// For each use of a Name, see all the reaching definitions for that Name
// If there exists only ONE reaching assignment definition that assigns to Name,
// replace Name with definition's LHS
private Name copyPropagateOnArg(Name arg, BlockDataFlowState bFlow) {
if (arg != null) {
HashMap<Name, HashSet<QuadrupletStmt>> nameToStmtsThatAssignIt =
assignmentDefGenerator.getNameToQStmtsThatAssignIt();
BitSet in = bFlow.getIn();
HashSet<QuadrupletStmt> stmtsAssigningName;
QuadrupletStmt reachingAssignmentStmt = null;
int numReachingDefs;
stmtsAssigningName = nameToStmtsThatAssignIt.get(arg);
numReachingDefs = 0;
if (stmtsAssigningName != null) {
for (QuadrupletStmt qs : stmtsAssigningName) {
if (in.get(qs.getMyId())) {
numReachingDefs++;
reachingAssignmentStmt = qs;
}
}
if (numReachingDefs == 1) {
// There is exactly one assignment statement reaching this block
// so we can perform copy propagation
// Return the name which we should replace the arg with
return reachingAssignmentStmt.getArg1();
}
}
// Check if Name is ArrayName and try to optimize index
if (arg.getClass().equals(ArrayName.class)) {
Name arrIndex = ((ArrayName) arg).getIndex();
Name propagatedName = copyPropagateOnArg(arrIndex, bFlow);
if (propagatedName != null) {
((ArrayName) arg).setIndex(propagatedName);
}
}
}
return null;
}
private void optimize(CFGBlock block) {
BlockDataFlowState bFlow = assignmentDefGenerator.getBlockAssignReachingDefs().get(block);
QuadrupletStmt qStmt;
PopStmt popStmt;
PushStmt pushStmt;
CmpStmt cStmt;
Name newArg1, newArg2, dest;
for (LIRStatement stmt : block.getStatements()) {
// Reset kill set
bFlow.getKill().clear();
if (stmt.getClass().equals(CallStmt.class)) {
CallStmt callStmt = (CallStmt) stmt;
if (callStmt.getMethodLabel().equals(ProgramFlattener.exceptionHandlerLabel)) continue;
// Update BlockDataFlowState kill set
assignmentDefGenerator.invalidateFunctionCall(bFlow);
// Update BlockDataFlowState in set by using updated kill set
bFlow.getIn().xor(bFlow.getKill());
} else if (stmt.getClass().equals(QuadrupletStmt.class)) {
qStmt = (QuadrupletStmt) stmt;
newArg1 = copyPropagateOnArg(qStmt.getArg1(), bFlow);
if (newArg1 != null) {
qStmt.setArg1(newArg1);
}
newArg2 = copyPropagateOnArg(qStmt.getArg2(), bFlow);
if (newArg2 != null) {
qStmt.setArg2(newArg2);
}
dest = qStmt.getDestination();
if (dest != null) {
// Check if dest is ArrayName and try to optimize index
if (dest.getClass().equals(ArrayName.class)) {
Name arrIndex = ((ArrayName) dest).getIndex();
Name propagatedName = copyPropagateOnArg(arrIndex, bFlow);
if (propagatedName != null) ((ArrayName) dest).setIndex(propagatedName);
}
}
// Update BlockDataFlowState kill set
assignmentDefGenerator.updateKillGenSet(dest, bFlow);
// Update BlockDataFlowState in set by using updated kill set
bFlow.getIn().xor(bFlow.getKill());
// Optimize PopStmt
} else if (stmt.getClass().equals(PopStmt.class)) {
popStmt = (PopStmt) stmt;
newArg1 = copyPropagateOnArg(popStmt.getName(), bFlow);
if (newArg1 != null) {
popStmt.setName(newArg1);
}
// Optimize PushStmt
} else if (stmt.getClass().equals(PushStmt.class)) {
pushStmt = (PushStmt) stmt;
newArg1 = copyPropagateOnArg(pushStmt.getName(), bFlow);
if (newArg1 != null) {
pushStmt.setName(newArg1);
}
// Optimize CmpStmt
} else if (stmt.getClass().equals(CmpStmt.class)) {
cStmt = (CmpStmt) stmt;
newArg1 = copyPropagateOnArg(cStmt.getArg1(), bFlow);
if (newArg1 != null) {
cStmt.setArg1(newArg1);
}
newArg2 = copyPropagateOnArg(cStmt.getArg2(), bFlow);
if (newArg2 != null) {
cStmt.setArg2(newArg2);
}
}
}
}