0928368f62
This adds the Arm Optimized Routines (see https://github.com/ARM-software/optimized-routines) source code under the the LLVM license. The version of the code provided in this patch is v20.02 of the Arm Optimized Routines project. This entire contribution is being committed as is even though it does not currently fit the LLVM libc model and does not follow the LLVM coding style. In the near future, implementations from this patch will be moved over to their right place in the LLVM-libc tree. This will be done over many small patches, all of which will go through the normal LLVM code review process. See this libc-dev post for the plan: http://lists.llvm.org/pipermail/libc-dev/2020-March/000044.html Differential revision of the original upload: https://reviews.llvm.org/D75355
133 lines
4.1 KiB
ArmAsm
133 lines
4.1 KiB
ArmAsm
/*
|
|
* strchr - find a character in a string
|
|
*
|
|
* Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|
* See https://llvm.org/LICENSE.txt for license information.
|
|
* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
*/
|
|
|
|
/* Assumptions:
|
|
*
|
|
* ARMv8-a, AArch64
|
|
* Neon Available.
|
|
*/
|
|
|
|
#include "../asmdefs.h"
|
|
|
|
/* Arguments and results. */
|
|
#define srcin x0
|
|
#define chrin w1
|
|
|
|
#define result x0
|
|
|
|
#define src x2
|
|
#define tmp1 x3
|
|
#define wtmp2 w4
|
|
#define tmp3 x5
|
|
|
|
#define vrepchr v0
|
|
#define vdata1 v1
|
|
#define vdata2 v2
|
|
#define vhas_nul1 v3
|
|
#define vhas_nul2 v4
|
|
#define vhas_chr1 v5
|
|
#define vhas_chr2 v6
|
|
#define vrepmask_0 v7
|
|
#define vrepmask_c v16
|
|
#define vend1 v17
|
|
#define vend2 v18
|
|
|
|
/* Core algorithm.
|
|
|
|
For each 32-byte hunk we calculate a 64-bit syndrome value, with
|
|
two bits per byte (LSB is always in bits 0 and 1, for both big
|
|
and little-endian systems). For each tuple, bit 0 is set iff
|
|
the relevant byte matched the requested character; bit 1 is set
|
|
iff the relevant byte matched the NUL end of string (we trigger
|
|
off bit0 for the special case of looking for NUL). Since the bits
|
|
in the syndrome reflect exactly the order in which things occur
|
|
in the original string a count_trailing_zeros() operation will
|
|
identify exactly which byte is causing the termination, and why. */
|
|
|
|
/* Locals and temporaries. */
|
|
|
|
ENTRY (__strchr_aarch64)
|
|
/* Magic constant 0x40100401 to allow us to identify which lane
|
|
matches the requested byte. Magic constant 0x80200802 used
|
|
similarly for NUL termination. */
|
|
mov wtmp2, #0x0401
|
|
movk wtmp2, #0x4010, lsl #16
|
|
dup vrepchr.16b, chrin
|
|
bic src, srcin, #31 /* Work with aligned 32-byte hunks. */
|
|
dup vrepmask_c.4s, wtmp2
|
|
ands tmp1, srcin, #31
|
|
add vrepmask_0.4s, vrepmask_c.4s, vrepmask_c.4s /* equiv: lsl #1 */
|
|
b.eq L(loop)
|
|
|
|
/* Input string is not 32-byte aligned. Rather than forcing
|
|
the padding bytes to a safe value, we calculate the syndrome
|
|
for all the bytes, but then mask off those bits of the
|
|
syndrome that are related to the padding. */
|
|
ld1 {vdata1.16b, vdata2.16b}, [src], #32
|
|
neg tmp1, tmp1
|
|
cmeq vhas_nul1.16b, vdata1.16b, #0
|
|
cmeq vhas_chr1.16b, vdata1.16b, vrepchr.16b
|
|
cmeq vhas_nul2.16b, vdata2.16b, #0
|
|
cmeq vhas_chr2.16b, vdata2.16b, vrepchr.16b
|
|
and vhas_nul1.16b, vhas_nul1.16b, vrepmask_0.16b
|
|
and vhas_nul2.16b, vhas_nul2.16b, vrepmask_0.16b
|
|
and vhas_chr1.16b, vhas_chr1.16b, vrepmask_c.16b
|
|
and vhas_chr2.16b, vhas_chr2.16b, vrepmask_c.16b
|
|
orr vend1.16b, vhas_nul1.16b, vhas_chr1.16b
|
|
orr vend2.16b, vhas_nul2.16b, vhas_chr2.16b
|
|
lsl tmp1, tmp1, #1
|
|
addp vend1.16b, vend1.16b, vend2.16b // 256->128
|
|
mov tmp3, #~0
|
|
addp vend1.16b, vend1.16b, vend2.16b // 128->64
|
|
lsr tmp1, tmp3, tmp1
|
|
|
|
mov tmp3, vend1.d[0]
|
|
bic tmp1, tmp3, tmp1 // Mask padding bits.
|
|
cbnz tmp1, L(tail)
|
|
|
|
L(loop):
|
|
ld1 {vdata1.16b, vdata2.16b}, [src], #32
|
|
cmeq vhas_nul1.16b, vdata1.16b, #0
|
|
cmeq vhas_chr1.16b, vdata1.16b, vrepchr.16b
|
|
cmeq vhas_nul2.16b, vdata2.16b, #0
|
|
cmeq vhas_chr2.16b, vdata2.16b, vrepchr.16b
|
|
/* Use a fast check for the termination condition. */
|
|
orr vend1.16b, vhas_nul1.16b, vhas_chr1.16b
|
|
orr vend2.16b, vhas_nul2.16b, vhas_chr2.16b
|
|
orr vend1.16b, vend1.16b, vend2.16b
|
|
addp vend1.2d, vend1.2d, vend1.2d
|
|
mov tmp1, vend1.d[0]
|
|
cbz tmp1, L(loop)
|
|
|
|
/* Termination condition found. Now need to establish exactly why
|
|
we terminated. */
|
|
and vhas_nul1.16b, vhas_nul1.16b, vrepmask_0.16b
|
|
and vhas_nul2.16b, vhas_nul2.16b, vrepmask_0.16b
|
|
and vhas_chr1.16b, vhas_chr1.16b, vrepmask_c.16b
|
|
and vhas_chr2.16b, vhas_chr2.16b, vrepmask_c.16b
|
|
orr vend1.16b, vhas_nul1.16b, vhas_chr1.16b
|
|
orr vend2.16b, vhas_nul2.16b, vhas_chr2.16b
|
|
addp vend1.16b, vend1.16b, vend2.16b // 256->128
|
|
addp vend1.16b, vend1.16b, vend2.16b // 128->64
|
|
|
|
mov tmp1, vend1.d[0]
|
|
L(tail):
|
|
/* Count the trailing zeros, by bit reversing... */
|
|
rbit tmp1, tmp1
|
|
/* Re-bias source. */
|
|
sub src, src, #32
|
|
clz tmp1, tmp1 /* And counting the leading zeros. */
|
|
/* Tmp1 is even if the target charager was found first. Otherwise
|
|
we've found the end of string and we weren't looking for NUL. */
|
|
tst tmp1, #1
|
|
add result, src, tmp1, lsr #1
|
|
csel result, result, xzr, eq
|
|
ret
|
|
|
|
END (__strchr_aarch64)
|