_text">
2032 <dt><b>Boolean constants</b></dt>
2033 <dd>The two strings '<tt>true</tt>' and '<tt>false</tt>' are both valid
2034 constants of the <tt><a href="#t_integer">i1</a></tt> type.</dd>
2036 <dt><b>Integer constants</b></dt>
2037 <dd>Standard integers (such as '4') are constants of
2038 the <a href="#t_integer">integer</a> type. Negative numbers may be used
2039 with integer types.</dd>
2041 <dt><b>Floating point constants</b></dt>
2042 <dd>Floating point constants use standard decimal notation (e.g. 123.421),
2043 exponential notation (e.g. 1.23421e+2), or a more precise hexadecimal
2044 notation (see below). The assembler requires the exact decimal value of a
2045 floating-point constant. For example, the assembler accepts 1.25 but
2046 rejects 1.3 because 1.3 is a repeating decimal in binary. Floating point
2047 constants must have a <a href="#t_floating">floating point</a> type. </dd>
2049 <dt><b>Null pointer constants</b></dt>
2050 <dd>The identifier '<tt>null</tt>' is recognized as a null pointer constant
2051 and must be of <a href="#t_pointer">pointer type</a>.</dd>
2054 <p>The one non-intuitive notation for constants is the hexadecimal form of
2055 floating point constants. For example, the form '<tt>double
2056 0x432ff973cafa8000</tt>' is equivalent to (but harder to read than)
2057 '<tt>double 4.5e+15</tt>'. The only time hexadecimal floating point
2058 constants are required (and the only time that they are generated by the
2059 disassembler) is when a floating point constant must be emitted but it cannot
2060 be represented as a decimal floating point number in a reasonable number of
2061 digits. For example, NaN's, infinities, and other special values are
2062 represented in their IEEE hexadecimal format so that assembly and disassembly
2063 do not cause any bits to change in the constants.</p>
2065 <p>When using the hexadecimal form, constants of types float and double are
2066 represented using the 16-digit form shown above (which matches the IEEE754
2067 representation for double); float values must, however, be exactly
2068 representable as IEE754 single precision. Hexadecimal format is always used
2069 for long double, and there are three forms of long double. The 80-bit format
2070 used by x86 is represented as <tt>0xK</tt> followed by 20 hexadecimal digits.
2071 The 128-bit format used by PowerPC (two adjacent doubles) is represented
2072 by <tt>0xM</tt> followed by 32 hexadecimal digits. The IEEE 128-bit format
2073 is represented by <tt>0xL</tt> followed by 32 hexadecimal digits; no
2074 currently supported target uses this format. Long doubles will only work if
2075 they match the long double format on your target. All hexadecimal formats
2076 are big-endian (sign bit at the left).</p>
2078 <p>There are no constants of type x86mmx.</p>
2081 <!-- ======================================================================= -->
2082 <div class="doc_subsection">
2083 <a name="aggregateconstants"></a> <!-- old anchor -->
2084 <a name="complexconstants">Complex Constants</a>
2087 <div class="doc_text">
2089 <p>Complex constants are a (potentially recursive) combination of simple
2090 constants and smaller complex constants.</p>
2093 <dt><b>Structure constants</b></dt>
2094 <dd>Structure constants are represented with notation similar to structure
2095 type definitions (a comma separated list of elements, surrounded by braces
2096 (<tt>{}</tt>)). For example: "<tt>{ i32 4, float 17.0, i32* @G }</tt>",
2097 where "<tt>@G</tt>" is declared as "<tt>@G = external global i32</tt>".
2098 Structure constants must have <a href="#t_struct">structure type</a>, and
2099 the number and types of elements must match those specified by the
2102 <dt><b>Array constants</b></dt>
2103 <dd>Array constants are represented with notation similar to array type
2104 definitions (a comma separated list of elements, surrounded by square
2105 brackets (<tt>[]</tt>)). For example: "<tt>[ i32 42, i32 11, i32 74
2106 ]</tt>". Array constants must have <a href="#t_array">array type</a>, and
2107 the number and types of elements must match those specified by the
2110 <dt><b>Vector constants</b></dt>
2111 <dd>Vector constants are represented with notation similar to vector type
2112 definitions (a comma separated list of elements, surrounded by
2113 less-than/greater-than's (<tt><></tt>)). For example: "<tt>< i32
2114 42, i32 11, i32 74, i32 100 ></tt>". Vector constants must
2115 have <a href="#t_vector">vector type</a>, and the number and types of
2116 elements must match those specified by the type.</dd>
2118 <dt><b>Zero initialization</b></dt>
2119 <dd>The string '<tt>zeroinitializer</tt>' can be used to zero initialize a
2120 value to zero of <em>any</em> type, including scalar and
2121 <a href="#t_aggregate">aggregate</a> types.
2122 This is often used to avoid having to print large zero initializers
2123 (e.g. for large arrays) and is always exactly equivalent to using explicit
2124 zero initializers.</dd>
2126 <dt><b>Metadata node</b></dt>
2127 <dd>A metadata node is a structure-like constant with
2128 <a href="#t_metadata">metadata type</a>. For example: "<tt>metadata !{
2129 i32 0, metadata !"test" }</tt>". Unlike other constants that are meant to
2130 be interpreted as part of the instruction stream, metadata is a place to
2131 attach additional information such as debug info.</dd>
2136 <!-- ======================================================================= -->
2137 <div class="doc_subsection">
2138 <a name="globalconstants">Global Variable and Function Addresses</a>
2141 <div class="doc_text">
2143 <p>The addresses of <a href="#globalvars">global variables</a>
2144 and <a href="#functionstructure">functions</a> are always implicitly valid
2145 (link-time) constants. These constants are explicitly referenced when
2146 the <a href="#identifiers">identifier for the global</a> is used and always
2147 have <a href="#t_pointer">pointer</a> type. For example, the following is a
2148 legal LLVM file:</p>
2150 <pre class="doc_code">
2153 @Z = global [2 x i32*] [ i32* @X, i32* @Y ]
2158 <!-- ======================================================================= -->
2159 <div class="doc_subsection"><a name="undefvalues">Undefined Values</a></div>
2160 <div class="doc_text">
2162 <p>The string '<tt>undef</tt>' can be used anywhere a constant is expected, and
2163 indicates that the user of the value may receive an unspecified bit-pattern.
2164 Undefined values may be of any type (other than label or void) and be used
2165 anywhere a constant is permitted.</p>
2167 <p>Undefined values are useful because they indicate to the compiler that the
2168 program is well defined no matter what value is used. This gives the
2169 compiler more freedom to optimize. Here are some examples of (potentially
2170 surprising) transformations that are valid (in pseudo IR):</p>
2173 <pre class="doc_code">
2183 <p>This is safe because all of the output bits are affected by the undef bits.
2184 Any output bit can have a zero or one depending on the input bits.</p>
2186 <pre class="doc_code">
2197 <p>These logical operations have bits that are not always affected by the input.
2198 For example, if "%X" has a zero bit, then the output of the 'and' operation will
2199 always be a zero, no matter what the corresponding bit from the undef is. As
2200 such, it is unsafe to optimize or assume that the result of the and is undef.
2201 However, it is safe to assume that all bits of the undef could be 0, and
2202 optimize the and to 0. Likewise, it is safe to assume that all the bits of
2203 the undef operand to the or could be set, allowing the or to be folded to
2206 <pre class="doc_code">
2207 %A = select undef, %X, %Y
2208 %B = select undef, 42, %Y
2209 %C = select %X, %Y, undef
2220 <p>This set of examples show that undefined select (and conditional branch)
2221 conditions can go "either way" but they have to come from one of the two
2222 operands. In the %A example, if %X and %Y were both known to have a clear low
2223 bit, then %A would have to have a cleared low bit. However, in the %C example,
2224 the optimizer is allowed to assume that the undef operand could be the same as
2225 %Y, allowing the whole select to be eliminated.</p>
2228 <pre class="doc_code">
2229 %A = xor undef, undef
2247 <p>This example points out that two undef operands are not necessarily the same.
2248 This can be surprising to people (and also matches C semantics) where they
2249 assume that "X^X" is always zero, even if X is undef. This isn't true for a
2250 number of reasons, but the short answer is that an undef "variable" can
2251 arbitrarily change its value over its "live range". This is true because the
2252 "variable" doesn't actually <em>have a live range</em>. Instead, the value is
2253 logically read from arbitrary registers that happen to be around when needed,
2254 so the value is not necessarily consistent over time. In fact, %A and %C need
2255 to have the same semantics or the core LLVM "replace all uses with" concept
2258 <pre class="doc_code">
2266 <p>These examples show the crucial difference between an <em>undefined
2267 value</em> and <em>undefined behavior</em>. An undefined value (like undef) is
2268 allowed to have an arbitrary bit-pattern. This means that the %A operation
2269 can be constant folded to undef because the undef could be an SNaN, and fdiv is
2270 not (currently) defined on SNaN's. However, in the second example, we can make
2271 a more aggressive assumption: because the undef is allowed to be an arbitrary
2272 value, we are allowed to assume that it could be zero. Since a divide by zero
2273 has <em>undefined behavior</em>, we are allowed to assume that the operation
2274 does not execute at all. This allows us to delete the divide and all code after
2275 it: since the undefined operation "can't happen", the optimizer can assume that
2276 it occurs in dead code.
2279 <pre class="doc_code">
2280 a: store undef -> %X
2281 b: store %X -> undef
2287 <p>These examples reiterate the fdiv example: a store "of" an undefined value
2288 can be assumed to not have any effect: we can assume that the value is
2289 overwritten with bits that happen to match what was already there. However, a
2290 store "to" an undefined location could clobber arbitrary memory, therefore, it
2291 has undefined behavior.</p>
2295 <!-- ======================================================================= -->
2296 <div class="doc_subsection"><a name="trapvalues">Trap Values</a></div>
2297 <div class="doc_text">
2299 <p>Trap values are similar to <a href="#undefvalues">undef values</a>, however
2300 instead of representing an unspecified bit pattern, they represent the
2301 fact that an instruction or constant expression which cannot evoke side
2302 effects has nevertheless detected a condition which results in undefined
2305 <p>There is currently no way of representing a trap value in the IR; they
2306 only exist when produced by operations such as
2307 <a href="#i_add"><tt>add</tt></a> with the <tt>nsw</tt> flag.</p>
2309 <p>Trap value behavior is defined in terms of value <i>dependence</i>:</p>
2312 <li>Values other than <a href="#i_phi"><tt>phi</tt></a> nodes depend on
2313 their operands.</li>
2315 <li><a href="#i_phi"><tt>Phi</tt></a> nodes depend on the operand corresponding
2316 to their dynamic predecessor basic block.</li>
2318 <li>Function arguments depend on the corresponding actual argument values in
2319 the dynamic callers of their functions.</li>
2321 <li><a href="#i_call"><tt>Call</tt></a> instructions depend on the
2322 <a href="#i_ret"><tt>ret</tt></a> instructions that dynamically transfer
2323 control back to them.</li>
2325 <li><a href="#i_invoke"><tt>Invoke</tt></a> instructions depend on the
2326 <a href="#i_ret"><tt>ret</tt></a>, <a href="#i_unwind"><tt>unwind</tt></a>,
2327 or exception-throwing call instructions that dynamically transfer control
2330 <li>Non-volatile loads and stores depend on the most recent stores to all of the
2331 referenced memory addresses, following the order in the IR
2332 (including loads and stores implied by intrinsics such as
2333 <a href="#int_memcpy"><tt>@llvm.memcpy</tt></a>.)</li>
2335 <!-- TODO: In the case of multiple threads, this only applies if the store
2336 "happens-before" the load or store. -->
2338 <!-- TODO: floating-point exception state -->
2340 <li>An instruction with externally visible side effects depends on the most
2341 recent preceding instruction with externally visible side effects, following
2342 the order in the IR. (This includes
2343 <a href="#volatile">volatile operations</a>.)</li>
2345 <li>An instruction <i>control-depends</i> on a
2346 <a href="#terminators">terminator instruction</a>
2347 if the terminator instruction has multiple successors and the instruction
2348 is always executed when control transfers to one of the successors, and
2349 may not be executed when control is transfered to another.</li>
2351 <li>Dependence is transitive.</li>
2355 <p>Whenever a trap value is generated, all values which depend on it evaluate
2356 to trap. If they have side effects, the evoke their side effects as if each
2357 operand with a trap value were undef. If they have externally-visible side
2358 effects, the behavior is undefined.</p>
2360 <p>Here are some examples:</p>
2362 <pre class="doc_code">
2364 %trap = sub nuw i32 0, 1 ; Results in a trap value.
2365 %still_trap = and i32 %trap, 0 ; Whereas (and i32 undef, 0) would return 0.
2366 %trap_yet_again = getelementptr i32* @h, i32 %still_trap
2367 store i32 0, i32* %trap_yet_again ; undefined behavior
2369 store i32 %trap, i32* @g ; Trap value conceptually stored to memory.
2370 %trap2 = load i32* @g ; Returns a trap value, not just undef.
2372 volatile store i32 %trap, i32* @g ; External observation; undefined behavior.
2374 %narrowaddr = bitcast i32* @g to i16*
2375 %wideaddr = bitcast i32* @g to i64*
2376 %trap3 = load 16* %narrowaddr ; Returns a trap value.
2377 %trap4 = load i64* %widaddr ; Returns a trap value.
2379 %cmp = icmp i32 slt %trap, 0 ; Returns a trap value.
2380 %br i1 %cmp, %true, %end ; Branch to either destination.
2383 volatile store i32 0, i32* @g ; This is control-dependent on %cmp, so
2384 ; it has undefined behavior.
2388 %p = phi i32 [ 0, %entry ], [ 1, %true ]
2389 ; Both edges into this PHI are
2390 ; control-dependent on %cmp, so this
2391 ; always results in a trap value.
2393 volatile store i32 0, i32* @g ; %end is control-equivalent to %entry
2394 ; so this is defined (ignoring earlier
2395 ; undefined behavior in this example).
2400 <!-- ======================================================================= -->
2401 <div class="doc_subsection"><a name="blockaddress">Addresses of Basic
2403 <div class="doc_text">
2405 <p><b><tt>blockaddress(@function, %block)</tt></b></p>
2407 <p>The '<tt>blockaddress</tt>' constant computes the address of the specified
2408 basic block in the specified function, and always has an i8* type. Taking
2409 the address of the entry block is illegal.</p>
2411 <p>This value only has defined behavior when used as an operand to the
2412 '<a href="#i_indirectbr"><tt>indirectbr</tt></a>' instruction or for comparisons
2413 against null. Pointer equality tests between labels addresses is undefined
2414 behavior - though, again, comparison against null is ok, and no label is
2415 equal to the null pointer. This may also be passed around as an opaque
2416 pointer sized value as long as the bits are not inspected. This allows
2417 <tt>ptrtoint</tt> and arithmetic to be performed on these values so long as
2418 the original value is reconstituted before the <tt>indirectbr</tt>.</p>
2420 <p>Finally, some targets may provide defined semantics when
2421 using the value as the operand to an inline assembly, but that is target
2428 <!-- ======================================================================= -->
2429 <div class="doc_subsection"><a name="constantexprs">Constant Expressions</a>
2432 <div class="doc_text">
2434 <p>Constant expressions are used to allow expressions involving other constants
2435 to be used as constants. Constant expressions may be of
2436 any <a href="#t_firstclass">first class</a> type and may involve any LLVM
2437 operation that does not have side effects (e.g. load and call are not
2438 supported). The following is the syntax for constant expressions:</p>
2441 <dt><b><tt>trunc (CST to TYPE)</tt></b></dt>
2442 <dd>Truncate a constant to another type. The bit size of CST must be larger
2443 than the bit size of TYPE. Both types must be integers.</dd>
2445 <dt><b><tt>zext (CST to TYPE)</tt></b></dt>
2446 <dd>Zero extend a constant to another type. The bit size of CST must be
2447 smaller than the bit size of TYPE. Both types must be integers.</dd>
2449 <dt><b><tt>sext (CST to TYPE)</tt></b></dt>
2450 <dd>Sign extend a constant to another type. The bit size of CST must be
2451 smaller than the bit size of TYPE. Both types must be integers.</dd>
2453 <dt><b><tt>fptrunc (CST to TYPE)</tt></b></dt>
2454 <dd>Truncate a floating point constant to another floating point type. The
2455 size of CST must be larger than the size of TYPE. Both types must be
2456 floating point.</dd>
2458 <dt><b><tt>fpext (CST to TYPE)</tt></b></dt>
2459 <dd>Floating point extend a constant to another type. The size of CST must be
2460 smaller or equal to the size of TYPE. Both types must be floating
2463 <dt><b><tt>fptoui (CST to TYPE)</tt></b></dt>
2464 <dd>Convert a floating point constant to the corresponding unsigned integer
2465 constant. TYPE must be a scalar or vector integer type. CST must be of
2466 scalar or vector floating point type. Both CST and TYPE must be scalars,
2467 or vectors of the same number of elements. If the value won't fit in the
2468 integer type, the results are undefined.</dd>
2470 <dt><b><tt>fptosi (CST to TYPE)</tt></b></dt>
2471 <dd>Convert a floating point constant to the corresponding signed integer
2472 constant. TYPE must be a scalar or vector integer type. CST must be of
2473 scalar or vector floating point type. Both CST and TYPE must be scalars,
2474 or vectors of the same number of elements. If the value won't fit in the
2475 integer type, the results are undefined.</dd>
2477 <dt><b><tt>uitofp (CST to TYPE)</tt></b></dt>
2478 <dd>Convert an unsigned integer constant to the corresponding floating point
2479 constant. TYPE must be a scalar or vector floating point type. CST must be
2480 of scalar or vector integer type. Both CST and TYPE must be scalars, or
2481 vectors of the same number of elements. If the value won't fit in the
2482 floating point type, the results are undefined.</dd>
2484 <dt><b><tt>sitofp (CST to TYPE)</tt></b></dt>
2485 <dd>Convert a signed integer constant to the corresponding floating point
2486 constant. TYPE must be a scalar or vector floating point type. CST must be
2487 of scalar or vector integer type. Both CST and TYPE must be scalars, or
2488 vectors of the same number of elements. If the value won't fit in the
2489 floating point type, the results are undefined.</dd>
2491 <dt><b><tt>ptrtoint (CST to TYPE)</tt></b></dt>
2492 <dd>Convert a pointer typed constant to the corresponding integer constant
2493 <tt>TYPE</tt> must be an integer type. <tt>CST</tt> must be of pointer
2494 type. The <tt>CST</tt> value is zero extended, truncated, or unchanged to
2495 make it fit in <tt>TYPE</tt>.</dd>
2497 <dt><b><tt>inttoptr (CST to TYPE)</tt></b></dt>
2498 <dd>Convert a integer constant to a pointer constant. TYPE must be a pointer
2499 type. CST must be of integer type. The CST value is zero extended,
2500 truncated, or unchanged to make it fit in a pointer size. This one is
2501 <i>really</i> dangerous!</dd>
2503 <dt><b><tt>bitcast (CST to TYPE)</tt></b></dt>
2504 <dd>Convert a constant, CST, to another TYPE. The constraints of the operands
2505 are the same as those for the <a href="#i_bitcast">bitcast
2506 instruction</a>.</dd>
2508 <dt><b><tt>getelementptr (CSTPTR, IDX0, IDX1, ...)</tt></b></dt>
2509 <dt><b><tt>getelementptr inbounds (CSTPTR, IDX0, IDX1, ...)</tt></b></dt>
2510 <dd>Perform the <a href="#i_getelementptr">getelementptr operation</a> on
2511 constants. As with the <a href="#i_getelementptr">getelementptr</a>
2512 instruction, the index list may have zero or more indexes, which are
2513 required to make sense for the type of "CSTPTR".</dd>
2515 <dt><b><tt>select (COND, VAL1, VAL2)</tt></b></dt>
2516 <dd>Perform the <a href="#i_select">select operation</a> on constants.</dd>
2518 <dt><b><tt>icmp COND (VAL1, VAL2)</tt></b></dt>
2519 <dd>Performs the <a href="#i_icmp">icmp operation</a> on constants.</dd>
2521 <dt><b><tt>fcmp COND (VAL1, VAL2)</tt></b></dt>
2522 <dd>Performs the <a href="#i_fcmp">fcmp operation</a> on constants.</dd>
2524 <dt><b><tt>extractelement (VAL, IDX)</tt></b></dt>
2525 <dd>Perform the <a href="#i_extractelement">extractelement operation</a> on
2528 <dt><b><tt>insertelement (VAL, ELT, IDX)</tt></b></dt>
2529 <dd>Perform the <a href="#i_insertelement">insertelement operation</a> on
2532 <dt><b><tt>shufflevector (VEC1, VEC2, IDXMASK)</tt></b></dt>
2533 <dd>Perform the <a href="#i_shufflevector">shufflevector operation</a> on
2536 <dt><b><tt>extractvalue (VAL, IDX0, IDX1, ...)</tt></b></dt>
2537 <dd>Perform the <a href="#i_extractvalue">extractvalue operation</a> on
2538 constants. The index list is interpreted in a similar manner as indices in
2539 a '<a href="#i_getelementptr">getelementptr</a>' operation. At least one
2540 index value must be specified.</dd>
2542 <dt><b><tt>insertvalue (VAL, ELT, IDX0, IDX1, ...)</tt></b></dt>
2543 <dd>Perform the <a href="#i_insertvalue">insertvalue operation</a> on
2544 constants. The index list is interpreted in a similar manner as indices in
2545 a '<a href="#i_getelementptr">getelementptr</a>' operation. At least one
2546 index value must be specified.</dd>
2548 <dt><b><tt>OPCODE (LHS, RHS)</tt></b></dt>
2549 <dd>Perform the specified operation of the LHS and RHS constants. OPCODE may
2550 be any of the <a href="#binaryops">binary</a>
2551 or <a href="#bitwiseops">bitwise binary</a> operations. The constraints
2552 on operands are the same as those for the corresponding instruction
2553 (e.g. no bitwise operations on floating point values are allowed).</dd>
2558 <!-- *********************************************************************** -->
2559 <div class="doc_section"> <a name="othervalues">Other Values</a> </div>
2560 <!-- *********************************************************************** -->
2562 <!-- ======================================================================= -->
2563 <div class="doc_subsection">
2564 <a name="inlineasm">Inline Assembler Expressions</a>
2567 <div class="doc_text">
2569 <p>LLVM supports inline assembler expressions (as opposed
2570 to <a href="#moduleasm"> Module-Level Inline Assembly</a>) through the use of
2571 a special value. This value represents the inline assembler as a string
2572 (containing the instructions to emit), a list of operand constraints (stored
2573 as a string), a flag that indicates whether or not the inline asm
2574 expression has side effects, and a flag indicating whether the function
2575 containing the asm needs to align its stack conservatively. An example
2576 inline assembler expression is:</p>
2578 <pre class="doc_code">
2579 i32 (i32) asm "bswap $0", "=r,r"
2582 <p>Inline assembler expressions may <b>only</b> be used as the callee operand of
2583 a <a href="#i_call"><tt>call</tt> instruction</a>. Thus, typically we
2586 <pre class="doc_code">
2587 %X = call i32 asm "<a href="#int_bswap">bswap</a> $0", "=r,r"(i32 %Y)
2590 <p>Inline asms with side effects not visible in the constraint list must be
2591 marked as having side effects. This is done through the use of the
2592 '<tt>sideeffect</tt>' keyword, like so:</p>
2594 <pre class="doc_code">
2595 call void asm sideeffect "eieio", ""()
2598 <p>In some cases inline asms will contain code that will not work unless the
2599 stack is aligned in some way, such as calls or SSE instructions on x86,
2600 yet will not contain code that does that alignment within the asm.
2601 The compiler should make conservative assumptions about what the asm might
2602 contain and should generate its usual stack alignment code in the prologue
2603 if the '<tt>alignstack</tt>' keyword is present:</p>
2605 <pre class="doc_code">
2606 call void asm alignstack "eieio", ""()
2609 <p>If both keywords appear the '<tt>sideeffect</tt>' keyword must come
2612 <p>TODO: The format of the asm and constraints string still need to be
2613 documented here. Constraints on what can be done (e.g. duplication, moving,
2614 etc need to be documented). This is probably best done by reference to
2615 another document that covers inline asm from a holistic perspective.</p>
2618 <div class="doc_subsubsection">
2619 <a name="inlineasm_md">Inline Asm Metadata</a>
2622 <div class="doc_text">
2624 <p>The call instructions that wrap inline asm nodes may have a "!srcloc" MDNode
2625 attached to it that contains a constant integer. If present, the code
2626 generator will use the integer as the location cookie value when report
2627 errors through the LLVMContext error reporting mechanisms. This allows a
2628 front-end to correlate backend errors that occur with inline asm back to the
2629 source code that produced it. For example:</p>
2631 <pre class="doc_code">
2632 call void asm sideeffect "something bad", ""()<b>, !srcloc !42</b>
2634 !42 = !{ i32 1234567 }
2637 <p>It is up to the front-end to make sense of the magic numbers it places in the
2642 <!-- ======================================================================= -->
2643 <div class="doc_subsection"><a name="metadata">Metadata Nodes and Metadata
2647 <div class="doc_text">
2649 <p>LLVM IR allows metadata to be attached to instructions in the program that
2650 can convey extra information about the code to the optimizers and code
2651 generator. One example application of metadata is source-level debug
2652 information. There are two metadata primitives: strings and nodes. All
2653 metadata has the <tt>metadata</tt> type and is identified in syntax by a
2654 preceding exclamation point ('<tt>!</tt>').</p>
2656 <p>A metadata string is a string surrounded by double quotes. It can contain
2657 any character by escaping non-printable characters with "\xx" where "xx" is
2658 the two digit hex code. For example: "<tt>!"test\00"</tt>".</p>
2660 <p>Metadata nodes are represented with notation similar to structure constants
2661 (a comma separated list of elements, surrounded by braces and preceded by an
2662 exclamation point). For example: "<tt>!{ metadata !"test\00", i32
2663 10}</tt>". Metadata nodes can have any values as their operand.</p>
2665 <p>A <a href="#namedmetadatastructure">named metadata</a> is a collection of
2666 metadata nodes, which can be looked up in the module symbol table. For
2667 example: "<tt>!foo = metadata !{!4, !3}</tt>".
2669 <p>Metadata can be used as function arguments. Here <tt>llvm.dbg.value</tt>
2670 function is using two metadata arguments.</p>
2672 <pre class="doc_code">
2673 call void @llvm.dbg.value(metadata !24, i64 0, metadata !25)
2676 <p>Metadata can be attached with an instruction. Here metadata <tt>!21</tt> is
2677 attached with <tt>add</tt> instruction using <tt>!dbg</tt> identifier.</p>
2679 <pre class="doc_code">
2680 %indvar.next = add i64 %indvar, 1, !dbg !21
2685 <!-- *********************************************************************** -->
2686 <div class="doc_section">
2687 <a name="intrinsic_globals">Intrinsic Global Variables</a>
2689 <!-- *********************************************************************** -->
2691 <p>LLVM has a number of "magic" global variables that contain data that affect
2692 code generation or other IR semantics. These are documented here. All globals
2693 of this sort should have a section specified as "<tt>llvm.metadata</tt>". This
2694 section and all globals that start with "<tt>llvm.</tt>" are reserved for use
2697 <!-- ======================================================================= -->
2698 <div class="doc_subsection">
2699 <a name="intg_used">The '<tt>llvm.used</tt>' Global Variable</a>
2702 <div class="doc_text">
2704 <p>The <tt>@llvm.used</tt> global is an array with i8* element type which has <a
2705 href="#linkage_appending">appending linkage</a>. This array contains a list of
2706 pointers to global variables and functions which may optionally have a pointer
2707 cast formed of bitcast or getelementptr. For example, a legal use of it is:</p>
2713 @llvm.used = appending global [2 x i8*] [
2715 i8* bitcast (i32* @Y to i8*)
2716 ], section "llvm.metadata"
2719 <p>If a global variable appears in the <tt>@llvm.used</tt> list, then the
2720 compiler, assembler, and linker are required to treat the symbol as if there is
2721 a reference to the global that it cannot see. For example, if a variable has
2722 internal linkage and no references other than that from the <tt>@llvm.used</tt>
2723 list, it cannot be deleted. This is commonly used to represent references from
2724 inline asms and other things the compiler cannot "see", and corresponds to
2725 "attribute((used))" in GNU C.</p>
2727 <p>On some targets, the code generator must emit a directive to the assembler or
2728 object file to prevent the assembler and linker from molesting the symbol.</p>
2732 <!-- ======================================================================= -->
2733 <div class="doc_subsection">
2734 <a name="intg_compiler_used">The '<tt>llvm.compiler.used</tt>' Global Variable</a>
2737 <div class="doc_text">
2739 <p>The <tt>@llvm.compiler.used</tt> directive is the same as the
2740 <tt>@llvm.used</tt> directive, except that it only prevents the compiler from
2741 touching the symbol. On targets that support it, this allows an intelligent
2742 linker to optimize references to the symbol without being impeded as it would be
2743 by <tt>@llvm.used</tt>.</p>
2745 <p>This is a rare construct that should only be used in rare circumstances, and
2746 should not be exposed to source languages.</p>
2750 <!-- ======================================================================= -->
2751 <div class="doc_subsection">
2752 <a name="intg_global_ctors">The '<tt>llvm.global_ctors</tt>' Global Variable</a>
2755 <div class="doc_text">
2757 %0 = type { i32, void ()* }
2758 @llvm.global_ctors = appending global [1 x %0] [%0 { i32 65535, void ()* @ctor }]
2760 <p>The <tt>@llvm.global_ctors</tt> array contains a list of constructor functions and associated priorities. The functions referenced by this array will be called in ascending order of priority (i.e. lowest first) when the module is loaded. The order of functions with the same priority is not defined.
2765 <!-- ======================================================================= -->
2766 <div class="doc_subsection">
2767 <a name="intg_global_dtors">The '<tt>llvm.global_dtors</tt>' Global Variable</a>
2770 <div class="doc_text">
2772 %0 = type { i32, void ()* }
2773 @llvm.global_dtors = appending global [1 x %0] [%0 { i32 65535, void ()* @dtor }]
2776 <p>The <tt>@llvm.global_dtors</tt> array contains a list of destructor functions and associated priorities. The functions referenced by this array will be called in descending order of priority (i.e. highest first) when the module is loaded. The order of functions with the same priority is not defined.
2782 <!-- *********************************************************************** -->
2783 <div class="doc_section"> <a name="instref">Instruction Reference</a> </div>
2784 <!-- *********************************************************************** -->
2786 <div class="doc_text">
2788 <p>The LLVM instruction set consists of several different classifications of
2789 instructions: <a href="#terminators">terminator
2790 instructions</a>, <a href="#binaryops">binary instructions</a>,
2791 <a href="#bitwiseops">bitwise binary instructions</a>,
2792 <a href="#memoryops">memory instructions</a>, and
2793 <a href="#otherops">other instructions</a>.</p>
2797 <!-- ======================================================================= -->
2798 <div class="doc_subsection"> <a name="terminators">Terminator
2799 Instructions</a> </div>
2801 <div class="doc_text">
2803 <p>As mentioned <a href="#functionstructure">previously</a>, every basic block
2804 in a program ends with a "Terminator" instruction, which indicates which
2805 block should be executed after the current block is finished. These
2806 terminator instructions typically yield a '<tt>void</tt>' value: they produce
2807 control flow, not values (the one exception being the
2808 '<a href="#i_invoke"><tt>invoke</tt></a>' instruction).</p>
2810 <p>There are seven different terminator instructions: the
2811 '<a href="#i_ret"><tt>ret</tt></a>' instruction, the
2812 '<a href="#i_br"><tt>br</tt></a>' instruction, the
2813 '<a href="#i_switch"><tt>switch</tt></a>' instruction, the
2814 '<a href="#i_indirectbr">'<tt>indirectbr</tt></a>' Instruction, the
2815 '<a href="#i_invoke"><tt>invoke</tt></a>' instruction, the
2816 '<a href="#i_unwind"><tt>unwind</tt></a>' instruction, and the
2817 '<a href="#i_unreachable"><tt>unreachable</tt></a>' instruction.</p>
2821 <!-- _______________________________________________________________________ -->
2822 <div class="doc_subsubsection"> <a name="i_ret">'<tt>ret</tt>'
2823 Instruction</a> </div>
2825 <div class="doc_text">
2829 ret <type> <value> <i>; Return a value from a non-void function</i>
2830 ret void <i>; Return from void function</i>
2834 <p>The '<tt>ret</tt>' instruction is used to return control flow (and optionally
2835 a value) from a function back to the caller.</p>
2837 <p>There are two forms of the '<tt>ret</tt>' instruction: one that returns a
2838 value and then causes control flow, and one that just causes control flow to
2842 <p>The '<tt>ret</tt>' instruction optionally accepts a single argument, the
2843 return value. The type of the return value must be a
2844 '<a href="#t_firstclass">first class</a>' type.</p>
2846 <p>A function is not <a href="#wellformed">well formed</a> if it it has a
2847 non-void return type and contains a '<tt>ret</tt>' instruction with no return
2848 value or a return value with a type that does not match its type, or if it
2849 has a void return type and contains a '<tt>ret</tt>' instruction with a
2853 <p>When the '<tt>ret</tt>' instruction is executed, control flow returns back to
2854 the calling function's context. If the caller is a
2855 "<a href="#i_call"><tt>call</tt></a>" instruction, execution continues at the
2856 instruction after the call. If the caller was an
2857 "<a href="#i_invoke"><tt>invoke</tt></a>" instruction, execution continues at
2858 the beginning of the "normal" destination block. If the instruction returns
2859 a value, that value shall set the call or invoke instruction's return
2864 ret i32 5 <i>; Return an integer value of 5</i>
2865 ret void <i>; Return from a void function</i>
2866 ret { i32, i8 } { i32 4, i8 2 } <i>; Return a struct of values 4 and 2</i>
2870 <!-- _______________________________________________________________________ -->
2871 <div class="doc_subsubsection"> <a name="i_br">'<tt>br</tt>' Instruction</a> </div>
2873 <div class="doc_text">
2877 br i1 <cond>, label <iftrue>, label <iffalse><br> br label <dest> <i>; Unconditional branch</i>
2881 <p>The '<tt>br</tt>' instruction is used to cause control flow to transfer to a
2882 different basic block in the current function. There are two forms of this
2883 instruction, corresponding to a conditional branch and an unconditional
2887 <p>The conditional branch form of the '<tt>br</tt>' instruction takes a single
2888 '<tt>i1</tt>' value and two '<tt>label</tt>' values. The unconditional form
2889 of the '<tt>br</tt>' instruction takes a single '<tt>label</tt>' value as a
2893 <p>Upon execution of a conditional '<tt>br</tt>' instruction, the '<tt>i1</tt>'
2894 argument is evaluated. If the value is <tt>true</tt>, control flows to the
2895 '<tt>iftrue</tt>' <tt>label</tt> argument. If "cond" is <tt>false</tt>,
2896 control flows to the '<tt>iffalse</tt>' <tt>label</tt> argument.</p>
2901 %cond = <a href="#i_icmp">icmp</a> eq i32 %a, %b
2902 br i1 %cond, label %IfEqual, label %IfUnequal
2904 <a href="#i_ret">ret</a> i32 1
2906 <a href="#i_ret">ret</a> i32 0
2911 <!-- _______________________________________________________________________ -->
2912 <div class="doc_subsubsection">
2913 <a name="i_switch">'<tt>switch</tt>' Instruction</a>
2916 <div class="doc_text">
2920 switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]
2924 <p>The '<tt>switch</tt>' instruction is used to transfer control flow to one of
2925 several different places. It is a generalization of the '<tt>br</tt>'
2926 instruction, allowing a branch to occur to one of many possible
2930 <p>The '<tt>switch</tt>' instruction uses three parameters: an integer
2931 comparison value '<tt>value</tt>', a default '<tt>label</tt>' destination,
2932 and an array of pairs of comparison value constants and '<tt>label</tt>'s.
2933 The table is not allowed to contain duplicate constant entries.</p>
2936 <p>The <tt>switch</tt> instruction specifies a table of values and
2937 destinations. When the '<tt>switch</tt>' instruction is executed, this table
2938 is searched for the given value. If the value is found, control flow is
2939 transferred to the corresponding destination; otherwise, control flow is
2940 transferred to the default destination.</p>
2942 <h5>Implementation:</h5>
2943 <p>Depending on properties of the target machine and the particular
2944 <tt>switch</tt> instruction, this instruction may be code generated in
2945 different ways. For example, it could be generated as a series of chained
2946 conditional branches or with a lookup table.</p>
2950 <i>; Emulate a conditional br instruction</i>
2951 %Val = <a href="#i_zext">zext</a> i1 %value to i32
2952 switch i32 %Val, label %truedest [ i32 0, label %falsedest ]
2954 <i>; Emulate an unconditional br instruction</i>
2955 switch i32 0, label %dest [ ]
2957 <i>; Implement a jump table:</i>
2958 switch i32 %val, label %otherwise [ i32 0, label %onzero
2960 i32 2, label %ontwo ]
2966 <!-- _______________________________________________________________________ -->
2967 <div class="doc_subsubsection">
2968 <a name="i_indirectbr">'<tt>indirectbr</tt>' Instruction</a>
2971 <div class="doc_text">
2975 indirectbr <somety>* <address>, [ label <dest1>, label <dest2>, ... ]
2980 <p>The '<tt>indirectbr</tt>' instruction implements an indirect branch to a label
2981 within the current function, whose address is specified by
2982 "<tt>address</tt>". Address must be derived from a <a
2983 href="#blockaddress">blockaddress</a> constant.</p>
2987 <p>The '<tt>address</tt>' argument is the address of the label to jump to. The
2988 rest of the arguments indicate the full set of possible destinations that the
2989 address may point to. Blocks are allowed to occur multiple times in the
2990 destination list, though this isn't particularly useful.</p>
2992 <p>This destination list is required so that dataflow analysis has an accurate
2993 understanding of the CFG.</p>
2997 <p>Control transfers to the block specified in the address argument. All
2998 possible destination blocks must be listed in the label list, otherwise this
2999 instruction has undefined behavior. This implies that jumps to labels
3000 defined in other functions have undefined behavior as well.</p>
3002 <h5>Implementation:</h5>
3004 <p>This is typically implemented with a jump through a register.</p>
3008 indirectbr i8* %Addr, [ label %bb1, label %bb2, label %bb3 ]
3014 <!-- _______________________________________________________________________ -->
3015 <div class="doc_subsubsection">
3016 <a name="i_invoke">'<tt>invoke</tt>' Instruction</a>
3019 <div class="doc_text">
3023 <result> = invoke [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] <ptr to function ty> <function ptr val>(<function args>) [<a href="#fnattrs">fn attrs</a>]
3024 to label <normal label> unwind label <exception label>
3028 <p>The '<tt>invoke</tt>' instruction causes control to transfer to a specified
3029 function, with the possibility of control flow transfer to either the
3030 '<tt>normal</tt>' label or the '<tt>exception</tt>' label. If the callee
3031 function returns with the "<tt><a href="#i_ret">ret</a></tt>" instruction,
3032 control flow will return to the "normal" label. If the callee (or any
3033 indirect callees) returns with the "<a href="#i_unwind"><tt>unwind</tt></a>"
3034 instruction, control is interrupted and continued at the dynamically nearest
3035 "exception" label.</p>
3038 <p>This instruction requires several arguments:</p>
3041 <li>The optional "cconv" marker indicates which <a href="#callingconv">calling
3042 convention</a> the call should use. If none is specified, the call
3043 defaults to using C calling conventions.</li>
3045 <li>The optional <a href="#paramattrs">Parameter Attributes</a> list for
3046 return values. Only '<tt>zeroext</tt>', '<tt>signext</tt>', and
3047 '<tt>inreg</tt>' attributes are valid here.</li>
3049 <li>'<tt>ptr to function ty</tt>': shall be the signature of the pointer to
3050 function value being invoked. In most cases, this is a direct function
3051 invocation, but indirect <tt>invoke</tt>s are just as possible, branching
3052 off an arbitrary pointer to function value.</li>
3054 <li>'<tt>function ptr val</tt>': An LLVM value containing a pointer to a
3055 function to be invoked. </li>
3057 <li>'<tt>function args</tt>': argument list whose types match the function
3058 signature argument types and parameter attributes. All arguments must be
3059 of <a href="#t_firstclass">first class</a> type. If the function
3060 signature indicates the function accepts a variable number of arguments,
3061 the extra arguments can be specified.</li>
3063 <li>'<tt>normal label</tt>': the label reached when the called function
3064 executes a '<tt><a href="#i_ret">ret</a></tt>' instruction. </li>
3066 <li>'<tt>exception label</tt>': the label reached when a callee returns with
3067 the <a href="#i_unwind"><tt>unwind</tt></a> instruction. </li>
3069 <li>The optional <a href="#fnattrs">function attributes</a> list. Only
3070 '<tt>noreturn</tt>', '<tt>nounwind</tt>', '<tt>readonly</tt>' and
3071 '<tt>readnone</tt>' attributes are valid here.</li>
3075 <p>This instruction is designed to operate as a standard
3076 '<tt><a href="#i_call">call</a></tt>' instruction in most regards. The
3077 primary difference is that it establishes an association with a label, which
3078 is used by the runtime library to unwind the stack.</p>
3080 <p>This instruction is used in languages with destructors to ensure that proper
3081 cleanup is performed in the case of either a <tt>longjmp</tt> or a thrown
3082 exception. Additionally, this is important for implementation of
3083 '<tt>catch</tt>' clauses in high-level languages that support them.</p>
3085 <p>For the purposes of the SSA form, the definition of the value returned by the
3086 '<tt>invoke</tt>' instruction is deemed to occur on the edge from the current
3087 block to the "normal" label. If the callee unwinds then no return value is
3090 <p>Note that the code generator does not yet completely support unwind, and
3091 that the invoke/unwind semantics are likely to change in future versions.</p>
3095 %retval = invoke i32 @Test(i32 15) to label %Continue
3096 unwind label %TestCleanup <i>; {i32}:retval set</i>
3097 %retval = invoke <a href="#callingconv">coldcc</a> i32 %Testfnptr(i32 15) to label %Continue
3098 unwind label %TestCleanup <i>; {i32}:retval set</i>
3103 <!-- _______________________________________________________________________ -->
3105 <div class="doc_subsubsection"> <a name="i_unwind">'<tt>unwind</tt>'
3106 Instruction</a> </div>
3108 <div class="doc_text">
3116 <p>The '<tt>unwind</tt>' instruction unwinds the stack, continuing control flow
3117 at the first callee in the dynamic call stack which used
3118 an <a href="#i_invoke"><tt>invoke</tt></a> instruction to perform the call.
3119 This is primarily used to implement exception handling.</p>
3122 <p>The '<tt>unwind</tt>' instruction causes execution of the current function to
3123 immediately halt. The dynamic call stack is then searched for the
3124 first <a href="#i_invoke"><tt>invoke</tt></a> instruction on the call stack.
3125 Once found, execution continues at the "exceptional" destination block
3126 specified by the <tt>invoke</tt> instruction. If there is no <tt>invoke</tt>
3127 instruction in the dynamic call chain, undefined behavior results.</p>
3129 <p>Note that the code generator does not yet completely support unwind, and
3130 that the invoke/unwind semantics are likely to change in future versions.</p>
3134 <!-- _______________________________________________________________________ -->
3136 <div class="doc_subsubsection"> <a name="i_unreachable">'<tt>unreachable</tt>'
3137 Instruction</a> </div>
3139 <div class="doc_text">
3147 <p>The '<tt>unreachable</tt>' instruction has no defined semantics. This
3148 instruction is used to inform the optimizer that a particular portion of the
3149 code is not reachable. This can be used to indicate that the code after a
3150 no-return function cannot be reached, and other facts.</p>
3153 <p>The '<tt>unreachable</tt>' instruction has no defined semantics.</p>
3157 <!-- ======================================================================= -->
3158 <div class="doc_subsection"> <a name="binaryops">Binary Operations</a> </div>
3160 <div class="doc_text">
3162 <p>Binary operators are used to do most of the computation in a program. They
3163 require two operands of the same type, execute an operation on them, and
3164 produce a single value. The operands might represent multiple data, as is
3165 the case with the <a href="#t_vector">vector</a> data type. The result value
3166 has the same type as its operands.</p>
3168 <p>There are several different binary operators:</p>
3172 <!-- _______________________________________________________________________ -->
3173 <div class="doc_subsubsection">
3174 <a name="i_add">'<tt>add</tt>' Instruction</a>
3177 <div class="doc_text">
3181 <result> = add <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3182 <result> = add nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3183 <result> = add nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3184 <result> = add nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3188 <p>The '<tt>add</tt>' instruction returns the sum of its two operands.</p>
3191 <p>The two arguments to the '<tt>add</tt>' instruction must
3192 be <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of
3193 integer values. Both arguments must have identical types.</p>
3196 <p>The value produced is the integer sum of the two operands.</p>
3198 <p>If the sum has unsigned overflow, the result returned is the mathematical
3199 result modulo 2<sup>n</sup>, where n is the bit width of the result.</p>
3201 <p>Because LLVM integers use a two's complement representation, this instruction
3202 is appropriate for both signed and unsigned integers.</p>
3204 <p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap"
3205 and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or
3206 <tt>nsw</tt> keywords are present, the result value of the <tt>add</tt>
3207 is a <a href="#trapvalues">trap value</a> if unsigned and/or signed overflow,
3208 respectively, occurs.</p>
3212 <result> = add i32 4, %var <i>; yields {i32}:result = 4 + %var</i>
3217 <!-- _______________________________________________________________________ -->
3218 <div class="doc_subsubsection">
3219 <a name="i_fadd">'<tt>fadd</tt>' Instruction</a>
3222 <div class="doc_text">
3226 <result> = fadd <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3230 <p>The '<tt>fadd</tt>' instruction returns the sum of its two operands.</p>
3233 <p>The two arguments to the '<tt>fadd</tt>' instruction must be
3234 <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
3235 floating point values. Both arguments must have identical types.</p>
3238 <p>The value produced is the floating point sum of the two operands.</p>
3242 <result> = fadd float 4.0, %var <i>; yields {float}:result = 4.0 + %var</i>
3247 <!-- _______________________________________________________________________ -->
3248 <div class="doc_subsubsection">
3249 <a name="i_sub">'<tt>sub</tt>' Instruction</a>
3252 <div class="doc_text">
3256 <result> = sub <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3257 <result> = sub nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3258 <result> = sub nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3259 <result> = sub nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3263 <p>The '<tt>sub</tt>' instruction returns the difference of its two
3266 <p>Note that the '<tt>sub</tt>' instruction is used to represent the
3267 '<tt>neg</tt>' instruction present in most other intermediate
3268 representations.</p>
3271 <p>The two arguments to the '<tt>sub</tt>' instruction must
3272 be <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of
3273 integer values. Both arguments must have identical types.</p>
3276 <p>The value produced is the integer difference of the two operands.</p>
3278 <p>If the difference has unsigned overflow, the result returned is the
3279 mathematical result modulo 2<sup>n</sup>, where n is the bit width of the
3282 <p>Because LLVM integers use a two's complement representation, this instruction
3283 is appropriate for both signed and unsigned integers.</p>
3285 <p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap"
3286 and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or
3287 <tt>nsw</tt> keywords are present, the result value of the <tt>sub</tt>
3288 is a <a href="#trapvalues">trap value</a> if unsigned and/or signed overflow,
3289 respectively, occurs.</p>
3293 <result> = sub i32 4, %var <i>; yields {i32}:result = 4 - %var</i>
3294 <result> = sub i32 0, %val <i>; yields {i32}:result = -%var</i>
3299 <!-- _______________________________________________________________________ -->
3300 <div class="doc_subsubsection">
3301 <a name="i_fsub">'<tt>fsub</tt>' Instruction</a>
3304 <div class="doc_text">
3308 <result> = fsub <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3312 <p>The '<tt>fsub</tt>' instruction returns the difference of its two
3315 <p>Note that the '<tt>fsub</tt>' instruction is used to represent the
3316 '<tt>fneg</tt>' instruction present in most other intermediate
3317 representations.</p>
3320 <p>The two arguments to the '<tt>fsub</tt>' instruction must be
3321 <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
3322 floating point values. Both arguments must have identical types.</p>
3325 <p>The value produced is the floating point difference of the two operands.</p>
3329 <result> = fsub float 4.0, %var <i>; yields {float}:result = 4.0 - %var</i>
3330 <result> = fsub float -0.0, %val <i>; yields {float}:result = -%var</i>
3335 <!-- _______________________________________________________________________ -->
3336 <div class="doc_subsubsection">
3337 <a name="i_mul">'<tt>mul</tt>' Instruction</a>
3340 <div class="doc_text">
3344 <result> = mul <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3345 <result> = mul nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3346 <result> = mul nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3347 <result> = mul nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3351 <p>The '<tt>mul</tt>' instruction returns the product of its two operands.</p>
3354 <p>The two arguments to the '<tt>mul</tt>' instruction must
3355 be <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of
3356 integer values. Both arguments must have identical types.</p>
3359 <p>The value produced is the integer product of the two operands.</p>
3361 <p>If the result of the multiplication has unsigned overflow, the result
3362 returned is the mathematical result modulo 2<sup>n</sup>, where n is the bit
3363 width of the result.</p>
3365 <p>Because LLVM integers use a two's complement representation, and the result
3366 is the same width as the operands, this instruction returns the correct
3367 result for both signed and unsigned integers. If a full product
3368 (e.g. <tt>i32</tt>x<tt>i32</tt>-><tt>i64</tt>) is needed, the operands should
3369 be sign-extended or zero-extended as appropriate to the width of the full
3372 <p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap"
3373 and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or
3374 <tt>nsw</tt> keywords are present, the result value of the <tt>mul</tt>
3375 is a <a href="#trapvalues">trap value</a> if unsigned and/or signed overflow,
3376 respectively, occurs.</p>
3380 <result> = mul i32 4, %var <i>; yields {i32}:result = 4 * %var</i>
3385 <!-- _______________________________________________________________________ -->
3386 <div class="doc_subsubsection">
3387 <a name="i_fmul">'<tt>fmul</tt>' Instruction</a>
3390 <div class="doc_text">
3394 <result> = fmul <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3398 <p>The '<tt>fmul</tt>' instruction returns the product of its two operands.</p>
3401 <p>The two arguments to the '<tt>fmul</tt>' instruction must be
3402 <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
3403 floating point values. Both arguments must have identical types.</p>
3406 <p>The value produced is the floating point product of the two operands.</p>
3410 <result> = fmul float 4.0, %var <i>; yields {float}:result = 4.0 * %var</i>
3415 <!-- _______________________________________________________________________ -->
3416 <div class="doc_subsubsection"> <a name="i_udiv">'<tt>udiv</tt>' Instruction
3419 <div class="doc_text">
3423 <result> = udiv <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3427 <p>The '<tt>udiv</tt>' instruction returns the quotient of its two operands.</p>
3430 <p>The two arguments to the '<tt>udiv</tt>' instruction must be
3431 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3432 values. Both arguments must have identical types.</p>
3435 <p>The value produced is the unsigned integer quotient of the two operands.</p>
3437 <p>Note that unsigned integer division and signed integer division are distinct
3438 operations; for signed integer division, use '<tt>sdiv</tt>'.</p>
3440 <p>Division by zero leads to undefined behavior.</p>
3444 <result> = udiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>
3449 <!-- _______________________________________________________________________ -->
3450 <div class="doc_subsubsection"> <a name="i_sdiv">'<tt>sdiv</tt>' Instruction
3453 <div class="doc_text">
3457 <result> = sdiv <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3458 <result> = sdiv exact <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3462 <p>The '<tt>sdiv</tt>' instruction returns the quotient of its two operands.</p>
3465 <p>The two arguments to the '<tt>sdiv</tt>' instruction must be
3466 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3467 values. Both arguments must have identical types.</p>
3470 <p>The value produced is the signed integer quotient of the two operands rounded
3473 <p>Note that signed integer division and unsigned integer division are distinct
3474 operations; for unsigned integer division, use '<tt>udiv</tt>'.</p>
3476 <p>Division by zero leads to undefined behavior. Overflow also leads to
3477 undefined behavior; this is a rare case, but can occur, for example, by doing
3478 a 32-bit division of -2147483648 by -1.</p>
3480 <p>If the <tt>exact</tt> keyword is present, the result value of the
3481 <tt>sdiv</tt> is a <a href="#trapvalues">trap value</a> if the result would
3486 <result> = sdiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>
3491 <!-- _______________________________________________________________________ -->
3492 <div class="doc_subsubsection"> <a name="i_fdiv">'<tt>fdiv</tt>'
3493 Instruction</a> </div>
3495 <div class="doc_text">
3499 <result> = fdiv <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3503 <p>The '<tt>fdiv</tt>' instruction returns the quotient of its two operands.</p>
3506 <p>The two arguments to the '<tt>fdiv</tt>' instruction must be
3507 <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
3508 floating point values. Both arguments must have identical types.</p>
3511 <p>The value produced is the floating point quotient of the two operands.</p>
3515 <result> = fdiv float 4.0, %var <i>; yields {float}:result = 4.0 / %var</i>
3520 <!-- _______________________________________________________________________ -->
3521 <div class="doc_subsubsection"> <a name="i_urem">'<tt>urem</tt>' Instruction</a>
3524 <div class="doc_text">
3528 <result> = urem <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3532 <p>The '<tt>urem</tt>' instruction returns the remainder from the unsigned
3533 division of its two arguments.</p>
3536 <p>The two arguments to the '<tt>urem</tt>' instruction must be
3537 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3538 values. Both arguments must have identical types.</p>
3541 <p>This instruction returns the unsigned integer <i>remainder</i> of a division.
3542 This instruction always performs an unsigned division to get the
3545 <p>Note that unsigned integer remainder and signed integer remainder are
3546 distinct operations; for signed integer remainder, use '<tt>srem</tt>'.</p>
3548 <p>Taking the remainder of a division by zero leads to undefined behavior.</p>
3552 <result> = urem i32 4, %var <i>; yields {i32}:result = 4 % %var</i>
3557 <!-- _______________________________________________________________________ -->
3558 <div class="doc_subsubsection">
3559 <a name="i_srem">'<tt>srem</tt>' Instruction</a>
3562 <div class="doc_text">
3566 <result> = srem <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3570 <p>The '<tt>srem</tt>' instruction returns the remainder from the signed
3571 division of its two operands. This instruction can also take
3572 <a href="#t_vector">vector</a> versions of the values in which case the
3573 elements must be integers.</p>
3576 <p>The two arguments to the '<tt>srem</tt>' instruction must be
3577 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3578 values. Both arguments must have identical types.</p>
3581 <p>This instruction returns the <i>remainder</i> of a division (where the result
3582 has the same sign as the dividend, <tt>op1</tt>), not the <i>modulo</i>
3583 operator (where the result has the same sign as the divisor, <tt>op2</tt>) of
3584 a value. For more information about the difference,
3585 see <a href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The
3586 Math Forum</a>. For a table of how this is implemented in various languages,
3587 please see <a href="http://en.wikipedia.org/wiki/Modulo_operation">
3588 Wikipedia: modulo operation</a>.</p>
3590 <p>Note that signed integer remainder and unsigned integer remainder are
3591 distinct operations; for unsigned integer remainder, use '<tt>urem</tt>'.</p>
3593 <p>Taking the remainder of a division by zero leads to undefined behavior.
3594 Overflow also leads to undefined behavior; this is a rare case, but can
3595 occur, for example, by taking the remainder of a 32-bit division of
3596 -2147483648 by -1. (The remainder doesn't actually overflow, but this rule
3597 lets srem be implemented using instructions that return both the result of
3598 the division and the remainder.)</p>
3602 <result> = srem i32 4, %var <i>; yields {i32}:result = 4 % %var</i>
3607 <!-- _______________________________________________________________________ -->
3608 <div class="doc_subsubsection">
3609 <a name="i_frem">'<tt>frem</tt>' Instruction</a> </div>
3611 <div class="doc_text">
3615 <result> = frem <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3619 <p>The '<tt>frem</tt>' instruction returns the remainder from the division of
3620 its two operands.</p>
3623 <p>The two arguments to the '<tt>frem</tt>' instruction must be
3624 <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
3625 floating point values. Both arguments must have identical types.</p>
3628 <p>This instruction returns the <i>remainder</i> of a division. The remainder
3629 has the same sign as the dividend.</p>
3633 <result> = frem float 4.0, %var <i>; yields {float}:result = 4.0 % %var</i>
3638 <!-- ======================================================================= -->
3639 <div class="doc_subsection"> <a name="bitwiseops">Bitwise Binary
3640 Operations</a> </div>
3642 <div class="doc_text">
3644 <p>Bitwise binary operators are used to do various forms of bit-twiddling in a
3645 program. They are generally very efficient instructions and can commonly be
3646 strength reduced from other instructions. They require two operands of the
3647 same type, execute an operation on them, and produce a single value. The
3648 resulting value is the same type as its operands.</p>
3652 <!-- _______________________________________________________________________ -->
3653 <div class="doc_subsubsection"> <a name="i_shl">'<tt>shl</tt>'
3654 Instruction</a> </div>
3656 <div class="doc_text">
3660 <result> = shl <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3664 <p>The '<tt>shl</tt>' instruction returns the first operand shifted to the left
3665 a specified number of bits.</p>
3668 <p>Both arguments to the '<tt>shl</tt>' instruction must be the
3669 same <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of
3670 integer type. '<tt>op2</tt>' is treated as an unsigned value.</p>
3673 <p>The value produced is <tt>op1</tt> * 2<sup><tt>op2</tt></sup> mod
3674 2<sup>n</sup>, where <tt>n</tt> is the width of the result. If <tt>op2</tt>
3675 is (statically or dynamically) negative or equal to or larger than the number
3676 of bits in <tt>op1</tt>, the result is undefined. If the arguments are
3677 vectors, each vector element of <tt>op1</tt> is shifted by the corresponding
3678 shift amount in <tt>op2</tt>.</p>
3682 <result> = shl i32 4, %var <i>; yields {i32}: 4 << %var</i>
3683 <result> = shl i32 4, 2 <i>; yields {i32}: 16</i>
3684 <result> = shl i32 1, 10 <i>; yields {i32}: 1024</i>
3685 <result> = shl i32 1, 32 <i>; undefined</i>
3686 <result> = shl <2 x i32> < i32 1, i32 1>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 2, i32 4></i>
3691 <!-- _______________________________________________________________________ -->
3692 <div class="doc_subsubsection"> <a name="i_lshr">'<tt>lshr</tt>'
3693 Instruction</a> </div>
3695 <div class="doc_text">
3699 <result> = lshr <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3703 <p>The '<tt>lshr</tt>' instruction (logical shift right) returns the first
3704 operand shifted to the right a specified number of bits with zero fill.</p>
3707 <p>Both arguments to the '<tt>lshr</tt>' instruction must be the same
3708 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3709 type. '<tt>op2</tt>' is treated as an unsigned value.</p>
3712 <p>This instruction always performs a logical shift right operation. The most
3713 significant bits of the result will be filled with zero bits after the shift.
3714 If <tt>op2</tt> is (statically or dynamically) equal to or larger than the
3715 number of bits in <tt>op1</tt>, the result is undefined. If the arguments are
3716 vectors, each vector element of <tt>op1</tt> is shifted by the corresponding
3717 shift amount in <tt>op2</tt>.</p>
3721 <result> = lshr i32 4, 1 <i>; yields {i32}:result = 2</i>
3722 <result> = lshr i32 4, 2 <i>; yields {i32}:result = 1</i>
3723 <result> = lshr i8 4, 3 <i>; yields {i8}:result = 0</i>
3724 <result> = lshr i8 -2, 1 <i>; yields {i8}:result = 0x7FFFFFFF </i>
3725 <result> = lshr i32 1, 32 <i>; undefined</i>
3726 <result> = lshr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 0x7FFFFFFF, i32 1></i>
3731 <!-- _______________________________________________________________________ -->
3732 <div class="doc_subsubsection"> <a name="i_ashr">'<tt>ashr</tt>'
3733 Instruction</a> </div>
3734 <div class="doc_text">
3738 <result> = ashr <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3742 <p>The '<tt>ashr</tt>' instruction (arithmetic shift right) returns the first
3743 operand shifted to the right a specified number of bits with sign
3747 <p>Both arguments to the '<tt>ashr</tt>' instruction must be the same
3748 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3749 type. '<tt>op2</tt>' is treated as an unsigned value.</p>
3752 <p>This instruction always performs an arithmetic shift right operation, The
3753 most significant bits of the result will be filled with the sign bit
3754 of <tt>op1</tt>. If <tt>op2</tt> is (statically or dynamically) equal to or
3755 larger than the number of bits in <tt>op1</tt>, the result is undefined. If
3756 the arguments are vectors, each vector element of <tt>op1</tt> is shifted by
3757 the corresponding shift amount in <tt>op2</tt>.</p>
3761 <result> = ashr i32 4, 1 <i>; yields {i32}:result = 2</i>
3762 <result> = ashr i32 4, 2 <i>; yields {i32}:result = 1</i>
3763 <result> = ashr i8 4, 3 <i>; yields {i8}:result = 0</i>
3764 <result> = ashr i8 -2, 1 <i>; yields {i8}:result = -1</i>
3765 <result> = ashr i32 1, 32 <i>; undefined</i>
3766 <result> = ashr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 3> <i>; yields: result=<2 x i32> < i32 -1, i32 0></i>
3771 <!-- _______________________________________________________________________ -->
3772 <div class="doc_subsubsection"> <a name="i_and">'<tt>and</tt>'
3773 Instruction</a> </div>
3775 <div class="doc_text">
3779 <result> = and <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3783 <p>The '<tt>and</tt>' instruction returns the bitwise logical and of its two
3787 <p>The two arguments to the '<tt>and</tt>' instruction must be
3788 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3789 values. Both arguments must have identical types.</p>
3792 <p>The truth table used for the '<tt>and</tt>' instruction is:</p>
3794 <table border="1" cellspacing="0" cellpadding="4">
3826 <result> = and i32 4, %var <i>; yields {i32}:result = 4 & %var</i>
3827 <result> = and i32 15, 40 <i>; yields {i32}:result = 8</i>
3828 <result> = and i32 4, 8 <i>; yields {i32}:result = 0</i>
3831 <!-- _______________________________________________________________________ -->
3832 <div class="doc_subsubsection"> <a name="i_or">'<tt>or</tt>' Instruction</a> </div>
3834 <div class="doc_text">
3838 <result> = or <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3842 <p>The '<tt>or</tt>' instruction returns the bitwise logical inclusive or of its
3846 <p>The two arguments to the '<tt>or</tt>' instruction must be
3847 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3848 values. Both arguments must have identical types.</p>
3851 <p>The truth table used for the '<tt>or</tt>' instruction is:</p>
3853 <table border="1" cellspacing="0" cellpadding="4">
3885 <result> = or i32 4, %var <i>; yields {i32}:result = 4 | %var</i>
3886 <result> = or i32 15, 40 <i>; yields {i32}:result = 47</i>
3887 <result> = or i32 4, 8 <i>; yields {i32}:result = 12</i>
3892 <!-- _______________________________________________________________________ -->
3893 <div class="doc_subsubsection"> <a name="i_xor">'<tt>xor</tt>'
3894 Instruction</a> </div>
3896 <div class="doc_text">
3900 <result> = xor <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3904 <p>The '<tt>xor</tt>' instruction returns the bitwise logical exclusive or of
3905 its two operands. The <tt>xor</tt> is used to implement the "one's
3906 complement" operation, which is the "~" operator in C.</p>
3909 <p>The two arguments to the '<tt>xor</tt>' instruction must be
3910 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3911 values. Both arguments must have identical types.</p>
3914 <p>The truth table used for the '<tt>xor</tt>' instruction is:</p>
3916 <table border="1" cellspacing="0" cellpadding="4">
3948 <result> = xor i32 4, %var <i>; yields {i32}:result = 4 ^ %var</i>
3949 <result> = xor i32 15, 40 <i>; yields {i32}:result = 39</i>
3950 <result> = xor i32 4, 8 <i>; yields {i32}:result = 12</i>
3951 <result> = xor i32 %V, -1 <i>; yields {i32}:result = ~%V</i>
3956 <!-- ======================================================================= -->
3957 <div class="doc_subsection">
3958 <a name="vectorops">Vector Operations</a>
3961 <div class="doc_text">
3963 <p>LLVM supports several instructions to represent vector operations in a
3964 target-independent manner. These instructions cover the element-access and
3965 vector-specific operations needed to process vectors effectively. While LLVM
3966 does directly support these vector operations, many sophisticated algorithms
3967 will want to use target-specific intrinsics to take full advantage of a
3968 specific target.</p>
3972 <!-- _______________________________________________________________________ -->
3973 <div class="doc_subsubsection">
3974 <a name="i_extractelement">'<tt>extractelement</tt>' Instruction</a>
3977 <div class="doc_text">
3981 <result> = extractelement <n x <ty>> <val>, i32 <idx> <i>; yields <ty></i>
3985 <p>The '<tt>extractelement</tt>' instruction extracts a single scalar element
3986 from a vector at a specified index.</p>
3990 <p>The first operand of an '<tt>extractelement</tt>' instruction is a value
3991 of <a href="#t_vector">vector</a> type. The second operand is an index
3992 indicating the position from which to extract the element. The index may be
3996 <p>The result is a scalar of the same type as the element type of
3997 <tt>val</tt>. Its value is the value at position <tt>idx</tt> of
3998 <tt>val</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the
3999 results are undefined.</p>
4003 <result> = extractelement <4 x i32> %vec, i32 0 <i>; yields i32</i>
4008 <!-- _______________________________________________________________________ -->
4009 <div class="doc_subsubsection">
4010 <a name="i_insertelement">'<tt>insertelement</tt>' Instruction</a>
4013 <div class="doc_text">
4017 <result> = insertelement <n x <ty>> <val>, <ty> <elt>, i32 <idx> <i>; yields <n x <ty>></i>
4021 <p>The '<tt>insertelement</tt>' instruction inserts a scalar element into a
4022 vector at a specified index.</p>
4025 <p>The first operand of an '<tt>insertelement</tt>' instruction is a value
4026 of <a href="#t_vector">vector</a> type. The second operand is a scalar value
4027 whose type must equal the element type of the first operand. The third
4028 operand is an index indicating the position at which to insert the value.
4029 The index may be a variable.</p>
4032 <p>The result is a vector of the same type as <tt>val</tt>. Its element values
4033 are those of <tt>val</tt> except at position <tt>idx</tt>, where it gets the
4034 value <tt>elt</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the
4035 results are undefined.</p>
4039 <result> = insertelement <4 x i32> %vec, i32 1, i32 0 <i>; yields <4 x i32></i>
4044 <!-- _______________________________________________________________________ -->
4045 <div class="doc_subsubsection">
4046 <a name="i_shufflevector">'<tt>shufflevector</tt>' Instruction</a>
4049 <div class="doc_text">
4053 <result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <m x i32> <mask> <i>; yields <m x <ty>></i>
4057 <p>The '<tt>shufflevector</tt>' instruction constructs a permutation of elements
4058 from two input vectors, returning a vector with the same element type as the
4059 input and length that is the same as the shuffle mask.</p>
4062 <p>The first two operands of a '<tt>shufflevector</tt>' instruction are vectors
4063 with types that match each other. The third argument is a shuffle mask whose
4064 element type is always 'i32'. The result of the instruction is a vector
4065 whose length is the same as the shuffle mask and whose element type is the
4066 same as the element type of the first two operands.</p>
4068 <p>The shuffle mask operand is required to be a constant vector with either
4069 constant integer or undef values.</p>
4072 <p>The elements of the two input vectors are numbered from left to right across
4073 both of the vectors. The shuffle mask operand specifies, for each element of
4074 the result vector, which element of the two input vectors the result element
4075 gets. The element selector may be undef (meaning "don't care") and the
4076 second operand may be undef if performing a shuffle from only one vector.</p>
4080 <result> = shufflevector <4 x i32> %v1, <4 x i32> %v2,
4081 <4 x i32> <i32 0, i32 4, i32 1, i32 5> <i>; yields <4 x i32></i>
4082 <result> = shufflevector <4 x i32> %v1, <4 x i32> undef,
4083 <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> - Identity shuffle.
4084 <result> = shufflevector <8 x i32> %v1, <8 x i32> undef,
4085 <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i>
4086 <result> = shufflevector <4 x i32> %v1, <4 x i32> %v2,
4087 <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7 > <i>; yields <8 x i32></i>
4092 <!-- ======================================================================= -->
4093 <div class="doc_subsection">
4094 <a name="aggregateops">Aggregate Operations</a>
4097 <div class="doc_text">
4099 <p>LLVM supports several instructions for working with
4100 <a href="#t_aggregate">aggregate</a> values.</p>
4104 <!-- _______________________________________________________________________ -->
4105 <div class="doc_subsubsection">
4106 <a name="i_extractvalue">'<tt>extractvalue</tt>' Instruction</a>
4109 <div class="doc_text">
4113 <result> = extractvalue <aggregate type> <val>, <idx>{, <idx>}*
4117 <p>The '<tt>extractvalue</tt>' instruction extracts the value of a member field
4118 from an <a href="#t_aggregate">aggregate</a> value.</p>
4121 <p>The first operand of an '<tt>extractvalue</tt>' instruction is a value
4122 of <a href="#t_struct">struct</a> or
4123 <a href="#t_array">array</a> type. The operands are constant indices to
4124 specify which value to extract in a similar manner as indices in a
4125 '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction.</p>
4128 <p>The result is the value at the position in the aggregate specified by the
4133 <result> = extractvalue {i32, float} %agg, 0 <i>; yields i32</i>
4138 <!-- _______________________________________________________________________ -->
4139 <div class="doc_subsubsection">
4140 <a name="i_insertvalue">'<tt>insertvalue</tt>' Instruction</a>
4143 <div class="doc_text">
4147 <result> = insertvalue <aggregate type> <val>, <ty> <elt>, <idx> <i>; yields <aggregate type></i>
4151 <p>The '<tt>insertvalue</tt>' instruction inserts a value into a member field
4152 in an <a href="#t_aggregate">aggregate</a> value.</p>
4155 <p>The first operand of an '<tt>insertvalue</tt>' instruction is a value
4156 of <a href="#t_struct">struct</a> or
4157 <a href="#t_array">array</a> type. The second operand is a first-class
4158 value to insert. The following operands are constant indices indicating
4159 the position at which to insert the value in a similar manner as indices in a
4160 '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction. The
4161 value to insert must have the same type as the value identified by the
4165 <p>The result is an aggregate of the same type as <tt>val</tt>. Its value is
4166 that of <tt>val</tt> except that the value at the position specified by the
4167 indices is that of <tt>elt</tt>.</p>
4171 %agg1 = insertvalue {i32, float} undef, i32 1, 0 <i>; yields {i32 1, float undef}</i>
4172 %agg2 = insertvalue {i32, float} %agg1, float %val, 1 <i>; yields {i32 1, float %val}</i>
4178 <!-- ======================================================================= -->
4179 <div class="doc_subsection">
4180 <a name="memoryops">Memory Access and Addressing Operations</a>
4183 <div class="doc_text">
4185 <p>A key design point of an SSA-based representation is how it represents
4186 memory. In LLVM, no memory locations are in SSA form, which makes things
4187 very simple. This section describes how to read, write, and allocate
4192 <!-- _______________________________________________________________________ -->
4193 <div class="doc_subsubsection">
4194 <a name="i_alloca">'<tt>alloca</tt>' Instruction</a>
4197 <div class="doc_text">
4201 <result> = alloca <type>[, <ty> <NumElements>][, align <alignment>] <i>; yields {type*}:result</i>
4205 <p>The '<tt>alloca</tt>' instruction allocates memory on the stack frame of the
4206 currently executing function, to be automatically released when this function
4207 returns to its caller. The object is always allocated in the generic address
4208 space (address space zero).</p>
4211 <p>The '<tt>alloca</tt>' instruction
4212 allocates <tt>sizeof(<type>)*NumElements</tt> bytes of memory on the
4213 runtime stack, returning a pointer of the appropriate type to the program.
4214 If "NumElements" is specified, it is the number of elements allocated,
4215 otherwise "NumElements" is defaulted to be one. If a constant alignment is
4216 specified, the value result of the allocation is guaranteed to be aligned to
4217 at least that boundary. If not specified, or if zero, the target can choose
4218 to align the allocation on any convenient boundary compatible with the
4221 <p>'<tt>type</tt>' may be any sized type.</p>
4224 <p>Memory is allocated; a pointer is returned. The operation is undefined if
4225 there is insufficient stack space for the allocation. '<tt>alloca</tt>'d
4226 memory is automatically released when the function returns. The
4227 '<tt>alloca</tt>' instruction is commonly used to represent automatic
4228 variables that must have an address available. When the function returns
4229 (either with the <tt><a href="#i_ret">ret</a></tt>
4230 or <tt><a href="#i_unwind">unwind</a></tt> instructions), the memory is
4231 reclaimed. Allocating zero bytes is legal, but the result is undefined.</p>
4235 %ptr = alloca i32 <i>; yields {i32*}:ptr</i>
4236 %ptr = alloca i32, i32 4 <i>; yields {i32*}:ptr</i>
4237 %ptr = alloca i32, i32 4, align 1024 <i>; yields {i32*}:ptr</i>
4238 %ptr = alloca i32, align 1024 <i>; yields {i32*}:ptr</i>
4243 <!-- _______________________________________________________________________ -->
4244 <div class="doc_subsubsection"> <a name="i_load">'<tt>load</tt>'
4245 Instruction</a> </div>
4247 <div class="doc_text">
4251 <result> = load <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>]
4252 <result> = volatile load <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>]
4253 !<index> = !{ i32 1 }
4257 <p>The '<tt>load</tt>' instruction is used to read from memory.</p>
4260 <p>The argument to the '<tt>load</tt>' instruction specifies the memory address
4261 from which to load. The pointer must point to
4262 a <a href="#t_firstclass">first class</a> type. If the <tt>load</tt> is
4263 marked as <tt>volatile</tt>, then the optimizer is not allowed to modify the
4264 number or order of execution of this <tt>load</tt> with other <a
4265 href="#volatile">volatile operations</a>.</p>
4267 <p>The optional constant <tt>align</tt> argument specifies the alignment of the
4268 operation (that is, the alignment of the memory address). A value of 0 or an
4269 omitted <tt>align</tt> argument means that the operation has the preferential
4270 alignment for the target. It is the responsibility of the code emitter to
4271 ensure that the alignment information is correct. Overestimating the
4272 alignment results in undefined behavior. Underestimating the alignment may
4273 produce less efficient code. An alignment of 1 is always safe.</p>
4275 <p>The optional <tt>!nontemporal</tt> metadata must reference a single
4276 metatadata name <index> corresponding to a metadata node with
4277 one <tt>i32</tt> entry of value 1. The existence of
4278 the <tt>!nontemporal</tt> metatadata on the instruction tells the optimizer
4279 and code generator that this load is not expected to be reused in the cache.
4280 The code generator may select special instructions to save cache bandwidth,
4281 such as the <tt>MOVNT</tt> instruction on x86.</p>
4284 <p>The location of memory pointed to is loaded. If the value being loaded is of
4285 scalar type then the number of bytes read does not exceed the minimum number
4286 of bytes needed to hold all bits of the type. For example, loading an
4287 <tt>i24</tt> reads at most three bytes. When loading a value of a type like
4288 <tt>i20</tt> with a size that is not an integral number of bytes, the result
4289 is undefined if the value was not originally written using a store of the
4294 %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i>
4295 <a href="#i_store">store</a> i32 3, i32* %ptr <i>; yields {void}</i>
4296 %val = load i32* %ptr <i>; yields {i32}:val = i32 3</i>
4301 <!-- _______________________________________________________________________ -->
4302 <div class="doc_subsubsection"> <a name="i_store">'<tt>store</tt>'
4303 Instruction</a> </div>
4305 <div class="doc_text">
4309 store <ty> <value>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>] <i>; yields {void}</i>
4310 volatile store <ty> <value>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>] <i>; yields {void}</i>
4314 <p>The '<tt>store</tt>' instruction is used to write to memory.</p>
4317 <p>There are two arguments to the '<tt>store</tt>' instruction: a value to store
4318 and an address at which to store it. The type of the
4319 '<tt><pointer></tt>' operand must be a pointer to
4320 the <a href="#t_firstclass">first class</a> type of the
4321 '<tt><value></tt>' operand. If the <tt>store</tt> is marked as
4322 <tt>volatile</tt>, then the optimizer is not allowed to modify the number or
4323 order of execution of this <tt>store</tt> with other <a
4324 href="#volatile">volatile operations</a>.</p>
4326 <p>The optional constant "align" argument specifies the alignment of the
4327 operation (that is, the alignment of the memory address). A value of 0 or an
4328 omitted "align" argument means that the operation has the preferential
4329 alignment for the target. It is the responsibility of the code emitter to
4330 ensure that the alignment information is correct. Overestimating the
4331 alignment results in an undefined behavior. Underestimating the alignment may
4332 produce less efficient code. An alignment of 1 is always safe.</p>
4334 <p>The optional !nontemporal metadata must reference a single metatadata
4335 name <index> corresponding to a metadata node with one i32 entry of
4336 value 1. The existence of the !nontemporal metatadata on the
4337 instruction tells the optimizer and code generator that this load is
4338 not expected to be reused in the cache. The code generator may
4339 select special instructions to save cache bandwidth, such as the
4340 MOVNT instruction on x86.</p>
4344 <p>The contents of memory are updated to contain '<tt><value></tt>' at the
4345 location specified by the '<tt><pointer></tt>' operand. If
4346 '<tt><value></tt>' is of scalar type then the number of bytes written
4347 does not exceed the minimum number of bytes needed to hold all bits of the
4348 type. For example, storing an <tt>i24</tt> writes at most three bytes. When
4349 writing a value of a type like <tt>i20</tt> with a size that is not an
4350 integral number of bytes, it is unspecified what happens to the extra bits
4351 that do not belong to the type, but they will typically be overwritten.</p>
4355 %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i>
4356 store i32 3, i32* %ptr <i>; yields {void}</i>
4357 %val = <a href="#i_load">load</a> i32* %ptr <i>; yields {i32}:val = i32 3</i>
4362 <!-- _______________________________________________________________________ -->
4363 <div class="doc_subsubsection">
4364 <a name="i_getelementptr">'<tt>getelementptr</tt>' Instruction</a>
4367 <div class="doc_text">
4371 <result> = getelementptr <pty>* <ptrval>{, <ty> <idx>}*
4372 <result> = getelementptr inbounds <pty>* <ptrval>{, <ty> <idx>}*
4376 <p>The '<tt>getelementptr</tt>' instruction is used to get the address of a
4377 subelement of an <a href="#t_aggregate">aggregate</a> data structure.
4378 It performs address calculation only and does not access memory.</p>
4381 <p>The first argument is always a pointer, and forms the basis of the
4382 calculation. The remaining arguments are indices that indicate which of the
4383 elements of the aggregate object are indexed. The interpretation of each
4384 index is dependent on the type being indexed into. The first index always
4385 indexes the pointer value given as the first argument, the second index
4386 indexes a value of the type pointed to (not necessarily the value directly
4387 pointed to, since the first index can be non-zero), etc. The first type
4388 indexed into must be a pointer value, subsequent types can be arrays,
4389 vectors, and structs. Note that subsequent types being indexed into
4390 can never be pointers, since that would require loading the pointer before
4391 continuing calculation.</p>
4393 <p>The type of each index argument depends on the type it is indexing into.
4394 When indexing into a (optionally packed) structure, only <tt>i32</tt>
4395 integer <b>constants</b> are allowed. When indexing into an array, pointer
4396 or vector, integers of any width are allowed, and they are not required to be
4399 <p>For example, let's consider a C code fragment and how it gets compiled to
4402 <pre class="doc_code">
4414 int *foo(struct ST *s) {
4415 return &s[1].Z.B[5][13];
4419 <p>The LLVM code generated by the GCC frontend is:</p>
4421 <pre class="doc_code">
4422 %RT = <a href="#namedtypes">type</a> { i8 , [10 x [20 x i32]], i8 }
4423 %ST = <a href="#namedtypes">type</a> { i32, double, %RT }
4425 define i32* @foo(%ST* %s) {
4427 %reg = getelementptr %ST* %s, i32 1, i32 2, i32 1, i32 5, i32 13
4433 <p>In the example above, the first index is indexing into the '<tt>%ST*</tt>'
4434 type, which is a pointer, yielding a '<tt>%ST</tt>' = '<tt>{ i32, double, %RT
4435 }</tt>' type, a structure. The second index indexes into the third element
4436 of the structure, yielding a '<tt>%RT</tt>' = '<tt>{ i8 , [10 x [20 x i32]],
4437 i8 }</tt>' type, another structure. The third index indexes into the second
4438 element of the structure, yielding a '<tt>[10 x [20 x i32]]</tt>' type, an
4439 array. The two dimensions of the array are subscripted into, yielding an
4440 '<tt>i32</tt>' type. The '<tt>getelementptr</tt>' instruction returns a
4441 pointer to this element, thus computing a value of '<tt>i32*</tt>' type.</p>
4443 <p>Note that it is perfectly legal to index partially through a structure,
4444 returning a pointer to an inner element. Because of this, the LLVM code for
4445 the given testcase is equivalent to:</p>
4448 define i32* @foo(%ST* %s) {
4449 %t1 = getelementptr %ST* %s, i32 1 <i>; yields %ST*:%t1</i>
4450 %t2 = getelementptr %ST* %t1, i32 0, i32 2 <i>; yields %RT*:%t2</i>
4451 %t3 = getelementptr %RT* %t2, i32 0, i32 1 <i>; yields [10 x [20 x i32]]*:%t3</i>
4452 %t4 = getelementptr [10 x [20 x i32]]* %t3, i32 0, i32 5 <i>; yields [20 x i32]*:%t4</i>
4453 %t5 = getelementptr [20 x i32]* %t4, i32 0, i32 13 <i>; yields i32*:%t5</i>
4458 <p>If the <tt>inbounds</tt> keyword is present, the result value of the
4459 <tt>getelementptr</tt> is a <a href="#trapvalues">trap value</a> if the
4460 base pointer is not an <i>in bounds</i> address of an allocated object,
4461 or if any of the addresses that would be formed by successive addition of
4462 the offsets implied by the indices to the base address with infinitely
4463 precise arithmetic are not an <i>in bounds</i> address of that allocated
4464 object. The <i>in bounds</i> addresses for an allocated object are all
4465 the addresses that point into the object, plus the address one byte past
4468 <p>If the <tt>inbounds</tt> keyword is not present, the offsets are added to
4469 the base address with silently-wrapping two's complement arithmetic, and
4470 the result value of the <tt>getelementptr</tt> may be outside the object
4471 pointed to by the base pointer. The result value may not necessarily be
4472 used to access memory though, even if it happens to point into allocated
4473 storage. See the <a href="#pointeraliasing">Pointer Aliasing Rules</a>
4474 section for more information.</p>
4476 <p>The getelementptr instruction is often confusing. For some more insight into
4477 how it works, see <a href="GetElementPtr.html">the getelementptr FAQ</a>.</p>
4481 <i>; yields [12 x i8]*:aptr</i>
4482 %aptr = getelementptr {i32, [12 x i8]}* %saptr, i64 0, i32 1
4483 <i>; yields i8*:vptr</i>
4484 %vptr = getelementptr {i32, <2 x i8>}* %svptr, i64 0, i32 1, i32 1
4485 <i>; yields i8*:eptr</i>
4486 %eptr = getelementptr [12 x i8]* %aptr, i64 0, i32 1
4487 <i>; yields i32*:iptr</i>
4488 %iptr = getelementptr [10 x i32]* @arr, i16 0, i16 0
4493 <!-- ======================================================================= -->
4494 <div class="doc_subsection"> <a name="convertops">Conversion Operations</a>
4497 <div class="doc_text">
4499 <p>The instructions in this category are the conversion instructions (casting)
4500 which all take a single operand and a type. They perform various bit
4501 conversions on the operand.</p>
4505 <!-- _______________________________________________________________________ -->
4506 <div class="doc_subsubsection">
4507 <a name="i_trunc">'<tt>trunc .. to</tt>' Instruction</a>
4509 <div class="doc_text">
4513 <result> = trunc <ty> <value> to <ty2> <i>; yields ty2</i>
4517 <p>The '<tt>trunc</tt>' instruction truncates its operand to the
4518 type <tt>ty2</tt>.</p>
4521 <p>The '<tt>trunc</tt>' instruction takes a <tt>value</tt> to trunc, which must
4522 be an <a href="#t_integer">integer</a> type, and a type that specifies the
4523 size and type of the result, which must be
4524 an <a href="#t_integer">integer</a> type. The bit size of <tt>value</tt> must
4525 be larger than the bit size of <tt>ty2</tt>. Equal sized types are not
4529 <p>The '<tt>trunc</tt>' instruction truncates the high order bits
4530 in <tt>value</tt> and converts the remaining bits to <tt>ty2</tt>. Since the
4531 source size must be larger than the destination size, <tt>trunc</tt> cannot
4532 be a <i>no-op cast</i>. It will always truncate bits.</p>
4536 %X = trunc i32 257 to i8 <i>; yields i8:1</i>
4537 %Y = trunc i32 123 to i1 <i>; yields i1:true</i>
4538 %Z = trunc i32 122 to i1 <i>; yields i1:false</i>
4543 <!-- _______________________________________________________________________ -->
4544 <div class="doc_subsubsection">
4545 <a name="i_zext">'<tt>zext .. to</tt>' Instruction</a>
4547 <div class="doc_text">
4551 <result> = zext <ty> <value> to <ty2> <i>; yields ty2</i>
4555 <p>The '<tt>zext</tt>' instruction zero extends its operand to type
4560 <p>The '<tt>zext</tt>' instruction takes a value to cast, which must be of
4561 <a href="#t_integer">integer</a> type, and a type to cast it to, which must
4562 also be of <a href="#t_integer">integer</a> type. The bit size of the
4563 <tt>value</tt> must be smaller than the bit size of the destination type,
4567 <p>The <tt>zext</tt> fills the high order bits of the <tt>value</tt> with zero
4568 bits until it reaches the size of the destination type, <tt>ty2</tt>.</p>
4570 <p>When zero extending from i1, the result will always be either 0 or 1.</p>
4574 %X = zext i32 257 to i64 <i>; yields i64:257</i>
4575 %Y = zext i1 true to i32 <i>; yields i32:1</i>
4580 <!-- _______________________________________________________________________ -->
4581 <div class="doc_subsubsection">
4582 <a name="i_sext">'<tt>sext .. to</tt>' Instruction</a>
4584 <div class="doc_text">
4588 <result> = sext <ty> <value> to <ty2> <i>; yields ty2</i>
4592 <p>The '<tt>sext</tt>' sign extends <tt>value</tt> to the type <tt>ty2</tt>.</p>
4595 <p>The '<tt>sext</tt>' instruction takes a value to cast, which must be of
4596 <a href="#t_integer">integer</a> type, and a type to cast it to, which must
4597 also be of <a href="#t_integer">integer</a> type. The bit size of the
4598 <tt>value</tt> must be smaller than the bit size of the destination type,
4602 <p>The '<tt>sext</tt>' instruction performs a sign extension by copying the sign
4603 bit (highest order bit) of the <tt>value</tt> until it reaches the bit size
4604 of the type <tt>ty2</tt>.</p>
4606 <p>When sign extending from i1, the extension always results in -1 or 0.</p>
4610 %X = sext i8 -1 to i16 <i>; yields i16 :65535</i>
4611 %Y = sext i1 true to i32 <i>; yields i32:-1</i>
4616 <!-- _______________________________________________________________________ -->
4617 <div class="doc_subsubsection">
4618 <a name="i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a>
4621 <div class="doc_text">
4625 <result> = fptrunc <ty> <value> to <ty2> <i>; yields ty2</i>
4629 <p>The '<tt>fptrunc</tt>' instruction truncates <tt>value</tt> to type
4633 <p>The '<tt>fptrunc</tt>' instruction takes a <a href="#t_floating">floating
4634 point</a> value to cast and a <a href="#t_floating">floating point</a> type
4635 to cast it to. The size of <tt>value</tt> must be larger than the size of
4636 <tt>ty2</tt>. This implies that <tt>fptrunc</tt> cannot be used to make a
4637 <i>no-op cast</i>.</p>
4640 <p>The '<tt>fptrunc</tt>' instruction truncates a <tt>value</tt> from a larger
4641 <a href="#t_floating">floating point</a> type to a smaller
4642 <a href="#t_floating">floating point</a> type. If the value cannot fit
4643 within the destination type, <tt>ty2</tt>, then the results are
4648 %X = fptrunc double 123.0 to float <i>; yields float:123.0</i>
4649 %Y = fptrunc double 1.0E+300 to float <i>; yields undefined</i>
4654 <!-- _______________________________________________________________________ -->
4655 <div class="doc_subsubsection">
4656 <a name="i_fpext">'<tt>fpext .. to</tt>' Instruction</a>
4658 <div class="doc_text">
4662 <result> = fpext <ty> <value> to <ty2> <i>; yields ty2</i>
4666 <p>The '<tt>fpext</tt>' extends a floating point <tt>value</tt> to a larger
4667 floating point value.</p>
4670 <p>The '<tt>fpext</tt>' instruction takes a
4671 <a href="#t_floating">floating point</a> <tt>value</tt> to cast, and
4672 a <a href="#t_floating">floating point</a> type to cast it to. The source
4673 type must be smaller than the destination type.</p>
4676 <p>The '<tt>fpext</tt>' instruction extends the <tt>value</tt> from a smaller
4677 <a href="#t_floating">floating point</a> type to a larger
4678 <a href="#t_floating">floating point</a> type. The <tt>fpext</tt> cannot be
4679 used to make a <i>no-op cast</i> because it always changes bits. Use
4680 <tt>bitcast</tt> to make a <i>no-op cast</i> for a floating point cast.</p>
4684 %X = fpext float 3.1415 to double <i>; yields double:3.1415</i>
4685 %Y = fpext float 1.0 to float <i>; yields float:1.0 (no-op)</i>
4690 <!-- _______________________________________________________________________ -->
4691 <div class="doc_subsubsection">
4692 <a name="i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a>
4694 <div class="doc_text">
4698 <result> = fptoui <ty> <value> to <ty2> <i>; yields ty2</i>
4702 <p>The '<tt>fptoui</tt>' converts a floating point <tt>value</tt> to its
4703 unsigned integer equivalent of type <tt>ty2</tt>.</p>
4706 <p>The '<tt>fptoui</tt>' instruction takes a value to cast, which must be a
4707 scalar or vector <a href="#t_floating">floating point</a> value, and a type
4708 to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a>
4709 type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a
4710 vector integer type with the same number of elements as <tt>ty</tt></p>
4713 <p>The '<tt>fptoui</tt>' instruction converts its
4714 <a href="#t_floating">floating point</a> operand into the nearest (rounding
4715 towards zero) unsigned integer value. If the value cannot fit
4716 in <tt>ty2</tt>, the results are undefined.</p>
4720 %X = fptoui double 123.0 to i32 <i>; yields i32:123</i>
4721 %Y = fptoui float 1.0E+300 to i1 <i>; yields undefined:1</i>
4722 %Z = fptoui float 1.04E+17 to i8 <i>; yields undefined:1</i>
4727 <!-- _______________________________________________________________________ -->
4728 <div class="doc_subsubsection">
4729 <a name="i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a>
4731 <div class="doc_text">
4735 <result> = fptosi <ty> <value> to <ty2> <i>; yields ty2</i>
4739 <p>The '<tt>fptosi</tt>' instruction converts
4740 <a href="#t_floating">floating point</a> <tt>value</tt> to
4741 type <tt>ty2</tt>.</p>
4744 <p>The '<tt>fptosi</tt>' instruction takes a value to cast, which must be a
4745 scalar or vector <a href="#t_floating">floating point</a> value, and a type
4746 to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a>
4747 type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a
4748 vector integer type with the same number of elements as <tt>ty</tt></p>
4751 <p>The '<tt>fptosi</tt>' instruction converts its
4752 <a href="#t_floating">floating point</a> operand into the nearest (rounding
4753 towards zero) signed integer value. If the value cannot fit in <tt>ty2</tt>,
4754 the results are undefined.</p>
4758 %X = fptosi double -123.0 to i32 <i>; yields i32:-123</i>
4759 %Y = fptosi float 1.0E-247 to i1 <i>; yields undefined:1</i>
4760 %Z = fptosi float 1.04E+17 to i8 <i>; yields undefined:1</i>
4765 <!-- _______________________________________________________________________ -->
4766 <div class="doc_subsubsection">
4767 <a name="i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a>
4769 <div class="doc_text">
4773 <result> = uitofp <ty> <value> to <ty2> <i>; yields ty2</i>
4777 <p>The '<tt>uitofp</tt>' instruction regards <tt>value</tt> as an unsigned
4778 integer and converts that value to the <tt>ty2</tt> type.</p>
4781 <p>The '<tt>uitofp</tt>' instruction takes a value to cast, which must be a
4782 scalar or vector <a href="#t_integer">integer</a> value, and a type to cast
4783 it to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a>
4784 type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector
4785 floating point type with the same number of elements as <tt>ty</tt></p>
4788 <p>The '<tt>uitofp</tt>' instruction interprets its operand as an unsigned
4789 integer quantity and converts it to the corresponding floating point
4790 value. If the value cannot fit in the floating point value, the results are
4795 %X = uitofp i32 257 to float <i>; yields float:257.0</i>
4796 %Y = uitofp i8 -1 to double <i>; yields double:255.0</i>
4801 <!-- _______________________________________________________________________ -->
4802 <div class="doc_subsubsection">
4803 <a name="i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a>
4805 <div class="doc_text">
4809 <result> = sitofp <ty> <value> to <ty2> <i>; yields ty2</i>
4813 <p>The '<tt>sitofp</tt>' instruction regards <tt>value</tt> as a signed integer
4814 and converts that value to the <tt>ty2</tt> type.</p>
4817 <p>The '<tt>sitofp</tt>' instruction takes a value to cast, which must be a
4818 scalar or vector <a href="#t_integer">integer</a> value, and a type to cast
4819 it to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a>
4820 type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector
4821 floating point type with the same number of elements as <tt>ty</tt></p>
4824 <p>The '<tt>sitofp</tt>' instruction interprets its operand as a signed integer
4825 quantity and converts it to the corresponding floating point value. If the
4826 value cannot fit in the floating point value, the results are undefined.</p>
4830 %X = sitofp i32 257 to float <i>; yields float:257.0</i>
4831 %Y = sitofp i8 -1 to double <i>; yields double:-1.0</i>
4836 <!-- _______________________________________________________________________ -->
4837 <div class="doc_subsubsection">
4838 <a name="i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a>
4840 <div class="doc_text">
4844 <result> = ptrtoint <ty> <value> to <ty2> <i>; yields ty2</i>
4848 <p>The '<tt>ptrtoint</tt>' instruction converts the pointer <tt>value</tt> to
4849 the integer type <tt>ty2</tt>.</p>
4852 <p>The '<tt>ptrtoint</tt>' instruction takes a <tt>value</tt> to cast, which
4853 must be a <a href="#t_pointer">pointer</a> value, and a type to cast it to
4854 <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> type.</p>
4857 <p>The '<tt>ptrtoint</tt>' instruction converts <tt>value</tt> to integer type
4858 <tt>ty2</tt> by interpreting the pointer value as an integer and either
4859 truncating or zero extending that value to the size of the integer type. If
4860 <tt>value</tt> is smaller than <tt>ty2</tt> then a zero extension is done. If
4861 <tt>value</tt> is larger than <tt>ty2</tt> then a truncation is done. If they
4862 are the same size, then nothing is done (<i>no-op cast</i>) other than a type
4867 %X = ptrtoint i32* %X to i8 <i>; yields truncation on 32-bit architecture</i>
4868 %Y = ptrtoint i32* %x to i64 <i>; yields zero extension on 32-bit architecture</i>
4873 <!-- _______________________________________________________________________ -->
4874 <div class="doc_subsubsection">
4875 <a name="i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a>
4877 <div class="doc_text">
4881 <result> = inttoptr <ty> <value> to <ty2> <i>; yields ty2</i>
4885 <p>The '<tt>inttoptr</tt>' instruction converts an integer <tt>value</tt> to a
4886 pointer type, <tt>ty2</tt>.</p>
4889 <p>The '<tt>inttoptr</tt>' instruction takes an <a href="#t_integer">integer</a>
4890 value to cast, and a type to cast it to, which must be a
4891 <a href="#t_pointer">pointer</a> type.</p>
4894 <p>The '<tt>inttoptr</tt>' instruction converts <tt>value</tt> to type
4895 <tt>ty2</tt> by applying either a zero extension or a truncation depending on
4896 the size of the integer <tt>value</tt>. If <tt>value</tt> is larger than the
4897 size of a pointer then a truncation is done. If <tt>value</tt> is smaller
4898 than the size of a pointer then a zero extension is done. If they are the
4899 same size, nothing is done (<i>no-op cast</i>).</p>
4903 %X = inttoptr i32 255 to i32* <i>; yields zero extension on 64-bit architecture</i>
4904 %Y = inttoptr i32 255 to i32* <i>; yields no-op on 32-bit architecture</i>
4905 %Z = inttoptr i64 0 to i32* <i>; yields truncation on 32-bit architecture</i>
4910 <!-- _______________________________________________________________________ -->
4911 <div class="doc_subsubsection">
4912 <a name="i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a>
4914 <div class="doc_text">
4918 <result> = bitcast <ty> <value> to <ty2> <i>; yields ty2</i>
4922 <p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type
4923 <tt>ty2</tt> without changing any bits.</p>
4926 <p>The '<tt>bitcast</tt>' instruction takes a value to cast, which must be a
4927 non-aggregate first class value, and a type to cast it to, which must also be
4928 a non-aggregate <a href="#t_firstclass">first class</a> type. The bit sizes
4929 of <tt>value</tt> and the destination type, <tt>ty2</tt>, must be
4930 identical. If the source type is a pointer, the destination type must also be
4931 a pointer. This instruction supports bitwise conversion of vectors to
4932 integers and to vectors of other types (as long as they have the same
4936 <p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type
4937 <tt>ty2</tt>. It is always a <i>no-op cast</i> because no bits change with
4938 this conversion. The conversion is done as if the <tt>value</tt> had been
4939 stored to memory and read back as type <tt>ty2</tt>. Pointer types may only
4940 be converted to other pointer types with this instruction. To convert
4941 pointers to other types, use the <a href="#i_inttoptr">inttoptr</a> or
4942 <a href="#i_ptrtoint">ptrtoint</a> instructions first.</p>
4946 %X = bitcast i8 255 to i8 <i>; yields i8 :-1</i>
4947 %Y = bitcast i32* %x to sint* <i>; yields sint*:%x</i>
4948 %Z = bitcast <2 x int> %V to i64; <i>; yields i64: %V</i>
4953 <!-- ======================================================================= -->
4954 <div class="doc_subsection"> <a name="otherops">Other Operations</a> </div>
4956 <div class="doc_text">
4958 <p>The instructions in this category are the "miscellaneous" instructions, which
4959 defy better classification.</p>
4963 <!-- _______________________________________________________________________ -->
4964 <div class="doc_subsubsection"><a name="i_icmp">'<tt>icmp</tt>' Instruction</a>
4967 <div class="doc_text">
4971 <result> = icmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i>
4975 <p>The '<tt>icmp</tt>' instruction returns a boolean value or a vector of
4976 boolean values based on comparison of its two integer, integer vector, or
4977 pointer operands.</p>
4980 <p>The '<tt>icmp</tt>' instruction takes three operands. The first operand is
4981 the condition code indicating the kind of comparison to perform. It is not a
4982 value, just a keyword. The possible condition code are:</p>
4985 <li><tt>eq</tt>: equal</li>
4986 <li><tt>ne</tt>: not equal </li>
4987 <li><tt>ugt</tt>: unsigned greater than</li>
4988 <li><tt>uge</tt>: unsigned greater or equal</li>
4989 <li><tt>ult</tt>: unsigned less than</li>
4990 <li><tt>ule</tt>: unsigned less or equal</li>
4991 <li><tt>sgt</tt>: signed greater than</li>
4992 <li><tt>sge</tt>: signed greater or equal</li>
4993 <li><tt>slt</tt>: signed less than</li>
4994 <li><tt>sle</tt>: signed less or equal</li>
4997 <p>The remaining two arguments must be <a href="#t_integer">integer</a> or
4998 <a href="#t_pointer">pointer</a> or integer <a href="#t_vector">vector</a>
4999 typed. They must also be identical types.</p>
5002 <p>The '<tt>icmp</tt>' compares <tt>op1</tt> and <tt>op2</tt> according to the
5003 condition code given as <tt>cond</tt>. The comparison performed always yields
5004 either an <a href="#t_integer"><tt>i1</tt></a> or vector of <tt>i1</tt>
5005 result, as follows:</p>
5008 <li><tt>eq</tt>: yields <tt>true</tt> if the operands are equal,
5009 <tt>false</tt> otherwise. No sign interpretation is necessary or
5012 <li><tt>ne</tt>: yields <tt>true</tt> if the operands are unequal,
5013 <tt>false</tt> otherwise. No sign interpretation is necessary or
5016 <li><tt>ugt</tt>: interprets the operands as unsigned values and yields
5017 <tt>true</tt> if <tt>op1</tt> is greater than <tt>op2</tt>.</li>
5019 <li><tt>uge</tt>: interprets the operands as unsigned values and yields
5020 <tt>true</tt> if <tt>op1</tt> is greater than or equal
5021 to <tt>op2</tt>.</li>
5023 <li><tt>ult</tt>: interprets the operands as unsigned values and yields
5024 <tt>true</tt> if <tt>op1</tt> is less than <tt>op2</tt>.</li>
5026 <li><tt>ule</tt>: interprets the operands as unsigned values and yields
5027 <tt>true</tt> if <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li>
5029 <li><tt>sgt</tt>: interprets the operands as signed values and yields
5030 <tt>true</tt> if <tt>op1</tt> is greater than <tt>op2</tt>.</li>
5032 <li><tt>sge</tt>: interprets the operands as signed values and yields
5033 <tt>true</tt> if <tt>op1</tt> is greater than or equal
5034 to <tt>op2</tt>.</li>
5036 <li><tt>slt</tt>: interprets the operands as signed values and yields
5037 <tt>true</tt> if <tt>op1</tt> is less than <tt>op2</tt>.</li>
5039 <li><tt>sle</tt>: interprets the operands as signed values and yields
5040 <tt>true</tt> if <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li>
5043 <p>If the operands are <a href="#t_pointer">pointer</a> typed, the pointer
5044 values are compared as if they were integers.</p>
5046 <p>If the operands are integer vectors, then they are compared element by
5047 element. The result is an <tt>i1</tt> vector with the same number of elements
5048 as the values being compared. Otherwise, the result is an <tt>i1</tt>.</p>
5052 <result> = icmp eq i32 4, 5 <i>; yields: result=false</i>
5053 <result> = icmp ne float* %X, %X <i>; yields: result=false</i>
5054 <result> = icmp ult i16 4, 5 <i>; yields: result=true</i>
5055 <result> = icmp sgt i16 4, 5 <i>; yields: result=false</i>
5056 <result> = icmp ule i16 -4, 5 <i>; yields: result=false</i>
5057 <result> = icmp sge i16 4, 5 <i>; yields: result=false</i>
5060 <p>Note that the code generator does not yet support vector types with
5061 the <tt>icmp</tt> instruction.</p>
5065 <!-- _______________________________________________________________________ -->
5066 <div class="doc_subsubsection"><a name="i_fcmp">'<tt>fcmp</tt>' Instruction</a>
5069 <div class="doc_text">
5073 <result> = fcmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i>
5077 <p>The '<tt>fcmp</tt>' instruction returns a boolean value or vector of boolean
5078 values based on comparison of its operands.</p>
5080 <p>If the operands are floating point scalars, then the result type is a boolean
5081 (<a href="#t_integer"><tt>i1</tt></a>).</p>
5083 <p>If the operands are floating point vectors, then the result type is a vector
5084 of boolean with the same number of elements as the operands being
5088 <p>The '<tt>fcmp</tt>' instruction takes three operands. The first operand is
5089 the condition code indicating the kind of comparison to perform. It is not a
5090 value, just a keyword. The possible condition code are:</p>
5093 <li><tt>false</tt>: no comparison, always returns false</li>
5094 <li><tt>oeq</tt>: ordered and equal</li>
5095 <li><tt>ogt</tt>: ordered and greater than </li>
5096 <li><tt>oge</tt>: ordered and greater than or equal</li>
5097 <li><tt>olt</tt>: ordered and less than </li>
5098 <li><tt>ole</tt>: ordered and less than or equal</li>
5099 <li><tt>one</tt>: ordered and not equal</li>
5100 <li><tt>ord</tt>: ordered (no nans)</li>
5101 <li><tt>ueq</tt>: unordered or equal</li>
5102 <li><tt>ugt</tt>: unordered or greater than </li>
5103 <li><tt>uge</tt>: unordered or greater than or equal</li>
5104 <li><tt>ult</tt>: unordered or less than </li>
5105 <li><tt>ule</tt>: unordered or less than or equal</li>
5106 <li><tt>une</tt>: unordered or not equal</li>
5107 <li><tt>uno</tt>: unordered (either nans)</li>
5108 <li><tt>true</tt>: no comparison, always returns true</li>
5111 <p><i>Ordered</i> means that neither operand is a QNAN while
5112 <i>unordered</i> means that either operand may be a QNAN.</p>
5114 <p>Each of <tt>val1</tt> and <tt>val2</tt> arguments must be either
5115 a <a href="#t_floating">floating point</a> type or
5116 a <a href="#t_vector">vector</a> of floating point type. They must have
5117 identical types.</p>
5120 <p>The '<tt>fcmp</tt>' instruction compares <tt>op1</tt> and <tt>op2</tt>
5121 according to the condition code given as <tt>cond</tt>. If the operands are
5122 vectors, then the vectors are compared element by element. Each comparison
5123 performed always yields an <a href="#t_integer">i1</a> result, as
5127 <li><tt>false</tt>: always yields <tt>false</tt>, regardless of operands.</li>
5129 <li><tt>oeq</tt>: yields <tt>true</tt> if both operands are not a QNAN and
5130 <tt>op1</tt> is equal to <tt>op2</tt>.</li>
5132 <li><tt>ogt</tt>: yields <tt>true</tt> if both operands are not a QNAN and
5133 <tt>op1</tt> is greater than <tt>op2</tt>.</li>
5135 <li><tt>oge</tt>: yields <tt>true</tt> if both operands are not a QNAN and
5136 <tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li>
5138 <li><tt>olt</tt>: yields <tt>true</tt> if both operands are not a QNAN and
5139 <tt>op1</tt> is less than <tt>op2</tt>.</li>
5141 <li><tt>ole</tt>: yields <tt>true</tt> if both operands are not a QNAN and
5142 <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li>
5144 <li><tt>one</tt>: yields <tt>true</tt> if both operands are not a QNAN and
5145 <tt>op1</tt> is not equal to <tt>op2</tt>.</li>
5147 <li><tt>ord</tt>: yields <tt>true</tt> if both operands are not a QNAN.</li>
5149 <li><tt>ueq</tt>: yields <tt>true</tt> if either operand is a QNAN or
5150 <tt>op1</tt> is equal to <tt>op2</tt>.</li>
5152 <li><tt>ugt</tt>: yields <tt>true</tt> if either operand is a QNAN or
5153 <tt>op1</tt> is greater than <tt>op2</tt>.</li>
5155 <li><tt>uge</tt>: yields <tt>true</tt> if either operand is a QNAN or
5156 <tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li>
5158 <li><tt>ult</tt>: yields <tt>true</tt> if either operand is a QNAN or
5159 <tt>op1</tt> is less than <tt>op2</tt>.</li>
5161 <li><tt>ule</tt>: yields <tt>true</tt> if either operand is a QNAN or
5162 <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li>
5164 <li><tt>une</tt>: yields <tt>true</tt> if either operand is a QNAN or
5165 <tt>op1</tt> is not equal to <tt>op2</tt>.</li>
5167 <li><tt>uno</tt>: yields <tt>true</tt> if either operand is a QNAN.</li>
5169 <li><tt>true</tt>: always yields <tt>true</tt>, regardless of operands.</li>
5174 <result> = fcmp oeq float 4.0, 5.0 <i>; yields: result=false</i>
5175 <result> = fcmp one float 4.0, 5.0 <i>; yields: result=true</i>
5176 <result> = fcmp olt float 4.0, 5.0 <i>; yields: result=true</i>
5177 <result> = fcmp ueq double 1.0, 2.0 <i>; yields: result=false</i>
5180 <p>Note that the code generator does not yet support vector types with
5181 the <tt>fcmp</tt> instruction.</p>
5185 <!-- _______________________________________________________________________ -->
5186 <div class="doc_subsubsection">
5187 <a name="i_phi">'<tt>phi</tt>' Instruction</a>
5190 <div class="doc_text">
5194 <result> = phi <ty> [ <val0>, <label0>], ...
5198 <p>The '<tt>phi</tt>' instruction is used to implement the φ node in the
5199 SSA graph representing the function.</p>
5202 <p>The type of the incoming values is specified with the first type field. After
5203 this, the '<tt>phi</tt>' instruction takes a list of pairs as arguments, with
5204 one pair for each predecessor basic block of the current block. Only values
5205 of <a href="#t_firstclass">first class</a> type may be used as the value
5206 arguments to the PHI node. Only labels may be used as the label
5209 <p>There must be no non-phi instructions between the start of a basic block and
5210 the PHI instructions: i.e. PHI instructions must be first in a basic
5213 <p>For the purposes of the SSA form, the use of each incoming value is deemed to
5214 occur on the edge from the corresponding predecessor block to the current
5215 block (but after any definition of an '<tt>invoke</tt>' instruction's return
5216 value on the same edge).</p>
5219 <p>At runtime, the '<tt>phi</tt>' instruction logically takes on the value
5220 specified by the pair corresponding to the predecessor basic block that
5221 executed just prior to the current block.</p>
5225 Loop: ; Infinite loop that counts from 0 on up...
5226 %indvar = phi i32 [ 0, %LoopHeader ], [ %nextindvar, %Loop ]
5227 %nextindvar = add i32 %indvar, 1
5233 <!-- _______________________________________________________________________ -->
5234 <div class="doc_subsubsection">
5235 <a name="i_select">'<tt>select</tt>' Instruction</a>
5238 <div class="doc_text">
5242 <result> = select <i>selty</i> <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i>
5244 <i>selty</i> is either i1 or {<N x i1>}
5248 <p>The '<tt>select</tt>' instruction is used to choose one value based on a
5249 condition, without branching.</p>
5253 <p>The '<tt>select</tt>' instruction requires an 'i1' value or a vector of 'i1'
5254 values indicating the condition, and two values of the
5255 same <a href="#t_firstclass">first class</a> type. If the val1/val2 are
5256 vectors and the condition is a scalar, then entire vectors are selected, not
5257 individual elements.</p>
5260 <p>If the condition is an i1 and it evaluates to 1, the instruction returns the
5261 first value argument; otherwise, it returns the second value argument.</p>
5263 <p>If the condition is a vector of i1, then the value arguments must be vectors
5264 of the same size, and the selection is done element by element.</p>
5268 %X = select i1 true, i8 17, i8 42 <i>; yields i8:17</i>
5271 <p>Note that the code generator does not yet support conditions
5272 with vector type.</p>
5276 <!-- _______________________________________________________________________ -->
5277 <div class="doc_subsubsection">
5278 <a name="i_call">'<tt>call</tt>' Instruction</a>
5281 <div class="doc_text">
5285 <result> = [tail] call [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] <ty> [<fnty>*] <fnptrval>(<function args>) [<a href="#fnattrs">fn attrs</a>]
5289 <p>The '<tt>call</tt>' instruction represents a simple function call.</p>
5292 <p>This instruction requires several arguments:</p>
5295 <li>The optional "tail" marker indicates that the callee function does not
5296 access any allocas or varargs in the caller. Note that calls may be
5297 marked "tail" even if they do not occur before
5298 a <a href="#i_ret"><tt>ret</tt></a> instruction. If the "tail" marker is
5299 present, the function call is eligible for tail call optimization,
5300 but <a href="CodeGenerator.html#tailcallopt">might not in fact be
5301 optimized into a jump</a>. The code generator may optimize calls marked
5302 "tail" with either 1) automatic <a href="CodeGenerator.html#sibcallopt">
5303 sibling call optimization</a> when the caller and callee have
5304 matching signatures, or 2) forced tail call optimization when the
5305 following extra requirements are met:
5307 <li>Caller and callee both have the calling
5308 convention <tt>fastcc</tt>.</li>
5309 <li>The call is in tail position (ret immediately follows call and ret
5310 uses value of call or is void).</li>
5311 <li>Option <tt>-tailcallopt</tt> is enabled,
5312 or <code>llvm::GuaranteedTailCallOpt</code> is <code>true</code>.</li>
5313 <li><a href="CodeGenerator.html#tailcallopt">Platform specific
5314 constraints are met.</a></li>
5318 <li>The optional "cconv" marker indicates which <a href="#callingconv">calling
5319 convention</a> the call should use. If none is specified, the call
5320 defaults to using C calling conventions. The calling convention of the
5321 call must match the calling convention of the target function, or else the
5322 behavior is undefined.</li>
5324 <li>The optional <a href="#paramattrs">Parameter Attributes</a> list for
5325 return values. Only '<tt>zeroext</tt>', '<tt>signext</tt>', and
5326 '<tt>inreg</tt>' attributes are valid here.</li>
5328 <li>'<tt>ty</tt>': the type of the call instruction itself which is also the
5329 type of the return value. Functions that return no value are marked
5330 <tt><a href="#t_void">void</a></tt>.</li>
5332 <li>'<tt>fnty</tt>': shall be the signature of the pointer to function value
5333 being invoked. The argument types must match the types implied by this
5334 signature. This type can be omitted if the function is not varargs and if
5335 the function type does not return a pointer to a function.</li>
5337 <li>'<tt>fnptrval</tt>': An LLVM value containing a pointer to a function to
5338 be invoked. In most cases, this is a direct function invocation, but
5339 indirect <tt>call</tt>s are just as possible, calling an arbitrary pointer
5340 to function value.</li>
5342 <li>'<tt>function args</tt>': argument list whose types match the function
5343 signature argument types and parameter attributes. All arguments must be
5344 of <a href="#t_firstclass">first class</a> type. If the function
5345 signature indicates the function accepts a variable number of arguments,
5346 the extra arguments can be specified.</li>
5348 <li>The optional <a href="#fnattrs">function attributes</a> list. Only
5349 '<tt>noreturn</tt>', '<tt>nounwind</tt>', '<tt>readonly</tt>' and
5350 '<tt>readnone</tt>' attributes are valid here.</li>
5354 <p>The '<tt>call</tt>' instruction is used to cause control flow to transfer to
5355 a specified function, with its incoming arguments bound to the specified
5356 values. Upon a '<tt><a href="#i_ret">ret</a></tt>' instruction in the called
5357 function, control flow continues with the instruction after the function
5358 call, and the return value of the function is bound to the result
5363 %retval = call i32 @test(i32 %argc)
5364 call i32 (i8*, ...)* @printf(i8* %msg, i32 12, i8 42) <i>; yields i32</i>
5365 %X = tail call i32 @foo() <i>; yields i32</i>
5366 %Y = tail call <a href="#callingconv">fastcc</a> i32 @foo() <i>; yields i32</i>
5367 call void %foo(i8 97 signext)
5369 %struct.A = type { i32, i8 }
5370 %r = call %struct.A @foo() <i>; yields { 32, i8 }</i>
5371 %gr = extractvalue %struct.A %r, 0 <i>; yields i32</i>
5372 %gr1 = extractvalue %struct.A %r, 1 <i>; yields i8</i>
5373 %Z = call void @foo() noreturn <i>; indicates that %foo never returns normally</i>
5374 %ZZ = call zeroext i32 @bar() <i>; Return value is %zero extended</i>
5377 <p>llvm treats calls to some functions with names and arguments that match the
5378 standard C99 library as being the C99 library functions, and may perform
5379 optimizations or generate code for them under that assumption. This is
5380 something we'd like to change in the future to provide better support for
5381 freestanding environments and non-C-based languages.</p>
5385 <!-- _______________________________________________________________________ -->
5386 <div class="doc_subsubsection">
5387 <a name="i_va_arg">'<tt>va_arg</tt>' Instruction</a>
5390 <div class="doc_text">
5394 <resultval> = va_arg <va_list*> <arglist>, <argty>
5398 <p>The '<tt>va_arg</tt>' instruction is used to access arguments passed through
5399 the "variable argument" area of a function call. It is used to implement the
5400 <tt>va_arg</tt> macro in C.</p>
5403 <p>This instruction takes a <tt>va_list*</tt> value and the type of the
5404 argument. It returns a value of the specified argument type and increments
5405 the <tt>va_list</tt> to point to the next argument. The actual type
5406 of <tt>va_list</tt> is target specific.</p>
5409 <p>The '<tt>va_arg</tt>' instruction loads an argument of the specified type
5410 from the specified <tt>va_list</tt> and causes the <tt>va_list</tt> to point
5411 to the next argument. For more information, see the variable argument
5412 handling <a href="#int_varargs">Intrinsic Functions</a>.</p>
5414 <p>It is legal for this instruction to be called in a function which does not
5415 take a variable number of arguments, for example, the <tt>vfprintf</tt>
5418 <p><tt>va_arg</tt> is an LLVM instruction instead of
5419 an <a href="#intrinsics">intrinsic function</a> because it takes a type as an
5423 <p>See the <a href="#int_varargs">variable argument processing</a> section.</p>
5425 <p>Note that the code generator does not yet fully support va_arg on many
5426 targets. Also, it does not currently support va_arg with aggregate types on
5431 <!-- *********************************************************************** -->
5432 <div class="doc_section"> <a name="intrinsics">Intrinsic Functions</a> </div>
5433 <!-- *********************************************************************** -->
5435 <div class="doc_text">
5437 <p>LLVM supports the notion of an "intrinsic function". These functions have
5438 well known names and semantics and are required to follow certain
5439 restrictions. Overall, these intrinsics represent an extension mechanism for
5440 the LLVM language that does not require changing all of the transformations
5441 in LLVM when adding to the language (or the bitcode reader/writer, the
5442 parser, etc...).</p>
5444 <p>Intrinsic function names must all start with an "<tt>llvm.</tt>" prefix. This
5445 prefix is reserved in LLVM for intrinsic names; thus, function names may not
5446 begin with this prefix. Intrinsic functions must always be external
5447 functions: you cannot define the body of intrinsic functions. Intrinsic
5448 functions may only be used in call or invoke instructions: it is illegal to
5449 take the address of an intrinsic function. Additionally, because intrinsic
5450 functions are part of the LLVM language, it is required if any are added that
5451 they be documented here.</p>
5453 <p>Some intrinsic functions can be overloaded, i.e., the intrinsic represents a
5454 family of functions that perform the same operation but on different data
5455 types. Because LLVM can represent over 8 million different integer types,
5456 overloading is used commonly to allow an intrinsic function to operate on any
5457 integer type. One or more of the argument types or the result type can be
5458 overloaded to accept any integer type. Argument types may also be defined as
5459 exactly matching a previous argument's type or the result type. This allows
5460 an intrinsic function which accepts multiple arguments, but needs all of them
5461 to be of the same type, to only be overloaded with respect to a single
5462 argument or the result.</p>
5464 <p>Overloaded intrinsics will have the names of its overloaded argument types
5465 encoded into its function name, each preceded by a period. Only those types
5466 which are overloaded result in a name suffix. Arguments whose type is matched
5467 against another type do not. For example, the <tt>llvm.ctpop</tt> function
5468 can take an integer of any width and returns an integer of exactly the same
5469 integer width. This leads to a family of functions such as
5470 <tt>i8 @llvm.ctpop.i8(i8 %val)</tt> and <tt>i29 @llvm.ctpop.i29(i29
5471 %val)</tt>. Only one type, the return type, is overloaded, and only one type
5472 suffix is required. Because the argument's type is matched against the return
5473 type, it does not require its own name suffix.</p>
5475 <p>To learn how to add an intrinsic function, please see the
5476 <a href="ExtendingLLVM.html">Extending LLVM Guide</a>.</p>
5480 <!-- ======================================================================= -->
5481 <div class="doc_subsection">
5482 <a name="int_varargs">Variable Argument Handling Intrinsics</a>
5485 <div class="doc_text">
5487 <p>Variable argument support is defined in LLVM with
5488 the <a href="#i_va_arg"><tt>va_arg</tt></a> instruction and these three
5489 intrinsic functions. These functions are related to the similarly named
5490 macros defined in the <tt><stdarg.h></tt> header file.</p>
5492 <p>All of these functions operate on arguments that use a target-specific value
5493 type "<tt>va_list</tt>". The LLVM assembly language reference manual does
5494 not define what this type is, so all transformations should be prepared to
5495 handle these functions regardless of the type used.</p>
5497 <p>This example shows how the <a href="#i_va_arg"><tt>va_arg</tt></a>
5498 instruction and the variable argument handling intrinsic functions are
5501 <pre class="doc_code">
5502 define i32 @test(i32 %X, ...) {
5503 ; Initialize variable argument processing
5505 %ap2 = bitcast i8** %ap to i8*
5506 call void @llvm.va_start(i8* %ap2)
5508 ; Read a single integer argument
5509 %tmp = va_arg i8** %ap, i32
5511 ; Demonstrate usage of llvm.va_copy and llvm.va_end
5513 %aq2 = bitcast i8** %aq to i8*
5514 call void @llvm.va_copy(i8* %aq2, i8* %ap2)
5515 call void @llvm.va_end(i8* %aq2)
5517 ; Stop processing of arguments.
5518 call void @llvm.va_end(i8* %ap2)
5522 declare void @llvm.va_start(i8*)
5523 declare void @llvm.va_copy(i8*, i8*)
5524 declare void @llvm.va_end(i8*)
5529 <!-- _______________________________________________________________________ -->
5530 <div class="doc_subsubsection">
5531 <a name="int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a>
5535 <div class="doc_text">
5539 declare void %llvm.va_start(i8* <arglist>)
5543 <p>The '<tt>llvm.va_start</tt>' intrinsic initializes <tt>*<arglist></tt>
5544 for subsequent use by <tt><a href="#i_va_arg">va_arg</a></tt>.</p>
5547 <p>The argument is a pointer to a <tt>va_list</tt> element to initialize.</p>
5550 <p>The '<tt>llvm.va_start</tt>' intrinsic works just like the <tt>va_start</tt>
5551 macro available in C. In a target-dependent way, it initializes
5552 the <tt>va_list</tt> element to which the argument points, so that the next
5553 call to <tt>va_arg</tt> will produce the first variable argument passed to
5554 the function. Unlike the C <tt>va_start</tt> macro, this intrinsic does not
5555 need to know the last argument of the function as the compiler can figure
5560 <!-- _______________________________________________________________________ -->
5561 <div class="doc_subsubsection">
5562 <a name="int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a>
5565 <div class="doc_text">
5569 declare void @llvm.va_end(i8* <arglist>)
5573 <p>The '<tt>llvm.va_end</tt>' intrinsic destroys <tt>*<arglist></tt>,
5574 which has been initialized previously
5575 with <tt><a href="#int_va_start">llvm.va_start</a></tt>
5576 or <tt><a href="#i_va_copy">llvm.va_copy</a></tt>.</p>
5579 <p>The argument is a pointer to a <tt>va_list</tt> to destroy.</p>
5582 <p>The '<tt>llvm.va_end</tt>' intrinsic works just like the <tt>va_end</tt>
5583 macro available in C. In a target-dependent way, it destroys
5584 the <tt>va_list</tt> element to which the argument points. Calls
5585 to <a href="#int_va_start"><tt>llvm.va_start</tt></a>
5586 and <a href="#int_va_copy"> <tt>llvm.va_copy</tt></a> must be matched exactly
5587 with calls to <tt>llvm.va_end</tt>.</p>
5591 <!-- _______________________________________________________________________ -->
5592 <div class="doc_subsubsection">
5593 <a name="int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a>
5596 <div class="doc_text">
5600 declare void @llvm.va_copy(i8* <destarglist>, i8* <srcarglist>)
5604 <p>The '<tt>llvm.va_copy</tt>' intrinsic copies the current argument position
5605 from the source argument list to the destination argument list.</p>
5608 <p>The first argument is a pointer to a <tt>va_list</tt> element to initialize.
5609 The second argument is a pointer to a <tt>va_list</tt> element to copy
5613 <p>The '<tt>llvm.va_copy</tt>' intrinsic works just like the <tt>va_copy</tt>
5614 macro available in C. In a target-dependent way, it copies the
5615 source <tt>va_list</tt> element into the destination <tt>va_list</tt>
5616 element. This intrinsic is necessary because
5617 the <tt><a href="#int_va_start"> llvm.va_start</a></tt> intrinsic may be
5618 arbitrarily complex and require, for example, memory allocation.</p>
5622 <!-- ======================================================================= -->
5623 <div class="doc_subsection">
5624 <a name="int_gc">Accurate Garbage Collection Intrinsics</a>
5627 <div class="doc_text">
5629 <p>LLVM support for <a href="GarbageCollection.html">Accurate Garbage
5630 Collection</a> (GC) requires the implementation and generation of these
5631 intrinsics. These intrinsics allow identification of <a href="#int_gcroot">GC
5632 roots on the stack</a>, as well as garbage collector implementations that
5633 require <a href="#int_gcread">read</a> and <a href="#int_gcwrite">write</a>
5634 barriers. Front-ends for type-safe garbage collected languages should generate
5635 these intrinsics to make use of the LLVM garbage collectors. For more details,
5636 see <a href="GarbageCollection.html">Accurate Garbage Collection with
5639 <p>The garbage collection intrinsics only operate on objects in the generic
5640 address space (address space zero).</p>
5644 <!-- _______________________________________________________________________ -->
5645 <div class="doc_subsubsection">
5646 <a name="int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a>
5649 <div class="doc_text">
5653 declare void @llvm.gcroot(i8** %ptrloc, i8* %metadata)
5657 <p>The '<tt>llvm.gcroot</tt>' intrinsic declares the existence of a GC root to
5658 the code generator, and allows some metadata to be associated with it.</p>
5661 <p>The first argument specifies the address of a stack object that contains the
5662 root pointer. The second pointer (which must be either a constant or a
5663 global value address) contains the meta-data to be associated with the
5667 <p>At runtime, a call to this intrinsic stores a null pointer into the "ptrloc"
5668 location. At compile-time, the code generator generates information to allow
5669 the runtime to find the pointer at GC safe points. The '<tt>llvm.gcroot</tt>'
5670 intrinsic may only be used in a function which <a href="#gc">specifies a GC
5675 <!-- _______________________________________________________________________ -->
5676 <div class="doc_subsubsection">
5677 <a name="int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a>
5680 <div class="doc_text">
5684 declare i8* @llvm.gcread(i8* %ObjPtr, i8** %Ptr)
5688 <p>The '<tt>llvm.gcread</tt>' intrinsic identifies reads of references from heap
5689 locations, allowing garbage collector implementations that require read
5693 <p>The second argument is the address to read from, which should be an address
5694 allocated from the garbage collector. The first object is a pointer to the
5695 start of the referenced object, if needed by the language runtime (otherwise
5699 <p>The '<tt>llvm.gcread</tt>' intrinsic has the same semantics as a load
5700 instruction, but may be replaced with substantially more complex code by the
5701 garbage collector runtime, as needed. The '<tt>llvm.gcread</tt>' intrinsic
5702 may only be used in a function which <a href="#gc">specifies a GC
5707 <!-- _______________________________________________________________________ -->
5708 <div class="doc_subsubsection">
5709 <a name="int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a>
5712 <div class="doc_text">
5716 declare void @llvm.gcwrite(i8* %P1, i8* %Obj, i8** %P2)
5720 <p>The '<tt>llvm.gcwrite</tt>' intrinsic identifies writes of references to heap
5721 locations, allowing garbage collector implementations that require write
5722 barriers (such as generational or reference counting collectors).</p>
5725 <p>The first argument is the reference to store, the second is the start of the
5726 object to store it to, and the third is the address of the field of Obj to
5727 store to. If the runtime does not require a pointer to the object, Obj may
5731 <p>The '<tt>llvm.gcwrite</tt>' intrinsic has the same semantics as a store
5732 instruction, but may be replaced with substantially more complex code by the
5733 garbage collector runtime, as needed. The '<tt>llvm.gcwrite</tt>' intrinsic
5734 may only be used in a function which <a href="#gc">specifies a GC
5739 <!-- ======================================================================= -->
5740 <div class="doc_subsection">
5741 <a name="int_codegen">Code Generator Intrinsics</a>
5744 <div class="doc_text">
5746 <p>These intrinsics are provided by LLVM to expose special features that may
5747 only be implemented with code generator support.</p>
5751 <!-- _______________________________________________________________________ -->
5752 <div class="doc_subsubsection">
5753 <a name="int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a>
5756 <div class="doc_text">
5760 declare i8 *@llvm.returnaddress(i32 <level>)
5764 <p>The '<tt>llvm.returnaddress</tt>' intrinsic attempts to compute a
5765 target-specific value indicating the return address of the current function
5766 or one of its callers.</p>
5769 <p>The argument to this intrinsic indicates which function to return the address
5770 for. Zero indicates the calling function, one indicates its caller, etc.
5771 The argument is <b>required</b> to be a constant integer value.</p>
5774 <p>The '<tt>llvm.returnaddress</tt>' intrinsic either returns a pointer
5775 indicating the return address of the specified call frame, or zero if it
5776 cannot be identified. The value returned by this intrinsic is likely to be
5777 incorrect or 0 for arguments other than zero, so it should only be used for
5778 debugging purposes.</p>
5780 <p>Note that calling this intrinsic does not prevent function inlining or other
5781 aggressive transformations, so the value returned may not be that of the
5782 obvious source-language caller.</p>
5786 <!-- _______________________________________________________________________ -->
5787 <div class="doc_subsubsection">
5788 <a name="int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a>
5791 <div class="doc_text">
5795 declare i8* @llvm.frameaddress(i32 <level>)
5799 <p>The '<tt>llvm.frameaddress</tt>' intrinsic attempts to return the
5800 target-specific frame pointer value for the specified stack frame.</p>
5803 <p>The argument to this intrinsic indicates which function to return the frame
5804 pointer for. Zero indicates the calling function, one indicates its caller,
5805 etc. The argument is <b>required</b> to be a constant integer value.</p>
5808 <p>The '<tt>llvm.frameaddress</tt>' intrinsic either returns a pointer
5809 indicating the frame address of the specified call frame, or zero if it
5810 cannot be identified. The value returned by this intrinsic is likely to be
5811 incorrect or 0 for arguments other than zero, so it should only be used for
5812 debugging purposes.</p>
5814 <p>Note that calling this intrinsic does not prevent function inlining or other
5815 aggressive transformations, so the value returned may not be that of the
5816 obvious source-language caller.</p>
5820 <!-- _______________________________________________________________________ -->
5821 <div class="doc_subsubsection">
5822 <a name="int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a>
5825 <div class="doc_text">
5829 declare i8* @llvm.stacksave()
5833 <p>The '<tt>llvm.stacksave</tt>' intrinsic is used to remember the current state
5834 of the function stack, for use
5835 with <a href="#int_stackrestore"> <tt>llvm.stackrestore</tt></a>. This is
5836 useful for implementing language features like scoped automatic variable
5837 sized arrays in C99.</p>
5840 <p>This intrinsic returns a opaque pointer value that can be passed
5841 to <a href="#int_stackrestore"><tt>llvm.stackrestore</tt></a>. When
5842 an <tt>llvm.stackrestore</tt> intrinsic is executed with a value saved
5843 from <tt>llvm.stacksave</tt>, it effectively restores the state of the stack
5844 to the state it was in when the <tt>llvm.stacksave</tt> intrinsic executed.
5845 In practice, this pops any <a href="#i_alloca">alloca</a> blocks from the
5846 stack that were allocated after the <tt>llvm.stacksave</tt> was executed.</p>
5850 <!-- _______________________________________________________________________ -->
5851 <div class="doc_subsubsection">
5852 <a name="int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a>
5855 <div class="doc_text">
5859 declare void @llvm.stackrestore(i8* %ptr)
5863 <p>The '<tt>llvm.stackrestore</tt>' intrinsic is used to restore the state of
5864 the function stack to the state it was in when the
5865 corresponding <a href="#int_stacksave"><tt>llvm.stacksave</tt></a> intrinsic
5866 executed. This is useful for implementing language features like scoped
5867 automatic variable sized arrays in C99.</p>
5870 <p>See the description
5871 for <a href="#int_stacksave"><tt>llvm.stacksave</tt></a>.</p>
5875 <!-- _______________________________________________________________________ -->
5876 <div class="doc_subsubsection">
5877 <a name="int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a>
5880 <div class="doc_text">
5884 declare void @llvm.prefetch(i8* <address>, i32 <rw>, i32 <locality>)
5888 <p>The '<tt>llvm.prefetch</tt>' intrinsic is a hint to the code generator to
5889 insert a prefetch instruction if supported; otherwise, it is a noop.
5890 Prefetches have no effect on the behavior of the program but can change its
5891 performance characteristics.</p>
5894 <p><tt>address</tt> is the address to be prefetched, <tt>rw</tt> is the
5895 specifier determining if the fetch should be for a read (0) or write (1),
5896 and <tt>locality</tt> is a temporal locality specifier ranging from (0) - no
5897 locality, to (3) - extremely local keep in cache. The <tt>rw</tt>
5898 and <tt>locality</tt> arguments must be constant integers.</p>
5901 <p>This intrinsic does not modify the behavior of the program. In particular,
5902 prefetches cannot trap and do not produce a value. On targets that support
5903 this intrinsic, the prefetch can provide hints to the processor cache for
5904 better performance.</p>
5908 <!-- _______________________________________________________________________ -->
5909 <div class="doc_subsubsection">
5910 <a name="int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a>
5913 <div class="doc_text">
5917 declare void @llvm.pcmarker(i32 <id>)
5921 <p>The '<tt>llvm.pcmarker</tt>' intrinsic is a method to export a Program
5922 Counter (PC) in a region of code to simulators and other tools. The method
5923 is target specific, but it is expected that the marker will use exported
5924 symbols to transmit the PC of the marker. The marker makes no guarantees
5925 that it will remain with any specific instruction after optimizations. It is
5926 possible that the presence of a marker will inhibit optimizations. The
5927 intended use is to be inserted after optimizations to allow correlations of
5928 simulation runs.</p>
5931 <p><tt>id</tt> is a numerical id identifying the marker.</p>
5934 <p>This intrinsic does not modify the behavior of the program. Backends that do
5935 not support this intrinsic may ignore it.</p>
5939 <!-- _______________________________________________________________________ -->
5940 <div class="doc_subsubsection">
5941 <a name="int_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a>
5944 <div class="doc_text">
5948 declare i64 @llvm.readcyclecounter()
5952 <p>The '<tt>llvm.readcyclecounter</tt>' intrinsic provides access to the cycle
5953 counter register (or similar low latency, high accuracy clocks) on those
5954 targets that support it. On X86, it should map to RDTSC. On Alpha, it
5955 should map to RPCC. As the backing counters overflow quickly (on the order
5956 of 9 seconds on alpha), this should only be used for small timings.</p>
5959 <p>When directly supported, reading the cycle counter should not modify any
5960 memory. Implementations are allowed to either return a application specific
5961 value or a system wide value. On backends without support, this is lowered
5962 to a constant 0.</p>
5966 <!-- ======================================================================= -->
5967 <div class="doc_subsection">
5968 <a name="int_libc">Standard C Library Intrinsics</a>
5971 <div class="doc_text">
5973 <p>LLVM provides intrinsics for a few important standard C library functions.
5974 These intrinsics allow source-language front-ends to pass information about
5975 the alignment of the pointer arguments to the code generator, providing
5976 opportunity for more efficient code generation.</p>
5980 <!-- _______________________________________________________________________ -->
5981 <div class="doc_subsubsection">
5982 <a name="int_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a>
5985 <div class="doc_text">
5988 <p>This is an overloaded intrinsic. You can use <tt>llvm.memcpy</tt> on any
5989 integer bit width and for different address spaces. Not all targets support
5990 all bit widths however.</p>
5993 declare void @llvm.memcpy.p0i8.p0i8.i32(i8* <dest>, i8* <src>,
5994 i32 <len>, i32 <align>, i1 <isvolatile>)
5995 declare void @llvm.memcpy.p0i8.p0i8.i64(i8* <dest>, i8* <src>,
5996 i64 <len>, i32 <align>, i1 <isvolatile>)
6000 <p>The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the
6001 source location to the destination location.</p>
6003 <p>Note that, unlike the standard libc function, the <tt>llvm.memcpy.*</tt>
6004 intrinsics do not return a value, takes extra alignment/isvolatile arguments
6005 and the pointers can be in specified address spaces.</p>
6009 <p>The first argument is a pointer to the destination, the second is a pointer
6010 to the source. The third argument is an integer argument specifying the
6011 number of bytes to copy, the fourth argument is the alignment of the
6012 source and destination locations, and the fifth is a boolean indicating a
6013 volatile access.</p>
6015 <p>If the call to this intrinsic has an alignment value that is not 0 or 1,
6016 then the caller guarantees that both the source and destination pointers are
6017 aligned to that boundary.</p>
6019 <p>If the <tt>isvolatile</tt> parameter is <tt>true</tt>, the
6020 <tt>llvm.memcpy</tt> call is a <a href="#volatile">volatile operation</a>.
6021 The detailed access behavior is not very cleanly specified and it is unwise
6022 to depend on it.</p>
6026 <p>The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the
6027 source location to the destination location, which are not allowed to
6028 overlap. It copies "len" bytes of memory over. If the argument is known to
6029 be aligned to some boundary, this can be specified as the fourth argument,
6030 otherwise it should be set to 0 or 1.</p>
6034 <!-- _______________________________________________________________________ -->
6035 <div class="doc_subsubsection">
6036 <a name="int_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a>
6039 <div class="doc_text">
6042 <p>This is an overloaded intrinsic. You can use llvm.memmove on any integer bit
6043 width and for different address space. Not all targets support all bit
6047 declare void @llvm.memmove.p0i8.p0i8.i32(i8* <dest>, i8* <src>,
6048 i32 <len>, i32 <align>, i1 <isvolatile>)
6049 declare void @llvm.memmove.p0i8.p0i8.i64(i8* <dest>, i8* <src>,
6050 i64 <len>, i32 <align>, i1 <isvolatile>)
6054 <p>The '<tt>llvm.memmove.*</tt>' intrinsics move a block of memory from the
6055 source location to the destination location. It is similar to the
6056 '<tt>llvm.memcpy</tt>' intrinsic but allows the two memory locations to
6059 <p>Note that, unlike the standard libc function, the <tt>llvm.memmove.*</tt>
6060 intrinsics do not return a value, takes extra alignment/isvolatile arguments
6061 and the pointers can be in specified address spaces.</p>
6065 <p>The first argument is a pointer to the destination, the second is a pointer
6066 to the source. The third argument is an integer argument specifying the
6067 number of bytes to copy, the fourth argument is the alignment of the
6068 source and destination locations, and the fifth is a boolean indicating a
6069 volatile access.</p>
6071 <p>If the call to this intrinsic has an alignment value that is not 0 or 1,
6072 then the caller guarantees that the source and destination pointers are
6073 aligned to that boundary.</p>
6075 <p>If the <tt>isvolatile</tt> parameter is <tt>true</tt>, the
6076 <tt>llvm.memmove</tt> call is a <a href="#volatile">volatile operation</a>.
6077 The detailed access behavior is not very cleanly specified and it is unwise
6078 to depend on it.</p>
6082 <p>The '<tt>llvm.memmove.*</tt>' intrinsics copy a block of memory from the
6083 source location to the destination location, which may overlap. It copies
6084 "len" bytes of memory over. If the argument is known to be aligned to some
6085 boundary, this can be specified as the fourth argument, otherwise it should
6086 be set to 0 or 1.</p>
6090 <!-- _______________________________________________________________________ -->
6091 <div class="doc_subsubsection">
6092 <a name="int_memset">'<tt>llvm.memset.*</tt>' Intrinsics</a>
6095 <div class="doc_text">
6098 <p>This is an overloaded intrinsic. You can use llvm.memset on any integer bit
6099 width and for different address spaces. However, not all targets support all
6103 declare void @llvm.memset.p0i8.i32(i8* <dest>, i8 <val>,
6104 i32 <len>, i32 <align>, i1 <isvolatile>)
6105 declare void @llvm.memset.p0i8.i64(i8* <dest>, i8 <val>,
6106 i64 <len>, i32 <align>, i1 <isvolatile>)
6110 <p>The '<tt>llvm.memset.*</tt>' intrinsics fill a block of memory with a
6111 particular byte value.</p>
6113 <p>Note that, unlike the standard libc function, the <tt>llvm.memset</tt>
6114 intrinsic does not return a value and takes extra alignment/volatile
6115 arguments. Also, the destination can be in an arbitrary address space.</p>
6118 <p>The first argument is a pointer to the destination to fill, the second is the
6119 byte value with which to fill it, the third argument is an integer argument
6120 specifying the number of bytes to fill, and the fourth argument is the known
6121 alignment of the destination location.</p>
6123 <p>If the call to this intrinsic has an alignment value that is not 0 or 1,
6124 then the caller guarantees that the destination pointer is aligned to that
6127 <p>If the <tt>isvolatile</tt> parameter is <tt>true</tt>, the
6128 <tt>llvm.memset</tt> call is a <a href="#volatile">volatile operation</a>.
6129 The detailed access behavior is not very cleanly specified and it is unwise
6130 to depend on it.</p>
6133 <p>The '<tt>llvm.memset.*</tt>' intrinsics fill "len" bytes of memory starting
6134 at the destination location. If the argument is known to be aligned to some
6135 boundary, this can be specified as the fourth argument, otherwise it should
6136 be set to 0 or 1.</p>
6140 <!-- _______________________________________________________________________ -->
6141 <div class="doc_subsubsection">
6142 <a name="int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a>
6145 <div class="doc_text">
6148 <p>This is an overloaded intrinsic. You can use <tt>llvm.sqrt</tt> on any
6149 floating point or vector of floating point type. Not all targets support all
6153 declare float @llvm.sqrt.f32(float %Val)
6154 declare double @llvm.sqrt.f64(double %Val)
6155 declare x86_fp80 @llvm.sqrt.f80(x86_fp80 %Val)
6156 declare fp128 @llvm.sqrt.f128(fp128 %Val)
6157 declare ppc_fp128 @llvm.sqrt.ppcf128(ppc_fp128 %Val)
6161 <p>The '<tt>llvm.sqrt</tt>' intrinsics return the sqrt of the specified operand,
6162 returning the same value as the libm '<tt>sqrt</tt>' functions would.
6163 Unlike <tt>sqrt</tt> in libm, however, <tt>llvm.sqrt</tt> has undefined
6164 behavior for negative numbers other than -0.0 (which allows for better
6165 optimization, because there is no need to worry about errno being
6166 set). <tt>llvm.sqrt(-0.0)</tt> is defined to return -0.0 like IEEE sqrt.</p>
6169 <p>The argument and return value are floating point numbers of the same
6173 <p>This function returns the sqrt of the specified operand if it is a
6174 nonnegative floating point number.</p>
6178 <!-- _______________________________________________________________________ -->
6179 <div class="doc_subsubsection">
6180 <a name="int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a>
6183 <div class="doc_text">
6186 <p>This is an overloaded intrinsic. You can use <tt>llvm.powi</tt> on any
6187 floating point or vector of floating point type. Not all targets support all
6191 declare float @llvm.powi.f32(float %Val, i32 %power)
6192 declare double @llvm.powi.f64(double %Val, i32 %power)
6193 declare x86_fp80 @llvm.powi.f80(x86_fp80 %Val, i32 %power)
6194 declare fp128 @llvm.powi.f128(fp128 %Val, i32 %power)
6195 declare ppc_fp128 @llvm.powi.ppcf128(ppc_fp128 %Val, i32 %power)
6199 <p>The '<tt>llvm.powi.*</tt>' intrinsics return the first operand raised to the
6200 specified (positive or negative) power. The order of evaluation of
6201 multiplications is not defined. When a vector of floating point type is
6202 used, the second argument remains a scalar integer value.</p>
6205 <p>The second argument is an integer power, and the first is a value to raise to
6209 <p>This function returns the first value raised to the second power with an
6210 unspecified sequence of rounding operations.</p>
6214 <!-- _______________________________________________________________________ -->
6215 <div class="doc_subsubsection">
6216 <a name="int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a>
6219 <div class="doc_text">
6222 <p>This is an overloaded intrinsic. You can use <tt>llvm.sin</tt> on any
6223 floating point or vector of floating point type. Not all targets support all
6227 declare float @llvm.sin.f32(float %Val)
6228 declare double @llvm.sin.f64(double %Val)
6229 declare x86_fp80 @llvm.sin.f80(x86_fp80 %Val)
6230 declare fp128 @llvm.sin.f128(fp128 %Val)
6231 declare ppc_fp128 @llvm.sin.ppcf128(ppc_fp128 %Val)
6235 <p>The '<tt>llvm.sin.*</tt>' intrinsics return the sine of the operand.</p>
6238 <p>The argument and return value are floating point numbers of the same
6242 <p>This function returns the sine of the specified operand, returning the same
6243 values as the libm <tt>sin</tt> functions would, and handles error conditions
6244 in the same way.</p>
6248 <!-- _______________________________________________________________________ -->
6249 <div class="doc_subsubsection">
6250 <a name="int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a>
6253 <div class="doc_text">
6256 <p>This is an overloaded intrinsic. You can use <tt>llvm.cos</tt> on any
6257 floating point or vector of floating point type. Not all targets support all
6261 declare float @llvm.cos.f32(float %Val)
6262 declare double @llvm.cos.f64(double %Val)
6263 declare x86_fp80 @llvm.cos.f80(x86_fp80 %Val)
6264 declare fp128 @llvm.cos.f128(fp128 %Val)
6265 declare ppc_fp128 @llvm.cos.ppcf128(ppc_fp128 %Val)
6269 <p>The '<tt>llvm.cos.*</tt>' intrinsics return the cosine of the operand.</p>
6272 <p>The argument and return value are floating point numbers of the same
6276 <p>This function returns the cosine of the specified operand, returning the same
6277 values as the libm <tt>cos</tt> functions would, and handles error conditions
6278 in the same way.</p>
6282 <!-- _______________________________________________________________________ -->
6283 <div class="doc_subsubsection">
6284 <a name="int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a>
6287 <div class="doc_text">
6290 <p>This is an overloaded intrinsic. You can use <tt>llvm.pow</tt> on any
6291 floating point or vector of floating point type. Not all targets support all
6295 declare float @llvm.pow.f32(float %Val, float %Power)
6296 declare double @llvm.pow.f64(double %Val, double %Power)
6297 declare x86_fp80 @llvm.pow.f80(x86_fp80 %Val, x86_fp80 %Power)
6298 declare fp128 @llvm.pow.f128(fp128 %Val, fp128 %Power)
6299 declare ppc_fp128 @llvm.pow.ppcf128(ppc_fp128 %Val, ppc_fp128 Power)
6303 <p>The '<tt>llvm.pow.*</tt>' intrinsics return the first operand raised to the
6304 specified (positive or negative) power.</p>
6307 <p>The second argument is a floating point power, and the first is a value to
6308 raise to that power.</p>
6311 <p>This function returns the first value raised to the second power, returning
6312 the same values as the libm <tt>pow</tt> functions would, and handles error
6313 conditions in the same way.</p>
6317 <!-- ======================================================================= -->
6318 <div class="doc_subsection">
6319 <a name="int_manip">Bit Manipulation Intrinsics</a>
6322 <div class="doc_text">
6324 <p>LLVM provides intrinsics for a few important bit manipulation operations.
6325 These allow efficient code generation for some algorithms.</p>
6329 <!-- _______________________________________________________________________ -->
6330 <div class="doc_subsubsection">
6331 <a name="int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a>
6334 <div class="doc_text">
6337 <p>This is an overloaded intrinsic function. You can use bswap on any integer
6338 type that is an even number of bytes (i.e. BitWidth % 16 == 0).</p>
6341 declare i16 @llvm.bswap.i16(i16 <id>)
6342 declare i32 @llvm.bswap.i32(i32 <id>)
6343 declare i64 @llvm.bswap.i64(i64 <id>)
6347 <p>The '<tt>llvm.bswap</tt>' family of intrinsics is used to byte swap integer
6348 values with an even number of bytes (positive multiple of 16 bits). These
6349 are useful for performing operations on data that is not in the target's
6350 native byte order.</p>
6353 <p>The <tt>llvm.bswap.i16</tt> intrinsic returns an i16 value that has the high
6354 and low byte of the input i16 swapped. Similarly,
6355 the <tt>llvm.bswap.i32</tt> intrinsic returns an i32 value that has the four
6356 bytes of the input i32 swapped, so that if the input bytes are numbered 0, 1,
6357 2, 3 then the returned i32 will have its bytes in 3, 2, 1, 0 order.
6358 The <tt>llvm.bswap.i48</tt>, <tt>llvm.bswap.i64</tt> and other intrinsics
6359 extend this concept to additional even-byte lengths (6 bytes, 8 bytes and
6360 more, respectively).</p>
6364 <!-- _______________________________________________________________________ -->
6365 <div class="doc_subsubsection">
6366 <a name="int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic</a>
6369 <div class="doc_text">
6372 <p>This is an overloaded intrinsic. You can use llvm.ctpop on any integer bit
6373 width. Not all targets support all bit widths however.</p>
6376 declare i8 @llvm.ctpop.i8(i8 <src>)
6377 declare i16 @llvm.ctpop.i16(i16 <src>)
6378 declare i32 @llvm.ctpop.i32(i32 <src>)
6379 declare i64 @llvm.ctpop.i64(i64 <src>)
6380 declare i256 @llvm.ctpop.i256(i256 <src>)
6384 <p>The '<tt>llvm.ctpop</tt>' family of intrinsics counts the number of bits set
6388 <p>The only argument is the value to be counted. The argument may be of any
6389 integer type. The return type must match the argument type.</p>
6392 <p>The '<tt>llvm.ctpop</tt>' intrinsic counts the 1's in a variable.</p>
6396 <!-- _______________________________________________________________________ -->
6397 <div class="doc_subsubsection">
6398 <a name="int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic</a>
6401 <div class="doc_text">
6404 <p>This is an overloaded intrinsic. You can use <tt>llvm.ctlz</tt> on any
6405 integer bit width. Not all targets support all bit widths however.</p>
6408 declare i8 @llvm.ctlz.i8 (i8 <src>)
6409 declare i16 @llvm.ctlz.i16(i16 <src>)
6410 declare i32 @llvm.ctlz.i32(i32 <src>)
6411 declare i64 @llvm.ctlz.i64(i64 <src>)
6412 declare i256 @llvm.ctlz.i256(i256 <src>)
6416 <p>The '<tt>llvm.ctlz</tt>' family of intrinsic functions counts the number of
6417 leading zeros in a variable.</p>
6420 <p>The only argument is the value to be counted. The argument may be of any
6421 integer type. The return type must match the argument type.</p>
6424 <p>The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant)
6425 zeros in a variable. If the src == 0 then the result is the size in bits of
6426 the type of src. For example, <tt>llvm.ctlz(i32 2) = 30</tt>.</p>
6430 <!-- _______________________________________________________________________ -->
6431 <div class="doc_subsubsection">
6432 <a name="int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic</a>
6435 <div class="doc_text">
6438 <p>This is an overloaded intrinsic. You can use <tt>llvm.cttz</tt> on any
6439 integer bit width. Not all targets support all bit widths however.</p>
6442 declare i8 @llvm.cttz.i8 (i8 <src>)
6443 declare i16 @llvm.cttz.i16(i16 <src>)
6444 declare i32 @llvm.cttz.i32(i32 <src>)
6445 declare i64 @llvm.cttz.i64(i64 <src>)
6446 declare i256 @llvm.cttz.i256(i256 <src>)
6450 <p>The '<tt>llvm.cttz</tt>' family of intrinsic functions counts the number of
6454 <p>The only argument is the value to be counted. The argument may be of any
6455 integer type. The return type must match the argument type.</p>
6458 <p>The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant)
6459 zeros in a variable. If the src == 0 then the result is the size in bits of
6460 the type of src. For example, <tt>llvm.cttz(2) = 1</tt>.</p>
6464 <!-- ======================================================================= -->
6465 <div class="doc_subsection">
6466 <a name="int_overflow">Arithmetic with Overflow Intrinsics</a>
6469 <div class="doc_text">
6471 <p>LLVM provides intrinsics for some arithmetic with overflow operations.</p>
6475 <!-- _______________________________________________________________________ -->
6476 <div class="doc_subsubsection">
6477 <a name="int_sadd_overflow">'<tt>llvm.sadd.with.overflow.*</tt>' Intrinsics</a>
6480 <div class="doc_text">
6483 <p>This is an overloaded intrinsic. You can use <tt>llvm.sadd.with.overflow</tt>
6484 on any integer bit width.</p>
6487 declare {i16, i1} @llvm.sadd.with.overflow.i16(i16 %a, i16 %b)
6488 declare {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
6489 declare {i64, i1} @llvm.sadd.with.overflow.i64(i64 %a, i64 %b)
6493 <p>The '<tt>llvm.sadd.with.overflow</tt>' family of intrinsic functions perform
6494 a signed addition of the two arguments, and indicate whether an overflow
6495 occurred during the signed summation.</p>
6498 <p>The arguments (%a and %b) and the first element of the result structure may
6499 be of integer types of any bit width, but they must have the same bit
6500 width. The second element of the result structure must be of
6501 type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
6502 undergo signed addition.</p>
6505 <p>The '<tt>llvm.sadd.with.overflow</tt>' family of intrinsic functions perform
6506 a signed addition of the two variables. They return a structure — the
6507 first element of which is the signed summation, and the second element of
6508 which is a bit specifying if the signed summation resulted in an
6513 %res = call {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
6514 %sum = extractvalue {i32, i1} %res, 0
6515 %obit = extractvalue {i32, i1} %res, 1
6516 br i1 %obit, label %overflow, label %normal
6521 <!-- _______________________________________________________________________ -->
6522 <div class="doc_subsubsection">
6523 <a name="int_uadd_overflow">'<tt>llvm.uadd.with.overflow.*</tt>' Intrinsics</a>
6526 <div class="doc_text">
6529 <p>This is an overloaded intrinsic. You can use <tt>llvm.uadd.with.overflow</tt>
6530 on any integer bit width.</p>
6533 declare {i16, i1} @llvm.uadd.with.overflow.i16(i16 %a, i16 %b)
6534 declare {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
6535 declare {i64, i1} @llvm.uadd.with.overflow.i64(i64 %a, i64 %b)
6539 <p>The '<tt>llvm.uadd.with.overflow</tt>' family of intrinsic functions perform
6540 an unsigned addition of the two arguments, and indicate whether a carry
6541 occurred during the unsigned summation.</p>
6544 <p>The arguments (%a and %b) and the first element of the result structure may
6545 be of integer types of any bit width, but they must have the same bit
6546 width. The second element of the result structure must be of
6547 type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
6548 undergo unsigned addition.</p>
6551 <p>The '<tt>llvm.uadd.with.overflow</tt>' family of intrinsic functions perform
6552 an unsigned addition of the two arguments. They return a structure —
6553 the first element of which is the sum, and the second element of which is a
6554 bit specifying if the unsigned summation resulted in a carry.</p>
6558 %res = call {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
6559 %sum = extractvalue {i32, i1} %res, 0
6560 %obit = extractvalue {i32, i1} %res, 1
6561 br i1 %obit, label %carry, label %normal
6566 <!-- _______________________________________________________________________ -->
6567 <div class="doc_subsubsection">
6568 <a name="int_ssub_overflow">'<tt>llvm.ssub.with.overflow.*</tt>' Intrinsics</a>
6571 <div class="doc_text">
6574 <p>This is an overloaded intrinsic. You can use <tt>llvm.ssub.with.overflow</tt>
6575 on any integer bit width.</p>
6578 declare {i16, i1} @llvm.ssub.with.overflow.i16(i16 %a, i16 %b)
6579 declare {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b)
6580 declare {i64, i1} @llvm.ssub.with.overflow.i64(i64 %a, i64 %b)
6584 <p>The '<tt>llvm.ssub.with.overflow</tt>' family of intrinsic functions perform
6585 a signed subtraction of the two arguments, and indicate whether an overflow
6586 occurred during the signed subtraction.</p>
6589 <p>The arguments (%a and %b) and the first element of the result structure may
6590 be of integer types of any bit width, but they must have the same bit
6591 width. The second element of the result structure must be of
6592 type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
6593 undergo signed subtraction.</p>
6596 <p>The '<tt>llvm.ssub.with.overflow</tt>' family of intrinsic functions perform
6597 a signed subtraction of the two arguments. They return a structure —
6598 the first element of which is the subtraction, and the second element of
6599 which is a bit specifying if the signed subtraction resulted in an
6604 %res = call {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b)
6605 %sum = extractvalue {i32, i1} %res, 0
6606 %obit = extractvalue {i32, i1} %res, 1
6607 br i1 %obit, label %overflow, label %normal
6612 <!-- _______________________________________________________________________ -->
6613 <div class="doc_subsubsection">
6614 <a name="int_usub_overflow">'<tt>llvm.usub.with.overflow.*</tt>' Intrinsics</a>
6617 <div class="doc_text">
6620 <p>This is an overloaded intrinsic. You can use <tt>llvm.usub.with.overflow</tt>
6621 on any integer bit width.</p>
6624 declare {i16, i1} @llvm.usub.with.overflow.i16(i16 %a, i16 %b)
6625 declare {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b)
6626 declare {i64, i1} @llvm.usub.with.overflow.i64(i64 %a, i64 %b)
6630 <p>The '<tt>llvm.usub.with.overflow</tt>' family of intrinsic functions perform
6631 an unsigned subtraction of the two arguments, and indicate whether an
6632 overflow occurred during the unsigned subtraction.</p>
6635 <p>The arguments (%a and %b) and the first element of the result structure may
6636 be of integer types of any bit width, but they must have the same bit
6637 width. The second element of the result structure must be of
6638 type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
6639 undergo unsigned subtraction.</p>
6642 <p>The '<tt>llvm.usub.with.overflow</tt>' family of intrinsic functions perform
6643 an unsigned subtraction of the two arguments. They return a structure —
6644 the first element of which is the subtraction, and the second element of
6645 which is a bit specifying if the unsigned subtraction resulted in an
6650 %res = call {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b)
6651 %sum = extractvalue {i32, i1} %res, 0
6652 %obit = extractvalue {i32, i1} %res, 1
6653 br i1 %obit, label %overflow, label %normal
6658 <!-- _______________________________________________________________________ -->
6659 <div class="doc_subsubsection">
6660 <a name="int_smul_overflow">'<tt>llvm.smul.with.overflow.*</tt>' Intrinsics</a>
6663 <div class="doc_text">
6666 <p>This is an overloaded intrinsic. You can use <tt>llvm.smul.with.overflow</tt>
6667 on any integer bit width.</p>
6670 declare {i16, i1} @llvm.smul.with.overflow.i16(i16 %a, i16 %b)
6671 declare {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b)
6672 declare {i64, i1} @llvm.smul.with.overflow.i64(i64 %a, i64 %b)
6677 <p>The '<tt>llvm.smul.with.overflow</tt>' family of intrinsic functions perform
6678 a signed multiplication of the two arguments, and indicate whether an
6679 overflow occurred during the signed multiplication.</p>
6682 <p>The arguments (%a and %b) and the first element of the result structure may
6683 be of integer types of any bit width, but they must have the same bit
6684 width. The second element of the result structure must be of
6685 type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
6686 undergo signed multiplication.</p>
6689 <p>The '<tt>llvm.smul.with.overflow</tt>' family of intrinsic functions perform
6690 a signed multiplication of the two arguments. They return a structure —
6691 the first element of which is the multiplication, and the second element of
6692 which is a bit specifying if the signed multiplication resulted in an
6697 %res = call {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b)
6698 %sum = extractvalue {i32, i1} %res, 0
6699 %obit = extractvalue {i32, i1} %res, 1
6700 br i1 %obit, label %overflow, label %normal
6705 <!-- _______________________________________________________________________ -->
6706 <div class="doc_subsubsection">
6707 <a name="int_umul_overflow">'<tt>llvm.umul.with.overflow.*</tt>' Intrinsics</a>
6710 <div class="doc_text">
6713 <p>This is an overloaded intrinsic. You can use <tt>llvm.umul.with.overflow</tt>
6714 on any integer bit width.</p>
6717 declare {i16, i1} @llvm.umul.with.overflow.i16(i16 %a, i16 %b)
6718 declare {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b)
6719 declare {i64, i1} @llvm.umul.with.overflow.i64(i64 %a, i64 %b)
6723 <p>The '<tt>llvm.umul.with.overflow</tt>' family of intrinsic functions perform
6724 a unsigned multiplication of the two arguments, and indicate whether an
6725 overflow occurred during the unsigned multiplication.</p>
6728 <p>The arguments (%a and %b) and the first element of the result structure may
6729 be of integer types of any bit width, but they must have the same bit
6730 width. The second element of the result structure must be of
6731 type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
6732 undergo unsigned multiplication.</p>
6735 <p>The '<tt>llvm.umul.with.overflow</tt>' family of intrinsic functions perform
6736 an unsigned multiplication of the two arguments. They return a structure
6737 — the first element of which is the multiplication, and the second
6738 element of which is a bit specifying if the unsigned multiplication resulted
6743 %res = call {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b)
6744 %sum = extractvalue {i32, i1} %res, 0
6745 %obit = extractvalue {i32, i1} %res, 1
6746 br i1 %obit, label %overflow, label %normal
6751 <!-- ======================================================================= -->
6752 <div class="doc_subsection">
6753 <a name="int_fp16">Half Precision Floating Point Intrinsics</a>
6756 <div class="doc_text">
6758 <p>Half precision floating point is a storage-only format. This means that it is
6759 a dense encoding (in memory) but does not support computation in the
6762 <p>This means that code must first load the half-precision floating point
6763 value as an i16, then convert it to float with <a
6764 href="#int_convert_from_fp16"><tt>llvm.convert.from.fp16</tt></a>.
6765 Computation can then be performed on the float value (including extending to
6766 double etc). To store the value back to memory, it is first converted to
6767 float if needed, then converted to i16 with
6768 <a href="#int_convert_to_fp16"><tt>llvm.convert.to.fp16</tt></a>, then
6769 storing as an i16 value.</p>
6772 <!-- _______________________________________________________________________ -->
6773 <div class="doc_subsubsection">
6774 <a name="int_convert_to_fp16">'<tt>llvm.convert.to.fp16</tt>' Intrinsic</a>
6777 <div class="doc_text">
6781 declare i16 @llvm.convert.to.fp16(f32 %a)
6785 <p>The '<tt>llvm.convert.to.fp16</tt>' intrinsic function performs
6786 a conversion from single precision floating point format to half precision
6787 floating point format.</p>
6790 <p>The intrinsic function contains single argument - the value to be
6794 <p>The '<tt>llvm.convert.to.fp16</tt>' intrinsic function performs
6795 a conversion from single precision floating point format to half precision
6796 floating point format. The return value is an <tt>i16</tt> which
6797 contains the converted number.</p>
6801 %res = call i16 @llvm.convert.to.fp16(f32 %a)
6802 store i16 %res, i16* @x, align 2
6807 <!-- _______________________________________________________________________ -->
6808 <div class="doc_subsubsection">
6809 <a name="int_convert_from_fp16">'<tt>llvm.convert.from.fp16</tt>' Intrinsic</a>
6812 <div class="doc_text">
6816 declare f32 @llvm.convert.from.fp16(i16 %a)
6820 <p>The '<tt>llvm.convert.from.fp16</tt>' intrinsic function performs
6821 a conversion from half precision floating point format to single precision
6822 floating point format.</p>
6825 <p>The intrinsic function contains single argument - the value to be
6829 <p>The '<tt>llvm.convert.from.fp16</tt>' intrinsic function performs a
6830 conversion from half single precision floating point format to single
6831 precision floating point format. The input half-float value is represented by
6832 an <tt>i16</tt> value.</p>
6836 %a = load i16* @x, align 2
6837 %res = call f32 @llvm.convert.from.fp16(i16 %a)
6842 <!-- ======================================================================= -->
6843 <div class="doc_subsection">
6844 <a name="int_debugger">Debugger Intrinsics</a>
6847 <div class="doc_text">
6849 <p>The LLVM debugger intrinsics (which all start with <tt>llvm.dbg.</tt>
6850 prefix), are described in
6851 the <a href="SourceLevelDebugging.html#format_common_intrinsics">LLVM Source
6852 Level Debugging</a> document.</p>
6856 <!-- ======================================================================= -->
6857 <div class="doc_subsection">
6858 <a name="int_eh">Exception Handling Intrinsics</a>
6861 <div class="doc_text">
6863 <p>The LLVM exception handling intrinsics (which all start with
6864 <tt>llvm.eh.</tt> prefix), are described in
6865 the <a href="ExceptionHandling.html#format_common_intrinsics">LLVM Exception
6866 Handling</a> document.</p>
6870 <!-- ======================================================================= -->
6871 <div class="doc_subsection">
6872 <a name="int_trampoline">Trampoline Intrinsic</a>
6875 <div class="doc_text">
6877 <p>This intrinsic makes it possible to excise one parameter, marked with
6878 the <a href="#nest"><tt>nest</tt></a> attribute, from a function.
6879 The result is a callable
6880 function pointer lacking the nest parameter - the caller does not need to
6881 provide a value for it. Instead, the value to use is stored in advance in a
6882 "trampoline", a block of memory usually allocated on the stack, which also
6883 contains code to splice the nest value into the argument list. This is used
6884 to implement the GCC nested function address extension.</p>
6886 <p>For example, if the function is
6887 <tt>i32 f(i8* nest %c, i32 %x, i32 %y)</tt> then the resulting function
6888 pointer has signature <tt>i32 (i32, i32)*</tt>. It can be created as
6891 <pre class="doc_code">
6892 %tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86
6893 %tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0
6894 %p = call i8* @llvm.init.trampoline(i8* %tramp1, i8* bitcast (i32 (i8* nest , i32, i32)* @f to i8*), i8* %nval)
6895 %fp = bitcast i8* %p to i32 (i32, i32)*
6898 <p>The call <tt>%val = call i32 %fp(i32 %x, i32 %y)</tt> is then equivalent
6899 to <tt>%val = call i32 %f(i8* %nval, i32 %x, i32 %y)</tt>.</p>
6903 <!-- _______________________________________________________________________ -->
6904 <div class="doc_subsubsection">
6905 <a name="int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a>
6908 <div class="doc_text">
6912 declare i8* @llvm.init.trampoline(i8* <tramp>, i8* <func>, i8* <nval>)
6916 <p>This fills the memory pointed to by <tt>tramp</tt> with code and returns a
6917 function pointer suitable for executing it.</p>
6920 <p>The <tt>llvm.init.trampoline</tt> intrinsic takes three arguments, all
6921 pointers. The <tt>tramp</tt> argument must point to a sufficiently large and
6922 sufficiently aligned block of memory; this memory is written to by the
6923 intrinsic. Note that the size and the alignment are target-specific - LLVM
6924 currently provides no portable way of determining them, so a front-end that
6925 generates this intrinsic needs to have some target-specific knowledge.
6926 The <tt>func</tt> argument must hold a function bitcast to
6927 an <tt>i8*</tt>.</p>
6930 <p>The block of memory pointed to by <tt>tramp</tt> is filled with target
6931 dependent code, turning it into a function. A pointer to this function is
6932 returned, but needs to be bitcast to an <a href="#int_trampoline">appropriate
6933 function pointer type</a> before being called. The new function's signature
6934 is the same as that of <tt>func</tt> with any arguments marked with
6935 the <tt>nest</tt> attribute removed. At most one such <tt>nest</tt> argument
6936 is allowed, and it must be of pointer type. Calling the new function is
6937 equivalent to calling <tt>func</tt> with the same argument list, but
6938 with <tt>nval</tt> used for the missing <tt>nest</tt> argument. If, after
6939 calling <tt>llvm.init.trampoline</tt>, the memory pointed to
6940 by <tt>tramp</tt> is modified, then the effect of any later call to the
6941 returned function pointer is undefined.</p>
6945 <!-- ======================================================================= -->
6946 <div class="doc_subsection">
6947 <a name="int_atomics">Atomic Operations and Synchronization Intrinsics</a>
6950 <div class="doc_text">
6952 <p>These intrinsic functions expand the "universal IR" of LLVM to represent
6953 hardware constructs for atomic operations and memory synchronization. This
6954 provides an interface to the hardware, not an interface to the programmer. It
6955 is aimed at a low enough level to allow any programming models or APIs
6956 (Application Programming Interfaces) which need atomic behaviors to map
6957 cleanly onto it. It is also modeled primarily on hardware behavior. Just as
6958 hardware provides a "universal IR" for source languages, it also provides a
6959 starting point for developing a "universal" atomic operation and
6960 synchronization IR.</p>
6962 <p>These do <em>not</em> form an API such as high-level threading libraries,
6963 software transaction memory systems, atomic primitives, and intrinsic
6964 functions as found in BSD, GNU libc, atomic_ops, APR, and other system and
6965 application libraries. The hardware interface provided by LLVM should allow
6966 a clean implementation of all of these APIs and parallel programming models.
6967 No one model or paradigm should be selected above others unless the hardware
6968 itself ubiquitously does so.</p>
6972 <!-- _______________________________________________________________________ -->
6973 <div class="doc_subsubsection">
6974 <a name="int_memory_barrier">'<tt>llvm.memory.barrier</tt>' Intrinsic</a>
6976 <div class="doc_text">
6979 declare void @llvm.memory.barrier(i1 <ll>, i1 <ls>, i1 <sl>, i1 <ss>, i1 <device>)
6983 <p>The <tt>llvm.memory.barrier</tt> intrinsic guarantees ordering between
6984 specific pairs of memory access types.</p>
6987 <p>The <tt>llvm.memory.barrier</tt> intrinsic requires five boolean arguments.
6988 The first four arguments enables a specific barrier as listed below. The
6989 fifth argument specifies that the barrier applies to io or device or uncached
6993 <li><tt>ll</tt>: load-load barrier</li>
6994 <li><tt>ls</tt>: load-store barrier</li>
6995 <li><tt>sl</tt>: store-load barrier</li>
6996 <li><tt>ss</tt>: store-store barrier</li>
6997 <li><tt>device</tt>: barrier applies to device and uncached memory also.</li>
7001 <p>This intrinsic causes the system to enforce some ordering constraints upon
7002 the loads and stores of the program. This barrier does not
7003 indicate <em>when</em> any events will occur, it only enforces
7004 an <em>order</em> in which they occur. For any of the specified pairs of load
7005 and store operations (f.ex. load-load, or store-load), all of the first
7006 operations preceding the barrier will complete before any of the second
7007 operations succeeding the barrier begin. Specifically the semantics for each
7008 pairing is as follows:</p>
7011 <li><tt>ll</tt>: All loads before the barrier must complete before any load
7012 after the barrier begins.</li>
7013 <li><tt>ls</tt>: All loads before the barrier must complete before any
7014 store after the barrier begins.</li>
7015 <li><tt>ss</tt>: All stores before the barrier must complete before any
7016 store after the barrier begins.</li>
7017 <li><tt>sl</tt>: All stores before the barrier must complete before any
7018 load after the barrier begins.</li>
7021 <p>These semantics are applied with a logical "and" behavior when more than one
7022 is enabled in a single memory barrier intrinsic.</p>
7024 <p>Backends may implement stronger barriers than those requested when they do
7025 not support as fine grained a barrier as requested. Some architectures do
7026 not need all types of barriers and on such architectures, these become
7031 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7032 %ptr = bitcast i8* %mallocP to i32*
7035 %result1 = load i32* %ptr <i>; yields {i32}:result1 = 4</i>
7036 call void @llvm.memory.barrier(i1 false, i1 true, i1 false, i1 false)
7037 <i>; guarantee the above finishes</i>
7038 store i32 8, %ptr <i>; before this begins</i>
7043 <!-- _______________________________________________________________________ -->
7044 <div class="doc_subsubsection">
7045 <a name="int_atomic_cmp_swap">'<tt>llvm.atomic.cmp.swap.*</tt>' Intrinsic</a>
7048 <div class="doc_text">
7051 <p>This is an overloaded intrinsic. You can use <tt>llvm.atomic.cmp.swap</tt> on
7052 any integer bit width and for different address spaces. Not all targets
7053 support all bit widths however.</p>
7056 declare i8 @llvm.atomic.cmp.swap.i8.p0i8(i8* <ptr>, i8 <cmp>, i8 <val>)
7057 declare i16 @llvm.atomic.cmp.swap.i16.p0i16(i16* <ptr>, i16 <cmp>, i16 <val>)
7058 declare i32 @llvm.atomic.cmp.swap.i32.p0i32(i32* <ptr>, i32 <cmp>, i32 <val>)
7059 declare i64 @llvm.atomic.cmp.swap.i64.p0i64(i64* <ptr>, i64 <cmp>, i64 <val>)
7063 <p>This loads a value in memory and compares it to a given value. If they are
7064 equal, it stores a new value into the memory.</p>
7067 <p>The <tt>llvm.atomic.cmp.swap</tt> intrinsic takes three arguments. The result
7068 as well as both <tt>cmp</tt> and <tt>val</tt> must be integer values with the
7069 same bit width. The <tt>ptr</tt> argument must be a pointer to a value of
7070 this integer type. While any bit width integer may be used, targets may only
7071 lower representations they support in hardware.</p>
7074 <p>This entire intrinsic must be executed atomically. It first loads the value
7075 in memory pointed to by <tt>ptr</tt> and compares it with the
7076 value <tt>cmp</tt>. If they are equal, <tt>val</tt> is stored into the
7077 memory. The loaded value is yielded in all cases. This provides the
7078 equivalent of an atomic compare-and-swap operation within the SSA
7083 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7084 %ptr = bitcast i8* %mallocP to i32*
7087 %val1 = add i32 4, 4
7088 %result1 = call i32 @llvm.atomic.cmp.swap.i32.p0i32(i32* %ptr, i32 4, %val1)
7089 <i>; yields {i32}:result1 = 4</i>
7090 %stored1 = icmp eq i32 %result1, 4 <i>; yields {i1}:stored1 = true</i>
7091 %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 8</i>
7093 %val2 = add i32 1, 1
7094 %result2 = call i32 @llvm.atomic.cmp.swap.i32.p0i32(i32* %ptr, i32 5, %val2)
7095 <i>; yields {i32}:result2 = 8</i>
7096 %stored2 = icmp eq i32 %result2, 5 <i>; yields {i1}:stored2 = false</i>
7098 %memval2 = load i32* %ptr <i>; yields {i32}:memval2 = 8</i>
7103 <!-- _______________________________________________________________________ -->
7104 <div class="doc_subsubsection">
7105 <a name="int_atomic_swap">'<tt>llvm.atomic.swap.*</tt>' Intrinsic</a>
7107 <div class="doc_text">
7110 <p>This is an overloaded intrinsic. You can use <tt>llvm.atomic.swap</tt> on any
7111 integer bit width. Not all targets support all bit widths however.</p>
7114 declare i8 @llvm.atomic.swap.i8.p0i8(i8* <ptr>, i8 <val>)
7115 declare i16 @llvm.atomic.swap.i16.p0i16(i16* <ptr>, i16 <val>)
7116 declare i32 @llvm.atomic.swap.i32.p0i32(i32* <ptr>, i32 <val>)
7117 declare i64 @llvm.atomic.swap.i64.p0i64(i64* <ptr>, i64 <val>)
7121 <p>This intrinsic loads the value stored in memory at <tt>ptr</tt> and yields
7122 the value from memory. It then stores the value in <tt>val</tt> in the memory
7123 at <tt>ptr</tt>.</p>
7126 <p>The <tt>llvm.atomic.swap</tt> intrinsic takes two arguments. Both
7127 the <tt>val</tt> argument and the result must be integers of the same bit
7128 width. The first argument, <tt>ptr</tt>, must be a pointer to a value of this
7129 integer type. The targets may only lower integer representations they
7133 <p>This intrinsic loads the value pointed to by <tt>ptr</tt>, yields it, and
7134 stores <tt>val</tt> back into <tt>ptr</tt> atomically. This provides the
7135 equivalent of an atomic swap operation within the SSA framework.</p>
7139 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7140 %ptr = bitcast i8* %mallocP to i32*
7143 %val1 = add i32 4, 4
7144 %result1 = call i32 @llvm.atomic.swap.i32.p0i32(i32* %ptr, i32 %val1)
7145 <i>; yields {i32}:result1 = 4</i>
7146 %stored1 = icmp eq i32 %result1, 4 <i>; yields {i1}:stored1 = true</i>
7147 %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 8</i>
7149 %val2 = add i32 1, 1
7150 %result2 = call i32 @llvm.atomic.swap.i32.p0i32(i32* %ptr, i32 %val2)
7151 <i>; yields {i32}:result2 = 8</i>
7153 %stored2 = icmp eq i32 %result2, 8 <i>; yields {i1}:stored2 = true</i>
7154 %memval2 = load i32* %ptr <i>; yields {i32}:memval2 = 2</i>
7159 <!-- _______________________________________________________________________ -->
7160 <div class="doc_subsubsection">
7161 <a name="int_atomic_load_add">'<tt>llvm.atomic.load.add.*</tt>' Intrinsic</a>
7165 <div class="doc_text">
7168 <p>This is an overloaded intrinsic. You can use <tt>llvm.atomic.load.add</tt> on
7169 any integer bit width. Not all targets support all bit widths however.</p>
7172 declare i8 @llvm.atomic.load.add.i8.p0i8(i8* <ptr>, i8 <delta>)
7173 declare i16 @llvm.atomic.load.add.i16.p0i16(i16* <ptr>, i16 <delta>)
7174 declare i32 @llvm.atomic.load.add.i32.p0i32(i32* <ptr>, i32 <delta>)
7175 declare i64 @llvm.atomic.load.add.i64.p0i64(i64* <ptr>, i64 <delta>)
7179 <p>This intrinsic adds <tt>delta</tt> to the value stored in memory
7180 at <tt>ptr</tt>. It yields the original value at <tt>ptr</tt>.</p>
7183 <p>The intrinsic takes two arguments, the first a pointer to an integer value
7184 and the second an integer value. The result is also an integer value. These
7185 integer types can have any bit width, but they must all have the same bit
7186 width. The targets may only lower integer representations they support.</p>
7189 <p>This intrinsic does a series of operations atomically. It first loads the
7190 value stored at <tt>ptr</tt>. It then adds <tt>delta</tt>, stores the result
7191 to <tt>ptr</tt>. It yields the original value stored at <tt>ptr</tt>.</p>
7195 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7196 %ptr = bitcast i8* %mallocP to i32*
7198 %result1 = call i32 @llvm.atomic.load.add.i32.p0i32(i32* %ptr, i32 4)
7199 <i>; yields {i32}:result1 = 4</i>
7200 %result2 = call i32 @llvm.atomic.load.add.i32.p0i32(i32* %ptr, i32 2)
7201 <i>; yields {i32}:result2 = 8</i>
7202 %result3 = call i32 @llvm.atomic.load.add.i32.p0i32(i32* %ptr, i32 5)
7203 <i>; yields {i32}:result3 = 10</i>
7204 %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 15</i>
7209 <!-- _______________________________________________________________________ -->
7210 <div class="doc_subsubsection">
7211 <a name="int_atomic_load_sub">'<tt>llvm.atomic.load.sub.*</tt>' Intrinsic</a>
7215 <div class="doc_text">
7218 <p>This is an overloaded intrinsic. You can use <tt>llvm.atomic.load.sub</tt> on
7219 any integer bit width and for different address spaces. Not all targets
7220 support all bit widths however.</p>
7223 declare i8 @llvm.atomic.load.sub.i8.p0i32(i8* <ptr>, i8 <delta>)
7224 declare i16 @llvm.atomic.load.sub.i16.p0i32(i16* <ptr>, i16 <delta>)
7225 declare i32 @llvm.atomic.load.sub.i32.p0i32(i32* <ptr>, i32 <delta>)
7226 declare i64 @llvm.atomic.load.sub.i64.p0i32(i64* <ptr>, i64 <delta>)
7230 <p>This intrinsic subtracts <tt>delta</tt> to the value stored in memory at
7231 <tt>ptr</tt>. It yields the original value at <tt>ptr</tt>.</p>
7234 <p>The intrinsic takes two arguments, the first a pointer to an integer value
7235 and the second an integer value. The result is also an integer value. These
7236 integer types can have any bit width, but they must all have the same bit
7237 width. The targets may only lower integer representations they support.</p>
7240 <p>This intrinsic does a series of operations atomically. It first loads the
7241 value stored at <tt>ptr</tt>. It then subtracts <tt>delta</tt>, stores the
7242 result to <tt>ptr</tt>. It yields the original value stored
7243 at <tt>ptr</tt>.</p>
7247 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7248 %ptr = bitcast i8* %mallocP to i32*
7250 %result1 = call i32 @llvm.atomic.load.sub.i32.p0i32(i32* %ptr, i32 4)
7251 <i>; yields {i32}:result1 = 8</i>
7252 %result2 = call i32 @llvm.atomic.load.sub.i32.p0i32(i32* %ptr, i32 2)
7253 <i>; yields {i32}:result2 = 4</i>
7254 %result3 = call i32 @llvm.atomic.load.sub.i32.p0i32(i32* %ptr, i32 5)
7255 <i>; yields {i32}:result3 = 2</i>
7256 %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = -3</i>
7261 <!-- _______________________________________________________________________ -->
7262 <div class="doc_subsubsection">
7263 <a name="int_atomic_load_and">'<tt>llvm.atomic.load.and.*</tt>' Intrinsic</a><br>
7264 <a name="int_atomic_load_nand">'<tt>llvm.atomic.load.nand.*</tt>' Intrinsic</a><br>
7265 <a name="int_atomic_load_or">'<tt>llvm.atomic.load.or.*</tt>' Intrinsic</a><br>
7266 <a name="int_atomic_load_xor">'<tt>llvm.atomic.load.xor.*</tt>' Intrinsic</a><br>
7269 <div class="doc_text">
7272 <p>These are overloaded intrinsics. You can
7273 use <tt>llvm.atomic.load_and</tt>, <tt>llvm.atomic.load_nand</tt>,
7274 <tt>llvm.atomic.load_or</tt>, and <tt>llvm.atomic.load_xor</tt> on any integer
7275 bit width and for different address spaces. Not all targets support all bit
7279 declare i8 @llvm.atomic.load.and.i8.p0i8(i8* <ptr>, i8 <delta>)
7280 declare i16 @llvm.atomic.load.and.i16.p0i16(i16* <ptr>, i16 <delta>)
7281 declare i32 @llvm.atomic.load.and.i32.p0i32(i32* <ptr>, i32 <delta>)
7282 declare i64 @llvm.atomic.load.and.i64.p0i64(i64* <ptr>, i64 <delta>)
7286 declare i8 @llvm.atomic.load.or.i8.p0i8(i8* <ptr>, i8 <delta>)
7287 declare i16 @llvm.atomic.load.or.i16.p0i16(i16* <ptr>, i16 <delta>)
7288 declare i32 @llvm.atomic.load.or.i32.p0i32(i32* <ptr>, i32 <delta>)
7289 declare i64 @llvm.atomic.load.or.i64.p0i64(i64* <ptr>, i64 <delta>)
7293 declare i8 @llvm.atomic.load.nand.i8.p0i32(i8* <ptr>, i8 <delta>)
7294 declare i16 @llvm.atomic.load.nand.i16.p0i32(i16* <ptr>, i16 <delta>)
7295 declare i32 @llvm.atomic.load.nand.i32.p0i32(i32* <ptr>, i32 <delta>)
7296 declare i64 @llvm.atomic.load.nand.i64.p0i32(i64* <ptr>, i64 <delta>)
7300 declare i8 @llvm.atomic.load.xor.i8.p0i32(i8* <ptr>, i8 <delta>)
7301 declare i16 @llvm.atomic.load.xor.i16.p0i32(i16* <ptr>, i16 <delta>)
7302 declare i32 @llvm.atomic.load.xor.i32.p0i32(i32* <ptr>, i32 <delta>)
7303 declare i64 @llvm.atomic.load.xor.i64.p0i32(i64* <ptr>, i64 <delta>)
7307 <p>These intrinsics bitwise the operation (and, nand, or, xor) <tt>delta</tt> to
7308 the value stored in memory at <tt>ptr</tt>. It yields the original value
7309 at <tt>ptr</tt>.</p>
7312 <p>These intrinsics take two arguments, the first a pointer to an integer value
7313 and the second an integer value. The result is also an integer value. These
7314 integer types can have any bit width, but they must all have the same bit
7315 width. The targets may only lower integer representations they support.</p>
7318 <p>These intrinsics does a series of operations atomically. They first load the
7319 value stored at <tt>ptr</tt>. They then do the bitwise
7320 operation <tt>delta</tt>, store the result to <tt>ptr</tt>. They yield the
7321 original value stored at <tt>ptr</tt>.</p>
7325 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7326 %ptr = bitcast i8* %mallocP to i32*
7327 store i32 0x0F0F, %ptr
7328 %result0 = call i32 @llvm.atomic.load.nand.i32.p0i32(i32* %ptr, i32 0xFF)
7329 <i>; yields {i32}:result0 = 0x0F0F</i>
7330 %result1 = call i32 @llvm.atomic.load.and.i32.p0i32(i32* %ptr, i32 0xFF)
7331 <i>; yields {i32}:result1 = 0xFFFFFFF0</i>
7332 %result2 = call i32 @llvm.atomic.load.or.i32.p0i32(i32* %ptr, i32 0F)
7333 <i>; yields {i32}:result2 = 0xF0</i>
7334 %result3 = call i32 @llvm.atomic.load.xor.i32.p0i32(i32* %ptr, i32 0F)
7335 <i>; yields {i32}:result3 = FF</i>
7336 %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = F0</i>
7341 <!-- _______________________________________________________________________ -->
7342 <div class="doc_subsubsection">
7343 <a name="int_atomic_load_max">'<tt>llvm.atomic.load.max.*</tt>' Intrinsic</a><br>
7344 <a name="int_atomic_load_min">'<tt>llvm.atomic.load.min.*</tt>' Intrinsic</a><br>
7345 <a name="int_atomic_load_umax">'<tt>llvm.atomic.load.umax.*</tt>' Intrinsic</a><br>
7346 <a name="int_atomic_load_umin">'<tt>llvm.atomic.load.umin.*</tt>' Intrinsic</a><br>
7349 <div class="doc_text">
7352 <p>These are overloaded intrinsics. You can use <tt>llvm.atomic.load_max</tt>,
7353 <tt>llvm.atomic.load_min</tt>, <tt>llvm.atomic.load_umax</tt>, and
7354 <tt>llvm.atomic.load_umin</tt> on any integer bit width and for different
7355 address spaces. Not all targets support all bit widths however.</p>
7358 declare i8 @llvm.atomic.load.max.i8.p0i8(i8* <ptr>, i8 <delta>)
7359 declare i16 @llvm.atomic.load.max.i16.p0i16(i16* <ptr>, i16 <delta>)
7360 declare i32 @llvm.atomic.load.max.i32.p0i32(i32* <ptr>, i32 <delta>)
7361 declare i64 @llvm.atomic.load.max.i64.p0i64(i64* <ptr>, i64 <delta>)
7365 declare i8 @llvm.atomic.load.min.i8.p0i8(i8* <ptr>, i8 <delta>)
7366 declare i16 @llvm.atomic.load.min.i16.p0i16(i16* <ptr>, i16 <delta>)
7367 declare i32 @llvm.atomic.load.min.i32.p0i32(i32* <ptr>, i32 <delta>)
7368 declare i64 @llvm.atomic.load.min.i64.p0i64(i64* <ptr>, i64 <delta>)
7372 declare i8 @llvm.atomic.load.umax.i8.p0i8(i8* <ptr>, i8 <delta>)
7373 declare i16 @llvm.atomic.load.umax.i16.p0i16(i16* <ptr>, i16 <delta>)
7374 declare i32 @llvm.atomic.load.umax.i32.p0i32(i32* <ptr>, i32 <delta>)
7375 declare i64 @llvm.atomic.load.umax.i64.p0i64(i64* <ptr>, i64 <delta>)
7379 declare i8 @llvm.atomic.load.umin.i8.p0i8(i8* <ptr>, i8 <delta>)
7380 declare i16 @llvm.atomic.load.umin.i16.p0i16(i16* <ptr>, i16 <delta>)
7381 declare i32 @llvm.atomic.load.umin.i32.p0i32(i32* <ptr>, i32 <delta>)
7382 declare i64 @llvm.atomic.load.umin.i64.p0i64(i64* <ptr>, i64 <delta>)
7386 <p>These intrinsics takes the signed or unsigned minimum or maximum of
7387 <tt>delta</tt> and the value stored in memory at <tt>ptr</tt>. It yields the
7388 original value at <tt>ptr</tt>.</p>
7391 <p>These intrinsics take two arguments, the first a pointer to an integer value
7392 and the second an integer value. The result is also an integer value. These
7393 integer types can have any bit width, but they must all have the same bit
7394 width. The targets may only lower integer representations they support.</p>
7397 <p>These intrinsics does a series of operations atomically. They first load the
7398 value stored at <tt>ptr</tt>. They then do the signed or unsigned min or
7399 max <tt>delta</tt> and the value, store the result to <tt>ptr</tt>. They
7400 yield the original value stored at <tt>ptr</tt>.</p>
7404 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7405 %ptr = bitcast i8* %mallocP to i32*
7407 %result0 = call i32 @llvm.atomic.load.min.i32.p0i32(i32* %ptr, i32 -2)
7408 <i>; yields {i32}:result0 = 7</i>
7409 %result1 = call i32 @llvm.atomic.load.max.i32.p0i32(i32* %ptr, i32 8)
7410 <i>; yields {i32}:result1 = -2</i>
7411 %result2 = call i32 @llvm.atomic.load.umin.i32.p0i32(i32* %ptr, i32 10)
7412 <i>; yields {i32}:result2 = 8</i>
7413 %result3 = call i32 @llvm.atomic.load.umax.i32.p0i32(i32* %ptr, i32 30)
7414 <i>; yields {i32}:result3 = 8</i>
7415 %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 30</i>
7421 <!-- ======================================================================= -->
7422 <div class="doc_subsection">
7423 <a name="int_memorymarkers">Memory Use Markers</a>
7426 <div class="doc_text">
7428 <p>This class of intrinsics exists to information about the lifetime of memory
7429 objects and ranges where variables are immutable.</p>
7433 <!-- _______________________________________________________________________ -->
7434 <div class="doc_subsubsection">
7435 <a name="int_lifetime_start">'<tt>llvm.lifetime.start</tt>' Intrinsic</a>
7438 <div class="doc_text">
7442 declare void @llvm.lifetime.start(i64 <size>, i8* nocapture <ptr>)
7446 <p>The '<tt>llvm.lifetime.start</tt>' intrinsic specifies the start of a memory
7447 object's lifetime.</p>
7450 <p>The first argument is a constant integer representing the size of the
7451 object, or -1 if it is variable sized. The second argument is a pointer to
7455 <p>This intrinsic indicates that before this point in the code, the value of the
7456 memory pointed to by <tt>ptr</tt> is dead. This means that it is known to
7457 never be used and has an undefined value. A load from the pointer that
7458 precedes this intrinsic can be replaced with
7459 <tt>'<a href="#undefvalues">undef</a>'</tt>.</p>
7463 <!-- _______________________________________________________________________ -->
7464 <div class="doc_subsubsection">
7465 <a name="int_lifetime_end">'<tt>llvm.lifetime.end</tt>' Intrinsic</a>
7468 <div class="doc_text">
7472 declare void @llvm.lifetime.end(i64 <size>, i8* nocapture <ptr>)
7476 <p>The '<tt>llvm.lifetime.end</tt>' intrinsic specifies the end of a memory
7477 object's lifetime.</p>
7480 <p>The first argument is a constant integer representing the size of the
7481 object, or -1 if it is variable sized. The second argument is a pointer to
7485 <p>This intrinsic indicates that after this point in the code, the value of the
7486 memory pointed to by <tt>ptr</tt> is dead. This means that it is known to
7487 never be used and has an undefined value. Any stores into the memory object
7488 following this intrinsic may be removed as dead.
7492 <!-- _______________________________________________________________________ -->
7493 <div class="doc_subsubsection">
7494 <a name="int_invariant_start">'<tt>llvm.invariant.start</tt>' Intrinsic</a>
7497 <div class="doc_text">
7501 declare {}* @llvm.invariant.start(i64 <size>, i8* nocapture <ptr>) readonly
7505 <p>The '<tt>llvm.invariant.start</tt>' intrinsic specifies that the contents of
7506 a memory object will not change.</p>
7509 <p>The first argument is a constant integer representing the size of the
7510 object, or -1 if it is variable sized. The second argument is a pointer to
7514 <p>This intrinsic indicates that until an <tt>llvm.invariant.end</tt> that uses
7515 the return value, the referenced memory location is constant and
7520 <!-- _______________________________________________________________________ -->
7521 <div class="doc_subsubsection">
7522 <a name="int_invariant_end">'<tt>llvm.invariant.end</tt>' Intrinsic</a>
7525 <div class="doc_text">
7529 declare void @llvm.invariant.end({}* <start>, i64 <size>, i8* nocapture <ptr>)
7533 <p>The '<tt>llvm.invariant.end</tt>' intrinsic specifies that the contents of
7534 a memory object are mutable.</p>
7537 <p>The first argument is the matching <tt>llvm.invariant.start</tt> intrinsic.
7538 The second argument is a constant integer representing the size of the
7539 object, or -1 if it is variable sized and the third argument is a pointer
7543 <p>This intrinsic indicates that the memory is mutable again.</p>
7547 <!-- ======================================================================= -->
7548 <div class="doc_subsection">
7549 <a name="int_general">General Intrinsics</a>
7552 <div class="doc_text">
7554 <p>This class of intrinsics is designed to be generic and has no specific
7559 <!-- _______________________________________________________________________ -->
7560 <div class="doc_subsubsection">
7561 <a name="int_var_annotation">'<tt>llvm.var.annotation</tt>' Intrinsic</a>
7564 <div class="doc_text">
7568 declare void @llvm.var.annotation(i8* <val>, i8* <str>, i8* <str>, i32 <int>)
7572 <p>The '<tt>llvm.var.annotation</tt>' intrinsic.</p>
7575 <p>The first argument is a pointer to a value, the second is a pointer to a
7576 global string, the third is a pointer to a global string which is the source
7577 file name, and the last argument is the line number.</p>
7580 <p>This intrinsic allows annotation of local variables with arbitrary strings.
7581 This can be useful for special purpose optimizations that want to look for
7582 these annotations. These have no other defined use, they are ignored by code
7583 generation and optimization.</p>
7587 <!-- _______________________________________________________________________ -->
7588 <div class="doc_subsubsection">
7589 <a name="int_annotation">'<tt>llvm.annotation.*</tt>' Intrinsic</a>
7592 <div class="doc_text">
7595 <p>This is an overloaded intrinsic. You can use '<tt>llvm.annotation</tt>' on
7596 any integer bit width.</p>
7599 declare i8 @llvm.annotation.i8(i8 <val>, i8* <str>, i8* <str>, i32 <int>)
7600 declare i16 @llvm.annotation.i16(i16 <val>, i8* <str>, i8* <str>, i32 <int>)
7601 declare i32 @llvm.annotation.i32(i32 <val>, i8* <str>, i8* <str>, i32 <int>)
7602 declare i64 @llvm.annotation.i64(i64 <val>, i8* <str>, i8* <str>, i32 <int>)
7603 declare i256 @llvm.annotation.i256(i256 <val>, i8* <str>, i8* <str>, i32 <int>)
7607 <p>The '<tt>llvm.annotation</tt>' intrinsic.</p>
7610 <p>The first argument is an integer value (result of some expression), the
7611 second is a pointer to a global string, the third is a pointer to a global
7612 string which is the source file name, and the last argument is the line
7613 number. It returns the value of the first argument.</p>
7616 <p>This intrinsic allows annotations to be put on arbitrary expressions with
7617 arbitrary strings. This can be useful for special purpose optimizations that
7618 want to look for these annotations. These have no other defined use, they
7619 are ignored by code generation and optimization.</p>
7623 <!-- _______________________________________________________________________ -->
7624 <div class="doc_subsubsection">
7625 <a name="int_trap">'<tt>llvm.trap</tt>' Intrinsic</a>
7628 <div class="doc_text">
7632 declare void @llvm.trap()
7636 <p>The '<tt>llvm.trap</tt>' intrinsic.</p>
7642 <p>This intrinsics is lowered to the target dependent trap instruction. If the
7643 target does not have a trap instruction, this intrinsic will be lowered to
7644 the call of the <tt>abort()</tt> function.</p>
7648 <!-- _______________________________________________________________________ -->
7649 <div class="doc_subsubsection">
7650 <a name="int_stackprotector">'<tt>llvm.stackprotector</tt>' Intrinsic</a>
7653 <div class="doc_text">
7657 declare void @llvm.stackprotector(i8* <guard>, i8** <slot>)
7661 <p>The <tt>llvm.stackprotector</tt> intrinsic takes the <tt>guard</tt> and
7662 stores it onto the stack at <tt>slot</tt>. The stack slot is adjusted to
7663 ensure that it is placed on the stack before local variables.</p>
7666 <p>The <tt>llvm.stackprotector</tt> intrinsic requires two pointer
7667 arguments. The first argument is the value loaded from the stack
7668 guard <tt>@__stack_chk_guard</tt>. The second variable is an <tt>alloca</tt>
7669 that has enough space to hold the value of the guard.</p>
7672 <p>This intrinsic causes the prologue/epilogue inserter to force the position of
7673 the <tt>AllocaInst</tt> stack slot to be before local variables on the
7674 stack. This is to ensure that if a local variable on the stack is
7675 overwritten, it will destroy the value of the guard. When the function exits,
7676 the guard on the stack is checked against the original guard. If they're
7677 different, then the program aborts by calling the <tt>__stack_chk_fail()</tt>
7682 <!-- _______________________________________________________________________ -->
7683 <div class="doc_subsubsection">
7684 <a name="int_objectsize">'<tt>llvm.objectsize</tt>' Intrinsic</a>
7687 <div class="doc_text">
7691 declare i32 @llvm.objectsize.i32(i8* <object>, i1 <type>)
7692 declare i64 @llvm.objectsize.i64(i8* <object>, i1 <type>)
7696 <p>The <tt>llvm.objectsize</tt> intrinsic is designed to provide information
7697 to the optimizers to discover at compile time either a) when an
7698 operation like memcpy will either overflow a buffer that corresponds to
7699 an object, or b) to determine that a runtime check for overflow isn't
7700 necessary. An object in this context means an allocation of a
7701 specific class, structure, array, or other object.</p>
7704 <p>The <tt>llvm.objectsize</tt> intrinsic takes two arguments. The first
7705 argument is a pointer to or into the <tt>object</tt>. The second argument
7706 is a boolean 0 or 1. This argument determines whether you want the
7707 maximum (0) or minimum (1) bytes remaining. This needs to be a literal 0 or
7708 1, variables are not allowed.</p>
7711 <p>The <tt>llvm.objectsize</tt> intrinsic is lowered to either a constant
7712 representing the size of the object concerned or <tt>i32/i64 -1 or 0</tt>
7713 (depending on the <tt>type</tt> argument if the size cannot be determined
7714 at compile time.</p>
7718 <!-- *********************************************************************** -->
7721 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
7722 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
7723 <a href="http://validator.w3.org/check/referer"><img
7724 src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
7726 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
7727 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
7728 Last modified: $Date$