riscv: cmpxchg: Use .option arch for Zacas and Zabha

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@iscas.ac.cn>
Reviewed-by: Jesse Taube <jtaubepe@redhat.com>
Link: https://patch.msgid.link/20260717-riscv-no-zacas-zabha-in-march-v1-1-82b5b0799fb6@iscas.ac.cn
Signed-off-by: Paul Walmsley <pjw@kernel.org>

0 files changed, 0 insertions, 0 deletions