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JIT: fix issue in redundant zero init opt #115698

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Merged
AndyAyersMS merged 1 commit into from
May 19, 2025
Merged

JIT: fix issue in redundant zero init opt #115698

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6 changes: 4 additions & 2 deletions src/coreclr/jit/optimizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5907,8 +5907,10 @@ void Compiler::optRemoveRedundantZeroInits()
defsInBlock.Set(lclNum, 1);
}
}
else if (varTypeIsStruct(lclDsc) && ((tree->gtFlags & GTF_VAR_USEASG) == 0) &&
lvaGetPromotionType(lclDsc) != PROMOTION_TYPE_NONE)
// Here we treat both "full" and "partial" tracked field defs as defs
// (that is, we ignore the state of GTF_VAR_USEASG).
Comment on lines +5910 to +5911
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Copilot AI May 18, 2025

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[nitpick] Consider clarifying this comment by removing the quotes around full/partial and explicitly stating that checks for GTF_VAR_USEASG are intentionally omitted to unify all tracked-field stores as definitions.

Suggested change
// Here we treat both "full" and "partial" tracked field defs as defs
// (that is, we ignore the state of GTF_VAR_USEASG).
// Here we treat both full and partial tracked field definitions as definitions.
// Checks for GTF_VAR_USEASG are intentionally omitted to unify all tracked-field stores as definitions.

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//
else if (varTypeIsStruct(lclDsc) && lvaGetPromotionType(lclDsc) != PROMOTION_TYPE_NONE)
{
for (unsigned i = lclDsc->lvFieldLclStart; i < lclDsc->lvFieldLclStart + lclDsc->lvFieldCnt;
++i)
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61 changes: 61 additions & 0 deletions src/tests/JIT/Regression/JitBlue/Runtime_115123/Runtime_115123.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,61 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

// Simplified from an Antigen test case

using System;
using System.Runtime.CompilerServices;
using Xunit;

public struct S1_D1_F2
{
public bool bool_1;
public bool bool_2;
}

public class Runtime_115123
{
[Fact]
public static void Test()
{
Problem(1);
}

[MethodImpl(MethodImplOptions.NoInlining)]
static void Problem(int a)
{
unchecked
{
bool b = false;
S1_D1_F2 s1_s1_d1_f2_1983 = new S1_D1_F2();
try
{
if (s1_s1_d1_f2_1983.bool_1 = (b = (s1_s1_d1_f2_1983.bool_1 = false) || (a == 0)))
{
SideEffect();
}
}
finally
{
switch (a)
{
case 0: SideEffect(); break;
case 1: SideEffect(); break;
case 2: SideEffect(); break;
case 3: SideEffect(); break;
case 4: SideEffect(); break;
default: SideEffect(); break;
}
}

Log("s1_s1_d1_f", s1_s1_d1_f2_1983);
}
}

[MethodImpl(MethodImplOptions.NoInlining)]
static void Log(string varName, object varValue) {}

[MethodImpl(MethodImplOptions.NoInlining)]
static void SideEffect() {}
}

8 changes: 8 additions & 0 deletions src/tests/JIT/Regression/JitBlue/Runtime_115123/Runtime_115123.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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