1/* 2 * Copyright (C) 2002 Frederic 'dilb' Boulay 3 * 4 * Author: Frederic Boulay <dilb@handhelds.org> 5 * 6 * The function defined in this file is derived from the simple_idct function 7 * from the libavcodec library part of the FFmpeg project. 8 * 9 * This file is part of FFmpeg. 10 * 11 * FFmpeg is free software; you can redistribute it and/or 12 * modify it under the terms of the GNU Lesser General Public 13 * License as published by the Free Software Foundation; either 14 * version 2.1 of the License, or (at your option) any later version. 15 * 16 * FFmpeg 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 GNU 19 * Lesser General Public License for more details. 20 * 21 * You should have received a copy of the GNU Lesser General Public 22 * License along with FFmpeg; if not, write to the Free Software 23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 24 */ 25 26#include "libavutil/arm/asm.S" 27 28/* useful constants for the algorithm */ 29#define W1 22725 30#define W2 21407 31#define W3 19266 32#define W4 16383 33#define W5 12873 34#define W6 8867 35#define W7 4520 36#define MASK_MSHW 0xFFFF0000 37 38#define ROW_SHIFT 11 39#define ROW_SHIFT2MSHW (16-11) 40#define COL_SHIFT 20 41#define ROW_SHIFTED_1 1024 /* 1<< (ROW_SHIFT-1) */ 42#define COL_SHIFTED_1 524288 /* 1<< (COL_SHIFT-1) */ 43 44 45function ff_simple_idct_arm, export=1 46 @@ void simple_idct_arm(int16_t *block) 47 @@ save stack for reg needed (take all of them), 48 @@ R0-R3 are scratch regs, so no need to save them, but R0 contains the pointer to block 49 @@ so it must not be overwritten, if it is not saved!! 50 @@ R12 is another scratch register, so it should not be saved too 51 @@ save all registers 52 stmfd sp!, {r4-r11, r14} @ R14 is also called LR 53 @@ at this point, R0=block, other registers are free. 54 add r14, r0, #112 @ R14=&block[8*7], better start from the last row, and decrease the value until row=0, i.e. R12=block. 55 @@ add 2 temporary variables in the stack: R0 and R14 56 sub sp, sp, #8 @ allow 2 local variables 57 str r0, [sp, #0] @ save block in sp[0] 58 @@ stack status 59 @@ sp+4 free 60 @@ sp+0 R0 (block) 61 62 63 @@ at this point, R0=block, R14=&block[56], R12=__const_ptr_, R1-R11 free 64 65 66__row_loop: 67 @@ read the row and check if it is null, almost null, or not, according to strongarm specs, it is not necessary to optimize ldr accesses (i.e. split 32bits in 2 16bits words), at least it gives more usable registers :) 68 ldr r1, [r14, #0] @ R1=(int32)(R12)[0]=ROWr32[0] (relative row cast to a 32b pointer) 69 ldr r2, [r14, #4] @ R2=(int32)(R12)[1]=ROWr32[1] 70 ldr r3, [r14, #8] @ R3=ROWr32[2] 71 ldr r4, [r14, #12] @ R4=ROWr32[3] 72 @@ check if the words are null, if all of them are null, then proceed with next row (branch __end_row_loop), 73 @@ if ROWr16[0] is the only one not null, then proceed with this special case (branch __almost_empty_row) 74 @@ else follow the complete algorithm. 75 @@ at this point, R0=block, R14=&block[n], R12=__const_ptr_, R1=ROWr32[0], R2=ROWr32[1], 76 @@ R3=ROWr32[2], R4=ROWr32[3], R5-R11 free 77 orr r5, r4, r3 @ R5=R4 | R3 78 orr r5, r5, r2 @ R5=R4 | R3 | R2 79 orrs r6, r5, r1 @ Test R5 | R1 (the aim is to check if everything is null) 80 beq __end_row_loop 81 mov r7, r1, asr #16 @ R7=R1>>16=ROWr16[1] (evaluate it now, as it could be useful later) 82 ldrsh r6, [r14, #0] @ R6=ROWr16[0] 83 orrs r5, r5, r7 @ R5=R4 | R3 | R2 | R7 84 beq __almost_empty_row 85 86@@ __b_evaluation: 87 @@ at this point, R0=block (temp), R1(free), R2=ROWr32[1], R3=ROWr32[2], R4=ROWr32[3], 88 @@ R5=(temp), R6=ROWr16[0], R7=ROWr16[1], R8-R11 free, 89 @@ R12=__const_ptr_, R14=&block[n] 90 @@ to save some registers/calls, proceed with b0-b3 first, followed by a0-a3 91 92 @@ MUL16(b0, W1, row[1]); 93 @@ MUL16(b1, W3, row[1]); 94 @@ MUL16(b2, W5, row[1]); 95 @@ MUL16(b3, W7, row[1]); 96 @@ MAC16(b0, W3, row[3]); 97 @@ MAC16(b1, -W7, row[3]); 98 @@ MAC16(b2, -W1, row[3]); 99 @@ MAC16(b3, -W5, row[3]); 100 ldr r8, =W1 @ R8=W1 101 mov r2, r2, asr #16 @ R2=ROWr16[3] 102 mul r0, r8, r7 @ R0=W1*ROWr16[1]=b0 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle) 103 ldr r9, =W3 @ R9=W3 104 ldr r10, =W5 @ R10=W5 105 mul r1, r9, r7 @ R1=W3*ROWr16[1]=b1 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle) 106 ldr r11, =W7 @ R11=W7 107 mul r5, r10, r7 @ R5=W5*ROWr16[1]=b2 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle) 108 mul r7, r11, r7 @ R7=W7*ROWr16[1]=b3 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle) 109 teq r2, #0 @ if null avoid muls 110 itttt ne 111 mlane r0, r9, r2, r0 @ R0+=W3*ROWr16[3]=b0 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle) 112 rsbne r2, r2, #0 @ R2=-ROWr16[3] 113 mlane r1, r11, r2, r1 @ R1-=W7*ROWr16[3]=b1 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle) 114 mlane r5, r8, r2, r5 @ R5-=W1*ROWr16[3]=b2 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle) 115 it ne 116 mlane r7, r10, r2, r7 @ R7-=W5*ROWr16[3]=b3 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle) 117 118 @@ at this point, R0=b0, R1=b1, R2 (free), R3=ROWr32[2], R4=ROWr32[3], 119 @@ R5=b2, R6=ROWr16[0], R7=b3, R8=W1, R9=W3, R10=W5, R11=W7, 120 @@ R12=__const_ptr_, R14=&block[n] 121 @@ temp = ((uint32_t*)row)[2] | ((uint32_t*)row)[3]; 122 @@ if (temp != 0) {} 123 orrs r2, r3, r4 @ R2=ROWr32[2] | ROWr32[3] 124 beq __end_b_evaluation 125 126 @@ at this point, R0=b0, R1=b1, R2 (free), R3=ROWr32[2], R4=ROWr32[3], 127 @@ R5=b2, R6=ROWr16[0], R7=b3, R8=W1, R9=W3, R10=W5, R11=W7, 128 @@ R12=__const_ptr_, R14=&block[n] 129 @@ MAC16(b0, W5, row[5]); 130 @@ MAC16(b2, W7, row[5]); 131 @@ MAC16(b3, W3, row[5]); 132 @@ MAC16(b1, -W1, row[5]); 133 @@ MAC16(b0, W7, row[7]); 134 @@ MAC16(b2, W3, row[7]); 135 @@ MAC16(b3, -W1, row[7]); 136 @@ MAC16(b1, -W5, row[7]); 137 mov r3, r3, asr #16 @ R3=ROWr16[5] 138 teq r3, #0 @ if null avoid muls 139 it ne 140 mlane r0, r10, r3, r0 @ R0+=W5*ROWr16[5]=b0 141 mov r4, r4, asr #16 @ R4=ROWr16[7] 142 itttt ne 143 mlane r5, r11, r3, r5 @ R5+=W7*ROWr16[5]=b2 144 mlane r7, r9, r3, r7 @ R7+=W3*ROWr16[5]=b3 145 rsbne r3, r3, #0 @ R3=-ROWr16[5] 146 mlane r1, r8, r3, r1 @ R7-=W1*ROWr16[5]=b1 147 @@ R3 is free now 148 teq r4, #0 @ if null avoid muls 149 itttt ne 150 mlane r0, r11, r4, r0 @ R0+=W7*ROWr16[7]=b0 151 mlane r5, r9, r4, r5 @ R5+=W3*ROWr16[7]=b2 152 rsbne r4, r4, #0 @ R4=-ROWr16[7] 153 mlane r7, r8, r4, r7 @ R7-=W1*ROWr16[7]=b3 154 it ne 155 mlane r1, r10, r4, r1 @ R1-=W5*ROWr16[7]=b1 156 @@ R4 is free now 157__end_b_evaluation: 158 @@ at this point, R0=b0, R1=b1, R2=ROWr32[2] | ROWr32[3] (tmp), R3 (free), R4 (free), 159 @@ R5=b2, R6=ROWr16[0], R7=b3, R8 (free), R9 (free), R10 (free), R11 (free), 160 @@ R12=__const_ptr_, R14=&block[n] 161 162@@ __a_evaluation: 163 @@ a0 = (W4 * row[0]) + (1 << (ROW_SHIFT - 1)); 164 @@ a1 = a0 + W6 * row[2]; 165 @@ a2 = a0 - W6 * row[2]; 166 @@ a3 = a0 - W2 * row[2]; 167 @@ a0 = a0 + W2 * row[2]; 168 ldr r9, =W4 @ R9=W4 169 mul r6, r9, r6 @ R6=W4*ROWr16[0] 170 ldr r10, =W6 @ R10=W6 171 ldrsh r4, [r14, #4] @ R4=ROWr16[2] (a3 not defined yet) 172 add r6, r6, #ROW_SHIFTED_1 @ R6=W4*ROWr16[0] + 1<<(ROW_SHIFT-1) (a0) 173 174 mul r11, r10, r4 @ R11=W6*ROWr16[2] 175 ldr r8, =W2 @ R8=W2 176 sub r3, r6, r11 @ R3=a0-W6*ROWr16[2] (a2) 177 @@ temp = ((uint32_t*)row)[2] | ((uint32_t*)row)[3]; 178 @@ if (temp != 0) {} 179 teq r2, #0 180 beq __end_bef_a_evaluation 181 182 add r2, r6, r11 @ R2=a0+W6*ROWr16[2] (a1) 183 mul r11, r8, r4 @ R11=W2*ROWr16[2] 184 sub r4, r6, r11 @ R4=a0-W2*ROWr16[2] (a3) 185 add r6, r6, r11 @ R6=a0+W2*ROWr16[2] (a0) 186 187 188 @@ at this point, R0=b0, R1=b1, R2=a1, R3=a2, R4=a3, 189 @@ R5=b2, R6=a0, R7=b3, R8=W2, R9=W4, R10=W6, R11 (free), 190 @@ R12=__const_ptr_, R14=&block[n] 191 192 193 @@ a0 += W4*row[4] 194 @@ a1 -= W4*row[4] 195 @@ a2 -= W4*row[4] 196 @@ a3 += W4*row[4] 197 ldrsh r11, [r14, #8] @ R11=ROWr16[4] 198 teq r11, #0 @ if null avoid muls 199 it ne 200 mulne r11, r9, r11 @ R11=W4*ROWr16[4] 201 @@ R9 is free now 202 ldrsh r9, [r14, #12] @ R9=ROWr16[6] 203 itttt ne 204 addne r6, r6, r11 @ R6+=W4*ROWr16[4] (a0) 205 subne r2, r2, r11 @ R2-=W4*ROWr16[4] (a1) 206 subne r3, r3, r11 @ R3-=W4*ROWr16[4] (a2) 207 addne r4, r4, r11 @ R4+=W4*ROWr16[4] (a3) 208 @@ W6 alone is no more useful, save W2*ROWr16[6] in it instead 209 teq r9, #0 @ if null avoid muls 210 itttt ne 211 mulne r11, r10, r9 @ R11=W6*ROWr16[6] 212 addne r6, r6, r11 @ R6+=W6*ROWr16[6] (a0) 213 mulne r10, r8, r9 @ R10=W2*ROWr16[6] 214 @@ a0 += W6*row[6]; 215 @@ a3 -= W6*row[6]; 216 @@ a1 -= W2*row[6]; 217 @@ a2 += W2*row[6]; 218 subne r4, r4, r11 @ R4-=W6*ROWr16[6] (a3) 219 itt ne 220 subne r2, r2, r10 @ R2-=W2*ROWr16[6] (a1) 221 addne r3, r3, r10 @ R3+=W2*ROWr16[6] (a2) 222 223__end_a_evaluation: 224 @@ at this point, R0=b0, R1=b1, R2=a1, R3=a2, R4=a3, 225 @@ R5=b2, R6=a0, R7=b3, R8 (free), R9 (free), R10 (free), R11 (free), 226 @@ R12=__const_ptr_, R14=&block[n] 227 @@ row[0] = (a0 + b0) >> ROW_SHIFT; 228 @@ row[1] = (a1 + b1) >> ROW_SHIFT; 229 @@ row[2] = (a2 + b2) >> ROW_SHIFT; 230 @@ row[3] = (a3 + b3) >> ROW_SHIFT; 231 @@ row[4] = (a3 - b3) >> ROW_SHIFT; 232 @@ row[5] = (a2 - b2) >> ROW_SHIFT; 233 @@ row[6] = (a1 - b1) >> ROW_SHIFT; 234 @@ row[7] = (a0 - b0) >> ROW_SHIFT; 235 add r8, r6, r0 @ R8=a0+b0 236 add r9, r2, r1 @ R9=a1+b1 237 @@ put 2 16 bits half-words in a 32bits word 238 @@ ROWr32[0]=ROWr16[0] | (ROWr16[1]<<16) (only Little Endian compliant then!!!) 239 ldr r10, =MASK_MSHW @ R10=0xFFFF0000 240 and r9, r10, r9, lsl #ROW_SHIFT2MSHW @ R9=0xFFFF0000 & ((a1+b1)<<5) 241 mvn r11, r10 @ R11= NOT R10= 0x0000FFFF 242 and r8, r11, r8, asr #ROW_SHIFT @ R8=0x0000FFFF & ((a0+b0)>>11) 243 orr r8, r8, r9 244 str r8, [r14, #0] 245 246 add r8, r3, r5 @ R8=a2+b2 247 add r9, r4, r7 @ R9=a3+b3 248 and r9, r10, r9, lsl #ROW_SHIFT2MSHW @ R9=0xFFFF0000 & ((a3+b3)<<5) 249 and r8, r11, r8, asr #ROW_SHIFT @ R8=0x0000FFFF & ((a2+b2)>>11) 250 orr r8, r8, r9 251 str r8, [r14, #4] 252 253 sub r8, r4, r7 @ R8=a3-b3 254 sub r9, r3, r5 @ R9=a2-b2 255 and r9, r10, r9, lsl #ROW_SHIFT2MSHW @ R9=0xFFFF0000 & ((a2-b2)<<5) 256 and r8, r11, r8, asr #ROW_SHIFT @ R8=0x0000FFFF & ((a3-b3)>>11) 257 orr r8, r8, r9 258 str r8, [r14, #8] 259 260 sub r8, r2, r1 @ R8=a1-b1 261 sub r9, r6, r0 @ R9=a0-b0 262 and r9, r10, r9, lsl #ROW_SHIFT2MSHW @ R9=0xFFFF0000 & ((a0-b0)<<5) 263 and r8, r11, r8, asr #ROW_SHIFT @ R8=0x0000FFFF & ((a1-b1)>>11) 264 orr r8, r8, r9 265 str r8, [r14, #12] 266 267 bal __end_row_loop 268 269__almost_empty_row: 270 @@ the row was empty, except ROWr16[0], now, management of this special case 271 @@ at this point, R0=block, R14=&block[n], R12=__const_ptr_, R1=ROWr32[0], R2=ROWr32[1], 272 @@ R3=ROWr32[2], R4=ROWr32[3], R5=(temp), R6=ROWr16[0], R7=ROWr16[1], 273 @@ R8=0xFFFF (temp), R9-R11 free 274 mov r8, #0x10000 @ R8=0xFFFF (2 steps needed!) it saves a ldr call (because of delay run). 275 sub r8, r8, #1 @ R8 is now ready. 276 and r5, r8, r6, lsl #3 @ R5=R8 & (R6<<3)= (ROWr16[0]<<3) & 0xFFFF 277 orr r5, r5, r5, lsl #16 @ R5=R5 | (R5<<16) 278 str r5, [r14, #0] @ R14[0]=ROWr32[0]=R5 279 str r5, [r14, #4] @ R14[4]=ROWr32[1]=R5 280 str r5, [r14, #8] @ R14[8]=ROWr32[2]=R5 281 str r5, [r14, #12] @ R14[12]=ROWr32[3]=R5 282 283__end_row_loop: 284 @@ at this point, R0-R11 (free) 285 @@ R12=__const_ptr_, R14=&block[n] 286 ldr r0, [sp, #0] @ R0=block 287 teq r0, r14 @ compare current &block[8*n] to block, when block is reached, the loop is finished. 288 sub r14, r14, #16 289 bne __row_loop 290 291 292 293 @@ at this point, R0=block, R1-R11 (free) 294 @@ R12=__const_ptr_, R14=&block[n] 295 add r14, r0, #14 @ R14=&block[7], better start from the last col, and decrease the value until col=0, i.e. R14=block. 296__col_loop: 297 298@@ __b_evaluation2: 299 @@ at this point, R0=block (temp), R1-R11 (free) 300 @@ R12=__const_ptr_, R14=&block[n] 301 @@ proceed with b0-b3 first, followed by a0-a3 302 @@ MUL16(b0, W1, col[8x1]); 303 @@ MUL16(b1, W3, col[8x1]); 304 @@ MUL16(b2, W5, col[8x1]); 305 @@ MUL16(b3, W7, col[8x1]); 306 @@ MAC16(b0, W3, col[8x3]); 307 @@ MAC16(b1, -W7, col[8x3]); 308 @@ MAC16(b2, -W1, col[8x3]); 309 @@ MAC16(b3, -W5, col[8x3]); 310 ldr r8, =W1 @ R8=W1 311 ldrsh r7, [r14, #16] 312 mul r0, r8, r7 @ R0=W1*ROWr16[1]=b0 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle) 313 ldr r9, =W3 @ R9=W3 314 ldr r10, =W5 @ R10=W5 315 mul r1, r9, r7 @ R1=W3*ROWr16[1]=b1 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle) 316 ldr r11, =W7 @ R11=W7 317 mul r5, r10, r7 @ R5=W5*ROWr16[1]=b2 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle) 318 ldrsh r2, [r14, #48] 319 mul r7, r11, r7 @ R7=W7*ROWr16[1]=b3 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle) 320 teq r2, #0 @ if 0, then avoid muls 321 itttt ne 322 mlane r0, r9, r2, r0 @ R0+=W3*ROWr16[3]=b0 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle) 323 rsbne r2, r2, #0 @ R2=-ROWr16[3] 324 mlane r1, r11, r2, r1 @ R1-=W7*ROWr16[3]=b1 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle) 325 mlane r5, r8, r2, r5 @ R5-=W1*ROWr16[3]=b2 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle) 326 it ne 327 mlane r7, r10, r2, r7 @ R7-=W5*ROWr16[3]=b3 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle) 328 329 @@ at this point, R0=b0, R1=b1, R2 (free), R3 (free), R4 (free), 330 @@ R5=b2, R6 (free), R7=b3, R8=W1, R9=W3, R10=W5, R11=W7, 331 @@ R12=__const_ptr_, R14=&block[n] 332 @@ MAC16(b0, W5, col[5x8]); 333 @@ MAC16(b2, W7, col[5x8]); 334 @@ MAC16(b3, W3, col[5x8]); 335 @@ MAC16(b1, -W1, col[5x8]); 336 @@ MAC16(b0, W7, col[7x8]); 337 @@ MAC16(b2, W3, col[7x8]); 338 @@ MAC16(b3, -W1, col[7x8]); 339 @@ MAC16(b1, -W5, col[7x8]); 340 ldrsh r3, [r14, #80] @ R3=COLr16[5x8] 341 teq r3, #0 @ if 0 then avoid muls 342 itttt ne 343 mlane r0, r10, r3, r0 @ R0+=W5*ROWr16[5x8]=b0 344 mlane r5, r11, r3, r5 @ R5+=W7*ROWr16[5x8]=b2 345 mlane r7, r9, r3, r7 @ R7+=W3*ROWr16[5x8]=b3 346 rsbne r3, r3, #0 @ R3=-ROWr16[5x8] 347 ldrsh r4, [r14, #112] @ R4=COLr16[7x8] 348 it ne 349 mlane r1, r8, r3, r1 @ R7-=W1*ROWr16[5x8]=b1 350 @@ R3 is free now 351 teq r4, #0 @ if 0 then avoid muls 352 itttt ne 353 mlane r0, r11, r4, r0 @ R0+=W7*ROWr16[7x8]=b0 354 mlane r5, r9, r4, r5 @ R5+=W3*ROWr16[7x8]=b2 355 rsbne r4, r4, #0 @ R4=-ROWr16[7x8] 356 mlane r7, r8, r4, r7 @ R7-=W1*ROWr16[7x8]=b3 357 it ne 358 mlane r1, r10, r4, r1 @ R1-=W5*ROWr16[7x8]=b1 359 @@ R4 is free now 360@@ __end_b_evaluation2: 361 @@ at this point, R0=b0, R1=b1, R2 (free), R3 (free), R4 (free), 362 @@ R5=b2, R6 (free), R7=b3, R8 (free), R9 (free), R10 (free), R11 (free), 363 @@ R12=__const_ptr_, R14=&block[n] 364 365@@ __a_evaluation2: 366 @@ a0 = (W4 * col[8x0]) + (1 << (COL_SHIFT - 1)); 367 @@ a1 = a0 + W6 * row[2]; 368 @@ a2 = a0 - W6 * row[2]; 369 @@ a3 = a0 - W2 * row[2]; 370 @@ a0 = a0 + W2 * row[2]; 371 ldrsh r6, [r14, #0] 372 ldr r9, =W4 @ R9=W4 373 mul r6, r9, r6 @ R6=W4*ROWr16[0] 374 ldr r10, =W6 @ R10=W6 375 ldrsh r4, [r14, #32] @ R4=ROWr16[2] (a3 not defined yet) 376 add r6, r6, #COL_SHIFTED_1 @ R6=W4*ROWr16[0] + 1<<(COL_SHIFT-1) (a0) 377 mul r11, r10, r4 @ R11=W6*ROWr16[2] 378 ldr r8, =W2 @ R8=W2 379 add r2, r6, r11 @ R2=a0+W6*ROWr16[2] (a1) 380 sub r3, r6, r11 @ R3=a0-W6*ROWr16[2] (a2) 381 mul r11, r8, r4 @ R11=W2*ROWr16[2] 382 sub r4, r6, r11 @ R4=a0-W2*ROWr16[2] (a3) 383 add r6, r6, r11 @ R6=a0+W2*ROWr16[2] (a0) 384 385 @@ at this point, R0=b0, R1=b1, R2=a1, R3=a2, R4=a3, 386 @@ R5=b2, R6=a0, R7=b3, R8=W2, R9=W4, R10=W6, R11 (free), 387 @@ R12=__const_ptr_, R14=&block[n] 388 @@ a0 += W4*row[4] 389 @@ a1 -= W4*row[4] 390 @@ a2 -= W4*row[4] 391 @@ a3 += W4*row[4] 392 ldrsh r11, [r14, #64] @ R11=ROWr16[4] 393 teq r11, #0 @ if null avoid muls 394 itttt ne 395 mulne r11, r9, r11 @ R11=W4*ROWr16[4] 396 @@ R9 is free now 397 addne r6, r6, r11 @ R6+=W4*ROWr16[4] (a0) 398 subne r2, r2, r11 @ R2-=W4*ROWr16[4] (a1) 399 subne r3, r3, r11 @ R3-=W4*ROWr16[4] (a2) 400 ldrsh r9, [r14, #96] @ R9=ROWr16[6] 401 it ne 402 addne r4, r4, r11 @ R4+=W4*ROWr16[4] (a3) 403 @@ W6 alone is no more useful, save W2*ROWr16[6] in it instead 404 teq r9, #0 @ if null avoid muls 405 itttt ne 406 mulne r11, r10, r9 @ R11=W6*ROWr16[6] 407 addne r6, r6, r11 @ R6+=W6*ROWr16[6] (a0) 408 mulne r10, r8, r9 @ R10=W2*ROWr16[6] 409 @@ a0 += W6*row[6]; 410 @@ a3 -= W6*row[6]; 411 @@ a1 -= W2*row[6]; 412 @@ a2 += W2*row[6]; 413 subne r4, r4, r11 @ R4-=W6*ROWr16[6] (a3) 414 itt ne 415 subne r2, r2, r10 @ R2-=W2*ROWr16[6] (a1) 416 addne r3, r3, r10 @ R3+=W2*ROWr16[6] (a2) 417@@ __end_a_evaluation2: 418 @@ at this point, R0=b0, R1=b1, R2=a1, R3=a2, R4=a3, 419 @@ R5=b2, R6=a0, R7=b3, R8 (free), R9 (free), R10 (free), R11 (free), 420 @@ R12=__const_ptr_, R14=&block[n] 421 @@ col[0 ] = ((a0 + b0) >> COL_SHIFT); 422 @@ col[8 ] = ((a1 + b1) >> COL_SHIFT); 423 @@ col[16] = ((a2 + b2) >> COL_SHIFT); 424 @@ col[24] = ((a3 + b3) >> COL_SHIFT); 425 @@ col[32] = ((a3 - b3) >> COL_SHIFT); 426 @@ col[40] = ((a2 - b2) >> COL_SHIFT); 427 @@ col[48] = ((a1 - b1) >> COL_SHIFT); 428 @@ col[56] = ((a0 - b0) >> COL_SHIFT); 429 @@@@@ no optimization here @@@@@ 430 add r8, r6, r0 @ R8=a0+b0 431 add r9, r2, r1 @ R9=a1+b1 432 mov r8, r8, asr #COL_SHIFT 433 mov r9, r9, asr #COL_SHIFT 434 strh r8, [r14, #0] 435 strh r9, [r14, #16] 436 add r8, r3, r5 @ R8=a2+b2 437 add r9, r4, r7 @ R9=a3+b3 438 mov r8, r8, asr #COL_SHIFT 439 mov r9, r9, asr #COL_SHIFT 440 strh r8, [r14, #32] 441 strh r9, [r14, #48] 442 sub r8, r4, r7 @ R8=a3-b3 443 sub r9, r3, r5 @ R9=a2-b2 444 mov r8, r8, asr #COL_SHIFT 445 mov r9, r9, asr #COL_SHIFT 446 strh r8, [r14, #64] 447 strh r9, [r14, #80] 448 sub r8, r2, r1 @ R8=a1-b1 449 sub r9, r6, r0 @ R9=a0-b0 450 mov r8, r8, asr #COL_SHIFT 451 mov r9, r9, asr #COL_SHIFT 452 strh r8, [r14, #96] 453 strh r9, [r14, #112] 454 455@@ __end_col_loop: 456 @@ at this point, R0-R11 (free) 457 @@ R12=__const_ptr_, R14=&block[n] 458 ldr r0, [sp, #0] @ R0=block 459 teq r0, r14 @ compare current &block[n] to block, when block is reached, the loop is finished. 460 sub r14, r14, #2 461 bne __col_loop 462 463 464 465 466@@ __end_simple_idct_arm: 467 @@ restore registers to previous status! 468 add sp, sp, #8 @@ the local variables! 469 ldmfd sp!, {r4-r11, r15} @@ update PC with LR content. 470 471 472 473@@ kind of sub-function, here not to overload the common case. 474__end_bef_a_evaluation: 475 add r2, r6, r11 @ R2=a0+W6*ROWr16[2] (a1) 476 mul r11, r8, r4 @ R11=W2*ROWr16[2] 477 sub r4, r6, r11 @ R4=a0-W2*ROWr16[2] (a3) 478 add r6, r6, r11 @ R6=a0+W2*ROWr16[2] (a0) 479 bal __end_a_evaluation 480endfunc 481