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[DomTree] Use a non-recursive DFS instead of a recursive one; NFC

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Summary: The recursive DFS can stack overflow in pathological cases.

Reviewers: kuhar

Subscribers: mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D36442

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310383 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das 2017-08-08 17:15:29 +00:00
parent c9b3b5dd57
commit 0128b415ef
1 changed files with 32 additions and 24 deletions
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56
include/llvm/Support/GenericDomTreeConstruction.h
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@ -433,34 +433,42 @@ struct SemiNCAInfo {
const unsigned NCDLevel = NCD->getLevel();
DEBUG(dbgs() << "Visiting " << BlockNamePrinter(TN) << "\n");
assert(TN->getBlock());
for (const NodePtr Succ :
ChildrenGetter<NodePtr, IsPostDom>::Get(TN->getBlock())) {
const TreeNodePtr SuccTN = DT.getNode(Succ);
assert(SuccTN && "Unreachable successor found at reachable insertion");
const unsigned SuccLevel = SuccTN->getLevel();
SmallVector<TreeNodePtr, 8> Stack = {TN};
assert(TN->getBlock() && II.Visited.count(TN) && "Preconditions!");
DEBUG(dbgs() << "\tSuccessor " << BlockNamePrinter(Succ)
<< ", level = " << SuccLevel << "\n");
do {
TreeNodePtr Next = Stack.pop_back_val();
// Succ dominated by subtree From -- not affected.
// (Based on the lemma 2.5 from the second paper.)
if (SuccLevel > RootLevel) {
DEBUG(dbgs() << "\t\tDominated by subtree From\n");
if (II.Visited.count(SuccTN) != 0) continue;
for (const NodePtr Succ :
ChildrenGetter<NodePtr, IsPostDom>::Get(Next->getBlock())) {
const TreeNodePtr SuccTN = DT.getNode(Succ);
assert(SuccTN && "Unreachable successor found at reachable insertion");
const unsigned SuccLevel = SuccTN->getLevel();
DEBUG(dbgs() << "\t\tMarking visited not affected "
<< BlockNamePrinter(Succ) << "\n");
II.Visited.insert(SuccTN);
II.VisitedNotAffectedQueue.push_back(SuccTN);
VisitInsertion(DT, SuccTN, RootLevel, NCD, II);
} else if ((SuccLevel > NCDLevel + 1) && II.Affected.count(SuccTN) == 0) {
DEBUG(dbgs() << "\t\tMarking affected and adding "
<< BlockNamePrinter(Succ) << " to a Bucket\n");
II.Affected.insert(SuccTN);
II.Bucket.push({SuccLevel, SuccTN});
DEBUG(dbgs() << "\tSuccessor " << BlockNamePrinter(Succ)
<< ", level = " << SuccLevel << "\n");
// Succ dominated by subtree From -- not affected.
// (Based on the lemma 2.5 from the second paper.)
if (SuccLevel > RootLevel) {
DEBUG(dbgs() << "\t\tDominated by subtree From\n");
if (II.Visited.count(SuccTN) != 0)
continue;
DEBUG(dbgs() << "\t\tMarking visited not affected "
<< BlockNamePrinter(Succ) << "\n");
II.Visited.insert(SuccTN);
II.VisitedNotAffectedQueue.push_back(SuccTN);
Stack.push_back(SuccTN);
} else if ((SuccLevel > NCDLevel + 1) &&
II.Affected.count(SuccTN) == 0) {
DEBUG(dbgs() << "\t\tMarking affected and adding "
<< BlockNamePrinter(Succ) << " to a Bucket\n");
II.Affected.insert(SuccTN);
II.Bucket.push({SuccLevel, SuccTN});
}
}
}
} while (!Stack.empty());
}
// Updates immediate dominators and levels after insertion.