llvm Assembly Language Reference Manual

From: Chris Lattner Date: Thu, 8 May 2003 04:57:36 +0000 (+0000) Subject: * Add information about LLVM intrinsics X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=d9ad5b329f73e36f7f539438867340b98068b857;p=oota-llvm.git * Add information about LLVM intrinsics * Add information about the va_arg instruction * Add information about the llvm.va_* intrinsics git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6036 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/docs/LangRef.html b/docs/LangRef.html index 8ed470c6def..f1a8e37a0bb 100644 --- a/docs/LangRef.html +++ b/docs/LangRef.html @@ -1,9 +1,9 @@ -llvm Assembly Language Reference Manual +LLVM Assembly Language Reference Manual - +

llvm Assembly Language Reference Manual

LLVM Language Reference Manual

'phi' Instruction
'cast .. to' Instruction
'call' Instruction +
'va_arg' Instruction

- +

Intrinsic Functions +

Variable Argument Handling Intrinsics +
+

Written by Chris Lattner and Vikram Adve

@@ -130,7 +137,7 @@ simple SSA value instead of a memory location.

Well Formedness

-It is important to note that this document describes 'well formed' llvm assembly +It is important to note that this document describes 'well formed' LLVM assembly language. There is a difference between what the parser accepts and what is considered 'well formed'. For example, the following instruction is syntactically okay, but not well formed:

@@ -139,11 +146,11 @@ syntactically okay, but not well formed:

%x = add int 1, %x -...because the definition of %x does not dominate all of its uses. The LLVM -infrastructure provides a verification pass that may be used to verify that an -LLVM module is well formed. This pass is automatically run by the parser after -parsing input assembly, and by the optimizer before it outputs bytecode. The -violations pointed out by the verifier pass indicate bugs in transformation +...because the definition of %x does not dominate all of its uses. The +LLVM infrastructure provides a verification pass that may be used to verify that +an LLVM module is well formed. This pass is automatically run by the parser +after parsing input assembly, and by the optimizer before it outputs bytecode. +The violations pointed out by the verifier pass indicate bugs in transformation passes or input to the parser.

@@ -212,7 +219,7 @@ demonstrating instructions, we will follow an instruction with a comment that defines the type and name of value produced. Comments are shown in italic text.

-The one unintuitive notation for constants is the optional hexidecimal form of +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 @@ -1627,73 +1634,200 @@ case of the invoke instruction.

- +

'`va_arg`' Instruction

+ +

Syntax:

+  <result> = va_arg <va_list>* <arglist>, <retty>
+

+ +

Overview:

+ +The 'va_arg' instruction is used to access arguments passed through the +"variable argument" area of a function call. It corresponds directly to the +va_arg macro in C.

+ +

Arguments:

+ +This instruction takes a pointer to a valist value to read a new +argument from. The return type of the instruction is defined by the second +argument, a type.

+ +

Semantics:

+ +The 'va_arg' instruction works just like the va_arg macro +available in C. In a target-dependent way, it reads the argument indicated by +the value the arglist points to, updates the arglist, then returns a value of +the specified type. This instruction should be used in conjunction with the +variable argument handling

Intrinsic Functions

+ +It is legal for this instruction to be called in a function which does not take +a variable number of arguments, for example, the vfprintf function.

- +va_arg is an LLVM instruction instead of an intrinsic function because the return type depends on an +argument.

+ +

Example:

variable argument processing

+ +

-Related Work +Intrinsic Functions

+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.

-Codesigned virtual machines.

+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.

SafeTSA -: Description here
- -
Java -: Desciption here
+ +

+Variable Argument Handling Intrinsics +

Microsoft .net -

Desciption here

+Variable argument support is defined in LLVM with the va_arg instruction and these three intrinsic +functions. These function correspond almost directly to the similarly named +macros defined in the <stdarg.h> header file.

- -

GNU RTL Intermediate Representation -

Desciption here

+All of these functions operate on arguments that use a target-specific 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.

- -

IA64 Architecture & Instruction Set -

Desciption here

+This example shows how the va_arg instruction +and the variable argument handling intrinsic functions are used.

- -

MMIX Instruction Set -

Desciption here

+int %test(int %X, ...) {
+  ; Allocate two va_list items.  On this target, va_list is of type sbyte*
+  %ap = alloca sbyte*
+  %aq = alloca sbyte*
 
-
-"Interview With Bjarne Stroustrup"
-
This interview influenced the design and thought process behind LLVM in several ways, most notably the way that derived types are written in text format. See the question that starts with "you defined the C declarator syntax as an experiment that failed".
-
+  ; Initialize variable argument processing
+  call void (sbyte**, ...)* %llvm.va_start(sbyte** %ap, int %X)
 
-
-

Vectorized Architectures

+ ; Read a single integer argument + %tmp =

va_arg

Intel MMX, MMX2, SSE, SSE2 -: Description here
+ ; Demonstrate usage of llvm.va_copy and llvm_va_end + %apv = load sbyte** %ap + call void %llvm.va_copy(sbyte** %aq, sbyte* %apv) + call void %llvm.va_end(sbyte** %aq) - -
AMD 3Dnow!, 3Dnow! 2 -: Desciption here
+ ; Stop processing of arguments. + call void %llvm.va_end(sbyte** %ap) + ret int %tmp +} + - -
Sun VIS ISA -: Desciption here
+ +

'`llvm.va_start`' Intrinsic

PowerPC Altivec -

Desciption here

Syntax:

+  call void (va_list*, ...)* %llvm.va_start(<va_list>* <arglist>, <argument>)
+

- +

Overview:

-more... +The 'llvm.va_start' intrinsic initializes *<arglist> for +subsequent use by va_arg and llvm.va_end, and must be called before either are +invoked.

---> +

Arguments:

+ +The first argument is a pointer to a va_list element to initialize. +The second argument is required to be the last LLVM argument before the +ellipsis. In the future, this restriction may be relaxed (to allow it to be +other arguments).

+ +

Semantics:

+ +The 'llvm.va_start' intrinsic works just like the va_start +macro available in C. In a target-dependent way, it initializes the +va_list element the first argument points to, so that the next call to +va_arg will produce the first variable argument passed to the +function.

+ + + +

'`llvm.va_end`' Intrinsic

+ +

Syntax:

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

+ +

Overview:

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

llvm.va_begin

+ +

Arguments:

va_list

+ +

Semantics:

llvm.va_end

va_end

va_list

llvm.va_start

llvm.va_copy

llvm.va_end

+ + + + +

'`llvm.va_copy`' Intrinsic

+ +

Syntax:

+  call void (va_list*, va_list)* %va_copy(<va_list>* <destarglist>,
+                                          <va_list> <srcarglist>)
+

+ +

Overview:

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

+ +

Arguments:

+ +The first argument is a pointer to a va_list element to initialize. +The second argument is a va_list element to copy from.

+ + +

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 destination list. This intrinsic is necessary +because the

llvm.va_begin

@@ -1706,7 +1840,7 @@ more...

Chris Lattner

Well Formedness

'va_arg' Instruction

Syntax:

Overview:

Arguments:

Semantics:

Example:

Vectorized Architectures

'llvm.va_start' Intrinsic

Syntax:

Overview:

Arguments:

Semantics:

'llvm.va_end' Intrinsic

Syntax:

Overview:

Arguments:

Semantics:

'llvm.va_copy' Intrinsic

Syntax:

Overview:

Arguments:

Semantics:

'`va_arg`' Instruction

'`llvm.va_start`' Intrinsic

'`llvm.va_end`' Intrinsic

'`llvm.va_copy`' Intrinsic