LoopIndexSplit can sometimes result in cases where a block in its own domfrontier.

Don't crash when we encounter one of these.

llvm-svn: 51915

1 files changed, 6 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp b/llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp
index bc9fdfde88b..a821423d17f 100644
--- a/llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp
+++ b/llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp
@@ -235,9 +235,12 @@ bool llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P,
       DominanceFrontier::iterator I = DF->find(DestBB);
       if (I != DF->end()) {
         DF->addBasicBlock(NewBB, I->second);
-        // However NewBB's frontier does not include DestBB.
-        DominanceFrontier::iterator NF = DF->find(NewBB);
-        DF->removeFromFrontier(NF, DestBB);
+        
+        if (I->second.count(DestBB)) {
+          // However NewBB's frontier does not include DestBB.
+          DominanceFrontier::iterator NF = DF->find(NewBB);
+          DF->removeFromFrontier(NF, DestBB);
+        }
       }
       else
         DF->addBasicBlock(NewBB, DominanceFrontier::DomSetType());