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></li>
24 <li><a href="#callingconv">Calling Conventions</a></li>
25 <li><a href="#globalvars">Global Variables</a></li>
26 <li><a href="#functionstructure">Functions</a></li>
27 <li><a href="#aliasstructure">Aliases</a>
28 <li><a href="#paramattrs">Parameter Attributes</a></li>
29 <li><a href="#moduleasm">Module-Level Inline Assembly</a></li>
30 <li><a href="#datalayout">Data Layout</a></li>
33 <li><a href="#typesystem">Type System</a>
35 <li><a href="#t_primitive">Primitive Types</a>
37 <li><a href="#t_classifications">Type Classifications</a></li>
40 <li><a href="#t_derived">Derived Types</a>
42 <li><a href="#t_array">Array Type</a></li>
43 <li><a href="#t_function">Function Type</a></li>
44 <li><a href="#t_pointer">Pointer Type</a></li>
45 <li><a href="#t_struct">Structure Type</a></li>
46 <li><a href="#t_pstruct">Packed Structure Type</a></li>
47 <li><a href="#t_vector">Vector Type</a></li>
48 <li><a href="#t_opaque">Opaque Type</a></li>
53 <li><a href="#constants">Constants</a>
55 <li><a href="#simpleconstants">Simple Constants</a>
56 <li><a href="#aggregateconstants">Aggregate Constants</a>
57 <li><a href="#globalconstants">Global Variable and Function Addresses</a>
58 <li><a href="#undefvalues">Undefined Values</a>
59 <li><a href="#constantexprs">Constant Expressions</a>
62 <li><a href="#othervalues">Other Values</a>
64 <li><a href="#inlineasm">Inline Assembler Expressions</a>
67 <li><a href="#instref">Instruction Reference</a>
69 <li><a href="#terminators">Terminator Instructions</a>
71 <li><a href="#i_ret">'<tt>ret</tt>' Instruction</a></li>
72 <li><a href="#i_br">'<tt>br</tt>' Instruction</a></li>
73 <li><a href="#i_switch">'<tt>switch</tt>' Instruction</a></li>
74 <li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a></li>
75 <li><a href="#i_unwind">'<tt>unwind</tt>' Instruction</a></li>
76 <li><a href="#i_unreachable">'<tt>unreachable</tt>' Instruction</a></li>
79 <li><a href="#binaryops">Binary Operations</a>
81 <li><a href="#i_add">'<tt>add</tt>' Instruction</a></li>
82 <li><a href="#i_sub">'<tt>sub</tt>' Instruction</a></li>
83 <li><a href="#i_mul">'<tt>mul</tt>' Instruction</a></li>
84 <li><a href="#i_udiv">'<tt>udiv</tt>' Instruction</a></li>
85 <li><a href="#i_sdiv">'<tt>sdiv</tt>' Instruction</a></li>
86 <li><a href="#i_fdiv">'<tt>fdiv</tt>' Instruction</a></li>
87 <li><a href="#i_urem">'<tt>urem</tt>' Instruction</a></li>
88 <li><a href="#i_srem">'<tt>srem</tt>' Instruction</a></li>
89 <li><a href="#i_frem">'<tt>frem</tt>' Instruction</a></li>
92 <li><a href="#bitwiseops">Bitwise Binary Operations</a>
94 <li><a href="#i_shl">'<tt>shl</tt>' Instruction</a></li>
95 <li><a href="#i_lshr">'<tt>lshr</tt>' Instruction</a></li>
96 <li><a href="#i_ashr">'<tt>ashr</tt>' Instruction</a></li>
97 <li><a href="#i_and">'<tt>and</tt>' Instruction</a></li>
98 <li><a href="#i_or">'<tt>or</tt>' Instruction</a></li>
99 <li><a href="#i_xor">'<tt>xor</tt>' Instruction</a></li>
102 <li><a href="#vectorops">Vector Operations</a>
104 <li><a href="#i_extractelement">'<tt>extractelement</tt>' Instruction</a></li>
105 <li><a href="#i_insertelement">'<tt>insertelement</tt>' Instruction</a></li>
106 <li><a href="#i_shufflevector">'<tt>shufflevector</tt>' Instruction</a></li>
109 <li><a href="#memoryops">Memory Access and Addressing Operations</a>
111 <li><a href="#i_malloc">'<tt>malloc</tt>' Instruction</a></li>
112 <li><a href="#i_free">'<tt>free</tt>' Instruction</a></li>
113 <li><a href="#i_alloca">'<tt>alloca</tt>' Instruction</a></li>
114 <li><a href="#i_load">'<tt>load</tt>' Instruction</a></li>
115 <li><a href="#i_store">'<tt>store</tt>' Instruction</a></li>
116 <li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a></li>
119 <li><a href="#convertops">Conversion Operations</a>
121 <li><a href="#i_trunc">'<tt>trunc .. to</tt>' Instruction</a></li>
122 <li><a href="#i_zext">'<tt>zext .. to</tt>' Instruction</a></li>
123 <li><a href="#i_sext">'<tt>sext .. to</tt>' Instruction</a></li>
124 <li><a href="#i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a></li>
125 <li><a href="#i_fpext">'<tt>fpext .. to</tt>' Instruction</a></li>
126 <li><a href="#i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a></li>
127 <li><a href="#i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a></li>
128 <li><a href="#i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a></li>
129 <li><a href="#i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a></li>
130 <li><a href="#i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a></li>
131 <li><a href="#i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a></li>
132 <li><a href="#i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a></li>
134 <li><a href="#otherops">Other Operations</a>
136 <li><a href="#i_icmp">'<tt>icmp</tt>' Instruction</a></li>
137 <li><a href="#i_fcmp">'<tt>fcmp</tt>' Instruction</a></li>
138 <li><a href="#i_phi">'<tt>phi</tt>' Instruction</a></li>
139 <li><a href="#i_select">'<tt>select</tt>' Instruction</a></li>
140 <li><a href="#i_call">'<tt>call</tt>' Instruction</a></li>
141 <li><a href="#i_va_arg">'<tt>va_arg</tt>' Instruction</a></li>
146 <li><a href="#intrinsics">Intrinsic Functions</a>
148 <li><a href="#int_varargs">Variable Argument Handling Intrinsics</a>
150 <li><a href="#int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a></li>
151 <li><a href="#int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a></li>
152 <li><a href="#int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a></li>
155 <li><a href="#int_gc">Accurate Garbage Collection Intrinsics</a>
157 <li><a href="#int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a></li>
158 <li><a href="#int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a></li>
159 <li><a href="#int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a></li>
162 <li><a href="#int_codegen">Code Generator Intrinsics</a>
164 <li><a href="#int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a></li>
165 <li><a href="#int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li>
166 <li><a href="#int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a></li>
167 <li><a href="#int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a></li>
168 <li><a href="#int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a></li>
169 <li><a href="#int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a></li>
170 <li><a href="#int_readcyclecounter"><tt>llvm.readcyclecounter</tt>' Intrinsic</a></li>
173 <li><a href="#int_libc">Standard C Library Intrinsics</a>
175 <li><a href="#int_memcpy">'<tt>llvm.memcpy.*</tt>' Intrinsic</a></li>
176 <li><a href="#int_memmove">'<tt>llvm.memmove.*</tt>' Intrinsic</a></li>
177 <li><a href="#int_memset">'<tt>llvm.memset.*</tt>' Intrinsic</a></li>
178 <li><a href="#int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a></li>
179 <li><a href="#int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a></li>
180 <li><a href="#int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a></li>
181 <li><a href="#int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a></li>
182 <li><a href="#int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a></li>
185 <li><a href="#int_manip">Bit Manipulation Intrinsics</a>
187 <li><a href="#int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a></li>
188 <li><a href="#int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic </a></li>
189 <li><a href="#int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic </a></li>
190 <li><a href="#int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic </a></li>
191 <li><a href="#int_part_select">'<tt>llvm.part.select.*</tt>' Intrinsic </a></li>
192 <li><a href="#int_part_set">'<tt>llvm.part.set.*</tt>' Intrinsic </a></li>
195 <li><a href="#int_debugger">Debugger intrinsics</a></li>
196 <li><a href="#int_eh">Exception Handling intrinsics</a></li>
197 <li><a href="#int_trampoline">Trampoline Intrinsic</a>
199 <li><a href="#int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a></li>
202 <li><a href="#int_general">General intrinsics</a>
204 <li><a href="#int_var_annotation">
205 <tt>llvm.var.annotation</tt>' Intrinsic</a></li>
208 <li><a href="#int_annotation">
209 <tt>llvm.annotation.*</tt>' Intrinsic</a></li>
216 <div class="doc_author">
217 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>
218 and <a href="mailto:vadve@cs.uiuc.edu">Vikram Adve</a></p>
221 <!-- *********************************************************************** -->
222 <div class="doc_section"> <a name="abstract">Abstract </a></div>
223 <!-- *********************************************************************** -->
225 <div class="doc_text">
226 <p>This document is a reference manual for the LLVM assembly language.
227 LLVM is an SSA based representation that provides type safety,
228 low-level operations, flexibility, and the capability of representing
229 'all' high-level languages cleanly. It is the common code
230 representation used throughout all phases of the LLVM compilation
234 <!-- *********************************************************************** -->
235 <div class="doc_section"> <a name="introduction">Introduction</a> </div>
236 <!-- *********************************************************************** -->
238 <div class="doc_text">
240 <p>The LLVM code representation is designed to be used in three
241 different forms: as an in-memory compiler IR, as an on-disk bitcode
242 representation (suitable for fast loading by a Just-In-Time compiler),
243 and as a human readable assembly language representation. This allows
244 LLVM to provide a powerful intermediate representation for efficient
245 compiler transformations and analysis, while providing a natural means
246 to debug and visualize the transformations. The three different forms
247 of LLVM are all equivalent. This document describes the human readable
248 representation and notation.</p>
250 <p>The LLVM representation aims to be light-weight and low-level
251 while being expressive, typed, and extensible at the same time. It
252 aims to be a "universal IR" of sorts, by being at a low enough level
253 that high-level ideas may be cleanly mapped to it (similar to how
254 microprocessors are "universal IR's", allowing many source languages to
255 be mapped to them). By providing type information, LLVM can be used as
256 the target of optimizations: for example, through pointer analysis, it
257 can be proven that a C automatic variable is never accessed outside of
258 the current function... allowing it to be promoted to a simple SSA
259 value instead of a memory location.</p>
263 <!-- _______________________________________________________________________ -->
264 <div class="doc_subsubsection"> <a name="wellformed">Well-Formedness</a> </div>
266 <div class="doc_text">
268 <p>It is important to note that this document describes 'well formed'
269 LLVM assembly language. There is a difference between what the parser
270 accepts and what is considered 'well formed'. For example, the
271 following instruction is syntactically okay, but not well formed:</p>
273 <div class="doc_code">
275 %x = <a href="#i_add">add</a> i32 1, %x
279 <p>...because the definition of <tt>%x</tt> does not dominate all of
280 its uses. The LLVM infrastructure provides a verification pass that may
281 be used to verify that an LLVM module is well formed. This pass is
282 automatically run by the parser after parsing input assembly and by
283 the optimizer before it outputs bitcode. The violations pointed out
284 by the verifier pass indicate bugs in transformation passes or input to
288 <!-- Describe the typesetting conventions here. -->
290 <!-- *********************************************************************** -->
291 <div class="doc_section"> <a name="identifiers">Identifiers</a> </div>
292 <!-- *********************************************************************** -->
294 <div class="doc_text">
296 <p>LLVM identifiers come in two basic types: global and local. Global
297 identifiers (functions, global variables) begin with the @ character. Local
298 identifiers (register names, types) begin with the % character. Additionally,
299 there are three different formats for identifiers, for different purposes:
302 <li>Named values are represented as a string of characters with their prefix.
303 For example, %foo, @DivisionByZero, %a.really.long.identifier. The actual
304 regular expression used is '<tt>[%@][a-zA-Z$._][a-zA-Z$._0-9]*</tt>'.
305 Identifiers which require other characters in their names can be surrounded
306 with quotes. In this way, anything except a <tt>"</tt> character can
307 be used in a named value.</li>
309 <li>Unnamed values are represented as an unsigned numeric value with their
310 prefix. For example, %12, @2, %44.</li>
312 <li>Constants, which are described in a <a href="#constants">section about
313 constants</a>, below.</li>
316 <p>LLVM requires that values start with a prefix for two reasons: Compilers
317 don't need to worry about name clashes with reserved words, and the set of
318 reserved words may be expanded in the future without penalty. Additionally,
319 unnamed identifiers allow a compiler to quickly come up with a temporary
320 variable without having to avoid symbol table conflicts.</p>
322 <p>Reserved words in LLVM are very similar to reserved words in other
323 languages. There are keywords for different opcodes
324 ('<tt><a href="#i_add">add</a></tt>',
325 '<tt><a href="#i_bitcast">bitcast</a></tt>',
326 '<tt><a href="#i_ret">ret</a></tt>', etc...), for primitive type names ('<tt><a
327 href="#t_void">void</a></tt>', '<tt><a href="#t_primitive">i32</a></tt>', etc...),
328 and others. These reserved words cannot conflict with variable names, because
329 none of them start with a prefix character ('%' or '@').</p>
331 <p>Here is an example of LLVM code to multiply the integer variable
332 '<tt>%X</tt>' by 8:</p>
336 <div class="doc_code">
338 %result = <a href="#i_mul">mul</a> i32 %X, 8
342 <p>After strength reduction:</p>
344 <div class="doc_code">
346 %result = <a href="#i_shl">shl</a> i32 %X, i8 3
350 <p>And the hard way:</p>
352 <div class="doc_code">
354 <a href="#i_add">add</a> i32 %X, %X <i>; yields {i32}:%0</i>
355 <a href="#i_add">add</a> i32 %0, %0 <i>; yields {i32}:%1</i>
356 %result = <a href="#i_add">add</a> i32 %1, %1
360 <p>This last way of multiplying <tt>%X</tt> by 8 illustrates several
361 important lexical features of LLVM:</p>
365 <li>Comments are delimited with a '<tt>;</tt>' and go until the end of
368 <li>Unnamed temporaries are created when the result of a computation is not
369 assigned to a named value.</li>
371 <li>Unnamed temporaries are numbered sequentially</li>
375 <p>...and it also shows a convention that we follow in this document. When
376 demonstrating instructions, we will follow an instruction with a comment that
377 defines the type and name of value produced. Comments are shown in italic
382 <!-- *********************************************************************** -->
383 <div class="doc_section"> <a name="highlevel">High Level Structure</a> </div>
384 <!-- *********************************************************************** -->
386 <!-- ======================================================================= -->
387 <div class="doc_subsection"> <a name="modulestructure">Module Structure</a>
390 <div class="doc_text">
392 <p>LLVM programs are composed of "Module"s, each of which is a
393 translation unit of the input programs. Each module consists of
394 functions, global variables, and symbol table entries. Modules may be
395 combined together with the LLVM linker, which merges function (and
396 global variable) definitions, resolves forward declarations, and merges
397 symbol table entries. Here is an example of the "hello world" module:</p>
399 <div class="doc_code">
400 <pre><i>; Declare the string constant as a global constant...</i>
401 <a href="#identifiers">@.LC0</a> = <a href="#linkage_internal">internal</a> <a
402 href="#globalvars">constant</a> <a href="#t_array">[13 x i8]</a> c"hello world\0A\00" <i>; [13 x i8]*</i>
404 <i>; External declaration of the puts function</i>
405 <a href="#functionstructure">declare</a> i32 @puts(i8 *) <i>; i32(i8 *)* </i>
407 <i>; Definition of main function</i>
408 define i32 @main() { <i>; i32()* </i>
409 <i>; Convert [13x i8 ]* to i8 *...</i>
411 href="#i_getelementptr">getelementptr</a> [13 x i8 ]* @.LC0, i64 0, i64 0 <i>; i8 *</i>
413 <i>; Call puts function to write out the string to stdout...</i>
415 href="#i_call">call</a> i32 @puts(i8 * %cast210) <i>; i32</i>
417 href="#i_ret">ret</a> i32 0<br>}<br>
421 <p>This example is made up of a <a href="#globalvars">global variable</a>
422 named "<tt>.LC0</tt>", an external declaration of the "<tt>puts</tt>"
423 function, and a <a href="#functionstructure">function definition</a>
424 for "<tt>main</tt>".</p>
426 <p>In general, a module is made up of a list of global values,
427 where both functions and global variables are global values. Global values are
428 represented by a pointer to a memory location (in this case, a pointer to an
429 array of char, and a pointer to a function), and have one of the following <a
430 href="#linkage">linkage types</a>.</p>
434 <!-- ======================================================================= -->
435 <div class="doc_subsection">
436 <a name="linkage">Linkage Types</a>
439 <div class="doc_text">
442 All Global Variables and Functions have one of the following types of linkage:
447 <dt><tt><b><a name="linkage_internal">internal</a></b></tt> </dt>
449 <dd>Global values with internal linkage are only directly accessible by
450 objects in the current module. In particular, linking code into a module with
451 an internal global value may cause the internal to be renamed as necessary to
452 avoid collisions. Because the symbol is internal to the module, all
453 references can be updated. This corresponds to the notion of the
454 '<tt>static</tt>' keyword in C.
457 <dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt>: </dt>
459 <dd>Globals with "<tt>linkonce</tt>" linkage are merged with other globals of
460 the same name when linkage occurs. This is typically used to implement
461 inline functions, templates, or other code which must be generated in each
462 translation unit that uses it. Unreferenced <tt>linkonce</tt> globals are
463 allowed to be discarded.
466 <dt><tt><b><a name="linkage_weak">weak</a></b></tt>: </dt>
468 <dd>"<tt>weak</tt>" linkage is exactly the same as <tt>linkonce</tt> linkage,
469 except that unreferenced <tt>weak</tt> globals may not be discarded. This is
470 used for globals that may be emitted in multiple translation units, but that
471 are not guaranteed to be emitted into every translation unit that uses them.
472 One example of this are common globals in C, such as "<tt>int X;</tt>" at
476 <dt><tt><b><a name="linkage_appending">appending</a></b></tt>: </dt>
478 <dd>"<tt>appending</tt>" linkage may only be applied to global variables of
479 pointer to array type. When two global variables with appending linkage are
480 linked together, the two global arrays are appended together. This is the
481 LLVM, typesafe, equivalent of having the system linker append together
482 "sections" with identical names when .o files are linked.
485 <dt><tt><b><a name="linkage_externweak">extern_weak</a></b></tt>: </dt>
486 <dd>The semantics of this linkage follow the ELF model: the symbol is weak
487 until linked, if not linked, the symbol becomes null instead of being an
491 <dt><tt><b><a name="linkage_external">externally visible</a></b></tt>:</dt>
493 <dd>If none of the above identifiers are used, the global is externally
494 visible, meaning that it participates in linkage and can be used to resolve
495 external symbol references.
500 The next two types of linkage are targeted for Microsoft Windows platform
501 only. They are designed to support importing (exporting) symbols from (to)
506 <dt><tt><b><a name="linkage_dllimport">dllimport</a></b></tt>: </dt>
508 <dd>"<tt>dllimport</tt>" linkage causes the compiler to reference a function
509 or variable via a global pointer to a pointer that is set up by the DLL
510 exporting the symbol. On Microsoft Windows targets, the pointer name is
511 formed by combining <code>_imp__</code> and the function or variable name.
514 <dt><tt><b><a name="linkage_dllexport">dllexport</a></b></tt>: </dt>
516 <dd>"<tt>dllexport</tt>" linkage causes the compiler to provide a global
517 pointer to a pointer in a DLL, so that it can be referenced with the
518 <tt>dllimport</tt> attribute. On Microsoft Windows targets, the pointer
519 name is formed by combining <code>_imp__</code> and the function or variable
525 <p><a name="linkage_external"></a>For example, since the "<tt>.LC0</tt>"
526 variable is defined to be internal, if another module defined a "<tt>.LC0</tt>"
527 variable and was linked with this one, one of the two would be renamed,
528 preventing a collision. Since "<tt>main</tt>" and "<tt>puts</tt>" are
529 external (i.e., lacking any linkage declarations), they are accessible
530 outside of the current module.</p>
531 <p>It is illegal for a function <i>declaration</i>
532 to have any linkage type other than "externally visible", <tt>dllimport</tt>,
533 or <tt>extern_weak</tt>.</p>
534 <p>Aliases can have only <tt>external</tt>, <tt>internal</tt> and <tt>weak</tt>
538 <!-- ======================================================================= -->
539 <div class="doc_subsection">
540 <a name="callingconv">Calling Conventions</a>
543 <div class="doc_text">
545 <p>LLVM <a href="#functionstructure">functions</a>, <a href="#i_call">calls</a>
546 and <a href="#i_invoke">invokes</a> can all have an optional calling convention
547 specified for the call. The calling convention of any pair of dynamic
548 caller/callee must match, or the behavior of the program is undefined. The
549 following calling conventions are supported by LLVM, and more may be added in
553 <dt><b>"<tt>ccc</tt>" - The C calling convention</b>:</dt>
555 <dd>This calling convention (the default if no other calling convention is
556 specified) matches the target C calling conventions. This calling convention
557 supports varargs function calls and tolerates some mismatch in the declared
558 prototype and implemented declaration of the function (as does normal C).
561 <dt><b>"<tt>fastcc</tt>" - The fast calling convention</b>:</dt>
563 <dd>This calling convention attempts to make calls as fast as possible
564 (e.g. by passing things in registers). This calling convention allows the
565 target to use whatever tricks it wants to produce fast code for the target,
566 without having to conform to an externally specified ABI. Implementations of
567 this convention should allow arbitrary tail call optimization to be supported.
568 This calling convention does not support varargs and requires the prototype of
569 all callees to exactly match the prototype of the function definition.
572 <dt><b>"<tt>coldcc</tt>" - The cold calling convention</b>:</dt>
574 <dd>This calling convention attempts to make code in the caller as efficient
575 as possible under the assumption that the call is not commonly executed. As
576 such, these calls often preserve all registers so that the call does not break
577 any live ranges in the caller side. This calling convention does not support
578 varargs and requires the prototype of all callees to exactly match the
579 prototype of the function definition.
582 <dt><b>"<tt>cc <<em>n</em>></tt>" - Numbered convention</b>:</dt>
584 <dd>Any calling convention may be specified by number, allowing
585 target-specific calling conventions to be used. Target specific calling
586 conventions start at 64.
590 <p>More calling conventions can be added/defined on an as-needed basis, to
591 support pascal conventions or any other well-known target-independent
596 <!-- ======================================================================= -->
597 <div class="doc_subsection">
598 <a name="visibility">Visibility Styles</a>
601 <div class="doc_text">
604 All Global Variables and Functions have one of the following visibility styles:
608 <dt><b>"<tt>default</tt>" - Default style</b>:</dt>
610 <dd>On ELF, default visibility means that the declaration is visible to other
611 modules and, in shared libraries, means that the declared entity may be
612 overridden. On Darwin, default visibility means that the declaration is
613 visible to other modules. Default visibility corresponds to "external
614 linkage" in the language.
617 <dt><b>"<tt>hidden</tt>" - Hidden style</b>:</dt>
619 <dd>Two declarations of an object with hidden visibility refer to the same
620 object if they are in the same shared object. Usually, hidden visibility
621 indicates that the symbol will not be placed into the dynamic symbol table,
622 so no other module (executable or shared library) can reference it
626 <dt><b>"<tt>protected</tt>" - Protected style</b>:</dt>
628 <dd>On ELF, protected visibility indicates that the symbol will be placed in
629 the dynamic symbol table, but that references within the defining module will
630 bind to the local symbol. That is, the symbol cannot be overridden by another
637 <!-- ======================================================================= -->
638 <div class="doc_subsection">
639 <a name="globalvars">Global Variables</a>
642 <div class="doc_text">
644 <p>Global variables define regions of memory allocated at compilation time
645 instead of run-time. Global variables may optionally be initialized, may have
646 an explicit section to be placed in, and may have an optional explicit alignment
647 specified. A variable may be defined as "thread_local", which means that it
648 will not be shared by threads (each thread will have a separated copy of the
649 variable). A variable may be defined as a global "constant," which indicates
650 that the contents of the variable will <b>never</b> be modified (enabling better
651 optimization, allowing the global data to be placed in the read-only section of
652 an executable, etc). Note that variables that need runtime initialization
653 cannot be marked "constant" as there is a store to the variable.</p>
656 LLVM explicitly allows <em>declarations</em> of global variables to be marked
657 constant, even if the final definition of the global is not. This capability
658 can be used to enable slightly better optimization of the program, but requires
659 the language definition to guarantee that optimizations based on the
660 'constantness' are valid for the translation units that do not include the
664 <p>As SSA values, global variables define pointer values that are in
665 scope (i.e. they dominate) all basic blocks in the program. Global
666 variables always define a pointer to their "content" type because they
667 describe a region of memory, and all memory objects in LLVM are
668 accessed through pointers.</p>
670 <p>LLVM allows an explicit section to be specified for globals. If the target
671 supports it, it will emit globals to the section specified.</p>
673 <p>An explicit alignment may be specified for a global. If not present, or if
674 the alignment is set to zero, the alignment of the global is set by the target
675 to whatever it feels convenient. If an explicit alignment is specified, the
676 global is forced to have at least that much alignment. All alignments must be
679 <p>For example, the following defines a global with an initializer, section,
682 <div class="doc_code">
684 @G = constant float 1.0, section "foo", align 4
691 <!-- ======================================================================= -->
692 <div class="doc_subsection">
693 <a name="functionstructure">Functions</a>
696 <div class="doc_text">
698 <p>LLVM function definitions consist of the "<tt>define</tt>" keyord,
699 an optional <a href="#linkage">linkage type</a>, an optional
700 <a href="#visibility">visibility style</a>, an optional
701 <a href="#callingconv">calling convention</a>, a return type, an optional
702 <a href="#paramattrs">parameter attribute</a> for the return type, a function
703 name, a (possibly empty) argument list (each with optional
704 <a href="#paramattrs">parameter attributes</a>), an optional section, an
705 optional alignment, an opening curly brace, a list of basic blocks, and a
708 LLVM function declarations consist of the "<tt>declare</tt>" keyword, an
709 optional <a href="#linkage">linkage type</a>, an optional
710 <a href="#visibility">visibility style</a>, an optional
711 <a href="#callingconv">calling convention</a>, a return type, an optional
712 <a href="#paramattrs">parameter attribute</a> for the return type, a function
713 name, a possibly empty list of arguments, and an optional alignment.</p>
715 <p>A function definition contains a list of basic blocks, forming the CFG for
716 the function. Each basic block may optionally start with a label (giving the
717 basic block a symbol table entry), contains a list of instructions, and ends
718 with a <a href="#terminators">terminator</a> instruction (such as a branch or
719 function return).</p>
721 <p>The first basic block in a function is special in two ways: it is immediately
722 executed on entrance to the function, and it is not allowed to have predecessor
723 basic blocks (i.e. there can not be any branches to the entry block of a
724 function). Because the block can have no predecessors, it also cannot have any
725 <a href="#i_phi">PHI nodes</a>.</p>
727 <p>LLVM allows an explicit section to be specified for functions. If the target
728 supports it, it will emit functions to the section specified.</p>
730 <p>An explicit alignment may be specified for a function. If not present, or if
731 the alignment is set to zero, the alignment of the function is set by the target
732 to whatever it feels convenient. If an explicit alignment is specified, the
733 function is forced to have at least that much alignment. All alignments must be
739 <!-- ======================================================================= -->
740 <div class="doc_subsection">
741 <a name="aliasstructure">Aliases</a>
743 <div class="doc_text">
744 <p>Aliases act as "second name" for the aliasee value (which can be either
745 function or global variable or bitcast of global value). Aliases may have an
746 optional <a href="#linkage">linkage type</a>, and an
747 optional <a href="#visibility">visibility style</a>.</p>
751 <div class="doc_code">
753 @<Name> = [Linkage] [Visibility] alias <AliaseeTy> @<Aliasee>
761 <!-- ======================================================================= -->
762 <div class="doc_subsection"><a name="paramattrs">Parameter Attributes</a></div>
763 <div class="doc_text">
764 <p>The return type and each parameter of a function type may have a set of
765 <i>parameter attributes</i> associated with them. Parameter attributes are
766 used to communicate additional information about the result or parameters of
767 a function. Parameter attributes are considered to be part of the function
768 type so two functions types that differ only by the parameter attributes
769 are different function types.</p>
771 <p>Parameter attributes are simple keywords that follow the type specified. If
772 multiple parameter attributes are needed, they are space separated. For
775 <div class="doc_code">
777 %someFunc = i16 (i8 signext %someParam) zeroext
778 %someFunc = i16 (i8 zeroext %someParam) zeroext
782 <p>Note that the two function types above are unique because the parameter has
783 a different attribute (<tt>signext</tt> in the first one, <tt>zeroext</tt> in
784 the second). Also note that the attribute for the function result
785 (<tt>zeroext</tt>) comes immediately after the argument list.</p>
787 <p>Currently, only the following parameter attributes are defined:</p>
789 <dt><tt>zeroext</tt></dt>
790 <dd>This indicates that the parameter should be zero extended just before
791 a call to this function.</dd>
792 <dt><tt>signext</tt></dt>
793 <dd>This indicates that the parameter should be sign extended just before
794 a call to this function.</dd>
795 <dt><tt>inreg</tt></dt>
796 <dd>This indicates that the parameter should be placed in register (if
797 possible) during assembling function call. Support for this attribute is
799 <dt><tt>sret</tt></dt>
800 <dd>This indicates that the parameter specifies the address of a structure
801 that is the return value of the function in the source program.</dd>
802 <dt><tt>noalias</tt></dt>
803 <dd>This indicates that the parameter not alias any other object or any
804 other "noalias" objects during the function call.
805 <dt><tt>noreturn</tt></dt>
806 <dd>This function attribute indicates that the function never returns. This
807 indicates to LLVM that every call to this function should be treated as if
808 an <tt>unreachable</tt> instruction immediately followed the call.</dd>
809 <dt><tt>nounwind</tt></dt>
810 <dd>This function attribute indicates that the function type does not use
811 the unwind instruction and does not allow stack unwinding to propagate
813 <dt><tt>nest</tt></dt>
814 <dd>This indicates that the parameter can be excised using the
815 <a href="#int_trampoline">trampoline intrinsics</a>.</dd>
820 <!-- ======================================================================= -->
821 <div class="doc_subsection">
822 <a name="moduleasm">Module-Level Inline Assembly</a>
825 <div class="doc_text">
827 Modules may contain "module-level inline asm" blocks, which corresponds to the
828 GCC "file scope inline asm" blocks. These blocks are internally concatenated by
829 LLVM and treated as a single unit, but may be separated in the .ll file if
830 desired. The syntax is very simple:
833 <div class="doc_code">
835 module asm "inline asm code goes here"
836 module asm "more can go here"
840 <p>The strings can contain any character by escaping non-printable characters.
841 The escape sequence used is simply "\xx" where "xx" is the two digit hex code
846 The inline asm code is simply printed to the machine code .s file when
847 assembly code is generated.
851 <!-- ======================================================================= -->
852 <div class="doc_subsection">
853 <a name="datalayout">Data Layout</a>
856 <div class="doc_text">
857 <p>A module may specify a target specific data layout string that specifies how
858 data is to be laid out in memory. The syntax for the data layout is simply:</p>
859 <pre> target datalayout = "<i>layout specification</i>"</pre>
860 <p>The <i>layout specification</i> consists of a list of specifications
861 separated by the minus sign character ('-'). Each specification starts with a
862 letter and may include other information after the letter to define some
863 aspect of the data layout. The specifications accepted are as follows: </p>
866 <dd>Specifies that the target lays out data in big-endian form. That is, the
867 bits with the most significance have the lowest address location.</dd>
869 <dd>Specifies that hte target lays out data in little-endian form. That is,
870 the bits with the least significance have the lowest address location.</dd>
871 <dt><tt>p:<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
872 <dd>This specifies the <i>size</i> of a pointer and its <i>abi</i> and
873 <i>preferred</i> alignments. All sizes are in bits. Specifying the <i>pref</i>
874 alignment is optional. If omitted, the preceding <tt>:</tt> should be omitted
876 <dt><tt>i<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
877 <dd>This specifies the alignment for an integer type of a given bit
878 <i>size</i>. The value of <i>size</i> must be in the range [1,2^23).</dd>
879 <dt><tt>v<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
880 <dd>This specifies the alignment for a vector type of a given bit
882 <dt><tt>f<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
883 <dd>This specifies the alignment for a floating point type of a given bit
884 <i>size</i>. The value of <i>size</i> must be either 32 (float) or 64
886 <dt><tt>a<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
887 <dd>This specifies the alignment for an aggregate type of a given bit
890 <p>When constructing the data layout for a given target, LLVM starts with a
891 default set of specifications which are then (possibly) overriden by the
892 specifications in the <tt>datalayout</tt> keyword. The default specifications
893 are given in this list:</p>
895 <li><tt>E</tt> - big endian</li>
896 <li><tt>p:32:64:64</tt> - 32-bit pointers with 64-bit alignment</li>
897 <li><tt>i1:8:8</tt> - i1 is 8-bit (byte) aligned</li>
898 <li><tt>i8:8:8</tt> - i8 is 8-bit (byte) aligned</li>
899 <li><tt>i16:16:16</tt> - i16 is 16-bit aligned</li>
900 <li><tt>i32:32:32</tt> - i32 is 32-bit aligned</li>
901 <li><tt>i64:32:64</tt> - i64 has abi alignment of 32-bits but preferred
902 alignment of 64-bits</li>
903 <li><tt>f32:32:32</tt> - float is 32-bit aligned</li>
904 <li><tt>f64:64:64</tt> - double is 64-bit aligned</li>
905 <li><tt>v64:64:64</tt> - 64-bit vector is 64-bit aligned</li>
906 <li><tt>v128:128:128</tt> - 128-bit vector is 128-bit aligned</li>
907 <li><tt>a0:0:1</tt> - aggregates are 8-bit aligned</li>
909 <p>When llvm is determining the alignment for a given type, it uses the
912 <li>If the type sought is an exact match for one of the specifications, that
913 specification is used.</li>
914 <li>If no match is found, and the type sought is an integer type, then the
915 smallest integer type that is larger than the bitwidth of the sought type is
916 used. If none of the specifications are larger than the bitwidth then the the
917 largest integer type is used. For example, given the default specifications
918 above, the i7 type will use the alignment of i8 (next largest) while both
919 i65 and i256 will use the alignment of i64 (largest specified).</li>
920 <li>If no match is found, and the type sought is a vector type, then the
921 largest vector type that is smaller than the sought vector type will be used
922 as a fall back. This happens because <128 x double> can be implemented in
923 terms of 64 <2 x double>, for example.</li>
927 <!-- *********************************************************************** -->
928 <div class="doc_section"> <a name="typesystem">Type System</a> </div>
929 <!-- *********************************************************************** -->
931 <div class="doc_text">
933 <p>The LLVM type system is one of the most important features of the
934 intermediate representation. Being typed enables a number of
935 optimizations to be performed on the IR directly, without having to do
936 extra analyses on the side before the transformation. A strong type
937 system makes it easier to read the generated code and enables novel
938 analyses and transformations that are not feasible to perform on normal
939 three address code representations.</p>
943 <!-- ======================================================================= -->
944 <div class="doc_subsection"> <a name="t_primitive">Primitive Types</a> </div>
945 <div class="doc_text">
946 <p>The primitive types are the fundamental building blocks of the LLVM
947 system. The current set of primitive types is as follows:</p>
949 <table class="layout">
954 <tr><th>Type</th><th>Description</th></tr>
955 <tr><td><tt><a name="t_void">void</a></tt></td><td>No value</td></tr>
956 <tr><td><tt>label</tt></td><td>Branch destination</td></tr>
963 <tr><th>Type</th><th>Description</th></tr>
964 <tr><td><tt>float</tt></td><td>32-bit floating point value</td></tr>
965 <tr><td><tt>double</tt></td><td>64-bit floating point value</td></tr>
973 <!-- _______________________________________________________________________ -->
974 <div class="doc_subsubsection"> <a name="t_classifications">Type
975 Classifications</a> </div>
976 <div class="doc_text">
977 <p>These different primitive types fall into a few useful
980 <table border="1" cellspacing="0" cellpadding="4">
982 <tr><th>Classification</th><th>Types</th></tr>
984 <td><a name="t_integer">integer</a></td>
985 <td><tt>i1, i2, i3, ... i8, ... i16, ... i32, ... i64, ... </tt></td>
988 <td><a name="t_floating">floating point</a></td>
989 <td><tt>float, double</tt></td>
992 <td><a name="t_firstclass">first class</a></td>
993 <td><tt>i1, ..., float, double, <br/>
994 <a href="#t_pointer">pointer</a>,<a href="#t_vector">vector</a></tt>
1000 <p>The <a href="#t_firstclass">first class</a> types are perhaps the
1001 most important. Values of these types are the only ones which can be
1002 produced by instructions, passed as arguments, or used as operands to
1003 instructions. This means that all structures and arrays must be
1004 manipulated either by pointer or by component.</p>
1007 <!-- ======================================================================= -->
1008 <div class="doc_subsection"> <a name="t_derived">Derived Types</a> </div>
1010 <div class="doc_text">
1012 <p>The real power in LLVM comes from the derived types in the system.
1013 This is what allows a programmer to represent arrays, functions,
1014 pointers, and other useful types. Note that these derived types may be
1015 recursive: For example, it is possible to have a two dimensional array.</p>
1019 <!-- _______________________________________________________________________ -->
1020 <div class="doc_subsubsection"> <a name="t_integer">Integer Type</a> </div>
1022 <div class="doc_text">
1025 <p>The integer type is a very simple derived type that simply specifies an
1026 arbitrary bit width for the integer type desired. Any bit width from 1 bit to
1027 2^23-1 (about 8 million) can be specified.</p>
1035 <p>The number of bits the integer will occupy is specified by the <tt>N</tt>
1039 <table class="layout">
1049 <tt>i1942652</tt><br/>
1052 A boolean integer of 1 bit<br/>
1053 A nibble sized integer of 4 bits.<br/>
1054 A byte sized integer of 8 bits.<br/>
1055 A half word sized integer of 16 bits.<br/>
1056 A word sized integer of 32 bits.<br/>
1057 An integer whose bit width is the answer. <br/>
1058 A double word sized integer of 64 bits.<br/>
1059 A really big integer of over 1 million bits.<br/>
1065 <!-- _______________________________________________________________________ -->
1066 <div class="doc_subsubsection"> <a name="t_array">Array Type</a> </div>
1068 <div class="doc_text">
1072 <p>The array type is a very simple derived type that arranges elements
1073 sequentially in memory. The array type requires a size (number of
1074 elements) and an underlying data type.</p>
1079 [<# elements> x <elementtype>]
1082 <p>The number of elements is a constant integer value; elementtype may
1083 be any type with a size.</p>
1086 <table class="layout">
1089 <tt>[40 x i32 ]</tt><br/>
1090 <tt>[41 x i32 ]</tt><br/>
1091 <tt>[40 x i8]</tt><br/>
1094 Array of 40 32-bit integer values.<br/>
1095 Array of 41 32-bit integer values.<br/>
1096 Array of 40 8-bit integer values.<br/>
1100 <p>Here are some examples of multidimensional arrays:</p>
1101 <table class="layout">
1104 <tt>[3 x [4 x i32]]</tt><br/>
1105 <tt>[12 x [10 x float]]</tt><br/>
1106 <tt>[2 x [3 x [4 x i16]]]</tt><br/>
1109 3x4 array of 32-bit integer values.<br/>
1110 12x10 array of single precision floating point values.<br/>
1111 2x3x4 array of 16-bit integer values.<br/>
1116 <p>Note that 'variable sized arrays' can be implemented in LLVM with a zero
1117 length array. Normally, accesses past the end of an array are undefined in
1118 LLVM (e.g. it is illegal to access the 5th element of a 3 element array).
1119 As a special case, however, zero length arrays are recognized to be variable
1120 length. This allows implementation of 'pascal style arrays' with the LLVM
1121 type "{ i32, [0 x float]}", for example.</p>
1125 <!-- _______________________________________________________________________ -->
1126 <div class="doc_subsubsection"> <a name="t_function">Function Type</a> </div>
1127 <div class="doc_text">
1129 <p>The function type can be thought of as a function signature. It
1130 consists of a return type and a list of formal parameter types.
1131 Function types are usually used to build virtual function tables
1132 (which are structures of pointers to functions), for indirect function
1133 calls, and when defining a function.</p>
1135 The return type of a function type cannot be an aggregate type.
1138 <pre> <returntype> (<parameter list>)<br></pre>
1139 <p>...where '<tt><parameter list></tt>' is a comma-separated list of type
1140 specifiers. Optionally, the parameter list may include a type <tt>...</tt>,
1141 which indicates that the function takes a variable number of arguments.
1142 Variable argument functions can access their arguments with the <a
1143 href="#int_varargs">variable argument handling intrinsic</a> functions.</p>
1145 <table class="layout">
1147 <td class="left"><tt>i32 (i32)</tt></td>
1148 <td class="left">function taking an <tt>i32</tt>, returning an <tt>i32</tt>
1150 </tr><tr class="layout">
1151 <td class="left"><tt>float (i16 signext, i32 *) *
1153 <td class="left"><a href="#t_pointer">Pointer</a> to a function that takes
1154 an <tt>i16</tt> that should be sign extended and a
1155 <a href="#t_pointer">pointer</a> to <tt>i32</tt>, returning
1158 </tr><tr class="layout">
1159 <td class="left"><tt>i32 (i8*, ...)</tt></td>
1160 <td class="left">A vararg function that takes at least one
1161 <a href="#t_pointer">pointer</a> to <tt>i8 </tt> (char in C),
1162 which returns an integer. This is the signature for <tt>printf</tt> in
1169 <!-- _______________________________________________________________________ -->
1170 <div class="doc_subsubsection"> <a name="t_struct">Structure Type</a> </div>
1171 <div class="doc_text">
1173 <p>The structure type is used to represent a collection of data members
1174 together in memory. The packing of the field types is defined to match
1175 the ABI of the underlying processor. The elements of a structure may
1176 be any type that has a size.</p>
1177 <p>Structures are accessed using '<tt><a href="#i_load">load</a></tt>
1178 and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a
1179 field with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>'
1182 <pre> { <type list> }<br></pre>
1184 <table class="layout">
1186 <td class="left"><tt>{ i32, i32, i32 }</tt></td>
1187 <td class="left">A triple of three <tt>i32</tt> values</td>
1188 </tr><tr class="layout">
1189 <td class="left"><tt>{ float, i32 (i32) * }</tt></td>
1190 <td class="left">A pair, where the first element is a <tt>float</tt> and the
1191 second element is a <a href="#t_pointer">pointer</a> to a
1192 <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
1193 an <tt>i32</tt>.</td>
1198 <!-- _______________________________________________________________________ -->
1199 <div class="doc_subsubsection"> <a name="t_pstruct">Packed Structure Type</a>
1201 <div class="doc_text">
1203 <p>The packed structure type is used to represent a collection of data members
1204 together in memory. There is no padding between fields. Further, the alignment
1205 of a packed structure is 1 byte. The elements of a packed structure may
1206 be any type that has a size.</p>
1207 <p>Structures are accessed using '<tt><a href="#i_load">load</a></tt>
1208 and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a
1209 field with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>'
1212 <pre> < { <type list> } > <br></pre>
1214 <table class="layout">
1216 <td class="left"><tt>< { i32, i32, i32 } ></tt></td>
1217 <td class="left">A triple of three <tt>i32</tt> values</td>
1218 </tr><tr class="layout">
1219 <td class="left"><tt>< { float, i32 (i32) * } ></tt></td>
1220 <td class="left">A pair, where the first element is a <tt>float</tt> and the
1221 second element is a <a href="#t_pointer">pointer</a> to a
1222 <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
1223 an <tt>i32</tt>.</td>
1228 <!-- _______________________________________________________________________ -->
1229 <div class="doc_subsubsection"> <a name="t_pointer">Pointer Type</a> </div>
1230 <div class="doc_text">
1232 <p>As in many languages, the pointer type represents a pointer or
1233 reference to another object, which must live in memory.</p>
1235 <pre> <type> *<br></pre>
1237 <table class="layout">
1240 <tt>[4x i32]*</tt><br/>
1241 <tt>i32 (i32 *) *</tt><br/>
1244 A <a href="#t_pointer">pointer</a> to <a href="#t_array">array</a> of
1245 four <tt>i32</tt> values<br/>
1246 A <a href="#t_pointer">pointer</a> to a <a
1247 href="#t_function">function</a> that takes an <tt>i32*</tt>, returning an
1254 <!-- _______________________________________________________________________ -->
1255 <div class="doc_subsubsection"> <a name="t_vector">Vector Type</a> </div>
1256 <div class="doc_text">
1260 <p>A vector type is a simple derived type that represents a vector
1261 of elements. Vector types are used when multiple primitive data
1262 are operated in parallel using a single instruction (SIMD).
1263 A vector type requires a size (number of
1264 elements) and an underlying primitive data type. Vectors must have a power
1265 of two length (1, 2, 4, 8, 16 ...). Vector types are
1266 considered <a href="#t_firstclass">first class</a>.</p>
1271 < <# elements> x <elementtype> >
1274 <p>The number of elements is a constant integer value; elementtype may
1275 be any integer or floating point type.</p>
1279 <table class="layout">
1282 <tt><4 x i32></tt><br/>
1283 <tt><8 x float></tt><br/>
1284 <tt><2 x i64></tt><br/>
1287 Vector of 4 32-bit integer values.<br/>
1288 Vector of 8 floating-point values.<br/>
1289 Vector of 2 64-bit integer values.<br/>
1295 <!-- _______________________________________________________________________ -->
1296 <div class="doc_subsubsection"> <a name="t_opaque">Opaque Type</a> </div>
1297 <div class="doc_text">
1301 <p>Opaque types are used to represent unknown types in the system. This
1302 corresponds (for example) to the C notion of a forward declared structure type.
1303 In LLVM, opaque types can eventually be resolved to any type (not just a
1304 structure type).</p>
1314 <table class="layout">
1320 An opaque type.<br/>
1327 <!-- *********************************************************************** -->
1328 <div class="doc_section"> <a name="constants">Constants</a> </div>
1329 <!-- *********************************************************************** -->
1331 <div class="doc_text">
1333 <p>LLVM has several different basic types of constants. This section describes
1334 them all and their syntax.</p>
1338 <!-- ======================================================================= -->
1339 <div class="doc_subsection"><a name="simpleconstants">Simple Constants</a></div>
1341 <div class="doc_text">
1344 <dt><b>Boolean constants</b></dt>
1346 <dd>The two strings '<tt>true</tt>' and '<tt>false</tt>' are both valid
1347 constants of the <tt><a href="#t_primitive">i1</a></tt> type.
1350 <dt><b>Integer constants</b></dt>
1352 <dd>Standard integers (such as '4') are constants of the <a
1353 href="#t_integer">integer</a> type. Negative numbers may be used with
1357 <dt><b>Floating point constants</b></dt>
1359 <dd>Floating point constants use standard decimal notation (e.g. 123.421),
1360 exponential notation (e.g. 1.23421e+2), or a more precise hexadecimal
1361 notation (see below). Floating point constants must have a <a
1362 href="#t_floating">floating point</a> type. </dd>
1364 <dt><b>Null pointer constants</b></dt>
1366 <dd>The identifier '<tt>null</tt>' is recognized as a null pointer constant
1367 and must be of <a href="#t_pointer">pointer type</a>.</dd>
1371 <p>The one non-intuitive notation for constants is the optional hexadecimal form
1372 of floating point constants. For example, the form '<tt>double
1373 0x432ff973cafa8000</tt>' is equivalent to (but harder to read than) '<tt>double
1374 4.5e+15</tt>'. The only time hexadecimal floating point constants are required
1375 (and the only time that they are generated by the disassembler) is when a
1376 floating point constant must be emitted but it cannot be represented as a
1377 decimal floating point number. For example, NaN's, infinities, and other
1378 special values are represented in their IEEE hexadecimal format so that
1379 assembly and disassembly do not cause any bits to change in the constants.</p>
1383 <!-- ======================================================================= -->
1384 <div class="doc_subsection"><a name="aggregateconstants">Aggregate Constants</a>
1387 <div class="doc_text">
1388 <p>Aggregate constants arise from aggregation of simple constants
1389 and smaller aggregate constants.</p>
1392 <dt><b>Structure constants</b></dt>
1394 <dd>Structure constants are represented with notation similar to structure
1395 type definitions (a comma separated list of elements, surrounded by braces
1396 (<tt>{}</tt>)). For example: "<tt>{ i32 4, float 17.0, i32* %G }</tt>",
1397 where "<tt>%G</tt>" is declared as "<tt>@G = external global i32</tt>". Structure constants
1398 must have <a href="#t_struct">structure type</a>, and the number and
1399 types of elements must match those specified by the type.
1402 <dt><b>Array constants</b></dt>
1404 <dd>Array constants are represented with notation similar to array type
1405 definitions (a comma separated list of elements, surrounded by square brackets
1406 (<tt>[]</tt>)). For example: "<tt>[ i32 42, i32 11, i32 74 ]</tt>". Array
1407 constants must have <a href="#t_array">array type</a>, and the number and
1408 types of elements must match those specified by the type.
1411 <dt><b>Vector constants</b></dt>
1413 <dd>Vector constants are represented with notation similar to vector type
1414 definitions (a comma separated list of elements, surrounded by
1415 less-than/greater-than's (<tt><></tt>)). For example: "<tt>< i32 42,
1416 i32 11, i32 74, i32 100 ></tt>". Vector constants must have <a
1417 href="#t_vector">vector type</a>, and the number and types of elements must
1418 match those specified by the type.
1421 <dt><b>Zero initialization</b></dt>
1423 <dd>The string '<tt>zeroinitializer</tt>' can be used to zero initialize a
1424 value to zero of <em>any</em> type, including scalar and aggregate types.
1425 This is often used to avoid having to print large zero initializers (e.g. for
1426 large arrays) and is always exactly equivalent to using explicit zero
1433 <!-- ======================================================================= -->
1434 <div class="doc_subsection">
1435 <a name="globalconstants">Global Variable and Function Addresses</a>
1438 <div class="doc_text">
1440 <p>The addresses of <a href="#globalvars">global variables</a> and <a
1441 href="#functionstructure">functions</a> are always implicitly valid (link-time)
1442 constants. These constants are explicitly referenced when the <a
1443 href="#identifiers">identifier for the global</a> is used and always have <a
1444 href="#t_pointer">pointer</a> type. For example, the following is a legal LLVM
1447 <div class="doc_code">
1451 @Z = global [2 x i32*] [ i32* @X, i32* @Y ]
1457 <!-- ======================================================================= -->
1458 <div class="doc_subsection"><a name="undefvalues">Undefined Values</a></div>
1459 <div class="doc_text">
1460 <p>The string '<tt>undef</tt>' is recognized as a type-less constant that has
1461 no specific value. Undefined values may be of any type and be used anywhere
1462 a constant is permitted.</p>
1464 <p>Undefined values indicate to the compiler that the program is well defined
1465 no matter what value is used, giving the compiler more freedom to optimize.
1469 <!-- ======================================================================= -->
1470 <div class="doc_subsection"><a name="constantexprs">Constant Expressions</a>
1473 <div class="doc_text">
1475 <p>Constant expressions are used to allow expressions involving other constants
1476 to be used as constants. Constant expressions may be of any <a
1477 href="#t_firstclass">first class</a> type and may involve any LLVM operation
1478 that does not have side effects (e.g. load and call are not supported). The
1479 following is the syntax for constant expressions:</p>
1482 <dt><b><tt>trunc ( CST to TYPE )</tt></b></dt>
1483 <dd>Truncate a constant to another type. The bit size of CST must be larger
1484 than the bit size of TYPE. Both types must be integers.</dd>
1486 <dt><b><tt>zext ( CST to TYPE )</tt></b></dt>
1487 <dd>Zero extend a constant to another type. The bit size of CST must be
1488 smaller or equal to the bit size of TYPE. Both types must be integers.</dd>
1490 <dt><b><tt>sext ( CST to TYPE )</tt></b></dt>
1491 <dd>Sign extend a constant to another type. The bit size of CST must be
1492 smaller or equal to the bit size of TYPE. Both types must be integers.</dd>
1494 <dt><b><tt>fptrunc ( CST to TYPE )</tt></b></dt>
1495 <dd>Truncate a floating point constant to another floating point type. The
1496 size of CST must be larger than the size of TYPE. Both types must be
1497 floating point.</dd>
1499 <dt><b><tt>fpext ( CST to TYPE )</tt></b></dt>
1500 <dd>Floating point extend a constant to another type. The size of CST must be
1501 smaller or equal to the size of TYPE. Both types must be floating point.</dd>
1503 <dt><b><tt>fptoui ( CST to TYPE )</tt></b></dt>
1504 <dd>Convert a floating point constant to the corresponding unsigned integer
1505 constant. TYPE must be an integer type. CST must be floating point. If the
1506 value won't fit in the integer type, the results are undefined.</dd>
1508 <dt><b><tt>fptosi ( CST to TYPE )</tt></b></dt>
1509 <dd>Convert a floating point constant to the corresponding signed integer
1510 constant. TYPE must be an integer type. CST must be floating point. If the
1511 value won't fit in the integer type, the results are undefined.</dd>
1513 <dt><b><tt>uitofp ( CST to TYPE )</tt></b></dt>
1514 <dd>Convert an unsigned integer constant to the corresponding floating point
1515 constant. TYPE must be floating point. CST must be of integer type. If the
1516 value won't fit in the floating point type, the results are undefined.</dd>
1518 <dt><b><tt>sitofp ( CST to TYPE )</tt></b></dt>
1519 <dd>Convert a signed integer constant to the corresponding floating point
1520 constant. TYPE must be floating point. CST must be of integer type. If the
1521 value won't fit in the floating point type, the results are undefined.</dd>
1523 <dt><b><tt>ptrtoint ( CST to TYPE )</tt></b></dt>
1524 <dd>Convert a pointer typed constant to the corresponding integer constant
1525 TYPE must be an integer type. CST must be of pointer type. The CST value is
1526 zero extended, truncated, or unchanged to make it fit in TYPE.</dd>
1528 <dt><b><tt>inttoptr ( CST to TYPE )</tt></b></dt>
1529 <dd>Convert a integer constant to a pointer constant. TYPE must be a
1530 pointer type. CST must be of integer type. The CST value is zero extended,
1531 truncated, or unchanged to make it fit in a pointer size. This one is
1532 <i>really</i> dangerous!</dd>
1534 <dt><b><tt>bitcast ( CST to TYPE )</tt></b></dt>
1535 <dd>Convert a constant, CST, to another TYPE. The size of CST and TYPE must be
1536 identical (same number of bits). The conversion is done as if the CST value
1537 was stored to memory and read back as TYPE. In other words, no bits change
1538 with this operator, just the type. This can be used for conversion of
1539 vector types to any other type, as long as they have the same bit width. For
1540 pointers it is only valid to cast to another pointer type.
1543 <dt><b><tt>getelementptr ( CSTPTR, IDX0, IDX1, ... )</tt></b></dt>
1545 <dd>Perform the <a href="#i_getelementptr">getelementptr operation</a> on
1546 constants. As with the <a href="#i_getelementptr">getelementptr</a>
1547 instruction, the index list may have zero or more indexes, which are required
1548 to make sense for the type of "CSTPTR".</dd>
1550 <dt><b><tt>select ( COND, VAL1, VAL2 )</tt></b></dt>
1552 <dd>Perform the <a href="#i_select">select operation</a> on
1555 <dt><b><tt>icmp COND ( VAL1, VAL2 )</tt></b></dt>
1556 <dd>Performs the <a href="#i_icmp">icmp operation</a> on constants.</dd>
1558 <dt><b><tt>fcmp COND ( VAL1, VAL2 )</tt></b></dt>
1559 <dd>Performs the <a href="#i_fcmp">fcmp operation</a> on constants.</dd>
1561 <dt><b><tt>extractelement ( VAL, IDX )</tt></b></dt>
1563 <dd>Perform the <a href="#i_extractelement">extractelement
1564 operation</a> on constants.
1566 <dt><b><tt>insertelement ( VAL, ELT, IDX )</tt></b></dt>
1568 <dd>Perform the <a href="#i_insertelement">insertelement
1569 operation</a> on constants.</dd>
1572 <dt><b><tt>shufflevector ( VEC1, VEC2, IDXMASK )</tt></b></dt>
1574 <dd>Perform the <a href="#i_shufflevector">shufflevector
1575 operation</a> on constants.</dd>
1577 <dt><b><tt>OPCODE ( LHS, RHS )</tt></b></dt>
1579 <dd>Perform the specified operation of the LHS and RHS constants. OPCODE may
1580 be any of the <a href="#binaryops">binary</a> or <a href="#bitwiseops">bitwise
1581 binary</a> operations. The constraints on operands are the same as those for
1582 the corresponding instruction (e.g. no bitwise operations on floating point
1583 values are allowed).</dd>
1587 <!-- *********************************************************************** -->
1588 <div class="doc_section"> <a name="othervalues">Other Values</a> </div>
1589 <!-- *********************************************************************** -->
1591 <!-- ======================================================================= -->
1592 <div class="doc_subsection">
1593 <a name="inlineasm">Inline Assembler Expressions</a>
1596 <div class="doc_text">
1599 LLVM supports inline assembler expressions (as opposed to <a href="#moduleasm">
1600 Module-Level Inline Assembly</a>) through the use of a special value. This
1601 value represents the inline assembler as a string (containing the instructions
1602 to emit), a list of operand constraints (stored as a string), and a flag that
1603 indicates whether or not the inline asm expression has side effects. An example
1604 inline assembler expression is:
1607 <div class="doc_code">
1609 i32 (i32) asm "bswap $0", "=r,r"
1614 Inline assembler expressions may <b>only</b> be used as the callee operand of
1615 a <a href="#i_call"><tt>call</tt> instruction</a>. Thus, typically we have:
1618 <div class="doc_code">
1620 %X = call i32 asm "<a href="#int_bswap">bswap</a> $0", "=r,r"(i32 %Y)
1625 Inline asms with side effects not visible in the constraint list must be marked
1626 as having side effects. This is done through the use of the
1627 '<tt>sideeffect</tt>' keyword, like so:
1630 <div class="doc_code">
1632 call void asm sideeffect "eieio", ""()
1636 <p>TODO: The format of the asm and constraints string still need to be
1637 documented here. Constraints on what can be done (e.g. duplication, moving, etc
1638 need to be documented).
1643 <!-- *********************************************************************** -->
1644 <div class="doc_section"> <a name="instref">Instruction Reference</a> </div>
1645 <!-- *********************************************************************** -->
1647 <div class="doc_text">
1649 <p>The LLVM instruction set consists of several different
1650 classifications of instructions: <a href="#terminators">terminator
1651 instructions</a>, <a href="#binaryops">binary instructions</a>,
1652 <a href="#bitwiseops">bitwise binary instructions</a>, <a
1653 href="#memoryops">memory instructions</a>, and <a href="#otherops">other
1654 instructions</a>.</p>
1658 <!-- ======================================================================= -->
1659 <div class="doc_subsection"> <a name="terminators">Terminator
1660 Instructions</a> </div>
1662 <div class="doc_text">
1664 <p>As mentioned <a href="#functionstructure">previously</a>, every
1665 basic block in a program ends with a "Terminator" instruction, which
1666 indicates which block should be executed after the current block is
1667 finished. These terminator instructions typically yield a '<tt>void</tt>'
1668 value: they produce control flow, not values (the one exception being
1669 the '<a href="#i_invoke"><tt>invoke</tt></a>' instruction).</p>
1670 <p>There are six different terminator instructions: the '<a
1671 href="#i_ret"><tt>ret</tt></a>' instruction, the '<a href="#i_br"><tt>br</tt></a>'
1672 instruction, the '<a href="#i_switch"><tt>switch</tt></a>' instruction,
1673 the '<a href="#i_invoke"><tt>invoke</tt></a>' instruction, the '<a
1674 href="#i_unwind"><tt>unwind</tt></a>' instruction, and the '<a
1675 href="#i_unreachable"><tt>unreachable</tt></a>' instruction.</p>
1679 <!-- _______________________________________________________________________ -->
1680 <div class="doc_subsubsection"> <a name="i_ret">'<tt>ret</tt>'
1681 Instruction</a> </div>
1682 <div class="doc_text">
1684 <pre> ret <type> <value> <i>; Return a value from a non-void function</i>
1685 ret void <i>; Return from void function</i>
1688 <p>The '<tt>ret</tt>' instruction is used to return control flow (and a
1689 value) from a function back to the caller.</p>
1690 <p>There are two forms of the '<tt>ret</tt>' instruction: one that
1691 returns a value and then causes control flow, and one that just causes
1692 control flow to occur.</p>
1694 <p>The '<tt>ret</tt>' instruction may return any '<a
1695 href="#t_firstclass">first class</a>' type. Notice that a function is
1696 not <a href="#wellformed">well formed</a> if there exists a '<tt>ret</tt>'
1697 instruction inside of the function that returns a value that does not
1698 match the return type of the function.</p>
1700 <p>When the '<tt>ret</tt>' instruction is executed, control flow
1701 returns back to the calling function's context. If the caller is a "<a
1702 href="#i_call"><tt>call</tt></a>" instruction, execution continues at
1703 the instruction after the call. If the caller was an "<a
1704 href="#i_invoke"><tt>invoke</tt></a>" instruction, execution continues
1705 at the beginning of the "normal" destination block. If the instruction
1706 returns a value, that value shall set the call or invoke instruction's
1709 <pre> ret i32 5 <i>; Return an integer value of 5</i>
1710 ret void <i>; Return from a void function</i>
1713 <!-- _______________________________________________________________________ -->
1714 <div class="doc_subsubsection"> <a name="i_br">'<tt>br</tt>' Instruction</a> </div>
1715 <div class="doc_text">
1717 <pre> br i1 <cond>, label <iftrue>, label <iffalse><br> br label <dest> <i>; Unconditional branch</i>
1720 <p>The '<tt>br</tt>' instruction is used to cause control flow to
1721 transfer to a different basic block in the current function. There are
1722 two forms of this instruction, corresponding to a conditional branch
1723 and an unconditional branch.</p>
1725 <p>The conditional branch form of the '<tt>br</tt>' instruction takes a
1726 single '<tt>i1</tt>' value and two '<tt>label</tt>' values. The
1727 unconditional form of the '<tt>br</tt>' instruction takes a single
1728 '<tt>label</tt>' value as a target.</p>
1730 <p>Upon execution of a conditional '<tt>br</tt>' instruction, the '<tt>i1</tt>'
1731 argument is evaluated. If the value is <tt>true</tt>, control flows
1732 to the '<tt>iftrue</tt>' <tt>label</tt> argument. If "cond" is <tt>false</tt>,
1733 control flows to the '<tt>iffalse</tt>' <tt>label</tt> argument.</p>
1735 <pre>Test:<br> %cond = <a href="#i_icmp">icmp</a> eq, i32 %a, %b<br> br i1 %cond, label %IfEqual, label %IfUnequal<br>IfEqual:<br> <a
1736 href="#i_ret">ret</a> i32 1<br>IfUnequal:<br> <a href="#i_ret">ret</a> i32 0<br></pre>
1738 <!-- _______________________________________________________________________ -->
1739 <div class="doc_subsubsection">
1740 <a name="i_switch">'<tt>switch</tt>' Instruction</a>
1743 <div class="doc_text">
1747 switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]
1752 <p>The '<tt>switch</tt>' instruction is used to transfer control flow to one of
1753 several different places. It is a generalization of the '<tt>br</tt>'
1754 instruction, allowing a branch to occur to one of many possible
1760 <p>The '<tt>switch</tt>' instruction uses three parameters: an integer
1761 comparison value '<tt>value</tt>', a default '<tt>label</tt>' destination, and
1762 an array of pairs of comparison value constants and '<tt>label</tt>'s. The
1763 table is not allowed to contain duplicate constant entries.</p>
1767 <p>The <tt>switch</tt> instruction specifies a table of values and
1768 destinations. When the '<tt>switch</tt>' instruction is executed, this
1769 table is searched for the given value. If the value is found, control flow is
1770 transfered to the corresponding destination; otherwise, control flow is
1771 transfered to the default destination.</p>
1773 <h5>Implementation:</h5>
1775 <p>Depending on properties of the target machine and the particular
1776 <tt>switch</tt> instruction, this instruction may be code generated in different
1777 ways. For example, it could be generated as a series of chained conditional
1778 branches or with a lookup table.</p>
1783 <i>; Emulate a conditional br instruction</i>
1784 %Val = <a href="#i_zext">zext</a> i1 %value to i32
1785 switch i32 %Val, label %truedest [i32 0, label %falsedest ]
1787 <i>; Emulate an unconditional br instruction</i>
1788 switch i32 0, label %dest [ ]
1790 <i>; Implement a jump table:</i>
1791 switch i32 %val, label %otherwise [ i32 0, label %onzero
1793 i32 2, label %ontwo ]
1797 <!-- _______________________________________________________________________ -->
1798 <div class="doc_subsubsection">
1799 <a name="i_invoke">'<tt>invoke</tt>' Instruction</a>
1802 <div class="doc_text">
1807 <result> = invoke [<a href="#callingconv">cconv</a>] <ptr to function ty> %<function ptr val>(<function args>)
1808 to label <normal label> unwind label <exception label>
1813 <p>The '<tt>invoke</tt>' instruction causes control to transfer to a specified
1814 function, with the possibility of control flow transfer to either the
1815 '<tt>normal</tt>' label or the
1816 '<tt>exception</tt>' label. If the callee function returns with the
1817 "<tt><a href="#i_ret">ret</a></tt>" instruction, control flow will return to the
1818 "normal" label. If the callee (or any indirect callees) returns with the "<a
1819 href="#i_unwind"><tt>unwind</tt></a>" instruction, control is interrupted and
1820 continued at the dynamically nearest "exception" label.</p>
1824 <p>This instruction requires several arguments:</p>
1828 The optional "cconv" marker indicates which <a href="#callingconv">calling
1829 convention</a> the call should use. If none is specified, the call defaults
1830 to using C calling conventions.
1832 <li>'<tt>ptr to function ty</tt>': shall be the signature of the pointer to
1833 function value being invoked. In most cases, this is a direct function
1834 invocation, but indirect <tt>invoke</tt>s are just as possible, branching off
1835 an arbitrary pointer to function value.
1838 <li>'<tt>function ptr val</tt>': An LLVM value containing a pointer to a
1839 function to be invoked. </li>
1841 <li>'<tt>function args</tt>': argument list whose types match the function
1842 signature argument types. If the function signature indicates the function
1843 accepts a variable number of arguments, the extra arguments can be
1846 <li>'<tt>normal label</tt>': the label reached when the called function
1847 executes a '<tt><a href="#i_ret">ret</a></tt>' instruction. </li>
1849 <li>'<tt>exception label</tt>': the label reached when a callee returns with
1850 the <a href="#i_unwind"><tt>unwind</tt></a> instruction. </li>
1856 <p>This instruction is designed to operate as a standard '<tt><a
1857 href="#i_call">call</a></tt>' instruction in most regards. The primary
1858 difference is that it establishes an association with a label, which is used by
1859 the runtime library to unwind the stack.</p>
1861 <p>This instruction is used in languages with destructors to ensure that proper
1862 cleanup is performed in the case of either a <tt>longjmp</tt> or a thrown
1863 exception. Additionally, this is important for implementation of
1864 '<tt>catch</tt>' clauses in high-level languages that support them.</p>
1868 %retval = invoke i32 %Test(i32 15) to label %Continue
1869 unwind label %TestCleanup <i>; {i32}:retval set</i>
1870 %retval = invoke <a href="#callingconv">coldcc</a> i32 %Test(i32 15) to label %Continue
1871 unwind label %TestCleanup <i>; {i32}:retval set</i>
1876 <!-- _______________________________________________________________________ -->
1878 <div class="doc_subsubsection"> <a name="i_unwind">'<tt>unwind</tt>'
1879 Instruction</a> </div>
1881 <div class="doc_text">
1890 <p>The '<tt>unwind</tt>' instruction unwinds the stack, continuing control flow
1891 at the first callee in the dynamic call stack which used an <a
1892 href="#i_invoke"><tt>invoke</tt></a> instruction to perform the call. This is
1893 primarily used to implement exception handling.</p>
1897 <p>The '<tt>unwind</tt>' intrinsic causes execution of the current function to
1898 immediately halt. The dynamic call stack is then searched for the first <a
1899 href="#i_invoke"><tt>invoke</tt></a> instruction on the call stack. Once found,
1900 execution continues at the "exceptional" destination block specified by the
1901 <tt>invoke</tt> instruction. If there is no <tt>invoke</tt> instruction in the
1902 dynamic call chain, undefined behavior results.</p>
1905 <!-- _______________________________________________________________________ -->
1907 <div class="doc_subsubsection"> <a name="i_unreachable">'<tt>unreachable</tt>'
1908 Instruction</a> </div>
1910 <div class="doc_text">
1919 <p>The '<tt>unreachable</tt>' instruction has no defined semantics. This
1920 instruction is used to inform the optimizer that a particular portion of the
1921 code is not reachable. This can be used to indicate that the code after a
1922 no-return function cannot be reached, and other facts.</p>
1926 <p>The '<tt>unreachable</tt>' instruction has no defined semantics.</p>
1931 <!-- ======================================================================= -->
1932 <div class="doc_subsection"> <a name="binaryops">Binary Operations</a> </div>
1933 <div class="doc_text">
1934 <p>Binary operators are used to do most of the computation in a
1935 program. They require two operands, execute an operation on them, and
1936 produce a single value. The operands might represent
1937 multiple data, as is the case with the <a href="#t_vector">vector</a> data type.
1938 The result value of a binary operator is not
1939 necessarily the same type as its operands.</p>
1940 <p>There are several different binary operators:</p>
1942 <!-- _______________________________________________________________________ -->
1943 <div class="doc_subsubsection"> <a name="i_add">'<tt>add</tt>'
1944 Instruction</a> </div>
1945 <div class="doc_text">
1947 <pre> <result> = add <ty> <var1>, <var2> <i>; yields {ty}:result</i>
1950 <p>The '<tt>add</tt>' instruction returns the sum of its two operands.</p>
1952 <p>The two arguments to the '<tt>add</tt>' instruction must be either <a
1953 href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> values.
1954 This instruction can also take <a href="#t_vector">vector</a> versions of the values.
1955 Both arguments must have identical types.</p>
1957 <p>The value produced is the integer or floating point sum of the two
1960 <pre> <result> = add i32 4, %var <i>; yields {i32}:result = 4 + %var</i>
1963 <!-- _______________________________________________________________________ -->
1964 <div class="doc_subsubsection"> <a name="i_sub">'<tt>sub</tt>'
1965 Instruction</a> </div>
1966 <div class="doc_text">
1968 <pre> <result> = sub <ty> <var1>, <var2> <i>; yields {ty}:result</i>
1971 <p>The '<tt>sub</tt>' instruction returns the difference of its two
1973 <p>Note that the '<tt>sub</tt>' instruction is used to represent the '<tt>neg</tt>'
1974 instruction present in most other intermediate representations.</p>
1976 <p>The two arguments to the '<tt>sub</tt>' instruction must be either <a
1977 href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
1979 This instruction can also take <a href="#t_vector">vector</a> versions of the values.
1980 Both arguments must have identical types.</p>
1982 <p>The value produced is the integer or floating point difference of
1983 the two operands.</p>
1986 <result> = sub i32 4, %var <i>; yields {i32}:result = 4 - %var</i>
1987 <result> = sub i32 0, %val <i>; yields {i32}:result = -%var</i>
1990 <!-- _______________________________________________________________________ -->
1991 <div class="doc_subsubsection"> <a name="i_mul">'<tt>mul</tt>'
1992 Instruction</a> </div>
1993 <div class="doc_text">
1995 <pre> <result> = mul <ty> <var1>, <var2> <i>; yields {ty}:result</i>
1998 <p>The '<tt>mul</tt>' instruction returns the product of its two
2001 <p>The two arguments to the '<tt>mul</tt>' instruction must be either <a
2002 href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
2004 This instruction can also take <a href="#t_vector">vector</a> versions of the values.
2005 Both arguments must have identical types.</p>
2007 <p>The value produced is the integer or floating point product of the
2009 <p>Because the operands are the same width, the result of an integer
2010 multiplication is the same whether the operands should be deemed unsigned or
2013 <pre> <result> = mul i32 4, %var <i>; yields {i32}:result = 4 * %var</i>
2016 <!-- _______________________________________________________________________ -->
2017 <div class="doc_subsubsection"> <a name="i_udiv">'<tt>udiv</tt>' Instruction
2019 <div class="doc_text">
2021 <pre> <result> = udiv <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2024 <p>The '<tt>udiv</tt>' instruction returns the quotient of its two
2027 <p>The two arguments to the '<tt>udiv</tt>' instruction must be
2028 <a href="#t_integer">integer</a> values. Both arguments must have identical
2029 types. This instruction can also take <a href="#t_vector">vector</a> versions
2030 of the values in which case the elements must be integers.</p>
2032 <p>The value produced is the unsigned integer quotient of the two operands. This
2033 instruction always performs an unsigned division operation, regardless of
2034 whether the arguments are unsigned or not.</p>
2036 <pre> <result> = udiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>
2039 <!-- _______________________________________________________________________ -->
2040 <div class="doc_subsubsection"> <a name="i_sdiv">'<tt>sdiv</tt>' Instruction
2042 <div class="doc_text">
2044 <pre> <result> = sdiv <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2047 <p>The '<tt>sdiv</tt>' instruction returns the quotient of its two
2050 <p>The two arguments to the '<tt>sdiv</tt>' instruction must be
2051 <a href="#t_integer">integer</a> values. Both arguments must have identical
2052 types. This instruction can also take <a href="#t_vector">vector</a> versions
2053 of the values in which case the elements must be integers.</p>
2055 <p>The value produced is the signed integer quotient of the two operands. This
2056 instruction always performs a signed division operation, regardless of whether
2057 the arguments are signed or not.</p>
2059 <pre> <result> = sdiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>
2062 <!-- _______________________________________________________________________ -->
2063 <div class="doc_subsubsection"> <a name="i_fdiv">'<tt>fdiv</tt>'
2064 Instruction</a> </div>
2065 <div class="doc_text">
2067 <pre> <result> = fdiv <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2070 <p>The '<tt>fdiv</tt>' instruction returns the quotient of its two
2073 <p>The two arguments to the '<tt>fdiv</tt>' instruction must be
2074 <a href="#t_floating">floating point</a> values. Both arguments must have
2075 identical types. This instruction can also take <a href="#t_vector">vector</a>
2076 versions of floating point values.</p>
2078 <p>The value produced is the floating point quotient of the two operands.</p>
2080 <pre> <result> = fdiv float 4.0, %var <i>; yields {float}:result = 4.0 / %var</i>
2083 <!-- _______________________________________________________________________ -->
2084 <div class="doc_subsubsection"> <a name="i_urem">'<tt>urem</tt>' Instruction</a>
2086 <div class="doc_text">
2088 <pre> <result> = urem <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2091 <p>The '<tt>urem</tt>' instruction returns the remainder from the
2092 unsigned division of its two arguments.</p>
2094 <p>The two arguments to the '<tt>urem</tt>' instruction must be
2095 <a href="#t_integer">integer</a> values. Both arguments must have identical
2096 types. This instruction can also take <a href="#t_vector">vector</a> versions
2097 of the values in which case the elements must be integers.</p>
2099 <p>This instruction returns the unsigned integer <i>remainder</i> of a division.
2100 This instruction always performs an unsigned division to get the remainder,
2101 regardless of whether the arguments are unsigned or not.</p>
2103 <pre> <result> = urem i32 4, %var <i>; yields {i32}:result = 4 % %var</i>
2107 <!-- _______________________________________________________________________ -->
2108 <div class="doc_subsubsection"> <a name="i_srem">'<tt>srem</tt>'
2109 Instruction</a> </div>
2110 <div class="doc_text">
2112 <pre> <result> = srem <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2115 <p>The '<tt>srem</tt>' instruction returns the remainder from the
2116 signed division of its two operands. This instruction can also take
2117 <a href="#t_vector">vector</a> versions of the values in which case
2118 the elements must be integers.</p>
2121 <p>The two arguments to the '<tt>srem</tt>' instruction must be
2122 <a href="#t_integer">integer</a> values. Both arguments must have identical
2125 <p>This instruction returns the <i>remainder</i> of a division (where the result
2126 has the same sign as the dividend, <tt>var1</tt>), not the <i>modulo</i>
2127 operator (where the result has the same sign as the divisor, <tt>var2</tt>) of
2128 a value. For more information about the difference, see <a
2129 href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The
2130 Math Forum</a>. For a table of how this is implemented in various languages,
2131 please see <a href="http://en.wikipedia.org/wiki/Modulo_operation">
2132 Wikipedia: modulo operation</a>.</p>
2134 <pre> <result> = srem i32 4, %var <i>; yields {i32}:result = 4 % %var</i>
2138 <!-- _______________________________________________________________________ -->
2139 <div class="doc_subsubsection"> <a name="i_frem">'<tt>frem</tt>'
2140 Instruction</a> </div>
2141 <div class="doc_text">
2143 <pre> <result> = frem <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2146 <p>The '<tt>frem</tt>' instruction returns the remainder from the
2147 division of its two operands.</p>
2149 <p>The two arguments to the '<tt>frem</tt>' instruction must be
2150 <a href="#t_floating">floating point</a> values. Both arguments must have
2151 identical types. This instruction can also take <a href="#t_vector">vector</a>
2152 versions of floating point values.</p>
2154 <p>This instruction returns the <i>remainder</i> of a division.</p>
2156 <pre> <result> = frem float 4.0, %var <i>; yields {float}:result = 4.0 % %var</i>
2160 <!-- ======================================================================= -->
2161 <div class="doc_subsection"> <a name="bitwiseops">Bitwise Binary
2162 Operations</a> </div>
2163 <div class="doc_text">
2164 <p>Bitwise binary operators are used to do various forms of
2165 bit-twiddling in a program. They are generally very efficient
2166 instructions and can commonly be strength reduced from other
2167 instructions. They require two operands, execute an operation on them,
2168 and produce a single value. The resulting value of the bitwise binary
2169 operators is always the same type as its first operand.</p>
2172 <!-- _______________________________________________________________________ -->
2173 <div class="doc_subsubsection"> <a name="i_shl">'<tt>shl</tt>'
2174 Instruction</a> </div>
2175 <div class="doc_text">
2177 <pre> <result> = shl <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2182 <p>The '<tt>shl</tt>' instruction returns the first operand shifted to
2183 the left a specified number of bits.</p>
2187 <p>Both arguments to the '<tt>shl</tt>' instruction must be the same <a
2188 href="#t_integer">integer</a> type.</p>
2192 <p>The value produced is <tt>var1</tt> * 2<sup><tt>var2</tt></sup>. If
2193 <tt>var2</tt> is (statically or dynamically) equal to or larger than the number
2194 of bits in <tt>var1</tt>, the result is undefined.</p>
2196 <h5>Example:</h5><pre>
2197 <result> = shl i32 4, %var <i>; yields {i32}: 4 << %var</i>
2198 <result> = shl i32 4, 2 <i>; yields {i32}: 16</i>
2199 <result> = shl i32 1, 10 <i>; yields {i32}: 1024</i>
2200 <result> = shl i32 1, 32 <i>; undefined</i>
2203 <!-- _______________________________________________________________________ -->
2204 <div class="doc_subsubsection"> <a name="i_lshr">'<tt>lshr</tt>'
2205 Instruction</a> </div>
2206 <div class="doc_text">
2208 <pre> <result> = lshr <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2212 <p>The '<tt>lshr</tt>' instruction (logical shift right) returns the first
2213 operand shifted to the right a specified number of bits with zero fill.</p>
2216 <p>Both arguments to the '<tt>lshr</tt>' instruction must be the same
2217 <a href="#t_integer">integer</a> type.</p>
2221 <p>This instruction always performs a logical shift right operation. The most
2222 significant bits of the result will be filled with zero bits after the
2223 shift. If <tt>var2</tt> is (statically or dynamically) equal to or larger than
2224 the number of bits in <tt>var1</tt>, the result is undefined.</p>
2228 <result> = lshr i32 4, 1 <i>; yields {i32}:result = 2</i>
2229 <result> = lshr i32 4, 2 <i>; yields {i32}:result = 1</i>
2230 <result> = lshr i8 4, 3 <i>; yields {i8}:result = 0</i>
2231 <result> = lshr i8 -2, 1 <i>; yields {i8}:result = 0x7FFFFFFF </i>
2232 <result> = lshr i32 1, 32 <i>; undefined</i>
2236 <!-- _______________________________________________________________________ -->
2237 <div class="doc_subsubsection"> <a name="i_ashr">'<tt>ashr</tt>'
2238 Instruction</a> </div>
2239 <div class="doc_text">
2242 <pre> <result> = ashr <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2246 <p>The '<tt>ashr</tt>' instruction (arithmetic shift right) returns the first
2247 operand shifted to the right a specified number of bits with sign extension.</p>
2250 <p>Both arguments to the '<tt>ashr</tt>' instruction must be the same
2251 <a href="#t_integer">integer</a> type.</p>
2254 <p>This instruction always performs an arithmetic shift right operation,
2255 The most significant bits of the result will be filled with the sign bit
2256 of <tt>var1</tt>. If <tt>var2</tt> is (statically or dynamically) equal to or
2257 larger than the number of bits in <tt>var1</tt>, the result is undefined.
2262 <result> = ashr i32 4, 1 <i>; yields {i32}:result = 2</i>
2263 <result> = ashr i32 4, 2 <i>; yields {i32}:result = 1</i>
2264 <result> = ashr i8 4, 3 <i>; yields {i8}:result = 0</i>
2265 <result> = ashr i8 -2, 1 <i>; yields {i8}:result = -1</i>
2266 <result> = ashr i32 1, 32 <i>; undefined</i>
2270 <!-- _______________________________________________________________________ -->
2271 <div class="doc_subsubsection"> <a name="i_and">'<tt>and</tt>'
2272 Instruction</a> </div>
2273 <div class="doc_text">
2275 <pre> <result> = and <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2278 <p>The '<tt>and</tt>' instruction returns the bitwise logical and of
2279 its two operands.</p>
2281 <p>The two arguments to the '<tt>and</tt>' instruction must be <a
2282 href="#t_integer">integer</a> values. Both arguments must have
2283 identical types.</p>
2285 <p>The truth table used for the '<tt>and</tt>' instruction is:</p>
2287 <div style="align: center">
2288 <table border="1" cellspacing="0" cellpadding="4">
2319 <pre> <result> = and i32 4, %var <i>; yields {i32}:result = 4 & %var</i>
2320 <result> = and i32 15, 40 <i>; yields {i32}:result = 8</i>
2321 <result> = and i32 4, 8 <i>; yields {i32}:result = 0</i>
2324 <!-- _______________________________________________________________________ -->
2325 <div class="doc_subsubsection"> <a name="i_or">'<tt>or</tt>' Instruction</a> </div>
2326 <div class="doc_text">
2328 <pre> <result> = or <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2331 <p>The '<tt>or</tt>' instruction returns the bitwise logical inclusive
2332 or of its two operands.</p>
2334 <p>The two arguments to the '<tt>or</tt>' instruction must be <a
2335 href="#t_integer">integer</a> values. Both arguments must have
2336 identical types.</p>
2338 <p>The truth table used for the '<tt>or</tt>' instruction is:</p>
2340 <div style="align: center">
2341 <table border="1" cellspacing="0" cellpadding="4">
2372 <pre> <result> = or i32 4, %var <i>; yields {i32}:result = 4 | %var</i>
2373 <result> = or i32 15, 40 <i>; yields {i32}:result = 47</i>
2374 <result> = or i32 4, 8 <i>; yields {i32}:result = 12</i>
2377 <!-- _______________________________________________________________________ -->
2378 <div class="doc_subsubsection"> <a name="i_xor">'<tt>xor</tt>'
2379 Instruction</a> </div>
2380 <div class="doc_text">
2382 <pre> <result> = xor <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2385 <p>The '<tt>xor</tt>' instruction returns the bitwise logical exclusive
2386 or of its two operands. The <tt>xor</tt> is used to implement the
2387 "one's complement" operation, which is the "~" operator in C.</p>
2389 <p>The two arguments to the '<tt>xor</tt>' instruction must be <a
2390 href="#t_integer">integer</a> values. Both arguments must have
2391 identical types.</p>
2393 <p>The truth table used for the '<tt>xor</tt>' instruction is:</p>
2395 <div style="align: center">
2396 <table border="1" cellspacing="0" cellpadding="4">
2428 <pre> <result> = xor i32 4, %var <i>; yields {i32}:result = 4 ^ %var</i>
2429 <result> = xor i32 15, 40 <i>; yields {i32}:result = 39</i>
2430 <result> = xor i32 4, 8 <i>; yields {i32}:result = 12</i>
2431 <result> = xor i32 %V, -1 <i>; yields {i32}:result = ~%V</i>
2435 <!-- ======================================================================= -->
2436 <div class="doc_subsection">
2437 <a name="vectorops">Vector Operations</a>
2440 <div class="doc_text">
2442 <p>LLVM supports several instructions to represent vector operations in a
2443 target-independent manner. These instructions cover the element-access and
2444 vector-specific operations needed to process vectors effectively. While LLVM
2445 does directly support these vector operations, many sophisticated algorithms
2446 will want to use target-specific intrinsics to take full advantage of a specific
2451 <!-- _______________________________________________________________________ -->
2452 <div class="doc_subsubsection">
2453 <a name="i_extractelement">'<tt>extractelement</tt>' Instruction</a>
2456 <div class="doc_text">
2461 <result> = extractelement <n x <ty>> <val>, i32 <idx> <i>; yields <ty></i>
2467 The '<tt>extractelement</tt>' instruction extracts a single scalar
2468 element from a vector at a specified index.
2475 The first operand of an '<tt>extractelement</tt>' instruction is a
2476 value of <a href="#t_vector">vector</a> type. The second operand is
2477 an index indicating the position from which to extract the element.
2478 The index may be a variable.</p>
2483 The result is a scalar of the same type as the element type of
2484 <tt>val</tt>. Its value is the value at position <tt>idx</tt> of
2485 <tt>val</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the
2486 results are undefined.
2492 %result = extractelement <4 x i32> %vec, i32 0 <i>; yields i32</i>
2497 <!-- _______________________________________________________________________ -->
2498 <div class="doc_subsubsection">
2499 <a name="i_insertelement">'<tt>insertelement</tt>' Instruction</a>
2502 <div class="doc_text">
2507 <result> = insertelement <n x <ty>> <val>, <ty> <elt>, i32 <idx> <i>; yields <n x <ty>></i>
2513 The '<tt>insertelement</tt>' instruction inserts a scalar
2514 element into a vector at a specified index.
2521 The first operand of an '<tt>insertelement</tt>' instruction is a
2522 value of <a href="#t_vector">vector</a> type. The second operand is a
2523 scalar value whose type must equal the element type of the first
2524 operand. The third operand is an index indicating the position at
2525 which to insert the value. The index may be a variable.</p>
2530 The result is a vector of the same type as <tt>val</tt>. Its
2531 element values are those of <tt>val</tt> except at position
2532 <tt>idx</tt>, where it gets the value <tt>elt</tt>. If <tt>idx</tt>
2533 exceeds the length of <tt>val</tt>, the results are undefined.
2539 %result = insertelement <4 x i32> %vec, i32 1, i32 0 <i>; yields <4 x i32></i>
2543 <!-- _______________________________________________________________________ -->
2544 <div class="doc_subsubsection">
2545 <a name="i_shufflevector">'<tt>shufflevector</tt>' Instruction</a>
2548 <div class="doc_text">
2553 <result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <n x i32> <mask> <i>; yields <n x <ty>></i>
2559 The '<tt>shufflevector</tt>' instruction constructs a permutation of elements
2560 from two input vectors, returning a vector of the same type.
2566 The first two operands of a '<tt>shufflevector</tt>' instruction are vectors
2567 with types that match each other and types that match the result of the
2568 instruction. The third argument is a shuffle mask, which has the same number
2569 of elements as the other vector type, but whose element type is always 'i32'.
2573 The shuffle mask operand is required to be a constant vector with either
2574 constant integer or undef values.
2580 The elements of the two input vectors are numbered from left to right across
2581 both of the vectors. The shuffle mask operand specifies, for each element of
2582 the result vector, which element of the two input registers the result element
2583 gets. The element selector may be undef (meaning "don't care") and the second
2584 operand may be undef if performing a shuffle from only one vector.
2590 %result = shufflevector <4 x i32> %v1, <4 x i32> %v2,
2591 <4 x i32> <i32 0, i32 4, i32 1, i32 5> <i>; yields <4 x i32></i>
2592 %result = shufflevector <4 x i32> %v1, <4 x i32> undef,
2593 <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> - Identity shuffle.
2598 <!-- ======================================================================= -->
2599 <div class="doc_subsection">
2600 <a name="memoryops">Memory Access and Addressing Operations</a>
2603 <div class="doc_text">
2605 <p>A key design point of an SSA-based representation is how it
2606 represents memory. In LLVM, no memory locations are in SSA form, which
2607 makes things very simple. This section describes how to read, write,
2608 allocate, and free memory in LLVM.</p>
2612 <!-- _______________________________________________________________________ -->
2613 <div class="doc_subsubsection">
2614 <a name="i_malloc">'<tt>malloc</tt>' Instruction</a>
2617 <div class="doc_text">
2622 <result> = malloc <type>[, i32 <NumElements>][, align <alignment>] <i>; yields {type*}:result</i>
2627 <p>The '<tt>malloc</tt>' instruction allocates memory from the system
2628 heap and returns a pointer to it.</p>
2632 <p>The '<tt>malloc</tt>' instruction allocates
2633 <tt>sizeof(<type>)*NumElements</tt>
2634 bytes of memory from the operating system and returns a pointer of the
2635 appropriate type to the program. If "NumElements" is specified, it is the
2636 number of elements allocated. If an alignment is specified, the value result
2637 of the allocation is guaranteed to be aligned to at least that boundary. If
2638 not specified, or if zero, the target can choose to align the allocation on any
2639 convenient boundary.</p>
2641 <p>'<tt>type</tt>' must be a sized type.</p>
2645 <p>Memory is allocated using the system "<tt>malloc</tt>" function, and
2646 a pointer is returned.</p>
2651 %array = malloc [4 x i8 ] <i>; yields {[%4 x i8]*}:array</i>
2653 %size = <a href="#i_add">add</a> i32 2, 2 <i>; yields {i32}:size = i32 4</i>
2654 %array1 = malloc i8, i32 4 <i>; yields {i8*}:array1</i>
2655 %array2 = malloc [12 x i8], i32 %size <i>; yields {[12 x i8]*}:array2</i>
2656 %array3 = malloc i32, i32 4, align 1024 <i>; yields {i32*}:array3</i>
2657 %array4 = malloc i32, align 1024 <i>; yields {i32*}:array4</i>
2661 <!-- _______________________________________________________________________ -->
2662 <div class="doc_subsubsection">
2663 <a name="i_free">'<tt>free</tt>' Instruction</a>
2666 <div class="doc_text">
2671 free <type> <value> <i>; yields {void}</i>
2676 <p>The '<tt>free</tt>' instruction returns memory back to the unused
2677 memory heap to be reallocated in the future.</p>
2681 <p>'<tt>value</tt>' shall be a pointer value that points to a value
2682 that was allocated with the '<tt><a href="#i_malloc">malloc</a></tt>'
2687 <p>Access to the memory pointed to by the pointer is no longer defined
2688 after this instruction executes.</p>
2693 %array = <a href="#i_malloc">malloc</a> [4 x i8] <i>; yields {[4 x i8]*}:array</i>
2694 free [4 x i8]* %array
2698 <!-- _______________________________________________________________________ -->
2699 <div class="doc_subsubsection">
2700 <a name="i_alloca">'<tt>alloca</tt>' Instruction</a>
2703 <div class="doc_text">
2708 <result> = alloca <type>[, i32 <NumElements>][, align <alignment>] <i>; yields {type*}:result</i>
2713 <p>The '<tt>alloca</tt>' instruction allocates memory on the stack frame of the
2714 currently executing function, to be automatically released when this function
2715 returns to its caller.</p>
2719 <p>The '<tt>alloca</tt>' instruction allocates <tt>sizeof(<type>)*NumElements</tt>
2720 bytes of memory on the runtime stack, returning a pointer of the
2721 appropriate type to the program. If "NumElements" is specified, it is the
2722 number of elements allocated. If an alignment is specified, the value result
2723 of the allocation is guaranteed to be aligned to at least that boundary. If
2724 not specified, or if zero, the target can choose to align the allocation on any
2725 convenient boundary.</p>
2727 <p>'<tt>type</tt>' may be any sized type.</p>
2731 <p>Memory is allocated; a pointer is returned. '<tt>alloca</tt>'d
2732 memory is automatically released when the function returns. The '<tt>alloca</tt>'
2733 instruction is commonly used to represent automatic variables that must
2734 have an address available. When the function returns (either with the <tt><a
2735 href="#i_ret">ret</a></tt> or <tt><a href="#i_unwind">unwind</a></tt>
2736 instructions), the memory is reclaimed.</p>
2741 %ptr = alloca i32 <i>; yields {i32*}:ptr</i>
2742 %ptr = alloca i32, i32 4 <i>; yields {i32*}:ptr</i>
2743 %ptr = alloca i32, i32 4, align 1024 <i>; yields {i32*}:ptr</i>
2744 %ptr = alloca i32, align 1024 <i>; yields {i32*}:ptr</i>
2748 <!-- _______________________________________________________________________ -->
2749 <div class="doc_subsubsection"> <a name="i_load">'<tt>load</tt>'
2750 Instruction</a> </div>
2751 <div class="doc_text">
2753 <pre> <result> = load <ty>* <pointer>[, align <alignment>]<br> <result> = volatile load <ty>* <pointer>[, align <alignment>]<br></pre>
2755 <p>The '<tt>load</tt>' instruction is used to read from memory.</p>
2757 <p>The argument to the '<tt>load</tt>' instruction specifies the memory
2758 address from which to load. The pointer must point to a <a
2759 href="#t_firstclass">first class</a> type. If the <tt>load</tt> is
2760 marked as <tt>volatile</tt>, then the optimizer is not allowed to modify
2761 the number or order of execution of this <tt>load</tt> with other
2762 volatile <tt>load</tt> and <tt><a href="#i_store">store</a></tt>
2765 <p>The location of memory pointed to is loaded.</p>
2767 <pre> %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i>
2769 href="#i_store">store</a> i32 3, i32* %ptr <i>; yields {void}</i>
2770 %val = load i32* %ptr <i>; yields {i32}:val = i32 3</i>
2773 <!-- _______________________________________________________________________ -->
2774 <div class="doc_subsubsection"> <a name="i_store">'<tt>store</tt>'
2775 Instruction</a> </div>
2776 <div class="doc_text">
2778 <pre> store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i>
2779 volatile store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i>
2782 <p>The '<tt>store</tt>' instruction is used to write to memory.</p>
2784 <p>There are two arguments to the '<tt>store</tt>' instruction: a value
2785 to store and an address at which to store it. The type of the '<tt><pointer></tt>'
2786 operand must be a pointer to the type of the '<tt><value></tt>'
2787 operand. If the <tt>store</tt> is marked as <tt>volatile</tt>, then the
2788 optimizer is not allowed to modify the number or order of execution of
2789 this <tt>store</tt> with other volatile <tt>load</tt> and <tt><a
2790 href="#i_store">store</a></tt> instructions.</p>
2792 <p>The contents of memory are updated to contain '<tt><value></tt>'
2793 at the location specified by the '<tt><pointer></tt>' operand.</p>
2795 <pre> %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i>
2796 store i32 3, i32* %ptr <i>; yields {void}</i>
2797 %val = <a href="#i_load">load</a> i32* %ptr <i>; yields {i32}:val = i32 3</i>
2801 <!-- _______________________________________________________________________ -->
2802 <div class="doc_subsubsection">
2803 <a name="i_getelementptr">'<tt>getelementptr</tt>' Instruction</a>
2806 <div class="doc_text">
2809 <result> = getelementptr <ty>* <ptrval>{, <ty> <idx>}*
2815 The '<tt>getelementptr</tt>' instruction is used to get the address of a
2816 subelement of an aggregate data structure.</p>
2820 <p>This instruction takes a list of integer operands that indicate what
2821 elements of the aggregate object to index to. The actual types of the arguments
2822 provided depend on the type of the first pointer argument. The
2823 '<tt>getelementptr</tt>' instruction is used to index down through the type
2824 levels of a structure or to a specific index in an array. When indexing into a
2825 structure, only <tt>i32</tt> integer constants are allowed. When indexing
2826 into an array or pointer, only integers of 32 or 64 bits are allowed, and will
2827 be sign extended to 64-bit values.</p>
2829 <p>For example, let's consider a C code fragment and how it gets
2830 compiled to LLVM:</p>
2832 <div class="doc_code">
2845 int *foo(struct ST *s) {
2846 return &s[1].Z.B[5][13];
2851 <p>The LLVM code generated by the GCC frontend is:</p>
2853 <div class="doc_code">
2855 %RT = type { i8 , [10 x [20 x i32]], i8 }
2856 %ST = type { i32, double, %RT }
2858 define i32* %foo(%ST* %s) {
2860 %reg = getelementptr %ST* %s, i32 1, i32 2, i32 1, i32 5, i32 13
2868 <p>The index types specified for the '<tt>getelementptr</tt>' instruction depend
2869 on the pointer type that is being indexed into. <a href="#t_pointer">Pointer</a>
2870 and <a href="#t_array">array</a> types can use a 32-bit or 64-bit
2871 <a href="#t_integer">integer</a> type but the value will always be sign extended
2872 to 64-bits. <a href="#t_struct">Structure</a> types require <tt>i32</tt>
2873 <b>constants</b>.</p>
2875 <p>In the example above, the first index is indexing into the '<tt>%ST*</tt>'
2876 type, which is a pointer, yielding a '<tt>%ST</tt>' = '<tt>{ i32, double, %RT
2877 }</tt>' type, a structure. The second index indexes into the third element of
2878 the structure, yielding a '<tt>%RT</tt>' = '<tt>{ i8 , [10 x [20 x i32]],
2879 i8 }</tt>' type, another structure. The third index indexes into the second
2880 element of the structure, yielding a '<tt>[10 x [20 x i32]]</tt>' type, an
2881 array. The two dimensions of the array are subscripted into, yielding an
2882 '<tt>i32</tt>' type. The '<tt>getelementptr</tt>' instruction returns a pointer
2883 to this element, thus computing a value of '<tt>i32*</tt>' type.</p>
2885 <p>Note that it is perfectly legal to index partially through a
2886 structure, returning a pointer to an inner element. Because of this,
2887 the LLVM code for the given testcase is equivalent to:</p>
2890 define i32* %foo(%ST* %s) {
2891 %t1 = getelementptr %ST* %s, i32 1 <i>; yields %ST*:%t1</i>
2892 %t2 = getelementptr %ST* %t1, i32 0, i32 2 <i>; yields %RT*:%t2</i>
2893 %t3 = getelementptr %RT* %t2, i32 0, i32 1 <i>; yields [10 x [20 x i32]]*:%t3</i>
2894 %t4 = getelementptr [10 x [20 x i32]]* %t3, i32 0, i32 5 <i>; yields [20 x i32]*:%t4</i>
2895 %t5 = getelementptr [20 x i32]* %t4, i32 0, i32 13 <i>; yields i32*:%t5</i>
2900 <p>Note that it is undefined to access an array out of bounds: array and
2901 pointer indexes must always be within the defined bounds of the array type.
2902 The one exception for this rules is zero length arrays. These arrays are
2903 defined to be accessible as variable length arrays, which requires access
2904 beyond the zero'th element.</p>
2906 <p>The getelementptr instruction is often confusing. For some more insight
2907 into how it works, see <a href="GetElementPtr.html">the getelementptr
2913 <i>; yields [12 x i8]*:aptr</i>
2914 %aptr = getelementptr {i32, [12 x i8]}* %sptr, i64 0, i32 1
2918 <!-- ======================================================================= -->
2919 <div class="doc_subsection"> <a name="convertops">Conversion Operations</a>
2921 <div class="doc_text">
2922 <p>The instructions in this category are the conversion instructions (casting)
2923 which all take a single operand and a type. They perform various bit conversions
2927 <!-- _______________________________________________________________________ -->
2928 <div class="doc_subsubsection">
2929 <a name="i_trunc">'<tt>trunc .. to</tt>' Instruction</a>
2931 <div class="doc_text">
2935 <result> = trunc <ty> <value> to <ty2> <i>; yields ty2</i>
2940 The '<tt>trunc</tt>' instruction truncates its operand to the type <tt>ty2</tt>.
2945 The '<tt>trunc</tt>' instruction takes a <tt>value</tt> to trunc, which must
2946 be an <a href="#t_integer">integer</a> type, and a type that specifies the size
2947 and type of the result, which must be an <a href="#t_integer">integer</a>
2948 type. The bit size of <tt>value</tt> must be larger than the bit size of
2949 <tt>ty2</tt>. Equal sized types are not allowed.</p>
2953 The '<tt>trunc</tt>' instruction truncates the high order bits in <tt>value</tt>
2954 and converts the remaining bits to <tt>ty2</tt>. Since the source size must be
2955 larger than the destination size, <tt>trunc</tt> cannot be a <i>no-op cast</i>.
2956 It will always truncate bits.</p>
2960 %X = trunc i32 257 to i8 <i>; yields i8:1</i>
2961 %Y = trunc i32 123 to i1 <i>; yields i1:true</i>
2962 %Y = trunc i32 122 to i1 <i>; yields i1:false</i>
2966 <!-- _______________________________________________________________________ -->
2967 <div class="doc_subsubsection">
2968 <a name="i_zext">'<tt>zext .. to</tt>' Instruction</a>
2970 <div class="doc_text">
2974 <result> = zext <ty> <value> to <ty2> <i>; yields ty2</i>
2978 <p>The '<tt>zext</tt>' instruction zero extends its operand to type
2983 <p>The '<tt>zext</tt>' instruction takes a value to cast, which must be of
2984 <a href="#t_integer">integer</a> type, and a type to cast it to, which must
2985 also be of <a href="#t_integer">integer</a> type. The bit size of the
2986 <tt>value</tt> must be smaller than the bit size of the destination type,
2990 <p>The <tt>zext</tt> fills the high order bits of the <tt>value</tt> with zero
2991 bits until it reaches the size of the destination type, <tt>ty2</tt>.</p>
2993 <p>When zero extending from i1, the result will always be either 0 or 1.</p>
2997 %X = zext i32 257 to i64 <i>; yields i64:257</i>
2998 %Y = zext i1 true to i32 <i>; yields i32:1</i>
3002 <!-- _______________________________________________________________________ -->
3003 <div class="doc_subsubsection">
3004 <a name="i_sext">'<tt>sext .. to</tt>' Instruction</a>
3006 <div class="doc_text">
3010 <result> = sext <ty> <value> to <ty2> <i>; yields ty2</i>
3014 <p>The '<tt>sext</tt>' sign extends <tt>value</tt> to the type <tt>ty2</tt>.</p>
3018 The '<tt>sext</tt>' instruction takes a value to cast, which must be of
3019 <a href="#t_integer">integer</a> type, and a type to cast it to, which must
3020 also be of <a href="#t_integer">integer</a> type. The bit size of the
3021 <tt>value</tt> must be smaller than the bit size of the destination type,
3026 The '<tt>sext</tt>' instruction performs a sign extension by copying the sign
3027 bit (highest order bit) of the <tt>value</tt> until it reaches the bit size of
3028 the type <tt>ty2</tt>.</p>
3030 <p>When sign extending from i1, the extension always results in -1 or 0.</p>
3034 %X = sext i8 -1 to i16 <i>; yields i16 :65535</i>
3035 %Y = sext i1 true to i32 <i>; yields i32:-1</i>
3039 <!-- _______________________________________________________________________ -->
3040 <div class="doc_subsubsection">
3041 <a name="i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a>
3044 <div class="doc_text">
3049 <result> = fptrunc <ty> <value> to <ty2> <i>; yields ty2</i>
3053 <p>The '<tt>fptrunc</tt>' instruction truncates <tt>value</tt> to type
3058 <p>The '<tt>fptrunc</tt>' instruction takes a <a href="#t_floating">floating
3059 point</a> value to cast and a <a href="#t_floating">floating point</a> type to
3060 cast it to. The size of <tt>value</tt> must be larger than the size of
3061 <tt>ty2</tt>. This implies that <tt>fptrunc</tt> cannot be used to make a
3062 <i>no-op cast</i>.</p>
3065 <p> The '<tt>fptrunc</tt>' instruction truncates a <tt>value</tt> from a larger
3066 <a href="#t_floating">floating point</a> type to a smaller
3067 <a href="#t_floating">floating point</a> type. If the value cannot fit within
3068 the destination type, <tt>ty2</tt>, then the results are undefined.</p>
3072 %X = fptrunc double 123.0 to float <i>; yields float:123.0</i>
3073 %Y = fptrunc double 1.0E+300 to float <i>; yields undefined</i>
3077 <!-- _______________________________________________________________________ -->
3078 <div class="doc_subsubsection">
3079 <a name="i_fpext">'<tt>fpext .. to</tt>' Instruction</a>
3081 <div class="doc_text">
3085 <result> = fpext <ty> <value> to <ty2> <i>; yields ty2</i>
3089 <p>The '<tt>fpext</tt>' extends a floating point <tt>value</tt> to a larger
3090 floating point value.</p>
3093 <p>The '<tt>fpext</tt>' instruction takes a
3094 <a href="#t_floating">floating point</a> <tt>value</tt> to cast,
3095 and a <a href="#t_floating">floating point</a> type to cast it to. The source
3096 type must be smaller than the destination type.</p>
3099 <p>The '<tt>fpext</tt>' instruction extends the <tt>value</tt> from a smaller
3100 <a href="#t_floating">floating point</a> type to a larger
3101 <a href="#t_floating">floating point</a> type. The <tt>fpext</tt> cannot be
3102 used to make a <i>no-op cast</i> because it always changes bits. Use
3103 <tt>bitcast</tt> to make a <i>no-op cast</i> for a floating point cast.</p>
3107 %X = fpext float 3.1415 to double <i>; yields double:3.1415</i>
3108 %Y = fpext float 1.0 to float <i>; yields float:1.0 (no-op)</i>
3112 <!-- _______________________________________________________________________ -->
3113 <div class="doc_subsubsection">
3114 <a name="i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a>
3116 <div class="doc_text">
3120 <result> = fptoui <ty> <value> to <ty2> <i>; yields ty2</i>
3124 <p>The '<tt>fptoui</tt>' converts a floating point <tt>value</tt> to its
3125 unsigned integer equivalent of type <tt>ty2</tt>.
3129 <p>The '<tt>fptoui</tt>' instruction takes a value to cast, which must be a
3130 <a href="#t_floating">floating point</a> value, and a type to cast it to, which
3131 must be an <a href="#t_integer">integer</a> type.</p>
3134 <p> The '<tt>fptoui</tt>' instruction converts its
3135 <a href="#t_floating">floating point</a> operand into the nearest (rounding
3136 towards zero) unsigned integer value. If the value cannot fit in <tt>ty2</tt>,
3137 the results are undefined.</p>
3141 %X = fptoui double 123.0 to i32 <i>; yields i32:123</i>
3142 %Y = fptoui float 1.0E+300 to i1 <i>; yields undefined:1</i>
3143 %X = fptoui float 1.04E+17 to i8 <i>; yields undefined:1</i>
3147 <!-- _______________________________________________________________________ -->
3148 <div class="doc_subsubsection">
3149 <a name="i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a>
3151 <div class="doc_text">
3155 <result> = fptosi <ty> <value> to <ty2> <i>; yields ty2</i>
3159 <p>The '<tt>fptosi</tt>' instruction converts
3160 <a href="#t_floating">floating point</a> <tt>value</tt> to type <tt>ty2</tt>.
3165 <p> The '<tt>fptosi</tt>' instruction takes a value to cast, which must be a
3166 <a href="#t_floating">floating point</a> value, and a type to cast it to, which
3167 must also be an <a href="#t_integer">integer</a> type.</p>
3170 <p>The '<tt>fptosi</tt>' instruction converts its
3171 <a href="#t_floating">floating point</a> operand into the nearest (rounding
3172 towards zero) signed integer value. If the value cannot fit in <tt>ty2</tt>,
3173 the results are undefined.</p>
3177 %X = fptosi double -123.0 to i32 <i>; yields i32:-123</i>
3178 %Y = fptosi float 1.0E-247 to i1 <i>; yields undefined:1</i>
3179 %X = fptosi float 1.04E+17 to i8 <i>; yields undefined:1</i>
3183 <!-- _______________________________________________________________________ -->
3184 <div class="doc_subsubsection">
3185 <a name="i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a>
3187 <div class="doc_text">
3191 <result> = uitofp <ty> <value> to <ty2> <i>; yields ty2</i>
3195 <p>The '<tt>uitofp</tt>' instruction regards <tt>value</tt> as an unsigned
3196 integer and converts that value to the <tt>ty2</tt> type.</p>
3200 <p>The '<tt>uitofp</tt>' instruction takes a value to cast, which must be an
3201 <a href="#t_integer">integer</a> value, and a type to cast it to, which must
3202 be a <a href="#t_floating">floating point</a> type.</p>
3205 <p>The '<tt>uitofp</tt>' instruction interprets its operand as an unsigned
3206 integer quantity and converts it to the corresponding floating point value. If
3207 the value cannot fit in the floating point value, the results are undefined.</p>
3212 %X = uitofp i32 257 to float <i>; yields float:257.0</i>
3213 %Y = uitofp i8 -1 to double <i>; yields double:255.0</i>
3217 <!-- _______________________________________________________________________ -->
3218 <div class="doc_subsubsection">
3219 <a name="i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a>
3221 <div class="doc_text">
3225 <result> = sitofp <ty> <value> to <ty2> <i>; yields ty2</i>
3229 <p>The '<tt>sitofp</tt>' instruction regards <tt>value</tt> as a signed
3230 integer and converts that value to the <tt>ty2</tt> type.</p>
3233 <p>The '<tt>sitofp</tt>' instruction takes a value to cast, which must be an
3234 <a href="#t_integer">integer</a> value, and a type to cast it to, which must be
3235 a <a href="#t_floating">floating point</a> type.</p>
3238 <p>The '<tt>sitofp</tt>' instruction interprets its operand as a signed
3239 integer quantity and converts it to the corresponding floating point value. If
3240 the value cannot fit in the floating point value, the results are undefined.</p>
3244 %X = sitofp i32 257 to float <i>; yields float:257.0</i>
3245 %Y = sitofp i8 -1 to double <i>; yields double:-1.0</i>
3249 <!-- _______________________________________________________________________ -->
3250 <div class="doc_subsubsection">
3251 <a name="i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a>
3253 <div class="doc_text">
3257 <result> = ptrtoint <ty> <value> to <ty2> <i>; yields ty2</i>
3261 <p>The '<tt>ptrtoint</tt>' instruction converts the pointer <tt>value</tt> to
3262 the integer type <tt>ty2</tt>.</p>
3265 <p>The '<tt>ptrtoint</tt>' instruction takes a <tt>value</tt> to cast, which
3266 must be a <a href="#t_pointer">pointer</a> value, and a type to cast it to
3267 <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> type.
3270 <p>The '<tt>ptrtoint</tt>' instruction converts <tt>value</tt> to integer type
3271 <tt>ty2</tt> by interpreting the pointer value as an integer and either
3272 truncating or zero extending that value to the size of the integer type. If
3273 <tt>value</tt> is smaller than <tt>ty2</tt> then a zero extension is done. If
3274 <tt>value</tt> is larger than <tt>ty2</tt> then a truncation is done. If they
3275 are the same size, then nothing is done (<i>no-op cast</i>) other than a type
3280 %X = ptrtoint i32* %X to i8 <i>; yields truncation on 32-bit architecture</i>
3281 %Y = ptrtoint i32* %x to i64 <i>; yields zero extension on 32-bit architecture</i>
3285 <!-- _______________________________________________________________________ -->
3286 <div class="doc_subsubsection">
3287 <a name="i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a>
3289 <div class="doc_text">
3293 <result> = inttoptr <ty> <value> to <ty2> <i>; yields ty2</i>
3297 <p>The '<tt>inttoptr</tt>' instruction converts an integer <tt>value</tt> to
3298 a pointer type, <tt>ty2</tt>.</p>
3301 <p>The '<tt>inttoptr</tt>' instruction takes an <a href="#t_integer">integer</a>
3302 value to cast, and a type to cast it to, which must be a
3303 <a href="#t_pointer">pointer</a> type.
3306 <p>The '<tt>inttoptr</tt>' instruction converts <tt>value</tt> to type
3307 <tt>ty2</tt> by applying either a zero extension or a truncation depending on
3308 the size of the integer <tt>value</tt>. If <tt>value</tt> is larger than the
3309 size of a pointer then a truncation is done. If <tt>value</tt> is smaller than
3310 the size of a pointer then a zero extension is done. If they are the same size,
3311 nothing is done (<i>no-op cast</i>).</p>
3315 %X = inttoptr i32 255 to i32* <i>; yields zero extension on 64-bit architecture</i>
3316 %X = inttoptr i32 255 to i32* <i>; yields no-op on 32-bit architecture</i>
3317 %Y = inttoptr i64 0 to i32* <i>; yields truncation on 32-bit architecture</i>
3321 <!-- _______________________________________________________________________ -->
3322 <div class="doc_subsubsection">
3323 <a name="i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a>
3325 <div class="doc_text">
3329 <result> = bitcast <ty> <value> to <ty2> <i>; yields ty2</i>
3333 <p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type
3334 <tt>ty2</tt> without changing any bits.</p>
3337 <p>The '<tt>bitcast</tt>' instruction takes a value to cast, which must be
3338 a first class value, and a type to cast it to, which must also be a <a
3339 href="#t_firstclass">first class</a> type. The bit sizes of <tt>value</tt>
3340 and the destination type, <tt>ty2</tt>, must be identical. If the source
3341 type is a pointer, the destination type must also be a pointer.</p>
3344 <p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type
3345 <tt>ty2</tt>. It is always a <i>no-op cast</i> because no bits change with
3346 this conversion. The conversion is done as if the <tt>value</tt> had been
3347 stored to memory and read back as type <tt>ty2</tt>. Pointer types may only be
3348 converted to other pointer types with this instruction. To convert pointers to
3349 other types, use the <a href="#i_inttoptr">inttoptr</a> or
3350 <a href="#i_ptrtoint">ptrtoint</a> instructions first.</p>
3354 %X = bitcast i8 255 to i8 <i>; yields i8 :-1</i>
3355 %Y = bitcast i32* %x to sint* <i>; yields sint*:%x</i>
3356 %Z = bitcast <2xint> %V to i64; <i>; yields i64: %V</i>
3360 <!-- ======================================================================= -->
3361 <div class="doc_subsection"> <a name="otherops">Other Operations</a> </div>
3362 <div class="doc_text">
3363 <p>The instructions in this category are the "miscellaneous"
3364 instructions, which defy better classification.</p>
3367 <!-- _______________________________________________________________________ -->
3368 <div class="doc_subsubsection"><a name="i_icmp">'<tt>icmp</tt>' Instruction</a>
3370 <div class="doc_text">
3372 <pre> <result> = icmp <cond> <ty> <var1>, <var2> <i>; yields {i1}:result</i>
3375 <p>The '<tt>icmp</tt>' instruction returns a boolean value based on comparison
3376 of its two integer operands.</p>
3378 <p>The '<tt>icmp</tt>' instruction takes three operands. The first operand is
3379 the condition code indicating the kind of comparison to perform. It is not
3380 a value, just a keyword. The possible condition code are:
3382 <li><tt>eq</tt>: equal</li>
3383 <li><tt>ne</tt>: not equal </li>
3384 <li><tt>ugt</tt>: unsigned greater than</li>
3385 <li><tt>uge</tt>: unsigned greater or equal</li>
3386 <li><tt>ult</tt>: unsigned less than</li>
3387 <li><tt>ule</tt>: unsigned less or equal</li>
3388 <li><tt>sgt</tt>: signed greater than</li>
3389 <li><tt>sge</tt>: signed greater or equal</li>
3390 <li><tt>slt</tt>: signed less than</li>
3391 <li><tt>sle</tt>: signed less or equal</li>
3393 <p>The remaining two arguments must be <a href="#t_integer">integer</a> or
3394 <a href="#t_pointer">pointer</a> typed. They must also be identical types.</p>
3396 <p>The '<tt>icmp</tt>' compares <tt>var1</tt> and <tt>var2</tt> according to
3397 the condition code given as <tt>cond</tt>. The comparison performed always
3398 yields a <a href="#t_primitive">i1</a> result, as follows:
3400 <li><tt>eq</tt>: yields <tt>true</tt> if the operands are equal,
3401 <tt>false</tt> otherwise. No sign interpretation is necessary or performed.
3403 <li><tt>ne</tt>: yields <tt>true</tt> if the operands are unequal,
3404 <tt>false</tt> otherwise. No sign interpretation is necessary or performed.
3405 <li><tt>ugt</tt>: interprets the operands as unsigned values and yields
3406 <tt>true</tt> if <tt>var1</tt> is greater than <tt>var2</tt>.</li>
3407 <li><tt>uge</tt>: interprets the operands as unsigned values and yields
3408 <tt>true</tt> if <tt>var1</tt> is greater than or equal to <tt>var2</tt>.</li>
3409 <li><tt>ult</tt>: interprets the operands as unsigned values and yields
3410 <tt>true</tt> if <tt>var1</tt> is less than <tt>var2</tt>.</li>
3411 <li><tt>ule</tt>: interprets the operands as unsigned values and yields
3412 <tt>true</tt> if <tt>var1</tt> is less than or equal to <tt>var2</tt>.</li>
3413 <li><tt>sgt</tt>: interprets the operands as signed values and yields
3414 <tt>true</tt> if <tt>var1</tt> is greater than <tt>var2</tt>.</li>
3415 <li><tt>sge</tt>: interprets the operands as signed values and yields
3416 <tt>true</tt> if <tt>var1</tt> is greater than or equal to <tt>var2</tt>.</li>
3417 <li><tt>slt</tt>: interprets the operands as signed values and yields
3418 <tt>true</tt> if <tt>var1</tt> is less than <tt>var2</tt>.</li>
3419 <li><tt>sle</tt>: interprets the operands as signed values and yields
3420 <tt>true</tt> if <tt>var1</tt> is less than or equal to <tt>var2</tt>.</li>
3422 <p>If the operands are <a href="#t_pointer">pointer</a> typed, the pointer
3423 values are compared as if they were integers.</p>
3426 <pre> <result> = icmp eq i32 4, 5 <i>; yields: result=false</i>
3427 <result> = icmp ne float* %X, %X <i>; yields: result=false</i>
3428 <result> = icmp ult i16 4, 5 <i>; yields: result=true</i>
3429 <result> = icmp sgt i16 4, 5 <i>; yields: result=false</i>
3430 <result> = icmp ule i16 -4, 5 <i>; yields: result=false</i>
3431 <result> = icmp sge i16 4, 5 <i>; yields: result=false</i>
3435 <!-- _______________________________________________________________________ -->
3436 <div class="doc_subsubsection"><a name="i_fcmp">'<tt>fcmp</tt>' Instruction</a>
3438 <div class="doc_text">
3440 <pre> <result> = fcmp <cond> <ty> <var1>, <var2> <i>; yields {i1}:result</i>
3443 <p>The '<tt>fcmp</tt>' instruction returns a boolean value based on comparison
3444 of its floating point operands.</p>
3446 <p>The '<tt>fcmp</tt>' instruction takes three operands. The first operand is
3447 the condition code indicating the kind of comparison to perform. It is not
3448 a value, just a keyword. The possible condition code are:
3450 <li><tt>false</tt>: no comparison, always returns false</li>
3451 <li><tt>oeq</tt>: ordered and equal</li>
3452 <li><tt>ogt</tt>: ordered and greater than </li>
3453 <li><tt>oge</tt>: ordered and greater than or equal</li>
3454 <li><tt>olt</tt>: ordered and less than </li>
3455 <li><tt>ole</tt>: ordered and less than or equal</li>
3456 <li><tt>one</tt>: ordered and not equal</li>
3457 <li><tt>ord</tt>: ordered (no nans)</li>
3458 <li><tt>ueq</tt>: unordered or equal</li>
3459 <li><tt>ugt</tt>: unordered or greater than </li>
3460 <li><tt>uge</tt>: unordered or greater than or equal</li>
3461 <li><tt>ult</tt>: unordered or less than </li>
3462 <li><tt>ule</tt>: unordered or less than or equal</li>
3463 <li><tt>une</tt>: unordered or not equal</li>
3464 <li><tt>uno</tt>: unordered (either nans)</li>
3465 <li><tt>true</tt>: no comparison, always returns true</li>
3467 <p><i>Ordered</i> means that neither operand is a QNAN while
3468 <i>unordered</i> means that either operand may be a QNAN.</p>
3469 <p>The <tt>val1</tt> and <tt>val2</tt> arguments must be
3470 <a href="#t_floating">floating point</a> typed. They must have identical
3473 <p>The '<tt>fcmp</tt>' compares <tt>var1</tt> and <tt>var2</tt> according to
3474 the condition code given as <tt>cond</tt>. The comparison performed always
3475 yields a <a href="#t_primitive">i1</a> result, as follows:
3477 <li><tt>false</tt>: always yields <tt>false</tt>, regardless of operands.</li>
3478 <li><tt>oeq</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3479 <tt>var1</tt> is equal to <tt>var2</tt>.</li>
3480 <li><tt>ogt</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3481 <tt>var1</tt> is greather than <tt>var2</tt>.</li>
3482 <li><tt>oge</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3483 <tt>var1</tt> is greater than or equal to <tt>var2</tt>.</li>
3484 <li><tt>olt</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3485 <tt>var1</tt> is less than <tt>var2</tt>.</li>
3486 <li><tt>ole</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3487 <tt>var1</tt> is less than or equal to <tt>var2</tt>.</li>
3488 <li><tt>one</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3489 <tt>var1</tt> is not equal to <tt>var2</tt>.</li>
3490 <li><tt>ord</tt>: yields <tt>true</tt> if both operands are not a QNAN.</li>
3491 <li><tt>ueq</tt>: yields <tt>true</tt> if either operand is a QNAN or
3492 <tt>var1</tt> is equal to <tt>var2</tt>.</li>
3493 <li><tt>ugt</tt>: yields <tt>true</tt> if either operand is a QNAN or
3494 <tt>var1</tt> is greater than <tt>var2</tt>.</li>
3495 <li><tt>uge</tt>: yields <tt>true</tt> if either operand is a QNAN or
3496 <tt>var1</tt> is greater than or equal to <tt>var2</tt>.</li>
3497 <li><tt>ult</tt>: yields <tt>true</tt> if either operand is a QNAN or
3498 <tt>var1</tt> is less than <tt>var2</tt>.</li>
3499 <li><tt>ule</tt>: yields <tt>true</tt> if either operand is a QNAN or
3500 <tt>var1</tt> is less than or equal to <tt>var2</tt>.</li>
3501 <li><tt>une</tt>: yields <tt>true</tt> if either operand is a QNAN or
3502 <tt>var1</tt> is not equal to <tt>var2</tt>.</li>
3503 <li><tt>uno</tt>: yields <tt>true</tt> if either operand is a QNAN.</li>
3504 <li><tt>true</tt>: always yields <tt>true</tt>, regardless of operands.</li>
3508 <pre> <result> = fcmp oeq float 4.0, 5.0 <i>; yields: result=false</i>
3509 <result> = icmp one float 4.0, 5.0 <i>; yields: result=true</i>
3510 <result> = icmp olt float 4.0, 5.0 <i>; yields: result=true</i>
3511 <result> = icmp ueq double 1.0, 2.0 <i>; yields: result=false</i>
3515 <!-- _______________________________________________________________________ -->
3516 <div class="doc_subsubsection"> <a name="i_phi">'<tt>phi</tt>'
3517 Instruction</a> </div>
3518 <div class="doc_text">
3520 <pre> <result> = phi <ty> [ <val0>, <label0>], ...<br></pre>
3522 <p>The '<tt>phi</tt>' instruction is used to implement the φ node in
3523 the SSA graph representing the function.</p>
3525 <p>The type of the incoming values is specified with the first type
3526 field. After this, the '<tt>phi</tt>' instruction takes a list of pairs
3527 as arguments, with one pair for each predecessor basic block of the
3528 current block. Only values of <a href="#t_firstclass">first class</a>
3529 type may be used as the value arguments to the PHI node. Only labels
3530 may be used as the label arguments.</p>
3531 <p>There must be no non-phi instructions between the start of a basic
3532 block and the PHI instructions: i.e. PHI instructions must be first in
3535 <p>At runtime, the '<tt>phi</tt>' instruction logically takes on the value
3536 specified by the pair corresponding to the predecessor basic block that executed
3537 just prior to the current block.</p>
3539 <pre>Loop: ; Infinite loop that counts from 0 on up...<br> %indvar = phi i32 [ 0, %LoopHeader ], [ %nextindvar, %Loop ]<br> %nextindvar = add i32 %indvar, 1<br> br label %Loop<br></pre>
3542 <!-- _______________________________________________________________________ -->
3543 <div class="doc_subsubsection">
3544 <a name="i_select">'<tt>select</tt>' Instruction</a>
3547 <div class="doc_text">
3552 <result> = select i1 <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i>
3558 The '<tt>select</tt>' instruction is used to choose one value based on a
3559 condition, without branching.
3566 The '<tt>select</tt>' instruction requires a boolean value indicating the condition, and two values of the same <a href="#t_firstclass">first class</a> type.
3572 If the boolean condition evaluates to true, the instruction returns the first
3573 value argument; otherwise, it returns the second value argument.
3579 %X = select i1 true, i8 17, i8 42 <i>; yields i8:17</i>
3584 <!-- _______________________________________________________________________ -->
3585 <div class="doc_subsubsection">
3586 <a name="i_call">'<tt>call</tt>' Instruction</a>
3589 <div class="doc_text">
3593 <result> = [tail] call [<a href="#callingconv">cconv</a>] <ty> [<fnty>*] <fnptrval>(<param list>)
3598 <p>The '<tt>call</tt>' instruction represents a simple function call.</p>
3602 <p>This instruction requires several arguments:</p>
3606 <p>The optional "tail" marker indicates whether the callee function accesses
3607 any allocas or varargs in the caller. If the "tail" marker is present, the
3608 function call is eligible for tail call optimization. Note that calls may
3609 be marked "tail" even if they do not occur before a <a
3610 href="#i_ret"><tt>ret</tt></a> instruction.
3613 <p>The optional "cconv" marker indicates which <a href="#callingconv">calling
3614 convention</a> the call should use. If none is specified, the call defaults
3615 to using C calling conventions.
3618 <p>'<tt>ty</tt>': the type of the call instruction itself which is also
3619 the type of the return value. Functions that return no value are marked
3620 <tt><a href="#t_void">void</a></tt>.</p>
3623 <p>'<tt>fnty</tt>': shall be the signature of the pointer to function
3624 value being invoked. The argument types must match the types implied by
3625 this signature. This type can be omitted if the function is not varargs
3626 and if the function type does not return a pointer to a function.</p>
3629 <p>'<tt>fnptrval</tt>': An LLVM value containing a pointer to a function to
3630 be invoked. In most cases, this is a direct function invocation, but
3631 indirect <tt>call</tt>s are just as possible, calling an arbitrary pointer
3632 to function value.</p>
3635 <p>'<tt>function args</tt>': argument list whose types match the
3636 function signature argument types. All arguments must be of
3637 <a href="#t_firstclass">first class</a> type. If the function signature
3638 indicates the function accepts a variable number of arguments, the extra
3639 arguments can be specified.</p>
3645 <p>The '<tt>call</tt>' instruction is used to cause control flow to
3646 transfer to a specified function, with its incoming arguments bound to
3647 the specified values. Upon a '<tt><a href="#i_ret">ret</a></tt>'
3648 instruction in the called function, control flow continues with the
3649 instruction after the function call, and the return value of the
3650 function is bound to the result argument. This is a simpler case of
3651 the <a href="#i_invoke">invoke</a> instruction.</p>
3656 %retval = call i32 @test(i32 %argc)
3657 call i32 (i8 *, ...)* @printf(i8 * %msg, i32 12, i8 42);
3658 %X = tail call i32 @foo()
3659 %Y = tail call <a href="#callingconv">fastcc</a> i32 @foo()
3660 %Z = call void %foo(i8 97 signext)
3665 <!-- _______________________________________________________________________ -->
3666 <div class="doc_subsubsection">
3667 <a name="i_va_arg">'<tt>va_arg</tt>' Instruction</a>
3670 <div class="doc_text">
3675 <resultval> = va_arg <va_list*> <arglist>, <argty>
3680 <p>The '<tt>va_arg</tt>' instruction is used to access arguments passed through
3681 the "variable argument" area of a function call. It is used to implement the
3682 <tt>va_arg</tt> macro in C.</p>
3686 <p>This instruction takes a <tt>va_list*</tt> value and the type of
3687 the argument. It returns a value of the specified argument type and
3688 increments the <tt>va_list</tt> to point to the next argument. The
3689 actual type of <tt>va_list</tt> is target specific.</p>
3693 <p>The '<tt>va_arg</tt>' instruction loads an argument of the specified
3694 type from the specified <tt>va_list</tt> and causes the
3695 <tt>va_list</tt> to point to the next argument. For more information,
3696 see the variable argument handling <a href="#int_varargs">Intrinsic
3699 <p>It is legal for this instruction to be called in a function which does not
3700 take a variable number of arguments, for example, the <tt>vfprintf</tt>
3703 <p><tt>va_arg</tt> is an LLVM instruction instead of an <a
3704 href="#intrinsics">intrinsic function</a> because it takes a type as an
3709 <p>See the <a href="#int_varargs">variable argument processing</a> section.</p>
3713 <!-- *********************************************************************** -->
3714 <div class="doc_section"> <a name="intrinsics">Intrinsic Functions</a> </div>
3715 <!-- *********************************************************************** -->
3717 <div class="doc_text">
3719 <p>LLVM supports the notion of an "intrinsic function". These functions have
3720 well known names and semantics and are required to follow certain restrictions.
3721 Overall, these intrinsics represent an extension mechanism for the LLVM
3722 language that does not require changing all of the transformations in LLVM when
3723 adding to the language (or the bitcode reader/writer, the parser, etc...).</p>
3725 <p>Intrinsic function names must all start with an "<tt>llvm.</tt>" prefix. This
3726 prefix is reserved in LLVM for intrinsic names; thus, function names may not
3727 begin with this prefix. Intrinsic functions must always be external functions:
3728 you cannot define the body of intrinsic functions. Intrinsic functions may
3729 only be used in call or invoke instructions: it is illegal to take the address
3730 of an intrinsic function. Additionally, because intrinsic functions are part
3731 of the LLVM language, it is required if any are added that they be documented
3734 <p>Some intrinsic functions can be overloaded, i.e., the intrinsic represents
3735 a family of functions that perform the same operation but on different data
3736 types. Because LLVM can represent over 8 million different integer types,
3737 overloading is used commonly to allow an intrinsic function to operate on any
3738 integer type. One or more of the argument types or the result type can be
3739 overloaded to accept any integer type. Argument types may also be defined as
3740 exactly matching a previous argument's type or the result type. This allows an
3741 intrinsic function which accepts multiple arguments, but needs all of them to
3742 be of the same type, to only be overloaded with respect to a single argument or
3745 <p>Overloaded intrinsics will have the names of its overloaded argument types
3746 encoded into its function name, each preceded by a period. Only those types
3747 which are overloaded result in a name suffix. Arguments whose type is matched
3748 against another type do not. For example, the <tt>llvm.ctpop</tt> function can
3749 take an integer of any width and returns an integer of exactly the same integer
3750 width. This leads to a family of functions such as
3751 <tt>i8 @llvm.ctpop.i8(i8 %val)</tt> and <tt>i29 @llvm.ctpop.i29(i29 %val)</tt>.
3752 Only one type, the return type, is overloaded, and only one type suffix is
3753 required. Because the argument's type is matched against the return type, it
3754 does not require its own name suffix.</p>
3756 <p>To learn how to add an intrinsic function, please see the
3757 <a href="ExtendingLLVM.html">Extending LLVM Guide</a>.
3762 <!-- ======================================================================= -->
3763 <div class="doc_subsection">
3764 <a name="int_varargs">Variable Argument Handling Intrinsics</a>
3767 <div class="doc_text">
3769 <p>Variable argument support is defined in LLVM with the <a
3770 href="#i_va_arg"><tt>va_arg</tt></a> instruction and these three
3771 intrinsic functions. These functions are related to the similarly
3772 named macros defined in the <tt><stdarg.h></tt> header file.</p>
3774 <p>All of these functions operate on arguments that use a
3775 target-specific value type "<tt>va_list</tt>". The LLVM assembly
3776 language reference manual does not define what this type is, so all
3777 transformations should be prepared to handle these functions regardless of
3780 <p>This example shows how the <a href="#i_va_arg"><tt>va_arg</tt></a>
3781 instruction and the variable argument handling intrinsic functions are
3784 <div class="doc_code">
3786 define i32 @test(i32 %X, ...) {
3787 ; Initialize variable argument processing
3789 %ap2 = bitcast i8** %ap to i8*
3790 call void @llvm.va_start(i8* %ap2)
3792 ; Read a single integer argument
3793 %tmp = va_arg i8** %ap, i32
3795 ; Demonstrate usage of llvm.va_copy and llvm.va_end
3797 %aq2 = bitcast i8** %aq to i8*
3798 call void @llvm.va_copy(i8* %aq2, i8* %ap2)
3799 call void @llvm.va_end(i8* %aq2)
3801 ; Stop processing of arguments.
3802 call void @llvm.va_end(i8* %ap2)
3806 declare void @llvm.va_start(i8*)
3807 declare void @llvm.va_copy(i8*, i8*)
3808 declare void @llvm.va_end(i8*)
3814 <!-- _______________________________________________________________________ -->
3815 <div class="doc_subsubsection">
3816 <a name="int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a>
3820 <div class="doc_text">
3822 <pre> declare void %llvm.va_start(i8* <arglist>)<br></pre>
3824 <P>The '<tt>llvm.va_start</tt>' intrinsic initializes
3825 <tt>*<arglist></tt> for subsequent use by <tt><a
3826 href="#i_va_arg">va_arg</a></tt>.</p>
3830 <P>The argument is a pointer to a <tt>va_list</tt> element to initialize.</p>
3834 <P>The '<tt>llvm.va_start</tt>' intrinsic works just like the <tt>va_start</tt>
3835 macro available in C. In a target-dependent way, it initializes the
3836 <tt>va_list</tt> element to which the argument points, so that the next call to
3837 <tt>va_arg</tt> will produce the first variable argument passed to the function.
3838 Unlike the C <tt>va_start</tt> macro, this intrinsic does not need to know the
3839 last argument of the function as the compiler can figure that out.</p>
3843 <!-- _______________________________________________________________________ -->
3844 <div class="doc_subsubsection">
3845 <a name="int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a>
3848 <div class="doc_text">
3850 <pre> declare void @llvm.va_end(i8* <arglist>)<br></pre>
3853 <p>The '<tt>llvm.va_end</tt>' intrinsic destroys <tt>*<arglist></tt>,
3854 which has been initialized previously with <tt><a href="#int_va_start">llvm.va_start</a></tt>
3855 or <tt><a href="#i_va_copy">llvm.va_copy</a></tt>.</p>
3859 <p>The argument is a pointer to a <tt>va_list</tt> to destroy.</p>
3863 <p>The '<tt>llvm.va_end</tt>' intrinsic works just like the <tt>va_end</tt>
3864 macro available in C. In a target-dependent way, it destroys the
3865 <tt>va_list</tt> element to which the argument points. Calls to <a
3866 href="#int_va_start"><tt>llvm.va_start</tt></a> and <a href="#int_va_copy">
3867 <tt>llvm.va_copy</tt></a> must be matched exactly with calls to
3868 <tt>llvm.va_end</tt>.</p>
3872 <!-- _______________________________________________________________________ -->
3873 <div class="doc_subsubsection">
3874 <a name="int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a>
3877 <div class="doc_text">
3882 declare void @llvm.va_copy(i8* <destarglist>, i8* <srcarglist>)
3887 <p>The '<tt>llvm.va_copy</tt>' intrinsic copies the current argument position
3888 from the source argument list to the destination argument list.</p>
3892 <p>The first argument is a pointer to a <tt>va_list</tt> element to initialize.
3893 The second argument is a pointer to a <tt>va_list</tt> element to copy from.</p>
3898 <p>The '<tt>llvm.va_copy</tt>' intrinsic works just like the <tt>va_copy</tt>
3899 macro available in C. In a target-dependent way, it copies the source
3900 <tt>va_list</tt> element into the destination <tt>va_list</tt> element. This
3901 intrinsic is necessary because the <tt><a href="#int_va_start">
3902 llvm.va_start</a></tt> intrinsic may be arbitrarily complex and require, for
3903 example, memory allocation.</p>
3907 <!-- ======================================================================= -->
3908 <div class="doc_subsection">
3909 <a name="int_gc">Accurate Garbage Collection Intrinsics</a>
3912 <div class="doc_text">
3915 LLVM support for <a href="GarbageCollection.html">Accurate Garbage
3916 Collection</a> requires the implementation and generation of these intrinsics.
3917 These intrinsics allow identification of <a href="#int_gcroot">GC roots on the
3918 stack</a>, as well as garbage collector implementations that require <a
3919 href="#int_gcread">read</a> and <a href="#int_gcwrite">write</a> barriers.
3920 Front-ends for type-safe garbage collected languages should generate these
3921 intrinsics to make use of the LLVM garbage collectors. For more details, see <a
3922 href="GarbageCollection.html">Accurate Garbage Collection with LLVM</a>.
3926 <!-- _______________________________________________________________________ -->
3927 <div class="doc_subsubsection">
3928 <a name="int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a>
3931 <div class="doc_text">
3936 declare void @llvm.gcroot(i8** %ptrloc, i8* %metadata)
3941 <p>The '<tt>llvm.gcroot</tt>' intrinsic declares the existence of a GC root to
3942 the code generator, and allows some metadata to be associated with it.</p>
3946 <p>The first argument specifies the address of a stack object that contains the
3947 root pointer. The second pointer (which must be either a constant or a global
3948 value address) contains the meta-data to be associated with the root.</p>
3952 <p>At runtime, a call to this intrinsics stores a null pointer into the "ptrloc"
3953 location. At compile-time, the code generator generates information to allow
3954 the runtime to find the pointer at GC safe points.
3960 <!-- _______________________________________________________________________ -->
3961 <div class="doc_subsubsection">
3962 <a name="int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a>
3965 <div class="doc_text">
3970 declare i8* @llvm.gcread(i8* %ObjPtr, i8** %Ptr)
3975 <p>The '<tt>llvm.gcread</tt>' intrinsic identifies reads of references from heap
3976 locations, allowing garbage collector implementations that require read
3981 <p>The second argument is the address to read from, which should be an address
3982 allocated from the garbage collector. The first object is a pointer to the
3983 start of the referenced object, if needed by the language runtime (otherwise
3988 <p>The '<tt>llvm.gcread</tt>' intrinsic has the same semantics as a load
3989 instruction, but may be replaced with substantially more complex code by the
3990 garbage collector runtime, as needed.</p>
3995 <!-- _______________________________________________________________________ -->
3996 <div class="doc_subsubsection">
3997 <a name="int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a>
4000 <div class="doc_text">
4005 declare void @llvm.gcwrite(i8* %P1, i8* %Obj, i8** %P2)
4010 <p>The '<tt>llvm.gcwrite</tt>' intrinsic identifies writes of references to heap
4011 locations, allowing garbage collector implementations that require write
4012 barriers (such as generational or reference counting collectors).</p>
4016 <p>The first argument is the reference to store, the second is the start of the
4017 object to store it to, and the third is the address of the field of Obj to
4018 store to. If the runtime does not require a pointer to the object, Obj may be
4023 <p>The '<tt>llvm.gcwrite</tt>' intrinsic has the same semantics as a store
4024 instruction, but may be replaced with substantially more complex code by the
4025 garbage collector runtime, as needed.</p>
4031 <!-- ======================================================================= -->
4032 <div class="doc_subsection">
4033 <a name="int_codegen">Code Generator Intrinsics</a>
4036 <div class="doc_text">
4038 These intrinsics are provided by LLVM to expose special features that may only
4039 be implemented with code generator support.
4044 <!-- _______________________________________________________________________ -->
4045 <div class="doc_subsubsection">
4046 <a name="int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a>
4049 <div class="doc_text">
4053 declare i8 *@llvm.returnaddress(i32 <level>)
4059 The '<tt>llvm.returnaddress</tt>' intrinsic attempts to compute a
4060 target-specific value indicating the return address of the current function
4061 or one of its callers.
4067 The argument to this intrinsic indicates which function to return the address
4068 for. Zero indicates the calling function, one indicates its caller, etc. The
4069 argument is <b>required</b> to be a constant integer value.
4075 The '<tt>llvm.returnaddress</tt>' intrinsic either returns a pointer indicating
4076 the return address of the specified call frame, or zero if it cannot be
4077 identified. The value returned by this intrinsic is likely to be incorrect or 0
4078 for arguments other than zero, so it should only be used for debugging purposes.
4082 Note that calling this intrinsic does not prevent function inlining or other
4083 aggressive transformations, so the value returned may not be that of the obvious
4084 source-language caller.
4089 <!-- _______________________________________________________________________ -->
4090 <div class="doc_subsubsection">
4091 <a name="int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a>
4094 <div class="doc_text">
4098 declare i8 *@llvm.frameaddress(i32 <level>)
4104 The '<tt>llvm.frameaddress</tt>' intrinsic attempts to return the
4105 target-specific frame pointer value for the specified stack frame.
4111 The argument to this intrinsic indicates which function to return the frame
4112 pointer for. Zero indicates the calling function, one indicates its caller,
4113 etc. The argument is <b>required</b> to be a constant integer value.
4119 The '<tt>llvm.frameaddress</tt>' intrinsic either returns a pointer indicating
4120 the frame address of the specified call frame, or zero if it cannot be
4121 identified. The value returned by this intrinsic is likely to be incorrect or 0
4122 for arguments other than zero, so it should only be used for debugging purposes.
4126 Note that calling this intrinsic does not prevent function inlining or other
4127 aggressive transformations, so the value returned may not be that of the obvious
4128 source-language caller.
4132 <!-- _______________________________________________________________________ -->
4133 <div class="doc_subsubsection">
4134 <a name="int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a>
4137 <div class="doc_text">
4141 declare i8 *@llvm.stacksave()
4147 The '<tt>llvm.stacksave</tt>' intrinsic is used to remember the current state of
4148 the function stack, for use with <a href="#int_stackrestore">
4149 <tt>llvm.stackrestore</tt></a>. This is useful for implementing language
4150 features like scoped automatic variable sized arrays in C99.
4156 This intrinsic returns a opaque pointer value that can be passed to <a
4157 href="#int_stackrestore"><tt>llvm.stackrestore</tt></a>. When an
4158 <tt>llvm.stackrestore</tt> intrinsic is executed with a value saved from
4159 <tt>llvm.stacksave</tt>, it effectively restores the state of the stack to the
4160 state it was in when the <tt>llvm.stacksave</tt> intrinsic executed. In
4161 practice, this pops any <a href="#i_alloca">alloca</a> blocks from the stack
4162 that were allocated after the <tt>llvm.stacksave</tt> was executed.
4167 <!-- _______________________________________________________________________ -->
4168 <div class="doc_subsubsection">
4169 <a name="int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a>
4172 <div class="doc_text">
4176 declare void @llvm.stackrestore(i8 * %ptr)
4182 The '<tt>llvm.stackrestore</tt>' intrinsic is used to restore the state of
4183 the function stack to the state it was in when the corresponding <a
4184 href="#int_stacksave"><tt>llvm.stacksave</tt></a> intrinsic executed. This is
4185 useful for implementing language features like scoped automatic variable sized
4192 See the description for <a href="#int_stacksave"><tt>llvm.stacksave</tt></a>.
4198 <!-- _______________________________________________________________________ -->
4199 <div class="doc_subsubsection">
4200 <a name="int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a>
4203 <div class="doc_text">
4207 declare void @llvm.prefetch(i8* <address>, i32 <rw>, i32 <locality>)
4214 The '<tt>llvm.prefetch</tt>' intrinsic is a hint to the code generator to insert
4215 a prefetch instruction if supported; otherwise, it is a noop. Prefetches have
4217 effect on the behavior of the program but can change its performance
4224 <tt>address</tt> is the address to be prefetched, <tt>rw</tt> is the specifier
4225 determining if the fetch should be for a read (0) or write (1), and
4226 <tt>locality</tt> is a temporal locality specifier ranging from (0) - no
4227 locality, to (3) - extremely local keep in cache. The <tt>rw</tt> and
4228 <tt>locality</tt> arguments must be constant integers.
4234 This intrinsic does not modify the behavior of the program. In particular,
4235 prefetches cannot trap and do not produce a value. On targets that support this
4236 intrinsic, the prefetch can provide hints to the processor cache for better
4242 <!-- _______________________________________________________________________ -->
4243 <div class="doc_subsubsection">
4244 <a name="int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a>
4247 <div class="doc_text">
4251 declare void @llvm.pcmarker(i32 <id>)
4258 The '<tt>llvm.pcmarker</tt>' intrinsic is a method to export a Program Counter
4260 code to simulators and other tools. The method is target specific, but it is
4261 expected that the marker will use exported symbols to transmit the PC of the marker.
4262 The marker makes no guarantees that it will remain with any specific instruction
4263 after optimizations. It is possible that the presence of a marker will inhibit
4264 optimizations. The intended use is to be inserted after optimizations to allow
4265 correlations of simulation runs.
4271 <tt>id</tt> is a numerical id identifying the marker.
4277 This intrinsic does not modify the behavior of the program. Backends that do not
4278 support this intrinisic may ignore it.
4283 <!-- _______________________________________________________________________ -->
4284 <div class="doc_subsubsection">
4285 <a name="int_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a>
4288 <div class="doc_text">
4292 declare i64 @llvm.readcyclecounter( )
4299 The '<tt>llvm.readcyclecounter</tt>' intrinsic provides access to the cycle
4300 counter register (or similar low latency, high accuracy clocks) on those targets
4301 that support it. On X86, it should map to RDTSC. On Alpha, it should map to RPCC.
4302 As the backing counters overflow quickly (on the order of 9 seconds on alpha), this
4303 should only be used for small timings.
4309 When directly supported, reading the cycle counter should not modify any memory.
4310 Implementations are allowed to either return a application specific value or a
4311 system wide value. On backends without support, this is lowered to a constant 0.
4316 <!-- ======================================================================= -->
4317 <div class="doc_subsection">
4318 <a name="int_libc">Standard C Library Intrinsics</a>
4321 <div class="doc_text">
4323 LLVM provides intrinsics for a few important standard C library functions.
4324 These intrinsics allow source-language front-ends to pass information about the
4325 alignment of the pointer arguments to the code generator, providing opportunity
4326 for more efficient code generation.
4331 <!-- _______________________________________________________________________ -->
4332 <div class="doc_subsubsection">
4333 <a name="int_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a>
4336 <div class="doc_text">
4340 declare void @llvm.memcpy.i32(i8 * <dest>, i8 * <src>,
4341 i32 <len>, i32 <align>)
4342 declare void @llvm.memcpy.i64(i8 * <dest>, i8 * <src>,
4343 i64 <len>, i32 <align>)
4349 The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the source
4350 location to the destination location.
4354 Note that, unlike the standard libc function, the <tt>llvm.memcpy.*</tt>
4355 intrinsics do not return a value, and takes an extra alignment argument.
4361 The first argument is a pointer to the destination, the second is a pointer to
4362 the source. The third argument is an integer argument
4363 specifying the number of bytes to copy, and the fourth argument is the alignment
4364 of the source and destination locations.
4368 If the call to this intrinisic has an alignment value that is not 0 or 1, then
4369 the caller guarantees that both the source and destination pointers are aligned
4376 The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the source
4377 location to the destination location, which are not allowed to overlap. It
4378 copies "len" bytes of memory over. If the argument is known to be aligned to
4379 some boundary, this can be specified as the fourth argument, otherwise it should
4385 <!-- _______________________________________________________________________ -->
4386 <div class="doc_subsubsection">
4387 <a name="int_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a>
4390 <div class="doc_text">
4394 declare void @llvm.memmove.i32(i8 * <dest>, i8 * <src>,
4395 i32 <len>, i32 <align>)
4396 declare void @llvm.memmove.i64(i8 * <dest>, i8 * <src>,
4397 i64 <len>, i32 <align>)
4403 The '<tt>llvm.memmove.*</tt>' intrinsics move a block of memory from the source
4404 location to the destination location. It is similar to the
4405 '<tt>llvm.memcmp</tt>' intrinsic but allows the two memory locations to overlap.
4409 Note that, unlike the standard libc function, the <tt>llvm.memmove.*</tt>
4410 intrinsics do not return a value, and takes an extra alignment argument.
4416 The first argument is a pointer to the destination, the second is a pointer to
4417 the source. The third argument is an integer argument
4418 specifying the number of bytes to copy, and the fourth argument is the alignment
4419 of the source and destination locations.
4423 If the call to this intrinisic has an alignment value that is not 0 or 1, then
4424 the caller guarantees that the source and destination pointers are aligned to
4431 The '<tt>llvm.memmove.*</tt>' intrinsics copy a block of memory from the source
4432 location to the destination location, which may overlap. It
4433 copies "len" bytes of memory over. If the argument is known to be aligned to
4434 some boundary, this can be specified as the fourth argument, otherwise it should
4440 <!-- _______________________________________________________________________ -->
4441 <div class="doc_subsubsection">
4442 <a name="int_memset">'<tt>llvm.memset.*</tt>' Intrinsics</a>
4445 <div class="doc_text">
4449 declare void @llvm.memset.i32(i8 * <dest>, i8 <val>,
4450 i32 <len>, i32 <align>)
4451 declare void @llvm.memset.i64(i8 * <dest>, i8 <val>,
4452 i64 <len>, i32 <align>)
4458 The '<tt>llvm.memset.*</tt>' intrinsics fill a block of memory with a particular
4463 Note that, unlike the standard libc function, the <tt>llvm.memset</tt> intrinsic
4464 does not return a value, and takes an extra alignment argument.
4470 The first argument is a pointer to the destination to fill, the second is the
4471 byte value to fill it with, the third argument is an integer
4472 argument specifying the number of bytes to fill, and the fourth argument is the
4473 known alignment of destination location.
4477 If the call to this intrinisic has an alignment value that is not 0 or 1, then
4478 the caller guarantees that the destination pointer is aligned to that boundary.
4484 The '<tt>llvm.memset.*</tt>' intrinsics fill "len" bytes of memory starting at
4486 destination location. If the argument is known to be aligned to some boundary,
4487 this can be specified as the fourth argument, otherwise it should be set to 0 or
4493 <!-- _______________________________________________________________________ -->
4494 <div class="doc_subsubsection">
4495 <a name="int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a>
4498 <div class="doc_text">
4501 <p>This is an overloaded intrinsic. You can use <tt>llvm.sqrt</tt> on any
4502 floating point or vector of floating point type. Not all targets support all
4505 declare float @llvm.sqrt.f32(float %Val)
4506 declare double @llvm.sqrt.f64(double %Val)
4507 declare x86_fp80 @llvm.sqrt.f80(x86_fp80 %Val)
4508 declare fp128 @llvm.sqrt.f128(fp128 %Val)
4509 declare ppc_fp128 @llvm.sqrt.ppcf128(ppc_fp128 %Val)
4515 The '<tt>llvm.sqrt</tt>' intrinsics return the sqrt of the specified operand,
4516 returning the same value as the libm '<tt>sqrt</tt>' functions would. Unlike
4517 <tt>sqrt</tt> in libm, however, <tt>llvm.sqrt</tt> has undefined behavior for
4518 negative numbers (which allows for better optimization).
4524 The argument and return value are floating point numbers of the same type.
4530 This function returns the sqrt of the specified operand if it is a nonnegative
4531 floating point number.
4535 <!-- _______________________________________________________________________ -->
4536 <div class="doc_subsubsection">
4537 <a name="int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a>
4540 <div class="doc_text">
4543 <p>This is an overloaded intrinsic. You can use <tt>llvm.powi</tt> on any
4544 floating point or vector of floating point type. Not all targets support all
4547 declare float @llvm.powi.f32(float %Val, i32 %power)
4548 declare double @llvm.powi.f64(double %Val, i32 %power)
4549 declare x86_fp80 @llvm.powi.f80(x86_fp80 %Val, i32 %power)
4550 declare fp128 @llvm.powi.f128(fp128 %Val, i32 %power)
4551 declare ppc_fp128 @llvm.powi.ppcf128(ppc_fp128 %Val, i32 %power)
4557 The '<tt>llvm.powi.*</tt>' intrinsics return the first operand raised to the
4558 specified (positive or negative) power. The order of evaluation of
4559 multiplications is not defined. When a vector of floating point type is
4560 used, the second argument remains a scalar integer value.
4566 The second argument is an integer power, and the first is a value to raise to
4573 This function returns the first value raised to the second power with an
4574 unspecified sequence of rounding operations.</p>
4577 <!-- _______________________________________________________________________ -->
4578 <div class="doc_subsubsection">
4579 <a name="int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a>
4582 <div class="doc_text">
4585 <p>This is an overloaded intrinsic. You can use <tt>llvm.sin</tt> on any
4586 floating point or vector of floating point type. Not all targets support all
4589 declare float @llvm.sin.f32(float %Val)
4590 declare double @llvm.sin.f64(double %Val)
4591 declare x86_fp80 @llvm.sin.f80(x86_fp80 %Val)
4592 declare fp128 @llvm.sin.f128(fp128 %Val)
4593 declare ppc_fp128 @llvm.sin.ppcf128(ppc_fp128 %Val)
4599 The '<tt>llvm.sin.*</tt>' intrinsics return the sine of the operand.
4605 The argument and return value are floating point numbers of the same type.
4611 This function returns the sine of the specified operand, returning the
4612 same values as the libm <tt>sin</tt> functions would, and handles error
4613 conditions in the same way.</p>
4616 <!-- _______________________________________________________________________ -->
4617 <div class="doc_subsubsection">
4618 <a name="int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a>
4621 <div class="doc_text">
4624 <p>This is an overloaded intrinsic. You can use <tt>llvm.cos</tt> on any
4625 floating point or vector of floating point type. Not all targets support all
4628 declare float @llvm.cos.f32(float %Val)
4629 declare double @llvm.cos.f64(double %Val)
4630 declare x86_fp80 @llvm.cos.f80(x86_fp80 %Val)
4631 declare fp128 @llvm.cos.f128(fp128 %Val)
4632 declare ppc_fp128 @llvm.cos.ppcf128(ppc_fp128 %Val)
4638 The '<tt>llvm.cos.*</tt>' intrinsics return the cosine of the operand.
4644 The argument and return value are floating point numbers of the same type.
4650 This function returns the cosine of the specified operand, returning the
4651 same values as the libm <tt>cos</tt> functions would, and handles error
4652 conditions in the same way.</p>
4655 <!-- _______________________________________________________________________ -->
4656 <div class="doc_subsubsection">
4657 <a name="int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a>
4660 <div class="doc_text">
4663 <p>This is an overloaded intrinsic. You can use <tt>llvm.pow</tt> on any
4664 floating point or vector of floating point type. Not all targets support all
4667 declare float @llvm.pow.f32(float %Val, float %Power)
4668 declare double @llvm.pow.f64(double %Val, double %Power)
4669 declare x86_fp80 @llvm.pow.f80(x86_fp80 %Val, x86_fp80 %Power)
4670 declare fp128 @llvm.pow.f128(fp128 %Val, fp128 %Power)
4671 declare ppc_fp128 @llvm.pow.ppcf128(ppc_fp128 %Val, ppc_fp128 Power)
4677 The '<tt>llvm.pow.*</tt>' intrinsics return the first operand raised to the
4678 specified (positive or negative) power.
4684 The second argument is a floating point power, and the first is a value to
4685 raise to that power.
4691 This function returns the first value raised to the second power,
4693 same values as the libm <tt>pow</tt> functions would, and handles error
4694 conditions in the same way.</p>
4698 <!-- ======================================================================= -->
4699 <div class="doc_subsection">
4700 <a name="int_manip">Bit Manipulation Intrinsics</a>
4703 <div class="doc_text">
4705 LLVM provides intrinsics for a few important bit manipulation operations.
4706 These allow efficient code generation for some algorithms.
4711 <!-- _______________________________________________________________________ -->
4712 <div class="doc_subsubsection">
4713 <a name="int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a>
4716 <div class="doc_text">
4719 <p>This is an overloaded intrinsic function. You can use bswap on any integer
4720 type that is an even number of bytes (i.e. BitWidth % 16 == 0).
4722 declare i16 @llvm.bswap.i16(i16 <id>)
4723 declare i32 @llvm.bswap.i32(i32 <id>)
4724 declare i64 @llvm.bswap.i64(i64 <id>)
4730 The '<tt>llvm.bswap</tt>' family of intrinsics is used to byte swap integer
4731 values with an even number of bytes (positive multiple of 16 bits). These are
4732 useful for performing operations on data that is not in the target's native
4739 The <tt>llvm.bswap.i16</tt> intrinsic returns an i16 value that has the high
4740 and low byte of the input i16 swapped. Similarly, the <tt>llvm.bswap.i32</tt>
4741 intrinsic returns an i32 value that has the four bytes of the input i32
4742 swapped, so that if the input bytes are numbered 0, 1, 2, 3 then the returned
4743 i32 will have its bytes in 3, 2, 1, 0 order. The <tt>llvm.bswap.i48</tt>,
4744 <tt>llvm.bswap.i64</tt> and other intrinsics extend this concept to
4745 additional even-byte lengths (6 bytes, 8 bytes and more, respectively).
4750 <!-- _______________________________________________________________________ -->
4751 <div class="doc_subsubsection">
4752 <a name="int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic</a>
4755 <div class="doc_text">
4758 <p>This is an overloaded intrinsic. You can use llvm.ctpop on any integer bit
4759 width. Not all targets support all bit widths however.
4761 declare i8 @llvm.ctpop.i8 (i8 <src>)
4762 declare i16 @llvm.ctpop.i16(i16 <src>)
4763 declare i32 @llvm.ctpop.i32(i32 <src>)
4764 declare i64 @llvm.ctpop.i64(i64 <src>)
4765 declare i256 @llvm.ctpop.i256(i256 <src>)
4771 The '<tt>llvm.ctpop</tt>' family of intrinsics counts the number of bits set in a
4778 The only argument is the value to be counted. The argument may be of any
4779 integer type. The return type must match the argument type.
4785 The '<tt>llvm.ctpop</tt>' intrinsic counts the 1's in a variable.
4789 <!-- _______________________________________________________________________ -->
4790 <div class="doc_subsubsection">
4791 <a name="int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic</a>
4794 <div class="doc_text">
4797 <p>This is an overloaded intrinsic. You can use <tt>llvm.ctlz</tt> on any
4798 integer bit width. Not all targets support all bit widths however.
4800 declare i8 @llvm.ctlz.i8 (i8 <src>)
4801 declare i16 @llvm.ctlz.i16(i16 <src>)
4802 declare i32 @llvm.ctlz.i32(i32 <src>)
4803 declare i64 @llvm.ctlz.i64(i64 <src>)
4804 declare i256 @llvm.ctlz.i256(i256 <src>)
4810 The '<tt>llvm.ctlz</tt>' family of intrinsic functions counts the number of
4811 leading zeros in a variable.
4817 The only argument is the value to be counted. The argument may be of any
4818 integer type. The return type must match the argument type.
4824 The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant) zeros
4825 in a variable. If the src == 0 then the result is the size in bits of the type
4826 of src. For example, <tt>llvm.ctlz(i32 2) = 30</tt>.
4832 <!-- _______________________________________________________________________ -->
4833 <div class="doc_subsubsection">
4834 <a name="int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic</a>
4837 <div class="doc_text">
4840 <p>This is an overloaded intrinsic. You can use <tt>llvm.cttz</tt> on any
4841 integer bit width. Not all targets support all bit widths however.
4843 declare i8 @llvm.cttz.i8 (i8 <src>)
4844 declare i16 @llvm.cttz.i16(i16 <src>)
4845 declare i32 @llvm.cttz.i32(i32 <src>)
4846 declare i64 @llvm.cttz.i64(i64 <src>)
4847 declare i256 @llvm.cttz.i256(i256 <src>)
4853 The '<tt>llvm.cttz</tt>' family of intrinsic functions counts the number of
4860 The only argument is the value to be counted. The argument may be of any
4861 integer type. The return type must match the argument type.
4867 The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant) zeros
4868 in a variable. If the src == 0 then the result is the size in bits of the type
4869 of src. For example, <tt>llvm.cttz(2) = 1</tt>.
4873 <!-- _______________________________________________________________________ -->
4874 <div class="doc_subsubsection">
4875 <a name="int_part_select">'<tt>llvm.part.select.*</tt>' Intrinsic</a>
4878 <div class="doc_text">
4881 <p>This is an overloaded intrinsic. You can use <tt>llvm.part.select</tt>
4882 on any integer bit width.
4884 declare i17 @llvm.part.select.i17 (i17 %val, i32 %loBit, i32 %hiBit)
4885 declare i29 @llvm.part.select.i29 (i29 %val, i32 %loBit, i32 %hiBit)
4889 <p>The '<tt>llvm.part.select</tt>' family of intrinsic functions selects a
4890 range of bits from an integer value and returns them in the same bit width as
4891 the original value.</p>
4894 <p>The first argument, <tt>%val</tt> and the result may be integer types of
4895 any bit width but they must have the same bit width. The second and third
4896 arguments must be <tt>i32</tt> type since they specify only a bit index.</p>
4899 <p>The operation of the '<tt>llvm.part.select</tt>' intrinsic has two modes
4900 of operation: forwards and reverse. If <tt>%loBit</tt> is greater than
4901 <tt>%hiBits</tt> then the intrinsic operates in reverse mode. Otherwise it
4902 operates in forward mode.</p>
4903 <p>In forward mode, this intrinsic is the equivalent of shifting <tt>%val</tt>
4904 right by <tt>%loBit</tt> bits and then ANDing it with a mask with
4905 only the <tt>%hiBit - %loBit</tt> bits set, as follows:</p>
4907 <li>The <tt>%val</tt> is shifted right (LSHR) by the number of bits specified
4908 by <tt>%loBits</tt>. This normalizes the value to the low order bits.</li>
4909 <li>The <tt>%loBits</tt> value is subtracted from the <tt>%hiBits</tt> value
4910 to determine the number of bits to retain.</li>
4911 <li>A mask of the retained bits is created by shifting a -1 value.</li>
4912 <li>The mask is ANDed with <tt>%val</tt> to produce the result.
4914 <p>In reverse mode, a similar computation is made except that the bits are
4915 returned in the reverse order. So, for example, if <tt>X</tt> has the value
4916 <tt>i16 0x0ACF (101011001111)</tt> and we apply
4917 <tt>part.select(i16 X, 8, 3)</tt> to it, we get back the value
4918 <tt>i16 0x0026 (000000100110)</tt>.</p>
4921 <div class="doc_subsubsection">
4922 <a name="int_part_set">'<tt>llvm.part.set.*</tt>' Intrinsic</a>
4925 <div class="doc_text">
4928 <p>This is an overloaded intrinsic. You can use <tt>llvm.part.set</tt>
4929 on any integer bit width.
4931 declare i17 @llvm.part.set.i17.i9 (i17 %val, i9 %repl, i32 %lo, i32 %hi)
4932 declare i29 @llvm.part.set.i29.i9 (i29 %val, i9 %repl, i32 %lo, i32 %hi)
4936 <p>The '<tt>llvm.part.set</tt>' family of intrinsic functions replaces a range
4937 of bits in an integer value with another integer value. It returns the integer
4938 with the replaced bits.</p>
4941 <p>The first argument, <tt>%val</tt> and the result may be integer types of
4942 any bit width but they must have the same bit width. <tt>%val</tt> is the value
4943 whose bits will be replaced. The second argument, <tt>%repl</tt> may be an
4944 integer of any bit width. The third and fourth arguments must be <tt>i32</tt>
4945 type since they specify only a bit index.</p>
4948 <p>The operation of the '<tt>llvm.part.set</tt>' intrinsic has two modes
4949 of operation: forwards and reverse. If <tt>%lo</tt> is greater than
4950 <tt>%hi</tt> then the intrinsic operates in reverse mode. Otherwise it
4951 operates in forward mode.</p>
4952 <p>For both modes, the <tt>%repl</tt> value is prepared for use by either
4953 truncating it down to the size of the replacement area or zero extending it
4954 up to that size.</p>
4955 <p>In forward mode, the bits between <tt>%lo</tt> and <tt>%hi</tt> (inclusive)
4956 are replaced with corresponding bits from <tt>%repl</tt>. That is the 0th bit
4957 in <tt>%repl</tt> replaces the <tt>%lo</tt>th bit in <tt>%val</tt> and etc. up
4958 to the <tt>%hi</tt>th bit.
4959 <p>In reverse mode, a similar computation is made except that the bits are
4960 reversed. That is, the <tt>0</tt>th bit in <tt>%repl</tt> replaces the
4961 <tt>%hi</tt> bit in <tt>%val</tt> and etc. down to the <tt>%lo</tt>th bit.
4964 llvm.part.set(0xFFFF, 0, 4, 7) -> 0xFF0F
4965 llvm.part.set(0xFFFF, 0, 7, 4) -> 0xFF0F
4966 llvm.part.set(0xFFFF, 1, 7, 4) -> 0xFF8F
4967 llvm.part.set(0xFFFF, F, 8, 3) -> 0xFFE7
4968 llvm.part.set(0xFFFF, 0, 3, 8) -> 0xFE07
4972 <!-- ======================================================================= -->
4973 <div class="doc_subsection">
4974 <a name="int_debugger">Debugger Intrinsics</a>
4977 <div class="doc_text">
4979 The LLVM debugger intrinsics (which all start with <tt>llvm.dbg.</tt> prefix),
4980 are described in the <a
4981 href="SourceLevelDebugging.html#format_common_intrinsics">LLVM Source Level
4982 Debugging</a> document.
4987 <!-- ======================================================================= -->
4988 <div class="doc_subsection">
4989 <a name="int_eh">Exception Handling Intrinsics</a>
4992 <div class="doc_text">
4993 <p> The LLVM exception handling intrinsics (which all start with
4994 <tt>llvm.eh.</tt> prefix), are described in the <a
4995 href="ExceptionHandling.html#format_common_intrinsics">LLVM Exception
4996 Handling</a> document. </p>
4999 <!-- ======================================================================= -->
5000 <div class="doc_subsection">
5001 <a name="int_trampoline">Trampoline Intrinsic</a>
5004 <div class="doc_text">
5006 This intrinsic makes it possible to excise one parameter, marked with
5007 the <tt>nest</tt> attribute, from a function. The result is a callable
5008 function pointer lacking the nest parameter - the caller does not need
5009 to provide a value for it. Instead, the value to use is stored in
5010 advance in a "trampoline", a block of memory usually allocated
5011 on the stack, which also contains code to splice the nest value into the
5012 argument list. This is used to implement the GCC nested function address
5016 For example, if the function is
5017 <tt>i32 f(i8* nest %c, i32 %x, i32 %y)</tt> then the resulting function
5018 pointer has signature <tt>i32 (i32, i32)*</tt>. It can be created as follows:</p>
5020 %tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86
5021 %tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0
5022 %p = call i8* @llvm.init.trampoline( i8* %tramp1, i8* bitcast (i32 (i8* nest , i32, i32)* @f to i8*), i8* %nval )
5023 %fp = bitcast i8* %p to i32 (i32, i32)*
5025 <p>The call <tt>%val = call i32 %fp( i32 %x, i32 %y )</tt> is then equivalent
5026 to <tt>%val = call i32 %f( i8* %nval, i32 %x, i32 %y )</tt>.</p>
5029 <!-- _______________________________________________________________________ -->
5030 <div class="doc_subsubsection">
5031 <a name="int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a>
5033 <div class="doc_text">
5036 declare i8* @llvm.init.trampoline(i8* <tramp>, i8* <func>, i8* <nval>)
5040 This fills the memory pointed to by <tt>tramp</tt> with code
5041 and returns a function pointer suitable for executing it.
5045 The <tt>llvm.init.trampoline</tt> intrinsic takes three arguments, all
5046 pointers. The <tt>tramp</tt> argument must point to a sufficiently large
5047 and sufficiently aligned block of memory; this memory is written to by the
5048 intrinsic. Note that the size and the alignment are target-specific - LLVM
5049 currently provides no portable way of determining them, so a front-end that
5050 generates this intrinsic needs to have some target-specific knowledge.
5051 The <tt>func</tt> argument must hold a function bitcast to an <tt>i8*</tt>.
5055 The block of memory pointed to by <tt>tramp</tt> is filled with target
5056 dependent code, turning it into a function. A pointer to this function is
5057 returned, but needs to be bitcast to an
5058 <a href="#int_trampoline">appropriate function pointer type</a>
5059 before being called. The new function's signature is the same as that of
5060 <tt>func</tt> with any arguments marked with the <tt>nest</tt> attribute
5061 removed. At most one such <tt>nest</tt> argument is allowed, and it must be
5062 of pointer type. Calling the new function is equivalent to calling
5063 <tt>func</tt> with the same argument list, but with <tt>nval</tt> used for the
5064 missing <tt>nest</tt> argument. If, after calling
5065 <tt>llvm.init.trampoline</tt>, the memory pointed to by <tt>tramp</tt> is
5066 modified, then the effect of any later call to the returned function pointer is
5071 <!-- ======================================================================= -->
5072 <div class="doc_subsection">
5073 <a name="int_general">General Intrinsics</a>
5076 <div class="doc_text">
5077 <p> This class of intrinsics is designed to be generic and has
5078 no specific purpose. </p>
5081 <!-- _______________________________________________________________________ -->
5082 <div class="doc_subsubsection">
5083 <a name="int_var_annotation">'<tt>llvm.var.annotation</tt>' Intrinsic</a>
5086 <div class="doc_text">
5090 declare void @llvm.var.annotation(i8* <val>, i8* <str>, i8* <str>, i32 <int> )
5096 The '<tt>llvm.var.annotation</tt>' intrinsic
5102 The first argument is a pointer to a value, the second is a pointer to a
5103 global string, the third is a pointer to a global string which is the source
5104 file name, and the last argument is the line number.
5110 This intrinsic allows annotation of local variables with arbitrary strings.
5111 This can be useful for special purpose optimizations that want to look for these
5112 annotations. These have no other defined use, they are ignored by code
5113 generation and optimization.
5116 <!-- _______________________________________________________________________ -->
5117 <div class="doc_subsubsection">
5118 <a name="int_annotation">'<tt>llvm.annotation.*</tt>' Intrinsic</a>
5121 <div class="doc_text">
5124 <p>This is an overloaded intrinsic. You can use '<tt>llvm.annotation</tt>' on
5125 any integer bit width.
5128 declare i8 @llvm.annotation.i8(i8 <val>, i8* <str>, i8* <str>, i32 <int> )
5129 declare i16 @llvm.annotation.i16(i16 <val>, i8* <str>, i8* <str>, i32 <int> )
5130 declare i32 @llvm.annotation.i32(i32 <val>, i8* <str>, i8* <str>, i32 <int> )
5131 declare i64 @llvm.annotation.i64(i64 <val>, i8* <str>, i8* <str>, i32 <int> )
5132 declare i256 @llvm.annotation.i256(i256 <val>, i8* <str>, i8* <str>, i32 <int> )
5138 The '<tt>llvm.annotation</tt>' intrinsic.
5144 The first argument is an integer value (result of some expression),
5145 the second is a pointer to a global string, the third is a pointer to a global
5146 string which is the source file name, and the last argument is the line number.
5147 It returns the value of the first argument.
5153 This intrinsic allows annotations to be put on arbitrary expressions
5154 with arbitrary strings. This can be useful for special purpose optimizations
5155 that want to look for these annotations. These have no other defined use, they
5156 are ignored by code generation and optimization.
5159 <!-- *********************************************************************** -->
5162 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
5163 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
5164 <a href="http://validator.w3.org/check/referer"><img
5165 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
5167 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
5168 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
5169 Last modified: $Date$