arm64: lib: Implement optimized string compare routines
This patch, based on Linaro's Cortex Strings library, adds an assembly optimized strcmp() and strncmp() functions. Signed-off-by: Zhichang Yuan <zhichang.yuan@linaro.org> Signed-off-by: Deepak Saxena <dsaxena@linaro.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
zhichang.yuan
committed by
Catalin Marinas
Catalin Marinas
parent
d875c9b372
commit
192c4d902f
234
arch/arm64/lib/strcmp.S
Normal file
234
arch/arm64/lib/strcmp.S
Normal file
@@ -0,0 +1,234 @@
|
||||
/*
|
||||
* Copyright (C) 2013 ARM Ltd.
|
||||
* Copyright (C) 2013 Linaro.
|
||||
*
|
||||
* This code is based on glibc cortex strings work originally authored by Linaro
|
||||
* and re-licensed under GPLv2 for the Linux kernel. The original code can
|
||||
* be found @
|
||||
*
|
||||
* http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
|
||||
* files/head:/src/aarch64/
|
||||
*
|
||||
* This program is free software; you can redistribute it and/or modify
|
||||
* it under the terms of the GNU General Public License version 2 as
|
||||
* published by the Free Software Foundation.
|
||||
*
|
||||
* This program 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 General Public License for more details.
|
||||
*
|
||||
* You should have received a copy of the GNU General Public License
|
||||
* along with this program. If not, see <http://www.gnu.org/licenses/>.
|
||||
*/
|
||||
|
||||
#include <linux/linkage.h>
|
||||
#include <asm/assembler.h>
|
||||
|
||||
/*
|
||||
* compare two strings
|
||||
*
|
||||
* Parameters:
|
||||
* x0 - const string 1 pointer
|
||||
* x1 - const string 2 pointer
|
||||
* Returns:
|
||||
* x0 - an integer less than, equal to, or greater than zero
|
||||
* if s1 is found, respectively, to be less than, to match,
|
||||
* or be greater than s2.
|
||||
*/
|
||||
|
||||
#define REP8_01 0x0101010101010101
|
||||
#define REP8_7f 0x7f7f7f7f7f7f7f7f
|
||||
#define REP8_80 0x8080808080808080
|
||||
|
||||
/* Parameters and result. */
|
||||
src1 .req x0
|
||||
src2 .req x1
|
||||
result .req x0
|
||||
|
||||
/* Internal variables. */
|
||||
data1 .req x2
|
||||
data1w .req w2
|
||||
data2 .req x3
|
||||
data2w .req w3
|
||||
has_nul .req x4
|
||||
diff .req x5
|
||||
syndrome .req x6
|
||||
tmp1 .req x7
|
||||
tmp2 .req x8
|
||||
tmp3 .req x9
|
||||
zeroones .req x10
|
||||
pos .req x11
|
||||
|
||||
ENTRY(strcmp)
|
||||
eor tmp1, src1, src2
|
||||
mov zeroones, #REP8_01
|
||||
tst tmp1, #7
|
||||
b.ne .Lmisaligned8
|
||||
ands tmp1, src1, #7
|
||||
b.ne .Lmutual_align
|
||||
|
||||
/*
|
||||
* NUL detection works on the principle that (X - 1) & (~X) & 0x80
|
||||
* (=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and
|
||||
* can be done in parallel across the entire word.
|
||||
*/
|
||||
.Lloop_aligned:
|
||||
ldr data1, [src1], #8
|
||||
ldr data2, [src2], #8
|
||||
.Lstart_realigned:
|
||||
sub tmp1, data1, zeroones
|
||||
orr tmp2, data1, #REP8_7f
|
||||
eor diff, data1, data2 /* Non-zero if differences found. */
|
||||
bic has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
|
||||
orr syndrome, diff, has_nul
|
||||
cbz syndrome, .Lloop_aligned
|
||||
b .Lcal_cmpresult
|
||||
|
||||
.Lmutual_align:
|
||||
/*
|
||||
* Sources are mutually aligned, but are not currently at an
|
||||
* alignment boundary. Round down the addresses and then mask off
|
||||
* the bytes that preceed the start point.
|
||||
*/
|
||||
bic src1, src1, #7
|
||||
bic src2, src2, #7
|
||||
lsl tmp1, tmp1, #3 /* Bytes beyond alignment -> bits. */
|
||||
ldr data1, [src1], #8
|
||||
neg tmp1, tmp1 /* Bits to alignment -64. */
|
||||
ldr data2, [src2], #8
|
||||
mov tmp2, #~0
|
||||
/* Big-endian. Early bytes are at MSB. */
|
||||
CPU_BE( lsl tmp2, tmp2, tmp1 ) /* Shift (tmp1 & 63). */
|
||||
/* Little-endian. Early bytes are at LSB. */
|
||||
CPU_LE( lsr tmp2, tmp2, tmp1 ) /* Shift (tmp1 & 63). */
|
||||
|
||||
orr data1, data1, tmp2
|
||||
orr data2, data2, tmp2
|
||||
b .Lstart_realigned
|
||||
|
||||
.Lmisaligned8:
|
||||
/*
|
||||
* Get the align offset length to compare per byte first.
|
||||
* After this process, one string's address will be aligned.
|
||||
*/
|
||||
and tmp1, src1, #7
|
||||
neg tmp1, tmp1
|
||||
add tmp1, tmp1, #8
|
||||
and tmp2, src2, #7
|
||||
neg tmp2, tmp2
|
||||
add tmp2, tmp2, #8
|
||||
subs tmp3, tmp1, tmp2
|
||||
csel pos, tmp1, tmp2, hi /*Choose the maximum. */
|
||||
.Ltinycmp:
|
||||
ldrb data1w, [src1], #1
|
||||
ldrb data2w, [src2], #1
|
||||
subs pos, pos, #1
|
||||
ccmp data1w, #1, #0, ne /* NZCV = 0b0000. */
|
||||
ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
|
||||
b.eq .Ltinycmp
|
||||
cbnz pos, 1f /*find the null or unequal...*/
|
||||
cmp data1w, #1
|
||||
ccmp data1w, data2w, #0, cs
|
||||
b.eq .Lstart_align /*the last bytes are equal....*/
|
||||
1:
|
||||
sub result, data1, data2
|
||||
ret
|
||||
|
||||
.Lstart_align:
|
||||
ands xzr, src1, #7
|
||||
b.eq .Lrecal_offset
|
||||
/*process more leading bytes to make str1 aligned...*/
|
||||
add src1, src1, tmp3
|
||||
add src2, src2, tmp3
|
||||
/*load 8 bytes from aligned str1 and non-aligned str2..*/
|
||||
ldr data1, [src1], #8
|
||||
ldr data2, [src2], #8
|
||||
|
||||
sub tmp1, data1, zeroones
|
||||
orr tmp2, data1, #REP8_7f
|
||||
bic has_nul, tmp1, tmp2
|
||||
eor diff, data1, data2 /* Non-zero if differences found. */
|
||||
orr syndrome, diff, has_nul
|
||||
cbnz syndrome, .Lcal_cmpresult
|
||||
/*How far is the current str2 from the alignment boundary...*/
|
||||
and tmp3, tmp3, #7
|
||||
.Lrecal_offset:
|
||||
neg pos, tmp3
|
||||
.Lloopcmp_proc:
|
||||
/*
|
||||
* Divide the eight bytes into two parts. First,backwards the src2
|
||||
* to an alignment boundary,load eight bytes from the SRC2 alignment
|
||||
* boundary,then compare with the relative bytes from SRC1.
|
||||
* If all 8 bytes are equal,then start the second part's comparison.
|
||||
* Otherwise finish the comparison.
|
||||
* This special handle can garantee all the accesses are in the
|
||||
* thread/task space in avoid to overrange access.
|
||||
*/
|
||||
ldr data1, [src1,pos]
|
||||
ldr data2, [src2,pos]
|
||||
sub tmp1, data1, zeroones
|
||||
orr tmp2, data1, #REP8_7f
|
||||
bic has_nul, tmp1, tmp2
|
||||
eor diff, data1, data2 /* Non-zero if differences found. */
|
||||
orr syndrome, diff, has_nul
|
||||
cbnz syndrome, .Lcal_cmpresult
|
||||
|
||||
/*The second part process*/
|
||||
ldr data1, [src1], #8
|
||||
ldr data2, [src2], #8
|
||||
sub tmp1, data1, zeroones
|
||||
orr tmp2, data1, #REP8_7f
|
||||
bic has_nul, tmp1, tmp2
|
||||
eor diff, data1, data2 /* Non-zero if differences found. */
|
||||
orr syndrome, diff, has_nul
|
||||
cbz syndrome, .Lloopcmp_proc
|
||||
|
||||
.Lcal_cmpresult:
|
||||
/*
|
||||
* reversed the byte-order as big-endian,then CLZ can find the most
|
||||
* significant zero bits.
|
||||
*/
|
||||
CPU_LE( rev syndrome, syndrome )
|
||||
CPU_LE( rev data1, data1 )
|
||||
CPU_LE( rev data2, data2 )
|
||||
|
||||
/*
|
||||
* For big-endian we cannot use the trick with the syndrome value
|
||||
* as carry-propagation can corrupt the upper bits if the trailing
|
||||
* bytes in the string contain 0x01.
|
||||
* However, if there is no NUL byte in the dword, we can generate
|
||||
* the result directly. We ca not just subtract the bytes as the
|
||||
* MSB might be significant.
|
||||
*/
|
||||
CPU_BE( cbnz has_nul, 1f )
|
||||
CPU_BE( cmp data1, data2 )
|
||||
CPU_BE( cset result, ne )
|
||||
CPU_BE( cneg result, result, lo )
|
||||
CPU_BE( ret )
|
||||
CPU_BE( 1: )
|
||||
/*Re-compute the NUL-byte detection, using a byte-reversed value. */
|
||||
CPU_BE( rev tmp3, data1 )
|
||||
CPU_BE( sub tmp1, tmp3, zeroones )
|
||||
CPU_BE( orr tmp2, tmp3, #REP8_7f )
|
||||
CPU_BE( bic has_nul, tmp1, tmp2 )
|
||||
CPU_BE( rev has_nul, has_nul )
|
||||
CPU_BE( orr syndrome, diff, has_nul )
|
||||
|
||||
clz pos, syndrome
|
||||
/*
|
||||
* The MS-non-zero bit of the syndrome marks either the first bit
|
||||
* that is different, or the top bit of the first zero byte.
|
||||
* Shifting left now will bring the critical information into the
|
||||
* top bits.
|
||||
*/
|
||||
lsl data1, data1, pos
|
||||
lsl data2, data2, pos
|
||||
/*
|
||||
* But we need to zero-extend (char is unsigned) the value and then
|
||||
* perform a signed 32-bit subtraction.
|
||||
*/
|
||||
lsr data1, data1, #56
|
||||
sub result, data1, data2, lsr #56
|
||||
ret
|
||||
ENDPROC(strcmp)
|
||||
Reference in New Issue
Block a user