llvm Assembly Language Reference Manual

X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=docs%2FLangRef.html;h=05de0bd4cfbb032ddfebb061c5badc6f4eb953b6;hb=22e4686974c01a7df8fa237ee541d0d514a1462e;hp=caba8f0ad8437cfee810b957a2ec01bd50794b3d;hpb=d816bcfe40295e2e4234ee7308d795b597d91a5d;p=oota-llvm.git diff --git a/docs/LangRef.html b/docs/LangRef.html index caba8f0ad84..05de0bd4cfb 100644 --- a/docs/LangRef.html +++ b/docs/LangRef.html @@ -1,1705 +1,1688 @@ - -llvm Assembly Language Reference Manual - - - - -

llvm Assembly Language Reference Manual

- + + + + LLVM Assembly Language Reference Manual + + + +

LLVM Language Reference Manual

Abstract -
Introduction -
Identifiers +
Abstract
Introduction
Identifiers
Type System
1. Primitive Types -
  1. Type Classifications +
  2. Primitive Types +
    1. Type Classifications
    +
  3. Derived Types
    1. Array Type -
    2. Function Type -
    3. Pointer Type -
    4. Structure Type - +
    5. Array Type
    6. Function Type
    7. Pointer Type
    8. Structure Type
    +
  +
2. High Level Structure
  +
3. Instruction Reference
  - - -
  Written by Chris Lattner and Vikram Adve
  - - +
4. Intrinsic Functions +
  1. Variable Argument Handling Intrinsics +
    +
  +
- - +
+
Written by Chris Lattner +and Vikram Adve
+

+
-
-
-Abstract -
-
-Introduction -
Well Formedness
-
-Identifiers -

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.

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:

The easy way:

  %result = mul uint %X, 8

After strength reduction:

  %result = shl uint %X, ubyte 3

And the hard way:

  add uint %X, %X           ; yields {uint}:%0
+  add uint %0, %0           ; yields {uint}:%1
+  %result = add uint %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. -
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 unintuitive notation for constants is the optional hexidecimal form of -floating point constants. For example, the form 'double +

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.

- - +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.

+ - -

-Type System -

Type System

- +

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.

- - - +href="#rw_stroustrup">1.

-->

-Primitive Types -

- -
- - - - - - - - - -
void No value
ubyte Unsigned 8 bit value
ushort Unsigned 16 bit value
uint Unsigned 32 bit value
ulong Unsigned 64 bit value
float 32 bit floating point value
label Branch destination
- - - - - - - - - - +
Primitive Types
+
+
The primitive types are the fundemental building blocks of the LLVM +system. The current set of primitive types are as follows:
+
+
bool True or False value
sbyte Signed 8 bit value
short Signed 16 bit value
int Signed 32 bit value
long Signed 64 bit value
double 64 bit floating point value
+ + + + + +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
void No value
ubyte Unsigned 8 bit value
ushort Unsigned 16 bit value
uint Unsigned 32 bit value
ulong Unsigned 64 bit value
float 32 bit floating point value
label Branch destination
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + +
bool True or False value
sbyte Signed 8 bit value
short Signed 16 bit value
int Signed 32 bit value
long Signed 64 bit value
double 64 bit floating point value
+

- -

- - - +

Type Classifications

- -These different primitive types fall into a few useful classifications:

- - - - - - - -
signed sbyte, short, int, long, float, double
unsigned ubyte, ushort, uint, ulong
integral 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

- - - - - +

Type +Classifications

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.

-Derived Types -

- - - +

Derived Types

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.

Array Type

- +

Array Type

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.

- +

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.

- +

  [<# elements> x <elementtype>]

The number of elements is a constant integer value, elementtype may +be any type with a size.

Examples:

[40 x int ]

[41 x int ]

[40 x uint]

- -Here are some examples of multidimensional arrays:

[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]]`	: 2x10 array of single precision floating point values.
`[2 x [3 x [4 x uint]]]`	: 2x3x4 array of unsigned integer values.

`[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.

- - +

Function Type

- +

Function Type

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.

- +

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 seperated list of type -specifiers. Optionally, the parameter list may include a type ..., -which indicates that the function takes a variable number of arguments. Note -that there currently is no way to define a function in LLVM that takes a -variable number of arguments, but it is possible to call a function that -is vararg.

- +

  <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.

`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.

- - - +

Structure Type

- +

Structure Type

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.

- +

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> }
-

- - +

  { <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`.

+ + + + + + + + + +

`{ 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`.

- - +

Pointer Type

- +

Pointer Type

Overview:

- -As in many languages, the pointer type represents a pointer or reference to -another object, which must live in memory.

- +

As in many languages, the pointer type represents a pointer or +reference to another object, which must live in memory.

Syntax:

-  <type> *
-

- +

  <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`.

+ + + + + + + + + + + +
[4x int]* : pointer to array +of four int values
int (int *) * : A pointer to a function that takes an int, returning +an int.
+

-High Level Structure -

- - - - - -

-Module Structure -

- -

-; Declare the string constant as a global constant...
-%.LC0 = internal constant [13 x sbyte] c"hello world\0A\00"          ; [13 x sbyte]*
-
-; Forward declaration of puts
-declare int "puts"(sbyte*)                                           ; int(sbyte*)* 
+
+
+-->
+ High Level Structure 
+
+ Module Structure 
+
+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]*
+
+; External declaration of the puts function
+declare int %puts(sbyte*)                                            ; int(sbyte*)* 
 
 ; Definition of main function
-int "main"() {                                                       ; int()* 
+int %main() {                                                        ; int()* 
         ; Convert [13x sbyte]* to sbyte *...
-        %cast210 = getelementptr [13 x sbyte]* %.LC0, uint 0, uint 0 ; sbyte*
+        %cast210 = getelementptr [13 x sbyte]* %.LC0, long 0, long 0 ; sbyte*
 
         ; Call puts function to write out the string to stdout...
-        call int %puts(sbyte* %cast210)                              ; int
-        ret int 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 can be either "internal" or externally accessible
-(which corresponds to the static keyword in C, when used at global scope).

-
-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 "internal"
-declarations), they are accessible outside of the current module.  It is illegal
-for a function declaration to be "internal".

-
-
+        call int %puts(sbyte* %cast210)                              ; int
+        ret int 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. +

+
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. +

+
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. +

+

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".

-Global Variables -

- -As SSA values, global variables define pointer values that are in scope -(i.e. they dominate) for 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.

- - - +

Global Variables

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.

As SSA values, global variables define pointer values that are in +scope (i.e. they dominate) for 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.

-Function Structure -

declare

- -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).

- - +

Functions

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.

-Instruction Reference -

Instruction Reference

terminator instructions

binary instructions

memory -instructions

other instructions

- - +

The LLVM instruction set consists of several different +classifications of instructions: terminator +instructions, binary instructions, memory instructions, and other +instructions.

-Terminator Instructions -

previously

void

invoke

- -There are four different terminator instructions: the 'ret' instruction, the 'br' instruction, the 'switch' instruction, and the 'invoke' instruction.

- - +

Terminator +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 five different terminator instructions: the 'ret' instruction, the 'br' +instruction, the 'switch' instruction, +the 'invoke' instruction, and the 'unwind' instruction.

'`ret`' Instruction

- +

'ret' +Instruction

Syntax:

-  ret <type> <value>       ; Return a value from a non-void function
+  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' instructruction: one that returns a
-value and then causes control flow, and one that just causes control flow to
-occur.

-
+
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.
 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 '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 instruction returns a value, that value
-shall be propogated into the calling function's data space.
-
+
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.
 Example:
--  ret int 5                       ; Return an integer value of 5
+  ret int 5                       ; Return an integer value of 5
   ret void                        ; Return from a void function
 
-
-
+

'`br`' Instruction

- +

'br' Instruction

Syntax:

- br bool <cond>, label <iftrue>, label <iffalse> - br label <dest> ; Unconditional branch +

  br bool <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.

- +

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 -'bool' value and two 'label' values. The unconditional form -of the 'br' instruction takes a single 'label' value as a -target.

- +

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.

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.

- +

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.

Example:

-Test:
-  %cond = seteq int %a, %b
-  br bool %cond, label %IfEqual, label %IfUnequal
-IfEqual:
-  ret int 1
-IfUnequal:
-  ret int 0
-

- - +

Test:
  %cond = seteq int %a, %b
  br bool %cond, label %IfEqual, label %IfUnequal
IfEqual:
  ret int 1
IfUnequal:
  ret int 0

'`switch`' Instruction

- +

'switch' +Instruction

Syntax:

-  ; Definitions for lookup indirect branch
-  %switchtype = type [<anysize> x { uint, label }]
-
-  ; Lookup indirect branch
-  switch uint <value>, label <defaultdest>, %switchtype <switchtable>
-
-  ; Indexed indirect branch
-  switch uint <idxvalue>, label <defaultdest>, [<anysize> x label] <desttable>
-

- +

  switch uint <value>, label <defaultdest> [ int <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.

- -The 'switch' statement supports two different styles of indirect -branching: lookup branching and indexed branching. Lookup branching is -generally useful if the values to switch on are spread far appart, where index -branching is useful if the values to switch on are generally dense.

- -The two different forms of the 'switch' statement are simple hints to -the underlying implementation. For example, the compiler may choose to -implement a small indirect branch table as a series of predicated comparisons: -if it is faster for the target architecture.

- +

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 lookup form of 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 sized array must be a constant value.

- -The indexed form of the 'switch' instruction uses three parameters: an -'uint' index value, a default 'label' and a sized array of -'label's. The 'dests' array must be a constant array. - +

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.

Semantics:

- -The lookup style switch statement 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.

- -The index branch form simply looks up a label element directly in a table and -branches to it.

- -In either case, the compiler knows the static size of the array, because it is -provided as part of the constant values type.

- +

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, [1 x label] [label %falsedest ]
-
-  ; Emulate an unconditional br instruction
-  switch uint 0, label %dest, [ 0 x label] [ ]
+  ; 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 [ ]
 
   ; Implement a jump table:
-  switch uint %val, label %otherwise, [3 x label] [ label %onzero, 
-                                                    label %onone, 
-                                                    label %ontwo ]
-
+  switch uint %val, label %otherwise [ int 0, label %onzero, 
+                                       int 1, label %onone, 
+                                       int 2, label %ontwo ]
 
-
-
-
+

'`invoke`' Instruction

- +

'invoke' +Instruction

Syntax:

-  <result> = invoke <ptr to function ty> %<function ptr val>(<function args>)
-                 to label <normal label> except label <exception label>
-

- +

  <result> = invoke <ptr to function ty> %<function ptr val>(<function args>)
                 to label <normal label> except label <exception label>

Overview:

- -The 'invoke' instruction is used to cause control flow to transfer to a -specified function, with the possibility of control flow transfer to either the -'normal label' label or the 'exception label'. The 'call' instruction is closely related, but guarantees -that control flow either never returns from the called function, or that it -returns to the instruction following the 'call' -instruction.

- +

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.

Arguments:

- -This instruction requires several arguments:

This instruction requires several arguments:

'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 invoke's 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 an exception is thrown. +
'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 associates a label with the function invocation that may -be accessed via the runtime library provided by the execution environment. 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.

- - - +

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 int %Test(int 15)
-              to label %Continue except label %TestCleanup     ; {int}:retval set
+  %retval = invoke int %Test(int 15)
              to label %Continue
              except label %TestCleanup     ; {int}:retval set
 
-
-
-
+

'unwind' +Instruction

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.

-Binary Operations -

- -There are several different binary operators:

- - +

Binary Operations

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.

-  <result> = seteq <ty> <var1>, <var2>   ; yields {bool}:result
+  <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
 
-
-Overview:
 The 'setcc' family of instructions returns a
-boolean value based on a comparison of their two operands.
-
-
Arguments:
 The two arguments to the 'setcc'
-instructions must be of first class or pointer type (it is not possible to compare
-'label's, 'array's, 'structure' or 'void'
-values, etc...).  Both arguments must have identical types.
-
-The 'setlt', 'setgt', 'setle', and 'setge'
-instructions do not operate on 'bool' typed arguments.

-
+
Overview:
+The 'setcc' family of instructions returns a boolean
+value based on a comparison of their two operands.
+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.
 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.
-
+
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> = 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
 
-
-
-
+

-Bitwise Binary Operations -

- +

Bitwise Binary +Operations

-  <result> = shr <ty> <var1>, ubyte <var2>   ; yields {ty}:result
+  <result> = shr <ty> <var1>, ubyte <var2>   ; yields {ty}:result
 
-
 Overview:
-The 'shr' instruction returns the first operand shifted to the right a specified number of bits.
-
+The 'shr' instruction returns the first operand shifted to
+the right a specified number of bits.
 Arguments:
-The first argument to the 'shr' instruction must be an  integral type.  The second argument must be an 'ubyte' type.
-
+
The first argument to the 'shr' instruction must be an integer type.  The second argument must be an 'ubyte'
+type.
 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.
-
+
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 int 4, ubyte 1      ; yields {int}:result = 2
+  <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 int 4, ubyte 3      ; yields {int}:result = 0
+  <result> = shr sbyte 4, ubyte 3    ; yields {sbyte}:result = 0
+  <result> = shr sbyte -2, ubyte 1   ; yields {sbyte}:result = -1
 
-
-
-
-
-
+

-Memory Access Operations -

- - +

Memory Access +Operations

-  <result> = load <ty>* <pointer>
-

- +

  <result> = load <ty>* <pointer>
  <result> = volatile load <ty>* <pointer>

Overview:

-The 'load' instruction is used to read from memory.

- +

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.

- +

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. - +

The location of memory pointed to is loaded.

Examples:

-  %ptr = alloca int                               ; yields {int*}:ptr
-  store int 3, int* %ptr                          ; yields {void}
+  %ptr = alloca int                               ; yields {int*}:ptr
+  store int 3, int* %ptr                          ; yields {void}
   %val = load int* %ptr                           ; yields {int}:val = int 3
 
-
-
-
-
+

'`store`' Instruction

- +

'store' +Instruction

Syntax:

-  store <ty> <value>, <ty>* <pointer>                   ; yields {void}
+  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.
-
+
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 to store it into.  The type of the '<pointer>'
+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.

-
-
Semantics: The contents of memory are updated to contain
-'<value>' at the location specified by the
-'<pointer>' operand.
-
+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 int                               ; yields {int*}:ptr
-  store int 3, int* %ptr                          ; yields {void}
+  %ptr = alloca int                               ; yields {int*}:ptr
+  store int 3, int* %ptr                          ; yields {void}
   %val = load int* %ptr                           ; yields {int}:val = int 3
 
-
-
-
-
 
-

'`getelementptr`' Instruction

- +

'getelementptr' +Instruction

Syntax:

-  <result> = getelementptr <ty>* <ptrval>{, uint <aidx>|, ubyte <sidx>}*
-

- +

  <result> = getelementptr <ty>* <ptrval>{, long <aidx>|, ubyte <sidx>}*

Overview:

- -The 'getelementptr' instruction is used to get the address of a -subelement of an aggregate data structure.

- +

The 'getelementptr' instruction is used to get the address +of a subelement of an aggregate data structure.

Arguments:

- -This instruction takes a list of uint 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, lets 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, uint 1, ubyte 2, ubyte 1, uint 5, uint 13
-  ret int* %reg
-}
-

- +

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
}

Semantics:

- -The index types specified for the 'getelementptr' instruction depend on -the pointer type that is being index into. Pointer and -array types require 'uint' 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 , uint 1                        ; yields %ST*:%t1
-  %t2 = getelementptr %ST* %t1, uint 0, ubyte 2               ; yields %RT*:%t2
-  %t3 = getelementptr %RT* %t2, uint 0, ubyte 1               ; yields [10 x [20 x int]]*:%t3
-  %t4 = getelementptr [10 x [20 x int]]* %t3, uint 0, uint 5  ; yields [20 x int]*:%t4
-  %t5 = getelementptr [20 x int]* %t4, uint 0, uint 13        ; yields int*:%t5
+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, uint 0, ubyte 1
-
-
-
-
+  ; 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

-Other Operations -

- - +

Other Operations

The instructions in this catagory are the "miscellaneous" +instructions, which defy better classification.

'`phi`' Instruction

- +

'phi' +Instruction

Syntax:

-  <result> = phi <ty> [ <val0>, <label0>], ...
-

- +

  <result> = phi <ty> [ <val0>, <label0>], ...

Overview:

- -The 'phi' instruction is used to implement the φ node in the SSA -graph representing the function.

- +

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.

- -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 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.

- +

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
-

- - +

Loop:       ; Infinite loop that counts from 0 on up...
  %indvar = phi uint [ 0, %LoopHeader ], [ %nextindvar, %Loop ]
  %nextindvar = add uint %indvar, 1
  br label %Loop

'`cast .. to`' Instruction

- +

'cast .. to' +Instruction

Syntax:

-  <result> = cast <ty> <value> to <ty2>             ; yields ty2
+  <result> = cast <ty> <value> to <ty2>             ; yields ty2
 
-
 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 '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).
 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.
-
+
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.

-
+
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
+  %X = cast int 257 to ubyte              ; yields ubyte:1
   %Y = cast int 123 to bool               ; yields bool:true
 
-
-
-
+

'`call`' Instruction

- +

'call' +Instruction

Syntax:

-  <result> = call <ty>* <fnptrval>(<param list>)
-

- +

  <result> = call <ty>* <fnptrval>(<param list>)

Overview:

- -The 'call' instruction represents a simple function call.

- +

The 'call' instruction represents a simple function call.

Arguments:

- -This instruction requires several 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 -call's 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. +
+
'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.
+

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.

- +

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);
-
-

- - - - +

  %retval = call int %test(int %argc)
  call int(sbyte*, ...) *%printf(sbyte* %msg, int 12, sbyte 42);

'vanext' +Instruction

Syntax:

  <resultarglist> = vanext <va_list> <arglist>, <argty>

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.

Arguments:

This instruction takes a valist value and the type of the +argument. It returns another valist.

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.

'vaarg' +Instruction

Syntax:

  <resultval> = vaarg <va_list> <arglist>, <argty>

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.

Arguments:

This instruction takes a valist value and the type of the +argument. It returns a value of the specified argument type.

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.

Intrinsic Functions

+ +

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.

+ +

Variable Argument +Handling Intrinsics

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
}

+ +

'llvm.va_start' +Intrinsic

Syntax:

  call va_list ()* %llvm.va_start()

Overview:

The 'llvm.va_start' intrinsic returns a new <arglist> +for subsequent use by the variable argument intrinsics.

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.

+ +

'llvm.va_end' +Intrinsic

Syntax:

  call void (va_list)* %llvm.va_end(va_list <arglist>)

Overview:

The 'llvm.va_end' intrinsic destroys <arglist> +which has been initialized previously with llvm.va_start +or llvm.va_copy.

Arguments:

The argument is a va_list to destroy.

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.

+ +

'llvm.va_copy' +Intrinsic

Syntax:

  call va_list (va_list)* %llvm.va_copy(va_list <destarglist>)

Overview:

The 'llvm.va_copy' intrinsic copies the current argument +position from the source argument list to the destination argument list.

Arguments:

The argument is the va_list to copy.

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.

- -

- +

Chris Lattner

- - -Last modified: Fri Aug 30 16:49:39 CDT 2002 - - - +The LLVM Compiler Infrastructure
+Last modified: $Date$

+ +

signed	`sbyte, short, int, long, float, double`
unsigned	`ubyte, ushort, uint, ulong`
integral	`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`

`[4x int]*`	: pointer to array +of four `int` values
`int (int ) `	: A pointer to a function that takes an `int`, returning +an `int`.

Well Formedness

Type Classifications

Array Type

Overview:

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Function Type

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Structure Type

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Pointer Type

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'ret' Instruction

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'br' Instruction

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'switch' Instruction

Syntax:

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Implementation:

Example:

'invoke' Instruction

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'add' Instruction

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'sub' Instruction

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Example:

'mul' Instruction

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'div' Instruction

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'rem' Instruction

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Example:

'setcc' Instructions

Syntax:

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'`ret`' Instruction

'`br`' Instruction

'`switch`' Instruction

'`invoke`' Instruction

'`add`' Instruction

'`sub`' Instruction

'`mul`' Instruction

'`div`' Instruction

'`rem`' Instruction

'`setcc`' Instructions

'`and`' Instruction

'`or`' Instruction

'`xor`' Instruction

'`shl`' Instruction

'`shr`' Instruction

'`malloc`' Instruction

'`free`' Instruction

'`alloca`' Instruction

'`load`' Instruction

'`store`' Instruction

'`getelementptr`' Instruction