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| <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">Functions</a></li> |
| <li><a href="#moduleasm">Module-Level Inline Assembly</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="#othervalues">Other Values</a> |
| <ol> |
| <li><a href="#inlineasm">Inline Assembler 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="#vectorops">Vector Operations</a> |
| <ol> |
| <li><a href="#i_extractelement">'<tt>extractelement</tt>' Instruction</a></li> |
| <li><a href="#i_insertelement">'<tt>insertelement</tt>' Instruction</a></li> |
| <li><a href="#i_shufflevector">'<tt>shufflevector</tt>' Instruction</a></li> |
| <li><a href="#i_vsetint">'<tt>vsetint</tt>' Instruction</a></li> |
| <li><a href="#i_vsetfp">'<tt>vsetfp</tt>' Instruction</a></li> |
| <li><a href="#i_vselect">'<tt>vselect</tt>' Instruction</a></li> |
| </ol> |
| </li> |
| <li><a href="#memoryops">Memory Access and Addressing 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_va_arg">'<tt>va_arg</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_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a></li> |
| <li><a href="#i_stackrestore">'<tt>llvm.stackrestore</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> |
| <li><a href="#i_readcyclecounter"><tt>llvm.readcyclecounter</tt>' Intrinsic</a></li> |
| </ol> |
| </li> |
| <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_manip">Bit Manipulation Intrinsics</a> |
| <ol> |
| <li><a href="#i_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a></li> |
| <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>; Global variable / Function body section separator</i> |
| implementation |
| |
| <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> |
| |
| <p>Due to a limitation in the current LLVM assembly parser (it is limited by |
| one-token lookahead), modules are split into two pieces by the "implementation" |
| keyword. Global variable prototypes and definitions must occur before the |
| keyword, and function definitions must occur after it. Function prototypes may |
| occur either before or after it. In the future, the implementation keyword may |
| become a noop, if the parser gets smarter.</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>csretcc</tt>" - The C struct return calling convention</b>:</dt> |
| |
| <dd>This calling convention matches the target C calling conventions, except |
| that functions with this convention are required to take a pointer as their |
| first argument, and the return type of the function must be void. This is |
| used for C functions that return aggregates by-value. In this case, the |
| function has been transformed to take a pointer to the struct as the first |
| argument to the function. For targets where the ABI specifies specific |
| behavior for structure-return calls, the calling convention can be used to |
| distinguish between struct return functions and other functions that take a |
| pointer to a struct as the first argument. |
| </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, may have |
| an explicit section to be placed in, and may |
| have an optional explicit alignment specified. 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> |
| |
| <p>LLVM allows an explicit section to be specified for globals. If the target |
| supports it, it will emit globals to the section specified.</p> |
| |
| <p>An explicit alignment may be specified for a global. If not present, or if |
| the alignment is set to zero, the alignment of the global is set by the target |
| to whatever it feels convenient. If an explicit alignment is specified, the |
| global is forced to have at least that much alignment. All alignments must be |
| a power of 2.</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 optional section, |
| an optional alignment, 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, |
| a possibly empty list of arguments, and an optional alignment.</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> |
| |
| <p>LLVM allows an explicit section to be specified for functions. If the target |
| supports it, it will emit functions to the section specified.</p> |
| |
| <p>An explicit alignment may be specified for a function. If not present, or if |
| the alignment is set to zero, the alignment of the function is set by the target |
| to whatever it feels convenient. If an explicit alignment is specified, the |
| function is forced to have at least that much alignment. All alignments must be |
| a power of 2.</p> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="moduleasm">Module-Level Inline Assembly</a> |
| </div> |
| |
| <div class="doc_text"> |
| <p> |
| Modules may contain "module-level inline asm" blocks, which corresponds to the |
| GCC "file scope inline asm" blocks. These blocks are internally concatenated by |
| LLVM and treated as a single unit, but may be separated in the .ll file if |
| desired. The syntax is very simple: |
| </p> |
| |
| <div class="doc_code"><pre> |
| module asm "inline asm code goes here" |
| module asm "more can go here" |
| </pre></div> |
| |
| <p>The strings can contain any character by escaping non-printable characters. |
| The escape sequence used is simply "\xx" where "xx" is the two digit hex code |
| for the number. |
| </p> |
| |
| <p> |
| The inline asm code is simply printed to the machine code .s file when |
| assembly code is generated. |
| </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. Vectors must have a power |
| of two length (1, 2, 4, 8, 16 ...). 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>select ( COND, VAL1, VAL2 )</tt></b></dt> |
| |
| <dd>Perform the <a href="#i_select">select operation</a> on |
| constants. |
| |
| <dt><b><tt>extractelement ( VAL, IDX )</tt></b></dt> |
| |
| <dd>Perform the <a href="#i_extractelement">extractelement |
| operation</a> on constants. |
| |
| <dt><b><tt>insertelement ( VAL, ELT, IDX )</tt></b></dt> |
| |
| <dd>Perform the <a href="#i_insertelement">insertelement |
| operation</a> on constants. |
| |
| |
| <dt><b><tt>shufflevector ( VEC1, VEC2, IDXMASK )</tt></b></dt> |
| |
| <dd>Perform the <a href="#i_shufflevector">shufflevector |
| operation</a> on constants. |
| |
| <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="othervalues">Other Values</a> </div> |
| <!-- *********************************************************************** --> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="inlineasm">Inline Assembler Expressions</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p> |
| LLVM supports inline assembler expressions (as opposed to <a href="#moduleasm"> |
| Module-Level Inline Assembly</a>) through the use of a special value. This |
| value represents the inline assembler as a string (containing the instructions |
| to emit), a list of operand constraints (stored as a string), and a flag that |
| indicates whether or not the inline asm expression has side effects. An example |
| inline assembler expression is: |
| </p> |
| |
| <pre> |
| int(int) asm "bswap $0", "=r,r" |
| </pre> |
| |
| <p> |
| Inline assembler expressions may <b>only</b> be used as the callee operand of |
| a <a href="#i_call"><tt>call</tt> instruction</a>. Thus, typically we have: |
| </p> |
| |
| <pre> |
| %X = call int asm "<a href="#i_bswap">bswap</a> $0", "=r,r"(int %Y) |
| </pre> |
| |
| <p> |
| Inline asms with side effects not visible in the constraint list must be marked |
| as having side effects. This is done through the use of the |
| '<tt>sideeffect</tt>' keyword, like so: |
| </p> |
| |
| <pre> |
| call void asm sideeffect "eieio", ""() |
| </pre> |
| |
| <p>TODO: The format of the asm and constraints string still need to be |
| documented here. Constraints on what can be done (e.g. duplication, moving, etc |
| need to be documented). |
| </p> |
| |
| </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> unwind 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 |
| unwind label %TestCleanup <i>; {int}:retval set</i> |
| %retval = invoke <a href="#callingconv">coldcc</a> int %Test(int 15) to label %Continue |
| unwind 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="vectorops">Vector Operations</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>LLVM supports several instructions to represent vector operations in a |
| target-independent manner. This instructions cover the element-access and |
| vector-specific operations needed to process vectors effectively. While LLVM |
| does directly support these vector operations, many sophisticated algorithms |
| will want to use target-specific intrinsics to take full advantage of a specific |
| target.</p> |
| |
| </div> |
| |
| <!-- _______________________________________________________________________ --> |
| <div class="doc_subsubsection"> |
| <a name="i_extractelement">'<tt>extractelement</tt>' Instruction</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <h5>Syntax:</h5> |
| |
| <pre> |
| <result> = extractelement <n x <ty>> <val>, uint <idx> <i>; yields <ty></i> |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>extractelement</tt>' instruction extracts a single scalar |
| element from a packed vector at a specified index. |
| </p> |
| |
| |
| <h5>Arguments:</h5> |
| |
| <p> |
| The first operand of an '<tt>extractelement</tt>' instruction is a |
| value of <a href="#t_packed">packed</a> type. The second operand is |
| an index indicating the position from which to extract the element. |
| The index may be a variable.</p> |
| |
| <h5>Semantics:</h5> |
| |
| <p> |
| The result is a scalar of the same type as the element type of |
| <tt>val</tt>. Its value is the value at position <tt>idx</tt> of |
| <tt>val</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the |
| results are undefined. |
| </p> |
| |
| <h5>Example:</h5> |
| |
| <pre> |
| %result = extractelement <4 x int> %vec, uint 0 <i>; yields int</i> |
| </pre> |
| </div> |
| |
| |
| <!-- _______________________________________________________________________ --> |
| <div class="doc_subsubsection"> |
| <a name="i_insertelement">'<tt>insertelement</tt>' Instruction</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <h5>Syntax:</h5> |
| |
| <pre> |
| <result> = insertelement <n x <ty>> <val>, <ty> <elt>, uint <idx> <i>; yields <n x <ty>></i> |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>insertelement</tt>' instruction inserts a scalar |
| element into a packed vector at a specified index. |
| </p> |
| |
| |
| <h5>Arguments:</h5> |
| |
| <p> |
| The first operand of an '<tt>insertelement</tt>' instruction is a |
| value of <a href="#t_packed">packed</a> type. The second operand is a |
| scalar value whose type must equal the element type of the first |
| operand. The third operand is an index indicating the position at |
| which to insert the value. The index may be a variable.</p> |
| |
| <h5>Semantics:</h5> |
| |
| <p> |
| The result is a packed vector of the same type as <tt>val</tt>. Its |
| element values are those of <tt>val</tt> except at position |
| <tt>idx</tt>, where it gets the value <tt>elt</tt>. If <tt>idx</tt> |
| exceeds the length of <tt>val</tt>, the results are undefined. |
| </p> |
| |
| <h5>Example:</h5> |
| |
| <pre> |
| %result = insertelement <4 x int> %vec, int 1, uint 0 <i>; yields <4 x int></i> |
| </pre> |
| </div> |
| |
| <!-- _______________________________________________________________________ --> |
| <div class="doc_subsubsection"> |
| <a name="i_shufflevector">'<tt>shufflevector</tt>' Instruction</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <h5>Syntax:</h5> |
| |
| <pre> |
| <result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <n x uint> <mask> <i>; yields <n x <ty>></i> |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>shufflevector</tt>' instruction constructs a permutation of elements |
| from two input vectors, returning a vector of the same type. |
| </p> |
| |
| <h5>Arguments:</h5> |
| |
| <p> |
| The first two operands of a '<tt>shufflevector</tt>' instruction are vectors |
| with types that match each other and types that match the result of the |
| instruction. The third argument is a shuffle mask, which has the same number |
| of elements as the other vector type, but whose element type is always 'uint'. |
| </p> |
| |
| <p> |
| The shuffle mask operand is required to be a constant vector with either |
| constant integer or undef values. |
| </p> |
| |
| <h5>Semantics:</h5> |
| |
| <p> |
| The elements of the two input vectors are numbered from left to right across |
| both of the vectors. The shuffle mask operand specifies, for each element of |
| the result vector, which element of the two input registers the result element |
| gets. The element selector may be undef (meaning "don't care") and the second |
| operand may be undef if performing a shuffle from only one vector. |
| </p> |
| |
| <h5>Example:</h5> |
| |
| <pre> |
| %result = shufflevector <4 x int> %v1, <4 x int> %v2, |
| <4 x uint> <uint 0, uint 4, uint 1, uint 5> <i>; yields <4 x int></i> |
| %result = shufflevector <4 x int> %v1, <4 x int> undef, |
| <4 x uint> <uint 0, uint 1, uint 2, uint 3> <i>; yields <4 x int></i> - Identity shuffle. |
| </pre> |
| </div> |
| |
| |
| <!-- _______________________________________________________________________ --> |
| <div class="doc_subsubsection"> <a name="i_vsetint">'<tt>vsetint</tt>' |
| Instruction</a> </div> |
| <div class="doc_text"> |
| <h5>Syntax:</h5> |
| <pre><result> = vsetint <op>, <n x <ty>> <var1>, <var2> <i>; yields <n x bool></i> |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p>The '<tt>vsetint</tt>' instruction takes two integer vectors and |
| returns a vector of boolean values representing, at each position, the |
| result of the comparison between the values at that position in the |
| two operands.</p> |
| |
| <h5>Arguments:</h5> |
| |
| <p>The arguments to a '<tt>vsetint</tt>' instruction are a comparison |
| operation and two value arguments. The value arguments must be of <a |
| href="#t_integral">integral</a> <a href="#t_packed">packed</a> type, |
| and they must have identical types. The operation argument must be |
| one of <tt>eq</tt>, <tt>ne</tt>, <tt>slt</tt>, <tt>sgt</tt>, |
| <tt>sle</tt>, <tt>sge</tt>, <tt>ult</tt>, <tt>ugt</tt>, <tt>ule</tt>, |
| <tt>uge</tt>, <tt>true</tt>, and <tt>false</tt>. The result is a |
| packed <tt>bool</tt> value with the same length as each operand.</p> |
| |
| <h5>Semantics:</h5> |
| |
| <p>The following table shows the semantics of '<tt>vsetint</tt>'. For |
| each position of the result, the comparison is done on the |
| corresponding positions of the two value arguments. Note that the |
| signedness of the comparison depends on the comparison opcode and |
| <i>not</i> on the signedness of the value operands. E.g., <tt>vsetint |
| slt <4 x unsigned> %x, %y</tt> does an elementwise <i>signed</i> |
| comparison of <tt>%x</tt> and <tt>%y</tt>.</p> |
| |
| <table border="1" cellspacing="0" cellpadding="4"> |
| <tbody> |
| <tr><th>Operation</th><th>Result is true iff</th><th>Comparison is</th></tr> |
| <tr><td><tt>eq</tt></td><td>var1 == var2</td><td>--</td></tr> |
| <tr><td><tt>ne</tt></td><td>var1 != var2</td><td>--</td></tr> |
| <tr><td><tt>slt</tt></td><td>var1 < var2</td><td>signed</td></tr> |
| <tr><td><tt>sgt</tt></td><td>var1 > var2</td><td>signed</td></tr> |
| <tr><td><tt>sle</tt></td><td>var1 <= var2</td><td>signed</td></tr> |
| <tr><td><tt>sge</tt></td><td>var1 >= var2</td><td>signed</td></tr> |
| <tr><td><tt>ult</tt></td><td>var1 < var2</td><td>unsigned</td></tr> |
| <tr><td><tt>ugt</tt></td><td>var1 > var2</td><td>unsigned</td></tr> |
| <tr><td><tt>ule</tt></td><td>var1 <= var2</td><td>unsigned</td></tr> |
| <tr><td><tt>uge</tt></td><td>var1 >= var2</td><td>unsigned</td></tr> |
| <tr><td><tt>true</tt></td><td>always</td><td>--</td></tr> |
| <tr><td><tt>false</tt></td><td>never</td><td>--</td></tr> |
| </tbody> |
| </table> |
| |
| <h5>Example:</h5> |
| <pre> <result> = vsetint eq <2 x int> <int 0, int 1>, <int 1, int 0> <i>; yields {<2 x bool>}:result = false, false</i> |
| <result> = vsetint ne <2 x int> <int 0, int 1>, <int 1, int 0> <i>; yields {<2 x bool>}:result = true, true</i> |
| <result> = vsetint slt <2 x int> <int 0, int 1>, <int 1, int 0> <i>; yields {<2 x bool>}:result = true, false</i> |
| <result> = vsetint sgt <2 x int> <int 0, int 1>, <int 1, int 0> <i>; yields {<2 x bool>}:result = false, true</i> |
| <result> = vsetint sle <2 x int> <int 0, int 1>, <int 1, int 0> <i>; yields {<2 x bool>}:result = true, false</i> |
| <result> = vsetint sge <2 x int> <int 0, int 1>, <int 1, int 0> <i>; yields {<2 x bool>}:result = false, true</i> |
| </pre> |
| </div> |
| |
| <!-- _______________________________________________________________________ --> |
| <div class="doc_subsubsection"> <a name="i_vsetfp">'<tt>vsetfp</tt>' |
| Instruction</a> </div> |
| <div class="doc_text"> |
| <h5>Syntax:</h5> |
| <pre><result> = vsetfp <op>, <n x <ty>> <var1>, <var2> <i>; yields <n x bool></i> |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p>The '<tt>vsetfp</tt>' instruction takes two floating point vector |
| arguments and returns a vector of boolean values representing, at each |
| position, the result of the comparison between the values at that |
| position in the two operands.</p> |
| |
| <h5>Arguments:</h5> |
| |
| <p>The arguments to a '<tt>vsetfp</tt>' instruction are a comparison |
| operation and two value arguments. The value arguments must be of <a |
| href="t_floating">floating point</a> <a href="#t_packed">packed</a> |
| type, and they must have identical types. The operation argument must |
| be one of <tt>eq</tt>, <tt>ne</tt>, <tt>lt</tt>, <tt>gt</tt>, |
| <tt>le</tt>, <tt>ge</tt>, <tt>oeq</tt>, <tt>one</tt>, <tt>olt</tt>, |
| <tt>ogt</tt>, <tt>ole</tt>, <tt>oge</tt>, <tt>ueq</tt>, <tt>une</tt>, |
| <tt>ult</tt>, <tt>ugt</tt>, <tt>ule</tt>, <tt>uge</tt>, <tt>o</tt>, |
| <tt>u</tt>, <tt>true</tt>, and <tt>false</tt>. The result is a packed |
| <tt>bool</tt> value with the same length as each operand.</p> |
| |
| <h5>Semantics:</h5> |
| |
| <p>The following table shows the semantics of '<tt>vsetfp</tt>' for |
| floating point types. If either operand is a floating point Not a |
| Number (NaN) value, the operation is unordered, and the value in the |
| first column below is produced at that position. Otherwise, the |
| operation is ordered, and the value in the second column is |
| produced.</p> |
| |
| <table border="1" cellspacing="0" cellpadding="4"> |
| <tbody> |
| <tr><th>Operation</th><th>If unordered<th>Otherwise true iff</th></tr> |
| <tr><td><tt>eq</tt></td><td>undefined</td><td>var1 == var2</td></tr> |
| <tr><td><tt>ne</tt></td><td>undefined</td><td>var1 != var2</td></tr> |
| <tr><td><tt>lt</tt></td><td>undefined</td><td>var1 < var2</td></tr> |
| <tr><td><tt>gt</tt></td><td>undefined</td><td>var1 > var2</td></tr> |
| <tr><td><tt>le</tt></td><td>undefined</td><td>var1 <= var2</td></tr> |
| <tr><td><tt>ge</tt></td><td>undefined</td><td>var1 >= var2</td></tr> |
| <tr><td><tt>oeq</tt></td><td>false</td><td>var1 == var2</td></tr> |
| <tr><td><tt>one</tt></td><td>false</td><td>var1 != var2</td></tr> |
| <tr><td><tt>olt</tt></td><td>false</td><td>var1 < var2</td></tr> |
| <tr><td><tt>ogt</tt></td><td>false</td><td>var1 > var2</td></tr> |
| <tr><td><tt>ole</tt></td><td>false</td><td>var1 <= var2</td></tr> |
| <tr><td><tt>oge</tt></td><td>false</td><td>var1 >= var2</td></tr> |
| <tr><td><tt>ueq</tt></td><td>true</td><td>var1 == var2</td></tr> |
| <tr><td><tt>une</tt></td><td>true</td><td>var1 != var2</td></tr> |
| <tr><td><tt>ult</tt></td><td>true</td><td>var1 < var2</td></tr> |
| <tr><td><tt>ugt</tt></td><td>true</td><td>var1 > var2</td></tr> |
| <tr><td><tt>ule</tt></td><td>true</td><td>var1 <= var2</td></tr> |
| <tr><td><tt>uge</tt></td><td>true</td><td>var1 >= var2</td></tr> |
| <tr><td><tt>o</tt></td><td>false</td><td>always</td></tr> |
| <tr><td><tt>u</tt></td><td>true</td><td>never</td></tr> |
| <tr><td><tt>true</tt></td><td>true</td><td>always</td></tr> |
| <tr><td><tt>false</tt></td><td>false</td><td>never</td></tr> |
| </tbody> |
| </table> |
| |
| <h5>Example:</h5> |
| <pre> <result> = vsetfp eq <2 x float> <float 0.0, float 1.0>, <float 1.0, float 0.0> <i>; yields {<2 x bool>}:result = false, false</i> |
| <result> = vsetfp ne <2 x float> <float 0.0, float 1.0>, <float 1.0, float 0.0> <i>; yields {<2 x bool>}:result = true, true</i> |
| <result> = vsetfp lt <2 x float> <float 0.0, float 1.0>, <float 1.0, float 0.0> <i>; yields {<2 x bool>}:result = true, false</i> |
| <result> = vsetfp gt <2 x float> <float 0.0, float 1.0>, <float 1.0, float 0.0> <i>; yields {<2 x bool>}:result = false, true</i> |
| <result> = vsetfp le <2 x float> <float 0.0, float 1.0>, <float 1.0, float 0.0> <i>; yields {<2 x bool>}:result = true, false</i> |
| <result> = vsetfp ge <2 x float> <float 0.0, float 1.0>, <float 1.0, float 0.0> <i>; yields {<2 x bool>}:result = false, true</i> |
| </pre> |
| </div> |
| |
| <!-- _______________________________________________________________________ --> |
| <div class="doc_subsubsection"> |
| <a name="i_vselect">'<tt>vselect</tt>' Instruction</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <h5>Syntax:</h5> |
| |
| <pre> |
| <result> = vselect <n x bool> <cond>, <n x <ty>> <val1>, <n x <ty>> <val2> <i>; yields <n x <ty>></i> |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>vselect</tt>' instruction chooses one value at each position |
| of a vector based on a condition. |
| </p> |
| |
| |
| <h5>Arguments:</h5> |
| |
| <p> |
| The '<tt>vselect</tt>' instruction requires a <a |
| href="#t_packed">packed</a> <tt>bool</tt> value indicating the |
| condition at each vector position, and two values of the same packed |
| type. All three operands must have the same length. The type of the |
| result is the same as the type of the two value operands.</p> |
| |
| <h5>Semantics:</h5> |
| |
| <p> |
| At each position where the <tt>bool</tt> vector is true, that position |
| of the result gets its value from the first value argument; otherwise, |
| it gets its value from the second value argument. |
| </p> |
| |
| <h5>Example:</h5> |
| |
| <pre> |
| %X = vselect bool <2 x bool> <bool true, bool false>, <2 x ubyte> <ubyte 17, ubyte 17>, |
| <2 x ubyte> <ubyte 42, ubyte 42> <i>; yields <2 x ubyte>:17, 42</i> |
| </pre> |
| </div> |
| |
| |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="memoryops">Memory Access and Addressing 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>][, align <alignment>] <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. If "NumElements" is specified, it is the |
| number of elements allocated. If an alignment is specified, the value result |
| of the allocation is guaranteed to be aligned to at least that boundary. If |
| not specified, or if zero, the target can choose to align the allocation on any |
| convenient boundary.</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> |
| %array3 = malloc int, uint 4, align 1024 <i>; yields {int*}:array3</i> |
| %array4 = malloc int, align 1024 <i>; yields {int*}:array4</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> |
| |
| <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>][, align <alignment>] <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. If "NumElements" is specified, it is the |
| number of elements allocated. If an alignment is specified, the value result |
| of the allocation is guaranteed to be aligned to at least that boundary. If |
| not specified, or if zero, the target can choose to align the allocation on any |
| convenient boundary.</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> |
| %ptr = alloca int, uint 4, align 1024 <i>; yields {int*}:ptr</i> |
| %ptr = alloca int, align 1024 <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> |
| |
| <p>The getelementptr instruction is often confusing. For some more insight |
| into how it works, see <a href="GetElementPtr.html">the getelementptr |
| FAQ</a>.</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_va_arg">'<tt>va_arg</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 point 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_va_arg"><tt>va_arg</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_va_arg"><tt>va_arg</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* %ObjPtr, 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 second argument is the address to read from, which should be an address |
| allocated from the garbage collector. The first object is a pointer to the |
| start of the referenced object, if needed by the language runtime (otherwise |
| null).</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* %Obj, 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, the second is the start of the |
| object to store it to, and the third is the address of the field of Obj to |
| store to. If the runtime does not require a pointer to the object, Obj may be |
| null.</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 sbyte *%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 sbyte *%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_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <h5>Syntax:</h5> |
| <pre> |
| declare sbyte *%llvm.stacksave() |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>llvm.stacksave</tt>' intrinsic is used to remember the current state of |
| the function stack, for use with <a href="#i_stackrestore"> |
| <tt>llvm.stackrestore</tt></a>. This is useful for implementing language |
| features like scoped automatic variable sized arrays in C99. |
| </p> |
| |
| <h5>Semantics:</h5> |
| |
| <p> |
| This intrinsic returns a opaque pointer value that can be passed to <a |
| href="#i_stackrestore"><tt>llvm.stackrestore</tt></a>. When an |
| <tt>llvm.stackrestore</tt> intrinsic is executed with a value saved from |
| <tt>llvm.stacksave</tt>, it effectively restores the state of the stack to the |
| state it was in when the <tt>llvm.stacksave</tt> intrinsic executed. In |
| practice, this pops any <a href="#i_alloca">alloca</a> blocks from the stack |
| that were allocated after the <tt>llvm.stacksave</tt> was executed. |
| </p> |
| |
| </div> |
| |
| <!-- _______________________________________________________________________ --> |
| <div class="doc_subsubsection"> |
| <a name="i_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <h5>Syntax:</h5> |
| <pre> |
| declare void %llvm.stackrestore(sbyte* %ptr) |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>llvm.stackrestore</tt>' intrinsic is used to restore the state of |
| the function stack to the state it was in when the corresponding <a |
| href="#llvm.stacksave"><tt>llvm.stacksave</tt></a> intrinsic executed. This is |
| useful for implementing language features like scoped automatic variable sized |
| arrays in C99. |
| </p> |
| |
| <h5>Semantics:</h5> |
| |
| <p> |
| See the description for <a href="#i_stacksave"><tt>llvm.stacksave</tt></a>. |
| </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 guarantees that it will remain with any specific instruction |
| after optimizations. It is possible that the presence of a marker will inhibit |
| optimizations. The intended use is to be inserted after optimizations 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_subsubsection"> |
| <a name="i_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <h5>Syntax:</h5> |
| <pre> |
| declare ulong %llvm.readcyclecounter( ) |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| |
| <p> |
| The '<tt>llvm.readcyclecounter</tt>' intrinsic provides access to the cycle |
| counter register (or similar low latency, high accuracy clocks) on those targets |
| that support it. On X86, it should map to RDTSC. On Alpha, it should map to RPCC. |
| As the backing counters overflow quickly (on the order of 9 seconds on alpha), this |
| should only be used for small timings. |
| </p> |
| |
| <h5>Semantics:</h5> |
| |
| <p> |
| When directly supported, reading the cycle counter should not modify any memory. |
| Implementations are allowed to either return a application specific value or a |
| system wide value. On backends without support, this is lowered to a constant 0. |
| </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.i32(sbyte* <dest>, sbyte* <src>, |
| uint <len>, uint <align>) |
| declare void %llvm.memcpy.i64(sbyte* <dest>, sbyte* <src>, |
| ulong <len>, uint <align>) |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>llvm.memcpy.*</tt>' intrinsics copy 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> |
| intrinsics do 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 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 both the source and destination pointers are aligned |
| to that boundary. |
| </p> |
| |
| <h5>Semantics:</h5> |
| |
| <p> |
| The '<tt>llvm.memcpy.*</tt>' intrinsics copy 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.i32(sbyte* <dest>, sbyte* <src>, |
| uint <len>, uint <align>) |
| declare void %llvm.memmove.i64(sbyte* <dest>, sbyte* <src>, |
| ulong <len>, uint <align>) |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>llvm.memmove.*</tt>' intrinsics move a block of memory from the source |
| location to the destination location. It is similar to the |
| '<tt>llvm.memcmp</tt>' intrinsic but allows the two memory locations to overlap. |
| </p> |
| |
| <p> |
| Note that, unlike the standard libc function, the <tt>llvm.memmove.*</tt> |
| intrinsics do 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 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 source and destination pointers are aligned to |
| that boundary. |
| </p> |
| |
| <h5>Semantics:</h5> |
| |
| <p> |
| The '<tt>llvm.memmove.*</tt>' intrinsics copy 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>' Intrinsics</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <h5>Syntax:</h5> |
| <pre> |
| declare void %llvm.memset.i32(sbyte* <dest>, ubyte <val>, |
| uint <len>, uint <align>) |
| declare void %llvm.memset.i64(sbyte* <dest>, ubyte <val>, |
| ulong <len>, uint <align>) |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>llvm.memset.*</tt>' intrinsics fill 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 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 destination pointer is aligned to that boundary. |
| </p> |
| |
| <h5>Semantics:</h5> |
| |
| <p> |
| The '<tt>llvm.memset.*</tt>' intrinsics fill "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.f32(float Val1, float Val2) |
| declare bool %llvm.isunordered.f64(double Val1, double Val2) |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>llvm.isunordered</tt>' intrinsics return 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 double %llvm.sqrt.f32(float Val) |
| declare double %llvm.sqrt.f64(double Val) |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>llvm.sqrt</tt>' intrinsics return 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_manip">Bit Manipulation Intrinsics</a> |
| </div> |
| |
| <div class="doc_text"> |
| <p> |
| LLVM provides intrinsics for a few important bit manipulation operations. |
| These allow efficient code generation for some algorithms. |
| </p> |
| |
| </div> |
| |
| <!-- _______________________________________________________________________ --> |
| <div class="doc_subsubsection"> |
| <a name="i_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <h5>Syntax:</h5> |
| <pre> |
| declare ushort %llvm.bswap.i16(ushort <id>) |
| declare uint %llvm.bswap.i32(uint <id>) |
| declare ulong %llvm.bswap.i64(ulong <id>) |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>llvm.bwsap</tt>' family of intrinsics is used to byteswap a 16, 32 or |
| 64 bit quantity. These are useful for performing operations on data that is not |
| in the target's native byte order. |
| </p> |
| |
| <h5>Semantics:</h5> |
| |
| <p> |
| The <tt>llvm.bswap.16</tt> intrinsic returns a ushort value that has the high and low |
| byte of the input ushort swapped. Similarly, the <tt>llvm.bswap.i32</tt> intrinsic |
| returns a uint value that has the four bytes of the input uint swapped, so that |
| if the input bytes are numbered 0, 1, 2, 3 then the returned uint will have its |
| bytes in 3, 2, 1, 0 order. The <tt>llvm.bswap.i64</tt> intrinsic extends this concept |
| to 64 bits. |
| </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 ubyte %llvm.ctpop.i8 (ubyte <src>) |
| declare ushort %llvm.ctpop.i16(ushort <src>) |
| declare uint %llvm.ctpop.i32(uint <src>) |
| declare ulong %llvm.ctpop.i64(ulong <src>) |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>llvm.ctpop</tt>' family of intrinsics counts the number of bits set in a |
| value. |
| </p> |
| |
| <h5>Arguments:</h5> |
| |
| <p> |
| The only argument is the value to be counted. The argument may be of any |
| unsigned 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 ubyte %llvm.ctlz.i8 (ubyte <src>) |
| declare ushort %llvm.ctlz.i16(ushort <src>) |
| declare uint %llvm.ctlz.i32(uint <src>) |
| declare ulong %llvm.ctlz.i64(ulong <src>) |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>llvm.ctlz</tt>' family of intrinsic functions 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 |
| unsigned 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.ctlz(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 ubyte %llvm.cttz.i8 (ubyte <src>) |
| declare ushort %llvm.cttz.i16(ushort <src>) |
| declare uint %llvm.cttz.i32(uint <src>) |
| declare ulong %llvm.cttz.i64(ulong <src>) |
| </pre> |
| |
| <h5>Overview:</h5> |
| |
| <p> |
| The '<tt>llvm.cttz</tt>' family of intrinsic functions 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 |
| unsigned 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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| <a href="mailto:sabre@nondot.org">Chris Lattner</a><br> |
| <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br> |
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