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Commit 020b199b authored by Sam Tebbs's avatar Sam Tebbs Committed by Will Deacon
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arm64: Import latest version of Cortex Strings' strncmp 

Import the latest version of the former Cortex Strings - now
Arm Optimized Routines - strncmp function based on the upstream
code of string/aarch64/strncmp.S at commit e823e3a from
https://github.com/ARM-software/optimized-routines

Note that for simplicity Arm have chosen to contribute this code
to Linux under GPLv2 rather than the original MIT license.
Signed-off-by: default avatarSam Tebbs <sam.tebbs@arm.com>
[ rm: update attribution and commit message ]
Signed-off-by: default avatarRobin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/26110bee02ad360596c9a7536af7eaaf6890d0e8.1622128527.git.robin.murphy@arm.comSigned-off-by: default avatarWill Deacon <will@kernel.org>
parent 325a1de8
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arch/arm64/lib/strncmp.S
View file @ 020b199b
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright (C) 2013 ARM Ltd.
* Copyright (C) 2013 Linaro.
* Copyright (c) 2013, Arm Limited.
*
* This code is based on glibc cortex strings work originally authored by Linaro
* be found @
*
* http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
* files/head:/src/aarch64/
* Adapted from the original at:
* https://github.com/ARM-software/optimized-routines/blob/master/string/aarch64/strncmp.S
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
/*
* compare two strings
/* Assumptions:
*
* Parameters:
* x0 - const string 1 pointer
* x1 - const string 2 pointer
* x2 - the maximal length to be compared
* 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.
* ARMv8-a, AArch64
*/
#define L(label) .L ## label
#define REP8_01 0x0101010101010101
#define REP8_7f 0x7f7f7f7f7f7f7f7f
#define REP8_80 0x8080808080808080
/* Parameters and result. */
src1 .req x0
src2 .req x1
limit .req x2
result .req x0
#define src1 x0
#define src2 x1
#define limit x2
#define result x0
/* Internal variables. */
data1 .req x3
data1w .req w3
data2 .req x4
data2w .req w4
has_nul .req x5
diff .req x6
syndrome .req x7
tmp1 .req x8
tmp2 .req x9
tmp3 .req x10
zeroones .req x11
pos .req x12
limit_wd .req x13
mask .req x14
endloop .req x15
#define data1 x3
#define data1w w3
#define data2 x4
#define data2w w4
#define has_nul x5
#define diff x6
#define syndrome x7
#define tmp1 x8
#define tmp2 x9
#define tmp3 x10
#define zeroones x11
#define pos x12
#define limit_wd x13
#define mask x14
#define endloop x15
#define count mask
SYM_FUNC_START_WEAK_PI(strncmp)
cbz limit, .Lret0
cbz limit, L(ret0)
eor tmp1, src1, src2
mov zeroones, #REP8_01
tst tmp1, #7
b.ne .Lmisaligned8
ands tmp1, src1, #7
b.ne .Lmutual_align
and count, src1, #7
b.ne L(misaligned8)
cbnz count, L(mutual_align)
/* Calculate the number of full and partial words -1. */
/*
* when limit is mulitply of 8, if not sub 1,
* the judgement of last dword will wrong.
*/
sub limit_wd, limit, #1 /* limit != 0, so no underflow. */
lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */
sub limit_wd, limit, #1 /* limit != 0, so no underflow. */
lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */
/*
* 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:
/* 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. */
.p2align 4
L(loop_aligned):
ldr data1, [src1], #8
ldr data2, [src2], #8
.Lstart_realigned:
L(start_realigned):
subs limit_wd, limit_wd, #1
sub tmp1, data1, zeroones
orr tmp2, data1, #REP8_7f
eor diff, data1, data2 /* Non-zero if differences found. */
csinv endloop, diff, xzr, pl /* Last Dword or differences.*/
bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
eor diff, data1, data2 /* Non-zero if differences found. */
csinv endloop, diff, xzr, pl /* Last Dword or differences. */
bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
ccmp endloop, #0, #0, eq
b.eq .Lloop_aligned
b.eq L(loop_aligned)
/* End of main loop */
/*Not reached the limit, must have found the end or a diff. */
tbz limit_wd, #63, .Lnot_limit
/* Not reached the limit, must have found the end or a diff. */
tbz limit_wd, #63, L(not_limit)
/* Limit % 8 == 0 => all bytes significant. */
ands limit, limit, #7
b.eq .Lnot_limit
b.eq L(not_limit)
lsl limit, limit, #3 /* Bits -> bytes. */
lsl limit, limit, #3 /* Bits -> bytes. */
mov mask, #~0
CPU_BE( lsr mask, mask, limit )
CPU_LE( lsl mask, mask, limit )
#ifdef __AARCH64EB__
lsr mask, mask, limit
#else
lsl mask, mask, limit
#endif
bic data1, data1, mask
bic data2, data2, mask
/* Make sure that the NUL byte is marked in the syndrome. */
orr has_nul, has_nul, mask
.Lnot_limit:
L(not_limit):
orr syndrome, diff, has_nul
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 precede the start point.
* We also need to adjust the limit calculations, but without
* overflowing if the limit is near ULONG_MAX.
*/
#ifndef __AARCH64EB__
rev syndrome, syndrome
rev data1, data1
/* 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. */
clz pos, syndrome
rev data2, data2
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
#else
/* 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 can't just subtract the bytes as the
MSB might be significant. */
cbnz has_nul, 1f
cmp data1, data2
cset result, ne
cneg result, result, lo
ret
1:
/* Re-compute the NUL-byte detection, using a byte-reversed value. */
rev tmp3, data1
sub tmp1, tmp3, zeroones
orr tmp2, tmp3, #REP8_7f
bic has_nul, tmp1, tmp2
rev has_nul, has_nul
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
#endif
L(mutual_align):
/* Sources are mutually aligned, but are not currently at an
alignment boundary. Round down the addresses and then mask off
the bytes that precede the start point.
We also need to adjust the limit calculations, but without
overflowing if the limit is near ULONG_MAX. */
bic src1, src1, #7
bic src2, src2, #7
ldr data1, [src1], #8
neg tmp3, tmp1, lsl #3 /* 64 - bits(bytes beyond align). */
neg tmp3, count, lsl #3 /* 64 - bits(bytes beyond align). */
ldr data2, [src2], #8
mov tmp2, #~0
sub limit_wd, limit, #1 /* limit != 0, so no underflow. */
sub limit_wd, limit, #1 /* limit != 0, so no underflow. */
#ifdef __AARCH64EB__
/* Big-endian. Early bytes are at MSB. */
CPU_BE( lsl tmp2, tmp2, tmp3 ) /* Shift (tmp1 & 63). */
lsl tmp2, tmp2, tmp3 /* Shift (count & 63). */
#else
/* Little-endian. Early bytes are at LSB. */
CPU_LE( lsr tmp2, tmp2, tmp3 ) /* Shift (tmp1 & 63). */
lsr tmp2, tmp2, tmp3 /* Shift (count & 63). */
#endif
and tmp3, limit_wd, #7
lsr limit_wd, limit_wd, #3
/* Adjust the limit. Only low 3 bits used, so overflow irrelevant.*/
add limit, limit, tmp1
add tmp3, tmp3, tmp1
/* Adjust the limit. Only low 3 bits used, so overflow irrelevant. */
add limit, limit, count
add tmp3, tmp3, count
orr data1, data1, tmp2
orr data2, data2, tmp2
add limit_wd, limit_wd, tmp3, lsr #3
b .Lstart_realigned
b L(start_realigned)
.p2align 4
/* Don't bother with dwords for up to 16 bytes. */
L(misaligned8):
cmp limit, #16
b.hs L(try_misaligned_words)
/*when src1 offset is not equal to src2 offset...*/
.Lmisaligned8:
cmp limit, #8
b.lo .Ltiny8proc /*limit < 8... */
/*
* 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. */
/*
* Here, limit is not less than 8, so directly run .Ltinycmp
* without checking the limit.*/
sub limit, limit, pos
.Ltinycmp:
L(byte_loop):
/* Perhaps we can do better than this. */
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:
subs limit, limit, #1
ccmp data1w, #1, #0, hi /* NZCV = 0b0000. */
ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
b.eq L(byte_loop)
L(done):
sub result, data1, data2
ret
.Lstart_align:
/* Align the SRC1 to a dword by doing a bytewise compare and then do
the dword loop. */
L(try_misaligned_words):
lsr limit_wd, limit, #3
cbz limit_wd, .Lremain8
/*process more leading bytes to make str1 aligned...*/
ands xzr, src1, #7
b.eq .Lrecal_offset
add src1, src1, tmp3 /*tmp3 is positive in this branch.*/
add src2, src2, tmp3
ldr data1, [src1], #8
ldr data2, [src2], #8
cbz count, L(do_misaligned)
sub limit, limit, tmp3
neg count, count
and count, count, #7
sub limit, limit, count
lsr limit_wd, limit, #3
subs limit_wd, limit_wd, #1
sub tmp1, data1, zeroones
orr tmp2, data1, #REP8_7f
eor diff, data1, data2 /* Non-zero if differences found. */
csinv endloop, diff, xzr, ne/*if limit_wd is 0,will finish the cmp*/
bics has_nul, tmp1, tmp2
ccmp endloop, #0, #0, eq /*has_null is ZERO: no null byte*/
b.ne .Lunequal_proc
/*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
bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
eor diff, data1, data2 /* Non-zero if differences found. */
csinv endloop, diff, xzr, eq
cbnz endloop, .Lunequal_proc
L(page_end_loop):
ldrb data1w, [src1], #1
ldrb data2w, [src2], #1
cmp data1w, #1
ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
b.ne L(done)
subs count, count, #1
b.hi L(page_end_loop)
L(do_misaligned):
/* Prepare ourselves for the next page crossing. Unlike the aligned
loop, we fetch 1 less dword because we risk crossing bounds on
SRC2. */
mov count, #8
subs limit_wd, limit_wd, #1
b.lo L(done_loop)
L(loop_misaligned):
and tmp2, src2, #0xff8
eor tmp2, tmp2, #0xff8
cbz tmp2, L(page_end_loop)
/*The second part process*/
ldr data1, [src1], #8
ldr data2, [src2], #8
subs limit_wd, limit_wd, #1
sub tmp1, data1, zeroones
orr tmp2, data1, #REP8_7f
eor diff, data1, data2 /* Non-zero if differences found. */
csinv endloop, diff, xzr, ne/*if limit_wd is 0,will finish the cmp*/
bics has_nul, tmp1, tmp2
ccmp endloop, #0, #0, eq /*has_null is ZERO: no null byte*/
b.eq .Lloopcmp_proc
.Lunequal_proc:
orr syndrome, diff, has_nul
cbz syndrome, .Lremain8
.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 can't 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 )
/*
* 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.
*/
clz pos, syndrome
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
.Lremain8:
/* Limit % 8 == 0 => all bytes significant. */
ands limit, limit, #7
b.eq .Lret0
.Ltiny8proc:
ldrb data1w, [src1], #1
ldrb data2w, [src2], #1
subs limit, limit, #1
eor diff, data1, data2 /* Non-zero if differences found. */
bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
ccmp diff, #0, #0, eq
b.ne L(not_limit)
subs limit_wd, limit_wd, #1
b.pl L(loop_misaligned)
ccmp data1w, #1, #0, ne /* NZCV = 0b0000. */
ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
b.eq .Ltiny8proc
sub result, data1, data2
ret
L(done_loop):
/* We found a difference or a NULL before the limit was reached. */
and limit, limit, #7
cbz limit, L(not_limit)
/* Read the last word. */
sub src1, src1, 8
sub src2, src2, 8
ldr data1, [src1, limit]
ldr data2, [src2, limit]
sub tmp1, data1, zeroones
orr tmp2, data1, #REP8_7f
eor diff, data1, data2 /* Non-zero if differences found. */
bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
ccmp diff, #0, #0, eq
b.ne L(not_limit)
.Lret0:
L(ret0):
mov result, #0
ret
SYM_FUNC_END_PI(strncmp)
EXPORT_SYMBOL_NOKASAN(strncmp)
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