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[mlir][arith] Add mulf(x, 0) -> 0 to mulf folder #161395

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Merged
merged 8 commits into from
Oct 2, 2025
Merged

[mlir][arith] Add mulf(x, 0) -> 0 to mulf folder #161395

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7e4a0d4
[mlir][arith] Add mulf(x, 0) -> 0 to mulf folder
Sep 30, 2025
8d49f3f
mulf(NaN, x) -> NaN
Sep 30, 2025
8c72844
Limit to fastmask nnan | ninf
Sep 30, 2025
e86191a
Update per comment.
Sep 30, 2025
bdb0f61
Add nsz.
Sep 30, 2025
18e9504
Remove ninf which is not needed.
Oct 1, 2025
f43001f
Add test for neg zero.
Oct 1, 2025
4019c36
Use CHECK_DAG.
Oct 1, 2025
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7 changes: 7 additions & 0 deletions mlir/lib/Dialect/Arith/IR/ArithOps.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1282,6 +1282,13 @@ OpFoldResult arith::MulFOp::fold(FoldAdaptor adaptor) {
if (matchPattern(adaptor.getRhs(), m_OneFloat()))
return getLhs();

if (arith::bitEnumContainsAll(getFastmath(), arith::FastMathFlags::nnan |
arith::FastMathFlags::nsz)) {
Comment on lines +1285 to +1286
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@ThomasRaoux ThomasRaoux Oct 2, 2025

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doesn't it need also ninf? inf * 0 -> Nan

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@kuhar kuhar Oct 2, 2025

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I tried to check this with Alive: https://alive2.llvm.org/ce/z/wvNkdy

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@kuhar kuhar Oct 2, 2025 •
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It's because nnan applies to the result as well:

nnan
No NaNs - Allow optimizations to assume the arguments and result are not NaN.

// mulf(x, 0) -> 0
if (matchPattern(adaptor.getRhs(), m_AnyZeroFloat()))
return getRhs();
}

return constFoldBinaryOp<FloatAttr>(
adaptor.getOperands(),
[](const APFloat &a, const APFloat &b) { return a * b; });
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12 changes: 12 additions & 0 deletions mlir/test/Dialect/Arith/canonicalize.mlir
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Expand Up @@ -2216,6 +2216,18 @@ func.func @test_mulf1(%arg0 : f32, %arg1 : f32) -> (f32) {
return %2 : f32
}

// CHECK-LABEL: @test_mulf2(
func.func @test_mulf2(%arg0 : f32) -> (f32, f32) {
// CHECK-DAG: %[[C0:.+]] = arith.constant 0.000000e+00 : f32
// CHECK-DAG: %[[C0n:.+]] = arith.constant -0.000000e+00 : f32
// CHECK-NEXT: return %[[C0]], %[[C0n]]
%c0 = arith.constant 0.0 : f32
%c0n = arith.constant -0.0 : f32
%0 = arith.mulf %c0, %arg0 fastmath<nnan,nsz> : f32
%1 = arith.mulf %c0n, %arg0 fastmath<nnan,nsz> : f32
return %0, %1 : f32, f32
}

// -----

// CHECK-LABEL: @test_divf(
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