[PATCH v2 1/2] riscv: introduce RISCV_EFFICIENT_UNALIGNED_ACCESS

[Eric Biggers]

On Tue, Dec 05, 2023 at 04:39:24PM +0800, Qingfang DENG wrote:
> Hi,
> 
> You may as well remove the -mstrict-align CFLAGS in the Makefile, if
> this option is enabled:
> 
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -108,7 +108,9 @@ KBUILD_AFLAGS_MODULE += $(call as-option,-Wa$(comma)-mno-relax)
>  # unaligned accesses.  While unaligned accesses are explicitly allowed in the
>  # RISC-V ISA, they're emulated by machine mode traps on all extant
>  # architectures.  It's faster to have GCC emit only aligned accesses.
> +ifneq ($(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS),y)
>  KBUILD_CFLAGS += $(call cc-option,-mstrict-align)
> +endif
>  

Agreed.  When CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y, we shouldn't use
-mstrict-align, so that the compiler can actually use unaligned memory accesses.

If I understand correctly, beyond the change requested above, people seem to be
happy with this patch.  Jisheng, can you resend it with the above feedback
addressed?  Thanks!

- Eric