Test Failure: runtime-coreclr jitstress-random, assertion in lsra

[dhartglassMSFT]

runtime-coreclr jitstress-random fails in outerloop

Fails on OSX arm64

Helix link:
https://helix.dot.net/api/2019-06-17/jobs/f6a720ab-8cc5-4e76-b5a4-eb87d6a2ddf1/workitems/HardwareIntrinsics_General_ro/console

Assert failure(PID 25723 [0x0000647b], Thread: 313971 [0x4ca73]): Assertion failed 'refPosition->RegOptional()' in 'JIT.HardwareIntrinsics.General._Vector512.VectorBinaryOpTest__DotByte:RunClsVarScenario():this' during 'LSRA build intervals' (IL size 49; hash 0x186ed855; FullOpts)

Failing run:
https://dev.azure.com/dnceng-public/public/_build/results?buildId=1386206

[dhartglassMSFT]

This is arm64 LSRA, grabbing this

[dotnet-policy-service]

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

[dhartglassMSFT]

Initial investigation here, it doesn't seem to be a regression but an extant issue that jitstress random found.