1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
2 "http://www.w3.org/TR/html4/strict.dtd">
5 <title>LLVM Assembly Language Reference Manual</title>
6 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
7 <meta name="author" content="Chris Lattner">
8 <meta name="description"
9 content="LLVM Assembly Language Reference Manual.">
10 <link rel="stylesheet" href="llvm.css" type="text/css">
15 <div class="doc_title"> LLVM Language Reference Manual </div>
17 <li><a href="#abstract">Abstract</a></li>
18 <li><a href="#introduction">Introduction</a></li>
19 <li><a href="#identifiers">Identifiers</a></li>
20 <li><a href="#highlevel">High Level Structure</a>
22 <li><a href="#modulestructure">Module Structure</a></li>
23 <li><a href="#linkage">Linkage Types</a></li>
24 <li><a href="#callingconv">Calling Conventions</a></li>
25 <li><a href="#globalvars">Global Variables</a></li>
26 <li><a href="#functionstructure">Functions</a></li>
27 <li><a href="#aliasstructure">Aliases</a>
28 <li><a href="#paramattrs">Parameter Attributes</a></li>
29 <li><a href="#moduleasm">Module-Level Inline Assembly</a></li>
30 <li><a href="#datalayout">Data Layout</a></li>
33 <li><a href="#typesystem">Type System</a>
35 <li><a href="#t_primitive">Primitive Types</a>
37 <li><a href="#t_classifications">Type Classifications</a></li>
40 <li><a href="#t_derived">Derived Types</a>
42 <li><a href="#t_array">Array Type</a></li>
43 <li><a href="#t_function">Function Type</a></li>
44 <li><a href="#t_pointer">Pointer Type</a></li>
45 <li><a href="#t_struct">Structure Type</a></li>
46 <li><a href="#t_pstruct">Packed Structure Type</a></li>
47 <li><a href="#t_vector">Vector Type</a></li>
48 <li><a href="#t_opaque">Opaque Type</a></li>
53 <li><a href="#constants">Constants</a>
55 <li><a href="#simpleconstants">Simple Constants</a>
56 <li><a href="#aggregateconstants">Aggregate Constants</a>
57 <li><a href="#globalconstants">Global Variable and Function Addresses</a>
58 <li><a href="#undefvalues">Undefined Values</a>
59 <li><a href="#constantexprs">Constant Expressions</a>
62 <li><a href="#othervalues">Other Values</a>
64 <li><a href="#inlineasm">Inline Assembler Expressions</a>
67 <li><a href="#instref">Instruction Reference</a>
69 <li><a href="#terminators">Terminator Instructions</a>
71 <li><a href="#i_ret">'<tt>ret</tt>' Instruction</a></li>
72 <li><a href="#i_br">'<tt>br</tt>' Instruction</a></li>
73 <li><a href="#i_switch">'<tt>switch</tt>' Instruction</a></li>
74 <li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a></li>
75 <li><a href="#i_unwind">'<tt>unwind</tt>' Instruction</a></li>
76 <li><a href="#i_unreachable">'<tt>unreachable</tt>' Instruction</a></li>
79 <li><a href="#binaryops">Binary Operations</a>
81 <li><a href="#i_add">'<tt>add</tt>' Instruction</a></li>
82 <li><a href="#i_sub">'<tt>sub</tt>' Instruction</a></li>
83 <li><a href="#i_mul">'<tt>mul</tt>' Instruction</a></li>
84 <li><a href="#i_udiv">'<tt>udiv</tt>' Instruction</a></li>
85 <li><a href="#i_sdiv">'<tt>sdiv</tt>' Instruction</a></li>
86 <li><a href="#i_fdiv">'<tt>fdiv</tt>' Instruction</a></li>
87 <li><a href="#i_urem">'<tt>urem</tt>' Instruction</a></li>
88 <li><a href="#i_srem">'<tt>srem</tt>' Instruction</a></li>
89 <li><a href="#i_frem">'<tt>frem</tt>' Instruction</a></li>
92 <li><a href="#bitwiseops">Bitwise Binary Operations</a>
94 <li><a href="#i_shl">'<tt>shl</tt>' Instruction</a></li>
95 <li><a href="#i_lshr">'<tt>lshr</tt>' Instruction</a></li>
96 <li><a href="#i_ashr">'<tt>ashr</tt>' Instruction</a></li>
97 <li><a href="#i_and">'<tt>and</tt>' Instruction</a></li>
98 <li><a href="#i_or">'<tt>or</tt>' Instruction</a></li>
99 <li><a href="#i_xor">'<tt>xor</tt>' Instruction</a></li>
102 <li><a href="#vectorops">Vector Operations</a>
104 <li><a href="#i_extractelement">'<tt>extractelement</tt>' Instruction</a></li>
105 <li><a href="#i_insertelement">'<tt>insertelement</tt>' Instruction</a></li>
106 <li><a href="#i_shufflevector">'<tt>shufflevector</tt>' Instruction</a></li>
109 <li><a href="#memoryops">Memory Access and Addressing Operations</a>
111 <li><a href="#i_malloc">'<tt>malloc</tt>' Instruction</a></li>
112 <li><a href="#i_free">'<tt>free</tt>' Instruction</a></li>
113 <li><a href="#i_alloca">'<tt>alloca</tt>' Instruction</a></li>
114 <li><a href="#i_load">'<tt>load</tt>' Instruction</a></li>
115 <li><a href="#i_store">'<tt>store</tt>' Instruction</a></li>
116 <li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a></li>
119 <li><a href="#convertops">Conversion Operations</a>
121 <li><a href="#i_trunc">'<tt>trunc .. to</tt>' Instruction</a></li>
122 <li><a href="#i_zext">'<tt>zext .. to</tt>' Instruction</a></li>
123 <li><a href="#i_sext">'<tt>sext .. to</tt>' Instruction</a></li>
124 <li><a href="#i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a></li>
125 <li><a href="#i_fpext">'<tt>fpext .. to</tt>' Instruction</a></li>
126 <li><a href="#i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a></li>
127 <li><a href="#i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a></li>
128 <li><a href="#i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a></li>
129 <li><a href="#i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a></li>
130 <li><a href="#i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a></li>
131 <li><a href="#i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a></li>
132 <li><a href="#i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a></li>
134 <li><a href="#otherops">Other Operations</a>
136 <li><a href="#i_icmp">'<tt>icmp</tt>' Instruction</a></li>
137 <li><a href="#i_fcmp">'<tt>fcmp</tt>' Instruction</a></li>
138 <li><a href="#i_phi">'<tt>phi</tt>' Instruction</a></li>
139 <li><a href="#i_select">'<tt>select</tt>' Instruction</a></li>
140 <li><a href="#i_call">'<tt>call</tt>' Instruction</a></li>
141 <li><a href="#i_va_arg">'<tt>va_arg</tt>' Instruction</a></li>
146 <li><a href="#intrinsics">Intrinsic Functions</a>
148 <li><a href="#int_varargs">Variable Argument Handling Intrinsics</a>
150 <li><a href="#int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a></li>
151 <li><a href="#int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a></li>
152 <li><a href="#int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a></li>
155 <li><a href="#int_gc">Accurate Garbage Collection Intrinsics</a>
157 <li><a href="#int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a></li>
158 <li><a href="#int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a></li>
159 <li><a href="#int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a></li>
162 <li><a href="#int_codegen">Code Generator Intrinsics</a>
164 <li><a href="#int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a></li>
165 <li><a href="#int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li>
166 <li><a href="#int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a></li>
167 <li><a href="#int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a></li>
168 <li><a href="#int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a></li>
169 <li><a href="#int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a></li>
170 <li><a href="#int_readcyclecounter"><tt>llvm.readcyclecounter</tt>' Intrinsic</a></li>
173 <li><a href="#int_libc">Standard C Library Intrinsics</a>
175 <li><a href="#int_memcpy">'<tt>llvm.memcpy.*</tt>' Intrinsic</a></li>
176 <li><a href="#int_memmove">'<tt>llvm.memmove.*</tt>' Intrinsic</a></li>
177 <li><a href="#int_memset">'<tt>llvm.memset.*</tt>' Intrinsic</a></li>
178 <li><a href="#int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a></li>
179 <li><a href="#int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a></li>
180 <li><a href="#int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a></li>
181 <li><a href="#int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a></li>
182 <li><a href="#int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a></li>
185 <li><a href="#int_manip">Bit Manipulation Intrinsics</a>
187 <li><a href="#int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a></li>
188 <li><a href="#int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic </a></li>
189 <li><a href="#int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic </a></li>
190 <li><a href="#int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic </a></li>
191 <li><a href="#int_part_select">'<tt>llvm.part.select.*</tt>' Intrinsic </a></li>
192 <li><a href="#int_part_set">'<tt>llvm.part.set.*</tt>' Intrinsic </a></li>
195 <li><a href="#int_debugger">Debugger intrinsics</a></li>
196 <li><a href="#int_eh">Exception Handling intrinsics</a></li>
197 <li><a href="#int_trampoline">Trampoline Intrinsic</a>
199 <li><a href="#int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a></li>
202 <li><a href="#int_general">General intrinsics</a>
204 <li><a href="#int_var_annotation">
205 <tt>llvm.var.annotation</tt>' Intrinsic</a></li>
208 <li><a href="#int_annotation">
209 <tt>llvm.annotation.*</tt>' Intrinsic</a></li>
216 <div class="doc_author">
217 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>
218 and <a href="mailto:vadve@cs.uiuc.edu">Vikram Adve</a></p>
221 <!-- *********************************************************************** -->
222 <div class="doc_section"> <a name="abstract">Abstract </a></div>
223 <!-- *********************************************************************** -->
225 <div class="doc_text">
226 <p>This document is a reference manual for the LLVM assembly language.
227 LLVM is an SSA based representation that provides type safety,
228 low-level operations, flexibility, and the capability of representing
229 'all' high-level languages cleanly. It is the common code
230 representation used throughout all phases of the LLVM compilation
234 <!-- *********************************************************************** -->
235 <div class="doc_section"> <a name="introduction">Introduction</a> </div>
236 <!-- *********************************************************************** -->
238 <div class="doc_text">
240 <p>The LLVM code representation is designed to be used in three
241 different forms: as an in-memory compiler IR, as an on-disk bitcode
242 representation (suitable for fast loading by a Just-In-Time compiler),
243 and as a human readable assembly language representation. This allows
244 LLVM to provide a powerful intermediate representation for efficient
245 compiler transformations and analysis, while providing a natural means
246 to debug and visualize the transformations. The three different forms
247 of LLVM are all equivalent. This document describes the human readable
248 representation and notation.</p>
250 <p>The LLVM representation aims to be light-weight and low-level
251 while being expressive, typed, and extensible at the same time. It
252 aims to be a "universal IR" of sorts, by being at a low enough level
253 that high-level ideas may be cleanly mapped to it (similar to how
254 microprocessors are "universal IR's", allowing many source languages to
255 be mapped to them). By providing type information, LLVM can be used as
256 the target of optimizations: for example, through pointer analysis, it
257 can be proven that a C automatic variable is never accessed outside of
258 the current function... allowing it to be promoted to a simple SSA
259 value instead of a memory location.</p>
263 <!-- _______________________________________________________________________ -->
264 <div class="doc_subsubsection"> <a name="wellformed">Well-Formedness</a> </div>
266 <div class="doc_text">
268 <p>It is important to note that this document describes 'well formed'
269 LLVM assembly language. There is a difference between what the parser
270 accepts and what is considered 'well formed'. For example, the
271 following instruction is syntactically okay, but not well formed:</p>
273 <div class="doc_code">
275 %x = <a href="#i_add">add</a> i32 1, %x
279 <p>...because the definition of <tt>%x</tt> does not dominate all of
280 its uses. The LLVM infrastructure provides a verification pass that may
281 be used to verify that an LLVM module is well formed. This pass is
282 automatically run by the parser after parsing input assembly and by
283 the optimizer before it outputs bitcode. The violations pointed out
284 by the verifier pass indicate bugs in transformation passes or input to
288 <!-- Describe the typesetting conventions here. -->
290 <!-- *********************************************************************** -->
291 <div class="doc_section"> <a name="identifiers">Identifiers</a> </div>
292 <!-- *********************************************************************** -->
294 <div class="doc_text">
296 <p>LLVM identifiers come in two basic types: global and local. Global
297 identifiers (functions, global variables) begin with the @ character. Local
298 identifiers (register names, types) begin with the % character. Additionally,
299 there are three different formats for identifiers, for different purposes:
302 <li>Named values are represented as a string of characters with their prefix.
303 For example, %foo, @DivisionByZero, %a.really.long.identifier. The actual
304 regular expression used is '<tt>[%@][a-zA-Z$._][a-zA-Z$._0-9]*</tt>'.
305 Identifiers which require other characters in their names can be surrounded
306 with quotes. In this way, anything except a <tt>"</tt> character can
307 be used in a named value.</li>
309 <li>Unnamed values are represented as an unsigned numeric value with their
310 prefix. For example, %12, @2, %44.</li>
312 <li>Constants, which are described in a <a href="#constants">section about
313 constants</a>, below.</li>
316 <p>LLVM requires that values start with a prefix for two reasons: Compilers
317 don't need to worry about name clashes with reserved words, and the set of
318 reserved words may be expanded in the future without penalty. Additionally,
319 unnamed identifiers allow a compiler to quickly come up with a temporary
320 variable without having to avoid symbol table conflicts.</p>
322 <p>Reserved words in LLVM are very similar to reserved words in other
323 languages. There are keywords for different opcodes
324 ('<tt><a href="#i_add">add</a></tt>',
325 '<tt><a href="#i_bitcast">bitcast</a></tt>',
326 '<tt><a href="#i_ret">ret</a></tt>', etc...), for primitive type names ('<tt><a
327 href="#t_void">void</a></tt>', '<tt><a href="#t_primitive">i32</a></tt>', etc...),
328 and others. These reserved words cannot conflict with variable names, because
329 none of them start with a prefix character ('%' or '@').</p>
331 <p>Here is an example of LLVM code to multiply the integer variable
332 '<tt>%X</tt>' by 8:</p>
336 <div class="doc_code">
338 %result = <a href="#i_mul">mul</a> i32 %X, 8
342 <p>After strength reduction:</p>
344 <div class="doc_code">
346 %result = <a href="#i_shl">shl</a> i32 %X, i8 3
350 <p>And the hard way:</p>
352 <div class="doc_code">
354 <a href="#i_add">add</a> i32 %X, %X <i>; yields {i32}:%0</i>
355 <a href="#i_add">add</a> i32 %0, %0 <i>; yields {i32}:%1</i>
356 %result = <a href="#i_add">add</a> i32 %1, %1
360 <p>This last way of multiplying <tt>%X</tt> by 8 illustrates several
361 important lexical features of LLVM:</p>
365 <li>Comments are delimited with a '<tt>;</tt>' and go until the end of
368 <li>Unnamed temporaries are created when the result of a computation is not
369 assigned to a named value.</li>
371 <li>Unnamed temporaries are numbered sequentially</li>
375 <p>...and it also shows a convention that we follow in this document. When
376 demonstrating instructions, we will follow an instruction with a comment that
377 defines the type and name of value produced. Comments are shown in italic
382 <!-- *********************************************************************** -->
383 <div class="doc_section"> <a name="highlevel">High Level Structure</a> </div>
384 <!-- *********************************************************************** -->
386 <!-- ======================================================================= -->
387 <div class="doc_subsection"> <a name="modulestructure">Module Structure</a>
390 <div class="doc_text">
392 <p>LLVM programs are composed of "Module"s, each of which is a
393 translation unit of the input programs. Each module consists of
394 functions, global variables, and symbol table entries. Modules may be
395 combined together with the LLVM linker, which merges function (and
396 global variable) definitions, resolves forward declarations, and merges
397 symbol table entries. Here is an example of the "hello world" module:</p>
399 <div class="doc_code">
400 <pre><i>; Declare the string constant as a global constant...</i>
401 <a href="#identifiers">@.LC0</a> = <a href="#linkage_internal">internal</a> <a
402 href="#globalvars">constant</a> <a href="#t_array">[13 x i8]</a> c"hello world\0A\00" <i>; [13 x i8]*</i>
404 <i>; External declaration of the puts function</i>
405 <a href="#functionstructure">declare</a> i32 @puts(i8 *) <i>; i32(i8 *)* </i>
407 <i>; Definition of main function</i>
408 define i32 @main() { <i>; i32()* </i>
409 <i>; Convert [13x i8 ]* to i8 *...</i>
411 href="#i_getelementptr">getelementptr</a> [13 x i8 ]* @.LC0, i64 0, i64 0 <i>; i8 *</i>
413 <i>; Call puts function to write out the string to stdout...</i>
415 href="#i_call">call</a> i32 @puts(i8 * %cast210) <i>; i32</i>
417 href="#i_ret">ret</a> i32 0<br>}<br>
421 <p>This example is made up of a <a href="#globalvars">global variable</a>
422 named "<tt>.LC0</tt>", an external declaration of the "<tt>puts</tt>"
423 function, and a <a href="#functionstructure">function definition</a>
424 for "<tt>main</tt>".</p>
426 <p>In general, a module is made up of a list of global values,
427 where both functions and global variables are global values. Global values are
428 represented by a pointer to a memory location (in this case, a pointer to an
429 array of char, and a pointer to a function), and have one of the following <a
430 href="#linkage">linkage types</a>.</p>
434 <!-- ======================================================================= -->
435 <div class="doc_subsection">
436 <a name="linkage">Linkage Types</a>
439 <div class="doc_text">
442 All Global Variables and Functions have one of the following types of linkage:
447 <dt><tt><b><a name="linkage_internal">internal</a></b></tt> </dt>
449 <dd>Global values with internal linkage are only directly accessible by
450 objects in the current module. In particular, linking code into a module with
451 an internal global value may cause the internal to be renamed as necessary to
452 avoid collisions. Because the symbol is internal to the module, all
453 references can be updated. This corresponds to the notion of the
454 '<tt>static</tt>' keyword in C.
457 <dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt>: </dt>
459 <dd>Globals with "<tt>linkonce</tt>" linkage are merged with other globals of
460 the same name when linkage occurs. This is typically used to implement
461 inline functions, templates, or other code which must be generated in each
462 translation unit that uses it. Unreferenced <tt>linkonce</tt> globals are
463 allowed to be discarded.
466 <dt><tt><b><a name="linkage_weak">weak</a></b></tt>: </dt>
468 <dd>"<tt>weak</tt>" linkage is exactly the same as <tt>linkonce</tt> linkage,
469 except that unreferenced <tt>weak</tt> globals may not be discarded. This is
470 used for globals that may be emitted in multiple translation units, but that
471 are not guaranteed to be emitted into every translation unit that uses them.
472 One example of this are common globals in C, such as "<tt>int X;</tt>" at
476 <dt><tt><b><a name="linkage_appending">appending</a></b></tt>: </dt>
478 <dd>"<tt>appending</tt>" linkage may only be applied to global variables of
479 pointer to array type. When two global variables with appending linkage are
480 linked together, the two global arrays are appended together. This is the
481 LLVM, typesafe, equivalent of having the system linker append together
482 "sections" with identical names when .o files are linked.
485 <dt><tt><b><a name="linkage_externweak">extern_weak</a></b></tt>: </dt>
486 <dd>The semantics of this linkage follow the ELF model: the symbol is weak
487 until linked, if not linked, the symbol becomes null instead of being an
491 <dt><tt><b><a name="linkage_external">externally visible</a></b></tt>:</dt>
493 <dd>If none of the above identifiers are used, the global is externally
494 visible, meaning that it participates in linkage and can be used to resolve
495 external symbol references.
500 The next two types of linkage are targeted for Microsoft Windows platform
501 only. They are designed to support importing (exporting) symbols from (to)
506 <dt><tt><b><a name="linkage_dllimport">dllimport</a></b></tt>: </dt>
508 <dd>"<tt>dllimport</tt>" linkage causes the compiler to reference a function
509 or variable via a global pointer to a pointer that is set up by the DLL
510 exporting the symbol. On Microsoft Windows targets, the pointer name is
511 formed by combining <code>_imp__</code> and the function or variable name.
514 <dt><tt><b><a name="linkage_dllexport">dllexport</a></b></tt>: </dt>
516 <dd>"<tt>dllexport</tt>" linkage causes the compiler to provide a global
517 pointer to a pointer in a DLL, so that it can be referenced with the
518 <tt>dllimport</tt> attribute. On Microsoft Windows targets, the pointer
519 name is formed by combining <code>_imp__</code> and the function or variable
525 <p><a name="linkage_external"></a>For example, since the "<tt>.LC0</tt>"
526 variable is defined to be internal, if another module defined a "<tt>.LC0</tt>"
527 variable and was linked with this one, one of the two would be renamed,
528 preventing a collision. Since "<tt>main</tt>" and "<tt>puts</tt>" are
529 external (i.e., lacking any linkage declarations), they are accessible
530 outside of the current module.</p>
531 <p>It is illegal for a function <i>declaration</i>
532 to have any linkage type other than "externally visible", <tt>dllimport</tt>,
533 or <tt>extern_weak</tt>.</p>
534 <p>Aliases can have only <tt>external</tt>, <tt>internal</tt> and <tt>weak</tt>
538 <!-- ======================================================================= -->
539 <div class="doc_subsection">
540 <a name="callingconv">Calling Conventions</a>
543 <div class="doc_text">
545 <p>LLVM <a href="#functionstructure">functions</a>, <a href="#i_call">calls</a>
546 and <a href="#i_invoke">invokes</a> can all have an optional calling convention
547 specified for the call. The calling convention of any pair of dynamic
548 caller/callee must match, or the behavior of the program is undefined. The
549 following calling conventions are supported by LLVM, and more may be added in
553 <dt><b>"<tt>ccc</tt>" - The C calling convention</b>:</dt>
555 <dd>This calling convention (the default if no other calling convention is
556 specified) matches the target C calling conventions. This calling convention
557 supports varargs function calls and tolerates some mismatch in the declared
558 prototype and implemented declaration of the function (as does normal C).
561 <dt><b>"<tt>fastcc</tt>" - The fast calling convention</b>:</dt>
563 <dd>This calling convention attempts to make calls as fast as possible
564 (e.g. by passing things in registers). This calling convention allows the
565 target to use whatever tricks it wants to produce fast code for the target,
566 without having to conform to an externally specified ABI. Implementations of
567 this convention should allow arbitrary tail call optimization to be supported.
568 This calling convention does not support varargs and requires the prototype of
569 all callees to exactly match the prototype of the function definition.
572 <dt><b>"<tt>coldcc</tt>" - The cold calling convention</b>:</dt>
574 <dd>This calling convention attempts to make code in the caller as efficient
575 as possible under the assumption that the call is not commonly executed. As
576 such, these calls often preserve all registers so that the call does not break
577 any live ranges in the caller side. This calling convention does not support
578 varargs and requires the prototype of all callees to exactly match the
579 prototype of the function definition.
582 <dt><b>"<tt>cc <<em>n</em>></tt>" - Numbered convention</b>:</dt>
584 <dd>Any calling convention may be specified by number, allowing
585 target-specific calling conventions to be used. Target specific calling
586 conventions start at 64.
590 <p>More calling conventions can be added/defined on an as-needed basis, to
591 support pascal conventions or any other well-known target-independent
596 <!-- ======================================================================= -->
597 <div class="doc_subsection">
598 <a name="visibility">Visibility Styles</a>
601 <div class="doc_text">
604 All Global Variables and Functions have one of the following visibility styles:
608 <dt><b>"<tt>default</tt>" - Default style</b>:</dt>
610 <dd>On ELF, default visibility means that the declaration is visible to other
611 modules and, in shared libraries, means that the declared entity may be
612 overridden. On Darwin, default visibility means that the declaration is
613 visible to other modules. Default visibility corresponds to "external
614 linkage" in the language.
617 <dt><b>"<tt>hidden</tt>" - Hidden style</b>:</dt>
619 <dd>Two declarations of an object with hidden visibility refer to the same
620 object if they are in the same shared object. Usually, hidden visibility
621 indicates that the symbol will not be placed into the dynamic symbol table,
622 so no other module (executable or shared library) can reference it
626 <dt><b>"<tt>protected</tt>" - Protected style</b>:</dt>
628 <dd>On ELF, protected visibility indicates that the symbol will be placed in
629 the dynamic symbol table, but that references within the defining module will
630 bind to the local symbol. That is, the symbol cannot be overridden by another
637 <!-- ======================================================================= -->
638 <div class="doc_subsection">
639 <a name="globalvars">Global Variables</a>
642 <div class="doc_text">
644 <p>Global variables define regions of memory allocated at compilation time
645 instead of run-time. Global variables may optionally be initialized, may have
646 an explicit section to be placed in, and may have an optional explicit alignment
647 specified. A variable may be defined as "thread_local", which means that it
648 will not be shared by threads (each thread will have a separated copy of the
649 variable). A variable may be defined as a global "constant," which indicates
650 that the contents of the variable will <b>never</b> be modified (enabling better
651 optimization, allowing the global data to be placed in the read-only section of
652 an executable, etc). Note that variables that need runtime initialization
653 cannot be marked "constant" as there is a store to the variable.</p>
656 LLVM explicitly allows <em>declarations</em> of global variables to be marked
657 constant, even if the final definition of the global is not. This capability
658 can be used to enable slightly better optimization of the program, but requires
659 the language definition to guarantee that optimizations based on the
660 'constantness' are valid for the translation units that do not include the
664 <p>As SSA values, global variables define pointer values that are in
665 scope (i.e. they dominate) all basic blocks in the program. Global
666 variables always define a pointer to their "content" type because they
667 describe a region of memory, and all memory objects in LLVM are
668 accessed through pointers.</p>
670 <p>LLVM allows an explicit section to be specified for globals. If the target
671 supports it, it will emit globals to the section specified.</p>
673 <p>An explicit alignment may be specified for a global. If not present, or if
674 the alignment is set to zero, the alignment of the global is set by the target
675 to whatever it feels convenient. If an explicit alignment is specified, the
676 global is forced to have at least that much alignment. All alignments must be
679 <p>For example, the following defines a global with an initializer, section,
682 <div class="doc_code">
684 @G = constant float 1.0, section "foo", align 4
691 <!-- ======================================================================= -->
692 <div class="doc_subsection">
693 <a name="functionstructure">Functions</a>
696 <div class="doc_text">
698 <p>LLVM function definitions consist of the "<tt>define</tt>" keyord,
699 an optional <a href="#linkage">linkage type</a>, an optional
700 <a href="#visibility">visibility style</a>, an optional
701 <a href="#callingconv">calling convention</a>, a return type, an optional
702 <a href="#paramattrs">parameter attribute</a> for the return type, a function
703 name, a (possibly empty) argument list (each with optional
704 <a href="#paramattrs">parameter attributes</a>), an optional section, an
705 optional alignment, an opening curly brace, a list of basic blocks, and a
708 LLVM function declarations consist of the "<tt>declare</tt>" keyword, an
709 optional <a href="#linkage">linkage type</a>, an optional
710 <a href="#visibility">visibility style</a>, an optional
711 <a href="#callingconv">calling convention</a>, a return type, an optional
712 <a href="#paramattrs">parameter attribute</a> for the return type, a function
713 name, a possibly empty list of arguments, and an optional alignment.</p>
715 <p>A function definition contains a list of basic blocks, forming the CFG for
716 the function. Each basic block may optionally start with a label (giving the
717 basic block a symbol table entry), contains a list of instructions, and ends
718 with a <a href="#terminators">terminator</a> instruction (such as a branch or
719 function return).</p>
721 <p>The first basic block in a function is special in two ways: it is immediately
722 executed on entrance to the function, and it is not allowed to have predecessor
723 basic blocks (i.e. there can not be any branches to the entry block of a
724 function). Because the block can have no predecessors, it also cannot have any
725 <a href="#i_phi">PHI nodes</a>.</p>
727 <p>LLVM allows an explicit section to be specified for functions. If the target
728 supports it, it will emit functions to the section specified.</p>
730 <p>An explicit alignment may be specified for a function. If not present, or if
731 the alignment is set to zero, the alignment of the function is set by the target
732 to whatever it feels convenient. If an explicit alignment is specified, the
733 function is forced to have at least that much alignment. All alignments must be
739 <!-- ======================================================================= -->
740 <div class="doc_subsection">
741 <a name="aliasstructure">Aliases</a>
743 <div class="doc_text">
744 <p>Aliases act as "second name" for the aliasee value (which can be either
745 function or global variable or bitcast of global value). Aliases may have an
746 optional <a href="#linkage">linkage type</a>, and an
747 optional <a href="#visibility">visibility style</a>.</p>
751 <div class="doc_code">
753 @<Name> = [Linkage] [Visibility] alias <AliaseeTy> @<Aliasee>
761 <!-- ======================================================================= -->
762 <div class="doc_subsection"><a name="paramattrs">Parameter Attributes</a></div>
763 <div class="doc_text">
764 <p>The return type and each parameter of a function type may have a set of
765 <i>parameter attributes</i> associated with them. Parameter attributes are
766 used to communicate additional information about the result or parameters of
767 a function. Parameter attributes are considered to be part of the function,
768 not of the function type, so functions with different parameter attributes
769 can have the same function type.</p>
771 <p>Parameter attributes are simple keywords that follow the type specified. If
772 multiple parameter attributes are needed, they are space separated. For
775 <div class="doc_code">
777 declare i32 @printf(i8* noalias , ...) nounwind
778 declare i32 @atoi(i8*) nounwind readonly
782 <p>Note that any attributes for the function result (<tt>nounwind</tt>,
783 <tt>readonly</tt>) come immediately after the argument list.</p>
785 <p>Currently, only the following parameter attributes are defined:</p>
787 <dt><tt>zeroext</tt></dt>
788 <dd>This indicates that the parameter should be zero extended just before
789 a call to this function.</dd>
790 <dt><tt>signext</tt></dt>
791 <dd>This indicates that the parameter should be sign extended just before
792 a call to this function.</dd>
793 <dt><tt>inreg</tt></dt>
794 <dd>This indicates that the parameter should be placed in register (if
795 possible) during assembling function call. Support for this attribute is
797 <dt><tt>sret</tt></dt>
798 <dd>This indicates that the parameter specifies the address of a structure
799 that is the return value of the function in the source program.</dd>
800 <dt><tt>noalias</tt></dt>
801 <dd>This indicates that the parameter not alias any other object or any
802 other "noalias" objects during the function call.
803 <dt><tt>noreturn</tt></dt>
804 <dd>This function attribute indicates that the function never returns. This
805 indicates to LLVM that every call to this function should be treated as if
806 an <tt>unreachable</tt> instruction immediately followed the call.</dd>
807 <dt><tt>nounwind</tt></dt>
808 <dd>This function attribute indicates that the function type does not use
809 the unwind instruction and does not allow stack unwinding to propagate
811 <dt><tt>nest</tt></dt>
812 <dd>This indicates that the parameter can be excised using the
813 <a href="#int_trampoline">trampoline intrinsics</a>.</dd>
814 <dt><tt>readonly</tt></dt>
815 <dd>This function attribute indicates that the function has no side-effects
816 except for producing a return value or throwing an exception. The value
817 returned must only depend on the function arguments and/or global variables.
818 It may use values obtained by dereferencing pointers.</dd>
819 <dt><tt>readnone</tt></dt>
820 <dd>A <tt>readnone</tt> function has the same restrictions as a <tt>readonly</tt>
821 function, but in addition it is not allowed to dereference any pointer arguments
827 <!-- ======================================================================= -->
828 <div class="doc_subsection">
829 <a name="moduleasm">Module-Level Inline Assembly</a>
832 <div class="doc_text">
834 Modules may contain "module-level inline asm" blocks, which corresponds to the
835 GCC "file scope inline asm" blocks. These blocks are internally concatenated by
836 LLVM and treated as a single unit, but may be separated in the .ll file if
837 desired. The syntax is very simple:
840 <div class="doc_code">
842 module asm "inline asm code goes here"
843 module asm "more can go here"
847 <p>The strings can contain any character by escaping non-printable characters.
848 The escape sequence used is simply "\xx" where "xx" is the two digit hex code
853 The inline asm code is simply printed to the machine code .s file when
854 assembly code is generated.
858 <!-- ======================================================================= -->
859 <div class="doc_subsection">
860 <a name="datalayout">Data Layout</a>
863 <div class="doc_text">
864 <p>A module may specify a target specific data layout string that specifies how
865 data is to be laid out in memory. The syntax for the data layout is simply:</p>
866 <pre> target datalayout = "<i>layout specification</i>"</pre>
867 <p>The <i>layout specification</i> consists of a list of specifications
868 separated by the minus sign character ('-'). Each specification starts with a
869 letter and may include other information after the letter to define some
870 aspect of the data layout. The specifications accepted are as follows: </p>
873 <dd>Specifies that the target lays out data in big-endian form. That is, the
874 bits with the most significance have the lowest address location.</dd>
876 <dd>Specifies that hte target lays out data in little-endian form. That is,
877 the bits with the least significance have the lowest address location.</dd>
878 <dt><tt>p:<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
879 <dd>This specifies the <i>size</i> of a pointer and its <i>abi</i> and
880 <i>preferred</i> alignments. All sizes are in bits. Specifying the <i>pref</i>
881 alignment is optional. If omitted, the preceding <tt>:</tt> should be omitted
883 <dt><tt>i<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
884 <dd>This specifies the alignment for an integer type of a given bit
885 <i>size</i>. The value of <i>size</i> must be in the range [1,2^23).</dd>
886 <dt><tt>v<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
887 <dd>This specifies the alignment for a vector type of a given bit
889 <dt><tt>f<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
890 <dd>This specifies the alignment for a floating point type of a given bit
891 <i>size</i>. The value of <i>size</i> must be either 32 (float) or 64
893 <dt><tt>a<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
894 <dd>This specifies the alignment for an aggregate type of a given bit
897 <p>When constructing the data layout for a given target, LLVM starts with a
898 default set of specifications which are then (possibly) overriden by the
899 specifications in the <tt>datalayout</tt> keyword. The default specifications
900 are given in this list:</p>
902 <li><tt>E</tt> - big endian</li>
903 <li><tt>p:32:64:64</tt> - 32-bit pointers with 64-bit alignment</li>
904 <li><tt>i1:8:8</tt> - i1 is 8-bit (byte) aligned</li>
905 <li><tt>i8:8:8</tt> - i8 is 8-bit (byte) aligned</li>
906 <li><tt>i16:16:16</tt> - i16 is 16-bit aligned</li>
907 <li><tt>i32:32:32</tt> - i32 is 32-bit aligned</li>
908 <li><tt>i64:32:64</tt> - i64 has abi alignment of 32-bits but preferred
909 alignment of 64-bits</li>
910 <li><tt>f32:32:32</tt> - float is 32-bit aligned</li>
911 <li><tt>f64:64:64</tt> - double is 64-bit aligned</li>
912 <li><tt>v64:64:64</tt> - 64-bit vector is 64-bit aligned</li>
913 <li><tt>v128:128:128</tt> - 128-bit vector is 128-bit aligned</li>
914 <li><tt>a0:0:1</tt> - aggregates are 8-bit aligned</li>
916 <p>When llvm is determining the alignment for a given type, it uses the
919 <li>If the type sought is an exact match for one of the specifications, that
920 specification is used.</li>
921 <li>If no match is found, and the type sought is an integer type, then the
922 smallest integer type that is larger than the bitwidth of the sought type is
923 used. If none of the specifications are larger than the bitwidth then the the
924 largest integer type is used. For example, given the default specifications
925 above, the i7 type will use the alignment of i8 (next largest) while both
926 i65 and i256 will use the alignment of i64 (largest specified).</li>
927 <li>If no match is found, and the type sought is a vector type, then the
928 largest vector type that is smaller than the sought vector type will be used
929 as a fall back. This happens because <128 x double> can be implemented in
930 terms of 64 <2 x double>, for example.</li>
934 <!-- *********************************************************************** -->
935 <div class="doc_section"> <a name="typesystem">Type System</a> </div>
936 <!-- *********************************************************************** -->
938 <div class="doc_text">
940 <p>The LLVM type system is one of the most important features of the
941 intermediate representation. Being typed enables a number of
942 optimizations to be performed on the IR directly, without having to do
943 extra analyses on the side before the transformation. A strong type
944 system makes it easier to read the generated code and enables novel
945 analyses and transformations that are not feasible to perform on normal
946 three address code representations.</p>
950 <!-- ======================================================================= -->
951 <div class="doc_subsection"> <a name="t_primitive">Primitive Types</a> </div>
952 <div class="doc_text">
953 <p>The primitive types are the fundamental building blocks of the LLVM
954 system. The current set of primitive types is as follows:</p>
956 <table class="layout">
961 <tr><th>Type</th><th>Description</th></tr>
962 <tr><td><tt><a name="t_void">void</a></tt></td><td>No value</td></tr>
963 <tr><td><tt>label</tt></td><td>Branch destination</td></tr>
970 <tr><th>Type</th><th>Description</th></tr>
971 <tr><td><tt>float</tt></td><td>32-bit floating point value</td></tr>
972 <tr><td><tt>double</tt></td><td>64-bit floating point value</td></tr>
980 <!-- _______________________________________________________________________ -->
981 <div class="doc_subsubsection"> <a name="t_classifications">Type
982 Classifications</a> </div>
983 <div class="doc_text">
984 <p>These different primitive types fall into a few useful
987 <table border="1" cellspacing="0" cellpadding="4">
989 <tr><th>Classification</th><th>Types</th></tr>
991 <td><a name="t_integer">integer</a></td>
992 <td><tt>i1, i2, i3, ... i8, ... i16, ... i32, ... i64, ... </tt></td>
995 <td><a name="t_floating">floating point</a></td>
996 <td><tt>float, double</tt></td>
999 <td><a name="t_firstclass">first class</a></td>
1000 <td><tt>i1, ..., float, double, <br/>
1001 <a href="#t_pointer">pointer</a>,<a href="#t_vector">vector</a></tt>
1007 <p>The <a href="#t_firstclass">first class</a> types are perhaps the
1008 most important. Values of these types are the only ones which can be
1009 produced by instructions, passed as arguments, or used as operands to
1010 instructions. This means that all structures and arrays must be
1011 manipulated either by pointer or by component.</p>
1014 <!-- ======================================================================= -->
1015 <div class="doc_subsection"> <a name="t_derived">Derived Types</a> </div>
1017 <div class="doc_text">
1019 <p>The real power in LLVM comes from the derived types in the system.
1020 This is what allows a programmer to represent arrays, functions,
1021 pointers, and other useful types. Note that these derived types may be
1022 recursive: For example, it is possible to have a two dimensional array.</p>
1026 <!-- _______________________________________________________________________ -->
1027 <div class="doc_subsubsection"> <a name="t_integer">Integer Type</a> </div>
1029 <div class="doc_text">
1032 <p>The integer type is a very simple derived type that simply specifies an
1033 arbitrary bit width for the integer type desired. Any bit width from 1 bit to
1034 2^23-1 (about 8 million) can be specified.</p>
1042 <p>The number of bits the integer will occupy is specified by the <tt>N</tt>
1046 <table class="layout">
1056 <tt>i1942652</tt><br/>
1059 A boolean integer of 1 bit<br/>
1060 A nibble sized integer of 4 bits.<br/>
1061 A byte sized integer of 8 bits.<br/>
1062 A half word sized integer of 16 bits.<br/>
1063 A word sized integer of 32 bits.<br/>
1064 An integer whose bit width is the answer. <br/>
1065 A double word sized integer of 64 bits.<br/>
1066 A really big integer of over 1 million bits.<br/>
1072 <!-- _______________________________________________________________________ -->
1073 <div class="doc_subsubsection"> <a name="t_array">Array Type</a> </div>
1075 <div class="doc_text">
1079 <p>The array type is a very simple derived type that arranges elements
1080 sequentially in memory. The array type requires a size (number of
1081 elements) and an underlying data type.</p>
1086 [<# elements> x <elementtype>]
1089 <p>The number of elements is a constant integer value; elementtype may
1090 be any type with a size.</p>
1093 <table class="layout">
1096 <tt>[40 x i32 ]</tt><br/>
1097 <tt>[41 x i32 ]</tt><br/>
1098 <tt>[40 x i8]</tt><br/>
1101 Array of 40 32-bit integer values.<br/>
1102 Array of 41 32-bit integer values.<br/>
1103 Array of 40 8-bit integer values.<br/>
1107 <p>Here are some examples of multidimensional arrays:</p>
1108 <table class="layout">
1111 <tt>[3 x [4 x i32]]</tt><br/>
1112 <tt>[12 x [10 x float]]</tt><br/>
1113 <tt>[2 x [3 x [4 x i16]]]</tt><br/>
1116 3x4 array of 32-bit integer values.<br/>
1117 12x10 array of single precision floating point values.<br/>
1118 2x3x4 array of 16-bit integer values.<br/>
1123 <p>Note that 'variable sized arrays' can be implemented in LLVM with a zero
1124 length array. Normally, accesses past the end of an array are undefined in
1125 LLVM (e.g. it is illegal to access the 5th element of a 3 element array).
1126 As a special case, however, zero length arrays are recognized to be variable
1127 length. This allows implementation of 'pascal style arrays' with the LLVM
1128 type "{ i32, [0 x float]}", for example.</p>
1132 <!-- _______________________________________________________________________ -->
1133 <div class="doc_subsubsection"> <a name="t_function">Function Type</a> </div>
1134 <div class="doc_text">
1136 <p>The function type can be thought of as a function signature. It
1137 consists of a return type and a list of formal parameter types.
1138 Function types are usually used to build virtual function tables
1139 (which are structures of pointers to functions), for indirect function
1140 calls, and when defining a function.</p>
1142 The return type of a function type cannot be an aggregate type.
1145 <pre> <returntype> (<parameter list>)<br></pre>
1146 <p>...where '<tt><parameter list></tt>' is a comma-separated list of type
1147 specifiers. Optionally, the parameter list may include a type <tt>...</tt>,
1148 which indicates that the function takes a variable number of arguments.
1149 Variable argument functions can access their arguments with the <a
1150 href="#int_varargs">variable argument handling intrinsic</a> functions.</p>
1152 <table class="layout">
1154 <td class="left"><tt>i32 (i32)</tt></td>
1155 <td class="left">function taking an <tt>i32</tt>, returning an <tt>i32</tt>
1157 </tr><tr class="layout">
1158 <td class="left"><tt>float (i16 signext, i32 *) *
1160 <td class="left"><a href="#t_pointer">Pointer</a> to a function that takes
1161 an <tt>i16</tt> that should be sign extended and a
1162 <a href="#t_pointer">pointer</a> to <tt>i32</tt>, returning
1165 </tr><tr class="layout">
1166 <td class="left"><tt>i32 (i8*, ...)</tt></td>
1167 <td class="left">A vararg function that takes at least one
1168 <a href="#t_pointer">pointer</a> to <tt>i8 </tt> (char in C),
1169 which returns an integer. This is the signature for <tt>printf</tt> in
1176 <!-- _______________________________________________________________________ -->
1177 <div class="doc_subsubsection"> <a name="t_struct">Structure Type</a> </div>
1178 <div class="doc_text">
1180 <p>The structure type is used to represent a collection of data members
1181 together in memory. The packing of the field types is defined to match
1182 the ABI of the underlying processor. The elements of a structure may
1183 be any type that has a size.</p>
1184 <p>Structures are accessed using '<tt><a href="#i_load">load</a></tt>
1185 and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a
1186 field with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>'
1189 <pre> { <type list> }<br></pre>
1191 <table class="layout">
1193 <td class="left"><tt>{ i32, i32, i32 }</tt></td>
1194 <td class="left">A triple of three <tt>i32</tt> values</td>
1195 </tr><tr class="layout">
1196 <td class="left"><tt>{ float, i32 (i32) * }</tt></td>
1197 <td class="left">A pair, where the first element is a <tt>float</tt> and the
1198 second element is a <a href="#t_pointer">pointer</a> to a
1199 <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
1200 an <tt>i32</tt>.</td>
1205 <!-- _______________________________________________________________________ -->
1206 <div class="doc_subsubsection"> <a name="t_pstruct">Packed Structure Type</a>
1208 <div class="doc_text">
1210 <p>The packed structure type is used to represent a collection of data members
1211 together in memory. There is no padding between fields. Further, the alignment
1212 of a packed structure is 1 byte. The elements of a packed structure may
1213 be any type that has a size.</p>
1214 <p>Structures are accessed using '<tt><a href="#i_load">load</a></tt>
1215 and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a
1216 field with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>'
1219 <pre> < { <type list> } > <br></pre>
1221 <table class="layout">
1223 <td class="left"><tt>< { i32, i32, i32 } ></tt></td>
1224 <td class="left">A triple of three <tt>i32</tt> values</td>
1225 </tr><tr class="layout">
1226 <td class="left"><tt>< { float, i32 (i32) * } ></tt></td>
1227 <td class="left">A pair, where the first element is a <tt>float</tt> and the
1228 second element is a <a href="#t_pointer">pointer</a> to a
1229 <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
1230 an <tt>i32</tt>.</td>
1235 <!-- _______________________________________________________________________ -->
1236 <div class="doc_subsubsection"> <a name="t_pointer">Pointer Type</a> </div>
1237 <div class="doc_text">
1239 <p>As in many languages, the pointer type represents a pointer or
1240 reference to another object, which must live in memory.</p>
1242 <pre> <type> *<br></pre>
1244 <table class="layout">
1247 <tt>[4x i32]*</tt><br/>
1248 <tt>i32 (i32 *) *</tt><br/>
1251 A <a href="#t_pointer">pointer</a> to <a href="#t_array">array</a> of
1252 four <tt>i32</tt> values<br/>
1253 A <a href="#t_pointer">pointer</a> to a <a
1254 href="#t_function">function</a> that takes an <tt>i32*</tt>, returning an
1261 <!-- _______________________________________________________________________ -->
1262 <div class="doc_subsubsection"> <a name="t_vector">Vector Type</a> </div>
1263 <div class="doc_text">
1267 <p>A vector type is a simple derived type that represents a vector
1268 of elements. Vector types are used when multiple primitive data
1269 are operated in parallel using a single instruction (SIMD).
1270 A vector type requires a size (number of
1271 elements) and an underlying primitive data type. Vectors must have a power
1272 of two length (1, 2, 4, 8, 16 ...). Vector types are
1273 considered <a href="#t_firstclass">first class</a>.</p>
1278 < <# elements> x <elementtype> >
1281 <p>The number of elements is a constant integer value; elementtype may
1282 be any integer or floating point type.</p>
1286 <table class="layout">
1289 <tt><4 x i32></tt><br/>
1290 <tt><8 x float></tt><br/>
1291 <tt><2 x i64></tt><br/>
1294 Vector of 4 32-bit integer values.<br/>
1295 Vector of 8 floating-point values.<br/>
1296 Vector of 2 64-bit integer values.<br/>
1302 <!-- _______________________________________________________________________ -->
1303 <div class="doc_subsubsection"> <a name="t_opaque">Opaque Type</a> </div>
1304 <div class="doc_text">
1308 <p>Opaque types are used to represent unknown types in the system. This
1309 corresponds (for example) to the C notion of a forward declared structure type.
1310 In LLVM, opaque types can eventually be resolved to any type (not just a
1311 structure type).</p>
1321 <table class="layout">
1327 An opaque type.<br/>
1334 <!-- *********************************************************************** -->
1335 <div class="doc_section"> <a name="constants">Constants</a> </div>
1336 <!-- *********************************************************************** -->
1338 <div class="doc_text">
1340 <p>LLVM has several different basic types of constants. This section describes
1341 them all and their syntax.</p>
1345 <!-- ======================================================================= -->
1346 <div class="doc_subsection"><a name="simpleconstants">Simple Constants</a></div>
1348 <div class="doc_text">
1351 <dt><b>Boolean constants</b></dt>
1353 <dd>The two strings '<tt>true</tt>' and '<tt>false</tt>' are both valid
1354 constants of the <tt><a href="#t_primitive">i1</a></tt> type.
1357 <dt><b>Integer constants</b></dt>
1359 <dd>Standard integers (such as '4') are constants of the <a
1360 href="#t_integer">integer</a> type. Negative numbers may be used with
1364 <dt><b>Floating point constants</b></dt>
1366 <dd>Floating point constants use standard decimal notation (e.g. 123.421),
1367 exponential notation (e.g. 1.23421e+2), or a more precise hexadecimal
1368 notation (see below). Floating point constants must have a <a
1369 href="#t_floating">floating point</a> type. </dd>
1371 <dt><b>Null pointer constants</b></dt>
1373 <dd>The identifier '<tt>null</tt>' is recognized as a null pointer constant
1374 and must be of <a href="#t_pointer">pointer type</a>.</dd>
1378 <p>The one non-intuitive notation for constants is the optional hexadecimal form
1379 of floating point constants. For example, the form '<tt>double
1380 0x432ff973cafa8000</tt>' is equivalent to (but harder to read than) '<tt>double
1381 4.5e+15</tt>'. The only time hexadecimal floating point constants are required
1382 (and the only time that they are generated by the disassembler) is when a
1383 floating point constant must be emitted but it cannot be represented as a
1384 decimal floating point number. For example, NaN's, infinities, and other
1385 special values are represented in their IEEE hexadecimal format so that
1386 assembly and disassembly do not cause any bits to change in the constants.</p>
1390 <!-- ======================================================================= -->
1391 <div class="doc_subsection"><a name="aggregateconstants">Aggregate Constants</a>
1394 <div class="doc_text">
1395 <p>Aggregate constants arise from aggregation of simple constants
1396 and smaller aggregate constants.</p>
1399 <dt><b>Structure constants</b></dt>
1401 <dd>Structure constants are represented with notation similar to structure
1402 type definitions (a comma separated list of elements, surrounded by braces
1403 (<tt>{}</tt>)). For example: "<tt>{ i32 4, float 17.0, i32* %G }</tt>",
1404 where "<tt>%G</tt>" is declared as "<tt>@G = external global i32</tt>". Structure constants
1405 must have <a href="#t_struct">structure type</a>, and the number and
1406 types of elements must match those specified by the type.
1409 <dt><b>Array constants</b></dt>
1411 <dd>Array constants are represented with notation similar to array type
1412 definitions (a comma separated list of elements, surrounded by square brackets
1413 (<tt>[]</tt>)). For example: "<tt>[ i32 42, i32 11, i32 74 ]</tt>". Array
1414 constants must have <a href="#t_array">array type</a>, and the number and
1415 types of elements must match those specified by the type.
1418 <dt><b>Vector constants</b></dt>
1420 <dd>Vector constants are represented with notation similar to vector type
1421 definitions (a comma separated list of elements, surrounded by
1422 less-than/greater-than's (<tt><></tt>)). For example: "<tt>< i32 42,
1423 i32 11, i32 74, i32 100 ></tt>". Vector constants must have <a
1424 href="#t_vector">vector type</a>, and the number and types of elements must
1425 match those specified by the type.
1428 <dt><b>Zero initialization</b></dt>
1430 <dd>The string '<tt>zeroinitializer</tt>' can be used to zero initialize a
1431 value to zero of <em>any</em> type, including scalar and aggregate types.
1432 This is often used to avoid having to print large zero initializers (e.g. for
1433 large arrays) and is always exactly equivalent to using explicit zero
1440 <!-- ======================================================================= -->
1441 <div class="doc_subsection">
1442 <a name="globalconstants">Global Variable and Function Addresses</a>
1445 <div class="doc_text">
1447 <p>The addresses of <a href="#globalvars">global variables</a> and <a
1448 href="#functionstructure">functions</a> are always implicitly valid (link-time)
1449 constants. These constants are explicitly referenced when the <a
1450 href="#identifiers">identifier for the global</a> is used and always have <a
1451 href="#t_pointer">pointer</a> type. For example, the following is a legal LLVM
1454 <div class="doc_code">
1458 @Z = global [2 x i32*] [ i32* @X, i32* @Y ]
1464 <!-- ======================================================================= -->
1465 <div class="doc_subsection"><a name="undefvalues">Undefined Values</a></div>
1466 <div class="doc_text">
1467 <p>The string '<tt>undef</tt>' is recognized as a type-less constant that has
1468 no specific value. Undefined values may be of any type and be used anywhere
1469 a constant is permitted.</p>
1471 <p>Undefined values indicate to the compiler that the program is well defined
1472 no matter what value is used, giving the compiler more freedom to optimize.
1476 <!-- ======================================================================= -->
1477 <div class="doc_subsection"><a name="constantexprs">Constant Expressions</a>
1480 <div class="doc_text">
1482 <p>Constant expressions are used to allow expressions involving other constants
1483 to be used as constants. Constant expressions may be of any <a
1484 href="#t_firstclass">first class</a> type and may involve any LLVM operation
1485 that does not have side effects (e.g. load and call are not supported). The
1486 following is the syntax for constant expressions:</p>
1489 <dt><b><tt>trunc ( CST to TYPE )</tt></b></dt>
1490 <dd>Truncate a constant to another type. The bit size of CST must be larger
1491 than the bit size of TYPE. Both types must be integers.</dd>
1493 <dt><b><tt>zext ( CST to TYPE )</tt></b></dt>
1494 <dd>Zero extend a constant to another type. The bit size of CST must be
1495 smaller or equal to the bit size of TYPE. Both types must be integers.</dd>
1497 <dt><b><tt>sext ( CST to TYPE )</tt></b></dt>
1498 <dd>Sign extend a constant to another type. The bit size of CST must be
1499 smaller or equal to the bit size of TYPE. Both types must be integers.</dd>
1501 <dt><b><tt>fptrunc ( CST to TYPE )</tt></b></dt>
1502 <dd>Truncate a floating point constant to another floating point type. The
1503 size of CST must be larger than the size of TYPE. Both types must be
1504 floating point.</dd>
1506 <dt><b><tt>fpext ( CST to TYPE )</tt></b></dt>
1507 <dd>Floating point extend a constant to another type. The size of CST must be
1508 smaller or equal to the size of TYPE. Both types must be floating point.</dd>
1510 <dt><b><tt>fptoui ( CST to TYPE )</tt></b></dt>
1511 <dd>Convert a floating point constant to the corresponding unsigned integer
1512 constant. TYPE must be a scalar or vector integer type. CST must be of scalar
1513 or vector floating point type. Both CST and TYPE must be scalars, or vectors
1514 of the same number of elements. If the value won't fit in the integer type,
1515 the results are undefined.</dd>
1517 <dt><b><tt>fptosi ( CST to TYPE )</tt></b></dt>
1518 <dd>Convert a floating point constant to the corresponding signed integer
1519 constant. TYPE must be a scalar or vector integer type. CST must be of scalar
1520 or vector floating point type. Both CST and TYPE must be scalars, or vectors
1521 of the same number of elements. If the value won't fit in the integer type,
1522 the results are undefined.</dd>
1524 <dt><b><tt>uitofp ( CST to TYPE )</tt></b></dt>
1525 <dd>Convert an unsigned integer constant to the corresponding floating point
1526 constant. TYPE must be a scalar or vector floating point type. CST must be of
1527 scalar or vector integer type. Both CST and TYPE must be scalars, or vectors
1528 of the same number of elements. If the value won't fit in the floating point
1529 type, the results are undefined.</dd>
1531 <dt><b><tt>sitofp ( CST to TYPE )</tt></b></dt>
1532 <dd>Convert a signed integer constant to the corresponding floating point
1533 constant. TYPE must be a scalar or vector floating point type. CST must be of
1534 scalar or vector integer type. Both CST and TYPE must be scalars, or vectors
1535 of the same number of elements. If the value won't fit in the floating point
1536 type, the results are undefined.</dd>
1538 <dt><b><tt>ptrtoint ( CST to TYPE )</tt></b></dt>
1539 <dd>Convert a pointer typed constant to the corresponding integer constant
1540 TYPE must be an integer type. CST must be of pointer type. The CST value is
1541 zero extended, truncated, or unchanged to make it fit in TYPE.</dd>
1543 <dt><b><tt>inttoptr ( CST to TYPE )</tt></b></dt>
1544 <dd>Convert a integer constant to a pointer constant. TYPE must be a
1545 pointer type. CST must be of integer type. The CST value is zero extended,
1546 truncated, or unchanged to make it fit in a pointer size. This one is
1547 <i>really</i> dangerous!</dd>
1549 <dt><b><tt>bitcast ( CST to TYPE )</tt></b></dt>
1550 <dd>Convert a constant, CST, to another TYPE. The size of CST and TYPE must be
1551 identical (same number of bits). The conversion is done as if the CST value
1552 was stored to memory and read back as TYPE. In other words, no bits change
1553 with this operator, just the type. This can be used for conversion of
1554 vector types to any other type, as long as they have the same bit width. For
1555 pointers it is only valid to cast to another pointer type.
1558 <dt><b><tt>getelementptr ( CSTPTR, IDX0, IDX1, ... )</tt></b></dt>
1560 <dd>Perform the <a href="#i_getelementptr">getelementptr operation</a> on
1561 constants. As with the <a href="#i_getelementptr">getelementptr</a>
1562 instruction, the index list may have zero or more indexes, which are required
1563 to make sense for the type of "CSTPTR".</dd>
1565 <dt><b><tt>select ( COND, VAL1, VAL2 )</tt></b></dt>
1567 <dd>Perform the <a href="#i_select">select operation</a> on
1570 <dt><b><tt>icmp COND ( VAL1, VAL2 )</tt></b></dt>
1571 <dd>Performs the <a href="#i_icmp">icmp operation</a> on constants.</dd>
1573 <dt><b><tt>fcmp COND ( VAL1, VAL2 )</tt></b></dt>
1574 <dd>Performs the <a href="#i_fcmp">fcmp operation</a> on constants.</dd>
1576 <dt><b><tt>extractelement ( VAL, IDX )</tt></b></dt>
1578 <dd>Perform the <a href="#i_extractelement">extractelement
1579 operation</a> on constants.
1581 <dt><b><tt>insertelement ( VAL, ELT, IDX )</tt></b></dt>
1583 <dd>Perform the <a href="#i_insertelement">insertelement
1584 operation</a> on constants.</dd>
1587 <dt><b><tt>shufflevector ( VEC1, VEC2, IDXMASK )</tt></b></dt>
1589 <dd>Perform the <a href="#i_shufflevector">shufflevector
1590 operation</a> on constants.</dd>
1592 <dt><b><tt>OPCODE ( LHS, RHS )</tt></b></dt>
1594 <dd>Perform the specified operation of the LHS and RHS constants. OPCODE may
1595 be any of the <a href="#binaryops">binary</a> or <a href="#bitwiseops">bitwise
1596 binary</a> operations. The constraints on operands are the same as those for
1597 the corresponding instruction (e.g. no bitwise operations on floating point
1598 values are allowed).</dd>
1602 <!-- *********************************************************************** -->
1603 <div class="doc_section"> <a name="othervalues">Other Values</a> </div>
1604 <!-- *********************************************************************** -->
1606 <!-- ======================================================================= -->
1607 <div class="doc_subsection">
1608 <a name="inlineasm">Inline Assembler Expressions</a>
1611 <div class="doc_text">
1614 LLVM supports inline assembler expressions (as opposed to <a href="#moduleasm">
1615 Module-Level Inline Assembly</a>) through the use of a special value. This
1616 value represents the inline assembler as a string (containing the instructions
1617 to emit), a list of operand constraints (stored as a string), and a flag that
1618 indicates whether or not the inline asm expression has side effects. An example
1619 inline assembler expression is:
1622 <div class="doc_code">
1624 i32 (i32) asm "bswap $0", "=r,r"
1629 Inline assembler expressions may <b>only</b> be used as the callee operand of
1630 a <a href="#i_call"><tt>call</tt> instruction</a>. Thus, typically we have:
1633 <div class="doc_code">
1635 %X = call i32 asm "<a href="#int_bswap">bswap</a> $0", "=r,r"(i32 %Y)
1640 Inline asms with side effects not visible in the constraint list must be marked
1641 as having side effects. This is done through the use of the
1642 '<tt>sideeffect</tt>' keyword, like so:
1645 <div class="doc_code">
1647 call void asm sideeffect "eieio", ""()
1651 <p>TODO: The format of the asm and constraints string still need to be
1652 documented here. Constraints on what can be done (e.g. duplication, moving, etc
1653 need to be documented).
1658 <!-- *********************************************************************** -->
1659 <div class="doc_section"> <a name="instref">Instruction Reference</a> </div>
1660 <!-- *********************************************************************** -->
1662 <div class="doc_text">
1664 <p>The LLVM instruction set consists of several different
1665 classifications of instructions: <a href="#terminators">terminator
1666 instructions</a>, <a href="#binaryops">binary instructions</a>,
1667 <a href="#bitwiseops">bitwise binary instructions</a>, <a
1668 href="#memoryops">memory instructions</a>, and <a href="#otherops">other
1669 instructions</a>.</p>
1673 <!-- ======================================================================= -->
1674 <div class="doc_subsection"> <a name="terminators">Terminator
1675 Instructions</a> </div>
1677 <div class="doc_text">
1679 <p>As mentioned <a href="#functionstructure">previously</a>, every
1680 basic block in a program ends with a "Terminator" instruction, which
1681 indicates which block should be executed after the current block is
1682 finished. These terminator instructions typically yield a '<tt>void</tt>'
1683 value: they produce control flow, not values (the one exception being
1684 the '<a href="#i_invoke"><tt>invoke</tt></a>' instruction).</p>
1685 <p>There are six different terminator instructions: the '<a
1686 href="#i_ret"><tt>ret</tt></a>' instruction, the '<a href="#i_br"><tt>br</tt></a>'
1687 instruction, the '<a href="#i_switch"><tt>switch</tt></a>' instruction,
1688 the '<a href="#i_invoke"><tt>invoke</tt></a>' instruction, the '<a
1689 href="#i_unwind"><tt>unwind</tt></a>' instruction, and the '<a
1690 href="#i_unreachable"><tt>unreachable</tt></a>' instruction.</p>
1694 <!-- _______________________________________________________________________ -->
1695 <div class="doc_subsubsection"> <a name="i_ret">'<tt>ret</tt>'
1696 Instruction</a> </div>
1697 <div class="doc_text">
1699 <pre> ret <type> <value> <i>; Return a value from a non-void function</i>
1700 ret void <i>; Return from void function</i>
1703 <p>The '<tt>ret</tt>' instruction is used to return control flow (and a
1704 value) from a function back to the caller.</p>
1705 <p>There are two forms of the '<tt>ret</tt>' instruction: one that
1706 returns a value and then causes control flow, and one that just causes
1707 control flow to occur.</p>
1709 <p>The '<tt>ret</tt>' instruction may return any '<a
1710 href="#t_firstclass">first class</a>' type. Notice that a function is
1711 not <a href="#wellformed">well formed</a> if there exists a '<tt>ret</tt>'
1712 instruction inside of the function that returns a value that does not
1713 match the return type of the function.</p>
1715 <p>When the '<tt>ret</tt>' instruction is executed, control flow
1716 returns back to the calling function's context. If the caller is a "<a
1717 href="#i_call"><tt>call</tt></a>" instruction, execution continues at
1718 the instruction after the call. If the caller was an "<a
1719 href="#i_invoke"><tt>invoke</tt></a>" instruction, execution continues
1720 at the beginning of the "normal" destination block. If the instruction
1721 returns a value, that value shall set the call or invoke instruction's
1724 <pre> ret i32 5 <i>; Return an integer value of 5</i>
1725 ret void <i>; Return from a void function</i>
1728 <!-- _______________________________________________________________________ -->
1729 <div class="doc_subsubsection"> <a name="i_br">'<tt>br</tt>' Instruction</a> </div>
1730 <div class="doc_text">
1732 <pre> br i1 <cond>, label <iftrue>, label <iffalse><br> br label <dest> <i>; Unconditional branch</i>
1735 <p>The '<tt>br</tt>' instruction is used to cause control flow to
1736 transfer to a different basic block in the current function. There are
1737 two forms of this instruction, corresponding to a conditional branch
1738 and an unconditional branch.</p>
1740 <p>The conditional branch form of the '<tt>br</tt>' instruction takes a
1741 single '<tt>i1</tt>' value and two '<tt>label</tt>' values. The
1742 unconditional form of the '<tt>br</tt>' instruction takes a single
1743 '<tt>label</tt>' value as a target.</p>
1745 <p>Upon execution of a conditional '<tt>br</tt>' instruction, the '<tt>i1</tt>'
1746 argument is evaluated. If the value is <tt>true</tt>, control flows
1747 to the '<tt>iftrue</tt>' <tt>label</tt> argument. If "cond" is <tt>false</tt>,
1748 control flows to the '<tt>iffalse</tt>' <tt>label</tt> argument.</p>
1750 <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
1751 href="#i_ret">ret</a> i32 1<br>IfUnequal:<br> <a href="#i_ret">ret</a> i32 0<br></pre>
1753 <!-- _______________________________________________________________________ -->
1754 <div class="doc_subsubsection">
1755 <a name="i_switch">'<tt>switch</tt>' Instruction</a>
1758 <div class="doc_text">
1762 switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]
1767 <p>The '<tt>switch</tt>' instruction is used to transfer control flow to one of
1768 several different places. It is a generalization of the '<tt>br</tt>'
1769 instruction, allowing a branch to occur to one of many possible
1775 <p>The '<tt>switch</tt>' instruction uses three parameters: an integer
1776 comparison value '<tt>value</tt>', a default '<tt>label</tt>' destination, and
1777 an array of pairs of comparison value constants and '<tt>label</tt>'s. The
1778 table is not allowed to contain duplicate constant entries.</p>
1782 <p>The <tt>switch</tt> instruction specifies a table of values and
1783 destinations. When the '<tt>switch</tt>' instruction is executed, this
1784 table is searched for the given value. If the value is found, control flow is
1785 transfered to the corresponding destination; otherwise, control flow is
1786 transfered to the default destination.</p>
1788 <h5>Implementation:</h5>
1790 <p>Depending on properties of the target machine and the particular
1791 <tt>switch</tt> instruction, this instruction may be code generated in different
1792 ways. For example, it could be generated as a series of chained conditional
1793 branches or with a lookup table.</p>
1798 <i>; Emulate a conditional br instruction</i>
1799 %Val = <a href="#i_zext">zext</a> i1 %value to i32
1800 switch i32 %Val, label %truedest [i32 0, label %falsedest ]
1802 <i>; Emulate an unconditional br instruction</i>
1803 switch i32 0, label %dest [ ]
1805 <i>; Implement a jump table:</i>
1806 switch i32 %val, label %otherwise [ i32 0, label %onzero
1808 i32 2, label %ontwo ]
1812 <!-- _______________________________________________________________________ -->
1813 <div class="doc_subsubsection">
1814 <a name="i_invoke">'<tt>invoke</tt>' Instruction</a>
1817 <div class="doc_text">
1822 <result> = invoke [<a href="#callingconv">cconv</a>] <ptr to function ty> %<function ptr val>(<function args>)
1823 to label <normal label> unwind label <exception label>
1828 <p>The '<tt>invoke</tt>' instruction causes control to transfer to a specified
1829 function, with the possibility of control flow transfer to either the
1830 '<tt>normal</tt>' label or the
1831 '<tt>exception</tt>' label. If the callee function returns with the
1832 "<tt><a href="#i_ret">ret</a></tt>" instruction, control flow will return to the
1833 "normal" label. If the callee (or any indirect callees) returns with the "<a
1834 href="#i_unwind"><tt>unwind</tt></a>" instruction, control is interrupted and
1835 continued at the dynamically nearest "exception" label.</p>
1839 <p>This instruction requires several arguments:</p>
1843 The optional "cconv" marker indicates which <a href="#callingconv">calling
1844 convention</a> the call should use. If none is specified, the call defaults
1845 to using C calling conventions.
1847 <li>'<tt>ptr to function ty</tt>': shall be the signature of the pointer to
1848 function value being invoked. In most cases, this is a direct function
1849 invocation, but indirect <tt>invoke</tt>s are just as possible, branching off
1850 an arbitrary pointer to function value.
1853 <li>'<tt>function ptr val</tt>': An LLVM value containing a pointer to a
1854 function to be invoked. </li>
1856 <li>'<tt>function args</tt>': argument list whose types match the function
1857 signature argument types. If the function signature indicates the function
1858 accepts a variable number of arguments, the extra arguments can be
1861 <li>'<tt>normal label</tt>': the label reached when the called function
1862 executes a '<tt><a href="#i_ret">ret</a></tt>' instruction. </li>
1864 <li>'<tt>exception label</tt>': the label reached when a callee returns with
1865 the <a href="#i_unwind"><tt>unwind</tt></a> instruction. </li>
1871 <p>This instruction is designed to operate as a standard '<tt><a
1872 href="#i_call">call</a></tt>' instruction in most regards. The primary
1873 difference is that it establishes an association with a label, which is used by
1874 the runtime library to unwind the stack.</p>
1876 <p>This instruction is used in languages with destructors to ensure that proper
1877 cleanup is performed in the case of either a <tt>longjmp</tt> or a thrown
1878 exception. Additionally, this is important for implementation of
1879 '<tt>catch</tt>' clauses in high-level languages that support them.</p>
1883 %retval = invoke i32 %Test(i32 15) to label %Continue
1884 unwind label %TestCleanup <i>; {i32}:retval set</i>
1885 %retval = invoke <a href="#callingconv">coldcc</a> i32 %Test(i32 15) to label %Continue
1886 unwind label %TestCleanup <i>; {i32}:retval set</i>
1891 <!-- _______________________________________________________________________ -->
1893 <div class="doc_subsubsection"> <a name="i_unwind">'<tt>unwind</tt>'
1894 Instruction</a> </div>
1896 <div class="doc_text">
1905 <p>The '<tt>unwind</tt>' instruction unwinds the stack, continuing control flow
1906 at the first callee in the dynamic call stack which used an <a
1907 href="#i_invoke"><tt>invoke</tt></a> instruction to perform the call. This is
1908 primarily used to implement exception handling.</p>
1912 <p>The '<tt>unwind</tt>' intrinsic causes execution of the current function to
1913 immediately halt. The dynamic call stack is then searched for the first <a
1914 href="#i_invoke"><tt>invoke</tt></a> instruction on the call stack. Once found,
1915 execution continues at the "exceptional" destination block specified by the
1916 <tt>invoke</tt> instruction. If there is no <tt>invoke</tt> instruction in the
1917 dynamic call chain, undefined behavior results.</p>
1920 <!-- _______________________________________________________________________ -->
1922 <div class="doc_subsubsection"> <a name="i_unreachable">'<tt>unreachable</tt>'
1923 Instruction</a> </div>
1925 <div class="doc_text">
1934 <p>The '<tt>unreachable</tt>' instruction has no defined semantics. This
1935 instruction is used to inform the optimizer that a particular portion of the
1936 code is not reachable. This can be used to indicate that the code after a
1937 no-return function cannot be reached, and other facts.</p>
1941 <p>The '<tt>unreachable</tt>' instruction has no defined semantics.</p>
1946 <!-- ======================================================================= -->
1947 <div class="doc_subsection"> <a name="binaryops">Binary Operations</a> </div>
1948 <div class="doc_text">
1949 <p>Binary operators are used to do most of the computation in a
1950 program. They require two operands, execute an operation on them, and
1951 produce a single value. The operands might represent
1952 multiple data, as is the case with the <a href="#t_vector">vector</a> data type.
1953 The result value of a binary operator is not
1954 necessarily the same type as its operands.</p>
1955 <p>There are several different binary operators:</p>
1957 <!-- _______________________________________________________________________ -->
1958 <div class="doc_subsubsection"> <a name="i_add">'<tt>add</tt>'
1959 Instruction</a> </div>
1960 <div class="doc_text">
1962 <pre> <result> = add <ty> <var1>, <var2> <i>; yields {ty}:result</i>
1965 <p>The '<tt>add</tt>' instruction returns the sum of its two operands.</p>
1967 <p>The two arguments to the '<tt>add</tt>' instruction must be either <a
1968 href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> values.
1969 This instruction can also take <a href="#t_vector">vector</a> versions of the values.
1970 Both arguments must have identical types.</p>
1972 <p>The value produced is the integer or floating point sum of the two
1975 <pre> <result> = add i32 4, %var <i>; yields {i32}:result = 4 + %var</i>
1978 <!-- _______________________________________________________________________ -->
1979 <div class="doc_subsubsection"> <a name="i_sub">'<tt>sub</tt>'
1980 Instruction</a> </div>
1981 <div class="doc_text">
1983 <pre> <result> = sub <ty> <var1>, <var2> <i>; yields {ty}:result</i>
1986 <p>The '<tt>sub</tt>' instruction returns the difference of its two
1988 <p>Note that the '<tt>sub</tt>' instruction is used to represent the '<tt>neg</tt>'
1989 instruction present in most other intermediate representations.</p>
1991 <p>The two arguments to the '<tt>sub</tt>' instruction must be either <a
1992 href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
1994 This instruction can also take <a href="#t_vector">vector</a> versions of the values.
1995 Both arguments must have identical types.</p>
1997 <p>The value produced is the integer or floating point difference of
1998 the two operands.</p>
2001 <result> = sub i32 4, %var <i>; yields {i32}:result = 4 - %var</i>
2002 <result> = sub i32 0, %val <i>; yields {i32}:result = -%var</i>
2005 <!-- _______________________________________________________________________ -->
2006 <div class="doc_subsubsection"> <a name="i_mul">'<tt>mul</tt>'
2007 Instruction</a> </div>
2008 <div class="doc_text">
2010 <pre> <result> = mul <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2013 <p>The '<tt>mul</tt>' instruction returns the product of its two
2016 <p>The two arguments to the '<tt>mul</tt>' instruction must be either <a
2017 href="#t_integer">integer</a> or <a href="#t_floating">floating point</a>
2019 This instruction can also take <a href="#t_vector">vector</a> versions of the values.
2020 Both arguments must have identical types.</p>
2022 <p>The value produced is the integer or floating point product of the
2024 <p>Because the operands are the same width, the result of an integer
2025 multiplication is the same whether the operands should be deemed unsigned or
2028 <pre> <result> = mul i32 4, %var <i>; yields {i32}:result = 4 * %var</i>
2031 <!-- _______________________________________________________________________ -->
2032 <div class="doc_subsubsection"> <a name="i_udiv">'<tt>udiv</tt>' Instruction
2034 <div class="doc_text">
2036 <pre> <result> = udiv <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2039 <p>The '<tt>udiv</tt>' instruction returns the quotient of its two
2042 <p>The two arguments to the '<tt>udiv</tt>' instruction must be
2043 <a href="#t_integer">integer</a> values. Both arguments must have identical
2044 types. This instruction can also take <a href="#t_vector">vector</a> versions
2045 of the values in which case the elements must be integers.</p>
2047 <p>The value produced is the unsigned integer quotient of the two operands. This
2048 instruction always performs an unsigned division operation, regardless of
2049 whether the arguments are unsigned or not.</p>
2051 <pre> <result> = udiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>
2054 <!-- _______________________________________________________________________ -->
2055 <div class="doc_subsubsection"> <a name="i_sdiv">'<tt>sdiv</tt>' Instruction
2057 <div class="doc_text">
2059 <pre> <result> = sdiv <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2062 <p>The '<tt>sdiv</tt>' instruction returns the quotient of its two
2065 <p>The two arguments to the '<tt>sdiv</tt>' instruction must be
2066 <a href="#t_integer">integer</a> values. Both arguments must have identical
2067 types. This instruction can also take <a href="#t_vector">vector</a> versions
2068 of the values in which case the elements must be integers.</p>
2070 <p>The value produced is the signed integer quotient of the two operands. This
2071 instruction always performs a signed division operation, regardless of whether
2072 the arguments are signed or not.</p>
2074 <pre> <result> = sdiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>
2077 <!-- _______________________________________________________________________ -->
2078 <div class="doc_subsubsection"> <a name="i_fdiv">'<tt>fdiv</tt>'
2079 Instruction</a> </div>
2080 <div class="doc_text">
2082 <pre> <result> = fdiv <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2085 <p>The '<tt>fdiv</tt>' instruction returns the quotient of its two
2088 <p>The two arguments to the '<tt>fdiv</tt>' instruction must be
2089 <a href="#t_floating">floating point</a> values. Both arguments must have
2090 identical types. This instruction can also take <a href="#t_vector">vector</a>
2091 versions of floating point values.</p>
2093 <p>The value produced is the floating point quotient of the two operands.</p>
2095 <pre> <result> = fdiv float 4.0, %var <i>; yields {float}:result = 4.0 / %var</i>
2098 <!-- _______________________________________________________________________ -->
2099 <div class="doc_subsubsection"> <a name="i_urem">'<tt>urem</tt>' Instruction</a>
2101 <div class="doc_text">
2103 <pre> <result> = urem <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2106 <p>The '<tt>urem</tt>' instruction returns the remainder from the
2107 unsigned division of its two arguments.</p>
2109 <p>The two arguments to the '<tt>urem</tt>' instruction must be
2110 <a href="#t_integer">integer</a> values. Both arguments must have identical
2111 types. This instruction can also take <a href="#t_vector">vector</a> versions
2112 of the values in which case the elements must be integers.</p>
2114 <p>This instruction returns the unsigned integer <i>remainder</i> of a division.
2115 This instruction always performs an unsigned division to get the remainder,
2116 regardless of whether the arguments are unsigned or not.</p>
2118 <pre> <result> = urem i32 4, %var <i>; yields {i32}:result = 4 % %var</i>
2122 <!-- _______________________________________________________________________ -->
2123 <div class="doc_subsubsection"> <a name="i_srem">'<tt>srem</tt>'
2124 Instruction</a> </div>
2125 <div class="doc_text">
2127 <pre> <result> = srem <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2130 <p>The '<tt>srem</tt>' instruction returns the remainder from the
2131 signed division of its two operands. This instruction can also take
2132 <a href="#t_vector">vector</a> versions of the values in which case
2133 the elements must be integers.</p>
2136 <p>The two arguments to the '<tt>srem</tt>' instruction must be
2137 <a href="#t_integer">integer</a> values. Both arguments must have identical
2140 <p>This instruction returns the <i>remainder</i> of a division (where the result
2141 has the same sign as the dividend, <tt>var1</tt>), not the <i>modulo</i>
2142 operator (where the result has the same sign as the divisor, <tt>var2</tt>) of
2143 a value. For more information about the difference, see <a
2144 href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The
2145 Math Forum</a>. For a table of how this is implemented in various languages,
2146 please see <a href="http://en.wikipedia.org/wiki/Modulo_operation">
2147 Wikipedia: modulo operation</a>.</p>
2149 <pre> <result> = srem i32 4, %var <i>; yields {i32}:result = 4 % %var</i>
2153 <!-- _______________________________________________________________________ -->
2154 <div class="doc_subsubsection"> <a name="i_frem">'<tt>frem</tt>'
2155 Instruction</a> </div>
2156 <div class="doc_text">
2158 <pre> <result> = frem <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2161 <p>The '<tt>frem</tt>' instruction returns the remainder from the
2162 division of its two operands.</p>
2164 <p>The two arguments to the '<tt>frem</tt>' instruction must be
2165 <a href="#t_floating">floating point</a> values. Both arguments must have
2166 identical types. This instruction can also take <a href="#t_vector">vector</a>
2167 versions of floating point values.</p>
2169 <p>This instruction returns the <i>remainder</i> of a division.</p>
2171 <pre> <result> = frem float 4.0, %var <i>; yields {float}:result = 4.0 % %var</i>
2175 <!-- ======================================================================= -->
2176 <div class="doc_subsection"> <a name="bitwiseops">Bitwise Binary
2177 Operations</a> </div>
2178 <div class="doc_text">
2179 <p>Bitwise binary operators are used to do various forms of
2180 bit-twiddling in a program. They are generally very efficient
2181 instructions and can commonly be strength reduced from other
2182 instructions. They require two operands, execute an operation on them,
2183 and produce a single value. The resulting value of the bitwise binary
2184 operators is always the same type as its first operand.</p>
2187 <!-- _______________________________________________________________________ -->
2188 <div class="doc_subsubsection"> <a name="i_shl">'<tt>shl</tt>'
2189 Instruction</a> </div>
2190 <div class="doc_text">
2192 <pre> <result> = shl <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2197 <p>The '<tt>shl</tt>' instruction returns the first operand shifted to
2198 the left a specified number of bits.</p>
2202 <p>Both arguments to the '<tt>shl</tt>' instruction must be the same <a
2203 href="#t_integer">integer</a> type.</p>
2207 <p>The value produced is <tt>var1</tt> * 2<sup><tt>var2</tt></sup>. If
2208 <tt>var2</tt> is (statically or dynamically) equal to or larger than the number
2209 of bits in <tt>var1</tt>, the result is undefined.</p>
2211 <h5>Example:</h5><pre>
2212 <result> = shl i32 4, %var <i>; yields {i32}: 4 << %var</i>
2213 <result> = shl i32 4, 2 <i>; yields {i32}: 16</i>
2214 <result> = shl i32 1, 10 <i>; yields {i32}: 1024</i>
2215 <result> = shl i32 1, 32 <i>; undefined</i>
2218 <!-- _______________________________________________________________________ -->
2219 <div class="doc_subsubsection"> <a name="i_lshr">'<tt>lshr</tt>'
2220 Instruction</a> </div>
2221 <div class="doc_text">
2223 <pre> <result> = lshr <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2227 <p>The '<tt>lshr</tt>' instruction (logical shift right) returns the first
2228 operand shifted to the right a specified number of bits with zero fill.</p>
2231 <p>Both arguments to the '<tt>lshr</tt>' instruction must be the same
2232 <a href="#t_integer">integer</a> type.</p>
2236 <p>This instruction always performs a logical shift right operation. The most
2237 significant bits of the result will be filled with zero bits after the
2238 shift. If <tt>var2</tt> is (statically or dynamically) equal to or larger than
2239 the number of bits in <tt>var1</tt>, the result is undefined.</p>
2243 <result> = lshr i32 4, 1 <i>; yields {i32}:result = 2</i>
2244 <result> = lshr i32 4, 2 <i>; yields {i32}:result = 1</i>
2245 <result> = lshr i8 4, 3 <i>; yields {i8}:result = 0</i>
2246 <result> = lshr i8 -2, 1 <i>; yields {i8}:result = 0x7FFFFFFF </i>
2247 <result> = lshr i32 1, 32 <i>; undefined</i>
2251 <!-- _______________________________________________________________________ -->
2252 <div class="doc_subsubsection"> <a name="i_ashr">'<tt>ashr</tt>'
2253 Instruction</a> </div>
2254 <div class="doc_text">
2257 <pre> <result> = ashr <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2261 <p>The '<tt>ashr</tt>' instruction (arithmetic shift right) returns the first
2262 operand shifted to the right a specified number of bits with sign extension.</p>
2265 <p>Both arguments to the '<tt>ashr</tt>' instruction must be the same
2266 <a href="#t_integer">integer</a> type.</p>
2269 <p>This instruction always performs an arithmetic shift right operation,
2270 The most significant bits of the result will be filled with the sign bit
2271 of <tt>var1</tt>. If <tt>var2</tt> is (statically or dynamically) equal to or
2272 larger than the number of bits in <tt>var1</tt>, the result is undefined.
2277 <result> = ashr i32 4, 1 <i>; yields {i32}:result = 2</i>
2278 <result> = ashr i32 4, 2 <i>; yields {i32}:result = 1</i>
2279 <result> = ashr i8 4, 3 <i>; yields {i8}:result = 0</i>
2280 <result> = ashr i8 -2, 1 <i>; yields {i8}:result = -1</i>
2281 <result> = ashr i32 1, 32 <i>; undefined</i>
2285 <!-- _______________________________________________________________________ -->
2286 <div class="doc_subsubsection"> <a name="i_and">'<tt>and</tt>'
2287 Instruction</a> </div>
2288 <div class="doc_text">
2290 <pre> <result> = and <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2293 <p>The '<tt>and</tt>' instruction returns the bitwise logical and of
2294 its two operands.</p>
2296 <p>The two arguments to the '<tt>and</tt>' instruction must be <a
2297 href="#t_integer">integer</a> values. Both arguments must have
2298 identical types.</p>
2300 <p>The truth table used for the '<tt>and</tt>' instruction is:</p>
2302 <div style="align: center">
2303 <table border="1" cellspacing="0" cellpadding="4">
2334 <pre> <result> = and i32 4, %var <i>; yields {i32}:result = 4 & %var</i>
2335 <result> = and i32 15, 40 <i>; yields {i32}:result = 8</i>
2336 <result> = and i32 4, 8 <i>; yields {i32}:result = 0</i>
2339 <!-- _______________________________________________________________________ -->
2340 <div class="doc_subsubsection"> <a name="i_or">'<tt>or</tt>' Instruction</a> </div>
2341 <div class="doc_text">
2343 <pre> <result> = or <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2346 <p>The '<tt>or</tt>' instruction returns the bitwise logical inclusive
2347 or of its two operands.</p>
2349 <p>The two arguments to the '<tt>or</tt>' instruction must be <a
2350 href="#t_integer">integer</a> values. Both arguments must have
2351 identical types.</p>
2353 <p>The truth table used for the '<tt>or</tt>' instruction is:</p>
2355 <div style="align: center">
2356 <table border="1" cellspacing="0" cellpadding="4">
2387 <pre> <result> = or i32 4, %var <i>; yields {i32}:result = 4 | %var</i>
2388 <result> = or i32 15, 40 <i>; yields {i32}:result = 47</i>
2389 <result> = or i32 4, 8 <i>; yields {i32}:result = 12</i>
2392 <!-- _______________________________________________________________________ -->
2393 <div class="doc_subsubsection"> <a name="i_xor">'<tt>xor</tt>'
2394 Instruction</a> </div>
2395 <div class="doc_text">
2397 <pre> <result> = xor <ty> <var1>, <var2> <i>; yields {ty}:result</i>
2400 <p>The '<tt>xor</tt>' instruction returns the bitwise logical exclusive
2401 or of its two operands. The <tt>xor</tt> is used to implement the
2402 "one's complement" operation, which is the "~" operator in C.</p>
2404 <p>The two arguments to the '<tt>xor</tt>' instruction must be <a
2405 href="#t_integer">integer</a> values. Both arguments must have
2406 identical types.</p>
2408 <p>The truth table used for the '<tt>xor</tt>' instruction is:</p>
2410 <div style="align: center">
2411 <table border="1" cellspacing="0" cellpadding="4">
2443 <pre> <result> = xor i32 4, %var <i>; yields {i32}:result = 4 ^ %var</i>
2444 <result> = xor i32 15, 40 <i>; yields {i32}:result = 39</i>
2445 <result> = xor i32 4, 8 <i>; yields {i32}:result = 12</i>
2446 <result> = xor i32 %V, -1 <i>; yields {i32}:result = ~%V</i>
2450 <!-- ======================================================================= -->
2451 <div class="doc_subsection">
2452 <a name="vectorops">Vector Operations</a>
2455 <div class="doc_text">
2457 <p>LLVM supports several instructions to represent vector operations in a
2458 target-independent manner. These instructions cover the element-access and
2459 vector-specific operations needed to process vectors effectively. While LLVM
2460 does directly support these vector operations, many sophisticated algorithms
2461 will want to use target-specific intrinsics to take full advantage of a specific
2466 <!-- _______________________________________________________________________ -->
2467 <div class="doc_subsubsection">
2468 <a name="i_extractelement">'<tt>extractelement</tt>' Instruction</a>
2471 <div class="doc_text">
2476 <result> = extractelement <n x <ty>> <val>, i32 <idx> <i>; yields <ty></i>
2482 The '<tt>extractelement</tt>' instruction extracts a single scalar
2483 element from a vector at a specified index.
2490 The first operand of an '<tt>extractelement</tt>' instruction is a
2491 value of <a href="#t_vector">vector</a> type. The second operand is
2492 an index indicating the position from which to extract the element.
2493 The index may be a variable.</p>
2498 The result is a scalar of the same type as the element type of
2499 <tt>val</tt>. Its value is the value at position <tt>idx</tt> of
2500 <tt>val</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the
2501 results are undefined.
2507 %result = extractelement <4 x i32> %vec, i32 0 <i>; yields i32</i>
2512 <!-- _______________________________________________________________________ -->
2513 <div class="doc_subsubsection">
2514 <a name="i_insertelement">'<tt>insertelement</tt>' Instruction</a>
2517 <div class="doc_text">
2522 <result> = insertelement <n x <ty>> <val>, <ty> <elt>, i32 <idx> <i>; yields <n x <ty>></i>
2528 The '<tt>insertelement</tt>' instruction inserts a scalar
2529 element into a vector at a specified index.
2536 The first operand of an '<tt>insertelement</tt>' instruction is a
2537 value of <a href="#t_vector">vector</a> type. The second operand is a
2538 scalar value whose type must equal the element type of the first
2539 operand. The third operand is an index indicating the position at
2540 which to insert the value. The index may be a variable.</p>
2545 The result is a vector of the same type as <tt>val</tt>. Its
2546 element values are those of <tt>val</tt> except at position
2547 <tt>idx</tt>, where it gets the value <tt>elt</tt>. If <tt>idx</tt>
2548 exceeds the length of <tt>val</tt>, the results are undefined.
2554 %result = insertelement <4 x i32> %vec, i32 1, i32 0 <i>; yields <4 x i32></i>
2558 <!-- _______________________________________________________________________ -->
2559 <div class="doc_subsubsection">
2560 <a name="i_shufflevector">'<tt>shufflevector</tt>' Instruction</a>
2563 <div class="doc_text">
2568 <result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <n x i32> <mask> <i>; yields <n x <ty>></i>
2574 The '<tt>shufflevector</tt>' instruction constructs a permutation of elements
2575 from two input vectors, returning a vector of the same type.
2581 The first two operands of a '<tt>shufflevector</tt>' instruction are vectors
2582 with types that match each other and types that match the result of the
2583 instruction. The third argument is a shuffle mask, which has the same number
2584 of elements as the other vector type, but whose element type is always 'i32'.
2588 The shuffle mask operand is required to be a constant vector with either
2589 constant integer or undef values.
2595 The elements of the two input vectors are numbered from left to right across
2596 both of the vectors. The shuffle mask operand specifies, for each element of
2597 the result vector, which element of the two input registers the result element
2598 gets. The element selector may be undef (meaning "don't care") and the second
2599 operand may be undef if performing a shuffle from only one vector.
2605 %result = shufflevector <4 x i32> %v1, <4 x i32> %v2,
2606 <4 x i32> <i32 0, i32 4, i32 1, i32 5> <i>; yields <4 x i32></i>
2607 %result = shufflevector <4 x i32> %v1, <4 x i32> undef,
2608 <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> - Identity shuffle.
2613 <!-- ======================================================================= -->
2614 <div class="doc_subsection">
2615 <a name="memoryops">Memory Access and Addressing Operations</a>
2618 <div class="doc_text">
2620 <p>A key design point of an SSA-based representation is how it
2621 represents memory. In LLVM, no memory locations are in SSA form, which
2622 makes things very simple. This section describes how to read, write,
2623 allocate, and free memory in LLVM.</p>
2627 <!-- _______________________________________________________________________ -->
2628 <div class="doc_subsubsection">
2629 <a name="i_malloc">'<tt>malloc</tt>' Instruction</a>
2632 <div class="doc_text">
2637 <result> = malloc <type>[, i32 <NumElements>][, align <alignment>] <i>; yields {type*}:result</i>
2642 <p>The '<tt>malloc</tt>' instruction allocates memory from the system
2643 heap and returns a pointer to it.</p>
2647 <p>The '<tt>malloc</tt>' instruction allocates
2648 <tt>sizeof(<type>)*NumElements</tt>
2649 bytes of memory from the operating system and returns a pointer of the
2650 appropriate type to the program. If "NumElements" is specified, it is the
2651 number of elements allocated. If an alignment is specified, the value result
2652 of the allocation is guaranteed to be aligned to at least that boundary. If
2653 not specified, or if zero, the target can choose to align the allocation on any
2654 convenient boundary.</p>
2656 <p>'<tt>type</tt>' must be a sized type.</p>
2660 <p>Memory is allocated using the system "<tt>malloc</tt>" function, and
2661 a pointer is returned.</p>
2666 %array = malloc [4 x i8 ] <i>; yields {[%4 x i8]*}:array</i>
2668 %size = <a href="#i_add">add</a> i32 2, 2 <i>; yields {i32}:size = i32 4</i>
2669 %array1 = malloc i8, i32 4 <i>; yields {i8*}:array1</i>
2670 %array2 = malloc [12 x i8], i32 %size <i>; yields {[12 x i8]*}:array2</i>
2671 %array3 = malloc i32, i32 4, align 1024 <i>; yields {i32*}:array3</i>
2672 %array4 = malloc i32, align 1024 <i>; yields {i32*}:array4</i>
2676 <!-- _______________________________________________________________________ -->
2677 <div class="doc_subsubsection">
2678 <a name="i_free">'<tt>free</tt>' Instruction</a>
2681 <div class="doc_text">
2686 free <type> <value> <i>; yields {void}</i>
2691 <p>The '<tt>free</tt>' instruction returns memory back to the unused
2692 memory heap to be reallocated in the future.</p>
2696 <p>'<tt>value</tt>' shall be a pointer value that points to a value
2697 that was allocated with the '<tt><a href="#i_malloc">malloc</a></tt>'
2702 <p>Access to the memory pointed to by the pointer is no longer defined
2703 after this instruction executes.</p>
2708 %array = <a href="#i_malloc">malloc</a> [4 x i8] <i>; yields {[4 x i8]*}:array</i>
2709 free [4 x i8]* %array
2713 <!-- _______________________________________________________________________ -->
2714 <div class="doc_subsubsection">
2715 <a name="i_alloca">'<tt>alloca</tt>' Instruction</a>
2718 <div class="doc_text">
2723 <result> = alloca <type>[, i32 <NumElements>][, align <alignment>] <i>; yields {type*}:result</i>
2728 <p>The '<tt>alloca</tt>' instruction allocates memory on the stack frame of the
2729 currently executing function, to be automatically released when this function
2730 returns to its caller.</p>
2734 <p>The '<tt>alloca</tt>' instruction allocates <tt>sizeof(<type>)*NumElements</tt>
2735 bytes of memory on the runtime stack, returning a pointer of the
2736 appropriate type to the program. If "NumElements" is specified, it is the
2737 number of elements allocated. If an alignment is specified, the value result
2738 of the allocation is guaranteed to be aligned to at least that boundary. If
2739 not specified, or if zero, the target can choose to align the allocation on any
2740 convenient boundary.</p>
2742 <p>'<tt>type</tt>' may be any sized type.</p>
2746 <p>Memory is allocated; a pointer is returned. '<tt>alloca</tt>'d
2747 memory is automatically released when the function returns. The '<tt>alloca</tt>'
2748 instruction is commonly used to represent automatic variables that must
2749 have an address available. When the function returns (either with the <tt><a
2750 href="#i_ret">ret</a></tt> or <tt><a href="#i_unwind">unwind</a></tt>
2751 instructions), the memory is reclaimed.</p>
2756 %ptr = alloca i32 <i>; yields {i32*}:ptr</i>
2757 %ptr = alloca i32, i32 4 <i>; yields {i32*}:ptr</i>
2758 %ptr = alloca i32, i32 4, align 1024 <i>; yields {i32*}:ptr</i>
2759 %ptr = alloca i32, align 1024 <i>; yields {i32*}:ptr</i>
2763 <!-- _______________________________________________________________________ -->
2764 <div class="doc_subsubsection"> <a name="i_load">'<tt>load</tt>'
2765 Instruction</a> </div>
2766 <div class="doc_text">
2768 <pre> <result> = load <ty>* <pointer>[, align <alignment>]<br> <result> = volatile load <ty>* <pointer>[, align <alignment>]<br></pre>
2770 <p>The '<tt>load</tt>' instruction is used to read from memory.</p>
2772 <p>The argument to the '<tt>load</tt>' instruction specifies the memory
2773 address from which to load. The pointer must point to a <a
2774 href="#t_firstclass">first class</a> type. If the <tt>load</tt> is
2775 marked as <tt>volatile</tt>, then the optimizer is not allowed to modify
2776 the number or order of execution of this <tt>load</tt> with other
2777 volatile <tt>load</tt> and <tt><a href="#i_store">store</a></tt>
2780 <p>The location of memory pointed to is loaded.</p>
2782 <pre> %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i>
2784 href="#i_store">store</a> i32 3, i32* %ptr <i>; yields {void}</i>
2785 %val = load i32* %ptr <i>; yields {i32}:val = i32 3</i>
2788 <!-- _______________________________________________________________________ -->
2789 <div class="doc_subsubsection"> <a name="i_store">'<tt>store</tt>'
2790 Instruction</a> </div>
2791 <div class="doc_text">
2793 <pre> store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i>
2794 volatile store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i>
2797 <p>The '<tt>store</tt>' instruction is used to write to memory.</p>
2799 <p>There are two arguments to the '<tt>store</tt>' instruction: a value
2800 to store and an address at which to store it. The type of the '<tt><pointer></tt>'
2801 operand must be a pointer to the type of the '<tt><value></tt>'
2802 operand. If the <tt>store</tt> is marked as <tt>volatile</tt>, then the
2803 optimizer is not allowed to modify the number or order of execution of
2804 this <tt>store</tt> with other volatile <tt>load</tt> and <tt><a
2805 href="#i_store">store</a></tt> instructions.</p>
2807 <p>The contents of memory are updated to contain '<tt><value></tt>'
2808 at the location specified by the '<tt><pointer></tt>' operand.</p>
2810 <pre> %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i>
2811 store i32 3, i32* %ptr <i>; yields {void}</i>
2812 %val = <a href="#i_load">load</a> i32* %ptr <i>; yields {i32}:val = i32 3</i>
2816 <!-- _______________________________________________________________________ -->
2817 <div class="doc_subsubsection">
2818 <a name="i_getelementptr">'<tt>getelementptr</tt>' Instruction</a>
2821 <div class="doc_text">
2824 <result> = getelementptr <ty>* <ptrval>{, <ty> <idx>}*
2830 The '<tt>getelementptr</tt>' instruction is used to get the address of a
2831 subelement of an aggregate data structure.</p>
2835 <p>This instruction takes a list of integer operands that indicate what
2836 elements of the aggregate object to index to. The actual types of the arguments
2837 provided depend on the type of the first pointer argument. The
2838 '<tt>getelementptr</tt>' instruction is used to index down through the type
2839 levels of a structure or to a specific index in an array. When indexing into a
2840 structure, only <tt>i32</tt> integer constants are allowed. When indexing
2841 into an array or pointer, only integers of 32 or 64 bits are allowed, and will
2842 be sign extended to 64-bit values.</p>
2844 <p>For example, let's consider a C code fragment and how it gets
2845 compiled to LLVM:</p>
2847 <div class="doc_code">
2860 int *foo(struct ST *s) {
2861 return &s[1].Z.B[5][13];
2866 <p>The LLVM code generated by the GCC frontend is:</p>
2868 <div class="doc_code">
2870 %RT = type { i8 , [10 x [20 x i32]], i8 }
2871 %ST = type { i32, double, %RT }
2873 define i32* %foo(%ST* %s) {
2875 %reg = getelementptr %ST* %s, i32 1, i32 2, i32 1, i32 5, i32 13
2883 <p>The index types specified for the '<tt>getelementptr</tt>' instruction depend
2884 on the pointer type that is being indexed into. <a href="#t_pointer">Pointer</a>
2885 and <a href="#t_array">array</a> types can use a 32-bit or 64-bit
2886 <a href="#t_integer">integer</a> type but the value will always be sign extended
2887 to 64-bits. <a href="#t_struct">Structure</a> types require <tt>i32</tt>
2888 <b>constants</b>.</p>
2890 <p>In the example above, the first index is indexing into the '<tt>%ST*</tt>'
2891 type, which is a pointer, yielding a '<tt>%ST</tt>' = '<tt>{ i32, double, %RT
2892 }</tt>' type, a structure. The second index indexes into the third element of
2893 the structure, yielding a '<tt>%RT</tt>' = '<tt>{ i8 , [10 x [20 x i32]],
2894 i8 }</tt>' type, another structure. The third index indexes into the second
2895 element of the structure, yielding a '<tt>[10 x [20 x i32]]</tt>' type, an
2896 array. The two dimensions of the array are subscripted into, yielding an
2897 '<tt>i32</tt>' type. The '<tt>getelementptr</tt>' instruction returns a pointer
2898 to this element, thus computing a value of '<tt>i32*</tt>' type.</p>
2900 <p>Note that it is perfectly legal to index partially through a
2901 structure, returning a pointer to an inner element. Because of this,
2902 the LLVM code for the given testcase is equivalent to:</p>
2905 define i32* %foo(%ST* %s) {
2906 %t1 = getelementptr %ST* %s, i32 1 <i>; yields %ST*:%t1</i>
2907 %t2 = getelementptr %ST* %t1, i32 0, i32 2 <i>; yields %RT*:%t2</i>
2908 %t3 = getelementptr %RT* %t2, i32 0, i32 1 <i>; yields [10 x [20 x i32]]*:%t3</i>
2909 %t4 = getelementptr [10 x [20 x i32]]* %t3, i32 0, i32 5 <i>; yields [20 x i32]*:%t4</i>
2910 %t5 = getelementptr [20 x i32]* %t4, i32 0, i32 13 <i>; yields i32*:%t5</i>
2915 <p>Note that it is undefined to access an array out of bounds: array and
2916 pointer indexes must always be within the defined bounds of the array type.
2917 The one exception for this rules is zero length arrays. These arrays are
2918 defined to be accessible as variable length arrays, which requires access
2919 beyond the zero'th element.</p>
2921 <p>The getelementptr instruction is often confusing. For some more insight
2922 into how it works, see <a href="GetElementPtr.html">the getelementptr
2928 <i>; yields [12 x i8]*:aptr</i>
2929 %aptr = getelementptr {i32, [12 x i8]}* %sptr, i64 0, i32 1
2933 <!-- ======================================================================= -->
2934 <div class="doc_subsection"> <a name="convertops">Conversion Operations</a>
2936 <div class="doc_text">
2937 <p>The instructions in this category are the conversion instructions (casting)
2938 which all take a single operand and a type. They perform various bit conversions
2942 <!-- _______________________________________________________________________ -->
2943 <div class="doc_subsubsection">
2944 <a name="i_trunc">'<tt>trunc .. to</tt>' Instruction</a>
2946 <div class="doc_text">
2950 <result> = trunc <ty> <value> to <ty2> <i>; yields ty2</i>
2955 The '<tt>trunc</tt>' instruction truncates its operand to the type <tt>ty2</tt>.
2960 The '<tt>trunc</tt>' instruction takes a <tt>value</tt> to trunc, which must
2961 be an <a href="#t_integer">integer</a> type, and a type that specifies the size
2962 and type of the result, which must be an <a href="#t_integer">integer</a>
2963 type. The bit size of <tt>value</tt> must be larger than the bit size of
2964 <tt>ty2</tt>. Equal sized types are not allowed.</p>
2968 The '<tt>trunc</tt>' instruction truncates the high order bits in <tt>value</tt>
2969 and converts the remaining bits to <tt>ty2</tt>. Since the source size must be
2970 larger than the destination size, <tt>trunc</tt> cannot be a <i>no-op cast</i>.
2971 It will always truncate bits.</p>
2975 %X = trunc i32 257 to i8 <i>; yields i8:1</i>
2976 %Y = trunc i32 123 to i1 <i>; yields i1:true</i>
2977 %Y = trunc i32 122 to i1 <i>; yields i1:false</i>
2981 <!-- _______________________________________________________________________ -->
2982 <div class="doc_subsubsection">
2983 <a name="i_zext">'<tt>zext .. to</tt>' Instruction</a>
2985 <div class="doc_text">
2989 <result> = zext <ty> <value> to <ty2> <i>; yields ty2</i>
2993 <p>The '<tt>zext</tt>' instruction zero extends its operand to type
2998 <p>The '<tt>zext</tt>' instruction takes a value to cast, which must be of
2999 <a href="#t_integer">integer</a> type, and a type to cast it to, which must
3000 also be of <a href="#t_integer">integer</a> type. The bit size of the
3001 <tt>value</tt> must be smaller than the bit size of the destination type,
3005 <p>The <tt>zext</tt> fills the high order bits of the <tt>value</tt> with zero
3006 bits until it reaches the size of the destination type, <tt>ty2</tt>.</p>
3008 <p>When zero extending from i1, the result will always be either 0 or 1.</p>
3012 %X = zext i32 257 to i64 <i>; yields i64:257</i>
3013 %Y = zext i1 true to i32 <i>; yields i32:1</i>
3017 <!-- _______________________________________________________________________ -->
3018 <div class="doc_subsubsection">
3019 <a name="i_sext">'<tt>sext .. to</tt>' Instruction</a>
3021 <div class="doc_text">
3025 <result> = sext <ty> <value> to <ty2> <i>; yields ty2</i>
3029 <p>The '<tt>sext</tt>' sign extends <tt>value</tt> to the type <tt>ty2</tt>.</p>
3033 The '<tt>sext</tt>' instruction takes a value to cast, which must be of
3034 <a href="#t_integer">integer</a> type, and a type to cast it to, which must
3035 also be of <a href="#t_integer">integer</a> type. The bit size of the
3036 <tt>value</tt> must be smaller than the bit size of the destination type,
3041 The '<tt>sext</tt>' instruction performs a sign extension by copying the sign
3042 bit (highest order bit) of the <tt>value</tt> until it reaches the bit size of
3043 the type <tt>ty2</tt>.</p>
3045 <p>When sign extending from i1, the extension always results in -1 or 0.</p>
3049 %X = sext i8 -1 to i16 <i>; yields i16 :65535</i>
3050 %Y = sext i1 true to i32 <i>; yields i32:-1</i>
3054 <!-- _______________________________________________________________________ -->
3055 <div class="doc_subsubsection">
3056 <a name="i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a>
3059 <div class="doc_text">
3064 <result> = fptrunc <ty> <value> to <ty2> <i>; yields ty2</i>
3068 <p>The '<tt>fptrunc</tt>' instruction truncates <tt>value</tt> to type
3073 <p>The '<tt>fptrunc</tt>' instruction takes a <a href="#t_floating">floating
3074 point</a> value to cast and a <a href="#t_floating">floating point</a> type to
3075 cast it to. The size of <tt>value</tt> must be larger than the size of
3076 <tt>ty2</tt>. This implies that <tt>fptrunc</tt> cannot be used to make a
3077 <i>no-op cast</i>.</p>
3080 <p> The '<tt>fptrunc</tt>' instruction truncates a <tt>value</tt> from a larger
3081 <a href="#t_floating">floating point</a> type to a smaller
3082 <a href="#t_floating">floating point</a> type. If the value cannot fit within
3083 the destination type, <tt>ty2</tt>, then the results are undefined.</p>
3087 %X = fptrunc double 123.0 to float <i>; yields float:123.0</i>
3088 %Y = fptrunc double 1.0E+300 to float <i>; yields undefined</i>
3092 <!-- _______________________________________________________________________ -->
3093 <div class="doc_subsubsection">
3094 <a name="i_fpext">'<tt>fpext .. to</tt>' Instruction</a>
3096 <div class="doc_text">
3100 <result> = fpext <ty> <value> to <ty2> <i>; yields ty2</i>
3104 <p>The '<tt>fpext</tt>' extends a floating point <tt>value</tt> to a larger
3105 floating point value.</p>
3108 <p>The '<tt>fpext</tt>' instruction takes a
3109 <a href="#t_floating">floating point</a> <tt>value</tt> to cast,
3110 and a <a href="#t_floating">floating point</a> type to cast it to. The source
3111 type must be smaller than the destination type.</p>
3114 <p>The '<tt>fpext</tt>' instruction extends the <tt>value</tt> from a smaller
3115 <a href="#t_floating">floating point</a> type to a larger
3116 <a href="#t_floating">floating point</a> type. The <tt>fpext</tt> cannot be
3117 used to make a <i>no-op cast</i> because it always changes bits. Use
3118 <tt>bitcast</tt> to make a <i>no-op cast</i> for a floating point cast.</p>
3122 %X = fpext float 3.1415 to double <i>; yields double:3.1415</i>
3123 %Y = fpext float 1.0 to float <i>; yields float:1.0 (no-op)</i>
3127 <!-- _______________________________________________________________________ -->
3128 <div class="doc_subsubsection">
3129 <a name="i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a>
3131 <div class="doc_text">
3135 <result> = fptoui <ty> <value> to <ty2> <i>; yields ty2</i>
3139 <p>The '<tt>fptoui</tt>' converts a floating point <tt>value</tt> to its
3140 unsigned integer equivalent of type <tt>ty2</tt>.
3144 <p>The '<tt>fptoui</tt>' instruction takes a value to cast, which must be a
3145 scalar or vector <a href="#t_floating">floating point</a> value, and a type
3146 to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a>
3147 type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a
3148 vector integer type with the same number of elements as <tt>ty</tt></p>
3151 <p> The '<tt>fptoui</tt>' instruction converts its
3152 <a href="#t_floating">floating point</a> operand into the nearest (rounding
3153 towards zero) unsigned integer value. If the value cannot fit in <tt>ty2</tt>,
3154 the results are undefined.</p>
3158 %X = fptoui double 123.0 to i32 <i>; yields i32:123</i>
3159 %Y = fptoui float 1.0E+300 to i1 <i>; yields undefined:1</i>
3160 %X = fptoui float 1.04E+17 to i8 <i>; yields undefined:1</i>
3164 <!-- _______________________________________________________________________ -->
3165 <div class="doc_subsubsection">
3166 <a name="i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a>
3168 <div class="doc_text">
3172 <result> = fptosi <ty> <value> to <ty2> <i>; yields ty2</i>
3176 <p>The '<tt>fptosi</tt>' instruction converts
3177 <a href="#t_floating">floating point</a> <tt>value</tt> to type <tt>ty2</tt>.
3181 <p> The '<tt>fptosi</tt>' instruction takes a value to cast, which must be a
3182 scalar or vector <a href="#t_floating">floating point</a> value, and a type
3183 to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a>
3184 type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a
3185 vector integer type with the same number of elements as <tt>ty</tt></p>
3188 <p>The '<tt>fptosi</tt>' instruction converts its
3189 <a href="#t_floating">floating point</a> operand into the nearest (rounding
3190 towards zero) signed integer value. If the value cannot fit in <tt>ty2</tt>,
3191 the results are undefined.</p>
3195 %X = fptosi double -123.0 to i32 <i>; yields i32:-123</i>
3196 %Y = fptosi float 1.0E-247 to i1 <i>; yields undefined:1</i>
3197 %X = fptosi float 1.04E+17 to i8 <i>; yields undefined:1</i>
3201 <!-- _______________________________________________________________________ -->
3202 <div class="doc_subsubsection">
3203 <a name="i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a>
3205 <div class="doc_text">
3209 <result> = uitofp <ty> <value> to <ty2> <i>; yields ty2</i>
3213 <p>The '<tt>uitofp</tt>' instruction regards <tt>value</tt> as an unsigned
3214 integer and converts that value to the <tt>ty2</tt> type.</p>
3217 <p>The '<tt>uitofp</tt>' instruction takes a value to cast, which must be a
3218 scalar or vector <a href="#t_integer">integer</a> value, and a type to cast it
3219 to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a>
3220 type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector
3221 floating point type with the same number of elements as <tt>ty</tt></p>
3224 <p>The '<tt>uitofp</tt>' instruction interprets its operand as an unsigned
3225 integer quantity and converts it to the corresponding floating point value. If
3226 the value cannot fit in the floating point value, the results are undefined.</p>
3230 %X = uitofp i32 257 to float <i>; yields float:257.0</i>
3231 %Y = uitofp i8 -1 to double <i>; yields double:255.0</i>
3235 <!-- _______________________________________________________________________ -->
3236 <div class="doc_subsubsection">
3237 <a name="i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a>
3239 <div class="doc_text">
3243 <result> = sitofp <ty> <value> to <ty2> <i>; yields ty2</i>
3247 <p>The '<tt>sitofp</tt>' instruction regards <tt>value</tt> as a signed
3248 integer and converts that value to the <tt>ty2</tt> type.</p>
3251 <p>The '<tt>sitofp</tt>' instruction takes a value to cast, which must be a
3252 scalar or vector <a href="#t_integer">integer</a> value, and a type to cast it
3253 to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a>
3254 type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector
3255 floating point type with the same number of elements as <tt>ty</tt></p>
3258 <p>The '<tt>sitofp</tt>' instruction interprets its operand as a signed
3259 integer quantity and converts it to the corresponding floating point value. If
3260 the value cannot fit in the floating point value, the results are undefined.</p>
3264 %X = sitofp i32 257 to float <i>; yields float:257.0</i>
3265 %Y = sitofp i8 -1 to double <i>; yields double:-1.0</i>
3269 <!-- _______________________________________________________________________ -->
3270 <div class="doc_subsubsection">
3271 <a name="i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a>
3273 <div class="doc_text">
3277 <result> = ptrtoint <ty> <value> to <ty2> <i>; yields ty2</i>
3281 <p>The '<tt>ptrtoint</tt>' instruction converts the pointer <tt>value</tt> to
3282 the integer type <tt>ty2</tt>.</p>
3285 <p>The '<tt>ptrtoint</tt>' instruction takes a <tt>value</tt> to cast, which
3286 must be a <a href="#t_pointer">pointer</a> value, and a type to cast it to
3287 <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> type.
3290 <p>The '<tt>ptrtoint</tt>' instruction converts <tt>value</tt> to integer type
3291 <tt>ty2</tt> by interpreting the pointer value as an integer and either
3292 truncating or zero extending that value to the size of the integer type. If
3293 <tt>value</tt> is smaller than <tt>ty2</tt> then a zero extension is done. If
3294 <tt>value</tt> is larger than <tt>ty2</tt> then a truncation is done. If they
3295 are the same size, then nothing is done (<i>no-op cast</i>) other than a type
3300 %X = ptrtoint i32* %X to i8 <i>; yields truncation on 32-bit architecture</i>
3301 %Y = ptrtoint i32* %x to i64 <i>; yields zero extension on 32-bit architecture</i>
3305 <!-- _______________________________________________________________________ -->
3306 <div class="doc_subsubsection">
3307 <a name="i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a>
3309 <div class="doc_text">
3313 <result> = inttoptr <ty> <value> to <ty2> <i>; yields ty2</i>
3317 <p>The '<tt>inttoptr</tt>' instruction converts an integer <tt>value</tt> to
3318 a pointer type, <tt>ty2</tt>.</p>
3321 <p>The '<tt>inttoptr</tt>' instruction takes an <a href="#t_integer">integer</a>
3322 value to cast, and a type to cast it to, which must be a
3323 <a href="#t_pointer">pointer</a> type.
3326 <p>The '<tt>inttoptr</tt>' instruction converts <tt>value</tt> to type
3327 <tt>ty2</tt> by applying either a zero extension or a truncation depending on
3328 the size of the integer <tt>value</tt>. If <tt>value</tt> is larger than the
3329 size of a pointer then a truncation is done. If <tt>value</tt> is smaller than
3330 the size of a pointer then a zero extension is done. If they are the same size,
3331 nothing is done (<i>no-op cast</i>).</p>
3335 %X = inttoptr i32 255 to i32* <i>; yields zero extension on 64-bit architecture</i>
3336 %X = inttoptr i32 255 to i32* <i>; yields no-op on 32-bit architecture</i>
3337 %Y = inttoptr i64 0 to i32* <i>; yields truncation on 32-bit architecture</i>
3341 <!-- _______________________________________________________________________ -->
3342 <div class="doc_subsubsection">
3343 <a name="i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a>
3345 <div class="doc_text">
3349 <result> = bitcast <ty> <value> to <ty2> <i>; yields ty2</i>
3353 <p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type
3354 <tt>ty2</tt> without changing any bits.</p>
3357 <p>The '<tt>bitcast</tt>' instruction takes a value to cast, which must be
3358 a first class value, and a type to cast it to, which must also be a <a
3359 href="#t_firstclass">first class</a> type. The bit sizes of <tt>value</tt>
3360 and the destination type, <tt>ty2</tt>, must be identical. If the source
3361 type is a pointer, the destination type must also be a pointer.</p>
3364 <p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type
3365 <tt>ty2</tt>. It is always a <i>no-op cast</i> because no bits change with
3366 this conversion. The conversion is done as if the <tt>value</tt> had been
3367 stored to memory and read back as type <tt>ty2</tt>. Pointer types may only be
3368 converted to other pointer types with this instruction. To convert pointers to
3369 other types, use the <a href="#i_inttoptr">inttoptr</a> or
3370 <a href="#i_ptrtoint">ptrtoint</a> instructions first.</p>
3374 %X = bitcast i8 255 to i8 <i>; yields i8 :-1</i>
3375 %Y = bitcast i32* %x to sint* <i>; yields sint*:%x</i>
3376 %Z = bitcast <2xint> %V to i64; <i>; yields i64: %V</i>
3380 <!-- ======================================================================= -->
3381 <div class="doc_subsection"> <a name="otherops">Other Operations</a> </div>
3382 <div class="doc_text">
3383 <p>The instructions in this category are the "miscellaneous"
3384 instructions, which defy better classification.</p>
3387 <!-- _______________________________________________________________________ -->
3388 <div class="doc_subsubsection"><a name="i_icmp">'<tt>icmp</tt>' Instruction</a>
3390 <div class="doc_text">
3392 <pre> <result> = icmp <cond> <ty> <var1>, <var2> <i>; yields {i1}:result</i>
3395 <p>The '<tt>icmp</tt>' instruction returns a boolean value based on comparison
3396 of its two integer operands.</p>
3398 <p>The '<tt>icmp</tt>' instruction takes three operands. The first operand is
3399 the condition code indicating the kind of comparison to perform. It is not
3400 a value, just a keyword. The possible condition code are:
3402 <li><tt>eq</tt>: equal</li>
3403 <li><tt>ne</tt>: not equal </li>
3404 <li><tt>ugt</tt>: unsigned greater than</li>
3405 <li><tt>uge</tt>: unsigned greater or equal</li>
3406 <li><tt>ult</tt>: unsigned less than</li>
3407 <li><tt>ule</tt>: unsigned less or equal</li>
3408 <li><tt>sgt</tt>: signed greater than</li>
3409 <li><tt>sge</tt>: signed greater or equal</li>
3410 <li><tt>slt</tt>: signed less than</li>
3411 <li><tt>sle</tt>: signed less or equal</li>
3413 <p>The remaining two arguments must be <a href="#t_integer">integer</a> or
3414 <a href="#t_pointer">pointer</a> typed. They must also be identical types.</p>
3416 <p>The '<tt>icmp</tt>' compares <tt>var1</tt> and <tt>var2</tt> according to
3417 the condition code given as <tt>cond</tt>. The comparison performed always
3418 yields a <a href="#t_primitive">i1</a> result, as follows:
3420 <li><tt>eq</tt>: yields <tt>true</tt> if the operands are equal,
3421 <tt>false</tt> otherwise. No sign interpretation is necessary or performed.
3423 <li><tt>ne</tt>: yields <tt>true</tt> if the operands are unequal,
3424 <tt>false</tt> otherwise. No sign interpretation is necessary or performed.
3425 <li><tt>ugt</tt>: interprets the operands as unsigned values and yields
3426 <tt>true</tt> if <tt>var1</tt> is greater than <tt>var2</tt>.</li>
3427 <li><tt>uge</tt>: interprets the operands as unsigned values and yields
3428 <tt>true</tt> if <tt>var1</tt> is greater than or equal to <tt>var2</tt>.</li>
3429 <li><tt>ult</tt>: interprets the operands as unsigned values and yields
3430 <tt>true</tt> if <tt>var1</tt> is less than <tt>var2</tt>.</li>
3431 <li><tt>ule</tt>: interprets the operands as unsigned values and yields
3432 <tt>true</tt> if <tt>var1</tt> is less than or equal to <tt>var2</tt>.</li>
3433 <li><tt>sgt</tt>: interprets the operands as signed values and yields
3434 <tt>true</tt> if <tt>var1</tt> is greater than <tt>var2</tt>.</li>
3435 <li><tt>sge</tt>: interprets the operands as signed values and yields
3436 <tt>true</tt> if <tt>var1</tt> is greater than or equal to <tt>var2</tt>.</li>
3437 <li><tt>slt</tt>: interprets the operands as signed values and yields
3438 <tt>true</tt> if <tt>var1</tt> is less than <tt>var2</tt>.</li>
3439 <li><tt>sle</tt>: interprets the operands as signed values and yields
3440 <tt>true</tt> if <tt>var1</tt> is less than or equal to <tt>var2</tt>.</li>
3442 <p>If the operands are <a href="#t_pointer">pointer</a> typed, the pointer
3443 values are compared as if they were integers.</p>
3446 <pre> <result> = icmp eq i32 4, 5 <i>; yields: result=false</i>
3447 <result> = icmp ne float* %X, %X <i>; yields: result=false</i>
3448 <result> = icmp ult i16 4, 5 <i>; yields: result=true</i>
3449 <result> = icmp sgt i16 4, 5 <i>; yields: result=false</i>
3450 <result> = icmp ule i16 -4, 5 <i>; yields: result=false</i>
3451 <result> = icmp sge i16 4, 5 <i>; yields: result=false</i>
3455 <!-- _______________________________________________________________________ -->
3456 <div class="doc_subsubsection"><a name="i_fcmp">'<tt>fcmp</tt>' Instruction</a>
3458 <div class="doc_text">
3460 <pre> <result> = fcmp <cond> <ty> <var1>, <var2> <i>; yields {i1}:result</i>
3463 <p>The '<tt>fcmp</tt>' instruction returns a boolean value based on comparison
3464 of its floating point operands.</p>
3466 <p>The '<tt>fcmp</tt>' instruction takes three operands. The first operand is
3467 the condition code indicating the kind of comparison to perform. It is not
3468 a value, just a keyword. The possible condition code are:
3470 <li><tt>false</tt>: no comparison, always returns false</li>
3471 <li><tt>oeq</tt>: ordered and equal</li>
3472 <li><tt>ogt</tt>: ordered and greater than </li>
3473 <li><tt>oge</tt>: ordered and greater than or equal</li>
3474 <li><tt>olt</tt>: ordered and less than </li>
3475 <li><tt>ole</tt>: ordered and less than or equal</li>
3476 <li><tt>one</tt>: ordered and not equal</li>
3477 <li><tt>ord</tt>: ordered (no nans)</li>
3478 <li><tt>ueq</tt>: unordered or equal</li>
3479 <li><tt>ugt</tt>: unordered or greater than </li>
3480 <li><tt>uge</tt>: unordered or greater than or equal</li>
3481 <li><tt>ult</tt>: unordered or less than </li>
3482 <li><tt>ule</tt>: unordered or less than or equal</li>
3483 <li><tt>une</tt>: unordered or not equal</li>
3484 <li><tt>uno</tt>: unordered (either nans)</li>
3485 <li><tt>true</tt>: no comparison, always returns true</li>
3487 <p><i>Ordered</i> means that neither operand is a QNAN while
3488 <i>unordered</i> means that either operand may be a QNAN.</p>
3489 <p>The <tt>val1</tt> and <tt>val2</tt> arguments must be
3490 <a href="#t_floating">floating point</a> typed. They must have identical
3493 <p>The '<tt>fcmp</tt>' compares <tt>var1</tt> and <tt>var2</tt> according to
3494 the condition code given as <tt>cond</tt>. The comparison performed always
3495 yields a <a href="#t_primitive">i1</a> result, as follows:
3497 <li><tt>false</tt>: always yields <tt>false</tt>, regardless of operands.</li>
3498 <li><tt>oeq</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3499 <tt>var1</tt> is equal to <tt>var2</tt>.</li>
3500 <li><tt>ogt</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3501 <tt>var1</tt> is greather than <tt>var2</tt>.</li>
3502 <li><tt>oge</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3503 <tt>var1</tt> is greater than or equal to <tt>var2</tt>.</li>
3504 <li><tt>olt</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3505 <tt>var1</tt> is less than <tt>var2</tt>.</li>
3506 <li><tt>ole</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3507 <tt>var1</tt> is less than or equal to <tt>var2</tt>.</li>
3508 <li><tt>one</tt>: yields <tt>true</tt> if both operands are not a QNAN and
3509 <tt>var1</tt> is not equal to <tt>var2</tt>.</li>
3510 <li><tt>ord</tt>: yields <tt>true</tt> if both operands are not a QNAN.</li>
3511 <li><tt>ueq</tt>: yields <tt>true</tt> if either operand is a QNAN or
3512 <tt>var1</tt> is equal to <tt>var2</tt>.</li>
3513 <li><tt>ugt</tt>: yields <tt>true</tt> if either operand is a QNAN or
3514 <tt>var1</tt> is greater than <tt>var2</tt>.</li>
3515 <li><tt>uge</tt>: yields <tt>true</tt> if either operand is a QNAN or
3516 <tt>var1</tt> is greater than or equal to <tt>var2</tt>.</li>
3517 <li><tt>ult</tt>: yields <tt>true</tt> if either operand is a QNAN or
3518 <tt>var1</tt> is less than <tt>var2</tt>.</li>
3519 <li><tt>ule</tt>: yields <tt>true</tt> if either operand is a QNAN or
3520 <tt>var1</tt> is less than or equal to <tt>var2</tt>.</li>
3521 <li><tt>une</tt>: yields <tt>true</tt> if either operand is a QNAN or
3522 <tt>var1</tt> is not equal to <tt>var2</tt>.</li>
3523 <li><tt>uno</tt>: yields <tt>true</tt> if either operand is a QNAN.</li>
3524 <li><tt>true</tt>: always yields <tt>true</tt>, regardless of operands.</li>
3528 <pre> <result> = fcmp oeq float 4.0, 5.0 <i>; yields: result=false</i>
3529 <result> = icmp one float 4.0, 5.0 <i>; yields: result=true</i>
3530 <result> = icmp olt float 4.0, 5.0 <i>; yields: result=true</i>
3531 <result> = icmp ueq double 1.0, 2.0 <i>; yields: result=false</i>
3535 <!-- _______________________________________________________________________ -->
3536 <div class="doc_subsubsection"> <a name="i_phi">'<tt>phi</tt>'
3537 Instruction</a> </div>
3538 <div class="doc_text">
3540 <pre> <result> = phi <ty> [ <val0>, <label0>], ...<br></pre>
3542 <p>The '<tt>phi</tt>' instruction is used to implement the φ node in
3543 the SSA graph representing the function.</p>
3545 <p>The type of the incoming values is specified with the first type
3546 field. After this, the '<tt>phi</tt>' instruction takes a list of pairs
3547 as arguments, with one pair for each predecessor basic block of the
3548 current block. Only values of <a href="#t_firstclass">first class</a>
3549 type may be used as the value arguments to the PHI node. Only labels
3550 may be used as the label arguments.</p>
3551 <p>There must be no non-phi instructions between the start of a basic
3552 block and the PHI instructions: i.e. PHI instructions must be first in
3555 <p>At runtime, the '<tt>phi</tt>' instruction logically takes on the value
3556 specified by the pair corresponding to the predecessor basic block that executed
3557 just prior to the current block.</p>
3559 <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>
3562 <!-- _______________________________________________________________________ -->
3563 <div class="doc_subsubsection">
3564 <a name="i_select">'<tt>select</tt>' Instruction</a>
3567 <div class="doc_text">
3572 <result> = select i1 <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i>
3578 The '<tt>select</tt>' instruction is used to choose one value based on a
3579 condition, without branching.
3586 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.
3592 If the boolean condition evaluates to true, the instruction returns the first
3593 value argument; otherwise, it returns the second value argument.
3599 %X = select i1 true, i8 17, i8 42 <i>; yields i8:17</i>
3604 <!-- _______________________________________________________________________ -->
3605 <div class="doc_subsubsection">
3606 <a name="i_call">'<tt>call</tt>' Instruction</a>
3609 <div class="doc_text">
3613 <result> = [tail] call [<a href="#callingconv">cconv</a>] <ty> [<fnty>*] <fnptrval>(<param list>)
3618 <p>The '<tt>call</tt>' instruction represents a simple function call.</p>
3622 <p>This instruction requires several arguments:</p>
3626 <p>The optional "tail" marker indicates whether the callee function accesses
3627 any allocas or varargs in the caller. If the "tail" marker is present, the
3628 function call is eligible for tail call optimization. Note that calls may
3629 be marked "tail" even if they do not occur before a <a
3630 href="#i_ret"><tt>ret</tt></a> instruction.
3633 <p>The optional "cconv" marker indicates which <a href="#callingconv">calling
3634 convention</a> the call should use. If none is specified, the call defaults
3635 to using C calling conventions.
3638 <p>'<tt>ty</tt>': the type of the call instruction itself which is also
3639 the type of the return value. Functions that return no value are marked
3640 <tt><a href="#t_void">void</a></tt>.</p>
3643 <p>'<tt>fnty</tt>': shall be the signature of the pointer to function
3644 value being invoked. The argument types must match the types implied by
3645 this signature. This type can be omitted if the function is not varargs
3646 and if the function type does not return a pointer to a function.</p>
3649 <p>'<tt>fnptrval</tt>': An LLVM value containing a pointer to a function to
3650 be invoked. In most cases, this is a direct function invocation, but
3651 indirect <tt>call</tt>s are just as possible, calling an arbitrary pointer
3652 to function value.</p>
3655 <p>'<tt>function args</tt>': argument list whose types match the
3656 function signature argument types. All arguments must be of
3657 <a href="#t_firstclass">first class</a> type. If the function signature
3658 indicates the function accepts a variable number of arguments, the extra
3659 arguments can be specified.</p>
3665 <p>The '<tt>call</tt>' instruction is used to cause control flow to
3666 transfer to a specified function, with its incoming arguments bound to
3667 the specified values. Upon a '<tt><a href="#i_ret">ret</a></tt>'
3668 instruction in the called function, control flow continues with the
3669 instruction after the function call, and the return value of the
3670 function is bound to the result argument. This is a simpler case of
3671 the <a href="#i_invoke">invoke</a> instruction.</p>
3676 %retval = call i32 @test(i32 %argc)
3677 call i32 (i8 *, ...)* @printf(i8 * %msg, i32 12, i8 42);
3678 %X = tail call i32 @foo()
3679 %Y = tail call <a href="#callingconv">fastcc</a> i32 @foo()
3680 %Z = call void %foo(i8 97 signext)
3685 <!-- _______________________________________________________________________ -->
3686 <div class="doc_subsubsection">
3687 <a name="i_va_arg">'<tt>va_arg</tt>' Instruction</a>
3690 <div class="doc_text">
3695 <resultval> = va_arg <va_list*> <arglist>, <argty>
3700 <p>The '<tt>va_arg</tt>' instruction is used to access arguments passed through
3701 the "variable argument" area of a function call. It is used to implement the
3702 <tt>va_arg</tt> macro in C.</p>
3706 <p>This instruction takes a <tt>va_list*</tt> value and the type of
3707 the argument. It returns a value of the specified argument type and
3708 increments the <tt>va_list</tt> to point to the next argument. The
3709 actual type of <tt>va_list</tt> is target specific.</p>
3713 <p>The '<tt>va_arg</tt>' instruction loads an argument of the specified
3714 type from the specified <tt>va_list</tt> and causes the
3715 <tt>va_list</tt> to point to the next argument. For more information,
3716 see the variable argument handling <a href="#int_varargs">Intrinsic
3719 <p>It is legal for this instruction to be called in a function which does not
3720 take a variable number of arguments, for example, the <tt>vfprintf</tt>
3723 <p><tt>va_arg</tt> is an LLVM instruction instead of an <a
3724 href="#intrinsics">intrinsic function</a> because it takes a type as an
3729 <p>See the <a href="#int_varargs">variable argument processing</a> section.</p>
3733 <!-- *********************************************************************** -->
3734 <div class="doc_section"> <a name="intrinsics">Intrinsic Functions</a> </div>
3735 <!-- *********************************************************************** -->
3737 <div class="doc_text">
3739 <p>LLVM supports the notion of an "intrinsic function". These functions have
3740 well known names and semantics and are required to follow certain restrictions.
3741 Overall, these intrinsics represent an extension mechanism for the LLVM
3742 language that does not require changing all of the transformations in LLVM when
3743 adding to the language (or the bitcode reader/writer, the parser, etc...).</p>
3745 <p>Intrinsic function names must all start with an "<tt>llvm.</tt>" prefix. This
3746 prefix is reserved in LLVM for intrinsic names; thus, function names may not
3747 begin with this prefix. Intrinsic functions must always be external functions:
3748 you cannot define the body of intrinsic functions. Intrinsic functions may
3749 only be used in call or invoke instructions: it is illegal to take the address
3750 of an intrinsic function. Additionally, because intrinsic functions are part
3751 of the LLVM language, it is required if any are added that they be documented
3754 <p>Some intrinsic functions can be overloaded, i.e., the intrinsic represents
3755 a family of functions that perform the same operation but on different data
3756 types. Because LLVM can represent over 8 million different integer types,
3757 overloading is used commonly to allow an intrinsic function to operate on any
3758 integer type. One or more of the argument types or the result type can be
3759 overloaded to accept any integer type. Argument types may also be defined as
3760 exactly matching a previous argument's type or the result type. This allows an
3761 intrinsic function which accepts multiple arguments, but needs all of them to
3762 be of the same type, to only be overloaded with respect to a single argument or
3765 <p>Overloaded intrinsics will have the names of its overloaded argument types
3766 encoded into its function name, each preceded by a period. Only those types
3767 which are overloaded result in a name suffix. Arguments whose type is matched
3768 against another type do not. For example, the <tt>llvm.ctpop</tt> function can
3769 take an integer of any width and returns an integer of exactly the same integer
3770 width. This leads to a family of functions such as
3771 <tt>i8 @llvm.ctpop.i8(i8 %val)</tt> and <tt>i29 @llvm.ctpop.i29(i29 %val)</tt>.
3772 Only one type, the return type, is overloaded, and only one type suffix is
3773 required. Because the argument's type is matched against the return type, it
3774 does not require its own name suffix.</p>
3776 <p>To learn how to add an intrinsic function, please see the
3777 <a href="ExtendingLLVM.html">Extending LLVM Guide</a>.
3782 <!-- ======================================================================= -->
3783 <div class="doc_subsection">
3784 <a name="int_varargs">Variable Argument Handling Intrinsics</a>
3787 <div class="doc_text">
3789 <p>Variable argument support is defined in LLVM with the <a
3790 href="#i_va_arg"><tt>va_arg</tt></a> instruction and these three
3791 intrinsic functions. These functions are related to the similarly
3792 named macros defined in the <tt><stdarg.h></tt> header file.</p>
3794 <p>All of these functions operate on arguments that use a
3795 target-specific value type "<tt>va_list</tt>". The LLVM assembly
3796 language reference manual does not define what this type is, so all
3797 transformations should be prepared to handle these functions regardless of
3800 <p>This example shows how the <a href="#i_va_arg"><tt>va_arg</tt></a>
3801 instruction and the variable argument handling intrinsic functions are
3804 <div class="doc_code">
3806 define i32 @test(i32 %X, ...) {
3807 ; Initialize variable argument processing
3809 %ap2 = bitcast i8** %ap to i8*
3810 call void @llvm.va_start(i8* %ap2)
3812 ; Read a single integer argument
3813 %tmp = va_arg i8** %ap, i32
3815 ; Demonstrate usage of llvm.va_copy and llvm.va_end
3817 %aq2 = bitcast i8** %aq to i8*
3818 call void @llvm.va_copy(i8* %aq2, i8* %ap2)
3819 call void @llvm.va_end(i8* %aq2)
3821 ; Stop processing of arguments.
3822 call void @llvm.va_end(i8* %ap2)
3826 declare void @llvm.va_start(i8*)
3827 declare void @llvm.va_copy(i8*, i8*)
3828 declare void @llvm.va_end(i8*)
3834 <!-- _______________________________________________________________________ -->
3835 <div class="doc_subsubsection">
3836 <a name="int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a>
3840 <div class="doc_text">
3842 <pre> declare void %llvm.va_start(i8* <arglist>)<br></pre>
3844 <P>The '<tt>llvm.va_start</tt>' intrinsic initializes
3845 <tt>*<arglist></tt> for subsequent use by <tt><a
3846 href="#i_va_arg">va_arg</a></tt>.</p>
3850 <P>The argument is a pointer to a <tt>va_list</tt> element to initialize.</p>
3854 <P>The '<tt>llvm.va_start</tt>' intrinsic works just like the <tt>va_start</tt>
3855 macro available in C. In a target-dependent way, it initializes the
3856 <tt>va_list</tt> element to which the argument points, so that the next call to
3857 <tt>va_arg</tt> will produce the first variable argument passed to the function.
3858 Unlike the C <tt>va_start</tt> macro, this intrinsic does not need to know the
3859 last argument of the function as the compiler can figure that out.</p>
3863 <!-- _______________________________________________________________________ -->
3864 <div class="doc_subsubsection">
3865 <a name="int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a>
3868 <div class="doc_text">
3870 <pre> declare void @llvm.va_end(i8* <arglist>)<br></pre>
3873 <p>The '<tt>llvm.va_end</tt>' intrinsic destroys <tt>*<arglist></tt>,
3874 which has been initialized previously with <tt><a href="#int_va_start">llvm.va_start</a></tt>
3875 or <tt><a href="#i_va_copy">llvm.va_copy</a></tt>.</p>
3879 <p>The argument is a pointer to a <tt>va_list</tt> to destroy.</p>
3883 <p>The '<tt>llvm.va_end</tt>' intrinsic works just like the <tt>va_end</tt>
3884 macro available in C. In a target-dependent way, it destroys the
3885 <tt>va_list</tt> element to which the argument points. Calls to <a
3886 href="#int_va_start"><tt>llvm.va_start</tt></a> and <a href="#int_va_copy">
3887 <tt>llvm.va_copy</tt></a> must be matched exactly with calls to
3888 <tt>llvm.va_end</tt>.</p>
3892 <!-- _______________________________________________________________________ -->
3893 <div class="doc_subsubsection">
3894 <a name="int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a>
3897 <div class="doc_text">
3902 declare void @llvm.va_copy(i8* <destarglist>, i8* <srcarglist>)
3907 <p>The '<tt>llvm.va_copy</tt>' intrinsic copies the current argument position
3908 from the source argument list to the destination argument list.</p>
3912 <p>The first argument is a pointer to a <tt>va_list</tt> element to initialize.
3913 The second argument is a pointer to a <tt>va_list</tt> element to copy from.</p>
3918 <p>The '<tt>llvm.va_copy</tt>' intrinsic works just like the <tt>va_copy</tt>
3919 macro available in C. In a target-dependent way, it copies the source
3920 <tt>va_list</tt> element into the destination <tt>va_list</tt> element. This
3921 intrinsic is necessary because the <tt><a href="#int_va_start">
3922 llvm.va_start</a></tt> intrinsic may be arbitrarily complex and require, for
3923 example, memory allocation.</p>
3927 <!-- ======================================================================= -->
3928 <div class="doc_subsection">
3929 <a name="int_gc">Accurate Garbage Collection Intrinsics</a>
3932 <div class="doc_text">
3935 LLVM support for <a href="GarbageCollection.html">Accurate Garbage
3936 Collection</a> requires the implementation and generation of these intrinsics.
3937 These intrinsics allow identification of <a href="#int_gcroot">GC roots on the
3938 stack</a>, as well as garbage collector implementations that require <a
3939 href="#int_gcread">read</a> and <a href="#int_gcwrite">write</a> barriers.
3940 Front-ends for type-safe garbage collected languages should generate these
3941 intrinsics to make use of the LLVM garbage collectors. For more details, see <a
3942 href="GarbageCollection.html">Accurate Garbage Collection with LLVM</a>.
3946 <!-- _______________________________________________________________________ -->
3947 <div class="doc_subsubsection">
3948 <a name="int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a>
3951 <div class="doc_text">
3956 declare void @llvm.gcroot(i8** %ptrloc, i8* %metadata)
3961 <p>The '<tt>llvm.gcroot</tt>' intrinsic declares the existence of a GC root to
3962 the code generator, and allows some metadata to be associated with it.</p>
3966 <p>The first argument specifies the address of a stack object that contains the
3967 root pointer. The second pointer (which must be either a constant or a global
3968 value address) contains the meta-data to be associated with the root.</p>
3972 <p>At runtime, a call to this intrinsics stores a null pointer into the "ptrloc"
3973 location. At compile-time, the code generator generates information to allow
3974 the runtime to find the pointer at GC safe points.
3980 <!-- _______________________________________________________________________ -->
3981 <div class="doc_subsubsection">
3982 <a name="int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a>
3985 <div class="doc_text">
3990 declare i8* @llvm.gcread(i8* %ObjPtr, i8** %Ptr)
3995 <p>The '<tt>llvm.gcread</tt>' intrinsic identifies reads of references from heap
3996 locations, allowing garbage collector implementations that require read
4001 <p>The second argument is the address to read from, which should be an address
4002 allocated from the garbage collector. The first object is a pointer to the
4003 start of the referenced object, if needed by the language runtime (otherwise
4008 <p>The '<tt>llvm.gcread</tt>' intrinsic has the same semantics as a load
4009 instruction, but may be replaced with substantially more complex code by the
4010 garbage collector runtime, as needed.</p>
4015 <!-- _______________________________________________________________________ -->
4016 <div class="doc_subsubsection">
4017 <a name="int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a>
4020 <div class="doc_text">
4025 declare void @llvm.gcwrite(i8* %P1, i8* %Obj, i8** %P2)
4030 <p>The '<tt>llvm.gcwrite</tt>' intrinsic identifies writes of references to heap
4031 locations, allowing garbage collector implementations that require write
4032 barriers (such as generational or reference counting collectors).</p>
4036 <p>The first argument is the reference to store, the second is the start of the
4037 object to store it to, and the third is the address of the field of Obj to
4038 store to. If the runtime does not require a pointer to the object, Obj may be
4043 <p>The '<tt>llvm.gcwrite</tt>' intrinsic has the same semantics as a store
4044 instruction, but may be replaced with substantially more complex code by the
4045 garbage collector runtime, as needed.</p>
4051 <!-- ======================================================================= -->
4052 <div class="doc_subsection">
4053 <a name="int_codegen">Code Generator Intrinsics</a>
4056 <div class="doc_text">
4058 These intrinsics are provided by LLVM to expose special features that may only
4059 be implemented with code generator support.
4064 <!-- _______________________________________________________________________ -->
4065 <div class="doc_subsubsection">
4066 <a name="int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a>
4069 <div class="doc_text">
4073 declare i8 *@llvm.returnaddress(i32 <level>)
4079 The '<tt>llvm.returnaddress</tt>' intrinsic attempts to compute a
4080 target-specific value indicating the return address of the current function
4081 or one of its callers.
4087 The argument to this intrinsic indicates which function to return the address
4088 for. Zero indicates the calling function, one indicates its caller, etc. The
4089 argument is <b>required</b> to be a constant integer value.
4095 The '<tt>llvm.returnaddress</tt>' intrinsic either returns a pointer indicating
4096 the return address of the specified call frame, or zero if it cannot be
4097 identified. The value returned by this intrinsic is likely to be incorrect or 0
4098 for arguments other than zero, so it should only be used for debugging purposes.
4102 Note that calling this intrinsic does not prevent function inlining or other
4103 aggressive transformations, so the value returned may not be that of the obvious
4104 source-language caller.
4109 <!-- _______________________________________________________________________ -->
4110 <div class="doc_subsubsection">
4111 <a name="int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a>
4114 <div class="doc_text">
4118 declare i8 *@llvm.frameaddress(i32 <level>)
4124 The '<tt>llvm.frameaddress</tt>' intrinsic attempts to return the
4125 target-specific frame pointer value for the specified stack frame.
4131 The argument to this intrinsic indicates which function to return the frame
4132 pointer for. Zero indicates the calling function, one indicates its caller,
4133 etc. The argument is <b>required</b> to be a constant integer value.
4139 The '<tt>llvm.frameaddress</tt>' intrinsic either returns a pointer indicating
4140 the frame address of the specified call frame, or zero if it cannot be
4141 identified. The value returned by this intrinsic is likely to be incorrect or 0
4142 for arguments other than zero, so it should only be used for debugging purposes.
4146 Note that calling this intrinsic does not prevent function inlining or other
4147 aggressive transformations, so the value returned may not be that of the obvious
4148 source-language caller.
4152 <!-- _______________________________________________________________________ -->
4153 <div class="doc_subsubsection">
4154 <a name="int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a>
4157 <div class="doc_text">
4161 declare i8 *@llvm.stacksave()
4167 The '<tt>llvm.stacksave</tt>' intrinsic is used to remember the current state of
4168 the function stack, for use with <a href="#int_stackrestore">
4169 <tt>llvm.stackrestore</tt></a>. This is useful for implementing language
4170 features like scoped automatic variable sized arrays in C99.
4176 This intrinsic returns a opaque pointer value that can be passed to <a
4177 href="#int_stackrestore"><tt>llvm.stackrestore</tt></a>. When an
4178 <tt>llvm.stackrestore</tt> intrinsic is executed with a value saved from
4179 <tt>llvm.stacksave</tt>, it effectively restores the state of the stack to the
4180 state it was in when the <tt>llvm.stacksave</tt> intrinsic executed. In
4181 practice, this pops any <a href="#i_alloca">alloca</a> blocks from the stack
4182 that were allocated after the <tt>llvm.stacksave</tt> was executed.
4187 <!-- _______________________________________________________________________ -->
4188 <div class="doc_subsubsection">
4189 <a name="int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a>
4192 <div class="doc_text">
4196 declare void @llvm.stackrestore(i8 * %ptr)
4202 The '<tt>llvm.stackrestore</tt>' intrinsic is used to restore the state of
4203 the function stack to the state it was in when the corresponding <a
4204 href="#int_stacksave"><tt>llvm.stacksave</tt></a> intrinsic executed. This is
4205 useful for implementing language features like scoped automatic variable sized
4212 See the description for <a href="#int_stacksave"><tt>llvm.stacksave</tt></a>.
4218 <!-- _______________________________________________________________________ -->
4219 <div class="doc_subsubsection">
4220 <a name="int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a>
4223 <div class="doc_text">
4227 declare void @llvm.prefetch(i8* <address>, i32 <rw>, i32 <locality>)
4234 The '<tt>llvm.prefetch</tt>' intrinsic is a hint to the code generator to insert
4235 a prefetch instruction if supported; otherwise, it is a noop. Prefetches have
4237 effect on the behavior of the program but can change its performance
4244 <tt>address</tt> is the address to be prefetched, <tt>rw</tt> is the specifier
4245 determining if the fetch should be for a read (0) or write (1), and
4246 <tt>locality</tt> is a temporal locality specifier ranging from (0) - no
4247 locality, to (3) - extremely local keep in cache. The <tt>rw</tt> and
4248 <tt>locality</tt> arguments must be constant integers.
4254 This intrinsic does not modify the behavior of the program. In particular,
4255 prefetches cannot trap and do not produce a value. On targets that support this
4256 intrinsic, the prefetch can provide hints to the processor cache for better
4262 <!-- _______________________________________________________________________ -->
4263 <div class="doc_subsubsection">
4264 <a name="int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a>
4267 <div class="doc_text">
4271 declare void @llvm.pcmarker(i32 <id>)
4278 The '<tt>llvm.pcmarker</tt>' intrinsic is a method to export a Program Counter
4280 code to simulators and other tools. The method is target specific, but it is
4281 expected that the marker will use exported symbols to transmit the PC of the marker.
4282 The marker makes no guarantees that it will remain with any specific instruction
4283 after optimizations. It is possible that the presence of a marker will inhibit
4284 optimizations. The intended use is to be inserted after optimizations to allow
4285 correlations of simulation runs.
4291 <tt>id</tt> is a numerical id identifying the marker.
4297 This intrinsic does not modify the behavior of the program. Backends that do not
4298 support this intrinisic may ignore it.
4303 <!-- _______________________________________________________________________ -->
4304 <div class="doc_subsubsection">
4305 <a name="int_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a>
4308 <div class="doc_text">
4312 declare i64 @llvm.readcyclecounter( )
4319 The '<tt>llvm.readcyclecounter</tt>' intrinsic provides access to the cycle
4320 counter register (or similar low latency, high accuracy clocks) on those targets
4321 that support it. On X86, it should map to RDTSC. On Alpha, it should map to RPCC.
4322 As the backing counters overflow quickly (on the order of 9 seconds on alpha), this
4323 should only be used for small timings.
4329 When directly supported, reading the cycle counter should not modify any memory.
4330 Implementations are allowed to either return a application specific value or a
4331 system wide value. On backends without support, this is lowered to a constant 0.
4336 <!-- ======================================================================= -->
4337 <div class="doc_subsection">
4338 <a name="int_libc">Standard C Library Intrinsics</a>
4341 <div class="doc_text">
4343 LLVM provides intrinsics for a few important standard C library functions.
4344 These intrinsics allow source-language front-ends to pass information about the
4345 alignment of the pointer arguments to the code generator, providing opportunity
4346 for more efficient code generation.
4351 <!-- _______________________________________________________________________ -->
4352 <div class="doc_subsubsection">
4353 <a name="int_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a>
4356 <div class="doc_text">
4360 declare void @llvm.memcpy.i32(i8 * <dest>, i8 * <src>,
4361 i32 <len>, i32 <align>)
4362 declare void @llvm.memcpy.i64(i8 * <dest>, i8 * <src>,
4363 i64 <len>, i32 <align>)
4369 The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the source
4370 location to the destination location.
4374 Note that, unlike the standard libc function, the <tt>llvm.memcpy.*</tt>
4375 intrinsics do not return a value, and takes an extra alignment argument.
4381 The first argument is a pointer to the destination, the second is a pointer to
4382 the source. The third argument is an integer argument
4383 specifying the number of bytes to copy, and the fourth argument is the alignment
4384 of the source and destination locations.
4388 If the call to this intrinisic has an alignment value that is not 0 or 1, then
4389 the caller guarantees that both the source and destination pointers are aligned
4396 The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the source
4397 location to the destination location, which are not allowed to overlap. It
4398 copies "len" bytes of memory over. If the argument is known to be aligned to
4399 some boundary, this can be specified as the fourth argument, otherwise it should
4405 <!-- _______________________________________________________________________ -->
4406 <div class="doc_subsubsection">
4407 <a name="int_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a>
4410 <div class="doc_text">
4414 declare void @llvm.memmove.i32(i8 * <dest>, i8 * <src>,
4415 i32 <len>, i32 <align>)
4416 declare void @llvm.memmove.i64(i8 * <dest>, i8 * <src>,
4417 i64 <len>, i32 <align>)
4423 The '<tt>llvm.memmove.*</tt>' intrinsics move a block of memory from the source
4424 location to the destination location. It is similar to the
4425 '<tt>llvm.memcmp</tt>' intrinsic but allows the two memory locations to overlap.
4429 Note that, unlike the standard libc function, the <tt>llvm.memmove.*</tt>
4430 intrinsics do not return a value, and takes an extra alignment argument.
4436 The first argument is a pointer to the destination, the second is a pointer to
4437 the source. The third argument is an integer argument
4438 specifying the number of bytes to copy, and the fourth argument is the alignment
4439 of the source and destination locations.
4443 If the call to this intrinisic has an alignment value that is not 0 or 1, then
4444 the caller guarantees that the source and destination pointers are aligned to
4451 The '<tt>llvm.memmove.*</tt>' intrinsics copy a block of memory from the source
4452 location to the destination location, which may overlap. It
4453 copies "len" bytes of memory over. If the argument is known to be aligned to
4454 some boundary, this can be specified as the fourth argument, otherwise it should
4460 <!-- _______________________________________________________________________ -->
4461 <div class="doc_subsubsection">
4462 <a name="int_memset">'<tt>llvm.memset.*</tt>' Intrinsics</a>
4465 <div class="doc_text">
4469 declare void @llvm.memset.i32(i8 * <dest>, i8 <val>,
4470 i32 <len>, i32 <align>)
4471 declare void @llvm.memset.i64(i8 * <dest>, i8 <val>,
4472 i64 <len>, i32 <align>)
4478 The '<tt>llvm.memset.*</tt>' intrinsics fill a block of memory with a particular
4483 Note that, unlike the standard libc function, the <tt>llvm.memset</tt> intrinsic
4484 does not return a value, and takes an extra alignment argument.
4490 The first argument is a pointer to the destination to fill, the second is the
4491 byte value to fill it with, the third argument is an integer
4492 argument specifying the number of bytes to fill, and the fourth argument is the
4493 known alignment of destination location.
4497 If the call to this intrinisic has an alignment value that is not 0 or 1, then
4498 the caller guarantees that the destination pointer is aligned to that boundary.
4504 The '<tt>llvm.memset.*</tt>' intrinsics fill "len" bytes of memory starting at
4506 destination location. If the argument is known to be aligned to some boundary,
4507 this can be specified as the fourth argument, otherwise it should be set to 0 or
4513 <!-- _______________________________________________________________________ -->
4514 <div class="doc_subsubsection">
4515 <a name="int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a>
4518 <div class="doc_text">
4521 <p>This is an overloaded intrinsic. You can use <tt>llvm.sqrt</tt> on any
4522 floating point or vector of floating point type. Not all targets support all
4525 declare float @llvm.sqrt.f32(float %Val)
4526 declare double @llvm.sqrt.f64(double %Val)
4527 declare x86_fp80 @llvm.sqrt.f80(x86_fp80 %Val)
4528 declare fp128 @llvm.sqrt.f128(fp128 %Val)
4529 declare ppc_fp128 @llvm.sqrt.ppcf128(ppc_fp128 %Val)
4535 The '<tt>llvm.sqrt</tt>' intrinsics return the sqrt of the specified operand,
4536 returning the same value as the libm '<tt>sqrt</tt>' functions would. Unlike
4537 <tt>sqrt</tt> in libm, however, <tt>llvm.sqrt</tt> has undefined behavior for
4538 negative numbers (which allows for better optimization).
4544 The argument and return value are floating point numbers of the same type.
4550 This function returns the sqrt of the specified operand if it is a nonnegative
4551 floating point number.
4555 <!-- _______________________________________________________________________ -->
4556 <div class="doc_subsubsection">
4557 <a name="int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a>
4560 <div class="doc_text">
4563 <p>This is an overloaded intrinsic. You can use <tt>llvm.powi</tt> on any
4564 floating point or vector of floating point type. Not all targets support all
4567 declare float @llvm.powi.f32(float %Val, i32 %power)
4568 declare double @llvm.powi.f64(double %Val, i32 %power)
4569 declare x86_fp80 @llvm.powi.f80(x86_fp80 %Val, i32 %power)
4570 declare fp128 @llvm.powi.f128(fp128 %Val, i32 %power)
4571 declare ppc_fp128 @llvm.powi.ppcf128(ppc_fp128 %Val, i32 %power)
4577 The '<tt>llvm.powi.*</tt>' intrinsics return the first operand raised to the
4578 specified (positive or negative) power. The order of evaluation of
4579 multiplications is not defined. When a vector of floating point type is
4580 used, the second argument remains a scalar integer value.
4586 The second argument is an integer power, and the first is a value to raise to
4593 This function returns the first value raised to the second power with an
4594 unspecified sequence of rounding operations.</p>
4597 <!-- _______________________________________________________________________ -->
4598 <div class="doc_subsubsection">
4599 <a name="int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a>
4602 <div class="doc_text">
4605 <p>This is an overloaded intrinsic. You can use <tt>llvm.sin</tt> on any
4606 floating point or vector of floating point type. Not all targets support all
4609 declare float @llvm.sin.f32(float %Val)
4610 declare double @llvm.sin.f64(double %Val)
4611 declare x86_fp80 @llvm.sin.f80(x86_fp80 %Val)
4612 declare fp128 @llvm.sin.f128(fp128 %Val)
4613 declare ppc_fp128 @llvm.sin.ppcf128(ppc_fp128 %Val)
4619 The '<tt>llvm.sin.*</tt>' intrinsics return the sine of the operand.
4625 The argument and return value are floating point numbers of the same type.
4631 This function returns the sine of the specified operand, returning the
4632 same values as the libm <tt>sin</tt> functions would, and handles error
4633 conditions in the same way.</p>
4636 <!-- _______________________________________________________________________ -->
4637 <div class="doc_subsubsection">
4638 <a name="int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a>
4641 <div class="doc_text">
4644 <p>This is an overloaded intrinsic. You can use <tt>llvm.cos</tt> on any
4645 floating point or vector of floating point type. Not all targets support all
4648 declare float @llvm.cos.f32(float %Val)
4649 declare double @llvm.cos.f64(double %Val)
4650 declare x86_fp80 @llvm.cos.f80(x86_fp80 %Val)
4651 declare fp128 @llvm.cos.f128(fp128 %Val)
4652 declare ppc_fp128 @llvm.cos.ppcf128(ppc_fp128 %Val)
4658 The '<tt>llvm.cos.*</tt>' intrinsics return the cosine of the operand.
4664 The argument and return value are floating point numbers of the same type.
4670 This function returns the cosine of the specified operand, returning the
4671 same values as the libm <tt>cos</tt> functions would, and handles error
4672 conditions in the same way.</p>
4675 <!-- _______________________________________________________________________ -->
4676 <div class="doc_subsubsection">
4677 <a name="int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a>
4680 <div class="doc_text">
4683 <p>This is an overloaded intrinsic. You can use <tt>llvm.pow</tt> on any
4684 floating point or vector of floating point type. Not all targets support all
4687 declare float @llvm.pow.f32(float %Val, float %Power)
4688 declare double @llvm.pow.f64(double %Val, double %Power)
4689 declare x86_fp80 @llvm.pow.f80(x86_fp80 %Val, x86_fp80 %Power)
4690 declare fp128 @llvm.pow.f128(fp128 %Val, fp128 %Power)
4691 declare ppc_fp128 @llvm.pow.ppcf128(ppc_fp128 %Val, ppc_fp128 Power)
4697 The '<tt>llvm.pow.*</tt>' intrinsics return the first operand raised to the
4698 specified (positive or negative) power.
4704 The second argument is a floating point power, and the first is a value to
4705 raise to that power.
4711 This function returns the first value raised to the second power,
4713 same values as the libm <tt>pow</tt> functions would, and handles error
4714 conditions in the same way.</p>
4718 <!-- ======================================================================= -->
4719 <div class="doc_subsection">
4720 <a name="int_manip">Bit Manipulation Intrinsics</a>
4723 <div class="doc_text">
4725 LLVM provides intrinsics for a few important bit manipulation operations.
4726 These allow efficient code generation for some algorithms.
4731 <!-- _______________________________________________________________________ -->
4732 <div class="doc_subsubsection">
4733 <a name="int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a>
4736 <div class="doc_text">
4739 <p>This is an overloaded intrinsic function. You can use bswap on any integer
4740 type that is an even number of bytes (i.e. BitWidth % 16 == 0).
4742 declare i16 @llvm.bswap.i16(i16 <id>)
4743 declare i32 @llvm.bswap.i32(i32 <id>)
4744 declare i64 @llvm.bswap.i64(i64 <id>)
4750 The '<tt>llvm.bswap</tt>' family of intrinsics is used to byte swap integer
4751 values with an even number of bytes (positive multiple of 16 bits). These are
4752 useful for performing operations on data that is not in the target's native
4759 The <tt>llvm.bswap.i16</tt> intrinsic returns an i16 value that has the high
4760 and low byte of the input i16 swapped. Similarly, the <tt>llvm.bswap.i32</tt>
4761 intrinsic returns an i32 value that has the four bytes of the input i32
4762 swapped, so that if the input bytes are numbered 0, 1, 2, 3 then the returned
4763 i32 will have its bytes in 3, 2, 1, 0 order. The <tt>llvm.bswap.i48</tt>,
4764 <tt>llvm.bswap.i64</tt> and other intrinsics extend this concept to
4765 additional even-byte lengths (6 bytes, 8 bytes and more, respectively).
4770 <!-- _______________________________________________________________________ -->
4771 <div class="doc_subsubsection">
4772 <a name="int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic</a>
4775 <div class="doc_text">
4778 <p>This is an overloaded intrinsic. You can use llvm.ctpop on any integer bit
4779 width. Not all targets support all bit widths however.
4781 declare i8 @llvm.ctpop.i8 (i8 <src>)
4782 declare i16 @llvm.ctpop.i16(i16 <src>)
4783 declare i32 @llvm.ctpop.i32(i32 <src>)
4784 declare i64 @llvm.ctpop.i64(i64 <src>)
4785 declare i256 @llvm.ctpop.i256(i256 <src>)
4791 The '<tt>llvm.ctpop</tt>' family of intrinsics counts the number of bits set in a
4798 The only argument is the value to be counted. The argument may be of any
4799 integer type. The return type must match the argument type.
4805 The '<tt>llvm.ctpop</tt>' intrinsic counts the 1's in a variable.
4809 <!-- _______________________________________________________________________ -->
4810 <div class="doc_subsubsection">
4811 <a name="int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic</a>
4814 <div class="doc_text">
4817 <p>This is an overloaded intrinsic. You can use <tt>llvm.ctlz</tt> on any
4818 integer bit width. Not all targets support all bit widths however.
4820 declare i8 @llvm.ctlz.i8 (i8 <src>)
4821 declare i16 @llvm.ctlz.i16(i16 <src>)
4822 declare i32 @llvm.ctlz.i32(i32 <src>)
4823 declare i64 @llvm.ctlz.i64(i64 <src>)
4824 declare i256 @llvm.ctlz.i256(i256 <src>)
4830 The '<tt>llvm.ctlz</tt>' family of intrinsic functions counts the number of
4831 leading zeros in a variable.
4837 The only argument is the value to be counted. The argument may be of any
4838 integer type. The return type must match the argument type.
4844 The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant) zeros
4845 in a variable. If the src == 0 then the result is the size in bits of the type
4846 of src. For example, <tt>llvm.ctlz(i32 2) = 30</tt>.
4852 <!-- _______________________________________________________________________ -->
4853 <div class="doc_subsubsection">
4854 <a name="int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic</a>
4857 <div class="doc_text">
4860 <p>This is an overloaded intrinsic. You can use <tt>llvm.cttz</tt> on any
4861 integer bit width. Not all targets support all bit widths however.
4863 declare i8 @llvm.cttz.i8 (i8 <src>)
4864 declare i16 @llvm.cttz.i16(i16 <src>)
4865 declare i32 @llvm.cttz.i32(i32 <src>)
4866 declare i64 @llvm.cttz.i64(i64 <src>)
4867 declare i256 @llvm.cttz.i256(i256 <src>)
4873 The '<tt>llvm.cttz</tt>' family of intrinsic functions counts the number of
4880 The only argument is the value to be counted. The argument may be of any
4881 integer type. The return type must match the argument type.
4887 The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant) zeros
4888 in a variable. If the src == 0 then the result is the size in bits of the type
4889 of src. For example, <tt>llvm.cttz(2) = 1</tt>.
4893 <!-- _______________________________________________________________________ -->
4894 <div class="doc_subsubsection">
4895 <a name="int_part_select">'<tt>llvm.part.select.*</tt>' Intrinsic</a>
4898 <div class="doc_text">
4901 <p>This is an overloaded intrinsic. You can use <tt>llvm.part.select</tt>
4902 on any integer bit width.
4904 declare i17 @llvm.part.select.i17 (i17 %val, i32 %loBit, i32 %hiBit)
4905 declare i29 @llvm.part.select.i29 (i29 %val, i32 %loBit, i32 %hiBit)
4909 <p>The '<tt>llvm.part.select</tt>' family of intrinsic functions selects a
4910 range of bits from an integer value and returns them in the same bit width as
4911 the original value.</p>
4914 <p>The first argument, <tt>%val</tt> and the result may be integer types of
4915 any bit width but they must have the same bit width. The second and third
4916 arguments must be <tt>i32</tt> type since they specify only a bit index.</p>
4919 <p>The operation of the '<tt>llvm.part.select</tt>' intrinsic has two modes
4920 of operation: forwards and reverse. If <tt>%loBit</tt> is greater than
4921 <tt>%hiBits</tt> then the intrinsic operates in reverse mode. Otherwise it
4922 operates in forward mode.</p>
4923 <p>In forward mode, this intrinsic is the equivalent of shifting <tt>%val</tt>
4924 right by <tt>%loBit</tt> bits and then ANDing it with a mask with
4925 only the <tt>%hiBit - %loBit</tt> bits set, as follows:</p>
4927 <li>The <tt>%val</tt> is shifted right (LSHR) by the number of bits specified
4928 by <tt>%loBits</tt>. This normalizes the value to the low order bits.</li>
4929 <li>The <tt>%loBits</tt> value is subtracted from the <tt>%hiBits</tt> value
4930 to determine the number of bits to retain.</li>
4931 <li>A mask of the retained bits is created by shifting a -1 value.</li>
4932 <li>The mask is ANDed with <tt>%val</tt> to produce the result.
4934 <p>In reverse mode, a similar computation is made except that the bits are
4935 returned in the reverse order. So, for example, if <tt>X</tt> has the value
4936 <tt>i16 0x0ACF (101011001111)</tt> and we apply
4937 <tt>part.select(i16 X, 8, 3)</tt> to it, we get back the value
4938 <tt>i16 0x0026 (000000100110)</tt>.</p>
4941 <div class="doc_subsubsection">
4942 <a name="int_part_set">'<tt>llvm.part.set.*</tt>' Intrinsic</a>
4945 <div class="doc_text">
4948 <p>This is an overloaded intrinsic. You can use <tt>llvm.part.set</tt>
4949 on any integer bit width.
4951 declare i17 @llvm.part.set.i17.i9 (i17 %val, i9 %repl, i32 %lo, i32 %hi)
4952 declare i29 @llvm.part.set.i29.i9 (i29 %val, i9 %repl, i32 %lo, i32 %hi)
4956 <p>The '<tt>llvm.part.set</tt>' family of intrinsic functions replaces a range
4957 of bits in an integer value with another integer value. It returns the integer
4958 with the replaced bits.</p>
4961 <p>The first argument, <tt>%val</tt> and the result may be integer types of
4962 any bit width but they must have the same bit width. <tt>%val</tt> is the value
4963 whose bits will be replaced. The second argument, <tt>%repl</tt> may be an
4964 integer of any bit width. The third and fourth arguments must be <tt>i32</tt>
4965 type since they specify only a bit index.</p>
4968 <p>The operation of the '<tt>llvm.part.set</tt>' intrinsic has two modes
4969 of operation: forwards and reverse. If <tt>%lo</tt> is greater than
4970 <tt>%hi</tt> then the intrinsic operates in reverse mode. Otherwise it
4971 operates in forward mode.</p>
4972 <p>For both modes, the <tt>%repl</tt> value is prepared for use by either
4973 truncating it down to the size of the replacement area or zero extending it
4974 up to that size.</p>
4975 <p>In forward mode, the bits between <tt>%lo</tt> and <tt>%hi</tt> (inclusive)
4976 are replaced with corresponding bits from <tt>%repl</tt>. That is the 0th bit
4977 in <tt>%repl</tt> replaces the <tt>%lo</tt>th bit in <tt>%val</tt> and etc. up
4978 to the <tt>%hi</tt>th bit.
4979 <p>In reverse mode, a similar computation is made except that the bits are
4980 reversed. That is, the <tt>0</tt>th bit in <tt>%repl</tt> replaces the
4981 <tt>%hi</tt> bit in <tt>%val</tt> and etc. down to the <tt>%lo</tt>th bit.
4984 llvm.part.set(0xFFFF, 0, 4, 7) -> 0xFF0F
4985 llvm.part.set(0xFFFF, 0, 7, 4) -> 0xFF0F
4986 llvm.part.set(0xFFFF, 1, 7, 4) -> 0xFF8F
4987 llvm.part.set(0xFFFF, F, 8, 3) -> 0xFFE7
4988 llvm.part.set(0xFFFF, 0, 3, 8) -> 0xFE07
4992 <!-- ======================================================================= -->
4993 <div class="doc_subsection">
4994 <a name="int_debugger">Debugger Intrinsics</a>
4997 <div class="doc_text">
4999 The LLVM debugger intrinsics (which all start with <tt>llvm.dbg.</tt> prefix),
5000 are described in the <a
5001 href="SourceLevelDebugging.html#format_common_intrinsics">LLVM Source Level
5002 Debugging</a> document.
5007 <!-- ======================================================================= -->
5008 <div class="doc_subsection">
5009 <a name="int_eh">Exception Handling Intrinsics</a>
5012 <div class="doc_text">
5013 <p> The LLVM exception handling intrinsics (which all start with
5014 <tt>llvm.eh.</tt> prefix), are described in the <a
5015 href="ExceptionHandling.html#format_common_intrinsics">LLVM Exception
5016 Handling</a> document. </p>
5019 <!-- ======================================================================= -->
5020 <div class="doc_subsection">
5021 <a name="int_trampoline">Trampoline Intrinsic</a>
5024 <div class="doc_text">
5026 This intrinsic makes it possible to excise one parameter, marked with
5027 the <tt>nest</tt> attribute, from a function. The result is a callable
5028 function pointer lacking the nest parameter - the caller does not need
5029 to provide a value for it. Instead, the value to use is stored in
5030 advance in a "trampoline", a block of memory usually allocated
5031 on the stack, which also contains code to splice the nest value into the
5032 argument list. This is used to implement the GCC nested function address
5036 For example, if the function is
5037 <tt>i32 f(i8* nest %c, i32 %x, i32 %y)</tt> then the resulting function
5038 pointer has signature <tt>i32 (i32, i32)*</tt>. It can be created as follows:</p>
5040 %tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86
5041 %tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0
5042 %p = call i8* @llvm.init.trampoline( i8* %tramp1, i8* bitcast (i32 (i8* nest , i32, i32)* @f to i8*), i8* %nval )
5043 %fp = bitcast i8* %p to i32 (i32, i32)*
5045 <p>The call <tt>%val = call i32 %fp( i32 %x, i32 %y )</tt> is then equivalent
5046 to <tt>%val = call i32 %f( i8* %nval, i32 %x, i32 %y )</tt>.</p>
5049 <!-- _______________________________________________________________________ -->
5050 <div class="doc_subsubsection">
5051 <a name="int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a>
5053 <div class="doc_text">
5056 declare i8* @llvm.init.trampoline(i8* <tramp>, i8* <func>, i8* <nval>)
5060 This fills the memory pointed to by <tt>tramp</tt> with code
5061 and returns a function pointer suitable for executing it.
5065 The <tt>llvm.init.trampoline</tt> intrinsic takes three arguments, all
5066 pointers. The <tt>tramp</tt> argument must point to a sufficiently large
5067 and sufficiently aligned block of memory; this memory is written to by the
5068 intrinsic. Note that the size and the alignment are target-specific - LLVM
5069 currently provides no portable way of determining them, so a front-end that
5070 generates this intrinsic needs to have some target-specific knowledge.
5071 The <tt>func</tt> argument must hold a function bitcast to an <tt>i8*</tt>.
5075 The block of memory pointed to by <tt>tramp</tt> is filled with target
5076 dependent code, turning it into a function. A pointer to this function is
5077 returned, but needs to be bitcast to an
5078 <a href="#int_trampoline">appropriate function pointer type</a>
5079 before being called. The new function's signature is the same as that of
5080 <tt>func</tt> with any arguments marked with the <tt>nest</tt> attribute
5081 removed. At most one such <tt>nest</tt> argument is allowed, and it must be
5082 of pointer type. Calling the new function is equivalent to calling
5083 <tt>func</tt> with the same argument list, but with <tt>nval</tt> used for the
5084 missing <tt>nest</tt> argument. If, after calling
5085 <tt>llvm.init.trampoline</tt>, the memory pointed to by <tt>tramp</tt> is
5086 modified, then the effect of any later call to the returned function pointer is
5091 <!-- ======================================================================= -->
5092 <div class="doc_subsection">
5093 <a name="int_general">General Intrinsics</a>
5096 <div class="doc_text">
5097 <p> This class of intrinsics is designed to be generic and has
5098 no specific purpose. </p>
5101 <!-- _______________________________________________________________________ -->
5102 <div class="doc_subsubsection">
5103 <a name="int_var_annotation">'<tt>llvm.var.annotation</tt>' Intrinsic</a>
5106 <div class="doc_text">
5110 declare void @llvm.var.annotation(i8* <val>, i8* <str>, i8* <str>, i32 <int> )
5116 The '<tt>llvm.var.annotation</tt>' intrinsic
5122 The first argument is a pointer to a value, the second is a pointer to a
5123 global string, the third is a pointer to a global string which is the source
5124 file name, and the last argument is the line number.
5130 This intrinsic allows annotation of local variables with arbitrary strings.
5131 This can be useful for special purpose optimizations that want to look for these
5132 annotations. These have no other defined use, they are ignored by code
5133 generation and optimization.
5136 <!-- _______________________________________________________________________ -->
5137 <div class="doc_subsubsection">
5138 <a name="int_annotation">'<tt>llvm.annotation.*</tt>' Intrinsic</a>
5141 <div class="doc_text">
5144 <p>This is an overloaded intrinsic. You can use '<tt>llvm.annotation</tt>' on
5145 any integer bit width.
5148 declare i8 @llvm.annotation.i8(i8 <val>, i8* <str>, i8* <str>, i32 <int> )
5149 declare i16 @llvm.annotation.i16(i16 <val>, i8* <str>, i8* <str>, i32 <int> )
5150 declare i32 @llvm.annotation.i32(i32 <val>, i8* <str>, i8* <str>, i32 <int> )
5151 declare i64 @llvm.annotation.i64(i64 <val>, i8* <str>, i8* <str>, i32 <int> )
5152 declare i256 @llvm.annotation.i256(i256 <val>, i8* <str>, i8* <str>, i32 <int> )
5158 The '<tt>llvm.annotation</tt>' intrinsic.
5164 The first argument is an integer value (result of some expression),
5165 the second is a pointer to a global string, the third is a pointer to a global
5166 string which is the source file name, and the last argument is the line number.
5167 It returns the value of the first argument.
5173 This intrinsic allows annotations to be put on arbitrary expressions
5174 with arbitrary strings. This can be useful for special purpose optimizations
5175 that want to look for these annotations. These have no other defined use, they
5176 are ignored by code generation and optimization.
5179 <!-- *********************************************************************** -->
5182 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
5183 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
5184 <a href="http://validator.w3.org/check/referer"><img
5185 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
5187 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
5188 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
5189 Last modified: $Date$