com.ibm.wala.ssa

Class SSAPiInstruction

java.lang.Object

com.ibm.wala.ssa.SSAInstruction

com.ibm.wala.ssa.SSAAbstractUnaryInstruction

com.ibm.wala.ssa.SSAUnaryOpInstruction

com.ibm.wala.ssa.SSAPiInstruction

public class SSAPiInstruction
extends SSAUnaryOpInstruction

A Pi instruction is a dummy assignment inserted at the tail of a basic block, in order to get a new variable name to associate with some flow-insensitive dataflow fact. You can build an IR with or without Pi instructions, depending on SSAOptions selected. A Pi instruction is linked to its "cause" instruction, which is usually a conditional branch. for example, the following pseudo-code

boolean condition = (x instanceof Integer); if (condition) { S1; else { S2; } could be translated roughly as follows: boolean condition = (x instanceof Integer); LABEL1: if (condition) { x_1 = pi(x, LABEL1); S1; else { x_2 = pi(x, LABEL2); S2; }

Nested Class Summary

Nested classes/interfaces inherited from class com.ibm.wala.ssa.SSAInstruction

SSAInstruction.IVisitor, SSAInstruction.Visitor

Field Summary

Fields inherited from class com.ibm.wala.ssa.SSAAbstractUnaryInstruction

result, val

Fields inherited from class com.ibm.wala.ssa.SSAInstruction

iindex, NO_INDEX

Constructor Summary

Constructors

Constructor and Description
SSAPiInstruction(int iindex, int result, int val, int piBlock, int successorBlock, SSAInstruction cause)

Method Summary

Methods

Modifier and Type	Method and Description
SSAInstruction	copyForSSA(SSAInstructionFactory insts, int[] defs, int[] uses) This method is meant to be used during SSA conversion for an IR that is not in SSA form.
SSAInstruction	getCause()
int	getPiBlock()
int	getSuccessor()
int	getVal()
String	toString(SymbolTable symbolTable)
void	visit(SSAInstruction.IVisitor v) Apply an IVisitor to this instruction.

Methods inherited from class com.ibm.wala.ssa.SSAUnaryOpInstruction

getOpcode

Methods inherited from class com.ibm.wala.ssa.SSAAbstractUnaryInstruction

getDef, getDef, getNumberOfDefs, getNumberOfUses, getUse, hasDef, hashCode, isFallThrough

Methods inherited from class com.ibm.wala.ssa.SSAInstruction

equals, getExceptionTypes, getValueString, isPEI, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

SSAPiInstruction

public SSAPiInstruction(int iindex,
                int result,
                int val,
                int piBlock,
                int successorBlock,
                SSAInstruction cause)

Parameters:

successorBlock - the successor block; this PI assignment happens on the transition between this basic block and the successor block.

Method Detail

copyForSSA

public SSAInstruction copyForSSA(SSAInstructionFactory insts,
                        int[] defs,
                        int[] uses)

Description copied from class: SSAInstruction

This method is meant to be used during SSA conversion for an IR that is not in SSA form. It creates a new SSAInstruction of the same type as the receiver, with a combination of the receiver's uses and defs and those from the method parameters. In particular, if the 'defs' parameter is null, then the new instruction has the same defs as the receiver. If 'defs' is not null, it must be an array with a size equal to the number of defs that the receiver instruction has. In this case, the new instruction has defs taken from the array. The uses of the new instruction work in the same way with the 'uses' parameter. Note that this only applies to CAst-based IR translation, since Java bytecode-based IR generation uses a different SSA construction mechanism. TODO: move this into the SSAInstructionFactory

Overrides:

copyForSSA in class SSAUnaryOpInstruction

toString

public String toString(SymbolTable symbolTable)

Overrides:

toString in class SSAUnaryOpInstruction

visit

public void visit(SSAInstruction.IVisitor v)

Description copied from class: SSAInstruction

Apply an IVisitor to this instruction. We invoke the appropriate IVisitor method according to the type of this instruction.

Overrides:

visit in class SSAUnaryOpInstruction

See Also:

SSAInstruction.visit(IVisitor)

getSuccessor

public int getSuccessor()

getPiBlock

public int getPiBlock()

getCause

public SSAInstruction getCause()

getVal

public int getVal()