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5 <title>LLVM Assembly Language Reference Manual</title>
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7 <meta name="author" content="Chris Lattner">
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9 content="LLVM Assembly Language Reference Manual.">
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15 <div class="doc_title"> LLVM Language Reference Manual </div>
17 <li><a href="#abstract">Abstract</a></li>
18 <li><a href="#introduction">Introduction</a></li>
19 <li><a href="#identifiers">Identifiers</a></li>
20 <li><a href="#highlevel">High Level Structure</a>
22 <li><a href="#modulestructure">Module Structure</a></li>
23 <li><a href="#linkage">Linkage Types</a>
25 <li><a href="#linkage_private">'<tt>private</tt>' Linkage</a></li>
26 <li><a href="#linkage_linker_private">'<tt>linker_private</tt>' Linkage</a></li>
27 <li><a href="#linkage_internal">'<tt>internal</tt>' Linkage</a></li>
28 <li><a href="#linkage_available_externally">'<tt>available_externally</tt>' Linkage</a></li>
29 <li><a href="#linkage_linkonce">'<tt>linkonce</tt>' Linkage</a></li>
30 <li><a href="#linkage_common">'<tt>common</tt>' Linkage</a></li>
31 <li><a href="#linkage_weak">'<tt>weak</tt>' Linkage</a></li>
32 <li><a href="#linkage_appending">'<tt>appending</tt>' Linkage</a></li>
33 <li><a href="#linkage_externweak">'<tt>extern_weak</tt>' Linkage</a></li>
34 <li><a href="#linkage_linkonce_odr">'<tt>linkonce_odr</tt>' Linkage</a></li>
35 <li><a href="#linkage_weak">'<tt>weak_odr</tt>' Linkage</a></li>
36 <li><a href="#linkage_external">'<tt>externally visible</tt>' Linkage</a></li>
37 <li><a href="#linkage_dllimport">'<tt>dllimport</tt>' Linkage</a></li>
38 <li><a href="#linkage_dllexport">'<tt>dllexport</tt>' Linkage</a></li>
41 <li><a href="#callingconv">Calling Conventions</a></li>
42 <li><a href="#namedtypes">Named Types</a></li>
43 <li><a href="#globalvars">Global Variables</a></li>
44 <li><a href="#functionstructure">Functions</a></li>
45 <li><a href="#aliasstructure">Aliases</a></li>
46 <li><a href="#namedmetadatastructure">Named Metadata</a></li>
47 <li><a href="#paramattrs">Parameter Attributes</a></li>
48 <li><a href="#fnattrs">Function Attributes</a></li>
49 <li><a href="#gc">Garbage Collector Names</a></li>
50 <li><a href="#moduleasm">Module-Level Inline Assembly</a></li>
51 <li><a href="#datalayout">Data Layout</a></li>
52 <li><a href="#pointeraliasing">Pointer Aliasing Rules</a></li>
53 <li><a href="#volatile">Volatile Memory Accesses</a></li>
56 <li><a href="#typesystem">Type System</a>
58 <li><a href="#t_classifications">Type Classifications</a></li>
59 <li><a href="#t_primitive">Primitive Types</a>
61 <li><a href="#t_integer">Integer Type</a></li>
62 <li><a href="#t_floating">Floating Point Types</a></li>
63 <li><a href="#t_void">Void Type</a></li>
64 <li><a href="#t_label">Label Type</a></li>
65 <li><a href="#t_metadata">Metadata Type</a></li>
68 <li><a href="#t_derived">Derived Types</a>
70 <li><a href="#t_aggregate">Aggregate Types</a>
72 <li><a href="#t_array">Array Type</a></li>
73 <li><a href="#t_struct">Structure Type</a></li>
74 <li><a href="#t_pstruct">Packed Structure Type</a></li>
75 <li><a href="#t_union">Union Type</a></li>
76 <li><a href="#t_vector">Vector Type</a></li>
79 <li><a href="#t_function">Function Type</a></li>
80 <li><a href="#t_pointer">Pointer Type</a></li>
81 <li><a href="#t_opaque">Opaque Type</a></li>
84 <li><a href="#t_uprefs">Type Up-references</a></li>
87 <li><a href="#constants">Constants</a>
89 <li><a href="#simpleconstants">Simple Constants</a></li>
90 <li><a href="#complexconstants">Complex Constants</a></li>
91 <li><a href="#globalconstants">Global Variable and Function Addresses</a></li>
92 <li><a href="#undefvalues">Undefined Values</a></li>
93 <li><a href="#trapvalues">Trap Values</a></li>
94 <li><a href="#blockaddress">Addresses of Basic Blocks</a></li>
95 <li><a href="#constantexprs">Constant Expressions</a></li>
98 <li><a href="#othervalues">Other Values</a>
100 <li><a href="#inlineasm">Inline Assembler Expressions</a></li>
101 <li><a href="#metadata">Metadata Nodes and Metadata Strings</a></li>
104 <li><a href="#intrinsic_globals">Intrinsic Global Variables</a>
106 <li><a href="#intg_used">The '<tt>llvm.used</tt>' Global Variable</a></li>
107 <li><a href="#intg_compiler_used">The '<tt>llvm.compiler.used</tt>'
108 Global Variable</a></li>
109 <li><a href="#intg_global_ctors">The '<tt>llvm.global_ctors</tt>'
110 Global Variable</a></li>
111 <li><a href="#intg_global_dtors">The '<tt>llvm.global_dtors</tt>'
112 Global Variable</a></li>
115 <li><a href="#instref">Instruction Reference</a>
117 <li><a href="#terminators">Terminator Instructions</a>
119 <li><a href="#i_ret">'<tt>ret</tt>' Instruction</a></li>
120 <li><a href="#i_br">'<tt>br</tt>' Instruction</a></li>
121 <li><a href="#i_switch">'<tt>switch</tt>' Instruction</a></li>
122 <li><a href="#i_indirectbr">'<tt>indirectbr</tt>' Instruction</a></li>
123 <li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a></li>
124 <li><a href="#i_unwind">'<tt>unwind</tt>' Instruction</a></li>
125 <li><a href="#i_unreachable">'<tt>unreachable</tt>' Instruction</a></li>
128 <li><a href="#binaryops">Binary Operations</a>
130 <li><a href="#i_add">'<tt>add</tt>' Instruction</a></li>
131 <li><a href="#i_fadd">'<tt>fadd</tt>' Instruction</a></li>
132 <li><a href="#i_sub">'<tt>sub</tt>' Instruction</a></li>
133 <li><a href="#i_fsub">'<tt>fsub</tt>' Instruction</a></li>
134 <li><a href="#i_mul">'<tt>mul</tt>' Instruction</a></li>
135 <li><a href="#i_fmul">'<tt>fmul</tt>' Instruction</a></li>
136 <li><a href="#i_udiv">'<tt>udiv</tt>' Instruction</a></li>
137 <li><a href="#i_sdiv">'<tt>sdiv</tt>' Instruction</a></li>
138 <li><a href="#i_fdiv">'<tt>fdiv</tt>' Instruction</a></li>
139 <li><a href="#i_urem">'<tt>urem</tt>' Instruction</a></li>
140 <li><a href="#i_srem">'<tt>srem</tt>' Instruction</a></li>
141 <li><a href="#i_frem">'<tt>frem</tt>' Instruction</a></li>
144 <li><a href="#bitwiseops">Bitwise Binary Operations</a>
146 <li><a href="#i_shl">'<tt>shl</tt>' Instruction</a></li>
147 <li><a href="#i_lshr">'<tt>lshr</tt>' Instruction</a></li>
148 <li><a href="#i_ashr">'<tt>ashr</tt>' Instruction</a></li>
149 <li><a href="#i_and">'<tt>and</tt>' Instruction</a></li>
150 <li><a href="#i_or">'<tt>or</tt>' Instruction</a></li>
151 <li><a href="#i_xor">'<tt>xor</tt>' Instruction</a></li>
154 <li><a href="#vectorops">Vector Operations</a>
156 <li><a href="#i_extractelement">'<tt>extractelement</tt>' Instruction</a></li>
157 <li><a href="#i_insertelement">'<tt>insertelement</tt>' Instruction</a></li>
158 <li><a href="#i_shufflevector">'<tt>shufflevector</tt>' Instruction</a></li>
161 <li><a href="#aggregateops">Aggregate Operations</a>
163 <li><a href="#i_extractvalue">'<tt>extractvalue</tt>' Instruction</a></li>
164 <li><a href="#i_insertvalue">'<tt>insertvalue</tt>' Instruction</a></li>
167 <li><a href="#memoryops">Memory Access and Addressing Operations</a>
169 <li><a href="#i_alloca">'<tt>alloca</tt>' Instruction</a></li>
170 <li><a href="#i_load">'<tt>load</tt>' Instruction</a></li>
171 <li><a href="#i_store">'<tt>store</tt>' Instruction</a></li>
172 <li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a></li>
175 <li><a href="#convertops">Conversion Operations</a>
177 <li><a href="#i_trunc">'<tt>trunc .. to</tt>' Instruction</a></li>
178 <li><a href="#i_zext">'<tt>zext .. to</tt>' Instruction</a></li>
179 <li><a href="#i_sext">'<tt>sext .. to</tt>' Instruction</a></li>
180 <li><a href="#i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a></li>
181 <li><a href="#i_fpext">'<tt>fpext .. to</tt>' Instruction</a></li>
182 <li><a href="#i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a></li>
183 <li><a href="#i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a></li>
184 <li><a href="#i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a></li>
185 <li><a href="#i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a></li>
186 <li><a href="#i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a></li>
187 <li><a href="#i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a></li>
188 <li><a href="#i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a></li>
191 <li><a href="#otherops">Other Operations</a>
193 <li><a href="#i_icmp">'<tt>icmp</tt>' Instruction</a></li>
194 <li><a href="#i_fcmp">'<tt>fcmp</tt>' Instruction</a></li>
195 <li><a href="#i_phi">'<tt>phi</tt>' Instruction</a></li>
196 <li><a href="#i_select">'<tt>select</tt>' Instruction</a></li>
197 <li><a href="#i_call">'<tt>call</tt>' Instruction</a></li>
198 <li><a href="#i_va_arg">'<tt>va_arg</tt>' Instruction</a></li>
203 <li><a href="#intrinsics">Intrinsic Functions</a>
205 <li><a href="#int_varargs">Variable Argument Handling Intrinsics</a>
207 <li><a href="#int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a></li>
208 <li><a href="#int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a></li>
209 <li><a href="#int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a></li>
212 <li><a href="#int_gc">Accurate Garbage Collection Intrinsics</a>
214 <li><a href="#int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a></li>
215 <li><a href="#int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a></li>
216 <li><a href="#int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a></li>
219 <li><a href="#int_codegen">Code Generator Intrinsics</a>
221 <li><a href="#int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a></li>
222 <li><a href="#int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li>
223 <li><a href="#int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a></li>
224 <li><a href="#int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a></li>
225 <li><a href="#int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a></li>
226 <li><a href="#int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a></li>
227 <li><a href="#int_readcyclecounter"><tt>llvm.readcyclecounter</tt>' Intrinsic</a></li>
230 <li><a href="#int_libc">Standard C Library Intrinsics</a>
232 <li><a href="#int_memcpy">'<tt>llvm.memcpy.*</tt>' Intrinsic</a></li>
233 <li><a href="#int_memmove">'<tt>llvm.memmove.*</tt>' Intrinsic</a></li>
234 <li><a href="#int_memset">'<tt>llvm.memset.*</tt>' Intrinsic</a></li>
235 <li><a href="#int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a></li>
236 <li><a href="#int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a></li>
237 <li><a href="#int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a></li>
238 <li><a href="#int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a></li>
239 <li><a href="#int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a></li>
242 <li><a href="#int_manip">Bit Manipulation Intrinsics</a>
244 <li><a href="#int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a></li>
245 <li><a href="#int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic </a></li>
246 <li><a href="#int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic </a></li>
247 <li><a href="#int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic </a></li>
250 <li><a href="#int_overflow">Arithmetic with Overflow Intrinsics</a>
252 <li><a href="#int_sadd_overflow">'<tt>llvm.sadd.with.overflow.*</tt> Intrinsics</a></li>
253 <li><a href="#int_uadd_overflow">'<tt>llvm.uadd.with.overflow.*</tt> Intrinsics</a></li>
254 <li><a href="#int_ssub_overflow">'<tt>llvm.ssub.with.overflow.*</tt> Intrinsics</a></li>
255 <li><a href="#int_usub_overflow">'<tt>llvm.usub.with.overflow.*</tt> Intrinsics</a></li>
256 <li><a href="#int_smul_overflow">'<tt>llvm.smul.with.overflow.*</tt> Intrinsics</a></li>
257 <li><a href="#int_umul_overflow">'<tt>llvm.umul.with.overflow.*</tt> Intrinsics</a></li>
260 <li><a href="#int_fp16">Half Precision Floating Point Intrinsics</a>
262 <li><a href="#int_convert_to_fp16">'<tt>llvm.convert.to.fp16</tt>' Intrinsic</a></li>
263 <li><a href="#int_convert_from_fp16">'<tt>llvm.convert.from.fp16</tt>' Intrinsic</a></li>
266 <li><a href="#int_debugger">Debugger intrinsics</a></li>
267 <li><a href="#int_eh">Exception Handling intrinsics</a></li>
268 <li><a href="#int_trampoline">Trampoline Intrinsic</a>
270 <li><a href="#int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a></li>
273 <li><a href="#int_atomics">Atomic intrinsics</a>
275 <li><a href="#int_memory_barrier"><tt>llvm.memory_barrier</tt></a></li>
276 <li><a href="#int_atomic_cmp_swap"><tt>llvm.atomic.cmp.swap</tt></a></li>
277 <li><a href="#int_atomic_swap"><tt>llvm.atomic.swap</tt></a></li>
278 <li><a href="#int_atomic_load_add"><tt>llvm.atomic.load.add</tt></a></li>
279 <li><a href="#int_atomic_load_sub"><tt>llvm.atomic.load.sub</tt></a></li>
280 <li><a href="#int_atomic_load_and"><tt>llvm.atomic.load.and</tt></a></li>
281 <li><a href="#int_atomic_load_nand"><tt>llvm.atomic.load.nand</tt></a></li>
282 <li><a href="#int_atomic_load_or"><tt>llvm.atomic.load.or</tt></a></li>
283 <li><a href="#int_atomic_load_xor"><tt>llvm.atomic.load.xor</tt></a></li>
284 <li><a href="#int_atomic_load_max"><tt>llvm.atomic.load.max</tt></a></li>
285 <li><a href="#int_atomic_load_min"><tt>llvm.atomic.load.min</tt></a></li>
286 <li><a href="#int_atomic_load_umax"><tt>llvm.atomic.load.umax</tt></a></li>
287 <li><a href="#int_atomic_load_umin"><tt>llvm.atomic.load.umin</tt></a></li>
290 <li><a href="#int_memorymarkers">Memory Use Markers</a>
292 <li><a href="#int_lifetime_start"><tt>llvm.lifetime.start</tt></a></li>
293 <li><a href="#int_lifetime_end"><tt>llvm.lifetime.end</tt></a></li>
294 <li><a href="#int_invariant_start"><tt>llvm.invariant.start</tt></a></li>
295 <li><a href="#int_invariant_end"><tt>llvm.invariant.end</tt></a></li>
298 <li><a href="#int_general">General intrinsics</a>
300 <li><a href="#int_var_annotation">
301 '<tt>llvm.var.annotation</tt>' Intrinsic</a></li>
302 <li><a href="#int_annotation">
303 '<tt>llvm.annotation.*</tt>' Intrinsic</a></li>
304 <li><a href="#int_trap">
305 '<tt>llvm.trap</tt>' Intrinsic</a></li>
306 <li><a href="#int_stackprotector">
307 '<tt>llvm.stackprotector</tt>' Intrinsic</a></li>
308 <li><a href="#int_objectsize">
309 '<tt>llvm.objectsize</tt>' Intrinsic</a></li>
316 <div class="doc_author">
317 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>
318 and <a href="mailto:vadve@cs.uiuc.edu">Vikram Adve</a></p>
321 <!-- *********************************************************************** -->
322 <div class="doc_section"> <a name="abstract">Abstract </a></div>
323 <!-- *********************************************************************** -->
325 <div class="doc_text">
327 <p>This document is a reference manual for the LLVM assembly language. LLVM is
328 a Static Single Assignment (SSA) based representation that provides type
329 safety, low-level operations, flexibility, and the capability of representing
330 'all' high-level languages cleanly. It is the common code representation
331 used throughout all phases of the LLVM compilation strategy.</p>
335 <!-- *********************************************************************** -->
336 <div class="doc_section"> <a name="introduction">Introduction</a> </div>
337 <!-- *********************************************************************** -->
339 <div class="doc_text">
341 <p>The LLVM code representation is designed to be used in three different forms:
342 as an in-memory compiler IR, as an on-disk bitcode representation (suitable
343 for fast loading by a Just-In-Time compiler), and as a human readable
344 assembly language representation. This allows LLVM to provide a powerful
345 intermediate representation for efficient compiler transformations and
346 analysis, while providing a natural means to debug and visualize the
347 transformations. The three different forms of LLVM are all equivalent. This
348 document describes the human readable representation and notation.</p>
350 <p>The LLVM representation aims to be light-weight and low-level while being
351 expressive, typed, and extensible at the same time. It aims to be a
352 "universal IR" of sorts, by being at a low enough level that high-level ideas
353 may be cleanly mapped to it (similar to how microprocessors are "universal
354 IR's", allowing many source languages to be mapped to them). By providing
355 type information, LLVM can be used as the target of optimizations: for
356 example, through pointer analysis, it can be proven that a C automatic
357 variable is never accessed outside of the current function, allowing it to
358 be promoted to a simple SSA value instead of a memory location.</p>
362 <!-- _______________________________________________________________________ -->
363 <div class="doc_subsubsection"> <a name="wellformed">Well-Formedness</a> </div>
365 <div class="doc_text">
367 <p>It is important to note that this document describes 'well formed' LLVM
368 assembly language. There is a difference between what the parser accepts and
369 what is considered 'well formed'. For example, the following instruction is
370 syntactically okay, but not well formed:</p>
372 <div class="doc_code">
374 %x = <a href="#i_add">add</a> i32 1, %x
378 <p>because the definition of <tt>%x</tt> does not dominate all of its uses. The
379 LLVM infrastructure provides a verification pass that may be used to verify
380 that an LLVM module is well formed. This pass is automatically run by the
381 parser after parsing input assembly and by the optimizer before it outputs
382 bitcode. The violations pointed out by the verifier pass indicate bugs in
383 transformation passes or input to the parser.</p>
387 <!-- Describe the typesetting conventions here. -->
389 <!-- *********************************************************************** -->
390 <div class="doc_section"> <a name="identifiers">Identifiers</a> </div>
391 <!-- *********************************************************************** -->
393 <div class="doc_text">
395 <p>LLVM identifiers come in two basic types: global and local. Global
396 identifiers (functions, global variables) begin with the <tt>'@'</tt>
397 character. Local identifiers (register names, types) begin with
398 the <tt>'%'</tt> character. Additionally, there are three different formats
399 for identifiers, for different purposes:</p>
402 <li>Named values are represented as a string of characters with their prefix.
403 For example, <tt>%foo</tt>, <tt>@DivisionByZero</tt>,
404 <tt>%a.really.long.identifier</tt>. The actual regular expression used is
405 '<tt>[%@][a-zA-Z$._][a-zA-Z$._0-9]*</tt>'. Identifiers which require
406 other characters in their names can be surrounded with quotes. Special
407 characters may be escaped using <tt>"\xx"</tt> where <tt>xx</tt> is the
408 ASCII code for the character in hexadecimal. In this way, any character
409 can be used in a name value, even quotes themselves.</li>
411 <li>Unnamed values are represented as an unsigned numeric value with their
412 prefix. For example, <tt>%12</tt>, <tt>@2</tt>, <tt>%44</tt>.</li>
414 <li>Constants, which are described in a <a href="#constants">section about
415 constants</a>, below.</li>
418 <p>LLVM requires that values start with a prefix for two reasons: Compilers
419 don't need to worry about name clashes with reserved words, and the set of
420 reserved words may be expanded in the future without penalty. Additionally,
421 unnamed identifiers allow a compiler to quickly come up with a temporary
422 variable without having to avoid symbol table conflicts.</p>
424 <p>Reserved words in LLVM are very similar to reserved words in other
425 languages. There are keywords for different opcodes
426 ('<tt><a href="#i_add">add</a></tt>',
427 '<tt><a href="#i_bitcast">bitcast</a></tt>',
428 '<tt><a href="#i_ret">ret</a></tt>', etc...), for primitive type names
429 ('<tt><a href="#t_void">void</a></tt>',
430 '<tt><a href="#t_primitive">i32</a></tt>', etc...), and others. These
431 reserved words cannot conflict with variable names, because none of them
432 start with a prefix character (<tt>'%'</tt> or <tt>'@'</tt>).</p>
434 <p>Here is an example of LLVM code to multiply the integer variable
435 '<tt>%X</tt>' by 8:</p>
439 <div class="doc_code">
441 %result = <a href="#i_mul">mul</a> i32 %X, 8
445 <p>After strength reduction:</p>
447 <div class="doc_code">
449 %result = <a href="#i_shl">shl</a> i32 %X, i8 3
453 <p>And the hard way:</p>
455 <div class="doc_code">
457 %0 = <a href="#i_add">add</a> i32 %X, %X <i>; yields {i32}:%0</i>
458 %1 = <a href="#i_add">add</a> i32 %0, %0 <i>; yields {i32}:%1</i>
459 %result = <a href="#i_add">add</a> i32 %1, %1
463 <p>This last way of multiplying <tt>%X</tt> by 8 illustrates several important
464 lexical features of LLVM:</p>
467 <li>Comments are delimited with a '<tt>;</tt>' and go until the end of
470 <li>Unnamed temporaries are created when the result of a computation is not
471 assigned to a named value.</li>
473 <li>Unnamed temporaries are numbered sequentially</li>
476 <p>It also shows a convention that we follow in this document. When
477 demonstrating instructions, we will follow an instruction with a comment that
478 defines the type and name of value produced. Comments are shown in italic
483 <!-- *********************************************************************** -->
484 <div class="doc_section"> <a name="highlevel">High Level Structure</a> </div>
485 <!-- *********************************************************************** -->
487 <!-- ======================================================================= -->
488 <div class="doc_subsection"> <a name="modulestructure">Module Structure</a>
491 <div class="doc_text">
493 <p>LLVM programs are composed of "Module"s, each of which is a translation unit
494 of the input programs. Each module consists of functions, global variables,
495 and symbol table entries. Modules may be combined together with the LLVM
496 linker, which merges function (and global variable) definitions, resolves
497 forward declarations, and merges symbol table entries. Here is an example of
498 the "hello world" module:</p>
500 <div class="doc_code">
502 <i>; Declare the string constant as a global constant.</i>
503 <a href="#identifiers">@.LC0</a> = <a href="#linkage_internal">internal</a> <a href="#globalvars">constant</a> <a href="#t_array">[13 x i8]</a> c"hello world\0A\00" <i>; [13 x i8]*</i>
505 <i>; External declaration of the puts function</i>
506 <a href="#functionstructure">declare</a> i32 @puts(i8 *) <i>; i32(i8 *)* </i>
508 <i>; Definition of main function</i>
509 define i32 @main() { <i>; i32()* </i>
510 <i>; Convert [13 x i8]* to i8 *...</i>
511 %cast210 = <a href="#i_getelementptr">getelementptr</a> [13 x i8]* @.LC0, i64 0, i64 0 <i>; i8 *</i>
513 <i>; Call puts function to write out the string to stdout.</i>
514 <a href="#i_call">call</a> i32 @puts(i8 * %cast210) <i>; i32</i>
515 <a href="#i_ret">ret</a> i32 0<br>}
517 <i>; Named metadata</i>
518 !1 = metadata !{i32 41}
523 <p>This example is made up of a <a href="#globalvars">global variable</a> named
524 "<tt>.LC0</tt>", an external declaration of the "<tt>puts</tt>" function,
525 a <a href="#functionstructure">function definition</a> for
526 "<tt>main</tt>" and <a href="#namedmetadatastructure">named metadata</a>
529 <p>In general, a module is made up of a list of global values, where both
530 functions and global variables are global values. Global values are
531 represented by a pointer to a memory location (in this case, a pointer to an
532 array of char, and a pointer to a function), and have one of the
533 following <a href="#linkage">linkage types</a>.</p>
537 <!-- ======================================================================= -->
538 <div class="doc_subsection">
539 <a name="linkage">Linkage Types</a>
542 <div class="doc_text">
544 <p>All Global Variables and Functions have one of the following types of
548 <dt><tt><b><a name="linkage_private">private</a></b></tt></dt>
549 <dd>Global values with private linkage are only directly accessible by objects
550 in the current module. In particular, linking code into a module with an
551 private global value may cause the private to be renamed as necessary to
552 avoid collisions. Because the symbol is private to the module, all
553 references can be updated. This doesn't show up in any symbol table in the
556 <dt><tt><b><a name="linkage_linker_private">linker_private</a></b></tt></dt>
557 <dd>Similar to private, but the symbol is passed through the assembler and
558 removed by the linker after evaluation. Note that (unlike private
559 symbols) linker_private symbols are subject to coalescing by the linker:
560 weak symbols get merged and redefinitions are rejected. However, unlike
561 normal strong symbols, they are removed by the linker from the final
562 linked image (executable or dynamic library).</dd>
564 <dt><tt><b><a name="linkage_internal">internal</a></b></tt></dt>
565 <dd>Similar to private, but the value shows as a local symbol
566 (<tt>STB_LOCAL</tt> in the case of ELF) in the object file. This
567 corresponds to the notion of the '<tt>static</tt>' keyword in C.</dd>
569 <dt><tt><b><a name="linkage_available_externally">available_externally</a></b></tt></dt>
570 <dd>Globals with "<tt>available_externally</tt>" linkage are never emitted
571 into the object file corresponding to the LLVM module. They exist to
572 allow inlining and other optimizations to take place given knowledge of
573 the definition of the global, which is known to be somewhere outside the
574 module. Globals with <tt>available_externally</tt> linkage are allowed to
575 be discarded at will, and are otherwise the same as <tt>linkonce_odr</tt>.
576 This linkage type is only allowed on definitions, not declarations.</dd>
578 <dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt></dt>
579 <dd>Globals with "<tt>linkonce</tt>" linkage are merged with other globals of
580 the same name when linkage occurs. This can be used to implement
581 some forms of inline functions, templates, or other code which must be
582 generated in each translation unit that uses it, but where the body may
583 be overridden with a more definitive definition later. Unreferenced
584 <tt>linkonce</tt> globals are allowed to be discarded. Note that
585 <tt>linkonce</tt> linkage does not actually allow the optimizer to
586 inline the body of this function into callers because it doesn't know if
587 this definition of the function is the definitive definition within the
588 program or whether it will be overridden by a stronger definition.
589 To enable inlining and other optimizations, use "<tt>linkonce_odr</tt>"
592 <dt><tt><b><a name="linkage_weak">weak</a></b></tt></dt>
593 <dd>"<tt>weak</tt>" linkage has the same merging semantics as
594 <tt>linkonce</tt> linkage, except that unreferenced globals with
595 <tt>weak</tt> linkage may not be discarded. This is used for globals that
596 are declared "weak" in C source code.</dd>
598 <dt><tt><b><a name="linkage_common">common</a></b></tt></dt>
599 <dd>"<tt>common</tt>" linkage is most similar to "<tt>weak</tt>" linkage, but
600 they are used for tentative definitions in C, such as "<tt>int X;</tt>" at
602 Symbols with "<tt>common</tt>" linkage are merged in the same way as
603 <tt>weak symbols</tt>, and they may not be deleted if unreferenced.
604 <tt>common</tt> symbols may not have an explicit section,
605 must have a zero initializer, and may not be marked '<a
606 href="#globalvars"><tt>constant</tt></a>'. Functions and aliases may not
607 have common linkage.</dd>
610 <dt><tt><b><a name="linkage_appending">appending</a></b></tt></dt>
611 <dd>"<tt>appending</tt>" linkage may only be applied to global variables of
612 pointer to array type. When two global variables with appending linkage
613 are linked together, the two global arrays are appended together. This is
614 the LLVM, typesafe, equivalent of having the system linker append together
615 "sections" with identical names when .o files are linked.</dd>
617 <dt><tt><b><a name="linkage_externweak">extern_weak</a></b></tt></dt>
618 <dd>The semantics of this linkage follow the ELF object file model: the symbol
619 is weak until linked, if not linked, the symbol becomes null instead of
620 being an undefined reference.</dd>
622 <dt><tt><b><a name="linkage_linkonce_odr">linkonce_odr</a></b></tt></dt>
623 <dt><tt><b><a name="linkage_weak_odr">weak_odr</a></b></tt></dt>
624 <dd>Some languages allow differing globals to be merged, such as two functions
625 with different semantics. Other languages, such as <tt>C++</tt>, ensure
626 that only equivalent globals are ever merged (the "one definition rule" -
627 "ODR"). Such languages can use the <tt>linkonce_odr</tt>
628 and <tt>weak_odr</tt> linkage types to indicate that the global will only
629 be merged with equivalent globals. These linkage types are otherwise the
630 same as their non-<tt>odr</tt> versions.</dd>
632 <dt><tt><b><a name="linkage_external">externally visible</a></b></tt>:</dt>
633 <dd>If none of the above identifiers are used, the global is externally
634 visible, meaning that it participates in linkage and can be used to
635 resolve external symbol references.</dd>
638 <p>The next two types of linkage are targeted for Microsoft Windows platform
639 only. They are designed to support importing (exporting) symbols from (to)
640 DLLs (Dynamic Link Libraries).</p>
643 <dt><tt><b><a name="linkage_dllimport">dllimport</a></b></tt></dt>
644 <dd>"<tt>dllimport</tt>" linkage causes the compiler to reference a function
645 or variable via a global pointer to a pointer that is set up by the DLL
646 exporting the symbol. On Microsoft Windows targets, the pointer name is
647 formed by combining <code>__imp_</code> and the function or variable
650 <dt><tt><b><a name="linkage_dllexport">dllexport</a></b></tt></dt>
651 <dd>"<tt>dllexport</tt>" linkage causes the compiler to provide a global
652 pointer to a pointer in a DLL, so that it can be referenced with the
653 <tt>dllimport</tt> attribute. On Microsoft Windows targets, the pointer
654 name is formed by combining <code>__imp_</code> and the function or
658 <p>For example, since the "<tt>.LC0</tt>" variable is defined to be internal, if
659 another module defined a "<tt>.LC0</tt>" variable and was linked with this
660 one, one of the two would be renamed, preventing a collision. Since
661 "<tt>main</tt>" and "<tt>puts</tt>" are external (i.e., lacking any linkage
662 declarations), they are accessible outside of the current module.</p>
664 <p>It is illegal for a function <i>declaration</i> to have any linkage type
665 other than "externally visible", <tt>dllimport</tt>
666 or <tt>extern_weak</tt>.</p>
668 <p>Aliases can have only <tt>external</tt>, <tt>internal</tt>, <tt>weak</tt>
669 or <tt>weak_odr</tt> linkages.</p>
673 <!-- ======================================================================= -->
674 <div class="doc_subsection">
675 <a name="callingconv">Calling Conventions</a>
678 <div class="doc_text">
680 <p>LLVM <a href="#functionstructure">functions</a>, <a href="#i_call">calls</a>
681 and <a href="#i_invoke">invokes</a> can all have an optional calling
682 convention specified for the call. The calling convention of any pair of
683 dynamic caller/callee must match, or the behavior of the program is
684 undefined. The following calling conventions are supported by LLVM, and more
685 may be added in the future:</p>
688 <dt><b>"<tt>ccc</tt>" - The C calling convention</b>:</dt>
689 <dd>This calling convention (the default if no other calling convention is
690 specified) matches the target C calling conventions. This calling
691 convention supports varargs function calls and tolerates some mismatch in
692 the declared prototype and implemented declaration of the function (as
695 <dt><b>"<tt>fastcc</tt>" - The fast calling convention</b>:</dt>
696 <dd>This calling convention attempts to make calls as fast as possible
697 (e.g. by passing things in registers). This calling convention allows the
698 target to use whatever tricks it wants to produce fast code for the
699 target, without having to conform to an externally specified ABI
700 (Application Binary Interface).
701 <a href="CodeGenerator.html#tailcallopt">Tail calls can only be optimized
702 when this or the GHC convention is used.</a> This calling convention
703 does not support varargs and requires the prototype of all callees to
704 exactly match the prototype of the function definition.</dd>
706 <dt><b>"<tt>coldcc</tt>" - The cold calling convention</b>:</dt>
707 <dd>This calling convention attempts to make code in the caller as efficient
708 as possible under the assumption that the call is not commonly executed.
709 As such, these calls often preserve all registers so that the call does
710 not break any live ranges in the caller side. This calling convention
711 does not support varargs and requires the prototype of all callees to
712 exactly match the prototype of the function definition.</dd>
714 <dt><b>"<tt>cc <em>10</em></tt>" - GHC convention</b>:</dt>
715 <dd>This calling convention has been implemented specifically for use by the
716 <a href="http://www.haskell.org/ghc">Glasgow Haskell Compiler (GHC)</a>.
717 It passes everything in registers, going to extremes to achieve this by
718 disabling callee save registers. This calling convention should not be
719 used lightly but only for specific situations such as an alternative to
720 the <em>register pinning</em> performance technique often used when
721 implementing functional programming languages.At the moment only X86
722 supports this convention and it has the following limitations:
724 <li>On <em>X86-32</em> only supports up to 4 bit type parameters. No
725 floating point types are supported.</li>
726 <li>On <em>X86-64</em> only supports up to 10 bit type parameters and
727 6 floating point parameters.</li>
729 This calling convention supports
730 <a href="CodeGenerator.html#tailcallopt">tail call optimization</a> but
731 requires both the caller and callee are using it.
734 <dt><b>"<tt>cc <<em>n</em>></tt>" - Numbered convention</b>:</dt>
735 <dd>Any calling convention may be specified by number, allowing
736 target-specific calling conventions to be used. Target specific calling
737 conventions start at 64.</dd>
740 <p>More calling conventions can be added/defined on an as-needed basis, to
741 support Pascal conventions or any other well-known target-independent
746 <!-- ======================================================================= -->
747 <div class="doc_subsection">
748 <a name="visibility">Visibility Styles</a>
751 <div class="doc_text">
753 <p>All Global Variables and Functions have one of the following visibility
757 <dt><b>"<tt>default</tt>" - Default style</b>:</dt>
758 <dd>On targets that use the ELF object file format, default visibility means
759 that the declaration is visible to other modules and, in shared libraries,
760 means that the declared entity may be overridden. On Darwin, default
761 visibility means that the declaration is visible to other modules. Default
762 visibility corresponds to "external linkage" in the language.</dd>
764 <dt><b>"<tt>hidden</tt>" - Hidden style</b>:</dt>
765 <dd>Two declarations of an object with hidden visibility refer to the same
766 object if they are in the same shared object. Usually, hidden visibility
767 indicates that the symbol will not be placed into the dynamic symbol
768 table, so no other module (executable or shared library) can reference it
771 <dt><b>"<tt>protected</tt>" - Protected style</b>:</dt>
772 <dd>On ELF, protected visibility indicates that the symbol will be placed in
773 the dynamic symbol table, but that references within the defining module
774 will bind to the local symbol. That is, the symbol cannot be overridden by
780 <!-- ======================================================================= -->
781 <div class="doc_subsection">
782 <a name="namedtypes">Named Types</a>
785 <div class="doc_text">
787 <p>LLVM IR allows you to specify name aliases for certain types. This can make
788 it easier to read the IR and make the IR more condensed (particularly when
789 recursive types are involved). An example of a name specification is:</p>
791 <div class="doc_code">
793 %mytype = type { %mytype*, i32 }
797 <p>You may give a name to any <a href="#typesystem">type</a> except
798 "<a href="t_void">void</a>". Type name aliases may be used anywhere a type
799 is expected with the syntax "%mytype".</p>
801 <p>Note that type names are aliases for the structural type that they indicate,
802 and that you can therefore specify multiple names for the same type. This
803 often leads to confusing behavior when dumping out a .ll file. Since LLVM IR
804 uses structural typing, the name is not part of the type. When printing out
805 LLVM IR, the printer will pick <em>one name</em> to render all types of a
806 particular shape. This means that if you have code where two different
807 source types end up having the same LLVM type, that the dumper will sometimes
808 print the "wrong" or unexpected type. This is an important design point and
809 isn't going to change.</p>
813 <!-- ======================================================================= -->
814 <div class="doc_subsection">
815 <a name="globalvars">Global Variables</a>
818 <div class="doc_text">
820 <p>Global variables define regions of memory allocated at compilation time
821 instead of run-time. Global variables may optionally be initialized, may
822 have an explicit section to be placed in, and may have an optional explicit
823 alignment specified. A variable may be defined as "thread_local", which
824 means that it will not be shared by threads (each thread will have a
825 separated copy of the variable). A variable may be defined as a global
826 "constant," which indicates that the contents of the variable
827 will <b>never</b> be modified (enabling better optimization, allowing the
828 global data to be placed in the read-only section of an executable, etc).
829 Note that variables that need runtime initialization cannot be marked
830 "constant" as there is a store to the variable.</p>
832 <p>LLVM explicitly allows <em>declarations</em> of global variables to be marked
833 constant, even if the final definition of the global is not. This capability
834 can be used to enable slightly better optimization of the program, but
835 requires the language definition to guarantee that optimizations based on the
836 'constantness' are valid for the translation units that do not include the
839 <p>As SSA values, global variables define pointer values that are in scope
840 (i.e. they dominate) all basic blocks in the program. Global variables
841 always define a pointer to their "content" type because they describe a
842 region of memory, and all memory objects in LLVM are accessed through
845 <p>A global variable may be declared to reside in a target-specific numbered
846 address space. For targets that support them, address spaces may affect how
847 optimizations are performed and/or what target instructions are used to
848 access the variable. The default address space is zero. The address space
849 qualifier must precede any other attributes.</p>
851 <p>LLVM allows an explicit section to be specified for globals. If the target
852 supports it, it will emit globals to the section specified.</p>
854 <p>An explicit alignment may be specified for a global. If not present, or if
855 the alignment is set to zero, the alignment of the global is set by the
856 target to whatever it feels convenient. If an explicit alignment is
857 specified, the global is forced to have at least that much alignment. All
858 alignments must be a power of 2.</p>
860 <p>For example, the following defines a global in a numbered address space with
861 an initializer, section, and alignment:</p>
863 <div class="doc_code">
865 @G = addrspace(5) constant float 1.0, section "foo", align 4
872 <!-- ======================================================================= -->
873 <div class="doc_subsection">
874 <a name="functionstructure">Functions</a>
877 <div class="doc_text">
879 <p>LLVM function definitions consist of the "<tt>define</tt>" keyword, an
880 optional <a href="#linkage">linkage type</a>, an optional
881 <a href="#visibility">visibility style</a>, an optional
882 <a href="#callingconv">calling convention</a>, a return type, an optional
883 <a href="#paramattrs">parameter attribute</a> for the return type, a function
884 name, a (possibly empty) argument list (each with optional
885 <a href="#paramattrs">parameter attributes</a>), optional
886 <a href="#fnattrs">function attributes</a>, an optional section, an optional
887 alignment, an optional <a href="#gc">garbage collector name</a>, an opening
888 curly brace, a list of basic blocks, and a closing curly brace.</p>
890 <p>LLVM function declarations consist of the "<tt>declare</tt>" keyword, an
891 optional <a href="#linkage">linkage type</a>, an optional
892 <a href="#visibility">visibility style</a>, an optional
893 <a href="#callingconv">calling convention</a>, a return type, an optional
894 <a href="#paramattrs">parameter attribute</a> for the return type, a function
895 name, a possibly empty list of arguments, an optional alignment, and an
896 optional <a href="#gc">garbage collector name</a>.</p>
898 <p>A function definition contains a list of basic blocks, forming the CFG
899 (Control Flow Graph) for the function. Each basic block may optionally start
900 with a label (giving the basic block a symbol table entry), contains a list
901 of instructions, and ends with a <a href="#terminators">terminator</a>
902 instruction (such as a branch or function return).</p>
904 <p>The first basic block in a function is special in two ways: it is immediately
905 executed on entrance to the function, and it is not allowed to have
906 predecessor basic blocks (i.e. there can not be any branches to the entry
907 block of a function). Because the block can have no predecessors, it also
908 cannot have any <a href="#i_phi">PHI nodes</a>.</p>
910 <p>LLVM allows an explicit section to be specified for functions. If the target
911 supports it, it will emit functions to the section specified.</p>
913 <p>An explicit alignment may be specified for a function. If not present, or if
914 the alignment is set to zero, the alignment of the function is set by the
915 target to whatever it feels convenient. If an explicit alignment is
916 specified, the function is forced to have at least that much alignment. All
917 alignments must be a power of 2.</p>
920 <div class="doc_code">
922 define [<a href="#linkage">linkage</a>] [<a href="#visibility">visibility</a>]
923 [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>]
924 <ResultType> @<FunctionName> ([argument list])
925 [<a href="#fnattrs">fn Attrs</a>] [section "name"] [align N]
926 [<a href="#gc">gc</a>] { ... }
932 <!-- ======================================================================= -->
933 <div class="doc_subsection">
934 <a name="aliasstructure">Aliases</a>
937 <div class="doc_text">
939 <p>Aliases act as "second name" for the aliasee value (which can be either
940 function, global variable, another alias or bitcast of global value). Aliases
941 may have an optional <a href="#linkage">linkage type</a>, and an
942 optional <a href="#visibility">visibility style</a>.</p>
945 <div class="doc_code">
947 @<Name> = alias [Linkage] [Visibility] <AliaseeTy> @<Aliasee>
953 <!-- ======================================================================= -->
954 <div class="doc_subsection">
955 <a name="namedmetadatastructure">Named Metadata</a>
958 <div class="doc_text">
960 <p>Named metadata is a collection of metadata. <a href="#metadata">Metadata
961 nodes</a> (but not metadata strings) and null are the only valid operands for
962 a named metadata.</p>
965 <div class="doc_code">
967 !1 = metadata !{metadata !"one"}
974 <!-- ======================================================================= -->
975 <div class="doc_subsection"><a name="paramattrs">Parameter Attributes</a></div>
977 <div class="doc_text">
979 <p>The return type and each parameter of a function type may have a set of
980 <i>parameter attributes</i> associated with them. Parameter attributes are
981 used to communicate additional information about the result or parameters of
982 a function. Parameter attributes are considered to be part of the function,
983 not of the function type, so functions with different parameter attributes
984 can have the same function type.</p>
986 <p>Parameter attributes are simple keywords that follow the type specified. If
987 multiple parameter attributes are needed, they are space separated. For
990 <div class="doc_code">
992 declare i32 @printf(i8* noalias nocapture, ...)
993 declare i32 @atoi(i8 zeroext)
994 declare signext i8 @returns_signed_char()
998 <p>Note that any attributes for the function result (<tt>nounwind</tt>,
999 <tt>readonly</tt>) come immediately after the argument list.</p>
1001 <p>Currently, only the following parameter attributes are defined:</p>
1004 <dt><tt><b>zeroext</b></tt></dt>
1005 <dd>This indicates to the code generator that the parameter or return value
1006 should be zero-extended to a 32-bit value by the caller (for a parameter)
1007 or the callee (for a return value).</dd>
1009 <dt><tt><b>signext</b></tt></dt>
1010 <dd>This indicates to the code generator that the parameter or return value
1011 should be sign-extended to a 32-bit value by the caller (for a parameter)
1012 or the callee (for a return value).</dd>
1014 <dt><tt><b>inreg</b></tt></dt>
1015 <dd>This indicates that this parameter or return value should be treated in a
1016 special target-dependent fashion during while emitting code for a function
1017 call or return (usually, by putting it in a register as opposed to memory,
1018 though some targets use it to distinguish between two different kinds of
1019 registers). Use of this attribute is target-specific.</dd>
1021 <dt><tt><b><a name="byval">byval</a></b></tt></dt>
1022 <dd>This indicates that the pointer parameter should really be passed by value
1023 to the function. The attribute implies that a hidden copy of the pointee
1024 is made between the caller and the callee, so the callee is unable to
1025 modify the value in the callee. This attribute is only valid on LLVM
1026 pointer arguments. It is generally used to pass structs and arrays by
1027 value, but is also valid on pointers to scalars. The copy is considered
1028 to belong to the caller not the callee (for example,
1029 <tt><a href="#readonly">readonly</a></tt> functions should not write to
1030 <tt>byval</tt> parameters). This is not a valid attribute for return
1031 values. The byval attribute also supports specifying an alignment with
1032 the align attribute. This has a target-specific effect on the code
1033 generator that usually indicates a desired alignment for the synthesized
1036 <dt><tt><b>sret</b></tt></dt>
1037 <dd>This indicates that the pointer parameter specifies the address of a
1038 structure that is the return value of the function in the source program.
1039 This pointer must be guaranteed by the caller to be valid: loads and
1040 stores to the structure may be assumed by the callee to not to trap. This
1041 may only be applied to the first parameter. This is not a valid attribute
1042 for return values. </dd>
1044 <dt><tt><b>noalias</b></tt></dt>
1045 <dd>This indicates that the pointer does not alias any global or any other
1046 parameter. The caller is responsible for ensuring that this is the
1047 case. On a function return value, <tt>noalias</tt> additionally indicates
1048 that the pointer does not alias any other pointers visible to the
1049 caller. For further details, please see the discussion of the NoAlias
1051 <a href="http://llvm.org/docs/AliasAnalysis.html#MustMayNo">alias
1054 <dt><tt><b>nocapture</b></tt></dt>
1055 <dd>This indicates that the callee does not make any copies of the pointer
1056 that outlive the callee itself. This is not a valid attribute for return
1059 <dt><tt><b>nest</b></tt></dt>
1060 <dd>This indicates that the pointer parameter can be excised using the
1061 <a href="#int_trampoline">trampoline intrinsics</a>. This is not a valid
1062 attribute for return values.</dd>
1067 <!-- ======================================================================= -->
1068 <div class="doc_subsection">
1069 <a name="gc">Garbage Collector Names</a>
1072 <div class="doc_text">
1074 <p>Each function may specify a garbage collector name, which is simply a
1077 <div class="doc_code">
1079 define void @f() gc "name" { ... }
1083 <p>The compiler declares the supported values of <i>name</i>. Specifying a
1084 collector which will cause the compiler to alter its output in order to
1085 support the named garbage collection algorithm.</p>
1089 <!-- ======================================================================= -->
1090 <div class="doc_subsection">
1091 <a name="fnattrs">Function Attributes</a>
1094 <div class="doc_text">
1096 <p>Function attributes are set to communicate additional information about a
1097 function. Function attributes are considered to be part of the function, not
1098 of the function type, so functions with different parameter attributes can
1099 have the same function type.</p>
1101 <p>Function attributes are simple keywords that follow the type specified. If
1102 multiple attributes are needed, they are space separated. For example:</p>
1104 <div class="doc_code">
1106 define void @f() noinline { ... }
1107 define void @f() alwaysinline { ... }
1108 define void @f() alwaysinline optsize { ... }
1109 define void @f() optsize { ... }
1114 <dt><tt><b>alignstack(<<em>n</em>>)</b></tt></dt>
1115 <dd>This attribute indicates that, when emitting the prologue and epilogue,
1116 the backend should forcibly align the stack pointer. Specify the
1117 desired alignment, which must be a power of two, in parentheses.
1119 <dt><tt><b>alwaysinline</b></tt></dt>
1120 <dd>This attribute indicates that the inliner should attempt to inline this
1121 function into callers whenever possible, ignoring any active inlining size
1122 threshold for this caller.</dd>
1124 <dt><tt><b>inlinehint</b></tt></dt>
1125 <dd>This attribute indicates that the source code contained a hint that inlining
1126 this function is desirable (such as the "inline" keyword in C/C++). It
1127 is just a hint; it imposes no requirements on the inliner.</dd>
1129 <dt><tt><b>noinline</b></tt></dt>
1130 <dd>This attribute indicates that the inliner should never inline this
1131 function in any situation. This attribute may not be used together with
1132 the <tt>alwaysinline</tt> attribute.</dd>
1134 <dt><tt><b>optsize</b></tt></dt>
1135 <dd>This attribute suggests that optimization passes and code generator passes
1136 make choices that keep the code size of this function low, and otherwise
1137 do optimizations specifically to reduce code size.</dd>
1139 <dt><tt><b>noreturn</b></tt></dt>
1140 <dd>This function attribute indicates that the function never returns
1141 normally. This produces undefined behavior at runtime if the function
1142 ever does dynamically return.</dd>
1144 <dt><tt><b>nounwind</b></tt></dt>
1145 <dd>This function attribute indicates that the function never returns with an
1146 unwind or exceptional control flow. If the function does unwind, its
1147 runtime behavior is undefined.</dd>
1149 <dt><tt><b>readnone</b></tt></dt>
1150 <dd>This attribute indicates that the function computes its result (or decides
1151 to unwind an exception) based strictly on its arguments, without
1152 dereferencing any pointer arguments or otherwise accessing any mutable
1153 state (e.g. memory, control registers, etc) visible to caller functions.
1154 It does not write through any pointer arguments
1155 (including <tt><a href="#byval">byval</a></tt> arguments) and never
1156 changes any state visible to callers. This means that it cannot unwind
1157 exceptions by calling the <tt>C++</tt> exception throwing methods, but
1158 could use the <tt>unwind</tt> instruction.</dd>
1160 <dt><tt><b><a name="readonly">readonly</a></b></tt></dt>
1161 <dd>This attribute indicates that the function does not write through any
1162 pointer arguments (including <tt><a href="#byval">byval</a></tt>
1163 arguments) or otherwise modify any state (e.g. memory, control registers,
1164 etc) visible to caller functions. It may dereference pointer arguments
1165 and read state that may be set in the caller. A readonly function always
1166 returns the same value (or unwinds an exception identically) when called
1167 with the same set of arguments and global state. It cannot unwind an
1168 exception by calling the <tt>C++</tt> exception throwing methods, but may
1169 use the <tt>unwind</tt> instruction.</dd>
1171 <dt><tt><b><a name="ssp">ssp</a></b></tt></dt>
1172 <dd>This attribute indicates that the function should emit a stack smashing
1173 protector. It is in the form of a "canary"—a random value placed on
1174 the stack before the local variables that's checked upon return from the
1175 function to see if it has been overwritten. A heuristic is used to
1176 determine if a function needs stack protectors or not.<br>
1178 If a function that has an <tt>ssp</tt> attribute is inlined into a
1179 function that doesn't have an <tt>ssp</tt> attribute, then the resulting
1180 function will have an <tt>ssp</tt> attribute.</dd>
1182 <dt><tt><b>sspreq</b></tt></dt>
1183 <dd>This attribute indicates that the function should <em>always</em> emit a
1184 stack smashing protector. This overrides
1185 the <tt><a href="#ssp">ssp</a></tt> function attribute.<br>
1187 If a function that has an <tt>sspreq</tt> attribute is inlined into a
1188 function that doesn't have an <tt>sspreq</tt> attribute or which has
1189 an <tt>ssp</tt> attribute, then the resulting function will have
1190 an <tt>sspreq</tt> attribute.</dd>
1192 <dt><tt><b>noredzone</b></tt></dt>
1193 <dd>This attribute indicates that the code generator should not use a red
1194 zone, even if the target-specific ABI normally permits it.</dd>
1196 <dt><tt><b>noimplicitfloat</b></tt></dt>
1197 <dd>This attributes disables implicit floating point instructions.</dd>
1199 <dt><tt><b>naked</b></tt></dt>
1200 <dd>This attribute disables prologue / epilogue emission for the function.
1201 This can have very system-specific consequences.</dd>
1206 <!-- ======================================================================= -->
1207 <div class="doc_subsection">
1208 <a name="moduleasm">Module-Level Inline Assembly</a>
1211 <div class="doc_text">
1213 <p>Modules may contain "module-level inline asm" blocks, which corresponds to
1214 the GCC "file scope inline asm" blocks. These blocks are internally
1215 concatenated by LLVM and treated as a single unit, but may be separated in
1216 the <tt>.ll</tt> file if desired. The syntax is very simple:</p>
1218 <div class="doc_code">
1220 module asm "inline asm code goes here"
1221 module asm "more can go here"
1225 <p>The strings can contain any character by escaping non-printable characters.
1226 The escape sequence used is simply "\xx" where "xx" is the two digit hex code
1229 <p>The inline asm code is simply printed to the machine code .s file when
1230 assembly code is generated.</p>
1234 <!-- ======================================================================= -->
1235 <div class="doc_subsection">
1236 <a name="datalayout">Data Layout</a>
1239 <div class="doc_text">
1241 <p>A module may specify a target specific data layout string that specifies how
1242 data is to be laid out in memory. The syntax for the data layout is
1245 <div class="doc_code">
1247 target datalayout = "<i>layout specification</i>"
1251 <p>The <i>layout specification</i> consists of a list of specifications
1252 separated by the minus sign character ('-'). Each specification starts with
1253 a letter and may include other information after the letter to define some
1254 aspect of the data layout. The specifications accepted are as follows:</p>
1258 <dd>Specifies that the target lays out data in big-endian form. That is, the
1259 bits with the most significance have the lowest address location.</dd>
1262 <dd>Specifies that the target lays out data in little-endian form. That is,
1263 the bits with the least significance have the lowest address
1266 <dt><tt>p:<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
1267 <dd>This specifies the <i>size</i> of a pointer and its <i>abi</i> and
1268 <i>preferred</i> alignments. All sizes are in bits. Specifying
1269 the <i>pref</i> alignment is optional. If omitted, the
1270 preceding <tt>:</tt> should be omitted too.</dd>
1272 <dt><tt>i<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
1273 <dd>This specifies the alignment for an integer type of a given bit
1274 <i>size</i>. The value of <i>size</i> must be in the range [1,2^23).</dd>
1276 <dt><tt>v<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
1277 <dd>This specifies the alignment for a vector type of a given bit
1280 <dt><tt>f<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
1281 <dd>This specifies the alignment for a floating point type of a given bit
1282 <i>size</i>. The value of <i>size</i> must be either 32 (float) or 64
1285 <dt><tt>a<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
1286 <dd>This specifies the alignment for an aggregate type of a given bit
1289 <dt><tt>s<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
1290 <dd>This specifies the alignment for a stack object of a given bit
1293 <dt><tt>n<i>size1</i>:<i>size2</i>:<i>size3</i>...</tt></dt>
1294 <dd>This specifies a set of native integer widths for the target CPU
1295 in bits. For example, it might contain "n32" for 32-bit PowerPC,
1296 "n32:64" for PowerPC 64, or "n8:16:32:64" for X86-64. Elements of
1297 this set are considered to support most general arithmetic
1298 operations efficiently.</dd>
1301 <p>When constructing the data layout for a given target, LLVM starts with a
1302 default set of specifications which are then (possibly) overriden by the
1303 specifications in the <tt>datalayout</tt> keyword. The default specifications
1304 are given in this list:</p>
1307 <li><tt>E</tt> - big endian</li>
1308 <li><tt>p:64:64:64</tt> - 64-bit pointers with 64-bit alignment</li>
1309 <li><tt>i1:8:8</tt> - i1 is 8-bit (byte) aligned</li>
1310 <li><tt>i8:8:8</tt> - i8 is 8-bit (byte) aligned</li>
1311 <li><tt>i16:16:16</tt> - i16 is 16-bit aligned</li>
1312 <li><tt>i32:32:32</tt> - i32 is 32-bit aligned</li>
1313 <li><tt>i64:32:64</tt> - i64 has ABI alignment of 32-bits but preferred
1314 alignment of 64-bits</li>
1315 <li><tt>f32:32:32</tt> - float is 32-bit aligned</li>
1316 <li><tt>f64:64:64</tt> - double is 64-bit aligned</li>
1317 <li><tt>v64:64:64</tt> - 64-bit vector is 64-bit aligned</li>
1318 <li><tt>v128:128:128</tt> - 128-bit vector is 128-bit aligned</li>
1319 <li><tt>a0:0:1</tt> - aggregates are 8-bit aligned</li>
1320 <li><tt>s0:64:64</tt> - stack objects are 64-bit aligned</li>
1323 <p>When LLVM is determining the alignment for a given type, it uses the
1324 following rules:</p>
1327 <li>If the type sought is an exact match for one of the specifications, that
1328 specification is used.</li>
1330 <li>If no match is found, and the type sought is an integer type, then the
1331 smallest integer type that is larger than the bitwidth of the sought type
1332 is used. If none of the specifications are larger than the bitwidth then
1333 the the largest integer type is used. For example, given the default
1334 specifications above, the i7 type will use the alignment of i8 (next
1335 largest) while both i65 and i256 will use the alignment of i64 (largest
1338 <li>If no match is found, and the type sought is a vector type, then the
1339 largest vector type that is smaller than the sought vector type will be
1340 used as a fall back. This happens because <128 x double> can be
1341 implemented in terms of 64 <2 x double>, for example.</li>
1346 <!-- ======================================================================= -->
1347 <div class="doc_subsection">
1348 <a name="pointeraliasing">Pointer Aliasing Rules</a>
1351 <div class="doc_text">
1353 <p>Any memory access must be done through a pointer value associated
1354 with an address range of the memory access, otherwise the behavior
1355 is undefined. Pointer values are associated with address ranges
1356 according to the following rules:</p>
1359 <li>A pointer value formed from a
1360 <tt><a href="#i_getelementptr">getelementptr</a></tt> instruction
1361 is associated with the addresses associated with the first operand
1362 of the <tt>getelementptr</tt>.</li>
1363 <li>An address of a global variable is associated with the address
1364 range of the variable's storage.</li>
1365 <li>The result value of an allocation instruction is associated with
1366 the address range of the allocated storage.</li>
1367 <li>A null pointer in the default address-space is associated with
1369 <li>A pointer value formed by an
1370 <tt><a href="#i_inttoptr">inttoptr</a></tt> is associated with all
1371 address ranges of all pointer values that contribute (directly or
1372 indirectly) to the computation of the pointer's value.</li>
1373 <li>The result value of a
1374 <tt><a href="#i_bitcast">bitcast</a></tt> is associated with all
1375 addresses associated with the operand of the <tt>bitcast</tt>.</li>
1376 <li>An integer constant other than zero or a pointer value returned
1377 from a function not defined within LLVM may be associated with address
1378 ranges allocated through mechanisms other than those provided by
1379 LLVM. Such ranges shall not overlap with any ranges of addresses
1380 allocated by mechanisms provided by LLVM.</li>
1383 <p>LLVM IR does not associate types with memory. The result type of a
1384 <tt><a href="#i_load">load</a></tt> merely indicates the size and
1385 alignment of the memory from which to load, as well as the
1386 interpretation of the value. The first operand of a
1387 <tt><a href="#i_store">store</a></tt> similarly only indicates the size
1388 and alignment of the store.</p>
1390 <p>Consequently, type-based alias analysis, aka TBAA, aka
1391 <tt>-fstrict-aliasing</tt>, is not applicable to general unadorned
1392 LLVM IR. <a href="#metadata">Metadata</a> may be used to encode
1393 additional information which specialized optimization passes may use
1394 to implement type-based alias analysis.</p>
1398 <!-- ======================================================================= -->
1399 <div class="doc_subsection">
1400 <a name="volatile">Volatile Memory Accesses</a>
1403 <div class="doc_text">
1405 <p>Certain memory accesses, such as <a href="#i_load"><tt>load</tt></a>s, <a
1406 href="#i_store"><tt>store</tt></a>s, and <a
1407 href="#int_memcpy"><tt>llvm.memcpy</tt></a>s may be marked <tt>volatile</tt>.
1408 The optimizers must not change the number of volatile operations or change their
1409 order of execution relative to other volatile operations. The optimizers
1410 <i>may</i> change the order of volatile operations relative to non-volatile
1411 operations. This is not Java's "volatile" and has no cross-thread
1412 synchronization behavior.</p>
1416 <!-- *********************************************************************** -->
1417 <div class="doc_section"> <a name="typesystem">Type System</a> </div>
1418 <!-- *********************************************************************** -->
1420 <div class="doc_text">
1422 <p>The LLVM type system is one of the most important features of the
1423 intermediate representation. Being typed enables a number of optimizations
1424 to be performed on the intermediate representation directly, without having
1425 to do extra analyses on the side before the transformation. A strong type
1426 system makes it easier to read the generated code and enables novel analyses
1427 and transformations that are not feasible to perform on normal three address
1428 code representations.</p>
1432 <!-- ======================================================================= -->
1433 <div class="doc_subsection"> <a name="t_classifications">Type
1434 Classifications</a> </div>
1436 <div class="doc_text">
1438 <p>The types fall into a few useful classifications:</p>
1440 <table border="1" cellspacing="0" cellpadding="4">
1442 <tr><th>Classification</th><th>Types</th></tr>
1444 <td><a href="#t_integer">integer</a></td>
1445 <td><tt>i1, i2, i3, ... i8, ... i16, ... i32, ... i64, ... </tt></td>
1448 <td><a href="#t_floating">floating point</a></td>
1449 <td><tt>float, double, x86_fp80, fp128, ppc_fp128</tt></td>
1452 <td><a name="t_firstclass">first class</a></td>
1453 <td><a href="#t_integer">integer</a>,
1454 <a href="#t_floating">floating point</a>,
1455 <a href="#t_pointer">pointer</a>,
1456 <a href="#t_vector">vector</a>,
1457 <a href="#t_struct">structure</a>,
1458 <a href="#t_union">union</a>,
1459 <a href="#t_array">array</a>,
1460 <a href="#t_label">label</a>,
1461 <a href="#t_metadata">metadata</a>.
1465 <td><a href="#t_primitive">primitive</a></td>
1466 <td><a href="#t_label">label</a>,
1467 <a href="#t_void">void</a>,
1468 <a href="#t_floating">floating point</a>,
1469 <a href="#t_metadata">metadata</a>.</td>
1472 <td><a href="#t_derived">derived</a></td>
1473 <td><a href="#t_array">array</a>,
1474 <a href="#t_function">function</a>,
1475 <a href="#t_pointer">pointer</a>,
1476 <a href="#t_struct">structure</a>,
1477 <a href="#t_pstruct">packed structure</a>,
1478 <a href="#t_union">union</a>,
1479 <a href="#t_vector">vector</a>,
1480 <a href="#t_opaque">opaque</a>.
1486 <p>The <a href="#t_firstclass">first class</a> types are perhaps the most
1487 important. Values of these types are the only ones which can be produced by
1492 <!-- ======================================================================= -->
1493 <div class="doc_subsection"> <a name="t_primitive">Primitive Types</a> </div>
1495 <div class="doc_text">
1497 <p>The primitive types are the fundamental building blocks of the LLVM
1502 <!-- _______________________________________________________________________ -->
1503 <div class="doc_subsubsection"> <a name="t_integer">Integer Type</a> </div>
1505 <div class="doc_text">
1508 <p>The integer type is a very simple type that simply specifies an arbitrary
1509 bit width for the integer type desired. Any bit width from 1 bit to
1510 2<sup>23</sup>-1 (about 8 million) can be specified.</p>
1517 <p>The number of bits the integer will occupy is specified by the <tt>N</tt>
1521 <table class="layout">
1523 <td class="left"><tt>i1</tt></td>
1524 <td class="left">a single-bit integer.</td>
1527 <td class="left"><tt>i32</tt></td>
1528 <td class="left">a 32-bit integer.</td>
1531 <td class="left"><tt>i1942652</tt></td>
1532 <td class="left">a really big integer of over 1 million bits.</td>
1538 <!-- _______________________________________________________________________ -->
1539 <div class="doc_subsubsection"> <a name="t_floating">Floating Point Types</a> </div>
1541 <div class="doc_text">
1545 <tr><th>Type</th><th>Description</th></tr>
1546 <tr><td><tt>float</tt></td><td>32-bit floating point value</td></tr>
1547 <tr><td><tt>double</tt></td><td>64-bit floating point value</td></tr>
1548 <tr><td><tt>fp128</tt></td><td>128-bit floating point value (112-bit mantissa)</td></tr>
1549 <tr><td><tt>x86_fp80</tt></td><td>80-bit floating point value (X87)</td></tr>
1550 <tr><td><tt>ppc_fp128</tt></td><td>128-bit floating point value (two 64-bits)</td></tr>
1556 <!-- _______________________________________________________________________ -->
1557 <div class="doc_subsubsection"> <a name="t_void">Void Type</a> </div>
1559 <div class="doc_text">
1562 <p>The void type does not represent any value and has no size.</p>
1571 <!-- _______________________________________________________________________ -->
1572 <div class="doc_subsubsection"> <a name="t_label">Label Type</a> </div>
1574 <div class="doc_text">
1577 <p>The label type represents code labels.</p>
1586 <!-- _______________________________________________________________________ -->
1587 <div class="doc_subsubsection"> <a name="t_metadata">Metadata Type</a> </div>
1589 <div class="doc_text">
1592 <p>The metadata type represents embedded metadata. No derived types may be
1593 created from metadata except for <a href="#t_function">function</a>
1604 <!-- ======================================================================= -->
1605 <div class="doc_subsection"> <a name="t_derived">Derived Types</a> </div>
1607 <div class="doc_text">
1609 <p>The real power in LLVM comes from the derived types in the system. This is
1610 what allows a programmer to represent arrays, functions, pointers, and other
1611 useful types. Each of these types contain one or more element types which
1612 may be a primitive type, or another derived type. For example, it is
1613 possible to have a two dimensional array, using an array as the element type
1614 of another array.</p>
1619 <!-- _______________________________________________________________________ -->
1620 <div class="doc_subsubsection"> <a name="t_aggregate">Aggregate Types</a> </div>
1622 <div class="doc_text">
1624 <p>Aggregate Types are a subset of derived types that can contain multiple
1625 member types. <a href="#t_array">Arrays</a>,
1626 <a href="#t_struct">structs</a>, <a href="#t_vector">vectors</a> and
1627 <a href="#t_union">unions</a> are aggregate types.</p>
1633 <!-- _______________________________________________________________________ -->
1634 <div class="doc_subsubsection"> <a name="t_array">Array Type</a> </div>
1636 <div class="doc_text">
1639 <p>The array type is a very simple derived type that arranges elements
1640 sequentially in memory. The array type requires a size (number of elements)
1641 and an underlying data type.</p>
1645 [<# elements> x <elementtype>]
1648 <p>The number of elements is a constant integer value; <tt>elementtype</tt> may
1649 be any type with a size.</p>
1652 <table class="layout">
1654 <td class="left"><tt>[40 x i32]</tt></td>
1655 <td class="left">Array of 40 32-bit integer values.</td>
1658 <td class="left"><tt>[41 x i32]</tt></td>
1659 <td class="left">Array of 41 32-bit integer values.</td>
1662 <td class="left"><tt>[4 x i8]</tt></td>
1663 <td class="left">Array of 4 8-bit integer values.</td>
1666 <p>Here are some examples of multidimensional arrays:</p>
1667 <table class="layout">
1669 <td class="left"><tt>[3 x [4 x i32]]</tt></td>
1670 <td class="left">3x4 array of 32-bit integer values.</td>
1673 <td class="left"><tt>[12 x [10 x float]]</tt></td>
1674 <td class="left">12x10 array of single precision floating point values.</td>
1677 <td class="left"><tt>[2 x [3 x [4 x i16]]]</tt></td>
1678 <td class="left">2x3x4 array of 16-bit integer values.</td>
1682 <p>There is no restriction on indexing beyond the end of the array implied by
1683 a static type (though there are restrictions on indexing beyond the bounds
1684 of an allocated object in some cases). This means that single-dimension
1685 'variable sized array' addressing can be implemented in LLVM with a zero
1686 length array type. An implementation of 'pascal style arrays' in LLVM could
1687 use the type "<tt>{ i32, [0 x float]}</tt>", for example.</p>
1691 <!-- _______________________________________________________________________ -->
1692 <div class="doc_subsubsection"> <a name="t_function">Function Type</a> </div>
1694 <div class="doc_text">
1697 <p>The function type can be thought of as a function signature. It consists of
1698 a return type and a list of formal parameter types. The return type of a
1699 function type is a scalar type, a void type, a struct type, or a union
1700 type. If the return type is a struct type then all struct elements must be
1701 of first class types, and the struct must have at least one element.</p>
1705 <returntype> (<parameter list>)
1708 <p>...where '<tt><parameter list></tt>' is a comma-separated list of type
1709 specifiers. Optionally, the parameter list may include a type <tt>...</tt>,
1710 which indicates that the function takes a variable number of arguments.
1711 Variable argument functions can access their arguments with
1712 the <a href="#int_varargs">variable argument handling intrinsic</a>
1713 functions. '<tt><returntype></tt>' is any type except
1714 <a href="#t_label">label</a>.</p>
1717 <table class="layout">
1719 <td class="left"><tt>i32 (i32)</tt></td>
1720 <td class="left">function taking an <tt>i32</tt>, returning an <tt>i32</tt>
1722 </tr><tr class="layout">
1723 <td class="left"><tt>float (i16, i32 *) *
1725 <td class="left"><a href="#t_pointer">Pointer</a> to a function that takes
1726 an <tt>i16</tt> and a <a href="#t_pointer">pointer</a> to <tt>i32</tt>,
1727 returning <tt>float</tt>.
1729 </tr><tr class="layout">
1730 <td class="left"><tt>i32 (i8*, ...)</tt></td>
1731 <td class="left">A vararg function that takes at least one
1732 <a href="#t_pointer">pointer</a> to <tt>i8 </tt> (char in C),
1733 which returns an integer. This is the signature for <tt>printf</tt> in
1736 </tr><tr class="layout">
1737 <td class="left"><tt>{i32, i32} (i32)</tt></td>
1738 <td class="left">A function taking an <tt>i32</tt>, returning a
1739 <a href="#t_struct">structure</a> containing two <tt>i32</tt> values
1746 <!-- _______________________________________________________________________ -->
1747 <div class="doc_subsubsection"> <a name="t_struct">Structure Type</a> </div>
1749 <div class="doc_text">
1752 <p>The structure type is used to represent a collection of data members together
1753 in memory. The packing of the field types is defined to match the ABI of the
1754 underlying processor. The elements of a structure may be any type that has a
1757 <p>Structures in memory are accessed using '<tt><a href="#i_load">load</a></tt>'
1758 and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a field
1759 with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction.
1760 Structures in registers are accessed using the
1761 '<tt><a href="#i_extractvalue">extractvalue</a></tt>' and
1762 '<tt><a href="#i_insertvalue">insertvalue</a></tt>' instructions.</p>
1765 { <type list> }
1769 <table class="layout">
1771 <td class="left"><tt>{ i32, i32, i32 }</tt></td>
1772 <td class="left">A triple of three <tt>i32</tt> values</td>
1773 </tr><tr class="layout">
1774 <td class="left"><tt>{ float, i32 (i32) * }</tt></td>
1775 <td class="left">A pair, where the first element is a <tt>float</tt> and the
1776 second element is a <a href="#t_pointer">pointer</a> to a
1777 <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
1778 an <tt>i32</tt>.</td>
1784 <!-- _______________________________________________________________________ -->
1785 <div class="doc_subsubsection"> <a name="t_pstruct">Packed Structure Type</a>
1788 <div class="doc_text">
1791 <p>The packed structure type is used to represent a collection of data members
1792 together in memory. There is no padding between fields. Further, the
1793 alignment of a packed structure is 1 byte. The elements of a packed
1794 structure may be any type that has a size.</p>
1796 <p>Structures are accessed using '<tt><a href="#i_load">load</a></tt> and
1797 '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a field with
1798 the '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction.</p>
1802 < { <type list> } >
1806 <table class="layout">
1808 <td class="left"><tt>< { i32, i32, i32 } ></tt></td>
1809 <td class="left">A triple of three <tt>i32</tt> values</td>
1810 </tr><tr class="layout">
1812 <tt>< { float, i32 (i32)* } ></tt></td>
1813 <td class="left">A pair, where the first element is a <tt>float</tt> and the
1814 second element is a <a href="#t_pointer">pointer</a> to a
1815 <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
1816 an <tt>i32</tt>.</td>
1822 <!-- _______________________________________________________________________ -->
1823 <div class="doc_subsubsection"> <a name="t_union">Union Type</a> </div>
1825 <div class="doc_text">
1828 <p>A union type describes an object with size and alignment suitable for
1829 an object of any one of a given set of types (also known as an "untagged"
1830 union). It is similar in concept and usage to a
1831 <a href="#t_struct">struct</a>, except that all members of the union
1832 have an offset of zero. The elements of a union may be any type that has a
1833 size. Unions must have at least one member - empty unions are not allowed.
1836 <p>The size of the union as a whole will be the size of its largest member,
1837 and the alignment requirements of the union as a whole will be the largest
1838 alignment requirement of any member.</p>
1840 <p>Union members are accessed using '<tt><a href="#i_load">load</a></tt> and
1841 '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a field with
1842 the '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction.
1843 Since all members are at offset zero, the getelementptr instruction does
1844 not affect the address, only the type of the resulting pointer.</p>
1848 union { <type list> }
1852 <table class="layout">
1854 <td class="left"><tt>union { i32, i32*, float }</tt></td>
1855 <td class="left">A union of three types: an <tt>i32</tt>, a pointer to
1856 an <tt>i32</tt>, and a <tt>float</tt>.</td>
1857 </tr><tr class="layout">
1859 <tt>union { float, i32 (i32) * }</tt></td>
1860 <td class="left">A union, where the first element is a <tt>float</tt> and the
1861 second element is a <a href="#t_pointer">pointer</a> to a
1862 <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning
1863 an <tt>i32</tt>.</td>
1869 <!-- _______________________________________________________________________ -->
1870 <div class="doc_subsubsection"> <a name="t_pointer">Pointer Type</a> </div>
1872 <div class="doc_text">
1875 <p>The pointer type is used to specify memory locations.
1876 Pointers are commonly used to reference objects in memory.</p>
1878 <p>Pointer types may have an optional address space attribute defining the
1879 numbered address space where the pointed-to object resides. The default
1880 address space is number zero. The semantics of non-zero address
1881 spaces are target-specific.</p>
1883 <p>Note that LLVM does not permit pointers to void (<tt>void*</tt>) nor does it
1884 permit pointers to labels (<tt>label*</tt>). Use <tt>i8*</tt> instead.</p>
1892 <table class="layout">
1894 <td class="left"><tt>[4 x i32]*</tt></td>
1895 <td class="left">A <a href="#t_pointer">pointer</a> to <a
1896 href="#t_array">array</a> of four <tt>i32</tt> values.</td>
1899 <td class="left"><tt>i32 (i32 *) *</tt></td>
1900 <td class="left"> A <a href="#t_pointer">pointer</a> to a <a
1901 href="#t_function">function</a> that takes an <tt>i32*</tt>, returning an
1905 <td class="left"><tt>i32 addrspace(5)*</tt></td>
1906 <td class="left">A <a href="#t_pointer">pointer</a> to an <tt>i32</tt> value
1907 that resides in address space #5.</td>
1913 <!-- _______________________________________________________________________ -->
1914 <div class="doc_subsubsection"> <a name="t_vector">Vector Type</a> </div>
1916 <div class="doc_text">
1919 <p>A vector type is a simple derived type that represents a vector of elements.
1920 Vector types are used when multiple primitive data are operated in parallel
1921 using a single instruction (SIMD). A vector type requires a size (number of
1922 elements) and an underlying primitive data type. Vector types are considered
1923 <a href="#t_firstclass">first class</a>.</p>
1927 < <# elements> x <elementtype> >
1930 <p>The number of elements is a constant integer value; elementtype may be any
1931 integer or floating point type.</p>
1934 <table class="layout">
1936 <td class="left"><tt><4 x i32></tt></td>
1937 <td class="left">Vector of 4 32-bit integer values.</td>
1940 <td class="left"><tt><8 x float></tt></td>
1941 <td class="left">Vector of 8 32-bit floating-point values.</td>
1944 <td class="left"><tt><2 x i64></tt></td>
1945 <td class="left">Vector of 2 64-bit integer values.</td>
1951 <!-- _______________________________________________________________________ -->
1952 <div class="doc_subsubsection"> <a name="t_opaque">Opaque Type</a> </div>
1953 <div class="doc_text">
1956 <p>Opaque types are used to represent unknown types in the system. This
1957 corresponds (for example) to the C notion of a forward declared structure
1958 type. In LLVM, opaque types can eventually be resolved to any type (not just
1959 a structure type).</p>
1967 <table class="layout">
1969 <td class="left"><tt>opaque</tt></td>
1970 <td class="left">An opaque type.</td>
1976 <!-- ======================================================================= -->
1977 <div class="doc_subsection">
1978 <a name="t_uprefs">Type Up-references</a>
1981 <div class="doc_text">
1984 <p>An "up reference" allows you to refer to a lexically enclosing type without
1985 requiring it to have a name. For instance, a structure declaration may
1986 contain a pointer to any of the types it is lexically a member of. Example
1987 of up references (with their equivalent as named type declarations)
1991 { \2 * } %x = type { %x* }
1992 { \2 }* %y = type { %y }*
1996 <p>An up reference is needed by the asmprinter for printing out cyclic types
1997 when there is no declared name for a type in the cycle. Because the
1998 asmprinter does not want to print out an infinite type string, it needs a
1999 syntax to handle recursive types that have no names (all names are optional
2007 <p>The level is the count of the lexical type that is being referred to.</p>
2010 <table class="layout">
2012 <td class="left"><tt>\1*</tt></td>
2013 <td class="left">Self-referential pointer.</td>
2016 <td class="left"><tt>{ { \3*, i8 }, i32 }</tt></td>
2017 <td class="left">Recursive structure where the upref refers to the out-most
2024 <!-- *********************************************************************** -->
2025 <div class="doc_section"> <a name="constants">Constants</a> </div>
2026 <!-- *********************************************************************** -->
2028 <div class="doc_text">
2030 <p>LLVM has several different basic types of constants. This section describes
2031 them all and their syntax.</p>
2035 <!-- ======================================================================= -->
2036 <div class="doc_subsection"><a name="simpleconstants">Simple Constants</a></div>
2038 <div class="doc_text">
2041 <dt><b>Boolean constants</b></dt>
2042 <dd>The two strings '<tt>true</tt>' and '<tt>false</tt>' are both valid
2043 constants of the <tt><a href="#t_integer">i1</a></tt> type.</dd>
2045 <dt><b>Integer constants</b></dt>
2046 <dd>Standard integers (such as '4') are constants of
2047 the <a href="#t_integer">integer</a> type. Negative numbers may be used
2048 with integer types.</dd>
2050 <dt><b>Floating point constants</b></dt>
2051 <dd>Floating point constants use standard decimal notation (e.g. 123.421),
2052 exponential notation (e.g. 1.23421e+2), or a more precise hexadecimal
2053 notation (see below). The assembler requires the exact decimal value of a
2054 floating-point constant. For example, the assembler accepts 1.25 but
2055 rejects 1.3 because 1.3 is a repeating decimal in binary. Floating point
2056 constants must have a <a href="#t_floating">floating point</a> type. </dd>
2058 <dt><b>Null pointer constants</b></dt>
2059 <dd>The identifier '<tt>null</tt>' is recognized as a null pointer constant
2060 and must be of <a href="#t_pointer">pointer type</a>.</dd>
2063 <p>The one non-intuitive notation for constants is the hexadecimal form of
2064 floating point constants. For example, the form '<tt>double
2065 0x432ff973cafa8000</tt>' is equivalent to (but harder to read than)
2066 '<tt>double 4.5e+15</tt>'. The only time hexadecimal floating point
2067 constants are required (and the only time that they are generated by the
2068 disassembler) is when a floating point constant must be emitted but it cannot
2069 be represented as a decimal floating point number in a reasonable number of
2070 digits. For example, NaN's, infinities, and other special values are
2071 represented in their IEEE hexadecimal format so that assembly and disassembly
2072 do not cause any bits to change in the constants.</p>
2074 <p>When using the hexadecimal form, constants of types float and double are
2075 represented using the 16-digit form shown above (which matches the IEEE754
2076 representation for double); float values must, however, be exactly
2077 representable as IEE754 single precision. Hexadecimal format is always used
2078 for long double, and there are three forms of long double. The 80-bit format
2079 used by x86 is represented as <tt>0xK</tt> followed by 20 hexadecimal digits.
2080 The 128-bit format used by PowerPC (two adjacent doubles) is represented
2081 by <tt>0xM</tt> followed by 32 hexadecimal digits. The IEEE 128-bit format
2082 is represented by <tt>0xL</tt> followed by 32 hexadecimal digits; no
2083 currently supported target uses this format. Long doubles will only work if
2084 they match the long double format on your target. All hexadecimal formats
2085 are big-endian (sign bit at the left).</p>
2089 <!-- ======================================================================= -->
2090 <div class="doc_subsection">
2091 <a name="aggregateconstants"></a> <!-- old anchor -->
2092 <a name="complexconstants">Complex Constants</a>
2095 <div class="doc_text">
2097 <p>Complex constants are a (potentially recursive) combination of simple
2098 constants and smaller complex constants.</p>
2101 <dt><b>Structure constants</b></dt>
2102 <dd>Structure constants are represented with notation similar to structure
2103 type definitions (a comma separated list of elements, surrounded by braces
2104 (<tt>{}</tt>)). For example: "<tt>{ i32 4, float 17.0, i32* @G }</tt>",
2105 where "<tt>@G</tt>" is declared as "<tt>@G = external global i32</tt>".
2106 Structure constants must have <a href="#t_struct">structure type</a>, and
2107 the number and types of elements must match those specified by the
2110 <dt><b>Union constants</b></dt>
2111 <dd>Union constants are represented with notation similar to a structure with
2112 a single element - that is, a single typed element surrounded
2113 by braces (<tt>{}</tt>)). For example: "<tt>{ i32 4 }</tt>". The
2114 <a href="#t_union">union type</a> can be initialized with a single-element
2115 struct as long as the type of the struct element matches the type of
2116 one of the union members.</dd>
2118 <dt><b>Array constants</b></dt>
2119 <dd>Array constants are represented with notation similar to array type
2120 definitions (a comma separated list of elements, surrounded by square
2121 brackets (<tt>[]</tt>)). For example: "<tt>[ i32 42, i32 11, i32 74
2122 ]</tt>". Array constants must have <a href="#t_array">array type</a>, and
2123 the number and types of elements must match those specified by the
2126 <dt><b>Vector constants</b></dt>
2127 <dd>Vector constants are represented with notation similar to vector type
2128 definitions (a comma separated list of elements, surrounded by
2129 less-than/greater-than's (<tt><></tt>)). For example: "<tt>< i32
2130 42, i32 11, i32 74, i32 100 ></tt>". Vector constants must
2131 have <a href="#t_vector">vector type</a>, and the number and types of
2132 elements must match those specified by the type.</dd>
2134 <dt><b>Zero initialization</b></dt>
2135 <dd>The string '<tt>zeroinitializer</tt>' can be used to zero initialize a
2136 value to zero of <em>any</em> type, including scalar and
2137 <a href="#t_aggregate">aggregate</a> types.
2138 This is often used to avoid having to print large zero initializers
2139 (e.g. for large arrays) and is always exactly equivalent to using explicit
2140 zero initializers.</dd>
2142 <dt><b>Metadata node</b></dt>
2143 <dd>A metadata node is a structure-like constant with
2144 <a href="#t_metadata">metadata type</a>. For example: "<tt>metadata !{
2145 i32 0, metadata !"test" }</tt>". Unlike other constants that are meant to
2146 be interpreted as part of the instruction stream, metadata is a place to
2147 attach additional information such as debug info.</dd>
2152 <!-- ======================================================================= -->
2153 <div class="doc_subsection">
2154 <a name="globalconstants">Global Variable and Function Addresses</a>
2157 <div class="doc_text">
2159 <p>The addresses of <a href="#globalvars">global variables</a>
2160 and <a href="#functionstructure">functions</a> are always implicitly valid
2161 (link-time) constants. These constants are explicitly referenced when
2162 the <a href="#identifiers">identifier for the global</a> is used and always
2163 have <a href="#t_pointer">pointer</a> type. For example, the following is a
2164 legal LLVM file:</p>
2166 <div class="doc_code">
2170 @Z = global [2 x i32*] [ i32* @X, i32* @Y ]
2176 <!-- ======================================================================= -->
2177 <div class="doc_subsection"><a name="undefvalues">Undefined Values</a></div>
2178 <div class="doc_text">
2180 <p>The string '<tt>undef</tt>' can be used anywhere a constant is expected, and
2181 indicates that the user of the value may receive an unspecified bit-pattern.
2182 Undefined values may be of any type (other than label or void) and be used
2183 anywhere a constant is permitted.</p>
2185 <p>Undefined values are useful because they indicate to the compiler that the
2186 program is well defined no matter what value is used. This gives the
2187 compiler more freedom to optimize. Here are some examples of (potentially
2188 surprising) transformations that are valid (in pseudo IR):</p>
2191 <div class="doc_code">
2203 <p>This is safe because all of the output bits are affected by the undef bits.
2204 Any output bit can have a zero or one depending on the input bits.</p>
2206 <div class="doc_code">
2219 <p>These logical operations have bits that are not always affected by the input.
2220 For example, if "%X" has a zero bit, then the output of the 'and' operation will
2221 always be a zero, no matter what the corresponding bit from the undef is. As
2222 such, it is unsafe to optimize or assume that the result of the and is undef.
2223 However, it is safe to assume that all bits of the undef could be 0, and
2224 optimize the and to 0. Likewise, it is safe to assume that all the bits of
2225 the undef operand to the or could be set, allowing the or to be folded to
2228 <div class="doc_code">
2230 %A = select undef, %X, %Y
2231 %B = select undef, 42, %Y
2232 %C = select %X, %Y, undef
2244 <p>This set of examples show that undefined select (and conditional branch)
2245 conditions can go "either way" but they have to come from one of the two
2246 operands. In the %A example, if %X and %Y were both known to have a clear low
2247 bit, then %A would have to have a cleared low bit. However, in the %C example,
2248 the optimizer is allowed to assume that the undef operand could be the same as
2249 %Y, allowing the whole select to be eliminated.</p>
2252 <div class="doc_code">
2254 %A = xor undef, undef
2273 <p>This example points out that two undef operands are not necessarily the same.
2274 This can be surprising to people (and also matches C semantics) where they
2275 assume that "X^X" is always zero, even if X is undef. This isn't true for a
2276 number of reasons, but the short answer is that an undef "variable" can
2277 arbitrarily change its value over its "live range". This is true because the
2278 "variable" doesn't actually <em>have a live range</em>. Instead, the value is
2279 logically read from arbitrary registers that happen to be around when needed,
2280 so the value is not necessarily consistent over time. In fact, %A and %C need
2281 to have the same semantics or the core LLVM "replace all uses with" concept
2284 <div class="doc_code">
2294 <p>These examples show the crucial difference between an <em>undefined
2295 value</em> and <em>undefined behavior</em>. An undefined value (like undef) is
2296 allowed to have an arbitrary bit-pattern. This means that the %A operation
2297 can be constant folded to undef because the undef could be an SNaN, and fdiv is
2298 not (currently) defined on SNaN's. However, in the second example, we can make
2299 a more aggressive assumption: because the undef is allowed to be an arbitrary
2300 value, we are allowed to assume that it could be zero. Since a divide by zero
2301 has <em>undefined behavior</em>, we are allowed to assume that the operation
2302 does not execute at all. This allows us to delete the divide and all code after
2303 it: since the undefined operation "can't happen", the optimizer can assume that
2304 it occurs in dead code.
2307 <div class="doc_code">
2309 a: store undef -> %X
2310 b: store %X -> undef
2317 <p>These examples reiterate the fdiv example: a store "of" an undefined value
2318 can be assumed to not have any effect: we can assume that the value is
2319 overwritten with bits that happen to match what was already there. However, a
2320 store "to" an undefined location could clobber arbitrary memory, therefore, it
2321 has undefined behavior.</p>
2325 <!-- ======================================================================= -->
2326 <div class="doc_subsection"><a name="trapvalues">Trap Values</a></div>
2327 <div class="doc_text">
2329 <p>Trap values are similar to <a href="#undefvalues">undef values</a>, however
2330 instead of representing an unspecified bit pattern, they represent the
2331 fact that an instruction or constant expression which cannot evoke side
2332 effects has nevertheless detected a condition which results in undefined
2335 <p>Any non-void instruction or constant expression other than a non-intrinsic
2336 call, invoke, or phi with a trap operand has trap as its result value.
2337 Any instruction with a trap operand which may have side effects emits
2338 those side effects as if it had an undef operand instead.</p>
2340 <p>If a <a href="#i_br"><tt>br</tt></a> or
2341 <a href="#i_switch"><tt>switch</tt></a> instruction has a trap value
2342 operand, all non-phi non-void instructions which control-depend on it
2343 have trap as their result value. If any instruction which
2344 control-depends on the <tt>br</tt> or <tt>switch</tt> invokes externally
2345 visible side effects, the behavior of the program is undefined.</p>
2347 <!-- FIXME: What about exceptions thrown from control-dependent instrs? -->
2349 <p>For example, an <a href="#i_and"><tt>and</tt></a> of a trap value with
2350 zero still has a trap value result. Using that value as an index in a
2351 <a href="#i_getelementptr"><tt>getelementptr</tt></a> yields a trap
2352 result. Using that result as the address of a
2353 <a href="#i_store"><tt>store</tt></a> produces undefined behavior.</p>
2355 <p>There is currently no way of representing a trap constant in the IR; they
2356 only exist when produced by certain instructions, such as an
2357 <a href="#i_add"><tt>add</tt></a> with the <tt>nsw</tt> flag
2358 set, when overflow occurs.</p>
2362 <!-- ======================================================================= -->
2363 <div class="doc_subsection"><a name="blockaddress">Addresses of Basic
2365 <div class="doc_text">
2367 <p><b><tt>blockaddress(@function, %block)</tt></b></p>
2369 <p>The '<tt>blockaddress</tt>' constant computes the address of the specified
2370 basic block in the specified function, and always has an i8* type. Taking
2371 the address of the entry block is illegal.</p>
2373 <p>This value only has defined behavior when used as an operand to the
2374 '<a href="#i_indirectbr"><tt>indirectbr</tt></a>' instruction or for comparisons
2375 against null. Pointer equality tests between labels addresses is undefined
2376 behavior - though, again, comparison against null is ok, and no label is
2377 equal to the null pointer. This may also be passed around as an opaque
2378 pointer sized value as long as the bits are not inspected. This allows
2379 <tt>ptrtoint</tt> and arithmetic to be performed on these values so long as
2380 the original value is reconstituted before the <tt>indirectbr</tt>.</p>
2382 <p>Finally, some targets may provide defined semantics when
2383 using the value as the operand to an inline assembly, but that is target
2390 <!-- ======================================================================= -->
2391 <div class="doc_subsection"><a name="constantexprs">Constant Expressions</a>
2394 <div class="doc_text">
2396 <p>Constant expressions are used to allow expressions involving other constants
2397 to be used as constants. Constant expressions may be of
2398 any <a href="#t_firstclass">first class</a> type and may involve any LLVM
2399 operation that does not have side effects (e.g. load and call are not
2400 supported). The following is the syntax for constant expressions:</p>
2403 <dt><b><tt>trunc ( CST to TYPE )</tt></b></dt>
2404 <dd>Truncate a constant to another type. The bit size of CST must be larger
2405 than the bit size of TYPE. Both types must be integers.</dd>
2407 <dt><b><tt>zext ( CST to TYPE )</tt></b></dt>
2408 <dd>Zero extend a constant to another type. The bit size of CST must be
2409 smaller or equal to the bit size of TYPE. Both types must be
2412 <dt><b><tt>sext ( CST to TYPE )</tt></b></dt>
2413 <dd>Sign extend a constant to another type. The bit size of CST must be
2414 smaller or equal to the bit size of TYPE. Both types must be
2417 <dt><b><tt>fptrunc ( CST to TYPE )</tt></b></dt>
2418 <dd>Truncate a floating point constant to another floating point type. The
2419 size of CST must be larger than the size of TYPE. Both types must be
2420 floating point.</dd>
2422 <dt><b><tt>fpext ( CST to TYPE )</tt></b></dt>
2423 <dd>Floating point extend a constant to another type. The size of CST must be
2424 smaller or equal to the size of TYPE. Both types must be floating
2427 <dt><b><tt>fptoui ( CST to TYPE )</tt></b></dt>
2428 <dd>Convert a floating point constant to the corresponding unsigned integer
2429 constant. TYPE must be a scalar or vector integer type. CST must be of
2430 scalar or vector floating point type. Both CST and TYPE must be scalars,
2431 or vectors of the same number of elements. If the value won't fit in the
2432 integer type, the results are undefined.</dd>
2434 <dt><b><tt>fptosi ( CST to TYPE )</tt></b></dt>
2435 <dd>Convert a floating point constant to the corresponding signed integer
2436 constant. TYPE must be a scalar or vector integer type. CST must be of
2437 scalar or vector floating point type. Both CST and TYPE must be scalars,
2438 or vectors of the same number of elements. If the value won't fit in the
2439 integer type, the results are undefined.</dd>
2441 <dt><b><tt>uitofp ( CST to TYPE )</tt></b></dt>
2442 <dd>Convert an unsigned integer constant to the corresponding floating point
2443 constant. TYPE must be a scalar or vector floating point type. CST must be
2444 of scalar or vector integer type. Both CST and TYPE must be scalars, or
2445 vectors of the same number of elements. If the value won't fit in the
2446 floating point type, the results are undefined.</dd>
2448 <dt><b><tt>sitofp ( CST to TYPE )</tt></b></dt>
2449 <dd>Convert a signed integer constant to the corresponding floating point
2450 constant. TYPE must be a scalar or vector floating point type. CST must be
2451 of scalar or vector integer type. Both CST and TYPE must be scalars, or
2452 vectors of the same number of elements. If the value won't fit in the
2453 floating point type, the results are undefined.</dd>
2455 <dt><b><tt>ptrtoint ( CST to TYPE )</tt></b></dt>
2456 <dd>Convert a pointer typed constant to the corresponding integer constant
2457 <tt>TYPE</tt> must be an integer type. <tt>CST</tt> must be of pointer
2458 type. The <tt>CST</tt> value is zero extended, truncated, or unchanged to
2459 make it fit in <tt>TYPE</tt>.</dd>
2461 <dt><b><tt>inttoptr ( CST to TYPE )</tt></b></dt>
2462 <dd>Convert a integer constant to a pointer constant. TYPE must be a pointer
2463 type. CST must be of integer type. The CST value is zero extended,
2464 truncated, or unchanged to make it fit in a pointer size. This one is
2465 <i>really</i> dangerous!</dd>
2467 <dt><b><tt>bitcast ( CST to TYPE )</tt></b></dt>
2468 <dd>Convert a constant, CST, to another TYPE. The constraints of the operands
2469 are the same as those for the <a href="#i_bitcast">bitcast
2470 instruction</a>.</dd>
2472 <dt><b><tt>getelementptr ( CSTPTR, IDX0, IDX1, ... )</tt></b></dt>
2473 <dt><b><tt>getelementptr inbounds ( CSTPTR, IDX0, IDX1, ... )</tt></b></dt>
2474 <dd>Perform the <a href="#i_getelementptr">getelementptr operation</a> on
2475 constants. As with the <a href="#i_getelementptr">getelementptr</a>
2476 instruction, the index list may have zero or more indexes, which are
2477 required to make sense for the type of "CSTPTR".</dd>
2479 <dt><b><tt>select ( COND, VAL1, VAL2 )</tt></b></dt>
2480 <dd>Perform the <a href="#i_select">select operation</a> on constants.</dd>
2482 <dt><b><tt>icmp COND ( VAL1, VAL2 )</tt></b></dt>
2483 <dd>Performs the <a href="#i_icmp">icmp operation</a> on constants.</dd>
2485 <dt><b><tt>fcmp COND ( VAL1, VAL2 )</tt></b></dt>
2486 <dd>Performs the <a href="#i_fcmp">fcmp operation</a> on constants.</dd>
2488 <dt><b><tt>extractelement ( VAL, IDX )</tt></b></dt>
2489 <dd>Perform the <a href="#i_extractelement">extractelement operation</a> on
2492 <dt><b><tt>insertelement ( VAL, ELT, IDX )</tt></b></dt>
2493 <dd>Perform the <a href="#i_insertelement">insertelement operation</a> on
2496 <dt><b><tt>shufflevector ( VEC1, VEC2, IDXMASK )</tt></b></dt>
2497 <dd>Perform the <a href="#i_shufflevector">shufflevector operation</a> on
2500 <dt><b><tt>OPCODE ( LHS, RHS )</tt></b></dt>
2501 <dd>Perform the specified operation of the LHS and RHS constants. OPCODE may
2502 be any of the <a href="#binaryops">binary</a>
2503 or <a href="#bitwiseops">bitwise binary</a> operations. The constraints
2504 on operands are the same as those for the corresponding instruction
2505 (e.g. no bitwise operations on floating point values are allowed).</dd>
2510 <!-- *********************************************************************** -->
2511 <div class="doc_section"> <a name="othervalues">Other Values</a> </div>
2512 <!-- *********************************************************************** -->
2514 <!-- ======================================================================= -->
2515 <div class="doc_subsection">
2516 <a name="inlineasm">Inline Assembler Expressions</a>
2519 <div class="doc_text">
2521 <p>LLVM supports inline assembler expressions (as opposed
2522 to <a href="#moduleasm"> Module-Level Inline Assembly</a>) through the use of
2523 a special value. This value represents the inline assembler as a string
2524 (containing the instructions to emit), a list of operand constraints (stored
2525 as a string), a flag that indicates whether or not the inline asm
2526 expression has side effects, and a flag indicating whether the function
2527 containing the asm needs to align its stack conservatively. An example
2528 inline assembler expression is:</p>
2530 <div class="doc_code">
2532 i32 (i32) asm "bswap $0", "=r,r"
2536 <p>Inline assembler expressions may <b>only</b> be used as the callee operand of
2537 a <a href="#i_call"><tt>call</tt> instruction</a>. Thus, typically we
2540 <div class="doc_code">
2542 %X = call i32 asm "<a href="#int_bswap">bswap</a> $0", "=r,r"(i32 %Y)
2546 <p>Inline asms with side effects not visible in the constraint list must be
2547 marked as having side effects. This is done through the use of the
2548 '<tt>sideeffect</tt>' keyword, like so:</p>
2550 <div class="doc_code">
2552 call void asm sideeffect "eieio", ""()
2556 <p>In some cases inline asms will contain code that will not work unless the
2557 stack is aligned in some way, such as calls or SSE instructions on x86,
2558 yet will not contain code that does that alignment within the asm.
2559 The compiler should make conservative assumptions about what the asm might
2560 contain and should generate its usual stack alignment code in the prologue
2561 if the '<tt>alignstack</tt>' keyword is present:</p>
2563 <div class="doc_code">
2565 call void asm alignstack "eieio", ""()
2569 <p>If both keywords appear the '<tt>sideeffect</tt>' keyword must come
2572 <p>TODO: The format of the asm and constraints string still need to be
2573 documented here. Constraints on what can be done (e.g. duplication, moving,
2574 etc need to be documented). This is probably best done by reference to
2575 another document that covers inline asm from a holistic perspective.</p>
2578 <div class="doc_subsubsection">
2579 <a name="inlineasm_md">Inline Asm Metadata</a>
2582 <div class="doc_text">
2584 <p>The call instructions that wrap inline asm nodes may have a "!srcloc" MDNode
2585 attached to it that contains a constant integer. If present, the code
2586 generator will use the integer as the location cookie value when report
2587 errors through the LLVMContext error reporting mechanisms. This allows a
2588 front-end to corrolate backend errors that occur with inline asm back to the
2589 source code that produced it. For example:</p>
2591 <div class="doc_code">
2593 call void asm sideeffect "something bad", ""()<b>, !srcloc !42</b>
2595 !42 = !{ i32 1234567 }
2599 <p>It is up to the front-end to make sense of the magic numbers it places in the
2604 <!-- ======================================================================= -->
2605 <div class="doc_subsection"><a name="metadata">Metadata Nodes and Metadata
2609 <div class="doc_text">
2611 <p>LLVM IR allows metadata to be attached to instructions in the program that
2612 can convey extra information about the code to the optimizers and code
2613 generator. One example application of metadata is source-level debug
2614 information. There are two metadata primitives: strings and nodes. All
2615 metadata has the <tt>metadata</tt> type and is identified in syntax by a
2616 preceding exclamation point ('<tt>!</tt>').</p>
2618 <p>A metadata string is a string surrounded by double quotes. It can contain
2619 any character by escaping non-printable characters with "\xx" where "xx" is
2620 the two digit hex code. For example: "<tt>!"test\00"</tt>".</p>
2622 <p>Metadata nodes are represented with notation similar to structure constants
2623 (a comma separated list of elements, surrounded by braces and preceded by an
2624 exclamation point). For example: "<tt>!{ metadata !"test\00", i32
2625 10}</tt>". Metadata nodes can have any values as their operand.</p>
2627 <p>A <a href="#namedmetadatastructure">named metadata</a> is a collection of
2628 metadata nodes, which can be looked up in the module symbol table. For
2629 example: "<tt>!foo = metadata !{!4, !3}</tt>".
2631 <p>Metadata can be used as function arguments. Here <tt>llvm.dbg.value</tt>
2632 function is using two metadata arguments.
2634 <div class="doc_code">
2636 call void @llvm.dbg.value(metadata !24, i64 0, metadata !25)
2640 <p>Metadata can be attached with an instruction. Here metadata <tt>!21</tt> is
2641 attached with <tt>add</tt> instruction using <tt>!dbg</tt> identifier.
2643 <div class="doc_code">
2645 %indvar.next = add i64 %indvar, 1, !dbg !21
2651 <!-- *********************************************************************** -->
2652 <div class="doc_section">
2653 <a name="intrinsic_globals">Intrinsic Global Variables</a>
2655 <!-- *********************************************************************** -->
2657 <p>LLVM has a number of "magic" global variables that contain data that affect
2658 code generation or other IR semantics. These are documented here. All globals
2659 of this sort should have a section specified as "<tt>llvm.metadata</tt>". This
2660 section and all globals that start with "<tt>llvm.</tt>" are reserved for use
2663 <!-- ======================================================================= -->
2664 <div class="doc_subsection">
2665 <a name="intg_used">The '<tt>llvm.used</tt>' Global Variable</a>
2668 <div class="doc_text">
2670 <p>The <tt>@llvm.used</tt> global is an array with i8* element type which has <a
2671 href="#linkage_appending">appending linkage</a>. This array contains a list of
2672 pointers to global variables and functions which may optionally have a pointer
2673 cast formed of bitcast or getelementptr. For example, a legal use of it is:</p>
2679 @llvm.used = appending global [2 x i8*] [
2681 i8* bitcast (i32* @Y to i8*)
2682 ], section "llvm.metadata"
2685 <p>If a global variable appears in the <tt>@llvm.used</tt> list, then the
2686 compiler, assembler, and linker are required to treat the symbol as if there is
2687 a reference to the global that it cannot see. For example, if a variable has
2688 internal linkage and no references other than that from the <tt>@llvm.used</tt>
2689 list, it cannot be deleted. This is commonly used to represent references from
2690 inline asms and other things the compiler cannot "see", and corresponds to
2691 "attribute((used))" in GNU C.</p>
2693 <p>On some targets, the code generator must emit a directive to the assembler or
2694 object file to prevent the assembler and linker from molesting the symbol.</p>
2698 <!-- ======================================================================= -->
2699 <div class="doc_subsection">
2700 <a name="intg_compiler_used">The '<tt>llvm.compiler.used</tt>' Global Variable</a>
2703 <div class="doc_text">
2705 <p>The <tt>@llvm.compiler.used</tt> directive is the same as the
2706 <tt>@llvm.used</tt> directive, except that it only prevents the compiler from
2707 touching the symbol. On targets that support it, this allows an intelligent
2708 linker to optimize references to the symbol without being impeded as it would be
2709 by <tt>@llvm.used</tt>.</p>
2711 <p>This is a rare construct that should only be used in rare circumstances, and
2712 should not be exposed to source languages.</p>
2716 <!-- ======================================================================= -->
2717 <div class="doc_subsection">
2718 <a name="intg_global_ctors">The '<tt>llvm.global_ctors</tt>' Global Variable</a>
2721 <div class="doc_text">
2723 <p>TODO: Describe this.</p>
2727 <!-- ======================================================================= -->
2728 <div class="doc_subsection">
2729 <a name="intg_global_dtors">The '<tt>llvm.global_dtors</tt>' Global Variable</a>
2732 <div class="doc_text">
2734 <p>TODO: Describe this.</p>
2739 <!-- *********************************************************************** -->
2740 <div class="doc_section"> <a name="instref">Instruction Reference</a> </div>
2741 <!-- *********************************************************************** -->
2743 <div class="doc_text">
2745 <p>The LLVM instruction set consists of several different classifications of
2746 instructions: <a href="#terminators">terminator
2747 instructions</a>, <a href="#binaryops">binary instructions</a>,
2748 <a href="#bitwiseops">bitwise binary instructions</a>,
2749 <a href="#memoryops">memory instructions</a>, and
2750 <a href="#otherops">other instructions</a>.</p>
2754 <!-- ======================================================================= -->
2755 <div class="doc_subsection"> <a name="terminators">Terminator
2756 Instructions</a> </div>
2758 <div class="doc_text">
2760 <p>As mentioned <a href="#functionstructure">previously</a>, every basic block
2761 in a program ends with a "Terminator" instruction, which indicates which
2762 block should be executed after the current block is finished. These
2763 terminator instructions typically yield a '<tt>void</tt>' value: they produce
2764 control flow, not values (the one exception being the
2765 '<a href="#i_invoke"><tt>invoke</tt></a>' instruction).</p>
2767 <p>There are seven different terminator instructions: the
2768 '<a href="#i_ret"><tt>ret</tt></a>' instruction, the
2769 '<a href="#i_br"><tt>br</tt></a>' instruction, the
2770 '<a href="#i_switch"><tt>switch</tt></a>' instruction, the
2771 '<a href="#i_indirectbr">'<tt>indirectbr</tt></a>' Instruction, the
2772 '<a href="#i_invoke"><tt>invoke</tt></a>' instruction, the
2773 '<a href="#i_unwind"><tt>unwind</tt></a>' instruction, and the
2774 '<a href="#i_unreachable"><tt>unreachable</tt></a>' instruction.</p>
2778 <!-- _______________________________________________________________________ -->
2779 <div class="doc_subsubsection"> <a name="i_ret">'<tt>ret</tt>'
2780 Instruction</a> </div>
2782 <div class="doc_text">
2786 ret <type> <value> <i>; Return a value from a non-void function</i>
2787 ret void <i>; Return from void function</i>
2791 <p>The '<tt>ret</tt>' instruction is used to return control flow (and optionally
2792 a value) from a function back to the caller.</p>
2794 <p>There are two forms of the '<tt>ret</tt>' instruction: one that returns a
2795 value and then causes control flow, and one that just causes control flow to
2799 <p>The '<tt>ret</tt>' instruction optionally accepts a single argument, the
2800 return value. The type of the return value must be a
2801 '<a href="#t_firstclass">first class</a>' type.</p>
2803 <p>A function is not <a href="#wellformed">well formed</a> if it it has a
2804 non-void return type and contains a '<tt>ret</tt>' instruction with no return
2805 value or a return value with a type that does not match its type, or if it
2806 has a void return type and contains a '<tt>ret</tt>' instruction with a
2810 <p>When the '<tt>ret</tt>' instruction is executed, control flow returns back to
2811 the calling function's context. If the caller is a
2812 "<a href="#i_call"><tt>call</tt></a>" instruction, execution continues at the
2813 instruction after the call. If the caller was an
2814 "<a href="#i_invoke"><tt>invoke</tt></a>" instruction, execution continues at
2815 the beginning of the "normal" destination block. If the instruction returns
2816 a value, that value shall set the call or invoke instruction's return
2821 ret i32 5 <i>; Return an integer value of 5</i>
2822 ret void <i>; Return from a void function</i>
2823 ret { i32, i8 } { i32 4, i8 2 } <i>; Return a struct of values 4 and 2</i>
2827 <!-- _______________________________________________________________________ -->
2828 <div class="doc_subsubsection"> <a name="i_br">'<tt>br</tt>' Instruction</a> </div>
2830 <div class="doc_text">
2834 br i1 <cond>, label <iftrue>, label <iffalse><br> br label <dest> <i>; Unconditional branch</i>
2838 <p>The '<tt>br</tt>' instruction is used to cause control flow to transfer to a
2839 different basic block in the current function. There are two forms of this
2840 instruction, corresponding to a conditional branch and an unconditional
2844 <p>The conditional branch form of the '<tt>br</tt>' instruction takes a single
2845 '<tt>i1</tt>' value and two '<tt>label</tt>' values. The unconditional form
2846 of the '<tt>br</tt>' instruction takes a single '<tt>label</tt>' value as a
2850 <p>Upon execution of a conditional '<tt>br</tt>' instruction, the '<tt>i1</tt>'
2851 argument is evaluated. If the value is <tt>true</tt>, control flows to the
2852 '<tt>iftrue</tt>' <tt>label</tt> argument. If "cond" is <tt>false</tt>,
2853 control flows to the '<tt>iffalse</tt>' <tt>label</tt> argument.</p>
2858 %cond = <a href="#i_icmp">icmp</a> eq i32 %a, %b
2859 br i1 %cond, label %IfEqual, label %IfUnequal
2861 <a href="#i_ret">ret</a> i32 1
2863 <a href="#i_ret">ret</a> i32 0
2868 <!-- _______________________________________________________________________ -->
2869 <div class="doc_subsubsection">
2870 <a name="i_switch">'<tt>switch</tt>' Instruction</a>
2873 <div class="doc_text">
2877 switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]
2881 <p>The '<tt>switch</tt>' instruction is used to transfer control flow to one of
2882 several different places. It is a generalization of the '<tt>br</tt>'
2883 instruction, allowing a branch to occur to one of many possible
2887 <p>The '<tt>switch</tt>' instruction uses three parameters: an integer
2888 comparison value '<tt>value</tt>', a default '<tt>label</tt>' destination,
2889 and an array of pairs of comparison value constants and '<tt>label</tt>'s.
2890 The table is not allowed to contain duplicate constant entries.</p>
2893 <p>The <tt>switch</tt> instruction specifies a table of values and
2894 destinations. When the '<tt>switch</tt>' instruction is executed, this table
2895 is searched for the given value. If the value is found, control flow is
2896 transferred to the corresponding destination; otherwise, control flow is
2897 transferred to the default destination.</p>
2899 <h5>Implementation:</h5>
2900 <p>Depending on properties of the target machine and the particular
2901 <tt>switch</tt> instruction, this instruction may be code generated in
2902 different ways. For example, it could be generated as a series of chained
2903 conditional branches or with a lookup table.</p>
2907 <i>; Emulate a conditional br instruction</i>
2908 %Val = <a href="#i_zext">zext</a> i1 %value to i32
2909 switch i32 %Val, label %truedest [ i32 0, label %falsedest ]
2911 <i>; Emulate an unconditional br instruction</i>
2912 switch i32 0, label %dest [ ]
2914 <i>; Implement a jump table:</i>
2915 switch i32 %val, label %otherwise [ i32 0, label %onzero
2917 i32 2, label %ontwo ]
2923 <!-- _______________________________________________________________________ -->
2924 <div class="doc_subsubsection">
2925 <a name="i_indirectbr">'<tt>indirectbr</tt>' Instruction</a>
2928 <div class="doc_text">
2932 indirectbr <somety>* <address>, [ label <dest1>, label <dest2>, ... ]
2937 <p>The '<tt>indirectbr</tt>' instruction implements an indirect branch to a label
2938 within the current function, whose address is specified by
2939 "<tt>address</tt>". Address must be derived from a <a
2940 href="#blockaddress">blockaddress</a> constant.</p>
2944 <p>The '<tt>address</tt>' argument is the address of the label to jump to. The
2945 rest of the arguments indicate the full set of possible destinations that the
2946 address may point to. Blocks are allowed to occur multiple times in the
2947 destination list, though this isn't particularly useful.</p>
2949 <p>This destination list is required so that dataflow analysis has an accurate
2950 understanding of the CFG.</p>
2954 <p>Control transfers to the block specified in the address argument. All
2955 possible destination blocks must be listed in the label list, otherwise this
2956 instruction has undefined behavior. This implies that jumps to labels
2957 defined in other functions have undefined behavior as well.</p>
2959 <h5>Implementation:</h5>
2961 <p>This is typically implemented with a jump through a register.</p>
2965 indirectbr i8* %Addr, [ label %bb1, label %bb2, label %bb3 ]
2971 <!-- _______________________________________________________________________ -->
2972 <div class="doc_subsubsection">
2973 <a name="i_invoke">'<tt>invoke</tt>' Instruction</a>
2976 <div class="doc_text">
2980 <result> = invoke [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] <ptr to function ty> <function ptr val>(<function args>) [<a href="#fnattrs">fn attrs</a>]
2981 to label <normal label> unwind label <exception label>
2985 <p>The '<tt>invoke</tt>' instruction causes control to transfer to a specified
2986 function, with the possibility of control flow transfer to either the
2987 '<tt>normal</tt>' label or the '<tt>exception</tt>' label. If the callee
2988 function returns with the "<tt><a href="#i_ret">ret</a></tt>" instruction,
2989 control flow will return to the "normal" label. If the callee (or any
2990 indirect callees) returns with the "<a href="#i_unwind"><tt>unwind</tt></a>"
2991 instruction, control is interrupted and continued at the dynamically nearest
2992 "exception" label.</p>
2995 <p>This instruction requires several arguments:</p>
2998 <li>The optional "cconv" marker indicates which <a href="#callingconv">calling
2999 convention</a> the call should use. If none is specified, the call
3000 defaults to using C calling conventions.</li>
3002 <li>The optional <a href="#paramattrs">Parameter Attributes</a> list for
3003 return values. Only '<tt>zeroext</tt>', '<tt>signext</tt>', and
3004 '<tt>inreg</tt>' attributes are valid here.</li>
3006 <li>'<tt>ptr to function ty</tt>': shall be the signature of the pointer to
3007 function value being invoked. In most cases, this is a direct function
3008 invocation, but indirect <tt>invoke</tt>s are just as possible, branching
3009 off an arbitrary pointer to function value.</li>
3011 <li>'<tt>function ptr val</tt>': An LLVM value containing a pointer to a
3012 function to be invoked. </li>
3014 <li>'<tt>function args</tt>': argument list whose types match the function
3015 signature argument types and parameter attributes. All arguments must be
3016 of <a href="#t_firstclass">first class</a> type. If the function
3017 signature indicates the function accepts a variable number of arguments,
3018 the extra arguments can be specified.</li>
3020 <li>'<tt>normal label</tt>': the label reached when the called function
3021 executes a '<tt><a href="#i_ret">ret</a></tt>' instruction. </li>
3023 <li>'<tt>exception label</tt>': the label reached when a callee returns with
3024 the <a href="#i_unwind"><tt>unwind</tt></a> instruction. </li>
3026 <li>The optional <a href="#fnattrs">function attributes</a> list. Only
3027 '<tt>noreturn</tt>', '<tt>nounwind</tt>', '<tt>readonly</tt>' and
3028 '<tt>readnone</tt>' attributes are valid here.</li>
3032 <p>This instruction is designed to operate as a standard
3033 '<tt><a href="#i_call">call</a></tt>' instruction in most regards. The
3034 primary difference is that it establishes an association with a label, which
3035 is used by the runtime library to unwind the stack.</p>
3037 <p>This instruction is used in languages with destructors to ensure that proper
3038 cleanup is performed in the case of either a <tt>longjmp</tt> or a thrown
3039 exception. Additionally, this is important for implementation of
3040 '<tt>catch</tt>' clauses in high-level languages that support them.</p>
3042 <p>For the purposes of the SSA form, the definition of the value returned by the
3043 '<tt>invoke</tt>' instruction is deemed to occur on the edge from the current
3044 block to the "normal" label. If the callee unwinds then no return value is
3047 <p>Note that the code generator does not yet completely support unwind, and
3048 that the invoke/unwind semantics are likely to change in future versions.</p>
3052 %retval = invoke i32 @Test(i32 15) to label %Continue
3053 unwind label %TestCleanup <i>; {i32}:retval set</i>
3054 %retval = invoke <a href="#callingconv">coldcc</a> i32 %Testfnptr(i32 15) to label %Continue
3055 unwind label %TestCleanup <i>; {i32}:retval set</i>
3060 <!-- _______________________________________________________________________ -->
3062 <div class="doc_subsubsection"> <a name="i_unwind">'<tt>unwind</tt>'
3063 Instruction</a> </div>
3065 <div class="doc_text">
3073 <p>The '<tt>unwind</tt>' instruction unwinds the stack, continuing control flow
3074 at the first callee in the dynamic call stack which used
3075 an <a href="#i_invoke"><tt>invoke</tt></a> instruction to perform the call.
3076 This is primarily used to implement exception handling.</p>
3079 <p>The '<tt>unwind</tt>' instruction causes execution of the current function to
3080 immediately halt. The dynamic call stack is then searched for the
3081 first <a href="#i_invoke"><tt>invoke</tt></a> instruction on the call stack.
3082 Once found, execution continues at the "exceptional" destination block
3083 specified by the <tt>invoke</tt> instruction. If there is no <tt>invoke</tt>
3084 instruction in the dynamic call chain, undefined behavior results.</p>
3086 <p>Note that the code generator does not yet completely support unwind, and
3087 that the invoke/unwind semantics are likely to change in future versions.</p>
3091 <!-- _______________________________________________________________________ -->
3093 <div class="doc_subsubsection"> <a name="i_unreachable">'<tt>unreachable</tt>'
3094 Instruction</a> </div>
3096 <div class="doc_text">
3104 <p>The '<tt>unreachable</tt>' instruction has no defined semantics. This
3105 instruction is used to inform the optimizer that a particular portion of the
3106 code is not reachable. This can be used to indicate that the code after a
3107 no-return function cannot be reached, and other facts.</p>
3110 <p>The '<tt>unreachable</tt>' instruction has no defined semantics.</p>
3114 <!-- ======================================================================= -->
3115 <div class="doc_subsection"> <a name="binaryops">Binary Operations</a> </div>
3117 <div class="doc_text">
3119 <p>Binary operators are used to do most of the computation in a program. They
3120 require two operands of the same type, execute an operation on them, and
3121 produce a single value. The operands might represent multiple data, as is
3122 the case with the <a href="#t_vector">vector</a> data type. The result value
3123 has the same type as its operands.</p>
3125 <p>There are several different binary operators:</p>
3129 <!-- _______________________________________________________________________ -->
3130 <div class="doc_subsubsection">
3131 <a name="i_add">'<tt>add</tt>' Instruction</a>
3134 <div class="doc_text">
3138 <result> = add <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3139 <result> = add nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3140 <result> = add nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3141 <result> = add nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3145 <p>The '<tt>add</tt>' instruction returns the sum of its two operands.</p>
3148 <p>The two arguments to the '<tt>add</tt>' instruction must
3149 be <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of
3150 integer values. Both arguments must have identical types.</p>
3153 <p>The value produced is the integer sum of the two operands.</p>
3155 <p>If the sum has unsigned overflow, the result returned is the mathematical
3156 result modulo 2<sup>n</sup>, where n is the bit width of the result.</p>
3158 <p>Because LLVM integers use a two's complement representation, this instruction
3159 is appropriate for both signed and unsigned integers.</p>
3161 <p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap"
3162 and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or
3163 <tt>nsw</tt> keywords are present, the result value of the <tt>add</tt>
3164 is a <a href="#trapvalues">trap value</a> if unsigned and/or signed overflow,
3165 respectively, occurs.</p>
3169 <result> = add i32 4, %var <i>; yields {i32}:result = 4 + %var</i>
3174 <!-- _______________________________________________________________________ -->
3175 <div class="doc_subsubsection">
3176 <a name="i_fadd">'<tt>fadd</tt>' Instruction</a>
3179 <div class="doc_text">
3183 <result> = fadd <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3187 <p>The '<tt>fadd</tt>' instruction returns the sum of its two operands.</p>
3190 <p>The two arguments to the '<tt>fadd</tt>' instruction must be
3191 <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
3192 floating point values. Both arguments must have identical types.</p>
3195 <p>The value produced is the floating point sum of the two operands.</p>
3199 <result> = fadd float 4.0, %var <i>; yields {float}:result = 4.0 + %var</i>
3204 <!-- _______________________________________________________________________ -->
3205 <div class="doc_subsubsection">
3206 <a name="i_sub">'<tt>sub</tt>' Instruction</a>
3209 <div class="doc_text">
3213 <result> = sub <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3214 <result> = sub nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3215 <result> = sub nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3216 <result> = sub nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3220 <p>The '<tt>sub</tt>' instruction returns the difference of its two
3223 <p>Note that the '<tt>sub</tt>' instruction is used to represent the
3224 '<tt>neg</tt>' instruction present in most other intermediate
3225 representations.</p>
3228 <p>The two arguments to the '<tt>sub</tt>' instruction must
3229 be <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of
3230 integer values. Both arguments must have identical types.</p>
3233 <p>The value produced is the integer difference of the two operands.</p>
3235 <p>If the difference has unsigned overflow, the result returned is the
3236 mathematical result modulo 2<sup>n</sup>, where n is the bit width of the
3239 <p>Because LLVM integers use a two's complement representation, this instruction
3240 is appropriate for both signed and unsigned integers.</p>
3242 <p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap"
3243 and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or
3244 <tt>nsw</tt> keywords are present, the result value of the <tt>sub</tt>
3245 is a <a href="#trapvalues">trap value</a> if unsigned and/or signed overflow,
3246 respectively, occurs.</p>
3250 <result> = sub i32 4, %var <i>; yields {i32}:result = 4 - %var</i>
3251 <result> = sub i32 0, %val <i>; yields {i32}:result = -%var</i>
3256 <!-- _______________________________________________________________________ -->
3257 <div class="doc_subsubsection">
3258 <a name="i_fsub">'<tt>fsub</tt>' Instruction</a>
3261 <div class="doc_text">
3265 <result> = fsub <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3269 <p>The '<tt>fsub</tt>' instruction returns the difference of its two
3272 <p>Note that the '<tt>fsub</tt>' instruction is used to represent the
3273 '<tt>fneg</tt>' instruction present in most other intermediate
3274 representations.</p>
3277 <p>The two arguments to the '<tt>fsub</tt>' instruction must be
3278 <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
3279 floating point values. Both arguments must have identical types.</p>
3282 <p>The value produced is the floating point difference of the two operands.</p>
3286 <result> = fsub float 4.0, %var <i>; yields {float}:result = 4.0 - %var</i>
3287 <result> = fsub float -0.0, %val <i>; yields {float}:result = -%var</i>
3292 <!-- _______________________________________________________________________ -->
3293 <div class="doc_subsubsection">
3294 <a name="i_mul">'<tt>mul</tt>' Instruction</a>
3297 <div class="doc_text">
3301 <result> = mul <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3302 <result> = mul nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3303 <result> = mul nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3304 <result> = mul nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3308 <p>The '<tt>mul</tt>' instruction returns the product of its two operands.</p>
3311 <p>The two arguments to the '<tt>mul</tt>' instruction must
3312 be <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of
3313 integer values. Both arguments must have identical types.</p>
3316 <p>The value produced is the integer product of the two operands.</p>
3318 <p>If the result of the multiplication has unsigned overflow, the result
3319 returned is the mathematical result modulo 2<sup>n</sup>, where n is the bit
3320 width of the result.</p>
3322 <p>Because LLVM integers use a two's complement representation, and the result
3323 is the same width as the operands, this instruction returns the correct
3324 result for both signed and unsigned integers. If a full product
3325 (e.g. <tt>i32</tt>x<tt>i32</tt>-><tt>i64</tt>) is needed, the operands should
3326 be sign-extended or zero-extended as appropriate to the width of the full
3329 <p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap"
3330 and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or
3331 <tt>nsw</tt> keywords are present, the result value of the <tt>mul</tt>
3332 is a <a href="#trapvalues">trap value</a> if unsigned and/or signed overflow,
3333 respectively, occurs.</p>
3337 <result> = mul i32 4, %var <i>; yields {i32}:result = 4 * %var</i>
3342 <!-- _______________________________________________________________________ -->
3343 <div class="doc_subsubsection">
3344 <a name="i_fmul">'<tt>fmul</tt>' Instruction</a>
3347 <div class="doc_text">
3351 <result> = fmul <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3355 <p>The '<tt>fmul</tt>' instruction returns the product of its two operands.</p>
3358 <p>The two arguments to the '<tt>fmul</tt>' instruction must be
3359 <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
3360 floating point values. Both arguments must have identical types.</p>
3363 <p>The value produced is the floating point product of the two operands.</p>
3367 <result> = fmul float 4.0, %var <i>; yields {float}:result = 4.0 * %var</i>
3372 <!-- _______________________________________________________________________ -->
3373 <div class="doc_subsubsection"> <a name="i_udiv">'<tt>udiv</tt>' Instruction
3376 <div class="doc_text">
3380 <result> = udiv <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3384 <p>The '<tt>udiv</tt>' instruction returns the quotient of its two operands.</p>
3387 <p>The two arguments to the '<tt>udiv</tt>' instruction must be
3388 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3389 values. Both arguments must have identical types.</p>
3392 <p>The value produced is the unsigned integer quotient of the two operands.</p>
3394 <p>Note that unsigned integer division and signed integer division are distinct
3395 operations; for signed integer division, use '<tt>sdiv</tt>'.</p>
3397 <p>Division by zero leads to undefined behavior.</p>
3401 <result> = udiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>
3406 <!-- _______________________________________________________________________ -->
3407 <div class="doc_subsubsection"> <a name="i_sdiv">'<tt>sdiv</tt>' Instruction
3410 <div class="doc_text">
3414 <result> = sdiv <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3415 <result> = sdiv exact <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3419 <p>The '<tt>sdiv</tt>' instruction returns the quotient of its two operands.</p>
3422 <p>The two arguments to the '<tt>sdiv</tt>' instruction must be
3423 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3424 values. Both arguments must have identical types.</p>
3427 <p>The value produced is the signed integer quotient of the two operands rounded
3430 <p>Note that signed integer division and unsigned integer division are distinct
3431 operations; for unsigned integer division, use '<tt>udiv</tt>'.</p>
3433 <p>Division by zero leads to undefined behavior. Overflow also leads to
3434 undefined behavior; this is a rare case, but can occur, for example, by doing
3435 a 32-bit division of -2147483648 by -1.</p>
3437 <p>If the <tt>exact</tt> keyword is present, the result value of the
3438 <tt>sdiv</tt> is a <a href="#trapvalues">trap value</a> if the result would
3439 be rounded or if overflow would occur.</p>
3443 <result> = sdiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>
3448 <!-- _______________________________________________________________________ -->
3449 <div class="doc_subsubsection"> <a name="i_fdiv">'<tt>fdiv</tt>'
3450 Instruction</a> </div>
3452 <div class="doc_text">
3456 <result> = fdiv <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3460 <p>The '<tt>fdiv</tt>' instruction returns the quotient of its two operands.</p>
3463 <p>The two arguments to the '<tt>fdiv</tt>' instruction must be
3464 <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
3465 floating point values. Both arguments must have identical types.</p>
3468 <p>The value produced is the floating point quotient of the two operands.</p>
3472 <result> = fdiv float 4.0, %var <i>; yields {float}:result = 4.0 / %var</i>
3477 <!-- _______________________________________________________________________ -->
3478 <div class="doc_subsubsection"> <a name="i_urem">'<tt>urem</tt>' Instruction</a>
3481 <div class="doc_text">
3485 <result> = urem <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3489 <p>The '<tt>urem</tt>' instruction returns the remainder from the unsigned
3490 division of its two arguments.</p>
3493 <p>The two arguments to the '<tt>urem</tt>' instruction must be
3494 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3495 values. Both arguments must have identical types.</p>
3498 <p>This instruction returns the unsigned integer <i>remainder</i> of a division.
3499 This instruction always performs an unsigned division to get the
3502 <p>Note that unsigned integer remainder and signed integer remainder are
3503 distinct operations; for signed integer remainder, use '<tt>srem</tt>'.</p>
3505 <p>Taking the remainder of a division by zero leads to undefined behavior.</p>
3509 <result> = urem i32 4, %var <i>; yields {i32}:result = 4 % %var</i>
3514 <!-- _______________________________________________________________________ -->
3515 <div class="doc_subsubsection">
3516 <a name="i_srem">'<tt>srem</tt>' Instruction</a>
3519 <div class="doc_text">
3523 <result> = srem <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3527 <p>The '<tt>srem</tt>' instruction returns the remainder from the signed
3528 division of its two operands. This instruction can also take
3529 <a href="#t_vector">vector</a> versions of the values in which case the
3530 elements must be integers.</p>
3533 <p>The two arguments to the '<tt>srem</tt>' instruction must be
3534 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3535 values. Both arguments must have identical types.</p>
3538 <p>This instruction returns the <i>remainder</i> of a division (where the result
3539 has the same sign as the dividend, <tt>op1</tt>), not the <i>modulo</i>
3540 operator (where the result has the same sign as the divisor, <tt>op2</tt>) of
3541 a value. For more information about the difference,
3542 see <a href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The
3543 Math Forum</a>. For a table of how this is implemented in various languages,
3544 please see <a href="http://en.wikipedia.org/wiki/Modulo_operation">
3545 Wikipedia: modulo operation</a>.</p>
3547 <p>Note that signed integer remainder and unsigned integer remainder are
3548 distinct operations; for unsigned integer remainder, use '<tt>urem</tt>'.</p>
3550 <p>Taking the remainder of a division by zero leads to undefined behavior.
3551 Overflow also leads to undefined behavior; this is a rare case, but can
3552 occur, for example, by taking the remainder of a 32-bit division of
3553 -2147483648 by -1. (The remainder doesn't actually overflow, but this rule
3554 lets srem be implemented using instructions that return both the result of
3555 the division and the remainder.)</p>
3559 <result> = srem i32 4, %var <i>; yields {i32}:result = 4 % %var</i>
3564 <!-- _______________________________________________________________________ -->
3565 <div class="doc_subsubsection">
3566 <a name="i_frem">'<tt>frem</tt>' Instruction</a> </div>
3568 <div class="doc_text">
3572 <result> = frem <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3576 <p>The '<tt>frem</tt>' instruction returns the remainder from the division of
3577 its two operands.</p>
3580 <p>The two arguments to the '<tt>frem</tt>' instruction must be
3581 <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of
3582 floating point values. Both arguments must have identical types.</p>
3585 <p>This instruction returns the <i>remainder</i> of a division. The remainder
3586 has the same sign as the dividend.</p>
3590 <result> = frem float 4.0, %var <i>; yields {float}:result = 4.0 % %var</i>
3595 <!-- ======================================================================= -->
3596 <div class="doc_subsection"> <a name="bitwiseops">Bitwise Binary
3597 Operations</a> </div>
3599 <div class="doc_text">
3601 <p>Bitwise binary operators are used to do various forms of bit-twiddling in a
3602 program. They are generally very efficient instructions and can commonly be
3603 strength reduced from other instructions. They require two operands of the
3604 same type, execute an operation on them, and produce a single value. The
3605 resulting value is the same type as its operands.</p>
3609 <!-- _______________________________________________________________________ -->
3610 <div class="doc_subsubsection"> <a name="i_shl">'<tt>shl</tt>'
3611 Instruction</a> </div>
3613 <div class="doc_text">
3617 <result> = shl <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3621 <p>The '<tt>shl</tt>' instruction returns the first operand shifted to the left
3622 a specified number of bits.</p>
3625 <p>Both arguments to the '<tt>shl</tt>' instruction must be the
3626 same <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of
3627 integer type. '<tt>op2</tt>' is treated as an unsigned value.</p>
3630 <p>The value produced is <tt>op1</tt> * 2<sup><tt>op2</tt></sup> mod
3631 2<sup>n</sup>, where <tt>n</tt> is the width of the result. If <tt>op2</tt>
3632 is (statically or dynamically) negative or equal to or larger than the number
3633 of bits in <tt>op1</tt>, the result is undefined. If the arguments are
3634 vectors, each vector element of <tt>op1</tt> is shifted by the corresponding
3635 shift amount in <tt>op2</tt>.</p>
3639 <result> = shl i32 4, %var <i>; yields {i32}: 4 << %var</i>
3640 <result> = shl i32 4, 2 <i>; yields {i32}: 16</i>
3641 <result> = shl i32 1, 10 <i>; yields {i32}: 1024</i>
3642 <result> = shl i32 1, 32 <i>; undefined</i>
3643 <result> = shl <2 x i32> < i32 1, i32 1>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 2, i32 4></i>
3648 <!-- _______________________________________________________________________ -->
3649 <div class="doc_subsubsection"> <a name="i_lshr">'<tt>lshr</tt>'
3650 Instruction</a> </div>
3652 <div class="doc_text">
3656 <result> = lshr <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3660 <p>The '<tt>lshr</tt>' instruction (logical shift right) returns the first
3661 operand shifted to the right a specified number of bits with zero fill.</p>
3664 <p>Both arguments to the '<tt>lshr</tt>' instruction must be the same
3665 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3666 type. '<tt>op2</tt>' is treated as an unsigned value.</p>
3669 <p>This instruction always performs a logical shift right operation. The most
3670 significant bits of the result will be filled with zero bits after the shift.
3671 If <tt>op2</tt> is (statically or dynamically) equal to or larger than the
3672 number of bits in <tt>op1</tt>, the result is undefined. If the arguments are
3673 vectors, each vector element of <tt>op1</tt> is shifted by the corresponding
3674 shift amount in <tt>op2</tt>.</p>
3678 <result> = lshr i32 4, 1 <i>; yields {i32}:result = 2</i>
3679 <result> = lshr i32 4, 2 <i>; yields {i32}:result = 1</i>
3680 <result> = lshr i8 4, 3 <i>; yields {i8}:result = 0</i>
3681 <result> = lshr i8 -2, 1 <i>; yields {i8}:result = 0x7FFFFFFF </i>
3682 <result> = lshr i32 1, 32 <i>; undefined</i>
3683 <result> = lshr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 0x7FFFFFFF, i32 1></i>
3688 <!-- _______________________________________________________________________ -->
3689 <div class="doc_subsubsection"> <a name="i_ashr">'<tt>ashr</tt>'
3690 Instruction</a> </div>
3691 <div class="doc_text">
3695 <result> = ashr <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3699 <p>The '<tt>ashr</tt>' instruction (arithmetic shift right) returns the first
3700 operand shifted to the right a specified number of bits with sign
3704 <p>Both arguments to the '<tt>ashr</tt>' instruction must be the same
3705 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3706 type. '<tt>op2</tt>' is treated as an unsigned value.</p>
3709 <p>This instruction always performs an arithmetic shift right operation, The
3710 most significant bits of the result will be filled with the sign bit
3711 of <tt>op1</tt>. If <tt>op2</tt> is (statically or dynamically) equal to or
3712 larger than the number of bits in <tt>op1</tt>, the result is undefined. If
3713 the arguments are vectors, each vector element of <tt>op1</tt> is shifted by
3714 the corresponding shift amount in <tt>op2</tt>.</p>
3718 <result> = ashr i32 4, 1 <i>; yields {i32}:result = 2</i>
3719 <result> = ashr i32 4, 2 <i>; yields {i32}:result = 1</i>
3720 <result> = ashr i8 4, 3 <i>; yields {i8}:result = 0</i>
3721 <result> = ashr i8 -2, 1 <i>; yields {i8}:result = -1</i>
3722 <result> = ashr i32 1, 32 <i>; undefined</i>
3723 <result> = ashr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 3> <i>; yields: result=<2 x i32> < i32 -1, i32 0></i>
3728 <!-- _______________________________________________________________________ -->
3729 <div class="doc_subsubsection"> <a name="i_and">'<tt>and</tt>'
3730 Instruction</a> </div>
3732 <div class="doc_text">
3736 <result> = and <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3740 <p>The '<tt>and</tt>' instruction returns the bitwise logical and of its two
3744 <p>The two arguments to the '<tt>and</tt>' instruction must be
3745 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3746 values. Both arguments must have identical types.</p>
3749 <p>The truth table used for the '<tt>and</tt>' instruction is:</p>
3751 <table border="1" cellspacing="0" cellpadding="4">
3783 <result> = and i32 4, %var <i>; yields {i32}:result = 4 & %var</i>
3784 <result> = and i32 15, 40 <i>; yields {i32}:result = 8</i>
3785 <result> = and i32 4, 8 <i>; yields {i32}:result = 0</i>
3788 <!-- _______________________________________________________________________ -->
3789 <div class="doc_subsubsection"> <a name="i_or">'<tt>or</tt>' Instruction</a> </div>
3791 <div class="doc_text">
3795 <result> = or <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3799 <p>The '<tt>or</tt>' instruction returns the bitwise logical inclusive or of its
3803 <p>The two arguments to the '<tt>or</tt>' instruction must be
3804 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3805 values. Both arguments must have identical types.</p>
3808 <p>The truth table used for the '<tt>or</tt>' instruction is:</p>
3810 <table border="1" cellspacing="0" cellpadding="4">
3842 <result> = or i32 4, %var <i>; yields {i32}:result = 4 | %var</i>
3843 <result> = or i32 15, 40 <i>; yields {i32}:result = 47</i>
3844 <result> = or i32 4, 8 <i>; yields {i32}:result = 12</i>
3849 <!-- _______________________________________________________________________ -->
3850 <div class="doc_subsubsection"> <a name="i_xor">'<tt>xor</tt>'
3851 Instruction</a> </div>
3853 <div class="doc_text">
3857 <result> = xor <ty> <op1>, <op2> <i>; yields {ty}:result</i>
3861 <p>The '<tt>xor</tt>' instruction returns the bitwise logical exclusive or of
3862 its two operands. The <tt>xor</tt> is used to implement the "one's
3863 complement" operation, which is the "~" operator in C.</p>
3866 <p>The two arguments to the '<tt>xor</tt>' instruction must be
3867 <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer
3868 values. Both arguments must have identical types.</p>
3871 <p>The truth table used for the '<tt>xor</tt>' instruction is:</p>
3873 <table border="1" cellspacing="0" cellpadding="4">
3905 <result> = xor i32 4, %var <i>; yields {i32}:result = 4 ^ %var</i>
3906 <result> = xor i32 15, 40 <i>; yields {i32}:result = 39</i>
3907 <result> = xor i32 4, 8 <i>; yields {i32}:result = 12</i>
3908 <result> = xor i32 %V, -1 <i>; yields {i32}:result = ~%V</i>
3913 <!-- ======================================================================= -->
3914 <div class="doc_subsection">
3915 <a name="vectorops">Vector Operations</a>
3918 <div class="doc_text">
3920 <p>LLVM supports several instructions to represent vector operations in a
3921 target-independent manner. These instructions cover the element-access and
3922 vector-specific operations needed to process vectors effectively. While LLVM
3923 does directly support these vector operations, many sophisticated algorithms
3924 will want to use target-specific intrinsics to take full advantage of a
3925 specific target.</p>
3929 <!-- _______________________________________________________________________ -->
3930 <div class="doc_subsubsection">
3931 <a name="i_extractelement">'<tt>extractelement</tt>' Instruction</a>
3934 <div class="doc_text">
3938 <result> = extractelement <n x <ty>> <val>, i32 <idx> <i>; yields <ty></i>
3942 <p>The '<tt>extractelement</tt>' instruction extracts a single scalar element
3943 from a vector at a specified index.</p>
3947 <p>The first operand of an '<tt>extractelement</tt>' instruction is a value
3948 of <a href="#t_vector">vector</a> type. The second operand is an index
3949 indicating the position from which to extract the element. The index may be
3953 <p>The result is a scalar of the same type as the element type of
3954 <tt>val</tt>. Its value is the value at position <tt>idx</tt> of
3955 <tt>val</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the
3956 results are undefined.</p>
3960 <result> = extractelement <4 x i32> %vec, i32 0 <i>; yields i32</i>
3965 <!-- _______________________________________________________________________ -->
3966 <div class="doc_subsubsection">
3967 <a name="i_insertelement">'<tt>insertelement</tt>' Instruction</a>
3970 <div class="doc_text">
3974 <result> = insertelement <n x <ty>> <val>, <ty> <elt>, i32 <idx> <i>; yields <n x <ty>></i>
3978 <p>The '<tt>insertelement</tt>' instruction inserts a scalar element into a
3979 vector at a specified index.</p>
3982 <p>The first operand of an '<tt>insertelement</tt>' instruction is a value
3983 of <a href="#t_vector">vector</a> type. The second operand is a scalar value
3984 whose type must equal the element type of the first operand. The third
3985 operand is an index indicating the position at which to insert the value.
3986 The index may be a variable.</p>
3989 <p>The result is a vector of the same type as <tt>val</tt>. Its element values
3990 are those of <tt>val</tt> except at position <tt>idx</tt>, where it gets the
3991 value <tt>elt</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the
3992 results are undefined.</p>
3996 <result> = insertelement <4 x i32> %vec, i32 1, i32 0 <i>; yields <4 x i32></i>
4001 <!-- _______________________________________________________________________ -->
4002 <div class="doc_subsubsection">
4003 <a name="i_shufflevector">'<tt>shufflevector</tt>' Instruction</a>
4006 <div class="doc_text">
4010 <result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <m x i32> <mask> <i>; yields <m x <ty>></i>
4014 <p>The '<tt>shufflevector</tt>' instruction constructs a permutation of elements
4015 from two input vectors, returning a vector with the same element type as the
4016 input and length that is the same as the shuffle mask.</p>
4019 <p>The first two operands of a '<tt>shufflevector</tt>' instruction are vectors
4020 with types that match each other. The third argument is a shuffle mask whose
4021 element type is always 'i32'. The result of the instruction is a vector
4022 whose length is the same as the shuffle mask and whose element type is the
4023 same as the element type of the first two operands.</p>
4025 <p>The shuffle mask operand is required to be a constant vector with either
4026 constant integer or undef values.</p>
4029 <p>The elements of the two input vectors are numbered from left to right across
4030 both of the vectors. The shuffle mask operand specifies, for each element of
4031 the result vector, which element of the two input vectors the result element
4032 gets. The element selector may be undef (meaning "don't care") and the
4033 second operand may be undef if performing a shuffle from only one vector.</p>
4037 <result> = shufflevector <4 x i32> %v1, <4 x i32> %v2,
4038 <4 x i32> <i32 0, i32 4, i32 1, i32 5> <i>; yields <4 x i32></i>
4039 <result> = shufflevector <4 x i32> %v1, <4 x i32> undef,
4040 <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> - Identity shuffle.
4041 <result> = shufflevector <8 x i32> %v1, <8 x i32> undef,
4042 <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i>
4043 <result> = shufflevector <4 x i32> %v1, <4 x i32> %v2,
4044 <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7 > <i>; yields <8 x i32></i>
4049 <!-- ======================================================================= -->
4050 <div class="doc_subsection">
4051 <a name="aggregateops">Aggregate Operations</a>
4054 <div class="doc_text">
4056 <p>LLVM supports several instructions for working with
4057 <a href="#t_aggregate">aggregate</a> values.</p>
4061 <!-- _______________________________________________________________________ -->
4062 <div class="doc_subsubsection">
4063 <a name="i_extractvalue">'<tt>extractvalue</tt>' Instruction</a>
4066 <div class="doc_text">
4070 <result> = extractvalue <aggregate type> <val>, <idx>{, <idx>}*
4074 <p>The '<tt>extractvalue</tt>' instruction extracts the value of a member field
4075 from an <a href="#t_aggregate">aggregate</a> value.</p>
4078 <p>The first operand of an '<tt>extractvalue</tt>' instruction is a value
4079 of <a href="#t_struct">struct</a>, <a href="#t_union">union</a> or
4080 <a href="#t_array">array</a> type. The operands are constant indices to
4081 specify which value to extract in a similar manner as indices in a
4082 '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction.</p>
4085 <p>The result is the value at the position in the aggregate specified by the
4090 <result> = extractvalue {i32, float} %agg, 0 <i>; yields i32</i>
4095 <!-- _______________________________________________________________________ -->
4096 <div class="doc_subsubsection">
4097 <a name="i_insertvalue">'<tt>insertvalue</tt>' Instruction</a>
4100 <div class="doc_text">
4104 <result> = insertvalue <aggregate type> <val>, <ty> <elt>, <idx> <i>; yields <aggregate type></i>
4108 <p>The '<tt>insertvalue</tt>' instruction inserts a value into a member field
4109 in an <a href="#t_aggregate">aggregate</a> value.</p>
4112 <p>The first operand of an '<tt>insertvalue</tt>' instruction is a value
4113 of <a href="#t_struct">struct</a>, <a href="#t_union">union</a> or
4114 <a href="#t_array">array</a> type. The second operand is a first-class
4115 value to insert. The following operands are constant indices indicating
4116 the position at which to insert the value in a similar manner as indices in a
4117 '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction. The
4118 value to insert must have the same type as the value identified by the
4122 <p>The result is an aggregate of the same type as <tt>val</tt>. Its value is
4123 that of <tt>val</tt> except that the value at the position specified by the
4124 indices is that of <tt>elt</tt>.</p>
4128 %agg1 = insertvalue {i32, float} undef, i32 1, 0 <i>; yields {i32 1, float undef}</i>
4129 %agg2 = insertvalue {i32, float} %agg1, float %val, 1 <i>; yields {i32 1, float %val}</i>
4135 <!-- ======================================================================= -->
4136 <div class="doc_subsection">
4137 <a name="memoryops">Memory Access and Addressing Operations</a>
4140 <div class="doc_text">
4142 <p>A key design point of an SSA-based representation is how it represents
4143 memory. In LLVM, no memory locations are in SSA form, which makes things
4144 very simple. This section describes how to read, write, and allocate
4149 <!-- _______________________________________________________________________ -->
4150 <div class="doc_subsubsection">
4151 <a name="i_alloca">'<tt>alloca</tt>' Instruction</a>
4154 <div class="doc_text">
4158 <result> = alloca <type>[, i32 <NumElements>][, align <alignment>] <i>; yields {type*}:result</i>
4162 <p>The '<tt>alloca</tt>' instruction allocates memory on the stack frame of the
4163 currently executing function, to be automatically released when this function
4164 returns to its caller. The object is always allocated in the generic address
4165 space (address space zero).</p>
4168 <p>The '<tt>alloca</tt>' instruction
4169 allocates <tt>sizeof(<type>)*NumElements</tt> bytes of memory on the
4170 runtime stack, returning a pointer of the appropriate type to the program.
4171 If "NumElements" is specified, it is the number of elements allocated,
4172 otherwise "NumElements" is defaulted to be one. If a constant alignment is
4173 specified, the value result of the allocation is guaranteed to be aligned to
4174 at least that boundary. If not specified, or if zero, the target can choose
4175 to align the allocation on any convenient boundary compatible with the
4178 <p>'<tt>type</tt>' may be any sized type.</p>
4181 <p>Memory is allocated; a pointer is returned. The operation is undefined if
4182 there is insufficient stack space for the allocation. '<tt>alloca</tt>'d
4183 memory is automatically released when the function returns. The
4184 '<tt>alloca</tt>' instruction is commonly used to represent automatic
4185 variables that must have an address available. When the function returns
4186 (either with the <tt><a href="#i_ret">ret</a></tt>
4187 or <tt><a href="#i_unwind">unwind</a></tt> instructions), the memory is
4188 reclaimed. Allocating zero bytes is legal, but the result is undefined.</p>
4192 %ptr = alloca i32 <i>; yields {i32*}:ptr</i>
4193 %ptr = alloca i32, i32 4 <i>; yields {i32*}:ptr</i>
4194 %ptr = alloca i32, i32 4, align 1024 <i>; yields {i32*}:ptr</i>
4195 %ptr = alloca i32, align 1024 <i>; yields {i32*}:ptr</i>
4200 <!-- _______________________________________________________________________ -->
4201 <div class="doc_subsubsection"> <a name="i_load">'<tt>load</tt>'
4202 Instruction</a> </div>
4204 <div class="doc_text">
4208 <result> = load <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>]
4209 <result> = volatile load <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>]
4210 !<index> = !{ i32 1 }
4214 <p>The '<tt>load</tt>' instruction is used to read from memory.</p>
4217 <p>The argument to the '<tt>load</tt>' instruction specifies the memory address
4218 from which to load. The pointer must point to
4219 a <a href="#t_firstclass">first class</a> type. If the <tt>load</tt> is
4220 marked as <tt>volatile</tt>, then the optimizer is not allowed to modify the
4221 number or order of execution of this <tt>load</tt> with other <a
4222 href="#volatile">volatile operations</a>.</p>
4224 <p>The optional constant <tt>align</tt> argument specifies the alignment of the
4225 operation (that is, the alignment of the memory address). A value of 0 or an
4226 omitted <tt>align</tt> argument means that the operation has the preferential
4227 alignment for the target. It is the responsibility of the code emitter to
4228 ensure that the alignment information is correct. Overestimating the
4229 alignment results in undefined behavior. Underestimating the alignment may
4230 produce less efficient code. An alignment of 1 is always safe.</p>
4232 <p>The optional <tt>!nontemporal</tt> metadata must reference a single
4233 metatadata name <index> corresponding to a metadata node with
4234 one <tt>i32</tt> entry of value 1. The existence of
4235 the <tt>!nontemporal</tt> metatadata on the instruction tells the optimizer
4236 and code generator that this load is not expected to be reused in the cache.
4237 The code generator may select special instructions to save cache bandwidth,
4238 such as the <tt>MOVNT</tt> instruction on x86.</p>
4241 <p>The location of memory pointed to is loaded. If the value being loaded is of
4242 scalar type then the number of bytes read does not exceed the minimum number
4243 of bytes needed to hold all bits of the type. For example, loading an
4244 <tt>i24</tt> reads at most three bytes. When loading a value of a type like
4245 <tt>i20</tt> with a size that is not an integral number of bytes, the result
4246 is undefined if the value was not originally written using a store of the
4251 %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i>
4252 <a href="#i_store">store</a> i32 3, i32* %ptr <i>; yields {void}</i>
4253 %val = load i32* %ptr <i>; yields {i32}:val = i32 3</i>
4258 <!-- _______________________________________________________________________ -->
4259 <div class="doc_subsubsection"> <a name="i_store">'<tt>store</tt>'
4260 Instruction</a> </div>
4262 <div class="doc_text">
4266 store <ty> <value>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>] <i>; yields {void}</i>
4267 volatile store <ty> <value>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>] <i>; yields {void}</i>
4271 <p>The '<tt>store</tt>' instruction is used to write to memory.</p>
4274 <p>There are two arguments to the '<tt>store</tt>' instruction: a value to store
4275 and an address at which to store it. The type of the
4276 '<tt><pointer></tt>' operand must be a pointer to
4277 the <a href="#t_firstclass">first class</a> type of the
4278 '<tt><value></tt>' operand. If the <tt>store</tt> is marked as
4279 <tt>volatile</tt>, then the optimizer is not allowed to modify the number or
4280 order of execution of this <tt>store</tt> with other <a
4281 href="#volatile">volatile operations</a>.</p>
4283 <p>The optional constant "align" argument specifies the alignment of the
4284 operation (that is, the alignment of the memory address). A value of 0 or an
4285 omitted "align" argument means that the operation has the preferential
4286 alignment for the target. It is the responsibility of the code emitter to
4287 ensure that the alignment information is correct. Overestimating the
4288 alignment results in an undefined behavior. Underestimating the alignment may
4289 produce less efficient code. An alignment of 1 is always safe.</p>
4291 <p>The optional !nontemporal metadata must reference a single metatadata
4292 name <index> corresponding to a metadata node with one i32 entry of
4293 value 1. The existence of the !nontemporal metatadata on the
4294 instruction tells the optimizer and code generator that this load is
4295 not expected to be reused in the cache. The code generator may
4296 select special instructions to save cache bandwidth, such as the
4297 MOVNT instruction on x86.</p>
4301 <p>The contents of memory are updated to contain '<tt><value></tt>' at the
4302 location specified by the '<tt><pointer></tt>' operand. If
4303 '<tt><value></tt>' is of scalar type then the number of bytes written
4304 does not exceed the minimum number of bytes needed to hold all bits of the
4305 type. For example, storing an <tt>i24</tt> writes at most three bytes. When
4306 writing a value of a type like <tt>i20</tt> with a size that is not an
4307 integral number of bytes, it is unspecified what happens to the extra bits
4308 that do not belong to the type, but they will typically be overwritten.</p>
4312 %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i>
4313 store i32 3, i32* %ptr <i>; yields {void}</i>
4314 %val = <a href="#i_load">load</a> i32* %ptr <i>; yields {i32}:val = i32 3</i>
4319 <!-- _______________________________________________________________________ -->
4320 <div class="doc_subsubsection">
4321 <a name="i_getelementptr">'<tt>getelementptr</tt>' Instruction</a>
4324 <div class="doc_text">
4328 <result> = getelementptr <pty>* <ptrval>{, <ty> <idx>}*
4329 <result> = getelementptr inbounds <pty>* <ptrval>{, <ty> <idx>}*
4333 <p>The '<tt>getelementptr</tt>' instruction is used to get the address of a
4334 subelement of an <a href="#t_aggregate">aggregate</a> data structure.
4335 It performs address calculation only and does not access memory.</p>
4338 <p>The first argument is always a pointer, and forms the basis of the
4339 calculation. The remaining arguments are indices that indicate which of the
4340 elements of the aggregate object are indexed. The interpretation of each
4341 index is dependent on the type being indexed into. The first index always
4342 indexes the pointer value given as the first argument, the second index
4343 indexes a value of the type pointed to (not necessarily the value directly
4344 pointed to, since the first index can be non-zero), etc. The first type
4345 indexed into must be a pointer value, subsequent types can be arrays,
4346 vectors, structs and unions. Note that subsequent types being indexed into
4347 can never be pointers, since that would require loading the pointer before
4348 continuing calculation.</p>
4350 <p>The type of each index argument depends on the type it is indexing into.
4351 When indexing into a (optionally packed) structure or union, only <tt>i32</tt>
4352 integer <b>constants</b> are allowed. When indexing into an array, pointer
4353 or vector, integers of any width are allowed, and they are not required to be
4356 <p>For example, let's consider a C code fragment and how it gets compiled to
4359 <div class="doc_code">
4372 int *foo(struct ST *s) {
4373 return &s[1].Z.B[5][13];
4378 <p>The LLVM code generated by the GCC frontend is:</p>
4380 <div class="doc_code">
4382 %RT = <a href="#namedtypes">type</a> { i8 , [10 x [20 x i32]], i8 }
4383 %ST = <a href="#namedtypes">type</a> { i32, double, %RT }
4385 define i32* @foo(%ST* %s) {
4387 %reg = getelementptr %ST* %s, i32 1, i32 2, i32 1, i32 5, i32 13
4394 <p>In the example above, the first index is indexing into the '<tt>%ST*</tt>'
4395 type, which is a pointer, yielding a '<tt>%ST</tt>' = '<tt>{ i32, double, %RT
4396 }</tt>' type, a structure. The second index indexes into the third element
4397 of the structure, yielding a '<tt>%RT</tt>' = '<tt>{ i8 , [10 x [20 x i32]],
4398 i8 }</tt>' type, another structure. The third index indexes into the second
4399 element of the structure, yielding a '<tt>[10 x [20 x i32]]</tt>' type, an
4400 array. The two dimensions of the array are subscripted into, yielding an
4401 '<tt>i32</tt>' type. The '<tt>getelementptr</tt>' instruction returns a
4402 pointer to this element, thus computing a value of '<tt>i32*</tt>' type.</p>
4404 <p>Note that it is perfectly legal to index partially through a structure,
4405 returning a pointer to an inner element. Because of this, the LLVM code for
4406 the given testcase is equivalent to:</p>
4409 define i32* @foo(%ST* %s) {
4410 %t1 = getelementptr %ST* %s, i32 1 <i>; yields %ST*:%t1</i>
4411 %t2 = getelementptr %ST* %t1, i32 0, i32 2 <i>; yields %RT*:%t2</i>
4412 %t3 = getelementptr %RT* %t2, i32 0, i32 1 <i>; yields [10 x [20 x i32]]*:%t3</i>
4413 %t4 = getelementptr [10 x [20 x i32]]* %t3, i32 0, i32 5 <i>; yields [20 x i32]*:%t4</i>
4414 %t5 = getelementptr [20 x i32]* %t4, i32 0, i32 13 <i>; yields i32*:%t5</i>
4419 <p>If the <tt>inbounds</tt> keyword is present, the result value of the
4420 <tt>getelementptr</tt> is a <a href="#trapvalues">trap value</a> if the
4421 base pointer is not an <i>in bounds</i> address of an allocated object,
4422 or if any of the addresses that would be formed by successive addition of
4423 the offsets implied by the indices to the base address with infinitely
4424 precise arithmetic are not an <i>in bounds</i> address of that allocated
4425 object. The <i>in bounds</i> addresses for an allocated object are all
4426 the addresses that point into the object, plus the address one byte past
4429 <p>If the <tt>inbounds</tt> keyword is not present, the offsets are added to
4430 the base address with silently-wrapping two's complement arithmetic, and
4431 the result value of the <tt>getelementptr</tt> may be outside the object
4432 pointed to by the base pointer. The result value may not necessarily be
4433 used to access memory though, even if it happens to point into allocated
4434 storage. See the <a href="#pointeraliasing">Pointer Aliasing Rules</a>
4435 section for more information.</p>
4437 <p>The getelementptr instruction is often confusing. For some more insight into
4438 how it works, see <a href="GetElementPtr.html">the getelementptr FAQ</a>.</p>
4442 <i>; yields [12 x i8]*:aptr</i>
4443 %aptr = getelementptr {i32, [12 x i8]}* %saptr, i64 0, i32 1
4444 <i>; yields i8*:vptr</i>
4445 %vptr = getelementptr {i32, <2 x i8>}* %svptr, i64 0, i32 1, i32 1
4446 <i>; yields i8*:eptr</i>
4447 %eptr = getelementptr [12 x i8]* %aptr, i64 0, i32 1
4448 <i>; yields i32*:iptr</i>
4449 %iptr = getelementptr [10 x i32]* @arr, i16 0, i16 0
4454 <!-- ======================================================================= -->
4455 <div class="doc_subsection"> <a name="convertops">Conversion Operations</a>
4458 <div class="doc_text">
4460 <p>The instructions in this category are the conversion instructions (casting)
4461 which all take a single operand and a type. They perform various bit
4462 conversions on the operand.</p>
4466 <!-- _______________________________________________________________________ -->
4467 <div class="doc_subsubsection">
4468 <a name="i_trunc">'<tt>trunc .. to</tt>' Instruction</a>
4470 <div class="doc_text">
4474 <result> = trunc <ty> <value> to <ty2> <i>; yields ty2</i>
4478 <p>The '<tt>trunc</tt>' instruction truncates its operand to the
4479 type <tt>ty2</tt>.</p>
4482 <p>The '<tt>trunc</tt>' instruction takes a <tt>value</tt> to trunc, which must
4483 be an <a href="#t_integer">integer</a> type, and a type that specifies the
4484 size and type of the result, which must be
4485 an <a href="#t_integer">integer</a> type. The bit size of <tt>value</tt> must
4486 be larger than the bit size of <tt>ty2</tt>. Equal sized types are not
4490 <p>The '<tt>trunc</tt>' instruction truncates the high order bits
4491 in <tt>value</tt> and converts the remaining bits to <tt>ty2</tt>. Since the
4492 source size must be larger than the destination size, <tt>trunc</tt> cannot
4493 be a <i>no-op cast</i>. It will always truncate bits.</p>
4497 %X = trunc i32 257 to i8 <i>; yields i8:1</i>
4498 %Y = trunc i32 123 to i1 <i>; yields i1:true</i>
4499 %Z = trunc i32 122 to i1 <i>; yields i1:false</i>
4504 <!-- _______________________________________________________________________ -->
4505 <div class="doc_subsubsection">
4506 <a name="i_zext">'<tt>zext .. to</tt>' Instruction</a>
4508 <div class="doc_text">
4512 <result> = zext <ty> <value> to <ty2> <i>; yields ty2</i>
4516 <p>The '<tt>zext</tt>' instruction zero extends its operand to type
4521 <p>The '<tt>zext</tt>' instruction takes a value to cast, which must be of
4522 <a href="#t_integer">integer</a> type, and a type to cast it to, which must
4523 also be of <a href="#t_integer">integer</a> type. The bit size of the
4524 <tt>value</tt> must be smaller than the bit size of the destination type,
4528 <p>The <tt>zext</tt> fills the high order bits of the <tt>value</tt> with zero
4529 bits until it reaches the size of the destination type, <tt>ty2</tt>.</p>
4531 <p>When zero extending from i1, the result will always be either 0 or 1.</p>
4535 %X = zext i32 257 to i64 <i>; yields i64:257</i>
4536 %Y = zext i1 true to i32 <i>; yields i32:1</i>
4541 <!-- _______________________________________________________________________ -->
4542 <div class="doc_subsubsection">
4543 <a name="i_sext">'<tt>sext .. to</tt>' Instruction</a>
4545 <div class="doc_text">
4549 <result> = sext <ty> <value> to <ty2> <i>; yields ty2</i>
4553 <p>The '<tt>sext</tt>' sign extends <tt>value</tt> to the type <tt>ty2</tt>.</p>
4556 <p>The '<tt>sext</tt>' instruction takes a value to cast, which must be of
4557 <a href="#t_integer">integer</a> type, and a type to cast it to, which must
4558 also be of <a href="#t_integer">integer</a> type. The bit size of the
4559 <tt>value</tt> must be smaller than the bit size of the destination type,
4563 <p>The '<tt>sext</tt>' instruction performs a sign extension by copying the sign
4564 bit (highest order bit) of the <tt>value</tt> until it reaches the bit size
4565 of the type <tt>ty2</tt>.</p>
4567 <p>When sign extending from i1, the extension always results in -1 or 0.</p>
4571 %X = sext i8 -1 to i16 <i>; yields i16 :65535</i>
4572 %Y = sext i1 true to i32 <i>; yields i32:-1</i>
4577 <!-- _______________________________________________________________________ -->
4578 <div class="doc_subsubsection">
4579 <a name="i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a>
4582 <div class="doc_text">
4586 <result> = fptrunc <ty> <value> to <ty2> <i>; yields ty2</i>
4590 <p>The '<tt>fptrunc</tt>' instruction truncates <tt>value</tt> to type
4594 <p>The '<tt>fptrunc</tt>' instruction takes a <a href="#t_floating">floating
4595 point</a> value to cast and a <a href="#t_floating">floating point</a> type
4596 to cast it to. The size of <tt>value</tt> must be larger than the size of
4597 <tt>ty2</tt>. This implies that <tt>fptrunc</tt> cannot be used to make a
4598 <i>no-op cast</i>.</p>
4601 <p>The '<tt>fptrunc</tt>' instruction truncates a <tt>value</tt> from a larger
4602 <a href="#t_floating">floating point</a> type to a smaller
4603 <a href="#t_floating">floating point</a> type. If the value cannot fit
4604 within the destination type, <tt>ty2</tt>, then the results are
4609 %X = fptrunc double 123.0 to float <i>; yields float:123.0</i>
4610 %Y = fptrunc double 1.0E+300 to float <i>; yields undefined</i>
4615 <!-- _______________________________________________________________________ -->
4616 <div class="doc_subsubsection">
4617 <a name="i_fpext">'<tt>fpext .. to</tt>' Instruction</a>
4619 <div class="doc_text">
4623 <result> = fpext <ty> <value> to <ty2> <i>; yields ty2</i>
4627 <p>The '<tt>fpext</tt>' extends a floating point <tt>value</tt> to a larger
4628 floating point value.</p>
4631 <p>The '<tt>fpext</tt>' instruction takes a
4632 <a href="#t_floating">floating point</a> <tt>value</tt> to cast, and
4633 a <a href="#t_floating">floating point</a> type to cast it to. The source
4634 type must be smaller than the destination type.</p>
4637 <p>The '<tt>fpext</tt>' instruction extends the <tt>value</tt> from a smaller
4638 <a href="#t_floating">floating point</a> type to a larger
4639 <a href="#t_floating">floating point</a> type. The <tt>fpext</tt> cannot be
4640 used to make a <i>no-op cast</i> because it always changes bits. Use
4641 <tt>bitcast</tt> to make a <i>no-op cast</i> for a floating point cast.</p>
4645 %X = fpext float 3.1415 to double <i>; yields double:3.1415</i>
4646 %Y = fpext float 1.0 to float <i>; yields float:1.0 (no-op)</i>
4651 <!-- _______________________________________________________________________ -->
4652 <div class="doc_subsubsection">
4653 <a name="i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a>
4655 <div class="doc_text">
4659 <result> = fptoui <ty> <value> to <ty2> <i>; yields ty2</i>
4663 <p>The '<tt>fptoui</tt>' converts a floating point <tt>value</tt> to its
4664 unsigned integer equivalent of type <tt>ty2</tt>.</p>
4667 <p>The '<tt>fptoui</tt>' instruction takes a value to cast, which must be a
4668 scalar or vector <a href="#t_floating">floating point</a> value, and a type
4669 to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a>
4670 type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a
4671 vector integer type with the same number of elements as <tt>ty</tt></p>
4674 <p>The '<tt>fptoui</tt>' instruction converts its
4675 <a href="#t_floating">floating point</a> operand into the nearest (rounding
4676 towards zero) unsigned integer value. If the value cannot fit
4677 in <tt>ty2</tt>, the results are undefined.</p>
4681 %X = fptoui double 123.0 to i32 <i>; yields i32:123</i>
4682 %Y = fptoui float 1.0E+300 to i1 <i>; yields undefined:1</i>
4683 %Z = fptoui float 1.04E+17 to i8 <i>; yields undefined:1</i>
4688 <!-- _______________________________________________________________________ -->
4689 <div class="doc_subsubsection">
4690 <a name="i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a>
4692 <div class="doc_text">
4696 <result> = fptosi <ty> <value> to <ty2> <i>; yields ty2</i>
4700 <p>The '<tt>fptosi</tt>' instruction converts
4701 <a href="#t_floating">floating point</a> <tt>value</tt> to
4702 type <tt>ty2</tt>.</p>
4705 <p>The '<tt>fptosi</tt>' instruction takes a value to cast, which must be a
4706 scalar or vector <a href="#t_floating">floating point</a> value, and a type
4707 to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a>
4708 type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a
4709 vector integer type with the same number of elements as <tt>ty</tt></p>
4712 <p>The '<tt>fptosi</tt>' instruction converts its
4713 <a href="#t_floating">floating point</a> operand into the nearest (rounding
4714 towards zero) signed integer value. If the value cannot fit in <tt>ty2</tt>,
4715 the results are undefined.</p>
4719 %X = fptosi double -123.0 to i32 <i>; yields i32:-123</i>
4720 %Y = fptosi float 1.0E-247 to i1 <i>; yields undefined:1</i>
4721 %Z = fptosi float 1.04E+17 to i8 <i>; yields undefined:1</i>
4726 <!-- _______________________________________________________________________ -->
4727 <div class="doc_subsubsection">
4728 <a name="i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a>
4730 <div class="doc_text">
4734 <result> = uitofp <ty> <value> to <ty2> <i>; yields ty2</i>
4738 <p>The '<tt>uitofp</tt>' instruction regards <tt>value</tt> as an unsigned
4739 integer and converts that value to the <tt>ty2</tt> type.</p>
4742 <p>The '<tt>uitofp</tt>' instruction takes a value to cast, which must be a
4743 scalar or vector <a href="#t_integer">integer</a> value, and a type to cast
4744 it to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a>
4745 type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector
4746 floating point type with the same number of elements as <tt>ty</tt></p>
4749 <p>The '<tt>uitofp</tt>' instruction interprets its operand as an unsigned
4750 integer quantity and converts it to the corresponding floating point
4751 value. If the value cannot fit in the floating point value, the results are
4756 %X = uitofp i32 257 to float <i>; yields float:257.0</i>
4757 %Y = uitofp i8 -1 to double <i>; yields double:255.0</i>
4762 <!-- _______________________________________________________________________ -->
4763 <div class="doc_subsubsection">
4764 <a name="i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a>
4766 <div class="doc_text">
4770 <result> = sitofp <ty> <value> to <ty2> <i>; yields ty2</i>
4774 <p>The '<tt>sitofp</tt>' instruction regards <tt>value</tt> as a signed integer
4775 and converts that value to the <tt>ty2</tt> type.</p>
4778 <p>The '<tt>sitofp</tt>' instruction takes a value to cast, which must be a
4779 scalar or vector <a href="#t_integer">integer</a> value, and a type to cast
4780 it to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a>
4781 type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector
4782 floating point type with the same number of elements as <tt>ty</tt></p>
4785 <p>The '<tt>sitofp</tt>' instruction interprets its operand as a signed integer
4786 quantity and converts it to the corresponding floating point value. If the
4787 value cannot fit in the floating point value, the results are undefined.</p>
4791 %X = sitofp i32 257 to float <i>; yields float:257.0</i>
4792 %Y = sitofp i8 -1 to double <i>; yields double:-1.0</i>
4797 <!-- _______________________________________________________________________ -->
4798 <div class="doc_subsubsection">
4799 <a name="i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a>
4801 <div class="doc_text">
4805 <result> = ptrtoint <ty> <value> to <ty2> <i>; yields ty2</i>
4809 <p>The '<tt>ptrtoint</tt>' instruction converts the pointer <tt>value</tt> to
4810 the integer type <tt>ty2</tt>.</p>
4813 <p>The '<tt>ptrtoint</tt>' instruction takes a <tt>value</tt> to cast, which
4814 must be a <a href="#t_pointer">pointer</a> value, and a type to cast it to
4815 <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> type.</p>
4818 <p>The '<tt>ptrtoint</tt>' instruction converts <tt>value</tt> to integer type
4819 <tt>ty2</tt> by interpreting the pointer value as an integer and either
4820 truncating or zero extending that value to the size of the integer type. If
4821 <tt>value</tt> is smaller than <tt>ty2</tt> then a zero extension is done. If
4822 <tt>value</tt> is larger than <tt>ty2</tt> then a truncation is done. If they
4823 are the same size, then nothing is done (<i>no-op cast</i>) other than a type
4828 %X = ptrtoint i32* %X to i8 <i>; yields truncation on 32-bit architecture</i>
4829 %Y = ptrtoint i32* %x to i64 <i>; yields zero extension on 32-bit architecture</i>
4834 <!-- _______________________________________________________________________ -->
4835 <div class="doc_subsubsection">
4836 <a name="i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a>
4838 <div class="doc_text">
4842 <result> = inttoptr <ty> <value> to <ty2> <i>; yields ty2</i>
4846 <p>The '<tt>inttoptr</tt>' instruction converts an integer <tt>value</tt> to a
4847 pointer type, <tt>ty2</tt>.</p>
4850 <p>The '<tt>inttoptr</tt>' instruction takes an <a href="#t_integer">integer</a>
4851 value to cast, and a type to cast it to, which must be a
4852 <a href="#t_pointer">pointer</a> type.</p>
4855 <p>The '<tt>inttoptr</tt>' instruction converts <tt>value</tt> to type
4856 <tt>ty2</tt> by applying either a zero extension or a truncation depending on
4857 the size of the integer <tt>value</tt>. If <tt>value</tt> is larger than the
4858 size of a pointer then a truncation is done. If <tt>value</tt> is smaller
4859 than the size of a pointer then a zero extension is done. If they are the
4860 same size, nothing is done (<i>no-op cast</i>).</p>
4864 %X = inttoptr i32 255 to i32* <i>; yields zero extension on 64-bit architecture</i>
4865 %Y = inttoptr i32 255 to i32* <i>; yields no-op on 32-bit architecture</i>
4866 %Z = inttoptr i64 0 to i32* <i>; yields truncation on 32-bit architecture</i>
4871 <!-- _______________________________________________________________________ -->
4872 <div class="doc_subsubsection">
4873 <a name="i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a>
4875 <div class="doc_text">
4879 <result> = bitcast <ty> <value> to <ty2> <i>; yields ty2</i>
4883 <p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type
4884 <tt>ty2</tt> without changing any bits.</p>
4887 <p>The '<tt>bitcast</tt>' instruction takes a value to cast, which must be a
4888 non-aggregate first class value, and a type to cast it to, which must also be
4889 a non-aggregate <a href="#t_firstclass">first class</a> type. The bit sizes
4890 of <tt>value</tt> and the destination type, <tt>ty2</tt>, must be
4891 identical. If the source type is a pointer, the destination type must also be
4892 a pointer. This instruction supports bitwise conversion of vectors to
4893 integers and to vectors of other types (as long as they have the same
4897 <p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type
4898 <tt>ty2</tt>. It is always a <i>no-op cast</i> because no bits change with
4899 this conversion. The conversion is done as if the <tt>value</tt> had been
4900 stored to memory and read back as type <tt>ty2</tt>. Pointer types may only
4901 be converted to other pointer types with this instruction. To convert
4902 pointers to other types, use the <a href="#i_inttoptr">inttoptr</a> or
4903 <a href="#i_ptrtoint">ptrtoint</a> instructions first.</p>
4907 %X = bitcast i8 255 to i8 <i>; yields i8 :-1</i>
4908 %Y = bitcast i32* %x to sint* <i>; yields sint*:%x</i>
4909 %Z = bitcast <2 x int> %V to i64; <i>; yields i64: %V</i>
4914 <!-- ======================================================================= -->
4915 <div class="doc_subsection"> <a name="otherops">Other Operations</a> </div>
4917 <div class="doc_text">
4919 <p>The instructions in this category are the "miscellaneous" instructions, which
4920 defy better classification.</p>
4924 <!-- _______________________________________________________________________ -->
4925 <div class="doc_subsubsection"><a name="i_icmp">'<tt>icmp</tt>' Instruction</a>
4928 <div class="doc_text">
4932 <result> = icmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i>
4936 <p>The '<tt>icmp</tt>' instruction returns a boolean value or a vector of
4937 boolean values based on comparison of its two integer, integer vector, or
4938 pointer operands.</p>
4941 <p>The '<tt>icmp</tt>' instruction takes three operands. The first operand is
4942 the condition code indicating the kind of comparison to perform. It is not a
4943 value, just a keyword. The possible condition code are:</p>
4946 <li><tt>eq</tt>: equal</li>
4947 <li><tt>ne</tt>: not equal </li>
4948 <li><tt>ugt</tt>: unsigned greater than</li>
4949 <li><tt>uge</tt>: unsigned greater or equal</li>
4950 <li><tt>ult</tt>: unsigned less than</li>
4951 <li><tt>ule</tt>: unsigned less or equal</li>
4952 <li><tt>sgt</tt>: signed greater than</li>
4953 <li><tt>sge</tt>: signed greater or equal</li>
4954 <li><tt>slt</tt>: signed less than</li>
4955 <li><tt>sle</tt>: signed less or equal</li>
4958 <p>The remaining two arguments must be <a href="#t_integer">integer</a> or
4959 <a href="#t_pointer">pointer</a> or integer <a href="#t_vector">vector</a>
4960 typed. They must also be identical types.</p>
4963 <p>The '<tt>icmp</tt>' compares <tt>op1</tt> and <tt>op2</tt> according to the
4964 condition code given as <tt>cond</tt>. The comparison performed always yields
4965 either an <a href="#t_integer"><tt>i1</tt></a> or vector of <tt>i1</tt>
4966 result, as follows:</p>
4969 <li><tt>eq</tt>: yields <tt>true</tt> if the operands are equal,
4970 <tt>false</tt> otherwise. No sign interpretation is necessary or
4973 <li><tt>ne</tt>: yields <tt>true</tt> if the operands are unequal,
4974 <tt>false</tt> otherwise. No sign interpretation is necessary or
4977 <li><tt>ugt</tt>: interprets the operands as unsigned values and yields
4978 <tt>true</tt> if <tt>op1</tt> is greater than <tt>op2</tt>.</li>
4980 <li><tt>uge</tt>: interprets the operands as unsigned values and yields
4981 <tt>true</tt> if <tt>op1</tt> is greater than or equal
4982 to <tt>op2</tt>.</li>
4984 <li><tt>ult</tt>: interprets the operands as unsigned values and yields
4985 <tt>true</tt> if <tt>op1</tt> is less than <tt>op2</tt>.</li>
4987 <li><tt>ule</tt>: interprets the operands as unsigned values and yields
4988 <tt>true</tt> if <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li>
4990 <li><tt>sgt</tt>: interprets the operands as signed values and yields
4991 <tt>true</tt> if <tt>op1</tt> is greater than <tt>op2</tt>.</li>
4993 <li><tt>sge</tt>: interprets the operands as signed values and yields
4994 <tt>true</tt> if <tt>op1</tt> is greater than or equal
4995 to <tt>op2</tt>.</li>
4997 <li><tt>slt</tt>: interprets the operands as signed values and yields
4998 <tt>true</tt> if <tt>op1</tt> is less than <tt>op2</tt>.</li>
5000 <li><tt>sle</tt>: interprets the operands as signed values and yields
5001 <tt>true</tt> if <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li>
5004 <p>If the operands are <a href="#t_pointer">pointer</a> typed, the pointer
5005 values are compared as if they were integers.</p>
5007 <p>If the operands are integer vectors, then they are compared element by
5008 element. The result is an <tt>i1</tt> vector with the same number of elements
5009 as the values being compared. Otherwise, the result is an <tt>i1</tt>.</p>
5013 <result> = icmp eq i32 4, 5 <i>; yields: result=false</i>
5014 <result> = icmp ne float* %X, %X <i>; yields: result=false</i>
5015 <result> = icmp ult i16 4, 5 <i>; yields: result=true</i>
5016 <result> = icmp sgt i16 4, 5 <i>; yields: result=false</i>
5017 <result> = icmp ule i16 -4, 5 <i>; yields: result=false</i>
5018 <result> = icmp sge i16 4, 5 <i>; yields: result=false</i>
5021 <p>Note that the code generator does not yet support vector types with
5022 the <tt>icmp</tt> instruction.</p>
5026 <!-- _______________________________________________________________________ -->
5027 <div class="doc_subsubsection"><a name="i_fcmp">'<tt>fcmp</tt>' Instruction</a>
5030 <div class="doc_text">
5034 <result> = fcmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i>
5038 <p>The '<tt>fcmp</tt>' instruction returns a boolean value or vector of boolean
5039 values based on comparison of its operands.</p>
5041 <p>If the operands are floating point scalars, then the result type is a boolean
5042 (<a href="#t_integer"><tt>i1</tt></a>).</p>
5044 <p>If the operands are floating point vectors, then the result type is a vector
5045 of boolean with the same number of elements as the operands being
5049 <p>The '<tt>fcmp</tt>' instruction takes three operands. The first operand is
5050 the condition code indicating the kind of comparison to perform. It is not a
5051 value, just a keyword. The possible condition code are:</p>
5054 <li><tt>false</tt>: no comparison, always returns false</li>
5055 <li><tt>oeq</tt>: ordered and equal</li>
5056 <li><tt>ogt</tt>: ordered and greater than </li>
5057 <li><tt>oge</tt>: ordered and greater than or equal</li>
5058 <li><tt>olt</tt>: ordered and less than </li>
5059 <li><tt>ole</tt>: ordered and less than or equal</li>
5060 <li><tt>one</tt>: ordered and not equal</li>
5061 <li><tt>ord</tt>: ordered (no nans)</li>
5062 <li><tt>ueq</tt>: unordered or equal</li>
5063 <li><tt>ugt</tt>: unordered or greater than </li>
5064 <li><tt>uge</tt>: unordered or greater than or equal</li>
5065 <li><tt>ult</tt>: unordered or less than </li>
5066 <li><tt>ule</tt>: unordered or less than or equal</li>
5067 <li><tt>une</tt>: unordered or not equal</li>
5068 <li><tt>uno</tt>: unordered (either nans)</li>
5069 <li><tt>true</tt>: no comparison, always returns true</li>
5072 <p><i>Ordered</i> means that neither operand is a QNAN while
5073 <i>unordered</i> means that either operand may be a QNAN.</p>
5075 <p>Each of <tt>val1</tt> and <tt>val2</tt> arguments must be either
5076 a <a href="#t_floating">floating point</a> type or
5077 a <a href="#t_vector">vector</a> of floating point type. They must have
5078 identical types.</p>
5081 <p>The '<tt>fcmp</tt>' instruction compares <tt>op1</tt> and <tt>op2</tt>
5082 according to the condition code given as <tt>cond</tt>. If the operands are
5083 vectors, then the vectors are compared element by element. Each comparison
5084 performed always yields an <a href="#t_integer">i1</a> result, as
5088 <li><tt>false</tt>: always yields <tt>false</tt>, regardless of operands.</li>
5090 <li><tt>oeq</tt>: yields <tt>true</tt> if both operands are not a QNAN and
5091 <tt>op1</tt> is equal to <tt>op2</tt>.</li>
5093 <li><tt>ogt</tt>: yields <tt>true</tt> if both operands are not a QNAN and
5094 <tt>op1</tt> is greater than <tt>op2</tt>.</li>
5096 <li><tt>oge</tt>: yields <tt>true</tt> if both operands are not a QNAN and
5097 <tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li>
5099 <li><tt>olt</tt>: yields <tt>true</tt> if both operands are not a QNAN and
5100 <tt>op1</tt> is less than <tt>op2</tt>.</li>
5102 <li><tt>ole</tt>: yields <tt>true</tt> if both operands are not a QNAN and
5103 <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li>
5105 <li><tt>one</tt>: yields <tt>true</tt> if both operands are not a QNAN and
5106 <tt>op1</tt> is not equal to <tt>op2</tt>.</li>
5108 <li><tt>ord</tt>: yields <tt>true</tt> if both operands are not a QNAN.</li>
5110 <li><tt>ueq</tt>: yields <tt>true</tt> if either operand is a QNAN or
5111 <tt>op1</tt> is equal to <tt>op2</tt>.</li>
5113 <li><tt>ugt</tt>: yields <tt>true</tt> if either operand is a QNAN or
5114 <tt>op1</tt> is greater than <tt>op2</tt>.</li>
5116 <li><tt>uge</tt>: yields <tt>true</tt> if either operand is a QNAN or
5117 <tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li>
5119 <li><tt>ult</tt>: yields <tt>true</tt> if either operand is a QNAN or
5120 <tt>op1</tt> is less than <tt>op2</tt>.</li>
5122 <li><tt>ule</tt>: yields <tt>true</tt> if either operand is a QNAN or
5123 <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li>
5125 <li><tt>une</tt>: yields <tt>true</tt> if either operand is a QNAN or
5126 <tt>op1</tt> is not equal to <tt>op2</tt>.</li>
5128 <li><tt>uno</tt>: yields <tt>true</tt> if either operand is a QNAN.</li>
5130 <li><tt>true</tt>: always yields <tt>true</tt>, regardless of operands.</li>
5135 <result> = fcmp oeq float 4.0, 5.0 <i>; yields: result=false</i>
5136 <result> = fcmp one float 4.0, 5.0 <i>; yields: result=true</i>
5137 <result> = fcmp olt float 4.0, 5.0 <i>; yields: result=true</i>
5138 <result> = fcmp ueq double 1.0, 2.0 <i>; yields: result=false</i>
5141 <p>Note that the code generator does not yet support vector types with
5142 the <tt>fcmp</tt> instruction.</p>
5146 <!-- _______________________________________________________________________ -->
5147 <div class="doc_subsubsection">
5148 <a name="i_phi">'<tt>phi</tt>' Instruction</a>
5151 <div class="doc_text">
5155 <result> = phi <ty> [ <val0>, <label0>], ...
5159 <p>The '<tt>phi</tt>' instruction is used to implement the φ node in the
5160 SSA graph representing the function.</p>
5163 <p>The type of the incoming values is specified with the first type field. After
5164 this, the '<tt>phi</tt>' instruction takes a list of pairs as arguments, with
5165 one pair for each predecessor basic block of the current block. Only values
5166 of <a href="#t_firstclass">first class</a> type may be used as the value
5167 arguments to the PHI node. Only labels may be used as the label
5170 <p>There must be no non-phi instructions between the start of a basic block and
5171 the PHI instructions: i.e. PHI instructions must be first in a basic
5174 <p>For the purposes of the SSA form, the use of each incoming value is deemed to
5175 occur on the edge from the corresponding predecessor block to the current
5176 block (but after any definition of an '<tt>invoke</tt>' instruction's return
5177 value on the same edge).</p>
5180 <p>At runtime, the '<tt>phi</tt>' instruction logically takes on the value
5181 specified by the pair corresponding to the predecessor basic block that
5182 executed just prior to the current block.</p>
5186 Loop: ; Infinite loop that counts from 0 on up...
5187 %indvar = phi i32 [ 0, %LoopHeader ], [ %nextindvar, %Loop ]
5188 %nextindvar = add i32 %indvar, 1
5194 <!-- _______________________________________________________________________ -->
5195 <div class="doc_subsubsection">
5196 <a name="i_select">'<tt>select</tt>' Instruction</a>
5199 <div class="doc_text">
5203 <result> = select <i>selty</i> <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i>
5205 <i>selty</i> is either i1 or {<N x i1>}
5209 <p>The '<tt>select</tt>' instruction is used to choose one value based on a
5210 condition, without branching.</p>
5214 <p>The '<tt>select</tt>' instruction requires an 'i1' value or a vector of 'i1'
5215 values indicating the condition, and two values of the
5216 same <a href="#t_firstclass">first class</a> type. If the val1/val2 are
5217 vectors and the condition is a scalar, then entire vectors are selected, not
5218 individual elements.</p>
5221 <p>If the condition is an i1 and it evaluates to 1, the instruction returns the
5222 first value argument; otherwise, it returns the second value argument.</p>
5224 <p>If the condition is a vector of i1, then the value arguments must be vectors
5225 of the same size, and the selection is done element by element.</p>
5229 %X = select i1 true, i8 17, i8 42 <i>; yields i8:17</i>
5232 <p>Note that the code generator does not yet support conditions
5233 with vector type.</p>
5237 <!-- _______________________________________________________________________ -->
5238 <div class="doc_subsubsection">
5239 <a name="i_call">'<tt>call</tt>' Instruction</a>
5242 <div class="doc_text">
5246 <result> = [tail] call [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] <ty> [<fnty>*] <fnptrval>(<function args>) [<a href="#fnattrs">fn attrs</a>]
5250 <p>The '<tt>call</tt>' instruction represents a simple function call.</p>
5253 <p>This instruction requires several arguments:</p>
5256 <li>The optional "tail" marker indicates that the callee function does not
5257 access any allocas or varargs in the caller. Note that calls may be
5258 marked "tail" even if they do not occur before
5259 a <a href="#i_ret"><tt>ret</tt></a> instruction. If the "tail" marker is
5260 present, the function call is eligible for tail call optimization,
5261 but <a href="CodeGenerator.html#tailcallopt">might not in fact be
5262 optimized into a jump</a>. The code generator may optimize calls marked
5263 "tail" with either 1) automatic <a href="CodeGenerator.html#sibcallopt">
5264 sibling call optimization</a> when the caller and callee have
5265 matching signatures, or 2) forced tail call optimization when the
5266 following extra requirements are met:
5268 <li>Caller and callee both have the calling
5269 convention <tt>fastcc</tt>.</li>
5270 <li>The call is in tail position (ret immediately follows call and ret
5271 uses value of call or is void).</li>
5272 <li>Option <tt>-tailcallopt</tt> is enabled,
5273 or <code>llvm::GuaranteedTailCallOpt</code> is <code>true</code>.</li>
5274 <li><a href="CodeGenerator.html#tailcallopt">Platform specific
5275 constraints are met.</a></li>
5279 <li>The optional "cconv" marker indicates which <a href="#callingconv">calling
5280 convention</a> the call should use. If none is specified, the call
5281 defaults to using C calling conventions. The calling convention of the
5282 call must match the calling convention of the target function, or else the
5283 behavior is undefined.</li>
5285 <li>The optional <a href="#paramattrs">Parameter Attributes</a> list for
5286 return values. Only '<tt>zeroext</tt>', '<tt>signext</tt>', and
5287 '<tt>inreg</tt>' attributes are valid here.</li>
5289 <li>'<tt>ty</tt>': the type of the call instruction itself which is also the
5290 type of the return value. Functions that return no value are marked
5291 <tt><a href="#t_void">void</a></tt>.</li>
5293 <li>'<tt>fnty</tt>': shall be the signature of the pointer to function value
5294 being invoked. The argument types must match the types implied by this
5295 signature. This type can be omitted if the function is not varargs and if
5296 the function type does not return a pointer to a function.</li>
5298 <li>'<tt>fnptrval</tt>': An LLVM value containing a pointer to a function to
5299 be invoked. In most cases, this is a direct function invocation, but
5300 indirect <tt>call</tt>s are just as possible, calling an arbitrary pointer
5301 to function value.</li>
5303 <li>'<tt>function args</tt>': argument list whose types match the function
5304 signature argument types and parameter attributes. All arguments must be
5305 of <a href="#t_firstclass">first class</a> type. If the function
5306 signature indicates the function accepts a variable number of arguments,
5307 the extra arguments can be specified.</li>
5309 <li>The optional <a href="#fnattrs">function attributes</a> list. Only
5310 '<tt>noreturn</tt>', '<tt>nounwind</tt>', '<tt>readonly</tt>' and
5311 '<tt>readnone</tt>' attributes are valid here.</li>
5315 <p>The '<tt>call</tt>' instruction is used to cause control flow to transfer to
5316 a specified function, with its incoming arguments bound to the specified
5317 values. Upon a '<tt><a href="#i_ret">ret</a></tt>' instruction in the called
5318 function, control flow continues with the instruction after the function
5319 call, and the return value of the function is bound to the result
5324 %retval = call i32 @test(i32 %argc)
5325 call i32 (i8 *, ...)* @printf(i8 * %msg, i32 12, i8 42) <i>; yields i32</i>
5326 %X = tail call i32 @foo() <i>; yields i32</i>
5327 %Y = tail call <a href="#callingconv">fastcc</a> i32 @foo() <i>; yields i32</i>
5328 call void %foo(i8 97 signext)
5330 %struct.A = type { i32, i8 }
5331 %r = call %struct.A @foo() <i>; yields { 32, i8 }</i>
5332 %gr = extractvalue %struct.A %r, 0 <i>; yields i32</i>
5333 %gr1 = extractvalue %struct.A %r, 1 <i>; yields i8</i>
5334 %Z = call void @foo() noreturn <i>; indicates that %foo never returns normally</i>
5335 %ZZ = call zeroext i32 @bar() <i>; Return value is %zero extended</i>
5338 <p>llvm treats calls to some functions with names and arguments that match the
5339 standard C99 library as being the C99 library functions, and may perform
5340 optimizations or generate code for them under that assumption. This is
5341 something we'd like to change in the future to provide better support for
5342 freestanding environments and non-C-based languages.</p>
5346 <!-- _______________________________________________________________________ -->
5347 <div class="doc_subsubsection">
5348 <a name="i_va_arg">'<tt>va_arg</tt>' Instruction</a>
5351 <div class="doc_text">
5355 <resultval> = va_arg <va_list*> <arglist>, <argty>
5359 <p>The '<tt>va_arg</tt>' instruction is used to access arguments passed through
5360 the "variable argument" area of a function call. It is used to implement the
5361 <tt>va_arg</tt> macro in C.</p>
5364 <p>This instruction takes a <tt>va_list*</tt> value and the type of the
5365 argument. It returns a value of the specified argument type and increments
5366 the <tt>va_list</tt> to point to the next argument. The actual type
5367 of <tt>va_list</tt> is target specific.</p>
5370 <p>The '<tt>va_arg</tt>' instruction loads an argument of the specified type
5371 from the specified <tt>va_list</tt> and causes the <tt>va_list</tt> to point
5372 to the next argument. For more information, see the variable argument
5373 handling <a href="#int_varargs">Intrinsic Functions</a>.</p>
5375 <p>It is legal for this instruction to be called in a function which does not
5376 take a variable number of arguments, for example, the <tt>vfprintf</tt>
5379 <p><tt>va_arg</tt> is an LLVM instruction instead of
5380 an <a href="#intrinsics">intrinsic function</a> because it takes a type as an
5384 <p>See the <a href="#int_varargs">variable argument processing</a> section.</p>
5386 <p>Note that the code generator does not yet fully support va_arg on many
5387 targets. Also, it does not currently support va_arg with aggregate types on
5392 <!-- *********************************************************************** -->
5393 <div class="doc_section"> <a name="intrinsics">Intrinsic Functions</a> </div>
5394 <!-- *********************************************************************** -->
5396 <div class="doc_text">
5398 <p>LLVM supports the notion of an "intrinsic function". These functions have
5399 well known names and semantics and are required to follow certain
5400 restrictions. Overall, these intrinsics represent an extension mechanism for
5401 the LLVM language that does not require changing all of the transformations
5402 in LLVM when adding to the language (or the bitcode reader/writer, the
5403 parser, etc...).</p>
5405 <p>Intrinsic function names must all start with an "<tt>llvm.</tt>" prefix. This
5406 prefix is reserved in LLVM for intrinsic names; thus, function names may not
5407 begin with this prefix. Intrinsic functions must always be external
5408 functions: you cannot define the body of intrinsic functions. Intrinsic
5409 functions may only be used in call or invoke instructions: it is illegal to
5410 take the address of an intrinsic function. Additionally, because intrinsic
5411 functions are part of the LLVM language, it is required if any are added that
5412 they be documented here.</p>
5414 <p>Some intrinsic functions can be overloaded, i.e., the intrinsic represents a
5415 family of functions that perform the same operation but on different data
5416 types. Because LLVM can represent over 8 million different integer types,
5417 overloading is used commonly to allow an intrinsic function to operate on any
5418 integer type. One or more of the argument types or the result type can be
5419 overloaded to accept any integer type. Argument types may also be defined as
5420 exactly matching a previous argument's type or the result type. This allows
5421 an intrinsic function which accepts multiple arguments, but needs all of them
5422 to be of the same type, to only be overloaded with respect to a single
5423 argument or the result.</p>
5425 <p>Overloaded intrinsics will have the names of its overloaded argument types
5426 encoded into its function name, each preceded by a period. Only those types
5427 which are overloaded result in a name suffix. Arguments whose type is matched
5428 against another type do not. For example, the <tt>llvm.ctpop</tt> function
5429 can take an integer of any width and returns an integer of exactly the same
5430 integer width. This leads to a family of functions such as
5431 <tt>i8 @llvm.ctpop.i8(i8 %val)</tt> and <tt>i29 @llvm.ctpop.i29(i29
5432 %val)</tt>. Only one type, the return type, is overloaded, and only one type
5433 suffix is required. Because the argument's type is matched against the return
5434 type, it does not require its own name suffix.</p>
5436 <p>To learn how to add an intrinsic function, please see the
5437 <a href="ExtendingLLVM.html">Extending LLVM Guide</a>.</p>
5441 <!-- ======================================================================= -->
5442 <div class="doc_subsection">
5443 <a name="int_varargs">Variable Argument Handling Intrinsics</a>
5446 <div class="doc_text">
5448 <p>Variable argument support is defined in LLVM with
5449 the <a href="#i_va_arg"><tt>va_arg</tt></a> instruction and these three
5450 intrinsic functions. These functions are related to the similarly named
5451 macros defined in the <tt><stdarg.h></tt> header file.</p>
5453 <p>All of these functions operate on arguments that use a target-specific value
5454 type "<tt>va_list</tt>". The LLVM assembly language reference manual does
5455 not define what this type is, so all transformations should be prepared to
5456 handle these functions regardless of the type used.</p>
5458 <p>This example shows how the <a href="#i_va_arg"><tt>va_arg</tt></a>
5459 instruction and the variable argument handling intrinsic functions are
5462 <div class="doc_code">
5464 define i32 @test(i32 %X, ...) {
5465 ; Initialize variable argument processing
5467 %ap2 = bitcast i8** %ap to i8*
5468 call void @llvm.va_start(i8* %ap2)
5470 ; Read a single integer argument
5471 %tmp = va_arg i8** %ap, i32
5473 ; Demonstrate usage of llvm.va_copy and llvm.va_end
5475 %aq2 = bitcast i8** %aq to i8*
5476 call void @llvm.va_copy(i8* %aq2, i8* %ap2)
5477 call void @llvm.va_end(i8* %aq2)
5479 ; Stop processing of arguments.
5480 call void @llvm.va_end(i8* %ap2)
5484 declare void @llvm.va_start(i8*)
5485 declare void @llvm.va_copy(i8*, i8*)
5486 declare void @llvm.va_end(i8*)
5492 <!-- _______________________________________________________________________ -->
5493 <div class="doc_subsubsection">
5494 <a name="int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a>
5498 <div class="doc_text">
5502 declare void %llvm.va_start(i8* <arglist>)
5506 <p>The '<tt>llvm.va_start</tt>' intrinsic initializes <tt>*<arglist></tt>
5507 for subsequent use by <tt><a href="#i_va_arg">va_arg</a></tt>.</p>
5510 <p>The argument is a pointer to a <tt>va_list</tt> element to initialize.</p>
5513 <p>The '<tt>llvm.va_start</tt>' intrinsic works just like the <tt>va_start</tt>
5514 macro available in C. In a target-dependent way, it initializes
5515 the <tt>va_list</tt> element to which the argument points, so that the next
5516 call to <tt>va_arg</tt> will produce the first variable argument passed to
5517 the function. Unlike the C <tt>va_start</tt> macro, this intrinsic does not
5518 need to know the last argument of the function as the compiler can figure
5523 <!-- _______________________________________________________________________ -->
5524 <div class="doc_subsubsection">
5525 <a name="int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a>
5528 <div class="doc_text">
5532 declare void @llvm.va_end(i8* <arglist>)
5536 <p>The '<tt>llvm.va_end</tt>' intrinsic destroys <tt>*<arglist></tt>,
5537 which has been initialized previously
5538 with <tt><a href="#int_va_start">llvm.va_start</a></tt>
5539 or <tt><a href="#i_va_copy">llvm.va_copy</a></tt>.</p>
5542 <p>The argument is a pointer to a <tt>va_list</tt> to destroy.</p>
5545 <p>The '<tt>llvm.va_end</tt>' intrinsic works just like the <tt>va_end</tt>
5546 macro available in C. In a target-dependent way, it destroys
5547 the <tt>va_list</tt> element to which the argument points. Calls
5548 to <a href="#int_va_start"><tt>llvm.va_start</tt></a>
5549 and <a href="#int_va_copy"> <tt>llvm.va_copy</tt></a> must be matched exactly
5550 with calls to <tt>llvm.va_end</tt>.</p>
5554 <!-- _______________________________________________________________________ -->
5555 <div class="doc_subsubsection">
5556 <a name="int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a>
5559 <div class="doc_text">
5563 declare void @llvm.va_copy(i8* <destarglist>, i8* <srcarglist>)
5567 <p>The '<tt>llvm.va_copy</tt>' intrinsic copies the current argument position
5568 from the source argument list to the destination argument list.</p>
5571 <p>The first argument is a pointer to a <tt>va_list</tt> element to initialize.
5572 The second argument is a pointer to a <tt>va_list</tt> element to copy
5576 <p>The '<tt>llvm.va_copy</tt>' intrinsic works just like the <tt>va_copy</tt>
5577 macro available in C. In a target-dependent way, it copies the
5578 source <tt>va_list</tt> element into the destination <tt>va_list</tt>
5579 element. This intrinsic is necessary because
5580 the <tt><a href="#int_va_start"> llvm.va_start</a></tt> intrinsic may be
5581 arbitrarily complex and require, for example, memory allocation.</p>
5585 <!-- ======================================================================= -->
5586 <div class="doc_subsection">
5587 <a name="int_gc">Accurate Garbage Collection Intrinsics</a>
5590 <div class="doc_text">
5592 <p>LLVM support for <a href="GarbageCollection.html">Accurate Garbage
5593 Collection</a> (GC) requires the implementation and generation of these
5594 intrinsics. These intrinsics allow identification of <a href="#int_gcroot">GC
5595 roots on the stack</a>, as well as garbage collector implementations that
5596 require <a href="#int_gcread">read</a> and <a href="#int_gcwrite">write</a>
5597 barriers. Front-ends for type-safe garbage collected languages should generate
5598 these intrinsics to make use of the LLVM garbage collectors. For more details,
5599 see <a href="GarbageCollection.html">Accurate Garbage Collection with
5602 <p>The garbage collection intrinsics only operate on objects in the generic
5603 address space (address space zero).</p>
5607 <!-- _______________________________________________________________________ -->
5608 <div class="doc_subsubsection">
5609 <a name="int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a>
5612 <div class="doc_text">
5616 declare void @llvm.gcroot(i8** %ptrloc, i8* %metadata)
5620 <p>The '<tt>llvm.gcroot</tt>' intrinsic declares the existence of a GC root to
5621 the code generator, and allows some metadata to be associated with it.</p>
5624 <p>The first argument specifies the address of a stack object that contains the
5625 root pointer. The second pointer (which must be either a constant or a
5626 global value address) contains the meta-data to be associated with the
5630 <p>At runtime, a call to this intrinsic stores a null pointer into the "ptrloc"
5631 location. At compile-time, the code generator generates information to allow
5632 the runtime to find the pointer at GC safe points. The '<tt>llvm.gcroot</tt>'
5633 intrinsic may only be used in a function which <a href="#gc">specifies a GC
5638 <!-- _______________________________________________________________________ -->
5639 <div class="doc_subsubsection">
5640 <a name="int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a>
5643 <div class="doc_text">
5647 declare i8* @llvm.gcread(i8* %ObjPtr, i8** %Ptr)
5651 <p>The '<tt>llvm.gcread</tt>' intrinsic identifies reads of references from heap
5652 locations, allowing garbage collector implementations that require read
5656 <p>The second argument is the address to read from, which should be an address
5657 allocated from the garbage collector. The first object is a pointer to the
5658 start of the referenced object, if needed by the language runtime (otherwise
5662 <p>The '<tt>llvm.gcread</tt>' intrinsic has the same semantics as a load
5663 instruction, but may be replaced with substantially more complex code by the
5664 garbage collector runtime, as needed. The '<tt>llvm.gcread</tt>' intrinsic
5665 may only be used in a function which <a href="#gc">specifies a GC
5670 <!-- _______________________________________________________________________ -->
5671 <div class="doc_subsubsection">
5672 <a name="int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a>
5675 <div class="doc_text">
5679 declare void @llvm.gcwrite(i8* %P1, i8* %Obj, i8** %P2)
5683 <p>The '<tt>llvm.gcwrite</tt>' intrinsic identifies writes of references to heap
5684 locations, allowing garbage collector implementations that require write
5685 barriers (such as generational or reference counting collectors).</p>
5688 <p>The first argument is the reference to store, the second is the start of the
5689 object to store it to, and the third is the address of the field of Obj to
5690 store to. If the runtime does not require a pointer to the object, Obj may
5694 <p>The '<tt>llvm.gcwrite</tt>' intrinsic has the same semantics as a store
5695 instruction, but may be replaced with substantially more complex code by the
5696 garbage collector runtime, as needed. The '<tt>llvm.gcwrite</tt>' intrinsic
5697 may only be used in a function which <a href="#gc">specifies a GC
5702 <!-- ======================================================================= -->
5703 <div class="doc_subsection">
5704 <a name="int_codegen">Code Generator Intrinsics</a>
5707 <div class="doc_text">
5709 <p>These intrinsics are provided by LLVM to expose special features that may
5710 only be implemented with code generator support.</p>
5714 <!-- _______________________________________________________________________ -->
5715 <div class="doc_subsubsection">
5716 <a name="int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a>
5719 <div class="doc_text">
5723 declare i8 *@llvm.returnaddress(i32 <level>)
5727 <p>The '<tt>llvm.returnaddress</tt>' intrinsic attempts to compute a
5728 target-specific value indicating the return address of the current function
5729 or one of its callers.</p>
5732 <p>The argument to this intrinsic indicates which function to return the address
5733 for. Zero indicates the calling function, one indicates its caller, etc.
5734 The argument is <b>required</b> to be a constant integer value.</p>
5737 <p>The '<tt>llvm.returnaddress</tt>' intrinsic either returns a pointer
5738 indicating the return address of the specified call frame, or zero if it
5739 cannot be identified. The value returned by this intrinsic is likely to be
5740 incorrect or 0 for arguments other than zero, so it should only be used for
5741 debugging purposes.</p>
5743 <p>Note that calling this intrinsic does not prevent function inlining or other
5744 aggressive transformations, so the value returned may not be that of the
5745 obvious source-language caller.</p>
5749 <!-- _______________________________________________________________________ -->
5750 <div class="doc_subsubsection">
5751 <a name="int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a>
5754 <div class="doc_text">
5758 declare i8 *@llvm.frameaddress(i32 <level>)
5762 <p>The '<tt>llvm.frameaddress</tt>' intrinsic attempts to return the
5763 target-specific frame pointer value for the specified stack frame.</p>
5766 <p>The argument to this intrinsic indicates which function to return the frame
5767 pointer for. Zero indicates the calling function, one indicates its caller,
5768 etc. The argument is <b>required</b> to be a constant integer value.</p>
5771 <p>The '<tt>llvm.frameaddress</tt>' intrinsic either returns a pointer
5772 indicating the frame address of the specified call frame, or zero if it
5773 cannot be identified. The value returned by this intrinsic is likely to be
5774 incorrect or 0 for arguments other than zero, so it should only be used for
5775 debugging purposes.</p>
5777 <p>Note that calling this intrinsic does not prevent function inlining or other
5778 aggressive transformations, so the value returned may not be that of the
5779 obvious source-language caller.</p>
5783 <!-- _______________________________________________________________________ -->
5784 <div class="doc_subsubsection">
5785 <a name="int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a>
5788 <div class="doc_text">
5792 declare i8 *@llvm.stacksave()
5796 <p>The '<tt>llvm.stacksave</tt>' intrinsic is used to remember the current state
5797 of the function stack, for use
5798 with <a href="#int_stackrestore"> <tt>llvm.stackrestore</tt></a>. This is
5799 useful for implementing language features like scoped automatic variable
5800 sized arrays in C99.</p>
5803 <p>This intrinsic returns a opaque pointer value that can be passed
5804 to <a href="#int_stackrestore"><tt>llvm.stackrestore</tt></a>. When
5805 an <tt>llvm.stackrestore</tt> intrinsic is executed with a value saved
5806 from <tt>llvm.stacksave</tt>, it effectively restores the state of the stack
5807 to the state it was in when the <tt>llvm.stacksave</tt> intrinsic executed.
5808 In practice, this pops any <a href="#i_alloca">alloca</a> blocks from the
5809 stack that were allocated after the <tt>llvm.stacksave</tt> was executed.</p>
5813 <!-- _______________________________________________________________________ -->
5814 <div class="doc_subsubsection">
5815 <a name="int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a>
5818 <div class="doc_text">
5822 declare void @llvm.stackrestore(i8 * %ptr)
5826 <p>The '<tt>llvm.stackrestore</tt>' intrinsic is used to restore the state of
5827 the function stack to the state it was in when the
5828 corresponding <a href="#int_stacksave"><tt>llvm.stacksave</tt></a> intrinsic
5829 executed. This is useful for implementing language features like scoped
5830 automatic variable sized arrays in C99.</p>
5833 <p>See the description
5834 for <a href="#int_stacksave"><tt>llvm.stacksave</tt></a>.</p>
5838 <!-- _______________________________________________________________________ -->
5839 <div class="doc_subsubsection">
5840 <a name="int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a>
5843 <div class="doc_text">
5847 declare void @llvm.prefetch(i8* <address>, i32 <rw>, i32 <locality>)
5851 <p>The '<tt>llvm.prefetch</tt>' intrinsic is a hint to the code generator to
5852 insert a prefetch instruction if supported; otherwise, it is a noop.
5853 Prefetches have no effect on the behavior of the program but can change its
5854 performance characteristics.</p>
5857 <p><tt>address</tt> is the address to be prefetched, <tt>rw</tt> is the
5858 specifier determining if the fetch should be for a read (0) or write (1),
5859 and <tt>locality</tt> is a temporal locality specifier ranging from (0) - no
5860 locality, to (3) - extremely local keep in cache. The <tt>rw</tt>
5861 and <tt>locality</tt> arguments must be constant integers.</p>
5864 <p>This intrinsic does not modify the behavior of the program. In particular,
5865 prefetches cannot trap and do not produce a value. On targets that support
5866 this intrinsic, the prefetch can provide hints to the processor cache for
5867 better performance.</p>
5871 <!-- _______________________________________________________________________ -->
5872 <div class="doc_subsubsection">
5873 <a name="int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a>
5876 <div class="doc_text">
5880 declare void @llvm.pcmarker(i32 <id>)
5884 <p>The '<tt>llvm.pcmarker</tt>' intrinsic is a method to export a Program
5885 Counter (PC) in a region of code to simulators and other tools. The method
5886 is target specific, but it is expected that the marker will use exported
5887 symbols to transmit the PC of the marker. The marker makes no guarantees
5888 that it will remain with any specific instruction after optimizations. It is
5889 possible that the presence of a marker will inhibit optimizations. The
5890 intended use is to be inserted after optimizations to allow correlations of
5891 simulation runs.</p>
5894 <p><tt>id</tt> is a numerical id identifying the marker.</p>
5897 <p>This intrinsic does not modify the behavior of the program. Backends that do
5898 not support this intrinsic may ignore it.</p>
5902 <!-- _______________________________________________________________________ -->
5903 <div class="doc_subsubsection">
5904 <a name="int_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a>
5907 <div class="doc_text">
5911 declare i64 @llvm.readcyclecounter( )
5915 <p>The '<tt>llvm.readcyclecounter</tt>' intrinsic provides access to the cycle
5916 counter register (or similar low latency, high accuracy clocks) on those
5917 targets that support it. On X86, it should map to RDTSC. On Alpha, it
5918 should map to RPCC. As the backing counters overflow quickly (on the order
5919 of 9 seconds on alpha), this should only be used for small timings.</p>
5922 <p>When directly supported, reading the cycle counter should not modify any
5923 memory. Implementations are allowed to either return a application specific
5924 value or a system wide value. On backends without support, this is lowered
5925 to a constant 0.</p>
5929 <!-- ======================================================================= -->
5930 <div class="doc_subsection">
5931 <a name="int_libc">Standard C Library Intrinsics</a>
5934 <div class="doc_text">
5936 <p>LLVM provides intrinsics for a few important standard C library functions.
5937 These intrinsics allow source-language front-ends to pass information about
5938 the alignment of the pointer arguments to the code generator, providing
5939 opportunity for more efficient code generation.</p>
5943 <!-- _______________________________________________________________________ -->
5944 <div class="doc_subsubsection">
5945 <a name="int_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a>
5948 <div class="doc_text">
5951 <p>This is an overloaded intrinsic. You can use <tt>llvm.memcpy</tt> on any
5952 integer bit width and for different address spaces. Not all targets support
5953 all bit widths however.</p>
5956 declare void @llvm.memcpy.p0i8.p0i8.i32(i8 * <dest>, i8 * <src>,
5957 i32 <len>, i32 <align>, i1 <isvolatile>)
5958 declare void @llvm.memcpy.p0i8.p0i8.i64(i8 * <dest>, i8 * <src>,
5959 i64 <len>, i32 <align>, i1 <isvolatile>)
5963 <p>The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the
5964 source location to the destination location.</p>
5966 <p>Note that, unlike the standard libc function, the <tt>llvm.memcpy.*</tt>
5967 intrinsics do not return a value, takes extra alignment/isvolatile arguments
5968 and the pointers can be in specified address spaces.</p>
5972 <p>The first argument is a pointer to the destination, the second is a pointer
5973 to the source. The third argument is an integer argument specifying the
5974 number of bytes to copy, the fourth argument is the alignment of the
5975 source and destination locations, and the fifth is a boolean indicating a
5976 volatile access.</p>
5978 <p>If the call to this intrinsic has an alignment value that is not 0 or 1,
5979 then the caller guarantees that both the source and destination pointers are
5980 aligned to that boundary.</p>
5982 <p>If the <tt>isvolatile</tt> parameter is <tt>true</tt>, the
5983 <tt>llvm.memcpy</tt> call is a <a href="#volatile">volatile operation</a>.
5984 The detailed access behavior is not very cleanly specified and it is unwise
5985 to depend on it.</p>
5989 <p>The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the
5990 source location to the destination location, which are not allowed to
5991 overlap. It copies "len" bytes of memory over. If the argument is known to
5992 be aligned to some boundary, this can be specified as the fourth argument,
5993 otherwise it should be set to 0 or 1.</p>
5997 <!-- _______________________________________________________________________ -->
5998 <div class="doc_subsubsection">
5999 <a name="int_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a>
6002 <div class="doc_text">
6005 <p>This is an overloaded intrinsic. You can use llvm.memmove on any integer bit
6006 width and for different address space. Not all targets support all bit
6010 declare void @llvm.memmove.p0i8.p0i8.i32(i8 * <dest>, i8 * <src>,
6011 i32 <len>, i32 <align>, i1 <isvolatile>)
6012 declare void @llvm.memmove.p0i8.p0i8.i64(i8 * <dest>, i8 * <src>,
6013 i64 <len>, i32 <align>, i1 <isvolatile>)
6017 <p>The '<tt>llvm.memmove.*</tt>' intrinsics move a block of memory from the
6018 source location to the destination location. It is similar to the
6019 '<tt>llvm.memcpy</tt>' intrinsic but allows the two memory locations to
6022 <p>Note that, unlike the standard libc function, the <tt>llvm.memmove.*</tt>
6023 intrinsics do not return a value, takes extra alignment/isvolatile arguments
6024 and the pointers can be in specified address spaces.</p>
6028 <p>The first argument is a pointer to the destination, the second is a pointer
6029 to the source. The third argument is an integer argument specifying the
6030 number of bytes to copy, the fourth argument is the alignment of the
6031 source and destination locations, and the fifth is a boolean indicating a
6032 volatile access.</p>
6034 <p>If the call to this intrinsic has an alignment value that is not 0 or 1,
6035 then the caller guarantees that the source and destination pointers are
6036 aligned to that boundary.</p>
6038 <p>If the <tt>isvolatile</tt> parameter is <tt>true</tt>, the
6039 <tt>llvm.memmove</tt> call is a <a href="#volatile">volatile operation</a>.
6040 The detailed access behavior is not very cleanly specified and it is unwise
6041 to depend on it.</p>
6045 <p>The '<tt>llvm.memmove.*</tt>' intrinsics copy a block of memory from the
6046 source location to the destination location, which may overlap. It copies
6047 "len" bytes of memory over. If the argument is known to be aligned to some
6048 boundary, this can be specified as the fourth argument, otherwise it should
6049 be set to 0 or 1.</p>
6053 <!-- _______________________________________________________________________ -->
6054 <div class="doc_subsubsection">
6055 <a name="int_memset">'<tt>llvm.memset.*</tt>' Intrinsics</a>
6058 <div class="doc_text">
6061 <p>This is an overloaded intrinsic. You can use llvm.memset on any integer bit
6062 width and for different address spaces. Not all targets support all bit
6066 declare void @llvm.memset.p0i8.i32(i8 * <dest>, i8 <val>,
6067 i32 <len>, i32 <align>, i1 <isvolatile>)
6068 declare void @llvm.memset.p0i8.i64(i8 * <dest>, i8 <val>,
6069 i64 <len>, i32 <align>, i1 <isvolatile>)
6073 <p>The '<tt>llvm.memset.*</tt>' intrinsics fill a block of memory with a
6074 particular byte value.</p>
6076 <p>Note that, unlike the standard libc function, the <tt>llvm.memset</tt>
6077 intrinsic does not return a value, takes extra alignment/volatile arguments,
6078 and the destination can be in an arbitrary address space.</p>
6081 <p>The first argument is a pointer to the destination to fill, the second is the
6082 byte value to fill it with, the third argument is an integer argument
6083 specifying the number of bytes to fill, and the fourth argument is the known
6084 alignment of destination location.</p>
6086 <p>If the call to this intrinsic has an alignment value that is not 0 or 1,
6087 then the caller guarantees that the destination pointer is aligned to that
6090 <p>If the <tt>isvolatile</tt> parameter is <tt>true</tt>, the
6091 <tt>llvm.memset</tt> call is a <a href="#volatile">volatile operation</a>.
6092 The detailed access behavior is not very cleanly specified and it is unwise
6093 to depend on it.</p>
6096 <p>The '<tt>llvm.memset.*</tt>' intrinsics fill "len" bytes of memory starting
6097 at the destination location. If the argument is known to be aligned to some
6098 boundary, this can be specified as the fourth argument, otherwise it should
6099 be set to 0 or 1.</p>
6103 <!-- _______________________________________________________________________ -->
6104 <div class="doc_subsubsection">
6105 <a name="int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a>
6108 <div class="doc_text">
6111 <p>This is an overloaded intrinsic. You can use <tt>llvm.sqrt</tt> on any
6112 floating point or vector of floating point type. Not all targets support all
6116 declare float @llvm.sqrt.f32(float %Val)
6117 declare double @llvm.sqrt.f64(double %Val)
6118 declare x86_fp80 @llvm.sqrt.f80(x86_fp80 %Val)
6119 declare fp128 @llvm.sqrt.f128(fp128 %Val)
6120 declare ppc_fp128 @llvm.sqrt.ppcf128(ppc_fp128 %Val)
6124 <p>The '<tt>llvm.sqrt</tt>' intrinsics return the sqrt of the specified operand,
6125 returning the same value as the libm '<tt>sqrt</tt>' functions would.
6126 Unlike <tt>sqrt</tt> in libm, however, <tt>llvm.sqrt</tt> has undefined
6127 behavior for negative numbers other than -0.0 (which allows for better
6128 optimization, because there is no need to worry about errno being
6129 set). <tt>llvm.sqrt(-0.0)</tt> is defined to return -0.0 like IEEE sqrt.</p>
6132 <p>The argument and return value are floating point numbers of the same
6136 <p>This function returns the sqrt of the specified operand if it is a
6137 nonnegative floating point number.</p>
6141 <!-- _______________________________________________________________________ -->
6142 <div class="doc_subsubsection">
6143 <a name="int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a>
6146 <div class="doc_text">
6149 <p>This is an overloaded intrinsic. You can use <tt>llvm.powi</tt> on any
6150 floating point or vector of floating point type. Not all targets support all
6154 declare float @llvm.powi.f32(float %Val, i32 %power)
6155 declare double @llvm.powi.f64(double %Val, i32 %power)
6156 declare x86_fp80 @llvm.powi.f80(x86_fp80 %Val, i32 %power)
6157 declare fp128 @llvm.powi.f128(fp128 %Val, i32 %power)
6158 declare ppc_fp128 @llvm.powi.ppcf128(ppc_fp128 %Val, i32 %power)
6162 <p>The '<tt>llvm.powi.*</tt>' intrinsics return the first operand raised to the
6163 specified (positive or negative) power. The order of evaluation of
6164 multiplications is not defined. When a vector of floating point type is
6165 used, the second argument remains a scalar integer value.</p>
6168 <p>The second argument is an integer power, and the first is a value to raise to
6172 <p>This function returns the first value raised to the second power with an
6173 unspecified sequence of rounding operations.</p>
6177 <!-- _______________________________________________________________________ -->
6178 <div class="doc_subsubsection">
6179 <a name="int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a>
6182 <div class="doc_text">
6185 <p>This is an overloaded intrinsic. You can use <tt>llvm.sin</tt> on any
6186 floating point or vector of floating point type. Not all targets support all
6190 declare float @llvm.sin.f32(float %Val)
6191 declare double @llvm.sin.f64(double %Val)
6192 declare x86_fp80 @llvm.sin.f80(x86_fp80 %Val)
6193 declare fp128 @llvm.sin.f128(fp128 %Val)
6194 declare ppc_fp128 @llvm.sin.ppcf128(ppc_fp128 %Val)
6198 <p>The '<tt>llvm.sin.*</tt>' intrinsics return the sine of the operand.</p>
6201 <p>The argument and return value are floating point numbers of the same
6205 <p>This function returns the sine of the specified operand, returning the same
6206 values as the libm <tt>sin</tt> functions would, and handles error conditions
6207 in the same way.</p>
6211 <!-- _______________________________________________________________________ -->
6212 <div class="doc_subsubsection">
6213 <a name="int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a>
6216 <div class="doc_text">
6219 <p>This is an overloaded intrinsic. You can use <tt>llvm.cos</tt> on any
6220 floating point or vector of floating point type. Not all targets support all
6224 declare float @llvm.cos.f32(float %Val)
6225 declare double @llvm.cos.f64(double %Val)
6226 declare x86_fp80 @llvm.cos.f80(x86_fp80 %Val)
6227 declare fp128 @llvm.cos.f128(fp128 %Val)
6228 declare ppc_fp128 @llvm.cos.ppcf128(ppc_fp128 %Val)
6232 <p>The '<tt>llvm.cos.*</tt>' intrinsics return the cosine of the operand.</p>
6235 <p>The argument and return value are floating point numbers of the same
6239 <p>This function returns the cosine of the specified operand, returning the same
6240 values as the libm <tt>cos</tt> functions would, and handles error conditions
6241 in the same way.</p>
6245 <!-- _______________________________________________________________________ -->
6246 <div class="doc_subsubsection">
6247 <a name="int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a>
6250 <div class="doc_text">
6253 <p>This is an overloaded intrinsic. You can use <tt>llvm.pow</tt> on any
6254 floating point or vector of floating point type. Not all targets support all
6258 declare float @llvm.pow.f32(float %Val, float %Power)
6259 declare double @llvm.pow.f64(double %Val, double %Power)
6260 declare x86_fp80 @llvm.pow.f80(x86_fp80 %Val, x86_fp80 %Power)
6261 declare fp128 @llvm.pow.f128(fp128 %Val, fp128 %Power)
6262 declare ppc_fp128 @llvm.pow.ppcf128(ppc_fp128 %Val, ppc_fp128 Power)
6266 <p>The '<tt>llvm.pow.*</tt>' intrinsics return the first operand raised to the
6267 specified (positive or negative) power.</p>
6270 <p>The second argument is a floating point power, and the first is a value to
6271 raise to that power.</p>
6274 <p>This function returns the first value raised to the second power, returning
6275 the same values as the libm <tt>pow</tt> functions would, and handles error
6276 conditions in the same way.</p>
6280 <!-- ======================================================================= -->
6281 <div class="doc_subsection">
6282 <a name="int_manip">Bit Manipulation Intrinsics</a>
6285 <div class="doc_text">
6287 <p>LLVM provides intrinsics for a few important bit manipulation operations.
6288 These allow efficient code generation for some algorithms.</p>
6292 <!-- _______________________________________________________________________ -->
6293 <div class="doc_subsubsection">
6294 <a name="int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a>
6297 <div class="doc_text">
6300 <p>This is an overloaded intrinsic function. You can use bswap on any integer
6301 type that is an even number of bytes (i.e. BitWidth % 16 == 0).</p>
6304 declare i16 @llvm.bswap.i16(i16 <id>)
6305 declare i32 @llvm.bswap.i32(i32 <id>)
6306 declare i64 @llvm.bswap.i64(i64 <id>)
6310 <p>The '<tt>llvm.bswap</tt>' family of intrinsics is used to byte swap integer
6311 values with an even number of bytes (positive multiple of 16 bits). These
6312 are useful for performing operations on data that is not in the target's
6313 native byte order.</p>
6316 <p>The <tt>llvm.bswap.i16</tt> intrinsic returns an i16 value that has the high
6317 and low byte of the input i16 swapped. Similarly,
6318 the <tt>llvm.bswap.i32</tt> intrinsic returns an i32 value that has the four
6319 bytes of the input i32 swapped, so that if the input bytes are numbered 0, 1,
6320 2, 3 then the returned i32 will have its bytes in 3, 2, 1, 0 order.
6321 The <tt>llvm.bswap.i48</tt>, <tt>llvm.bswap.i64</tt> and other intrinsics
6322 extend this concept to additional even-byte lengths (6 bytes, 8 bytes and
6323 more, respectively).</p>
6327 <!-- _______________________________________________________________________ -->
6328 <div class="doc_subsubsection">
6329 <a name="int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic</a>
6332 <div class="doc_text">
6335 <p>This is an overloaded intrinsic. You can use llvm.ctpop on any integer bit
6336 width. Not all targets support all bit widths however.</p>
6339 declare i8 @llvm.ctpop.i8(i8 <src>)
6340 declare i16 @llvm.ctpop.i16(i16 <src>)
6341 declare i32 @llvm.ctpop.i32(i32 <src>)
6342 declare i64 @llvm.ctpop.i64(i64 <src>)
6343 declare i256 @llvm.ctpop.i256(i256 <src>)
6347 <p>The '<tt>llvm.ctpop</tt>' family of intrinsics counts the number of bits set
6351 <p>The only argument is the value to be counted. The argument may be of any
6352 integer type. The return type must match the argument type.</p>
6355 <p>The '<tt>llvm.ctpop</tt>' intrinsic counts the 1's in a variable.</p>
6359 <!-- _______________________________________________________________________ -->
6360 <div class="doc_subsubsection">
6361 <a name="int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic</a>
6364 <div class="doc_text">
6367 <p>This is an overloaded intrinsic. You can use <tt>llvm.ctlz</tt> on any
6368 integer bit width. Not all targets support all bit widths however.</p>
6371 declare i8 @llvm.ctlz.i8 (i8 <src>)
6372 declare i16 @llvm.ctlz.i16(i16 <src>)
6373 declare i32 @llvm.ctlz.i32(i32 <src>)
6374 declare i64 @llvm.ctlz.i64(i64 <src>)
6375 declare i256 @llvm.ctlz.i256(i256 <src>)
6379 <p>The '<tt>llvm.ctlz</tt>' family of intrinsic functions counts the number of
6380 leading zeros in a variable.</p>
6383 <p>The only argument is the value to be counted. The argument may be of any
6384 integer type. The return type must match the argument type.</p>
6387 <p>The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant)
6388 zeros in a variable. If the src == 0 then the result is the size in bits of
6389 the type of src. For example, <tt>llvm.ctlz(i32 2) = 30</tt>.</p>
6393 <!-- _______________________________________________________________________ -->
6394 <div class="doc_subsubsection">
6395 <a name="int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic</a>
6398 <div class="doc_text">
6401 <p>This is an overloaded intrinsic. You can use <tt>llvm.cttz</tt> on any
6402 integer bit width. Not all targets support all bit widths however.</p>
6405 declare i8 @llvm.cttz.i8 (i8 <src>)
6406 declare i16 @llvm.cttz.i16(i16 <src>)
6407 declare i32 @llvm.cttz.i32(i32 <src>)
6408 declare i64 @llvm.cttz.i64(i64 <src>)
6409 declare i256 @llvm.cttz.i256(i256 <src>)
6413 <p>The '<tt>llvm.cttz</tt>' family of intrinsic functions counts the number of
6417 <p>The only argument is the value to be counted. The argument may be of any
6418 integer type. The return type must match the argument type.</p>
6421 <p>The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant)
6422 zeros in a variable. If the src == 0 then the result is the size in bits of
6423 the type of src. For example, <tt>llvm.cttz(2) = 1</tt>.</p>
6427 <!-- ======================================================================= -->
6428 <div class="doc_subsection">
6429 <a name="int_overflow">Arithmetic with Overflow Intrinsics</a>
6432 <div class="doc_text">
6434 <p>LLVM provides intrinsics for some arithmetic with overflow operations.</p>
6438 <!-- _______________________________________________________________________ -->
6439 <div class="doc_subsubsection">
6440 <a name="int_sadd_overflow">'<tt>llvm.sadd.with.overflow.*</tt>' Intrinsics</a>
6443 <div class="doc_text">
6446 <p>This is an overloaded intrinsic. You can use <tt>llvm.sadd.with.overflow</tt>
6447 on any integer bit width.</p>
6450 declare {i16, i1} @llvm.sadd.with.overflow.i16(i16 %a, i16 %b)
6451 declare {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
6452 declare {i64, i1} @llvm.sadd.with.overflow.i64(i64 %a, i64 %b)
6456 <p>The '<tt>llvm.sadd.with.overflow</tt>' family of intrinsic functions perform
6457 a signed addition of the two arguments, and indicate whether an overflow
6458 occurred during the signed summation.</p>
6461 <p>The arguments (%a and %b) and the first element of the result structure may
6462 be of integer types of any bit width, but they must have the same bit
6463 width. The second element of the result structure must be of
6464 type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
6465 undergo signed addition.</p>
6468 <p>The '<tt>llvm.sadd.with.overflow</tt>' family of intrinsic functions perform
6469 a signed addition of the two variables. They return a structure — the
6470 first element of which is the signed summation, and the second element of
6471 which is a bit specifying if the signed summation resulted in an
6476 %res = call {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
6477 %sum = extractvalue {i32, i1} %res, 0
6478 %obit = extractvalue {i32, i1} %res, 1
6479 br i1 %obit, label %overflow, label %normal
6484 <!-- _______________________________________________________________________ -->
6485 <div class="doc_subsubsection">
6486 <a name="int_uadd_overflow">'<tt>llvm.uadd.with.overflow.*</tt>' Intrinsics</a>
6489 <div class="doc_text">
6492 <p>This is an overloaded intrinsic. You can use <tt>llvm.uadd.with.overflow</tt>
6493 on any integer bit width.</p>
6496 declare {i16, i1} @llvm.uadd.with.overflow.i16(i16 %a, i16 %b)
6497 declare {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
6498 declare {i64, i1} @llvm.uadd.with.overflow.i64(i64 %a, i64 %b)
6502 <p>The '<tt>llvm.uadd.with.overflow</tt>' family of intrinsic functions perform
6503 an unsigned addition of the two arguments, and indicate whether a carry
6504 occurred during the unsigned summation.</p>
6507 <p>The arguments (%a and %b) and the first element of the result structure may
6508 be of integer types of any bit width, but they must have the same bit
6509 width. The second element of the result structure must be of
6510 type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
6511 undergo unsigned addition.</p>
6514 <p>The '<tt>llvm.uadd.with.overflow</tt>' family of intrinsic functions perform
6515 an unsigned addition of the two arguments. They return a structure —
6516 the first element of which is the sum, and the second element of which is a
6517 bit specifying if the unsigned summation resulted in a carry.</p>
6521 %res = call {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
6522 %sum = extractvalue {i32, i1} %res, 0
6523 %obit = extractvalue {i32, i1} %res, 1
6524 br i1 %obit, label %carry, label %normal
6529 <!-- _______________________________________________________________________ -->
6530 <div class="doc_subsubsection">
6531 <a name="int_ssub_overflow">'<tt>llvm.ssub.with.overflow.*</tt>' Intrinsics</a>
6534 <div class="doc_text">
6537 <p>This is an overloaded intrinsic. You can use <tt>llvm.ssub.with.overflow</tt>
6538 on any integer bit width.</p>
6541 declare {i16, i1} @llvm.ssub.with.overflow.i16(i16 %a, i16 %b)
6542 declare {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b)
6543 declare {i64, i1} @llvm.ssub.with.overflow.i64(i64 %a, i64 %b)
6547 <p>The '<tt>llvm.ssub.with.overflow</tt>' family of intrinsic functions perform
6548 a signed subtraction of the two arguments, and indicate whether an overflow
6549 occurred during the signed subtraction.</p>
6552 <p>The arguments (%a and %b) and the first element of the result structure may
6553 be of integer types of any bit width, but they must have the same bit
6554 width. The second element of the result structure must be of
6555 type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
6556 undergo signed subtraction.</p>
6559 <p>The '<tt>llvm.ssub.with.overflow</tt>' family of intrinsic functions perform
6560 a signed subtraction of the two arguments. They return a structure —
6561 the first element of which is the subtraction, and the second element of
6562 which is a bit specifying if the signed subtraction resulted in an
6567 %res = call {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b)
6568 %sum = extractvalue {i32, i1} %res, 0
6569 %obit = extractvalue {i32, i1} %res, 1
6570 br i1 %obit, label %overflow, label %normal
6575 <!-- _______________________________________________________________________ -->
6576 <div class="doc_subsubsection">
6577 <a name="int_usub_overflow">'<tt>llvm.usub.with.overflow.*</tt>' Intrinsics</a>
6580 <div class="doc_text">
6583 <p>This is an overloaded intrinsic. You can use <tt>llvm.usub.with.overflow</tt>
6584 on any integer bit width.</p>
6587 declare {i16, i1} @llvm.usub.with.overflow.i16(i16 %a, i16 %b)
6588 declare {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b)
6589 declare {i64, i1} @llvm.usub.with.overflow.i64(i64 %a, i64 %b)
6593 <p>The '<tt>llvm.usub.with.overflow</tt>' family of intrinsic functions perform
6594 an unsigned subtraction of the two arguments, and indicate whether an
6595 overflow occurred during the unsigned subtraction.</p>
6598 <p>The arguments (%a and %b) and the first element of the result structure may
6599 be of integer types of any bit width, but they must have the same bit
6600 width. The second element of the result structure must be of
6601 type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
6602 undergo unsigned subtraction.</p>
6605 <p>The '<tt>llvm.usub.with.overflow</tt>' family of intrinsic functions perform
6606 an unsigned subtraction of the two arguments. They return a structure —
6607 the first element of which is the subtraction, and the second element of
6608 which is a bit specifying if the unsigned subtraction resulted in an
6613 %res = call {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b)
6614 %sum = extractvalue {i32, i1} %res, 0
6615 %obit = extractvalue {i32, i1} %res, 1
6616 br i1 %obit, label %overflow, label %normal
6621 <!-- _______________________________________________________________________ -->
6622 <div class="doc_subsubsection">
6623 <a name="int_smul_overflow">'<tt>llvm.smul.with.overflow.*</tt>' Intrinsics</a>
6626 <div class="doc_text">
6629 <p>This is an overloaded intrinsic. You can use <tt>llvm.smul.with.overflow</tt>
6630 on any integer bit width.</p>
6633 declare {i16, i1} @llvm.smul.with.overflow.i16(i16 %a, i16 %b)
6634 declare {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b)
6635 declare {i64, i1} @llvm.smul.with.overflow.i64(i64 %a, i64 %b)
6640 <p>The '<tt>llvm.smul.with.overflow</tt>' family of intrinsic functions perform
6641 a signed multiplication of the two arguments, and indicate whether an
6642 overflow occurred during the signed multiplication.</p>
6645 <p>The arguments (%a and %b) and the first element of the result structure may
6646 be of integer types of any bit width, but they must have the same bit
6647 width. The second element of the result structure must be of
6648 type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
6649 undergo signed multiplication.</p>
6652 <p>The '<tt>llvm.smul.with.overflow</tt>' family of intrinsic functions perform
6653 a signed multiplication of the two arguments. They return a structure —
6654 the first element of which is the multiplication, and the second element of
6655 which is a bit specifying if the signed multiplication resulted in an
6660 %res = call {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b)
6661 %sum = extractvalue {i32, i1} %res, 0
6662 %obit = extractvalue {i32, i1} %res, 1
6663 br i1 %obit, label %overflow, label %normal
6668 <!-- _______________________________________________________________________ -->
6669 <div class="doc_subsubsection">
6670 <a name="int_umul_overflow">'<tt>llvm.umul.with.overflow.*</tt>' Intrinsics</a>
6673 <div class="doc_text">
6676 <p>This is an overloaded intrinsic. You can use <tt>llvm.umul.with.overflow</tt>
6677 on any integer bit width.</p>
6680 declare {i16, i1} @llvm.umul.with.overflow.i16(i16 %a, i16 %b)
6681 declare {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b)
6682 declare {i64, i1} @llvm.umul.with.overflow.i64(i64 %a, i64 %b)
6686 <p>The '<tt>llvm.umul.with.overflow</tt>' family of intrinsic functions perform
6687 a unsigned multiplication of the two arguments, and indicate whether an
6688 overflow occurred during the unsigned multiplication.</p>
6691 <p>The arguments (%a and %b) and the first element of the result structure may
6692 be of integer types of any bit width, but they must have the same bit
6693 width. The second element of the result structure must be of
6694 type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will
6695 undergo unsigned multiplication.</p>
6698 <p>The '<tt>llvm.umul.with.overflow</tt>' family of intrinsic functions perform
6699 an unsigned multiplication of the two arguments. They return a structure
6700 — the first element of which is the multiplication, and the second
6701 element of which is a bit specifying if the unsigned multiplication resulted
6706 %res = call {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b)
6707 %sum = extractvalue {i32, i1} %res, 0
6708 %obit = extractvalue {i32, i1} %res, 1
6709 br i1 %obit, label %overflow, label %normal
6714 <!-- ======================================================================= -->
6715 <div class="doc_subsection">
6716 <a name="int_fp16">Half Precision Floating Point Intrinsics</a>
6719 <div class="doc_text">
6721 <p>Half precision floating point is a storage-only format. This means that it is
6722 a dense encoding (in memory) but does not support computation in the
6725 <p>This means that code must first load the half-precision floating point
6726 value as an i16, then convert it to float with <a
6727 href="#int_convert_from_fp16"><tt>llvm.convert.from.fp16</tt></a>.
6728 Computation can then be performed on the float value (including extending to
6729 double etc). To store the value back to memory, it is first converted to
6730 float if needed, then converted to i16 with
6731 <a href="#int_convert_to_fp16"><tt>llvm.convert.to.fp16</tt></a>, then
6732 storing as an i16 value.</p>
6735 <!-- _______________________________________________________________________ -->
6736 <div class="doc_subsubsection">
6737 <a name="int_convert_to_fp16">'<tt>llvm.convert.to.fp16</tt>' Intrinsic</a>
6740 <div class="doc_text">
6744 declare i16 @llvm.convert.to.fp16(f32 %a)
6748 <p>The '<tt>llvm.convert.to.fp16</tt>' intrinsic function performs
6749 a conversion from single precision floating point format to half precision
6750 floating point format.</p>
6753 <p>The intrinsic function contains single argument - the value to be
6757 <p>The '<tt>llvm.convert.to.fp16</tt>' intrinsic function performs
6758 a conversion from single precision floating point format to half precision
6759 floating point format. The return value is an <tt>i16</tt> which
6760 contains the converted number.</p>
6764 %res = call i16 @llvm.convert.to.fp16(f32 %a)
6765 store i16 %res, i16* @x, align 2
6770 <!-- _______________________________________________________________________ -->
6771 <div class="doc_subsubsection">
6772 <a name="int_convert_from_fp16">'<tt>llvm.convert.from.fp16</tt>' Intrinsic</a>
6775 <div class="doc_text">
6779 declare f32 @llvm.convert.from.fp16(i16 %a)
6783 <p>The '<tt>llvm.convert.from.fp16</tt>' intrinsic function performs
6784 a conversion from half precision floating point format to single precision
6785 floating point format.</p>
6788 <p>The intrinsic function contains single argument - the value to be
6792 <p>The '<tt>llvm.convert.from.fp16</tt>' intrinsic function performs a
6793 conversion from half single precision floating point format to single
6794 precision floating point format. The input half-float value is represented by
6795 an <tt>i16</tt> value.</p>
6799 %a = load i16* @x, align 2
6800 %res = call f32 @llvm.convert.from.fp16(i16 %a)
6805 <!-- ======================================================================= -->
6806 <div class="doc_subsection">
6807 <a name="int_debugger">Debugger Intrinsics</a>
6810 <div class="doc_text">
6812 <p>The LLVM debugger intrinsics (which all start with <tt>llvm.dbg.</tt>
6813 prefix), are described in
6814 the <a href="SourceLevelDebugging.html#format_common_intrinsics">LLVM Source
6815 Level Debugging</a> document.</p>
6819 <!-- ======================================================================= -->
6820 <div class="doc_subsection">
6821 <a name="int_eh">Exception Handling Intrinsics</a>
6824 <div class="doc_text">
6826 <p>The LLVM exception handling intrinsics (which all start with
6827 <tt>llvm.eh.</tt> prefix), are described in
6828 the <a href="ExceptionHandling.html#format_common_intrinsics">LLVM Exception
6829 Handling</a> document.</p>
6833 <!-- ======================================================================= -->
6834 <div class="doc_subsection">
6835 <a name="int_trampoline">Trampoline Intrinsic</a>
6838 <div class="doc_text">
6840 <p>This intrinsic makes it possible to excise one parameter, marked with
6841 the <tt>nest</tt> attribute, from a function. The result is a callable
6842 function pointer lacking the nest parameter - the caller does not need to
6843 provide a value for it. Instead, the value to use is stored in advance in a
6844 "trampoline", a block of memory usually allocated on the stack, which also
6845 contains code to splice the nest value into the argument list. This is used
6846 to implement the GCC nested function address extension.</p>
6848 <p>For example, if the function is
6849 <tt>i32 f(i8* nest %c, i32 %x, i32 %y)</tt> then the resulting function
6850 pointer has signature <tt>i32 (i32, i32)*</tt>. It can be created as
6853 <div class="doc_code">
6855 %tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86
6856 %tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0
6857 %p = call i8* @llvm.init.trampoline( i8* %tramp1, i8* bitcast (i32 (i8* nest , i32, i32)* @f to i8*), i8* %nval )
6858 %fp = bitcast i8* %p to i32 (i32, i32)*
6862 <p>The call <tt>%val = call i32 %fp( i32 %x, i32 %y )</tt> is then equivalent
6863 to <tt>%val = call i32 %f( i8* %nval, i32 %x, i32 %y )</tt>.</p>
6867 <!-- _______________________________________________________________________ -->
6868 <div class="doc_subsubsection">
6869 <a name="int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a>
6872 <div class="doc_text">
6876 declare i8* @llvm.init.trampoline(i8* <tramp>, i8* <func>, i8* <nval>)
6880 <p>This fills the memory pointed to by <tt>tramp</tt> with code and returns a
6881 function pointer suitable for executing it.</p>
6884 <p>The <tt>llvm.init.trampoline</tt> intrinsic takes three arguments, all
6885 pointers. The <tt>tramp</tt> argument must point to a sufficiently large and
6886 sufficiently aligned block of memory; this memory is written to by the
6887 intrinsic. Note that the size and the alignment are target-specific - LLVM
6888 currently provides no portable way of determining them, so a front-end that
6889 generates this intrinsic needs to have some target-specific knowledge.
6890 The <tt>func</tt> argument must hold a function bitcast to
6891 an <tt>i8*</tt>.</p>
6894 <p>The block of memory pointed to by <tt>tramp</tt> is filled with target
6895 dependent code, turning it into a function. A pointer to this function is
6896 returned, but needs to be bitcast to an <a href="#int_trampoline">appropriate
6897 function pointer type</a> before being called. The new function's signature
6898 is the same as that of <tt>func</tt> with any arguments marked with
6899 the <tt>nest</tt> attribute removed. At most one such <tt>nest</tt> argument
6900 is allowed, and it must be of pointer type. Calling the new function is
6901 equivalent to calling <tt>func</tt> with the same argument list, but
6902 with <tt>nval</tt> used for the missing <tt>nest</tt> argument. If, after
6903 calling <tt>llvm.init.trampoline</tt>, the memory pointed to
6904 by <tt>tramp</tt> is modified, then the effect of any later call to the
6905 returned function pointer is undefined.</p>
6909 <!-- ======================================================================= -->
6910 <div class="doc_subsection">
6911 <a name="int_atomics">Atomic Operations and Synchronization Intrinsics</a>
6914 <div class="doc_text">
6916 <p>These intrinsic functions expand the "universal IR" of LLVM to represent
6917 hardware constructs for atomic operations and memory synchronization. This
6918 provides an interface to the hardware, not an interface to the programmer. It
6919 is aimed at a low enough level to allow any programming models or APIs
6920 (Application Programming Interfaces) which need atomic behaviors to map
6921 cleanly onto it. It is also modeled primarily on hardware behavior. Just as
6922 hardware provides a "universal IR" for source languages, it also provides a
6923 starting point for developing a "universal" atomic operation and
6924 synchronization IR.</p>
6926 <p>These do <em>not</em> form an API such as high-level threading libraries,
6927 software transaction memory systems, atomic primitives, and intrinsic
6928 functions as found in BSD, GNU libc, atomic_ops, APR, and other system and
6929 application libraries. The hardware interface provided by LLVM should allow
6930 a clean implementation of all of these APIs and parallel programming models.
6931 No one model or paradigm should be selected above others unless the hardware
6932 itself ubiquitously does so.</p>
6936 <!-- _______________________________________________________________________ -->
6937 <div class="doc_subsubsection">
6938 <a name="int_memory_barrier">'<tt>llvm.memory.barrier</tt>' Intrinsic</a>
6940 <div class="doc_text">
6943 declare void @llvm.memory.barrier( i1 <ll>, i1 <ls>, i1 <sl>, i1 <ss>, i1 <device> )
6947 <p>The <tt>llvm.memory.barrier</tt> intrinsic guarantees ordering between
6948 specific pairs of memory access types.</p>
6951 <p>The <tt>llvm.memory.barrier</tt> intrinsic requires five boolean arguments.
6952 The first four arguments enables a specific barrier as listed below. The
6953 fifth argument specifies that the barrier applies to io or device or uncached
6957 <li><tt>ll</tt>: load-load barrier</li>
6958 <li><tt>ls</tt>: load-store barrier</li>
6959 <li><tt>sl</tt>: store-load barrier</li>
6960 <li><tt>ss</tt>: store-store barrier</li>
6961 <li><tt>device</tt>: barrier applies to device and uncached memory also.</li>
6965 <p>This intrinsic causes the system to enforce some ordering constraints upon
6966 the loads and stores of the program. This barrier does not
6967 indicate <em>when</em> any events will occur, it only enforces
6968 an <em>order</em> in which they occur. For any of the specified pairs of load
6969 and store operations (f.ex. load-load, or store-load), all of the first
6970 operations preceding the barrier will complete before any of the second
6971 operations succeeding the barrier begin. Specifically the semantics for each
6972 pairing is as follows:</p>
6975 <li><tt>ll</tt>: All loads before the barrier must complete before any load
6976 after the barrier begins.</li>
6977 <li><tt>ls</tt>: All loads before the barrier must complete before any
6978 store after the barrier begins.</li>
6979 <li><tt>ss</tt>: All stores before the barrier must complete before any
6980 store after the barrier begins.</li>
6981 <li><tt>sl</tt>: All stores before the barrier must complete before any
6982 load after the barrier begins.</li>
6985 <p>These semantics are applied with a logical "and" behavior when more than one
6986 is enabled in a single memory barrier intrinsic.</p>
6988 <p>Backends may implement stronger barriers than those requested when they do
6989 not support as fine grained a barrier as requested. Some architectures do
6990 not need all types of barriers and on such architectures, these become
6995 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
6996 %ptr = bitcast i8* %mallocP to i32*
6999 %result1 = load i32* %ptr <i>; yields {i32}:result1 = 4</i>
7000 call void @llvm.memory.barrier( i1 false, i1 true, i1 false, i1 false )
7001 <i>; guarantee the above finishes</i>
7002 store i32 8, %ptr <i>; before this begins</i>
7007 <!-- _______________________________________________________________________ -->
7008 <div class="doc_subsubsection">
7009 <a name="int_atomic_cmp_swap">'<tt>llvm.atomic.cmp.swap.*</tt>' Intrinsic</a>
7012 <div class="doc_text">
7015 <p>This is an overloaded intrinsic. You can use <tt>llvm.atomic.cmp.swap</tt> on
7016 any integer bit width and for different address spaces. Not all targets
7017 support all bit widths however.</p>
7020 declare i8 @llvm.atomic.cmp.swap.i8.p0i8( i8* <ptr>, i8 <cmp>, i8 <val> )
7021 declare i16 @llvm.atomic.cmp.swap.i16.p0i16( i16* <ptr>, i16 <cmp>, i16 <val> )
7022 declare i32 @llvm.atomic.cmp.swap.i32.p0i32( i32* <ptr>, i32 <cmp>, i32 <val> )
7023 declare i64 @llvm.atomic.cmp.swap.i64.p0i64( i64* <ptr>, i64 <cmp>, i64 <val> )
7027 <p>This loads a value in memory and compares it to a given value. If they are
7028 equal, it stores a new value into the memory.</p>
7031 <p>The <tt>llvm.atomic.cmp.swap</tt> intrinsic takes three arguments. The result
7032 as well as both <tt>cmp</tt> and <tt>val</tt> must be integer values with the
7033 same bit width. The <tt>ptr</tt> argument must be a pointer to a value of
7034 this integer type. While any bit width integer may be used, targets may only
7035 lower representations they support in hardware.</p>
7038 <p>This entire intrinsic must be executed atomically. It first loads the value
7039 in memory pointed to by <tt>ptr</tt> and compares it with the
7040 value <tt>cmp</tt>. If they are equal, <tt>val</tt> is stored into the
7041 memory. The loaded value is yielded in all cases. This provides the
7042 equivalent of an atomic compare-and-swap operation within the SSA
7047 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7048 %ptr = bitcast i8* %mallocP to i32*
7051 %val1 = add i32 4, 4
7052 %result1 = call i32 @llvm.atomic.cmp.swap.i32.p0i32( i32* %ptr, i32 4, %val1 )
7053 <i>; yields {i32}:result1 = 4</i>
7054 %stored1 = icmp eq i32 %result1, 4 <i>; yields {i1}:stored1 = true</i>
7055 %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 8</i>
7057 %val2 = add i32 1, 1
7058 %result2 = call i32 @llvm.atomic.cmp.swap.i32.p0i32( i32* %ptr, i32 5, %val2 )
7059 <i>; yields {i32}:result2 = 8</i>
7060 %stored2 = icmp eq i32 %result2, 5 <i>; yields {i1}:stored2 = false</i>
7062 %memval2 = load i32* %ptr <i>; yields {i32}:memval2 = 8</i>
7067 <!-- _______________________________________________________________________ -->
7068 <div class="doc_subsubsection">
7069 <a name="int_atomic_swap">'<tt>llvm.atomic.swap.*</tt>' Intrinsic</a>
7071 <div class="doc_text">
7074 <p>This is an overloaded intrinsic. You can use <tt>llvm.atomic.swap</tt> on any
7075 integer bit width. Not all targets support all bit widths however.</p>
7078 declare i8 @llvm.atomic.swap.i8.p0i8( i8* <ptr>, i8 <val> )
7079 declare i16 @llvm.atomic.swap.i16.p0i16( i16* <ptr>, i16 <val> )
7080 declare i32 @llvm.atomic.swap.i32.p0i32( i32* <ptr>, i32 <val> )
7081 declare i64 @llvm.atomic.swap.i64.p0i64( i64* <ptr>, i64 <val> )
7085 <p>This intrinsic loads the value stored in memory at <tt>ptr</tt> and yields
7086 the value from memory. It then stores the value in <tt>val</tt> in the memory
7087 at <tt>ptr</tt>.</p>
7090 <p>The <tt>llvm.atomic.swap</tt> intrinsic takes two arguments. Both
7091 the <tt>val</tt> argument and the result must be integers of the same bit
7092 width. The first argument, <tt>ptr</tt>, must be a pointer to a value of this
7093 integer type. The targets may only lower integer representations they
7097 <p>This intrinsic loads the value pointed to by <tt>ptr</tt>, yields it, and
7098 stores <tt>val</tt> back into <tt>ptr</tt> atomically. This provides the
7099 equivalent of an atomic swap operation within the SSA framework.</p>
7103 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7104 %ptr = bitcast i8* %mallocP to i32*
7107 %val1 = add i32 4, 4
7108 %result1 = call i32 @llvm.atomic.swap.i32.p0i32( i32* %ptr, i32 %val1 )
7109 <i>; yields {i32}:result1 = 4</i>
7110 %stored1 = icmp eq i32 %result1, 4 <i>; yields {i1}:stored1 = true</i>
7111 %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 8</i>
7113 %val2 = add i32 1, 1
7114 %result2 = call i32 @llvm.atomic.swap.i32.p0i32( i32* %ptr, i32 %val2 )
7115 <i>; yields {i32}:result2 = 8</i>
7117 %stored2 = icmp eq i32 %result2, 8 <i>; yields {i1}:stored2 = true</i>
7118 %memval2 = load i32* %ptr <i>; yields {i32}:memval2 = 2</i>
7123 <!-- _______________________________________________________________________ -->
7124 <div class="doc_subsubsection">
7125 <a name="int_atomic_load_add">'<tt>llvm.atomic.load.add.*</tt>' Intrinsic</a>
7129 <div class="doc_text">
7132 <p>This is an overloaded intrinsic. You can use <tt>llvm.atomic.load.add</tt> on
7133 any integer bit width. Not all targets support all bit widths however.</p>
7136 declare i8 @llvm.atomic.load.add.i8..p0i8( i8* <ptr>, i8 <delta> )
7137 declare i16 @llvm.atomic.load.add.i16..p0i16( i16* <ptr>, i16 <delta> )
7138 declare i32 @llvm.atomic.load.add.i32..p0i32( i32* <ptr>, i32 <delta> )
7139 declare i64 @llvm.atomic.load.add.i64..p0i64( i64* <ptr>, i64 <delta> )
7143 <p>This intrinsic adds <tt>delta</tt> to the value stored in memory
7144 at <tt>ptr</tt>. It yields the original value at <tt>ptr</tt>.</p>
7147 <p>The intrinsic takes two arguments, the first a pointer to an integer value
7148 and the second an integer value. The result is also an integer value. These
7149 integer types can have any bit width, but they must all have the same bit
7150 width. The targets may only lower integer representations they support.</p>
7153 <p>This intrinsic does a series of operations atomically. It first loads the
7154 value stored at <tt>ptr</tt>. It then adds <tt>delta</tt>, stores the result
7155 to <tt>ptr</tt>. It yields the original value stored at <tt>ptr</tt>.</p>
7159 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7160 %ptr = bitcast i8* %mallocP to i32*
7162 %result1 = call i32 @llvm.atomic.load.add.i32.p0i32( i32* %ptr, i32 4 )
7163 <i>; yields {i32}:result1 = 4</i>
7164 %result2 = call i32 @llvm.atomic.load.add.i32.p0i32( i32* %ptr, i32 2 )
7165 <i>; yields {i32}:result2 = 8</i>
7166 %result3 = call i32 @llvm.atomic.load.add.i32.p0i32( i32* %ptr, i32 5 )
7167 <i>; yields {i32}:result3 = 10</i>
7168 %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 15</i>
7173 <!-- _______________________________________________________________________ -->
7174 <div class="doc_subsubsection">
7175 <a name="int_atomic_load_sub">'<tt>llvm.atomic.load.sub.*</tt>' Intrinsic</a>
7179 <div class="doc_text">
7182 <p>This is an overloaded intrinsic. You can use <tt>llvm.atomic.load.sub</tt> on
7183 any integer bit width and for different address spaces. Not all targets
7184 support all bit widths however.</p>
7187 declare i8 @llvm.atomic.load.sub.i8.p0i32( i8* <ptr>, i8 <delta> )
7188 declare i16 @llvm.atomic.load.sub.i16.p0i32( i16* <ptr>, i16 <delta> )
7189 declare i32 @llvm.atomic.load.sub.i32.p0i32( i32* <ptr>, i32 <delta> )
7190 declare i64 @llvm.atomic.load.sub.i64.p0i32( i64* <ptr>, i64 <delta> )
7194 <p>This intrinsic subtracts <tt>delta</tt> to the value stored in memory at
7195 <tt>ptr</tt>. It yields the original value at <tt>ptr</tt>.</p>
7198 <p>The intrinsic takes two arguments, the first a pointer to an integer value
7199 and the second an integer value. The result is also an integer value. These
7200 integer types can have any bit width, but they must all have the same bit
7201 width. The targets may only lower integer representations they support.</p>
7204 <p>This intrinsic does a series of operations atomically. It first loads the
7205 value stored at <tt>ptr</tt>. It then subtracts <tt>delta</tt>, stores the
7206 result to <tt>ptr</tt>. It yields the original value stored
7207 at <tt>ptr</tt>.</p>
7211 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7212 %ptr = bitcast i8* %mallocP to i32*
7214 %result1 = call i32 @llvm.atomic.load.sub.i32.p0i32( i32* %ptr, i32 4 )
7215 <i>; yields {i32}:result1 = 8</i>
7216 %result2 = call i32 @llvm.atomic.load.sub.i32.p0i32( i32* %ptr, i32 2 )
7217 <i>; yields {i32}:result2 = 4</i>
7218 %result3 = call i32 @llvm.atomic.load.sub.i32.p0i32( i32* %ptr, i32 5 )
7219 <i>; yields {i32}:result3 = 2</i>
7220 %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = -3</i>
7225 <!-- _______________________________________________________________________ -->
7226 <div class="doc_subsubsection">
7227 <a name="int_atomic_load_and">'<tt>llvm.atomic.load.and.*</tt>' Intrinsic</a><br>
7228 <a name="int_atomic_load_nand">'<tt>llvm.atomic.load.nand.*</tt>' Intrinsic</a><br>
7229 <a name="int_atomic_load_or">'<tt>llvm.atomic.load.or.*</tt>' Intrinsic</a><br>
7230 <a name="int_atomic_load_xor">'<tt>llvm.atomic.load.xor.*</tt>' Intrinsic</a><br>
7233 <div class="doc_text">
7236 <p>These are overloaded intrinsics. You can
7237 use <tt>llvm.atomic.load_and</tt>, <tt>llvm.atomic.load_nand</tt>,
7238 <tt>llvm.atomic.load_or</tt>, and <tt>llvm.atomic.load_xor</tt> on any integer
7239 bit width and for different address spaces. Not all targets support all bit
7243 declare i8 @llvm.atomic.load.and.i8.p0i8( i8* <ptr>, i8 <delta> )
7244 declare i16 @llvm.atomic.load.and.i16.p0i16( i16* <ptr>, i16 <delta> )
7245 declare i32 @llvm.atomic.load.and.i32.p0i32( i32* <ptr>, i32 <delta> )
7246 declare i64 @llvm.atomic.load.and.i64.p0i64( i64* <ptr>, i64 <delta> )
7250 declare i8 @llvm.atomic.load.or.i8.p0i8( i8* <ptr>, i8 <delta> )
7251 declare i16 @llvm.atomic.load.or.i16.p0i16( i16* <ptr>, i16 <delta> )
7252 declare i32 @llvm.atomic.load.or.i32.p0i32( i32* <ptr>, i32 <delta> )
7253 declare i64 @llvm.atomic.load.or.i64.p0i64( i64* <ptr>, i64 <delta> )
7257 declare i8 @llvm.atomic.load.nand.i8.p0i32( i8* <ptr>, i8 <delta> )
7258 declare i16 @llvm.atomic.load.nand.i16.p0i32( i16* <ptr>, i16 <delta> )
7259 declare i32 @llvm.atomic.load.nand.i32.p0i32( i32* <ptr>, i32 <delta> )
7260 declare i64 @llvm.atomic.load.nand.i64.p0i32( i64* <ptr>, i64 <delta> )
7264 declare i8 @llvm.atomic.load.xor.i8.p0i32( i8* <ptr>, i8 <delta> )
7265 declare i16 @llvm.atomic.load.xor.i16.p0i32( i16* <ptr>, i16 <delta> )
7266 declare i32 @llvm.atomic.load.xor.i32.p0i32( i32* <ptr>, i32 <delta> )
7267 declare i64 @llvm.atomic.load.xor.i64.p0i32( i64* <ptr>, i64 <delta> )
7271 <p>These intrinsics bitwise the operation (and, nand, or, xor) <tt>delta</tt> to
7272 the value stored in memory at <tt>ptr</tt>. It yields the original value
7273 at <tt>ptr</tt>.</p>
7276 <p>These intrinsics take two arguments, the first a pointer to an integer value
7277 and the second an integer value. The result is also an integer value. These
7278 integer types can have any bit width, but they must all have the same bit
7279 width. The targets may only lower integer representations they support.</p>
7282 <p>These intrinsics does a series of operations atomically. They first load the
7283 value stored at <tt>ptr</tt>. They then do the bitwise
7284 operation <tt>delta</tt>, store the result to <tt>ptr</tt>. They yield the
7285 original value stored at <tt>ptr</tt>.</p>
7289 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7290 %ptr = bitcast i8* %mallocP to i32*
7291 store i32 0x0F0F, %ptr
7292 %result0 = call i32 @llvm.atomic.load.nand.i32.p0i32( i32* %ptr, i32 0xFF )
7293 <i>; yields {i32}:result0 = 0x0F0F</i>
7294 %result1 = call i32 @llvm.atomic.load.and.i32.p0i32( i32* %ptr, i32 0xFF )
7295 <i>; yields {i32}:result1 = 0xFFFFFFF0</i>
7296 %result2 = call i32 @llvm.atomic.load.or.i32.p0i32( i32* %ptr, i32 0F )
7297 <i>; yields {i32}:result2 = 0xF0</i>
7298 %result3 = call i32 @llvm.atomic.load.xor.i32.p0i32( i32* %ptr, i32 0F )
7299 <i>; yields {i32}:result3 = FF</i>
7300 %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = F0</i>
7305 <!-- _______________________________________________________________________ -->
7306 <div class="doc_subsubsection">
7307 <a name="int_atomic_load_max">'<tt>llvm.atomic.load.max.*</tt>' Intrinsic</a><br>
7308 <a name="int_atomic_load_min">'<tt>llvm.atomic.load.min.*</tt>' Intrinsic</a><br>
7309 <a name="int_atomic_load_umax">'<tt>llvm.atomic.load.umax.*</tt>' Intrinsic</a><br>
7310 <a name="int_atomic_load_umin">'<tt>llvm.atomic.load.umin.*</tt>' Intrinsic</a><br>
7313 <div class="doc_text">
7316 <p>These are overloaded intrinsics. You can use <tt>llvm.atomic.load_max</tt>,
7317 <tt>llvm.atomic.load_min</tt>, <tt>llvm.atomic.load_umax</tt>, and
7318 <tt>llvm.atomic.load_umin</tt> on any integer bit width and for different
7319 address spaces. Not all targets support all bit widths however.</p>
7322 declare i8 @llvm.atomic.load.max.i8.p0i8( i8* <ptr>, i8 <delta> )
7323 declare i16 @llvm.atomic.load.max.i16.p0i16( i16* <ptr>, i16 <delta> )
7324 declare i32 @llvm.atomic.load.max.i32.p0i32( i32* <ptr>, i32 <delta> )
7325 declare i64 @llvm.atomic.load.max.i64.p0i64( i64* <ptr>, i64 <delta> )
7329 declare i8 @llvm.atomic.load.min.i8.p0i8( i8* <ptr>, i8 <delta> )
7330 declare i16 @llvm.atomic.load.min.i16.p0i16( i16* <ptr>, i16 <delta> )
7331 declare i32 @llvm.atomic.load.min.i32..p0i32( i32* <ptr>, i32 <delta> )
7332 declare i64 @llvm.atomic.load.min.i64..p0i64( i64* <ptr>, i64 <delta> )
7336 declare i8 @llvm.atomic.load.umax.i8.p0i8( i8* <ptr>, i8 <delta> )
7337 declare i16 @llvm.atomic.load.umax.i16.p0i16( i16* <ptr>, i16 <delta> )
7338 declare i32 @llvm.atomic.load.umax.i32.p0i32( i32* <ptr>, i32 <delta> )
7339 declare i64 @llvm.atomic.load.umax.i64.p0i64( i64* <ptr>, i64 <delta> )
7343 declare i8 @llvm.atomic.load.umin.i8..p0i8( i8* <ptr>, i8 <delta> )
7344 declare i16 @llvm.atomic.load.umin.i16.p0i16( i16* <ptr>, i16 <delta> )
7345 declare i32 @llvm.atomic.load.umin.i32..p0i32( i32* <ptr>, i32 <delta> )
7346 declare i64 @llvm.atomic.load.umin.i64..p0i64( i64* <ptr>, i64 <delta> )
7350 <p>These intrinsics takes the signed or unsigned minimum or maximum of
7351 <tt>delta</tt> and the value stored in memory at <tt>ptr</tt>. It yields the
7352 original value at <tt>ptr</tt>.</p>
7355 <p>These intrinsics take two arguments, the first a pointer to an integer value
7356 and the second an integer value. The result is also an integer value. These
7357 integer types can have any bit width, but they must all have the same bit
7358 width. The targets may only lower integer representations they support.</p>
7361 <p>These intrinsics does a series of operations atomically. They first load the
7362 value stored at <tt>ptr</tt>. They then do the signed or unsigned min or
7363 max <tt>delta</tt> and the value, store the result to <tt>ptr</tt>. They
7364 yield the original value stored at <tt>ptr</tt>.</p>
7368 %mallocP = tail call i8* @malloc(i32 ptrtoint (i32* getelementptr (i32* null, i32 1) to i32))
7369 %ptr = bitcast i8* %mallocP to i32*
7371 %result0 = call i32 @llvm.atomic.load.min.i32.p0i32( i32* %ptr, i32 -2 )
7372 <i>; yields {i32}:result0 = 7</i>
7373 %result1 = call i32 @llvm.atomic.load.max.i32.p0i32( i32* %ptr, i32 8 )
7374 <i>; yields {i32}:result1 = -2</i>
7375 %result2 = call i32 @llvm.atomic.load.umin.i32.p0i32( i32* %ptr, i32 10 )
7376 <i>; yields {i32}:result2 = 8</i>
7377 %result3 = call i32 @llvm.atomic.load.umax.i32.p0i32( i32* %ptr, i32 30 )
7378 <i>; yields {i32}:result3 = 8</i>
7379 %memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 30</i>
7385 <!-- ======================================================================= -->
7386 <div class="doc_subsection">
7387 <a name="int_memorymarkers">Memory Use Markers</a>
7390 <div class="doc_text">
7392 <p>This class of intrinsics exists to information about the lifetime of memory
7393 objects and ranges where variables are immutable.</p>
7397 <!-- _______________________________________________________________________ -->
7398 <div class="doc_subsubsection">
7399 <a name="int_lifetime_start">'<tt>llvm.lifetime.start</tt>' Intrinsic</a>
7402 <div class="doc_text">
7406 declare void @llvm.lifetime.start(i64 <size>, i8* nocapture <ptr>)
7410 <p>The '<tt>llvm.lifetime.start</tt>' intrinsic specifies the start of a memory
7411 object's lifetime.</p>
7414 <p>The first argument is a constant integer representing the size of the
7415 object, or -1 if it is variable sized. The second argument is a pointer to
7419 <p>This intrinsic indicates that before this point in the code, the value of the
7420 memory pointed to by <tt>ptr</tt> is dead. This means that it is known to
7421 never be used and has an undefined value. A load from the pointer that
7422 precedes this intrinsic can be replaced with
7423 <tt>'<a href="#undefvalues">undef</a>'</tt>.</p>
7427 <!-- _______________________________________________________________________ -->
7428 <div class="doc_subsubsection">
7429 <a name="int_lifetime_end">'<tt>llvm.lifetime.end</tt>' Intrinsic</a>
7432 <div class="doc_text">
7436 declare void @llvm.lifetime.end(i64 <size>, i8* nocapture <ptr>)
7440 <p>The '<tt>llvm.lifetime.end</tt>' intrinsic specifies the end of a memory
7441 object's lifetime.</p>
7444 <p>The first argument is a constant integer representing the size of the
7445 object, or -1 if it is variable sized. The second argument is a pointer to
7449 <p>This intrinsic indicates that after this point in the code, the value of the
7450 memory pointed to by <tt>ptr</tt> is dead. This means that it is known to
7451 never be used and has an undefined value. Any stores into the memory object
7452 following this intrinsic may be removed as dead.
7456 <!-- _______________________________________________________________________ -->
7457 <div class="doc_subsubsection">
7458 <a name="int_invariant_start">'<tt>llvm.invariant.start</tt>' Intrinsic</a>
7461 <div class="doc_text">
7465 declare {}* @llvm.invariant.start(i64 <size>, i8* nocapture <ptr>) readonly
7469 <p>The '<tt>llvm.invariant.start</tt>' intrinsic specifies that the contents of
7470 a memory object will not change.</p>
7473 <p>The first argument is a constant integer representing the size of the
7474 object, or -1 if it is variable sized. The second argument is a pointer to
7478 <p>This intrinsic indicates that until an <tt>llvm.invariant.end</tt> that uses
7479 the return value, the referenced memory location is constant and
7484 <!-- _______________________________________________________________________ -->
7485 <div class="doc_subsubsection">
7486 <a name="int_invariant_end">'<tt>llvm.invariant.end</tt>' Intrinsic</a>
7489 <div class="doc_text">
7493 declare void @llvm.invariant.end({}* <start>, i64 <size>, i8* nocapture <ptr>)
7497 <p>The '<tt>llvm.invariant.end</tt>' intrinsic specifies that the contents of
7498 a memory object are mutable.</p>
7501 <p>The first argument is the matching <tt>llvm.invariant.start</tt> intrinsic.
7502 The second argument is a constant integer representing the size of the
7503 object, or -1 if it is variable sized and the third argument is a pointer
7507 <p>This intrinsic indicates that the memory is mutable again.</p>
7511 <!-- ======================================================================= -->
7512 <div class="doc_subsection">
7513 <a name="int_general">General Intrinsics</a>
7516 <div class="doc_text">
7518 <p>This class of intrinsics is designed to be generic and has no specific
7523 <!-- _______________________________________________________________________ -->
7524 <div class="doc_subsubsection">
7525 <a name="int_var_annotation">'<tt>llvm.var.annotation</tt>' Intrinsic</a>
7528 <div class="doc_text">
7532 declare void @llvm.var.annotation(i8* <val>, i8* <str>, i8* <str>, i32 <int> )
7536 <p>The '<tt>llvm.var.annotation</tt>' intrinsic.</p>
7539 <p>The first argument is a pointer to a value, the second is a pointer to a
7540 global string, the third is a pointer to a global string which is the source
7541 file name, and the last argument is the line number.</p>
7544 <p>This intrinsic allows annotation of local variables with arbitrary strings.
7545 This can be useful for special purpose optimizations that want to look for
7546 these annotations. These have no other defined use, they are ignored by code
7547 generation and optimization.</p>
7551 <!-- _______________________________________________________________________ -->
7552 <div class="doc_subsubsection">
7553 <a name="int_annotation">'<tt>llvm.annotation.*</tt>' Intrinsic</a>
7556 <div class="doc_text">
7559 <p>This is an overloaded intrinsic. You can use '<tt>llvm.annotation</tt>' on
7560 any integer bit width.</p>
7563 declare i8 @llvm.annotation.i8(i8 <val>, i8* <str>, i8* <str>, i32 <int> )
7564 declare i16 @llvm.annotation.i16(i16 <val>, i8* <str>, i8* <str>, i32 <int> )
7565 declare i32 @llvm.annotation.i32(i32 <val>, i8* <str>, i8* <str>, i32 <int> )
7566 declare i64 @llvm.annotation.i64(i64 <val>, i8* <str>, i8* <str>, i32 <int> )
7567 declare i256 @llvm.annotation.i256(i256 <val>, i8* <str>, i8* <str>, i32 <int> )
7571 <p>The '<tt>llvm.annotation</tt>' intrinsic.</p>
7574 <p>The first argument is an integer value (result of some expression), the
7575 second is a pointer to a global string, the third is a pointer to a global
7576 string which is the source file name, and the last argument is the line
7577 number. It returns the value of the first argument.</p>
7580 <p>This intrinsic allows annotations to be put on arbitrary expressions with
7581 arbitrary strings. This can be useful for special purpose optimizations that
7582 want to look for these annotations. These have no other defined use, they
7583 are ignored by code generation and optimization.</p>
7587 <!-- _______________________________________________________________________ -->
7588 <div class="doc_subsubsection">
7589 <a name="int_trap">'<tt>llvm.trap</tt>' Intrinsic</a>
7592 <div class="doc_text">
7596 declare void @llvm.trap()
7600 <p>The '<tt>llvm.trap</tt>' intrinsic.</p>
7606 <p>This intrinsics is lowered to the target dependent trap instruction. If the
7607 target does not have a trap instruction, this intrinsic will be lowered to
7608 the call of the <tt>abort()</tt> function.</p>
7612 <!-- _______________________________________________________________________ -->
7613 <div class="doc_subsubsection">
7614 <a name="int_stackprotector">'<tt>llvm.stackprotector</tt>' Intrinsic</a>
7617 <div class="doc_text">
7621 declare void @llvm.stackprotector( i8* <guard>, i8** <slot> )
7625 <p>The <tt>llvm.stackprotector</tt> intrinsic takes the <tt>guard</tt> and
7626 stores it onto the stack at <tt>slot</tt>. The stack slot is adjusted to
7627 ensure that it is placed on the stack before local variables.</p>
7630 <p>The <tt>llvm.stackprotector</tt> intrinsic requires two pointer
7631 arguments. The first argument is the value loaded from the stack
7632 guard <tt>@__stack_chk_guard</tt>. The second variable is an <tt>alloca</tt>
7633 that has enough space to hold the value of the guard.</p>
7636 <p>This intrinsic causes the prologue/epilogue inserter to force the position of
7637 the <tt>AllocaInst</tt> stack slot to be before local variables on the
7638 stack. This is to ensure that if a local variable on the stack is
7639 overwritten, it will destroy the value of the guard. When the function exits,
7640 the guard on the stack is checked against the original guard. If they're
7641 different, then the program aborts by calling the <tt>__stack_chk_fail()</tt>
7646 <!-- _______________________________________________________________________ -->
7647 <div class="doc_subsubsection">
7648 <a name="int_objectsize">'<tt>llvm.objectsize</tt>' Intrinsic</a>
7651 <div class="doc_text">
7655 declare i32 @llvm.objectsize.i32( i8* <object>, i1 <type> )
7656 declare i64 @llvm.objectsize.i64( i8* <object>, i1 <type> )
7660 <p>The <tt>llvm.objectsize</tt> intrinsic is designed to provide information
7661 to the optimizers to discover at compile time either a) when an
7662 operation like memcpy will either overflow a buffer that corresponds to
7663 an object, or b) to determine that a runtime check for overflow isn't
7664 necessary. An object in this context means an allocation of a
7665 specific class, structure, array, or other object.</p>
7668 <p>The <tt>llvm.objectsize</tt> intrinsic takes two arguments. The first
7669 argument is a pointer to or into the <tt>object</tt>. The second argument
7670 is a boolean 0 or 1. This argument determines whether you want the
7671 maximum (0) or minimum (1) bytes remaining. This needs to be a literal 0 or
7672 1, variables are not allowed.</p>
7675 <p>The <tt>llvm.objectsize</tt> intrinsic is lowered to either a constant
7676 representing the size of the object concerned or <tt>i32/i64 -1 or 0</tt>
7677 (depending on the <tt>type</tt> argument if the size cannot be determined
7678 at compile time.</p>
7682 <!-- *********************************************************************** -->
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7690 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
7691 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
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