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SubjectRe: [PATCH v5 3/3] powerpc/lib: optimise PPC32 memcmp
On Mon, May 28, 2018 at 12:49 PM, Christophe Leroy
<christophe.leroy@c-s.fr> wrote:
> At the time being, memcmp() compares two chunks of memory
> byte per byte.
>
> This patch optimises the comparison by comparing word by word.
>
> A small benchmark performed on an 8xx comparing two chuncks
> of 512 bytes performed 100000 times gives:
>
> Before : 5852274 TB ticks
> After: 1488638 TB ticks
>
> This is almost 4 times faster
>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
> arch/powerpc/lib/string_32.S | 37 +++++++++++++++++++++++++++----------
> 1 file changed, 27 insertions(+), 10 deletions(-)

Would it possible for you to move the actual code instead to:

./arch/powerpc/lib/memcmp_32.S

This will seat right next to memcmp_64.S implementation.

> diff --git a/arch/powerpc/lib/string_32.S b/arch/powerpc/lib/string_32.S
> index 40a576d56ac7..4fbaa046aa84 100644
> --- a/arch/powerpc/lib/string_32.S
> +++ b/arch/powerpc/lib/string_32.S
> @@ -16,17 +16,34 @@
> .text
>
> _GLOBAL(memcmp)
> - cmpwi cr0, r5, 0
> - beq- 2f
> - mtctr r5
> - addi r6,r3,-1
> - addi r4,r4,-1
> -1: lbzu r3,1(r6)
> - lbzu r0,1(r4)
> - subf. r3,r0,r3
> - bdnzt 2,1b
> + srawi. r7, r5, 2 /* Divide len by 4 */
> + mr r6, r3
> + beq- 3f
> + mtctr r7
> + li r7, 0
> +1: lwzx r3, r6, r7
> + lwzx r0, r4, r7
> + addi r7, r7, 4
> + cmplw cr0, r3, r0
> + bdnzt eq, 1b
> + bne 5f
> +3: andi. r3, r5, 3
> + beqlr
> + cmplwi cr1, r3, 2
> + blt- cr1, 4f
> + lhzx r3, r6, r7
> + lhzx r0, r4, r7
> + addi r7, r7, 2
> + subf. r3, r0, r3
> + beqlr cr1
> + bnelr
> +4: lbzx r3, r6, r7
> + lbzx r0, r4, r7
> + subf. r3, r0, r3
> blr
> -2: li r3,0
> +5: li r3, 1
> + bgtlr
> + li r3, -1
> blr
> EXPORT_SYMBOL(memcmp)
>
> --
> 2.13.3
>

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