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JIT: (bug) complementing an AVX comparison drops the complement #133518
Description
Repro
using System;
using System.Runtime.CompilerServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;
class Program {
[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
static Vector256<float> Test(Vector256<float> a, Vector256<float> b) =>
~Avx.Compare(a, b, FloatComparisonMode.OrderedNotEqualNonSignaling);
static void Main() {
if (!Avx.IsSupported)
throw new PlatformNotSupportedException("AVX is required.");
Vector256<float> value = Vector256.Create(1.0f);
Console.WriteLine(Test(value, value).AsUInt32().GetElement(0).ToString("X8"));
}
}Expected
FFFFFFFF
Equal non-NaN lanes fail ordered-not-equal, so the comparison yields zero bits and the complement is all-bits-set.
Actual
00000000
Platform
Windows x64 with AVX, .NET 11.0.0-rc.1.26425.128.
Activity
dotnet-policy-service commentedon Sep 9, 2026
Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.
MihuBot commentedon Sep 9, 2026
I'm a bot. Here is a possible related and/or duplicate issue (I may be wrong):
~x op kwithout inverting the comparison #129076[-]JIT: complementing an AVX comparison drops the complement[/-][+]JIT: (bug) complementing an AVX comparison drops the complement[/+]Fix SIMD complement and scalar FMA folding (dotnet#133542)
EgorBo commentedon Sep 18, 2026
Affected SDK versions: