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authorWilco Dijkstra <wilco.dijkstra@arm.com>2023-01-11 13:50:59 +0000
committerWilco Dijkstra <wilco.dijkstra@arm.com>2023-01-17 15:09:18 +0000
commitce758d4f063820c2bc743e12797d7454c66be718 (patch)
treed362dabf820729f03ea658b43d033390842af6dd
parent569cfcc6bf35c28112ca8d7112e9eb4a22bed5b8 (diff)
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AArch64: Optimize memchr
Optimize the main loop - large strings are 40% faster on modern CPUs. Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
-rw-r--r--sysdeps/aarch64/memchr.S27
1 files changed, 14 insertions, 13 deletions
diff --git a/sysdeps/aarch64/memchr.S b/sysdeps/aarch64/memchr.S
index 1cd32bf..1c99d45 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