177 lines
5.3 KiB
ArmAsm
177 lines
5.3 KiB
ArmAsm
/*
|
|
* memchr - find a character in a memory zone
|
|
*
|
|
* Copyright (c) 2014, ARM Limited
|
|
* All rights Reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions are met:
|
|
* * Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* * Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
* * Neither the name of the company nor the names of its contributors
|
|
* may be used to endorse or promote products derived from this
|
|
* software without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
|
|
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
|
|
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
|
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
|
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
|
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
*/
|
|
|
|
#if (defined (__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED))
|
|
/* See memchr-stub.c */
|
|
#else
|
|
/* Assumptions:
|
|
*
|
|
* ARMv8-a, AArch64
|
|
* Neon Available.
|
|
*/
|
|
|
|
/* Arguments and results. */
|
|
#define srcin x0
|
|
#define chrin w1
|
|
#define cntin x2
|
|
|
|
#define result x0
|
|
|
|
#define src x3
|
|
#define tmp x4
|
|
#define wtmp2 w5
|
|
#define synd x6
|
|
#define soff x9
|
|
#define cntrem x10
|
|
|
|
#define vrepchr v0
|
|
#define vdata1 v1
|
|
#define vdata2 v2
|
|
#define vhas_chr1 v3
|
|
#define vhas_chr2 v4
|
|
#define vrepmask v5
|
|
#define vend v6
|
|
|
|
/*
|
|
* Core algorithm:
|
|
*
|
|
* For each 32-byte chunk we calculate a 64-bit syndrome value, with two bits
|
|
* per byte. For each tuple, bit 0 is set if the relevant byte matched the
|
|
* requested character and bit 1 is not used (faster than using a 32bit
|
|
* syndrome). Since the bits in the syndrome reflect exactly the order in which
|
|
* things occur in the original string, counting trailing zeros allows to
|
|
* identify exactly which byte has matched.
|
|
*/
|
|
|
|
.macro def_fn f p2align=0
|
|
.text
|
|
.p2align \p2align
|
|
.global \f
|
|
.type \f, %function
|
|
\f:
|
|
.endm
|
|
|
|
def_fn memchr
|
|
/* Do not dereference srcin if no bytes to compare. */
|
|
cbz cntin, .Lzero_length
|
|
/*
|
|
* Magic constant 0x40100401 allows us to identify which lane matches
|
|
* the requested byte.
|
|
*/
|
|
mov wtmp2, #0x0401
|
|
movk wtmp2, #0x4010, lsl #16
|
|
dup vrepchr.16b, chrin
|
|
/* Work with aligned 32-byte chunks */
|
|
bic src, srcin, #31
|
|
dup vrepmask.4s, wtmp2
|
|
ands soff, srcin, #31
|
|
and cntrem, cntin, #31
|
|
b.eq .Lloop
|
|
|
|
/*
|
|
* Input string is not 32-byte aligned. We calculate the syndrome
|
|
* value for the aligned 32 bytes block containing the first bytes
|
|
* and mask the irrelevant part.
|
|
*/
|
|
|
|
ld1 {vdata1.16b, vdata2.16b}, [src], #32
|
|
sub tmp, soff, #32
|
|
adds cntin, cntin, tmp
|
|
cmeq vhas_chr1.16b, vdata1.16b, vrepchr.16b
|
|
cmeq vhas_chr2.16b, vdata2.16b, vrepchr.16b
|
|
and vhas_chr1.16b, vhas_chr1.16b, vrepmask.16b
|
|
and vhas_chr2.16b, vhas_chr2.16b, vrepmask.16b
|
|
addp vend.16b, vhas_chr1.16b, vhas_chr2.16b /* 256->128 */
|
|
addp vend.16b, vend.16b, vend.16b /* 128->64 */
|
|
mov synd, vend.2d[0]
|
|
/* Clear the soff*2 lower bits */
|
|
lsl tmp, soff, #1
|
|
lsr synd, synd, tmp
|
|
lsl synd, synd, tmp
|
|
/* The first block can also be the last */
|
|
b.ls .Lmasklast
|
|
/* Have we found something already? */
|
|
cbnz synd, .Ltail
|
|
|
|
.Lloop:
|
|
ld1 {vdata1.16b, vdata2.16b}, [src], #32
|
|
subs cntin, cntin, #32
|
|
cmeq vhas_chr1.16b, vdata1.16b, vrepchr.16b
|
|
cmeq vhas_chr2.16b, vdata2.16b, vrepchr.16b
|
|
/* If we're out of data we finish regardless of the result */
|
|
b.ls .Lend
|
|
/* Use a fast check for the termination condition */
|
|
orr vend.16b, vhas_chr1.16b, vhas_chr2.16b
|
|
addp vend.2d, vend.2d, vend.2d
|
|
mov synd, vend.2d[0]
|
|
/* We're not out of data, loop if we haven't found the character */
|
|
cbz synd, .Lloop
|
|
|
|
.Lend:
|
|
/* Termination condition found, let's calculate the syndrome value */
|
|
and vhas_chr1.16b, vhas_chr1.16b, vrepmask.16b
|
|
and vhas_chr2.16b, vhas_chr2.16b, vrepmask.16b
|
|
addp vend.16b, vhas_chr1.16b, vhas_chr2.16b /* 256->128 */
|
|
addp vend.16b, vend.16b, vend.16b /* 128->64 */
|
|
mov synd, vend.2d[0]
|
|
/* Only do the clear for the last possible block */
|
|
b.hi .Ltail
|
|
|
|
.Lmasklast:
|
|
/* Clear the (32 - ((cntrem + soff) % 32)) * 2 upper bits */
|
|
add tmp, cntrem, soff
|
|
and tmp, tmp, #31
|
|
sub tmp, tmp, #32
|
|
neg tmp, tmp, lsl #1
|
|
lsl synd, synd, tmp
|
|
lsr synd, synd, tmp
|
|
|
|
.Ltail:
|
|
/* Count the trailing zeros using bit reversing */
|
|
rbit synd, synd
|
|
/* Compensate the last post-increment */
|
|
sub src, src, #32
|
|
/* Check that we have found a character */
|
|
cmp synd, #0
|
|
/* And count the leading zeros */
|
|
clz synd, synd
|
|
/* Compute the potential result */
|
|
add result, src, synd, lsr #1
|
|
/* Select result or NULL */
|
|
csel result, xzr, result, eq
|
|
ret
|
|
|
|
.Lzero_length:
|
|
mov result, #0
|
|
ret
|
|
|
|
.size memchr, . - memchr
|
|
#endif
|