Add tests and extra max trip count debug output

Author: david-arm

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -3958,6 +3958,8 @@ LoopVectorizationCostModel::computeMaxVF(ElementCount UserVF, unsigned UserIC) {
   unsigned TC = PSE.getSE()->getSmallConstantTripCount(TheLoop);
   unsigned MaxTC = PSE.getSE()->getSmallConstantMaxTripCount(TheLoop);
   LLVM_DEBUG(dbgs() << "LV: Found trip count: " << TC << '\n');
+  if (TC != MaxTC)
+    LLVM_DEBUG(dbgs() << "LV: Found maximum trip count: " << MaxTC << '\n');
   if (TC == 1) {
     reportVectorizationFailure("Single iteration (non) loop",
         "loop trip count is one, irrelevant for vectorization",