* [PATCH] AArch64: Optimize memchr
@ 2023-01-12 15:56 Wilco Dijkstra
2023-01-13 12:27 ` Szabolcs Nagy
0 siblings, 1 reply; 2+ messages in thread
From: Wilco Dijkstra @ 2023-01-12 15:56 UTC (permalink / raw)
To: 'GNU C Library'; +Cc: Szabolcs Nagy
Optimize the main loop - large strings are 40% faster on modern CPUs.
Passes regress.
---
diff --git a/sysdeps/aarch64/memchr.S b/sysdeps/aarch64/memchr.S
index 1cd32bf8cffa82d665304d54d2a4d4f75d4ff541..1c99d45fbb506c86a1db5b4d45de49b33d8635c9 100644
--- a/sysdeps/aarch64/memchr.S
+++ b/sysdeps/aarch64/memchr.S
@@ -30,7 +30,6 @@
# define MEMCHR __memchr
#endif
-/* Arguments and results. */
#define srcin x0
#define chrin w1
#define cntin x2
@@ -73,42 +72,44 @@ ENTRY (MEMCHR)
rbit synd, synd
clz synd, synd
- add result, srcin, synd, lsr 2
cmp cntin, synd, lsr 2
+ add result, srcin, synd, lsr 2
csel result, result, xzr, hi
ret
+ .p2align 3
L(start_loop):
sub tmp, src, srcin
- add tmp, tmp, 16
+ add tmp, tmp, 17
subs cntrem, cntin, tmp
- b.ls L(nomatch)
+ b.lo L(nomatch)
/* Make sure that it won't overread by a 16-byte chunk */
- add tmp, cntrem, 15
- tbnz tmp, 4, L(loop32_2)
-
+ tbz cntrem, 4, L(loop32_2)
+ sub src, src, 16
.p2align 4
L(loop32):
- ldr qdata, [src, 16]!
+ ldr qdata, [src, 32]!
cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */
fmov synd, dend
cbnz synd, L(end)
L(loop32_2):
- ldr qdata, [src, 16]!
- subs cntrem, cntrem, 32
+ ldr qdata, [src, 16]
cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
- b.ls L(end)
+ subs cntrem, cntrem, 32
+ b.lo L(end_2)
umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */
fmov synd, dend
cbz synd, L(loop32)
+L(end_2):
+ add src, src, 16
L(end):
shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */
+ sub cntrem, src, srcin
fmov synd, dend
- add tmp, srcin, cntin
- sub cntrem, tmp, src
+ sub cntrem, cntin, cntrem
#ifndef __AARCH64EB__
rbit synd, synd
#endif
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] AArch64: Optimize memchr
2023-01-12 15:56 [PATCH] AArch64: Optimize memchr Wilco Dijkstra
@ 2023-01-13 12:27 ` Szabolcs Nagy
0 siblings, 0 replies; 2+ messages in thread
From: Szabolcs Nagy @ 2023-01-13 12:27 UTC (permalink / raw)
To: Wilco Dijkstra; +Cc: 'GNU C Library'
The 01/12/2023 15:56, Wilco Dijkstra wrote:
> Optimize the main loop - large strings are 40% faster on modern CPUs.
> Passes regress.
please commit it, thanks.
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
>
> ---
>
> diff --git a/sysdeps/aarch64/memchr.S b/sysdeps/aarch64/memchr.S
> index 1cd32bf8cffa82d665304d54d2a4d4f75d4ff541..1c99d45fbb506c86a1db5b4d45de49b33d8635c9 100644
> --- a/sysdeps/aarch64/memchr.S
> +++ b/sysdeps/aarch64/memchr.S
> @@ -30,7 +30,6 @@
> # define MEMCHR __memchr
> #endif
>
> -/* Arguments and results. */
> #define srcin x0
> #define chrin w1
> #define cntin x2
> @@ -73,42 +72,44 @@ ENTRY (MEMCHR)
>
> rbit synd, synd
> clz synd, synd
> - add result, srcin, synd, lsr 2
> cmp cntin, synd, lsr 2
> + add result, srcin, synd, lsr 2
> csel result, result, xzr, hi
> ret
>
> + .p2align 3
> L(start_loop):
> sub tmp, src, srcin
> - add tmp, tmp, 16
> + add tmp, tmp, 17
> subs cntrem, cntin, tmp
> - b.ls L(nomatch)
> + b.lo L(nomatch)
>
> /* Make sure that it won't overread by a 16-byte chunk */
> - add tmp, cntrem, 15
> - tbnz tmp, 4, L(loop32_2)
> -
> + tbz cntrem, 4, L(loop32_2)
> + sub src, src, 16
> .p2align 4
> L(loop32):
> - ldr qdata, [src, 16]!
> + ldr qdata, [src, 32]!
> cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
> umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */
> fmov synd, dend
> cbnz synd, L(end)
>
> L(loop32_2):
> - ldr qdata, [src, 16]!
> - subs cntrem, cntrem, 32
> + ldr qdata, [src, 16]
> cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
> - b.ls L(end)
> + subs cntrem, cntrem, 32
> + b.lo L(end_2)
> umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */
> fmov synd, dend
> cbz synd, L(loop32)
> +L(end_2):
> + add src, src, 16
> L(end):
> shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */
> + sub cntrem, src, srcin
> fmov synd, dend
> - add tmp, srcin, cntin
> - sub cntrem, tmp, src
> + sub cntrem, cntin, cntrem
> #ifndef __AARCH64EB__
> rbit synd, synd
> #endif
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2023-01-13 12:27 ` Szabolcs Nagy
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