[ConstantRange] Fix sdiv() with one bit values (PR56333)

Signed one bit values can only be -1 or 0, not positive. The code
was interpreting the 1 as -1 and intersecting with a full range
rather than an empty one.

Fixes https://github.com/llvm/llvm-project/issues/56333.

1 files changed, 4 insertions, 1 deletions

diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
index be6386c..9d23910 100644
--- a/llvm/lib/IR/ConstantRange.cpp
+++ b/llvm/lib/IR/ConstantRange.cpp
@@ -1238,7 +1238,10 @@ ConstantRange ConstantRange::sdiv(const ConstantRange &RHS) const {
   // separately by combining division results with the appropriate signs.
   APInt Zero = APInt::getZero(getBitWidth());
   APInt SignedMin = APInt::getSignedMinValue(getBitWidth());
-  ConstantRange PosFilter(APInt(getBitWidth(), 1), SignedMin);
+  // There are no positive 1-bit values. The 1 would get interpreted as -1.
+  ConstantRange PosFilter =
+      getBitWidth() == 1 ? getEmpty()
+                         : ConstantRange(APInt(getBitWidth(), 1), SignedMin);
   ConstantRange NegFilter(SignedMin, Zero);
   ConstantRange PosL = intersectWith(PosFilter);
   ConstantRange NegL = intersectWith(NegFilter);