harden assertion

Author: Mel-Chen

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -3548,6 +3548,8 @@ void VPInterleaveRecipe::execute(VPTransformState &State) {
   // Vectorize the interleaved store group.
   Value *MaskForGaps =
       createBitMaskForGaps(State.Builder, State.VF.getKnownMinValue(), *Group);
+  assert(((MaskForGaps != nullptr) == NeedsMaskForGaps) &&
+         "Mismatch between NeedsMaskForGaps and MaskForGaps");
   assert((!MaskForGaps || !State.VF.isScalable()) &&
          "masking gaps for scalable vectors is not yet supported.");
   ArrayRef<VPValue *> StoredValues = getStoredValues();