| /* |
| * 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 |
| |
| ENTRY(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 differnence occured 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 |
| ENDPROC(memcmp) |
