RE: [PATCH v3 4/5] AArch64: Improve A64FX memset

[naohirot--- via Libc-alpha <libc-alpha@sourceware.org>]

Hi Wilco,

Thank you for the patch.

LGTM, I confirmed that no performance change [1][2].

Reviewed-by: Naohiro Tamura <naohirot@fujitsu.com>
Tested-by: Naohiro Tamura <naohirot@fujitsu.com>

Regarding commit title, how about like this?
"AArch64: Improve A64FX memset by removing unroll32"

[1] https://drive.google.com/file/d/1SIw7bXX9Pi2G7wga9j5X9M2xzOHYQlIx/view?usp=sharing
[2] https://drive.google.com/file/d/1gdcuRFZbtlIpnINUMar4DIt9Ao04K36o/view?usp=sharing

Thanks.
Naohiro

> -----Original Message-----
> From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
> Sent: Friday, July 23, 2021 1:03 AM
> To: Tamura, Naohiro/田村 直広 <naohirot@fujitsu.com>
> Cc: 'GNU C Library' <libc-alpha@sourceware.org>
> Subject: [PATCH v3 4/5] AArch64: Improve A64FX memset
> 
> Remove unroll32 code since it doesn't improve performance.
> 
> ---
> diff --git a/sysdeps/aarch64/multiarch/memset_a64fx.S b/sysdeps/aarch64/multiarch/memset_a64fx.S
> index fce257fa68120c2b101f29b438c397e10b4c275e..8665c272431b46dadea53c63ab74829c3aa99312 100644
> --- a/sysdeps/aarch64/multiarch/memset_a64fx.S
> +++ b/sysdeps/aarch64/multiarch/memset_a64fx.S
> @@ -102,22 +102,6 @@ L(vl_agnostic): // VL Agnostic
>  	ccmp	vector_length, tmp1, 0, cs
>  	b.eq	L(L1_prefetch)
> 
> -L(unroll32):
> -	lsl	tmp1, vector_length, 3	// vector_length * 8
> -	lsl	tmp2, vector_length, 5	// vector_length * 32
> -	.p2align 3
> -1:	cmp	rest, tmp2
> -	b.cc	L(unroll8)
> -	st1b_unroll
> -	add	dst, dst, tmp1
> -	st1b_unroll
> -	add	dst, dst, tmp1
> -	st1b_unroll
> -	add	dst, dst, tmp1
> -	st1b_unroll
> -	add	dst, dst, tmp1
> -	sub	rest, rest, tmp2
> -	b	1b
> 
>  L(unroll8):
>  	lsl	tmp1, vector_length, 3
> @@ -155,7 +139,7 @@ L(L1_prefetch): // if rest >= L1_SIZE
>  	sub	rest, rest, CACHE_LINE_SIZE * 2
>  	cmp	rest, L1_SIZE
>  	b.ge	1b
> -	cbnz	rest, L(unroll32)
> +	cbnz	rest, L(unroll8)
>  	ret
> 
>  	// count >= L2_SIZE