Re: [PATCH] MIPS: asm: asmmacro: Replace "add" instructions with "addu"

[David Daney <ddaney.cavm@gmail.com>]

On 01/21/2015 07:26 AM, Markos Chandras wrote:
> The "add" instruction is actually a macro in binutils and depending on
> the size of the immediate it can expand to an "addi" instruction.
> However, the "addi" instruction traps on overflows which is not
> something we want on address calculation.
>

I like it:

Acked-by: David Daney <david.daney@cavium.com>


> Link: http://www.linux-mips.org/archives/linux-mips/2015-01/msg00121.html
> Cc: Paul Burton <paul.burton@imgtec.com>
> Cc: Maciej W. Rozycki <macro@linux-mips.org>
> Cc: <stable@vger.kernel.org> # v3.15+

Is it causing problems with existing kernels, or is it only in 
preparation for MIPS r6?  If the later, it probably isn't stable material.


> Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
> ---
> Moving this out of the R6 patchset as requested by Maciej
> ---
>   arch/mips/include/asm/asmmacro.h | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/mips/include/asm/asmmacro.h b/arch/mips/include/asm/asmmacro.h
> index fe08084f5adb..42b90c9fd756 100644
> --- a/arch/mips/include/asm/asmmacro.h
> +++ b/arch/mips/include/asm/asmmacro.h
> @@ -304,7 +304,7 @@
>   	.set	push
>   	.set	noat
>   	SET_HARDFLOAT
> -	add	$1, \base, \off
> +	addu	$1, \base, \off
>   	.word	LDD_MSA_INSN | (\wd << 6)
>   	.set	pop
>   	.endm
> @@ -313,7 +313,7 @@
>   	.set	push
>   	.set	noat
>   	SET_HARDFLOAT
> -	add	$1, \base, \off
> +	addu	$1, \base, \off
>   	.word	STD_MSA_INSN | (\wd << 6)
>   	.set	pop
>   	.endm
>