Index: lib/CodeGen/CodeGenPrepare.cpp
===================================================================
--- lib/CodeGen/CodeGenPrepare.cpp
+++ lib/CodeGen/CodeGenPrepare.cpp
@@ -668,6 +668,20 @@
   return MadeChange;
 }
 
+/// Check to see if all of the operands of the PHI are not simple constants
+/// (constantint/constantfp/undef).
+static bool HasAllNonCstPhiOps(BasicBlock *DestBB) {
+  BasicBlock::const_iterator DestBBI = DestBB->begin();
+  while (const PHINode *DestPN = dyn_cast<PHINode>(DestBBI++)) {
+    for (unsigned I = 0, E = DestPN->getNumIncomingValues(); I != E; ++I) {
+      if (isa<Constant>(DestPN->getIncomingValue(I)) &&
+          !isa<ConstantExpr>(DestPN->getIncomingValue(I)))
+        return false;
+    }
+  }
+  return true;
+}
+
 bool CodeGenPrepare::isMergingEmptyBlockProfitable(BasicBlock *BB,
                                                    BasicBlock *DestBB,
                                                    bool isPreheader) {
@@ -740,6 +754,12 @@
   if (SameIncomingValueBBs.count(Pred))
     return true;
 
+  // Check to see if phi operands are of constants, in such case extra COPYs
+  // are likely needed. If all the operands of the phis are not constant there
+  // is no reason to skip merging.
+  if (HasAllNonCstPhiOps(DestBB))
+    return true;
+
   if (!BFI) {
     Function &F = *BB->getParent();
     LoopInfo LI{DominatorTree(F)};