/**
* Check to see if the instruction has a null check associated with it, and if so, add a
* dereference.
*
* @param location the Location of the instruction
* @param vnaFrame ValueNumberFrame at the Location of the instruction
* @param fact the dataflow value to modify
* @throws DataflowAnalysisException
*/
private void checkInstance(
Location location, ValueNumberFrame vnaFrame, UnconditionalValueDerefSet fact)
throws DataflowAnalysisException {
// See if this instruction has a null check.
// If it does, the fall through predecessor will be
// identify itself as the null check.
if (!location.isFirstInstructionInBasicBlock()) {
return;
}
if (invDataflow == null) {
return;
}
BasicBlock fallThroughPredecessor =
cfg.getPredecessorWithEdgeType(location.getBasicBlock(), EdgeTypes.FALL_THROUGH_EDGE);
if (fallThroughPredecessor == null || !fallThroughPredecessor.isNullCheck()) {
return;
}
// Get the null-checked value
ValueNumber vn =
vnaFrame.getInstance(location.getHandle().getInstruction(), methodGen.getConstantPool());
// Ignore dereferences of this
if (!methodGen.isStatic()) {
ValueNumber v = vnaFrame.getValue(0);
if (v.equals(vn)) {
return;
}
}
if (vn.hasFlag(ValueNumber.CONSTANT_CLASS_OBJECT)) {
return;
}
IsNullValueFrame startFact = null;
startFact = invDataflow.getStartFact(fallThroughPredecessor);
if (!startFact.isValid()) {
return;
}
int slot =
startFact.getInstanceSlot(
location.getHandle().getInstruction(), methodGen.getConstantPool());
if (!reportDereference(startFact, slot)) {
return;
}
if (DEBUG) {
System.out.println("FOUND GUARANTEED DEREFERENCE");
System.out.println("Load: " + vnaFrame.getLoad(vn));
System.out.println("Pred: " + fallThroughPredecessor);
System.out.println("startFact: " + startFact);
System.out.println("Location: " + location);
System.out.println("Value number frame: " + vnaFrame);
System.out.println("Dereferenced valueNumber: " + vn);
System.out.println("invDataflow: " + startFact);
System.out.println("IGNORE_DEREF_OF_NCP: " + IGNORE_DEREF_OF_NCP);
}
// Mark the value number as being dereferenced at this location
fact.addDeref(vn, location);
}
