/**
* Reverse if-convert a block. Return a new hyperblock starting with the reverse if-converted
* block or null.
*/
private Hyperblock reverseIfConvertBlock(PredicateBlock block) {
int rp = block.getPredicate();
boolean sense = block.isPredicatedOnTrue();
// Insert a label at the beginning of the block.
TripsLabel lab = (TripsLabel) gen.createLabel();
gen.updateLabelIndex(lab);
block.insertInstructionAtHead(lab);
// Insert a branch to this block in its predecessors.
for (int i = block.numInEdges() - 1; i > -1; i--) {
PredicateBlock pred = (PredicateBlock) block.getInEdge(i);
int rpPred = pred.getPredicate();
boolean sensePred = pred.isPredicatedOnTrue();
boolean needThunk = true;
// Check if we need a thunk.
if (!block.isPredicated()) {
needThunk = false;
} else if (pred.numOutEdges() == 1) {
needThunk = false;
} else if ((rp == rpPred) && (sense == sensePred)) {
needThunk = false;
}
// Create a branch to the label and insert it.
if (needThunk) {
TripsBranch br = new TripsBranch(Opcodes.BRO, lab, 1, rp, sense);
PredicateBlock thunk = new PredicateBlock(rp, sense);
br.addTarget(lab, 0);
thunk.appendInstruction(br);
pred.addOutEdge(thunk);
thunk.addInEdge(pred);
} else {
TripsBranch br = new TripsBranch(Opcodes.BRO, lab, 1, rpPred, sensePred);
br.addTarget(lab, 0);
pred.appendInstruction(br);
}
pred.deleteOutEdge(block);
block.deleteInEdge(pred);
}
blocksReverseIfConvertedCount++;
// Create the new hyperblock.
BitVect predicates = removePredicates(block);
Hyperblock hnew = new Hyperblock(block, predicates, regs);
hnew.updateLastBlock();
return hnew;
}
/** Remove all the predicates which are not defined in the hyperblock. */
private BitVect removePredicates(PredicateBlock start) {
BitVect predicates = new BitVect();
Stack<Node> wl = new Stack<Node>();
// Determine all the predicates defined outside this hyperblock.
start.nextVisit();
start.setVisited();
wl.add(start);
while (!wl.isEmpty()) {
PredicateBlock block = (PredicateBlock) wl.pop();
block.pushOutEdges(wl);
for (Instruction inst = block.getFirstInstruction(); inst != null; inst = inst.getNext()) {
if (inst.isMarker()) {
continue;
}
if (inst.isBranch()) {
continue;
}
if (((TripsInstruction) inst).definesPredicate()) {
predicates.set(inst.getDestRegister());
}
}
}
// Remove the predicates.
start.nextVisit();
start.setVisited();
wl.add(start);
while (!wl.isEmpty()) {
PredicateBlock block = (PredicateBlock) wl.pop();
block.pushOutEdges(wl);
if (!block.isPredicated()) {
continue;
}
int rp = block.getPredicate();
if (predicates.get(rp)) {
continue;
}
block.removePredicates();
for (Instruction inst = block.getFirstInstruction(); inst != null; inst = inst.getNext()) {
inst.removePredicates();
}
}
return predicates;
}