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| <title>LLVM Assembly Language Reference Manual</title> | |
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| <body> | |
| <div class="doc_title"> LLVM Language Reference Manual </div> | |
| <ol> | |
| <li><a href="#abstract">Abstract</a></li> | |
| <li><a href="#introduction">Introduction</a></li> | |
| <li><a href="#identifiers">Identifiers</a></li> | |
| <li><a href="#highlevel">High Level Structure</a> | |
| <ol> | |
| <li><a href="#modulestructure">Module Structure</a></li> | |
| <li><a href="#linkage">Linkage Types</a></li> | |
| <li><a href="#callingconv">Calling Conventions</a></li> | |
| <li><a href="#globalvars">Global Variables</a></li> | |
| <li><a href="#functionstructure">Function Structure</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#typesystem">Type System</a> | |
| <ol> | |
| <li><a href="#t_primitive">Primitive Types</a> | |
| <ol> | |
| <li><a href="#t_classifications">Type Classifications</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#t_derived">Derived Types</a> | |
| <ol> | |
| <li><a href="#t_array">Array Type</a></li> | |
| <li><a href="#t_function">Function Type</a></li> | |
| <li><a href="#t_pointer">Pointer Type</a></li> | |
| <li><a href="#t_struct">Structure Type</a></li> | |
| <li><a href="#t_packed">Packed Type</a></li> | |
| <li><a href="#t_opaque">Opaque Type</a></li> | |
| </ol> | |
| </li> | |
| </ol> | |
| </li> | |
| <li><a href="#constants">Constants</a> | |
| <ol> | |
| <li><a href="#simpleconstants">Simple Constants</a> | |
| <li><a href="#aggregateconstants">Aggregate Constants</a> | |
| <li><a href="#globalconstants">Global Variable and Function Addresses</a> | |
| <li><a href="#undefvalues">Undefined Values</a> | |
| <li><a href="#constantexprs">Constant Expressions</a> | |
| </ol> | |
| </li> | |
| <li><a href="#instref">Instruction Reference</a> | |
| <ol> | |
| <li><a href="#terminators">Terminator Instructions</a> | |
| <ol> | |
| <li><a href="#i_ret">'<tt>ret</tt>' Instruction</a></li> | |
| <li><a href="#i_br">'<tt>br</tt>' Instruction</a></li> | |
| <li><a href="#i_switch">'<tt>switch</tt>' Instruction</a></li> | |
| <li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a></li> | |
| <li><a href="#i_unwind">'<tt>unwind</tt>' Instruction</a></li> | |
| <li><a href="#i_unreachable">'<tt>unreachable</tt>' Instruction</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#binaryops">Binary Operations</a> | |
| <ol> | |
| <li><a href="#i_add">'<tt>add</tt>' Instruction</a></li> | |
| <li><a href="#i_sub">'<tt>sub</tt>' Instruction</a></li> | |
| <li><a href="#i_mul">'<tt>mul</tt>' Instruction</a></li> | |
| <li><a href="#i_div">'<tt>div</tt>' Instruction</a></li> | |
| <li><a href="#i_rem">'<tt>rem</tt>' Instruction</a></li> | |
| <li><a href="#i_setcc">'<tt>set<i>cc</i></tt>' Instructions</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#bitwiseops">Bitwise Binary Operations</a> | |
| <ol> | |
| <li><a href="#i_and">'<tt>and</tt>' Instruction</a></li> | |
| <li><a href="#i_or">'<tt>or</tt>' Instruction</a></li> | |
| <li><a href="#i_xor">'<tt>xor</tt>' Instruction</a></li> | |
| <li><a href="#i_shl">'<tt>shl</tt>' Instruction</a></li> | |
| <li><a href="#i_shr">'<tt>shr</tt>' Instruction</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#memoryops">Memory Access Operations</a> | |
| <ol> | |
| <li><a href="#i_malloc">'<tt>malloc</tt>' Instruction</a></li> | |
| <li><a href="#i_free">'<tt>free</tt>' Instruction</a></li> | |
| <li><a href="#i_alloca">'<tt>alloca</tt>' Instruction</a></li> | |
| <li><a href="#i_load">'<tt>load</tt>' Instruction</a></li> | |
| <li><a href="#i_store">'<tt>store</tt>' Instruction</a></li> | |
| <li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#otherops">Other Operations</a> | |
| <ol> | |
| <li><a href="#i_phi">'<tt>phi</tt>' Instruction</a></li> | |
| <li><a href="#i_cast">'<tt>cast .. to</tt>' Instruction</a></li> | |
| <li><a href="#i_select">'<tt>select</tt>' Instruction</a></li> | |
| <li><a href="#i_call">'<tt>call</tt>' Instruction</a></li> | |
| <li><a href="#i_vaarg">'<tt>vaarg</tt>' Instruction</a></li> | |
| </ol> | |
| </li> | |
| </ol> | |
| </li> | |
| <li><a href="#intrinsics">Intrinsic Functions</a> | |
| <ol> | |
| <li><a href="#int_varargs">Variable Argument Handling Intrinsics</a> | |
| <ol> | |
| <li><a href="#i_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a></li> | |
| <li><a href="#i_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a></li> | |
| <li><a href="#i_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_gc">Accurate Garbage Collection Intrinsics</a> | |
| <ol> | |
| <li><a href="#i_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a></li> | |
| <li><a href="#i_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a></li> | |
| <li><a href="#i_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_codegen">Code Generator Intrinsics</a> | |
| <ol> | |
| <li><a href="#i_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a></li> | |
| <li><a href="#i_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li> | |
| <li><a href="#i_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a></li> | |
| <li><a href="#i_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_os">Operating System Intrinsics</a> | |
| <ol> | |
| <li><a href="#i_readport">'<tt>llvm.readport</tt>' Intrinsic</a></li> | |
| <li><a href="#i_writeport">'<tt>llvm.writeport</tt>' Intrinsic</a></li> | |
| <li><a href="#i_readio">'<tt>llvm.readio</tt>' Intrinsic</a></li> | |
| <li><a href="#i_writeio">'<tt>llvm.writeio</tt>' Intrinsic</a></li> | |
| </ol> | |
| <li><a href="#int_libc">Standard C Library Intrinsics</a> | |
| <ol> | |
| <li><a href="#i_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a></li> | |
| <li><a href="#i_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a></li> | |
| <li><a href="#i_memset">'<tt>llvm.memset</tt>' Intrinsic</a></li> | |
| <li><a href="#i_isunordered">'<tt>llvm.isunordered</tt>' Intrinsic</a></li> | |
| <li><a href="#i_sqrt">'<tt>llvm.sqrt</tt>' Intrinsic</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_count">Bit counting Intrinsics</a> | |
| <ol> | |
| <li><a href="#int_ctpop">'<tt>llvm.ctpop</tt>' Intrinsic </a></li> | |
| <li><a href="#int_ctlz">'<tt>llvm.ctlz</tt>' Intrinsic </a></li> | |
| <li><a href="#int_cttz">'<tt>llvm.cttz</tt>' Intrinsic </a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#int_debugger">Debugger intrinsics</a></li> | |
| </ol> | |
| </li> | |
| </ol> | |
| <div class="doc_author"> | |
| <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a> | |
| and <a href="mailto:vadve@cs.uiuc.edu">Vikram Adve</a></p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="abstract">Abstract </a></div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>This document is a reference manual for the LLVM assembly language. | |
| LLVM is an SSA based representation that provides type safety, | |
| low-level operations, flexibility, and the capability of representing | |
| 'all' high-level languages cleanly. It is the common code | |
| representation used throughout all phases of the LLVM compilation | |
| strategy.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="introduction">Introduction</a> </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>The LLVM code representation is designed to be used in three | |
| different forms: as an in-memory compiler IR, as an on-disk bytecode | |
| representation (suitable for fast loading by a Just-In-Time compiler), | |
| and as a human readable assembly language representation. This allows | |
| LLVM to provide a powerful intermediate representation for efficient | |
| compiler transformations and analysis, while providing a natural means | |
| to debug and visualize the transformations. The three different forms | |
| of LLVM are all equivalent. This document describes the human readable | |
| representation and notation.</p> | |
| <p>The LLVM representation aims to be light-weight and low-level | |
| while being expressive, typed, and extensible at the same time. It | |
| aims to be a "universal IR" of sorts, by being at a low enough level | |
| that high-level ideas may be cleanly mapped to it (similar to how | |
| microprocessors are "universal IR's", allowing many source languages to | |
| be mapped to them). By providing type information, LLVM can be used as | |
| the target of optimizations: for example, through pointer analysis, it | |
| can be proven that a C automatic variable is never accessed outside of | |
| the current function... allowing it to be promoted to a simple SSA | |
| value instead of a memory location.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="wellformed">Well-Formedness</a> </div> | |
| <div class="doc_text"> | |
| <p>It is important to note that this document describes 'well formed' | |
| LLVM assembly language. There is a difference between what the parser | |
| accepts and what is considered 'well formed'. For example, the | |
| following instruction is syntactically okay, but not well formed:</p> | |
| <pre> | |
| %x = <a href="#i_add">add</a> int 1, %x | |
| </pre> | |
| <p>...because the definition of <tt>%x</tt> does not dominate all of | |
| its uses. The LLVM infrastructure provides a verification pass that may | |
| be used to verify that an LLVM module is well formed. This pass is | |
| automatically run by the parser after parsing input assembly and by | |
| the optimizer before it outputs bytecode. The violations pointed out | |
| by the verifier pass indicate bugs in transformation passes or input to | |
| the parser.</p> | |
| <!-- Describe the typesetting conventions here. --> </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="identifiers">Identifiers</a> </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>LLVM uses three different forms of identifiers, for different | |
| purposes:</p> | |
| <ol> | |
| <li>Named values are represented as a string of characters with a '%' prefix. | |
| For example, %foo, %DivisionByZero, %a.really.long.identifier. The actual | |
| regular expression used is '<tt>%[a-zA-Z$._][a-zA-Z$._0-9]*</tt>'. | |
| Identifiers which require other characters in their names can be surrounded | |
| with quotes. In this way, anything except a <tt>"</tt> character can be used | |
| in a name.</li> | |
| <li>Unnamed values are represented as an unsigned numeric value with a '%' | |
| prefix. For example, %12, %2, %44.</li> | |
| <li>Constants, which are described in a <a href="#constants">section about | |
| constants</a>, below.</li> | |
| </ol> | |
| <p>LLVM requires that values start with a '%' sign for two reasons: Compilers | |
| don't need to worry about name clashes with reserved words, and the set of | |
| reserved words may be expanded in the future without penalty. Additionally, | |
| unnamed identifiers allow a compiler to quickly come up with a temporary | |
| variable without having to avoid symbol table conflicts.</p> | |
| <p>Reserved words in LLVM are very similar to reserved words in other | |
| languages. There are keywords for different opcodes ('<tt><a | |
| href="#i_add">add</a></tt>', '<tt><a href="#i_cast">cast</a></tt>', '<tt><a | |
| href="#i_ret">ret</a></tt>', etc...), for primitive type names ('<tt><a | |
| href="#t_void">void</a></tt>', '<tt><a href="#t_uint">uint</a></tt>', etc...), | |
| and others. These reserved words cannot conflict with variable names, because | |
| none of them start with a '%' character.</p> | |
| <p>Here is an example of LLVM code to multiply the integer variable | |
| '<tt>%X</tt>' by 8:</p> | |
| <p>The easy way:</p> | |
| <pre> | |
| %result = <a href="#i_mul">mul</a> uint %X, 8 | |
| </pre> | |
| <p>After strength reduction:</p> | |
| <pre> | |
| %result = <a href="#i_shl">shl</a> uint %X, ubyte 3 | |
| </pre> | |
| <p>And the hard way:</p> | |
| <pre> | |
| <a href="#i_add">add</a> uint %X, %X <i>; yields {uint}:%0</i> | |
| <a href="#i_add">add</a> uint %0, %0 <i>; yields {uint}:%1</i> | |
| %result = <a href="#i_add">add</a> uint %1, %1 | |
| </pre> | |
| <p>This last way of multiplying <tt>%X</tt> by 8 illustrates several | |
| important lexical features of LLVM:</p> | |
| <ol> | |
| <li>Comments are delimited with a '<tt>;</tt>' and go until the end of | |
| line.</li> | |
| <li>Unnamed temporaries are created when the result of a computation is not | |
| assigned to a named value.</li> | |
| <li>Unnamed temporaries are numbered sequentially</li> | |
| </ol> | |
| <p>...and it also shows a convention that we follow in this document. When | |
| demonstrating instructions, we will follow an instruction with a comment that | |
| defines the type and name of value produced. Comments are shown in italic | |
| text.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="highlevel">High Level Structure</a> </div> | |
| <!-- *********************************************************************** --> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> <a name="modulestructure">Module Structure</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM programs are composed of "Module"s, each of which is a | |
| translation unit of the input programs. Each module consists of | |
| functions, global variables, and symbol table entries. Modules may be | |
| combined together with the LLVM linker, which merges function (and | |
| global variable) definitions, resolves forward declarations, and merges | |
| symbol table entries. Here is an example of the "hello world" module:</p> | |
| <pre><i>; Declare the string constant as a global constant...</i> | |
| <a href="#identifiers">%.LC0</a> = <a href="#linkage_internal">internal</a> <a | |
| href="#globalvars">constant</a> <a href="#t_array">[13 x sbyte]</a> c"hello world\0A\00" <i>; [13 x sbyte]*</i> | |
| <i>; External declaration of the puts function</i> | |
| <a href="#functionstructure">declare</a> int %puts(sbyte*) <i>; int(sbyte*)* </i> | |
| <i>; Definition of main function</i> | |
| int %main() { <i>; int()* </i> | |
| <i>; Convert [13x sbyte]* to sbyte *...</i> | |
| %cast210 = <a | |
| href="#i_getelementptr">getelementptr</a> [13 x sbyte]* %.LC0, long 0, long 0 <i>; sbyte*</i> | |
| <i>; Call puts function to write out the string to stdout...</i> | |
| <a | |
| href="#i_call">call</a> int %puts(sbyte* %cast210) <i>; int</i> | |
| <a | |
| href="#i_ret">ret</a> int 0<br>}<br></pre> | |
| <p>This example is made up of a <a href="#globalvars">global variable</a> | |
| named "<tt>.LC0</tt>", an external declaration of the "<tt>puts</tt>" | |
| function, and a <a href="#functionstructure">function definition</a> | |
| for "<tt>main</tt>".</p> | |
| <p>In general, a module is made up of a list of global values, | |
| where both functions and global variables are global values. Global values are | |
| represented by a pointer to a memory location (in this case, a pointer to an | |
| array of char, and a pointer to a function), and have one of the following <a | |
| href="#linkage">linkage types</a>.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="linkage">Linkage Types</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| All Global Variables and Functions have one of the following types of linkage: | |
| </p> | |
| <dl> | |
| <dt><tt><b><a name="linkage_internal">internal</a></b></tt> </dt> | |
| <dd>Global values with internal linkage are only directly accessible by | |
| objects in the current module. In particular, linking code into a module with | |
| an internal global value may cause the internal to be renamed as necessary to | |
| avoid collisions. Because the symbol is internal to the module, all | |
| references can be updated. This corresponds to the notion of the | |
| '<tt>static</tt>' keyword in C, or the idea of "anonymous namespaces" in C++. | |
| </dd> | |
| <dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt>: </dt> | |
| <dd>"<tt>linkonce</tt>" linkage is similar to <tt>internal</tt> linkage, with | |
| the twist that linking together two modules defining the same | |
| <tt>linkonce</tt> globals will cause one of the globals to be discarded. This | |
| is typically used to implement inline functions. Unreferenced | |
| <tt>linkonce</tt> globals are allowed to be discarded. | |
| </dd> | |
| <dt><tt><b><a name="linkage_weak">weak</a></b></tt>: </dt> | |
| <dd>"<tt>weak</tt>" linkage is exactly the same as <tt>linkonce</tt> linkage, | |
| except that unreferenced <tt>weak</tt> globals may not be discarded. This is | |
| used to implement constructs in C such as "<tt>int X;</tt>" at global scope. | |
| </dd> | |
| <dt><tt><b><a name="linkage_appending">appending</a></b></tt>: </dt> | |
| <dd>"<tt>appending</tt>" linkage may only be applied to global variables of | |
| pointer to array type. When two global variables with appending linkage are | |
| linked together, the two global arrays are appended together. This is the | |
| LLVM, typesafe, equivalent of having the system linker append together | |
| "sections" with identical names when .o files are linked. | |
| </dd> | |
| <dt><tt><b><a name="linkage_external">externally visible</a></b></tt>:</dt> | |
| <dd>If none of the above identifiers are used, the global is externally | |
| visible, meaning that it participates in linkage and can be used to resolve | |
| external symbol references. | |
| </dd> | |
| </dl> | |
| <p><a name="linkage_external">For example, since the "<tt>.LC0</tt>" | |
| variable is defined to be internal, if another module defined a "<tt>.LC0</tt>" | |
| variable and was linked with this one, one of the two would be renamed, | |
| preventing a collision. Since "<tt>main</tt>" and "<tt>puts</tt>" are | |
| external (i.e., lacking any linkage declarations), they are accessible | |
| outside of the current module. It is illegal for a function <i>declaration</i> | |
| to have any linkage type other than "externally visible".</a></p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="callingconv">Calling Conventions</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM <a href="#functionstructure">functions</a>, <a href="#i_call">calls</a> | |
| and <a href="#i_invoke">invokes</a> can all have an optional calling convention | |
| specified for the call. The calling convention of any pair of dynamic | |
| caller/callee must match, or the behavior of the program is undefined. The | |
| following calling conventions are supported by LLVM, and more may be added in | |
| the future:</p> | |
| <dl> | |
| <dt><b>"<tt>ccc</tt>" - The C calling convention</b>:</dt> | |
| <dd>This calling convention (the default if no other calling convention is | |
| specified) matches the target C calling conventions. This calling convention | |
| supports varargs function calls and tolerates some mismatch in the declared | |
| prototype and implemented declaration of the function (as does normal C). | |
| </dd> | |
| <dt><b>"<tt>fastcc</tt>" - The fast calling convention</b>:</dt> | |
| <dd>This calling convention attempts to make calls as fast as possible | |
| (e.g. by passing things in registers). This calling convention allows the | |
| target to use whatever tricks it wants to produce fast code for the target, | |
| without having to conform to an externally specified ABI. Implementations of | |
| this convention should allow arbitrary tail call optimization to be supported. | |
| This calling convention does not support varargs and requires the prototype of | |
| all callees to exactly match the prototype of the function definition. | |
| </dd> | |
| <dt><b>"<tt>coldcc</tt>" - The cold calling convention</b>:</dt> | |
| <dd>This calling convention attempts to make code in the caller as efficient | |
| as possible under the assumption that the call is not commonly executed. As | |
| such, these calls often preserve all registers so that the call does not break | |
| any live ranges in the caller side. This calling convention does not support | |
| varargs and requires the prototype of all callees to exactly match the | |
| prototype of the function definition. | |
| </dd> | |
| <dt><b>"<tt>cc <<em>n</em>></tt>" - Numbered convention</b>:</dt> | |
| <dd>Any calling convention may be specified by number, allowing | |
| target-specific calling conventions to be used. Target specific calling | |
| conventions start at 64. | |
| </dd> | |
| </dl> | |
| <p>More calling conventions can be added/defined on an as-needed basis, to | |
| support pascal conventions or any other well-known target-independent | |
| convention.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="globalvars">Global Variables</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>Global variables define regions of memory allocated at compilation time | |
| instead of run-time. Global variables may optionally be initialized. A | |
| variable may be defined as a global "constant," which indicates that the | |
| contents of the variable will <b>never</b> be modified (enabling better | |
| optimization, allowing the global data to be placed in the read-only section of | |
| an executable, etc). Note that variables that need runtime initialization | |
| cannot be marked "constant" as there is a store to the variable.</p> | |
| <p> | |
| LLVM explicitly allows <em>declarations</em> of global variables to be marked | |
| constant, even if the final definition of the global is not. This capability | |
| can be used to enable slightly better optimization of the program, but requires | |
| the language definition to guarantee that optimizations based on the | |
| 'constantness' are valid for the translation units that do not include the | |
| definition. | |
| </p> | |
| <p>As SSA values, global variables define pointer values that are in | |
| scope (i.e. they dominate) all basic blocks in the program. Global | |
| variables always define a pointer to their "content" type because they | |
| describe a region of memory, and all memory objects in LLVM are | |
| accessed through pointers.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="functionstructure">Functions</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM function definitions consist of an optional <a href="#linkage">linkage | |
| type</a>, an optional <a href="#callingconv">calling convention</a>, a return | |
| type, a function name, a (possibly empty) argument list, an opening curly brace, | |
| a list of basic blocks, and a closing curly brace. LLVM function declarations | |
| are defined with the "<tt>declare</tt>" keyword, an optional <a | |
| href="#callingconv">calling convention</a>, a return type, a function name, and | |
| a possibly empty list of arguments.</p> | |
| <p>A function definition contains a list of basic blocks, forming the CFG for | |
| the function. Each basic block may optionally start with a label (giving the | |
| basic block a symbol table entry), contains a list of instructions, and ends | |
| with a <a href="#terminators">terminator</a> instruction (such as a branch or | |
| function return).</p> | |
| <p>The first basic block in a program is special in two ways: it is immediately | |
| executed on entrance to the function, and it is not allowed to have predecessor | |
| basic blocks (i.e. there can not be any branches to the entry block of a | |
| function). Because the block can have no predecessors, it also cannot have any | |
| <a href="#i_phi">PHI nodes</a>.</p> | |
| <p>LLVM functions are identified by their name and type signature. Hence, two | |
| functions with the same name but different parameter lists or return values are | |
| considered different functions, and LLVM will resolve references to each | |
| appropriately.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="typesystem">Type System</a> </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>The LLVM type system is one of the most important features of the | |
| intermediate representation. Being typed enables a number of | |
| optimizations to be performed on the IR directly, without having to do | |
| extra analyses on the side before the transformation. A strong type | |
| system makes it easier to read the generated code and enables novel | |
| analyses and transformations that are not feasible to perform on normal | |
| three address code representations.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> <a name="t_primitive">Primitive Types</a> </div> | |
| <div class="doc_text"> | |
| <p>The primitive types are the fundamental building blocks of the LLVM | |
| system. The current set of primitive types is as follows:</p> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"> | |
| <table> | |
| <tbody> | |
| <tr><th>Type</th><th>Description</th></tr> | |
| <tr><td><tt>void</tt></td><td>No value</td></tr> | |
| <tr><td><tt>ubyte</tt></td><td>Unsigned 8-bit value</td></tr> | |
| <tr><td><tt>ushort</tt></td><td>Unsigned 16-bit value</td></tr> | |
| <tr><td><tt>uint</tt></td><td>Unsigned 32-bit value</td></tr> | |
| <tr><td><tt>ulong</tt></td><td>Unsigned 64-bit value</td></tr> | |
| <tr><td><tt>float</tt></td><td>32-bit floating point value</td></tr> | |
| <tr><td><tt>label</tt></td><td>Branch destination</td></tr> | |
| </tbody> | |
| </table> | |
| </td> | |
| <td class="right"> | |
| <table> | |
| <tbody> | |
| <tr><th>Type</th><th>Description</th></tr> | |
| <tr><td><tt>bool</tt></td><td>True or False value</td></tr> | |
| <tr><td><tt>sbyte</tt></td><td>Signed 8-bit value</td></tr> | |
| <tr><td><tt>short</tt></td><td>Signed 16-bit value</td></tr> | |
| <tr><td><tt>int</tt></td><td>Signed 32-bit value</td></tr> | |
| <tr><td><tt>long</tt></td><td>Signed 64-bit value</td></tr> | |
| <tr><td><tt>double</tt></td><td>64-bit floating point value</td></tr> | |
| </tbody> | |
| </table> | |
| </td> | |
| </tr> | |
| </table> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_classifications">Type | |
| Classifications</a> </div> | |
| <div class="doc_text"> | |
| <p>These different primitive types fall into a few useful | |
| classifications:</p> | |
| <table border="1" cellspacing="0" cellpadding="4"> | |
| <tbody> | |
| <tr><th>Classification</th><th>Types</th></tr> | |
| <tr> | |
| <td><a name="t_signed">signed</a></td> | |
| <td><tt>sbyte, short, int, long, float, double</tt></td> | |
| </tr> | |
| <tr> | |
| <td><a name="t_unsigned">unsigned</a></td> | |
| <td><tt>ubyte, ushort, uint, ulong</tt></td> | |
| </tr> | |
| <tr> | |
| <td><a name="t_integer">integer</a></td> | |
| <td><tt>ubyte, sbyte, ushort, short, uint, int, ulong, long</tt></td> | |
| </tr> | |
| <tr> | |
| <td><a name="t_integral">integral</a></td> | |
| <td><tt>bool, ubyte, sbyte, ushort, short, uint, int, ulong, long</tt> | |
| </td> | |
| </tr> | |
| <tr> | |
| <td><a name="t_floating">floating point</a></td> | |
| <td><tt>float, double</tt></td> | |
| </tr> | |
| <tr> | |
| <td><a name="t_firstclass">first class</a></td> | |
| <td><tt>bool, ubyte, sbyte, ushort, short, uint, int, ulong, long,<br> | |
| float, double, <a href="#t_pointer">pointer</a>, | |
| <a href="#t_packed">packed</a></tt></td> | |
| </tr> | |
| </tbody> | |
| </table> | |
| <p>The <a href="#t_firstclass">first class</a> types are perhaps the | |
| most important. Values of these types are the only ones which can be | |
| produced by instructions, passed as arguments, or used as operands to | |
| instructions. This means that all structures and arrays must be | |
| manipulated either by pointer or by component.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> <a name="t_derived">Derived Types</a> </div> | |
| <div class="doc_text"> | |
| <p>The real power in LLVM comes from the derived types in the system. | |
| This is what allows a programmer to represent arrays, functions, | |
| pointers, and other useful types. Note that these derived types may be | |
| recursive: For example, it is possible to have a two dimensional array.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_array">Array Type</a> </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>The array type is a very simple derived type that arranges elements | |
| sequentially in memory. The array type requires a size (number of | |
| elements) and an underlying data type.</p> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| [<# elements> x <elementtype>] | |
| </pre> | |
| <p>The number of elements is a constant integer value; elementtype may | |
| be any type with a size.</p> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"> | |
| <tt>[40 x int ]</tt><br/> | |
| <tt>[41 x int ]</tt><br/> | |
| <tt>[40 x uint]</tt><br/> | |
| </td> | |
| <td class="left"> | |
| Array of 40 integer values.<br/> | |
| Array of 41 integer values.<br/> | |
| Array of 40 unsigned integer values.<br/> | |
| </td> | |
| </tr> | |
| </table> | |
| <p>Here are some examples of multidimensional arrays:</p> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"> | |
| <tt>[3 x [4 x int]]</tt><br/> | |
| <tt>[12 x [10 x float]]</tt><br/> | |
| <tt>[2 x [3 x [4 x uint]]]</tt><br/> | |
| </td> | |
| <td class="left"> | |
| 3x4 array of integer values.<br/> | |
| 12x10 array of single precision floating point values.<br/> | |
| 2x3x4 array of unsigned integer values.<br/> | |
| </td> | |
| </tr> | |
| </table> | |
| <p>Note that 'variable sized arrays' can be implemented in LLVM with a zero | |
| length array. Normally, accesses past the end of an array are undefined in | |
| LLVM (e.g. it is illegal to access the 5th element of a 3 element array). | |
| As a special case, however, zero length arrays are recognized to be variable | |
| length. This allows implementation of 'pascal style arrays' with the LLVM | |
| type "{ int, [0 x float]}", for example.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_function">Function Type</a> </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>The function type can be thought of as a function signature. It | |
| consists of a return type and a list of formal parameter types. | |
| Function types are usually used to build virtual function tables | |
| (which are structures of pointers to functions), for indirect function | |
| calls, and when defining a function.</p> | |
| <p> | |
| The return type of a function type cannot be an aggregate type. | |
| </p> | |
| <h5>Syntax:</h5> | |
| <pre> <returntype> (<parameter list>)<br></pre> | |
| <p>...where '<tt><parameter list></tt>' is a comma-separated list of type | |
| specifiers. Optionally, the parameter list may include a type <tt>...</tt>, | |
| which indicates that the function takes a variable number of arguments. | |
| Variable argument functions can access their arguments with the <a | |
| href="#int_varargs">variable argument handling intrinsic</a> functions.</p> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"> | |
| <tt>int (int)</tt> <br/> | |
| <tt>float (int, int *) *</tt><br/> | |
| <tt>int (sbyte *, ...)</tt><br/> | |
| </td> | |
| <td class="left"> | |
| function taking an <tt>int</tt>, returning an <tt>int</tt><br/> | |
| <a href="#t_pointer">Pointer</a> to a function that takes an | |
| <tt>int</tt> and a <a href="#t_pointer">pointer</a> to <tt>int</tt>, | |
| returning <tt>float</tt>.<br/> | |
| A vararg function that takes at least one <a href="#t_pointer">pointer</a> | |
| to <tt>sbyte</tt> (signed char in C), which returns an integer. This is | |
| the signature for <tt>printf</tt> in LLVM.<br/> | |
| </td> | |
| </tr> | |
| </table> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_struct">Structure Type</a> </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>The structure type is used to represent a collection of data members | |
| together in memory. The packing of the field types is defined to match | |
| the ABI of the underlying processor. The elements of a structure may | |
| be any type that has a size.</p> | |
| <p>Structures are accessed using '<tt><a href="#i_load">load</a></tt> | |
| and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a | |
| field with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>' | |
| instruction.</p> | |
| <h5>Syntax:</h5> | |
| <pre> { <type list> }<br></pre> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"> | |
| <tt>{ int, int, int }</tt><br/> | |
| <tt>{ float, int (int) * }</tt><br/> | |
| </td> | |
| <td class="left"> | |
| a triple of three <tt>int</tt> values<br/> | |
| A pair, where the first element is a <tt>float</tt> and the second element | |
| is a <a href="#t_pointer">pointer</a> to a <a href="#t_function">function</a> | |
| that takes an <tt>int</tt>, returning an <tt>int</tt>.<br/> | |
| </td> | |
| </tr> | |
| </table> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_pointer">Pointer Type</a> </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>As in many languages, the pointer type represents a pointer or | |
| reference to another object, which must live in memory.</p> | |
| <h5>Syntax:</h5> | |
| <pre> <type> *<br></pre> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"> | |
| <tt>[4x int]*</tt><br/> | |
| <tt>int (int *) *</tt><br/> | |
| </td> | |
| <td class="left"> | |
| A <a href="#t_pointer">pointer</a> to <a href="#t_array">array</a> of | |
| four <tt>int</tt> values<br/> | |
| A <a href="#t_pointer">pointer</a> to a <a | |
| href="#t_function">function</a> that takes an <tt>int*</tt>, returning an | |
| <tt>int</tt>.<br/> | |
| </td> | |
| </tr> | |
| </table> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_packed">Packed Type</a> </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>A packed type is a simple derived type that represents a vector | |
| of elements. Packed types are used when multiple primitive data | |
| are operated in parallel using a single instruction (SIMD). | |
| A packed type requires a size (number of | |
| elements) and an underlying primitive data type. Packed types are | |
| considered <a href="#t_firstclass">first class</a>.</p> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| < <# elements> x <elementtype> > | |
| </pre> | |
| <p>The number of elements is a constant integer value; elementtype may | |
| be any integral or floating point type.</p> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"> | |
| <tt><4 x int></tt><br/> | |
| <tt><8 x float></tt><br/> | |
| <tt><2 x uint></tt><br/> | |
| </td> | |
| <td class="left"> | |
| Packed vector of 4 integer values.<br/> | |
| Packed vector of 8 floating-point values.<br/> | |
| Packed vector of 2 unsigned integer values.<br/> | |
| </td> | |
| </tr> | |
| </table> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="t_opaque">Opaque Type</a> </div> | |
| <div class="doc_text"> | |
| <h5>Overview:</h5> | |
| <p>Opaque types are used to represent unknown types in the system. This | |
| corresponds (for example) to the C notion of a foward declared structure type. | |
| In LLVM, opaque types can eventually be resolved to any type (not just a | |
| structure type).</p> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| opaque | |
| </pre> | |
| <h5>Examples:</h5> | |
| <table class="layout"> | |
| <tr class="layout"> | |
| <td class="left"> | |
| <tt>opaque</tt> | |
| </td> | |
| <td class="left"> | |
| An opaque type.<br/> | |
| </td> | |
| </tr> | |
| </table> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="constants">Constants</a> </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>LLVM has several different basic types of constants. This section describes | |
| them all and their syntax.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"><a name="simpleconstants">Simple Constants</a></div> | |
| <div class="doc_text"> | |
| <dl> | |
| <dt><b>Boolean constants</b></dt> | |
| <dd>The two strings '<tt>true</tt>' and '<tt>false</tt>' are both valid | |
| constants of the <tt><a href="#t_primitive">bool</a></tt> type. | |
| </dd> | |
| <dt><b>Integer constants</b></dt> | |
| <dd>Standard integers (such as '4') are constants of the <a | |
| href="#t_integer">integer</a> type. Negative numbers may be used with signed | |
| integer types. | |
| </dd> | |
| <dt><b>Floating point constants</b></dt> | |
| <dd>Floating point constants use standard decimal notation (e.g. 123.421), | |
| exponential notation (e.g. 1.23421e+2), or a more precise hexadecimal | |
| notation (see below). Floating point constants must have a <a | |
| href="#t_floating">floating point</a> type. </dd> | |
| <dt><b>Null pointer constants</b></dt> | |
| <dd>The identifier '<tt>null</tt>' is recognized as a null pointer constant | |
| and must be of <a href="#t_pointer">pointer type</a>.</dd> | |
| </dl> | |
| <p>The one non-intuitive notation for constants is the optional hexadecimal form | |
| of floating point constants. For example, the form '<tt>double | |
| 0x432ff973cafa8000</tt>' is equivalent to (but harder to read than) '<tt>double | |
| 4.5e+15</tt>'. The only time hexadecimal floating point constants are required | |
| (and the only time that they are generated by the disassembler) is when a | |
| floating point constant must be emitted but it cannot be represented as a | |
| decimal floating point number. For example, NaN's, infinities, and other | |
| special values are represented in their IEEE hexadecimal format so that | |
| assembly and disassembly do not cause any bits to change in the constants.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"><a name="aggregateconstants">Aggregate Constants</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>Aggregate constants arise from aggregation of simple constants | |
| and smaller aggregate constants.</p> | |
| <dl> | |
| <dt><b>Structure constants</b></dt> | |
| <dd>Structure constants are represented with notation similar to structure | |
| type definitions (a comma separated list of elements, surrounded by braces | |
| (<tt>{}</tt>)). For example: "<tt>{ int 4, float 17.0, int* %G }</tt>", | |
| where "<tt>%G</tt>" is declared as "<tt>%G = external global int</tt>". Structure constants | |
| must have <a href="#t_struct">structure type</a>, and the number and | |
| types of elements must match those specified by the type. | |
| </dd> | |
| <dt><b>Array constants</b></dt> | |
| <dd>Array constants are represented with notation similar to array type | |
| definitions (a comma separated list of elements, surrounded by square brackets | |
| (<tt>[]</tt>)). For example: "<tt>[ int 42, int 11, int 74 ]</tt>". Array | |
| constants must have <a href="#t_array">array type</a>, and the number and | |
| types of elements must match those specified by the type. | |
| </dd> | |
| <dt><b>Packed constants</b></dt> | |
| <dd>Packed constants are represented with notation similar to packed type | |
| definitions (a comma separated list of elements, surrounded by | |
| less-than/greater-than's (<tt><></tt>)). For example: "<tt>< int 42, | |
| int 11, int 74, int 100 ></tt>". Packed constants must have <a | |
| href="#t_packed">packed type</a>, and the number and types of elements must | |
| match those specified by the type. | |
| </dd> | |
| <dt><b>Zero initialization</b></dt> | |
| <dd>The string '<tt>zeroinitializer</tt>' can be used to zero initialize a | |
| value to zero of <em>any</em> type, including scalar and aggregate types. | |
| This is often used to avoid having to print large zero initializers (e.g. for | |
| large arrays) and is always exactly equivalent to using explicit zero | |
| initializers. | |
| </dd> | |
| </dl> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="globalconstants">Global Variable and Function Addresses</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>The addresses of <a href="#globalvars">global variables</a> and <a | |
| href="#functionstructure">functions</a> are always implicitly valid (link-time) | |
| constants. These constants are explicitly referenced when the <a | |
| href="#identifiers">identifier for the global</a> is used and always have <a | |
| href="#t_pointer">pointer</a> type. For example, the following is a legal LLVM | |
| file:</p> | |
| <pre> | |
| %X = global int 17 | |
| %Y = global int 42 | |
| %Z = global [2 x int*] [ int* %X, int* %Y ] | |
| </pre> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"><a name="undefvalues">Undefined Values</a></div> | |
| <div class="doc_text"> | |
| <p>The string '<tt>undef</tt>' is recognized as a type-less constant that has | |
| no specific value. Undefined values may be of any type and be used anywhere | |
| a constant is permitted.</p> | |
| <p>Undefined values indicate to the compiler that the program is well defined | |
| no matter what value is used, giving the compiler more freedom to optimize. | |
| </p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"><a name="constantexprs">Constant Expressions</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>Constant expressions are used to allow expressions involving other constants | |
| to be used as constants. Constant expressions may be of any <a | |
| href="#t_firstclass">first class</a> type and may involve any LLVM operation | |
| that does not have side effects (e.g. load and call are not supported). The | |
| following is the syntax for constant expressions:</p> | |
| <dl> | |
| <dt><b><tt>cast ( CST to TYPE )</tt></b></dt> | |
| <dd>Cast a constant to another type.</dd> | |
| <dt><b><tt>getelementptr ( CSTPTR, IDX0, IDX1, ... )</tt></b></dt> | |
| <dd>Perform the <a href="#i_getelementptr">getelementptr operation</a> on | |
| constants. As with the <a href="#i_getelementptr">getelementptr</a> | |
| instruction, the index list may have zero or more indexes, which are required | |
| to make sense for the type of "CSTPTR".</dd> | |
| <dt><b><tt>OPCODE ( LHS, RHS )</tt></b></dt> | |
| <dd>Perform the specified operation of the LHS and RHS constants. OPCODE may | |
| be any of the <a href="#binaryops">binary</a> or <a href="#bitwiseops">bitwise | |
| binary</a> operations. The constraints on operands are the same as those for | |
| the corresponding instruction (e.g. no bitwise operations on floating point | |
| values are allowed).</dd> | |
| </dl> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="instref">Instruction Reference</a> </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>The LLVM instruction set consists of several different | |
| classifications of instructions: <a href="#terminators">terminator | |
| instructions</a>, <a href="#binaryops">binary instructions</a>, | |
| <a href="#bitwiseops">bitwise binary instructions</a>, <a | |
| href="#memoryops">memory instructions</a>, and <a href="#otherops">other | |
| instructions</a>.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> <a name="terminators">Terminator | |
| Instructions</a> </div> | |
| <div class="doc_text"> | |
| <p>As mentioned <a href="#functionstructure">previously</a>, every | |
| basic block in a program ends with a "Terminator" instruction, which | |
| indicates which block should be executed after the current block is | |
| finished. These terminator instructions typically yield a '<tt>void</tt>' | |
| value: they produce control flow, not values (the one exception being | |
| the '<a href="#i_invoke"><tt>invoke</tt></a>' instruction).</p> | |
| <p>There are six different terminator instructions: the '<a | |
| href="#i_ret"><tt>ret</tt></a>' instruction, the '<a href="#i_br"><tt>br</tt></a>' | |
| instruction, the '<a href="#i_switch"><tt>switch</tt></a>' instruction, | |
| the '<a href="#i_invoke"><tt>invoke</tt></a>' instruction, the '<a | |
| href="#i_unwind"><tt>unwind</tt></a>' instruction, and the '<a | |
| href="#i_unreachable"><tt>unreachable</tt></a>' instruction.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_ret">'<tt>ret</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> ret <type> <value> <i>; Return a value from a non-void function</i> | |
| ret void <i>; Return from void function</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>ret</tt>' instruction is used to return control flow (and a | |
| value) from a function back to the caller.</p> | |
| <p>There are two forms of the '<tt>ret</tt>' instruction: one that | |
| returns a value and then causes control flow, and one that just causes | |
| control flow to occur.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>ret</tt>' instruction may return any '<a | |
| href="#t_firstclass">first class</a>' type. Notice that a function is | |
| not <a href="#wellformed">well formed</a> if there exists a '<tt>ret</tt>' | |
| instruction inside of the function that returns a value that does not | |
| match the return type of the function.</p> | |
| <h5>Semantics:</h5> | |
| <p>When the '<tt>ret</tt>' instruction is executed, control flow | |
| returns back to the calling function's context. If the caller is a "<a | |
| href="#i_call"><tt>call</tt></a>" instruction, execution continues at | |
| the instruction after the call. If the caller was an "<a | |
| href="#i_invoke"><tt>invoke</tt></a>" instruction, execution continues | |
| at the beginning of the "normal" destination block. If the instruction | |
| returns a value, that value shall set the call or invoke instruction's | |
| return value.</p> | |
| <h5>Example:</h5> | |
| <pre> ret int 5 <i>; Return an integer value of 5</i> | |
| ret void <i>; Return from a void function</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_br">'<tt>br</tt>' Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> br bool <cond>, label <iftrue>, label <iffalse><br> br label <dest> <i>; Unconditional branch</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>br</tt>' instruction is used to cause control flow to | |
| transfer to a different basic block in the current function. There are | |
| two forms of this instruction, corresponding to a conditional branch | |
| and an unconditional branch.</p> | |
| <h5>Arguments:</h5> | |
| <p>The conditional branch form of the '<tt>br</tt>' instruction takes a | |
| single '<tt>bool</tt>' value and two '<tt>label</tt>' values. The | |
| unconditional form of the '<tt>br</tt>' instruction takes a single '<tt>label</tt>' | |
| value as a target.</p> | |
| <h5>Semantics:</h5> | |
| <p>Upon execution of a conditional '<tt>br</tt>' instruction, the '<tt>bool</tt>' | |
| argument is evaluated. If the value is <tt>true</tt>, control flows | |
| to the '<tt>iftrue</tt>' <tt>label</tt> argument. If "cond" is <tt>false</tt>, | |
| control flows to the '<tt>iffalse</tt>' <tt>label</tt> argument.</p> | |
| <h5>Example:</h5> | |
| <pre>Test:<br> %cond = <a href="#i_setcc">seteq</a> int %a, %b<br> br bool %cond, label %IfEqual, label %IfUnequal<br>IfEqual:<br> <a | |
| href="#i_ret">ret</a> int 1<br>IfUnequal:<br> <a href="#i_ret">ret</a> int 0<br></pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_switch">'<tt>switch</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ] | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>switch</tt>' instruction is used to transfer control flow to one of | |
| several different places. It is a generalization of the '<tt>br</tt>' | |
| instruction, allowing a branch to occur to one of many possible | |
| destinations.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>switch</tt>' instruction uses three parameters: an integer | |
| comparison value '<tt>value</tt>', a default '<tt>label</tt>' destination, and | |
| an array of pairs of comparison value constants and '<tt>label</tt>'s. The | |
| table is not allowed to contain duplicate constant entries.</p> | |
| <h5>Semantics:</h5> | |
| <p>The <tt>switch</tt> instruction specifies a table of values and | |
| destinations. When the '<tt>switch</tt>' instruction is executed, this | |
| table is searched for the given value. If the value is found, control flow is | |
| transfered to the corresponding destination; otherwise, control flow is | |
| transfered to the default destination.</p> | |
| <h5>Implementation:</h5> | |
| <p>Depending on properties of the target machine and the particular | |
| <tt>switch</tt> instruction, this instruction may be code generated in different | |
| ways. For example, it could be generated as a series of chained conditional | |
| branches or with a lookup table.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <i>; Emulate a conditional br instruction</i> | |
| %Val = <a href="#i_cast">cast</a> bool %value to int | |
| switch int %Val, label %truedest [int 0, label %falsedest ] | |
| <i>; Emulate an unconditional br instruction</i> | |
| switch uint 0, label %dest [ ] | |
| <i>; Implement a jump table:</i> | |
| switch uint %val, label %otherwise [ uint 0, label %onzero | |
| uint 1, label %onone | |
| uint 2, label %ontwo ] | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_invoke">'<tt>invoke</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = invoke [<a href="#callingconv">cconv</a>] <ptr to function ty> %<function ptr val>(<function args>) | |
| to label <normal label> except label <exception label> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>invoke</tt>' instruction causes control to transfer to a specified | |
| function, with the possibility of control flow transfer to either the | |
| '<tt>normal</tt>' label or the | |
| '<tt>exception</tt>' label. If the callee function returns with the | |
| "<tt><a href="#i_ret">ret</a></tt>" instruction, control flow will return to the | |
| "normal" label. If the callee (or any indirect callees) returns with the "<a | |
| href="#i_unwind"><tt>unwind</tt></a>" instruction, control is interrupted and | |
| continued at the dynamically nearest "exception" label.</p> | |
| <h5>Arguments:</h5> | |
| <p>This instruction requires several arguments:</p> | |
| <ol> | |
| <li> | |
| The optional "cconv" marker indicates which <a href="callingconv">calling | |
| convention</a> the call should use. If none is specified, the call defaults | |
| to using C calling conventions. | |
| </li> | |
| <li>'<tt>ptr to function ty</tt>': shall be the signature of the pointer to | |
| function value being invoked. In most cases, this is a direct function | |
| invocation, but indirect <tt>invoke</tt>s are just as possible, branching off | |
| an arbitrary pointer to function value. | |
| </li> | |
| <li>'<tt>function ptr val</tt>': An LLVM value containing a pointer to a | |
| function to be invoked. </li> | |
| <li>'<tt>function args</tt>': argument list whose types match the function | |
| signature argument types. If the function signature indicates the function | |
| accepts a variable number of arguments, the extra arguments can be | |
| specified. </li> | |
| <li>'<tt>normal label</tt>': the label reached when the called function | |
| executes a '<tt><a href="#i_ret">ret</a></tt>' instruction. </li> | |
| <li>'<tt>exception label</tt>': the label reached when a callee returns with | |
| the <a href="#i_unwind"><tt>unwind</tt></a> instruction. </li> | |
| </ol> | |
| <h5>Semantics:</h5> | |
| <p>This instruction is designed to operate as a standard '<tt><a | |
| href="#i_call">call</a></tt>' instruction in most regards. The primary | |
| difference is that it establishes an association with a label, which is used by | |
| the runtime library to unwind the stack.</p> | |
| <p>This instruction is used in languages with destructors to ensure that proper | |
| cleanup is performed in the case of either a <tt>longjmp</tt> or a thrown | |
| exception. Additionally, this is important for implementation of | |
| '<tt>catch</tt>' clauses in high-level languages that support them.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %retval = invoke int %Test(int 15) to label %Continue | |
| except label %TestCleanup <i>; {int}:retval set</i> | |
| %retval = invoke <a href="#callingconv">coldcc</a> int %Test(int 15) to label %Continue | |
| except label %TestCleanup <i>; {int}:retval set</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_unwind">'<tt>unwind</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| unwind | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>unwind</tt>' instruction unwinds the stack, continuing control flow | |
| at the first callee in the dynamic call stack which used an <a | |
| href="#i_invoke"><tt>invoke</tt></a> instruction to perform the call. This is | |
| primarily used to implement exception handling.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>unwind</tt>' intrinsic causes execution of the current function to | |
| immediately halt. The dynamic call stack is then searched for the first <a | |
| href="#i_invoke"><tt>invoke</tt></a> instruction on the call stack. Once found, | |
| execution continues at the "exceptional" destination block specified by the | |
| <tt>invoke</tt> instruction. If there is no <tt>invoke</tt> instruction in the | |
| dynamic call chain, undefined behavior results.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_unreachable">'<tt>unreachable</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| unreachable | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>unreachable</tt>' instruction has no defined semantics. This | |
| instruction is used to inform the optimizer that a particular portion of the | |
| code is not reachable. This can be used to indicate that the code after a | |
| no-return function cannot be reached, and other facts.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>unreachable</tt>' instruction has no defined semantics.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> <a name="binaryops">Binary Operations</a> </div> | |
| <div class="doc_text"> | |
| <p>Binary operators are used to do most of the computation in a | |
| program. They require two operands, execute an operation on them, and | |
| produce a single value. The operands might represent | |
| multiple data, as is the case with the <a href="#t_packed">packed</a> data type. | |
| The result value of a binary operator is not | |
| necessarily the same type as its operands.</p> | |
| <p>There are several different binary operators:</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_add">'<tt>add</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = add <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>add</tt>' instruction returns the sum of its two operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>add</tt>' instruction must be either <a | |
| href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> values. | |
| This instruction can also take <a href="#t_packed">packed</a> versions of the values. | |
| Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the integer or floating point sum of the two | |
| operands.</p> | |
| <h5>Example:</h5> | |
| <pre> <result> = add int 4, %var <i>; yields {int}:result = 4 + %var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_sub">'<tt>sub</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = sub <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>sub</tt>' instruction returns the difference of its two | |
| operands.</p> | |
| <p>Note that the '<tt>sub</tt>' instruction is used to represent the '<tt>neg</tt>' | |
| instruction present in most other intermediate representations.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>sub</tt>' instruction must be either <a | |
| href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> | |
| values. | |
| This instruction can also take <a href="#t_packed">packed</a> versions of the values. | |
| Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the integer or floating point difference of | |
| the two operands.</p> | |
| <h5>Example:</h5> | |
| <pre> <result> = sub int 4, %var <i>; yields {int}:result = 4 - %var</i> | |
| <result> = sub int 0, %val <i>; yields {int}:result = -%var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_mul">'<tt>mul</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = mul <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>mul</tt>' instruction returns the product of its two | |
| operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>mul</tt>' instruction must be either <a | |
| href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> | |
| values. | |
| This instruction can also take <a href="#t_packed">packed</a> versions of the values. | |
| Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the integer or floating point product of the | |
| two operands.</p> | |
| <p>There is no signed vs unsigned multiplication. The appropriate | |
| action is taken based on the type of the operand.</p> | |
| <h5>Example:</h5> | |
| <pre> <result> = mul int 4, %var <i>; yields {int}:result = 4 * %var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_div">'<tt>div</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = div <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>div</tt>' instruction returns the quotient of its two | |
| operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>div</tt>' instruction must be either <a | |
| href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> | |
| values. | |
| This instruction can also take <a href="#t_packed">packed</a> versions of the values. | |
| Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is the integer or floating point quotient of the | |
| two operands.</p> | |
| <h5>Example:</h5> | |
| <pre> <result> = div int 4, %var <i>; yields {int}:result = 4 / %var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_rem">'<tt>rem</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = rem <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>rem</tt>' instruction returns the remainder from the | |
| division of its two operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>rem</tt>' instruction must be either <a | |
| href="#t_integer">integer</a> or <a href="#t_floating">floating point</a> | |
| values. | |
| This instruction can also take <a href="#t_packed">packed</a> versions of the values. | |
| Both arguments must have identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>This returns the <i>remainder</i> of a division (where the result | |
| has the same sign as the divisor), not the <i>modulus</i> (where the | |
| result has the same sign as the dividend) of a value. For more | |
| information about the difference, see <a | |
| href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The | |
| Math Forum</a>.</p> | |
| <h5>Example:</h5> | |
| <pre> <result> = rem int 4, %var <i>; yields {int}:result = 4 % %var</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_setcc">'<tt>set<i>cc</i></tt>' | |
| Instructions</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = seteq <ty> <var1>, <var2> <i>; yields {bool}:result</i> | |
| <result> = setne <ty> <var1>, <var2> <i>; yields {bool}:result</i> | |
| <result> = setlt <ty> <var1>, <var2> <i>; yields {bool}:result</i> | |
| <result> = setgt <ty> <var1>, <var2> <i>; yields {bool}:result</i> | |
| <result> = setle <ty> <var1>, <var2> <i>; yields {bool}:result</i> | |
| <result> = setge <ty> <var1>, <var2> <i>; yields {bool}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>set<i>cc</i></tt>' family of instructions returns a boolean | |
| value based on a comparison of their two operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>set<i>cc</i></tt>' instructions must | |
| be of <a href="#t_firstclass">first class</a> type (it is not possible | |
| to compare '<tt>label</tt>'s, '<tt>array</tt>'s, '<tt>structure</tt>' | |
| or '<tt>void</tt>' values, etc...). Both arguments must have identical | |
| types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>seteq</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>' | |
| value if both operands are equal.<br> | |
| The '<tt>setne</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>' | |
| value if both operands are unequal.<br> | |
| The '<tt>setlt</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>' | |
| value if the first operand is less than the second operand.<br> | |
| The '<tt>setgt</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>' | |
| value if the first operand is greater than the second operand.<br> | |
| The '<tt>setle</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>' | |
| value if the first operand is less than or equal to the second operand.<br> | |
| The '<tt>setge</tt>' instruction yields a <tt>true</tt> '<tt>bool</tt>' | |
| value if the first operand is greater than or equal to the second | |
| operand.</p> | |
| <h5>Example:</h5> | |
| <pre> <result> = seteq int 4, 5 <i>; yields {bool}:result = false</i> | |
| <result> = setne float 4, 5 <i>; yields {bool}:result = true</i> | |
| <result> = setlt uint 4, 5 <i>; yields {bool}:result = true</i> | |
| <result> = setgt sbyte 4, 5 <i>; yields {bool}:result = false</i> | |
| <result> = setle sbyte 4, 5 <i>; yields {bool}:result = true</i> | |
| <result> = setge sbyte 4, 5 <i>; yields {bool}:result = false</i> | |
| </pre> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> <a name="bitwiseops">Bitwise Binary | |
| Operations</a> </div> | |
| <div class="doc_text"> | |
| <p>Bitwise binary operators are used to do various forms of | |
| bit-twiddling in a program. They are generally very efficient | |
| instructions and can commonly be strength reduced from other | |
| instructions. They require two operands, execute an operation on them, | |
| and produce a single value. The resulting value of the bitwise binary | |
| operators is always the same type as its first operand.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_and">'<tt>and</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = and <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>and</tt>' instruction returns the bitwise logical and of | |
| its two operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>and</tt>' instruction must be <a | |
| href="#t_integral">integral</a> values. Both arguments must have | |
| identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The truth table used for the '<tt>and</tt>' instruction is:</p> | |
| <p> </p> | |
| <div style="align: center"> | |
| <table border="1" cellspacing="0" cellpadding="4"> | |
| <tbody> | |
| <tr> | |
| <td>In0</td> | |
| <td>In1</td> | |
| <td>Out</td> | |
| </tr> | |
| <tr> | |
| <td>0</td> | |
| <td>0</td> | |
| <td>0</td> | |
| </tr> | |
| <tr> | |
| <td>0</td> | |
| <td>1</td> | |
| <td>0</td> | |
| </tr> | |
| <tr> | |
| <td>1</td> | |
| <td>0</td> | |
| <td>0</td> | |
| </tr> | |
| <tr> | |
| <td>1</td> | |
| <td>1</td> | |
| <td>1</td> | |
| </tr> | |
| </tbody> | |
| </table> | |
| </div> | |
| <h5>Example:</h5> | |
| <pre> <result> = and int 4, %var <i>; yields {int}:result = 4 & %var</i> | |
| <result> = and int 15, 40 <i>; yields {int}:result = 8</i> | |
| <result> = and int 4, 8 <i>; yields {int}:result = 0</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_or">'<tt>or</tt>' Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = or <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>or</tt>' instruction returns the bitwise logical inclusive | |
| or of its two operands.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>or</tt>' instruction must be <a | |
| href="#t_integral">integral</a> values. Both arguments must have | |
| identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The truth table used for the '<tt>or</tt>' instruction is:</p> | |
| <p> </p> | |
| <div style="align: center"> | |
| <table border="1" cellspacing="0" cellpadding="4"> | |
| <tbody> | |
| <tr> | |
| <td>In0</td> | |
| <td>In1</td> | |
| <td>Out</td> | |
| </tr> | |
| <tr> | |
| <td>0</td> | |
| <td>0</td> | |
| <td>0</td> | |
| </tr> | |
| <tr> | |
| <td>0</td> | |
| <td>1</td> | |
| <td>1</td> | |
| </tr> | |
| <tr> | |
| <td>1</td> | |
| <td>0</td> | |
| <td>1</td> | |
| </tr> | |
| <tr> | |
| <td>1</td> | |
| <td>1</td> | |
| <td>1</td> | |
| </tr> | |
| </tbody> | |
| </table> | |
| </div> | |
| <h5>Example:</h5> | |
| <pre> <result> = or int 4, %var <i>; yields {int}:result = 4 | %var</i> | |
| <result> = or int 15, 40 <i>; yields {int}:result = 47</i> | |
| <result> = or int 4, 8 <i>; yields {int}:result = 12</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_xor">'<tt>xor</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = xor <ty> <var1>, <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>xor</tt>' instruction returns the bitwise logical exclusive | |
| or of its two operands. The <tt>xor</tt> is used to implement the | |
| "one's complement" operation, which is the "~" operator in C.</p> | |
| <h5>Arguments:</h5> | |
| <p>The two arguments to the '<tt>xor</tt>' instruction must be <a | |
| href="#t_integral">integral</a> values. Both arguments must have | |
| identical types.</p> | |
| <h5>Semantics:</h5> | |
| <p>The truth table used for the '<tt>xor</tt>' instruction is:</p> | |
| <p> </p> | |
| <div style="align: center"> | |
| <table border="1" cellspacing="0" cellpadding="4"> | |
| <tbody> | |
| <tr> | |
| <td>In0</td> | |
| <td>In1</td> | |
| <td>Out</td> | |
| </tr> | |
| <tr> | |
| <td>0</td> | |
| <td>0</td> | |
| <td>0</td> | |
| </tr> | |
| <tr> | |
| <td>0</td> | |
| <td>1</td> | |
| <td>1</td> | |
| </tr> | |
| <tr> | |
| <td>1</td> | |
| <td>0</td> | |
| <td>1</td> | |
| </tr> | |
| <tr> | |
| <td>1</td> | |
| <td>1</td> | |
| <td>0</td> | |
| </tr> | |
| </tbody> | |
| </table> | |
| </div> | |
| <p> </p> | |
| <h5>Example:</h5> | |
| <pre> <result> = xor int 4, %var <i>; yields {int}:result = 4 ^ %var</i> | |
| <result> = xor int 15, 40 <i>; yields {int}:result = 39</i> | |
| <result> = xor int 4, 8 <i>; yields {int}:result = 12</i> | |
| <result> = xor int %V, -1 <i>; yields {int}:result = ~%V</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_shl">'<tt>shl</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = shl <ty> <var1>, ubyte <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>shl</tt>' instruction returns the first operand shifted to | |
| the left a specified number of bits.</p> | |
| <h5>Arguments:</h5> | |
| <p>The first argument to the '<tt>shl</tt>' instruction must be an <a | |
| href="#t_integer">integer</a> type. The second argument must be an '<tt>ubyte</tt>' | |
| type.</p> | |
| <h5>Semantics:</h5> | |
| <p>The value produced is <tt>var1</tt> * 2<sup><tt>var2</tt></sup>.</p> | |
| <h5>Example:</h5> | |
| <pre> <result> = shl int 4, ubyte %var <i>; yields {int}:result = 4 << %var</i> | |
| <result> = shl int 4, ubyte 2 <i>; yields {int}:result = 16</i> | |
| <result> = shl int 1, ubyte 10 <i>; yields {int}:result = 1024</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_shr">'<tt>shr</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = shr <ty> <var1>, ubyte <var2> <i>; yields {ty}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>shr</tt>' instruction returns the first operand shifted to | |
| the right a specified number of bits.</p> | |
| <h5>Arguments:</h5> | |
| <p>The first argument to the '<tt>shr</tt>' instruction must be an <a | |
| href="#t_integer">integer</a> type. The second argument must be an '<tt>ubyte</tt>' | |
| type.</p> | |
| <h5>Semantics:</h5> | |
| <p>If the first argument is a <a href="#t_signed">signed</a> type, the | |
| most significant bit is duplicated in the newly free'd bit positions. | |
| If the first argument is unsigned, zero bits shall fill the empty | |
| positions.</p> | |
| <h5>Example:</h5> | |
| <pre> <result> = shr int 4, ubyte %var <i>; yields {int}:result = 4 >> %var</i> | |
| <result> = shr uint 4, ubyte 1 <i>; yields {uint}:result = 2</i> | |
| <result> = shr int 4, ubyte 2 <i>; yields {int}:result = 1</i> | |
| <result> = shr sbyte 4, ubyte 3 <i>; yields {sbyte}:result = 0</i> | |
| <result> = shr sbyte -2, ubyte 1 <i>; yields {sbyte}:result = -1</i> | |
| </pre> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> <a name="memoryops">Memory Access | |
| Operations</a></div> | |
| <div class="doc_text"> | |
| <p>A key design point of an SSA-based representation is how it | |
| represents memory. In LLVM, no memory locations are in SSA form, which | |
| makes things very simple. This section describes how to read, write, | |
| allocate, and free memory in LLVM.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_malloc">'<tt>malloc</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = malloc <type>, uint <NumElements> <i>; yields {type*}:result</i> | |
| <result> = malloc <type> <i>; yields {type*}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>malloc</tt>' instruction allocates memory from the system | |
| heap and returns a pointer to it.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>malloc</tt>' instruction allocates <tt>sizeof(<type>)*NumElements</tt> | |
| bytes of memory from the operating system and returns a pointer of the | |
| appropriate type to the program. The second form of the instruction is | |
| a shorter version of the first instruction that defaults to allocating | |
| one element.</p> | |
| <p>'<tt>type</tt>' must be a sized type.</p> | |
| <h5>Semantics:</h5> | |
| <p>Memory is allocated using the system "<tt>malloc</tt>" function, and | |
| a pointer is returned.</p> | |
| <h5>Example:</h5> | |
| <pre> %array = malloc [4 x ubyte ] <i>; yields {[%4 x ubyte]*}:array</i> | |
| %size = <a | |
| href="#i_add">add</a> uint 2, 2 <i>; yields {uint}:size = uint 4</i> | |
| %array1 = malloc ubyte, uint 4 <i>; yields {ubyte*}:array1</i> | |
| %array2 = malloc [12 x ubyte], uint %size <i>; yields {[12 x ubyte]*}:array2</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_free">'<tt>free</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> free <type> <value> <i>; yields {void}</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>free</tt>' instruction returns memory back to the unused | |
| memory heap to be reallocated in the future.</p> | |
| <p> </p> | |
| <h5>Arguments:</h5> | |
| <p>'<tt>value</tt>' shall be a pointer value that points to a value | |
| that was allocated with the '<tt><a href="#i_malloc">malloc</a></tt>' | |
| instruction.</p> | |
| <h5>Semantics:</h5> | |
| <p>Access to the memory pointed to by the pointer is no longer defined | |
| after this instruction executes.</p> | |
| <h5>Example:</h5> | |
| <pre> %array = <a href="#i_malloc">malloc</a> [4 x ubyte] <i>; yields {[4 x ubyte]*}:array</i> | |
| free [4 x ubyte]* %array | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_alloca">'<tt>alloca</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = alloca <type>, uint <NumElements> <i>; yields {type*}:result</i> | |
| <result> = alloca <type> <i>; yields {type*}:result</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>alloca</tt>' instruction allocates memory on the current | |
| stack frame of the procedure that is live until the current function | |
| returns to its caller.</p> | |
| <h5>Arguments:</h5> | |
| <p>The '<tt>alloca</tt>' instruction allocates <tt>sizeof(<type>)*NumElements</tt> | |
| bytes of memory on the runtime stack, returning a pointer of the | |
| appropriate type to the program. The second form of the instruction is | |
| a shorter version of the first that defaults to allocating one element.</p> | |
| <p>'<tt>type</tt>' may be any sized type.</p> | |
| <h5>Semantics:</h5> | |
| <p>Memory is allocated; a pointer is returned. '<tt>alloca</tt>'d | |
| memory is automatically released when the function returns. The '<tt>alloca</tt>' | |
| instruction is commonly used to represent automatic variables that must | |
| have an address available. When the function returns (either with the <tt><a | |
| href="#i_ret">ret</a></tt> or <tt><a href="#i_unwind">unwind</a></tt> | |
| instructions), the memory is reclaimed.</p> | |
| <h5>Example:</h5> | |
| <pre> %ptr = alloca int <i>; yields {int*}:ptr</i> | |
| %ptr = alloca int, uint 4 <i>; yields {int*}:ptr</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_load">'<tt>load</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = load <ty>* <pointer><br> <result> = volatile load <ty>* <pointer><br></pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>load</tt>' instruction is used to read from memory.</p> | |
| <h5>Arguments:</h5> | |
| <p>The argument to the '<tt>load</tt>' instruction specifies the memory | |
| address from which to load. The pointer must point to a <a | |
| href="#t_firstclass">first class</a> type. If the <tt>load</tt> is | |
| marked as <tt>volatile</tt>, then the optimizer is not allowed to modify | |
| the number or order of execution of this <tt>load</tt> with other | |
| volatile <tt>load</tt> and <tt><a href="#i_store">store</a></tt> | |
| instructions. </p> | |
| <h5>Semantics:</h5> | |
| <p>The location of memory pointed to is loaded.</p> | |
| <h5>Examples:</h5> | |
| <pre> %ptr = <a href="#i_alloca">alloca</a> int <i>; yields {int*}:ptr</i> | |
| <a | |
| href="#i_store">store</a> int 3, int* %ptr <i>; yields {void}</i> | |
| %val = load int* %ptr <i>; yields {int}:val = int 3</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_store">'<tt>store</tt>' | |
| Instruction</a> </div> | |
| <h5>Syntax:</h5> | |
| <pre> store <ty> <value>, <ty>* <pointer> <i>; yields {void}</i> | |
| volatile store <ty> <value>, <ty>* <pointer> <i>; yields {void}</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>store</tt>' instruction is used to write to memory.</p> | |
| <h5>Arguments:</h5> | |
| <p>There are two arguments to the '<tt>store</tt>' instruction: a value | |
| to store and an address in which to store it. The type of the '<tt><pointer></tt>' | |
| operand must be a pointer to the type of the '<tt><value></tt>' | |
| operand. If the <tt>store</tt> is marked as <tt>volatile</tt>, then the | |
| optimizer is not allowed to modify the number or order of execution of | |
| this <tt>store</tt> with other volatile <tt>load</tt> and <tt><a | |
| href="#i_store">store</a></tt> instructions.</p> | |
| <h5>Semantics:</h5> | |
| <p>The contents of memory are updated to contain '<tt><value></tt>' | |
| at the location specified by the '<tt><pointer></tt>' operand.</p> | |
| <h5>Example:</h5> | |
| <pre> %ptr = <a href="#i_alloca">alloca</a> int <i>; yields {int*}:ptr</i> | |
| <a | |
| href="#i_store">store</a> int 3, int* %ptr <i>; yields {void}</i> | |
| %val = load int* %ptr <i>; yields {int}:val = int 3</i> | |
| </pre> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_getelementptr">'<tt>getelementptr</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = getelementptr <ty>* <ptrval>{, <ty> <idx>}* | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>getelementptr</tt>' instruction is used to get the address of a | |
| subelement of an aggregate data structure.</p> | |
| <h5>Arguments:</h5> | |
| <p>This instruction takes a list of integer constants that indicate what | |
| elements of the aggregate object to index to. The actual types of the arguments | |
| provided depend on the type of the first pointer argument. The | |
| '<tt>getelementptr</tt>' instruction is used to index down through the type | |
| levels of a structure or to a specific index in an array. When indexing into a | |
| structure, only <tt>uint</tt> | |
| integer constants are allowed. When indexing into an array or pointer, | |
| <tt>int</tt> and <tt>long</tt> indexes are allowed of any sign.</p> | |
| <p>For example, let's consider a C code fragment and how it gets | |
| compiled to LLVM:</p> | |
| <pre> | |
| struct RT { | |
| char A; | |
| int B[10][20]; | |
| char C; | |
| }; | |
| struct ST { | |
| int X; | |
| double Y; | |
| struct RT Z; | |
| }; | |
| int *foo(struct ST *s) { | |
| return &s[1].Z.B[5][13]; | |
| } | |
| </pre> | |
| <p>The LLVM code generated by the GCC frontend is:</p> | |
| <pre> | |
| %RT = type { sbyte, [10 x [20 x int]], sbyte } | |
| %ST = type { int, double, %RT } | |
| implementation | |
| int* %foo(%ST* %s) { | |
| entry: | |
| %reg = getelementptr %ST* %s, int 1, uint 2, uint 1, int 5, int 13 | |
| ret int* %reg | |
| } | |
| </pre> | |
| <h5>Semantics:</h5> | |
| <p>The index types specified for the '<tt>getelementptr</tt>' instruction depend | |
| on the pointer type that is being indexed into. <a href="#t_pointer">Pointer</a> | |
| and <a href="#t_array">array</a> types require <tt>uint</tt>, <tt>int</tt>, | |
| <tt>ulong</tt>, or <tt>long</tt> values, and <a href="#t_struct">structure</a> | |
| types require <tt>uint</tt> <b>constants</b>.</p> | |
| <p>In the example above, the first index is indexing into the '<tt>%ST*</tt>' | |
| type, which is a pointer, yielding a '<tt>%ST</tt>' = '<tt>{ int, double, %RT | |
| }</tt>' type, a structure. The second index indexes into the third element of | |
| the structure, yielding a '<tt>%RT</tt>' = '<tt>{ sbyte, [10 x [20 x int]], | |
| sbyte }</tt>' type, another structure. The third index indexes into the second | |
| element of the structure, yielding a '<tt>[10 x [20 x int]]</tt>' type, an | |
| array. The two dimensions of the array are subscripted into, yielding an | |
| '<tt>int</tt>' type. The '<tt>getelementptr</tt>' instruction returns a pointer | |
| to this element, thus computing a value of '<tt>int*</tt>' type.</p> | |
| <p>Note that it is perfectly legal to index partially through a | |
| structure, returning a pointer to an inner element. Because of this, | |
| the LLVM code for the given testcase is equivalent to:</p> | |
| <pre> | |
| int* %foo(%ST* %s) { | |
| %t1 = getelementptr %ST* %s, int 1 <i>; yields %ST*:%t1</i> | |
| %t2 = getelementptr %ST* %t1, int 0, uint 2 <i>; yields %RT*:%t2</i> | |
| %t3 = getelementptr %RT* %t2, int 0, uint 1 <i>; yields [10 x [20 x int]]*:%t3</i> | |
| %t4 = getelementptr [10 x [20 x int]]* %t3, int 0, int 5 <i>; yields [20 x int]*:%t4</i> | |
| %t5 = getelementptr [20 x int]* %t4, int 0, int 13 <i>; yields int*:%t5</i> | |
| ret int* %t5 | |
| } | |
| </pre> | |
| <p>Note that it is undefined to access an array out of bounds: array and | |
| pointer indexes must always be within the defined bounds of the array type. | |
| The one exception for this rules is zero length arrays. These arrays are | |
| defined to be accessible as variable length arrays, which requires access | |
| beyond the zero'th element.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| <i>; yields [12 x ubyte]*:aptr</i> | |
| %aptr = getelementptr {int, [12 x ubyte]}* %sptr, long 0, uint 1 | |
| </pre> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> <a name="otherops">Other Operations</a> </div> | |
| <div class="doc_text"> | |
| <p>The instructions in this category are the "miscellaneous" | |
| instructions, which defy better classification.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> <a name="i_phi">'<tt>phi</tt>' | |
| Instruction</a> </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> <result> = phi <ty> [ <val0>, <label0>], ...<br></pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>phi</tt>' instruction is used to implement the φ node in | |
| the SSA graph representing the function.</p> | |
| <h5>Arguments:</h5> | |
| <p>The type of the incoming values are specified with the first type | |
| field. After this, the '<tt>phi</tt>' instruction takes a list of pairs | |
| as arguments, with one pair for each predecessor basic block of the | |
| current block. Only values of <a href="#t_firstclass">first class</a> | |
| type may be used as the value arguments to the PHI node. Only labels | |
| may be used as the label arguments.</p> | |
| <p>There must be no non-phi instructions between the start of a basic | |
| block and the PHI instructions: i.e. PHI instructions must be first in | |
| a basic block.</p> | |
| <h5>Semantics:</h5> | |
| <p>At runtime, the '<tt>phi</tt>' instruction logically takes on the | |
| value specified by the parameter, depending on which basic block we | |
| came from in the last <a href="#terminators">terminator</a> instruction.</p> | |
| <h5>Example:</h5> | |
| <pre>Loop: ; Infinite loop that counts from 0 on up...<br> %indvar = phi uint [ 0, %LoopHeader ], [ %nextindvar, %Loop ]<br> %nextindvar = add uint %indvar, 1<br> br label %Loop<br></pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_cast">'<tt>cast .. to</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = cast <ty> <value> to <ty2> <i>; yields ty2</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>cast</tt>' instruction is used as the primitive means to convert | |
| integers to floating point, change data type sizes, and break type safety (by | |
| casting pointers). | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The '<tt>cast</tt>' instruction takes a value to cast, which must be a first | |
| class value, and a type to cast it to, which must also be a <a | |
| href="#t_firstclass">first class</a> type. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| This instruction follows the C rules for explicit casts when determining how the | |
| data being cast must change to fit in its new container. | |
| </p> | |
| <p> | |
| When casting to bool, any value that would be considered true in the context of | |
| a C '<tt>if</tt>' condition is converted to the boolean '<tt>true</tt>' values, | |
| all else are '<tt>false</tt>'. | |
| </p> | |
| <p> | |
| When extending an integral value from a type of one signness to another (for | |
| example '<tt>sbyte</tt>' to '<tt>ulong</tt>'), the value is sign-extended if the | |
| <b>source</b> value is signed, and zero-extended if the source value is | |
| unsigned. <tt>bool</tt> values are always zero extended into either zero or | |
| one. | |
| </p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = cast int 257 to ubyte <i>; yields ubyte:1</i> | |
| %Y = cast int 123 to bool <i>; yields bool:true</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_select">'<tt>select</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = select bool <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>select</tt>' instruction is used to choose one value based on a | |
| condition, without branching. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The '<tt>select</tt>' instruction requires a boolean value indicating the condition, and two values of the same <a href="#t_firstclass">first class</a> type. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| If the boolean condition evaluates to true, the instruction returns the first | |
| value argument; otherwise, it returns the second value argument. | |
| </p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %X = select bool true, ubyte 17, ubyte 42 <i>; yields ubyte:17</i> | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_call">'<tt>call</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <result> = [tail] call [<a href="#callingconv">cconv</a>] <ty>* <fnptrval>(<param list>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>call</tt>' instruction represents a simple function call.</p> | |
| <h5>Arguments:</h5> | |
| <p>This instruction requires several arguments:</p> | |
| <ol> | |
| <li> | |
| <p>The optional "tail" marker indicates whether the callee function accesses | |
| any allocas or varargs in the caller. If the "tail" marker is present, the | |
| function call is eligible for tail call optimization. Note that calls may | |
| be marked "tail" even if they do not occur before a <a | |
| href="#i_ret"><tt>ret</tt></a> instruction. | |
| </li> | |
| <li> | |
| <p>The optional "cconv" marker indicates which <a href="callingconv">calling | |
| convention</a> the call should use. If none is specified, the call defaults | |
| to using C calling conventions. | |
| </li> | |
| <li> | |
| <p>'<tt>ty</tt>': shall be the signature of the pointer to function value | |
| being invoked. The argument types must match the types implied by this | |
| signature. This type can be omitted if the function is not varargs and | |
| if the function type does not return a pointer to a function.</p> | |
| </li> | |
| <li> | |
| <p>'<tt>fnptrval</tt>': An LLVM value containing a pointer to a function to | |
| be invoked. In most cases, this is a direct function invocation, but | |
| indirect <tt>call</tt>s are just as possible, calling an arbitrary pointer | |
| to function value.</p> | |
| </li> | |
| <li> | |
| <p>'<tt>function args</tt>': argument list whose types match the | |
| function signature argument types. All arguments must be of | |
| <a href="#t_firstclass">first class</a> type. If the function signature | |
| indicates the function accepts a variable number of arguments, the extra | |
| arguments can be specified.</p> | |
| </li> | |
| </ol> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>call</tt>' instruction is used to cause control flow to | |
| transfer to a specified function, with its incoming arguments bound to | |
| the specified values. Upon a '<tt><a href="#i_ret">ret</a></tt>' | |
| instruction in the called function, control flow continues with the | |
| instruction after the function call, and the return value of the | |
| function is bound to the result argument. This is a simpler case of | |
| the <a href="#i_invoke">invoke</a> instruction.</p> | |
| <h5>Example:</h5> | |
| <pre> | |
| %retval = call int %test(int %argc) | |
| call int(sbyte*, ...) *%printf(sbyte* %msg, int 12, sbyte 42); | |
| %X = tail call int %foo() | |
| %Y = tail call <a href="#callingconv">fastcc</a> int %foo() | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_vaarg">'<tt>vaarg</tt>' Instruction</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| <resultval> = va_arg <va_list*> <arglist>, <argty> | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>va_arg</tt>' instruction is used to access arguments passed through | |
| the "variable argument" area of a function call. It is used to implement the | |
| <tt>va_arg</tt> macro in C.</p> | |
| <h5>Arguments:</h5> | |
| <p>This instruction takes a <tt>va_list*</tt> value and the type of | |
| the argument. It returns a value of the specified argument type and | |
| increments the <tt>va_list</tt> to poin to the next argument. Again, the | |
| actual type of <tt>va_list</tt> is target specific.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>va_arg</tt>' instruction loads an argument of the specified | |
| type from the specified <tt>va_list</tt> and causes the | |
| <tt>va_list</tt> to point to the next argument. For more information, | |
| see the variable argument handling <a href="#int_varargs">Intrinsic | |
| Functions</a>.</p> | |
| <p>It is legal for this instruction to be called in a function which does not | |
| take a variable number of arguments, for example, the <tt>vfprintf</tt> | |
| function.</p> | |
| <p><tt>va_arg</tt> is an LLVM instruction instead of an <a | |
| href="#intrinsics">intrinsic function</a> because it takes a type as an | |
| argument.</p> | |
| <h5>Example:</h5> | |
| <p>See the <a href="#int_varargs">variable argument processing</a> section.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="intrinsics">Intrinsic Functions</a> </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>LLVM supports the notion of an "intrinsic function". These functions have | |
| well known names and semantics and are required to follow certain | |
| restrictions. Overall, these instructions represent an extension mechanism for | |
| the LLVM language that does not require changing all of the transformations in | |
| LLVM to add to the language (or the bytecode reader/writer, the parser, | |
| etc...).</p> | |
| <p>Intrinsic function names must all start with an "<tt>llvm.</tt>" prefix. This | |
| prefix is reserved in LLVM for intrinsic names; thus, functions may not be named | |
| this. Intrinsic functions must always be external functions: you cannot define | |
| the body of intrinsic functions. Intrinsic functions may only be used in call | |
| or invoke instructions: it is illegal to take the address of an intrinsic | |
| function. Additionally, because intrinsic functions are part of the LLVM | |
| language, it is required that they all be documented here if any are added.</p> | |
| <p>To learn how to add an intrinsic function, please see the <a | |
| href="ExtendingLLVM.html">Extending LLVM Guide</a>. | |
| </p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_varargs">Variable Argument Handling Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>Variable argument support is defined in LLVM with the <a | |
| href="#i_vanext"><tt>vanext</tt></a> instruction and these three | |
| intrinsic functions. These functions are related to the similarly | |
| named macros defined in the <tt><stdarg.h></tt> header file.</p> | |
| <p>All of these functions operate on arguments that use a | |
| target-specific value type "<tt>va_list</tt>". The LLVM assembly | |
| language reference manual does not define what this type is, so all | |
| transformations should be prepared to handle intrinsics with any type | |
| used.</p> | |
| <p>This example shows how the <a href="#i_vanext"><tt>vanext</tt></a> | |
| instruction and the variable argument handling intrinsic functions are | |
| used.</p> | |
| <pre> | |
| int %test(int %X, ...) { | |
| ; Initialize variable argument processing | |
| %ap = alloca sbyte* | |
| call void %<a href="#i_va_start">llvm.va_start</a>(sbyte** %ap) | |
| ; Read a single integer argument | |
| %tmp = va_arg sbyte** %ap, int | |
| ; Demonstrate usage of llvm.va_copy and llvm.va_end | |
| %aq = alloca sbyte* | |
| call void %<a href="#i_va_copy">llvm.va_copy</a>(sbyte** %aq, sbyte** %ap) | |
| call void %<a href="#i_va_end">llvm.va_end</a>(sbyte** %aq) | |
| ; Stop processing of arguments. | |
| call void %<a href="#i_va_end">llvm.va_end</a>(sbyte** %ap) | |
| ret int %tmp | |
| } | |
| </pre> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> declare void %llvm.va_start(<va_list>* <arglist>)<br></pre> | |
| <h5>Overview:</h5> | |
| <P>The '<tt>llvm.va_start</tt>' intrinsic initializes | |
| <tt>*<arglist></tt> for subsequent use by <tt><a | |
| href="#i_va_arg">va_arg</a></tt>.</p> | |
| <h5>Arguments:</h5> | |
| <P>The argument is a pointer to a <tt>va_list</tt> element to initialize.</p> | |
| <h5>Semantics:</h5> | |
| <P>The '<tt>llvm.va_start</tt>' intrinsic works just like the <tt>va_start</tt> | |
| macro available in C. In a target-dependent way, it initializes the | |
| <tt>va_list</tt> element the argument points to, so that the next call to | |
| <tt>va_arg</tt> will produce the first variable argument passed to the function. | |
| Unlike the C <tt>va_start</tt> macro, this intrinsic does not need to know the | |
| last argument of the function, the compiler can figure that out.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> declare void %llvm.va_end(<va_list*> <arglist>)<br></pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.va_end</tt>' intrinsic destroys <tt><arglist></tt> | |
| which has been initialized previously with <tt><a href="#i_va_start">llvm.va_start</a></tt> | |
| or <tt><a href="#i_va_copy">llvm.va_copy</a></tt>.</p> | |
| <h5>Arguments:</h5> | |
| <p>The argument is a <tt>va_list</tt> to destroy.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.va_end</tt>' intrinsic works just like the <tt>va_end</tt> | |
| macro available in C. In a target-dependent way, it destroys the <tt>va_list</tt>. | |
| Calls to <a href="#i_va_start"><tt>llvm.va_start</tt></a> and <a | |
| href="#i_va_copy"><tt>llvm.va_copy</tt></a> must be matched exactly | |
| with calls to <tt>llvm.va_end</tt>.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void %llvm.va_copy(<va_list>* <destarglist>, | |
| <va_list>* <srcarglist>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.va_copy</tt>' intrinsic copies the current argument position from | |
| the source argument list to the destination argument list.</p> | |
| <h5>Arguments:</h5> | |
| <p>The first argument is a pointer to a <tt>va_list</tt> element to initialize. | |
| The second argument is a pointer to a <tt>va_list</tt> element to copy from.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.va_copy</tt>' intrinsic works just like the <tt>va_copy</tt> macro | |
| available in C. In a target-dependent way, it copies the source | |
| <tt>va_list</tt> element into the destination list. This intrinsic is necessary | |
| because the <tt><a href="i_va_begin">llvm.va_begin</a></tt> intrinsic may be | |
| arbitrarily complex and require memory allocation, for example.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_gc">Accurate Garbage Collection Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| LLVM support for <a href="GarbageCollection.html">Accurate Garbage | |
| Collection</a> requires the implementation and generation of these intrinsics. | |
| These intrinsics allow identification of <a href="#i_gcroot">GC roots on the | |
| stack</a>, as well as garbage collector implementations that require <a | |
| href="#i_gcread">read</a> and <a href="#i_gcwrite">write</a> barriers. | |
| Front-ends for type-safe garbage collected languages should generate these | |
| intrinsics to make use of the LLVM garbage collectors. For more details, see <a | |
| href="GarbageCollection.html">Accurate Garbage Collection with LLVM</a>. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void %llvm.gcroot(<ty>** %ptrloc, <ty2>* %metadata) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.gcroot</tt>' intrinsic declares the existence of a GC root to | |
| the code generator, and allows some metadata to be associated with it.</p> | |
| <h5>Arguments:</h5> | |
| <p>The first argument specifies the address of a stack object that contains the | |
| root pointer. The second pointer (which must be either a constant or a global | |
| value address) contains the meta-data to be associated with the root.</p> | |
| <h5>Semantics:</h5> | |
| <p>At runtime, a call to this intrinsics stores a null pointer into the "ptrloc" | |
| location. At compile-time, the code generator generates information to allow | |
| the runtime to find the pointer at GC safe points. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare sbyte* %llvm.gcread(sbyte** %Ptr) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.gcread</tt>' intrinsic identifies reads of references from heap | |
| locations, allowing garbage collector implementations that require read | |
| barriers.</p> | |
| <h5>Arguments:</h5> | |
| <p>The argument is the address to read from, which should be an address | |
| allocated from the garbage collector.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.gcread</tt>' intrinsic has the same semantics as a load | |
| instruction, but may be replaced with substantially more complex code by the | |
| garbage collector runtime, as needed.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void %llvm.gcwrite(sbyte* %P1, sbyte** %P2) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p>The '<tt>llvm.gcwrite</tt>' intrinsic identifies writes of references to heap | |
| locations, allowing garbage collector implementations that require write | |
| barriers (such as generational or reference counting collectors).</p> | |
| <h5>Arguments:</h5> | |
| <p>The first argument is the reference to store, and the second is the heap | |
| location to store to.</p> | |
| <h5>Semantics:</h5> | |
| <p>The '<tt>llvm.gcwrite</tt>' intrinsic has the same semantics as a store | |
| instruction, but may be replaced with substantially more complex code by the | |
| garbage collector runtime, as needed.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_codegen">Code Generator Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| These intrinsics are provided by LLVM to expose special features that may only | |
| be implemented with code generator support. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void* %llvm.returnaddress(uint <level>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.returnaddress</tt>' intrinsic returns a target-specific value | |
| indicating the return address of the current function or one of its callers. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The argument to this intrinsic indicates which function to return the address | |
| for. Zero indicates the calling function, one indicates its caller, etc. The | |
| argument is <b>required</b> to be a constant integer value. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| The '<tt>llvm.returnaddress</tt>' intrinsic either returns a pointer indicating | |
| the return address of the specified call frame, or zero if it cannot be | |
| identified. The value returned by this intrinsic is likely to be incorrect or 0 | |
| for arguments other than zero, so it should only be used for debugging purposes. | |
| </p> | |
| <p> | |
| Note that calling this intrinsic does not prevent function inlining or other | |
| aggressive transformations, so the value returned may not be that of the obvious | |
| source-language caller. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void* %llvm.frameaddress(uint <level>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.frameaddress</tt>' intrinsic returns the target-specific frame | |
| pointer value for the specified stack frame. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The argument to this intrinsic indicates which function to return the frame | |
| pointer for. Zero indicates the calling function, one indicates its caller, | |
| etc. The argument is <b>required</b> to be a constant integer value. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| The '<tt>llvm.frameaddress</tt>' intrinsic either returns a pointer indicating | |
| the frame address of the specified call frame, or zero if it cannot be | |
| identified. The value returned by this intrinsic is likely to be incorrect or 0 | |
| for arguments other than zero, so it should only be used for debugging purposes. | |
| </p> | |
| <p> | |
| Note that calling this intrinsic does not prevent function inlining or other | |
| aggressive transformations, so the value returned may not be that of the obvious | |
| source-language caller. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void %llvm.prefetch(sbyte * <address>, | |
| uint <rw>, uint <locality>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.prefetch</tt>' intrinsic is a hint to the code generator to insert | |
| a prefetch instruction if supported; otherwise, it is a noop. Prefetches have | |
| no | |
| effect on the behavior of the program but can change its performance | |
| characteristics. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| <tt>address</tt> is the address to be prefetched, <tt>rw</tt> is the specifier | |
| determining if the fetch should be for a read (0) or write (1), and | |
| <tt>locality</tt> is a temporal locality specifier ranging from (0) - no | |
| locality, to (3) - extremely local keep in cache. The <tt>rw</tt> and | |
| <tt>locality</tt> arguments must be constant integers. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| This intrinsic does not modify the behavior of the program. In particular, | |
| prefetches cannot trap and do not produce a value. On targets that support this | |
| intrinsic, the prefetch can provide hints to the processor cache for better | |
| performance. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void %llvm.pcmarker( uint <id> ) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.pcmarker</tt>' intrinsic is a method to export a Program Counter | |
| (PC) in a region of | |
| code to simulators and other tools. The method is target specific, but it is | |
| expected that the marker will use exported symbols to transmit the PC of the marker. | |
| The marker makes no guaranties that it will remain with any specific instruction | |
| after optimizations. It is possible that the presense of a marker will inhibit | |
| optimizations. The intended use is to be inserted after optmizations to allow | |
| correlations of simulation runs. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| <tt>id</tt> is a numerical id identifying the marker. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| This intrinsic does not modify the behavior of the program. Backends that do not | |
| support this intrinisic may ignore it. | |
| </p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_os">Operating System Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| These intrinsics are provided by LLVM to support the implementation of | |
| operating system level code. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_readport">'<tt>llvm.readport</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare <integer type> %llvm.readport (<integer type> <address>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.readport</tt>' intrinsic reads data from the specified hardware | |
| I/O port. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The argument to this intrinsic indicates the hardware I/O address from which | |
| to read the data. The address is in the hardware I/O address namespace (as | |
| opposed to being a memory location for memory mapped I/O). | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| The '<tt>llvm.readport</tt>' intrinsic reads data from the hardware I/O port | |
| specified by <i>address</i> and returns the value. The address and return | |
| value must be integers, but the size is dependent upon the platform upon which | |
| the program is code generated. For example, on x86, the address must be an | |
| unsigned 16-bit value, and the return value must be 8, 16, or 32 bits. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_writeport">'<tt>llvm.writeport</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| call void (<integer type>, <integer type>)* | |
| %llvm.writeport (<integer type> <value>, | |
| <integer type> <address>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.writeport</tt>' intrinsic writes data to the specified hardware | |
| I/O port. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The first argument is the value to write to the I/O port. | |
| </p> | |
| <p> | |
| The second argument indicates the hardware I/O address to which data should be | |
| written. The address is in the hardware I/O address namespace (as opposed to | |
| being a memory location for memory mapped I/O). | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| The '<tt>llvm.writeport</tt>' intrinsic writes <i>value</i> to the I/O port | |
| specified by <i>address</i>. The address and value must be integers, but the | |
| size is dependent upon the platform upon which the program is code generated. | |
| For example, on x86, the address must be an unsigned 16-bit value, and the | |
| value written must be 8, 16, or 32 bits in length. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_readio">'<tt>llvm.readio</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare <result> %llvm.readio (<ty> * <pointer>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.readio</tt>' intrinsic reads data from a memory mapped I/O | |
| address. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The argument to this intrinsic is a pointer indicating the memory address from | |
| which to read the data. The data must be a | |
| <a href="#t_firstclass">first class</a> type. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| The '<tt>llvm.readio</tt>' intrinsic reads data from a memory mapped I/O | |
| location specified by <i>pointer</i> and returns the value. The argument must | |
| be a pointer, and the return value must be a | |
| <a href="#t_firstclass">first class</a> type. However, certain architectures | |
| may not support I/O on all first class types. For example, 32-bit processors | |
| may only support I/O on data types that are 32 bits or less. | |
| </p> | |
| <p> | |
| This intrinsic enforces an in-order memory model for llvm.readio and | |
| llvm.writeio calls on machines that use dynamic scheduling. Dynamically | |
| scheduled processors may execute loads and stores out of order, re-ordering at | |
| run time accesses to memory mapped I/O registers. Using these intrinsics | |
| ensures that accesses to memory mapped I/O registers occur in program order. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_writeio">'<tt>llvm.writeio</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void %llvm.writeio (<ty1> <value>, <ty2> * <pointer>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.writeio</tt>' intrinsic writes data to the specified memory | |
| mapped I/O address. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The first argument is the value to write to the memory mapped I/O location. | |
| The second argument is a pointer indicating the memory address to which the | |
| data should be written. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| The '<tt>llvm.writeio</tt>' intrinsic writes <i>value</i> to the memory mapped | |
| I/O address specified by <i>pointer</i>. The value must be a | |
| <a href="#t_firstclass">first class</a> type. However, certain architectures | |
| may not support I/O on all first class types. For example, 32-bit processors | |
| may only support I/O on data types that are 32 bits or less. | |
| </p> | |
| <p> | |
| This intrinsic enforces an in-order memory model for llvm.readio and | |
| llvm.writeio calls on machines that use dynamic scheduling. Dynamically | |
| scheduled processors may execute loads and stores out of order, re-ordering at | |
| run time accesses to memory mapped I/O registers. Using these intrinsics | |
| ensures that accesses to memory mapped I/O registers occur in program order. | |
| </p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_libc">Standard C Library Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| LLVM provides intrinsics for a few important standard C library functions. | |
| These intrinsics allow source-language front-ends to pass information about the | |
| alignment of the pointer arguments to the code generator, providing opportunity | |
| for more efficient code generation. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void %llvm.memcpy(sbyte* <dest>, sbyte* <src>, | |
| uint <len>, uint <align>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.memcpy</tt>' intrinsic copies a block of memory from the source | |
| location to the destination location. | |
| </p> | |
| <p> | |
| Note that, unlike the standard libc function, the <tt>llvm.memcpy</tt> intrinsic | |
| does not return a value, and takes an extra alignment argument. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The first argument is a pointer to the destination, the second is a pointer to | |
| the source. The third argument is an (arbitrarily sized) integer argument | |
| specifying the number of bytes to copy, and the fourth argument is the alignment | |
| of the source and destination locations. | |
| </p> | |
| <p> | |
| If the call to this intrinisic has an alignment value that is not 0 or 1, then | |
| the caller guarantees that the size of the copy is a multiple of the alignment | |
| and that both the source and destination pointers are aligned to that boundary. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| The '<tt>llvm.memcpy</tt>' intrinsic copies a block of memory from the source | |
| location to the destination location, which are not allowed to overlap. It | |
| copies "len" bytes of memory over. If the argument is known to be aligned to | |
| some boundary, this can be specified as the fourth argument, otherwise it should | |
| be set to 0 or 1. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void %llvm.memmove(sbyte* <dest>, sbyte* <src>, | |
| uint <len>, uint <align>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.memmove</tt>' intrinsic moves a block of memory from the source | |
| location to the destination location. It is similar to the '<tt>llvm.memcpy</tt>' | |
| intrinsic but allows the two memory locations to overlap. | |
| </p> | |
| <p> | |
| Note that, unlike the standard libc function, the <tt>llvm.memmove</tt> intrinsic | |
| does not return a value, and takes an extra alignment argument. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The first argument is a pointer to the destination, the second is a pointer to | |
| the source. The third argument is an (arbitrarily sized) integer argument | |
| specifying the number of bytes to copy, and the fourth argument is the alignment | |
| of the source and destination locations. | |
| </p> | |
| <p> | |
| If the call to this intrinisic has an alignment value that is not 0 or 1, then | |
| the caller guarantees that the size of the copy is a multiple of the alignment | |
| and that both the source and destination pointers are aligned to that boundary. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| The '<tt>llvm.memmove</tt>' intrinsic copies a block of memory from the source | |
| location to the destination location, which may overlap. It | |
| copies "len" bytes of memory over. If the argument is known to be aligned to | |
| some boundary, this can be specified as the fourth argument, otherwise it should | |
| be set to 0 or 1. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_memset">'<tt>llvm.memset</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare void %llvm.memset(sbyte* <dest>, ubyte <val>, | |
| uint <len>, uint <align>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.memset</tt>' intrinsic fills a block of memory with a particular | |
| byte value. | |
| </p> | |
| <p> | |
| Note that, unlike the standard libc function, the <tt>llvm.memset</tt> intrinsic | |
| does not return a value, and takes an extra alignment argument. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The first argument is a pointer to the destination to fill, the second is the | |
| byte value to fill it with, the third argument is an (arbitrarily sized) integer | |
| argument specifying the number of bytes to fill, and the fourth argument is the | |
| known alignment of destination location. | |
| </p> | |
| <p> | |
| If the call to this intrinisic has an alignment value that is not 0 or 1, then | |
| the caller guarantees that the size of the copy is a multiple of the alignment | |
| and that the destination pointer is aligned to that boundary. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| The '<tt>llvm.memset</tt>' intrinsic fills "len" bytes of memory starting at the | |
| destination location. If the argument is known to be aligned to some boundary, | |
| this can be specified as the fourth argument, otherwise it should be set to 0 or | |
| 1. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_isunordered">'<tt>llvm.isunordered</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare bool %llvm.isunordered(<float or double> Val1, <float or double> Val2) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.isunordered</tt>' intrinsic returns true if either or both of the | |
| specified floating point values is a NAN. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The arguments are floating point numbers of the same type. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| If either or both of the arguments is a SNAN or QNAN, it returns true, otherwise | |
| false. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="i_sqrt">'<tt>llvm.sqrt</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare <float or double> %llvm.sqrt(<float or double> Val) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.sqrt</tt>' intrinsic returns the sqrt of the specified operand, | |
| returning the same value as the libm '<tt>sqrt</tt>' function would. Unlike | |
| <tt>sqrt</tt> in libm, however, <tt>llvm.sqrt</tt> has undefined behavior for | |
| negative numbers (which allows for better optimization). | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The argument and return value are floating point numbers of the same type. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| This function returns the sqrt of the specified operand if it is a positive | |
| floating point number. | |
| </p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_count">Bit Counting Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| LLVM provides intrinsics for a few important bit counting operations. | |
| These allow efficient code generation for some algorithms. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_ctpop">'<tt>llvm.ctpop</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare int %llvm.ctpop(int <src>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.ctpop</tt>' intrinsic counts the number of ones in a variable. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The only argument is the value to be counted. The argument may be of any | |
| integer type. The return type must match the argument type. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| The '<tt>llvm.ctpop</tt>' intrinsic counts the 1's in a variable. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_ctlz">'<tt>llvm.ctlz</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare int %llvm.ctlz(int <src>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.ctlz</tt>' intrinsic counts the number of leading zeros in a | |
| variable. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The only argument is the value to be counted. The argument may be of any | |
| integer type. The return type must match the argument type. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant) zeros | |
| in a variable. If the src == 0 then the result is the size in bits of the type | |
| of src. For example, <tt>llvm.cttz(int 2) = 30</tt>. | |
| </p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"> | |
| <a name="int_cttz">'<tt>llvm.cttz</tt>' Intrinsic</a> | |
| </div> | |
| <div class="doc_text"> | |
| <h5>Syntax:</h5> | |
| <pre> | |
| declare int %llvm.cttz(int <src>) | |
| </pre> | |
| <h5>Overview:</h5> | |
| <p> | |
| The '<tt>llvm.cttz</tt>' intrinsic counts the number of trailing zeros. | |
| </p> | |
| <h5>Arguments:</h5> | |
| <p> | |
| The only argument is the value to be counted. The argument may be of any | |
| integer type. The return type must match the argument type. | |
| </p> | |
| <h5>Semantics:</h5> | |
| <p> | |
| The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant) zeros | |
| in a variable. If the src == 0 then the result is the size in bits of the type | |
| of src. For example, <tt>llvm.cttz(2) = 1</tt>. | |
| </p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="int_debugger">Debugger Intrinsics</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| The LLVM debugger intrinsics (which all start with <tt>llvm.dbg.</tt> prefix), | |
| are described in the <a | |
| href="SourceLevelDebugging.html#format_common_intrinsics">LLVM Source Level | |
| Debugging</a> document. | |
| </p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
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