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Diffstat (limited to 'arch/arm64/lib/memcmp.S')
| -rw-r--r-- | arch/arm64/lib/memcmp.S | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/arch/arm64/lib/memcmp.S b/arch/arm64/lib/memcmp.S new file mode 100644 index 000000000..fb295f52e --- /dev/null +++ b/arch/arm64/lib/memcmp.S @@ -0,0 +1,258 @@ +/* + * 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 memory areas(when two memory areas' offset are different, +* alignment handled by the hardware) +* +* Parameters: +* x0 - const memory area 1 pointer +* x1 - const memory area 2 pointer +* x2 - the maximal compare byte length +* Returns: +* x0 - a compare result, maybe less than, equal to, or greater than ZERO +*/ + +/* Parameters and result. */ +src1 .req x0 +src2 .req x1 +limit .req x2 +result .req x0 + +/* Internal variables. */ +data1 .req x3 +data1w .req w3 +data2 .req x4 +data2w .req w4 +has_nul .req x5 +diff .req x6 +endloop .req x7 +tmp1 .req x8 +tmp2 .req x9 +tmp3 .req x10 +pos .req x11 +limit_wd .req x12 +mask .req x13 + +WEAK(memcmp) + cbz limit, .Lret0 + eor tmp1, src1, src2 + tst tmp1, #7 + b.ne .Lmisaligned8 + ands tmp1, src1, #7 + b.ne .Lmutual_align + sub limit_wd, limit, #1 /* limit != 0, so no underflow. */ + lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */ + /* + * The input source addresses are at alignment boundary. + * Directly compare eight bytes each time. + */ +.Lloop_aligned: + ldr data1, [src1], #8 + ldr data2, [src2], #8 +.Lstart_realigned: + subs limit_wd, limit_wd, #1 + eor diff, data1, data2 /* Non-zero if differences found. */ + csinv endloop, diff, xzr, cs /* Last Dword or differences. */ + cbz endloop, .Lloop_aligned + + /* Not reached the limit, must have found a diff. */ + tbz limit_wd, #63, .Lnot_limit + + /* Limit % 8 == 0 => the diff is in the last 8 bytes. */ + ands limit, limit, #7 + b.eq .Lnot_limit + /* + * The remained bytes less than 8. It is needed to extract valid data + * from last eight bytes of the intended memory range. + */ + lsl limit, limit, #3 /* bytes-> bits. */ + mov mask, #~0 +CPU_BE( lsr mask, mask, limit ) +CPU_LE( lsl mask, mask, limit ) + bic data1, data1, mask + bic data2, data2, mask + + orr diff, diff, mask + b .Lnot_limit + +.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. + */ + bic src1, src1, #7 + bic src2, src2, #7 + ldr data1, [src1], #8 + ldr data2, [src2], #8 + /* + * We can not add limit with alignment offset(tmp1) here. Since the + * addition probably make the limit overflown. + */ + sub limit_wd, limit, #1/*limit != 0, so no underflow.*/ + and tmp3, limit_wd, #7 + lsr limit_wd, limit_wd, #3 + add tmp3, tmp3, tmp1 + add limit_wd, limit_wd, tmp3, lsr #3 + add limit, limit, tmp1/* Adjust the limit for the extra. */ + + lsl tmp1, tmp1, #3/* Bytes beyond alignment -> bits.*/ + neg tmp1, tmp1/* Bits to alignment -64. */ + mov tmp2, #~0 + /*mask off the non-intended bytes before the start address.*/ +CPU_BE( lsl tmp2, tmp2, tmp1 )/*Big-endian.Early bytes are at MSB*/ + /* Little-endian. Early bytes are at LSB. */ +CPU_LE( lsr tmp2, tmp2, tmp1 ) + + orr data1, data1, tmp2 + orr data2, data2, tmp2 + b .Lstart_realigned + + /*src1 and src2 have different alignment offset.*/ +.Lmisaligned8: + cmp limit, #8 + b.lo .Ltiny8proc /*limit < 8: compare byte by byte*/ + + and tmp1, src1, #7 + neg tmp1, tmp1 + add tmp1, tmp1, #8/*valid length in the first 8 bytes of src1*/ + and tmp2, src2, #7 + neg tmp2, tmp2 + add tmp2, tmp2, #8/*valid length in the first 8 bytes of src2*/ + subs tmp3, tmp1, tmp2 + csel pos, tmp1, tmp2, hi /*Choose the maximum.*/ + + sub limit, limit, pos + /*compare the proceeding bytes in the first 8 byte segment.*/ +.Ltinycmp: + ldrb data1w, [src1], #1 + ldrb data2w, [src2], #1 + subs pos, pos, #1 + ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */ + b.eq .Ltinycmp + cbnz pos, 1f /*diff occurred before the last byte.*/ + cmp data1w, data2w + b.eq .Lstart_align +1: + sub result, data1, data2 + ret + +.Lstart_align: + lsr limit_wd, limit, #3 + cbz limit_wd, .Lremain8 + + ands xzr, src1, #7 + b.eq .Lrecal_offset + /*process more leading bytes to make src1 aligned...*/ + add src1, src1, tmp3 /*backwards src1 to alignment boundary*/ + add src2, src2, tmp3 + sub limit, limit, tmp3 + lsr limit_wd, limit, #3 + cbz limit_wd, .Lremain8 + /*load 8 bytes from aligned SRC1..*/ + ldr data1, [src1], #8 + ldr data2, [src2], #8 + + subs limit_wd, limit_wd, #1 + eor diff, data1, data2 /*Non-zero if differences found.*/ + csinv endloop, diff, xzr, ne + cbnz endloop, .Lunequal_proc + /*How far is the current SRC2 from the alignment boundary...*/ + and tmp3, tmp3, #7 + +.Lrecal_offset:/*src1 is aligned now..*/ + neg pos, tmp3 +.Lloopcmp_proc: + /* + * Divide the eight bytes into two parts. First,backwards the src2 + * to an alignment boundary,load eight bytes and compare from + * the SRC2 alignment boundary. 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] + eor diff, data1, data2 /* Non-zero if differences found. */ + cbnz diff, .Lnot_limit + + /*The second part process*/ + ldr data1, [src1], #8 + ldr data2, [src2], #8 + eor diff, data1, data2 /* Non-zero if differences found. */ + subs limit_wd, limit_wd, #1 + csinv endloop, diff, xzr, ne/*if limit_wd is 0,will finish the cmp*/ + cbz endloop, .Lloopcmp_proc +.Lunequal_proc: + cbz diff, .Lremain8 + +/* There is difference occurred in the latest comparison. */ +.Lnot_limit: +/* +* For little endian,reverse the low significant equal bits into MSB,then +* following CLZ can find how many equal bits exist. +*/ +CPU_LE( rev diff, diff ) +CPU_LE( rev data1, data1 ) +CPU_LE( rev data2, data2 ) + + /* + * The MS-non-zero bit of DIFF marks either the first bit + * that is different, or the end of the significant data. + * Shifting left now will bring the critical information into the + * top bits. + */ + clz pos, diff + lsl data1, data1, pos + lsl data2, data2, pos + /* + * We need to zero-extend (char is unsigned) the value and then + * perform a signed subtraction. + */ + lsr data1, data1, #56 + sub result, data1, data2, lsr #56 + ret + +.Lremain8: + /* Limit % 8 == 0 =>. all data are equal.*/ + ands limit, limit, #7 + b.eq .Lret0 + +.Ltiny8proc: + ldrb data1w, [src1], #1 + ldrb data2w, [src2], #1 + subs limit, limit, #1 + + ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */ + b.eq .Ltiny8proc + sub result, data1, data2 + ret +.Lret0: + mov result, #0 + ret +ENDPIPROC(memcmp) |