Fix a crash in LSR replaceCongruentIVs.

Indirect branch in the preheader crashes replaceCongruentIVs.
Fixes rdar://12910141.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171653 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index acae9b4..70ccc54 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -4820,7 +4820,7 @@
 
   // Remove any extra phis created by processing inner loops.
   Changed |= DeleteDeadPHIs(L->getHeader());
-  if (EnablePhiElim) {
+  if (EnablePhiElim && L->isLoopSimplifyForm()) {
     SmallVector<WeakVH, 16> DeadInsts;
     SCEVExpander Rewriter(getAnalysis<ScalarEvolution>(), "lsr");
 #ifndef NDEBUG