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Fix PR8247: JumpThreading can cause a block to become unreachable while still having predecessor, if it is part of a self-loop.

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Because of this, we cannot use the Simplify* APIs, as they can assert-fail on unreachable code.  Since it's not easy to determine
if a given threading will cause a block to become unreachable, simply defer simplifying simplification to later InstCombine and/or
DCE passes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115082 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson
2010-09-29 20:34:41 +00:00
parent 18d52f2fb5
commit 36c4debc94
2 changed files with 31 additions and 4 deletions
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8
lib/Transforms/Scalar/JumpThreading.cpp
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@@ -613,7 +613,7 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
TerminatorInst *BBTerm = BB->getTerminator();
for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i) {
if (i == BestSucc) continue;
RemovePredecessorAndSimplify(BBTerm->getSuccessor(i), BB, TD);
BBTerm->getSuccessor(i)->removePredecessor(BB, true);
}
DEBUG(dbgs() << " In block '" << BB->getName()
@@ -664,7 +664,7 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
if (PI == PE) {
unsigned ToRemove = Baseline == LazyValueInfo::True ? 1 : 0;
unsigned ToKeep = Baseline == LazyValueInfo::True ? 0 : 1;
RemovePredecessorAndSimplify(CondBr->getSuccessor(ToRemove), BB, TD);
CondBr->getSuccessor(ToRemove)->removePredecessor(BB, true);
BranchInst::Create(CondBr->getSuccessor(ToKeep), CondBr);
CondBr->eraseFromParent();
return true;
@@ -1470,7 +1470,7 @@ bool JumpThreading::ThreadEdge(BasicBlock *BB,
TerminatorInst *PredTerm = PredBB->getTerminator();
for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i)
if (PredTerm->getSuccessor(i) == BB) {
RemovePredecessorAndSimplify(BB, PredBB, TD);
BB->removePredecessor(PredBB, true);
PredTerm->setSuccessor(i, NewBB);
}
@@ -1620,7 +1620,7 @@ bool JumpThreading::DuplicateCondBranchOnPHIIntoPred(BasicBlock *BB,
// PredBB no longer jumps to BB, remove entries in the PHI node for the edge
// that we nuked.
RemovePredecessorAndSimplify(BB, PredBB, TD);
BB->removePredecessor(PredBB, true);
// Remove the unconditional branch at the end of the PredBB block.
OldPredBranch->eraseFromParent();