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Refactor my fix for PR5652 to terminate the predecessor lookups after the first failure.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112620 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -715,37 +715,36 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
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// the branch based on that.
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BranchInst *CondBr = dyn_cast<BranchInst>(BB->getTerminator());
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Constant *CondConst = dyn_cast<Constant>(CondCmp->getOperand(1));
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if (LVI && CondBr && CondConst && CondBr->isConditional() &&
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pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
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if (LVI && CondBr && CondConst && CondBr->isConditional() && PI != PE &&
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(!isa<Instruction>(CondCmp->getOperand(0)) ||
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cast<Instruction>(CondCmp->getOperand(0))->getParent() != BB)) {
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// For predecessor edge, determine if the comparison is true or false
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// on that edge. If they're all true or all false, we can simplify the
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// branch.
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// FIXME: We could handle mixed true/false by duplicating code.
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unsigned Trues = 0, Falses = 0, predcount = 0;
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for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB);PI != PE; ++PI){
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++predcount;
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LazyValueInfo::Tristate Ret =
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LVI->getPredicateOnEdge(CondCmp->getPredicate(),
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CondCmp->getOperand(0), CondConst, *PI, BB);
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if (Ret == LazyValueInfo::True)
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++Trues;
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else if (Ret == LazyValueInfo::False)
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++Falses;
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}
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// If we can determine the branch direction statically, convert
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// the conditional branch to an unconditional one.
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if (Trues && Trues == predcount) {
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RemovePredecessorAndSimplify(CondBr->getSuccessor(1), BB, TD);
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BranchInst::Create(CondBr->getSuccessor(0), CondBr);
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CondBr->eraseFromParent();
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return true;
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} else if (Falses && Falses == predcount) {
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RemovePredecessorAndSimplify(CondBr->getSuccessor(0), BB, TD);
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BranchInst::Create(CondBr->getSuccessor(1), CondBr);
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CondBr->eraseFromParent();
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return true;
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LazyValueInfo::Tristate Baseline =
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LVI->getPredicateOnEdge(CondCmp->getPredicate(), CondCmp->getOperand(0),
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CondConst, *PI, BB);
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if (Baseline != LazyValueInfo::Unknown) {
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// Check that all remaining incoming values match the first one.
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while (++PI != PE) {
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LazyValueInfo::Tristate Ret = LVI->getPredicateOnEdge(
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CondCmp->getPredicate(),
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CondCmp->getOperand(0),
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CondConst, *PI, BB);
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if (Ret != Baseline) break;
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}
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// If we terminated early, then one of the values didn't match.
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if (PI == PE) {
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unsigned ToRemove = Baseline == LazyValueInfo::True ? 1 : 0;
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unsigned ToKeep = Baseline == LazyValueInfo::True ? 0 : 1;
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RemovePredecessorAndSimplify(CondBr->getSuccessor(ToRemove), BB, TD);
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BranchInst::Create(CondBr->getSuccessor(ToKeep), CondBr);
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CondBr->eraseFromParent();
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return true;
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}
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}
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}
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}
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