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glibc/sysdeps/aarch64/memrchr.S

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aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
/* memrchr - find the last occurrence of a byte in a memory block
Update copyright dates with scripts/update-copyrights I used these shell commands: ../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright (cd ../glibc && git commit -am"[this commit message]") and then ignored the output, which consisted lines saying "FOO: warning: copyright statement not found" for each of 7061 files FOO. I then removed trailing white space from math/tgmath.h, support/tst-support-open-dev-null-range.c, and sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following obscure pre-commit check failure diagnostics from Savannah. I don't know why I run into these diagnostics whereas others evidently do not. remote: *** 912-#endif remote: *** 913: remote: *** 914- remote: *** error: lines with trailing whitespace found ... remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines
2022-01-01 18:54:23 +00:00
Copyright (C) 2015-2022 Free Software Foundation, Inc.
aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library. If not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
/* Assumptions:
*
aarch64: MTE compatible memrchr Add support for MTE to memrchr. Regression tested with xcheck and benchmarked with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1. The existing implementation assumes that any access to the pages in which the string resides is safe. This assumption is not true when MTE is enabled. This patch updates the algorithm to ensure that accesses remain within the bounds of an MTE tag (16-byte chunks) and improves overall performance. Co-authored-by: Wilco Dijkstra <wilco.dijkstra@arm.com>
2020-06-09 16:08:07 +00:00
* ARMv8-a, AArch64, Advanced SIMD.
* MTE compatible.
aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
*/
/* Arguments and results. */
#define srcin x0
#define chrin w1
#define cntin x2
#define result x0
#define src x3
aarch64: MTE compatible memrchr Add support for MTE to memrchr. Regression tested with xcheck and benchmarked with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1. The existing implementation assumes that any access to the pages in which the string resides is safe. This assumption is not true when MTE is enabled. This patch updates the algorithm to ensure that accesses remain within the bounds of an MTE tag (16-byte chunks) and improves overall performance. Co-authored-by: Wilco Dijkstra <wilco.dijkstra@arm.com>
2020-06-09 16:08:07 +00:00
#define cntrem x4
#define synd x5
#define shift x6
#define tmp x7
#define end x8
#define endm1 x9
aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
#define vrepchr v0
aarch64: MTE compatible memrchr Add support for MTE to memrchr. Regression tested with xcheck and benchmarked with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1. The existing implementation assumes that any access to the pages in which the string resides is safe. This assumption is not true when MTE is enabled. This patch updates the algorithm to ensure that accesses remain within the bounds of an MTE tag (16-byte chunks) and improves overall performance. Co-authored-by: Wilco Dijkstra <wilco.dijkstra@arm.com>
2020-06-09 16:08:07 +00:00
#define qdata q1
#define vdata v1
#define vhas_chr v2
aarch64: Optimize string functions with shrn instruction We found that string functions were using AND+ADDP to find the nibble/syndrome mask but there is an easier opportunity through `SHRN dst.8b, src.8h, 4` (shift right every 2 bytes by 4 and narrow to 1 byte) and has same latency on all SIMD ARMv8 targets as ADDP. There are also possible gaps for memcmp but that's for another patch. We see 10-20% savings for small-mid size cases (<=128) which are primary cases for general workloads.
2022-06-27 16:12:13 +00:00
#define vend v3
#define dend d3
aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
/*
aarch64: MTE compatible memrchr Add support for MTE to memrchr. Regression tested with xcheck and benchmarked with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1. The existing implementation assumes that any access to the pages in which the string resides is safe. This assumption is not true when MTE is enabled. This patch updates the algorithm to ensure that accesses remain within the bounds of an MTE tag (16-byte chunks) and improves overall performance. Co-authored-by: Wilco Dijkstra <wilco.dijkstra@arm.com>
2020-06-09 16:08:07 +00:00
Core algorithm:
aarch64: Optimize string functions with shrn instruction We found that string functions were using AND+ADDP to find the nibble/syndrome mask but there is an easier opportunity through `SHRN dst.8b, src.8h, 4` (shift right every 2 bytes by 4 and narrow to 1 byte) and has same latency on all SIMD ARMv8 targets as ADDP. There are also possible gaps for memcmp but that's for another patch. We see 10-20% savings for small-mid size cases (<=128) which are primary cases for general workloads.
2022-06-27 16:12:13 +00:00
For each 16-byte chunk we calculate a 64-bit nibble mask value with four bits
per byte. We take 4 bits of every comparison byte with shift right and narrow
by 4 instruction. Since the bits in the nibble mask reflect the order in
which things occur in the original string, counting leading zeros identifies
exactly which byte matched. */
aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
ENTRY (__memrchr)
aarch64: use PTR_ARG and SIZE_ARG instead of DELOUSE DELOUSE was added to asm code to make them compatible with non-LP64 ABIs, but it is an unfortunate name and the code was not compatible with ABIs where pointer and size_t are different. Glibc currently only supports the LP64 ABI so these macros are not really needed or tested, but for now the name is changed to be more meaningful instead of removing them completely. Some DELOUSE macros were dropped: clone, strlen and strnlen used it unnecessarily. The out of tree ILP32 patches are currently not maintained and will likely need a rework to rebase them on top of the time64 changes.
2020-12-17 10:03:05 +00:00
PTR_ARG (0)
SIZE_ARG (2)
aarch64: MTE compatible memrchr Add support for MTE to memrchr. Regression tested with xcheck and benchmarked with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1. The existing implementation assumes that any access to the pages in which the string resides is safe. This assumption is not true when MTE is enabled. This patch updates the algorithm to ensure that accesses remain within the bounds of an MTE tag (16-byte chunks) and improves overall performance. Co-authored-by: Wilco Dijkstra <wilco.dijkstra@arm.com>
2020-06-09 16:08:07 +00:00
add end, srcin, cntin
sub endm1, end, 1
bic src, endm1, 15
cbz cntin, L(nomatch)
ld1 {vdata.16b}, [src]
aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
dup vrepchr.16b, chrin
aarch64: MTE compatible memrchr Add support for MTE to memrchr. Regression tested with xcheck and benchmarked with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1. The existing implementation assumes that any access to the pages in which the string resides is safe. This assumption is not true when MTE is enabled. This patch updates the algorithm to ensure that accesses remain within the bounds of an MTE tag (16-byte chunks) and improves overall performance. Co-authored-by: Wilco Dijkstra <wilco.dijkstra@arm.com>
2020-06-09 16:08:07 +00:00
cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
neg shift, end, lsl 2
aarch64: Optimize string functions with shrn instruction We found that string functions were using AND+ADDP to find the nibble/syndrome mask but there is an easier opportunity through `SHRN dst.8b, src.8h, 4` (shift right every 2 bytes by 4 and narrow to 1 byte) and has same latency on all SIMD ARMv8 targets as ADDP. There are also possible gaps for memcmp but that's for another patch. We see 10-20% savings for small-mid size cases (<=128) which are primary cases for general workloads.
2022-06-27 16:12:13 +00:00
shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */
aarch64: MTE compatible memrchr Add support for MTE to memrchr. Regression tested with xcheck and benchmarked with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1. The existing implementation assumes that any access to the pages in which the string resides is safe. This assumption is not true when MTE is enabled. This patch updates the algorithm to ensure that accesses remain within the bounds of an MTE tag (16-byte chunks) and improves overall performance. Co-authored-by: Wilco Dijkstra <wilco.dijkstra@arm.com>
2020-06-09 16:08:07 +00:00
fmov synd, dend
lsl synd, synd, shift
cbz synd, L(start_loop)
aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
aarch64: MTE compatible memrchr Add support for MTE to memrchr. Regression tested with xcheck and benchmarked with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1. The existing implementation assumes that any access to the pages in which the string resides is safe. This assumption is not true when MTE is enabled. This patch updates the algorithm to ensure that accesses remain within the bounds of an MTE tag (16-byte chunks) and improves overall performance. Co-authored-by: Wilco Dijkstra <wilco.dijkstra@arm.com>
2020-06-09 16:08:07 +00:00
clz synd, synd
sub result, endm1, synd, lsr 2
cmp cntin, synd, lsr 2
csel result, result, xzr, hi
ret
L(start_loop):
sub tmp, end, src
subs cntrem, cntin, tmp
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)
.p2align 4
L(loop32):
ldr qdata, [src, -16]!
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
cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
b.ls L(end)
umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */
fmov synd, dend
cbz synd, L(loop32)
aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
L(end):
aarch64: Optimize string functions with shrn instruction We found that string functions were using AND+ADDP to find the nibble/syndrome mask but there is an easier opportunity through `SHRN dst.8b, src.8h, 4` (shift right every 2 bytes by 4 and narrow to 1 byte) and has same latency on all SIMD ARMv8 targets as ADDP. There are also possible gaps for memcmp but that's for another patch. We see 10-20% savings for small-mid size cases (<=128) which are primary cases for general workloads.
2022-06-27 16:12:13 +00:00
shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */
aarch64: MTE compatible memrchr Add support for MTE to memrchr. Regression tested with xcheck and benchmarked with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1. The existing implementation assumes that any access to the pages in which the string resides is safe. This assumption is not true when MTE is enabled. This patch updates the algorithm to ensure that accesses remain within the bounds of an MTE tag (16-byte chunks) and improves overall performance. Co-authored-by: Wilco Dijkstra <wilco.dijkstra@arm.com>
2020-06-09 16:08:07 +00:00
fmov synd, dend
add tmp, src, 15
#ifdef __AARCH64EB__
rbit synd, synd
#endif
aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
clz synd, synd
aarch64: MTE compatible memrchr Add support for MTE to memrchr. Regression tested with xcheck and benchmarked with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1. The existing implementation assumes that any access to the pages in which the string resides is safe. This assumption is not true when MTE is enabled. This patch updates the algorithm to ensure that accesses remain within the bounds of an MTE tag (16-byte chunks) and improves overall performance. Co-authored-by: Wilco Dijkstra <wilco.dijkstra@arm.com>
2020-06-09 16:08:07 +00:00
sub tmp, tmp, synd, lsr 2
cmp tmp, srcin
csel result, tmp, xzr, hs
aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
ret
aarch64: MTE compatible memrchr Add support for MTE to memrchr. Regression tested with xcheck and benchmarked with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1. The existing implementation assumes that any access to the pages in which the string resides is safe. This assumption is not true when MTE is enabled. This patch updates the algorithm to ensure that accesses remain within the bounds of an MTE tag (16-byte chunks) and improves overall performance. Co-authored-by: Wilco Dijkstra <wilco.dijkstra@arm.com>
2020-06-09 16:08:07 +00:00
L(nomatch):
mov result, 0
aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
ret
aarch64: MTE compatible memrchr Add support for MTE to memrchr. Regression tested with xcheck and benchmarked with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1. The existing implementation assumes that any access to the pages in which the string resides is safe. This assumption is not true when MTE is enabled. This patch updates the algorithm to ensure that accesses remain within the bounds of an MTE tag (16-byte chunks) and improves overall performance. Co-authored-by: Wilco Dijkstra <wilco.dijkstra@arm.com>
2020-06-09 16:08:07 +00:00
aarch64: Optimized implementation of memrchr Considering the excellent performance of memchr.S on glibc 2.30, the same algorithm is used to find chrin. Compared to memrchr.c, this method with memrchr.S achieves an average performance improvement of 58% based on benchtest and its extension cases. Checked on aarch64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
2019-12-19 14:53:29 +00:00
END (__memrchr)
weak_alias (__memrchr, memrchr)
libc_hidden_builtin_def (memrchr)
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