Written by Chris Lattner -and Vikram Adve
-+ + + +
This document is a reference manual for the LLVM assembly language. LLVM is an SSA based representation that provides type safety, @@ -114,10 +209,13 @@ low-level operations, flexibility, and the capability of representing representation used throughout all phases of the LLVM compilation strategy.
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), @@ -127,7 +225,8 @@ 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.
-The LLVM representation aims to be a light-weight and low-level + +
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 @@ -137,1552 +236,4383 @@ 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.
+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:
-%x = add int 1, %x+ +
+ %x = add i32 1, %x ++
...because the definition of %x 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 +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.
+LLVM uses three different forms of identifiers, for different purposes:
+-
-
- Numeric constants are represented as you would expect: 12, -3 -123.421, etc. Floating point constants have an optional hexidecimal -notation. -
- 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 '%[a-zA-Z$._][a-zA-Z$._0-9]*'. -Identifiers which require other characters in their names can be -surrounded with quotes. In this way, anything except a " -character can be used in a name. -
- Unnamed values are represented as an unsigned numeric value with -a '%' prefix. For example, %12, %2, %44. +
- 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 '%[a-zA-Z$._][a-zA-Z$._0-9]*'. + Identifiers which require other characters in their names can be surrounded + with quotes. In this way, anything except a " character can be used + in a name. + +
- Unnamed values are represented as an unsigned numeric value with a '%' + prefix. For example, %12, %2, %44. + +
- Constants, which are described in a section about + constants, below.
LLVM requires the 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.
+ +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.
+Reserved words in LLVM are very similar to reserved words in other -languages. There are keywords for different opcodes ('add', 'cast', 'ret', etc...), for primitive type names ('void', 'uint', -etc...), and others. These reserved words cannot conflict with -variable names, because none of them start with a '%' character.
-Here is an example of LLVM code to multiply the integer variable '%X' -by 8:
+languages. There are keywords for different opcodes +('add', + 'bitcast', + 'ret', etc...), for primitive type names ('void', 'i32', etc...), +and others. These reserved words cannot conflict with variable names, because +none of them start with a '%' character. + +Here is an example of LLVM code to multiply the integer variable +'%X' by 8:
+The easy way:
-%result = mul uint %X, 8+ +
+ %result = mul i32 %X, 8 ++
After strength reduction:
-%result = shl uint %X, ubyte 3+ +
+ %result = shl i32 %X, i8 3 ++
And the hard way:
-add uint %X, %X ; yields {uint}:%0 - add uint %0, %0 ; yields {uint}:%1 - %result = add uint %1, %1+ +
+ add i32 %X, %X ; yields {i32}:%0 + add i32 %0, %0 ; yields {i32}:%1 + %result = add i32 %1, %1 ++
This last way of multiplying %X by 8 illustrates several important lexical features of LLVM:
+-
-
- Comments are delimited with a ';' and go until the end -of line. -
- Unnamed temporaries are created when the result of a computation -is not assigned to a named value. + +
- Comments are delimited with a ';' and go until the end of + line. + +
- Unnamed temporaries are created when the result of a computation is not + assigned to a named value. +
- Unnamed temporaries are numbered sequentially +
...and it also show 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.
-The one non-intuitive notation for constants is the optional -hexidecimal form of floating point constants. For example, the form 'double -0x432ff973cafa8000' is equivalent to (but harder to read than) 'double -4.5e+15' which is also supported by the parser. The only time -hexadecimal floating point constants are useful (and the only time that -they are generated by the disassembler) is when an FP constant has to -be emitted that is not representable as a decimal floating point number -exactly. For example, NaN's, infinities, and other special cases are -represented in their IEEE hexadecimal format so that assembly and -disassembly do not cause any bits to change in the constants.
+ +...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.
+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.
-The primitive types are the fundemental building blocks of the LLVM -system. The current set of primitive types are as follows:
--
-
|
-
-
|
-
These different primitive types fall into a few useful -classifications:
--
| signed | -sbyte, short, int, long, float, double | -
| unsigned | -ubyte, ushort, uint, ulong | -
| integer | -ubyte, sbyte, ushort, short, uint, int, ulong, long | -
| integral | -bool, ubyte, sbyte, ushort, short, uint, int, ulong, long | -
| floating point | -float, double | -
| first class | -bool, ubyte, sbyte, ushort, short, -uint, int, ulong, long, float, double, pointer |
-
The first class 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.
-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.
-Overview:
-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.
-Syntax:
-[<# elements> x <elementtype>]-
The number of elements is a constant integer value, elementtype may -be any type with a size.
-Examples:
- [40 x int ]: Array of 40 integer values.
-[41 x int ]: Array of 41 integer values.
-[40 x uint]: Array of 40 unsigned integer values.
-
Here are some examples of multidimensional arrays:
--
| [3 x [4 x int]] | -: 3x4 array integer values. | -
| [12 x [10 x float]] | -: 12x10 array of single precision floating point values. | -
| [2 x [3 x [4 x uint]]] | -: 2x3x4 array of unsigned integer values. | -
Overview:
-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 when to build virtual function tables -(which are structures of pointers to functions), for indirect function -calls, and when defining a function.
-Syntax:
-<returntype> (<parameter list>)-
Where '<parameter list>' is a comma-separated list of -type specifiers. Optionally, the parameter list may include a type ..., -which indicates that the function takes a variable number of arguments. -Variable argument functions can access their arguments with the variable argument handling intrinsic functions.
-Examples:
--
| int (int) | -: function taking an int, returning an int | -
| float (int, int *) * | -: Pointer to a function that takes -an int and a pointer to int, -returning float. | -
| int (sbyte *, ...) | -: A vararg function that takes at least one pointer to sbyte (signed char in C), -which returns an integer. This is the signature for printf -in LLVM. | -
Overview:
-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.
-Structures are accessed using 'load -and 'store' by getting a pointer to a -field with the 'getelementptr' -instruction.
-Syntax:
- { <type list> }
-Examples:
--
| { int, int, int } | -: a triple of three int values | -
| { float, int (int) * } | -: A pair, where the first element is a float and the -second element is a pointer to a function that takes an int, returning -an int. | -
Overview:
-As in many languages, the pointer type represents a pointer or -reference to another object, which must live in memory.
-Syntax:
-<type> *-
Examples:
--
| [4x int]* | -: pointer to array -of four int values | -
| int (int *) * | -: A pointer to a function that takes an int, returning -an int. | -
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:
+; Declare the string constant as a global constant... %.LC0 = internal constant [13 x sbyte] c"hello world\0A\00" ; [13 x sbyte]* + href="#globalvars">constant [13 x i8 ] c"hello world\0A\00" ; [13 x i8 ]* ; External declaration of the puts function -declare int %puts(sbyte*) ; int(sbyte*)* +declare i32 %puts(i8 *) ; i32(i8 *)* + +; Global variable / Function body section separator +implementation ; Definition of main function -int %main() { ; int()* - ; Convert [13x sbyte]* to sbyte *... +define i32 %main() { ; i32()* + ; Convert [13x i8 ]* to i8 *... %cast210 = getelementptr [13 x sbyte]* %.LC0, long 0, long 0 ; sbyte* + href="#i_getelementptr">getelementptr [13 x i8 ]* %.LC0, i64 0, i64 0 ; i8 * ; Call puts function to write out the string to stdout... call int %puts(sbyte* %cast210) ; int + href="#i_call">call i32 %puts(i8 * %cast210) ; i32 ret int 0+ href="#i_ret">ret i32 0
}
}
+
This example is made up of a global variable named ".LC0", an external declaration of the "puts" function, and a function definition for "main".
- 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 linkage types: --
-
-
- internal -
- 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 'static' keyword in C, or the
-idea of "anonymous namespaces" in C++.
-
-
- - linkonce: -
- "linkonce" linkage is similar to internal
-linkage, with the twist that linking together two modules defining the
-same linkonce globals will cause one of the globals to be
-discarded. This is typically used to implement inline functions.
-Unreferenced linkonce globals are allowed to be discarded.
-
+ +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 linkage types.
+ +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.
+ +
+All Global Variables and Functions have one of the following types of linkage: +
+ +-
+
+
- internal + +
- 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 + 'static' keyword in C. -
- weak: -
- "weak" linkage is exactly the same as linkonce
-linkage, except that unreferenced weak globals may not be
-discarded. This is used to implement constructs in C such as "int
-X;" at global scope.
-
+ + - linkonce: + +
- Globals with "linkonce" linkage are merged with other globals of + the same name when linkage occurs. This is typically used to implement + inline functions, templates, or other code which must be generated in each + translation unit that uses it. Unreferenced linkonce globals are + allowed to be discarded. + + +
- weak: + +
- "weak" linkage is exactly the same as linkonce linkage, + except that unreferenced weak globals may not be discarded. This is + used for globals that may be emitted in multiple translation units, but that + are not guaranteed to be emitted into every translation unit that uses them. + One example of this are common globals in C, such as "int X;" at + global scope. -
- appending: -
- "appending" 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.
-
+ + - appending: + +
- "appending" 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. -
- externally visible: -
- 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.
-
+ + - extern_weak: +
- The semantics of this linkage follow the ELF model: the symbol is weak + until linked, if not linked, the symbol becomes null instead of being an + undefined reference. -
-
For example, since the ".LC0"
+
+
+ The next two types of linkage are targeted for Microsoft Windows platform
+ only. They are designed to support importing (exporting) symbols from (to)
+ DLLs.
+ For example, since the ".LC0"
variable is defined to be internal, if another module defined a ".LC0"
variable and was linked with this one, one of the two would be renamed,
preventing a collision. Since "main" and "puts" are
external (i.e., lacking any linkage declarations), they are accessible
-outside of the current module. It is illegal for a function declaration
-to have any linkage type other than "externally visible".
+
+
+_imp__ and the function or variable name.
+ _imp__ and the function or variable
+ name.
+
It is illegal for a function declaration +to have any linkage type other than "externally visible", dllimport, +or extern_weak.
+ +LLVM functions, calls +and invokes 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:
+ +-
+
- "ccc" - The C calling convention: + +
- 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). + + +
- "fastcc" - The fast calling convention: + +
- 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. + + +
- "coldcc" - The cold calling convention: + +
- 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. + + +
- "cc <n>" - Numbered convention: + +
- Any calling convention may be specified by number, allowing + target-specific calling conventions to be used. Target specific calling + conventions start at 64. + +
More calling conventions can be added/defined on an as-needed basis, to +support pascal conventions or any other well-known target-independent +convention.
+ ++All Global Variables and Functions have one of the following visibility styles: +
+ +-
+
- "default" - Default style: + +
- On ELF, default visibility means that the declaration is visible to other + modules and, in shared libraries, means that the declared entity may be + overridden. On Darwin, default visibility means that the declaration is + visible to other modules. Default visibility corresponds to "external + linkage" in the language. + + +
- "hidden" - Hidden style: + +
- Two declarations of an object with hidden visibility refer to the same + object if they are in the same shared object. Usually, hidden visibility + indicates that the symbol will not be placed into the dynamic symbol table, + so no other module (executable or shared library) can reference it + directly. + + +
Global variables define regions of memory allocated at compilation -time instead of run-time. Global variables may optionally be -initialized. A variable may be defined as a global "constant", which -indicates that the contents of the variable will never be modified -(opening options for optimization). Constants must always have an -initial value.
+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 never 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.
+ ++LLVM explicitly allows declarations 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. +
+As SSA values, global variables define pointer values that are in -scope (i.e. they dominate) for all basic blocks in the program. Global +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.
+ +LLVM allows an explicit section to be specified for globals. If the target +supports it, it will emit globals to the section specified.
+ +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.
+ +For example, the following defines a global with an initializer, section, + and alignment:
+ ++ %G = constant float 1.0, section "foo", align 4 ++ +
LLVM function definitions consist of the "define" keyord, +an optional linkage type, an optional +visibility style, an optional +calling convention, a return type, an optional +parameter attribute for the return type, a function +name, a (possibly empty) argument list (each with optional +parameter attributes), an optional section, an +optional alignment, an opening curly brace, a list of basic blocks, and a +closing curly brace. + +LLVM function declarations consist of the "declare" keyword, an +optional linkage type, an optional +visibility style, an optional +calling convention, a return type, an optional +parameter attribute for the return type, a function +name, a possibly empty list of arguments, and an optional alignment.
+ +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 terminator instruction (such as a branch or +function return).
+ +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 +PHI nodes.
+ +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.
+ +LLVM allows an explicit section to be specified for functions. If the target +supports it, it will emit functions to the section specified.
+ +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.
+ +The return type and each parameter of a function type may have a set of + parameter attributes associated with them. Parameter attributes are + used to communicate additional information about the result or parameters of + a function. Parameter attributes are considered to be part of the function + type so two functions types that differ only by the parameter attributes + are different function types.
+ +Parameter attributes are simple keywords that follow the type specified. If + multiple parameter attributes are needed, they are space separated. For + example:
+ %someFunc = i16 (i8 sext %someParam) zext + %someFunc = i16 (i8 zext %someParam) zext+
Note that the two function types above are unique because the parameter has + a different attribute (sext in the first one, zext in the second). Also note + that the attribute for the function result (zext) comes immediately after the + argument list.
+ +Currently, only the following parameter attributes are defined:
+-
+
- zext +
- This indicates that the parameter should be zero extended just before + a call to this function. +
- sext +
- This indicates that the parameter should be sign extended just before + a call to this function. +
- inreg +
- This indicates that the parameter should be placed in register (if + possible) during assembling function call. Support for this attribute is + target-specific +
- sret +
- This indicates that the parameter specifies the address of a structure + that is the return value of the function in the source program. +
- noreturn +
- This function attribute indicates that the function never returns. This + indicates to LLVM that every call to this function should be treated as if + an unreachable instruction immediately followed the call. +
- nounwind +
- This function attribute indicates that the function type does not use + the unwind instruction and does not allow stack unwinding to propagate + through it. +
+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: +
+ ++ module asm "inline asm code goes here" + module asm "more can go here" +
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. +
+ ++ The inline asm code is simply printed to the machine code .s file when + assembly code is generated. +
LLVM function definitions are composed of a (possibly empty) -argument list, an opening curly brace, a list of basic blocks, and a -closing curly brace. LLVM function declarations are defined with the "declare" -keyword, a function name, and a function signature.
-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 terminator -instruction (such as a branch or function return).
-The first basic block in 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 PHI nodes.
+A module may specify a target specific data layout string that specifies how
+data is to be laid out in memory. The syntax for the data layout is simply:
+
target datalayout = "layout specification" ++The layout specification consists of a list of specifications separated +by the minus sign character ('-'). Each specification starts with a letter +and may include other information after the letter to define some aspect of the +data layout. The specifications accepted are as follows: +
-
+
- E +
- Specifies that the target lays out data in big-endian form. That is, the + bits with the most significance have the lowest address location. +
- e +
- Specifies that hte target lays out data in little-endian form. That is, + the bits with the least significance have the lowest address location. +
- p:size:abi:pref +
- This specifies the size of a pointer and its abi and + preferred alignments. All sizes are in bits. Specifying the pref + alignment is optional. If omitted, the preceding : should be omitted + too. +
- isize:abi:pref +
- This specifies the alignment for an integer type of a given bit + size. The value of size must be in the range [1,2^23). +
- vsize:abi:pref +
- This specifies the alignment for a vector type of a given bit + size. +
- fsize:abi:pref +
- This specifies the alignment for a floating point type of a given bit + size. The value of size must be either 32 (float) or 64 + (double). +
- asize:abi:pref +
- This specifies the alignment for an aggregate type of a given bit + size. +
When constructing the data layout for a given target, LLVM starts with a +default set of specifications which are then (possibly) overriden by the +specifications in the datalayout keyword. The default specifications +are given in this list:
+-
+
- E - big endian +
- p:32:64:64 - 32-bit pointers with 64-bit alignment +
- i1:8:8 - i1 is 8-bit (byte) aligned +
- i8:8:8 - i8 is 8-bit (byte) aligned +
- i16:16:16 - i16 is 16-bit aligned +
- i32:32:32 - i32 is 32-bit aligned +
- i64:32:64 - i64 has abi alignment of 32-bits but preferred + alignment of 64-bits +
- f32:32:32 - float is 32-bit aligned +
- f64:64:64 - double is 64-bit aligned +
- v64:64:64 - 64-bit vector is 64-bit aligned +
- v128:128:128 - 128-bit vector is 128-bit aligned +
- a0:0:1 - aggregates are 8-bit aligned +
When llvm is determining the alignment for a given type, it uses the +following rules: +
-
+
- If the type sought is an exact match for one of the specifications, that + specification is used. +
- If no match is found, and the type sought is an integer type, then the + smallest integer type that is larger than the bitwidth of the sought type is + used. If none of the specifications are larger than the bitwidth then the the + largest integer type is used. For example, given the default specifications + above, the i7 type will use the alignment of i8 (next largest) while both + i65 and i256 will use the alignment of i64 (largest specified). +
- If no match is found, and the type sought is a vector type, then the + largest vector type that is smaller than the sought vector type will be used + as a fall back. This happens because <128 x double> can be implemented in + terms of 64 <2 x double>, for example. +
The LLVM instruction set consists of several different -classifications of instructions: terminator -instructions, binary instructions, memory instructions, and other -instructions.
+ +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.
+As mentioned previously, 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 'void' -value: they produce control flow, not values (the one exception being -the 'invoke' instruction).
-There are five different terminator instructions: the 'ret' instruction, the 'br' -instruction, the 'switch' instruction, -the 'invoke' instruction, and the 'unwind' instruction.
+The primitive types are the fundamental building blocks of the LLVM +system. The current set of primitive types is as follows:
+ +
+
|
+
+
|
+
These different primitive types fall into a few useful +classifications:
+ +| Classification | Types |
|---|---|
| integer | +i1, i8, i16, i32, i64 | +
| floating point | +float, double | +
| first class | +i1, i8, i16, i32, i64, float, double, + pointer,vector + |
+
The first class 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.
+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.
+ +Overview:
+ +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.
+ +Syntax:
+ ++ [<# elements> x <elementtype>] ++ +
The number of elements is a constant integer value; elementtype may +be any type with a size.
+ +Examples:
+|
+ [40 x i32 ] + [41 x i32 ] + [40 x i8] + |
+
+ Array of 40 32-bit integer values. + Array of 41 32-bit integer values. + Array of 40 8-bit integer values. + |
+
Here are some examples of multidimensional arrays:
+|
+ [3 x [4 x i32]] + [12 x [10 x float]] + [2 x [3 x [4 x i16]]] + |
+
+ 3x4 array of 32-bit integer values. + 12x10 array of single precision floating point values. + 2x3x4 array of 16-bit integer values. + |
+
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 "{ i32, [0 x float]}", for example.
+ +Overview:
+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.
++The return type of a function type cannot be an aggregate type. +
+Syntax:
+<returntype> (<parameter list>)+
...where '<parameter list>' is a comma-separated list of type +specifiers. Optionally, the parameter list may include a type ..., +which indicates that the function takes a variable number of arguments. +Variable argument functions can access their arguments with the variable argument handling intrinsic functions.
+Examples:
+| i32 (i32) | +function taking an i32, returning an i32 + | +
| float (i16 sext, i32 *) * + | +Pointer to a function that takes + an i16 that should be sign extended and a + pointer to i32, returning + float. + | +
| i32 (i8*, ...) | +A vararg function that takes at least one + pointer to i8 (char in C), + which returns an integer. This is the signature for printf in + LLVM. + | +
Overview:
+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.
+Structures are accessed using 'load +and 'store' by getting a pointer to a +field with the 'getelementptr' +instruction.
+Syntax:
+ { <type list> }
+Examples:
+|
+ { i32, i32, i32 } + { float, i32 (i32) * } + |
+
+ a triple of three i32 values + A pair, where the first element is a float and the second element + is a pointer to a function + that takes an i32, returning an i32. + |
+
Overview:
+The packed structure type is used to represent a collection of data members +together in memory. There is no padding between fields. Further, the alignment +of a packed structure is 1 byte. The elements of a packed structure may +be any type that has a size.
+Structures are accessed using 'load +and 'store' by getting a pointer to a +field with the 'getelementptr' +instruction.
+Syntax:
+ < { <type list> } >
+Examples:
+|
+ < { i32, i32, i32 } > + < { float, i32 (i32) * } > + |
+
+ a triple of three i32 values + A pair, where the first element is a float and the second element + is a pointer to a function + that takes an i32, returning an i32. + |
+
Overview:
+As in many languages, the pointer type represents a pointer or +reference to another object, which must live in memory.
+Syntax:
+<type> *+
Examples:
+|
+ [4x i32]* + i32 (i32 *) * + |
+
+ A pointer to array of
+ four i32 values + A pointer to a function that takes an i32*, returning an + i32. + |
+
Overview:
+ +A vector type is a simple derived type that represents a vector +of elements. Vector types are used when multiple primitive data +are operated in parallel using a single instruction (SIMD). +A vector 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 ...). Vector types are +considered first class.
+ +Syntax:
+ ++ < <# elements> x <elementtype> > ++ +
The number of elements is a constant integer value; elementtype may +be any integer or floating point type.
+ +Examples:
+ +|
+ <4 x i32> + <8 x float> + <2 x i64> + |
+
+ Vector of 4 32-bit integer values. + Vector of 8 floating-point values. + Vector of 2 64-bit integer values. + |
+
Overview:
+ +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).
+ +Syntax:
+ ++ opaque ++ +
Examples:
+ +| + opaque + | +
+ An opaque type. + |
+
LLVM has several different basic types of constants. This section describes +them all and their syntax.
+ +-
+
- Boolean constants + +
- The two strings 'true' and 'false' are both valid + constants of the i1 type. + + +
- Integer constants + +
- Standard integers (such as '4') are constants of the integer type. Negative numbers may be used with + integer types. + + +
- Floating point constants + +
- 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 floating point type. + +
- Null pointer constants + +
- The identifier 'null' is recognized as a null pointer constant + and must be of pointer type. + +
The one non-intuitive notation for constants is the optional hexadecimal form +of floating point constants. For example, the form 'double +0x432ff973cafa8000' is equivalent to (but harder to read than) 'double +4.5e+15'. 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.
+ +Aggregate constants arise from aggregation of simple constants +and smaller aggregate constants.
+ +-
+
- Structure constants + +
- Structure constants are represented with notation similar to structure + type definitions (a comma separated list of elements, surrounded by braces + ({})). For example: "{ i32 4, float 17.0, i32* %G }", + where "%G" is declared as "%G = external global i32". Structure constants + must have structure type, and the number and + types of elements must match those specified by the type. + + +
- Array constants + +
- Array constants are represented with notation similar to array type + definitions (a comma separated list of elements, surrounded by square brackets + ([])). For example: "[ i32 42, i32 11, i32 74 ]". Array + constants must have array type, and the number and + types of elements must match those specified by the type. + + +
- Vector constants + +
- Vector constants are represented with notation similar to vector type + definitions (a comma separated list of elements, surrounded by + less-than/greater-than's (<>)). For example: "< i32 42, + i32 11, i32 74, i32 100 >". VEctor constants must have vector type, and the number and types of elements must + match those specified by the type. + + +
- Zero initialization + +
- The string 'zeroinitializer' can be used to zero initialize a + value to zero of any 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. + +
The addresses of global variables and functions are always implicitly valid (link-time) +constants. These constants are explicitly referenced when the identifier for the global is used and always have pointer type. For example, the following is a legal LLVM +file:
+ ++ %X = global i32 17 + %Y = global i32 42 + %Z = global [2 x i32*] [ i32* %X, i32* %Y ] ++ +
The string 'undef' 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.
+ +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. +
+Constant expressions are used to allow expressions involving other constants +to be used as constants. Constant expressions may be of any first class 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:
+ +-
+
- trunc ( CST to TYPE ) +
- Truncate a constant to another type. The bit size of CST must be larger + than the bit size of TYPE. Both types must be integers. + +
- zext ( CST to TYPE ) +
- Zero extend a constant to another type. The bit size of CST must be + smaller or equal to the bit size of TYPE. Both types must be integers. + +
- sext ( CST to TYPE ) +
- Sign extend a constant to another type. The bit size of CST must be + smaller or equal to the bit size of TYPE. Both types must be integers. + +
- fptrunc ( CST to TYPE ) +
- Truncate a floating point constant to another floating point type. The + size of CST must be larger than the size of TYPE. Both types must be + floating point. + +
- fpext ( CST to TYPE ) +
- Floating point extend a constant to another type. The size of CST must be + smaller or equal to the size of TYPE. Both types must be floating point. + +
- fp2uint ( CST to TYPE ) +
- Convert a floating point constant to the corresponding unsigned integer + constant. TYPE must be an integer type. CST must be floating point. If the + value won't fit in the integer type, the results are undefined. + +
- fptosi ( CST to TYPE ) +
- Convert a floating point constant to the corresponding signed integer + constant. TYPE must be an integer type. CST must be floating point. If the + value won't fit in the integer type, the results are undefined. + +
- uitofp ( CST to TYPE ) +
- Convert an unsigned integer constant to the corresponding floating point + constant. TYPE must be floating point. CST must be of integer type. If the + value won't fit in the floating point type, the results are undefined. + +
- sitofp ( CST to TYPE ) +
- Convert a signed integer constant to the corresponding floating point + constant. TYPE must be floating point. CST must be of integer type. If the + value won't fit in the floating point type, the results are undefined. + +
- ptrtoint ( CST to TYPE ) +
- Convert a pointer typed constant to the corresponding integer constant + TYPE must be an integer type. CST must be of pointer type. The CST value is + zero extended, truncated, or unchanged to make it fit in TYPE. + +
- inttoptr ( CST to TYPE ) +
- Convert a integer constant to a pointer constant. TYPE must be a + pointer type. CST must be of integer type. The CST value is zero extended, + truncated, or unchanged to make it fit in a pointer size. This one is + really dangerous! + +
- bitcast ( CST to TYPE ) +
- Convert a constant, CST, to another TYPE. The size of CST and TYPE must be + identical (same number of bits). The conversion is done as if the CST value + was stored to memory and read back as TYPE. In other words, no bits change + with this operator, just the type. This can be used for conversion of + vector types to any other type, as long as they have the same bit width. For + pointers it is only valid to cast to another pointer type. + + +
- getelementptr ( CSTPTR, IDX0, IDX1, ... ) + +
- Perform the getelementptr operation on + constants. As with the getelementptr + instruction, the index list may have zero or more indexes, which are required + to make sense for the type of "CSTPTR". + +
- select ( COND, VAL1, VAL2 ) + +
- Perform the select operation on + constants. + +
- icmp COND ( VAL1, VAL2 ) +
- Performs the icmp operation on constants. + +
- fcmp COND ( VAL1, VAL2 ) +
- Performs the fcmp operation on constants. + +
- extractelement ( VAL, IDX ) + +
- Perform the extractelement + operation on constants. + +
- insertelement ( VAL, ELT, IDX ) + +
- Perform the insertelement + operation on constants. + + +
- shufflevector ( VEC1, VEC2, IDXMASK ) + +
- Perform the shufflevector + operation on constants. + +
- OPCODE ( LHS, RHS ) + +
- Perform the specified operation of the LHS and RHS constants. OPCODE may + be any of the binary or bitwise + binary 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). +
+LLVM supports inline assembler expressions (as opposed to +Module-Level Inline Assembly) 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: +
+ ++ i32 (i32) asm "bswap $0", "=r,r" ++ +
+Inline assembler expressions may only be used as the callee operand of +a call instruction. Thus, typically we have: +
+ ++ %X = call i32 asm "bswap $0", "=r,r"(i32 %Y) ++ +
+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 +'sideeffect' keyword, like so: +
+ ++ call void asm sideeffect "eieio", ""() ++ +
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). +
+ +The LLVM instruction set consists of several different +classifications of instructions: terminator +instructions, binary instructions, +bitwise binary instructions, memory instructions, and other +instructions.
+ +As mentioned previously, 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 'void' +value: they produce control flow, not values (the one exception being +the 'invoke' instruction).
+There are six different terminator instructions: the 'ret' instruction, the 'br' +instruction, the 'switch' instruction, +the 'invoke' instruction, the 'unwind' instruction, and the 'unreachable' instruction.
+ +Syntax:
+ret <type> <value> ; Return a value from a non-void function + ret void ; Return from void function ++
Overview:
+The 'ret' instruction is used to return control flow (and a +value) from a function back to the caller.
+There are two forms of the 'ret' instruction: one that +returns a value and then causes control flow, and one that just causes +control flow to occur.
+Arguments:
+The 'ret' instruction may return any 'first class' type. Notice that a function is +not well formed if there exists a 'ret' +instruction inside of the function that returns a value that does not +match the return type of the function.
+Semantics:
+When the 'ret' instruction is executed, control flow +returns back to the calling function's context. If the caller is a "call" instruction, execution continues at +the instruction after the call. If the caller was an "invoke" 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.
+Example:
+ret i32 5 ; Return an integer value of 5 + ret void ; Return from a void function ++
Syntax:
+br i1 <cond>, label <iftrue>, label <iffalse>+
br label <dest> ; Unconditional branch +
Overview:
+The 'br' 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.
+Arguments:
+The conditional branch form of the 'br' instruction takes a +single 'i1' value and two 'label' values. The +unconditional form of the 'br' instruction takes a single +'label' value as a target.
+Semantics:
+Upon execution of a conditional 'br' instruction, the 'i1' +argument is evaluated. If the value is true, control flows +to the 'iftrue' label argument. If "cond" is false, +control flows to the 'iffalse' label argument.
+Example:
+Test:+
%cond = icmp eq, i32 %a, %b
br i1 %cond, label %IfEqual, label %IfUnequal
IfEqual:
ret i32 1
IfUnequal:
ret i32 0
Syntax:
+ ++ switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ] ++ +
Overview:
+ +The 'switch' instruction is used to transfer control flow to one of +several different places. It is a generalization of the 'br' +instruction, allowing a branch to occur to one of many possible +destinations.
+ + +Arguments:
+ +The 'switch' instruction uses three parameters: an integer +comparison value 'value', a default 'label' destination, and +an array of pairs of comparison value constants and 'label's. The +table is not allowed to contain duplicate constant entries.
+ +Semantics:
+ +The switch instruction specifies a table of values and +destinations. When the 'switch' 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.
+ +Implementation:
+ +Depending on properties of the target machine and the particular +switch 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.
+ +Example:
+ ++ ; Emulate a conditional br instruction + %Val = zext i1 %value to i32 + switch i32 %Val, label %truedest [i32 0, label %falsedest ] + + ; Emulate an unconditional br instruction + switch i32 0, label %dest [ ] + + ; Implement a jump table: + switch i32 %val, label %otherwise [ i32 0, label %onzero + i32 1, label %onone + i32 2, label %ontwo ] ++
Syntax:
+ ++ <result> = invoke [cconv] <ptr to function ty> %<function ptr val>(<function args>) + to label <normal label> unwind label <exception label> ++ +
Overview:
+ +The 'invoke' instruction causes control to transfer to a specified +function, with the possibility of control flow transfer to either the +'normal' label or the +'exception' label. If the callee function returns with the +"ret" instruction, control flow will return to the +"normal" label. If the callee (or any indirect callees) returns with the "unwind" instruction, control is interrupted and +continued at the dynamically nearest "exception" label.
+ +Arguments:
+ +This instruction requires several arguments:
+ +-
+
- + The optional "cconv" marker indicates which calling + convention the call should use. If none is specified, the call defaults + to using C calling conventions. + +
- 'ptr to function ty': shall be the signature of the pointer to + function value being invoked. In most cases, this is a direct function + invocation, but indirect invokes are just as possible, branching off + an arbitrary pointer to function value. + + +
- 'function ptr val': An LLVM value containing a pointer to a + function to be invoked. + +
- 'function args': 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. + +
- 'normal label': the label reached when the called function + executes a 'ret' instruction. + +
- 'exception label': the label reached when a callee returns with + the unwind instruction. + +
Semantics:
+ +This instruction is designed to operate as a standard 'call' 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.
+ +This instruction is used in languages with destructors to ensure that proper +cleanup is performed in the case of either a longjmp or a thrown +exception. Additionally, this is important for implementation of +'catch' clauses in high-level languages that support them.
+ +Example:
+
+ %retval = invoke i32 %Test(i32 15) to label %Continue
+ unwind label %TestCleanup ; {i32}:retval set
+ %retval = invoke coldcc i32 %Test(i32 15) to label %Continue
+ unwind label %TestCleanup ; {i32}:retval set
+
+Syntax:
++ unwind ++ +
Overview:
+ +The 'unwind' instruction unwinds the stack, continuing control flow +at the first callee in the dynamic call stack which used an invoke instruction to perform the call. This is +primarily used to implement exception handling.
+ +Semantics:
+ +The 'unwind' intrinsic causes execution of the current function to +immediately halt. The dynamic call stack is then searched for the first invoke instruction on the call stack. Once found, +execution continues at the "exceptional" destination block specified by the +invoke instruction. If there is no invoke instruction in the +dynamic call chain, undefined behavior results.
+Syntax:
++ unreachable ++ +
Overview:
+ +The 'unreachable' 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.
+ +Semantics:
+ +The 'unreachable' instruction has no defined semantics.
+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 vector data type. +The result value of a binary operator is not +necessarily the same type as its operands.
+There are several different binary operators:
+Syntax:
+ <result> = add <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'add' instruction returns the sum of its two operands.
+Arguments:
+The two arguments to the 'add' instruction must be either integer or floating point values. + This instruction can also take vector versions of the values. +Both arguments must have identical types.
+Semantics:
+The value produced is the integer or floating point sum of the two +operands.
+Example:
+ <result> = add i32 4, %var ; yields {i32}:result = 4 + %var
+
+Syntax:
+ <result> = sub <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'sub' instruction returns the difference of its two +operands.
+Note that the 'sub' instruction is used to represent the 'neg' +instruction present in most other intermediate representations.
+Arguments:
+The two arguments to the 'sub' instruction must be either integer or floating point +values. +This instruction can also take vector versions of the values. +Both arguments must have identical types.
+Semantics:
+The value produced is the integer or floating point difference of +the two operands.
+Example:
+ <result> = sub i32 4, %var ; yields {i32}:result = 4 - %var
+ <result> = sub i32 0, %val ; yields {i32}:result = -%var
+
+Syntax:
+ <result> = mul <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'mul' instruction returns the product of its two +operands.
+Arguments:
+The two arguments to the 'mul' instruction must be either integer or floating point +values. +This instruction can also take vector versions of the values. +Both arguments must have identical types.
+Semantics:
+The value produced is the integer or floating point product of the +two operands.
+Because the operands are the same width, the result of an integer +multiplication is the same whether the operands should be deemed unsigned or +signed.
+Example:
+ <result> = mul i32 4, %var ; yields {i32}:result = 4 * %var
+
+Syntax:
+ <result> = udiv <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'udiv' instruction returns the quotient of its two +operands.
+Arguments:
+The two arguments to the 'udiv' instruction must be +integer values. Both arguments must have identical +types. This instruction can also take vector versions +of the values in which case the elements must be integers.
+Semantics:
+The value produced is the unsigned integer quotient of the two operands. This +instruction always performs an unsigned division operation, regardless of +whether the arguments are unsigned or not.
+Example:
+ <result> = udiv i32 4, %var ; yields {i32}:result = 4 / %var
+
+Syntax:
+ <result> = sdiv <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'sdiv' instruction returns the quotient of its two +operands.
+Arguments:
+The two arguments to the 'sdiv' instruction must be +integer values. Both arguments must have identical +types. This instruction can also take vector versions +of the values in which case the elements must be integers.
+Semantics:
+The value produced is the signed integer quotient of the two operands. This +instruction always performs a signed division operation, regardless of whether +the arguments are signed or not.
+Example:
+ <result> = sdiv i32 4, %var ; yields {i32}:result = 4 / %var
+
+Syntax:
+ <result> = fdiv <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'fdiv' instruction returns the quotient of its two +operands.
+Arguments:
+The two arguments to the 'div' instruction must be +floating point values. Both arguments must have +identical types. This instruction can also take vector +versions of the values in which case the elements must be floating point.
+Semantics:
+The value produced is the floating point quotient of the two operands.
+Example:
+ <result> = fdiv float 4.0, %var ; yields {float}:result = 4.0 / %var
+
+Syntax:
+ <result> = urem <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'urem' instruction returns the remainder from the +unsigned division of its two arguments.
+Arguments:
+The two arguments to the 'urem' instruction must be +integer values. Both arguments must have identical +types.
+Semantics:
+This instruction returns the unsigned integer remainder of a division. +This instruction always performs an unsigned division to get the remainder, +regardless of whether the arguments are unsigned or not.
+Example:
+ <result> = urem i32 4, %var ; yields {i32}:result = 4 % %var
+
+
+Syntax:
+ <result> = srem <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'srem' instruction returns the remainder from the +signed division of its two operands.
+Arguments:
+The two arguments to the 'srem' instruction must be +integer values. Both arguments must have identical +types.
+Semantics:
+This instruction returns the remainder of a division (where the result +has the same sign as the dividend, var1), not the modulo +operator (where the result has the same sign as the divisor, var2) of +a value. For more information about the difference, see The +Math Forum. For a table of how this is implemented in various languages, +please see +Wikipedia: modulo operation.
+Example:
+ <result> = srem i32 4, %var ; yields {i32}:result = 4 % %var
+
+
+Syntax:
+ <result> = frem <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'frem' instruction returns the remainder from the +division of its two operands.
+Arguments:
+The two arguments to the 'frem' instruction must be +floating point values. Both arguments must have +identical types.
+Semantics:
+This instruction returns the remainder of a division.
+Example:
+ <result> = frem float 4.0, %var ; yields {float}:result = 4.0 % %var
+
+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.
+Syntax:
+ <result> = shl <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'shl' instruction returns the first operand shifted to +the left a specified number of bits.
+Arguments:
+Both arguments to the 'shl' instruction must be the same integer type.
+Semantics:
+The value produced is var1 * 2var2.
+Example:
+ <result> = shl i32 4, %var ; yields {i32}: 4 << %var
+ <result> = shl i32 4, 2 ; yields {i32}: 16
+ <result> = shl i32 1, 10 ; yields {i32}: 1024
+
+Syntax:
+ <result> = lshr <ty> <var1>, <var2> ; yields {ty}:result
+
+
+Overview:
+The 'lshr' instruction (logical shift right) returns the first +operand shifted to the right a specified number of bits.
+ +Arguments:
+Both arguments to the 'lshr' instruction must be the same +integer type.
+ +Semantics:
+This instruction always performs a logical shift right operation. The most +significant bits of the result will be filled with zero bits after the +shift.
+ +Example:
+
+ <result> = lshr i32 4, 1 ; yields {i32}:result = 2
+ <result> = lshr i32 4, 2 ; yields {i32}:result = 1
+ <result> = lshr i8 4, 3 ; yields {i8}:result = 0
+ <result> = lshr i8 -2, 1 ; yields {i8}:result = 0x7FFFFFFF
+
+Syntax:
+ <result> = ashr <ty> <var1>, <var2> ; yields {ty}:result
+
+
+Overview:
+The 'ashr' instruction (arithmetic shift right) returns the first +operand shifted to the right a specified number of bits.
+ +Arguments:
+Both arguments to the 'ashr' instruction must be the same +integer type.
+ +Semantics:
+This instruction always performs an arithmetic shift right operation, +The most significant bits of the result will be filled with the sign bit +of var1.
+ +Example:
+
+ <result> = ashr i32 4, 1 ; yields {i32}:result = 2
+ <result> = ashr i32 4, 2 ; yields {i32}:result = 1
+ <result> = ashr i8 4, 3 ; yields {i8}:result = 0
+ <result> = ashr i8 -2, 1 ; yields {i8}:result = -1
+
+Syntax:
+ <result> = and <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'and' instruction returns the bitwise logical and of +its two operands.
+Arguments:
+The two arguments to the 'and' instruction must be integer values. Both arguments must have +identical types.
+Semantics:
+The truth table used for the 'and' instruction is:
++
| In0 | +In1 | +Out | +
| 0 | +0 | +0 | +
| 0 | +1 | +0 | +
| 1 | +0 | +0 | +
| 1 | +1 | +1 | +
Example:
+ <result> = and i32 4, %var ; yields {i32}:result = 4 & %var
+ <result> = and i32 15, 40 ; yields {i32}:result = 8
+ <result> = and i32 4, 8 ; yields {i32}:result = 0
+
+Syntax:
+ <result> = or <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'or' instruction returns the bitwise logical inclusive +or of its two operands.
+Arguments:
+The two arguments to the 'or' instruction must be integer values. Both arguments must have +identical types.
+Semantics:
+The truth table used for the 'or' instruction is:
++
| In0 | +In1 | +Out | +
| 0 | +0 | +0 | +
| 0 | +1 | +1 | +
| 1 | +0 | +1 | +
| 1 | +1 | +1 | +
Example:
+ <result> = or i32 4, %var ; yields {i32}:result = 4 | %var
+ <result> = or i32 15, 40 ; yields {i32}:result = 47
+ <result> = or i32 4, 8 ; yields {i32}:result = 12
+
+Syntax:
+ <result> = xor <ty> <var1>, <var2> ; yields {ty}:result
+
+Overview:
+The 'xor' instruction returns the bitwise logical exclusive +or of its two operands. The xor is used to implement the +"one's complement" operation, which is the "~" operator in C.
+Arguments:
+The two arguments to the 'xor' instruction must be integer values. Both arguments must have +identical types.
+Semantics:
+The truth table used for the 'xor' instruction is:
++
| In0 | +In1 | +Out | +
| 0 | +0 | +0 | +
| 0 | +1 | +1 | +
| 1 | +0 | +1 | +
| 1 | +1 | +0 | +
+
Example:
+ <result> = xor i32 4, %var ; yields {i32}:result = 4 ^ %var
+ <result> = xor i32 15, 40 ; yields {i32}:result = 39
+ <result> = xor i32 4, 8 ; yields {i32}:result = 12
+ <result> = xor i32 %V, -1 ; yields {i32}:result = ~%V
+
+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.
+ +Syntax:
+ ++ <result> = extractelement <n x <ty>> <val>, i32 <idx> ; yields <ty> ++ +
Overview:
+ ++The 'extractelement' instruction extracts a single scalar +element from a vector at a specified index. +
+ + +Arguments:
+ ++The first operand of an 'extractelement' instruction is a +value of vector type. The second operand is +an index indicating the position from which to extract the element. +The index may be a variable.
+ +Semantics:
+ ++The result is a scalar of the same type as the element type of +val. Its value is the value at position idx of +val. If idx exceeds the length of val, the +results are undefined. +
+ +Example:
+ ++ %result = extractelement <4 x i32> %vec, i32 0 ; yields i32 ++
Syntax:
+ ++ <result> = insertelement <n x <ty>> <val>, <ty> <elt>, i32 <idx> ; yields <n x <ty>> ++ +
Overview:
+ ++The 'insertelement' instruction inserts a scalar +element into a vector at a specified index. +
+ + +Arguments:
+ ++The first operand of an 'insertelement' instruction is a +value of vector 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.
+ +Semantics:
+ ++The result is a vector of the same type as val. Its +element values are those of val except at position +idx, where it gets the value elt. If idx +exceeds the length of val, the results are undefined. +
+ +Example:
+ ++ %result = insertelement <4 x i32> %vec, i32 1, i32 0 ; yields <4 x i32> ++
Syntax:
+ ++ <result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <n x i32> <mask> ; yields <n x <ty>> ++ +
Overview:
+ ++The 'shufflevector' instruction constructs a permutation of elements +from two input vectors, returning a vector of the same type. +
+ +Arguments:
+ ++The first two operands of a 'shufflevector' 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 'i32'. +
+ ++The shuffle mask operand is required to be a constant vector with either +constant integer or undef values. +
+ +Semantics:
+ ++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. +
+ +Example:
+ ++ %result = shufflevector <4 x i32> %v1, <4 x i32> %v2, + <4 x i32> <i32 0, i32 4, i32 1, i32 5> ; yields <4 x i32> + %result = shufflevector <4 x i32> %v1, <4 x i32> undef, + <4 x i32> <i32 0, i32 1, i32 2, i32 3> ; yields <4 x i32> - Identity shuffle. ++
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.
+ +Syntax:
+ +
+ <result> = malloc <type>[, i32 <NumElements>][, align <alignment>] ; yields {type*}:result
+
+
+Overview:
+ +The 'malloc' instruction allocates memory from the system +heap and returns a pointer to it.
+ +Arguments:
+ +The 'malloc' instruction allocates +sizeof(<type>)*NumElements +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.
+ +'type' must be a sized type.
+ +Semantics:
+ +Memory is allocated using the system "malloc" function, and +a pointer is returned.
+ +Example:
+ +
+ %array = malloc [4 x i8 ] ; yields {[%4 x i8]*}:array
+
+ %size = add i32 2, 2 ; yields {i32}:size = i32 4
+ %array1 = malloc i8, i32 4 ; yields {i8*}:array1
+ %array2 = malloc [12 x i8], i32 %size ; yields {[12 x i8]*}:array2
+ %array3 = malloc i32, i32 4, align 1024 ; yields {i32*}:array3
+ %array4 = malloc i32, align 1024 ; yields {i32*}:array4
+
+Syntax:
+ +
+ free <type> <value> ; yields {void}
+
+
+Overview:
+ +The 'free' instruction returns memory back to the unused +memory heap to be reallocated in the future.
+ +Arguments:
+ +'value' shall be a pointer value that points to a value +that was allocated with the 'malloc' +instruction.
+ +Semantics:
+ +Access to the memory pointed to by the pointer is no longer defined +after this instruction executes.
+ +Example:
+ ++ %array = malloc [4 x i8] ; yields {[4 x i8]*}:array + free [4 x i8]* %array ++
Syntax:
+ +
+ <result> = alloca <type>[, i32 <NumElements>][, align <alignment>] ; yields {type*}:result
+
+
+Overview:
+ +The 'alloca' instruction allocates memory on the current +stack frame of the procedure that is live until the current function +returns to its caller.
+ +Arguments:
+ +The 'alloca' instruction allocates sizeof(<type>)*NumElements +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.
+ +'type' may be any sized type.
+ +Semantics:
+ +Memory is allocated; a pointer is returned. 'alloca'd +memory is automatically released when the function returns. The 'alloca' +instruction is commonly used to represent automatic variables that must +have an address available. When the function returns (either with the ret or unwind +instructions), the memory is reclaimed.
+ +Example:
+ +
+ %ptr = alloca i32 ; yields {i32*}:ptr
+ %ptr = alloca i32, i32 4 ; yields {i32*}:ptr
+ %ptr = alloca i32, i32 4, align 1024 ; yields {i32*}:ptr
+ %ptr = alloca i32, align 1024 ; yields {i32*}:ptr
+
+Syntax:
+<result> = load <ty>* <pointer>+
<result> = volatile load <ty>* <pointer>
Overview:
+The 'load' instruction is used to read from memory.
+Arguments:
+The argument to the 'load' instruction specifies the memory +address from which to load. The pointer must point to a first class type. If the load is +marked as volatile, then the optimizer is not allowed to modify +the number or order of execution of this load with other +volatile load and store +instructions.
+Semantics:
+The location of memory pointed to is loaded.
+Examples:
+%ptr = alloca i32 ; yields {i32*}:ptr + store i32 3, i32* %ptr ; yields {void} + %val = load i32* %ptr ; yields {i32}:val = i32 3 ++
Syntax:
+ store <ty> <value>, <ty>* <pointer> ; yields {void}
+ volatile store <ty> <value>, <ty>* <pointer> ; yields {void}
+
+Overview:
+The 'store' instruction is used to write to memory.
+Arguments:
+There are two arguments to the 'store' instruction: a value +to store and an address in which to store it. The type of the '<pointer>' +operand must be a pointer to the type of the '<value>' +operand. If the store is marked as volatile, then the +optimizer is not allowed to modify the number or order of execution of +this store with other volatile load and store instructions.
+Semantics:
+The contents of memory are updated to contain '<value>' +at the location specified by the '<pointer>' operand.
+Example:
+%ptr = alloca i32 ; yields {i32*}:ptr + store i32 3, i32* %ptr ; yields {void} + %val = load i32* %ptr ; yields {i32}:val = i32 3 ++
Syntax:
+
+ <result> = getelementptr <ty>* <ptrval>{, <ty> <idx>}*
+
+
+Overview:
+ ++The 'getelementptr' instruction is used to get the address of a +subelement of an aggregate data structure.
+ +Arguments:
+ +This instruction takes a list of integer operands 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 +'getelementptr' 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 i32 integer constants are allowed. When indexing +into an array or pointer, only integers of 32 or 64 bits are allowed, and will +be sign extended to 64-bit values.
+ +For example, let's consider a C code fragment and how it gets +compiled to LLVM:
+ +
+ struct RT {
+ char A;
+ i32 B[10][20];
+ char C;
+ };
+ struct ST {
+ i32 X;
+ double Y;
+ struct RT Z;
+ };
+
+ define i32 *foo(struct ST *s) {
+ return &s[1].Z.B[5][13];
+ }
+
+
+The LLVM code generated by the GCC frontend is:
+ +
+ %RT = type { i8 , [10 x [20 x i32]], i8 }
+ %ST = type { i32, double, %RT }
+
+ implementation
+
+ define i32* %foo(%ST* %s) {
+ entry:
+ %reg = getelementptr %ST* %s, i32 1, i32 2, i32 1, i32 5, i32 13
+ ret i32* %reg
+ }
+
+
+Semantics:
+ +The index types specified for the 'getelementptr' instruction depend +on the pointer type that is being indexed into. Pointer +and array types can use a 32-bit or 64-bit +integer type but the value will always be sign extended +to 64-bits. Structure types, require i32 +constants.
+ +In the example above, the first index is indexing into the '%ST*' +type, which is a pointer, yielding a '%ST' = '{ i32, double, %RT +}' type, a structure. The second index indexes into the third element of +the structure, yielding a '%RT' = '{ i8 , [10 x [20 x i32]], +i8 }' type, another structure. The third index indexes into the second +element of the structure, yielding a '[10 x [20 x i32]]' type, an +array. The two dimensions of the array are subscripted into, yielding an +'i32' type. The 'getelementptr' instruction returns a pointer +to this element, thus computing a value of 'i32*' type.
+ +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:
+ +
+ define i32* %foo(%ST* %s) {
+ %t1 = getelementptr %ST* %s, i32 1 ; yields %ST*:%t1
+ %t2 = getelementptr %ST* %t1, i32 0, i32 2 ; yields %RT*:%t2
+ %t3 = getelementptr %RT* %t2, i32 0, i32 1 ; yields [10 x [20 x i32]]*:%t3
+ %t4 = getelementptr [10 x [20 x i32]]* %t3, i32 0, i32 5 ; yields [20 x i32]*:%t4
+ %t5 = getelementptr [20 x i32]* %t4, i32 0, i32 13 ; yields i32*:%t5
+ ret i32* %t5
+ }
+
+
+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.
+ +The getelementptr instruction is often confusing. For some more insight +into how it works, see the getelementptr +FAQ.
+ +Example:
+ +
+ ; yields [12 x i8]*:aptr
+ %aptr = getelementptr {i32, [12 x i8]}* %sptr, i64 0, i32 1
+
+The instructions in this category are the conversion instructions (casting) +which all take a single operand and a type. They perform various bit conversions +on the operand.
+Syntax:
++ <result> = trunc <ty> <value> to <ty2> ; yields ty2 ++ +
Overview:
++The 'trunc' instruction truncates its operand to the type ty2. +
+ +Arguments:
++The 'trunc' instruction takes a value to trunc, which must +be an integer type, and a type that specifies the size +and type of the result, which must be an integer +type. The bit size of value must be larger than the bit size of +ty2. Equal sized types are not allowed.
+ +Semantics:
++The 'trunc' instruction truncates the high order bits in value +and converts the remaining bits to ty2. Since the source size must be +larger than the destination size, trunc cannot be a no-op cast. +It will always truncate bits.
+ +Example:
++ %X = trunc i32 257 to i8 ; yields i8:1 + %Y = trunc i32 123 to i1 ; yields i1:true + %Y = trunc i32 122 to i1 ; yields i1:false ++
Syntax:
++ <result> = zext <ty> <value> to <ty2> ; yields ty2 ++ +
Overview:
+The 'zext' instruction zero extends its operand to type +ty2.
+ + +Arguments:
+The 'zext' instruction takes a value to cast, which must be of +integer type, and a type to cast it to, which must +also be of integer type. The bit size of the +value must be smaller than the bit size of the destination type, +ty2.
+ +Semantics:
+The zext fills the high order bits of the value with zero +bits until it reaches the size of the destination type, ty2. When the +the operand and the type are the same size, no bit filling is done and the +cast is considered a no-op cast because no bits change (only the type +changes).
+ +When zero extending from i1, the result will always be either 0 or 1.
+ +Example:
++ %X = zext i32 257 to i64 ; yields i64:257 + %Y = zext i1 true to i32 ; yields i32:1 ++
Syntax:
++ <result> = sext <ty> <value> to <ty2> ; yields ty2 ++ +
Overview:
+The 'sext' sign extends value to the type ty2.
+ +Arguments:
++The 'sext' instruction takes a value to cast, which must be of +integer type, and a type to cast it to, which must +also be of integer type. The bit size of the +value must be smaller than the bit size of the destination type, +ty2.
+ +Semantics:
++The 'sext' instruction performs a sign extension by copying the sign +bit (highest order bit) of the value until it reaches the bit size of +the type ty2. When the the operand and the type are the same size, +no bit filling is done and the cast is considered a no-op cast because +no bits change (only the type changes).
+ +When sign extending from i1, the extension always results in -1 or 0.
+ +Example:
++ %X = sext i8 -1 to i16 ; yields i16 :65535 + %Y = sext i1 true to i32 ; yields i32:-1 ++
Syntax:
+ ++ <result> = fptrunc <ty> <value> to <ty2> ; yields ty2 ++ +
Overview:
+The 'fptrunc' instruction truncates value to type +ty2.
+ + +Arguments:
+The 'fptrunc' instruction takes a floating + point value to cast and a floating point type to +cast it to. The size of value must be larger than the size of +ty2. This implies that fptrunc cannot be used to make a +no-op cast.
+ +Semantics:
+The 'fptrunc' instruction truncates a value from a larger +floating point type to a smaller +floating point type. If the value cannot fit within +the destination type, ty2, then the results are undefined.
+ +Example:
++ %X = fptrunc double 123.0 to float ; yields float:123.0 + %Y = fptrunc double 1.0E+300 to float ; yields undefined ++
Syntax:
++ <result> = fpext <ty> <value> to <ty2> ; yields ty2 ++ +
Overview:
+The 'fpext' extends a floating point value to a larger +floating point value.
+ +Arguments:
+The 'fpext' instruction takes a +floating point value to cast, +and a floating point type to cast it to. The source +type must be smaller than the destination type.
+ +Semantics:
+The 'fpext' instruction extends the value from a smaller +floating point type to a larger +floating point type. The fpext cannot be +used to make a no-op cast because it always changes bits. Use +bitcast to make a no-op cast for a floating point cast.
+ +Example:
++ %X = fpext float 3.1415 to double ; yields double:3.1415 + %Y = fpext float 1.0 to float ; yields float:1.0 (no-op) ++
Syntax:
++ <result> = fp2uint <ty> <value> to <ty2> ; yields ty2 ++ +
Overview:
+The 'fp2uint' converts a floating point value to its +unsigned integer equivalent of type ty2. +
+ +Arguments:
+The 'fp2uint' instruction takes a value to cast, which must be a +floating point value, and a type to cast it to, which +must be an integer type.
+ +Semantics:
+The 'fp2uint' instruction converts its +floating point operand into the nearest (rounding +towards zero) unsigned integer value. If the value cannot fit in ty2, +the results are undefined.
+ +When converting to i1, the conversion is done as a comparison against +zero. If the value was zero, the i1 result will be false. +If the value was non-zero, the i1 result will be true.
+ +Example:
++ %X = fp2uint double 123.0 to i32 ; yields i32:123 + %Y = fp2uint float 1.0E+300 to i1 ; yields i1:true + %X = fp2uint float 1.04E+17 to i8 ; yields undefined:1 ++
Syntax:
++ <result> = fptosi <ty> <value> to <ty2> ; yields ty2 ++ +
Overview:
+The 'fptosi' instruction converts +floating point value to type ty2. +
+ + +Arguments:
+The 'fptosi' instruction takes a value to cast, which must be a +floating point value, and a type to cast it to, which +must also be an integer type.
+ +Semantics:
+The 'fptosi' instruction converts its +floating point operand into the nearest (rounding +towards zero) signed integer value. If the value cannot fit in ty2, +the results are undefined.
+ +When converting to i1, the conversion is done as a comparison against +zero. If the value was zero, the i1 result will be false. +If the value was non-zero, the i1 result will be true.
+ +Example:
++ %X = fptosi double -123.0 to i32 ; yields i32:-123 + %Y = fptosi float 1.0E-247 to i1 ; yields i1:true + %X = fptosi float 1.04E+17 to i8 ; yields undefined:1 ++
Syntax:
++ <result> = uitofp <ty> <value> to <ty2> ; yields ty2 ++ +
Overview:
+The 'uitofp' instruction regards value as an unsigned +integer and converts that value to the ty2 type.
+ + +Arguments:
+The 'uitofp' instruction takes a value to cast, which must be an +integer value, and a type to cast it to, which must +be a floating point type.
+ +Semantics:
+The 'uitofp' instruction interprets its operand as an unsigned +integer quantity and converts it to the corresponding floating point value. If +the value cannot fit in the floating point value, the results are undefined.
+ + +Example:
++ %X = uitofp i32 257 to float ; yields float:257.0 + %Y = uitofp i8 -1 to double ; yields double:255.0 ++
Syntax:
++ <result> = sitofp <ty> <value> to <ty2> ; yields ty2 ++ +
Overview:
+The 'sitofp' instruction regards value as a signed +integer and converts that value to the ty2 type.
+ +Arguments:
+The 'sitofp' instruction takes a value to cast, which must be an +integer value, and a type to cast it to, which must be +a floating point type.
+ +Semantics:
+The 'sitofp' instruction interprets its operand as a signed +integer quantity and converts it to the corresponding floating point value. If +the value cannot fit in the floating point value, the results are undefined.
+ +Example:
++ %X = sitofp i32 257 to float ; yields float:257.0 + %Y = sitofp i8 -1 to double ; yields double:-1.0 ++
Syntax:
-ret <type> <value> ; Return a value from a non-void function - ret void ; Return from void function ++ <result> = ptrtoint <ty> <value> to <ty2> ; yields ty2+Overview:
-The 'ret' instruction is used to return control flow (and a -value) from a function, back to the caller.
-There are two forms of the 'ret' instructruction: one that -returns a value and then causes control flow, and one that just causes -control flow to occur.
+The 'ptrtoint' instruction converts the pointer value to +the integer type ty2.
+Arguments:
-The 'ret' instruction may return any 'first class' type. Notice that a function is -not well formed if there exists a 'ret' -instruction inside of the function that returns a value that does not -match the return type of the function.
+The 'ptrtoint' instruction takes a value to cast, which +must be a pointer value, and a type to cast it to +ty2, which must be an integer type. +
Semantics:
-When the 'ret' instruction is executed, control flow -returns back to the calling function's context. If the caller is a "call instruction, execution continues at -the instruction after the call. If the caller was an "invoke" instruction, execution continues -at the beginning "normal" of the destination block. If the instruction -returns a value, that value shall set the call or invoke instruction's -return value.
+The 'ptrtoint' instruction converts value to integer type +ty2 by interpreting the pointer value as an integer and either +truncating or zero extending that value to the size of the integer type. If +value is smaller than ty2 then a zero extension is done. If +value is larger than ty2 then a truncation is done. If they +are the same size, then nothing is done (no-op cast).
+Example:
-ret int 5 ; Return an integer value of 5 - ret void ; Return from a void function ++ %X = ptrtoint i32* %X to i8 ; yields truncation on 32-bit + %Y = ptrtoint i32* %x to i64 ; yields zero extend on 32-bit
Syntax:
-br bool <cond>, label <iftrue>, label <iffalse>
br label <dest> ; Unconditional branch ++ <result> = inttoptr <ty> <value> to <ty2> ; yields ty2+Overview:
-The 'br' 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.
+The 'inttoptr' instruction converts an integer value to +a pointer type, ty2.
+Arguments:
-The conditional branch form of the 'br' instruction takes a -single 'bool' value and two 'label' values. The -unconditional form of the 'br' instruction takes a single 'label' -value as a target.
+The 'inttoptr' instruction takes an integer +value to cast, and a type to cast it to, which must be a +pointer type. +
Semantics:
-Upon execution of a conditional 'br' instruction, the 'bool' -argument is evaluated. If the value is true, control flows -to the 'iftrue' label argument. If "cond" is false, -control flows to the 'iffalse' label argument.
+The 'inttoptr' instruction converts value to type +ty2 by applying either a zero extension or a truncation depending on +the size of the integer value. If value is larger than the +size of a pointer then a truncation is done. If value is smaller than +the size of a pointer then a zero extension is done. If they are the same size, +nothing is done (no-op cast).
+Example:
-Test:+
%cond = seteq int %a, %b
br bool %cond, label %IfEqual, label %IfUnequal
IfEqual:
ret int 1
IfUnequal:
ret int 0+ %X = inttoptr i32 255 to i32* ; yields zero extend on 64-bit + %X = inttoptr i32 255 to i32* ; yields no-op on 32-bit + %Y = inttoptr i16 0 to i32* ; yields zero extend on 32-bit +
Syntax:
-switch uint <value>, label <defaultdest> [ int <val>, label &dest>, ... ]+
+ <result> = bitcast <ty> <value> to <ty2> ; yields ty2 ++
Overview:
-The 'switch' instruction is used to transfer control flow -to one of several different places. It is a generalization of the 'br' -instruction, allowing a branch to occur to one of many possible -destinations.
+The 'bitcast' instruction converts value to type +ty2 without changing any bits.
+Arguments:
-The 'switch' instruction uses three parameters: a 'uint' -comparison value 'value', a default 'label' -destination, and an array of pairs of comparison value constants and 'label's.
+The 'bitcast' 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 first class type. The bit sizes of value +and the destination type, ty2, must be identical. If the source +type is a pointer, the destination type must also be a pointer.
+Semantics:
-The switch instruction specifies a table of values and -destinations. When the 'switch' instruction is executed, this -table is searched for the given value. If the value is found, the -corresponding destination is branched to, otherwise the default value -it transfered to.
-Implementation:
-Depending on properties of the target machine and the particular switch -instruction, this instruction may be code generated as a series of -chained conditional branches, or with a lookup table.
-Example:
-; Emulate a conditional br instruction - %Val = cast bool %value to uint
switch uint %Val, label %truedest [int 0, label %falsedest ]
; Emulate an unconditional br instruction - switch uint 0, label %dest [ ] +The 'bitcast' instruction converts value to type +ty2. It is always a no-op cast because no bits change with +this conversion. The conversion is done as if the value had been +stored to memory and read back as type ty2. Pointer types may only be +converted to other pointer types with this instruction. To convert pointers to +other types, use the inttoptr or +ptrtoint instructions first.
- ; Implement a jump table: - switch uint %val, label %otherwise [ int 0, label %onzero, - int 1, label %onone, - int 2, label %ontwo ] +Example:
++ %X = bitcast i8 255 to i8 ; yields i8 :-1 + %Y = bitcast i32* %x to sint* ; yields sint*:%x + %Z = bitcast <2xint> %V to i64; ; yields i64: %V
The instructions in this category are the "miscellaneous" +instructions, which defy better classification.
+Syntax:
-<result> = invoke <ptr to function ty> %<function ptr val>(<function args>)+
to label <normal label> except label <exception label>
<result> = icmp <cond> <ty> <var1>, <var2>
+; yields {i1}:result
+
Overview:
-The 'invoke' instruction causes control to transfer to a -specified function, with the possibility of control flow transfer to -either the 'normal' label label or the 'exception'label. -If the callee function returns with the "ret" -instruction, control flow will return to the "normal" label. If the -callee (or any indirect callees) returns with the "unwind" -instruction, control is interrupted, and continued at the dynamically -nearest "except" label.
+The 'icmp' instruction returns a boolean value based on comparison +of its two integer operands.
Arguments:
-This instruction requires several arguments:
+The 'icmp' instruction takes three operands. The first operand is +the condition code which indicates the kind of comparison to perform. It is not +a value, just a keyword. The possibilities for the condition code are:
-
-
- 'ptr to function ty': shall be the signature of the -pointer to function value being invoked. In most cases, this is a -direct function invocation, but indirect invokes are just as -possible, branching off an arbitrary pointer to function value. -
- 'function ptr val': An LLVM value containing a pointer -to a function to be invoked. -
- 'function args': 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. -
- 'normal label': the label reached when the called -function executes a 'ret' instruction. -
- 'exception label': the label reached when a callee -returns with the unwind instruction. +
- eq: equal +
- ne: not equal +
- ugt: unsigned greater than +
- uge: unsigned greater or equal +
- ult: unsigned less than +
- ule: unsigned less or equal +
- sgt: signed greater than +
- sge: signed greater or equal +
- slt: signed less than +
- sle: signed less or equal
The remaining two arguments must be integer or +pointer typed. They must also be identical types.
Semantics:
-This instruction is designed to operate as a standard 'call' 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.
-This instruction is used in languages with destructors to ensure -that proper cleanup is performed in the case of either a longjmp -or a thrown exception. Additionally, this is important for -implementation of 'catch' clauses in high-level languages that -support them.
+The 'icmp' compares var1 and var2 according to +the condition code given as cond. The comparison performed always +yields a i1 result, as follows: +
-
+
- eq: yields true if the operands are equal, + false otherwise. No sign interpretation is necessary or performed. + +
- ne: yields true if the operands are unequal, + false otherwise. No sign interpretation is necessary or performed. +
- ugt: interprets the operands as unsigned values and yields + true if var1 is greater than var2. +
- uge: interprets the operands as unsigned values and yields + true if var1 is greater than or equal to var2. +
- ult: interprets the operands as unsigned values and yields + true if var1 is less than var2. +
- ule: interprets the operands as unsigned values and yields + true if var1 is less than or equal to var2. +
- sgt: interprets the operands as signed values and yields + true if var1 is greater than var2. +
- sge: interprets the operands as signed values and yields + true if var1 is greater than or equal to var2. +
- slt: interprets the operands as signed values and yields + true if var1 is less than var2. +
- sle: interprets the operands as signed values and yields + true if var1 is less than or equal to var2. +
If the operands are pointer typed, the pointer +values are treated as integers and then compared.
+Example:
-%retval = invoke int %Test(int 15)
to label %Continue
except label %TestCleanup ; {int}:retval set +<result> = icmp eq i32 4, 5 ; yields: result=false + <result> = icmp ne float* %X, %X ; yields: result=false + <result> = icmp ult i16 4, 5 ; yields: result=true + <result> = icmp sgt i16 4, 5 ; yields: result=false + <result> = icmp ule i16 -4, 5 ; yields: result=false + <result> = icmp sge i16 4, 5 ; yields: result=false
Syntax:
-unwind+
<result> = fcmp <cond> <ty> <var1>, <var2>
+; yields {i1}:result
+
Overview:
-The 'unwind' instruction unwinds the stack, continuing -control flow at the first callee in the dynamic call stack which used -an invoke instruction to perform the -call. This is primarily used to implement exception handling.
+The 'fcmp' instruction returns a boolean value based on comparison +of its floating point operands.
+Arguments:
+The 'fcmp' instruction takes three operands. The first operand is +the condition code which indicates the kind of comparison to perform. It is not +a value, just a keyword. The possibilities for the condition code are: +
-
+
- false: no comparison, always returns false +
- oeq: ordered and equal +
- ogt: ordered and greater than +
- oge: ordered and greater than or equal +
- olt: ordered and less than +
- ole: ordered and less than or equal +
- one: ordered and not equal +
- ord: ordered (no nans) +
- ueq: unordered or equal +
- ugt: unordered or greater than +
- uge: unordered or greater than or equal +
- ult: unordered or less than +
- ule: unordered or less than or equal +
- une: unordered or not equal +
- uno: unordered (either nans) +
- true: no comparison, always returns true +
In the preceding, ordered means that neither operand is a QNAN while +unordered means that either operand may be a QNAN.
+The val1 and val2 arguments must be +floating point typed. They must have identical +types.
+In the foregoing, ordered means that neither operand is a QNAN and +unordered means that either operand is a QNAN.
Semantics:
-The 'unwind' intrinsic causes execution of the current -function to immediately halt. The dynamic call stack is then searched -for the first invoke instruction on -the call stack. Once found, execution continues at the "exceptional" -destination block specified by the invoke instruction. If -there is no invoke instruction in the dynamic call chain, -undefined behavior results.
+The 'fcmp' compares var1 and var2 according to +the condition code given as cond. The comparison performed always +yields a i1 result, as follows: +
-
+
- false: always yields false, regardless of operands. +
- oeq: yields true if both operands are not a QNAN and + var1 is equal to var2. +
- ogt: yields true if both operands are not a QNAN and + var1 is greather than var2. +
- oge: yields true if both operands are not a QNAN and + var1 is greater than or equal to var2. +
- olt: yields true if both operands are not a QNAN and + var1 is less than var2. +
- ole: yields true if both operands are not a QNAN and + var1 is less than or equal to var2. +
- one: yields true if both operands are not a QNAN and + var1 is not equal to var2. +
- ord: yields true if both operands are not a QNAN. +
- ueq: yields true if either operand is a QNAN or + var1 is equal to var2. +
- ugt: yields true if either operand is a QNAN or + var1 is greater than var2. +
- uge: yields true if either operand is a QNAN or + var1 is greater than or equal to var2. +
- ult: yields true if either operand is a QNAN or + var1 is less than var2. +
- ule: yields true if either operand is a QNAN or + var1 is less than or equal to var2. +
- une: yields true if either operand is a QNAN or + var1 is not equal to var2. +
- uno: yields true if either operand is a QNAN. +
- true: always yields true, regardless of operands. +
Example:
+<result> = fcmp oeq float 4.0, 5.0 ; yields: result=false + <result> = icmp one float 4.0, 5.0 ; yields: result=true + <result> = icmp olt float 4.0, 5.0 ; yields: result=true + <result> = icmp ueq double 1.0, 2.0 ; yields: result=false +
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 result value of a binary operator is not -necessarily the same type as its operands.
-There are several different binary operators:
+Syntax:
+<result> = phi <ty> [ <val0>, <label0>], ...+
Overview:
+The 'phi' instruction is used to implement the φ node in +the SSA graph representing the function.
+Arguments:
+The type of the incoming values are specified with the first type +field. After this, the 'phi' instruction takes a list of pairs +as arguments, with one pair for each predecessor basic block of the +current block. Only values of first class +type may be used as the value arguments to the PHI node. Only labels +may be used as the label arguments.
+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.
+Semantics:
+At runtime, the 'phi' instruction logically takes on the +value specified by the parameter, depending on which basic block we +came from in the last terminator instruction.
+Example:
+Loop: ; Infinite loop that counts from 0 on up...
%indvar = phi i32 [ 0, %LoopHeader ], [ %nextindvar, %Loop ]
%nextindvar = add i32 %indvar, 1
br label %Loop
Syntax:
- <result> = add <ty> <var1>, <var2> ; yields {ty}:result
+
+
+ <result> = select i1 <cond>, <ty> <val1>, <ty> <val2> ; yields ty
+
Overview:
-The 'add' instruction returns the sum of its two operands.
+
+
+The 'select' instruction is used to choose one value based on a
+condition, without branching.
+
+
+
Arguments:
-The two arguments to the 'add' instruction must be either integer or floating point
-values. Both arguments must have identical types.
+
+
+The 'select' instruction requires a boolean value indicating the condition, and two values of the same first class type.
+
+
Semantics:
-The value produced is the integer or floating point sum of the two
-operands.
+
+
+If the boolean condition evaluates to true, the instruction returns the first
+value argument; otherwise, it returns the second value argument.
+
+
Example:
- <result> = add int 4, %var ; yields {int}:result = 4 + %var
+
+
+ %X = select i1 true, i8 17, i8 42 ; yields i8:17
Syntax:
- <result> = sub <ty> <var1>, <var2> ; yields {ty}:result
+
+ <result> = [tail] call [cconv] <ty>* <fnptrval>(<param list>)
+
Overview:
-The 'sub' instruction returns the difference of its two
-operands.
-Note that the 'sub' instruction is used to represent the 'neg'
-instruction present in most other intermediate representations.
+
+The 'call' instruction represents a simple function call.
+
Arguments:
-The two arguments to the 'sub' instruction must be either integer or floating point
-values. Both arguments must have identical types.
+
+This instruction requires several arguments:
+
+
+ -
+
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 ret instruction.
+
+ -
+
The optional "cconv" marker indicates which calling
+ convention the call should use. If none is specified, the call defaults
+ to using C calling conventions.
+
+ -
+
'ty': 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.
+
+ -
+
'fnptrval': An LLVM value containing a pointer to a function to
+ be invoked. In most cases, this is a direct function invocation, but
+ indirect calls are just as possible, calling an arbitrary pointer
+ to function value.
+
+ -
+
'function args': argument list whose types match the
+ function signature argument types. All arguments must be of
+ first class type. If the function signature
+ indicates the function accepts a variable number of arguments, the extra
+ arguments can be specified.
+
+
+
Semantics:
-The value produced is the integer or floating point difference of
-the two operands.
+
+The 'call' instruction is used to cause control flow to
+transfer to a specified function, with its incoming arguments bound to
+the specified values. Upon a 'ret'
+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 invoke instruction.
+
Example:
- <result> = sub int 4, %var ; yields {int}:result = 4 - %var
- <result> = sub int 0, %val ; yields {int}:result = -%var
+
+
+ %retval = call i32 %test(i32 %argc)
+ call i32(i8 *, ...) *%printf(i8 * %msg, i32 12, i8 42);
+ %X = tail call i32 %foo()
+ %Y = tail call fastcc i32 %foo()
+
Syntax:
- <result> = mul <ty> <var1>, <var2> ; yields {ty}:result
+
+
+ <resultval> = va_arg <va_list*> <arglist>, <argty>
+
Overview:
-The 'mul' instruction returns the product of its two
-operands.
+
+The 'va_arg' instruction is used to access arguments passed through
+the "variable argument" area of a function call. It is used to implement the
+va_arg macro in C.
+
Arguments:
-The two arguments to the 'mul' instruction must be either integer or floating point
-values. Both arguments must have identical types.
+
+This instruction takes a va_list* value and the type of
+the argument. It returns a value of the specified argument type and
+increments the va_list to point to the next argument. Again, the
+actual type of va_list is target specific.
+
Semantics:
-The value produced is the integer or floating point product of the
-two operands.
-There is no signed vs unsigned multiplication. The appropriate
-action is taken based on the type of the operand.
+
+The 'va_arg' instruction loads an argument of the specified
+type from the specified va_list and causes the
+va_list to point to the next argument. For more information,
+see the variable argument handling Intrinsic
+Functions.
+
+It is legal for this instruction to be called in a function which does not
+take a variable number of arguments, for example, the vfprintf
+function.
+
+va_arg is an LLVM instruction instead of an intrinsic function because it takes a type as an
+argument.
+
Example:
- <result> = mul int 4, %var ; yields {int}:result = 4 * %var
+
+See the variable argument processing section.
+
+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...).
+ +Intrinsic function names must all start with an "llvm." 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.
+ + +To learn how to add an intrinsic function, please see the Extending LLVM Guide. +
+ +Variable argument support is defined in LLVM with the va_arg instruction and these three +intrinsic functions. These functions are related to the similarly +named macros defined in the <stdarg.h> header file.
+ +All of these functions operate on arguments that use a +target-specific value type "va_list". 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.
+ +This example shows how the va_arg +instruction and the variable argument handling intrinsic functions are +used.
+ +
+define i32 @test(i32 %X, ...) {
+ ; Initialize variable argument processing
+ %ap = alloca i8 *
+ %ap2 = bitcast i8** %ap to i8*
+ call void @llvm.va_start(i8* %ap2)
+
+ ; Read a single integer argument
+ %tmp = va_arg i8 ** %ap, i32
+
+ ; Demonstrate usage of llvm.va_copy and llvm.va_end
+ %aq = alloca i8 *
+ %aq2 = bitcast i8** %aq to i8*
+ call void @llvm.va_copy(i8 *%aq2, i8* %ap2)
+ call void @llvm.va_end(i8* %aq2)
+
+ ; Stop processing of arguments.
+ call void @llvm.va_end(i8* %ap2)
+ ret i32 %tmp
+}
+
+declare void @llvm.va_start(i8*)
+declare void @llvm.va_copy(i8*, i8*)
+declare void @llvm.va_end(i8*)
Syntax:
- <result> = div <ty> <var1>, <var2> ; yields {ty}:result
-
+declare void %llvm.va_start(i8* <arglist>)
Overview:
-The 'div' instruction returns the quotient of its two -operands.
+The 'llvm.va_start' intrinsic initializes +*<arglist> for subsequent use by va_arg.
+Arguments:
-The two arguments to the 'div' instruction must be either integer or floating point -values. Both arguments must have identical types.
+ +The argument is a pointer to a va_list element to initialize.
+Semantics:
-The value produced is the integer or floating point quotient of the -two operands.
-Example:
- <result> = div int 4, %var ; yields {int}:result = 4 / %var
-
+
+The 'llvm.va_start' intrinsic works just like the va_start +macro available in C. In a target-dependent way, it initializes the +va_list element the argument points to, so that the next call to +va_arg will produce the first variable argument passed to the function. +Unlike the C va_start macro, this intrinsic does not need to know the +last argument of the function, the compiler can figure that out.
+Syntax:
- <result> = rem <ty> <var1>, <var2> ; yields {ty}:result
-
+declare void @llvm.va_end(i8* <arglist>)
Overview:
-The 'rem' instruction returns the remainder from the -division of its two operands.
+ +The 'llvm.va_end' intrinsic destroys <arglist> +which has been initialized previously with llvm.va_start +or llvm.va_copy.
+Arguments:
-The two arguments to the 'rem' instruction must be either integer or floating point -values. Both arguments must have identical types.
+ +The argument is a va_list to destroy.
+Semantics:
-This returns the remainder of a division (where the result -has the same sign as the divisor), not the modulus (where the -result has the same sign as the dividend) of a value. For more -information about the difference, see: The -Math Forum.
-Example:
- <result> = rem int 4, %var ; yields {int}:result = 4 % %var
-
+
+The 'llvm.va_end' intrinsic works just like the va_end +macro available in C. In a target-dependent way, it destroys the va_list. +Calls to llvm.va_start and llvm.va_copy must be matched exactly +with calls to llvm.va_end.
+Syntax:
- <result> = seteq <ty> <var1>, <var2> ; yields {bool}:result
- <result> = setne <ty> <var1>, <var2> ; yields {bool}:result
- <result> = setlt <ty> <var1>, <var2> ; yields {bool}:result
- <result> = setgt <ty> <var1>, <var2> ; yields {bool}:result
- <result> = setle <ty> <var1>, <var2> ; yields {bool}:result
- <result> = setge <ty> <var1>, <var2> ; yields {bool}:result
+
+
+ declare void @llvm.va_copy(i8* <destarglist>, i8* <srcarglist>)
+
Overview:
-The 'setcc' family of instructions returns a boolean
-value based on a comparison of their two operands.
+
+The 'llvm.va_copy' intrinsic copies the current argument position from
+the source argument list to the destination argument list.
+
Arguments:
-The two arguments to the 'setcc' instructions must
-be of first class type (it is not possible
-to compare 'label's, 'array's, 'structure'
-or 'void' values, etc...). Both arguments must have identical
-types.
+
+The first argument is a pointer to a va_list element to initialize.
+The second argument is a pointer to a va_list element to copy from.
+
+
Semantics:
-The 'seteq' instruction yields a true 'bool'
-value if both operands are equal.
-The 'setne' instruction yields a true 'bool'
-value if both operands are unequal.
-The 'setlt' instruction yields a true 'bool'
-value if the first operand is less than the second operand.
-The 'setgt' instruction yields a true 'bool'
-value if the first operand is greater than the second operand.
-The 'setle' instruction yields a true 'bool'
-value if the first operand is less than or equal to the second operand.
-The 'setge' instruction yields a true 'bool'
-value if the first operand is greater than or equal to the second
-operand.
-Example:
- <result> = seteq int 4, 5 ; yields {bool}:result = false
- <result> = setne float 4, 5 ; yields {bool}:result = true
- <result> = setlt uint 4, 5 ; yields {bool}:result = true
- <result> = setgt sbyte 4, 5 ; yields {bool}:result = false
- <result> = setle sbyte 4, 5 ; yields {bool}:result = true
- <result> = setge sbyte 4, 5 ; yields {bool}:result = false
-
+
+The 'llvm.va_copy' intrinsic works just like the va_copy macro
+available in C. In a target-dependent way, it copies the source
+va_list element into the destination list. This intrinsic is necessary
+because the llvm.va_begin intrinsic may be
+arbitrarily complex and require memory allocation, for example.
+
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.
+ ++LLVM support for Accurate Garbage +Collection requires the implementation and generation of these intrinsics. +These intrinsics allow identification of GC roots on the +stack, as well as garbage collector implementations that require read and write 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 Accurate Garbage Collection with LLVM. +
Syntax:
- <result> = and <ty> <var1>, <var2> ; yields {ty}:result
+
+
+ declare void @llvm.gcroot(<ty>** %ptrloc, <ty2>* %metadata)
+
Overview:
-The 'and' instruction returns the bitwise logical and of
-its two operands.
+
+The 'llvm.gcroot' intrinsic declares the existence of a GC root to
+the code generator, and allows some metadata to be associated with it.
+
Arguments:
-The two arguments to the 'and' instruction must be integral values. Both arguments must have
-identical types.
+
+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.
+
Semantics:
-The truth table used for the 'and' instruction is:
-
-
-
-
-
- In0
- In1
- Out
-
-
- 0
- 0
- 0
-
-
- 0
- 1
- 0
-
-
- 1
- 0
- 0
-
-
- 1
- 1
- 1
-
-
-
-
-Example:
- <result> = and int 4, %var ; yields {int}:result = 4 & %var
- <result> = and int 15, 40 ; yields {int}:result = 8
- <result> = and int 4, 8 ; yields {int}:result = 0
-
+
+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.
+
+
Syntax:
- <result> = or <ty> <var1>, <var2> ; yields {ty}:result
+
+
+ declare i8 * @llvm.gcread(i8 * %ObjPtr, i8 ** %Ptr)
+
Overview:
-The 'or' instruction returns the bitwise logical inclusive
-or of its two operands.
+
+The 'llvm.gcread' intrinsic identifies reads of references from heap
+locations, allowing garbage collector implementations that require read
+barriers.
+
Arguments:
-The two arguments to the 'or' instruction must be integral values. Both arguments must have
-identical types.
+
+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).
+
Semantics:
-The truth table used for the 'or' instruction is:
-
-
-
-
-
- In0
- In1
- Out
-
-
- 0
- 0
- 0
-
-
- 0
- 1
- 1
-
-
- 1
- 0
- 1
-
-
- 1
- 1
- 1
-
-
-
-
-Example:
- <result> = or int 4, %var ; yields {int}:result = 4 | %var
- <result> = or int 15, 40 ; yields {int}:result = 47
- <result> = or int 4, 8 ; yields {int}:result = 12
-
+
+The 'llvm.gcread' 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.
+
Syntax:
- <result> = xor <ty> <var1>, <var2> ; yields {ty}:result
+
+
+ declare void @llvm.gcwrite(i8 * %P1, i8 * %Obj, i8 ** %P2)
+
Overview:
-The 'xor' instruction returns the bitwise logical exclusive
-or of its two operands. The xor is used to implement the
-"one's complement" operation, which is the "~" operator in C.
+
+The 'llvm.gcwrite' intrinsic identifies writes of references to heap
+locations, allowing garbage collector implementations that require write
+barriers (such as generational or reference counting collectors).
+
Arguments:
-The two arguments to the 'xor' instruction must be integral values. Both arguments must have
-identical types.
+
+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.
+
Semantics:
-The truth table used for the 'xor' instruction is:
-
-
-
-
-
- In0
- In1
- Out
-
-
- 0
- 0
- 0
-
-
- 0
- 1
- 1
-
-
- 1
- 0
- 1
-
-
- 1
- 1
- 0
-
-
-
-
-
-Example:
- <result> = xor int 4, %var ; yields {int}:result = 4 ^ %var
- <result> = xor int 15, 40 ; yields {int}:result = 39
- <result> = xor int 4, 8 ; yields {int}:result = 12
- <result> = xor int %V, -1 ; yields {int}:result = ~%V
-
+
+The 'llvm.gcwrite' 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.
+
++These intrinsics are provided by LLVM to expose special features that may only +be implemented with code generator support. +
+Syntax:
- <result> = shl <ty> <var1>, ubyte <var2> ; yields {ty}:result
+
+ declare i8 *@llvm.returnaddress(i32 <level>)
+
Overview:
-The 'shl' instruction returns the first operand shifted to
-the left a specified number of bits.
+
+
+The 'llvm.returnaddress' intrinsic attempts to compute a
+target-specific value indicating the return address of the current function
+or one of its callers.
+
+
Arguments:
-The first argument to the 'shl' instruction must be an integer type. The second argument must be an 'ubyte'
-type.
+
+
+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 required to be a constant integer value.
+
+
Semantics:
-The value produced is var1 * 2var2.
-Example:
- <result> = shl int 4, ubyte %var ; yields {int}:result = 4 << %var
- <result> = shl int 4, ubyte 2 ; yields {int}:result = 16
- <result> = shl int 1, ubyte 10 ; yields {int}:result = 1024
-
+
+
+The 'llvm.returnaddress' 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.
+
+
+
+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.
+
Syntax:
- <result> = shr <ty> <var1>, ubyte <var2> ; yields {ty}:result
+
+ declare i8 *@llvm.frameaddress(i32 <level>)
+
Overview:
-The 'shr' instruction returns the first operand shifted to
-the right a specified number of bits.
+
+
+The 'llvm.frameaddress' intrinsic attempts to return the
+target-specific frame pointer value for the specified stack frame.
+
+
Arguments:
-The first argument to the 'shr' instruction must be an integer type. The second argument must be an 'ubyte'
-type.
+
+
+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 required to be a constant integer value.
+
+
Semantics:
-If the first argument is a signed 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.
-Example:
- <result> = shr int 4, ubyte %var ; yields {int}:result = 4 >> %var
- <result> = shr uint 4, ubyte 1 ; yields {uint}:result = 2
- <result> = shr int 4, ubyte 2 ; yields {int}:result = 1
- <result> = shr sbyte 4, ubyte 3 ; yields {sbyte}:result = 0
- <result> = shr sbyte -2, ubyte 1 ; yields {sbyte}:result = -1
-
-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.
+ ++The 'llvm.frameaddress' 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. +
+ ++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. +
Syntax:
- <result> = malloc <type>, uint <NumElements> ; yields {type*}:result
- <result> = malloc <type> ; yields {type*}:result
+
+ declare i8 *@llvm.stacksave()
+
Overview:
-The 'malloc' instruction allocates memory from the system
-heap and returns a pointer to it.
-Arguments:
-The the 'malloc' instruction allocates sizeof(<type>)*NumElements
-bytes of memory from the operating system, and returns a pointer of the
-appropriate type to the program. The second form of the instruction is
-a shorter version of the first instruction that defaults to allocating
-one element.
-'type' must be a sized type.
+
+
+The 'llvm.stacksave' intrinsic is used to remember the current state of
+the function stack, for use with
+llvm.stackrestore. This is useful for implementing language
+features like scoped automatic variable sized arrays in C99.
+
+
Semantics:
-Memory is allocated using the system "malloc" function, and
-a pointer is returned.
-Example:
- %array = malloc [4 x ubyte ] ; yields {[%4 x ubyte]*}:array
- %size = add uint 2, 2 ; yields {uint}:size = uint 4
- %array1 = malloc ubyte, uint 4 ; yields {ubyte*}:array1
- %array2 = malloc [12 x ubyte], uint %size ; yields {[12 x ubyte]*}:array2
-
+
+This intrinsic returns a opaque pointer value that can be passed to llvm.stackrestore. When an
+llvm.stackrestore intrinsic is executed with a value saved from
+llvm.stacksave, it effectively restores the state of the stack to the
+state it was in when the llvm.stacksave intrinsic executed. In
+practice, this pops any alloca blocks from the stack
+that were allocated after the llvm.stacksave was executed.
+
+
Syntax:
- free <type> <value> ; yields {void}
+
+ declare void @llvm.stackrestore(i8 * %ptr)
+
Overview:
-The 'free' instruction returns memory back to the unused
-memory heap, to be reallocated in the future.
-
-Arguments:
-'value' shall be a pointer value that points to a value
-that was allocated with the 'malloc'
-instruction.
+
+
+The 'llvm.stackrestore' intrinsic is used to restore the state of
+the function stack to the state it was in when the corresponding llvm.stacksave intrinsic executed. This is
+useful for implementing language features like scoped automatic variable sized
+arrays in C99.
+
+
Semantics:
-Access to the memory pointed to by the pointer is not longer defined
-after this instruction executes.
-Example:
- %array = malloc [4 x ubyte] ; yields {[4 x ubyte]*}:array
- free [4 x ubyte]* %array
-
+
+
+See the description for llvm.stacksave.
+
+
Syntax:
- <result> = alloca <type>, uint <NumElements> ; yields {type*}:result
- <result> = alloca <type> ; yields {type*}:result
+
+ declare void @llvm.prefetch(i8 * <address>,
+ i32 <rw>, i32 <locality>)
+
Overview:
-The 'alloca' instruction allocates memory on the current
-stack frame of the procedure that is live until the current function
-returns to its caller.
+
+
+
+The 'llvm.prefetch' 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.
+
+
Arguments:
-The the 'alloca' instruction allocates sizeof(<type>)*NumElements
-bytes of memory on the runtime stack, returning a pointer of the
-appropriate type to the program. The second form of the instruction is
-a shorter version of the first that defaults to allocating one element.
-'type' may be any sized type.
+
+
+address is the address to be prefetched, rw is the specifier
+determining if the fetch should be for a read (0) or write (1), and
+locality is a temporal locality specifier ranging from (0) - no
+locality, to (3) - extremely local keep in cache. The rw and
+locality arguments must be constant integers.
+
+
Semantics:
-Memory is allocated, a pointer is returned. 'alloca'd
-memory is automatically released when the function returns. The 'alloca'
-instruction is commonly used to represent automatic variables that must
-have an address available. When the function returns (either with the ret or invoke
-instructions), the memory is reclaimed.
-Example:
- %ptr = alloca int ; yields {int*}:ptr
- %ptr = alloca int, uint 4 ; yields {int*}:ptr
-
+
+
+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.
+
+
Syntax:
-<result> = load <ty>* <pointer>-
<result> = volatile load <ty>* <pointer>
Overview:
-The 'load' instruction is used to read from memory.
-Arguments:
-The argument to the 'load' instruction specifies the memory -address to load from. The pointer must point to a first class type. If the load is -marked as volatile then the optimizer is not allowed to modify -the number or order of execution of this load with other -volatile load and store -instructions.
-Semantics:
-The location of memory pointed to is loaded.
-Examples:
-%ptr = alloca int ; yields {int*}:ptr - store int 3, int* %ptr ; yields {void} - %val = load int* %ptr ; yields {int}:val = int 3 -+ - - + +
Syntax:
- store <ty> <value>, <ty>* <pointer> ; yields {void}
- volatile store <ty> <value>, <ty>* <pointer> ; yields {void}
+
+ declare void @llvm.pcmarker( i32 <id> )
+
Overview:
-The 'store' instruction is used to write to memory.
+
+
+
+The 'llvm.pcmarker' 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.
+
+
Arguments:
-There are two arguments to the 'store' instruction: a value
-to store and an address to store it into. The type of the '<pointer>'
-operand must be a pointer to the type of the '<value>'
-operand. If the store is marked as volatile then the
-optimizer is not allowed to modify the number or order of execution of
-this store with other volatile load and store instructions.
+
+
+id is a numerical id identifying the marker.
+
+
Semantics:
-The contents of memory are updated to contain '<value>'
-at the location specified by the '<pointer>' operand.
-Example:
- %ptr = alloca int ; yields {int*}:ptr
- store int 3, int* %ptr ; yields {void}
- %val = load int* %ptr ; yields {int}:val = int 3
-
+
+
+This intrinsic does not modify the behavior of the program. Backends that do not
+support this intrinisic may ignore it.
+
+
+Syntax:
- <result> = getelementptr <ty>* <ptrval>{, long <aidx>|, ubyte <sidx>}*
++ declare i64 @llvm.readcyclecounter( ) ++
Overview:
-The 'getelementptr' instruction is used to get the address -of a subelement of an aggregate data structure.
-Arguments:
-This instruction takes a list of long values and ubyte -constants that indicate what form of addressing to perform. The actual -types of the arguments provided depend on the type of the first pointer -argument. The 'getelementptr' instruction is used to index -down through the type levels of a structure.
-For example, let's consider a C code fragment and how it gets -compiled to LLVM:
-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];
}
-The LLVM code generated by the GCC frontend is:
-%RT = type { sbyte, [10 x [20 x int]], sbyte }
%ST = type { int, double, %RT }
int* "foo"(%ST* %s) {
%reg = getelementptr %ST* %s, long 1, ubyte 2, ubyte 1, long 5, long 13
ret int* %reg
}
+
+
++The 'llvm.readcyclecounter' 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. +
+Semantics:
-The index types specified for the 'getelementptr' -instruction depend on the pointer type that is being index into. Pointer and array types -require 'long' values, and structure -types require 'ubyte' constants.
-In the example above, the first index is indexing into the '%ST*' -type, which is a pointer, yielding a '%ST' = '{ int, -double, %RT }' type, a structure. The second index indexes into -the third element of the structure, yielding a '%RT' = '{ -sbyte, [10 x [20 x int]], sbyte }' type, another structure. The -third index indexes into the second element of the structure, yielding -a '[10 x [20 x int]]' type, an array. The two dimensions of -the array are subscripted into, yielding an 'int' type. The 'getelementptr' -instruction return a pointer to this element, thus yielding a 'int*' -type.
-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:
-int* "foo"(%ST* %s) {
%t1 = getelementptr %ST* %s , long 1 ; yields %ST*:%t1
- %t2 = getelementptr %ST* %t1, long 0, ubyte 2 ; yields %RT*:%t2
- %t3 = getelementptr %RT* %t2, long 0, ubyte 1 ; yields [10 x [20 x int]]*:%t3
- %t4 = getelementptr [10 x [20 x int]]* %t3, long 0, long 5 ; yields [20 x int]*:%t4
- %t5 = getelementptr [20 x int]* %t4, long 0, long 13 ; yields int*:%t5
- ret int* %t5
-}
-
-Example:
- ; yields [12 x ubyte]*:aptr
- %aptr = getelementptr {int, [12 x ubyte]}* %sptr, long 0, ubyte 1
-Note To The Novice:
-When using indexing into global arrays with the 'getelementptr' -instruction, you must remember that the+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. +
+ +The instructions in this catagory are the "miscellaneous" -instructions, which defy better classification.
++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. +
+Syntax:
-<result> = phi <ty> [ <val0>, <label0>], ...+
+ declare void @llvm.memcpy.i32(i8 * <dest>, i8 * <src>, + i32 <len>, i32 <align>) + declare void @llvm.memcpy.i64(i8 * <dest>, i8 * <src>, + i64 <len>, i32 <align>) ++
Overview:
-The 'phi' instruction is used to implement the φ node in -the SSA graph representing the function.
+ ++The 'llvm.memcpy.*' intrinsics copy a block of memory from the source +location to the destination location. +
+ ++Note that, unlike the standard libc function, the llvm.memcpy.* +intrinsics do not return a value, and takes an extra alignment argument. +
+Arguments:
-The type of the incoming values are specified with the first type -field. After this, the 'phi' instruction takes a list of pairs -as arguments, with one pair for each predecessor basic block of the -current block. Only values of first class -type may be used as the value arguments to the PHI node. Only labels -may be used as the label arguments.
-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.
+ ++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. +
+ ++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. +
+Semantics:
-At runtime, the 'phi' instruction logically takes on the -value specified by the parameter, depending on which basic block we -came from in the last terminator instruction.
-Example:
-Loop: ; Infinite loop that counts from 0 on up...+ +
%indvar = phi uint [ 0, %LoopHeader ], [ %nextindvar, %Loop ]
%nextindvar = add uint %indvar, 1
br label %Loop
+The 'llvm.memcpy.*' 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. +
Syntax:
-<result> = cast <ty> <value> to <ty2> ; yields ty2 ++ declare void @llvm.memmove.i32(i8 * <dest>, i8 * <src>, + i32 <len>, i32 <align>) + declare void @llvm.memmove.i64(i8 * <dest>, i8 * <src>, + i64 <len>, i32 <align>)+Overview:
-The 'cast' instruction is used as the primitive means to -convert integers to floating point, change data type sizes, and break -type safety (by casting pointers).
+ ++The 'llvm.memmove.*' intrinsics move a block of memory from the source +location to the destination location. It is similar to the +'llvm.memcmp' intrinsic but allows the two memory locations to overlap. +
+ ++Note that, unlike the standard libc function, the llvm.memmove.* +intrinsics do not return a value, and takes an extra alignment argument. +
+Arguments:
-The 'cast' 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 first class type.
-Semantics:
-This instruction follows the C rules for explicit casts when -determining how the data being cast must change to fit in its new -container.
-When casting to bool, any value that would be considered true in the -context of a C 'if' condition is converted to the boolean 'true' -values, all else are 'false'.
-When extending an integral value from a type of one signness to -another (for example 'sbyte' to 'ulong'), the value -is sign-extended if the source value is signed, and -zero-extended if the source value is unsigned. bool values -are always zero extended into either zero or one.
-Example:
-%X = cast int 257 to ubyte ; yields ubyte:1 - %Y = cast int 123 to bool ; yields bool:true -+ ++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. +
+ ++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. +
+ +Semantics:
+ ++The 'llvm.memmove.*' 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. +
Syntax:
-<result> = call <ty>* <fnptrval>(<param list>)+
+ declare void @llvm.memset.i32(i8 * <dest>, i8 <val>, + i32 <len>, i32 <align>) + declare void @llvm.memset.i64(i8 * <dest>, i8 <val>, + i64 <len>, i32 <align>) ++
Overview:
-The 'call' instruction represents a simple function call.
+ ++The 'llvm.memset.*' intrinsics fill a block of memory with a particular +byte value. +
+ ++Note that, unlike the standard libc function, the llvm.memset intrinsic +does not return a value, and takes an extra alignment argument. +
+Arguments:
-This instruction requires several arguments:
--
-
-
-
'ty': shall be the signature of the pointer to function -value being invoked. The argument types must match the types implied -by this signature.
-
- -
-
'fnptrval': An LLVM value containing a pointer to a -function to be invoked. In most cases, this is a direct function -invocation, but indirect calls are just as possible, -calling an arbitrary pointer to function values.
-
- -
-
'function args': 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.
-
-
+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. +
+ ++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. +
+Semantics:
-The 'call' instruction is used to cause control flow to -transfer to a specified function, with its incoming arguments bound to -the specified values. Upon a 'ret' -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 invoke instruction.
-Example:
-%retval = call int %test(int %argc)+ +
call int(sbyte*, ...) *%printf(sbyte* %msg, int 12, sbyte 42);
+The 'llvm.memset.*' 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. +
Syntax:
-<resultarglist> = vanext <va_list> <arglist>, <argty>+
+ declare float @llvm.sqrt.f32(float %Val) + declare double @llvm.sqrt.f64(double %Val) ++
Overview:
-The 'vanext' instruction is used to access arguments passed -through the "variable argument" area of a function call. It is used to -implement the va_arg macro in C.
+ ++The 'llvm.sqrt' intrinsics return the sqrt of the specified operand, +returning the same value as the libm 'sqrt' function would. Unlike +sqrt in libm, however, llvm.sqrt has undefined behavior for +negative numbers (which allows for better optimization). +
+Arguments:
-This instruction takes a valist value and the type of the -argument. It returns another valist.
+ ++The argument and return value are floating point numbers of the same type. +
+Semantics:
-The 'vanext' instruction advances the specified valist -past an argument of the specified type. In conjunction with the vaarg instruction, it is used to implement -the va_arg macro available in C. For more information, see -the variable argument handling Intrinsic -Functions.
-It is legal for this instruction to be called in a function which -does not take a variable number of arguments, for example, the vfprintf -function.
-vanext is an LLVM instruction instead of an intrinsic function because it takes an type as -an argument.
-Example:
-See the variable argument processing -section.
+ ++This function returns the sqrt of the specified operand if it is a positive +floating point number. +
Syntax:
-<resultval> = vaarg <va_list> <arglist>, <argty>+
+ declare float @llvm.powi.f32(float %Val, i32 %power) + declare double @llvm.powi.f64(double %Val, i32 %power) ++
Overview:
-The 'vaarg' instruction is used to access arguments passed -through the "variable argument" area of a function call. It is used to -implement the va_arg macro in C.
+ ++The 'llvm.powi.*' intrinsics return the first operand raised to the +specified (positive or negative) power. The order of evaluation of +multiplications is not defined. +
+Arguments:
-This instruction takes a valist value and the type of the -argument. It returns a value of the specified argument type.
+ ++The second argument is an integer power, and the first is a value to raise to +that power. +
+Semantics:
-The 'vaarg' instruction loads an argument of the specified -type from the specified va_list. In conjunction with the vanext instruction, it is used to -implement the va_arg macro available in C. For more -information, see the variable argument handling Intrinsic -Functions.
-It is legal for this instruction to be called in a function which -does not take a variable number of arguments, for example, the vfprintf -function.
-vaarg is an LLVM instruction instead of an intrinsic function because it takes an type as -an argument.
-Example:
-See the variable argument processing -section.
+ ++This function returns the first value raised to the second power with an +unspecified sequence of rounding operations.
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...).
-Intrinsic function names must all start with an "llvm." -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.
-Unless an intrinsic function is target-specific, there must be a -lowering pass to eliminate the intrinsic or all backends must support -the intrinsic function.
++LLVM provides intrinsics for a few important bit manipulation operations. +These allow efficient code generation for some algorithms. +
+Variable argument support is defined in LLVM with the vanext instruction and these three -intrinsic functions. These functions are related to the similarly -named macros defined in the <stdarg.h> header file.
-All of these functions operate on arguments that use a -target-specific value type "va_list". 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.
-This example shows how the vanext -instruction and the variable argument handling intrinsic functions are -used.
-int %test(int %X, ...) {
; Initialize variable argument processing
%ap = call sbyte*()* %llvm.va_start()
; Read a single integer argument
%tmp = vaarg sbyte* %ap, int
; Advance to the next argument
%ap2 = vanext sbyte* %ap, int
; Demonstrate usage of llvm.va_copy and llvm.va_end
%aq = call sbyte* (sbyte*)* %llvm.va_copy(sbyte* %ap2)
call void %llvm.va_end(sbyte* %aq)
; Stop processing of arguments.
call void %llvm.va_end(sbyte* %ap2)
ret int %tmp
}
+
+Syntax:
++ declare i16 @llvm.bswap.i16(i16 <id>) + declare i32 @llvm.bswap.i32(i32 <id>) + declare i64 @llvm.bswap.i64(i64 <id>) ++ +
Overview:
+ ++The 'llvm.bwsap' 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. +
+ +Semantics:
+ ++The llvm.bswap.16 intrinsic returns an i16 value that has the high +and low byte of the input i16 swapped. Similarly, the llvm.bswap.i32 +intrinsic returns an i32 value that has the four bytes of the input i32 +swapped, so that if the input bytes are numbered 0, 1, 2, 3 then the returned +i32 will have its bytes in 3, 2, 1, 0 order. The llvm.bswap.i64 +intrinsic extends this concept to 64 bits. +
+Syntax:
-call va_list ()* %llvm.va_start()+
+ declare i8 @llvm.ctpop.i8 (i8 <src>) + declare i16 @llvm.ctpop.i16(i16 <src>) + declare i32 @llvm.ctpop.i32(i32 <src>) + declare i64 @llvm.ctpop.i64(i64 <src>) ++
Overview:
-The 'llvm.va_start' intrinsic returns a new <arglist> -for subsequent use by the variable argument intrinsics.
+ ++The 'llvm.ctpop' family of intrinsics counts the number of bits set in a +value. +
+ +Arguments:
+ ++The only argument is the value to be counted. The argument may be of any +integer type. The return type must match the argument type. +
+Semantics:
-The 'llvm.va_start' intrinsic works just like the va_start -macro available in C. In a target-dependent way, it initializes and -returns a va_list element, so that the next vaarg -will produce the first variable argument passed to the function. Unlike -the C va_start macro, this intrinsic does not need to know the -last argument of the function, the compiler can figure that out.
-Note that this intrinsic function is only legal to be called from -within the body of a variable argument function.
+ ++The 'llvm.ctpop' intrinsic counts the 1's in a variable. +
Syntax:
-call void (va_list)* %llvm.va_end(va_list <arglist>)+
+ declare i8 @llvm.ctlz.i8 (i8 <src>) + declare i16 @llvm.ctlz.i16(i16 <src>) + declare i32 @llvm.ctlz.i32(i32 <src>) + declare i64 @llvm.ctlz.i64(i64 <src>) ++
Overview:
-The 'llvm.va_end' intrinsic destroys <arglist> -which has been initialized previously with llvm.va_start -or llvm.va_copy.
+ ++The 'llvm.ctlz' family of intrinsic functions counts the number of +leading zeros in a variable. +
+Arguments:
-The argument is a va_list to destroy.
+ ++The only argument is the value to be counted. The argument may be of any +integer type. The return type must match the argument type. +
+Semantics:
-The 'llvm.va_end' intrinsic works just like the va_end -macro available in C. In a target-dependent way, it destroys the va_list. -Calls to llvm.va_start and llvm.va_copy must be matched exactly -with calls to llvm.va_end.
+ ++The 'llvm.ctlz' 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, llvm.ctlz(i32 2) = 30. +
Syntax:
-call va_list (va_list)* %llvm.va_copy(va_list <destarglist>)+
+ declare i8 @llvm.cttz.i8 (i8 <src>) + declare i16 @llvm.cttz.i16(i16 <src>) + declare i32 @llvm.cttz.i32(i32 <src>) + declare i64 @llvm.cttz.i64(i64 <src>) ++
Overview:
-The 'llvm.va_copy' intrinsic copies the current argument -position from the source argument list to the destination argument list.
+ ++The 'llvm.cttz' family of intrinsic functions counts the number of +trailing zeros. +
+Arguments:
-The argument is the va_list to copy.
+ ++The only argument is the value to be counted. The argument may be of any +integer type. The return type must match the argument type. +
+Semantics:
-The 'llvm.va_copy' intrinsic works just like the va_copy -macro available in C. In a target-dependent way, it copies the source va_list -element into the returned list. This intrinsic is necessary because the llvm.va_start intrinsic may be arbitrarily -complex and require memory allocation, for example.
+ ++The 'llvm.cttz' 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, llvm.cttz(2) = 1. +
++The LLVM debugger intrinsics (which all start with llvm.dbg. prefix), +are described in the LLVM Source Level +Debugging document. +
+The LLVM exception handling intrinsics (which all start with +llvm.eh. prefix), are described in the LLVM Exception +Handling document.
- + +
+ + The LLVM Compiler Infrastructure
+ Last modified: $Date$ +