don't call MergeBasicBlockIntoOnlyPred on a block whose only

predecessor is itself.  This doesn't make sense, and this is
a dead infinite loop anyway.

llvm-svn: 60210

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 5de5fb3b776..114603dabb0 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -164,7 +164,8 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
   // because now the condition in this block can be threaded through
   // predecessors of our predecessor block.
   if (BasicBlock *SinglePred = BB->getSinglePredecessor())
-    if (SinglePred->getTerminator()->getNumSuccessors() == 1) {
+    if (SinglePred->getTerminator()->getNumSuccessors() == 1 &&
+        SinglePred != BB) {
       // Remember if SinglePred was the entry block of the function.  If so, we
       // will need to move BB back to the entry position.
       bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();