Va_Arg_Instruction

class Va_Arg_Instruction (concrete, logical)

Obtains a pointer to a variable argument, as in: Left = &va_arg(*Operand, Argument_Type).

C int i = va_arg(ap, int); will compile to two instructions: * b2h1: int* = Va_Arg_Instruction int(&ap) : int* * ``i = Copy_Assignment_Instruction *b2h1

This instruction obtains a pointer of appropriate type to the variable argument that the va_list is currently pointing to. It also mutates the va_list, advancing it to the next variable argument.

The input operand is passed as a pointer (va_list*) to represent this mutation of the input argument pointer. The output is a pointer because some modes (e.g. MSVC) allow taking the address of the variable arguments (&va_arg(ap, int)).

Direct parents:
Ancestor classes and implemented interfaces:

Execution_Node, Instruction, Logical_IR_Root, Unary_Instruction, Variable_Argument_Instruction

Field

Kind

Type

Description

Argument_Type

semantic

class Type

The type of the variable argument.

Right (from Unary_Instruction)

syntactic

interface Reading_Or_Address_Operand_Interface

The input operand of the unary operator.

Left (from Instruction)

syntactic

class Operand

Where the result will be stored. This is always a write operand. (can be NULL, e.g., for calls to void funcs or assertion instructions. Check cafe’s can_omit_lhs() for the full list of instructions that can have Left equal to NoNode.)

Left_Physical (from Instruction)

semantic to physical

class Physical_IR_Root

This edge instead points to the expression that represents the left operand, i.e., the expression that computed the glvalue where the result of the instruction will be stored.

For example, in v = 42; (a LIR Integer_Literal_Instruction):

Its_Type (from Instruction)

semantic

class Type

Result type of the instruction, needed especially to distinguish assignments of complete structs from assignments of their first fields. Also needed to determine multiplication factor for pointer additions. For Cast_Instructions, this is the type casted to

Physical_For_Assignment (from Instruction)

semantic to physical

class Physical_IR_Root

Returns a PIR node for the assignment of the value that was computed by this instruction.

For example, in v = 42; (a LIR Integer_Literal_Instruction):

Parent (from Logical_IR_Root)

semantic

class Logical_IR_Root

Physical (from Logical_IR_Root)

semantic to physical

class Physical_IR_Root