[PATCH] riscv: cmpxchg: Use .option arch for Zacas and Zabha

[Paul Walmsley]

On Fri, 17 Jul 2026, Vivian Wang wrote:

> Instead of adding these to -march globally, use .option arch to use
> instructions from these extensions only in code paths where we know they
> are available, like how it is done for most other extensions.
> TOOLCHAIN_HAS_{ZACAS,ZABHA} already depend on AS_HAS_OPTION_ARCH, so
> this is not a functionality regression even on older assemblers.
> 
> Although the compiler is unlikely to generate atomics on its own accord,
> this aligns handling of Zacas and Zabha with most other extensions and
> improves consistency on how assembly code requiring extra extensions is
> written in kernel code.
> 
> This is analogous to the use of __LSE_PREAMBLE or .arch_extension lse in
> arm64 code.
> 
> Signed-off-by: Vivian Wang <wangruikang at iscas.ac.cn>

Thanks, queued for v7.3.


- Paul