[WarnMissedTransforms] Set default to 1.

[asbirlea]

Summary

Set default value for retrieved attributes to 1, since the check is against 1.
Eliminates the warning noise generated when the attributes are not present.

[sanjoy]

lgtm

llvm/trunk/lib/Transforms/Scalar/WarnMissedTransforms.cpp

static void warnAboutLeftoverTransformations(Loop *L,
 
   if (hasVectorizeTransformation(L) == TM_ForcedByUser) {
     LLVM_DEBUG(dbgs() << "Leftover vectorization transformation\n");
     Optional<int> VectorizeWidth =
         getOptionalIntLoopAttribute(L, "llvm.loop.vectorize.width");
     Optional<int> InterleaveCount =
         getOptionalIntLoopAttribute(L, "llvm.loop.interleave.count");
 
-    if (VectorizeWidth.getValueOr(0) != 1)
+    if (VectorizeWidth.getValueOr(1) != 1)
       ORE->emit(
           DiagnosticInfoOptimizationFailure(DEBUG_TYPE,
                                             "FailedRequestedVectorization",
                                             L->getStartLoc(), L->getHeader())
           << "loop not vectorized: the optimizer was unable to perform the "
              "requested transformation; the transformation might be disabled "
              "or specified as part of an unsupported transformation ordering");
-    else if (InterleaveCount.getValueOr(0) != 1)
+    else if (InterleaveCount.getValueOr(1) != 1)
       ORE->emit(
           DiagnosticInfoOptimizationFailure(DEBUG_TYPE,
                                             "FailedRequestedInterleaving",
                                             L->getStartLoc(), L->getHeader())
           << "loop not interleaved: the optimizer was unable to perform the "
              "requested transformation; the transformation might be disabled "
              "or specified as part of an unsupported transformation ordering");
   }