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99 Global Variable</a></li>
101 Global Variable</a></li>
103 Global Variable</a></li>
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295 </div>
297 <!-- *********************************************************************** -->
299 <!-- *********************************************************************** -->
303 <p>This document is a reference manual for the LLVM assembly language. LLVM is
304 a Static Single Assignment (SSA) based representation that provides type
305 safety, low-level operations, flexibility, and the capability of representing
306 'all' high-level languages cleanly. It is the common code representation
307 used throughout all phases of the LLVM compilation strategy.</p>
309 </div>
311 <!-- *********************************************************************** -->
313 <!-- *********************************************************************** -->
317 <p>The LLVM code representation is designed to be used in three different forms:
318 as an in-memory compiler IR, as an on-disk bitcode representation (suitable
319 for fast loading by a Just-In-Time compiler), and as a human readable
320 assembly language representation. This allows LLVM to provide a powerful
321 intermediate representation for efficient compiler transformations and
322 analysis, while providing a natural means to debug and visualize the
323 transformations. The three different forms of LLVM are all equivalent. This
324 document describes the human readable representation and notation.</p>
326 <p>The LLVM representation aims to be light-weight and low-level while being
327 expressive, typed, and extensible at the same time. It aims to be a
328 "universal IR" of sorts, by being at a low enough level that high-level ideas
329 may be cleanly mapped to it (similar to how microprocessors are "universal
330 IR's", allowing many source languages to be mapped to them). By providing
331 type information, LLVM can be used as the target of optimizations: for
332 example, through pointer analysis, it can be proven that a C automatic
333 variable is never accessed outside of the current function... allowing it to
334 be promoted to a simple SSA value instead of a memory location.</p>
336 </div>
338 <!-- _______________________________________________________________________ -->
343 <p>It is important to note that this document describes 'well formed' LLVM
344 assembly language. There is a difference between what the parser accepts and
345 what is considered 'well formed'. For example, the following instruction is
346 syntactically okay, but not well formed:</p>
349 <pre>
351 </pre>
352 </div>
355 uses. The LLVM infrastructure provides a verification pass that may be used
356 to verify that an LLVM module is well formed. This pass is automatically run
357 by the parser after parsing input assembly and by the optimizer before it
358 outputs bitcode. The violations pointed out by the verifier pass indicate
359 bugs in transformation passes or input to the parser.</p>
361 </div>
363 <!-- Describe the typesetting conventions here. -->
365 <!-- *********************************************************************** -->
367 <!-- *********************************************************************** -->
371 <p>LLVM identifiers come in two basic types: global and local. Global
373 character. Local identifiers (register names, types) begin with
375 for identifiers, for different purposes:</p>
377 <ol>
378 <li>Named values are represented as a string of characters with their prefix.
382 other characters in their names can be surrounded with quotes. Special
384 ASCII code for the character in hexadecimal. In this way, any character
385 can be used in a name value, even quotes themselves.</li>
387 <li>Unnamed values are represented as an unsigned numeric value with their
392 </ol>
394 <p>LLVM requires that values start with a prefix for two reasons: Compilers
395 don't need to worry about name clashes with reserved words, and the set of
396 reserved words may be expanded in the future without penalty. Additionally,
397 unnamed identifiers allow a compiler to quickly come up with a temporary
398 variable without having to avoid symbol table conflicts.</p>
400 <p>Reserved words in LLVM are very similar to reserved words in other
401 languages. There are keywords for different opcodes
407 reserved words cannot conflict with variable names, because none of them
410 <p>Here is an example of LLVM code to multiply the integer variable
416 <pre>
418 </pre>
419 </div>
424 <pre>
426 </pre>
427 </div>
432 <pre>
436 </pre>
437 </div>
440 lexical features of LLVM:</p>
442 <ol>
444 line.</li>
446 <li>Unnamed temporaries are created when the result of a computation is not
447 assigned to a named value.</li>
450 </ol>
452 <p>...and it also shows a convention that we follow in this document. When
453 demonstrating instructions, we will follow an instruction with a comment that
454 defines the type and name of value produced. Comments are shown in italic
455 text.</p>
457 </div>
459 <!-- *********************************************************************** -->
461 <!-- *********************************************************************** -->
463 <!-- ======================================================================= -->
465 </div>
470 of the input programs. Each module consists of functions, global variables,
471 and symbol table entries. Modules may be combined together with the LLVM
472 linker, which merges function (and global variable) definitions, resolves
473 forward declarations, and merges symbol table entries. Here is an example of
479 href="#globalvars">constant</a> <a href="#t_array">[13 x i8]</a> c"hello world\0A\00" <i>; [13 x i8]*</i>
487 %cast210 = <a
491 <a
493 <a
495 </pre>
496 </div>
503 <p>In general, a module is made up of a list of global values, where both
504 functions and global variables are global values. Global values are
505 represented by a pointer to a memory location (in this case, a pointer to an
506 array of char, and a pointer to a function), and have one of the
509 </div>
511 <!-- ======================================================================= -->
514 </div>
518 <p>All Global Variables and Functions have one of the following types of
519 linkage:</p>
521 <dl>
523 <dd>Global values with private linkage are only directly accessible by objects
524 in the current module. In particular, linking code into a module with an
525 private global value may cause the private to be renamed as necessary to
526 avoid collisions. Because the symbol is private to the module, all
527 references can be updated. This doesn't show up in any symbol table in the
528 object file.</dd>
531 <dd>Similar to private, but the symbol is passed through the assembler and
532 removed by the linker after evaluation. Note that (unlike private
533 symbols) linker_private symbols are subject to coalescing by the linker:
534 weak symbols get merged and redefinitions are rejected. However, unlike
535 normal strong symbols, they are removed by the linker from the final
536 linked image (executable or dynamic library).</dd>
539 <dd>Similar to private, but the value shows as a local symbol
545 into the object file corresponding to the LLVM module. They exist to
546 allow inlining and other optimizations to take place given knowledge of
547 the definition of the global, which is known to be somewhere outside the
550 This linkage type is only allowed on definitions, not declarations.</dd>
554 the same name when linkage occurs. This is typically used to implement
555 inline functions, templates, or other code which must be generated in each
557 allowed to be discarded.</dd>
567 they are used for tentative definitions in C, such as "<tt>int X;</tt>" at
568 global scope.
569 Symbols with "<tt>common</tt>" linkage are merged in the same way as
572 must have a zero initializer, and may not be marked '<a
574 have common linkage.</dd>
579 pointer to array type. When two global variables with appending linkage
580 are linked together, the two global arrays are appended together. This is
581 the LLVM, typesafe, equivalent of having the system linker append together
585 <dd>The semantics of this linkage follow the ELF object file model: the symbol
586 is weak until linked, if not linked, the symbol becomes null instead of
587 being an undefined reference.</dd>
591 <dd>Some languages allow differing globals to be merged, such as two functions
593 that only equivalent globals are ever merged (the "one definition rule" -
596 be merged with equivalent globals. These linkage types are otherwise the
600 <dd>If none of the above identifiers are used, the global is externally
601 visible, meaning that it participates in linkage and can be used to
602 resolve external symbol references.</dd>
603 </dl>
605 <p>The next two types of linkage are targeted for Microsoft Windows platform
606 only. They are designed to support importing (exporting) symbols from (to)
607 DLLs (Dynamic Link Libraries).</p>
609 <dl>
612 or variable via a global pointer to a pointer that is set up by the DLL
613 exporting the symbol. On Microsoft Windows targets, the pointer name is
615 name.</dd>
619 pointer to a pointer in a DLL, so that it can be referenced with the
622 variable name.</dd>
623 </dl>
626 another module defined a "<tt>.LC0</tt>" variable and was linked with this
627 one, one of the two would be renamed, preventing a collision. Since
629 declarations), they are accessible outside of the current module.</p>
638 </div>
640 <!-- ======================================================================= -->
643 </div>
649 convention specified for the call. The calling convention of any pair of
650 dynamic caller/callee must match, or the behavior of the program is
651 undefined. The following calling conventions are supported by LLVM, and more
652 may be added in the future:</p>
654 <dl>
656 <dd>This calling convention (the default if no other calling convention is
657 specified) matches the target C calling conventions. This calling
658 convention supports varargs function calls and tolerates some mismatch in
659 the declared prototype and implemented declaration of the function (as
660 does normal C).</dd>
663 <dd>This calling convention attempts to make calls as fast as possible
664 (e.g. by passing things in registers). This calling convention allows the
665 target to use whatever tricks it wants to produce fast code for the
666 target, without having to conform to an externally specified ABI
667 (Application Binary Interface). Implementations of this convention should
669 optimization</a> to be supported. This calling convention does not
670 support varargs and requires the prototype of all callees to exactly match
671 the prototype of the function definition.</dd>
674 <dd>This calling convention attempts to make code in the caller as efficient
675 as possible under the assumption that the call is not commonly executed.
676 As such, these calls often preserve all registers so that the call does
677 not break any live ranges in the caller side. This calling convention
678 does not support varargs and requires the prototype of all callees to
679 exactly match the prototype of the function definition.</dd>
682 <dd>Any calling convention may be specified by number, allowing
683 target-specific calling conventions to be used. Target specific calling
685 </dl>
687 <p>More calling conventions can be added/defined on an as-needed basis, to
688 support Pascal conventions or any other well-known target-independent
689 convention.</p>
691 </div>
693 <!-- ======================================================================= -->
696 </div>
700 <p>All Global Variables and Functions have one of the following visibility
701 styles:</p>
703 <dl>
705 <dd>On targets that use the ELF object file format, default visibility means
706 that the declaration is visible to other modules and, in shared libraries,
707 means that the declared entity may be overridden. On Darwin, default
708 visibility means that the declaration is visible to other modules. Default
712 <dd>Two declarations of an object with hidden visibility refer to the same
713 object if they are in the same shared object. Usually, hidden visibility
714 indicates that the symbol will not be placed into the dynamic symbol
715 table, so no other module (executable or shared library) can reference it
716 directly.</dd>
719 <dd>On ELF, protected visibility indicates that the symbol will be placed in
720 the dynamic symbol table, but that references within the defining module
721 will bind to the local symbol. That is, the symbol cannot be overridden by
722 another module.</dd>
723 </dl>
725 </div>
727 <!-- ======================================================================= -->
730 </div>
734 <p>LLVM IR allows you to specify name aliases for certain types. This can make
735 it easier to read the IR and make the IR more condensed (particularly when
736 recursive types are involved). An example of a name specification is:</p>
739 <pre>
740 %mytype = type { %mytype*, i32 }
741 </pre>
742 </div>
748 <p>Note that type names are aliases for the structural type that they indicate,
749 and that you can therefore specify multiple names for the same type. This
750 often leads to confusing behavior when dumping out a .ll file. Since LLVM IR
751 uses structural typing, the name is not part of the type. When printing out
753 particular shape. This means that if you have code where two different
754 source types end up having the same LLVM type, that the dumper will sometimes
755 print the "wrong" or unexpected type. This is an important design point and
756 isn't going to change.</p>
758 </div>
760 <!-- ======================================================================= -->
763 </div>
767 <p>Global variables define regions of memory allocated at compilation time
768 instead of run-time. Global variables may optionally be initialized, may
769 have an explicit section to be placed in, and may have an optional explicit
770 alignment specified. A variable may be defined as "thread_local", which
771 means that it will not be shared by threads (each thread will have a
772 separated copy of the variable). A variable may be defined as a global
773 "constant," which indicates that the contents of the variable
775 global data to be placed in the read-only section of an executable, etc).
776 Note that variables that need runtime initialization cannot be marked
780 constant, even if the final definition of the global is not. This capability
781 can be used to enable slightly better optimization of the program, but
782 requires the language definition to guarantee that optimizations based on the
783 'constantness' are valid for the translation units that do not include the
784 definition.</p>
786 <p>As SSA values, global variables define pointer values that are in scope
787 (i.e. they dominate) all basic blocks in the program. Global variables
788 always define a pointer to their "content" type because they describe a
789 region of memory, and all memory objects in LLVM are accessed through
790 pointers.</p>
792 <p>A global variable may be declared to reside in a target-specific numbered
793 address space. For targets that support them, address spaces may affect how
794 optimizations are performed and/or what target instructions are used to
795 access the variable. The default address space is zero. The address space
796 qualifier must precede any other attributes.</p>
798 <p>LLVM allows an explicit section to be specified for globals. If the target
799 supports it, it will emit globals to the section specified.</p>
801 <p>An explicit alignment may be specified for a global. If not present, or if
802 the alignment is set to zero, the alignment of the global is set by the
803 target to whatever it feels convenient. If an explicit alignment is
804 specified, the global is forced to have at least that much alignment. All
807 <p>For example, the following defines a global in a numbered address space with
808 an initializer, section, and alignment:</p>
811 <pre>
813 </pre>
814 </div>
816 </div>
819 <!-- ======================================================================= -->
822 </div>
831 name, a (possibly empty) argument list (each with optional
835 curly brace, a list of basic blocks, and a closing curly brace.</p>
842 name, a possibly empty list of arguments, an optional alignment, and an
845 <p>A function definition contains a list of basic blocks, forming the CFG
846 (Control Flow Graph) for the function. Each basic block may optionally start
847 with a label (giving the basic block a symbol table entry), contains a list
849 instruction (such as a branch or function return).</p>
851 <p>The first basic block in a function is special in two ways: it is immediately
852 executed on entrance to the function, and it is not allowed to have
853 predecessor basic blocks (i.e. there can not be any branches to the entry
854 block of a function). Because the block can have no predecessors, it also
857 <p>LLVM allows an explicit section to be specified for functions. If the target
858 supports it, it will emit functions to the section specified.</p>
860 <p>An explicit alignment may be specified for a function. If not present, or if
861 the alignment is set to zero, the alignment of the function is set by the
862 target to whatever it feels convenient. If an explicit alignment is
863 specified, the function is forced to have at least that much alignment. All
868 <pre>
874 </pre>
875 </div>
877 </div>
879 <!-- ======================================================================= -->
882 </div>
887 function, global variable, another alias or bitcast of global value). Aliases
893 <pre>
895 </pre>
896 </div>
898 </div>
900 <!-- ======================================================================= -->
905 <p>The return type and each parameter of a function type may have a set of
907 used to communicate additional information about the result or parameters of
908 a function. Parameter attributes are considered to be part of the function,
909 not of the function type, so functions with different parameter attributes
910 can have the same function type.</p>
912 <p>Parameter attributes are simple keywords that follow the type specified. If
913 multiple parameter attributes are needed, they are space separated. For
914 example:</p>
917 <pre>
918 declare i32 @printf(i8* noalias nocapture, ...)
919 declare i32 @atoi(i8 zeroext)
920 declare signext i8 @returns_signed_char()
921 </pre>
922 </div>
929 <dl>
931 <dd>This indicates to the code generator that the parameter or return value
932 should be zero-extended to a 32-bit value by the caller (for a parameter)
933 or the callee (for a return value).</dd>
936 <dd>This indicates to the code generator that the parameter or return value
937 should be sign-extended to a 32-bit value by the caller (for a parameter)
938 or the callee (for a return value).</dd>
941 <dd>This indicates that this parameter or return value should be treated in a
942 special target-dependent fashion during while emitting code for a function
943 call or return (usually, by putting it in a register as opposed to memory,
944 though some targets use it to distinguish between two different kinds of
945 registers). Use of this attribute is target-specific.</dd>
948 <dd>This indicates that the pointer parameter should really be passed by value
949 to the function. The attribute implies that a hidden copy of the pointee
950 is made between the caller and the callee, so the callee is unable to
951 modify the value in the callee. This attribute is only valid on LLVM
952 pointer arguments. It is generally used to pass structs and arrays by
953 value, but is also valid on pointers to scalars. The copy is considered
954 to belong to the caller not the callee (for example,
957 values. The byval attribute also supports specifying an alignment with
958 the align attribute. This has a target-specific effect on the code
959 generator that usually indicates a desired alignment for the synthesized
960 stack slot.</dd>
963 <dd>This indicates that the pointer parameter specifies the address of a
964 structure that is the return value of the function in the source program.
965 This pointer must be guaranteed by the caller to be valid: loads and
966 stores to the structure may be assumed by the callee to not to trap. This
967 may only be applied to the first parameter. This is not a valid attribute
968 for return values. </dd>
971 <dd>This indicates that the pointer does not alias any global or any other
972 parameter. The caller is responsible for ensuring that this is the
974 that the pointer does not alias any other pointers visible to the
975 caller. For further details, please see the discussion of the NoAlias
976 response in
981 <dd>This indicates that the callee does not make any copies of the pointer
982 that outlive the callee itself. This is not a valid attribute for return
983 values.</dd>
986 <dd>This indicates that the pointer parameter can be excised using the
988 attribute for return values.</dd>
989 </dl>
991 </div>
993 <!-- ======================================================================= -->
996 </div>
1000 <p>Each function may specify a garbage collector name, which is simply a
1001 string:</p>
1004 <pre>
1005 define void @f() gc "name" { ...
1006 </pre>
1007 </div>
1010 collector which will cause the compiler to alter its output in order to
1011 support the named garbage collection algorithm.</p>
1013 </div>
1015 <!-- ======================================================================= -->
1018 </div>
1022 <p>Function attributes are set to communicate additional information about a
1023 function. Function attributes are considered to be part of the function, not
1024 of the function type, so functions with different parameter attributes can
1025 have the same function type.</p>
1027 <p>Function attributes are simple keywords that follow the type specified. If
1028 multiple attributes are needed, they are space separated. For example:</p>
1031 <pre>
1032 define void @f() noinline { ... }
1033 define void @f() alwaysinline { ... }
1034 define void @f() alwaysinline optsize { ... }
1035 define void @f() optsize
1036 </pre>
1037 </div>
1039 <dl>
1041 <dd>This attribute indicates that the inliner should attempt to inline this
1042 function into callers whenever possible, ignoring any active inlining size
1043 threshold for this caller.</dd>
1046 <dd>This attribute indicates that the source code contained a hint that inlining
1047 this function is desirable (such as the "inline" keyword in C/C++). It
1048 is just a hint; it imposes no requirements on the inliner.</dd>
1051 <dd>This attribute indicates that the inliner should never inline this
1052 function in any situation. This attribute may not be used together with
1056 <dd>This attribute suggests that optimization passes and code generator passes
1057 make choices that keep the code size of this function low, and otherwise
1058 do optimizations specifically to reduce code size.</dd>
1061 <dd>This function attribute indicates that the function never returns
1062 normally. This produces undefined behavior at runtime if the function
1063 ever does dynamically return.</dd>
1066 <dd>This function attribute indicates that the function never returns with an
1067 unwind or exceptional control flow. If the function does unwind, its
1068 runtime behavior is undefined.</dd>
1071 <dd>This attribute indicates that the function computes its result (or decides
1072 to unwind an exception) based strictly on its arguments, without
1073 dereferencing any pointer arguments or otherwise accessing any mutable
1074 state (e.g. memory, control registers, etc) visible to caller functions.
1075 It does not write through any pointer arguments
1077 changes any state visible to callers. This means that it cannot unwind
1082 <dd>This attribute indicates that the function does not write through any
1084 arguments) or otherwise modify any state (e.g. memory, control registers,
1085 etc) visible to caller functions. It may dereference pointer arguments
1086 and read state that may be set in the caller. A readonly function always
1087 returns the same value (or unwinds an exception identically) when called
1088 with the same set of arguments and global state. It cannot unwind an
1093 <dd>This attribute indicates that the function should emit a stack smashing
1095 the stack before the local variables that's checked upon return from the
1096 function to see if it has been overwritten. A heuristic is used to
1097 determine if a function needs stack protectors or not.<br>
1098 <br>
1105 stack smashing protector. This overrides
1107 <br>
1114 <dd>This attribute indicates that the code generator should not use a red
1115 zone, even if the target-specific ABI normally permits it.</dd>
1121 <dd>This attribute disables prologue / epilogue emission for the function.
1122 This can have very system-specific consequences.</dd>
1123 </dl>
1125 </div>
1127 <!-- ======================================================================= -->
1130 </div>
1135 the GCC "file scope inline asm" blocks. These blocks are internally
1136 concatenated by LLVM and treated as a single unit, but may be separated in
1140 <pre>
1141 module asm "inline asm code goes here"
1142 module asm "more can go here"
1143 </pre>
1144 </div>
1146 <p>The strings can contain any character by escaping non-printable characters.
1148 for the number.</p>
1150 <p>The inline asm code is simply printed to the machine code .s file when
1151 assembly code is generated.</p>
1153 </div>
1155 <!-- ======================================================================= -->
1158 </div>
1162 <p>A module may specify a target specific data layout string that specifies how
1163 data is to be laid out in memory. The syntax for the data layout is
1164 simply:</p>
1167 <pre>
1168 target datalayout = "<i>layout specification</i>"
1169 </pre>
1170 </div>
1173 separated by the minus sign character ('-'). Each specification starts with
1174 a letter and may include other information after the letter to define some
1175 aspect of the data layout. The specifications accepted are as follows:</p>
1177 <dl>
1179 <dd>Specifies that the target lays out data in big-endian form. That is, the
1180 bits with the most significance have the lowest address location.</dd>
1183 <dd>Specifies that the target lays out data in little-endian form. That is,
1184 the bits with the least significance have the lowest address
1185 location.</dd>
1194 <dd>This specifies the alignment for an integer type of a given bit
1198 <dd>This specifies the alignment for a vector type of a given bit
1202 <dd>This specifies the alignment for a floating point type of a given bit
1204 (double).</dd>
1207 <dd>This specifies the alignment for an aggregate type of a given bit
1211 <dd>This specifies the alignment for a stack object of a given bit
1213 </dl>
1215 <p>When constructing the data layout for a given target, LLVM starts with a
1216 default set of specifications which are then (possibly) overriden by the
1218 are given in this list:</p>
1220 <ul>
1235 </ul>
1237 <p>When LLVM is determining the alignment for a given type, it uses the
1238 following rules:</p>
1240 <ol>
1241 <li>If the type sought is an exact match for one of the specifications, that
1242 specification is used.</li>
1244 <li>If no match is found, and the type sought is an integer type, then the
1245 smallest integer type that is larger than the bitwidth of the sought type
1246 is used. If none of the specifications are larger than the bitwidth then
1247 the the largest integer type is used. For example, given the default
1248 specifications above, the i7 type will use the alignment of i8 (next
1249 largest) while both i65 and i256 will use the alignment of i64 (largest
1250 specified).</li>
1252 <li>If no match is found, and the type sought is a vector type, then the
1253 largest vector type that is smaller than the sought vector type will be
1256 </ol>
1258 </div>
1260 <!-- ======================================================================= -->
1263 </div>
1267 <p>Any memory access must be done through a pointer value associated
1268 with an address range of the memory access, otherwise the behavior
1269 is undefined. Pointer values are associated with address ranges
1270 according to the following rules:</p>
1272 <ul>
1273 <li>A pointer value formed from a
1275 is associated with the addresses associated with the first operand
1277 <li>An address of a global variable is associated with the address
1278 range of the variable's storage.</li>
1279 <li>The result value of an allocation instruction is associated with
1280 the address range of the allocated storage.</li>
1281 <li>A null pointer in the default address-space is associated with
1282 no address.</li>
1283 <li>A pointer value formed by an
1285 address ranges of all pointer values that contribute (directly or
1286 indirectly) to the computation of the pointer's value.</li>
1287 <li>The result value of a
1290 <li>An integer constant other than zero or a pointer value returned
1291 from a function not defined within LLVM may be associated with address
1292 ranges allocated through mechanisms other than those provided by
1293 LLVM. Such ranges shall not overlap with any ranges of addresses
1294 allocated by mechanisms provided by LLVM.</li>
1295 </ul>
1297 <p>LLVM IR does not associate types with memory. The result type of a
1299 alignment of the memory from which to load, as well as the
1300 interpretation of the value. The first operand of a
1302 and alignment of the store.</p>
1304 <p>Consequently, type-based alias analysis, aka TBAA, aka
1307 additional information which specialized optimization passes may use
1308 to implement type-based alias analysis.</p>
1310 </div>
1312 <!-- *********************************************************************** -->
1314 <!-- *********************************************************************** -->
1318 <p>The LLVM type system is one of the most important features of the
1319 intermediate representation. Being typed enables a number of optimizations
1320 to be performed on the intermediate representation directly, without having
1321 to do extra analyses on the side before the transformation. A strong type
1322 system makes it easier to read the generated code and enables novel analyses
1323 and transformations that are not feasible to perform on normal three address
1324 code representations.</p>
1326 </div>
1328 <!-- ======================================================================= -->
1330 Classifications</a> </div>
1337 <tbody>
1339 <tr>
1342 </tr>
1343 <tr>
1346 </tr>
1347 <tr>
1357 </td>
1358 </tr>
1359 <tr>
1365 </tr>
1366 <tr>
1376 </td>
1377 </tr>
1378 </tbody>
1379 </table>
1382 important. Values of these types are the only ones which can be produced by
1383 instructions, passed as arguments, or used as operands to instructions.</p>
1385 </div>
1387 <!-- ======================================================================= -->
1392 <p>The primitive types are the fundamental building blocks of the LLVM
1393 system.</p>
1395 </div>
1397 <!-- _______________________________________________________________________ -->
1402 <table>
1403 <tbody>
1410 </tbody>
1411 </table>
1413 </div>
1415 <!-- _______________________________________________________________________ -->
1424 <pre>
1425 void
1426 </pre>
1428 </div>
1430 <!-- _______________________________________________________________________ -->
1439 <pre>
1440 label
1441 </pre>
1443 </div>
1445 <!-- _______________________________________________________________________ -->
1451 <p>The metadata type represents embedded metadata. The only derived type that
1453 takes metadata typed parameters, but not pointer to metadata types.</p>
1456 <pre>
1457 metadata
1458 </pre>
1460 </div>
1463 <!-- ======================================================================= -->
1468 <p>The real power in LLVM comes from the derived types in the system. This is
1469 what allows a programmer to represent arrays, functions, pointers, and other
1470 useful types. Note that these derived types may be recursive: For example,
1471 it is possible to have a two dimensional array.</p>
1473 </div>
1475 <!-- _______________________________________________________________________ -->
1481 <p>The integer type is a very simple derived type that simply specifies an
1482 arbitrary bit width for the integer type desired. Any bit width from 1 bit to
1486 <pre>
1487 iN
1488 </pre>
1491 value.</p>
1498 </tr>
1502 </tr>
1506 </tr>
1507 </table>
1509 <p>Note that the code generator does not yet support large integer types to be
1510 used as function return types. The specific limit on how large a return type
1511 the code generator can currently handle is target-dependent; currently it's
1514 </div>
1516 <!-- _______________________________________________________________________ -->
1522 <p>The array type is a very simple derived type that arranges elements
1523 sequentially in memory. The array type requires a size (number of elements)
1524 and an underlying data type.</p>
1527 <pre>
1529 </pre>
1532 be any type with a size.</p>
1539 </tr>
1543 </tr>
1547 </tr>
1548 </table>
1554 </tr>
1558 </tr>
1562 </tr>
1563 </table>
1565 <p>Note that 'variable sized arrays' can be implemented in LLVM with a zero
1566 length array. Normally, accesses past the end of an array are undefined in
1568 a special case, however, zero length arrays are recognized to be variable
1569 length. This allows implementation of 'pascal style arrays' with the LLVM
1572 <p>Note that the code generator does not yet support large aggregate types to be
1573 used as function return types. The specific limit on how large an aggregate
1574 return type the code generator can currently handle is target-dependent, and
1575 also dependent on the aggregate element types.</p>
1577 </div>
1579 <!-- _______________________________________________________________________ -->
1585 <p>The function type can be thought of as a function signature. It consists of
1586 a return type and a list of formal parameter types. The return type of a
1587 function type is a scalar type, a void type, or a struct type. If the return
1588 type is a struct type then all struct elements must be of first class types,
1589 and the struct must have at least one element.</p>
1592 <pre>
1594 </pre>
1598 which indicates that the function takes a variable number of arguments.
1599 Variable argument functions can access their arguments with
1609 </td>
1612 </tt></td>
1617 </td>
1623 LLVM.
1624 </td>
1629 </td>
1630 </tr>
1631 </table>
1633 </div>
1635 <!-- _______________________________________________________________________ -->
1641 <p>The structure type is used to represent a collection of data members together
1642 in memory. The packing of the field types is defined to match the ABI of the
1643 underlying processor. The elements of a structure may be any type that has a
1644 size.</p>
1651 <pre>
1653 </pre>
1666 </tr>
1667 </table>
1669 <p>Note that the code generator does not yet support large aggregate types to be
1670 used as function return types. The specific limit on how large an aggregate
1671 return type the code generator can currently handle is target-dependent, and
1672 also dependent on the aggregate element types.</p>
1674 </div>
1676 <!-- _______________________________________________________________________ -->
1678 </div>
1683 <p>The packed structure type is used to represent a collection of data members
1684 together in memory. There is no padding between fields. Further, the
1685 alignment of a packed structure is 1 byte. The elements of a packed
1686 structure may be any type that has a size.</p>
1693 <pre>
1695 </pre>
1709 </tr>
1710 </table>
1712 </div>
1714 <!-- _______________________________________________________________________ -->
1720 <p>As in many languages, the pointer type represents a pointer or reference to
1721 another object, which must live in memory. Pointer types may have an optional
1722 address space attribute defining the target-specific numbered address space
1723 where the pointed-to object resides. The default address space is zero.</p>
1729 <pre>
1731 </pre>
1739 </tr>
1745 </tr>
1750 </tr>
1751 </table>
1753 </div>
1755 <!-- _______________________________________________________________________ -->
1761 <p>A vector type is a simple derived type that represents a vector of elements.
1762 Vector types are used when multiple primitive data are operated in parallel
1763 using a single instruction (SIMD). A vector type requires a size (number of
1764 elements) and an underlying primitive data type. Vectors must have a power
1769 <pre>
1771 </pre>
1773 <p>The number of elements is a constant integer value; elementtype may be any
1774 integer or floating point type.</p>
1781 </tr>
1785 </tr>
1789 </tr>
1790 </table>
1792 <p>Note that the code generator does not yet support large vector types to be
1793 used as function return types. The specific limit on how large a vector
1794 return type codegen can currently handle is target-dependent; currently it's
1795 often a few times longer than a hardware vector register.</p>
1797 </div>
1799 <!-- _______________________________________________________________________ -->
1804 <p>Opaque types are used to represent unknown types in the system. This
1805 corresponds (for example) to the C notion of a forward declared structure
1806 type. In LLVM, opaque types can eventually be resolved to any type (not just
1807 a structure type).</p>
1810 <pre>
1811 opaque
1812 </pre>
1819 </tr>
1820 </table>
1822 </div>
1824 <!-- ======================================================================= -->
1827 </div>
1833 requiring it to have a name. For instance, a structure declaration may
1834 contain a pointer to any of the types it is lexically a member of. Example
1835 of up references (with their equivalent as named type declarations)
1836 include:</p>
1838 <pre>
1839 { \2 * } %x = type { %x* }
1840 { \2 }* %y = type { %y }*
1841 \1* %z = type %z*
1842 </pre>
1844 <p>An up reference is needed by the asmprinter for printing out cyclic types
1845 when there is no declared name for a type in the cycle. Because the
1846 asmprinter does not want to print out an infinite type string, it needs a
1847 syntax to handle recursive types that have no names (all names are optional
1848 in llvm IR).</p>
1851 <pre>
1853 </pre>
1862 </tr>
1866 structure.</td>
1867 </tr>
1868 </table>
1870 </div>
1872 <!-- *********************************************************************** -->
1874 <!-- *********************************************************************** -->
1878 <p>LLVM has several different basic types of constants. This section describes
1879 them all and their syntax.</p>
1881 </div>
1883 <!-- ======================================================================= -->
1888 <dl>
1896 with integer types.</dd>
1900 exponential notation (e.g. 1.23421e+2), or a more precise hexadecimal
1901 notation (see below). The assembler requires the exact decimal value of a
1902 floating-point constant. For example, the assembler accepts 1.25 but
1909 </dl>
1911 <p>The one non-intuitive notation for constants is the hexadecimal form of
1912 floating point constants. For example, the form '<tt>double
1915 constants are required (and the only time that they are generated by the
1916 disassembler) is when a floating point constant must be emitted but it cannot
1917 be represented as a decimal floating point number in a reasonable number of
1918 digits. For example, NaN's, infinities, and other special values are
1919 represented in their IEEE hexadecimal format so that assembly and disassembly
1920 do not cause any bits to change in the constants.</p>
1922 <p>When using the hexadecimal form, constants of types float and double are
1923 represented using the 16-digit form shown above (which matches the IEEE754
1924 representation for double); float values must, however, be exactly
1925 representable as IEE754 single precision. Hexadecimal format is always used
1926 for long double, and there are three forms of long double. The 80-bit format
1928 The 128-bit format used by PowerPC (two adjacent doubles) is represented
1931 currently supported target uses this format. Long doubles will only work if
1932 they match the long double format on your target. All hexadecimal formats
1933 are big-endian (sign bit at the left).</p>
1935 </div>
1937 <!-- ======================================================================= -->
1941 </div>
1945 <p>Complex constants are a (potentially recursive) combination of simple
1946 constants and smaller complex constants.</p>
1948 <dl>
1950 <dd>Structure constants are represented with notation similar to structure
1951 type definitions (a comma separated list of elements, surrounded by braces
1955 the number and types of elements must match those specified by the
1956 type.</dd>
1959 <dd>Array constants are represented with notation similar to array type
1960 definitions (a comma separated list of elements, surrounded by square
1963 the number and types of elements must match those specified by the
1964 type.</dd>
1967 <dd>Vector constants are represented with notation similar to vector type
1968 definitions (a comma separated list of elements, surrounded by
1970 42, i32 11, i32 74, i32 100 ></tt>". Vector constants must
1972 elements must match those specified by the type.</dd>
1977 This is often used to avoid having to print large zero initializers
1978 (e.g. for large arrays) and is always exactly equivalent to using explicit
1979 zero initializers.</dd>
1982 <dd>A metadata node is a structure-like constant with
1985 be interpreted as part of the instruction stream, metadata is a place to
1986 attach additional information such as debug info.</dd>
1987 </dl>
1989 </div>
1991 <!-- ======================================================================= -->
1994 </div>
2000 (link-time) constants. These constants are explicitly referenced when
2003 legal LLVM file:</p>
2006 <pre>
2007 @X = global i32 17
2008 @Y = global i32 42
2009 @Z = global [2 x i32*] [ i32* @X, i32* @Y ]
2010 </pre>
2011 </div>
2013 </div>
2015 <!-- ======================================================================= -->
2020 indicates that the user of the value may recieve an unspecified bit-pattern.
2021 Undefined values may be of any type (other than label or void) and be used
2022 anywhere a constant is permitted.</p>
2024 <p>Undefined values are useful because they indicate to the compiler that the
2025 program is well defined no matter what value is used. This gives the
2026 compiler more freedom to optimize. Here are some examples of (potentially
2027 surprising) transformations that are valid (in pseudo IR):</p>
2031 <pre>
2032 %A = add %X, undef
2033 %B = sub %X, undef
2034 %C = xor %X, undef
2035 Safe:
2036 %A = undef
2037 %B = undef
2038 %C = undef
2039 </pre>
2040 </div>
2042 <p>This is safe because all of the output bits are affected by the undef bits.
2043 Any output bit can have a zero or one depending on the input bits.</p>
2046 <pre>
2047 %A = or %X, undef
2048 %B = and %X, undef
2049 Safe:
2050 %A = -1
2051 %B = 0
2052 Unsafe:
2053 %A = undef
2054 %B = undef
2055 </pre>
2056 </div>
2058 <p>These logical operations have bits that are not always affected by the input.
2059 For example, if "%X" has a zero bit, then the output of the 'and' operation will
2060 always be a zero, no matter what the corresponding bit from the undef is. As
2061 such, it is unsafe to optimize or assume that the result of the and is undef.
2062 However, it is safe to assume that all bits of the undef could be 0, and
2063 optimize the and to 0. Likewise, it is safe to assume that all the bits of
2064 the undef operand to the or could be set, allowing the or to be folded to
2068 <pre>
2069 %A = select undef, %X, %Y
2070 %B = select undef, 42, %Y
2071 %C = select %X, %Y, undef
2072 Safe:
2073 %A = %X (or %Y)
2074 %B = 42 (or %Y)
2075 %C = %Y
2076 Unsafe:
2077 %A = undef
2078 %B = undef
2079 %C = undef
2080 </pre>
2081 </div>
2083 <p>This set of examples show that undefined select (and conditional branch)
2084 conditions can go "either way" but they have to come from one of the two
2085 operands. In the %A example, if %X and %Y were both known to have a clear low
2086 bit, then %A would have to have a cleared low bit. However, in the %C example,
2087 the optimizer is allowed to assume that the undef operand could be the same as
2088 %Y, allowing the whole select to be eliminated.</p>
2092 <pre>
2093 %A = xor undef, undef
2095 %B = undef
2096 %C = xor %B, %B
2098 %D = undef
2099 %E = icmp lt %D, 4
2100 %F = icmp gte %D, 4
2102 Safe:
2103 %A = undef
2104 %B = undef
2105 %C = undef
2106 %D = undef
2107 %E = undef
2108 %F = undef
2109 </pre>
2110 </div>
2112 <p>This example points out that two undef operands are not necessarily the same.
2113 This can be surprising to people (and also matches C semantics) where they
2114 assume that "X^X" is always zero, even if X is undef. This isn't true for a
2115 number of reasons, but the short answer is that an undef "variable" can
2116 arbitrarily change its value over its "live range". This is true because the
2118 logically read from arbitrary registers that happen to be around when needed,
2119 so the value is not neccesarily consistent over time. In fact, %A and %C need
2120 to have the same semantics or the core LLVM "replace all uses with" concept
2121 would not hold.</p>
2124 <pre>
2125 %A = fdiv undef, %X
2126 %B = fdiv %X, undef
2127 Safe:
2128 %A = undef
2129 b: unreachable
2130 </pre>
2131 </div>
2135 allowed to have an arbitrary bit-pattern. This means that the %A operation
2136 can be constant folded to undef because the undef could be an SNaN, and fdiv is
2137 not (currently) defined on SNaN's. However, in the second example, we can make
2138 a more aggressive assumption: because the undef is allowed to be an arbitrary
2139 value, we are allowed to assume that it could be zero. Since a divide by zero
2141 does not execute at all. This allows us to delete the divide and all code after
2142 it: since the undefined operation "can't happen", the optimizer can assume that
2143 it occurs in dead code.
2144 </p>
2147 <pre>
2148 a: store undef -> %X
2149 b: store %X -> undef
2150 Safe:
2152 b: unreachable
2153 </pre>
2154 </div>
2157 can be assumed to not have any effect: we can assume that the value is
2158 overwritten with bits that happen to match what was already there. However, a
2159 store "to" an undefined location could clobber arbitrary memory, therefore, it
2160 has undefined behavior.</p>
2162 </div>
2164 <!-- ======================================================================= -->
2166 </div>
2170 <p>Constant expressions are used to allow expressions involving other constants
2171 to be used as constants. Constant expressions may be of
2173 operation that does not have side effects (e.g. load and call are not
2174 supported). The following is the syntax for constant expressions:</p>
2176 <dl>
2178 <dd>Truncate a constant to another type. The bit size of CST must be larger
2179 than the bit size of TYPE. Both types must be integers.</dd>
2182 <dd>Zero extend a constant to another type. The bit size of CST must be
2183 smaller or equal to the bit size of TYPE. Both types must be
2184 integers.</dd>
2187 <dd>Sign extend a constant to another type. The bit size of CST must be
2188 smaller or equal to the bit size of TYPE. Both types must be
2189 integers.</dd>
2192 <dd>Truncate a floating point constant to another floating point type. The
2193 size of CST must be larger than the size of TYPE. Both types must be
2194 floating point.</dd>
2197 <dd>Floating point extend a constant to another type. The size of CST must be
2198 smaller or equal to the size of TYPE. Both types must be floating
2199 point.</dd>
2202 <dd>Convert a floating point constant to the corresponding unsigned integer
2203 constant. TYPE must be a scalar or vector integer type. CST must be of
2204 scalar or vector floating point type. Both CST and TYPE must be scalars,
2205 or vectors of the same number of elements. If the value won't fit in the
2206 integer type, the results are undefined.</dd>
2209 <dd>Convert a floating point constant to the corresponding signed integer
2210 constant. TYPE must be a scalar or vector integer type. CST must be of
2211 scalar or vector floating point type. Both CST and TYPE must be scalars,
2212 or vectors of the same number of elements. If the value won't fit in the
2213 integer type, the results are undefined.</dd>
2216 <dd>Convert an unsigned integer constant to the corresponding floating point
2217 constant. TYPE must be a scalar or vector floating point type. CST must be
2218 of scalar or vector integer type. Both CST and TYPE must be scalars, or
2219 vectors of the same number of elements. If the value won't fit in the
2220 floating point type, the results are undefined.</dd>
2223 <dd>Convert a signed integer constant to the corresponding floating point
2224 constant. TYPE must be a scalar or vector floating point type. CST must be
2225 of scalar or vector integer type. Both CST and TYPE must be scalars, or
2226 vectors of the same number of elements. If the value won't fit in the
2227 floating point type, the results are undefined.</dd>
2230 <dd>Convert a pointer typed constant to the corresponding integer constant
2236 <dd>Convert a integer constant to a pointer constant. TYPE must be a pointer
2237 type. CST must be of integer type. The CST value is zero extended,
2238 truncated, or unchanged to make it fit in a pointer size. This one is
2242 <dd>Convert a constant, CST, to another TYPE. The constraints of the operands
2250 instruction, the index list may have zero or more indexes, which are
2264 constants.</dd>
2268 constants.</dd>
2272 constants.</dd>
2275 <dd>Perform the specified operation of the LHS and RHS constants. OPCODE may
2278 on operands are the same as those for the corresponding instruction
2279 (e.g. no bitwise operations on floating point values are allowed).</dd>
2280 </dl>
2282 </div>
2284 <!-- ======================================================================= -->
2286 </div>
2290 <p>Embedded metadata provides a way to attach arbitrary data to the instruction
2291 stream without affecting the behaviour of the program. There are two
2292 metadata primitives, strings and nodes. All metadata has the
2296 <p>A metadata string is a string surrounded by double quotes. It can contain
2300 <p>Metadata nodes are represented with notation similar to structure constants
2301 (a comma separated list of elements, surrounded by braces and preceeded by an
2305 <p>A metadata node will attempt to track changes to the values it holds. In the
2306 event that a value is deleted, it will be replaced with a typeless
2309 <p>Optimizations may rely on metadata to provide additional information about
2310 the program that isn't available in the instructions, or that isn't easily
2311 computable. Similarly, the code generator may expect a certain metadata
2312 format to be used to express debugging information.</p>
2314 </div>
2316 <!-- *********************************************************************** -->
2318 <!-- *********************************************************************** -->
2320 <!-- ======================================================================= -->
2323 </div>
2327 <p>LLVM supports inline assembler expressions (as opposed
2329 a special value. This value represents the inline assembler as a string
2330 (containing the instructions to emit), a list of operand constraints (stored
2331 as a string), and a flag that indicates whether or not the inline asm
2332 expression has side effects. An example inline assembler expression is:</p>
2335 <pre>
2337 </pre>
2338 </div>
2342 have:</p>
2345 <pre>
2347 </pre>
2348 </div>
2350 <p>Inline asms with side effects not visible in the constraint list must be
2351 marked as having side effects. This is done through the use of the
2355 <pre>
2357 </pre>
2358 </div>
2360 <p>TODO: The format of the asm and constraints string still need to be
2361 documented here. Constraints on what can be done (e.g. duplication, moving,
2362 etc need to be documented). This is probably best done by reference to
2363 another document that covers inline asm from a holistic perspective.</p>
2365 </div>
2368 <!-- *********************************************************************** -->
2371 </div>
2372 <!-- *********************************************************************** -->
2375 code generation or other IR semantics. These are documented here. All globals
2376 of this sort should have a section specified as "<tt>llvm.metadata</tt>". This
2377 section and all globals that start with "<tt>llvm.</tt>" are reserved for use
2378 by LLVM.</p>
2380 <!-- ======================================================================= -->
2383 </div>
2389 pointers to global variables and functions which may optionally have a pointer
2390 cast formed of bitcast or getelementptr. For example, a legal use of it is:</p>
2392 <pre>
2393 @X = global i8 4
2394 @Y = global i32 123
2396 @llvm.used = appending global [2 x i8*] [
2397 i8* @X,
2398 i8* bitcast (i32* @Y to i8*)
2399 ], section "llvm.metadata"
2400 </pre>
2403 compiler, assembler, and linker are required to treat the symbol as if there is
2404 a reference to the global that it cannot see. For example, if a variable has
2406 list, it cannot be deleted. This is commonly used to represent references from
2407 inline asms and other things the compiler cannot "see", and corresponds to
2410 <p>On some targets, the code generator must emit a directive to the assembler or
2411 object file to prevent the assembler and linker from molesting the symbol.</p>
2413 </div>
2415 <!-- ======================================================================= -->
2418 </div>
2424 touching the symbol. On targets that support it, this allows an intelligent
2425 linker to optimize references to the symbol without being impeded as it would be
2428 <p>This is a rare construct that should only be used in rare circumstances, and
2429 should not be exposed to source languages.</p>
2431 </div>
2433 <!-- ======================================================================= -->
2436 </div>
2442 </div>
2444 <!-- ======================================================================= -->
2447 </div>
2453 </div>
2456 <!-- *********************************************************************** -->
2458 <!-- *********************************************************************** -->
2462 <p>The LLVM instruction set consists of several different classifications of
2469 </div>
2471 <!-- ======================================================================= -->
2473 Instructions</a> </div>
2478 in a program ends with a "Terminator" instruction, which indicates which
2479 block should be executed after the current block is finished. These
2481 control flow, not values (the one exception being the
2484 <p>There are six different terminator instructions: the
2492 </div>
2494 <!-- _______________________________________________________________________ -->
2496 Instruction</a> </div>
2501 <pre>
2504 </pre>
2508 a value) from a function back to the caller.</p>
2511 value and then causes control flow, and one that just causes control flow to
2512 occur.</p>
2516 return value. The type of the return value must be a
2521 value or a return value with a type that does not match its type, or if it
2523 return value.</p>
2527 the calling function's context. If the caller is a
2529 instruction after the call. If the caller was an
2531 the beginning of the "normal" destination block. If the instruction returns
2532 a value, that value shall set the call or invoke instruction's return
2533 value.</p>
2536 <pre>
2540 </pre>
2542 <p>Note that the code generator does not yet fully support large
2543 return values. The specific sizes that are currently supported are
2544 dependent on the target. For integers, on 32-bit targets the limit
2546 For aggregate types, the current limits are dependent on the element
2547 types; for example targets are often limited to 2 total integer
2550 </div>
2551 <!-- _______________________________________________________________________ -->
2557 <pre>
2558 br i1 <cond>, label <iftrue>, label <iffalse><br> br label <dest> <i>; Unconditional branch</i>
2559 </pre>
2563 different basic block in the current function. There are two forms of this
2564 instruction, corresponding to a conditional branch and an unconditional
2565 branch.</p>
2571 target.</p>
2580 <pre>
2581 Test:
2583 br i1 %cond, label %IfEqual, label %IfUnequal
2584 IfEqual:
2586 IfUnequal:
2588 </pre>
2590 </div>
2592 <!-- _______________________________________________________________________ -->
2595 </div>
2600 <pre>
2601 switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]
2602 </pre>
2607 instruction, allowing a branch to occur to one of many possible
2608 destinations.</p>
2614 The table is not allowed to contain duplicate constant entries.</p>
2619 is searched for the given value. If the value is found, control flow is
2620 transfered to the corresponding destination; otherwise, control flow is
2621 transfered to the default destination.</p>
2624 <p>Depending on properties of the target machine and the particular
2626 different ways. For example, it could be generated as a series of chained
2627 conditional branches or with a lookup table.</p>
2630 <pre>
2633 switch i32 %Val, label %truedest [ i32 0, label %falsedest ]
2636 switch i32 0, label %dest [ ]
2639 switch i32 %val, label %otherwise [ i32 0, label %onzero
2640 i32 1, label %onone
2641 i32 2, label %ontwo ]
2642 </pre>
2644 </div>
2646 <!-- _______________________________________________________________________ -->
2649 </div>
2654 <pre>
2655 <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>]
2657 </pre>
2661 function, with the possibility of control flow transfer to either the
2664 control flow will return to the "normal" label. If the callee (or any
2666 instruction, control is interrupted and continued at the dynamically nearest
2672 <ol>
2674 convention</a> the call should use. If none is specified, the call
2675 defaults to using C calling conventions.</li>
2682 function value being invoked. In most cases, this is a direct function
2684 off an arbitrary pointer to function value.</li>
2687 function to be invoked. </li>
2690 signature argument types. If the function signature indicates the
2691 function accepts a variable number of arguments, the extra arguments can
2692 be specified.</li>
2703 </ol>
2706 <p>This instruction is designed to operate as a standard
2708 primary difference is that it establishes an association with a label, which
2709 is used by the runtime library to unwind the stack.</p>
2711 <p>This instruction is used in languages with destructors to ensure that proper
2713 exception. Additionally, this is important for implementation of
2716 <p>For the purposes of the SSA form, the definition of the value returned by the
2718 block to the "normal" label. If the callee unwinds then no return value is
2719 available.</p>
2722 <pre>
2723 %retval = invoke i32 @Test(i32 15) to label %Continue
2727 </pre>
2729 </div>
2731 <!-- _______________________________________________________________________ -->
2734 Instruction</a> </div>
2739 <pre>
2740 unwind
2741 </pre>
2745 at the first callee in the dynamic call stack which used
2747 This is primarily used to implement exception handling.</p>
2751 immediately halt. The dynamic call stack is then searched for the
2753 Once found, execution continues at the "exceptional" destination block
2755 instruction in the dynamic call chain, undefined behavior results.</p>
2757 </div>
2759 <!-- _______________________________________________________________________ -->
2762 Instruction</a> </div>
2767 <pre>
2768 unreachable
2769 </pre>
2773 instruction is used to inform the optimizer that a particular portion of the
2774 code is not reachable. This can be used to indicate that the code after a
2775 no-return function cannot be reached, and other facts.</p>
2780 </div>
2782 <!-- ======================================================================= -->
2787 <p>Binary operators are used to do most of the computation in a program. They
2788 require two operands of the same type, execute an operation on them, and
2789 produce a single value. The operands might represent multiple data, as is
2791 has the same type as its operands.</p>
2795 </div>
2797 <!-- _______________________________________________________________________ -->
2800 </div>
2805 <pre>
2810 </pre>
2818 integer values. Both arguments must have identical types.</p>
2823 <p>If the sum has unsigned overflow, the result returned is the mathematical
2826 <p>Because LLVM integers use a two's complement representation, this instruction
2827 is appropriate for both signed and unsigned integers.</p>
2832 is undefined if unsigned and/or signed overflow, respectively, occurs.</p>
2835 <pre>
2837 </pre>
2839 </div>
2841 <!-- _______________________________________________________________________ -->
2844 </div>
2849 <pre>
2851 </pre>
2859 floating point values. Both arguments must have identical types.</p>
2865 <pre>
2867 </pre>
2869 </div>
2871 <!-- _______________________________________________________________________ -->
2874 </div>
2879 <pre>
2884 </pre>
2888 operands.</p>
2892 representations.</p>
2897 integer values. Both arguments must have identical types.</p>
2902 <p>If the difference has unsigned overflow, the result returned is the
2904 result.</p>
2906 <p>Because LLVM integers use a two's complement representation, this instruction
2907 is appropriate for both signed and unsigned integers.</p>
2912 is undefined if unsigned and/or signed overflow, respectively, occurs.</p>
2915 <pre>
2918 </pre>
2920 </div>
2922 <!-- _______________________________________________________________________ -->
2925 </div>
2930 <pre>
2932 </pre>
2936 operands.</p>
2940 representations.</p>
2945 floating point values. Both arguments must have identical types.</p>
2951 <pre>
2954 </pre>
2956 </div>
2958 <!-- _______________________________________________________________________ -->
2961 </div>
2966 <pre>
2971 </pre>
2979 integer values. Both arguments must have identical types.</p>
2984 <p>If the result of the multiplication has unsigned overflow, the result
2986 width of the result.</p>
2988 <p>Because LLVM integers use a two's complement representation, and the result
2989 is the same width as the operands, this instruction returns the correct
2990 result for both signed and unsigned integers. If a full product
2992 be sign-extended or zero-extended as appropriate to the width of the full
2993 product.</p>
2998 is undefined if unsigned and/or signed overflow, respectively, occurs.</p>
3001 <pre>
3003 </pre>
3005 </div>
3007 <!-- _______________________________________________________________________ -->
3010 </div>
3015 <pre>
3017 </pre>
3025 floating point values. Both arguments must have identical types.</p>
3031 <pre>
3033 </pre>
3035 </div>
3037 <!-- _______________________________________________________________________ -->
3039 </a></div>
3044 <pre>
3046 </pre>
3054 values. Both arguments must have identical types.</p>
3059 <p>Note that unsigned integer division and signed integer division are distinct
3065 <pre>
3067 </pre>
3069 </div>
3071 <!-- _______________________________________________________________________ -->
3073 </a> </div>
3078 <pre>
3081 </pre>
3089 values. Both arguments must have identical types.</p>
3092 <p>The value produced is the signed integer quotient of the two operands rounded
3093 towards zero.</p>
3095 <p>Note that signed integer division and unsigned integer division are distinct
3098 <p>Division by zero leads to undefined behavior. Overflow also leads to
3099 undefined behavior; this is a rare case, but can occur, for example, by doing
3104 would occur.</p>
3107 <pre>
3109 </pre>
3111 </div>
3113 <!-- _______________________________________________________________________ -->
3115 Instruction</a> </div>
3120 <pre>
3122 </pre>
3130 floating point values. Both arguments must have identical types.</p>
3136 <pre>
3138 </pre>
3140 </div>
3142 <!-- _______________________________________________________________________ -->
3144 </div>
3149 <pre>
3151 </pre>
3155 division of its two arguments.</p>
3160 values. Both arguments must have identical types.</p>
3164 This instruction always performs an unsigned division to get the
3165 remainder.</p>
3167 <p>Note that unsigned integer remainder and signed integer remainder are
3173 <pre>
3175 </pre>
3177 </div>
3179 <!-- _______________________________________________________________________ -->
3182 </div>
3187 <pre>
3189 </pre>
3193 division of its two operands. This instruction can also take
3195 elements must be integers.</p>
3200 values. Both arguments must have identical types.</p>
3206 a value. For more information about the difference,
3208 Math Forum</a>. For a table of how this is implemented in various languages,
3212 <p>Note that signed integer remainder and unsigned integer remainder are
3215 <p>Taking the remainder of a division by zero leads to undefined behavior.
3216 Overflow also leads to undefined behavior; this is a rare case, but can
3217 occur, for example, by taking the remainder of a 32-bit division of
3219 lets srem be implemented using instructions that return both the result of
3220 the division and the remainder.)</p>
3223 <pre>
3225 </pre>
3227 </div>
3229 <!-- _______________________________________________________________________ -->
3236 <pre>
3238 </pre>
3242 its two operands.</p>
3247 floating point values. Both arguments must have identical types.</p>
3251 has the same sign as the dividend.</p>
3254 <pre>
3256 </pre>
3258 </div>
3260 <!-- ======================================================================= -->
3262 Operations</a> </div>
3266 <p>Bitwise binary operators are used to do various forms of bit-twiddling in a
3267 program. They are generally very efficient instructions and can commonly be
3268 strength reduced from other instructions. They require two operands of the
3269 same type, execute an operation on them, and produce a single value. The
3270 resulting value is the same type as its operands.</p>
3272 </div>
3274 <!-- _______________________________________________________________________ -->
3276 Instruction</a> </div>
3281 <pre>
3283 </pre>
3287 a specified number of bits.</p>
3297 is (statically or dynamically) negative or equal to or larger than the number
3303 <pre>
3308 <result> = shl <2 x i32> < i32 1, i32 1>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 2, i32 4></i>
3309 </pre>
3311 </div>
3313 <!-- _______________________________________________________________________ -->
3315 Instruction</a> </div>
3320 <pre>
3322 </pre>
3326 operand shifted to the right a specified number of bits with zero fill.</p>
3334 <p>This instruction always performs a logical shift right operation. The most
3335 significant bits of the result will be filled with zero bits after the shift.
3342 <pre>
3348 <result> = lshr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 0x7FFFFFFF, i32 1></i>
3349 </pre>
3351 </div>
3353 <!-- _______________________________________________________________________ -->
3355 Instruction</a> </div>
3359 <pre>
3361 </pre>
3365 operand shifted to the right a specified number of bits with sign
3366 extension.</p>
3374 <p>This instruction always performs an arithmetic shift right operation, The
3375 most significant bits of the result will be filled with the sign bit
3382 <pre>
3388 <result> = ashr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 3> <i>; yields: result=<2 x i32> < i32 -1, i32 0></i>
3389 </pre>
3391 </div>
3393 <!-- _______________________________________________________________________ -->
3395 Instruction</a> </div>
3400 <pre>
3402 </pre>
3406 operands.</p>
3411 values. Both arguments must have identical types.</p>
3417 <tbody>
3418 <tr>
3422 </tr>
3423 <tr>
3427 </tr>
3428 <tr>
3432 </tr>
3433 <tr>
3437 </tr>
3438 <tr>
3442 </tr>
3443 </tbody>
3444 </table>
3447 <pre>
3451 </pre>
3452 </div>
3453 <!-- _______________________________________________________________________ -->
3459 <pre>
3461 </pre>
3465 two operands.</p>
3470 values. Both arguments must have identical types.</p>
3476 <tbody>
3477 <tr>
3481 </tr>
3482 <tr>
3486 </tr>
3487 <tr>
3491 </tr>
3492 <tr>
3496 </tr>
3497 <tr>
3501 </tr>
3502 </tbody>
3503 </table>
3506 <pre>
3510 </pre>
3512 </div>
3514 <!-- _______________________________________________________________________ -->
3516 Instruction</a> </div>
3521 <pre>
3523 </pre>
3533 values. Both arguments must have identical types.</p>
3539 <tbody>
3540 <tr>
3544 </tr>
3545 <tr>
3549 </tr>
3550 <tr>
3554 </tr>
3555 <tr>
3559 </tr>
3560 <tr>
3564 </tr>
3565 </tbody>
3566 </table>
3569 <pre>
3574 </pre>
3576 </div>
3578 <!-- ======================================================================= -->
3581 </div>
3585 <p>LLVM supports several instructions to represent vector operations in a
3586 target-independent manner. These instructions cover the element-access and
3587 vector-specific operations needed to process vectors effectively. While LLVM
3588 does directly support these vector operations, many sophisticated algorithms
3589 will want to use target-specific intrinsics to take full advantage of a
3590 specific target.</p>
3592 </div>
3594 <!-- _______________________________________________________________________ -->
3597 </div>
3602 <pre>
3603 <result> = extractelement <n x <ty>> <val>, i32 <idx> <i>; yields <ty></i>
3604 </pre>
3608 from a vector at a specified index.</p>
3614 indicating the position from which to extract the element. The index may be
3615 a variable.</p>
3618 <p>The result is a scalar of the same type as the element type of
3621 results are undefined.</p>
3624 <pre>
3626 </pre>
3628 </div>
3630 <!-- _______________________________________________________________________ -->
3633 </div>
3638 <pre>
3639 <result> = insertelement <n x <ty>> <val>, <ty> <elt>, i32 <idx> <i>; yields <n x <ty>></i>
3640 </pre>
3644 vector at a specified index.</p>
3649 whose type must equal the element type of the first operand. The third
3650 operand is an index indicating the position at which to insert the value.
3651 The index may be a variable.</p>
3657 results are undefined.</p>
3660 <pre>
3662 </pre>
3664 </div>
3666 <!-- _______________________________________________________________________ -->
3669 </div>
3674 <pre>
3675 <result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <m x i32> <mask> <i>; yields <m x <ty>></i>
3676 </pre>
3680 from two input vectors, returning a vector with the same element type as the
3681 input and length that is the same as the shuffle mask.</p>
3685 with types that match each other. The third argument is a shuffle mask whose
3686 element type is always 'i32'. The result of the instruction is a vector
3687 whose length is the same as the shuffle mask and whose element type is the
3688 same as the element type of the first two operands.</p>
3690 <p>The shuffle mask operand is required to be a constant vector with either
3691 constant integer or undef values.</p>
3694 <p>The elements of the two input vectors are numbered from left to right across
3695 both of the vectors. The shuffle mask operand specifies, for each element of
3696 the result vector, which element of the two input vectors the result element
3697 gets. The element selector may be undef (meaning "don't care") and the
3698 second operand may be undef if performing a shuffle from only one vector.</p>
3701 <pre>
3705 <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> - Identity shuffle.
3709 <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>
3710 </pre>
3712 </div>
3714 <!-- ======================================================================= -->
3717 </div>
3723 </div>
3725 <!-- _______________________________________________________________________ -->
3728 </div>
3733 <pre>
3735 </pre>
3739 or array element from an aggregate value.</p>
3744 operands are constant indices to specify which value to extract in a similar
3745 manner as indices in a
3749 <p>The result is the value at the position in the aggregate specified by the
3750 index operands.</p>
3753 <pre>
3755 </pre>
3757 </div>
3759 <!-- _______________________________________________________________________ -->
3762 </div>
3767 <pre>
3768 <result> = insertvalue <aggregate type> <val>, <ty> <val>, <idx> <i>; yields <n x <ty>></i>
3769 </pre>
3773 array element in an aggregate.</p>
3779 second operand is a first-class value to insert. The following operands are
3780 constant indices indicating the position at which to insert the value in a
3781 similar manner as indices in a
3783 value to insert must have the same type as the value identified by the
3784 indices.</p>
3792 <pre>
3794 </pre>
3796 </div>
3799 <!-- ======================================================================= -->
3802 </div>
3806 <p>A key design point of an SSA-based representation is how it represents
3807 memory. In LLVM, no memory locations are in SSA form, which makes things
3808 very simple. This section describes how to read, write, allocate, and free
3809 memory in LLVM.</p>
3811 </div>
3813 <!-- _______________________________________________________________________ -->
3816 </div>
3821 <pre>
3822 <result> = malloc <type>[, i32 <NumElements>][, align <alignment>] <i>; yields {type*}:result</i>
3823 </pre>
3827 returns a pointer to it. The object is always allocated in the generic
3828 address space (address space zero).</p>
3833 system and returns a pointer of the appropriate type to the program. If
3834 "NumElements" is specified, it is the number of elements allocated, otherwise
3835 "NumElements" is defaulted to be one. If a constant alignment is specified,
3836 the value result of the allocation is guaranteed to be aligned to at least
3837 that boundary. If not specified, or if zero, the target can choose to align
3838 the allocation on any convenient boundary compatible with the type.</p>
3844 pointer is returned. The result of a zero byte allocation is undefined. The
3845 result is null if there is insufficient memory available.</p>
3848 <pre>
3856 </pre>
3860 </div>
3862 <!-- _______________________________________________________________________ -->
3865 </div>
3870 <pre>
3872 </pre>
3876 to be reallocated in the future.</p>
3883 <p>Access to the memory pointed to by the pointer is no longer defined after
3884 this instruction executes. If the pointer is null, the operation is a
3885 noop.</p>
3888 <pre>
3890 free [4 x i8]* %array
3891 </pre>
3893 </div>
3895 <!-- _______________________________________________________________________ -->
3898 </div>
3903 <pre>
3904 <result> = alloca <type>[, i32 <NumElements>][, align <alignment>] <i>; yields {type*}:result</i>
3905 </pre>
3909 currently executing function, to be automatically released when this function
3910 returns to its caller. The object is always allocated in the generic address
3911 space (address space zero).</p>
3916 runtime stack, returning a pointer of the appropriate type to the program.
3917 If "NumElements" is specified, it is the number of elements allocated,
3918 otherwise "NumElements" is defaulted to be one. If a constant alignment is
3919 specified, the value result of the allocation is guaranteed to be aligned to
3920 at least that boundary. If not specified, or if zero, the target can choose
3921 to align the allocation on any convenient boundary compatible with the
3922 type.</p>
3927 <p>Memory is allocated; a pointer is returned. The operation is undefined if
3929 memory is automatically released when the function returns. The
3931 variables that must have an address available. When the function returns
3934 reclaimed. Allocating zero bytes is legal, but the result is undefined.</p>
3937 <pre>
3942 </pre>
3944 </div>
3946 <!-- _______________________________________________________________________ -->
3948 Instruction</a> </div>
3953 <pre>
3956 </pre>
3963 from which to load. The pointer must point to
3968 instructions. </p>
3971 operation (that is, the alignment of the memory address). A value of 0 or an
3972 omitted "align" argument means that the operation has the preferential
3973 alignment for the target. It is the responsibility of the code emitter to
3974 ensure that the alignment information is correct. Overestimating the
3975 alignment results in an undefined behavior. Underestimating the alignment may
3979 <p>The location of memory pointed to is loaded. If the value being loaded is of
3980 scalar type then the number of bytes read does not exceed the minimum number
3981 of bytes needed to hold all bits of the type. For example, loading an
3984 is undefined if the value was not originally written using a store of the
3985 same type.</p>
3988 <pre>
3992 </pre>
3994 </div>
3996 <!-- _______________________________________________________________________ -->
3998 Instruction</a> </div>
4003 <pre>
4004 store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i>
4005 volatile store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i>
4006 </pre>
4013 and an address at which to store it. The type of the
4020 instructions.</p>
4023 operation (that is, the alignment of the memory address). A value of 0 or an
4024 omitted "align" argument means that the operation has the preferential
4025 alignment for the target. It is the responsibility of the code emitter to
4026 ensure that the alignment information is correct. Overestimating the
4027 alignment results in an undefined behavior. Underestimating the alignment may
4034 does not exceed the minimum number of bytes needed to hold all bits of the
4037 integral number of bytes, it is unspecified what happens to the extra bits
4038 that do not belong to the type, but they will typically be overwritten.</p>
4041 <pre>
4045 </pre>
4047 </div>
4049 <!-- _______________________________________________________________________ -->
4052 </div>
4057 <pre>
4060 </pre>
4064 subelement of an aggregate data structure. It performs address calculation
4065 only and does not access memory.</p>
4068 <p>The first argument is always a pointer, and forms the basis of the
4069 calculation. The remaining arguments are indices that indicate which of the
4070 elements of the aggregate object are indexed. The interpretation of each
4071 index is dependent on the type being indexed into. The first index always
4072 indexes the pointer value given as the first argument, the second index
4073 indexes a value of the type pointed to (not necessarily the value directly
4074 pointed to, since the first index can be non-zero), etc. The first type
4075 indexed into must be a pointer value, subsequent types can be arrays, vectors
4076 and structs. Note that subsequent types being indexed into can never be
4077 pointers, since that would require loading the pointer before continuing
4078 calculation.</p>
4080 <p>The type of each index argument depends on the type it is indexing into.
4083 vector, integers of any width are allowed, and they are not required to be
4084 constant.</p>
4086 <p>For example, let's consider a C code fragment and how it gets compiled to
4087 LLVM:</p>
4090 <pre>
4091 struct RT {
4092 char A;
4094 char C;
4095 };
4096 struct ST {
4097 int X;
4098 double Y;
4099 struct RT Z;
4100 };
4102 int *foo(struct ST *s) {
4104 }
4105 </pre>
4106 </div>
4111 <pre>
4115 define i32* @foo(%ST* %s) {
4116 entry:
4118 ret i32* %reg
4119 }
4120 </pre>
4121 </div>
4126 }</tt>' type, a structure. The second index indexes into the third element
4128 i8 }</tt>' type, another structure. The third index indexes into the second
4130 array. The two dimensions of the array are subscripted into, yielding an
4134 <p>Note that it is perfectly legal to index partially through a structure,
4135 returning a pointer to an inner element. Because of this, the LLVM code for
4136 the given testcase is equivalent to:</p>
4138 <pre>
4139 define i32* @foo(%ST* %s) {
4145 ret i32* %t5
4146 }
4147 </pre>
4152 that would be formed by successive addition of the offsets implied by the
4153 indices to the base address with infinitely precise arithmetic are not an
4156 that point into the object, plus the address one byte past the end.</p>
4159 the base address with silently-wrapping two's complement arithmetic, and
4161 pointed to by the base pointer. The result value may not necessarily be
4162 used to access memory though, even if it happens to point into allocated
4164 section for more information.</p>
4166 <p>The getelementptr instruction is often confusing. For some more insight into
4170 <pre>
4179 </pre>
4181 </div>
4183 <!-- ======================================================================= -->
4185 </div>
4189 <p>The instructions in this category are the conversion instructions (casting)
4190 which all take a single operand and a type. They perform various bit
4191 conversions on the operand.</p>
4193 </div>
4195 <!-- _______________________________________________________________________ -->
4198 </div>
4202 <pre>
4204 </pre>
4213 size and type of the result, which must be
4216 allowed.</p>
4225 <pre>
4229 </pre>
4231 </div>
4233 <!-- _______________________________________________________________________ -->
4236 </div>
4240 <pre>
4242 </pre>
4263 <pre>
4266 </pre>
4268 </div>
4270 <!-- _______________________________________________________________________ -->
4273 </div>
4277 <pre>
4279 </pre>
4299 <pre>
4302 </pre>
4304 </div>
4306 <!-- _______________________________________________________________________ -->
4309 </div>
4314 <pre>
4316 </pre>
4334 undefined.</p>
4337 <pre>
4340 </pre>
4342 </div>
4344 <!-- _______________________________________________________________________ -->
4347 </div>
4351 <pre>
4353 </pre>
4357 floating point value.</p>
4363 type must be smaller than the destination type.</p>
4373 <pre>
4376 </pre>
4378 </div>
4380 <!-- _______________________________________________________________________ -->
4383 </div>
4387 <pre>
4389 </pre>
4405 towards zero) unsigned integer value. If the value cannot fit
4409 <pre>
4413 </pre>
4415 </div>
4417 <!-- _______________________________________________________________________ -->
4420 </div>
4424 <pre>
4426 </pre>
4444 the results are undefined.</p>
4447 <pre>
4451 </pre>
4453 </div>
4455 <!-- _______________________________________________________________________ -->
4458 </div>
4462 <pre>
4464 </pre>
4479 integer quantity and converts it to the corresponding floating point
4480 value. If the value cannot fit in the floating point value, the results are
4481 undefined.</p>
4484 <pre>
4487 </pre>
4489 </div>
4491 <!-- _______________________________________________________________________ -->
4494 </div>
4498 <pre>
4500 </pre>
4515 quantity and converts it to the corresponding floating point value. If the
4516 value cannot fit in the floating point value, the results are undefined.</p>
4519 <pre>
4522 </pre>
4524 </div>
4526 <!-- _______________________________________________________________________ -->
4529 </div>
4533 <pre>
4535 </pre>
4549 truncating or zero extending that value to the size of the integer type. If
4553 change.</p>
4556 <pre>
4559 </pre>
4561 </div>
4563 <!-- _______________________________________________________________________ -->
4566 </div>
4570 <pre>
4572 </pre>
4580 value to cast, and a type to cast it to, which must be a
4588 than the size of a pointer then a zero extension is done. If they are the
4592 <pre>
4596 </pre>
4598 </div>
4600 <!-- _______________________________________________________________________ -->
4603 </div>
4607 <pre>
4609 </pre>
4617 non-aggregate first class value, and a type to cast it to, which must also be
4620 identical. If the source type is a pointer, the destination type must also be
4621 a pointer. This instruction supports bitwise conversion of vectors to
4622 integers and to vectors of other types (as long as they have the same
4623 size).</p>
4630 be converted to other pointer types with this instruction. To convert
4635 <pre>
4639 </pre>
4641 </div>
4643 <!-- ======================================================================= -->
4649 defy better classification.</p>
4651 </div>
4653 <!-- _______________________________________________________________________ -->
4655 </div>
4660 <pre>
4661 <result> = icmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i>
4662 </pre>
4666 boolean values based on comparison of its two integer, integer vector, or
4667 pointer operands.</p>
4671 the condition code indicating the kind of comparison to perform. It is not a
4672 value, just a keyword. The possible condition code are:</p>
4674 <ol>
4685 </ol>
4689 typed. They must also be identical types.</p>
4695 result, as follows:</p>
4697 <ol>
4700 performed.</li>
4704 performed.</li>
4731 </ol>
4734 values are compared as if they were integers.</p>
4736 <p>If the operands are integer vectors, then they are compared element by
4741 <pre>
4748 </pre>
4750 <p>Note that the code generator does not yet support vector types with
4753 </div>
4755 <!-- _______________________________________________________________________ -->
4757 </div>
4762 <pre>
4763 <result> = fcmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i>
4764 </pre>
4768 values based on comparison of its operands.</p>
4770 <p>If the operands are floating point scalars, then the result type is a boolean
4773 <p>If the operands are floating point vectors, then the result type is a vector
4774 of boolean with the same number of elements as the operands being
4775 compared.</p>
4779 the condition code indicating the kind of comparison to perform. It is not a
4780 value, just a keyword. The possible condition code are:</p>
4782 <ol>
4799 </ol>
4807 identical types.</p>
4812 vectors, then the vectors are compared element by element. Each comparison
4814 follows:</p>
4816 <ol>
4860 </ol>
4863 <pre>
4868 </pre>
4870 <p>Note that the code generator does not yet support vector types with
4873 </div>
4875 <!-- _______________________________________________________________________ -->
4878 </div>
4883 <pre>
4885 </pre>
4889 SSA graph representing the function.</p>
4892 <p>The type of the incoming values is specified with the first type field. After
4894 one pair for each predecessor basic block of the current block. Only values
4896 arguments to the PHI node. Only labels may be used as the label
4897 arguments.</p>
4899 <p>There must be no non-phi instructions between the start of a basic block and
4900 the PHI instructions: i.e. PHI instructions must be first in a basic
4901 block.</p>
4903 <p>For the purposes of the SSA form, the use of each incoming value is deemed to
4904 occur on the edge from the corresponding predecessor block to the current
4906 value on the same edge).</p>
4910 specified by the pair corresponding to the predecessor basic block that
4911 executed just prior to the current block.</p>
4914 <pre>
4915 Loop: ; Infinite loop that counts from 0 on up...
4916 %indvar = phi i32 [ 0, %LoopHeader ], [ %nextindvar, %Loop ]
4917 %nextindvar = add i32 %indvar, 1
4918 br label %Loop
4919 </pre>
4921 </div>
4923 <!-- _______________________________________________________________________ -->
4926 </div>
4931 <pre>
4932 <result> = select <i>selty</i> <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i>
4935 </pre>
4939 condition, without branching.</p>
4944 values indicating the condition, and two values of the
4946 vectors and the condition is a scalar, then entire vectors are selected, not
4947 individual elements.</p>
4951 first value argument; otherwise, it returns the second value argument.</p>
4953 <p>If the condition is a vector of i1, then the value arguments must be vectors
4954 of the same size, and the selection is done element by element.</p>
4957 <pre>
4959 </pre>
4961 <p>Note that the code generator does not yet support conditions
4962 with vector type.</p>
4964 </div>
4966 <!-- _______________________________________________________________________ -->
4969 </div>
4974 <pre>
4975 <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>]
4976 </pre>
4984 <ol>
4986 any allocas or varargs in the caller. If the "tail" marker is present,
4987 the function call is eligible for tail call optimization. Note that calls
4988 may be marked "tail" even if they do not occur before
4992 convention</a> the call should use. If none is specified, the call
4993 defaults to using C calling conventions.</li>
5000 type of the return value. Functions that return no value are marked
5004 being invoked. The argument types must match the types implied by this
5005 signature. This type can be omitted if the function is not varargs and if
5006 the function type does not return a pointer to a function.</li>
5009 be invoked. In most cases, this is a direct function invocation, but
5011 to function value.</li>
5014 signature argument types. All arguments must be of
5016 indicates the function accepts a variable number of arguments, the extra
5017 arguments can be specified.</li>
5022 </ol>
5026 a specified function, with its incoming arguments bound to the specified
5028 function, control flow continues with the instruction after the function
5029 call, and the return value of the function is bound to the result
5030 argument.</p>
5033 <pre>
5034 %retval = call i32 @test(i32 %argc)
5038 call void %foo(i8 97 signext)
5040 %struct.A = type { i32, i8 }
5046 </pre>
5048 </div>
5050 <!-- _______________________________________________________________________ -->
5053 </div>
5058 <pre>
5060 </pre>
5064 the "variable argument" area of a function call. It is used to implement the
5069 argument. It returns a value of the specified argument type and increments
5076 to the next argument. For more information, see the variable argument
5079 <p>It is legal for this instruction to be called in a function which does not
5081 function.</p>
5085 argument.</p>
5090 <p>Note that the code generator does not yet fully support va_arg on many
5091 targets. Also, it does not currently support va_arg with aggregate types on
5092 any target.</p>
5094 </div>
5096 <!-- *********************************************************************** -->
5098 <!-- *********************************************************************** -->
5103 well known names and semantics and are required to follow certain
5104 restrictions. Overall, these intrinsics represent an extension mechanism for
5105 the LLVM language that does not require changing all of the transformations
5106 in LLVM when adding to the language (or the bitcode reader/writer, the
5107 parser, etc...).</p>
5110 prefix is reserved in LLVM for intrinsic names; thus, function names may not
5111 begin with this prefix. Intrinsic functions must always be external
5112 functions: you cannot define the body of intrinsic functions. Intrinsic
5113 functions may only be used in call or invoke instructions: it is illegal to
5114 take the address of an intrinsic function. Additionally, because intrinsic
5115 functions are part of the LLVM language, it is required if any are added that
5116 they be documented here.</p>
5118 <p>Some intrinsic functions can be overloaded, i.e., the intrinsic represents a
5119 family of functions that perform the same operation but on different data
5120 types. Because LLVM can represent over 8 million different integer types,
5121 overloading is used commonly to allow an intrinsic function to operate on any
5122 integer type. One or more of the argument types or the result type can be
5123 overloaded to accept any integer type. Argument types may also be defined as
5124 exactly matching a previous argument's type or the result type. This allows
5125 an intrinsic function which accepts multiple arguments, but needs all of them
5126 to be of the same type, to only be overloaded with respect to a single
5127 argument or the result.</p>
5129 <p>Overloaded intrinsics will have the names of its overloaded argument types
5130 encoded into its function name, each preceded by a period. Only those types
5131 which are overloaded result in a name suffix. Arguments whose type is matched
5133 can take an integer of any width and returns an integer of exactly the same
5134 integer width. This leads to a family of functions such as
5136 %val)</tt>. Only one type, the return type, is overloaded, and only one type
5137 suffix is required. Because the argument's type is matched against the return
5138 type, it does not require its own name suffix.</p>
5140 <p>To learn how to add an intrinsic function, please see the
5143 </div>
5145 <!-- ======================================================================= -->
5148 </div>
5152 <p>Variable argument support is defined in LLVM with
5154 intrinsic functions. These functions are related to the similarly named
5157 <p>All of these functions operate on arguments that use a target-specific value
5158 type "<tt>va_list</tt>". The LLVM assembly language reference manual does
5159 not define what this type is, so all transformations should be prepared to
5160 handle these functions regardless of the type used.</p>
5163 instruction and the variable argument handling intrinsic functions are
5164 used.</p>
5167 <pre>
5168 define i32 @test(i32 %X, ...) {
5169 ; Initialize variable argument processing
5170 %ap = alloca i8*
5171 %ap2 = bitcast i8** %ap to i8*
5172 call void @llvm.va_start(i8* %ap2)
5174 ; Read a single integer argument
5175 %tmp = va_arg i8** %ap, i32
5177 ; Demonstrate usage of llvm.va_copy and llvm.va_end
5178 %aq = alloca i8*
5179 %aq2 = bitcast i8** %aq to i8*
5180 call void @llvm.va_copy(i8* %aq2, i8* %ap2)
5181 call void @llvm.va_end(i8* %aq2)
5183 ; Stop processing of arguments.
5184 call void @llvm.va_end(i8* %ap2)
5185 ret i32 %tmp
5186 }
5188 declare void @llvm.va_start(i8*)
5189 declare void @llvm.va_copy(i8*, i8*)
5190 declare void @llvm.va_end(i8*)
5191 </pre>
5192 </div>
5194 </div>
5196 <!-- _______________________________________________________________________ -->
5199 </div>
5205 <pre>
5207 </pre>
5218 macro available in C. In a target-dependent way, it initializes
5222 need to know the last argument of the function as the compiler can figure
5223 that out.</p>
5225 </div>
5227 <!-- _______________________________________________________________________ -->
5230 </div>
5235 <pre>
5237 </pre>
5241 which has been initialized previously
5250 macro available in C. In a target-dependent way, it destroys
5256 </div>
5258 <!-- _______________________________________________________________________ -->
5261 </div>
5266 <pre>
5268 </pre>
5272 from the source argument list to the destination argument list.</p>
5277 from.</p>
5281 macro available in C. In a target-dependent way, it copies the
5283 element. This intrinsic is necessary because
5285 arbitrarily complex and require, for example, memory allocation.</p>
5287 </div>
5289 <!-- ======================================================================= -->
5292 </div>
5297 Collection</a> (GC) requires the implementation and generation of these
5299 roots on the stack</a>, as well as garbage collector implementations that
5301 barriers. Front-ends for type-safe garbage collected languages should generate
5302 these intrinsics to make use of the LLVM garbage collectors. For more details,
5306 <p>The garbage collection intrinsics only operate on objects in the generic
5307 address space (address space zero).</p>
5309 </div>
5311 <!-- _______________________________________________________________________ -->
5314 </div>
5319 <pre>
5320 declare void @llvm.gcroot(i8** %ptrloc, i8* %metadata)
5321 </pre>
5325 the code generator, and allows some metadata to be associated with it.</p>
5328 <p>The first argument specifies the address of a stack object that contains the
5329 root pointer. The second pointer (which must be either a constant or a
5330 global value address) contains the meta-data to be associated with the
5331 root.</p>
5335 location. At compile-time, the code generator generates information to allow
5340 </div>
5342 <!-- _______________________________________________________________________ -->
5345 </div>
5350 <pre>
5351 declare i8* @llvm.gcread(i8* %ObjPtr, i8** %Ptr)
5352 </pre>
5356 locations, allowing garbage collector implementations that require read
5357 barriers.</p>
5360 <p>The second argument is the address to read from, which should be an address
5361 allocated from the garbage collector. The first object is a pointer to the
5362 start of the referenced object, if needed by the language runtime (otherwise
5363 null).</p>
5367 instruction, but may be replaced with substantially more complex code by the
5372 </div>
5374 <!-- _______________________________________________________________________ -->
5377 </div>
5382 <pre>
5383 declare void @llvm.gcwrite(i8* %P1, i8* %Obj, i8** %P2)
5384 </pre>
5388 locations, allowing garbage collector implementations that require write
5389 barriers (such as generational or reference counting collectors).</p>
5392 <p>The first argument is the reference to store, the second is the start of the
5393 object to store it to, and the third is the address of the field of Obj to
5394 store to. If the runtime does not require a pointer to the object, Obj may
5395 be null.</p>
5399 instruction, but may be replaced with substantially more complex code by the
5404 </div>
5406 <!-- ======================================================================= -->
5409 </div>
5413 <p>These intrinsics are provided by LLVM to expose special features that may
5414 only be implemented with code generator support.</p>
5416 </div>
5418 <!-- _______________________________________________________________________ -->
5421 </div>
5426 <pre>
5428 </pre>
5432 target-specific value indicating the return address of the current function
5433 or one of its callers.</p>
5436 <p>The argument to this intrinsic indicates which function to return the address
5437 for. Zero indicates the calling function, one indicates its caller, etc.
5442 indicating the return address of the specified call frame, or zero if it
5443 cannot be identified. The value returned by this intrinsic is likely to be
5444 incorrect or 0 for arguments other than zero, so it should only be used for
5445 debugging purposes.</p>
5447 <p>Note that calling this intrinsic does not prevent function inlining or other
5448 aggressive transformations, so the value returned may not be that of the
5449 obvious source-language caller.</p>
5451 </div>
5453 <!-- _______________________________________________________________________ -->
5456 </div>
5461 <pre>
5463 </pre>
5467 target-specific frame pointer value for the specified stack frame.</p>
5470 <p>The argument to this intrinsic indicates which function to return the frame
5471 pointer for. Zero indicates the calling function, one indicates its caller,
5476 indicating the frame address of the specified call frame, or zero if it
5477 cannot be identified. The value returned by this intrinsic is likely to be
5478 incorrect or 0 for arguments other than zero, so it should only be used for
5479 debugging purposes.</p>
5481 <p>Note that calling this intrinsic does not prevent function inlining or other
5482 aggressive transformations, so the value returned may not be that of the
5483 obvious source-language caller.</p>
5485 </div>
5487 <!-- _______________________________________________________________________ -->
5490 </div>
5495 <pre>
5496 declare i8 *@llvm.stacksave()
5497 </pre>
5501 of the function stack, for use
5503 useful for implementing language features like scoped automatic variable
5504 sized arrays in C99.</p>
5507 <p>This intrinsic returns a opaque pointer value that can be passed
5515 </div>
5517 <!-- _______________________________________________________________________ -->
5520 </div>
5525 <pre>
5526 declare void @llvm.stackrestore(i8 * %ptr)
5527 </pre>
5531 the function stack to the state it was in when the
5533 executed. This is useful for implementing language features like scoped
5534 automatic variable sized arrays in C99.</p>
5537 <p>See the description
5540 </div>
5542 <!-- _______________________________________________________________________ -->
5545 </div>
5550 <pre>
5552 </pre>
5556 insert a prefetch instruction if supported; otherwise, it is a noop.
5557 Prefetches have no effect on the behavior of the program but can change its
5558 performance characteristics.</p>
5568 <p>This intrinsic does not modify the behavior of the program. In particular,
5569 prefetches cannot trap and do not produce a value. On targets that support
5570 this intrinsic, the prefetch can provide hints to the processor cache for
5571 better performance.</p>
5573 </div>
5575 <!-- _______________________________________________________________________ -->
5578 </div>
5583 <pre>
5585 </pre>
5589 Counter (PC) in a region of code to simulators and other tools. The method
5590 is target specific, but it is expected that the marker will use exported
5591 symbols to transmit the PC of the marker. The marker makes no guarantees
5592 that it will remain with any specific instruction after optimizations. It is
5593 possible that the presence of a marker will inhibit optimizations. The
5594 intended use is to be inserted after optimizations to allow correlations of
5595 simulation runs.</p>
5601 <p>This intrinsic does not modify the behavior of the program. Backends that do
5602 not support this intrinisic may ignore it.</p>
5604 </div>
5606 <!-- _______________________________________________________________________ -->
5609 </div>
5614 <pre>
5615 declare i64 @llvm.readcyclecounter( )
5616 </pre>
5620 counter register (or similar low latency, high accuracy clocks) on those
5621 targets that support it. On X86, it should map to RDTSC. On Alpha, it
5622 should map to RPCC. As the backing counters overflow quickly (on the order
5626 <p>When directly supported, reading the cycle counter should not modify any
5627 memory. Implementations are allowed to either return a application specific
5628 value or a system wide value. On backends without support, this is lowered
5631 </div>
5633 <!-- ======================================================================= -->
5636 </div>
5640 <p>LLVM provides intrinsics for a few important standard C library functions.
5641 These intrinsics allow source-language front-ends to pass information about
5642 the alignment of the pointer arguments to the code generator, providing
5643 opportunity for more efficient code generation.</p>
5645 </div>
5647 <!-- _______________________________________________________________________ -->
5650 </div>
5656 integer bit width. Not all targets support all bit widths however.</p>
5658 <pre>
5667 </pre>
5671 source location to the destination location.</p>
5674 intrinsics do not return a value, and takes an extra alignment argument.</p>
5677 <p>The first argument is a pointer to the destination, the second is a pointer
5678 to the source. The third argument is an integer argument specifying the
5679 number of bytes to copy, and the fourth argument is the alignment of the
5680 source and destination locations.</p>
5683 then the caller guarantees that both the source and destination pointers are
5684 aligned to that boundary.</p>
5688 source location to the destination location, which are not allowed to
5689 overlap. It copies "len" bytes of memory over. If the argument is known to
5690 be aligned to some boundary, this can be specified as the fourth argument,
5693 </div>
5695 <!-- _______________________________________________________________________ -->
5698 </div>
5703 <p>This is an overloaded intrinsic. You can use llvm.memmove on any integer bit
5704 width. Not all targets support all bit widths however.</p>
5706 <pre>
5715 </pre>
5719 source location to the destination location. It is similar to the
5721 overlap.</p>
5724 intrinsics do not return a value, and takes an extra alignment argument.</p>
5727 <p>The first argument is a pointer to the destination, the second is a pointer
5728 to the source. The third argument is an integer argument specifying the
5729 number of bytes to copy, and the fourth argument is the alignment of the
5730 source and destination locations.</p>
5733 then the caller guarantees that the source and destination pointers are
5734 aligned to that boundary.</p>
5738 source location to the destination location, which may overlap. It copies
5739 "len" bytes of memory over. If the argument is known to be aligned to some
5740 boundary, this can be specified as the fourth argument, otherwise it should
5743 </div>
5745 <!-- _______________________________________________________________________ -->
5748 </div>
5753 <p>This is an overloaded intrinsic. You can use llvm.memset on any integer bit
5754 width. Not all targets support all bit widths however.</p>
5756 <pre>
5765 </pre>
5769 particular byte value.</p>
5772 intrinsic does not return a value, and takes an extra alignment argument.</p>
5775 <p>The first argument is a pointer to the destination to fill, the second is the
5776 byte value to fill it with, the third argument is an integer argument
5777 specifying the number of bytes to fill, and the fourth argument is the known
5778 alignment of destination location.</p>
5781 then the caller guarantees that the destination pointer is aligned to that
5782 boundary.</p>
5786 at the destination location. If the argument is known to be aligned to some
5787 boundary, this can be specified as the fourth argument, otherwise it should
5790 </div>
5792 <!-- _______________________________________________________________________ -->
5795 </div>
5801 floating point or vector of floating point type. Not all targets support all
5802 types however.</p>
5804 <pre>
5805 declare float @llvm.sqrt.f32(float %Val)
5806 declare double @llvm.sqrt.f64(double %Val)
5807 declare x86_fp80 @llvm.sqrt.f80(x86_fp80 %Val)
5808 declare fp128 @llvm.sqrt.f128(fp128 %Val)
5809 declare ppc_fp128 @llvm.sqrt.ppcf128(ppc_fp128 %Val)
5810 </pre>
5816 behavior for negative numbers other than -0.0 (which allows for better
5817 optimization, because there is no need to worry about errno being
5821 <p>The argument and return value are floating point numbers of the same
5822 type.</p>
5825 <p>This function returns the sqrt of the specified operand if it is a
5826 nonnegative floating point number.</p>
5828 </div>
5830 <!-- _______________________________________________________________________ -->
5833 </div>
5839 floating point or vector of floating point type. Not all targets support all
5840 types however.</p>
5842 <pre>
5843 declare float @llvm.powi.f32(float %Val, i32 %power)
5844 declare double @llvm.powi.f64(double %Val, i32 %power)
5845 declare x86_fp80 @llvm.powi.f80(x86_fp80 %Val, i32 %power)
5846 declare fp128 @llvm.powi.f128(fp128 %Val, i32 %power)
5847 declare ppc_fp128 @llvm.powi.ppcf128(ppc_fp128 %Val, i32 %power)
5848 </pre>
5852 specified (positive or negative) power. The order of evaluation of
5853 multiplications is not defined. When a vector of floating point type is
5854 used, the second argument remains a scalar integer value.</p>
5857 <p>The second argument is an integer power, and the first is a value to raise to
5858 that power.</p>
5861 <p>This function returns the first value raised to the second power with an
5862 unspecified sequence of rounding operations.</p>
5864 </div>
5866 <!-- _______________________________________________________________________ -->
5869 </div>
5875 floating point or vector of floating point type. Not all targets support all
5876 types however.</p>
5878 <pre>
5879 declare float @llvm.sin.f32(float %Val)
5880 declare double @llvm.sin.f64(double %Val)
5881 declare x86_fp80 @llvm.sin.f80(x86_fp80 %Val)
5882 declare fp128 @llvm.sin.f128(fp128 %Val)
5883 declare ppc_fp128 @llvm.sin.ppcf128(ppc_fp128 %Val)
5884 </pre>
5890 <p>The argument and return value are floating point numbers of the same
5891 type.</p>
5894 <p>This function returns the sine of the specified operand, returning the same
5896 in the same way.</p>
5898 </div>
5900 <!-- _______________________________________________________________________ -->
5903 </div>
5909 floating point or vector of floating point type. Not all targets support all
5910 types however.</p>
5912 <pre>
5913 declare float @llvm.cos.f32(float %Val)
5914 declare double @llvm.cos.f64(double %Val)
5915 declare x86_fp80 @llvm.cos.f80(x86_fp80 %Val)
5916 declare fp128 @llvm.cos.f128(fp128 %Val)
5917 declare ppc_fp128 @llvm.cos.ppcf128(ppc_fp128 %Val)
5918 </pre>
5924 <p>The argument and return value are floating point numbers of the same
5925 type.</p>
5928 <p>This function returns the cosine of the specified operand, returning the same
5930 in the same way.</p>
5932 </div>
5934 <!-- _______________________________________________________________________ -->
5937 </div>
5943 floating point or vector of floating point type. Not all targets support all
5944 types however.</p>
5946 <pre>
5947 declare float @llvm.pow.f32(float %Val, float %Power)
5948 declare double @llvm.pow.f64(double %Val, double %Power)
5949 declare x86_fp80 @llvm.pow.f80(x86_fp80 %Val, x86_fp80 %Power)
5950 declare fp128 @llvm.pow.f128(fp128 %Val, fp128 %Power)
5951 declare ppc_fp128 @llvm.pow.ppcf128(ppc_fp128 %Val, ppc_fp128 Power)
5952 </pre>
5956 specified (positive or negative) power.</p>
5959 <p>The second argument is a floating point power, and the first is a value to
5960 raise to that power.</p>
5963 <p>This function returns the first value raised to the second power, returning
5965 conditions in the same way.</p>
5967 </div>
5969 <!-- ======================================================================= -->
5972 </div>
5976 <p>LLVM provides intrinsics for a few important bit manipulation operations.
5977 These allow efficient code generation for some algorithms.</p>
5979 </div>
5981 <!-- _______________________________________________________________________ -->
5984 </div>
5989 <p>This is an overloaded intrinsic function. You can use bswap on any integer
5992 <pre>
5996 </pre>
6000 values with an even number of bytes (positive multiple of 16 bits). These
6001 are useful for performing operations on data that is not in the target's
6002 native byte order.</p>
6006 and low byte of the input i16 swapped. Similarly,
6012 more, respectively).</p>
6014 </div>
6016 <!-- _______________________________________________________________________ -->
6019 </div>
6024 <p>This is an overloaded intrinsic. You can use llvm.ctpop on any integer bit
6025 width. Not all targets support all bit widths however.</p>
6027 <pre>
6033 </pre>
6037 in a value.</p>
6040 <p>The only argument is the value to be counted. The argument may be of any
6041 integer type. The return type must match the argument type.</p>
6046 </div>
6048 <!-- _______________________________________________________________________ -->
6051 </div>
6057 integer bit width. Not all targets support all bit widths however.</p>
6059 <pre>
6065 </pre>
6069 leading zeros in a variable.</p>
6072 <p>The only argument is the value to be counted. The argument may be of any
6073 integer type. The return type must match the argument type.</p>
6077 zeros in a variable. If the src == 0 then the result is the size in bits of
6080 </div>
6082 <!-- _______________________________________________________________________ -->
6085 </div>
6091 integer bit width. Not all targets support all bit widths however.</p>
6093 <pre>
6099 </pre>
6103 trailing zeros.</p>
6106 <p>The only argument is the value to be counted. The argument may be of any
6107 integer type. The return type must match the argument type.</p>
6111 zeros in a variable. If the src == 0 then the result is the size in bits of
6114 </div>
6116 <!-- ======================================================================= -->
6119 </div>
6125 </div>
6127 <!-- _______________________________________________________________________ -->
6130 </div>
6136 on any integer bit width.</p>
6138 <pre>
6139 declare {i16, i1} @llvm.sadd.with.overflow.i16(i16 %a, i16 %b)
6140 declare {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
6141 declare {i64, i1} @llvm.sadd.with.overflow.i64(i64 %a, i64 %b)
6142 </pre>
6146 a signed addition of the two arguments, and indicate whether an overflow
6147 occurred during the signed summation.</p>
6150 <p>The arguments (%a and %b) and the first element of the result structure may
6151 be of integer types of any bit width, but they must have the same bit
6152 width. The second element of the result structure must be of
6154 undergo signed addition.</p>
6158 a signed addition of the two variables. They return a structure — the
6159 first element of which is the signed summation, and the second element of
6160 which is a bit specifying if the signed summation resulted in an
6161 overflow.</p>
6164 <pre>
6165 %res = call {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
6166 %sum = extractvalue {i32, i1} %res, 0
6167 %obit = extractvalue {i32, i1} %res, 1
6168 br i1 %obit, label %overflow, label %normal
6169 </pre>
6171 </div>
6173 <!-- _______________________________________________________________________ -->
6176 </div>
6182 on any integer bit width.</p>
6184 <pre>
6185 declare {i16, i1} @llvm.uadd.with.overflow.i16(i16 %a, i16 %b)
6186 declare {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
6187 declare {i64, i1} @llvm.uadd.with.overflow.i64(i64 %a, i64 %b)
6188 </pre>
6192 an unsigned addition of the two arguments, and indicate whether a carry
6193 occurred during the unsigned summation.</p>
6196 <p>The arguments (%a and %b) and the first element of the result structure may
6197 be of integer types of any bit width, but they must have the same bit
6198 width. The second element of the result structure must be of
6200 undergo unsigned addition.</p>
6204 an unsigned addition of the two arguments. They return a structure —
6205 the first element of which is the sum, and the second element of which is a
6206 bit specifying if the unsigned summation resulted in a carry.</p>
6209 <pre>
6210 %res = call {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
6211 %sum = extractvalue {i32, i1} %res, 0
6212 %obit = extractvalue {i32, i1} %res, 1
6213 br i1 %obit, label %carry, label %normal
6214 </pre>
6216 </div>
6218 <!-- _______________________________________________________________________ -->
6221 </div>
6227 on any integer bit width.</p>
6229 <pre>
6230 declare {i16, i1} @llvm.ssub.with.overflow.i16(i16 %a, i16 %b)
6231 declare {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b)
6232 declare {i64, i1} @llvm.ssub.with.overflow.i64(i64 %a, i64 %b)
6233 </pre>
6237 a signed subtraction of the two arguments, and indicate whether an overflow
6238 occurred during the signed subtraction.</p>
6241 <p>The arguments (%a and %b) and the first element of the result structure may
6242 be of integer types of any bit width, but they must have the same bit
6243 width. The second element of the result structure must be of
6245 undergo signed subtraction.</p>
6249 a signed subtraction of the two arguments. They return a structure —
6250 the first element of which is the subtraction, and the second element of
6251 which is a bit specifying if the signed subtraction resulted in an
6252 overflow.</p>
6255 <pre>
6256 %res = call {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b)
6257 %sum = extractvalue {i32, i1} %res, 0
6258 %obit = extractvalue {i32, i1} %res, 1
6259 br i1 %obit, label %overflow, label %normal
6260 </pre>
6262 </div>
6264 <!-- _______________________________________________________________________ -->
6267 </div>
6273 on any integer bit width.</p>
6275 <pre>
6276 declare {i16, i1} @llvm.usub.with.overflow.i16(i16 %a, i16 %b)
6277 declare {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b)
6278 declare {i64, i1} @llvm.usub.with.overflow.i64(i64 %a, i64 %b)
6279 </pre>
6283 an unsigned subtraction of the two arguments, and indicate whether an
6284 overflow occurred during the unsigned subtraction.</p>
6287 <p>The arguments (%a and %b) and the first element of the result structure may
6288 be of integer types of any bit width, but they must have the same bit
6289 width. The second element of the result structure must be of
6291 undergo unsigned subtraction.</p>
6295 an unsigned subtraction of the two arguments. They return a structure —
6296 the first element of which is the subtraction, and the second element of
6297 which is a bit specifying if the unsigned subtraction resulted in an
6298 overflow.</p>
6301 <pre>
6302 %res = call {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b)
6303 %sum = extractvalue {i32, i1} %res, 0
6304 %obit = extractvalue {i32, i1} %res, 1
6305 br i1 %obit, label %overflow, label %normal
6306 </pre>
6308 </div>
6310 <!-- _______________________________________________________________________ -->
6313 </div>
6319 on any integer bit width.</p>
6321 <pre>
6322 declare {i16, i1} @llvm.smul.with.overflow.i16(i16 %a, i16 %b)
6323 declare {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b)
6324 declare {i64, i1} @llvm.smul.with.overflow.i64(i64 %a, i64 %b)
6325 </pre>
6330 a signed multiplication of the two arguments, and indicate whether an
6331 overflow occurred during the signed multiplication.</p>
6334 <p>The arguments (%a and %b) and the first element of the result structure may
6335 be of integer types of any bit width, but they must have the same bit
6336 width. The second element of the result structure must be of
6338 undergo signed multiplication.</p>
6342 a signed multiplication of the two arguments. They return a structure —
6343 the first element of which is the multiplication, and the second element of
6344 which is a bit specifying if the signed multiplication resulted in an
6345 overflow.</p>
6348 <pre>
6349 %res = call {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b)
6350 %sum = extractvalue {i32, i1} %res, 0
6351 %obit = extractvalue {i32, i1} %res, 1
6352 br i1 %obit, label %overflow, label %normal
6353 </pre>
6355 </div>
6357 <!-- _______________________________________________________________________ -->
6360 </div>
6366 on any integer bit width.</p>
6368 <pre>
6369 declare {i16, i1} @llvm.umul.with.overflow.i16(i16 %a, i16 %b)
6370 declare {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b)
6371 declare {i64, i1} @llvm.umul.with.overflow.i64(i64 %a, i64 %b)
6372 </pre>
6376 a unsigned multiplication of the two arguments, and indicate whether an
6377 overflow occurred during the unsigned multiplication.</p>
6380 <p>The arguments (%a and %b) and the first element of the result structure may
6381 be of integer types of any bit width, but they must have the same bit
6382 width. The second element of the result structure must be of
6384 undergo unsigned multiplication.</p>
6388 an unsigned multiplication of the two arguments. They return a structure
6389 — the first element of which is the multiplication, and the second
6390 element of which is a bit specifying if the unsigned multiplication resulted
6391 in an overflow.</p>
6394 <pre>
6395 %res = call {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b)
6396 %sum = extractvalue {i32, i1} %res, 0
6397 %obit = extractvalue {i32, i1} %res, 1
6398 br i1 %obit, label %overflow, label %normal
6399 </pre>
6401 </div>
6403 <!-- ======================================================================= -->
6406 </div>
6411 prefix), are described in
6415 </div>
6417 <!-- ======================================================================= -->
6420 </div>
6424 <p>The LLVM exception handling intrinsics (which all start with
6429 </div>
6431 <!-- ======================================================================= -->
6434 </div>
6438 <p>This intrinsic makes it possible to excise one parameter, marked with
6440 function pointer lacking the nest parameter - the caller does not need to
6441 provide a value for it. Instead, the value to use is stored in advance in a
6442 "trampoline", a block of memory usually allocated on the stack, which also
6443 contains code to splice the nest value into the argument list. This is used
6444 to implement the GCC nested function address extension.</p>
6446 <p>For example, if the function is
6449 follows:</p>
6452 <pre>
6455 %p = call i8* @llvm.init.trampoline( i8* %tramp1, i8* bitcast (i32 (i8* nest , i32, i32)* @f to i8*), i8* %nval )
6456 %fp = bitcast i8* %p to i32 (i32, i32)*
6457 </pre>
6458 </div>
6463 </div>
6465 <!-- _______________________________________________________________________ -->
6468 </div>
6473 <pre>
6475 </pre>
6479 function pointer suitable for executing it.</p>
6484 sufficiently aligned block of memory; this memory is written to by the
6485 intrinsic. Note that the size and the alignment are target-specific - LLVM
6486 currently provides no portable way of determining them, so a front-end that
6487 generates this intrinsic needs to have some target-specific knowledge.
6493 dependent code, turning it into a function. A pointer to this function is
6495 function pointer type</a> before being called. The new function's signature
6498 is allowed, and it must be of pointer type. Calling the new function is
6503 returned function pointer is undefined.</p>
6505 </div>
6507 <!-- ======================================================================= -->
6510 </div>
6515 hardware constructs for atomic operations and memory synchronization. This
6516 provides an interface to the hardware, not an interface to the programmer. It
6517 is aimed at a low enough level to allow any programming models or APIs
6518 (Application Programming Interfaces) which need atomic behaviors to map
6519 cleanly onto it. It is also modeled primarily on hardware behavior. Just as
6520 hardware provides a "universal IR" for source languages, it also provides a
6521 starting point for developing a "universal" atomic operation and
6522 synchronization IR.</p>
6525 software transaction memory systems, atomic primitives, and intrinsic
6526 functions as found in BSD, GNU libc, atomic_ops, APR, and other system and
6527 application libraries. The hardware interface provided by LLVM should allow
6528 a clean implementation of all of these APIs and parallel programming models.
6529 No one model or paradigm should be selected above others unless the hardware
6530 itself ubiquitously does so.</p>
6532 </div>
6534 <!-- _______________________________________________________________________ -->
6537 </div>
6540 <pre>
6541 declare void @llvm.memory.barrier( i1 <ll>, i1 <ls>, i1 <sl>, i1 <ss>, i1 <device> )
6542 </pre>
6546 specific pairs of memory access types.</p>
6550 The first four arguments enables a specific barrier as listed below. The
6551 fith argument specifies that the barrier applies to io or device or uncached
6552 memory.</p>
6554 <ul>
6560 </ul>
6563 <p>This intrinsic causes the system to enforce some ordering constraints upon
6564 the loads and stores of the program. This barrier does not
6567 and store operations (f.ex. load-load, or store-load), all of the first
6568 operations preceding the barrier will complete before any of the second
6569 operations succeeding the barrier begin. Specifically the semantics for each
6570 pairing is as follows:</p>
6572 <ul>
6574 after the barrier begins.</li>
6576 store after the barrier begins.</li>
6578 store after the barrier begins.</li>
6580 load after the barrier begins.</li>
6581 </ul>
6584 is enabled in a single memory barrier intrinsic.</p>
6586 <p>Backends may implement stronger barriers than those requested when they do
6587 not support as fine grained a barrier as requested. Some architectures do
6588 not need all types of barriers and on such architectures, these become
6589 noops.</p>
6592 <pre>
6593 %ptr = malloc i32
6594 store i32 4, %ptr
6597 call void @llvm.memory.barrier( i1 false, i1 true, i1 false, i1 false )
6600 </pre>
6602 </div>
6604 <!-- _______________________________________________________________________ -->
6607 </div>
6613 any integer bit width and for different address spaces. Not all targets
6614 support all bit widths however.</p>
6616 <pre>
6618 declare i16 @llvm.atomic.cmp.swap.i16.p0i16( i16* <ptr>, i16 <cmp>, i16 <val> )
6619 declare i32 @llvm.atomic.cmp.swap.i32.p0i32( i32* <ptr>, i32 <cmp>, i32 <val> )
6620 declare i64 @llvm.atomic.cmp.swap.i64.p0i64( i64* <ptr>, i64 <cmp>, i64 <val> )
6621 </pre>
6624 <p>This loads a value in memory and compares it to a given value. If they are
6625 equal, it stores a new value into the memory.</p>
6631 this integer type. While any bit width integer may be used, targets may only
6632 lower representations they support in hardware.</p>
6635 <p>This entire intrinsic must be executed atomically. It first loads the value
6638 memory. The loaded value is yielded in all cases. This provides the
6639 equivalent of an atomic compare-and-swap operation within the SSA
6640 framework.</p>
6643 <pre>
6644 %ptr = malloc i32
6645 store i32 4, %ptr
6648 %result1 = call i32 @llvm.atomic.cmp.swap.i32.p0i32( i32* %ptr, i32 4, %val1 )
6654 %result2 = call i32 @llvm.atomic.cmp.swap.i32.p0i32( i32* %ptr, i32 5, %val2 )
6659 </pre>
6661 </div>
6663 <!-- _______________________________________________________________________ -->
6666 </div>
6671 integer bit width. Not all targets support all bit widths however.</p>
6673 <pre>
6678 </pre>
6689 integer type. The targets may only lower integer representations they
6690 support.</p>
6695 equivalent of an atomic swap operation within the SSA framework.</p>
6698 <pre>
6699 %ptr = malloc i32
6700 store i32 4, %ptr
6703 %result1 = call i32 @llvm.atomic.swap.i32.p0i32( i32* %ptr, i32 %val1 )
6709 %result2 = call i32 @llvm.atomic.swap.i32.p0i32( i32* %ptr, i32 %val2 )
6714 </pre>
6716 </div>
6718 <!-- _______________________________________________________________________ -->
6722 </div>
6728 any integer bit width. Not all targets support all bit widths however.</p>
6730 <pre>
6735 </pre>
6742 <p>The intrinsic takes two arguments, the first a pointer to an integer value
6743 and the second an integer value. The result is also an integer value. These
6744 integer types can have any bit width, but they must all have the same bit
6745 width. The targets may only lower integer representations they support.</p>
6748 <p>This intrinsic does a series of operations atomically. It first loads the
6753 <pre>
6754 %ptr = malloc i32
6755 store i32 4, %ptr
6756 %result1 = call i32 @llvm.atomic.load.add.i32.p0i32( i32* %ptr, i32 4 )
6758 %result2 = call i32 @llvm.atomic.load.add.i32.p0i32( i32* %ptr, i32 2 )
6760 %result3 = call i32 @llvm.atomic.load.add.i32.p0i32( i32* %ptr, i32 5 )
6763 </pre>
6765 </div>
6767 <!-- _______________________________________________________________________ -->
6771 </div>
6777 any integer bit width and for different address spaces. Not all targets
6778 support all bit widths however.</p>
6780 <pre>
6785 </pre>
6792 <p>The intrinsic takes two arguments, the first a pointer to an integer value
6793 and the second an integer value. The result is also an integer value. These
6794 integer types can have any bit width, but they must all have the same bit
6795 width. The targets may only lower integer representations they support.</p>
6798 <p>This intrinsic does a series of operations atomically. It first loads the
6804 <pre>
6805 %ptr = malloc i32
6806 store i32 8, %ptr
6807 %result1 = call i32 @llvm.atomic.load.sub.i32.p0i32( i32* %ptr, i32 4 )
6809 %result2 = call i32 @llvm.atomic.load.sub.i32.p0i32( i32* %ptr, i32 2 )
6811 %result3 = call i32 @llvm.atomic.load.sub.i32.p0i32( i32* %ptr, i32 5 )
6814 </pre>
6816 </div>
6818 <!-- _______________________________________________________________________ -->
6824 </div>
6829 <p>These are overloaded intrinsics. You can
6832 bit width and for different address spaces. Not all targets support all bit
6833 widths however.</p>
6835 <pre>
6840 </pre>
6842 <pre>
6847 </pre>
6849 <pre>
6854 </pre>
6856 <pre>
6861 </pre>
6869 <p>These intrinsics take two arguments, the first a pointer to an integer value
6870 and the second an integer value. The result is also an integer value. These
6871 integer types can have any bit width, but they must all have the same bit
6872 width. The targets may only lower integer representations they support.</p>
6875 <p>These intrinsics does a series of operations atomically. They first load the
6881 <pre>
6882 %ptr = malloc i32
6883 store i32 0x0F0F, %ptr
6884 %result0 = call i32 @llvm.atomic.load.nand.i32.p0i32( i32* %ptr, i32 0xFF )
6886 %result1 = call i32 @llvm.atomic.load.and.i32.p0i32( i32* %ptr, i32 0xFF )
6888 %result2 = call i32 @llvm.atomic.load.or.i32.p0i32( i32* %ptr, i32 0F )
6890 %result3 = call i32 @llvm.atomic.load.xor.i32.p0i32( i32* %ptr, i32 0F )
6893 </pre>
6895 </div>
6897 <!-- _______________________________________________________________________ -->
6903 </div>
6911 address spaces. Not all targets support all bit widths however.</p>
6913 <pre>
6918 </pre>
6920 <pre>
6925 </pre>
6927 <pre>
6932 </pre>
6934 <pre>
6939 </pre>
6942 <p>These intrinsics takes the signed or unsigned minimum or maximum of
6947 <p>These intrinsics take two arguments, the first a pointer to an integer value
6948 and the second an integer value. The result is also an integer value. These
6949 integer types can have any bit width, but they must all have the same bit
6950 width. The targets may only lower integer representations they support.</p>
6953 <p>These intrinsics does a series of operations atomically. They first load the
6959 <pre>
6960 %ptr = malloc i32
6961 store i32 7, %ptr
6962 %result0 = call i32 @llvm.atomic.load.min.i32.p0i32( i32* %ptr, i32 -2 )
6964 %result1 = call i32 @llvm.atomic.load.max.i32.p0i32( i32* %ptr, i32 8 )
6966 %result2 = call i32 @llvm.atomic.load.umin.i32.p0i32( i32* %ptr, i32 10 )
6968 %result3 = call i32 @llvm.atomic.load.umax.i32.p0i32( i32* %ptr, i32 30 )
6971 </pre>
6973 </div>
6975 <!-- ======================================================================= -->
6978 </div>
6982 <p>This class of intrinsics is designed to be generic and has no specific
6983 purpose.</p>
6985 </div>
6987 <!-- _______________________________________________________________________ -->
6990 </div>
6995 <pre>
6996 declare void @llvm.var.annotation(i8* <val>, i8* <str>, i8* <str>, i32 <int> )
6997 </pre>
7003 <p>The first argument is a pointer to a value, the second is a pointer to a
7004 global string, the third is a pointer to a global string which is the source
7005 file name, and the last argument is the line number.</p>
7008 <p>This intrinsic allows annotation of local variables with arbitrary strings.
7009 This can be useful for special purpose optimizations that want to look for
7010 these annotations. These have no other defined use, they are ignored by code
7011 generation and optimization.</p>
7013 </div>
7015 <!-- _______________________________________________________________________ -->
7018 </div>
7024 any integer bit width.</p>
7026 <pre>
7027 declare i8 @llvm.annotation.i8(i8 <val>, i8* <str>, i8* <str>, i32 <int> )
7028 declare i16 @llvm.annotation.i16(i16 <val>, i8* <str>, i8* <str>, i32 <int> )
7029 declare i32 @llvm.annotation.i32(i32 <val>, i8* <str>, i8* <str>, i32 <int> )
7030 declare i64 @llvm.annotation.i64(i64 <val>, i8* <str>, i8* <str>, i32 <int> )
7031 declare i256 @llvm.annotation.i256(i256 <val>, i8* <str>, i8* <str>, i32 <int> )
7032 </pre>
7038 <p>The first argument is an integer value (result of some expression), the
7039 second is a pointer to a global string, the third is a pointer to a global
7040 string which is the source file name, and the last argument is the line
7041 number. It returns the value of the first argument.</p>
7044 <p>This intrinsic allows annotations to be put on arbitrary expressions with
7045 arbitrary strings. This can be useful for special purpose optimizations that
7046 want to look for these annotations. These have no other defined use, they
7047 are ignored by code generation and optimization.</p>
7049 </div>
7051 <!-- _______________________________________________________________________ -->
7054 </div>
7059 <pre>
7060 declare void @llvm.trap()
7061 </pre>
7070 <p>This intrinsics is lowered to the target dependent trap instruction. If the
7071 target does not have a trap instruction, this intrinsic will be lowered to
7074 </div>
7076 <!-- _______________________________________________________________________ -->
7079 </div>
7084 <pre>
7086 </pre>
7091 ensure that it is placed on the stack before local variables.</p>
7095 arguments. The first argument is the value loaded from the stack
7097 that has enough space to hold the value of the guard.</p>
7100 <p>This intrinsic causes the prologue/epilogue inserter to force the position of
7102 stack. This is to ensure that if a local variable on the stack is
7103 overwritten, it will destroy the value of the guard. When the function exits,
7104 the guard on the stack is checked against the original guard. If they're
7106 function.</p>
7108 </div>
7110 <!-- *********************************************************************** -->
7111 <hr>
7112 <address>
7120 Last modified: $Date$
7121 </address>
7123 </body>
7124 </html>