[ConstantRange] Add getNonEmpty() constructor

ConstantRanges have an annoying special case: If upper and lower are
the same, it can be either an empty or a full set. When constructing
constant ranges nearly always a full set is intended, but this still
requires an explicit check in many places.

This revision adds a getNonEmpty() constructor that disambiguates this
case: If upper and lower are the same, a full set is created.

Differential Revision: https://reviews.llvm.org/D60947

llvm-svn: 358854

1 files changed, 1 insertions, 5 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 01b4019..1f69bc8 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -5808,12 +5808,8 @@ static ConstantRange getRangeForAffineARHelper(APInt Step,
       Descending ? std::move(StartUpper) : std::move(MovedBoundary);
   NewUpper += 1;
 
-  // If we end up with full range, return a proper full range.
-  if (NewLower == NewUpper)
-    return ConstantRange::getFull(BitWidth);
-
   // No overflow detected, return [StartLower, StartUpper + Offset + 1) range.
-  return ConstantRange(std::move(NewLower), std::move(NewUpper));
+  return ConstantRange::getNonEmpty(std::move(NewLower), std::move(NewUpper));
 }
 
 ConstantRange ScalarEvolution::getRangeForAffineAR(const SCEV *Start,