| 1 | /* memchr (str, ch, n) -- Return pointer to first occurrence of CH in the |
|---|
| 2 | first N bytes of STR. |
|---|
| 3 | For Motorola 68000. |
|---|
| 4 | Copyright (C) 1999-2022 Free Software Foundation, Inc. |
|---|
| 5 | This file is part of the GNU C Library. |
|---|
| 6 | |
|---|
| 7 | The GNU C Library is free software; you can redistribute it and/or |
|---|
| 8 | modify it under the terms of the GNU Lesser General Public |
|---|
| 9 | License as published by the Free Software Foundation; either |
|---|
| 10 | version 2.1 of the License, or (at your option) any later version. |
|---|
| 11 | |
|---|
| 12 | The GNU C Library is distributed in the hope that it will be useful, |
|---|
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
|---|
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
|---|
| 15 | Lesser General Public License for more details. |
|---|
| 16 | |
|---|
| 17 | You should have received a copy of the GNU Lesser General Public |
|---|
| 18 | License along with the GNU C Library. If not, see |
|---|
| 19 | <https://www.gnu.org/licenses/>. */ |
|---|
| 20 | |
|---|
| 21 | #include <sysdep.h> |
|---|
| 22 | #include "asm-syntax.h" |
|---|
| 23 | |
|---|
| 24 | TEXT |
|---|
| 25 | ENTRY(__memchr) |
|---|
| 26 | /* Save the callee-saved registers we use. */ |
|---|
| 27 | #ifdef __mcoldfire__ |
|---|
| 28 | movel R(d2),MEM_PREDEC(sp) |
|---|
| 29 | cfi_adjust_cfa_offset (4) |
|---|
| 30 | movel R(d3),MEM_PREDEC(sp) |
|---|
| 31 | cfi_adjust_cfa_offset (4) |
|---|
| 32 | movel R(d4),MEM_PREDEC(sp) |
|---|
| 33 | cfi_adjust_cfa_offset (4) |
|---|
| 34 | cfi_rel_offset (R(d2), 8) |
|---|
| 35 | cfi_rel_offset (R(d3), 4) |
|---|
| 36 | cfi_rel_offset (R(d4), 0) |
|---|
| 37 | #else |
|---|
| 38 | moveml R(d2)-R(d4),MEM_PREDEC(sp) |
|---|
| 39 | cfi_adjust_cfa_offset (3*4) |
|---|
| 40 | cfi_rel_offset (R(d2), 0) |
|---|
| 41 | cfi_rel_offset (R(d3), 4) |
|---|
| 42 | cfi_rel_offset (R(d4), 8) |
|---|
| 43 | #endif |
|---|
| 44 | |
|---|
| 45 | /* Get string pointer, character and length. */ |
|---|
| 46 | movel MEM_DISP(sp,16),R(a0) |
|---|
| 47 | moveb MEM_DISP(sp,23),R(d0) |
|---|
| 48 | movel MEM_DISP(sp,24),R(d4) |
|---|
| 49 | |
|---|
| 50 | /* Check if at least four bytes left to search. */ |
|---|
| 51 | #ifdef __mcoldfire__ |
|---|
| 52 | subql #4,R(d4) |
|---|
| 53 | bcs L(L6) |
|---|
| 54 | addql #4,R(d4) |
|---|
| 55 | #else |
|---|
| 56 | moveql #4,R(d1) |
|---|
| 57 | cmpl R(d1),R(d4) |
|---|
| 58 | bcs L(L6) |
|---|
| 59 | #endif |
|---|
| 60 | |
|---|
| 61 | /* Distribute the character to all bytes of a longword. */ |
|---|
| 62 | movel R(d0),R(d1) |
|---|
| 63 | lsll #8,R(d1) |
|---|
| 64 | moveb R(d0),R(d1) |
|---|
| 65 | movel R(d1),R(d0) |
|---|
| 66 | swap R(d0) |
|---|
| 67 | movew R(d1),R(d0) |
|---|
| 68 | |
|---|
| 69 | /* First search for the character one byte at a time until the |
|---|
| 70 | pointer is aligned to a longword boundary. */ |
|---|
| 71 | movel R(a0),R(d1) |
|---|
| 72 | #ifdef __mcoldfire__ |
|---|
| 73 | andl #3,R(d1) |
|---|
| 74 | #else |
|---|
| 75 | andw #3,R(d1) |
|---|
| 76 | #endif |
|---|
| 77 | beq L(L1) |
|---|
| 78 | cmpb MEM(a0),R(d0) |
|---|
| 79 | beq L(L9) |
|---|
| 80 | addql #1,R(a0) |
|---|
| 81 | subql #1,R(d4) |
|---|
| 82 | beq L(L7) |
|---|
| 83 | |
|---|
| 84 | #ifdef __mcoldfire__ |
|---|
| 85 | subql #3,R(d1) |
|---|
| 86 | #else |
|---|
| 87 | subqw #3,R(d1) |
|---|
| 88 | #endif |
|---|
| 89 | beq L(L1) |
|---|
| 90 | cmpb MEM(a0),R(d0) |
|---|
| 91 | beq L(L9) |
|---|
| 92 | addql #1,R(a0) |
|---|
| 93 | subql #1,R(d4) |
|---|
| 94 | beq L(L7) |
|---|
| 95 | |
|---|
| 96 | #ifdef __mcoldfire__ |
|---|
| 97 | addql #1,R(d1) |
|---|
| 98 | #else |
|---|
| 99 | addqw #1,R(d1) |
|---|
| 100 | #endif |
|---|
| 101 | beq L(L1) |
|---|
| 102 | cmpb MEM(a0),R(d0) |
|---|
| 103 | beq L(L9) |
|---|
| 104 | addql #1,R(a0) |
|---|
| 105 | subql #1,R(d4) |
|---|
| 106 | beq L(L7) |
|---|
| 107 | |
|---|
| 108 | L(L1:) |
|---|
| 109 | /* Load the magic bits. Unlike the generic implementation we can |
|---|
| 110 | use the carry bit as the fourth hole. */ |
|---|
| 111 | movel #0xfefefeff,R(d3) |
|---|
| 112 | |
|---|
| 113 | /* We exit the loop if adding MAGIC_BITS to LONGWORD fails to |
|---|
| 114 | change any of the hole bits of LONGWORD. |
|---|
| 115 | |
|---|
| 116 | 1) Is this safe? Will it catch all the zero bytes? |
|---|
| 117 | Suppose there is a byte with all zeros. Any carry bits |
|---|
| 118 | propagating from its left will fall into the hole at its |
|---|
| 119 | least significant bit and stop. Since there will be no |
|---|
| 120 | carry from its most significant bit, the LSB of the |
|---|
| 121 | byte to the left will be unchanged, and the zero will be |
|---|
| 122 | detected. |
|---|
| 123 | |
|---|
| 124 | 2) Is this worthwhile? Will it ignore everything except |
|---|
| 125 | zero bytes? Suppose every byte of LONGWORD has a bit set |
|---|
| 126 | somewhere. There will be a carry into bit 8. If bit 8 |
|---|
| 127 | is set, this will carry into bit 16. If bit 8 is clear, |
|---|
| 128 | one of bits 9-15 must be set, so there will be a carry |
|---|
| 129 | into bit 16. Similarly, there will be a carry into bit |
|---|
| 130 | 24. If one of bits 24-31 is set, there will be a carry |
|---|
| 131 | into bit 32 (=carry flag), so all of the hole bits will |
|---|
| 132 | be changed. |
|---|
| 133 | |
|---|
| 134 | 3) But wait! Aren't we looking for C, not zero? |
|---|
| 135 | Good point. So what we do is XOR LONGWORD with a longword, |
|---|
| 136 | each of whose bytes is C. This turns each byte that is C |
|---|
| 137 | into a zero. */ |
|---|
| 138 | |
|---|
| 139 | /* Still at least 4 bytes to search? */ |
|---|
| 140 | subql #4,R(d4) |
|---|
| 141 | bcs L(L6) |
|---|
| 142 | |
|---|
| 143 | L(L2:) |
|---|
| 144 | /* Get the longword in question. */ |
|---|
| 145 | movel MEM_POSTINC(a0),R(d1) |
|---|
| 146 | /* XOR with the byte we search for. */ |
|---|
| 147 | eorl R(d0),R(d1) |
|---|
| 148 | |
|---|
| 149 | /* Add the magic value. We get carry bits reported for each byte |
|---|
| 150 | which is not C. */ |
|---|
| 151 | movel R(d3),R(d2) |
|---|
| 152 | addl R(d1),R(d2) |
|---|
| 153 | |
|---|
| 154 | /* Check the fourth carry bit before it is clobbered by the next |
|---|
| 155 | XOR. If it is not set we have a hit. */ |
|---|
| 156 | bcc L(L8) |
|---|
| 157 | |
|---|
| 158 | /* We are only interested in carry bits that change due to the |
|---|
| 159 | previous add, so remove original bits. */ |
|---|
| 160 | eorl R(d1),R(d2) |
|---|
| 161 | |
|---|
| 162 | /* Now test for the other three overflow bits. |
|---|
| 163 | Set all non-carry bits. */ |
|---|
| 164 | orl R(d3),R(d2) |
|---|
| 165 | /* Add 1 to get zero if all carry bits were set. */ |
|---|
| 166 | addql #1,R(d2) |
|---|
| 167 | |
|---|
| 168 | /* If we don't get zero then at least one byte of the word equals |
|---|
| 169 | C. */ |
|---|
| 170 | bne L(L8) |
|---|
| 171 | |
|---|
| 172 | /* Still at least 4 bytes to search? */ |
|---|
| 173 | subql #4,R(d4) |
|---|
| 174 | bcs L(L6) |
|---|
| 175 | |
|---|
| 176 | /* Get the longword in question. */ |
|---|
| 177 | movel MEM_POSTINC(a0),R(d1) |
|---|
| 178 | /* XOR with the byte we search for. */ |
|---|
| 179 | eorl R(d0),R(d1) |
|---|
| 180 | |
|---|
| 181 | /* Add the magic value. We get carry bits reported for each byte |
|---|
| 182 | which is not C. */ |
|---|
| 183 | movel R(d3),R(d2) |
|---|
| 184 | addl R(d1),R(d2) |
|---|
| 185 | |
|---|
| 186 | /* Check the fourth carry bit before it is clobbered by the next |
|---|
| 187 | XOR. If it is not set we have a hit. */ |
|---|
| 188 | bcc L(L8) |
|---|
| 189 | |
|---|
| 190 | /* We are only interested in carry bits that change due to the |
|---|
| 191 | previous add, so remove original bits */ |
|---|
| 192 | eorl R(d1),R(d2) |
|---|
| 193 | |
|---|
| 194 | /* Now test for the other three overflow bits. |
|---|
| 195 | Set all non-carry bits. */ |
|---|
| 196 | orl R(d3),R(d2) |
|---|
| 197 | /* Add 1 to get zero if all carry bits were set. */ |
|---|
| 198 | addql #1,R(d2) |
|---|
| 199 | |
|---|
| 200 | /* If we don't get zero then at least one byte of the word equals |
|---|
| 201 | C. */ |
|---|
| 202 | bne L(L8) |
|---|
| 203 | |
|---|
| 204 | /* Still at least 4 bytes to search? */ |
|---|
| 205 | subql #4,R(d4) |
|---|
| 206 | bcc L(L2) |
|---|
| 207 | |
|---|
| 208 | L(L6:) |
|---|
| 209 | /* Search one byte at a time in the remaining less than 4 bytes. */ |
|---|
| 210 | #ifdef __mcoldfire__ |
|---|
| 211 | addql #4,R(d4) |
|---|
| 212 | #else |
|---|
| 213 | andw #3,R(d4) |
|---|
| 214 | #endif |
|---|
| 215 | beq L(L7) |
|---|
| 216 | cmpb MEM(a0),R(d0) |
|---|
| 217 | beq L(L9) |
|---|
| 218 | addql #1,R(a0) |
|---|
| 219 | |
|---|
| 220 | #ifdef __mcoldfire__ |
|---|
| 221 | subql #1,R(d4) |
|---|
| 222 | #else |
|---|
| 223 | subqw #1,R(d4) |
|---|
| 224 | #endif |
|---|
| 225 | beq L(L7) |
|---|
| 226 | cmpb MEM(a0),R(d0) |
|---|
| 227 | beq L(L9) |
|---|
| 228 | addql #1,R(a0) |
|---|
| 229 | |
|---|
| 230 | #ifdef __mcoldfire__ |
|---|
| 231 | subql #1,R(d4) |
|---|
| 232 | #else |
|---|
| 233 | subqw #1,R(d4) |
|---|
| 234 | #endif |
|---|
| 235 | beq L(L7) |
|---|
| 236 | cmpb MEM(a0),R(d0) |
|---|
| 237 | beq L(L9) |
|---|
| 238 | |
|---|
| 239 | L(L7:) |
|---|
| 240 | /* Return NULL. */ |
|---|
| 241 | clrl R(d0) |
|---|
| 242 | movel R(d0),R(a0) |
|---|
| 243 | #ifdef __mcoldfire__ |
|---|
| 244 | movel MEM_POSTINC(sp),R(d4) |
|---|
| 245 | cfi_remember_state |
|---|
| 246 | cfi_adjust_cfa_offset (-4) |
|---|
| 247 | cfi_restore (R(d4)) |
|---|
| 248 | movel MEM_POSTINC(sp),R(d3) |
|---|
| 249 | cfi_adjust_cfa_offset (-4) |
|---|
| 250 | cfi_restore (R(d3)) |
|---|
| 251 | movel MEM_POSTINC(sp),R(d2) |
|---|
| 252 | cfi_adjust_cfa_offset (-4) |
|---|
| 253 | cfi_restore (R(d2)) |
|---|
| 254 | #else |
|---|
| 255 | moveml MEM_POSTINC(sp),R(d2)-R(d4) |
|---|
| 256 | cfi_remember_state |
|---|
| 257 | cfi_adjust_cfa_offset (-3*4) |
|---|
| 258 | cfi_restore (R(d2)) |
|---|
| 259 | cfi_restore (R(d3)) |
|---|
| 260 | cfi_restore (R(d4)) |
|---|
| 261 | #endif |
|---|
| 262 | rts |
|---|
| 263 | |
|---|
| 264 | cfi_restore_state |
|---|
| 265 | L(L8:) |
|---|
| 266 | /* We have a hit. Check to see which byte it was. First |
|---|
| 267 | compensate for the autoincrement in the loop. */ |
|---|
| 268 | subql #4,R(a0) |
|---|
| 269 | |
|---|
| 270 | cmpb MEM(a0),R(d0) |
|---|
| 271 | beq L(L9) |
|---|
| 272 | addql #1,R(a0) |
|---|
| 273 | |
|---|
| 274 | cmpb MEM(a0),R(d0) |
|---|
| 275 | beq L(L9) |
|---|
| 276 | addql #1,R(a0) |
|---|
| 277 | |
|---|
| 278 | cmpb MEM(a0),R(d0) |
|---|
| 279 | beq L(L9) |
|---|
| 280 | addql #1,R(a0) |
|---|
| 281 | |
|---|
| 282 | /* Otherwise the fourth byte must equal C. */ |
|---|
| 283 | L(L9:) |
|---|
| 284 | movel R(a0),R(d0) |
|---|
| 285 | #ifdef __mcoldfire__ |
|---|
| 286 | movel MEM_POSTINC(sp),R(d4) |
|---|
| 287 | cfi_adjust_cfa_offset (-4) |
|---|
| 288 | cfi_restore (R(d4)) |
|---|
| 289 | movel MEM_POSTINC(sp),R(d3) |
|---|
| 290 | cfi_adjust_cfa_offset (-4) |
|---|
| 291 | cfi_restore (R(d3)) |
|---|
| 292 | movel MEM_POSTINC(sp),R(d2) |
|---|
| 293 | cfi_adjust_cfa_offset (-4) |
|---|
| 294 | cfi_restore (R(d2)) |
|---|
| 295 | #else |
|---|
| 296 | moveml MEM_POSTINC(sp),R(d2)-R(d4) |
|---|
| 297 | cfi_adjust_cfa_offset (-3*4) |
|---|
| 298 | cfi_restore (R(d2)) |
|---|
| 299 | cfi_restore (R(d3)) |
|---|
| 300 | cfi_restore (R(d4)) |
|---|
| 301 | #endif |
|---|
| 302 | rts |
|---|
| 303 | END(__memchr) |
|---|
| 304 | |
|---|
| 305 | weak_alias (__memchr, memchr) |
|---|
| 306 | libc_hidden_builtin_def (memchr) |
|---|
| 307 | |
|---|
