Re: [PATCH] RISC-V: fix compile error from decuplicated __ALTERNATIVE_CFG_2

[Conor Dooley <conor@kernel.org>]

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On Tue, Jan 03, 2023 at 10:42:28PM +0100, Heiko Stuebner wrote:
> From: Heiko Stuebner <heiko.stuebner@vrull.eu>

> RISC-V: fix compile error from decuplicated __ALTERNATIVE_CFG_2

Hey Heiko/Palmer,

Was a little hard to tell from Drew's mail if he was objecting to this
variant of the patch, but FWIW s/decup/dedup/ if this gets applied
as-is.

Thanks,
Conor.

> On the non-assembler-side wrapping alternative-macros inside other macros
> to prevent duplication of code works, as the end result will just be a
> string that gets fed to the asm instruction.
> 
> In real assembler code, wrapping .macro blocks inside other .macro blocks
> brings more restrictions on usage and the optimization done by
> commit 2ba8c7dc71c0 ("riscv: Don't duplicate __ALTERNATIVE_CFG in __ALTERNATIVE_CFG_2")
> results in a compile error like:
> 
> ../arch/riscv/lib/strcmp.S: Assembler messages:
> ../arch/riscv/lib/strcmp.S:15: Error: too many positional arguments
> ../arch/riscv/lib/strcmp.S:15: Error: backward ref to unknown label "886:"
> ../arch/riscv/lib/strcmp.S:15: Error: backward ref to unknown label "887:"
> ../arch/riscv/lib/strcmp.S:15: Error: backward ref to unknown label "886:"
> ../arch/riscv/lib/strcmp.S:15: Error: backward ref to unknown label "887:"
> ../arch/riscv/lib/strcmp.S:15: Error: backward ref to unknown label "886:"
> ../arch/riscv/lib/strcmp.S:15: Error: attempt to move .org backwards
> 
> Going back to the original code for the non-assembler-part makes that
> code work again. So this reverts the #ifdef ASSEMBLY part of that commit
> to the previous variant with duplicated base.
> 
> Fixes: 2ba8c7dc71c0 ("riscv: Don't duplicate __ALTERNATIVE_CFG in __ALTERNATIVE_CFG_2")
> Signed-off-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
> ---
> I was of two minds about either to revert the full patch, or doing just
> this partial one for the ASSEMBLY part. I did go with this variant, as I
> still like the idea of deduplicating as much as possible :-)
> 
>  arch/riscv/include/asm/alternative-macros.h | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/include/asm/alternative-macros.h b/arch/riscv/include/asm/alternative-macros.h
> index 7226e2462584..e7bdb2a510a4 100644
> --- a/arch/riscv/include/asm/alternative-macros.h
> +++ b/arch/riscv/include/asm/alternative-macros.h
> @@ -44,9 +44,20 @@
>  	ALT_NEW_CONTENT \vendor_id, \errata_id, \enable, \new_c
>  .endm
>  
> +/*
> + * Using ALTERNATIVE_CFG inside ALTERNATIVE_CFG_2 results in compile errors.
> + * So the common code needs to stay duplicated.
> + */
>  .macro ALTERNATIVE_CFG_2 old_c, new_c_1, vendor_id_1, errata_id_1, enable_1,	\
>  				new_c_2, vendor_id_2, errata_id_2, enable_2
> -	ALTERNATIVE_CFG \old_c, \new_c_1, \vendor_id_1, \errata_id_1, \enable_1
> +886 :
> +	.option push
> +	.option norvc
> +	.option norelax
> +	\old_c
> +	.option pop
> +887 :
> +	ALT_NEW_CONTENT \vendor_id_1, \errata_id_1, \enable_1, \new_c_1
>  	ALT_NEW_CONTENT \vendor_id_2, \errata_id_2, \enable_2, \new_c_2
>  .endm
>  
> -- 
> 2.35.1
> 
> 
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