Fix assert(isByteReg(ireg)).

[sandreenko]

We had a similar code in the non-multi reg case:

runtime/src/coreclr/jit/lsrabuild.cpp

Lines 3380 to 3386 in 867ba80

	#ifdef TARGET_X86
	var_types type = varDsc->GetRegisterType(storeLoc);
	if (varTypeIsByte(type))
	{
	srcCandidates = allByteRegs();
	}
	#endif// TARGET_X86

so repeat the logic for MultiReg.

When we do a call we then copy the arguments to the temp location and we should choose registers that can be used in byte instructions on x86.

Fixes#46277.

No diffs.

[sandreenko]

/azp run runtime-coreclr outerloop, runtime-coreclr jitstressregs

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Azure Pipelines successfully started running 2 pipeline(s).

[sandreenko]

PTAL @dotnet/jit-contrib , cc @jkoritzinsky

[sandreenko]

/azp run runtime-coreclr jitstressregs

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[kunalspathak]

Looks good to me. However, I am wondering what changed that we hit issue #46277? I see that the assert in the issue was added last year in 9781175?

[sandreenko]

Looks good to me. However, I am wondering what changed that we hit issue #46277? I see that the assert in the issue was added last year in 9781175?

It was exposed by #39294, before Jit did not see struct returns like <int, byte> on x86.

[sandreenko]

The failures in the stress job are covered by #46085.