[InstSimplify] Simplify (fmul -x, +/-0) -> -/+0
#85345
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llvmbot
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goldsteinn
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(fmul -x, +/-0) -> -/+0
|
@llvm/pr-subscribers-llvm-analysis @llvm/pr-subscribers-llvm-transforms Author: None (goldsteinn) Changes
Full diff: https://github.com/llvm/llvm-project/pull/85345.diff 2 Files Affected:
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index ce651783caf16b..434ee26ef01aa5 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -5767,11 +5767,18 @@ static Value *simplifyFMAFMul(Value *Op0, Value *Op1, FastMathFlags FMF,
if (FMF.noNaNs() && FMF.noSignedZeros())
return ConstantFP::getZero(Op0->getType());
- // +normal number * (-)0.0 --> (-)0.0
KnownFPClass Known =
computeKnownFPClass(Op0, FMF, fcInf | fcNan, /*Depth=*/0, Q);
- if (Known.SignBit == false && Known.isKnownNever(fcInf | fcNan))
- return Op1;
+ if (Known.isKnownNever(fcInf | fcNan)) {
+ // +normal number * (-)0.0 --> (-)0.0
+ if (Known.SignBit == false)
+ return Op1;
+ // -normal number * (-)0.0 --> -(-)0.0
+ if (Known.SignBit == true)
+ return match(Op1, m_PosZeroFP())
+ ? ConstantFP::getNegativeZero(Op0->getType())
+ : ConstantFP::getZero(Op0->getType());
+ }
}
// sqrt(X) * sqrt(X) --> X, if we can:
diff --git a/llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll b/llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
index b8244b1d508c62..9b913d68f4004e 100644
--- a/llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
+++ b/llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
@@ -211,6 +211,22 @@ define double @fmul_nnan_ninf_nneg_n0.0_commute(i127 %x) {
ret double %r
}
+define float @src_mul_nzero_neg(float nofpclass(inf nan pzero psub pnorm) %f) {
+; CHECK-LABEL: @src_mul_nzero_neg(
+; CHECK-NEXT: ret float 0.000000e+00
+;
+ %r = fmul float %f, -0.0
+ ret float %r
+}
+
+define float @src_mul_zero_neg(float nofpclass(inf nan pzero psub pnorm) %f) {
+; CHECK-LABEL: @src_mul_zero_neg(
+; CHECK-NEXT: ret float -0.000000e+00
+;
+ %r = fmul float %f, 0.0
+ ret float %r
+}
+
; Make sure we can infer %x can't be 0 based on assumes.
define { float, float } @test_fmul_0_assumed_finite(float %x) {
; CHECK-LABEL: @test_fmul_0_assumed_finite(
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arsenm
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| %r = fmul float %f, 0.0 | ||
| ret float %r | ||
| } | ||
|
|
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Can you also test the FMA / fmuladd cases? Also vectors
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Done, although neither of those cases get simplified by instsimplify alone.
| if (Known.SignBit == true) | ||
| return match(Op1, m_PosZeroFP()) | ||
| ? ConstantFP::getNegativeZero(Op0->getType()) | ||
| : ConstantFP::getZero(Op0->getType()); |
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Can also just pass the bool condition to the parameter to getZero to make it signed
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Switching to just fneg, that's necessary for handling mismatch vector.
dtcxzyw
changed the title
(fmul -x, +/-0) -> -/+0(fmul -x, +/-0) -> -/+0
We already handle the `+x` case, and noticed it was missing in the bug affecting llvm#82555 Proofs: https://alive2.llvm.org/ce/z/WUSvmV
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| ; CHECK-NEXT: [[R:%.*]] = call float @llvm.fmuladd.f32(float [[F:%.*]], float 0.000000e+00, float [[ADD:%.*]]) | ||
| ; CHECK-NEXT: ret float [[R]] | ||
| ; | ||
| %r = call float @llvm.fmuladd.f32(float %f, float 0.0, float %add) |
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I think the case fmuladd/fma will be handled is if the last operand is 0
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Doesn't seem to be the case, although note instcombine does handle the fmuladd/fma. Just not simplify.
arsenm
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Mar 18, 2024
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We already handle the `+x` case, and noticed it was missing in the bug affecting llvm#82555 Proofs: https://alive2.llvm.org/ce/z/WUSvmV Closes llvm#85345
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(fmul -x, +/-0); NFC(fmul -x, +/-0)->-/+0Proofs: https://alive2.llvm.org/ce/z/WUSvmV