JIT: Assertion failed 'unreached' during 'LSRA build intervals'

[amanasifkhalid]

// Found by Antigen
// Reduced from 11.53 KB to 1.76 KB.


using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.Arm;
using System.Runtime.Intrinsics.X86;
using System.Numerics;
public class TestClass
{
    public struct S1
    {
    }
    public struct S2
    {
        public struct S2_D1_F1
        {
        }
    }
    static byte s_byte_5 = 5;
    static short s_short_9 = 2;
    float float_31 = -5f;
    S1 s1_37 = new S1();
    S2.S2_D1_F1 s2_s2_d1_f1_38 = new S2.S2_D1_F1();
    static int s_loopInvariant = 6;
    private static List<string> toPrint = new List<string>();
    [MethodImpl(MethodImplOptions.NoInlining)]
    public short LeafMethod5()
    {
        unchecked
        {
            return 15%4;
        }
    }
    public short Method1(byte p_byte_40, out S2.S2_D1_F1 p_s2_s2_d1_f1_41, ref S2.S2_D1_F1 p_s2_s2_d1_f1_42, ref S1 p_s1_43, ref byte p_byte_44)
    {
        unchecked
        {
            ulong ulong_58 = 41;
            int __loopvar0 = 15-4;
            while (float_31 > float_31)
            {
                if (__loopvar0 > s_loopInvariant)
                    break;
            }
            Log("ulong_58", ulong_58);
            return LeafMethod5();
        }
    }
    public void Method0()
    {
        unchecked
        {
            s_short_9 = Method1(15-4, out s2_s2_d1_f1_38, ref s2_s2_d1_f1_38, ref s1_37, ref s_byte_5);
            return;
        }
    }
    public static int Main(string[] args)
    {
        return Antigen();
    }
    public static int Antigen()
    {
        new TestClass().Method0();
        return string.Join(Environment.NewLine, toPrint).GetHashCode();
    }
    [MethodImpl(MethodImplOptions.NoInlining)]
    public static void Log(string varName, object varValue)
{}}
/*
Environment:

set DOTNET_TieredCompilation=0
set DOTNET_JitStressRegs=0x1000

Debug: 1681498316

Release: 0
Assert failure(PID 30624 [0x000077a0], Thread: 31100 [0x797c]): Assertion failed 'unreached' in 'System.Guid:FormatGuidVector128Utf8(System.Guid,bool):System.ValueTuple`3[System.Runtime.Intrinsics.Vector128`1[byte],System.Runtime.Intrinsics.Vector128`1[byte],System.Runtime.Intrinsics.Vector128`1[byte]]' during 'LSRA build intervals' (IL size 332; hash 0x10ce27ce; FullOpts)

    File: C:\wk\runtime\src\coreclr\jit\lsra.cpp:673
    Image: C:\wk\runtime\artifacts\tests\coreclr\windows.x64.Checked\Tests\Core_Root\corerun.exe
*/

Peeled off from #116704. cc @dotnet/jit-contrib.

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[amanasifkhalid]

Turns out this isn't a JIT issue, but a PowerShell vs cmd issue: We can prefix the JitStressRegs value with 0x from cmd, and the JIT will interpret the hex value correctly. For whatever reason, PS interprets a different value if the prefix is given, thus yielding an invalid LSRA stress mask value in this case.

[jakobbotsch]

Turns out this isn't a JIT issue, but a PowerShell vs cmd issue: We can prefix the JitStressRegs value with 0x from cmd, and the JIT will interpret the hex value correctly. For whatever reason, PS interprets a different value if the prefix is given, thus yielding an invalid LSRA stress mask value in this case.

Just in case you are curious, $env:DOTNET_JitStressRegs=0x1234 in powershell interprets 0x1234 as a number, and converts it to a string, resulting in being equivalent to $env:DOTNET_JitStressRegs="4660". Since coreclr treats environment variables as hex, that results in the value being set to 0x4660. To set the string value to "0x1234" you need $env:DOTNET_JitStressRegs="0x1234" or $env:DOTNET_JitStressRegs="1234".

[amanasifkhalid]

Just in case you are curious, $env:DOTNET_JitStressRegs=0x1234 in powershell interprets 0x1234 as a number, and converts it to a string, resulting in being equivalent to $env:DOTNET_JitStressRegs="4660". Since coreclr treats environment variables as hex, that results in the value being set to 0x4660. To set the string value to "0x1234" you need $env:DOTNET_JitStressRegs="0x1234" or $env:DOTNET_JitStressRegs="1234".

Interesting, thanks for sharing -- looks like I've been running stress modes over 9 incorrectly this whole time...