mlkem-native / mldsa-native AArch64 local-label clash

[hanno-becker]

• Sibling of mlkem-native / mldsa-native AArch64 local-label clash mlkem-native#1812

When both mlkem-native and mldsa-native AArch64 assembly backends are linked into a single translation unit (as in AWS-LC), the build fails because of a duplicate-symbol. The issue here is mlkem-native and mldsa-native using the same local labels in the AArch64 assembly files. Other symbols are prefixed with the ASM namespace via MLX_ASM_NAMESPACE(...), but labels aren't.

At the moment, AWS-LC patches up the labels at import time. Not a big issue, but avoidable. Complete list of conflicts:

Label	mlkem file	mldsa file
Lntt_layer123_start	ntt_aarch64_asm.S	ntt_aarch64_asm.S
Lrej_uniform_initial_zero	rej_uniform_aarch64_asm.S	rej_uniform_aarch64_asm.S
Lrej_uniform_loop48	rej_uniform_aarch64_asm.S	rej_uniform_aarch64_asm.S
Lrej_uniform_loop48_end	rej_uniform_aarch64_asm.S	rej_uniform_aarch64_asm.S
Lrej_uniform_memory_copy	rej_uniform_aarch64_asm.S	rej_uniform_aarch64_asm.S
Lrej_uniform_final_copy	rej_uniform_aarch64_asm.S	rej_uniform_aarch64_asm.S
Lrej_uniform_return	rej_uniform_aarch64_asm.S	rej_uniform_aarch64_asm.S

Interestingly, the x86_64 backends do not clash (0 shared local labels), so this is AArch64-specific.

Suggested fix

Add explicit label prefixes so mlkem-native and mldsa-native do not share any two label names.