NativeAOT/Arm64: Do not overwrite gcinfo tracking registers for TLS

[kunalspathak]

Fields reg1 and reg2 of instrDesc were repurposed for saving live gc registers. However, this field was getting overwritten when we populate the register for the blr instruction that is needed for TLS access pattern. Since the pattern of the instructions including register requirements for them is very specific and has to be like following:

runtime/src/coreclr/jit/codegenarmarch.cpp

Lines 3578 to 3591 in 07f8ebd

	// For NativeAOT, linux/arm64, linker wants the following pattern, so we will generate
	// it as part of the call. Generating individual instructions is tricky to get it
	// correct in the format the way linker needs. Also, we might end up spilling or
	// reloading a register, which can break the pattern.
	//
	// mrs x1, tpidr_el0
	// adrp x0, :tlsdesc:tlsRoot ; R_AARCH64_TLSDESC_ADR_PAGE21
	// ldr x2, [x0] ; R_AARCH64_TLSDESC_LD64_LO12
	// add x0, x0, #0 ; R_AARCH64_TLSDESC_ADD_LO12
	// blr x2 ; R_AARCH64_TLSDESC_CALL
	// add x0, x1, x0
	// We guaranteed in LSRA that r0, r1 and r2 are assigned to this node.
	// mrs

In LSRA, we already ensure that those requirements are met.

runtime/src/coreclr/jit/lsraarmarch.cpp

Lines 265 to 267 in 07f8ebd

	newRefPosition(REG_R0, currentLoc, RefTypeFixedReg, nullptr, genSingleTypeRegMask(REG_R0));
	newRefPosition(REG_R1, currentLoc, RefTypeFixedReg, nullptr, genSingleTypeRegMask(REG_R1));
	ctrlExprCandidates = genSingleTypeRegMask(REG_R2);

As such, there is no need to track the target handle register separately in a field but can just be used directly in codegen/emitter logic. Also, I noticed that the display was not using the right register, so fixed that as well.

Fixes: #112351

[kunalspathak]

/azp run runtime-nativeaot-outerloop

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• src/coreclr/jit/emitarm64.cpp: Language not supported

[kunalspathak]

@dotnet/jit-contrib

[kunalspathak]

@jkotas - I think this should be backported to net9.0?

[jkotas]

Yes, could you please backport this to net9.0?

[kunalspathak]

/backport to release/9.0-staging

[github-actions]

Started backporting to release/9.0-staging: https://github.com/dotnet/runtime/actions/runs/13321667412