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* [glibc/release/2.32/master] AArch64: Optimize memrchr
@ 2024-04-10 17:18 Wilco Dijkstra
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From: Wilco Dijkstra @ 2024-04-10 17:18 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f55ba2fedc90438dcba7d3fdc4dea80233d149c9
commit f55ba2fedc90438dcba7d3fdc4dea80233d149c9
Author: Wilco Dijkstra <wilco.dijkstra@arm.com>
Date: Wed Jan 11 13:51:17 2023 +0000
AArch64: Optimize memrchr
Optimize the main loop - large strings are 43% faster on modern CPUs.
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
(cherry picked from commit 00776241776e67fc666b896c1e85770f4f3ec1e1)
Diff:
---
sysdeps/aarch64/memrchr.S | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/sysdeps/aarch64/memrchr.S b/sysdeps/aarch64/memrchr.S
index 9925d8dcbf..e6a87f325e 100644
--- a/sysdeps/aarch64/memrchr.S
+++ b/sysdeps/aarch64/memrchr.S
@@ -26,7 +26,6 @@
* MTE compatible.
*/
-/* Arguments and results. */
#define srcin x0
#define chrin w1
#define cntin x2
@@ -77,31 +76,34 @@ ENTRY (__memrchr)
csel result, result, xzr, hi
ret
+ nop
L(start_loop):
- sub tmp, end, src
- subs cntrem, cntin, tmp
+ subs cntrem, src, srcin
b.ls L(nomatch)
/* Make sure that it won't overread by a 16-byte chunk */
- add tmp, cntrem, 15
- tbnz tmp, 4, L(loop32_2)
+ sub cntrem, cntrem, 1
+ tbz cntrem, 4, L(loop32_2)
+ add src, src, 16
- .p2align 4
+ .p2align 5
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]!
+ ldr qdata, [src, -16]
subs cntrem, cntrem, 32
cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
- b.ls L(end)
+ 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):
+ sub src, src, 16
L(end):
shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */
fmov synd, dend
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2024-04-10 17:18 [glibc/release/2.32/master] AArch64: Optimize memrchr Wilco Dijkstra
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