Index: lib/Transforms/Utils/LoopUnrollPeel.cpp
===================================================================
--- lib/Transforms/Utils/LoopUnrollPeel.cpp
+++ lib/Transforms/Utils/LoopUnrollPeel.cpp
@@ -75,25 +75,27 @@
   // its only back edge. If there is such Phi, peeling 1 iteration from the
   // loop is profitable, because starting from 2nd iteration we will have an
   // invariant instead of this Phi.
-  if (auto *BackEdge = L->getLoopLatch()) {
-    BasicBlock *Header = L->getHeader();
-    // Iterate over Phis to find one with invariant input on back edge.
-    bool FoundCandidate = false;
-    PHINode *Phi;
-    for (auto BI = Header->begin(); isa<PHINode>(&*BI); ++BI) {
-      Phi = cast<PHINode>(&*BI);
-      Value *Input = Phi->getIncomingValueForBlock(BackEdge);
-      if (L->isLoopInvariant(Input)) {
-        FoundCandidate = true;
-        break;
+  if (LoopSize <= UP.Threshold) {
+    if (auto *BackEdge = L->getLoopLatch()) {
+      BasicBlock *Header = L->getHeader();
+      // Iterate over Phis to find one with invariant input on back edge.
+      bool FoundCandidate = false;
+      PHINode *Phi;
+      for (auto BI = Header->begin(); isa<PHINode>(&*BI); ++BI) {
+        Phi = cast<PHINode>(&*BI);
+        Value *Input = Phi->getIncomingValueForBlock(BackEdge);
+        if (L->isLoopInvariant(Input)) {
+          FoundCandidate = true;
+          break;
+        }
+      }
+      if (FoundCandidate) {
+        DEBUG(dbgs() << "Peel one iteration to get rid of " << *Phi
+                     << " because starting from 2nd iteration it is always"
+                     << " an invariant\n");
+        UP.PeelCount = 1;
+        return;
       }
-    }
-    if (FoundCandidate) {
-      DEBUG(dbgs() << "Peel one iteration to get rid of " << *Phi
-                   << " because starting from 2nd iteration it is always"
-                   << " an invariant\n");
-      UP.PeelCount = 1;
-      return;
     }
   }