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Merged
merged 2 commits into from
Sep 30, 2022
Merged

PR for llvm/llvm-project#58046 #174

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0865ce4
[InstSimplify] Add test for PR58046 (NFC)
nikic Sep 29, 2022
7ba4428
[ValueTracking] Fix CannotBeOrderedLessThanZero() for fdiv (PR58046)
nikic Sep 29, 2022
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13 changes: 11 additions & 2 deletions llvm/lib/Analysis/ValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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:
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16 changes: 16 additions & 0 deletions llvm/test/Transforms/InstSimplify/floating-point-compare.ll
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Expand Up @@ -999,6 +999,22 @@ define <2 x i1> @known_positive_une_with_negative_constant_splat_vec(<2 x i32> %
ret <2 x i1> %cmp
}

; TODO: This could fold to true.
define i1 @pr58046(i64 %arg) {
; CHECK-LABEL: @pr58046(
; 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
%div = fdiv double 1.000000e+00, %mul
%cmp = fcmp oeq double %div, 0xFFF0000000000000
ret i1 %cmp
}

define i1 @nonans1(double %in1, double %in2) {
; CHECK-LABEL: @nonans1(
; CHECK-NEXT: ret i1 false
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