OSR stress failure in System.Diagnostics.DiagnosticsSource.Tests

[AndyAyersMS]

From libraries pgo CI job: https://dev.azure.com/dnceng/public/_test/analytics?definitionId=1002&contextType=build

;; x64 windows

set COMPlus_JitRandomOnStackReplacement=15
set COMPlus_OSR_HitLimit=2
set COMPlus_TC_OnStackReplacement=1
set COMPlus_TC_OnStackReplacement_InitialCounter=1
set COMPlus_TC_QuickJitForLoops=1
set COMPlus_TieredCompilation=1

  Starting:    System.Diagnostics.DiagnosticSource.Tests (parallel test collections = on, max threads = 12)
    System.Diagnostics.Metrics.Tests.AggregationStoreTests.GetOneLabel [FAIL]
      Assert.Equal() Failure
      Expected: LastValue { }
      Actual:   LastValue { }
      Stack Trace:
        C:\repos\runtime0\src\libraries\System.Diagnostics.DiagnosticSource\tests\AggregationManagerTests.cs(48,0): at System.Diagnostics.Metrics.Tests.AggregationStoreTests.GetOneLabel()

Have isolated this via COMPlus_JitEnablePatchpointRange to this method:

System.Diagnostics.Metrics.LabelInstructionInterpretter`2[ObjectSequence1,__Canon][System.Diagnostics.Metrics.ObjectSequence1,System.__Canon]::GetAggregator, IL size = 255, hash=0xfe17726d Tier1-OSR @0xaa

Tagging subscribers to this area: @tarekgh, @tommcdon, @pjanotti
See info in area-owners.md if you want to be subscribed.

Issue Details

---

From libraries pgo CI job: https://dev.azure.com/dnceng/public/_test/analytics?definitionId=1002&contextType=build

;; x64 windows

set COMPlus_JitRandomOnStackReplacement=15
set COMPlus_OSR_HitLimit=2
set COMPlus_TC_OnStackReplacement=1
set COMPlus_TC_OnStackReplacement_InitialCounter=1
set COMPlus_TC_QuickJitForLoops=1
set COMPlus_TieredCompilation=1

  Starting:    System.Diagnostics.DiagnosticSource.Tests (parallel test collections = on, max threads = 12)
    System.Diagnostics.Metrics.Tests.AggregationStoreTests.GetOneLabel [FAIL]
      Assert.Equal() Failure
      Expected: LastValue { }
      Actual:   LastValue { }
      Stack Trace:
        C:\repos\runtime0\src\libraries\System.Diagnostics.DiagnosticSource\tests\AggregationManagerTests.cs(48,0): at System.Diagnostics.Metrics.Tests.AggregationStoreTests.GetOneLabel()

Have isolated this via COMPlus_JitEnablePatchpointRange to this method:

System.Diagnostics.Metrics.LabelInstructionInterpretter`2[ObjectSequence1,__Canon][System.Diagnostics.Metrics.ObjectSequence1,System.__Canon]::GetAggregator, IL size = 255, hash=0xfe17726d Tier1-OSR @0xaa

Author:	AndyAyersMS
Assignees:	-
Labels:	area-System.Diagnostics.Tracing, untriaged
Milestone:	-

Tagging subscribers to this area: @JulieLeeMSFT
See info in area-owners.md if you want to be subscribed.

Issue Details

---

From libraries pgo CI job: https://dev.azure.com/dnceng/public/_test/analytics?definitionId=1002&contextType=build

;; x64 windows

set COMPlus_JitRandomOnStackReplacement=15
set COMPlus_OSR_HitLimit=2
set COMPlus_TC_OnStackReplacement=1
set COMPlus_TC_OnStackReplacement_InitialCounter=1
set COMPlus_TC_QuickJitForLoops=1
set COMPlus_TieredCompilation=1

  Starting:    System.Diagnostics.DiagnosticSource.Tests (parallel test collections = on, max threads = 12)
    System.Diagnostics.Metrics.Tests.AggregationStoreTests.GetOneLabel [FAIL]
      Assert.Equal() Failure
      Expected: LastValue { }
      Actual:   LastValue { }
      Stack Trace:
        C:\repos\runtime0\src\libraries\System.Diagnostics.DiagnosticSource\tests\AggregationManagerTests.cs(48,0): at System.Diagnostics.Metrics.Tests.AggregationStoreTests.GetOneLabel()

Have isolated this via COMPlus_JitEnablePatchpointRange to this method:

System.Diagnostics.Metrics.LabelInstructionInterpretter`2[ObjectSequence1,__Canon][System.Diagnostics.Metrics.ObjectSequence1,System.__Canon]::GetAggregator, IL size = 255, hash=0xfe17726d Tier1-OSR @0xaa

Author:	AndyAyersMS
Assignees:	-
Labels:	area-System.Diagnostics.Tracing, area-CodeGen-coreclr, untriaged
Milestone:	-

[AndyAyersMS]

The problem is that we're too aggressive with struct promotion (likely a result of #65903).

Relatively simple repro case

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

interface IFoo 
{
    public Span<object> AsSpan();
}

public struct ObjectSequence1 : IFoo
{
    public object Value1;
    
    public Span<object> AsSpan()
    {
        return MemoryMarshal.CreateSpan(ref Value1, 1);
    }
}

public struct ObjectSequenceMany : IFoo
{
    public object[] _values;

    public Span<object> AsSpan()
    {
        return _values.AsSpan();
    }

    public ObjectSequenceMany(object[] x)
    {
        _values = x;
    }
}

public class InvalidOSRPromotion
{
    [MethodImpl(MethodImplOptions.NoInlining)]
    static bool G<T>(int n) where T : IFoo
    {
        T values = default;

        if (values is ObjectSequenceMany)
        {
            values = (T)(object)new ObjectSequenceMany(new object[5]);
        }

        Span<object> indexedValues = values.AsSpan();

        for (int i = 0; i < n; i++)
        {
            indexedValues[i] = "foo";
        }

        if (values is ObjectSequence1)
        {
            return (indexedValues[0] == ((ObjectSequence1)(object)values).Value1);
        }
        
        return false;
    }

    public static int Main()
    {
        return G<ObjectSequence1>(1) ? 100 : -1;
    }
}

run this with

set COMPlus_TieredCompilation=1
set COMPlus_OSR_HitLimit=1
set COMPlus_TC_OnStackReplacement=1
set COMPlus_TC_OnStackReplacement_InitialCounter=1

The OSR method will unsoundly promote the values local and erroneously return false from G<ObjectSequence1>.