Test failure: Assertion failed 'isByteReg(ireg)' in 'StructABI:EchoByteAndFloatWrapper():bool' during 'Generate code'

[v-haren]

failed in job: runtime-coreclr jitstressregs 20201220.1

failed tests:
JIT\Directed\StructABI\StructABI\StructABI.cmd

CoreCLR windows x86 Checked jitstressregs1 @ Windows.10.Amd64.Open

CoreCLR Linux arm64 Checked jitstressregs3 @ (Ubuntu.1804.Arm64.Open)Ubuntu.1804.Armarch.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-18.04-helix-arm64v8-a45aeeb-20190620155855

Error message

Assert failure(PID 3456 [0x00000d80], Thread: 1888 [0x0760]): Assertion failed 'isByteReg(ireg)' in 'StructABI:EchoByteAndFloatWrapper():bool' during 'Generate code' (IL size 157)

    File: F:\workspace\_work\1\s\src\coreclr\jit\emitxarch.cpp Line: 6622
    Image: C:\h\w\AB3408EC\p\CoreRun.exe


Return code:      1
Raw output file:      C:\h\w\AB3408EC\w\ACCD092F\e\JIT\Directed\Reports\JIT.Directed\StructABI\StructABI\StructABI.output.txt
Raw output:
BEGIN EXECUTION
 "C:\h\w\AB3408EC\p\corerun.exe" StructABI.dll 
Expected: 100
Actual: -1073740286
END EXECUTION - FAILED
FAILED
Test Harness Exitcode is : 1
To run the test:
> set CORE_ROOT=C:\h\w\AB3408EC\p
> C:\h\w\AB3408EC\w\ACCD092F\e\JIT\Directed\StructABI\StructABI\StructABI.cmd
Expected: True
Actual:   False


Stack trace
   at JIT_Directed._StructABI_StructABI_StructABI_._StructABI_StructABI_StructABI_cmd() in F:\workspace\_work\1\s\artifacts\tests\coreclr\windows.x86.Checked\TestWrappers\JIT.Directed\JIT.Directed.XUnitWrapper.cs:line 60929