Reapply r316582 [Local] Fix a bug in the domtree update logic for MergeBasicBlockIntoOnlyPred.
Summary: This reverts r316612 to reapply r316582. The buildbot failure was unrelated to this commit.
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llvm-svn: 316669
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index fd33677..8c643c9 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -649,9 +649,13 @@
DestBB->moveAfter(PredBB);
if (DT) {
- BasicBlock *PredBBIDom = DT->getNode(PredBB)->getIDom()->getBlock();
- DT->changeImmediateDominator(DestBB, PredBBIDom);
- DT->eraseNode(PredBB);
+ // For some irreducible CFG we end up having forward-unreachable blocks
+ // so check if getNode returns a valid node before updating the domtree.
+ if (DomTreeNode *DTN = DT->getNode(PredBB)) {
+ BasicBlock *PredBBIDom = DTN->getIDom()->getBlock();
+ DT->changeImmediateDominator(DestBB, PredBBIDom);
+ DT->eraseNode(PredBB);
+ }
}
// Nuke BB.
PredBB->eraseFromParent();