Package com.ibm.wala.ssa

Class NullTestPiPolicy

java.lang.Object

com.ibm.wala.ssa.NullTestPiPolicy

All Implemented Interfaces:

SSAPiNodePolicy

public class NullTestPiPolicy
extends Object
implements SSAPiNodePolicy

A pi node policy with the following rule:

If we have the following code:

 S1: if (c op null) { ... } 

replace it with:

 S1: if (c op null) { v2 = PI(c, S1) .... } 

This renaming allows SSA-based analysis to reason about the nullness of v2 depending on the outcome of the branch.

Method Summary

Modifier and Type	Method	Description
static NullTestPiPolicy	createNullTestPiPolicy()
Pair<Integer,SSAInstruction>	getPi(SSAAbstractInvokeInstruction call, SymbolTable symbolTable)	Do we need to introduce a new name for some value immediately after a call?
Pair<Integer,SSAInstruction>	getPi(SSAConditionalBranchInstruction cond, SSAInstruction def1, SSAInstruction def2, SymbolTable symbolTable)	Do we need to introduce a new name for some value after deciding on an outcome for a conditional branch instruction?
List<Pair<Integer,SSAInstruction>>	getPis(SSAConditionalBranchInstruction cond, SSAInstruction def1, SSAInstruction def2, SymbolTable symbolTable)

Methods inherited from class java.lang.Object

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

Method Details

createNullTestPiPolicy

public static NullTestPiPolicy createNullTestPiPolicy()

getPi

public Pair<Integer,SSAInstruction> getPi(SSAConditionalBranchInstruction cond,
 SSAInstruction def1,
 SSAInstruction def2,
 SymbolTable symbolTable)

Description copied from interface: SSAPiNodePolicy

Do we need to introduce a new name for some value after deciding on an outcome for a conditional branch instruction?

If so, returns a pair consisting of the value number needing renaming, and the instruction which should be recorded as the cause of the pi instruction

Specified by:

getPi in interface SSAPiNodePolicy

Parameters:

cond - the conditional branch instruction in question

def1 - the SSAInstruction that defs cond.getUse(0), or null if none

def2 - the SSAInstruction that defs cond.getUse(1), or null if none

symbolTable - current state of the symbol table for the IR under construction

Returns:

description of the necessary pi instruction, or null if no pi instruction is needed.

getPi

public Pair<Integer,SSAInstruction> getPi(SSAAbstractInvokeInstruction call,
 SymbolTable symbolTable)

Description copied from interface: SSAPiNodePolicy

Do we need to introduce a new name for some value immediately after a call?

If so, returns a pair consisting of the value number needing renaming, and the instruction which should be recorded as the cause of the pi instruction

Specified by:

getPi in interface SSAPiNodePolicy

Parameters:

call - the call instruction in question

symbolTable - current state of the symbol table for the IR under construction

Returns:

description of the necessary pi instruction, or null if no pi instruction is needed.

getPis

public List<Pair<Integer,SSAInstruction>> getPis(SSAConditionalBranchInstruction cond,
 SSAInstruction def1,
 SSAInstruction def2,
 SymbolTable symbolTable)

Specified by:

getPis in interface SSAPiNodePolicy