Fix PR3353, infinitely jump threading an infinite loop make from switches.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62529 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index 94d33aa787..f96fc208ae 100644
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -419,6 +419,11 @@ bool JumpThreading::ProcessBranchOnDuplicateCond(BasicBlock *PredBB,
 /// switches out of repeated 'if' conditions.
 bool JumpThreading::ProcessSwitchOnDuplicateCond(BasicBlock *PredBB,
                                                  BasicBlock *DestBB) {
+  // Can't thread edge to self.
+  if (PredBB == DestBB)
+    return false;
+  
+  
   SwitchInst *PredSI = cast<SwitchInst>(PredBB->getTerminator());
   SwitchInst *DestSI = cast<SwitchInst>(DestBB->getTerminator());