[libraries-pgo] Assertion failed 'newType == TYP_I_IMPL' during 'Allocate Objects' in System.Memory.Tests

[jakobbotsch]

This fails under OSR stress.
Pipeline run: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1056248&view=results
Console log: https://helixr18s23ayyeko0k025g8.blob.core.windows.net/dotnet-runtime-refs-heads-main-b87fca762efb466696/System.Memory.Tests/1/console.a408b4fb.log?helixlogtype=result

DOTNET_TC_OnStackReplacement=1
DOTNET_OSR_HitLimit=1
DOTNET_TieredCompilation=1
DOTNET_DbgMiniDumpName=/home/helixbot/dotnetbuild/dumps/coredump.%d.dmp
DOTNET_TC_OnStackReplacement_InitialCounter=1
DOTNET_TC_QuickJitForLoops=1
DOTNET_DbgEnableMiniDump=1
DOTNET_EnableCrashReport=1
...
/root/helix/work/workitem/e /root/helix/work/workitem/e
  Discovering: System.Memory.Tests (method display = ClassAndMethod, method display options = None)
  Discovered:  System.Memory.Tests (found 2812 of 2841 test cases)
  Starting:    System.Memory.Tests (parallel test collections = on [2 threads], stop on fail = off)

Assert failure(PID 37 [0x00000025], Thread: 50 [0x0032]): Assertion failed 'newType == TYP_I_IMPL' in 'System.SpanTests.ReadOnlySpanTests:TestAlignmentNotCount_Byte()' during 'Allocate Objects' (IL size 92; hash 0xdc408f97; Tier1-OSR)

    File: /__w/1/s/src/coreclr/jit/objectalloc.cpp:2319
    Image: /root/helix/work/correlation/dotnet

cc @AndyAyersMS @dotnet/jit-contrib

[AndyAyersMS]

Looks like issues with GT_SUB... we are "retyping" a local that is already TYP_BYREF to TYP_BYREF.