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[release/6.0] Fix fgValueNumberArrIndexVal for wide reads #58427

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Aug 31, 2021
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5 changes: 3 additions & 2 deletions src/coreclr/jit/valuenum.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -4242,11 +4242,12 @@ ValueNum Compiler::fgValueNumberArrIndexVal(GenTree* tree,
var_types elemTyp = DecodeElemType(elemTypeEq);
var_types indType = (tree == nullptr) ? elemTyp : tree->TypeGet();
ValueNum selectedElem;
unsigned elemWidth = elemTyp == TYP_STRUCT ? info.compCompHnd->getClassSize(elemTypeEq) : genTypeSize(elemTyp);

if (fldSeq == FieldSeqStore::NotAField())
if ((fldSeq == FieldSeqStore::NotAField()) || (genTypeSize(indType) > elemWidth))
{
// This doesn't represent a proper array access
JITDUMP(" *** NotAField sequence encountered in fgValueNumberArrIndexVal\n");
JITDUMP(" *** Not a proper arrray access encountered in fgValueNumberArrIndexVal\n");

// a new unique value number
selectedElem = vnStore->VNForExpr(compCurBB, elemTyp);
Expand Down
50 changes: 50 additions & 0 deletions src/tests/JIT/Regression/JitBlue/Runtime_57914/Runtime_57914.cs
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.

using System;
using System.Runtime.CompilerServices;

public class Program
{
public static int Main()
{
return (Test1() && Test2()) ? 100 : 101;
}

private static bool Test1()
{
byte[] array = new byte[2];
array[0] = 1;
array[1] = 2;

// a1, a2 and a3 all have different values here
byte a1 = Unsafe.ReadUnaligned<byte>(ref array[0]);
short a2 = Unsafe.ReadUnaligned<short>(ref array[0]);
array[1] = 42;
short a3 = Unsafe.ReadUnaligned<short>(ref array[0]);

return a1 != a2 && a1 != a3 && a2 != a3;
}

private static bool Test2()
{
bool result = true;
byte[] buffer = new byte[4];
buffer[0] = 0x1;
buffer[1] = 0x2;
buffer[2] = 0x3;
buffer[3] = 0x4;

if (buffer.Length > 0)
{
int n = Unsafe.ReadUnaligned<int>(ref buffer[0]);
if (n != 0x4030201)
result = false;
Consume(n);
}
return result;
}

[MethodImpl(MethodImplOptions.NoInlining)]
static void Consume(int n) {}
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>Exe</OutputType>
</PropertyGroup>
<PropertyGroup>
<DebugType>None</DebugType>
<Optimize>True</Optimize>
</PropertyGroup>
<ItemGroup>
<Compile Include="$(MSBuildProjectName).cs" />
</ItemGroup>
</Project>