mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
223 lines
6.0 KiB
223 lines
6.0 KiB
/* SPDX-License-Identifier: GPL-2.0-only */ |
|
/* |
|
* Copyright (C) 2013 ARM Ltd. |
|
* Copyright (C) 2013 Linaro. |
|
* |
|
* 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/ |
|
*/ |
|
|
|
#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 |
|
|
|
SYM_FUNC_START_WEAK_PI(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 cannot 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 |
|
SYM_FUNC_END_PI(strcmp) |
|
EXPORT_SYMBOL_NOKASAN(strcmp)
|
|
|