org.jikesrvm.compilers.opt.bc2ir

Class OperandStack

java.lang.Object

org.jikesrvm.compilers.opt.bc2ir.OperandStack

final class OperandStack
extends Object

Simulates the Java stack for abstract interpretation in BC2IR.

This class is intended to be used by a single thread. Methods from this class do not provide any error handling.

The total amount of Operands that can be accepted by an operand stack is called the capacity of the operand stack. It is determined when the stack is created. The capacity is distinct from the current number of operands on the stack which is called the size of the operand stack.

Field Summary

Fields

Modifier and Type	Field and Description
private Operand[]	stack
private int	top

Constructor Summary

Constructors

Constructor and Description
OperandStack(int capacity) Creates an operand stack.

Method Summary

Modifier and Type	Method and Description
(package private) void	clear()
(package private) OperandStack	createEmptyOperandStackWithSameCapacity() Returns a new, empty operand stack that has the same capacity as this one.
(package private) OperandStack	deepCopy() Returns a deep copy of the stack.
(package private) Operand	getFromBottom(int pos)
(package private) Operand	getFromTop(int n)
(package private) int	getSize() Returns the current size of the stack.
(package private) boolean	isEmpty()
(package private) Operand	pop()
(package private) void	pop2() Pops the two topmost operands from the stack and discards them.
(package private) void	push(Operand val)
(package private) void	replaceFromTop(int n, Operand op)
(package private) void	swap() Swaps the two topmost operands on the stack.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

stack

private final Operand[] stack

top

private int top

Constructor Detail

OperandStack

OperandStack(int capacity)

Creates an operand stack.

Parameters:

capacity - the maximum number of operands that the stack must be able to hold, must be >= 0

Method Detail

push

void push(Operand val)

pop

Operand pop()

pop2

void pop2()

Pops the two topmost operands from the stack and discards them.

This implements the pop2 bytecode.

getFromBottom

Operand getFromBottom(int pos)

getFromTop

Operand getFromTop(int n)

replaceFromTop

void replaceFromTop(int n,
                    Operand op)

swap

void swap()

Swaps the two topmost operands on the stack.

This implements the swap bytecode.

clear

void clear()

deepCopy

OperandStack deepCopy()

Returns a deep copy of the stack.

The copied stack has copies of the operands from the original stack. The size and capacity of the copied stack are equal to the original stack at the time of the copy.

Returns:

a copy of the stack

isEmpty

boolean isEmpty()

getSize

int getSize()

Returns the current size of the stack.

Returns:

the current number of operands on the stack

createEmptyOperandStackWithSameCapacity

OperandStack createEmptyOperandStackWithSameCapacity()

Returns a new, empty operand stack that has the same capacity as this one.

Returns:

a new operand stack