1 files changed, 13 insertions, 3 deletions
diff --git a/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp b/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
index cc0f2c5bb48..9cdc1d18963 100644
--- a/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
@@ -176,6 +176,7 @@ public:
     Type *getType() const { return Begin->getType(); }
     const SCEV *getBegin() const { return Begin; }
     const SCEV *getEnd() const { return End; }
+    bool isEmpty() const { return Begin == End; }
   };
 
   /// This is the value the condition of the branch needs to evaluate to for the
@@ -1654,8 +1655,11 @@ static Optional<InductiveRangeCheck::Range>
 IntersectRange(ScalarEvolution &SE,
                const Optional<InductiveRangeCheck::Range> &R1,
                const InductiveRangeCheck::Range &R2) {
-  if (!R1.hasValue())
-    return R2;
+  if (!R1.hasValue()) {
+    if (!R2.isEmpty())
+      return R2;
+    return None;
+  }
   auto &R1Value = R1.getValue();
 
   // TODO: we could widen the smaller range and have this work; but for now we
@@ -1666,7 +1670,11 @@ IntersectRange(ScalarEvolution &SE,
   const SCEV *NewBegin = SE.getSMaxExpr(R1Value.getBegin(), R2.getBegin());
   const SCEV *NewEnd = SE.getSMinExpr(R1Value.getEnd(), R2.getEnd());
 
-  return InductiveRangeCheck::Range(NewBegin, NewEnd);
+  // If the resulting range is empty, just return None.
+  auto Ret = InductiveRangeCheck::Range(NewBegin, NewEnd);
+  if (Ret.isEmpty())
+    return None;
+  return Ret;
 }
 
 bool InductiveRangeCheckElimination::runOnLoop(Loop *L, LPPassManager &LPM) {
@@ -1735,6 +1743,8 @@ bool InductiveRangeCheckElimination::runOnLoop(Loop *L, LPPassManager &LPM) {
       auto MaybeSafeIterRange =
           IntersectRange(SE, SafeIterRange, Result.getValue());
       if (MaybeSafeIterRange.hasValue()) {
+        assert(!MaybeSafeIterRange.getValue().isEmpty() &&
+               "We should never return empty ranges!");
         RangeChecksToEliminate.push_back(IRC);
         SafeIterRange = MaybeSafeIterRange.getValue();
       }