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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="#gc">Garbage Collector Names</a></li>
30 <li><a href="#moduleasm">Module-Level Inline Assembly</a></li>
31 <li><a href="#datalayout">Data Layout</a></li>
34 <li><a href="#typesystem">Type System</a>
36 <li><a href="#t_primitive">Primitive Types</a>
38 <li><a href="#t_classifications">Type Classifications</a></li>
41 <li><a href="#t_derived">Derived Types</a>
43 <li><a href="#t_integer">Integer Type</a></li>
44 <li><a href="#t_array">Array Type</a></li>
45 <li><a href="#t_function">Function Type</a></li>
46 <li><a href="#t_pointer">Pointer Type</a></li>
47 <li><a href="#t_struct">Structure Type</a></li>
48 <li><a href="#t_pstruct">Packed Structure Type</a></li>
49 <li><a href="#t_vector">Vector Type</a></li>
50 <li><a href="#t_opaque">Opaque Type</a></li>
55 <li><a href="#constants">Constants</a>
57 <li><a href="#simpleconstants">Simple Constants</a>
58 <li><a href="#aggregateconstants">Aggregate Constants</a>
59 <li><a href="#globalconstants">Global Variable and Function Addresses</a>
60 <li><a href="#undefvalues">Undefined Values</a>
61 <li><a href="#constantexprs">Constant Expressions</a>
64 <li><a href="#othervalues">Other Values</a>
66 <li><a href="#inlineasm">Inline Assembler Expressions</a>
69 <li><a href="#instref">Instruction Reference</a>
71 <li><a href="#terminators">Terminator Instructions</a>
73 <li><a href="#i_ret">'<tt>ret</tt>' Instruction</a></li>
74 <li><a href="#i_br">'<tt>br</tt>' Instruction</a></li>
75 <li><a href="#i_switch">'<tt>switch</tt>' Instruction</a></li>
76 <li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a></li>
77 <li><a href="#i_unwind">'<tt>unwind</tt>' Instruction</a></li>
78 <li><a href="#i_unreachable">'<tt>unreachable</tt>' Instruction</a></li>
81 <li><a href="#binaryops">Binary Operations</a>
83 <li><a href="#i_add">'<tt>add</tt>' Instruction</a></li>
84 <li><a href="#i_sub">'<tt>sub</tt>' Instruction</a></li>
85 <li><a href="#i_mul">'<tt>mul</tt>' Instruction</a></li>
86 <li><a href="#i_udiv">'<tt>udiv</tt>' Instruction</a></li>
87 <li><a href="#i_sdiv">'<tt>sdiv</tt>' Instruction</a></li>
88 <li><a href="#i_fdiv">'<tt>fdiv</tt>' Instruction</a></li>
89 <li><a href="#i_urem">'<tt>urem</tt>' Instruction</a></li>
90 <li><a href="#i_srem">'<tt>srem</tt>' Instruction</a></li>
91 <li><a href="#i_frem">'<tt>frem</tt>' Instruction</a></li>
94 <li><a href="#bitwiseops">Bitwise Binary Operations</a>
96 <li><a href="#i_shl">'<tt>shl</tt>' Instruction</a></li>
97 <li><a href="#i_lshr">'<tt>lshr</tt>' Instruction</a></li>
98 <li><a href="#i_ashr">'<tt>ashr</tt>' Instruction</a></li>
99 <li><a href="#i_and">'<tt>and</tt>' Instruction</a></li>
100 <li><a href="#i_or">'<tt>or</tt>' Instruction</a></li>
101 <li><a href="#i_xor">'<tt>xor</tt>' Instruction</a></li>
104 <li><a href="#vectorops">Vector Operations</a>
106 <li><a href="#i_extractelement">'<tt>extractelement</tt>' Instruction</a></li>
107 <li><a href="#i_insertelement">'<tt>insertelement</tt>' Instruction</a></li>
108 <li><a href="#i_shufflevector">'<tt>shufflevector</tt>' Instruction</a></li>
111 <li><a href="#memoryops">Memory Access and Addressing Operations</a>
113 <li><a href="#i_malloc">'<tt>malloc</tt>' Instruction</a></li>
114 <li><a href="#i_free">'<tt>free</tt>' Instruction</a></li>
115 <li><a href="#i_alloca">'<tt>alloca</tt>' Instruction</a></li>
116 <li><a href="#i_load">'<tt>load</tt>' Instruction</a></li>
117 <li><a href="#i_store">'<tt>store</tt>' Instruction</a></li>
118 <li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a></li>
121 <li><a href="#convertops">Conversion Operations</a>
123 <li><a href="#i_trunc">'<tt>trunc .. to</tt>' Instruction</a></li>
124 <li><a href="#i_zext">'<tt>zext .. to</tt>' Instruction</a></li>
125 <li><a href="#i_sext">'<tt>sext .. to</tt>' Instruction</a></li>
126 <li><a href="#i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a></li>
127 <li><a href="#i_fpext">'<tt>fpext .. to</tt>' Instruction</a></li>
128 <li><a href="#i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a></li>
129 <li><a href="#i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a></li>
130 <li><a href="#i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a></li>
131 <li><a href="#i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a></li>
132 <li><a href="#i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a></li>
133 <li><a href="#i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a></li>
134 <li><a href="#i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a></li>
136 <li><a href="#otherops">Other Operations</a>
138 <li><a href="#i_icmp">'<tt>icmp</tt>' Instruction</a></li>
139 <li><a href="#i_fcmp">'<tt>fcmp</tt>' Instruction</a></li>
140 <li><a href="#i_phi">'<tt>phi</tt>' Instruction</a></li>
141 <li><a href="#i_select">'<tt>select</tt>' Instruction</a></li>
142 <li><a href="#i_call">'<tt>call</tt>' Instruction</a></li>
143 <li><a href="#i_va_arg">'<tt>va_arg</tt>' Instruction</a></li>
148 <li><a href="#intrinsics">Intrinsic Functions</a>
150 <li><a href="#int_varargs">Variable Argument Handling Intrinsics</a>
152 <li><a href="#int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a></li>
153 <li><a href="#int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a></li>
154 <li><a href="#int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a></li>
157 <li><a href="#int_gc">Accurate Garbage Collection Intrinsics</a>
159 <li><a href="#int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a></li>
160 <li><a href="#int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a></li>
161 <li><a href="#int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a></li>
164 <li><a href="#int_codegen">Code Generator Intrinsics</a>
166 <li><a href="#int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a></li>
167 <li><a href="#int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li>
168 <li><a href="#int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a></li>
169 <li><a href="#int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a></li>
170 <li><a href="#int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a></li>
171 <li><a href="#int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a></li>
172 <li><a href="#int_readcyclecounter"><tt>llvm.readcyclecounter</tt>' Intrinsic</a></li>
175 <li><a href="#int_libc">Standard C Library Intrinsics</a>
177 <li><a href="#int_memcpy">'<tt>llvm.memcpy.*</tt>' Intrinsic</a></li>
178 <li><a href="#int_memmove">'<tt>llvm.memmove.*</tt>' Intrinsic</a></li>
179 <li><a href="#int_memset">'<tt>llvm.memset.*</tt>' Intrinsic</a></li>
180 <li><a href="#int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a></li>
181 <li><a href="#int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a></li>
182 <li><a href="#int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a></li>
183 <li><a href="#int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a></li>
184 <li><a href="#int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a></li>
187 <li><a href="#int_manip">Bit Manipulation Intrinsics</a>
189 <li><a href="#int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a></li>
190 <li><a href="#int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic </a></li>
191 <li><a href="#int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic </a></li>
192 <li><a href="#int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic </a></li>
193 <li><a href="#int_part_select">'<tt>llvm.part.select.*</tt>' Intrinsic </a></li>
194 <li><a href="#int_part_set">'<tt>llvm.part.set.*</tt>' Intrinsic </a></li>
197 <li><a href="#int_debugger">Debugger intrinsics</a></li>
198 <li><a href="#int_eh">Exception Handling intrinsics</a></li>
199 <li><a href="#int_trampoline">Trampoline Intrinsic</a>
201 <li><a href="#int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a></li>
204 <li><a href="#int_general">General intrinsics</a>
206 <li><a href="#int_var_annotation">
207 <tt>llvm.var.annotation</tt>' Intrinsic</a></li>
210 <li><a href="#int_annotation">
211 <tt>llvm.annotation.*</tt>' Intrinsic</a></li>
218 <div class="doc_author">
219 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>
220 and <a href="mailto:vadve@cs.uiuc.edu">Vikram Adve</a></p>
223 <!-- *********************************************************************** -->
224 <div class="doc_section"> <a name="abstract">Abstract </a></div>
225 <!-- *********************************************************************** -->
227 <div class="doc_text">
228 <p>This document is a reference manual for the LLVM assembly language.
229 LLVM is an SSA based representation that provides type safety,
230 low-level operations, flexibility, and the capability of representing
231 'all' high-level languages cleanly. It is the common code
232 representation used throughout all phases of the LLVM compilation
236 <!-- *********************************************************************** -->
237 <div class="doc_section"> <a name="introduction">Introduction</a> </div>
238 <!-- *********************************************************************** -->
240 <div class="doc_text">
242 <p>The LLVM code representation is designed to be used in three
243 different forms: as an in-memory compiler IR, as an on-disk bitcode
244 representation (suitable for fast loading by a Just-In-Time compiler),
245 and as a human readable assembly language representation. This allows
246 LLVM to provide a powerful intermediate representation for efficient
247 compiler transformations and analysis, while providing a natural means
248 to debug and visualize the transformations. The three different forms
249 of LLVM are all equivalent. This document describes the human readable
250 representation and notation.</p>
252 <p>The LLVM representation aims to be light-weight and low-level
253 while being expressive, typed, and extensible at the same time. It
254 aims to be a "universal IR" of sorts, by being at a low enough level
255 that high-level ideas may be cleanly mapped to it (similar to how
256 microprocessors are "universal IR's", allowing many source languages to
257 be mapped to them). By providing type information, LLVM can be used as
258 the target of optimizations: for example, through pointer analysis, it
259 can be proven that a C automatic variable is never accessed outside of
260 the current function... allowing it to be promoted to a simple SSA
261 value instead of a memory location.</p>
265 <!-- _______________________________________________________________________ -->
266 <div class="doc_subsubsection"> <a name="wellformed">Well-Formedness</a> </div>
268 <div class="doc_text">
270 <p>It is important to note that this document describes 'well formed'
271 LLVM assembly language. There is a difference between what the parser
272 accepts and what is considered 'well formed'. For example, the
273 following instruction is syntactically okay, but not well formed:</p>
275 <div class="doc_code">
277 %x = <a href="#i_add">add</a> i32 1, %x
281 <p>...because the definition of <tt>%x</tt> does not dominate all of
282 its uses. The LLVM infrastructure provides a verification pass that may
283 be used to verify that an LLVM module is well formed. This pass is
284 automatically run by the parser after parsing input assembly and by
285 the optimizer before it outputs bitcode. The violations pointed out
286 by the verifier pass indicate bugs in transformation passes or input to
290 <!-- Describe the typesetting conventions here. -->
292 <!-- *********************************************************************** -->
293 <div class="doc_section"> <a name="identifiers">Identifiers</a> </div>
294 <!-- *********************************************************************** -->
296 <div class="doc_text">
298 <p>LLVM identifiers come in two basic types: global and local. Global
299 identifiers (functions, global variables) begin with the @ character. Local
300 identifiers (register names, types) begin with the % character. Additionally,
301 there are three different formats for identifiers, for different purposes:
304 <li>Named values are represented as a string of characters with their prefix.
305 For example, %foo, @DivisionByZero, %a.really.long.identifier. The actual
306 regular expression used is '<tt>[%@][a-zA-Z$._][a-zA-Z$._0-9]*</tt>'.
307 Identifiers which require other characters in their names can be surrounded
308 with quotes. In this way, anything except a <tt>"</tt> character can
309 be used in a named value.</li>
311 <li>Unnamed values are represented as an unsigned numeric value with their
312 prefix. For example, %12, @2, %44.</li>
314 <li>Constants, which are described in a <a href="#constants">section about
315 constants</a>, below.</li>
318 <p>LLVM requires that values start with a prefix for two reasons: Compilers
319 don't need to worry about name clashes with reserved words, and the set of
320 reserved words may be expanded in the future without penalty. Additionally,
321 unnamed identifiers allow a compiler to quickly come up with a temporary
322 variable without having to avoid symbol table conflicts.</p>
324 <p>Reserved words in LLVM are very similar to reserved words in other
325 languages. There are keywords for different opcodes
326 ('<tt><a href="#i_add">add</a></tt>',
327 '<tt><a href="#i_bitcast">bitcast</a></tt>',
328 '<tt><a href="#i_ret">ret</a></tt>', etc...), for primitive type names ('<tt><a
329 href="#t_void">void</a></tt>', '<tt><a href="#t_primitive">i32</a></tt>', etc...),
330 and others. These reserved words cannot conflict with variable names, because
331 none of them start with a prefix character ('%' or '@').</p>
333 <p>Here is an example of LLVM code to multiply the integer variable
334 '<tt>%X</tt>' by 8:</p>
338 <div class="doc_code">
340 %result = <a href="#i_mul">mul</a> i32 %X, 8
344 <p>After strength reduction:</p>
346 <div class="doc_code">
348 %result = <a href="#i_shl">shl</a> i32 %X, i8 3
352 <p>And the hard way:</p>
354 <div class="doc_code">
356 <a href="#i_add">add</a> i32 %X, %X <i>; yields {i32}:%0</i>
357 <a href="#i_add">add</a> i32 %0, %0 <i>; yields {i32}:%1</i>
358 %result = <a href="#i_add">add</a> i32 %1, %1
362 <p>This last way of multiplying <tt>%X</tt> by 8 illustrates several
363 important lexical features of LLVM:</p>
367 <li>Comments are delimited with a '<tt>;</tt>' and go until the end of
370 <li>Unnamed temporaries are created when the result of a computation is not
371 assigned to a named value.</li>
373 <li>Unnamed temporaries are numbered sequentially</li>
377 <p>...and it also shows a convention that we follow in this document. When
378 demonstrating instructions, we will follow an instruction with a comment that
379 defines the type and name of value produced. Comments are shown in italic
384 <!-- *********************************************************************** -->
385 <div class="doc_section"> <a name="highlevel">High Level Structure</a> </div>
386 <!-- *********************************************************************** -->
388 <!-- ======================================================================= -->
389 <div class="doc_subsection"> <a name="modulestructure">Module Structure</a>
392 <div class="doc_text">
394 <p>LLVM programs are composed of "Module"s, each of which is a
395 translation unit of the input programs. Each module consists of
396 functions, global variables, and symbol table entries. Modules may be
397 combined together with the LLVM linker, which merges function (and
398 global variable) definitions, resolves forward declarations, and merges
399 symbol table entries. Here is an example of the "hello world" module:</p>
401 <div class="doc_code">
402 <pre><i>; Declare the string constant as a global constant...</i>
403 <a href="#identifiers">@.LC0</a> = <a href="#linkage_internal">internal</a> <a
404 href="#globalvars">constant</a> <a href="#t_array">[13 x i8]</a> c"hello world\0A\00" <i>; [13 x i8]*</i>
406 <i>; External declaration of the puts function</i>
407 <a href="#functionstructure">declare</a> i32 @puts(i8 *) <i>; i32(i8 *)* </i>
409 <i>; Definition of main function</i>
410 define i32 @main() { <i>; i32()* </i>
411 <i>; Convert [13x i8 ]* to i8 *...</i>
413 href="#i_getelementptr">getelementptr</a> [13 x i8 ]* @.LC0, i64 0, i64 0 <i>; i8 *</i>
415 <i>; Call puts function to write out the string to stdout...</i>
417 href="#i_call">call</a> i32 @puts(i8 * %cast210) <i>; i32</i>
419 href="#i_ret">ret</a> i32 0<br>}<br>
423 <p>This example is made up of a <a href="#globalvars">global variable</a>
424 named "<tt>.LC0</tt>", an external declaration of the "<tt>puts</tt>"
425 function, and a <a href="#functionstructure">function definition</a>
426 for "<tt>main</tt>".</p>
428 <p>In general, a module is made up of a list of global values,
429 where both functions and global variables are global values. Global values are
430 represented by a pointer to a memory location (in this case, a pointer to an
431 array of char, and a pointer to a function), and have one of the following <a
432 href="#linkage">linkage types</a>.</p>
436 <!-- ======================================================================= -->
437 <div class="doc_subsection">
438 <a name="linkage">Linkage Types</a>
441 <div class="doc_text">
444 All Global Variables and Functions have one of the following types of linkage:
449 <dt><tt><b><a name="linkage_internal">internal</a></b></tt> </dt>
451 <dd>Global values with internal linkage are only directly accessible by
452 objects in the current module. In particular, linking code into a module with
453 an internal global value may cause the internal to be renamed as necessary to
454 avoid collisions. Because the symbol is internal to the module, all
455 references can be updated. This corresponds to the notion of the
456 '<tt>static</tt>' keyword in C.
459 <dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt>: </dt>
461 <dd>Globals with "<tt>linkonce</tt>" linkage are merged with other globals of
462 the same name when linkage occurs. This is typically used to implement
463 inline functions, templates, or other code which must be generated in each
464 translation unit that uses it. Unreferenced <tt>linkonce</tt> globals are
465 allowed to be discarded.
468 <dt><tt><b><a name="linkage_weak">weak</a></b></tt>: </dt>
470 <dd>"<tt>weak</tt>" linkage is exactly the same as <tt>linkonce</tt> linkage,
471 except that unreferenced <tt>weak</tt> globals may not be discarded. This is
472 used for globals that may be emitted in multiple translation units, but that
473 are not guaranteed to be emitted into every translation unit that uses them.
474 One example of this are common globals in C, such as "<tt>int X;</tt>" at
478 <dt><tt><b><a name="linkage_appending">appending</a></b></tt>: </dt>
480 <dd>"<tt>appending</tt>" linkage may only be applied to global variables of
481 pointer to array type. When two global variables with appending linkage are
482 linked together, the two global arrays are appended together. This is the
483 LLVM, typesafe, equivalent of having the system linker append together
484 "sections" with identical names when .o files are linked.
487 <dt><tt><b><a name="linkage_externweak">extern_weak</a></b></tt>: </dt>
488 <dd>The semantics of this linkage follow the ELF model: the symbol is weak
489 until linked, if not linked, the symbol becomes null instead of being an
493 <dt><tt><b><a name="linkage_external">externally visible</a></b></tt>:</dt>
495 <dd>If none of the above identifiers are used, the global is externally
496 visible, meaning that it participates in linkage and can be used to resolve
497 external symbol references.
502 The next two types of linkage are targeted for Microsoft Windows platform
503 only. They are designed to support importing (exporting) symbols from (to)
508 <dt><tt><b><a name="linkage_dllimport">dllimport</a></b></tt>: </dt>
510 <dd>"<tt>dllimport</tt>" linkage causes the compiler to reference a function
511 or variable via a global pointer to a pointer that is set up by the DLL
512 exporting the symbol. On Microsoft Windows targets, the pointer name is
513 formed by combining <code>_imp__</code> and the function or variable name.
516 <dt><tt><b><a name="linkage_dllexport">dllexport</a></b></tt>: </dt>
518 <dd>"<tt>dllexport</tt>" linkage causes the compiler to provide a global
519 pointer to a pointer in a DLL, so that it can be referenced with the
520 <tt>dllimport</tt> attribute. On Microsoft Windows targets, the pointer
521 name is formed by combining <code>_imp__</code> and the function or variable
527 <p><a name="linkage_external"></a>For example, since the "<tt>.LC0</tt>"
528 variable is defined to be internal, if another module defined a "<tt>.LC0</tt>"
529 variable and was linked with this one, one of the two would be renamed,
530 preventing a collision. Since "<tt>main</tt>" and "<tt>puts</tt>" are
531 external (i.e., lacking any linkage declarations), they are accessible
532 outside of the current module.</p>
533 <p>It is illegal for a function <i>declaration</i>
534 to have any linkage type other than "externally visible", <tt>dllimport</tt>,
535 or <tt>extern_weak</tt>.</p>
536 <p>Aliases can have only <tt>external</tt>, <tt>internal</tt> and <tt>weak</tt>
540 <!-- ======================================================================= -->
541 <div class="doc_subsection">
542 <a name="callingconv">Calling Conventions</a>
545 <div class="doc_text">
547 <p>LLVM <a href="#functionstructure">functions</a>, <a href="#i_call">calls</a>
548 and <a href="#i_invoke">invokes</a> can all have an optional calling convention
549 specified for the call. The calling convention of any pair of dynamic
550 caller/callee must match, or the behavior of the program is undefined. The
551 following calling conventions are supported by LLVM, and more may be added in
555 <dt><b>"<tt>ccc</tt>" - The C calling convention</b>:</dt>
557 <dd>This calling convention (the default if no other calling convention is
558 specified) matches the target C calling conventions. This calling convention
559 supports varargs function calls and tolerates some mismatch in the declared
560 prototype and implemented declaration of the function (as does normal C).
563 <dt><b>"<tt>fastcc</tt>" - The fast calling convention</b>:</dt>
565 <dd>This calling convention attempts to make calls as fast as possible
566 (e.g. by passing things in registers). This calling convention allows the
567 target to use whatever tricks it wants to produce fast code for the target,
568 without having to conform to an externally specified ABI. Implementations of
569 this convention should allow arbitrary tail call optimization to be supported.
570 This calling convention does not support varargs and requires the prototype of
571 all callees to exactly match the prototype of the function definition.
574 <dt><b>"<tt>coldcc</tt>" - The cold calling convention</b>:</dt>
576 <dd>This calling convention attempts to make code in the caller as efficient
577 as possible under the assumption that the call is not commonly executed. As
578 such, these calls often preserve all registers so that the call does not break
579 any live ranges in the caller side. This calling convention does not support
580 varargs and requires the prototype of all callees to exactly match the
581 prototype of the function definition.
584 <dt><b>"<tt>cc <<em>n</em>></tt>" - Numbered convention</b>:</dt>
586 <dd>Any calling convention may be specified by number, allowing
587 target-specific calling conventions to be used. Target specific calling
588 conventions start at 64.
592 <p>More calling conventions can be added/defined on an as-needed basis, to
593 support pascal conventions or any other well-known target-independent
598 <!-- ======================================================================= -->
599 <div class="doc_subsection">
600 <a name="visibility">Visibility Styles</a>
603 <div class="doc_text">
606 All Global Variables and Functions have one of the following visibility styles:
610 <dt><b>"<tt>default</tt>" - Default style</b>:</dt>
612 <dd>On ELF, default visibility means that the declaration is visible to other
613 modules and, in shared libraries, means that the declared entity may be
614 overridden. On Darwin, default visibility means that the declaration is
615 visible to other modules. Default visibility corresponds to "external
616 linkage" in the language.
619 <dt><b>"<tt>hidden</tt>" - Hidden style</b>:</dt>
621 <dd>Two declarations of an object with hidden visibility refer to the same
622 object if they are in the same shared object. Usually, hidden visibility
623 indicates that the symbol will not be placed into the dynamic symbol table,
624 so no other module (executable or shared library) can reference it
628 <dt><b>"<tt>protected</tt>" - Protected style</b>:</dt>
630 <dd>On ELF, protected visibility indicates that the symbol will be placed in
631 the dynamic symbol table, but that references within the defining module will
632 bind to the local symbol. That is, the symbol cannot be overridden by another
639 <!-- ======================================================================= -->
640 <div class="doc_subsection">
641 <a name="globalvars">Global Variables</a>
644 <div class="doc_text">
646 <p>Global variables define regions of memory allocated at compilation time
647 instead of run-time. Global variables may optionally be initialized, may have
648 an explicit section to be placed in, and may have an optional explicit alignment
649 specified. A variable may be defined as "thread_local", which means that it
650 will not be shared by threads (each thread will have a separated copy of the
651 variable). A variable may be defined as a global "constant," which indicates
652 that the contents of the variable will <b>never</b> be modified (enabling better
653 optimization, allowing the global data to be placed in the read-only section of
654 an executable, etc). Note that variables that need runtime initialization
655 cannot be marked "constant" as there is a store to the variable.</p>
658 LLVM explicitly allows <em>declarations</em> of global variables to be marked
659 constant, even if the final definition of the global is not. This capability
660 can be used to enable slightly better optimization of the program, but requires
661 the language definition to guarantee that optimizations based on the
662 'constantness' are valid for the translation units that do not include the
666 <p>As SSA values, global variables define pointer values that are in
667 scope (i.e. they dominate) all basic blocks in the program. Global
668 variables always define a pointer to their "content" type because they
669 describe a region of memory, and all memory objects in LLVM are
670 accessed through pointers.</p>
672 <p>A global variable may be declared to reside in a target-specifc numbered
673 address space. For targets that support them, address spaces may affect how
674 optimizations are performed and/or what target instructions are used to access
675 the variable. The default address space is zero. The address space qualifier
676 must precede any other attributes.</p>
678 <p>LLVM allows an explicit section to be specified for globals. If the target
679 supports it, it will emit globals to the section specified.</p>
681 <p>An explicit alignment may be specified for a global. If not present, or if
682 the alignment is set to zero, the alignment of the global is set by the target
683 to whatever it feels convenient. If an explicit alignment is specified, the
684 global is forced to have at least that much alignment. All alignments must be
687 <p>For example, the following defines a global in a numbered address space with
688 an initializer, section, and alignment:</p>
690 <div class="doc_code">
692 @G = constant float 1.0 addrspace(5), section "foo", align 4
699 <!-- ======================================================================= -->
700 <div class="doc_subsection">
701 <a name="functionstructure">Functions</a>
704 <div class="doc_text">
706 <p>LLVM function definitions consist of the "<tt>define</tt>" keyord,
707 an optional <a href="#linkage">linkage type</a>, an optional
708 <a href="#visibility">visibility style</a>, an optional
709 <a href="#callingconv">calling convention</a>, a return type, an optional
710 <a href="#paramattrs">parameter attribute</a> for the return type, a function
711 name, a (possibly empty) argument list (each with optional
712 <a href="#paramattrs">parameter attributes</a>), an optional section, an
713 optional alignment, an optional <a href="#gc">garbage collector name</a>, an
714 opening curly brace, a list of basic blocks, and a closing curly brace.
716 LLVM function declarations consist of the "<tt>declare</tt>" keyword, an
717 optional <a href="#linkage">linkage type</a>, an optional
718 <a href="#visibility">visibility style</a>, an optional
719 <a href="#callingconv">calling convention</a>, a return type, an optional
720 <a href="#paramattrs">parameter attribute</a> for the return type, a function
721 name, a possibly empty list of arguments, an optional alignment, and an optional
722 <a href="#gc">garbage collector name</a>.</p>
724 <p>A function definition contains a list of basic blocks, forming the CFG for
725 the function. Each basic block may optionally start with a label (giving the
726 basic block a symbol table entry), contains a list of instructions, and ends
727 with a <a href="#terminators">terminator</a> instruction (such as a branch or
728 function return).</p>
730 <p>The first basic block in a function is special in two ways: it is immediately
731 executed on entrance to the function, and it is not allowed to have predecessor
732 basic blocks (i.e. there can not be any branches to the entry block of a
733 function). Because the block can have no predecessors, it also cannot have any
734 <a href="#i_phi">PHI nodes</a>.</p>
736 <p>LLVM allows an explicit section to be specified for functions. If the target
737 supports it, it will emit functions to the section specified.</p>
739 <p>An explicit alignment may be specified for a function. If not present, or if
740 the alignment is set to zero, the alignment of the function is set by the target
741 to whatever it feels convenient. If an explicit alignment is specified, the
742 function is forced to have at least that much alignment. All alignments must be
748 <!-- ======================================================================= -->
749 <div class="doc_subsection">
750 <a name="aliasstructure">Aliases</a>
752 <div class="doc_text">
753 <p>Aliases act as "second name" for the aliasee value (which can be either
754 function or global variable or bitcast of global value). Aliases may have an
755 optional <a href="#linkage">linkage type</a>, and an
756 optional <a href="#visibility">visibility style</a>.</p>
760 <div class="doc_code">
762 @<Name> = [Linkage] [Visibility] alias <AliaseeTy> @<Aliasee>
770 <!-- ======================================================================= -->
771 <div class="doc_subsection"><a name="paramattrs">Parameter Attributes</a></div>
772 <div class="doc_text">
773 <p>The return type and each parameter of a function type may have a set of
774 <i>parameter attributes</i> associated with them. Parameter attributes are
775 used to communicate additional information about the result or parameters of
776 a function. Parameter attributes are considered to be part of the function,
777 not of the function type, so functions with different parameter attributes
778 can have the same function type.</p>
780 <p>Parameter attributes are simple keywords that follow the type specified. If
781 multiple parameter attributes are needed, they are space separated. For
784 <div class="doc_code">
786 declare i32 @printf(i8* noalias , ...) nounwind
787 declare i32 @atoi(i8*) nounwind readonly
791 <p>Note that any attributes for the function result (<tt>nounwind</tt>,
792 <tt>readonly</tt>) come immediately after the argument list.</p>
794 <p>Currently, only the following parameter attributes are defined:</p>
796 <dt><tt>zeroext</tt></dt>
797 <dd>This indicates that the parameter should be zero extended just before
798 a call to this function.</dd>
799 <dt><tt>signext</tt></dt>
800 <dd>This indicates that the parameter should be sign extended just before
801 a call to this function.</dd>
802 <dt><tt>inreg</tt></dt>
803 <dd>This indicates that the parameter should be placed in register (if
804 possible) during assembling function call. Support for this attribute is
806 <dt><tt>sret</tt></dt>
807 <dd>This indicates that the parameter specifies the address of a structure
808 that is the return value of the function in the source program.</dd>
809 <dt><tt>noalias</tt></dt>
810 <dd>This indicates that the parameter not alias any other object or any
811 other "noalias" objects during the function call.
812 <dt><tt>noreturn</tt></dt>
813 <dd>This function attribute indicates that the function never returns. This
814 indicates to LLVM that every call to this function should be treated as if
815 an <tt>unreachable</tt> instruction immediately followed the call.</dd>
816 <dt><tt>nounwind</tt></dt>
817 <dd>This function attribute indicates that the function type does not use
818 the unwind instruction and does not allow stack unwinding to propagate
820 <dt><tt>nest</tt></dt>
821 <dd>This indicates that the parameter can be excised using the
822 <a href="#int_trampoline">trampoline intrinsics</a>.</dd>
823 <dt><tt>readonly</tt></dt>
824 <dd>This function attribute indicates that the function has no side-effects
825 except for producing a return value or throwing an exception. The value
826 returned must only depend on the function arguments and/or global variables.
827 It may use values obtained by dereferencing pointers.</dd>
828 <dt><tt>readnone</tt></dt>
829 <dd>A <tt>readnone</tt> function has the same restrictions as a <tt>readonly</tt>
830 function, but in addition it is not allowed to dereference any pointer arguments
836 <!-- ======================================================================= -->
837 <div class="doc_subsection">
838 <a name="gc">Garbage Collector Names</a>
841 <div class="doc_text">
842 <p>Each function may specify a garbage collector name, which is simply a
845 <div class="doc_code"><pre
846 >define void @f() gc "name" { ...</pre></div>
848 <p>The compiler declares the supported values of <i>name</i>. Specifying a
849 collector which will cause the compiler to alter its output in order to support
850 the named garbage collection algorithm.</p>
853 <!-- ======================================================================= -->
854 <div class="doc_subsection">
855 <a name="moduleasm">Module-Level Inline Assembly</a>
858 <div class="doc_text">
860 Modules may contain "module-level inline asm" blocks, which corresponds to the
861 GCC "file scope inline asm" blocks. These blocks are internally concatenated by
862 LLVM and treated as a single unit, but may be separated in the .ll file if
863 desired. The syntax is very simple:
866 <div class="doc_code">
868 module asm "inline asm code goes here"
869 module asm "more can go here"
873 <p>The strings can contain any character by escaping non-printable characters.
874 The escape sequence used is simply "\xx" where "xx" is the two digit hex code
879 The inline asm code is simply printed to the machine code .s file when
880 assembly code is generated.
884 <!-- ======================================================================= -->
885 <div class="doc_subsection">
886 <a name="datalayout">Data Layout</a>
889 <div class="doc_text">
890 <p>A module may specify a target specific data layout string that specifies how
891 data is to be laid out in memory. The syntax for the data layout is simply:</p>
892 <pre> target datalayout = "<i>layout specification</i>"</pre>
893 <p>The <i>layout specification</i> consists of a list of specifications
894 separated by the minus sign character ('-'). Each specification starts with a
895 letter and may include other information after the letter to define some
896 aspect of the data layout. The specifications accepted are as follows: </p>
899 <dd>Specifies that the target lays out data in big-endian form. That is, the
900 bits with the most significance have the lowest address location.</dd>
902 <dd>Specifies that hte target lays out data in little-endian form. That is,
903 the bits with the least significance have the lowest address location.</dd>
904 <dt><tt>p:<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
905 <dd>This specifies the <i>size</i> of a pointer and its <i>abi</i> and
906 <i>preferred</i> alignments. All sizes are in bits. Specifying the <i>pref</i>
907 alignment is optional. If omitted, the preceding <tt>:</tt> should be omitted
909 <dt><tt>i<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
910 <dd>This specifies the alignment for an integer type of a given bit
911 <i>size</i>. The value of <i>size</i> must be in the range [1,2^23).</dd>
912 <dt><tt>v<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
913 <dd>This specifies the alignment for a vector type of a given bit
915 <dt><tt>f<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
916 <dd>This specifies the alignment for a floating point type of a given bit
917 <i>size</i>. The value of <i>size</i> must be either 32 (float) or 64
919 <dt><tt>a<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
920 <dd>This specifies the alignment for an aggregate type of a given bit
923 <p>When constructing the data layout for a given target, LLVM starts with a
924 default set of specifications which are then (possibly) overriden by the
925 specifications in the <tt>datalayout</tt> keyword. The default specifications
926 are given in this list:</p>
928 <li><tt>E</tt> - big endian</li>
929 <li><tt>p:32:64:64</tt> - 32-bit pointers with 64-bit alignment</li>
930 <li><tt>i1:8:8</tt> - i1 is 8-bit (byte) aligned</li>
931 <li><tt>i8:8:8</tt> - i8 is 8-bit (byte) aligned</li>
932 <li><tt>i16:16:16</tt> - i16 is 16-bit aligned</li>
933 <li><tt>i32:32:32</tt> - i32 is 32-bit aligned</li>
934 <li><tt>i64:32:64</tt> - i64 has abi alignment of 32-bits but preferred
935 alignment of 64-bits</li>
936 <li><tt>f32:32:32</tt> - float is 32-bit aligned</li>
937 <li><tt>f64:64:64</tt> - double is 64-bit aligned</li>
938 <li><tt>v64:64:64</tt> - 64-bit vector is 64-bit aligned</li>
939 <li><tt>v128:128:128</tt> - 128-bit vector is 128-bit aligned</li>
940 <li><tt>a0:0:1</tt> - aggregates are 8-bit aligned</li>
942 <p>When llvm is determining the alignment for a given type, it uses the
945 <li>If the type sought is an exact match for one of the specifications, that
946 specification is used.</li>
947 <li>If no match is found, and the type sought is an integer type, then the
948 smallest integer type that is larger than the bitwidth of the sought type is
949 used. If none of the specifications are larger than the bitwidth then the the
950 largest integer type is used. For example, given the default specifications
951 above, the i7 type will use the alignment of i8 (next largest) while both
952 i65 and i256 will use the alignment of i64 (largest specified).</li>
953 <li>If no match is found, and the type sought is a vector type, then the
954 largest vector type that is smaller than the sought vector type will be used
955 as a fall back. This happens because <128 x double> can be implemented in
956 terms of 64 <2 x double>, for example.</li>
960 <!-- *********************************************************************** -->
961 <div class="doc_section"> <a name="typesystem">Type System</a> </div>
962 <!-- *********************************************************************** -->
964 <div class="doc_text">
966 <p>The LLVM type system is one of the most important features of the
967 intermediate representation. Being typed enables a number of
968 optimizations to be performed on the IR directly, without having to do
969 extra analyses on the side before the transformation. A strong type
970 system makes it easier to read the generated code and enables novel
971 analyses and transformations that are not feasible to perform on normal
972 three address code representations.</p>
976 <!-- ======================================================================= -->
977 <div class="doc_subsection"> <a name="t_primitive">Primitive Types</a> </div>
978 <div class="doc_text">
979 <p>The primitive types are the fundamental building blocks of the LLVM
980 system. The current set of primitive types is as follows:</p>
982 <table class="layout">
987 <tr><th>Type</th><th>Description</th></tr>
988 <tr><td><tt><a name="t_void">void</a></tt></td><td>No value</td></tr>
989 <tr><td><tt>label</tt></td><td>Branch destination</td></tr>
996 <tr><th>Type</th><th>Description</th></tr>
997 <tr><td><tt>float</tt></td><td>32-bit floating point value</td></tr>
998 <tr><td><tt>double</tt></td><td>64-bit floating point value</td></tr>
1006 <!-- _______________________________________________________________________ -->
1007 <div class="doc_subsubsection"> <a name="t_classifications">Type
1008 Classifications</a> </div>
1009 <div class="doc_text">
1010 <p>These different primitive types fall into a few useful
1011 classifications:</p>
1013 <table border="1" cellspacing="0" cellpadding="4">
1015 <tr><th>Classification</th><th>Types</th></tr>
1017 <td><a name="t_integer">integer</a></td>
1018 <td><tt>i1, i2, i3, ... i8, ... i16, ... i32, ... i64, ... </tt></td>
1021 <td><a name="t_floating">floating point</a></td>
1022 <td><tt>float, double</tt></td>
1025 <td><a name="t_firstclass">first class</a></td>
1026 <td><tt>i1, ..., float, double, <br/>
1027 <a href="#t_pointer">pointer</a>,<a href="#t_vector">vector</a></tt>
1033 <p>The <a href="#t_firstclass">first class</a> types are perhaps the
1034 most important. Values of these types are the only ones which can be
1035 produced by instructions, passed as arguments, or used as operands to
1036 instructions. This means that all structures and arrays must be
1037 manipulated either by pointer or by component.</p>
1040 <!-- ======================================================================= -->
1041 <div class="doc_subsection"> <a name="t_derived">Derived Types</a> </div>
1043 <div class="doc_text">
1045 <p>The real power in LLVM comes from the derived types in the system.
1046 This is what allows a programmer to represent arrays, functions,
1047 pointers, and other useful types. Note that these derived types may be
1048 recursive: For example, it is possible to have a two dimensional array.</p>
1052 <!-- _______________________________________________________________________ -->
1053 <div class="doc_subsubsection"> <a name="t_integer">Integer Type</a> </div>
1055 <div class="doc_text">
1058 <p>The integer type is a very simple derived type that simply specifies an
1059 arbitrary bit width for the integer type desired. Any bit width from 1 bit to
1060 2^23-1 (about 8 million) can be specified.</p>
1068 <p>The number of bits the integer will occupy is specified by the <tt>N</tt>
1072 <table class="layout">
1075 <td><tt>i1</tt></td>
1076 <td>a single-bit integer.</td>
1078 <td><tt>i32</tt></td>
1079 <td>a 32-bit integer.</td>
1081 <td><tt>i1942652</tt></td>
1082 <td>a really big integer of over 1 million bits.</td>
1088 <!-- _______________________________________________________________________ -->
1089 <div class="doc_subsubsection"> <a name="t_array">Array Type</a> </div>
1091 <div class="doc_text">
1095 <p>The array type is a very simple derived type that arranges elements
1096 sequentially in memory. The array type requires a size (number of
1097 elements) and an underlying data type.</p>
1102 [<# elements> x <elementtype>]
1105 <p>The number of elements is a constant integer value; elementtype may
1106 be any type with a size.</p>
1109 <table class="layout">
1112 <tt>[40 x i32 ]</tt><br/>
1113 <tt>[41 x i32 ]</tt><br/>
1114 <tt>[40 x i8]</tt><br/>
1117 Array of 40 32-bit integer values.<br/>
1118 Array of 41 32-bit integer values.<br/>
1119 Array of 40 8-bit integer values.<br/>
1123 <p>Here are some examples of multidimensional arrays:</p>
1124 <table class="layout">
1127 <tt>[3 x [4 x i32]]</tt><br/>
1128 <tt>[12 x [10 x float]]</tt><br/>
1129 <tt>[2 x [3 x [4 x i16]]]</tt><br/>
1132 3x4 array of 32-bit integer values.<br/>
1133 12x10 array of single precision floating point values.<br/>
1134 2x3x4 array of 16-bit integer values.<br/>
1139 <p>Note that 'variable sized arrays' can be implemented in LLVM with a zero
1140 length array. Normally, accesses past the end of an array are undefined in
1141 LLVM (e.g. it is illegal to access the 5th element of a 3 element array).
1142 As a special case, however, zero length arrays are recognized to be variable
1143 length. This allows implementation of 'pascal style arrays' with the LLVM
1144 type "{ i32, [0 x float]}", for example.</p>
1148 <!-- _______________________________________________________________________ -->
1149 <div class="doc_subsubsection"> <a name="t_function">Function Type</a> </div>
1150 <div class="doc_text">
1152 <p>The function type can be thought of as a function signature. It
1153 consists of a return type and a list of formal parameter types.
1154 Function types are usually used to build virtual function tables
1155 (which are structures of pointers to functions), for indirect function
1156 calls, and when defining a function.</p>
1158 The return type of a function type cannot be an aggregate type.
1161 <pre> <returntype> (<parameter list>)<br></pre>
1162 <p>...where '<tt><parameter list></tt>' is a comma-separated list of type
1163 specifiers. Optionally, the parameter list may include a type <tt>...</tt>,
1164 which indicates that the function takes a variable number of arguments.
1165 Variable argument functions can access their arguments with the <a
1166 href="#int_varargs">variable argument handling intrinsic</a> functions.</p>
1168 <table class="layout">
1170 <td class="left"><tt>i32 (i32)</tt></td>
1171 <td class="left">function taking an <tt>i32</tt>, returning an <tt>i32</tt>
1173 </tr><tr class="layout">
1174 <td class="left"><tt>float (i16 signext, i32 *) *
1176 <td class="left"><a href="#t_pointer">Pointer</a> to a function that takes
1177 an <tt>i16</tt> that should be sign extended and a
1178 <a href="#t_pointer">pointer</a> to <tt>i32</tt>, returning
1181 </tr><tr class="layout">
1182 <td class="left"><tt>i32 (i8*, ...)</tt></td>
1183 <td class="left">A vararg function that takes at least one
1184 <a href="#t_pointer">pointer</a> to <tt>i8 </tt> (char in C),
1185 which returns an integer. This is the signature for <tt>printf</tt> in
1192 <!-- _______________________________________________________________________ -->
1193 <div class="doc_subsubsection"> <a name="t_struct">Structure Type</a> </div>
1194 <div class="doc_text">
1196 <p>The structure type is used to represent a collection of data members
1197 together in memory. The packing of the field types is defined to match
1198 the ABI of the underlying processor. The elements of a structure may
1199 be any type that has a size.</p>
1200 <p>Structures are accessed using '<tt><a href="#i_load">load</a></tt>
1201 and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a
1202 field with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>'
1205 <pre> { <type list> }<br></pre>
1207 <table class="layout">
1209 <td class="left"><tt>{ i32, i32, i32 }</tt></td>
1210 <td class="left">A triple of three <tt>i32</tt> values</td>
1211 </tr><tr class="layout">
1212 <td class="left"><tt>{ float, i32 (i32) * }</tt></td>
1213 <td class="left">A pair, where the first element is a <tt>float</tt> and the
1214 second element is a <a href="#t_pointer">pointer</a> to a
1215 <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
1216 an <tt>i32</tt>.</td>
1221 <!-- _______________________________________________________________________ -->
1222 <div class="doc_subsubsection"> <a name="t_pstruct">Packed Structure Type</a>
1224 <div class="doc_text">
1226 <p>The packed structure type is used to represent a collection of data members
1227 together in memory. There is no padding between fields. Further, the alignment
1228 of a packed structure is 1 byte. The elements of a packed structure may
1229 be any type that has a size.</p>
1230 <p>Structures are accessed using '<tt><a href="#i_load">load</a></tt>
1231 and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a
1232 field with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>'
1235 <pre> < { <type list> } > <br></pre>
1237 <table class="layout">
1239 <td class="left"><tt>< { i32, i32, i32 } ></tt></td>
1240 <td class="left">A triple of three <tt>i32</tt> values</td>
1241 </tr><tr class="layout">
1242 <td class="left"><tt>< { float, i32 (i32) * } ></tt></td>
1243 <td class="left">A pair, where the first element is a <tt>float</tt> and the
1244 second element is a <a href="#t_pointer">pointer</a> to a
1245 <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
1246 an <tt>i32</tt>.</td>
1251 <!-- _______________________________________________________________________ -->
1252 <div class="doc_subsubsection"> <a name="t_pointer">Pointer Type</a> </div>
1253 <div class="doc_text">
1255 <p>As in many languages, the pointer type represents a pointer or
1256 reference to another object, which must live in memory. Pointer types may have
1257 an optional address space attribute defining the target-specific numbered
1258 address space where the pointed-to object resides. The default address space is
1261 <pre> <type> *<br></pre>
1263 <table class="layout">
1266 <tt>[4x i32]*</tt><br/>
1267 <tt>i32 (i32 *) *</tt><br/>
1268 <tt>i32 addrspace(5)*</tt><br/>
1271 A <a href="#t_pointer">pointer</a> to <a href="#t_array">array</a> of
1272 four <tt>i32</tt> values<br/>
1273 A <a href="#t_pointer">pointer</a> to a <a
1274 href="#t_function">function</a> that takes an <tt>i32*</tt>, returning an
1276 A <a href="#t_pointer">pointer</a> to an <tt>i32</tt> value that resides
1277 in address space 5.<br/>
1283 <!-- _______________________________________________________________________ -->
1284 <div class="doc_subsubsection"> <a name="t_vector">Vector Type</a> </div>
1285 <div class="doc_text">
1289 <p>A vector type is a simple derived type that represents a vector
1290 of elements. Vector types are used when multiple primitive data
1291 are operated in parallel using a single instruction (SIMD).
1292 A vector type requires a size (number of
1293 elements) and an underlying primitive data type. Vectors must have a power
1294 of two length (1, 2, 4, 8, 16 ...). Vector types are
1295 considered <a href="#t_firstclass">first class</a>.</p>
1300 < <# elements> x <elementtype> >
1303 <p>The number of elements is a constant integer value; elementtype may
1304 be any integer or floating point type.</p>
1308 <table class="layout">
1311 <tt><4 x i32></tt><br/>
1312 <tt><8 x float></tt><br/>
1313 <tt><2 x i64></tt><br/>
1316 Vector of 4 32-bit integer values.<br/>
1317 Vector of 8 floating-point values.<br/>
1318 Vector of 2 64-bit integer values.<br/>
1324 <!-- _______________________________________________________________________ -->
1325 <div class="doc_subsubsection"> <a name="t_opaque">Opaque Type</a> </div>
1326 <div class="doc_text">
1330 <p>Opaque types are used to represent unknown types in the system. This
1331 corresponds (for example) to the C notion of a forward declared structure type.
1332 In LLVM, opaque types can eventually be resolved to any type (not just a
1333 structure type).</p>
1343 <table class="layout">
1349 An opaque type.<br/>
1356 <!-- *********************************************************************** -->
1357 <div class="doc_section"> <a name="constants">Constants</a> </div>
1358 <!-- *********************************************************************** -->
1360 <div class="doc_text">
1362 <p>LLVM has several different basic types of constants. This section describes
1363 them all and their syntax.</p>
1367 <!-- ======================================================================= -->
1368 <div class="doc_subsection"><a name="simpleconstants">Simple Constants</a></div>
1370 <div class="doc_text">
1373 <dt><b>Boolean constants</b></dt>
1375 <dd>The two strings '<tt>true</tt>' and '<tt>false</tt>' are both valid
1376 constants of the <tt><a href="#t_primitive">i1</a></tt> type.
1379 <dt><b>Integer constants</b></dt>
1381 <dd>Standard integers (such as '4') are constants of the <a
1382 href="#t_integer">integer</a> type. Negative numbers may be used with
1386 <dt><b>Floating point constants</b></dt>
1388 <dd>Floating point constants use standard decimal notation (e.g. 123.421),
1389 exponential notation (e.g. 1.23421e+2), or a more precise hexadecimal
1390 notation (see below). Floating point constants must have a <a
1391 href="#t_floating">floating point</a> type. </dd>
1393 <dt><b>Null pointer constants</b></dt>
1395 <dd>The identifier '<tt>null</tt>' is recognized as a null pointer constant
1396 and must be of <a href="#t_pointer">pointer type</a>.</dd>
1400 <p>The one non-intuitive notation for constants is the optional hexadecimal form
1401 of floating point constants. For example, the form '<tt>double
1402 0x432ff973cafa8000</tt>' is equivalent to (but harder to read than) '<tt>double
1403 4.5e+15</tt>'. The only time hexadecimal floating point constants are required
1404 (and the only time that they are generated by the disassembler) is when a
1405 floating point constant must be emitted but it cannot be represented as a
1406 decimal floating point number. For example, NaN's, infinities, and other
1407 special values are represented in their IEEE hexadecimal format so that
1408 assembly and disassembly do not cause any bits to change in the constants.</p>
1412 <!-- ======================================================================= -->
1413 <div class="doc_subsection"><a name="aggregateconstants">Aggregate Constants</a>
1416 <div class="doc_text">
1417 <p>Aggregate constants arise from aggregation of simple constants
1418 and smaller aggregate constants.</p>
1421 <dt><b>Structure constants</b></dt>
1423 <dd>Structure constants are represented with notation similar to structure
1424 type definitions (a comma separated list of elements, surrounded by braces
1425 (<tt>{}</tt>)). For example: "<tt>{ i32 4, float 17.0, i32* %G }</tt>",
1426 where "<tt>%G</tt>" is declared as "<tt>@G = external global i32</tt>". Structure constants
1427 must have <a href="#t_struct">structure type</a>, and the number and
1428 types of elements must match those specified by the type.
1431 <dt><b>Array constants</b></dt>
1433 <dd>Array constants are represented with notation similar to array type
1434 definitions (a comma separated list of elements, surrounded by square brackets
1435 (<tt>[]</tt>)). For example: "<tt>[ i32 42, i32 11, i32 74 ]</tt>". Array
1436 constants must have <a href="#t_array">array type</a>, and the number and
1437 types of elements must match those specified by the type.
1440 <dt><b>Vector constants</b></dt>
1442 <dd>Vector constants are represented with notation similar to vector type
1443 definitions (a comma separated list of elements, surrounded by
1444 less-than/greater-than's (<tt><></tt>)). For example: "<tt>< i32 42,
1445 i32 11, i32 74, i32 100 ></tt>". Vector constants must have <a
1446 href="#t_vector">vector type</a>, and the number and types of elements must
1447 match those specified by the type.
1450 <dt><b>Zero initialization</b></dt>
1452 <dd>The string '<tt>zeroinitializer</tt>' can be used to zero initialize a
1453 value to zero of <em>any</em> type, including scalar and aggregate types.
1454 This is often used to avoid having to print large zero initializers (e.g. for
1455 large arrays) and is always exactly equivalent to using explicit zero
1462 <!-- ======================================================================= -->
1463 <div class="doc_subsection">
1464 <a name="globalconstants">Global Variable and Function Addresses</a>
1467 <div class="doc_text">
1469 <p>The addresses of <a href="#globalvars">global variables</a> and <a
1470 href="#functionstructure">functions</a> are always implicitly valid (link-time)
1471 constants. These constants are explicitly referenced when the <a
1472 href="#identifiers">identifier for the global</a> is used and always have <a
1473 href="#t_pointer">pointer</a> type. For example, the following is a legal LLVM
1476 <div class="doc_code">
1480 @Z = global [2 x i32*] [ i32* @X, i32* @Y ]
1486 <!-- ======================================================================= -->
1487 <div class="doc_subsection"><a name="undefvalues">Undefined Values</a></div>
1488 <div class="doc_text">
1489 <p>The string '<tt>undef</tt>' is recognized as a type-less constant that has
1490 no specific value. Undefined values may be of any type and be used anywhere
1491 a constant is permitted.</p>
1493 <p>Undefined values indicate to the compiler that the program is well defined
1494 no matter what value is used, giving the compiler more freedom to optimize.
1498 <!-- ======================================================================= -->
1499 <div class="doc_subsection"><a name="constantexprs">Constant Expressions</a>
1502 <div class="doc_text">
1504 <p>Constant expressions are used to allow expressions involving other constants
1505 to be used as constants. Constant expressions may be of any <a
1506 href="#t_firstclass">first class</a> type and may involve any LLVM operation
1507 that does not have side effects (e.g. load and call are not supported). The
1508 following is the syntax for constant expressions:</p>
1511 <dt><b><tt>trunc ( CST to TYPE )</tt></b></dt>
1512 <dd>Truncate a constant to another type. The bit size of CST must be larger
1513 than the bit size of TYPE. Both types must be integers.</dd>
1515 <dt><b><tt>zext ( CST to TYPE )</tt></b></dt>
1516 <dd>Zero extend a constant to another type. The bit size of CST must be
1517 smaller or equal to the bit size of TYPE. Both types must be integers.</dd>
1519 <dt><b><tt>sext ( CST to TYPE )</tt></b></dt>
1520 <dd>Sign extend a constant to another type. The bit size of CST must be
1521 smaller or equal to the bit size of TYPE. Both types must be integers.</dd>
1523 <dt><b><tt>fptrunc ( CST to TYPE )</tt></b></dt>
1524 <dd>Truncate a floating point constant to another floating point type. The
1525 size of CST must be larger than the size of TYPE. Both types must be
1526 floating point.</dd>
1528 <dt><b><tt>fpext ( CST to TYPE )</tt></b></dt>
1529 <dd>Floating point extend a constant to another type. The size of CST must be
1530 smaller or equal to the size of TYPE. Both types must be floating point.</dd>
1532 <dt><b><tt>fptoui ( CST to TYPE )</tt></b></dt>
1533 <dd>Convert a floating point constant to the corresponding unsigned integer
1534 constant. TYPE must be a scalar or vector integer type. CST must be of scalar
1535 or vector floating point type. Both CST and TYPE must be scalars, or vectors
1536 of the same number of elements. If the value won't fit in the integer type,
1537 the results are undefined.</dd>
1539 <dt><b><tt>fptosi ( CST to TYPE )</tt></b></dt>
1540 <dd>Convert a floating point constant to the corresponding signed integer
1541 constant. TYPE must be a scalar or vector integer type. CST must be of scalar
1542 or vector floating point type. Both CST and TYPE must be scalars, or vectors
1543 of the same number of elements. If the value won't fit in the integer type,
1544 the results are undefined.</dd>
1546 <dt><b><tt>uitofp ( CST to TYPE )</tt></b></dt>
1547 <dd>Convert an unsigned integer constant to the corresponding floating point
1548 constant. TYPE must be a scalar or vector floating point type. CST must be of
1549 scalar or vector integer type. Both CST and TYPE must be scalars, or vectors
1550 of the same number of elements. If the value won't fit in the floating point
1551 type, the results are undefined.</dd>
1553 <dt><b><tt>sitofp ( CST to TYPE )</tt></b></dt>
1554 <dd>Convert a signed integer constant to the corresponding floating point
1555 constant. TYPE must be a scalar or vector floating point type. CST must be of
1556 scalar or vector integer type. Both CST and TYPE must be scalars, or vectors
1557 of the same number of elements. If the value won't fit in the floating point
1558 type, the results are undefined.</dd>
1560 <dt><b><tt>ptrtoint ( CST to TYPE )</tt></b></dt>
1561 <dd>Convert a pointer typed constant to the corresponding integer constant
1562 TYPE must be an integer type. CST must be of pointer type. The CST value is
1563 zero extended, truncated, or unchanged to make it fit in TYPE.</dd>
1565 <dt><b><tt>inttoptr ( CST to TYPE )</tt></b></dt>
1566 <dd>Convert a integer constant to a pointer constant. TYPE must be a
1567 pointer type. CST must be of integer type. The CST value is zero extended,
1568 truncated, or unchanged to make it fit in a pointer size. This one is
1569 <i>really</i> dangerous!</dd>
1571 <dt><b><tt>bitcast ( CST to TYPE )</tt></b></dt>
1572 <dd>Convert a constant, CST, to another TYPE. The size of CST and TYPE must be
1573 identical (same number of bits). The conversion is done as if the CST value
1574 was stored to memory and read back as TYPE. In other words, no bits change
1575 with this operator, just the type. This can be used for conversion of
1576 vector types to any other type, as long as they have the same bit width. For
1577 pointers it is only valid to cast to another pointer type.
1580 <dt><b><tt>getelementptr ( CSTPTR, IDX0, IDX1, ... )</tt></b></dt>
1582 <dd>Perform the <a href="#i_getelementptr">getelementptr operation</a> on
1583 constants. As with the <a href="#i_getelementptr">getelementptr</a>
1584 instruction, the index list may have zero or more indexes, which are required
1585 to make sense for the type of "CSTPTR".</dd>
1587 <dt><b><tt>select ( COND, VAL1, VAL2 )</tt></b></dt>
1589 <dd>Perform the <a href="#i_select">select operation</a> on
1592 <dt><b><tt>icmp COND ( VAL1, VAL2 )</tt></b></dt>
1593 <dd>Performs the <a href="#i_icmp">icmp operation</a> on constants.</dd>
1595 <dt><b><tt>fcmp COND ( VAL1, VAL2 )</tt></b></dt>
1596 <dd>Performs the <a href="#i_fcmp">fcmp operation</a> on constants.</dd>
1598 <dt><b><tt>extractelement ( VAL, IDX )</tt></b></dt>
1600 <dd>Perform the <a href="#i_extractelement">extractelement
1601 operation</a> on constants.
1603 <dt><b><tt>insertelement ( VAL, ELT, IDX )</tt></b></dt>
1605 <dd>Perform the <a href="#i_insertelement">insertelement
1606 operation</a> on constants.</dd>
1609 <dt><b><tt>shufflevector ( VEC1, VEC2, IDXMASK )</tt></b></dt>
1611 <dd>Perform the <a href="#i_shufflevector">shufflevector
1612 operation</a> on constants.</dd>
1614 <dt><b><tt>OPCODE ( LHS, RHS )</tt></b></dt>
1616 <dd>Perform the specified operation of the LHS and RHS constants. OPCODE may
1617 be any of the <a href="#binaryops">binary</a> or <a href="#bitwiseops">bitwise
1618 binary</a> operations. The constraints on operands are the same as those for
1619 the corresponding instruction (e.g. no bitwise operations on floating point
1620 values are allowed).</dd>
1624 <!-- *********************************************************************** -->
1625 <div class="doc_section"> <a name="othervalues">Other Values</a> </div>
1626 <!-- *********************************************************************** -->
1628 <!-- ======================================================================= -->
1629 <div class="doc_subsection">
1630 <a name="inlineasm">Inline Assembler Expressions</a>
1633 <div class="doc_text">
1636 LLVM supports inline assembler expressions (as opposed to <a href="#moduleasm">
1637 Module-Level Inline Assembly</a>) through the use of a special value. This
1638 value represents the inline assembler as a string (containing the instructions
1639 to emit), a list of operand constraints (stored as a string), and a flag that
1640 indicates whether or not the inline asm expression has side effects. An example
1641 inline assembler expression is:
1644 <div class="doc_code">
1646 i32 (i32) asm "bswap $0", "=r,r"
1651 Inline assembler expressions may <b>only</b> be used as the callee operand of
1652 a <a href="#i_call"><tt>call</tt> instruction</a>. Thus, typically we have:
1655 <div class="doc_code">
1657 %X = call i32 asm "<a href="#int_bswap">bswap</a> $0", "=r,r"(i32 %Y)
1662 Inline asms with side effects not visible in the constraint list must be marked
1663 as having side effects. This is done through the use of the
1664 '<tt>sideeffect</tt>' keyword, like so:
1667 <div class="doc_code">
1669 call void asm sideeffect "eieio", ""()
1673 <p>TODO: The format of the asm and constraints string still need to be
1674 documented here. Constraints on what can be done (e.g. duplication, moving, etc
1675 need to be documented).
1680 <!-- *********************************************************************** -->
1681 <div class="doc_section"> <a name="instref">Instruction Reference</a> </div>
1682 <!-- *********************************************************************** -->
1684 <div class="doc_text">
1686 <p>The LLVM instruction set consists of several different
1687 classifications of instructions: <a href="#terminators">terminator
1688 instructions</a>, <a href="#binaryops">binary instructions</a>,
1689 <a href="#bitwiseops">bitwise binary instructions</a>, <a
1690 href="#memoryops">memory instructions</a>, and <a href="#otherops">other
1691 instructions</a>.</p>
1695 <!-- ======================================================================= -->
1696 <div class="doc_subsection"> <a name="terminators">Terminator
1697 Instructions</a> </div>
1699 <div class="doc_text">
1701 <p>As mentioned <a href="#functionstructure">previously</a>, every
1702 basic block in a program ends with a "Terminator" instruction, which
1703 indicates which block should be executed after the current block is
1704 finished. These terminator instructions typically yield a '<tt>void</tt>'
1705 value: they produce control flow, not values (the one exception being
1706 the '<a href="#i_invoke"><tt>invoke</tt></a>' instruction).</p>
1707 <p>There are six different terminator instructions: the '<a
1708 href="#i_ret"><tt>ret</tt></a>' instruction, the '<a href="#i_br"><tt>br</tt></a>'
1709 instruction, the '<a href="#i_switch"><tt>switch</tt></a>' instruction,
1710 the '<a href="#i_invoke"><tt>invoke</tt></a>' instruction, the '<a
1711 href="#i_unwind"><tt>unwind</tt></a>' instruction, and the '<a
1712 href="#i_unreachable"><tt>unreachable</tt></a>' instruction.</p>
1716 <!-- _______________________________________________________________________ -->
1717 <div class="doc_subsubsection"> <a name="i_ret">'<tt>ret</tt>'
1718 Instruction</a> </div>
1719 <div class="doc_text">
1721 <pre> ret <type> <value> <i>; Return a value from a non-void function</i>
1722 ret void <i>; Return from void function</i>
1725 <p>The '<tt>ret</tt>' instruction is used to return control flow (and a
1726 value) from a function back to the caller.</p>
1727 <p>There are two forms of the '<tt>ret</tt>' instruction: one that
1728 returns a value and then causes control flow, and one that just causes
1729 control flow to occur.</p>
1731 <p>The '<tt>ret</tt>' instruction may return any '<a
1732 href="#t_firstclass">first class</a>' type. Notice that a function is
1733 not <a href="#wellformed">well formed</a> if there exists a '<tt>ret</tt>'
1734 instruction inside of the function that returns a value that does not
1735 match the return type of the function.</p>
1737 <p>When the '<tt>ret</tt>' instruction is executed, control flow
1738 returns back to the calling function's context. If the caller is a "<a
1739 href="#i_call"><tt>call</tt></a>" instruction, execution continues at
1740 the instruction after the call. If the caller was an "<a
1741 href="#i_invoke"><tt>invoke</tt></a>" instruction, execution continues
1742 at the beginning of the "normal" destination block. If the instruction
1743 returns a value, that value shall set the call or invoke instruction's
1746 <pre> ret i32 5 <i>; Return an integer value of 5</i>
1747 ret void <i>; Return from a void function</i>
1750 <!-- _______________________________________________________________________ -->
1751 <div class="doc_subsubsection"> <a name="i_br">'<tt>br</tt>' Instruction</a> </div>
1752 <div class="doc_text">
1754 <pre> br i1 <cond>, label <iftrue>, label <iffalse><br> br label <dest> <i>; Unconditional branch</i>
1757 <p>The '<tt>br</tt>' instruction is used to cause control flow to
1758 transfer to a different basic block in the current function. There are
1759 two forms of this instruction, corresponding to a conditional branch
1760 and an unconditional branch.</p>
1762 <p>The conditional branch form of the '<tt>br</tt>' instruction takes a
1763 single '<tt>i1</tt>' value and two '<tt>label</tt>' values. The
1764 unconditional form of the '<tt>br</tt>' instruction takes a single
1765 '<tt>label</tt>' value as a target.</p>
1767 <p>Upon execution of a conditional '<tt>br</tt>' instruction, the '<tt>i1</tt>'
1768 argument is evaluated. If the value is <tt>true</tt>, control flows
1769 to the '<tt>iftrue</tt>' <tt>label</tt> argument. If "cond" is <tt>false</tt>,
1770 control flows to the '<tt>iffalse</tt>' <tt>label</tt> argument.</p>
1772 <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
1773 href="#i_ret">ret</a> i32 1<br>IfUnequal:<br> <a href="#i_ret">ret</a> i32 0<br></pre>
1775 <!-- _______________________________________________________________________ -->
1776 <div class="doc_subsubsection">
1777 <a name="i_switch">'<tt>switch</tt>' Instruction</a>
1780 <div class="doc_text">
1784 switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]
1789 <p>The '<tt>switch</tt>' instruction is used to transfer control flow to one of
1790 several different places. It is a generalization of the '<tt>br</tt>'
1791 instruction, allowing a branch to occur to one of many possible
1797 <p>The '<tt>switch</tt>' instruction uses three parameters: an integer
1798 comparison value '<tt>value</tt>', a default '<tt>label</tt>' destination, and
1799 an array of pairs of comparison value constants and '<tt>label</tt>'s. The
1800 table is not allowed to contain duplicate constant entries.</p>
1804 <p>The <tt>switch</tt> instruction specifies a table of values and
1805 destinations. When the '<tt>switch</tt>' instruction is executed, this
1806 table is searched for the given value. If the value is found, control flow is
1807 transfered to the corresponding destination; otherwise, control flow is
1808 transfered to the default destination.</p>
1810 <h5>Implementation:</h5>
1812 <p>Depending on properties of the target machine and the particular
1813 <tt>switch</tt> instruction, this instruction may be code generated in different
1814 ways. For example, it could be generated as a series of chained conditional
1815 branches or with a lookup table.</p>
1820 <i>; Emulate a conditional br instruction</i>
1821 %Val = <a href="#i_zext">zext</a> i1 %value to i32
1822 switch i32 %Val, label %truedest [i32 0, label %falsedest ]
1824 <i>; Emulate an unconditional br instruction</i>
1825 switch i32 0, label %dest [ ]
1827 <i>; Implement a jump table:</i>
1828 switch i32 %val, label %otherwise [ i32 0, label %onzero
1830 i32 2, label %ontwo ]
1834 <!-- _______________________________________________________________________ -->
1835 <div class="doc_subsubsection">
1836 <a name="i_invoke">'<tt>invoke</tt>' Instruction</a>
1839 <div class="doc_text">
1844 <result> = invoke [<a href="#callingconv">cconv</a>] <ptr to function ty> %<function ptr val>(<function args>)
1845 to label <normal label> unwind label <exception label>
1850 <p>The '<tt>invoke</tt>' instruction causes control to transfer to a specified
1851 function, with the possibility of control flow transfer to either the
1852 '<tt>normal</tt>' label or the
1853 '<tt>exception</tt>' label. If the callee function returns with the
1854 "<tt><a href="#i_ret">ret</a></tt>" instruction, control flow will return to the
1855 "normal" label. If the callee (or any indirect callees) returns with the "<a
1856 href="#i_unwind"><tt>unwind</tt></a>" instruction, control is interrupted and
1857 continued at the dynamically nearest "exception" label.</p>
1861 <p>This instruction requires several arguments:</p>
1865 The optional "cconv" marker indicates which <a href="#callingconv">calling
1866 convention</a> the call should use. If none is specified, the call defaults
1867 to using C calling conventions.
1869 <li>'<tt>ptr to function ty</tt>': shall be the signature of the pointer to
1870 function value being invoked. In most cases, this is a direct function
1871 invocation, but indirect <tt>invoke</tt>s are just as possible, branching off
1872 an arbitrary pointer to function value.
1875 <li>'<tt>function ptr val</tt>': An LLVM value containing a pointer to a
1876 function to be invoked. </li>
1878 <li>'<tt>function args</tt>': argument list whose types match the function
1879 signature argument types. If the function signature indicates the function
1880 accepts a variable number of arguments, the extra arguments can be
1883 <li>'<tt>normal label</tt>': the label reached when the called function
1884 executes a '<tt><a href="#i_ret">ret</a></tt>' instruction. </li>
1886 <li>'<tt>exception label</tt>': the label reached when a callee returns with
1887 the <a href="#i_unwind"><tt>unwind</tt></a> instruction. </li>
1893 <p>This instruction is designed to operate as a standard '<tt><a
1894 href="#i_call">call</a></tt>' instruction in most regards. The primary
1895 difference is that it establishes an association with a label, which is used by
1896 the runtime library to unwind the stack.</p>
1898 <p>This instruction is used in languages with destructors to ensure that proper
1899 cleanup is performed in the case of either a <tt>longjmp</tt> or a thrown
1900 exception. Additionally, this is important for implementation of
1901 '<tt>catch</tt>' clauses in high-level languages that support them.</p>
1905 %retval = invoke i32 %Test(i32 15) to label %Continue
1906 unwind label %TestCleanup <i>; {i32}:retval set</i>
1907 %retval = invoke <a href="#callingconv">coldcc</a> i32 %Test(i32 15) to label %Continue
1908 unwind label %TestCleanup <i>; {i32}:retval set</i>
1913 <!-- _______________________________________________________________________ -->
1915 <div class="doc_subsubsection"> <a name="i_unwind">'<tt>unwind</tt>'
1916 Instruction</a> </div>
1918 <div class="doc_text">
1927 <p>The '<tt>unwind</tt>' instruction unwinds the stack, continuing control flow
1928 at the first callee in the dynamic call stack which used an <a
1929 href="#i_invoke"><tt>invoke</tt></a> instruction to perform the call. This is
1930 primarily used to implement exception handling.</p>
1934 <p>The '<tt>unwind</tt>' intrinsic causes execution of the current function to
1935 immediately halt. The dynamic call stack is then searched for the first <a
1936 href="#i_invoke"><tt>invoke</tt></a> instruction on the call stack. Once found,
1937 execution continues at the "exceptional" destination block specified by the
1938 <tt>invoke</tt> instruction. If there is no <tt>invoke</tt> instruction in the
1939 dynamic call chain, undefined behavior results.</p>
1942 <!-- _______________________________________________________________________ -->
1944 <div class="doc_subsubsection"> <a name="i_unreachable">'<tt>unreachable</tt>'
1945 Instruction</a> </div>
1947 <div class="doc_text">
1956 <p>The '<tt>unreachable</tt>' instruction has no defined semantics. This
1957 instruction is used to inform the optimizer that a particular portion of the
1958 code is not reachable. This can be used to indicate that the code after a
1959 no-return function cannot be reached, and other facts.</p>
1963 <p>The '<tt>unreachable</tt>' instruction has no defined semantics.</p>
1968 <!-- ======================================================================= -->
1969 <div class="doc_subsection"> <a name="binaryops">Binary Operations</a> </div>
1970 <div class="doc_text">
1971 <p>Binary operators are used to do most of the computation in a
1972 program. They require two operands, execute an operation on them, and
1973 produce a single value. The operands might represent
1974 multiple data, as is the case with the <a href="#t_vector">vector</a> data type.
1975 The result value of a binary operator is not
1976 necessarily the same type as its operands.</p>
1977 <p>There are several different binary operators:</p>
1979 <!-- _______________________________________________________________________ -->
1980 <div class="doc_subsubsection"> <a name="i_add">'<tt>add</tt>'
1981 Instruction</a> </div>
1982 <div class="doc_text">
1984 <pre> <result> = add <ty> <var1>, <var2> <i>; yields {ty}:result</i>
1987 <p>The '<tt>add</tt>' instruction returns the sum of its two operands.</p>
1989 <p>The two arguments to the '<tt>add</tt>' instruction must be either <a
1990 href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> values.
1991 This instruction can also take <a href="#t_vector">vector</a> versions of the values.
1992 Both arguments must have identical types.</p>
1994 <p>The value produced is the integer or floating point sum of the two
1997 <pre> <result> = add i32 4, %var <i>; yields {i32}:result = 4 + %var</i>
2000 <!-- _______________________________________________________________________ -->
2001 <div class="doc_subsubsection"> <a name="i_sub">'<tt>sub</tt>'
2002 Instruction</a> </div>
2003 <div class="doc_text">
2005 <pre> <result> = sub <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2008 <p>The '<tt>sub</tt>' instruction returns the difference of its two
2010 <p>Note that the '<tt>sub</tt>' instruction is used to represent the '<tt>neg</tt>'
2011 instruction present in most other intermediate representations.</p>
2013 <p>The two arguments to the '<tt>sub</tt>' instruction must be either <a
2014 href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
2016 This instruction can also take <a href="#t_vector">vector</a> versions of the values.
2017 Both arguments must have identical types.</p>
2019 <p>The value produced is the integer or floating point difference of
2020 the two operands.</p>
2023 <result> = sub i32 4, %var <i>; yields {i32}:result = 4 - %var</i>
2024 <result> = sub i32 0, %val <i>; yields {i32}:result = -%var</i>
2027 <!-- _______________________________________________________________________ -->
2028 <div class="doc_subsubsection"> <a name="i_mul">'<tt>mul</tt>'
2029 Instruction</a> </div>
2030 <div class="doc_text">
2032 <pre> <result> = mul <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2035 <p>The '<tt>mul</tt>' instruction returns the product of its two
2038 <p>The two arguments to the '<tt>mul</tt>' instruction must be either <a
2039 href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
2041 This instruction can also take <a href="#t_vector">vector</a> versions of the values.
2042 Both arguments must have identical types.</p>
2044 <p>The value produced is the integer or floating point product of the
2046 <p>Because the operands are the same width, the result of an integer
2047 multiplication is the same whether the operands should be deemed unsigned or
2050 <pre> <result> = mul i32 4, %var <i>; yields {i32}:result = 4 * %var</i>
2053 <!-- _______________________________________________________________________ -->
2054 <div class="doc_subsubsection"> <a name="i_udiv">'<tt>udiv</tt>' Instruction
2056 <div class="doc_text">
2058 <pre> <result> = udiv <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2061 <p>The '<tt>udiv</tt>' instruction returns the quotient of its two
2064 <p>The two arguments to the '<tt>udiv</tt>' instruction must be
2065 <a href="#t_integer">integer</a> values. Both arguments must have identical
2066 types. This instruction can also take <a href="#t_vector">vector</a> versions
2067 of the values in which case the elements must be integers.</p>
2069 <p>The value produced is the unsigned integer quotient of the two operands. This
2070 instruction always performs an unsigned division operation, regardless of
2071 whether the arguments are unsigned or not.</p>
2073 <pre> <result> = udiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>
2076 <!-- _______________________________________________________________________ -->
2077 <div class="doc_subsubsection"> <a name="i_sdiv">'<tt>sdiv</tt>' Instruction
2079 <div class="doc_text">
2081 <pre> <result> = sdiv <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2084 <p>The '<tt>sdiv</tt>' instruction returns the quotient of its two
2087 <p>The two arguments to the '<tt>sdiv</tt>' instruction must be
2088 <a href="#t_integer">integer</a> values. Both arguments must have identical
2089 types. This instruction can also take <a href="#t_vector">vector</a> versions
2090 of the values in which case the elements must be integers.</p>
2092 <p>The value produced is the signed integer quotient of the two operands. This
2093 instruction always performs a signed division operation, regardless of whether
2094 the arguments are signed or not.</p>
2096 <pre> <result> = sdiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>
2099 <!-- _______________________________________________________________________ -->
2100 <div class="doc_subsubsection"> <a name="i_fdiv">'<tt>fdiv</tt>'
2101 Instruction</a> </div>
2102 <div class="doc_text">
2104 <pre> <result> = fdiv <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2107 <p>The '<tt>fdiv</tt>' instruction returns the quotient of its two
2110 <p>The two arguments to the '<tt>fdiv</tt>' instruction must be
2111 <a href="#t_floating">floating point</a> values. Both arguments must have
2112 identical types. This instruction can also take <a href="#t_vector">vector</a>
2113 versions of floating point values.</p>
2115 <p>The value produced is the floating point quotient of the two operands.</p>
2117 <pre> <result> = fdiv float 4.0, %var <i>; yields {float}:result = 4.0 / %var</i>
2120 <!-- _______________________________________________________________________ -->
2121 <div class="doc_subsubsection"> <a name="i_urem">'<tt>urem</tt>' Instruction</a>
2123 <div class="doc_text">
2125 <pre> <result> = urem <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2128 <p>The '<tt>urem</tt>' instruction returns the remainder from the
2129 unsigned division of its two arguments.</p>
2131 <p>The two arguments to the '<tt>urem</tt>' instruction must be
2132 <a href="#t_integer">integer</a> values. Both arguments must have identical
2133 types. This instruction can also take <a href="#t_vector">vector</a> versions
2134 of the values in which case the elements must be integers.</p>
2136 <p>This instruction returns the unsigned integer <i>remainder</i> of a division.
2137 This instruction always performs an unsigned division to get the remainder,
2138 regardless of whether the arguments are unsigned or not.</p>
2140 <pre> <result> = urem i32 4, %var <i>; yields {i32}:result = 4 % %var</i>
2144 <!-- _______________________________________________________________________ -->
2145 <div class="doc_subsubsection"> <a name="i_srem">'<tt>srem</tt>'
2146 Instruction</a> </div>
2147 <div class="doc_text">
2149 <pre> <result> = srem <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2152 <p>The '<tt>srem</tt>' instruction returns the remainder from the
2153 signed division of its two operands. This instruction can also take
2154 <a href="#t_vector">vector</a> versions of the values in which case
2155 the elements must be integers.</p>
2158 <p>The two arguments to the '<tt>srem</tt>' instruction must be
2159 <a href="#t_integer">integer</a> values. Both arguments must have identical
2162 <p>This instruction returns the <i>remainder</i> of a division (where the result
2163 has the same sign as the dividend, <tt>var1</tt>), not the <i>modulo</i>
2164 operator (where the result has the same sign as the divisor, <tt>var2</tt>) of
2165 a value. For more information about the difference, see <a
2166 href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The
2167 Math Forum</a>. For a table of how this is implemented in various languages,
2168 please see <a href="http://en.wikipedia.org/wiki/Modulo_operation">
2169 Wikipedia: modulo operation</a>.</p>
2171 <pre> <result> = srem i32 4, %var <i>; yields {i32}:result = 4 % %var</i>
2175 <!-- _______________________________________________________________________ -->
2176 <div class="doc_subsubsection"> <a name="i_frem">'<tt>frem</tt>'
2177 Instruction</a> </div>
2178 <div class="doc_text">
2180 <pre> <result> = frem <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2183 <p>The '<tt>frem</tt>' instruction returns the remainder from the
2184 division of its two operands.</p>
2186 <p>The two arguments to the '<tt>frem</tt>' instruction must be
2187 <a href="#t_floating">floating point</a> values. Both arguments must have
2188 identical types. This instruction can also take <a href="#t_vector">vector</a>
2189 versions of floating point values.</p>
2191 <p>This instruction returns the <i>remainder</i> of a division.</p>
2193 <pre> <result> = frem float 4.0, %var <i>; yields {float}:result = 4.0 % %var</i>
2197 <!-- ======================================================================= -->
2198 <div class="doc_subsection"> <a name="bitwiseops">Bitwise Binary
2199 Operations</a> </div>
2200 <div class="doc_text">
2201 <p>Bitwise binary operators are used to do various forms of
2202 bit-twiddling in a program. They are generally very efficient
2203 instructions and can commonly be strength reduced from other
2204 instructions. They require two operands, execute an operation on them,
2205 and produce a single value. The resulting value of the bitwise binary
2206 operators is always the same type as its first operand.</p>
2209 <!-- _______________________________________________________________________ -->
2210 <div class="doc_subsubsection"> <a name="i_shl">'<tt>shl</tt>'
2211 Instruction</a> </div>
2212 <div class="doc_text">
2214 <pre> <result> = shl <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2219 <p>The '<tt>shl</tt>' instruction returns the first operand shifted to
2220 the left a specified number of bits.</p>
2224 <p>Both arguments to the '<tt>shl</tt>' instruction must be the same <a
2225 href="#t_integer">integer</a> type.</p>
2229 <p>The value produced is <tt>var1</tt> * 2<sup><tt>var2</tt></sup>. If
2230 <tt>var2</tt> is (statically or dynamically) equal to or larger than the number
2231 of bits in <tt>var1</tt>, the result is undefined.</p>
2233 <h5>Example:</h5><pre>
2234 <result> = shl i32 4, %var <i>; yields {i32}: 4 << %var</i>
2235 <result> = shl i32 4, 2 <i>; yields {i32}: 16</i>
2236 <result> = shl i32 1, 10 <i>; yields {i32}: 1024</i>
2237 <result> = shl i32 1, 32 <i>; undefined</i>
2240 <!-- _______________________________________________________________________ -->
2241 <div class="doc_subsubsection"> <a name="i_lshr">'<tt>lshr</tt>'
2242 Instruction</a> </div>
2243 <div class="doc_text">
2245 <pre> <result> = lshr <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2249 <p>The '<tt>lshr</tt>' instruction (logical shift right) returns the first
2250 operand shifted to the right a specified number of bits with zero fill.</p>
2253 <p>Both arguments to the '<tt>lshr</tt>' instruction must be the same
2254 <a href="#t_integer">integer</a> type.</p>
2258 <p>This instruction always performs a logical shift right operation. The most
2259 significant bits of the result will be filled with zero bits after the
2260 shift. If <tt>var2</tt> is (statically or dynamically) equal to or larger than
2261 the number of bits in <tt>var1</tt>, the result is undefined.</p>
2265 <result> = lshr i32 4, 1 <i>; yields {i32}:result = 2</i>
2266 <result> = lshr i32 4, 2 <i>; yields {i32}:result = 1</i>
2267 <result> = lshr i8 4, 3 <i>; yields {i8}:result = 0</i>
2268 <result> = lshr i8 -2, 1 <i>; yields {i8}:result = 0x7FFFFFFF </i>
2269 <result> = lshr i32 1, 32 <i>; undefined</i>
2273 <!-- _______________________________________________________________________ -->
2274 <div class="doc_subsubsection"> <a name="i_ashr">'<tt>ashr</tt>'
2275 Instruction</a> </div>
2276 <div class="doc_text">
2279 <pre> <result> = ashr <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2283 <p>The '<tt>ashr</tt>' instruction (arithmetic shift right) returns the first
2284 operand shifted to the right a specified number of bits with sign extension.</p>
2287 <p>Both arguments to the '<tt>ashr</tt>' instruction must be the same
2288 <a href="#t_integer">integer</a> type.</p>
2291 <p>This instruction always performs an arithmetic shift right operation,
2292 The most significant bits of the result will be filled with the sign bit
2293 of <tt>var1</tt>. If <tt>var2</tt> is (statically or dynamically) equal to or
2294 larger than the number of bits in <tt>var1</tt>, the result is undefined.
2299 <result> = ashr i32 4, 1 <i>; yields {i32}:result = 2</i>
2300 <result> = ashr i32 4, 2 <i>; yields {i32}:result = 1</i>
2301 <result> = ashr i8 4, 3 <i>; yields {i8}:result = 0</i>
2302 <result> = ashr i8 -2, 1 <i>; yields {i8}:result = -1</i>
2303 <result> = ashr i32 1, 32 <i>; undefined</i>
2307 <!-- _______________________________________________________________________ -->
2308 <div class="doc_subsubsection"> <a name="i_and">'<tt>and</tt>'
2309 Instruction</a> </div>
2310 <div class="doc_text">
2312 <pre> <result> = and <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2315 <p>The '<tt>and</tt>' instruction returns the bitwise logical and of
2316 its two operands.</p>
2318 <p>The two arguments to the '<tt>and</tt>' instruction must be <a
2319 href="#t_integer">integer</a> values. Both arguments must have
2320 identical types.</p>
2322 <p>The truth table used for the '<tt>and</tt>' instruction is:</p>
2324 <div style="align: center">
2325 <table border="1" cellspacing="0" cellpadding="4">
2356 <pre> <result> = and i32 4, %var <i>; yields {i32}:result = 4 & %var</i>
2357 <result> = and i32 15, 40 <i>; yields {i32}:result = 8</i>
2358 <result> = and i32 4, 8 <i>; yields {i32}:result = 0</i>
2361 <!-- _______________________________________________________________________ -->
2362 <div class="doc_subsubsection"> <a name="i_or">'<tt>or</tt>' Instruction</a> </div>
2363 <div class="doc_text">
2365 <pre> <result> = or <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2368 <p>The '<tt>or</tt>' instruction returns the bitwise logical inclusive
2369 or of its two operands.</p>
2371 <p>The two arguments to the '<tt>or</tt>' instruction must be <a
2372 href="#t_integer">integer</a> values. Both arguments must have
2373 identical types.</p>
2375 <p>The truth table used for the '<tt>or</tt>' instruction is:</p>
2377 <div style="align: center">
2378 <table border="1" cellspacing="0" cellpadding="4">
2409 <pre> <result> = or i32 4, %var <i>; yields {i32}:result = 4 | %var</i>
2410 <result> = or i32 15, 40 <i>; yields {i32}:result = 47</i>
2411 <result> = or i32 4, 8 <i>; yields {i32}:result = 12</i>
2414 <!-- _______________________________________________________________________ -->
2415 <div class="doc_subsubsection"> <a name="i_xor">'<tt>xor</tt>'
2416 Instruction</a> </div>
2417 <div class="doc_text">
2419 <pre> <result> = xor <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2422 <p>The '<tt>xor</tt>' instruction returns the bitwise logical exclusive
2423 or of its two operands. The <tt>xor</tt> is used to implement the
2424 "one's complement" operation, which is the "~" operator in C.</p>
2426 <p>The two arguments to the '<tt>xor</tt>' instruction must be <a
2427 href="#t_integer">integer</a> values. Both arguments must have
2428 identical types.</p>
2430 <p>The truth table used for the '<tt>xor</tt>' instruction is:</p>
2432 <div style="align: center">
2433 <table border="1" cellspacing="0" cellpadding="4">
2465 <pre> <result> = xor i32 4, %var <i>; yields {i32}:result = 4 ^ %var</i>
2466 <result> = xor i32 15, 40 <i>; yields {i32}:result = 39</i>
2467 <result> = xor i32 4, 8 <i>; yields {i32}:result = 12</i>
2468 <result> = xor i32 %V, -1 <i>; yields {i32}:result = ~%V</i>
2472 <!-- ======================================================================= -->
2473 <div class="doc_subsection">
2474 <a name="vectorops">Vector Operations</a>
2477 <div class="doc_text">
2479 <p>LLVM supports several instructions to represent vector operations in a
2480 target-independent manner. These instructions cover the element-access and
2481 vector-specific operations needed to process vectors effectively. While LLVM
2482 does directly support these vector operations, many sophisticated algorithms
2483 will want to use target-specific intrinsics to take full advantage of a specific
2488 <!-- _______________________________________________________________________ -->
2489 <div class="doc_subsubsection">
2490 <a name="i_extractelement">'<tt>extractelement</tt>' Instruction</a>
2493 <div class="doc_text">
2498 <result> = extractelement <n x <ty>> <val>, i32 <idx> <i>; yields <ty></i>
2504 The '<tt>extractelement</tt>' instruction extracts a single scalar
2505 element from a vector at a specified index.
2512 The first operand of an '<tt>extractelement</tt>' instruction is a
2513 value of <a href="#t_vector">vector</a> type. The second operand is
2514 an index indicating the position from which to extract the element.
2515 The index may be a variable.</p>
2520 The result is a scalar of the same type as the element type of
2521 <tt>val</tt>. Its value is the value at position <tt>idx</tt> of
2522 <tt>val</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the
2523 results are undefined.
2529 %result = extractelement <4 x i32> %vec, i32 0 <i>; yields i32</i>
2534 <!-- _______________________________________________________________________ -->
2535 <div class="doc_subsubsection">
2536 <a name="i_insertelement">'<tt>insertelement</tt>' Instruction</a>
2539 <div class="doc_text">
2544 <result> = insertelement <n x <ty>> <val>, <ty> <elt>, i32 <idx> <i>; yields <n x <ty>></i>
2550 The '<tt>insertelement</tt>' instruction inserts a scalar
2551 element into a vector at a specified index.
2558 The first operand of an '<tt>insertelement</tt>' instruction is a
2559 value of <a href="#t_vector">vector</a> type. The second operand is a
2560 scalar value whose type must equal the element type of the first
2561 operand. The third operand is an index indicating the position at
2562 which to insert the value. The index may be a variable.</p>
2567 The result is a vector of the same type as <tt>val</tt>. Its
2568 element values are those of <tt>val</tt> except at position
2569 <tt>idx</tt>, where it gets the value <tt>elt</tt>. If <tt>idx</tt>
2570 exceeds the length of <tt>val</tt>, the results are undefined.
2576 %result = insertelement <4 x i32> %vec, i32 1, i32 0 <i>; yields <4 x i32></i>
2580 <!-- _______________________________________________________________________ -->
2581 <div class="doc_subsubsection">
2582 <a name="i_shufflevector">'<tt>shufflevector</tt>' Instruction</a>
2585 <div class="doc_text">
2590 <result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <n x i32> <mask> <i>; yields <n x <ty>></i>
2596 The '<tt>shufflevector</tt>' instruction constructs a permutation of elements
2597 from two input vectors, returning a vector of the same type.
2603 The first two operands of a '<tt>shufflevector</tt>' instruction are vectors
2604 with types that match each other and types that match the result of the
2605 instruction. The third argument is a shuffle mask, which has the same number
2606 of elements as the other vector type, but whose element type is always 'i32'.
2610 The shuffle mask operand is required to be a constant vector with either
2611 constant integer or undef values.
2617 The elements of the two input vectors are numbered from left to right across
2618 both of the vectors. The shuffle mask operand specifies, for each element of
2619 the result vector, which element of the two input registers the result element
2620 gets. The element selector may be undef (meaning "don't care") and the second
2621 operand may be undef if performing a shuffle from only one vector.
2627 %result = shufflevector <4 x i32> %v1, <4 x i32> %v2,
2628 <4 x i32> <i32 0, i32 4, i32 1, i32 5> <i>; yields <4 x i32></i>
2629 %result = shufflevector <4 x i32> %v1, <4 x i32> undef,
2630 <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> - Identity shuffle.
2635 <!-- ======================================================================= -->
2636 <div class="doc_subsection">
2637 <a name="memoryops">Memory Access and Addressing Operations</a>
2640 <div class="doc_text">
2642 <p>A key design point of an SSA-based representation is how it
2643 represents memory. In LLVM, no memory locations are in SSA form, which
2644 makes things very simple. This section describes how to read, write,
2645 allocate, and free memory in LLVM.</p>
2649 <!-- _______________________________________________________________________ -->
2650 <div class="doc_subsubsection">
2651 <a name="i_malloc">'<tt>malloc</tt>' Instruction</a>
2654 <div class="doc_text">
2659 <result> = malloc <type>[, i32 <NumElements>][, align <alignment>] <i>; yields {type*}:result</i>
2664 <p>The '<tt>malloc</tt>' instruction allocates memory from the system
2665 heap and returns a pointer to it. The object is always allocated in the generic
2666 address space (address space zero).</p>
2670 <p>The '<tt>malloc</tt>' instruction allocates
2671 <tt>sizeof(<type>)*NumElements</tt>
2672 bytes of memory from the operating system and returns a pointer of the
2673 appropriate type to the program. If "NumElements" is specified, it is the
2674 number of elements allocated. If an alignment is specified, the value result
2675 of the allocation is guaranteed to be aligned to at least that boundary. If
2676 not specified, or if zero, the target can choose to align the allocation on any
2677 convenient boundary.</p>
2679 <p>'<tt>type</tt>' must be a sized type.</p>
2683 <p>Memory is allocated using the system "<tt>malloc</tt>" function, and
2684 a pointer is returned.</p>
2689 %array = malloc [4 x i8 ] <i>; yields {[%4 x i8]*}:array</i>
2691 %size = <a href="#i_add">add</a> i32 2, 2 <i>; yields {i32}:size = i32 4</i>
2692 %array1 = malloc i8, i32 4 <i>; yields {i8*}:array1</i>
2693 %array2 = malloc [12 x i8], i32 %size <i>; yields {[12 x i8]*}:array2</i>
2694 %array3 = malloc i32, i32 4, align 1024 <i>; yields {i32*}:array3</i>
2695 %array4 = malloc i32, align 1024 <i>; yields {i32*}:array4</i>
2699 <!-- _______________________________________________________________________ -->
2700 <div class="doc_subsubsection">
2701 <a name="i_free">'<tt>free</tt>' Instruction</a>
2704 <div class="doc_text">
2709 free <type> <value> <i>; yields {void}</i>
2714 <p>The '<tt>free</tt>' instruction returns memory back to the unused
2715 memory heap to be reallocated in the future.</p>
2719 <p>'<tt>value</tt>' shall be a pointer value that points to a value
2720 that was allocated with the '<tt><a href="#i_malloc">malloc</a></tt>'
2725 <p>Access to the memory pointed to by the pointer is no longer defined
2726 after this instruction executes.</p>
2731 %array = <a href="#i_malloc">malloc</a> [4 x i8] <i>; yields {[4 x i8]*}:array</i>
2732 free [4 x i8]* %array
2736 <!-- _______________________________________________________________________ -->
2737 <div class="doc_subsubsection">
2738 <a name="i_alloca">'<tt>alloca</tt>' Instruction</a>
2741 <div class="doc_text">
2746 <result> = alloca <type>[, i32 <NumElements>][, align <alignment>] <i>; yields {type*}:result</i>
2751 <p>The '<tt>alloca</tt>' instruction allocates memory on the stack frame of the
2752 currently executing function, to be automatically released when this function
2753 returns to its caller. The object is always allocated in the generic address
2754 space (address space zero).</p>
2758 <p>The '<tt>alloca</tt>' instruction allocates <tt>sizeof(<type>)*NumElements</tt>
2759 bytes of memory on the runtime stack, returning a pointer of the
2760 appropriate type to the program. If "NumElements" is specified, it is the
2761 number of elements allocated. If an alignment is specified, the value result
2762 of the allocation is guaranteed to be aligned to at least that boundary. If
2763 not specified, or if zero, the target can choose to align the allocation on any
2764 convenient boundary.</p>
2766 <p>'<tt>type</tt>' may be any sized type.</p>
2770 <p>Memory is allocated; a pointer is returned. '<tt>alloca</tt>'d
2771 memory is automatically released when the function returns. The '<tt>alloca</tt>'
2772 instruction is commonly used to represent automatic variables that must
2773 have an address available. When the function returns (either with the <tt><a
2774 href="#i_ret">ret</a></tt> or <tt><a href="#i_unwind">unwind</a></tt>
2775 instructions), the memory is reclaimed.</p>
2780 %ptr = alloca i32 <i>; yields {i32*}:ptr</i>
2781 %ptr = alloca i32, i32 4 <i>; yields {i32*}:ptr</i>
2782 %ptr = alloca i32, i32 4, align 1024 <i>; yields {i32*}:ptr</i>
2783 %ptr = alloca i32, align 1024 <i>; yields {i32*}:ptr</i>
2787 <!-- _______________________________________________________________________ -->
2788 <div class="doc_subsubsection"> <a name="i_load">'<tt>load</tt>'
2789 Instruction</a> </div>
2790 <div class="doc_text">
2792 <pre> <result> = load <ty>* <pointer>[, align <alignment>]<br> <result> = volatile load <ty>* <pointer>[, align <alignment>]<br></pre>
2794 <p>The '<tt>load</tt>' instruction is used to read from memory.</p>
2796 <p>The argument to the '<tt>load</tt>' instruction specifies the memory
2797 address from which to load. The pointer must point to a <a
2798 href="#t_firstclass">first class</a> type. If the <tt>load</tt> is
2799 marked as <tt>volatile</tt>, then the optimizer is not allowed to modify
2800 the number or order of execution of this <tt>load</tt> with other
2801 volatile <tt>load</tt> and <tt><a href="#i_store">store</a></tt>
2804 <p>The location of memory pointed to is loaded.</p>
2806 <pre> %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i>
2808 href="#i_store">store</a> i32 3, i32* %ptr <i>; yields {void}</i>
2809 %val = load i32* %ptr <i>; yields {i32}:val = i32 3</i>
2812 <!-- _______________________________________________________________________ -->
2813 <div class="doc_subsubsection"> <a name="i_store">'<tt>store</tt>'
2814 Instruction</a> </div>
2815 <div class="doc_text">
2817 <pre> store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i>
2818 volatile store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i>
2821 <p>The '<tt>store</tt>' instruction is used to write to memory.</p>
2823 <p>There are two arguments to the '<tt>store</tt>' instruction: a value
2824 to store and an address at which to store it. The type of the '<tt><pointer></tt>'
2825 operand must be a pointer to the type of the '<tt><value></tt>'
2826 operand. If the <tt>store</tt> is marked as <tt>volatile</tt>, then the
2827 optimizer is not allowed to modify the number or order of execution of
2828 this <tt>store</tt> with other volatile <tt>load</tt> and <tt><a
2829 href="#i_store">store</a></tt> instructions.</p>
2831 <p>The contents of memory are updated to contain '<tt><value></tt>'
2832 at the location specified by the '<tt><pointer></tt>' operand.</p>
2834 <pre> %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i>
2835 store i32 3, i32* %ptr <i>; yields {void}</i>
2836 %val = <a href="#i_load">load</a> i32* %ptr <i>; yields {i32}:val = i32 3</i>
2840 <!-- _______________________________________________________________________ -->
2841 <div class="doc_subsubsection">
2842 <a name="i_getelementptr">'<tt>getelementptr</tt>' Instruction</a>
2845 <div class="doc_text">
2848 <result> = getelementptr <ty>* <ptrval>{, <ty> <idx>}*
2854 The '<tt>getelementptr</tt>' instruction is used to get the address of a
2855 subelement of an aggregate data structure.</p>
2859 <p>This instruction takes a list of integer operands that indicate what
2860 elements of the aggregate object to index to. The actual types of the arguments
2861 provided depend on the type of the first pointer argument. The
2862 '<tt>getelementptr</tt>' instruction is used to index down through the type
2863 levels of a structure or to a specific index in an array. When indexing into a
2864 structure, only <tt>i32</tt> integer constants are allowed. When indexing
2865 into an array or pointer, only integers of 32 or 64 bits are allowed, and will
2866 be sign extended to 64-bit values.</p>
2868 <p>For example, let's consider a C code fragment and how it gets
2869 compiled to LLVM:</p>
2871 <div class="doc_code">
2884 int *foo(struct ST *s) {
2885 return &s[1].Z.B[5][13];
2890 <p>The LLVM code generated by the GCC frontend is:</p>
2892 <div class="doc_code">
2894 %RT = type { i8 , [10 x [20 x i32]], i8 }
2895 %ST = type { i32, double, %RT }
2897 define i32* %foo(%ST* %s) {
2899 %reg = getelementptr %ST* %s, i32 1, i32 2, i32 1, i32 5, i32 13
2907 <p>The index types specified for the '<tt>getelementptr</tt>' instruction depend
2908 on the pointer type that is being indexed into. <a href="#t_pointer">Pointer</a>
2909 and <a href="#t_array">array</a> types can use a 32-bit or 64-bit
2910 <a href="#t_integer">integer</a> type but the value will always be sign extended
2911 to 64-bits. <a href="#t_struct">Structure</a> types require <tt>i32</tt>
2912 <b>constants</b>.</p>
2914 <p>In the example above, the first index is indexing into the '<tt>%ST*</tt>'
2915 type, which is a pointer, yielding a '<tt>%ST</tt>' = '<tt>{ i32, double, %RT
2916 }</tt>' type, a structure. The second index indexes into the third element of
2917 the structure, yielding a '<tt>%RT</tt>' = '<tt>{ i8 , [10 x [20 x i32]],
2918 i8 }</tt>' type, another structure. The third index indexes into the second
2919 element of the structure, yielding a '<tt>[10 x [20 x i32]]</tt>' type, an
2920 array. The two dimensions of the array are subscripted into, yielding an
2921 '<tt>i32</tt>' type. The '<tt>getelementptr</tt>' instruction returns a pointer
2922 to this element, thus computing a value of '<tt>i32*</tt>' type.</p>
2924 <p>Note that it is perfectly legal to index partially through a
2925 structure, returning a pointer to an inner element. Because of this,
2926 the LLVM code for the given testcase is equivalent to:</p>
2929 define i32* %foo(%ST* %s) {
2930 %t1 = getelementptr %ST* %s, i32 1 <i>; yields %ST*:%t1</i>
2931 %t2 = getelementptr %ST* %t1, i32 0, i32 2 <i>; yields %RT*:%t2</i>
2932 %t3 = getelementptr %RT* %t2, i32 0, i32 1 <i>; yields [10 x [20 x i32]]*:%t3</i>
2933 %t4 = getelementptr [10 x [20 x i32]]* %t3, i32 0, i32 5 <i>; yields [20 x i32]*:%t4</i>
2934 %t5 = getelementptr [20 x i32]* %t4, i32 0, i32 13 <i>; yields i32*:%t5</i>
2939 <p>Note that it is undefined to access an array out of bounds: array and
2940 pointer indexes must always be within the defined bounds of the array type.
2941 The one exception for this rules is zero length arrays. These arrays are
2942 defined to be accessible as variable length arrays, which requires access
2943 beyond the zero'th element.</p>
2945 <p>The getelementptr instruction is often confusing. For some more insight
2946 into how it works, see <a href="GetElementPtr.html">the getelementptr
2952 <i>; yields [12 x i8]*:aptr</i>
2953 %aptr = getelementptr {i32, [12 x i8]}* %sptr, i64 0, i32 1
2957 <!-- ======================================================================= -->
2958 <div class="doc_subsection"> <a name="convertops">Conversion Operations</a>
2960 <div class="doc_text">
2961 <p>The instructions in this category are the conversion instructions (casting)
2962 which all take a single operand and a type. They perform various bit conversions
2966 <!-- _______________________________________________________________________ -->
2967 <div class="doc_subsubsection">
2968 <a name="i_trunc">'<tt>trunc .. to</tt>' Instruction</a>
2970 <div class="doc_text">
2974 <result> = trunc <ty> <value> to <ty2> <i>; yields ty2</i>
2979 The '<tt>trunc</tt>' instruction truncates its operand to the type <tt>ty2</tt>.
2984 The '<tt>trunc</tt>' instruction takes a <tt>value</tt> to trunc, which must
2985 be an <a href="#t_integer">integer</a> type, and a type that specifies the size
2986 and type of the result, which must be an <a href="#t_integer">integer</a>
2987 type. The bit size of <tt>value</tt> must be larger than the bit size of
2988 <tt>ty2</tt>. Equal sized types are not allowed.</p>
2992 The '<tt>trunc</tt>' instruction truncates the high order bits in <tt>value</tt>
2993 and converts the remaining bits to <tt>ty2</tt>. Since the source size must be
2994 larger than the destination size, <tt>trunc</tt> cannot be a <i>no-op cast</i>.
2995 It will always truncate bits.</p>
2999 %X = trunc i32 257 to i8 <i>; yields i8:1</i>
3000 %Y = trunc i32 123 to i1 <i>; yields i1:true</i>
3001 %Y = trunc i32 122 to i1 <i>; yields i1:false</i>
3005 <!-- _______________________________________________________________________ -->
3006 <div class="doc_subsubsection">
3007 <a name="i_zext">'<tt>zext .. to</tt>' Instruction</a>
3009 <div class="doc_text">
3013 <result> = zext <ty> <value> to <ty2> <i>; yields ty2</i>
3017 <p>The '<tt>zext</tt>' instruction zero extends its operand to type
3022 <p>The '<tt>zext</tt>' instruction takes a value to cast, which must be of
3023 <a href="#t_integer">integer</a> type, and a type to cast it to, which must
3024 also be of <a href="#t_integer">integer</a> type. The bit size of the
3025 <tt>value</tt> must be smaller than the bit size of the destination type,
3029 <p>The <tt>zext</tt> fills the high order bits of the <tt>value</tt> with zero
3030 bits until it reaches the size of the destination type, <tt>ty2</tt>.</p>
3032 <p>When zero extending from i1, the result will always be either 0 or 1.</p>
3036 %X = zext i32 257 to i64 <i>; yields i64:257</i>
3037 %Y = zext i1 true to i32 <i>; yields i32:1</i>
3041 <!-- _______________________________________________________________________ -->
3042 <div class="doc_subsubsection">
3043 <a name="i_sext">'<tt>sext .. to</tt>' Instruction</a>
3045 <div class="doc_text">
3049 <result> = sext <ty> <value> to <ty2> <i>; yields ty2</i>
3053 <p>The '<tt>sext</tt>' sign extends <tt>value</tt> to the type <tt>ty2</tt>.</p>
3057 The '<tt>sext</tt>' instruction takes a value to cast, which must be of
3058 <a href="#t_integer">integer</a> type, and a type to cast it to, which must
3059 also be of <a href="#t_integer">integer</a> type. The bit size of the
3060 <tt>value</tt> must be smaller than the bit size of the destination type,
3065 The '<tt>sext</tt>' instruction performs a sign extension by copying the sign
3066 bit (highest order bit) of the <tt>value</tt> until it reaches the bit size of
3067 the type <tt>ty2</tt>.</p>
3069 <p>When sign extending from i1, the extension always results in -1 or 0.</p>
3073 %X = sext i8 -1 to i16 <i>; yields i16 :65535</i>
3074 %Y = sext i1 true to i32 <i>; yields i32:-1</i>
3078 <!-- _______________________________________________________________________ -->
3079 <div class="doc_subsubsection">
3080 <a name="i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a>
3083 <div class="doc_text">
3088 <result> = fptrunc <ty> <value> to <ty2> <i>; yields ty2</i>
3092 <p>The '<tt>fptrunc</tt>' instruction truncates <tt>value</tt> to type
3097 <p>The '<tt>fptrunc</tt>' instruction takes a <a href="#t_floating">floating
3098 point</a> value to cast and a <a href="#t_floating">floating point</a> type to
3099 cast it to. The size of <tt>value</tt> must be larger than the size of
3100 <tt>ty2</tt>. This implies that <tt>fptrunc</tt> cannot be used to make a
3101 <i>no-op cast</i>.</p>
3104 <p> The '<tt>fptrunc</tt>' instruction truncates a <tt>value</tt> from a larger
3105 <a href="#t_floating">floating point</a> type to a smaller
3106 <a href="#t_floating">floating point</a> type. If the value cannot fit within
3107 the destination type, <tt>ty2</tt>, then the results are undefined.</p>
3111 %X = fptrunc double 123.0 to float <i>; yields float:123.0</i>
3112 %Y = fptrunc double 1.0E+300 to float <i>; yields undefined</i>
3116 <!-- _______________________________________________________________________ -->
3117 <div class="doc_subsubsection">
3118 <a name="i_fpext">'<tt>fpext .. to</tt>' Instruction</a>
3120 <div class="doc_text">
3124 <result> = fpext <ty> <value> to <ty2> <i>; yields ty2</i>
3128 <p>The '<tt>fpext</tt>' extends a floating point <tt>value</tt> to a larger
3129 floating point value.</p>
3132 <p>The '<tt>fpext</tt>' instruction takes a
3133 <a href="#t_floating">floating point</a> <tt>value</tt> to cast,
3134 and a <a href="#t_floating">floating point</a> type to cast it to. The source
3135 type must be smaller than the destination type.</p>
3138 <p>The '<tt>fpext</tt>' instruction extends the <tt>value</tt> from a smaller
3139 <a href="#t_floating">floating point</a> type to a larger
3140 <a href="#t_floating">floating point</a> type. The <tt>fpext</tt> cannot be
3141 used to make a <i>no-op cast</i> because it always changes bits. Use
3142 <tt>bitcast</tt> to make a <i>no-op cast</i> for a floating point cast.</p>
3146 %X = fpext float 3.1415 to double <i>; yields double:3.1415</i>
3147 %Y = fpext float 1.0 to float <i>; yields float:1.0 (no-op)</i>
3151 <!-- _______________________________________________________________________ -->
3152 <div class="doc_subsubsection">
3153 <a name="i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a>
3155 <div class="doc_text">
3159 <result> = fptoui <ty> <value> to <ty2> <i>; yields ty2</i>
3163 <p>The '<tt>fptoui</tt>' converts a floating point <tt>value</tt> to its
3164 unsigned integer equivalent of type <tt>ty2</tt>.
3168 <p>The '<tt>fptoui</tt>' instruction takes a value to cast, which must be a
3169 scalar or vector <a href="#t_floating">floating point</a> value, and a type
3170 to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a>
3171 type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a
3172 vector integer type with the same number of elements as <tt>ty</tt></p>
3175 <p> The '<tt>fptoui</tt>' instruction converts its
3176 <a href="#t_floating">floating point</a> operand into the nearest (rounding
3177 towards zero) unsigned integer value. If the value cannot fit in <tt>ty2</tt>,
3178 the results are undefined.</p>
3182 %X = fptoui double 123.0 to i32 <i>; yields i32:123</i>
3183 %Y = fptoui float 1.0E+300 to i1 <i>; yields undefined:1</i>
3184 %X = fptoui float 1.04E+17 to i8 <i>; yields undefined:1</i>
3188 <!-- _______________________________________________________________________ -->
3189 <div class="doc_subsubsection">
3190 <a name="i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a>
3192 <div class="doc_text">
3196 <result> = fptosi <ty> <value> to <ty2> <i>; yields ty2</i>
3200 <p>The '<tt>fptosi</tt>' instruction converts
3201 <a href="#t_floating">floating point</a> <tt>value</tt> to type <tt>ty2</tt>.
3205 <p> The '<tt>fptosi</tt>' instruction takes a value to cast, which must be a
3206 scalar or vector <a href="#t_floating">floating point</a> value, and a type
3207 to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a>
3208 type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a
3209 vector integer type with the same number of elements as <tt>ty</tt></p>
3212 <p>The '<tt>fptosi</tt>' instruction converts its
3213 <a href="#t_floating">floating point</a> operand into the nearest (rounding
3214 towards zero) signed integer value. If the value cannot fit in <tt>ty2</tt>,
3215 the results are undefined.</p>
3219 %X = fptosi double -123.0 to i32 <i>; yields i32:-123</i>
3220 %Y = fptosi float 1.0E-247 to i1 <i>; yields undefined:1</i>
3221 %X = fptosi float 1.04E+17 to i8 <i>; yields undefined:1</i>
3225 <!-- _______________________________________________________________________ -->
3226 <div class="doc_subsubsection">
3227 <a name="i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a>
3229 <div class="doc_text">
3233 <result> = uitofp <ty> <value> to <ty2> <i>; yields ty2</i>
3237 <p>The '<tt>uitofp</tt>' instruction regards <tt>value</tt> as an unsigned
3238 integer and converts that value to the <tt>ty2</tt> type.</p>
3241 <p>The '<tt>uitofp</tt>' instruction takes a value to cast, which must be a
3242 scalar or vector <a href="#t_integer">integer</a> value, and a type to cast it
3243 to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a>
3244 type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector
3245 floating point type with the same number of elements as <tt>ty</tt></p>
3248 <p>The '<tt>uitofp</tt>' instruction interprets its operand as an unsigned
3249 integer quantity and converts it to the corresponding floating point value. If
3250 the value cannot fit in the floating point value, the results are undefined.</p>
3254 %X = uitofp i32 257 to float <i>; yields float:257.0</i>
3255 %Y = uitofp i8 -1 to double <i>; yields double:255.0</i>
3259 <!-- _______________________________________________________________________ -->
3260 <div class="doc_subsubsection">
3261 <a name="i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a>
3263 <div class="doc_text">
3267 <result> = sitofp <ty> <value> to <ty2> <i>; yields ty2</i>
3271 <p>The '<tt>sitofp</tt>' instruction regards <tt>value</tt> as a signed
3272 integer and converts that value to the <tt>ty2</tt> type.</p>
3275 <p>The '<tt>sitofp</tt>' instruction takes a value to cast, which must be a
3276 scalar or vector <a href="#t_integer">integer</a> value, and a type to cast it
3277 to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a>
3278 type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector
3279 floating point type with the same number of elements as <tt>ty</tt></p>
3282 <p>The '<tt>sitofp</tt>' instruction interprets its operand as a signed
3283 integer quantity and converts it to the corresponding floating point value. If
3284 the value cannot fit in the floating point value, the results are undefined.</p>
3288 %X = sitofp i32 257 to float <i>; yields float:257.0</i>
3289 %Y = sitofp i8 -1 to double <i>; yields double:-1.0</i>
3293 <!-- _______________________________________________________________________ -->
3294 <div class="doc_subsubsection">
3295 <a name="i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a>
3297 <div class="doc_text">
3301 <result> = ptrtoint <ty> <value> to <ty2> <i>; yields ty2</i>
3305 <p>The '<tt>ptrtoint</tt>' instruction converts the pointer <tt>value</tt> to
3306 the integer type <tt>ty2</tt>.</p>
3309 <p>The '<tt>ptrtoint</tt>' instruction takes a <tt>value</tt> to cast, which
3310 must be a <a href="#t_pointer">pointer</a> value, and a type to cast it to
3311 <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> type.
3314 <p>The '<tt>ptrtoint</tt>' instruction converts <tt>value</tt> to integer type
3315 <tt>ty2</tt> by interpreting the pointer value as an integer and either
3316 truncating or zero extending that value to the size of the integer type. If
3317 <tt>value</tt> is smaller than <tt>ty2</tt> then a zero extension is done. If
3318 <tt>value</tt> is larger than <tt>ty2</tt> then a truncation is done. If they
3319 are the same size, then nothing is done (<i>no-op cast</i>) other than a type
3324 %X = ptrtoint i32* %X to i8 <i>; yields truncation on 32-bit architecture</i>
3325 %Y = ptrtoint i32* %x to i64 <i>; yields zero extension on 32-bit architecture</i>
3329 <!-- _______________________________________________________________________ -->
3330 <div class="doc_subsubsection">
3331 <a name="i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a>
3333 <div class="doc_text">
3337 <result> = inttoptr <ty> <value> to <ty2> <i>; yields ty2</i>
3341 <p>The '<tt>inttoptr</tt>' instruction converts an integer <tt>value</tt> to
3342 a pointer type, <tt>ty2</tt>.</p>
3345 <p>The '<tt>inttoptr</tt>' instruction takes an <a href="#t_integer">integer</a>
3346 value to cast, and a type to cast it to, which must be a
3347 <a href="#t_pointer">pointer</a> type.
3350 <p>The '<tt>inttoptr</tt>' instruction converts <tt>value</tt> to type
3351 <tt>ty2</tt> by applying either a zero extension or a truncation depending on
3352 the size of the integer <tt>value</tt>. If <tt>value</tt> is larger than the
3353 size of a pointer then a truncation is done. If <tt>value</tt> is smaller than
3354 the size of a pointer then a zero extension is done. If they are the same size,
3355 nothing is done (<i>no-op cast</i>).</p>
3359 %X = inttoptr i32 255 to i32* <i>; yields zero extension on 64-bit architecture</i>
3360 %X = inttoptr i32 255 to i32* <i>; yields no-op on 32-bit architecture</i>
3361 %Y = inttoptr i64 0 to i32* <i>; yields truncation on 32-bit architecture</i>
3365 <!-- _______________________________________________________________________ -->
3366 <div class="doc_subsubsection">
3367 <a name="i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a>
3369 <div class="doc_text">
3373 <result> = bitcast <ty> <value> to <ty2> <i>; yields ty2</i>
3377 <p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type
3378 <tt>ty2</tt> without changing any bits.</p>
3381 <p>The '<tt>bitcast</tt>' instruction takes a value to cast, which must be
3382 a first class value, and a type to cast it to, which must also be a <a
3383 href="#t_firstclass">first class</a> type. The bit sizes of <tt>value</tt>
3384 and the destination type, <tt>ty2</tt>, must be identical. If the source
3385 type is a pointer, the destination type must also be a pointer.</p>
3388 <p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type
3389 <tt>ty2</tt>. It is always a <i>no-op cast</i> because no bits change with
3390 this conversion. The conversion is done as if the <tt>value</tt> had been
3391 stored to memory and read back as type <tt>ty2</tt>. Pointer types may only be
3392 converted to other pointer types with this instruction. To convert pointers to
3393 other types, use the <a href="#i_inttoptr">inttoptr</a> or
3394 <a href="#i_ptrtoint">ptrtoint</a> instructions first.</p>
3398 %X = bitcast i8 255 to i8 <i>; yields i8 :-1</i>
3399 %Y = bitcast i32* %x to sint* <i>; yields sint*:%x</i>
3400 %Z = bitcast <2xint> %V to i64; <i>; yields i64: %V</i>
3404 <!-- ======================================================================= -->
3405 <div class="doc_subsection"> <a name="otherops">Other Operations</a> </div>
3406 <div class="doc_text">
3407 <p>The instructions in this category are the "miscellaneous"
3408 instructions, which defy better classification.</p>
3411 <!-- _______________________________________________________________________ -->
3412 <div class="doc_subsubsection"><a name="i_icmp">'<tt>icmp</tt>' Instruction</a>
3414 <div class="doc_text">
3416 <pre> <result> = icmp <cond> <ty> <var1>, <var2> <i>; yields {i1}:result</i>
3419 <p>The '<tt>icmp</tt>' instruction returns a boolean value based on comparison
3420 of its two integer operands.</p>
3422 <p>The '<tt>icmp</tt>' instruction takes three operands. The first operand is
3423 the condition code indicating the kind of comparison to perform. It is not
3424 a value, just a keyword. The possible condition code are:
3426 <li><tt>eq</tt>: equal</li>
3427 <li><tt>ne</tt>: not equal </li>
3428 <li><tt>ugt</tt>: unsigned greater than</li>
3429 <li><tt>uge</tt>: unsigned greater or equal</li>
3430 <li><tt>ult</tt>: unsigned less than</li>
3431 <li><tt>ule</tt>: unsigned less or equal</li>
3432 <li><tt>sgt</tt>: signed greater than</li>
3433 <li><tt>sge</tt>: signed greater or equal</li>
3434 <li><tt>slt</tt>: signed less than</li>
3435 <li><tt>sle</tt>: signed less or equal</li>
3437 <p>The remaining two arguments must be <a href="#t_integer">integer</a> or
3438 <a href="#t_pointer">pointer</a> typed. They must also be identical types.</p>
3440 <p>The '<tt>icmp</tt>' compares <tt>var1</tt> and <tt>var2</tt> according to
3441 the condition code given as <tt>cond</tt>. The comparison performed always
3442 yields a <a href="#t_primitive">i1</a> result, as follows:
3444 <li><tt>eq</tt>: yields <tt>true</tt> if the operands are equal,
3445 <tt>false</tt> otherwise. No sign interpretation is necessary or performed.
3447 <li><tt>ne</tt>: yields <tt>true</tt> if the operands are unequal,
3448 <tt>false</tt> otherwise. No sign interpretation is necessary or performed.
3449 <li><tt>ugt</tt>: interprets the operands as unsigned values and yields
3450 <tt>true</tt> if <tt>var1</tt> is greater than <tt>var2</tt>.</li>
3451 <li><tt>uge</tt>: interprets the operands as unsigned values and yields
3452 <tt>true</tt> if <tt>var1</tt> is greater than or equal to <tt>var2</tt>.</li>
3453 <li><tt>ult</tt>: interprets the operands as unsigned values and yields
3454 <tt>true</tt> if <tt>var1</tt> is less than <tt>var2</tt>.</li>
3455 <li><tt>ule</tt>: interprets the operands as unsigned values and yields
3456 <tt>true</tt> if <tt>var1</tt> is less than or equal to <tt>var2</tt>.</li>
3457 <li><tt>sgt</tt>: interprets the operands as signed values and yields
3458 <tt>true</tt> if <tt>var1</tt> is greater than <tt>var2</tt>.</li>
3459 <li><tt>sge</tt>: interprets the operands as signed values and yields
3460 <tt>true</tt> if <tt>var1</tt> is greater than or equal to <tt>var2</tt>.</li>
3461 <li><tt>slt</tt>: interprets the operands as signed values and yields
3462 <tt>true</tt> if <tt>var1</tt> is less than <tt>var2</tt>.</li>
3463 <li><tt>sle</tt>: interprets the operands as signed values and yields
3464 <tt>true</tt> if <tt>var1</tt> is less than or equal to <tt>var2</tt>.</li>
3466 <p>If the operands are <a href="#t_pointer">pointer</a> typed, the pointer
3467 values are compared as if they were integers.</p>
3470 <pre> <result> = icmp eq i32 4, 5 <i>; yields: result=false</i>
3471 <result> = icmp ne float* %X, %X <i>; yields: result=false</i>
3472 <result> = icmp ult i16 4, 5 <i>; yields: result=true</i>
3473 <result> = icmp sgt i16 4, 5 <i>; yields: result=false</i>
3474 <result> = icmp ule i16 -4, 5 <i>; yields: result=false</i>
3475 <result> = icmp sge i16 4, 5 <i>; yields: result=false</i>
3479 <!-- _______________________________________________________________________ -->
3480 <div class="doc_subsubsection"><a name="i_fcmp">'<tt>fcmp</tt>' Instruction</a>
3482 <div class="doc_text">
3484 <pre> <result> = fcmp <cond> <ty> <var1>, <var2> <i>; yields {i1}:result</i>
3487 <p>The '<tt>fcmp</tt>' instruction returns a boolean value based on comparison
3488 of its floating point operands.</p>
3490 <p>The '<tt>fcmp</tt>' instruction takes three operands. The first operand is
3491 the condition code indicating the kind of comparison to perform. It is not
3492 a value, just a keyword. The possible condition code are:
3494 <li><tt>false</tt>: no comparison, always returns false</li>
3495 <li><tt>oeq</tt>: ordered and equal</li>
3496 <li><tt>ogt</tt>: ordered and greater than </li>
3497 <li><tt>oge</tt>: ordered and greater than or equal</li>
3498 <li><tt>olt</tt>: ordered and less than </li>
3499 <li><tt>ole</tt>: ordered and less than or equal</li>
3500 <li><tt>one</tt>: ordered and not equal</li>
3501 <li><tt>ord</tt>: ordered (no nans)</li>
3502 <li><tt>ueq</tt>: unordered or equal</li>
3503 <li><tt>ugt</tt>: unordered or greater than </li>
3504 <li><tt>uge</tt>: unordered or greater than or equal</li>
3505 <li><tt>ult</tt>: unordered or less than </li>
3506 <li><tt>ule</tt>: unordered or less than or equal</li>
3507 <li><tt>une</tt>: unordered or not equal</li>
3508 <li><tt>uno</tt>: unordered (either nans)</li>
3509 <li><tt>true</tt>: no comparison, always returns true</li>
3511 <p><i>Ordered</i> means that neither operand is a QNAN while
3512 <i>unordered</i> means that either operand may be a QNAN.</p>
3513 <p>The <tt>val1</tt> and <tt>val2</tt> arguments must be
3514 <a href="#t_floating">floating point</a> typed. They must have identical
3517 <p>The '<tt>fcmp</tt>' compares <tt>var1</tt> and <tt>var2</tt> according to
3518 the condition code given as <tt>cond</tt>. The comparison performed always
3519 yields a <a href="#t_primitive">i1</a> result, as follows:
3521 <li><tt>false</tt>: always yields <tt>false</tt>, regardless of operands.</li>
3522 <li><tt>oeq</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3523 <tt>var1</tt> is equal to <tt>var2</tt>.</li>
3524 <li><tt>ogt</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3525 <tt>var1</tt> is greather than <tt>var2</tt>.</li>
3526 <li><tt>oge</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3527 <tt>var1</tt> is greater than or equal to <tt>var2</tt>.</li>
3528 <li><tt>olt</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3529 <tt>var1</tt> is less than <tt>var2</tt>.</li>
3530 <li><tt>ole</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3531 <tt>var1</tt> is less than or equal to <tt>var2</tt>.</li>
3532 <li><tt>one</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3533 <tt>var1</tt> is not equal to <tt>var2</tt>.</li>
3534 <li><tt>ord</tt>: yields <tt>true</tt> if both operands are not a QNAN.</li>
3535 <li><tt>ueq</tt>: yields <tt>true</tt> if either operand is a QNAN or
3536 <tt>var1</tt> is equal to <tt>var2</tt>.</li>
3537 <li><tt>ugt</tt>: yields <tt>true</tt> if either operand is a QNAN or
3538 <tt>var1</tt> is greater than <tt>var2</tt>.</li>
3539 <li><tt>uge</tt>: yields <tt>true</tt> if either operand is a QNAN or
3540 <tt>var1</tt> is greater than or equal to <tt>var2</tt>.</li>
3541 <li><tt>ult</tt>: yields <tt>true</tt> if either operand is a QNAN or
3542 <tt>var1</tt> is less than <tt>var2</tt>.</li>
3543 <li><tt>ule</tt>: yields <tt>true</tt> if either operand is a QNAN or
3544 <tt>var1</tt> is less than or equal to <tt>var2</tt>.</li>
3545 <li><tt>une</tt>: yields <tt>true</tt> if either operand is a QNAN or
3546 <tt>var1</tt> is not equal to <tt>var2</tt>.</li>
3547 <li><tt>uno</tt>: yields <tt>true</tt> if either operand is a QNAN.</li>
3548 <li><tt>true</tt>: always yields <tt>true</tt>, regardless of operands.</li>
3552 <pre> <result> = fcmp oeq float 4.0, 5.0 <i>; yields: result=false</i>
3553 <result> = icmp one float 4.0, 5.0 <i>; yields: result=true</i>
3554 <result> = icmp olt float 4.0, 5.0 <i>; yields: result=true</i>
3555 <result> = icmp ueq double 1.0, 2.0 <i>; yields: result=false</i>
3559 <!-- _______________________________________________________________________ -->
3560 <div class="doc_subsubsection"> <a name="i_phi">'<tt>phi</tt>'
3561 Instruction</a> </div>
3562 <div class="doc_text">
3564 <pre> <result> = phi <ty> [ <val0>, <label0>], ...<br></pre>
3566 <p>The '<tt>phi</tt>' instruction is used to implement the φ node in
3567 the SSA graph representing the function.</p>
3569 <p>The type of the incoming values is specified with the first type
3570 field. After this, the '<tt>phi</tt>' instruction takes a list of pairs
3571 as arguments, with one pair for each predecessor basic block of the
3572 current block. Only values of <a href="#t_firstclass">first class</a>
3573 type may be used as the value arguments to the PHI node. Only labels
3574 may be used as the label arguments.</p>
3575 <p>There must be no non-phi instructions between the start of a basic
3576 block and the PHI instructions: i.e. PHI instructions must be first in
3579 <p>At runtime, the '<tt>phi</tt>' instruction logically takes on the value
3580 specified by the pair corresponding to the predecessor basic block that executed
3581 just prior to the current block.</p>
3583 <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>
3586 <!-- _______________________________________________________________________ -->
3587 <div class="doc_subsubsection">
3588 <a name="i_select">'<tt>select</tt>' Instruction</a>
3591 <div class="doc_text">
3596 <result> = select i1 <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i>
3602 The '<tt>select</tt>' instruction is used to choose one value based on a
3603 condition, without branching.
3610 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.
3616 If the boolean condition evaluates to true, the instruction returns the first
3617 value argument; otherwise, it returns the second value argument.
3623 %X = select i1 true, i8 17, i8 42 <i>; yields i8:17</i>
3628 <!-- _______________________________________________________________________ -->
3629 <div class="doc_subsubsection">
3630 <a name="i_call">'<tt>call</tt>' Instruction</a>
3633 <div class="doc_text">
3637 <result> = [tail] call [<a href="#callingconv">cconv</a>] <ty> [<fnty>*] <fnptrval>(<param list>)
3642 <p>The '<tt>call</tt>' instruction represents a simple function call.</p>
3646 <p>This instruction requires several arguments:</p>
3650 <p>The optional "tail" marker indicates whether the callee function accesses
3651 any allocas or varargs in the caller. If the "tail" marker is present, the
3652 function call is eligible for tail call optimization. Note that calls may
3653 be marked "tail" even if they do not occur before a <a
3654 href="#i_ret"><tt>ret</tt></a> instruction.
3657 <p>The optional "cconv" marker indicates which <a href="#callingconv">calling
3658 convention</a> the call should use. If none is specified, the call defaults
3659 to using C calling conventions.
3662 <p>'<tt>ty</tt>': the type of the call instruction itself which is also
3663 the type of the return value. Functions that return no value are marked
3664 <tt><a href="#t_void">void</a></tt>.</p>
3667 <p>'<tt>fnty</tt>': shall be the signature of the pointer to function
3668 value being invoked. The argument types must match the types implied by
3669 this signature. This type can be omitted if the function is not varargs
3670 and if the function type does not return a pointer to a function.</p>
3673 <p>'<tt>fnptrval</tt>': An LLVM value containing a pointer to a function to
3674 be invoked. In most cases, this is a direct function invocation, but
3675 indirect <tt>call</tt>s are just as possible, calling an arbitrary pointer
3676 to function value.</p>
3679 <p>'<tt>function args</tt>': argument list whose types match the
3680 function signature argument types. All arguments must be of
3681 <a href="#t_firstclass">first class</a> type. If the function signature
3682 indicates the function accepts a variable number of arguments, the extra
3683 arguments can be specified.</p>
3689 <p>The '<tt>call</tt>' instruction is used to cause control flow to
3690 transfer to a specified function, with its incoming arguments bound to
3691 the specified values. Upon a '<tt><a href="#i_ret">ret</a></tt>'
3692 instruction in the called function, control flow continues with the
3693 instruction after the function call, and the return value of the
3694 function is bound to the result argument. This is a simpler case of
3695 the <a href="#i_invoke">invoke</a> instruction.</p>
3700 %retval = call i32 @test(i32 %argc)
3701 call i32 (i8 *, ...)* @printf(i8 * %msg, i32 12, i8 42);
3702 %X = tail call i32 @foo()
3703 %Y = tail call <a href="#callingconv">fastcc</a> i32 @foo()
3704 %Z = call void %foo(i8 97 signext)
3709 <!-- _______________________________________________________________________ -->
3710 <div class="doc_subsubsection">
3711 <a name="i_va_arg">'<tt>va_arg</tt>' Instruction</a>
3714 <div class="doc_text">
3719 <resultval> = va_arg <va_list*> <arglist>, <argty>
3724 <p>The '<tt>va_arg</tt>' instruction is used to access arguments passed through
3725 the "variable argument" area of a function call. It is used to implement the
3726 <tt>va_arg</tt> macro in C.</p>
3730 <p>This instruction takes a <tt>va_list*</tt> value and the type of
3731 the argument. It returns a value of the specified argument type and
3732 increments the <tt>va_list</tt> to point to the next argument. The
3733 actual type of <tt>va_list</tt> is target specific.</p>
3737 <p>The '<tt>va_arg</tt>' instruction loads an argument of the specified
3738 type from the specified <tt>va_list</tt> and causes the
3739 <tt>va_list</tt> to point to the next argument. For more information,
3740 see the variable argument handling <a href="#int_varargs">Intrinsic
3743 <p>It is legal for this instruction to be called in a function which does not
3744 take a variable number of arguments, for example, the <tt>vfprintf</tt>
3747 <p><tt>va_arg</tt> is an LLVM instruction instead of an <a
3748 href="#intrinsics">intrinsic function</a> because it takes a type as an
3753 <p>See the <a href="#int_varargs">variable argument processing</a> section.</p>
3757 <!-- *********************************************************************** -->
3758 <div class="doc_section"> <a name="intrinsics">Intrinsic Functions</a> </div>
3759 <!-- *********************************************************************** -->
3761 <div class="doc_text">
3763 <p>LLVM supports the notion of an "intrinsic function". These functions have
3764 well known names and semantics and are required to follow certain restrictions.
3765 Overall, these intrinsics represent an extension mechanism for the LLVM
3766 language that does not require changing all of the transformations in LLVM when
3767 adding to the language (or the bitcode reader/writer, the parser, etc...).</p>
3769 <p>Intrinsic function names must all start with an "<tt>llvm.</tt>" prefix. This
3770 prefix is reserved in LLVM for intrinsic names; thus, function names may not
3771 begin with this prefix. Intrinsic functions must always be external functions:
3772 you cannot define the body of intrinsic functions. Intrinsic functions may
3773 only be used in call or invoke instructions: it is illegal to take the address
3774 of an intrinsic function. Additionally, because intrinsic functions are part
3775 of the LLVM language, it is required if any are added that they be documented
3778 <p>Some intrinsic functions can be overloaded, i.e., the intrinsic represents
3779 a family of functions that perform the same operation but on different data
3780 types. Because LLVM can represent over 8 million different integer types,
3781 overloading is used commonly to allow an intrinsic function to operate on any
3782 integer type. One or more of the argument types or the result type can be
3783 overloaded to accept any integer type. Argument types may also be defined as
3784 exactly matching a previous argument's type or the result type. This allows an
3785 intrinsic function which accepts multiple arguments, but needs all of them to
3786 be of the same type, to only be overloaded with respect to a single argument or
3789 <p>Overloaded intrinsics will have the names of its overloaded argument types
3790 encoded into its function name, each preceded by a period. Only those types
3791 which are overloaded result in a name suffix. Arguments whose type is matched
3792 against another type do not. For example, the <tt>llvm.ctpop</tt> function can
3793 take an integer of any width and returns an integer of exactly the same integer
3794 width. This leads to a family of functions such as
3795 <tt>i8 @llvm.ctpop.i8(i8 %val)</tt> and <tt>i29 @llvm.ctpop.i29(i29 %val)</tt>.
3796 Only one type, the return type, is overloaded, and only one type suffix is
3797 required. Because the argument's type is matched against the return type, it
3798 does not require its own name suffix.</p>
3800 <p>To learn how to add an intrinsic function, please see the
3801 <a href="ExtendingLLVM.html">Extending LLVM Guide</a>.
3806 <!-- ======================================================================= -->
3807 <div class="doc_subsection">
3808 <a name="int_varargs">Variable Argument Handling Intrinsics</a>
3811 <div class="doc_text">
3813 <p>Variable argument support is defined in LLVM with the <a
3814 href="#i_va_arg"><tt>va_arg</tt></a> instruction and these three
3815 intrinsic functions. These functions are related to the similarly
3816 named macros defined in the <tt><stdarg.h></tt> header file.</p>
3818 <p>All of these functions operate on arguments that use a
3819 target-specific value type "<tt>va_list</tt>". The LLVM assembly
3820 language reference manual does not define what this type is, so all
3821 transformations should be prepared to handle these functions regardless of
3824 <p>This example shows how the <a href="#i_va_arg"><tt>va_arg</tt></a>
3825 instruction and the variable argument handling intrinsic functions are
3828 <div class="doc_code">
3830 define i32 @test(i32 %X, ...) {
3831 ; Initialize variable argument processing
3833 %ap2 = bitcast i8** %ap to i8*
3834 call void @llvm.va_start(i8* %ap2)
3836 ; Read a single integer argument
3837 %tmp = va_arg i8** %ap, i32
3839 ; Demonstrate usage of llvm.va_copy and llvm.va_end
3841 %aq2 = bitcast i8** %aq to i8*
3842 call void @llvm.va_copy(i8* %aq2, i8* %ap2)
3843 call void @llvm.va_end(i8* %aq2)
3845 ; Stop processing of arguments.
3846 call void @llvm.va_end(i8* %ap2)
3850 declare void @llvm.va_start(i8*)
3851 declare void @llvm.va_copy(i8*, i8*)
3852 declare void @llvm.va_end(i8*)
3858 <!-- _______________________________________________________________________ -->
3859 <div class="doc_subsubsection">
3860 <a name="int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a>
3864 <div class="doc_text">
3866 <pre> declare void %llvm.va_start(i8* <arglist>)<br></pre>
3868 <P>The '<tt>llvm.va_start</tt>' intrinsic initializes
3869 <tt>*<arglist></tt> for subsequent use by <tt><a
3870 href="#i_va_arg">va_arg</a></tt>.</p>
3874 <P>The argument is a pointer to a <tt>va_list</tt> element to initialize.</p>
3878 <P>The '<tt>llvm.va_start</tt>' intrinsic works just like the <tt>va_start</tt>
3879 macro available in C. In a target-dependent way, it initializes the
3880 <tt>va_list</tt> element to which the argument points, so that the next call to
3881 <tt>va_arg</tt> will produce the first variable argument passed to the function.
3882 Unlike the C <tt>va_start</tt> macro, this intrinsic does not need to know the
3883 last argument of the function as the compiler can figure that out.</p>
3887 <!-- _______________________________________________________________________ -->
3888 <div class="doc_subsubsection">
3889 <a name="int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a>
3892 <div class="doc_text">
3894 <pre> declare void @llvm.va_end(i8* <arglist>)<br></pre>
3897 <p>The '<tt>llvm.va_end</tt>' intrinsic destroys <tt>*<arglist></tt>,
3898 which has been initialized previously with <tt><a href="#int_va_start">llvm.va_start</a></tt>
3899 or <tt><a href="#i_va_copy">llvm.va_copy</a></tt>.</p>
3903 <p>The argument is a pointer to a <tt>va_list</tt> to destroy.</p>
3907 <p>The '<tt>llvm.va_end</tt>' intrinsic works just like the <tt>va_end</tt>
3908 macro available in C. In a target-dependent way, it destroys the
3909 <tt>va_list</tt> element to which the argument points. Calls to <a
3910 href="#int_va_start"><tt>llvm.va_start</tt></a> and <a href="#int_va_copy">
3911 <tt>llvm.va_copy</tt></a> must be matched exactly with calls to
3912 <tt>llvm.va_end</tt>.</p>
3916 <!-- _______________________________________________________________________ -->
3917 <div class="doc_subsubsection">
3918 <a name="int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a>
3921 <div class="doc_text">
3926 declare void @llvm.va_copy(i8* <destarglist>, i8* <srcarglist>)
3931 <p>The '<tt>llvm.va_copy</tt>' intrinsic copies the current argument position
3932 from the source argument list to the destination argument list.</p>
3936 <p>The first argument is a pointer to a <tt>va_list</tt> element to initialize.
3937 The second argument is a pointer to a <tt>va_list</tt> element to copy from.</p>
3942 <p>The '<tt>llvm.va_copy</tt>' intrinsic works just like the <tt>va_copy</tt>
3943 macro available in C. In a target-dependent way, it copies the source
3944 <tt>va_list</tt> element into the destination <tt>va_list</tt> element. This
3945 intrinsic is necessary because the <tt><a href="#int_va_start">
3946 llvm.va_start</a></tt> intrinsic may be arbitrarily complex and require, for
3947 example, memory allocation.</p>
3951 <!-- ======================================================================= -->
3952 <div class="doc_subsection">
3953 <a name="int_gc">Accurate Garbage Collection Intrinsics</a>
3956 <div class="doc_text">
3959 LLVM support for <a href="GarbageCollection.html">Accurate Garbage
3960 Collection</a> requires the implementation and generation of these intrinsics.
3961 These intrinsics allow identification of <a href="#int_gcroot">GC roots on the
3962 stack</a>, as well as garbage collector implementations that require <a
3963 href="#int_gcread">read</a> and <a href="#int_gcwrite">write</a> barriers.
3964 Front-ends for type-safe garbage collected languages should generate these
3965 intrinsics to make use of the LLVM garbage collectors. For more details, see <a
3966 href="GarbageCollection.html">Accurate Garbage Collection with LLVM</a>.
3969 <p>The garbage collection intrinsics only operate on objects in the generic
3970 address space (address space zero).</p>
3974 <!-- _______________________________________________________________________ -->
3975 <div class="doc_subsubsection">
3976 <a name="int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a>
3979 <div class="doc_text">
3984 declare void @llvm.gcroot(i8** %ptrloc, i8* %metadata)
3989 <p>The '<tt>llvm.gcroot</tt>' intrinsic declares the existence of a GC root to
3990 the code generator, and allows some metadata to be associated with it.</p>
3994 <p>The first argument specifies the address of a stack object that contains the
3995 root pointer. The second pointer (which must be either a constant or a global
3996 value address) contains the meta-data to be associated with the root.</p>
4000 <p>At runtime, a call to this intrinsics stores a null pointer into the "ptrloc"
4001 location. At compile-time, the code generator generates information to allow
4002 the runtime to find the pointer at GC safe points.
4008 <!-- _______________________________________________________________________ -->
4009 <div class="doc_subsubsection">
4010 <a name="int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a>
4013 <div class="doc_text">
4018 declare i8* @llvm.gcread(i8* %ObjPtr, i8** %Ptr)
4023 <p>The '<tt>llvm.gcread</tt>' intrinsic identifies reads of references from heap
4024 locations, allowing garbage collector implementations that require read
4029 <p>The second argument is the address to read from, which should be an address
4030 allocated from the garbage collector. The first object is a pointer to the
4031 start of the referenced object, if needed by the language runtime (otherwise
4036 <p>The '<tt>llvm.gcread</tt>' intrinsic has the same semantics as a load
4037 instruction, but may be replaced with substantially more complex code by the
4038 garbage collector runtime, as needed.</p>
4043 <!-- _______________________________________________________________________ -->
4044 <div class="doc_subsubsection">
4045 <a name="int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a>
4048 <div class="doc_text">
4053 declare void @llvm.gcwrite(i8* %P1, i8* %Obj, i8** %P2)
4058 <p>The '<tt>llvm.gcwrite</tt>' intrinsic identifies writes of references to heap
4059 locations, allowing garbage collector implementations that require write
4060 barriers (such as generational or reference counting collectors).</p>
4064 <p>The first argument is the reference to store, the second is the start of the
4065 object to store it to, and the third is the address of the field of Obj to
4066 store to. If the runtime does not require a pointer to the object, Obj may be
4071 <p>The '<tt>llvm.gcwrite</tt>' intrinsic has the same semantics as a store
4072 instruction, but may be replaced with substantially more complex code by the
4073 garbage collector runtime, as needed.</p>
4079 <!-- ======================================================================= -->
4080 <div class="doc_subsection">
4081 <a name="int_codegen">Code Generator Intrinsics</a>
4084 <div class="doc_text">
4086 These intrinsics are provided by LLVM to expose special features that may only
4087 be implemented with code generator support.
4092 <!-- _______________________________________________________________________ -->
4093 <div class="doc_subsubsection">
4094 <a name="int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a>
4097 <div class="doc_text">
4101 declare i8 *@llvm.returnaddress(i32 <level>)
4107 The '<tt>llvm.returnaddress</tt>' intrinsic attempts to compute a
4108 target-specific value indicating the return address of the current function
4109 or one of its callers.
4115 The argument to this intrinsic indicates which function to return the address
4116 for. Zero indicates the calling function, one indicates its caller, etc. The
4117 argument is <b>required</b> to be a constant integer value.
4123 The '<tt>llvm.returnaddress</tt>' intrinsic either returns a pointer indicating
4124 the return address of the specified call frame, or zero if it cannot be
4125 identified. The value returned by this intrinsic is likely to be incorrect or 0
4126 for arguments other than zero, so it should only be used for debugging purposes.
4130 Note that calling this intrinsic does not prevent function inlining or other
4131 aggressive transformations, so the value returned may not be that of the obvious
4132 source-language caller.
4137 <!-- _______________________________________________________________________ -->
4138 <div class="doc_subsubsection">
4139 <a name="int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a>
4142 <div class="doc_text">
4146 declare i8 *@llvm.frameaddress(i32 <level>)
4152 The '<tt>llvm.frameaddress</tt>' intrinsic attempts to return the
4153 target-specific frame pointer value for the specified stack frame.
4159 The argument to this intrinsic indicates which function to return the frame
4160 pointer for. Zero indicates the calling function, one indicates its caller,
4161 etc. The argument is <b>required</b> to be a constant integer value.
4167 The '<tt>llvm.frameaddress</tt>' intrinsic either returns a pointer indicating
4168 the frame address of the specified call frame, or zero if it cannot be
4169 identified. The value returned by this intrinsic is likely to be incorrect or 0
4170 for arguments other than zero, so it should only be used for debugging purposes.
4174 Note that calling this intrinsic does not prevent function inlining or other
4175 aggressive transformations, so the value returned may not be that of the obvious
4176 source-language caller.
4180 <!-- _______________________________________________________________________ -->
4181 <div class="doc_subsubsection">
4182 <a name="int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a>
4185 <div class="doc_text">
4189 declare i8 *@llvm.stacksave()
4195 The '<tt>llvm.stacksave</tt>' intrinsic is used to remember the current state of
4196 the function stack, for use with <a href="#int_stackrestore">
4197 <tt>llvm.stackrestore</tt></a>. This is useful for implementing language
4198 features like scoped automatic variable sized arrays in C99.
4204 This intrinsic returns a opaque pointer value that can be passed to <a
4205 href="#int_stackrestore"><tt>llvm.stackrestore</tt></a>. When an
4206 <tt>llvm.stackrestore</tt> intrinsic is executed with a value saved from
4207 <tt>llvm.stacksave</tt>, it effectively restores the state of the stack to the
4208 state it was in when the <tt>llvm.stacksave</tt> intrinsic executed. In
4209 practice, this pops any <a href="#i_alloca">alloca</a> blocks from the stack
4210 that were allocated after the <tt>llvm.stacksave</tt> was executed.
4215 <!-- _______________________________________________________________________ -->
4216 <div class="doc_subsubsection">
4217 <a name="int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a>
4220 <div class="doc_text">
4224 declare void @llvm.stackrestore(i8 * %ptr)
4230 The '<tt>llvm.stackrestore</tt>' intrinsic is used to restore the state of
4231 the function stack to the state it was in when the corresponding <a
4232 href="#int_stacksave"><tt>llvm.stacksave</tt></a> intrinsic executed. This is
4233 useful for implementing language features like scoped automatic variable sized
4240 See the description for <a href="#int_stacksave"><tt>llvm.stacksave</tt></a>.
4246 <!-- _______________________________________________________________________ -->
4247 <div class="doc_subsubsection">
4248 <a name="int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a>
4251 <div class="doc_text">
4255 declare void @llvm.prefetch(i8* <address>, i32 <rw>, i32 <locality>)
4262 The '<tt>llvm.prefetch</tt>' intrinsic is a hint to the code generator to insert
4263 a prefetch instruction if supported; otherwise, it is a noop. Prefetches have
4265 effect on the behavior of the program but can change its performance
4272 <tt>address</tt> is the address to be prefetched, <tt>rw</tt> is the specifier
4273 determining if the fetch should be for a read (0) or write (1), and
4274 <tt>locality</tt> is a temporal locality specifier ranging from (0) - no
4275 locality, to (3) - extremely local keep in cache. The <tt>rw</tt> and
4276 <tt>locality</tt> arguments must be constant integers.
4282 This intrinsic does not modify the behavior of the program. In particular,
4283 prefetches cannot trap and do not produce a value. On targets that support this
4284 intrinsic, the prefetch can provide hints to the processor cache for better
4290 <!-- _______________________________________________________________________ -->
4291 <div class="doc_subsubsection">
4292 <a name="int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a>
4295 <div class="doc_text">
4299 declare void @llvm.pcmarker(i32 <id>)
4306 The '<tt>llvm.pcmarker</tt>' intrinsic is a method to export a Program Counter
4308 code to simulators and other tools. The method is target specific, but it is
4309 expected that the marker will use exported symbols to transmit the PC of the marker.
4310 The marker makes no guarantees that it will remain with any specific instruction
4311 after optimizations. It is possible that the presence of a marker will inhibit
4312 optimizations. The intended use is to be inserted after optimizations to allow
4313 correlations of simulation runs.
4319 <tt>id</tt> is a numerical id identifying the marker.
4325 This intrinsic does not modify the behavior of the program. Backends that do not
4326 support this intrinisic may ignore it.
4331 <!-- _______________________________________________________________________ -->
4332 <div class="doc_subsubsection">
4333 <a name="int_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a>
4336 <div class="doc_text">
4340 declare i64 @llvm.readcyclecounter( )
4347 The '<tt>llvm.readcyclecounter</tt>' intrinsic provides access to the cycle
4348 counter register (or similar low latency, high accuracy clocks) on those targets
4349 that support it. On X86, it should map to RDTSC. On Alpha, it should map to RPCC.
4350 As the backing counters overflow quickly (on the order of 9 seconds on alpha), this
4351 should only be used for small timings.
4357 When directly supported, reading the cycle counter should not modify any memory.
4358 Implementations are allowed to either return a application specific value or a
4359 system wide value. On backends without support, this is lowered to a constant 0.
4364 <!-- ======================================================================= -->
4365 <div class="doc_subsection">
4366 <a name="int_libc">Standard C Library Intrinsics</a>
4369 <div class="doc_text">
4371 LLVM provides intrinsics for a few important standard C library functions.
4372 These intrinsics allow source-language front-ends to pass information about the
4373 alignment of the pointer arguments to the code generator, providing opportunity
4374 for more efficient code generation.
4379 <!-- _______________________________________________________________________ -->
4380 <div class="doc_subsubsection">
4381 <a name="int_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a>
4384 <div class="doc_text">
4388 declare void @llvm.memcpy.i32(i8 * <dest>, i8 * <src>,
4389 i32 <len>, i32 <align>)
4390 declare void @llvm.memcpy.i64(i8 * <dest>, i8 * <src>,
4391 i64 <len>, i32 <align>)
4397 The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the source
4398 location to the destination location.
4402 Note that, unlike the standard libc function, the <tt>llvm.memcpy.*</tt>
4403 intrinsics do not return a value, and takes an extra alignment argument.
4409 The first argument is a pointer to the destination, the second is a pointer to
4410 the source. The third argument is an integer argument
4411 specifying the number of bytes to copy, and the fourth argument is the alignment
4412 of the source and destination locations.
4416 If the call to this intrinisic has an alignment value that is not 0 or 1, then
4417 the caller guarantees that both the source and destination pointers are aligned
4424 The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the source
4425 location to the destination location, which are not allowed to overlap. It
4426 copies "len" bytes of memory over. If the argument is known to be aligned to
4427 some boundary, this can be specified as the fourth argument, otherwise it should
4433 <!-- _______________________________________________________________________ -->
4434 <div class="doc_subsubsection">
4435 <a name="int_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a>
4438 <div class="doc_text">
4442 declare void @llvm.memmove.i32(i8 * <dest>, i8 * <src>,
4443 i32 <len>, i32 <align>)
4444 declare void @llvm.memmove.i64(i8 * <dest>, i8 * <src>,
4445 i64 <len>, i32 <align>)
4451 The '<tt>llvm.memmove.*</tt>' intrinsics move a block of memory from the source
4452 location to the destination location. It is similar to the
4453 '<tt>llvm.memcmp</tt>' intrinsic but allows the two memory locations to overlap.
4457 Note that, unlike the standard libc function, the <tt>llvm.memmove.*</tt>
4458 intrinsics do not return a value, and takes an extra alignment argument.
4464 The first argument is a pointer to the destination, the second is a pointer to
4465 the source. The third argument is an integer argument
4466 specifying the number of bytes to copy, and the fourth argument is the alignment
4467 of the source and destination locations.
4471 If the call to this intrinisic has an alignment value that is not 0 or 1, then
4472 the caller guarantees that the source and destination pointers are aligned to
4479 The '<tt>llvm.memmove.*</tt>' intrinsics copy a block of memory from the source
4480 location to the destination location, which may overlap. It
4481 copies "len" bytes of memory over. If the argument is known to be aligned to
4482 some boundary, this can be specified as the fourth argument, otherwise it should
4488 <!-- _______________________________________________________________________ -->
4489 <div class="doc_subsubsection">
4490 <a name="int_memset">'<tt>llvm.memset.*</tt>' Intrinsics</a>
4493 <div class="doc_text">
4497 declare void @llvm.memset.i32(i8 * <dest>, i8 <val>,
4498 i32 <len>, i32 <align>)
4499 declare void @llvm.memset.i64(i8 * <dest>, i8 <val>,
4500 i64 <len>, i32 <align>)
4506 The '<tt>llvm.memset.*</tt>' intrinsics fill a block of memory with a particular
4511 Note that, unlike the standard libc function, the <tt>llvm.memset</tt> intrinsic
4512 does not return a value, and takes an extra alignment argument.
4518 The first argument is a pointer to the destination to fill, the second is the
4519 byte value to fill it with, the third argument is an integer
4520 argument specifying the number of bytes to fill, and the fourth argument is the
4521 known alignment of destination location.
4525 If the call to this intrinisic has an alignment value that is not 0 or 1, then
4526 the caller guarantees that the destination pointer is aligned to that boundary.
4532 The '<tt>llvm.memset.*</tt>' intrinsics fill "len" bytes of memory starting at
4534 destination location. If the argument is known to be aligned to some boundary,
4535 this can be specified as the fourth argument, otherwise it should be set to 0 or
4541 <!-- _______________________________________________________________________ -->
4542 <div class="doc_subsubsection">
4543 <a name="int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a>
4546 <div class="doc_text">
4549 <p>This is an overloaded intrinsic. You can use <tt>llvm.sqrt</tt> on any
4550 floating point or vector of floating point type. Not all targets support all
4553 declare float @llvm.sqrt.f32(float %Val)
4554 declare double @llvm.sqrt.f64(double %Val)
4555 declare x86_fp80 @llvm.sqrt.f80(x86_fp80 %Val)
4556 declare fp128 @llvm.sqrt.f128(fp128 %Val)
4557 declare ppc_fp128 @llvm.sqrt.ppcf128(ppc_fp128 %Val)
4563 The '<tt>llvm.sqrt</tt>' intrinsics return the sqrt of the specified operand,
4564 returning the same value as the libm '<tt>sqrt</tt>' functions would. Unlike
4565 <tt>sqrt</tt> in libm, however, <tt>llvm.sqrt</tt> has undefined behavior for
4566 negative numbers (which allows for better optimization).
4572 The argument and return value are floating point numbers of the same type.
4578 This function returns the sqrt of the specified operand if it is a nonnegative
4579 floating point number.
4583 <!-- _______________________________________________________________________ -->
4584 <div class="doc_subsubsection">
4585 <a name="int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a>
4588 <div class="doc_text">
4591 <p>This is an overloaded intrinsic. You can use <tt>llvm.powi</tt> on any
4592 floating point or vector of floating point type. Not all targets support all
4595 declare float @llvm.powi.f32(float %Val, i32 %power)
4596 declare double @llvm.powi.f64(double %Val, i32 %power)
4597 declare x86_fp80 @llvm.powi.f80(x86_fp80 %Val, i32 %power)
4598 declare fp128 @llvm.powi.f128(fp128 %Val, i32 %power)
4599 declare ppc_fp128 @llvm.powi.ppcf128(ppc_fp128 %Val, i32 %power)
4605 The '<tt>llvm.powi.*</tt>' intrinsics return the first operand raised to the
4606 specified (positive or negative) power. The order of evaluation of
4607 multiplications is not defined. When a vector of floating point type is
4608 used, the second argument remains a scalar integer value.
4614 The second argument is an integer power, and the first is a value to raise to
4621 This function returns the first value raised to the second power with an
4622 unspecified sequence of rounding operations.</p>
4625 <!-- _______________________________________________________________________ -->
4626 <div class="doc_subsubsection">
4627 <a name="int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a>
4630 <div class="doc_text">
4633 <p>This is an overloaded intrinsic. You can use <tt>llvm.sin</tt> on any
4634 floating point or vector of floating point type. Not all targets support all
4637 declare float @llvm.sin.f32(float %Val)
4638 declare double @llvm.sin.f64(double %Val)
4639 declare x86_fp80 @llvm.sin.f80(x86_fp80 %Val)
4640 declare fp128 @llvm.sin.f128(fp128 %Val)
4641 declare ppc_fp128 @llvm.sin.ppcf128(ppc_fp128 %Val)
4647 The '<tt>llvm.sin.*</tt>' intrinsics return the sine of the operand.
4653 The argument and return value are floating point numbers of the same type.
4659 This function returns the sine of the specified operand, returning the
4660 same values as the libm <tt>sin</tt> functions would, and handles error
4661 conditions in the same way.</p>
4664 <!-- _______________________________________________________________________ -->
4665 <div class="doc_subsubsection">
4666 <a name="int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a>
4669 <div class="doc_text">
4672 <p>This is an overloaded intrinsic. You can use <tt>llvm.cos</tt> on any
4673 floating point or vector of floating point type. Not all targets support all
4676 declare float @llvm.cos.f32(float %Val)
4677 declare double @llvm.cos.f64(double %Val)
4678 declare x86_fp80 @llvm.cos.f80(x86_fp80 %Val)
4679 declare fp128 @llvm.cos.f128(fp128 %Val)
4680 declare ppc_fp128 @llvm.cos.ppcf128(ppc_fp128 %Val)
4686 The '<tt>llvm.cos.*</tt>' intrinsics return the cosine of the operand.
4692 The argument and return value are floating point numbers of the same type.
4698 This function returns the cosine of the specified operand, returning the
4699 same values as the libm <tt>cos</tt> functions would, and handles error
4700 conditions in the same way.</p>
4703 <!-- _______________________________________________________________________ -->
4704 <div class="doc_subsubsection">
4705 <a name="int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a>
4708 <div class="doc_text">
4711 <p>This is an overloaded intrinsic. You can use <tt>llvm.pow</tt> on any
4712 floating point or vector of floating point type. Not all targets support all
4715 declare float @llvm.pow.f32(float %Val, float %Power)
4716 declare double @llvm.pow.f64(double %Val, double %Power)
4717 declare x86_fp80 @llvm.pow.f80(x86_fp80 %Val, x86_fp80 %Power)
4718 declare fp128 @llvm.pow.f128(fp128 %Val, fp128 %Power)
4719 declare ppc_fp128 @llvm.pow.ppcf128(ppc_fp128 %Val, ppc_fp128 Power)
4725 The '<tt>llvm.pow.*</tt>' intrinsics return the first operand raised to the
4726 specified (positive or negative) power.
4732 The second argument is a floating point power, and the first is a value to
4733 raise to that power.
4739 This function returns the first value raised to the second power,
4741 same values as the libm <tt>pow</tt> functions would, and handles error
4742 conditions in the same way.</p>
4746 <!-- ======================================================================= -->
4747 <div class="doc_subsection">
4748 <a name="int_manip">Bit Manipulation Intrinsics</a>
4751 <div class="doc_text">
4753 LLVM provides intrinsics for a few important bit manipulation operations.
4754 These allow efficient code generation for some algorithms.
4759 <!-- _______________________________________________________________________ -->
4760 <div class="doc_subsubsection">
4761 <a name="int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a>
4764 <div class="doc_text">
4767 <p>This is an overloaded intrinsic function. You can use bswap on any integer
4768 type that is an even number of bytes (i.e. BitWidth % 16 == 0).
4770 declare i16 @llvm.bswap.i16(i16 <id>)
4771 declare i32 @llvm.bswap.i32(i32 <id>)
4772 declare i64 @llvm.bswap.i64(i64 <id>)
4778 The '<tt>llvm.bswap</tt>' family of intrinsics is used to byte swap integer
4779 values with an even number of bytes (positive multiple of 16 bits). These are
4780 useful for performing operations on data that is not in the target's native
4787 The <tt>llvm.bswap.i16</tt> intrinsic returns an i16 value that has the high
4788 and low byte of the input i16 swapped. Similarly, the <tt>llvm.bswap.i32</tt>
4789 intrinsic returns an i32 value that has the four bytes of the input i32
4790 swapped, so that if the input bytes are numbered 0, 1, 2, 3 then the returned
4791 i32 will have its bytes in 3, 2, 1, 0 order. The <tt>llvm.bswap.i48</tt>,
4792 <tt>llvm.bswap.i64</tt> and other intrinsics extend this concept to
4793 additional even-byte lengths (6 bytes, 8 bytes and more, respectively).
4798 <!-- _______________________________________________________________________ -->
4799 <div class="doc_subsubsection">
4800 <a name="int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic</a>
4803 <div class="doc_text">
4806 <p>This is an overloaded intrinsic. You can use llvm.ctpop on any integer bit
4807 width. Not all targets support all bit widths however.
4809 declare i8 @llvm.ctpop.i8 (i8 <src>)
4810 declare i16 @llvm.ctpop.i16(i16 <src>)
4811 declare i32 @llvm.ctpop.i32(i32 <src>)
4812 declare i64 @llvm.ctpop.i64(i64 <src>)
4813 declare i256 @llvm.ctpop.i256(i256 <src>)
4819 The '<tt>llvm.ctpop</tt>' family of intrinsics counts the number of bits set in a
4826 The only argument is the value to be counted. The argument may be of any
4827 integer type. The return type must match the argument type.
4833 The '<tt>llvm.ctpop</tt>' intrinsic counts the 1's in a variable.
4837 <!-- _______________________________________________________________________ -->
4838 <div class="doc_subsubsection">
4839 <a name="int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic</a>
4842 <div class="doc_text">
4845 <p>This is an overloaded intrinsic. You can use <tt>llvm.ctlz</tt> on any
4846 integer bit width. Not all targets support all bit widths however.
4848 declare i8 @llvm.ctlz.i8 (i8 <src>)
4849 declare i16 @llvm.ctlz.i16(i16 <src>)
4850 declare i32 @llvm.ctlz.i32(i32 <src>)
4851 declare i64 @llvm.ctlz.i64(i64 <src>)
4852 declare i256 @llvm.ctlz.i256(i256 <src>)
4858 The '<tt>llvm.ctlz</tt>' family of intrinsic functions counts the number of
4859 leading zeros in a variable.
4865 The only argument is the value to be counted. The argument may be of any
4866 integer type. The return type must match the argument type.
4872 The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant) zeros
4873 in a variable. If the src == 0 then the result is the size in bits of the type
4874 of src. For example, <tt>llvm.ctlz(i32 2) = 30</tt>.
4880 <!-- _______________________________________________________________________ -->
4881 <div class="doc_subsubsection">
4882 <a name="int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic</a>
4885 <div class="doc_text">
4888 <p>This is an overloaded intrinsic. You can use <tt>llvm.cttz</tt> on any
4889 integer bit width. Not all targets support all bit widths however.
4891 declare i8 @llvm.cttz.i8 (i8 <src>)
4892 declare i16 @llvm.cttz.i16(i16 <src>)
4893 declare i32 @llvm.cttz.i32(i32 <src>)
4894 declare i64 @llvm.cttz.i64(i64 <src>)
4895 declare i256 @llvm.cttz.i256(i256 <src>)
4901 The '<tt>llvm.cttz</tt>' family of intrinsic functions counts the number of
4908 The only argument is the value to be counted. The argument may be of any
4909 integer type. The return type must match the argument type.
4915 The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant) zeros
4916 in a variable. If the src == 0 then the result is the size in bits of the type
4917 of src. For example, <tt>llvm.cttz(2) = 1</tt>.
4921 <!-- _______________________________________________________________________ -->
4922 <div class="doc_subsubsection">
4923 <a name="int_part_select">'<tt>llvm.part.select.*</tt>' Intrinsic</a>
4926 <div class="doc_text">
4929 <p>This is an overloaded intrinsic. You can use <tt>llvm.part.select</tt>
4930 on any integer bit width.
4932 declare i17 @llvm.part.select.i17 (i17 %val, i32 %loBit, i32 %hiBit)
4933 declare i29 @llvm.part.select.i29 (i29 %val, i32 %loBit, i32 %hiBit)
4937 <p>The '<tt>llvm.part.select</tt>' family of intrinsic functions selects a
4938 range of bits from an integer value and returns them in the same bit width as
4939 the original value.</p>
4942 <p>The first argument, <tt>%val</tt> and the result may be integer types of
4943 any bit width but they must have the same bit width. The second and third
4944 arguments must be <tt>i32</tt> type since they specify only a bit index.</p>
4947 <p>The operation of the '<tt>llvm.part.select</tt>' intrinsic has two modes
4948 of operation: forwards and reverse. If <tt>%loBit</tt> is greater than
4949 <tt>%hiBits</tt> then the intrinsic operates in reverse mode. Otherwise it
4950 operates in forward mode.</p>
4951 <p>In forward mode, this intrinsic is the equivalent of shifting <tt>%val</tt>
4952 right by <tt>%loBit</tt> bits and then ANDing it with a mask with
4953 only the <tt>%hiBit - %loBit</tt> bits set, as follows:</p>
4955 <li>The <tt>%val</tt> is shifted right (LSHR) by the number of bits specified
4956 by <tt>%loBits</tt>. This normalizes the value to the low order bits.</li>
4957 <li>The <tt>%loBits</tt> value is subtracted from the <tt>%hiBits</tt> value
4958 to determine the number of bits to retain.</li>
4959 <li>A mask of the retained bits is created by shifting a -1 value.</li>
4960 <li>The mask is ANDed with <tt>%val</tt> to produce the result.
4962 <p>In reverse mode, a similar computation is made except that the bits are
4963 returned in the reverse order. So, for example, if <tt>X</tt> has the value
4964 <tt>i16 0x0ACF (101011001111)</tt> and we apply
4965 <tt>part.select(i16 X, 8, 3)</tt> to it, we get back the value
4966 <tt>i16 0x0026 (000000100110)</tt>.</p>
4969 <div class="doc_subsubsection">
4970 <a name="int_part_set">'<tt>llvm.part.set.*</tt>' Intrinsic</a>
4973 <div class="doc_text">
4976 <p>This is an overloaded intrinsic. You can use <tt>llvm.part.set</tt>
4977 on any integer bit width.
4979 declare i17 @llvm.part.set.i17.i9 (i17 %val, i9 %repl, i32 %lo, i32 %hi)
4980 declare i29 @llvm.part.set.i29.i9 (i29 %val, i9 %repl, i32 %lo, i32 %hi)
4984 <p>The '<tt>llvm.part.set</tt>' family of intrinsic functions replaces a range
4985 of bits in an integer value with another integer value. It returns the integer
4986 with the replaced bits.</p>
4989 <p>The first argument, <tt>%val</tt> and the result may be integer types of
4990 any bit width but they must have the same bit width. <tt>%val</tt> is the value
4991 whose bits will be replaced. The second argument, <tt>%repl</tt> may be an
4992 integer of any bit width. The third and fourth arguments must be <tt>i32</tt>
4993 type since they specify only a bit index.</p>
4996 <p>The operation of the '<tt>llvm.part.set</tt>' intrinsic has two modes
4997 of operation: forwards and reverse. If <tt>%lo</tt> is greater than
4998 <tt>%hi</tt> then the intrinsic operates in reverse mode. Otherwise it
4999 operates in forward mode.</p>
5000 <p>For both modes, the <tt>%repl</tt> value is prepared for use by either
5001 truncating it down to the size of the replacement area or zero extending it
5002 up to that size.</p>
5003 <p>In forward mode, the bits between <tt>%lo</tt> and <tt>%hi</tt> (inclusive)
5004 are replaced with corresponding bits from <tt>%repl</tt>. That is the 0th bit
5005 in <tt>%repl</tt> replaces the <tt>%lo</tt>th bit in <tt>%val</tt> and etc. up
5006 to the <tt>%hi</tt>th bit.
5007 <p>In reverse mode, a similar computation is made except that the bits are
5008 reversed. That is, the <tt>0</tt>th bit in <tt>%repl</tt> replaces the
5009 <tt>%hi</tt> bit in <tt>%val</tt> and etc. down to the <tt>%lo</tt>th bit.
5012 llvm.part.set(0xFFFF, 0, 4, 7) -> 0xFF0F
5013 llvm.part.set(0xFFFF, 0, 7, 4) -> 0xFF0F
5014 llvm.part.set(0xFFFF, 1, 7, 4) -> 0xFF8F
5015 llvm.part.set(0xFFFF, F, 8, 3) -> 0xFFE7
5016 llvm.part.set(0xFFFF, 0, 3, 8) -> 0xFE07
5020 <!-- ======================================================================= -->
5021 <div class="doc_subsection">
5022 <a name="int_debugger">Debugger Intrinsics</a>
5025 <div class="doc_text">
5027 The LLVM debugger intrinsics (which all start with <tt>llvm.dbg.</tt> prefix),
5028 are described in the <a
5029 href="SourceLevelDebugging.html#format_common_intrinsics">LLVM Source Level
5030 Debugging</a> document.
5035 <!-- ======================================================================= -->
5036 <div class="doc_subsection">
5037 <a name="int_eh">Exception Handling Intrinsics</a>
5040 <div class="doc_text">
5041 <p> The LLVM exception handling intrinsics (which all start with
5042 <tt>llvm.eh.</tt> prefix), are described in the <a
5043 href="ExceptionHandling.html#format_common_intrinsics">LLVM Exception
5044 Handling</a> document. </p>
5047 <!-- ======================================================================= -->
5048 <div class="doc_subsection">
5049 <a name="int_trampoline">Trampoline Intrinsic</a>
5052 <div class="doc_text">
5054 This intrinsic makes it possible to excise one parameter, marked with
5055 the <tt>nest</tt> attribute, from a function. The result is a callable
5056 function pointer lacking the nest parameter - the caller does not need
5057 to provide a value for it. Instead, the value to use is stored in
5058 advance in a "trampoline", a block of memory usually allocated
5059 on the stack, which also contains code to splice the nest value into the
5060 argument list. This is used to implement the GCC nested function address
5064 For example, if the function is
5065 <tt>i32 f(i8* nest %c, i32 %x, i32 %y)</tt> then the resulting function
5066 pointer has signature <tt>i32 (i32, i32)*</tt>. It can be created as follows:</p>
5068 %tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86
5069 %tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0
5070 %p = call i8* @llvm.init.trampoline( i8* %tramp1, i8* bitcast (i32 (i8* nest , i32, i32)* @f to i8*), i8* %nval )
5071 %fp = bitcast i8* %p to i32 (i32, i32)*
5073 <p>The call <tt>%val = call i32 %fp( i32 %x, i32 %y )</tt> is then equivalent
5074 to <tt>%val = call i32 %f( i8* %nval, i32 %x, i32 %y )</tt>.</p>
5077 <!-- _______________________________________________________________________ -->
5078 <div class="doc_subsubsection">
5079 <a name="int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a>
5081 <div class="doc_text">
5084 declare i8* @llvm.init.trampoline(i8* <tramp>, i8* <func>, i8* <nval>)
5088 This fills the memory pointed to by <tt>tramp</tt> with code
5089 and returns a function pointer suitable for executing it.
5093 The <tt>llvm.init.trampoline</tt> intrinsic takes three arguments, all
5094 pointers. The <tt>tramp</tt> argument must point to a sufficiently large
5095 and sufficiently aligned block of memory; this memory is written to by the
5096 intrinsic. Note that the size and the alignment are target-specific - LLVM
5097 currently provides no portable way of determining them, so a front-end that
5098 generates this intrinsic needs to have some target-specific knowledge.
5099 The <tt>func</tt> argument must hold a function bitcast to an <tt>i8*</tt>.
5103 The block of memory pointed to by <tt>tramp</tt> is filled with target
5104 dependent code, turning it into a function. A pointer to this function is
5105 returned, but needs to be bitcast to an
5106 <a href="#int_trampoline">appropriate function pointer type</a>
5107 before being called. The new function's signature is the same as that of
5108 <tt>func</tt> with any arguments marked with the <tt>nest</tt> attribute
5109 removed. At most one such <tt>nest</tt> argument is allowed, and it must be
5110 of pointer type. Calling the new function is equivalent to calling
5111 <tt>func</tt> with the same argument list, but with <tt>nval</tt> used for the
5112 missing <tt>nest</tt> argument. If, after calling
5113 <tt>llvm.init.trampoline</tt>, the memory pointed to by <tt>tramp</tt> is
5114 modified, then the effect of any later call to the returned function pointer is
5119 <!-- ======================================================================= -->
5120 <div class="doc_subsection">
5121 <a name="int_general">General Intrinsics</a>
5124 <div class="doc_text">
5125 <p> This class of intrinsics is designed to be generic and has
5126 no specific purpose. </p>
5129 <!-- _______________________________________________________________________ -->
5130 <div class="doc_subsubsection">
5131 <a name="int_var_annotation">'<tt>llvm.var.annotation</tt>' Intrinsic</a>
5134 <div class="doc_text">
5138 declare void @llvm.var.annotation(i8* <val>, i8* <str>, i8* <str>, i32 <int> )
5144 The '<tt>llvm.var.annotation</tt>' intrinsic
5150 The first argument is a pointer to a value, the second is a pointer to a
5151 global string, the third is a pointer to a global string which is the source
5152 file name, and the last argument is the line number.
5158 This intrinsic allows annotation of local variables with arbitrary strings.
5159 This can be useful for special purpose optimizations that want to look for these
5160 annotations. These have no other defined use, they are ignored by code
5161 generation and optimization.
5164 <!-- _______________________________________________________________________ -->
5165 <div class="doc_subsubsection">
5166 <a name="int_annotation">'<tt>llvm.annotation.*</tt>' Intrinsic</a>
5169 <div class="doc_text">
5172 <p>This is an overloaded intrinsic. You can use '<tt>llvm.annotation</tt>' on
5173 any integer bit width.
5176 declare i8 @llvm.annotation.i8(i8 <val>, i8* <str>, i8* <str>, i32 <int> )
5177 declare i16 @llvm.annotation.i16(i16 <val>, i8* <str>, i8* <str>, i32 <int> )
5178 declare i32 @llvm.annotation.i32(i32 <val>, i8* <str>, i8* <str>, i32 <int> )
5179 declare i64 @llvm.annotation.i64(i64 <val>, i8* <str>, i8* <str>, i32 <int> )
5180 declare i256 @llvm.annotation.i256(i256 <val>, i8* <str>, i8* <str>, i32 <int> )
5186 The '<tt>llvm.annotation</tt>' intrinsic.
5192 The first argument is an integer value (result of some expression),
5193 the second is a pointer to a global string, the third is a pointer to a global
5194 string which is the source file name, and the last argument is the line number.
5195 It returns the value of the first argument.
5201 This intrinsic allows annotations to be put on arbitrary expressions
5202 with arbitrary strings. This can be useful for special purpose optimizations
5203 that want to look for these annotations. These have no other defined use, they
5204 are ignored by code generation and optimization.
5207 <!-- *********************************************************************** -->
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5215 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
5216 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
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