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[SimplifyCFG] ConstantFoldTerminator(): switch to non-permissive DomTree updates in `indirectbr` handling 

... which requires not deleting edges that were just deleted already.
This commit is contained in:
Roman Lebedev 2021-01-07 22:32:04 +03:00
parent 8b9a0e6f7e
commit b3822728fa
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GPG Key ID: 083C3EBB4A1689E0
1 changed files with 16 additions and 13 deletions
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29
llvm/lib/Transforms/Utils/Local.cpp
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@ -329,22 +329,20 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
if (auto *BA =
dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
BasicBlock *TheOnlyDest = BA->getBasicBlock();
std::vector <DominatorTree::UpdateType> Updates;
if (DTU)
Updates.reserve(IBI->getNumDestinations() - 1);
SmallSetVector<BasicBlock *, 8> RemovedSuccessors;
// Insert the new branch.
Builder.CreateBr(TheOnlyDest);
BasicBlock *SuccToKeep = TheOnlyDest;
for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
if (IBI->getDestination(i) == TheOnlyDest) {
TheOnlyDest = nullptr;
BasicBlock *DestBB = IBI->getDestination(i);
if (DTU && DestBB != TheOnlyDest)
RemovedSuccessors.insert(DestBB);
if (IBI->getDestination(i) == SuccToKeep) {
SuccToKeep = nullptr;
} else {
BasicBlock *ParentBB = IBI->getParent();
BasicBlock *DestBB = IBI->getDestination(i);
DestBB->removePredecessor(ParentBB);
if (DTU)
Updates.push_back({DominatorTree::Delete, ParentBB, DestBB});
DestBB->removePredecessor(BB);
}
}
Value *Address = IBI->getAddress();
@ -361,13 +359,18 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
// If we didn't find our destination in the IBI successor list, then we
// have undefined behavior. Replace the unconditional branch with an
// 'unreachable' instruction.
if (TheOnlyDest) {
if (SuccToKeep) {
BB->getTerminator()->eraseFromParent();
new UnreachableInst(BB->getContext(), BB);
}
if (DTU)
DTU->applyUpdatesPermissive(Updates);
if (DTU) {
std::vector<DominatorTree::UpdateType> Updates;
Updates.reserve(RemovedSuccessors.size());
for (auto *RemovedSuccessor : RemovedSuccessors)
Updates.push_back({DominatorTree::Delete, BB, RemovedSuccessor});
DTU->applyUpdates(Updates);
}
return true;
}
}