diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -567,6 +567,9 @@
   if (!MaxRecurse--)
     return nullptr;
 
+  // Prevent this function from being recursively called more than once.
+  MaxRecurse = 0;
+
   // Make sure the phi is on the LHS.
   if (!isa<PHINode>(LHS)) {
     std::swap(LHS, RHS);