diff --git a/lib/CodeGen/CodeGenPrepare.cpp b/lib/CodeGen/CodeGenPrepare.cpp
index 68bab28c0b7..85c1dc4ec87 100644
--- a/lib/CodeGen/CodeGenPrepare.cpp
+++ b/lib/CodeGen/CodeGenPrepare.cpp
@@ -1183,9 +1183,10 @@ static bool replaceMathCmpWithIntrinsic(BinaryOperator *BO, CmpInst *Cmp,
 
     // Check that the insertion doesn't create a value that is live across more
     // than two blocks, so to minimise the increase in register pressure.
-    if (BO->getParent() != Cmp->getParent()) {
-      BasicBlock *Dominator = MathDominates ? BO->getParent() : Cmp->getParent();
-      BasicBlock *Dominated = MathDominates ? Cmp->getParent() : BO->getParent();
+    BasicBlock *MathBB = BO->getParent(), *CmpBB = Cmp->getParent();
+    if (MathBB != CmpBB) {
+      BasicBlock *Dominator = MathDominates ? MathBB : CmpBB;
+      BasicBlock *Dominated = MathDominates ? CmpBB : MathBB;
       auto Successors = successors(Dominator);
       if (llvm::find(Successors, Dominated) == Successors.end())
         return false;