Package org.codehaus.groovy.classgen.asm

Class OperandStack

java.lang.Object

org.codehaus.groovy.classgen.asm.OperandStack

public class OperandStack
extends Object

Tracks the JVM operand stack during bytecode generation, maintaining a parallel list of ClassNode type descriptors for each slot. Used to emit correct pop/cast/box instructions and to verify stack discipline.

Constructor Summary

Constructors

Constructor	Description
OperandStack(WriterController controller)	Creates an operand stack tracker backed by the given controller.

Method Summary

Modifier and Type	Method	Description
ClassNode	box()	Boxes the top operand if it is a primitive type, emitting the appropriate wrapper-creation bytecode, and returns the resulting (possibly wrapped) type.
void	castToBool(int mark, boolean emptyDefault)	ensure last marked parameter on the stack is a primitive boolean if mark==stack size, we assume an empty expression or statement.
void	doAsType(ClassNode targetType)	Performs an as-coercion of the top operand to targetType.
void	doGroovyCast(ClassNode targetType)	do Groovy cast for top level element
void	doGroovyCast(Variable v)	Performs a Groovy cast of the top operand to the declared origin type of v.
void	dup()	duplicate top element
int	getStackLength()	Returns the number of tracked entries on the operand stack.
ClassNode	getTopOperand()	Returns the type of the top element on the tracked operand stack without removing it.
org.objectweb.asm.Label	jump(int ifIns)	Emits a conditional jump instruction and returns the newly created target label.
void	jump(int ifIns, org.objectweb.asm.Label label)	Emits a conditional jump to the given label.
void	load(ClassNode type, int idx)	Emits a load instruction for the given type from the specified local variable slot and pushes the type onto the tracked stack.
void	loadOrStoreVariable(BytecodeVariable variable, boolean useReferenceDirectly)	Either loads or stores a local variable depending on the current LHS flag.
void	pop()	remove operand stack top element using bytecode pop
void	popDownTo(int elements)	Pops all stack entries above elements, emitting the appropriate POP or POP2 instruction for each popped value.
void	push(ClassNode type)	push operand on stack
void	pushBool(boolean value)	Pushes an integer literal (0 or 1) representing a boolean value and tracks it as boolean on the operand stack.
void	pushConstant(ConstantExpression expression)	load the constant on the operand stack.
void	pushDynamicName(Expression name)	Pushes the name expression as a String onto the operand stack.
void	remove(int amount)	Remove amount elements from the operand stack, without using pop.
void	replace(ClassNode type)	replace top level element with new element of given type
void	replace(ClassNode type, int n)	replace n top level elements with new element of given type
void	storeVar(BytecodeVariable variable)	Stores the top operand stack value into variable, casting to the variable's declared type.
void	swap()	swap two top level operands
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Details

OperandStack

public OperandStack(WriterController controller)

Creates an operand stack tracker backed by the given controller.

Parameters:

controller - the writer controller for the current compilation

Method Details

getStackLength

public int getStackLength()

Returns the number of tracked entries on the operand stack.

popDownTo

public void popDownTo(int elements)

Pops all stack entries above elements, emitting the appropriate POP or POP2 instruction for each popped value.

Parameters:

elements - the target stack depth to reduce to

castToBool

public void castToBool(int mark,
 boolean emptyDefault)

ensure last marked parameter on the stack is a primitive boolean if mark==stack size, we assume an empty expression or statement. was used and we will use the value given in emptyDefault as boolean if mark==stack.size()-1 the top element will be cast to boolean using Groovy truth. In other cases we throw a GroovyBugError

pop

public void pop()

remove operand stack top element using bytecode pop

jump

public org.objectweb.asm.Label jump(int ifIns)

Emits a conditional jump instruction and returns the newly created target label. The boolean operand is removed from the tracked stack.

Parameters:

ifIns - the branch opcode (e.g. IFEQ, IFNE)

Returns:

the label that the jump will branch to

jump

public void jump(int ifIns,
 org.objectweb.asm.Label label)

Emits a conditional jump to the given label. The boolean operand is removed from the tracked stack.

Parameters:

ifIns - the branch opcode (e.g. IFEQ, IFNE)

label - the branch target

dup

public void dup()

duplicate top element

box

public ClassNode box()

Boxes the top operand if it is a primitive type, emitting the appropriate wrapper-creation bytecode, and returns the resulting (possibly wrapped) type.

Returns:

the type of the top operand after boxing

remove

public void remove(int amount)

Remove amount elements from the operand stack, without using pop. For example after a method invocation

push

public void push(ClassNode type)

push operand on stack

swap

public void swap()

swap two top level operands

replace

public void replace(ClassNode type)

replace top level element with new element of given type

replace

public void replace(ClassNode type,
 int n)

replace n top level elements with new element of given type

doGroovyCast

public void doGroovyCast(ClassNode targetType)

do Groovy cast for top level element

doGroovyCast

public void doGroovyCast(Variable v)

Performs a Groovy cast of the top operand to the declared origin type of v.

Parameters:

v - the variable whose origin type is the cast target

doAsType

public void doAsType(ClassNode targetType)

Performs an as-coercion of the top operand to targetType.

Parameters:

targetType - the target type

pushConstant

public void pushConstant(ConstantExpression expression)

load the constant on the operand stack.

pushDynamicName

public void pushDynamicName(Expression name)

Pushes the name expression as a String onto the operand stack. Constant string expressions are pushed as LDC literals; other expressions are cast to String via the Groovy runtime.

Parameters:

name - the expression representing the method or property name

loadOrStoreVariable

public void loadOrStoreVariable(BytecodeVariable variable,
 boolean useReferenceDirectly)

Either loads or stores a local variable depending on the current LHS flag. If in LHS context, stores the top of the operand stack into variable; otherwise loads the variable's value onto the stack.

Parameters:

variable - the bytecode variable to load or store

useReferenceDirectly - if true, loads the Reference wrapper directly rather than unboxing it

storeVar

public void storeVar(BytecodeVariable variable)

Stores the top operand stack value into variable, casting to the variable's declared type. Handles both plain variables and Reference-wrapped closure-shared variables.

Parameters:

variable - the bytecode variable slot to store into

load

public void load(ClassNode type,
 int idx)

Emits a load instruction for the given type from the specified local variable slot and pushes the type onto the tracked stack.

Parameters:

type - the type of the value to load

idx - the local variable slot index

pushBool

public void pushBool(boolean value)

Pushes an integer literal (0 or 1) representing a boolean value and tracks it as boolean on the operand stack.

Parameters:

value - the boolean value to push

toString

public String toString()

Overrides:

toString in class Object

getTopOperand

public ClassNode getTopOperand()

Returns the type of the top element on the tracked operand stack without removing it.