Index: llvm/trunk/lib/Transforms/Scalar/LoopSink.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopSink.cpp
+++ llvm/trunk/lib/Transforms/Scalar/LoopSink.cpp
@@ -283,6 +283,9 @@
   // sinked.
   for (auto II = Preheader->rbegin(), E = Preheader->rend(); II != E;) {
     Instruction *I = &*II++;
+    // No need to check for instruction's operands are loop invariant.
+    assert(L.hasLoopInvariantOperands(I) &&
+           "Insts in a loop's preheader should have loop invariant operands!");
     if (!canSinkOrHoistInst(*I, &AA, &DT, &L, &CurAST, nullptr))
       continue;
     if (sinkInstruction(L, *I, ColdLoopBBs, LoopBlockNumber, LI, DT, BFI))