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JIT: Keep side effects in promotion decomposition #115221

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Merged
jakobbotsch merged 1 commit into from
May 1, 2025
Merged

JIT: Keep side effects in promotion decomposition #115221

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12 changes: 11 additions & 1 deletion src/coreclr/jit/promotiondecomposition.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -588,7 +588,17 @@ class DecompositionPlan
numAddrUses++;
}

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Copilot AI May 1, 2025

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[nitpick] Consider adding a comment explaining why side effects are extracted when numAddrUses equals 0 to clarify that this branch preserves the side effects of the address computation for unused loads.

Suggested change
// If the address is not used (numAddrUses == 0), we still need to preserve
// any side effects from the address computation. Extract these side effects
// and add them to the statement list to ensure they are not lost.

Copilot uses AI. Check for mistakes.
if (numAddrUses > 1)
if (numAddrUses == 0)
{
GenTree* sideEffects = nullptr;
m_compiler->gtExtractSideEffList(addr, &sideEffects);

if (sideEffects != nullptr)
{
statements->AddStatement(sideEffects);
}
}
else if (numAddrUses > 1)
{
m_compiler->gtPeelOffsets(&addr, &addrBaseOffs, &addrBaseOffsFldSeq);

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50 changes: 50 additions & 0 deletions src/tests/JIT/Regression/JitBlue/Runtime_114571/Runtime_114571.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,50 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

// Generated by Fuzzlyn v2.5 on 2025-04-11 19:54:45
// Run on Arm64 MacOS
// Seed: 17225220246896154744-vectort,vector64,vector128,armadvsimd,armadvsimdarm64,armaes,armarmbase,armarmbasearm64,armcrc32,armcrc32arm64,armdp,armrdm,armrdmarm64,armsha1,armsha256
// Reduced from 24.9 KiB to 0.7 KiB in 00:00:20
// Debug: Throws 'System.NullReferenceException'
// Release: Runs successfully
using System;
using System.Numerics;
using System.Runtime.CompilerServices;
using Xunit;

public struct S0
{
public sbyte F2;
public Vector<int> F4;
public bool F7;
}

public class C0
{
public S0 F2;
}

public class Runtime_114571
{
public static Vector<long> s_1;
public static S0[] s_5 = new S0[]
{
new S0()
};

[Fact]
public static void TestEntryPoint()
{
Assert.Throws<NullReferenceException>(() => M1(new C0()));
}

[MethodImpl(MethodImplOptions.NoInlining)]
private static bool M1(C0 argThis)
{
S0[] vr9 = default(S0[]);
S0 var6 = vr9[0];
var6.F2 = 0;
argThis.F2.F2 = var6.F2;
return s_5[0].F7;
}
}
8 changes: 8 additions & 0 deletions src/tests/JIT/Regression/JitBlue/Runtime_114571/Runtime_114571.csproj
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@@ -0,0 +1,8 @@
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<Optimize>True</Optimize>
</PropertyGroup>
<ItemGroup>
<Compile Include="$(MSBuildProjectName).cs" />
</ItemGroup>
</Project>
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