1/* 2 * Copyright (C) 2013 ARM Ltd. 3 * Copyright (C) 2013 Linaro. 4 * 5 * This code is based on glibc cortex strings work originally authored by Linaro 6 * and re-licensed under GPLv2 for the Linux kernel. The original code can 7 * be found @ 8 * 9 * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/ 10 * files/head:/src/aarch64/ 11 * 12 * This program is free software; you can redistribute it and/or modify 13 * it under the terms of the GNU General Public License version 2 as 14 * published by the Free Software Foundation. 15 * 16 * This program is distributed in the hope that it will be useful, 17 * but WITHOUT ANY WARRANTY; without even the implied warranty of 18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 * GNU General Public License for more details. 20 * 21 * You should have received a copy of the GNU General Public License 22 * along with this program. If not, see <http://www.gnu.org/licenses/>. 23 */ 24 25#include <linux/linkage.h> 26#include <asm/assembler.h> 27 28/* 29* compare memory areas(when two memory areas' offset are different, 30* alignment handled by the hardware) 31* 32* Parameters: 33* x0 - const memory area 1 pointer 34* x1 - const memory area 2 pointer 35* x2 - the maximal compare byte length 36* Returns: 37* x0 - a compare result, maybe less than, equal to, or greater than ZERO 38*/ 39 40/* Parameters and result. */ 41src1 .req x0 42src2 .req x1 43limit .req x2 44result .req x0 45 46/* Internal variables. */ 47data1 .req x3 48data1w .req w3 49data2 .req x4 50data2w .req w4 51has_nul .req x5 52diff .req x6 53endloop .req x7 54tmp1 .req x8 55tmp2 .req x9 56tmp3 .req x10 57pos .req x11 58limit_wd .req x12 59mask .req x13 60 61ENTRY(memcmp) 62 cbz limit, .Lret0 63 eor tmp1, src1, src2 64 tst tmp1, #7 65 b.ne .Lmisaligned8 66 ands tmp1, src1, #7 67 b.ne .Lmutual_align 68 sub limit_wd, limit, #1 /* limit != 0, so no underflow. */ 69 lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */ 70 /* 71 * The input source addresses are at alignment boundary. 72 * Directly compare eight bytes each time. 73 */ 74.Lloop_aligned: 75 ldr data1, [src1], #8 76 ldr data2, [src2], #8 77.Lstart_realigned: 78 subs limit_wd, limit_wd, #1 79 eor diff, data1, data2 /* Non-zero if differences found. */ 80 csinv endloop, diff, xzr, cs /* Last Dword or differences. */ 81 cbz endloop, .Lloop_aligned 82 83 /* Not reached the limit, must have found a diff. */ 84 tbz limit_wd, #63, .Lnot_limit 85 86 /* Limit % 8 == 0 => the diff is in the last 8 bytes. */ 87 ands limit, limit, #7 88 b.eq .Lnot_limit 89 /* 90 * The remained bytes less than 8. It is needed to extract valid data 91 * from last eight bytes of the intended memory range. 92 */ 93 lsl limit, limit, #3 /* bytes-> bits. */ 94 mov mask, #~0 95CPU_BE( lsr mask, mask, limit ) 96CPU_LE( lsl mask, mask, limit ) 97 bic data1, data1, mask 98 bic data2, data2, mask 99 100 orr diff, diff, mask 101 b .Lnot_limit 102 103.Lmutual_align: 104 /* 105 * Sources are mutually aligned, but are not currently at an 106 * alignment boundary. Round down the addresses and then mask off 107 * the bytes that precede the start point. 108 */ 109 bic src1, src1, #7 110 bic src2, src2, #7 111 ldr data1, [src1], #8 112 ldr data2, [src2], #8 113 /* 114 * We can not add limit with alignment offset(tmp1) here. Since the 115 * addition probably make the limit overflown. 116 */ 117 sub limit_wd, limit, #1/*limit != 0, so no underflow.*/ 118 and tmp3, limit_wd, #7 119 lsr limit_wd, limit_wd, #3 120 add tmp3, tmp3, tmp1 121 add limit_wd, limit_wd, tmp3, lsr #3 122 add limit, limit, tmp1/* Adjust the limit for the extra. */ 123 124 lsl tmp1, tmp1, #3/* Bytes beyond alignment -> bits.*/ 125 neg tmp1, tmp1/* Bits to alignment -64. */ 126 mov tmp2, #~0 127 /*mask off the non-intended bytes before the start address.*/ 128CPU_BE( lsl tmp2, tmp2, tmp1 )/*Big-endian.Early bytes are at MSB*/ 129 /* Little-endian. Early bytes are at LSB. */ 130CPU_LE( lsr tmp2, tmp2, tmp1 ) 131 132 orr data1, data1, tmp2 133 orr data2, data2, tmp2 134 b .Lstart_realigned 135 136 /*src1 and src2 have different alignment offset.*/ 137.Lmisaligned8: 138 cmp limit, #8 139 b.lo .Ltiny8proc /*limit < 8: compare byte by byte*/ 140 141 and tmp1, src1, #7 142 neg tmp1, tmp1 143 add tmp1, tmp1, #8/*valid length in the first 8 bytes of src1*/ 144 and tmp2, src2, #7 145 neg tmp2, tmp2 146 add tmp2, tmp2, #8/*valid length in the first 8 bytes of src2*/ 147 subs tmp3, tmp1, tmp2 148 csel pos, tmp1, tmp2, hi /*Choose the maximum.*/ 149 150 sub limit, limit, pos 151 /*compare the proceeding bytes in the first 8 byte segment.*/ 152.Ltinycmp: 153 ldrb data1w, [src1], #1 154 ldrb data2w, [src2], #1 155 subs pos, pos, #1 156 ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */ 157 b.eq .Ltinycmp 158 cbnz pos, 1f /*diff occurred before the last byte.*/ 159 cmp data1w, data2w 160 b.eq .Lstart_align 1611: 162 sub result, data1, data2 163 ret 164 165.Lstart_align: 166 lsr limit_wd, limit, #3 167 cbz limit_wd, .Lremain8 168 169 ands xzr, src1, #7 170 b.eq .Lrecal_offset 171 /*process more leading bytes to make src1 aligned...*/ 172 add src1, src1, tmp3 /*backwards src1 to alignment boundary*/ 173 add src2, src2, tmp3 174 sub limit, limit, tmp3 175 lsr limit_wd, limit, #3 176 cbz limit_wd, .Lremain8 177 /*load 8 bytes from aligned SRC1..*/ 178 ldr data1, [src1], #8 179 ldr data2, [src2], #8 180 181 subs limit_wd, limit_wd, #1 182 eor diff, data1, data2 /*Non-zero if differences found.*/ 183 csinv endloop, diff, xzr, ne 184 cbnz endloop, .Lunequal_proc 185 /*How far is the current SRC2 from the alignment boundary...*/ 186 and tmp3, tmp3, #7 187 188.Lrecal_offset:/*src1 is aligned now..*/ 189 neg pos, tmp3 190.Lloopcmp_proc: 191 /* 192 * Divide the eight bytes into two parts. First,backwards the src2 193 * to an alignment boundary,load eight bytes and compare from 194 * the SRC2 alignment boundary. If all 8 bytes are equal,then start 195 * the second part's comparison. Otherwise finish the comparison. 196 * This special handle can garantee all the accesses are in the 197 * thread/task space in avoid to overrange access. 198 */ 199 ldr data1, [src1,pos] 200 ldr data2, [src2,pos] 201 eor diff, data1, data2 /* Non-zero if differences found. */ 202 cbnz diff, .Lnot_limit 203 204 /*The second part process*/ 205 ldr data1, [src1], #8 206 ldr data2, [src2], #8 207 eor diff, data1, data2 /* Non-zero if differences found. */ 208 subs limit_wd, limit_wd, #1 209 csinv endloop, diff, xzr, ne/*if limit_wd is 0,will finish the cmp*/ 210 cbz endloop, .Lloopcmp_proc 211.Lunequal_proc: 212 cbz diff, .Lremain8 213 214/* There is difference occurred in the latest comparison. */ 215.Lnot_limit: 216/* 217* For little endian,reverse the low significant equal bits into MSB,then 218* following CLZ can find how many equal bits exist. 219*/ 220CPU_LE( rev diff, diff ) 221CPU_LE( rev data1, data1 ) 222CPU_LE( rev data2, data2 ) 223 224 /* 225 * The MS-non-zero bit of DIFF marks either the first bit 226 * that is different, or the end of the significant data. 227 * Shifting left now will bring the critical information into the 228 * top bits. 229 */ 230 clz pos, diff 231 lsl data1, data1, pos 232 lsl data2, data2, pos 233 /* 234 * We need to zero-extend (char is unsigned) the value and then 235 * perform a signed subtraction. 236 */ 237 lsr data1, data1, #56 238 sub result, data1, data2, lsr #56 239 ret 240 241.Lremain8: 242 /* Limit % 8 == 0 =>. all data are equal.*/ 243 ands limit, limit, #7 244 b.eq .Lret0 245 246.Ltiny8proc: 247 ldrb data1w, [src1], #1 248 ldrb data2w, [src2], #1 249 subs limit, limit, #1 250 251 ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */ 252 b.eq .Ltiny8proc 253 sub result, data1, data2 254 ret 255.Lret0: 256 mov result, #0 257 ret 258ENDPIPROC(memcmp) 259