VLA_Allocate_Instruction

class VLA_Allocate_Instruction (concrete, logical)

Allocate memory for a C99 variable-length-array. The VLA variable is listed as Direct_Full_Write_Operand. After this instruction completes, the VLA is allocated but still uninitialized.

Direct parents:

• inherits Instruction

Ancestor classes and implemented interfaces:

Execution_Node, Instruction, Logical_IR_Root

Field	Kind	Type	Description
Left (from Instruction)	syntactic	class Direct_Full_Write_Operand	Operand specifying the VLA variable being allocated.
Variable_Dimensions	syntactic	list of class Direct_Full_Read_Operand	Operands reading from helper variables that hold the number of elements of this VLA. (one helper for each variable-length dimension, e.g., int arr[2][n][3][m] has two dimension variables: [n, m]) Note that a single dimension variable can be reused for multiple arrays, e.g., in typedef int vla_t[n]; vla_t arr1, arr2;. Dimension variables are always compiler-generated helpers which are initialized prior to the VLA_Allocate_Instruction and are never mutated after initialization.
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): The Physical edge points to the PIR Integer_Literal. The Left_Physical edge points to the Unqualified_Direct_Object_Selection for the variable v. And the Physical_For_Assignment edge points to the Assignment expression.
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): The Physical edge points to the PIR Integer_Literal. The Left_Physical edge points to the Unqualified_Direct_Object_Selection for the variable v. And the Physical_For_Assignment edge points to the Assignment expression.
Parent (from Logical_IR_Root)	semantic	class Logical_IR_Root
Physical (from Logical_IR_Root)	semantic to physical	class Physical_IR_Root