startcode_armv6.S (7543B)
1 /* 2 * Copyright (c) 2013 RISC OS Open Ltd 3 * Author: Ben Avison <bavison@riscosopen.org> 4 * 5 * This file is part of FFmpeg. 6 * 7 * FFmpeg 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 * FFmpeg 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 FFmpeg; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21 22 #include "libavutil/arm/asm.S" 23 24 RESULT .req a1 25 BUF .req a1 26 SIZE .req a2 27 PATTERN .req a3 28 PTR .req a4 29 DAT0 .req v1 30 DAT1 .req v2 31 DAT2 .req v3 32 DAT3 .req v4 33 TMP0 .req v5 34 TMP1 .req v6 35 TMP2 .req ip 36 TMP3 .req lr 37 38 #define PRELOAD_DISTANCE 4 39 40 .macro innerloop4 41 ldr DAT0, [PTR], #4 42 subs SIZE, SIZE, #4 @ C flag survives rest of macro 43 sub TMP0, DAT0, PATTERN, lsr #14 44 bic TMP0, TMP0, DAT0 45 ands TMP0, TMP0, PATTERN 46 .endm 47 48 .macro innerloop16 decrement, do_preload 49 ldmia PTR!, {DAT0,DAT1,DAT2,DAT3} 50 .ifnc "\do_preload","" 51 pld [PTR, #PRELOAD_DISTANCE*32] 52 .endif 53 .ifnc "\decrement","" 54 subs SIZE, SIZE, #\decrement @ C flag survives rest of macro 55 .endif 56 sub TMP0, DAT0, PATTERN, lsr #14 57 sub TMP1, DAT1, PATTERN, lsr #14 58 bic TMP0, TMP0, DAT0 59 bic TMP1, TMP1, DAT1 60 sub TMP2, DAT2, PATTERN, lsr #14 61 sub TMP3, DAT3, PATTERN, lsr #14 62 ands TMP0, TMP0, PATTERN 63 bic TMP2, TMP2, DAT2 64 it eq 65 andseq TMP1, TMP1, PATTERN 66 bic TMP3, TMP3, DAT3 67 itt eq 68 andseq TMP2, TMP2, PATTERN 69 andseq TMP3, TMP3, PATTERN 70 .endm 71 72 /* int ff_startcode_find_candidate_armv6(const uint8_t *buf, int size) */ 73 function ff_startcode_find_candidate_armv6, export=1 74 push {v1-v6,lr} 75 mov PTR, BUF 76 @ Ensure there are at least (PRELOAD_DISTANCE+2) complete cachelines to go 77 @ before using code that does preloads 78 cmp SIZE, #(PRELOAD_DISTANCE+3)*32 - 1 79 blo 60f 80 81 @ Get to word-alignment, 1 byte at a time 82 tst PTR, #3 83 beq 2f 84 1: ldrb DAT0, [PTR], #1 85 sub SIZE, SIZE, #1 86 teq DAT0, #0 87 beq 90f 88 tst PTR, #3 89 bne 1b 90 2: @ Get to 4-word alignment, 1 word at a time 91 ldr PATTERN, =0x80008000 92 setend be 93 tst PTR, #12 94 beq 4f 95 3: innerloop4 96 bne 91f 97 tst PTR, #12 98 bne 3b 99 4: @ Get to cacheline (8-word) alignment 100 tst PTR, #16 101 beq 5f 102 innerloop16 16 103 bne 93f 104 5: @ Check complete cachelines, with preloading 105 @ We need to stop when there are still (PRELOAD_DISTANCE+1) 106 @ complete cachelines to go 107 sub SIZE, SIZE, #(PRELOAD_DISTANCE+2)*32 108 6: innerloop16 , do_preload 109 bne 93f 110 innerloop16 32 111 bne 93f 112 bcs 6b 113 @ Preload trailing part-cacheline, if any 114 tst SIZE, #31 115 beq 7f 116 pld [PTR, #(PRELOAD_DISTANCE+1)*32] 117 @ Check remaining data without doing any more preloads. First 118 @ do in chunks of 4 words: 119 7: adds SIZE, SIZE, #(PRELOAD_DISTANCE+2)*32 - 16 120 bmi 9f 121 8: innerloop16 16 122 bne 93f 123 bcs 8b 124 @ Then in words: 125 9: adds SIZE, SIZE, #16 - 4 126 bmi 11f 127 10: innerloop4 128 bne 91f 129 bcs 10b 130 11: setend le 131 @ Check second byte of final halfword 132 ldrb DAT0, [PTR, #-1] 133 teq DAT0, #0 134 beq 90f 135 @ Check any remaining bytes 136 tst SIZE, #3 137 beq 13f 138 12: ldrb DAT0, [PTR], #1 139 sub SIZE, SIZE, #1 140 teq DAT0, #0 141 beq 90f 142 tst SIZE, #3 143 bne 12b 144 @ No candidate found 145 13: sub RESULT, PTR, BUF 146 b 99f 147 148 60: @ Small buffer - simply check by looping over bytes 149 subs SIZE, SIZE, #1 150 bcc 99f 151 61: ldrb DAT0, [PTR], #1 152 subs SIZE, SIZE, #1 153 teq DAT0, #0 154 beq 90f 155 bcs 61b 156 @ No candidate found 157 sub RESULT, PTR, BUF 158 b 99f 159 160 90: @ Found a candidate at the preceding byte 161 sub RESULT, PTR, BUF 162 sub RESULT, RESULT, #1 163 b 99f 164 165 91: @ Found a candidate somewhere in the preceding 4 bytes 166 sub RESULT, PTR, BUF 167 sub RESULT, RESULT, #4 168 sub TMP0, DAT0, #0x20000 169 bics TMP0, TMP0, DAT0 170 itt pl 171 ldrbpl DAT0, [PTR, #-3] 172 addpl RESULT, RESULT, #2 173 bpl 92f 174 teq RESULT, #0 175 beq 98f @ don't look back a byte if found at first byte in buffer 176 ldrb DAT0, [PTR, #-5] 177 92: teq DAT0, #0 178 it eq 179 subeq RESULT, RESULT, #1 180 b 98f 181 182 93: @ Found a candidate somewhere in the preceding 16 bytes 183 sub RESULT, PTR, BUF 184 sub RESULT, RESULT, #16 185 teq TMP0, #0 186 beq 95f @ not in first 4 bytes 187 sub TMP0, DAT0, #0x20000 188 bics TMP0, TMP0, DAT0 189 itt pl 190 ldrbpl DAT0, [PTR, #-15] 191 addpl RESULT, RESULT, #2 192 bpl 94f 193 teq RESULT, #0 194 beq 98f @ don't look back a byte if found at first byte in buffer 195 ldrb DAT0, [PTR, #-17] 196 94: teq DAT0, #0 197 it eq 198 subeq RESULT, RESULT, #1 199 b 98f 200 95: add RESULT, RESULT, #4 201 teq TMP1, #0 202 beq 96f @ not in next 4 bytes 203 sub TMP1, DAT1, #0x20000 204 bics TMP1, TMP1, DAT1 205 itee mi 206 ldrbmi DAT0, [PTR, #-13] 207 ldrbpl DAT0, [PTR, #-11] 208 addpl RESULT, RESULT, #2 209 teq DAT0, #0 210 it eq 211 subeq RESULT, RESULT, #1 212 b 98f 213 96: add RESULT, RESULT, #4 214 teq TMP2, #0 215 beq 97f @ not in next 4 bytes 216 sub TMP2, DAT2, #0x20000 217 bics TMP2, TMP2, DAT2 218 itee mi 219 ldrbmi DAT0, [PTR, #-9] 220 ldrbpl DAT0, [PTR, #-7] 221 addpl RESULT, RESULT, #2 222 teq DAT0, #0 223 it eq 224 subeq RESULT, RESULT, #1 225 b 98f 226 97: add RESULT, RESULT, #4 227 sub TMP3, DAT3, #0x20000 228 bics TMP3, TMP3, DAT3 229 itee mi 230 ldrbmi DAT0, [PTR, #-5] 231 ldrbpl DAT0, [PTR, #-3] 232 addpl RESULT, RESULT, #2 233 teq DAT0, #0 234 it eq 235 subeq RESULT, RESULT, #1 236 @ drop through to 98f 237 98: setend le 238 99: pop {v1-v6,pc} 239 endfunc 240 241 .unreq RESULT 242 .unreq BUF 243 .unreq SIZE 244 .unreq PATTERN 245 .unreq PTR 246 .unreq DAT0 247 .unreq DAT1 248 .unreq DAT2 249 .unreq DAT3 250 .unreq TMP0 251 .unreq TMP1 252 .unreq TMP2 253 .unreq TMP3