From ba1e04b9668b3502362f2ee36232f5f56e72b4e2 Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Fri, 1 Jul 2022 15:43:27 +0200 Subject: [PATCH] [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. --- llvm/lib/IR/ConstantRange.cpp | 5 ++++- llvm/unittests/IR/ConstantRangeTest.cpp | 3 +++ 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp index be6386c571b5..9d239101d8fd 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); diff --git a/llvm/unittests/IR/ConstantRangeTest.cpp b/llvm/unittests/IR/ConstantRangeTest.cpp index ced38a28977b..edea097aae76 100644 --- a/llvm/unittests/IR/ConstantRangeTest.cpp +++ b/llvm/unittests/IR/ConstantRangeTest.cpp @@ -1259,6 +1259,9 @@ TEST_F(ConstantRangeTest, UDiv) { } TEST_F(ConstantRangeTest, SDiv) { + ConstantRange OneBit = ConstantRange::getFull(1); + EXPECT_EQ(OneBit.sdiv(OneBit), ConstantRange(APInt(1, 0))); + unsigned Bits = 4; EnumerateTwoConstantRanges(Bits, [&](const ConstantRange &CR1, const ConstantRange &CR2) {