Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4095,6 +4095,11 @@
 
 /// See if we can fold the given phi. If not, returns null.
 static Value *SimplifyPHINode(PHINode *PN, const SimplifyQuery &Q) {
+  // LCSSA PHIs only have one input value
+  // return nullptr here to avoid simplifying them away
+  // since they are necessary to hold out of the loop dependecies.
+  if (PN->getNumIncomingValues() < 2)
+    return nullptr;
   // If all of the PHI's incoming values are the same then replace the PHI node
   // with the common value.
   Value *CommonValue = nullptr;