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Refactor my fix for PR5652 to terminate the predecessor lookups after the first failure.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112620 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2010-08-31 18:48:48 +00:00
parent 0676984117
commit c1bdac66ff
1 changed files with 24 additions and 25 deletions

49
lib/Transforms/Scalar/JumpThreading.cpp

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