continue;
}
- // Ensure that any values used in the bonus instruction are also used
- // by the terminator of the predecessor. This means that those values
- // must already have been resolved, so we won't be inhibiting the
- // out-of-order core by speculating them earlier. We also allow
- // instructions that are used by the terminator's condition because it
- // exposes more merging opportunities.
- bool UsedByBranch = (BonusInst && BonusInst->hasOneUse() &&
- BonusInst->user_back() == Cond);
-
- if (BonusInst && !UsedByBranch) {
- // Collect the values used by the bonus inst
- SmallPtrSet<Value*, 4> UsedValues;
- for (Instruction::op_iterator OI = BonusInst->op_begin(),
- OE = BonusInst->op_end(); OI != OE; ++OI) {
- Value *V = *OI;
- if (!isa<Constant>(V) && !isa<Argument>(V))
- UsedValues.insert(V);
- }
-
- SmallVector<std::pair<Value*, unsigned>, 4> Worklist;
- Worklist.push_back(std::make_pair(PBI->getOperand(0), 0));
-
- // Walk up to four levels back up the use-def chain of the predecessor's
- // terminator to see if all those values were used. The choice of four
- // levels is arbitrary, to provide a compile-time-cost bound.
- while (!Worklist.empty()) {
- std::pair<Value*, unsigned> Pair = Worklist.back();
- Worklist.pop_back();
-
- if (Pair.second >= 4) continue;
- UsedValues.erase(Pair.first);
- if (UsedValues.empty()) break;
-
- if (Instruction *I = dyn_cast<Instruction>(Pair.first)) {
- for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end();
- OI != OE; ++OI)
- Worklist.push_back(std::make_pair(OI->get(), Pair.second+1));
- }
- }
-
- if (!UsedValues.empty()) return false;
- }
-
DEBUG(dbgs() << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB);
IRBuilder<> Builder(PBI);