From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
To: 'GNU C Library' <libc-alpha@sourceware.org>
Cc: Szabolcs Nagy <Szabolcs.Nagy@arm.com>
Subject: [PATCH] AArch64: Improve strlen_asimd
Date: Thu, 12 Jan 2023 15:51:32 +0000 [thread overview]
Message-ID: <PAWPR08MB8982BE5A8C1635DBCB89700D83FD9@PAWPR08MB8982.eurprd08.prod.outlook.com> (raw)
Use shrn for the mask, merge tst+bne into cbnz, and tweak code alignment.
Performance improves slightly as a result. Passes regress.
---
diff --git a/sysdeps/aarch64/multiarch/strlen_asimd.S b/sysdeps/aarch64/multiarch/strlen_asimd.S
index ca6ab96ecf2de45def79539facd8e0b86f4edc95..490439491d19c3f14b0228f42248bc8aa6e9e8bd 100644
--- a/sysdeps/aarch64/multiarch/strlen_asimd.S
+++ b/sysdeps/aarch64/multiarch/strlen_asimd.S
@@ -48,6 +48,7 @@
#define tmp x2
#define tmpw w2
#define synd x3
+#define syndw w3
#define shift x4
/* For the first 32 bytes, NUL detection works on the principle that
@@ -87,7 +88,6 @@
ENTRY (__strlen_asimd)
PTR_ARG (0)
-
and tmp1, srcin, MIN_PAGE_SIZE - 1
cmp tmp1, MIN_PAGE_SIZE - 32
b.hi L(page_cross)
@@ -123,7 +123,6 @@ ENTRY (__strlen_asimd)
add len, len, tmp1, lsr 3
ret
- .p2align 3
/* Look for a NUL byte at offset 16..31 in the string. */
L(bytes16_31):
ldp data1, data2, [srcin, 16]
@@ -151,6 +150,7 @@ L(bytes16_31):
add len, len, tmp1, lsr 3
ret
+ nop
L(loop_entry):
bic src, srcin, 31
@@ -166,18 +166,12 @@ L(loop):
/* Low 32 bits of synd are non-zero if a NUL was found in datav1. */
cmeq maskv.16b, datav1.16b, 0
sub len, src, srcin
- tst synd, 0xffffffff
- b.ne 1f
+ cbnz syndw, 1f
cmeq maskv.16b, datav2.16b, 0
add len, len, 16
1:
/* Generate a bitmask and compute correct byte offset. */
-#ifdef __AARCH64EB__
- bic maskv.8h, 0xf0
-#else
- bic maskv.8h, 0x0f, lsl 8
-#endif
- umaxp maskv.16b, maskv.16b, maskv.16b
+ shrn maskv.8b, maskv.8h, 4
fmov synd, maskd
#ifndef __AARCH64EB__
rbit synd, synd
@@ -186,8 +180,6 @@ L(loop):
add len, len, tmp, lsr 2
ret
- .p2align 4
-
L(page_cross):
bic src, srcin, 31
mov tmpw, 0x0c03
next reply other threads:[~2023-01-12 15:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-12 15:51 Wilco Dijkstra [this message]
2023-01-13 12:25 ` Szabolcs Nagy
2023-01-16 22:16 ` Carlos O'Donell
2023-01-17 16:37 ` Wilco Dijkstra
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