- | float (int, int *) * |
- : Pointer to a function that takes an
+
+
+
+ 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. |
-
-
- | 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. |
-
+ 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.
+
+
-
+
+
+
+
+ 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.
+ |
+
+
- Structure 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.
+ |
+
+
+
+
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.
+ 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 list> }
+ < <# elements> x <elementtype> >
+ The number of elements is a constant integer value; elementtype may
+be any integral or floating point type.
+
Examples:
-
-
-
- | { int, int, int } |
- : a triple of three int values |
-
-
- | { float, int (int) * } |
- : A pair, where the first element is a float and the second
- element is a pointer to a function that takes an int, returning an
- int. |
-
+
+
+
+ <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.
+ |
+
-
-
-
-
+
Overview:
- As in many languages, the pointer type represents a pointer or reference to
-another object, which must live in memory.
+ Opaque types are used to represent unknown types in the system. This
+corresponds (for example) to the C notion of a foward declared structure type.
+In LLVM, opaque types can eventually be resolved to any type (not just a
+structure type).
Syntax:
+
- <type> *
+ opaque
Examples:
-
-
-
- | [4x int]* |
- : pointer to array of four
- int values |
-
-
- | int (int *) * |
- : A pointer to a function that takes an int, returning an
- int. |
-
+
+
+ |
+ opaque
+ |
+
+ An opaque type.
+ |
+
-
-
-
-
-
-
+
+
--->
+
+ LLVM has several different basic types of constants. This section describes
+them all and their syntax.
-
-
-
-
-
+
- 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:
+
+ - Boolean constants
-
-; Declare the string constant as a global constant...
-%.LC0 = internal constant [13 x sbyte] c"hello world\0A\00" ; [13 x sbyte]*
+ - The two strings 'true' and 'false' are both valid
+ constants of the bool type.
+
-; External declaration of the puts function
-declare int %puts(sbyte*) ; int(sbyte*)*
+ - Integer constants
-; Definition of main function
-int %main() { ; int()*
- ; Convert [13x sbyte]* to sbyte *...
- %cast210 = getelementptr [13 x sbyte]* %.LC0, long 0, long 0 ; sbyte*
+ - Standard integers (such as '4') are constants of the integer type. Negative numbers may be used with signed
+ integer types.
+
- ; Call puts function to write out the string to stdout...
- call int %puts(sbyte* %cast210) ; int
- ret int 0
-}
-
+ - Floating point constants
-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 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.
-
-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:
+ - Null pointer constants
-
-
-- internal
+
- The identifier 'null' is recognized as a null pointer constant
+ and must be of pointer type.
-- 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:
+
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.
+
+
- "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.
+
+
+
+
+ Aggregate constants arise from aggregation of simple constants
+and smaller aggregate constants.
-
-weak:
+
+ - Structure 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.
+ - Structure constants are represented with notation similar to structure
+ type definitions (a comma separated list of elements, surrounded by braces
+ ({})). For example: "{ int 4, float 17.0, int* %G }",
+ where "%G" is declared as "%G = external global int". Structure constants
+ must have structure type, and the number and
+ types of elements must match those specified by the type.
+
-
-- appending:
+
- Array constants
- - "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.
+ - Array constants are represented with notation similar to array type
+ definitions (a comma separated list of elements, surrounded by square brackets
+ ([])). For example: "[ int 42, int 11, int 74 ]". Array
+ constants must have array type, and the number and
+ types of elements must match those specified by the type.
+
-
-- externally visible:
+
- Packed constants
- - 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.
+ - Packed constants are represented with notation similar to packed type
+ definitions (a comma separated list of elements, surrounded by
+ less-than/greater-than's (<>)). For example: "< int 42,
+ int 11, int 74, int 100 >". Packed constants must have packed type, and the number and types of elements must
+ match those specified by the type.
+
-
+ Zero initialization
-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".
+ The string 'zeroinitializer' can be used to zero initialize a
+ value to zero of any type, including scalar and aggregate types.
+ This is often used to avoid having to print large zero initializers (e.g. for
+ large arrays), and is always exactly equivalent to using explicit zero
+ initializers.
+
+
- Global variables define regions of memory allocated at compilation time
-instead of run-time. Global variables may optionally be initialized. A
-variable may be defined as a global "constant", which indicates that the
-contents of the variable will never be modified (opening options for
-optimization). Constants must always have an initial value.
+ 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:
- 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.
+
+ %X = global int 17
+ %Y = global int 42
+ %Z = global [2 x int*] [ int* %X, int* %Y ]
+
- Functions
+
+
+ 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.
+
+
+
+
+
- LLVM function definitions are composed of a (possibly empty) argument list,
-an opening curly brace, a list of basic blocks, and a closing curly brace. LLVM
-function declarations are defined with the "declare" keyword, a
-function name, and a function signature.
+ 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:
- 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).
+
+ - cast ( CST to TYPE )
-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.
+ - Cast a constant to another type.
+ - getelementptr ( CSTPTR, IDX0, IDX1, ... )
+
+ - Perform the getelementptr operation on
+ constants. As with the getelementptr
+ instruction, the index list may have zero or more indexes, which are required
+ to make sense for the type of "CSTPTR".
+
+ - 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).
+
-
+
- The LLVM instruction set consists of several different classifications of
-instructions: terminator instructions, binary instructions, memory
-instructions, and 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.
-
+
- As mentioned previously, every basic block
-in a program ends with a "Terminator" instruction, which indicates which block
-should be executed after the current block is finished. These terminator
-instructions typically yield a 'void' value: they produce control flow,
-not values (the one exception being the 'invoke' instruction).
-
- There are five different terminator instructions: the 'ret' instruction, the 'br' instruction, the 'switch' instruction, the 'invoke' instruction, and the 'unwind' instruction.
+ As mentioned previously, every
+basic block in a program ends with a "Terminator" instruction, which
+indicates which block should be executed after the current block is
+finished. These terminator instructions typically yield a 'void'
+value: they produce control flow, not values (the one exception being
+the 'invoke' instruction).
+ There are six different terminator instructions: the 'ret' instruction, the 'br'
+instruction, the 'switch' instruction,
+the 'invoke' instruction, the 'unwind' instruction, and the 'unreachable' instruction.
-
-
+
-
Syntax:
-
- ret <type> <value> ; Return a value from a non-void function
+ ret <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
-
-
-
-
+
-
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
-
-
Syntax:
- switch uint <value>, label <defaultdest> [ int <val>, label &dest>, ... ]
+ switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]
Overview:
@@ -897,41 +1186,44 @@ several different places. It is a generalization of the ' br'
instruction, allowing a branch to occur to one of many possible
destinations.
+
Arguments:
- The 'switch' instruction uses three parameters: 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.
+ 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 ]
-
@@ -944,51 +1236,59 @@ of chained conditional branches, or with a lookup table.
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
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:
+ -
+ The optional "cconv" marker indicates which calling
+ convention the call should use. If none is specified, the call defaults
+ to using C calling conventions.
+
+ - 'ptr to function ty': shall be the signature of the pointer to
+ function value being invoked. In most cases, this is a direct function
+ invocation, but indirect invokes are just as possible, branching off
+ an arbitrary pointer to function value.
+
+
+ - 'function ptr val': An LLVM value containing a pointer to a
+ function to be invoked.
+
+ - 'function args': argument list whose types match the function
+ signature argument types. If the function signature indicates the function
+ accepts a variable number of arguments, the extra arguments can be
+ specified.
-- 'ptr to function ty': shall be the signature of the pointer to
-function value being invoked. In most cases, this is a direct function
-invocation, but indirect invokes are just as possible, branching off
-an arbitrary pointer to function value.
-
-
- 'function ptr val': An LLVM value containing a pointer to a
-function to be invoked.
-
-
- 'function args': argument list whose types match the function
-signature argument types. If the function signature indicates the function
-accepts a variable number of arguments, the extra arguments can be specified.
+
- 'normal label': the label reached when the called function
+ executes a 'ret' instruction.
-- 'normal label': the label reached when the called function executes
-a 'ret' instruction.
+
- 'exception label': the label reached when a callee returns with
+ the unwind instruction.
-- 'exception label': the label reached when a callee returns with the
-unwind instruction.
Semantics:
This instruction is designed to operate as a standard 'call' instruction in most regards. The primary
-difference is that it establishes an association with a label, which is used by the runtime library to unwind the stack.
+difference is that it establishes an association with a label, which is used by
+the runtime library to unwind the stack.
This instruction is used in languages with destructors to ensure that proper
cleanup is performed in the case of either a longjmp or a thrown
@@ -996,24 +1296,23 @@ exception. Additionally, this is important for implementation of
'catch' clauses in high-level languages that support them.
Example:
-
- %retval = invoke int %Test(int 15)
- to label %Continue
+ %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
-
Syntax:
-
unwind
@@ -1033,814 +1332,648 @@ href="#i_invoke"> invoke instruction on the call stack. Once found,
execution continues at the "exceptional" destination block specified by the
invoke instruction. If there is no invoke instruction in the
dynamic call chain, undefined behavior results.
-
-
-
+
+
+
- Binary 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.
+ Syntax:
+
+ unreachable
+
- There are several different binary operators:
+ Overview:
- The 'unreachable' instruction has no defined semantics. This
+instruction is used to inform the optimizer that a particular portion of the
+code is not reachable. This can be used to indicate that the code after a
+no-return function cannot be reached, and other facts.
-
-
- 'add' Instruction
+ Semantics:
+
+ The 'unreachable' instruction has no defined semantics.
- Syntax:
-
- <result> = add <ty> <var1>, <var2> ; yields {ty}:result
+
+
+
+ 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:
+
+ Syntax:
+ <result> = add <ty> <var1>, <var2> ; yields {ty}:result
-
Overview:
-
The 'add' instruction returns the sum of its two operands.
-
Arguments:
-
The two arguments to the 'add' instruction must be either integer or floating point
-values. Both arguments must have identical types.
-
+ href="#t_integer">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 sum of the two
operands.
-
Example:
-
-
- <result> = add int 4, %var ; yields {int}:result = 4 + %var
+ <result> = add int 4, %var ; yields {int}:result = 4 + %var
-
-
Syntax:
-
-
- <result> = sub <ty> <var1>, <var2> ; yields {ty}:result
+ <result> = sub <ty> <var1>, <var2> ; yields {ty}:result
-
Overview:
-
The 'sub' instruction returns the difference of its two
operands.
-
-Note that the 'sub' instruction is used to represent the
-'neg' instruction present in most other intermediate
-representations.
-
+Note that the 'sub' instruction is used to represent the 'neg'
+instruction present in most other intermediate representations.
Arguments:
-
The two arguments to the 'sub' instruction must be either integer or floating point
-values. Both arguments must have identical types.
-
+ href="#t_integer">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 difference of
+the two operands.
Example:
-
-
- <result> = sub 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
-
-
Syntax:
-
-
- <result> = mul <ty> <var1>, <var2> ; yields {ty}:result
+ <result> = mul <ty> <var1>, <var2> ; yields {ty}:result
-
Overview:
-
-The 'mul' instruction returns the product of its two operands.
-
+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. Both arguments must have identical types.
-
+ href="#t_integer">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 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
+ <result> = mul int 4, %var ; yields {int}:result = 4 * %var
-
-
Syntax:
-
-
- <result> = div <ty> <var1>, <var2> ; yields {ty}:result
+ <result> = div <ty> <var1>, <var2> ; yields {ty}:result
-
Overview:
-
-The 'div' instruction returns the quotient of its two operands.
-
+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. Both arguments must have identical types.
-
+ href="#t_integer">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.
-
+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
+ <result> = div int 4, %var ; yields {int}:result = 4 / %var
-
-
Syntax:
-
-
- <result> = rem <ty> <var1>, <var2> ; yields {ty}:result
+ <result> = rem <ty> <var1>, <var2> ; yields {ty}:result
-
Overview:
-
-The 'rem' instruction returns the remainder from the division of its
-two operands.
-
+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. Both arguments must have identical types.
-
+ href="#t_integer">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.
-
+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
+ <result> = rem int 4, %var ; yields {int}:result = 4 % %var
-
-
Syntax:
-
-
- <result> = seteq <ty> <var1>, <var2> ; yields {bool}:result
+ <result> = seteq <ty> <var1>, <var2> ; yields {bool}:result
<result> = setne <ty> <var1>, <var2> ; yields {bool}:result
<result> = setlt <ty> <var1>, <var2> ; yields {bool}:result
<result> = setgt <ty> <var1>, <var2> ; yields {bool}:result
<result> = setle <ty> <var1>, <var2> ; yields {bool}:result
<result> = setge <ty> <var1>, <var2> ; yields {bool}:result
-
-Overview:
-
-The 'setcc' family of instructions returns a boolean value
-based on a comparison of their two operands.
-
-Arguments:
-
-The two arguments to the 'setcc' instructions must be of first class type (it is not possible to compare
-'label's, 'array's, 'structure' or 'void'
-values, etc...). Both arguments must have identical types.
-
+Overview:
+The 'setcc' family of instructions returns a boolean
+value based on a comparison of their two operands.
+Arguments:
+The two arguments to the 'setcc' instructions must
+be of first class type (it is not possible
+to compare 'label's, 'array's, 'structure'
+or 'void' values, etc...). Both arguments must have identical
+types.
Semantics:
-
-The 'seteq' instruction yields a true 'bool' value
-if both operands are equal.
-
-The 'setne' instruction yields a true 'bool' value if
-both operands are unequal.
-
-The 'setlt' instruction yields a true 'bool' value if
-the first operand is less than the second operand.
-
-The 'setgt' instruction yields a true 'bool' value if
-the first operand is greater than the second operand.
-
-The 'setle' instruction yields a true 'bool' value if
-the first operand is less than or equal to the second operand.
-
-The 'setge' instruction yields a true 'bool' value if
-the first operand is greater than or equal to the second operand.
-
+The 'seteq' instruction yields a true 'bool'
+value if both operands are equal.
+The 'setne' instruction yields a true 'bool'
+value if both operands are unequal.
+The 'setlt' instruction yields a true 'bool'
+value if the first operand is less than the second operand.
+The 'setgt' instruction yields a true 'bool'
+value if the first operand is greater than the second operand.
+The 'setle' instruction yields a true 'bool'
+value if the first operand is less than or equal to the second operand.
+The 'setge' instruction yields a true 'bool'
+value if the first operand is greater than or equal to the second
+operand.
Example:
-
-
- <result> = seteq int 4, 5 ; yields {bool}:result = false
+ <result> = seteq int 4, 5 ; yields {bool}:result = false
<result> = setne float 4, 5 ; yields {bool}:result = true
<result> = setlt uint 4, 5 ; yields {bool}:result = true
<result> = setgt sbyte 4, 5 ; yields {bool}:result = false
<result> = setle sbyte 4, 5 ; yields {bool}:result = true
<result> = setge sbyte 4, 5 ; yields {bool}:result = false
-
-
- Bitwise binary 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.
-
+ Bitwise binary operators are used to do various forms of
+bit-twiddling in a program. They are generally very efficient
+instructions and can commonly be strength reduced from other
+instructions. They require two operands, execute an operation on them,
+and produce a single value. The resulting value of the bitwise binary
+operators is always the same type as its first operand.
-
Syntax:
-
-
- <result> = and <ty> <var1>, <var2> ; yields {ty}:result
+ <result> = and <ty> <var1>, <var2> ; yields {ty}:result
-
Overview:
-
-The 'and' instruction returns the bitwise logical and of its two
-operands.
-
+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.
-
+ href="#t_integral">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 |
-
-
-
+
+
+ | 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 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
-
-
-
-
+
-
Syntax:
-
-
- <result> = or <ty> <var1>, <var2> ; yields {ty}:result
+ <result> = or <ty> <var1>, <var2> ; yields {ty}:result
-
-Overview:
-
-The 'or' instruction returns the bitwise logical inclusive or of its
-two operands.
-
+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.
-
+ href="#t_integral">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 |
-
-
-
+
+
+
+
+
+ | 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 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
-
-
Syntax:
-
-
- <result> = xor <ty> <var1>, <var2> ; yields {ty}:result
+ <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.
-
+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.
-
+ href="#t_integral">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 |
-
-
-
+
+
+
+
+
+ | 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 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
-
-
Syntax:
-
-
- <result> = shl <ty> <var1>, ubyte <var2> ; yields {ty}:result
+ <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.
-
+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.
-
+ href="#t_integer">integer type. The second argument must be an 'ubyte'
+type.
Semantics:
-
The value produced is var1 * 2var2.
-
Example:
-
-
- <result> = shl int 4, ubyte %var ; yields {int}:result = 4 << %var
+ <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
-
-
Syntax:
-
-
- <result> = shr <ty> <var1>, ubyte <var2> ; yields {ty}:result
+ <result> = shr <ty> <var1>, ubyte <var2> ; yields {ty}:result
-
Overview:
-
-The 'shr' instruction returns the first operand shifted to the right
-a specified number of bits.
-
+The 'shr' instruction returns the first operand shifted to
+the right a specified number of bits.
Arguments:
-
The first argument to the 'shr' instruction must be an integer type. The second argument must be an
-'ubyte' type.
-
+ href="#t_integer">integer type. The second argument must be an 'ubyte'
+type.
Semantics:
-
-If the first argument is a signed type, the most
-significant bit is duplicated in the newly free'd bit positions. If the first
-argument is unsigned, zero bits shall fill the empty positions.
-
+If the first argument is a signed type, the
+most significant bit is duplicated in the newly free'd bit positions.
+If the first argument is unsigned, zero bits shall fill the empty
+positions.
Example:
-
-
- <result> = shr int 4, ubyte %var ; yields {int}:result = 4 >> %var
+ <result> = shr int 4, ubyte %var ; yields {int}:result = 4 >> %var
<result> = shr uint 4, ubyte 1 ; yields {uint}:result = 2
<result> = shr int 4, ubyte 2 ; yields {int}:result = 1
<result> = shr sbyte 4, ubyte 3 ; yields {sbyte}:result = 0
<result> = shr sbyte -2, ubyte 1 ; yields {sbyte}:result = -1
-
-
- A key design point of an SSA-based representation is how it represents
-memory. In LLVM, no memory locations are in SSA form, which makes things very
-simple. This section describes how to read, write, allocate and free memory in
-LLVM.
-
+ A key design point of an SSA-based representation is how it
+represents memory. In LLVM, no memory locations are in SSA form, which
+makes things very simple. This section describes how to read, write,
+allocate, and free memory in LLVM.
-
Syntax:
-
-
- <result> = malloc <type>, uint <NumElements> ; yields {type*}:result
+ <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.
-
+The 'malloc' instruction allocates memory from the system
+heap and returns a pointer to it.
Arguments:
-
-The the 'malloc' instruction allocates
-sizeof(<type>)*NumElements bytes of memory from the operating
-system, and returns a pointer of the appropriate type to the program. The
-second form of the instruction is a shorter version of the first instruction
-that defaults to allocating one element.
-
+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.
-
+Memory is allocated using the system "malloc" function, and
+a pointer is returned.
Example:
+ %array = malloc [4 x ubyte ] ; yields {[%4 x ubyte]*}:array
-
- %array = malloc [4 x ubyte ] ; yields {[%4 x ubyte]*}:array
-
- %size = add uint 2, 2 ; yields {uint}:size = uint 4
+ %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
-
-
Syntax:
-
-
- free <type> <value> ; yields {void}
+ free <type> <value> ; yields {void}
-
Overview:
-
-The 'free' instruction returns memory back to the unused memory
-heap, to be reallocated in the future.
-
+ 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.
-
+'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 not longer defined after
-this instruction executes.
-
+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
+ %array = malloc [4 x ubyte] ; yields {[4 x ubyte]*}:array
free [4 x ubyte]* %array
-
-
Syntax:
-
-
- <result> = alloca <type>, uint <NumElements> ; yields {type*}:result
+ <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.
-
+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 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.
-
+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 invoke
+ 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 ; yields {int*}:ptr
%ptr = alloca int, uint 4 ; yields {int*}:ptr
-
-
Syntax:
-
-
- <result> = load <ty>* <pointer>
- <result> = volatile load <ty>* <pointer>
-
-
+ <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.
-
+ 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}
+ %ptr = alloca int ; yields {int*}:ptr
+ store int 3, int* %ptr ; yields {void}
%val = load int* %ptr ; yields {int}:val = int 3
-
Syntax:
-
-
- store <ty> <value>, <ty>* <pointer> ; yields {void}
+ 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.
-
+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}
+ %ptr = alloca int ; yields {int*}:ptr
+ store int 3, int* %ptr ; yields {void}
%val = load int* %ptr ; yields {int}:val = int 3
-
-
-
-
Syntax:
-
- <result> = getelementptr <ty>* <ptrval>{, long <aidx>|, ubyte <sidx>}*
+ <result> = getelementptr <ty>* <ptrval>{, <ty> <idx>}*
Overview:
- The 'getelementptr' instruction is used to get the address of a
+
+The 'getelementptr' instruction is used to get the address of a
subelement of an aggregate data structure.
Arguments:
- This instruction takes a list of long values and ubyte
-constants that indicate what form of addressing to perform. The actual types of
-the arguments provided depend on the type of the first pointer argument. The
+ 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.
+levels of a structure or to a specific index in an array. 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:
+ 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];
-}
+ 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 }
+ %RT = type { sbyte, [10 x [20 x int]], sbyte }
+ %ST = type { int, double, %RT }
-int* "foo"(%ST* %s) {
- %reg = getelementptr %ST* %s, long 1, ubyte 2, ubyte 1, long 5, long 13
- ret int* %reg
-}
+ 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 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.
+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
@@ -1849,48 +1982,74 @@ 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.
+' int' type. The ' getelementptr' instruction returns 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:
+ Note that it is perfectly legal to index partially through a
+structure, returning a pointer to an inner element. Because of this,
+the LLVM code for the given testcase is equivalent to:
-int* "foo"(%ST* %s) {
- %t1 = getelementptr %ST* %s , long 1 ; yields %ST*:%t1
- %t2 = getelementptr %ST* %t1, long 0, ubyte 2 ; yields %RT*:%t2
- %t3 = getelementptr %RT* %t2, long 0, ubyte 1 ; yields [10 x [20 x int]]*:%t3
- %t4 = getelementptr [10 x [20 x int]]* %t3, long 0, long 5 ; yields [20 x int]*:%t4
- %t5 = getelementptr [20 x int]* %t4, long 0, long 13 ; yields int*:%t5
- ret int* %t5
-}
+ 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
+ }
+ Note that it is undefined to access an array out of bounds: array and
+pointer indexes must always be within the defined bounds of the array type.
+The one exception for this rules is zero length arrays. These arrays are
+defined to be accessible as variable length arrays, which requires access
+beyond the zero'th element.
+
Example:
- ; yields [12 x ubyte]*:aptr
- %aptr = getelementptr {int, [12 x ubyte]}* %sptr, long 0, ubyte 1
+ ; 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.
-
+
+
-
- The instructions in this catagory are the "miscellaneous" instructions, which
-defy better classification.
-
+ 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
@@ -1898,45 +2057,58 @@ defy better classification.
Syntax:
- <result> = phi <ty> [ <val0>, <label0>], ...
+ <result> = cast <ty> <value> to <ty2> ; yields ty2
Overview:
- The 'phi' instruction is used to implement the φ node in the SSA
-graph representing the function.
+
+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 type of the incoming values are specified with the first type field.
-After this, the 'phi' instruction takes a list of pairs as arguments,
-with one pair for each predecessor basic block of the current block. Only
-values of first class type may be used as the value
-arguments to the PHI node. Only labels may be used as the label arguments.
-
- There must be no non-phi instructions between the start of a basic block and
-the PHI instructions: i.e. PHI instructions must be first in a basic block.
+
+The '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:
- 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.
+
+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:
-Loop: ; Infinite loop that counts from 0 on up...
- %indvar = phi uint [ 0, %LoopHeader ], [ %nextindvar, %Loop ]
- %nextindvar = add uint %indvar, 1
- br label %Loop
+ %X = cast int 257 to ubyte ; yields ubyte:1
+ %Y = cast int 123 to bool ; yields bool:true
-
@@ -1944,45 +2116,41 @@ Loop: ; Infinite loop that counts from 0 on up...
Syntax:
- <result> = cast <ty> <value> to <ty2> ; yields ty2
+ <result> = select bool <cond>, <ty> <val1>, <ty> <val2> ; yields ty
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 'select' instruction is used to choose one value based on a
+condition, without branching.
+
+
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 'select' instruction requires a boolean value indicating the condition, and two values of the same first class type.
+
Semantics:
- This instruction follows the C rules for explicit casts when determining how
-the data being cast must change to fit in its new container.
-
- When casting to bool, any value that would be considered true in the context
-of a C 'if' condition is converted to the boolean 'true'
-values, all else are 'false'.
-
- When extending an integral value from a type of one signness to another (for
-example 'sbyte' to 'ulong'), the value is sign-extended if the
-source value is signed, and zero-extended if the source value is
-unsigned. bool values are always zero extended into either zero or
-one.
+
+If the boolean condition evaluates to true, the instruction returns the first
+value argument; otherwise, it returns the second value argument.
+
Example:
- %X = cast int 257 to ubyte ; yields ubyte:1
- %Y = cast int 123 to bool ; yields bool:true
+ %X = select bool true, ubyte 17, ubyte 42 ; yields ubyte:17
-
+
+
+
+
'call' Instruction
@@ -1991,9 +2159,8 @@ one.
Syntax:
-
- <result> = call <ty>* <fnptrval>(<param list>)
+ <result> = [tail] call [cconv] <ty>* <fnptrval>(<param list>)
Overview:
@@ -2005,44 +2172,63 @@ one.
This instruction requires several arguments:
-
- 'ty': shall be the signature of the pointer to function value
- being invoked. The argument types must match the types implied by this
- signature. 'fnptrval': An LLVM value containing a pointer to a function
- to be invoked. In most cases, this is a direct function invocation, but
- indirect calls are just as possible, calling an arbitrary pointer to
- function values. 'function args': argument list whose types match the function
- signature argument types. If the function signature indicates the function
- accepts a variable number of arguments, the extra arguments can be
- specified. -
+
The optional "tail" marker indicates whether the callee function accesses
+ any allocas or varargs in the caller. If the "tail" marker is present, the
+ function call is eligible for tail call optimization. Note that calls may
+ be marked "tail" even if they do not occur before a ret instruction.
+
+ -
+
The optional "cconv" marker indicates which calling
+ convention the call should use. If none is specified, the call defaults
+ to using C calling conventions.
+
+ -
+
'ty': shall be the signature of the pointer to function value
+ being invoked. The argument types must match the types implied by this
+ signature. This type can be omitted if the function is not varargs and
+ if the function type does not return a pointer to a function.
+
+ -
+
'fnptrval': An LLVM value containing a pointer to a function to
+ be invoked. In most cases, this is a direct function invocation, but
+ indirect calls are just as possible, calling an arbitrary pointer
+ to function value.
+
+ -
+
'function args': argument list whose types match the
+ function signature argument types. All arguments must be of
+ first class type. If the function signature
+ indicates the function accepts a variable number of arguments, the extra
+ arguments can be specified.
+
Semantics:
- The 'call' instruction is used to cause control flow to transfer to
-a specified function, with its incoming arguments bound to the specified values.
-Upon a 'ret' instruction in the called function,
-control flow continues with the instruction after the function call, and the
-return value of the function is bound to the result argument. This is a simpler
-case of the invoke instruction.
+ The 'call' instruction is used to cause control flow to
+transfer to a specified function, with its incoming arguments bound to
+the specified values. Upon a 'ret'
+instruction in the called function, control flow continues with the
+instruction after the function call, and the return value of the
+function is bound to the result argument. This is a simpler case of
+the invoke instruction.
Example:
%retval = call int %test(int %argc)
call int(sbyte*, ...) *%printf(sbyte* %msg, int 12, sbyte 42);
+ %X = tail call int %foo()
+ %Y = tail call fastcc int %foo()
@@ -2050,34 +2236,36 @@ case of the invoke instruction.
Syntax:
- <resultarglist> = vanext <va_list> <arglist>, <argty>
+ <resultval> = va_arg <va_list*> <arglist>, <argty>
Overview:
- The 'vanext' instruction is used to access arguments passed through
+ The 'va_arg' instruction is used to access arguments passed through
the "variable argument" area of a function call. It is used to implement the
va_arg macro in C.
Arguments:
- This instruction takes a valist value and the type of the argument.
-It returns another valist.
+ This instruction takes a va_list* value and the type of
+the argument. It returns a value of the specified argument type and
+increments the va_list to poin to the next argument. Again, the
+actual type of va_list is target specific.
Semantics:
- The 'vanext' instruction advances the specified valist past
-an argument of the specified type. In conjunction with the vaarg instruction, it is used to implement the
-va_arg macro available in C. For more information, see the variable
-argument handling Intrinsic Functions.
+ The 'va_arg' instruction loads an argument of the specified
+type from the specified va_list and causes the
+va_list to point to the next argument. For more information,
+see the variable argument handling Intrinsic
+Functions.
It is legal for this instruction to be called in a function which does not
take a variable number of arguments, for example, the vfprintf
function.
- vanext is an LLVM instruction instead of an intrinsic function because it takes an type as an
+ va_arg is an LLVM instruction instead of an intrinsic function because it takes a type as an
argument.
Example:
@@ -2086,126 +2274,252 @@ argument.
-
-
+
+
+
- Syntax:
+ 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.
-
- <resultval> = vaarg <va_list> <arglist>, <argty>
-
- Overview:
+ To learn how to add an intrinsic function, please see the Extending LLVM Guide.
+
- The 'vaarg' instruction is used to access arguments passed through
-the "variable argument" area of a function call. It is used to implement the
-va_arg macro in C.
+
- Arguments:
+
+
- This instruction takes a valist value and the type of the argument.
-It returns a value of the specified argument type.
+
- Semantics:
+ 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.
- 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.
+ 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.
- 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.
+ This example shows how the vanext
+instruction and the variable argument handling intrinsic functions are
+used.
- vaarg is an LLVM instruction instead of an intrinsic function because it takes an type as an
-argument.
+
+int %test(int %X, ...) {
+ ; Initialize variable argument processing
+ %ap = alloca sbyte*
+ call void %llvm.va_start(sbyte** %ap)
-Example:
+ ; Read a single integer argument
+ %tmp = va_arg sbyte** %ap, int
-See the variable argument processing section.
+ ; Demonstrate usage of llvm.va_copy and llvm.va_end
+ %aq = alloca sbyte*
+ call void %llvm.va_copy(sbyte** %aq, sbyte** %ap)
+ call void %llvm.va_end(sbyte** %aq)
+ ; Stop processing of arguments.
+ call void %llvm.va_end(sbyte** %ap)
+ ret int %tmp
+}
+
-
-
- Intrinsic Functions
+
+
-
+
+ Syntax:
+ declare void %llvm.va_start(<va_list>* <arglist>)
+ Overview:
+ The 'llvm.va_start' intrinsic initializes
+*<arglist> for subsequent use by va_arg.
- 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...).
+ Arguments:
- 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.
+ The argument is a pointer to a va_list element to initialize.
+
+ 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 argument points to, so that the next call to
+va_arg will produce the first variable argument passed to the function.
+Unlike the C va_start macro, this intrinsic does not need to know the
+last argument of the function, the compiler can figure that out.
+
+
+
+
+
+
+
+ Syntax:
+ 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.
+
+
+
+
+
+
+
+ Syntax:
+
+
+ declare void %llvm.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 pointer to a va_list element to copy from.
- 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.
+
+ 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 intrinsic may be
+arbitrarily complex and require memory allocation, for example.
- 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.
+
+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.
+
+
+
+
+
- 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.
+ Syntax:
-int %test(int %X, ...) {
- ; Initialize variable argument processing
- %ap = call sbyte*()* %llvm.va_start()
+ declare void %llvm.gcroot(<ty>** %ptrloc, <ty2>* %metadata)
+
- ; Read a single integer argument
- %tmp = vaarg sbyte* %ap, int
+ Overview:
- ; Advance to the next argument
- %ap2 = vanext sbyte* %ap, int
+ The 'llvm.gcroot' intrinsic declares the existence of a GC root to
+the code generator, and allows some metadata to be associated with it.
- ; 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)
+ Arguments:
- ; Stop processing of arguments.
- call void % llvm.va_end(sbyte* %ap2)
- ret int %tmp
-}
+ 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:
+
+ At runtime, a call to this intrinsics stores a null pointer into the "ptrloc"
+location. At compile-time, the code generator generates information to allow
+the runtime to find the pointer at GC safe points.
+
+
+
+
+
+
+
+
+
+
+ Syntax:
+
+
+ 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:
+
+ 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.
+
+
@@ -2213,103 +2527,794 @@ int %test(int %X, ...) {
Syntax:
- call va_list ()* %llvm.va_start()
+ declare void %llvm.gcwrite(sbyte* %P1, sbyte** %P2)
Overview:
- The 'llvm.va_start' intrinsic returns a new <arglist>
-for subsequent use by the variable argument intrinsics.
+ The 'llvm.gcwrite' intrinsic identifies writes of references to heap
+locations, allowing garbage collector implementations that require write
+barriers (such as generational or reference counting collectors).
+
+ Arguments:
+
+ The first argument is the reference to store, and the second is the heap
+location to store to.
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.
+ 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.
+
+
+
+
+
+
+
- Note that this intrinsic function is only legal to be called from within the
-body of a variable argument function.
+
+
+These intrinsics are provided by LLVM to expose special features that may only
+be implemented with code generator support.
+
Syntax:
+
+ declare void* %llvm.returnaddress(uint <level>)
+
+
+ Overview:
+
+
+The 'llvm.returnaddress' intrinsic returns a target-specific value
+indicating the return address of the current function or one of its callers.
+
+
+ Arguments:
+
+
+The argument to this intrinsic indicates which function to return the address
+for. Zero indicates the calling function, one indicates its caller, etc. The
+argument is required to be a constant integer value.
+
+ Semantics:
+
+
+The 'llvm.returnaddress' intrinsic either returns a pointer indicating
+the return address of the specified call frame, or zero if it cannot be
+identified. The value returned by this intrinsic is likely to be incorrect or 0
+for arguments other than zero, so it should only be used for debugging purposes.
+
+
+
+Note that calling this intrinsic does not prevent function inlining or other
+aggressive transformations, so the value returned may not be that of the obvious
+source-language caller.
+
+
+
+
+
+
+
+
+
+ Syntax:
- call void (va_list)* %llvm.va_end(va_list <arglist>)
+ declare void* %llvm.frameaddress(uint <level>)
Overview:
- The 'llvm.va_end' intrinsic destroys <arglist> which
-has been initialized previously with llvm.va_start or llvm.va_copy.
+
+The 'llvm.frameaddress' intrinsic returns the target-specific frame
+pointer value for the specified stack frame.
+
Arguments:
- The argument is a va_list to destroy.
+
+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:
- 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.frameaddress' intrinsic either returns a pointer indicating
+the frame address of the specified call frame, or zero if it cannot be
+identified. The value returned by this intrinsic is likely to be incorrect or 0
+for arguments other than zero, so it should only be used for debugging purposes.
+
+
+Note that calling this intrinsic does not prevent function inlining or other
+aggressive transformations, so the value returned may not be that of the obvious
+source-language caller.
+
Syntax:
+
+ declare void %llvm.prefetch(sbyte * <address>,
+ uint <rw>, uint <locality>)
+
+
+ Overview:
+
+
+The 'llvm.prefetch' intrinsic is a hint to the code generator to insert
+a prefetch instruction if supported; otherwise, it is a noop. Prefetches have
+no
+effect on the behavior of the program but can change its performance
+characteristics.
+
+
+ Arguments:
+
+
+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.
+
+
+
+
+
+
+
+
+
+ Syntax:
- call va_list (va_list)* %llvm.va_copy(va_list <destarglist>)
+ declare void %llvm.pcmarker( uint <id> )
Overview:
- The 'llvm.va_copy' intrinsic copies the current argument position
-from the source argument list to the destination argument list.
+
+
+The 'llvm.pcmarker' intrinsic is a method to export a Program Counter
+(PC) in a region of
+code to simulators and other tools. The method is target specific, but it is
+expected that the marker will use exported symbols to transmit the PC of the marker.
+The marker makes no 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
+correlations of simulation runs.
+
Arguments:
- The argument is the va_list to copy.
+
+id is a numerical id identifying the marker.
+
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.
+
+This intrinsic does not modify the behavior of the program. Backends that do not
+support this intrinisic may ignore it.
+
-
-
- |
