LLVM Assembly Language Reference Manual

X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=docs%2FLangRef.html;h=23911e2540f43504fd172e0c536f61e35f9d8141;hb=120bc6da2fe9b6706de2f5ee890a844cb91ae2d5;hp=a664f328d5d54596850162c028d22f03c2038306;hpb=478921b11a9e9f6ffac0c4eb96c4275e2b2ce3cd;p=oota-llvm.git diff --git a/docs/LangRef.html b/docs/LangRef.html index a664f328d5d..23911e2540f 100644 --- a/docs/LangRef.html +++ b/docs/LangRef.html @@ -1,865 +1,1307 @@ - -LLVM Assembly Language Reference Manual - - - - -

LLVM Language Reference Manual

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

LLVM Language Reference Manual

Abstract -
Introduction -
Identifiers +
Abstract
Introduction
Identifiers
High Level Structure +
1. Module Structure
2. Linkage Types
3. Calling Conventions
4. Global Variables
5. Function Structure
+
Type System
+
+
Written by Chris Lattner + and Vikram Adve
+
-
-
-Abstract -
-
-Introduction -
Well Formedness
-
-Identifiers -

+ +

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:

+ +

The easy way:

   %result = mul uint %X, 8

-After strength reduction: +

After strength reduction:

   %result = shl uint %X, ubyte 3

-And the hard way: +

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:

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 +

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 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 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.

+text.

+ - -

-Type System -

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()* 
+        ; Convert [13x sbyte]* to 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 have one of the following linkage types.

-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
+
+ Linkage Types +
- +
- - - - - - - -
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
+
+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, or the idea of "anonymous namespaces" in C++. +

linkonce:

Type Classifications

"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:

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`

"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. +

first class

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".

-Derived Types -

+ Calling Conventions +

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:

Array Type

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). +

Overview:

"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. +

Syntax:

-  [<# elements> x <elementtype>]
-

"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. +

Examples:

[40 x int ]

[41 x int ]

[40 x uint]

`[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.

"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. +

Function Type

More calling conventions can be added/defined on an as-needed basis, to +support pascal conventions or any other well-known target-independent +convention.

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.

+ +

+ Global Variables +

Syntax:

-  <returntype> (<parameter list>)
-

+ +

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 (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.

-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.

+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) 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.

+ +

+ Functions +

+ +

LLVM function definitions consist of an optional linkage +type, an optional calling convention, a return +type, a function name, a (possibly empty) argument list, an opening curly brace, +a list of basic blocks, and a closing curly brace. LLVM function declarations +are defined with the "declare" keyword, an optional calling convention, a return type, a function name, and +a possibly empty list of arguments.

+ +

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.

+ +

Examples:

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.

Primitive Types

The primitive types are the fundamental building blocks of the LLVM +system. The current set of primitive types is as follows:

+ +

`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.

+ + + + + + + + + + + +

Type	Description
`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

+ + + + + + + + + + +

Type	Description
`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:

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + +

Classification	Types
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, + packed`

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

+ +

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.

+ +

Structure Type

Array 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.

Overview:

-Structures are accessed using 'load and 'store' by getting a pointer to a field with the 'getelementptr' instruction.

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:

-  { <type list> }
+  [<# elements> x <elementtype>]

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

Examples:

- - - +

{ int, int, int } : a triple of three int -values

+ + + + +

+ [40 x int ]
+ [41 x int ]
+ [40 x uint]
+ + Array of 40 integer values.
+ Array of 41 integer values.
+ Array of 40 unsigned integer values.
+

Here are some examples of multidimensional arrays:

+ + + + + +

+ [3 x [4 x int]]
+ [12 x [10 x float]]
+ [2 x [3 x [4 x uint]]]
+ + 3x4 array of integer values.
+ 12x10 array of single precision floating point values.
+ 2x3x4 array of unsigned integer values.
+

{ float, int (int) * }

float

pointer

function

int

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 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:

+ + + + + +

+ int (int)
+ float (int, int *) *
+ int (sbyte *, ...)
+ + function taking an int, returning an int
+ Pointer to a function that takes an + int and a pointer to int, + returning float.
+ 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

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 }
+ { float, int (int) * }
+ + a triple of three int values
+ 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

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

Pointer Type

Packed Type

Overview:

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

A packed type is a simple derived type that represents a vector +of elements. Packed types are used when multiple primitive data +are operated in parallel using a single instruction (SIMD). +A packed type requires a size (number of +elements) and an underlying primitive data type. Packed types are +considered first class.

Syntax:

-  <type> *
+  < <# elements> x <elementtype> >

Examples:

The number of elements is a constant integer value; elementtype may +be any integral or floating point type.

- +

Examples:

- +

[4x int]* : pointer to array of four int values

+ + + + +

+ <4 x int>
+ <8 x float>
+ <2 x uint>
+ + Packed vector of 4 integer values.
+ Packed vector of 8 floating-point values.
+ Packed vector of 2 unsigned integer values.
+

int (int *) *

pointer

function

int

Opaque Type

- -

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).

- - + + + + + +

+ opaque + + An opaque type.
+

-High Level Structure -

Constants

+ +

LLVM has several different basic types of constants. This section describes +them all and their syntax.

+ +

-Module Structure -

Simple Constants

-; Declare the string constant as a global constant...
-%.LC0 = internal constant [13 x sbyte] c"hello world\0A\00"          ; [13 x sbyte]*
+
+  Boolean constants
 
-; External declaration of the puts function
-declare int %puts(sbyte*)                                            ; int(sbyte*)* 
+  The two strings 'true' and 'false' are both valid
+  constants of the bool type.
+  
 
-; Definition of main function
-int %main() {                                                        ; int()* 
-        ; Convert [13x sbyte]* to sbyte *...
-        %cast210 = getelementptr [13 x sbyte]* %.LC0, long 0, long 0 ; sbyte*
+  Integer constants
 
-        ; Call puts function to write out the string to stdout...
-        call int %puts(sbyte* %cast210)                              ; int
-        ret int 0
-}
-

Standard integers (such as '4') are constants of the integer type. Negative numbers may be used with signed + integer types. +

-This example is made up of a global variable named -".LC0", an external declaration of the "puts" function, and a -function definition for "main".

Floating point constants

- -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:

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.

internal +
Null pointer constants: 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++.
+; The identifier 'null' is recognized as a null pointer constant + and must be of pointer type.
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.

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.

+ +

weak: + +

Aggregate Constants +

"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.

Aggregate constants arise from aggregation of simple constants +and smaller aggregate constants.

- -

appending: +

Structure constants

+ + -

"appending" linkage may only 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.

+ +

+ Global Variable and Function Addresses +

- -

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.

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 int 17
+  %Y = global int 42
+  %Z = global [2 x int*] [ int* %X, int* %Y ]
+

+ -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".

+ +

Undefined Values

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. +

-Global Variables -

Constant Expressions +

-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.

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:

cast ( CST to TYPE ): Cast a constant to another type.

-Functions -

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). Because the block can have no predecessors, it also cannot have any -PHI nodes.

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".

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).

-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, +bitwise binary instructions, memory instructions, and other +instructions.

- -

-Terminator Instructions -

previously

void

invoke

- -There are five different terminator instructions: the 'ret' instruction, the 'br' instruction, the 'switch' instruction, the 'invoke' instruction, and the 'unwind' 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 six different terminator instructions: the 'ret' instruction, the 'br' +instruction, the 'switch' instruction, +the 'invoke' instruction, the 'unwind' instruction, and the 'unreachable' 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' 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.
-
+
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 "normal" of the destination block.  If the instruction returns a
-value, that value shall set the call or invoke instruction's return value.
-
-
+
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 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:

- switch uint <value>, label <defaultdest> [ int <val>, label &dest>, ... ] +

+  switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]

Overview:

-The 'switch' instruction is used to transfer control flow to one of +

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.

+instruction, allowing a branch to occur to one of many possible +destinations.

Arguments:

-The 'switch' instruction uses three parameters: a 'uint' +

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.

+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, the corresponding destination is -branched to, otherwise the default value it transfered to.

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 as a series of chained -conditional branches, or with a lookup table.

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 = cast bool %value to uint
-  switch uint %Val, label %truedest [int 0, label %falsedest ]
+ ; Emulate a conditional br instruction
+ %Val = cast bool %value to int
+ switch int %Val, label %truedest [int 0, label %falsedest ]
 
-  ; Emulate an unconditional br instruction
-  switch uint 0, label %dest [ ]
+ ; Emulate an unconditional br instruction
+ switch uint 0, label %dest [ ]
 
-  ; Implement a jump table:
-  switch uint %val, label %otherwise [ int 0, label %onzero, 
-                                       int 1, label %onone, 
-                                       int 2, label %ontwo ]
+ ; Implement a jump table:
+ switch uint %val, label %otherwise [ uint 0, label %onzero 
+                                      uint 1, label %onone 
+                                      uint 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 [cconv] <ptr to function ty> %<function ptr val>(<function args>) 
+                to label <normal label> except label <exception label>

Overview:

-The 'invoke' instruction causes control to transfer to a specified +

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 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.

- +href="#i_unwind">unwind" instruction, control is interrupted and +continued at the dynamically nearest "exception" label.

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 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. +
This instruction requires several arguments:
-
'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. +
1. + The optional "cconv" marker indicates which calling + convention the call should use. If none is specified, the call defaults + to using C calling conventions. +
2. '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. +
3. 'function ptr val': An LLVM value containing a pointer to a + function to be invoked.
4. '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.
5. 'normal label': the label reached when the called function + executes a 'ret' instruction.
6. 'exception label': the label reached when a callee returns with + the unwind instruction.
7. 'exception label': the label reached when a callee returns with the -unwind instruction.
Semantics:
-This instruction is designed to operate as a standard '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. +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 +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. +'catch' clauses in high-level languages that support them. Example: - %retval = invoke int %Test(int 15) - to label %Continue + %retval = invoke int %Test(int 15) to label %Continue + except label %TestCleanup ; {int}:retval set + %retval = invoke coldcc int %Test(int 15) to label %Continue except label %TestCleanup ; {int}:retval set +

+ -

'unwind' Instruction + + 'unwind' +Instruction + + Syntax: @@ -868,1096 +1310,1995 @@ exception. Additionally, this is important for implementation of Overview: -The 'unwind' instruction unwinds the stack, continuing control flow at -the first callee in the dynamic call stack which used an 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. +primarily used to implement exception handling. Semantics: -The 'unwind' intrinsic causes execution of the current function to +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. - - +dynamic call chain, undefined behavior results. + - - -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. - -There are several different binary operators: + + 'unreachable' +Instruction - - 'add' Instruction + Syntax: - <result> = add <ty> <var1>, <var2> ; yields {ty}:result + unreachable 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. Both arguments must have identical types. + 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 value produced is the integer or floating point sum of the two operands. + The 'unreachable' instruction has no defined semantics. + -Example: -- <result> = add int 4, %var ; yields {int}:result = 4 + %var - + + 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 operands might represent +multiple data, as is the case with the packed data type. +The result value of a binary operator is not +necessarily the same type as its operands. +There are several different binary operators: + - 'sub' Instruction - + 'add' +Instruction + Syntax: -- <result> = sub <ty> <var1>, <var2> ; yields {ty}:result + <result> = add <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. - + The 'add' instruction returns the sum of its two operands. Arguments: - -The two arguments to the 'sub' instruction must be either integer or floating point -values. Both arguments must have identical types. - + The two arguments to the 'add' instruction must be either integer or floating point values. + This instruction can also take packed 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. - + The value produced is the integer or floating point sum of the two +operands. Example: -- <result> = sub int 4, %var ; yields {int}:result = 4 - %var - <result> = sub int 0, %val ; yields {int}:result = -%var + <result> = add int 4, %var ; yields {int}:result = 4 + %var - + - 'mul' Instruction - + 'sub' +Instruction + Syntax: -- <result> = mul <ty> <var1>, <var2> ; yields {ty}:result + <result> = sub <ty> <var1>, <var2> ; yields {ty}:result - Overview: -The 'mul' instruction returns the product of its two operands. - + 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 'mul' instruction must be either integer or floating point values. Both arguments must have identical types. - + The two arguments to the 'sub' instruction must be either integer or floating point +values. +This instruction can also take packed 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. - -There is no signed vs unsigned multiplication. The appropriate action is taken -based on the type of the operand. - - + The value produced is the integer or floating point difference of +the two operands. Example: -- <result> = mul int 4, %var ; yields {int}:result = 4 * %var + <result> = sub int 4, %var ; yields {int}:result = 4 - %var + <result> = sub int 0, %val ; yields {int}:result = -%var + + + 'mul' +Instruction + +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 packed 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. +There is no signed vs unsigned multiplication. The appropriate +action is taken based on the type of the operand. +Example: + <result> = mul int 4, %var ; yields {int}:result = 4 * %var + + + + 'div' +Instruction + +Syntax: + <result> = div <ty> <var1>, <var2> ; yields {ty}:result + +Overview: +The 'div' instruction returns the quotient of its two +operands. +Arguments: +The two arguments to the 'div' instruction must be either integer or floating point +values. +This instruction can also take packed versions of the values. +Both arguments must have identical types. +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 + + + + 'rem' +Instruction + +Syntax: + <result> = rem <ty> <var1>, <var2> ; yields {ty}:result + +Overview: +The 'rem' instruction returns the remainder from the +division of its two operands. +Arguments: +The two arguments to the 'rem' instruction must be either integer or floating point +values. +This instruction can also take packed versions of the values. +Both arguments must have identical types. +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 + + + + 'setcc' +Instructions + +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 + +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. +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 + + + + Bitwise Binary +Operations + +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. + + + 'and' +Instruction + +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 integral 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 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 + + + + 'or' Instruction + +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 integral 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 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 + + + + 'xor' +Instruction + +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 integral 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 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 + + + + 'shl' +Instruction + +Syntax: + <result> = shl <ty> <var1>, ubyte <var2> ; yields {ty}:result + +Overview: +The 'shl' instruction returns the first operand shifted to +the left a specified number of bits. +Arguments: +The first argument to the 'shl' instruction must be an integer type. The second argument must be an 'ubyte' +type. +Semantics: +The value produced is var1 * 2^var2. +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 + + + + 'shr' +Instruction + +Syntax: + <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. +Arguments: +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. +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 + + + + Memory Access +Operations + +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. + + + 'malloc' +Instruction + +Syntax: + <result> = malloc <type>, uint <NumElements> ; yields {type*}:result + <result> = malloc <type> ; 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. 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. +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 + + + + 'free' +Instruction + +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 ubyte] ; yields {[4 x ubyte]*}:array + free [4 x ubyte]* %array + + - 'div' Instruction + 'alloca' +Instruction + +Syntax: + <result> = alloca <type>, uint <NumElements> ; yields {type*}:result + <result> = alloca <type> ; 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. 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. +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 int ; yields {int*}:ptr + %ptr = alloca int, uint 4 ; yields {int*}:ptr + + + + 'load' +Instruction + +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 + + + + 'store' +Instruction +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 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. +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 + + + + 'getelementptr' Instruction + + Syntax: - <result> = div <ty> <var1>, <var2> ; yields {ty}:result + <result> = getelementptr <ty>* <ptrval>{, <ty> <idx>}* Overview: -The 'div' instruction returns the quotient of its two operands. + +The 'getelementptr' instruction is used to get the address of a +subelement of an aggregate data structure. Arguments: -The two arguments to the 'div' instruction must be either integer or floating point -values. Both arguments must have identical types. + This instruction takes a list of integer constants that indicate what +elements of the aggregate object to index to. The actual types of the arguments +provided depend on the type of the first pointer argument. The +'getelementptr' instruction is used to index down through the type +levels of a structure. When indexing into a structure, only uint +integer constants are allowed. When indexing into an array or pointer, +int and long indexes are allowed of any sign. + +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 } + + implementation + + int* %foo(%ST* %s) { + entry: + %reg = getelementptr %ST* %s, int 1, uint 2, uint 1, int 5, int 13 + ret int* %reg + } + Semantics: -The value produced is the integer or floating point quotient of the two -operands. + The index types specified for the 'getelementptr' instruction depend +on the pointer type that is being indexed into. Pointer +and array types require uint, int, +ulong, or long values, and structure +types require uint 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 computing a value of '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, int 1 ; yields %ST*:%t1 + %t2 = getelementptr %ST* %t1, int 0, uint 2 ; yields %RT*:%t2 + %t3 = getelementptr %RT* %t2, int 0, uint 1 ; yields [10 x [20 x int]]*:%t3 + %t4 = getelementptr [10 x [20 x int]]* %t3, int 0, int 5 ; yields [20 x int]*:%t4 + %t5 = getelementptr [20 x int]* %t4, int 0, int 13 ; yields int*:%t5 + ret int* %t5 + } + Example: - <result> = div int 4, %var ; yields {int}:result = 4 / %var + ; yields [12 x ubyte]*:aptr + %aptr = getelementptr {int, [12 x ubyte]}* %sptr, long 0, uint 1 + + + Other Operations + +The instructions in this category are the "miscellaneous" +instructions, which defy better classification. + + + 'phi' +Instruction + +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 uint [ 0, %LoopHeader ], [ %nextindvar, %Loop ] %nextindvar = add uint %indvar, 1 br label %Loop + - 'rem' Instruction + + 'cast .. to' Instruction + + + Syntax: + - <result> = rem <ty> <var1>, <var2> ; yields {ty}:result + <result> = cast <ty> <value> to <ty2> ; yields ty2 Overview: -The 'rem' instruction returns the remainder from the division of its two operands. + + +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 two arguments to the 'rem' instruction must be either integer or floating point values. Both arguments must have identical types. + + +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 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. + +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: + - <result> = rem int 4, %var ; yields {int}:result = 4 % %var + %X = cast int 257 to ubyte ; yields ubyte:1 + %Y = cast int 123 to bool ; yields bool:true - + - 'setcc' Instructions + + 'select' Instruction + + + 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 + <result> = select bool <cond>, <ty> <val1>, <ty> <val2> ; yields ty -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: +Overview: -The 'seteq' instruction yields a true 'bool' value if -both operands are equal. + +The 'select' instruction is used to choose one value based on a +condition, without branching. + -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. +Arguments: -The 'setgt' instruction yields a true 'bool' value if -the first operand is greater than the second operand. + +The 'select' instruction requires a boolean value indicating the condition, and two values of the same first class type. + -The 'setle' instruction yields a true 'bool' value if -the first operand is less than or equal to the second operand. +Semantics: -The 'setge' instruction yields a true 'bool' value if -the first operand is greater than or equal to the second operand. + +If the boolean condition evaluates to true, the instruction returns the first +value argument, otherwise it returns the second value argument. + 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 + %X = select bool true, ubyte 17, ubyte 42 ; yields ubyte:17 + - - - -Bitwise Binary Operations - -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. - 'and' Instruction + + 'call' Instruction + + + Syntax: - <result> = and <ty> <var1>, <var2> ; yields {ty}:result + <result> = [tail] call [cconv] <ty>* <fnptrval>(<param list>) Overview: -The 'and' instruction returns the bitwise logical and of its two operands. + + The 'call' instruction represents a simple function call. Arguments: -The two arguments to the 'and' instruction must be integral 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. + + + '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. 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 truth table used for the 'and' instruction is: - - - - - - - -In0 In1 Out 0 0 0 0 1 0 1 0 0 1 1 1 - + 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> = 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 + %retval = call int %test(int %argc) + call int(sbyte*, ...) *%printf(sbyte* %msg, int 12, sbyte 42); + %X = tail call int %foo() + %Y = tail call fastcc int %foo() - + - 'or' Instruction + + 'vanext' Instruction + + + Syntax: + - <result> = or <ty> <var1>, <var2> ; yields {ty}:result + <resultarglist> = vanext <va_list> <arglist>, <argty> -Overview: The 'or' instruction returns the bitwise logical -inclusive or of its two operands. + Overview: -Arguments: +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 two arguments to the 'or' instruction must be integral values. Both arguments must have identical -types. + Arguments: +This instruction takes a va_list value and the type of the +argument. It returns another va_list. The actual type of +va_list may be defined differently for different targets. Most targets +use a va_list type of sbyte* or some other pointer type. Semantics: -The truth table used for the 'or' instruction is: + The 'vanext' instruction advances the specified va_list +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. - - - - - - -In0 In1 Out 0 0 0 0 1 1 1 0 1 1 1 1 + 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 a type as an +argument. The type refers to the current argument in the va_list, it +tells the compiler how far on the stack it needs to advance to find the next +argument 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 - +See the variable argument processing +section. + + - 'xor' Instruction + + 'vaarg' Instruction + + + Syntax: + - <result> = xor <ty> <var1>, <var2> ; yields {ty}:result + <resultval> = vaarg <va_list> <arglist>, <argty> 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 '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: -The two arguments to the 'xor' instruction must be integral 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. Again, the actual +type of va_list is target specific. Semantics: -The truth table used for the 'xor' instruction is: + 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. - - - - - - -In0 In1 Out 0 0 0 0 1 1 1 0 1 1 1 0 + 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. + + +To learn how to add an intrinsics, please see the Extending LLVM Guide. + + + + + + + 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. + - <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 +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* %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: + declare <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: + declare void %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. + - 'shl' Instruction + + 'llvm.va_copy' Intrinsic + + + Syntax: + - <result> = shl <ty> <var1>, ubyte <var2> ; yields {ty}:result + declare <va_list> %llvm.va_copy(<va_list> <destarglist>) Overview: -The 'shl' instruction returns the first operand shifted to the left a -specified number of bits. +The 'llvm.va_copy' intrinsic copies the current argument position +from the source argument list to the destination argument list. Arguments: -The first argument to the 'shl' instruction must be an integer type. The second argument must be an -'ubyte' type. + The argument is the va_list to copy. Semantics: -The value produced is var1 * 2^var2. + 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. + -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 - + + + Accurate Garbage Collection Intrinsics + + + + +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. + + - 'shr' Instruction + + 'llvm.gcroot' Intrinsic + + Syntax: + - <result> = shr <ty> <var1>, ubyte <var2> ; yields {ty}:result + declare void %llvm.gcroot(<ty>** %ptrloc, <ty2>* %metadata) Overview: -The 'shr' instruction returns the first operand shifted to the right a specified number of bits. + +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 first argument to the 'shr' instruction must be an integer type. The second argument must be an 'ubyte' type. + + 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: -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. + 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. + + + + + + + + 'llvm.gcread' Intrinsic + + + + +Syntax: -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 + declare sbyte* %llvm.gcread(sbyte** %Ptr) +Overview: +The 'llvm.gcread' intrinsic identifies reads of references from heap +locations, allowing garbage collector implementations that require read +barriers. + +Arguments: +The argument is the address to read from, which should be an address +allocated from the garbage collector. +Semantics: - - - -Memory Access Operations - +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. -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. + - 'malloc' Instruction + + 'llvm.gcwrite' Intrinsic + + + Syntax: + - <result> = malloc <type>, uint <NumElements> ; yields {type*}:result - <result> = malloc <type> ; yields {type*}:result + declare void %llvm.gcwrite(sbyte* %P1, sbyte** %P2) Overview: -The 'malloc' instruction allocates memory from the system heap and returns a pointer to it. - Arguments: +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). -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. + Arguments: -'type' must be a sized type. + The first argument is the reference to store, and the second is the heap +location to store to. Semantics: -Memory is allocated using the system "malloc" function, and a pointer -is returned. + 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. -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 - + + + Code Generator Intrinsics + + + + +These intrinsics are provided by LLVM to expose special features that may only +be implemented with code generator support. + + + + - 'free' Instruction + + 'llvm.returnaddress' Intrinsic + + + Syntax: - free <type> <value> ; yields {void} + declare void* %llvm.returnaddress(uint <level>) - Overview: -The 'free' instruction returns memory back to the unused memory heap, to be reallocated in the future. + +The 'llvm.returnaddress' intrinsic returns a target-specific value +indicating the return address of the current function or one of its callers. + Arguments: -'value' shall be a pointer value that points to a value that was -allocated with the 'malloc' instruction. - + +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: -Access to the memory pointed to by the pointer is not longer defined after this instruction executes. + +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. + -Example: -- %array = malloc [4 x ubyte] ; yields {[4 x ubyte]*}:array - free [4 x ubyte]* %array - + +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. + + - 'alloca' Instruction + + 'llvm.frameaddress' Intrinsic + + + Syntax: - <result> = alloca <type>, uint <NumElements> ; yields {type*}:result - <result> = alloca <type> ; yields {type*}:result + declare void* %llvm.frameaddress(uint <level>) 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.frameaddress' intrinsic returns the target-specific frame +pointer value for the specified stack frame. + 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. + +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: -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 - + +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. + + - 'load' Instruction + + 'llvm.prefetch' Intrinsic + + + Syntax: - <result> = load <ty>* <pointer> - <result> = volatile load <ty>* <pointer> + declare void %llvm.prefetch(sbyte * <address>, + uint <rw>, uint <locality>) 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 '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. + -The location of memory pointed to is loaded. +Arguments: -Examples: -- %ptr = alloca int ; yields {int*}:ptr - store int 3, int* %ptr ; yields {void} - %val = load int* %ptr ; yields {int}:val = int 3 - + +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: + +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. + + - 'store' Instruction + + 'llvm.pcmarker' Intrinsic + + + Syntax: - store <ty> <value>, <ty>* <pointer> ; yields {void} - volatile store <ty> <value>, <ty>* <pointer> ; yields {void} + declare void %llvm.pcmarker( uint <id> ) Overview: -The 'store' instruction is used to write to memory. + + + +The 'llvm.pcmarker' intrinsic is a method to export a PC in a region of +code to simulators and other tools. The method is target specific, but it is +expected that the marker will use exported symbols to transmit the PC of the marker. +The marker makes no guaranties that it will remain with any specific instruction +after optimizations. It is possible that the presense of a marker will inhibit +optimizations. The intended use is to be inserted after optmizations to allow +corrolations 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. + Semantics: -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. + + + + + + Operating System Intrinsics + + + + +These intrinsics are provided by LLVM to support the implementation of +operating system level code. + + - 'getelementptr' Instruction + + 'llvm.readport' Intrinsic + + + Syntax: - <result> = getelementptr <ty>* <ptrval>{, long <aidx>|, ubyte <sidx>}* + declare <integer type> %llvm.readport (<integer type> <address>) Overview: -The 'getelementptr' instruction is used to get the address of a -subelement of an aggregate data structure. + +The 'llvm.readport' intrinsic reads data from the specified hardware +I/O port. + 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, 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: + +The argument to this intrinsic indicates the hardware I/O address from which +to read the data. The address is in the hardware I/O address namespace (as +opposed to being a memory location for memory mapped I/O). + --%RT = type { sbyte, [10 x [20 x int]], sbyte } -%ST = type { int, double, %RT } +Semantics: -int* "foo"(%ST* %s) { - %reg = getelementptr %ST* %s, long 1, ubyte 2, ubyte 1, long 5, long 13 - ret int* %reg -} - + +The 'llvm.readport' intrinsic reads data from the hardware I/O port +specified by address and returns the value. The address and return +value must be integers, but the size is dependent upon the platform upon which +the program is code generated. For example, on x86, the address must be an +unsigned 16-bit value, and the return value must be 8, 16, or 32 bits. + -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. + + + 'llvm.writeport' Intrinsic + -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: + +Syntax: -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 -} + call void (<integer type>, <integer type>)* + %llvm.writeport (<integer type> <value>, + <integer type> <address>) +Overview: + +The 'llvm.writeport' intrinsic writes data to the specified hardware +I/O port. + -Example: -- ; yields [12 x ubyte]*:aptr - %aptr = getelementptr {int, [12 x ubyte]}* %sptr, long 0, ubyte 1 - +Arguments: + +The first argument is the value to write to the I/O port. + + +The second argument indicates the hardware I/O address to which data should be +written. The address is in the hardware I/O address namespace (as opposed to +being a memory location for memory mapped I/O). + - - - -Other Operations - +Semantics: -The instructions in this catagory are the "miscellaneous" instructions, which defy better classification. + +The 'llvm.writeport' intrinsic writes value to the I/O port +specified by address. The address and value must be integers, but the +size is dependent upon the platform upon which the program is code generated. +For example, on x86, the address must be an unsigned 16-bit value, and the +value written must be 8, 16, or 32 bits in length. + + - 'phi' Instruction + + 'llvm.readio' Intrinsic + + + Syntax: - <result> = phi <ty> [ <val0>, <label0>], ... + declare <result> %llvm.readio (<ty> * <pointer>) Overview: -The 'phi' instruction is used to implement the φ node in the SSA -graph representing the function. + +The 'llvm.readio' intrinsic reads data from a memory mapped I/O +address. + 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 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 argument to this intrinsic is a pointer indicating the memory address from +which to read the data. The data must be a +first class type. + 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: + +The 'llvm.readio' intrinsic reads data from a memory mapped I/O +location specified by pointer and returns the value. The argument must +be a pointer, and the return value must be a +first class type. However, certain architectures +may not support I/O on all first class types. For example, 32-bit processors +may only support I/O on data types that are 32 bits or less. + --Loop: ; Infinite loop that counts from 0 on up... - %indvar = phi uint [ 0, %LoopHeader ], [ %nextindvar, %Loop ] - %nextindvar = add uint %indvar, 1 - br label %Loop - + +This intrinsic enforces an in-order memory model for llvm.readio and +llvm.writeio calls on machines that use dynamic scheduling. Dynamically +scheduled processors may execute loads and stores out of order, re-ordering at +run time accesses to memory mapped I/O registers. Using these intrinsics +ensures that accesses to memory mapped I/O registers occur in program order. + + - 'cast .. to' Instruction + + 'llvm.writeio' Intrinsic + + + Syntax: - <result> = cast <ty> <value> to <ty2> ; yields ty2 + declare void %llvm.writeio (<ty1> <value>, <ty2> * <pointer>) 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.writeio' intrinsic writes data to the specified memory +mapped I/O address. + 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 first argument is the value to write to the memory mapped I/O location. +The second argument is a pointer indicating the memory address to which the +data should be written. + 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. + +The 'llvm.writeio' intrinsic writes value to the memory mapped +I/O address specified by pointer. The value must be a +first class type. However, certain architectures +may not support I/O on all first class types. For example, 32-bit processors +may only support I/O on data types that are 32 bits or less. + -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'. + +This intrinsic enforces an in-order memory model for llvm.readio and +llvm.writeio calls on machines that use dynamic scheduling. Dynamically +scheduled processors may execute loads and stores out of order, re-ordering at +run time accesses to memory mapped I/O registers. Using these intrinsics +ensures that accesses to memory mapped I/O registers occur in program order. + -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 - + + + Standard C Library Intrinsics + + + +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. + + - 'call' Instruction + + 'llvm.memcpy' Intrinsic + + + Syntax: - <result> = call <ty>* <fnptrval>(<param list>) + declare void %llvm.memcpy(sbyte* <dest>, sbyte* <src>, + uint <len>, uint <align>) Overview: -The 'call' instruction represents a simple function call. - - Arguments: + +The 'llvm.memcpy' intrinsic copies a block of memory from the source +location to the destination location. + -This instruction requires several arguments: - + +Note that, unlike the standard libc function, the llvm.memcpy intrinsic +does not return a value, and takes an extra alignment argument. + -'ty': shall be the signature of the pointer to function value being -invoked. The argument types must match the types implied by this signature. + Arguments: - '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. + +The first argument is a pointer to the destination, the second is a pointer to +the source. The third argument is an (arbitrarily sized) integer argument +specifying the number of bytes to copy, and the fourth argument is the alignment +of the source and destination locations. + - '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. - + +If the call to this intrinisic has an alignment value that is not 0 or 1, then +the caller guarantees that the size of the copy is a multiple of the alignment +and that both the source and destination pointers are aligned to that boundary. + 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.memcpy' intrinsic copies a block of memory from the source +location to the destination location, which are not allowed to overlap. It +copies "len" bytes of memory over. If the argument is known to be aligned to +some boundary, this can be specified as the fourth argument, otherwise it should +be set to 0 or 1. + + - - 'vanext' Instruction + + 'llvm.memmove' Intrinsic + + + Syntax: - <resultarglist> = vanext <va_list> <arglist>, <argty> + declare void %llvm.memmove(sbyte* <dest>, sbyte* <src>, + uint <len>, uint <align>) 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 'llvm.memmove' intrinsic moves a block of memory from the source +location to the destination location. It is similar to the 'llvm.memcpy' +intrinsic but allows the two memory locations to overlap. + -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. + +Note that, unlike the standard libc function, the llvm.memmove intrinsic +does not return a value, and takes an extra alignment argument. + -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. + Arguments: -vanext is an LLVM instruction instead of an intrinsic function because it takes an type as an -argument. + +The first argument is a pointer to the destination, the second is a pointer to +the source. The third argument is an (arbitrarily sized) integer argument +specifying the number of bytes to copy, and the fourth argument is the alignment +of the source and destination locations. + -Example: + +If the call to this intrinisic has an alignment value that is not 0 or 1, then +the caller guarantees that the size of the copy is a multiple of the alignment +and that both the source and destination pointers are aligned to that boundary. + -See the variable argument processing section. + Semantics: + +The 'llvm.memmove' intrinsic copies a block of memory from the source +location to the destination location, which may overlap. It +copies "len" bytes of memory over. If the argument is known to be aligned to +some boundary, this can be specified as the fourth argument, otherwise it should +be set to 0 or 1. + + - 'vaarg' Instruction + + 'llvm.memset' Intrinsic + + + Syntax: - <resultval> = vaarg <va_list> <arglist>, <argty> + declare void %llvm.memset(sbyte* <dest>, ubyte <val>, + uint <len>, uint <align>) 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.memset' intrinsic fills a block of memory with a particular +byte value. + -Arguments: + +Note that, unlike the standard libc function, the llvm.memset intrinsic +does not return a value, and takes an extra alignment argument. + -This instruction takes a valist value and the type of the argument. It -returns a value of the specified argument type. +Arguments: -Semantics: + +The first argument is a pointer to the destination to fill, the second is the +byte value to fill it with, the third argument is an (arbitrarily sized) integer +argument specifying the number of bytes to fill, and the fourth argument is the +known alignment of destination location. + -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. + +If the call to this intrinisic has an alignment value that is not 0 or 1, then +the caller guarantees that the size of the copy is a multiple of the alignment +and that the destination pointer is aligned to that boundary. + -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. + Semantics: -vaarg is an LLVM instruction instead of an intrinsic function because it takes an type as an -argument. + +The 'llvm.memset' intrinsic fills "len" bytes of memory starting at the +destination location. If the argument is known to be aligned to some boundary, +this can be specified as the fourth argument, otherwise it should be set to 0 or +1. + + -Example: -See the variable argument processing section. + + + 'llvm.isunordered' Intrinsic + + +Syntax: ++ declare bool %llvm.isunordered(<float or double> Val1, <float or double> Val2) + +Overview: + +The 'llvm.isunordered' intrinsic returns true if either or both of the +specified floating point values is a NAN. + - - - -Intrinsic Functions - - +Arguments: -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...). + +The arguments are floating point numbers of the same type. + -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. + Semantics: -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. + +If either or both of the arguments is a SNAN or QNAN, it returns true, otherwise +false. + + - - -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. + + Bit Counting Intrinsics + -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) + + +LLVM provides intrinsics for a few important bit counting operations. +These allow efficient code generation for some algorithms. + - ; Stop processing of arguments. - call void %llvm.va_end(sbyte* %ap2) - ret int %tmp -} - + - 'llvm.va_start' Intrinsic + + 'llvm.ctpop' Intrinsic + + + Syntax: - call va_list ()* %llvm.va_start() + declare int %llvm.ctpop(int <src>) + Overview: -The 'llvm.va_start' intrinsic returns a new <arglist> -for subsequent use by the variable argument intrinsics. + +The 'llvm.ctpop' intrinsic counts the number of ones in a variable. + -Semantics: +Arguments: -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. + +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. + -Note that this intrinsic function is only legal to be called from within the -body of a variable argument function. + Semantics: + +The 'llvm.ctpop' intrinsic counts the 1's in a variable. + + - 'llvm.va_end' Intrinsic + + 'llvm.cttz' Intrinsic + + + Syntax: - call void (va_list)* %llvm.va_end(va_list <arglist>) + declare int %llvm.cttz(int <src>) + Overview: -The 'llvm.va_end' intrinsic destroys <arglist> which has -been initialized previously with llvm.va_start or llvm.va_copy. + +The 'llvm.cttz' intrinsic counts the number of trailing zeros. + 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.cttz' intrinsic counts the trailing zeros in a variable. If +the src == 0 then the result is the size in bits of the type of src. + + - 'llvm.va_copy' Intrinsic + + 'llvm.ctlz' Intrinsic + + + Syntax: - call va_list (va_list)* %llvm.va_copy(va_list <destarglist>) + declare int %llvm.ctlz(int <src>) + Overview: -The 'llvm.va_copy' intrinsic copies the current argument position from -the source argument list to the destination argument list. + +The 'llvm.ctlz' intrinsic counts the number of leading zeros in a +variable. + 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.ctlz' intrinsic counts the leading zeros in a variable. If +the src == 0 then the result is the size in bits of the type of src. + + - - - + + + Debugger Intrinsics + + + + +The LLVM debugger intrinsics (which all start with llvm.dbg. prefix), +are described in the LLVM Source Level +Debugging document. + + + - -Chris Lattner -The LLVM Compiler Infrastructure - - - -Last modified: Wed Oct 29 19:30:46 CST 2003 - - - + + + + + Chris Lattner + The LLVM Compiler Infrastructure + Last modified: $Date$ + + +

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