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| author | Nikita Popov <npopov@redhat.com> | 2022-09-29 15:51:05 +0200 |
|---|---|---|
| committer | Tobias Hieta <tobias@hieta.se> | 2022-09-30 08:20:33 +0200 |
| commit | 77ff99c10bee11a202dbe5fd1a08d8394d7828af (patch) | |
| tree | 0836e174b48afa79cfd7b40ab827daaec7c6fcd2 | |
| parent | 6ba100a83f14e3a361c2dd298405dc747a4a02c4 (diff) | |
| download | llvm-77ff99c10bee11a202dbe5fd1a08d8394d7828af.tar.gz | |
[ValueTracking] Fix CannotBeOrderedLessThanZero() for fdiv (PR58046)
When checking the RHS of fdiv, we should set the SignBitOnly flag,
because a negative zero can become -Inf, which is ordered less
than zero.
Fixes https://github.com/llvm/llvm-project/issues/58046.
Differential Revision: https://reviews.llvm.org/D134876
| -rw-r--r-- | llvm/lib/Analysis/ValueTracking.cpp | 13 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstSimplify/floating-point-compare.ll | 8 |
2 files changed, 17 insertions, 4 deletions
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index 2dd671b4ab9e..569ee6b3ea86 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -3593,14 +3593,23 @@ static bool cannotBeOrderedLessThanZeroImpl(const Value *V, // Unsigned integers are always nonnegative. case Instruction::UIToFP: return true; - case Instruction::FMul: case Instruction::FDiv: - // X * X is always non-negative or a NaN. // X / X is always exactly 1.0 or a NaN. if (I->getOperand(0) == I->getOperand(1) && (!SignBitOnly || cast<FPMathOperator>(I)->hasNoNaNs())) return true; + // Set SignBitOnly for RHS, because X / -0.0 is -Inf (or NaN). + return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly, + Depth + 1) && + cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, + /*SignBitOnly*/ true, Depth + 1); + case Instruction::FMul: + // X * X is always non-negative or a NaN. + if (I->getOperand(0) == I->getOperand(1) && + (!SignBitOnly || cast<FPMathOperator>(I)->hasNoNaNs())) + return true; + LLVM_FALLTHROUGH; case Instruction::FAdd: case Instruction::FRem: diff --git a/llvm/test/Transforms/InstSimplify/floating-point-compare.ll b/llvm/test/Transforms/InstSimplify/floating-point-compare.ll index 399950b65de2..a32717aed236 100644 --- a/llvm/test/Transforms/InstSimplify/floating-point-compare.ll +++ b/llvm/test/Transforms/InstSimplify/floating-point-compare.ll @@ -999,10 +999,14 @@ define <2 x i1> @known_positive_une_with_negative_constant_splat_vec(<2 x i32> % ret <2 x i1> %cmp } -; FIXME: Miscompile. +; TODO: This could fold to true. define i1 @pr58046(i64 %arg) { ; CHECK-LABEL: @pr58046( -; CHECK-NEXT: ret i1 false +; CHECK-NEXT: [[FP:%.*]] = uitofp i64 [[ARG:%.*]] to double +; CHECK-NEXT: [[MUL:%.*]] = fmul double -0.000000e+00, [[FP]] +; CHECK-NEXT: [[DIV:%.*]] = fdiv double 1.000000e+00, [[MUL]] +; CHECK-NEXT: [[CMP:%.*]] = fcmp oeq double [[DIV]], 0xFFF0000000000000 +; CHECK-NEXT: ret i1 [[CMP]] ; %fp = uitofp i64 %arg to double %mul = fmul double -0.000000e+00, %fp |