1 /* 2 * match.S -- optimized version of longest_match() 3 * based on the similar work by Gilles Vollant, and Brian Raiter, written 1998 4 * 5 * This is free software; you can redistribute it and/or modify it 6 * under the terms of the BSD License. Use by owners of Che Guevarra 7 * parafernalia is prohibited, where possible, and highly discouraged 8 * elsewhere. 9 */ 10 11 #ifndef NO_UNDERLINE 12 # define match_init _match_init 13 # define longest_match _longest_match 14 #endif 15 16 #define scanend ebx 17 #define scanendw bx 18 #define chainlenwmask edx /* high word: current chain len low word: s->wmask */ 19 #define curmatch rsi 20 #define curmatchd esi 21 #define windowbestlen r8 22 #define scanalign r9 23 #define scanalignd r9d 24 #define window r10 25 #define bestlen r11 26 #define bestlend r11d 27 #define scanstart r12d 28 #define scanstartw r12w 29 #define scan r13 30 #define nicematch r14d 31 #define limit r15 32 #define limitd r15d 33 #define prev rcx 34 35 /* 36 * The 258 is a "magic number, not a parameter -- changing it 37 * breaks the hell loose 38 */ 39 #define MAX_MATCH (258) 40 #define MIN_MATCH (3) 41 #define MIN_LOOKAHEAD (MAX_MATCH + MIN_MATCH + 1) 42 #define MAX_MATCH_8 ((MAX_MATCH + 7) & ~7) 43 44 /* stack frame offsets */ 45 #define LocalVarsSize (112) 46 #define _chainlenwmask ( 8-LocalVarsSize)(%rsp) 47 #define _windowbestlen (16-LocalVarsSize)(%rsp) 48 #define save_r14 (24-LocalVarsSize)(%rsp) 49 #define save_rsi (32-LocalVarsSize)(%rsp) 50 #define save_rbx (40-LocalVarsSize)(%rsp) 51 #define save_r12 (56-LocalVarsSize)(%rsp) 52 #define save_r13 (64-LocalVarsSize)(%rsp) 53 #define save_r15 (80-LocalVarsSize)(%rsp) 54 55 56 .globl match_init, longest_match 57 58 /* 59 * On AMD64 the first argument of a function (in our case -- the pointer to 60 * deflate_state structure) is passed in %rdi, hence our offsets below are 61 * all off of that. 62 */ 63 64 /* you can check the structure offset by running 65 66 #include <stdlib.h> 67 #include <stdio.h> 68 #include "deflate.h" 69 70 void print_depl() 71 { 72 deflate_state ds; 73 deflate_state *s=&ds; 74 printf("size pointer=%u\n",(int)sizeof(void*)); 75 76 printf("#define dsWSize (%3u)(%%rdi)\n",(int)(((char*)&(s->w_size))-((char*)s))); 77 printf("#define dsWMask (%3u)(%%rdi)\n",(int)(((char*)&(s->w_mask))-((char*)s))); 78 printf("#define dsWindow (%3u)(%%rdi)\n",(int)(((char*)&(s->window))-((char*)s))); 79 printf("#define dsPrev (%3u)(%%rdi)\n",(int)(((char*)&(s->prev))-((char*)s))); 80 printf("#define dsMatchLen (%3u)(%%rdi)\n",(int)(((char*)&(s->match_length))-((char*)s))); 81 printf("#define dsPrevMatch (%3u)(%%rdi)\n",(int)(((char*)&(s->prev_match))-((char*)s))); 82 printf("#define dsStrStart (%3u)(%%rdi)\n",(int)(((char*)&(s->strstart))-((char*)s))); 83 printf("#define dsMatchStart (%3u)(%%rdi)\n",(int)(((char*)&(s->match_start))-((char*)s))); 84 printf("#define dsLookahead (%3u)(%%rdi)\n",(int)(((char*)&(s->lookahead))-((char*)s))); 85 printf("#define dsPrevLen (%3u)(%%rdi)\n",(int)(((char*)&(s->prev_length))-((char*)s))); 86 printf("#define dsMaxChainLen (%3u)(%%rdi)\n",(int)(((char*)&(s->max_chain_length))-((char*)s))); 87 printf("#define dsGoodMatch (%3u)(%%rdi)\n",(int)(((char*)&(s->good_match))-((char*)s))); 88 printf("#define dsNiceMatch (%3u)(%%rdi)\n",(int)(((char*)&(s->nice_match))-((char*)s))); 89 } 90 91 */ 92 93 94 /* 95 to compile for XCode 3.2 on MacOSX x86_64 96 - run "gcc -g -c -DXCODE_MAC_X64_STRUCTURE amd64-match.S" 97 */ 98 99 100 #ifndef CURRENT_LINX_XCODE_MAC_X64_STRUCTURE 101 #define dsWSize ( 68)(%rdi) 102 #define dsWMask ( 76)(%rdi) 103 #define dsWindow ( 80)(%rdi) 104 #define dsPrev ( 96)(%rdi) 105 #define dsMatchLen (144)(%rdi) 106 #define dsPrevMatch (148)(%rdi) 107 #define dsStrStart (156)(%rdi) 108 #define dsMatchStart (160)(%rdi) 109 #define dsLookahead (164)(%rdi) 110 #define dsPrevLen (168)(%rdi) 111 #define dsMaxChainLen (172)(%rdi) 112 #define dsGoodMatch (188)(%rdi) 113 #define dsNiceMatch (192)(%rdi) 114 115 #else 116 117 #ifndef STRUCT_OFFSET 118 # define STRUCT_OFFSET (0) 119 #endif 120 121 122 #define dsWSize ( 56 + STRUCT_OFFSET)(%rdi) 123 #define dsWMask ( 64 + STRUCT_OFFSET)(%rdi) 124 #define dsWindow ( 72 + STRUCT_OFFSET)(%rdi) 125 #define dsPrev ( 88 + STRUCT_OFFSET)(%rdi) 126 #define dsMatchLen (136 + STRUCT_OFFSET)(%rdi) 127 #define dsPrevMatch (140 + STRUCT_OFFSET)(%rdi) 128 #define dsStrStart (148 + STRUCT_OFFSET)(%rdi) 129 #define dsMatchStart (152 + STRUCT_OFFSET)(%rdi) 130 #define dsLookahead (156 + STRUCT_OFFSET)(%rdi) 131 #define dsPrevLen (160 + STRUCT_OFFSET)(%rdi) 132 #define dsMaxChainLen (164 + STRUCT_OFFSET)(%rdi) 133 #define dsGoodMatch (180 + STRUCT_OFFSET)(%rdi) 134 #define dsNiceMatch (184 + STRUCT_OFFSET)(%rdi) 135 136 #endif 137 138 139 140 141 .text 142 143 /* uInt longest_match(deflate_state *deflatestate, IPos curmatch) */ 144 145 longest_match: 146 /* 147 * Retrieve the function arguments. %curmatch will hold cur_match 148 * throughout the entire function (passed via rsi on amd64). 149 * rdi will hold the pointer to the deflate_state (first arg on amd64) 150 */ 151 mov %rsi, save_rsi 152 mov %rbx, save_rbx 153 mov %r12, save_r12 154 mov %r13, save_r13 155 mov %r14, save_r14 156 mov %r15, save_r15 157 158 /* uInt wmask = s->w_mask; */ 159 /* unsigned chain_length = s->max_chain_length; */ 160 /* if (s->prev_length >= s->good_match) { */ 161 /* chain_length >>= 2; */ 162 /* } */ 163 164 movl dsPrevLen, %eax 165 movl dsGoodMatch, %ebx 166 cmpl %ebx, %eax 167 movl dsWMask, %eax 168 movl dsMaxChainLen, %chainlenwmask 169 jl LastMatchGood 170 shrl $2, %chainlenwmask 171 LastMatchGood: 172 173 /* chainlen is decremented once beforehand so that the function can */ 174 /* use the sign flag instead of the zero flag for the exit test. */ 175 /* It is then shifted into the high word, to make room for the wmask */ 176 /* value, which it will always accompany. */ 177 178 decl %chainlenwmask 179 shll $16, %chainlenwmask 180 orl %eax, %chainlenwmask 181 182 /* if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead; */ 183 184 movl dsNiceMatch, %eax 185 movl dsLookahead, %ebx 186 cmpl %eax, %ebx 187 jl LookaheadLess 188 movl %eax, %ebx 189 LookaheadLess: movl %ebx, %nicematch 190 191 /* register Bytef *scan = s->window + s->strstart; */ 192 193 mov dsWindow, %window 194 movl dsStrStart, %limitd 195 lea (%limit, %window), %scan 196 197 /* Determine how many bytes the scan ptr is off from being */ 198 /* dword-aligned. */ 199 200 mov %scan, %scanalign 201 negl %scanalignd 202 andl $3, %scanalignd 203 204 /* IPos limit = s->strstart > (IPos)MAX_DIST(s) ? */ 205 /* s->strstart - (IPos)MAX_DIST(s) : NIL; */ 206 207 movl dsWSize, %eax 208 subl $MIN_LOOKAHEAD, %eax 209 xorl %ecx, %ecx 210 subl %eax, %limitd 211 cmovng %ecx, %limitd 212 213 /* int best_len = s->prev_length; */ 214 215 movl dsPrevLen, %bestlend 216 217 /* Store the sum of s->window + best_len in %windowbestlen locally, and in memory. */ 218 219 lea (%window, %bestlen), %windowbestlen 220 mov %windowbestlen, _windowbestlen 221 222 /* register ush scan_start = *(ushf*)scan; */ 223 /* register ush scan_end = *(ushf*)(scan+best_len-1); */ 224 /* Posf *prev = s->prev; */ 225 226 movzwl (%scan), %scanstart 227 movzwl -1(%scan, %bestlen), %scanend 228 mov dsPrev, %prev 229 230 /* Jump into the main loop. */ 231 232 movl %chainlenwmask, _chainlenwmask 233 jmp LoopEntry 234 235 .balign 16 236 237 /* do { 238 * match = s->window + cur_match; 239 * if (*(ushf*)(match+best_len-1) != scan_end || 240 * *(ushf*)match != scan_start) continue; 241 * [...] 242 * } while ((cur_match = prev[cur_match & wmask]) > limit 243 * && --chain_length != 0); 244 * 245 * Here is the inner loop of the function. The function will spend the 246 * majority of its time in this loop, and majority of that time will 247 * be spent in the first ten instructions. 248 */ 249 LookupLoop: 250 andl %chainlenwmask, %curmatchd 251 movzwl (%prev, %curmatch, 2), %curmatchd 252 cmpl %limitd, %curmatchd 253 jbe LeaveNow 254 subl $0x00010000, %chainlenwmask 255 js LeaveNow 256 LoopEntry: cmpw -1(%windowbestlen, %curmatch), %scanendw 257 jne LookupLoop 258 cmpw %scanstartw, (%window, %curmatch) 259 jne LookupLoop 260 261 /* Store the current value of chainlen. */ 262 movl %chainlenwmask, _chainlenwmask 263 264 /* %scan is the string under scrutiny, and %prev to the string we */ 265 /* are hoping to match it up with. In actuality, %esi and %edi are */ 266 /* both pointed (MAX_MATCH_8 - scanalign) bytes ahead, and %edx is */ 267 /* initialized to -(MAX_MATCH_8 - scanalign). */ 268 269 mov $(-MAX_MATCH_8), %rdx 270 lea (%curmatch, %window), %windowbestlen 271 lea MAX_MATCH_8(%windowbestlen, %scanalign), %windowbestlen 272 lea MAX_MATCH_8(%scan, %scanalign), %prev 273 274 /* the prefetching below makes very little difference... */ 275 prefetcht1 (%windowbestlen, %rdx) 276 prefetcht1 (%prev, %rdx) 277 278 /* 279 * Test the strings for equality, 8 bytes at a time. At the end, 280 * adjust %rdx so that it is offset to the exact byte that mismatched. 281 * 282 * It should be confessed that this loop usually does not represent 283 * much of the total running time. Replacing it with a more 284 * straightforward "rep cmpsb" would not drastically degrade 285 * performance -- unrolling it, for example, makes no difference. 286 */ 287 288 #undef USE_SSE /* works, but is 6-7% slower, than non-SSE... */ 289 290 LoopCmps: 291 #ifdef USE_SSE 292 /* Preload the SSE registers */ 293 movdqu (%windowbestlen, %rdx), %xmm1 294 movdqu (%prev, %rdx), %xmm2 295 pcmpeqb %xmm2, %xmm1 296 movdqu 16(%windowbestlen, %rdx), %xmm3 297 movdqu 16(%prev, %rdx), %xmm4 298 pcmpeqb %xmm4, %xmm3 299 movdqu 32(%windowbestlen, %rdx), %xmm5 300 movdqu 32(%prev, %rdx), %xmm6 301 pcmpeqb %xmm6, %xmm5 302 movdqu 48(%windowbestlen, %rdx), %xmm7 303 movdqu 48(%prev, %rdx), %xmm8 304 pcmpeqb %xmm8, %xmm7 305 306 /* Check the comparisions' results */ 307 pmovmskb %xmm1, %rax 308 notw %ax 309 bsfw %ax, %ax 310 jnz LeaveLoopCmps 311 312 /* this is the only iteration of the loop with a possibility of having 313 incremented rdx by 0x108 (each loop iteration add 16*4 = 0x40 314 and (0x40*4)+8=0x108 */ 315 add $8, %rdx 316 jz LenMaximum 317 add $8, %rdx 318 319 320 pmovmskb %xmm3, %rax 321 notw %ax 322 bsfw %ax, %ax 323 jnz LeaveLoopCmps 324 325 326 add $16, %rdx 327 328 329 pmovmskb %xmm5, %rax 330 notw %ax 331 bsfw %ax, %ax 332 jnz LeaveLoopCmps 333 334 add $16, %rdx 335 336 337 pmovmskb %xmm7, %rax 338 notw %ax 339 bsfw %ax, %ax 340 jnz LeaveLoopCmps 341 342 add $16, %rdx 343 344 jmp LoopCmps 345 LeaveLoopCmps: add %rax, %rdx 346 #else 347 mov (%windowbestlen, %rdx), %rax 348 xor (%prev, %rdx), %rax 349 jnz LeaveLoopCmps 350 351 mov 8(%windowbestlen, %rdx), %rax 352 xor 8(%prev, %rdx), %rax 353 jnz LeaveLoopCmps8 354 355 mov 16(%windowbestlen, %rdx), %rax 356 xor 16(%prev, %rdx), %rax 357 jnz LeaveLoopCmps16 358 359 add $24, %rdx 360 jnz LoopCmps 361 jmp LenMaximum 362 # if 0 363 /* 364 * This three-liner is tantalizingly simple, but bsf is a slow instruction, 365 * and the complicated alternative down below is quite a bit faster. Sad... 366 */ 367 368 LeaveLoopCmps: bsf %rax, %rax /* find the first non-zero bit */ 369 shrl $3, %eax /* divide by 8 to get the byte */ 370 add %rax, %rdx 371 # else 372 LeaveLoopCmps16: 373 add $8, %rdx 374 LeaveLoopCmps8: 375 add $8, %rdx 376 LeaveLoopCmps: testl $0xFFFFFFFF, %eax /* Check the first 4 bytes */ 377 jnz Check16 378 add $4, %rdx 379 shr $32, %rax 380 Check16: testw $0xFFFF, %ax 381 jnz LenLower 382 add $2, %rdx 383 shrl $16, %eax 384 LenLower: subb $1, %al 385 adc $0, %rdx 386 # endif 387 #endif 388 389 /* Calculate the length of the match. If it is longer than MAX_MATCH, */ 390 /* then automatically accept it as the best possible match and leave. */ 391 392 lea (%prev, %rdx), %rax 393 sub %scan, %rax 394 cmpl $MAX_MATCH, %eax 395 jge LenMaximum 396 397 /* If the length of the match is not longer than the best match we */ 398 /* have so far, then forget it and return to the lookup loop. */ 399 400 cmpl %bestlend, %eax 401 jg LongerMatch 402 mov _windowbestlen, %windowbestlen 403 mov dsPrev, %prev 404 movl _chainlenwmask, %edx 405 jmp LookupLoop 406 407 /* s->match_start = cur_match; */ 408 /* best_len = len; */ 409 /* if (len >= nice_match) break; */ 410 /* scan_end = *(ushf*)(scan+best_len-1); */ 411 412 LongerMatch: 413 movl %eax, %bestlend 414 movl %curmatchd, dsMatchStart 415 cmpl %nicematch, %eax 416 jge LeaveNow 417 418 lea (%window, %bestlen), %windowbestlen 419 mov %windowbestlen, _windowbestlen 420 421 movzwl -1(%scan, %rax), %scanend 422 mov dsPrev, %prev 423 movl _chainlenwmask, %chainlenwmask 424 jmp LookupLoop 425 426 /* Accept the current string, with the maximum possible length. */ 427 428 LenMaximum: 429 movl $MAX_MATCH, %bestlend 430 movl %curmatchd, dsMatchStart 431 432 /* if ((uInt)best_len <= s->lookahead) return (uInt)best_len; */ 433 /* return s->lookahead; */ 434 435 LeaveNow: 436 movl dsLookahead, %eax 437 cmpl %eax, %bestlend 438 cmovngl %bestlend, %eax 439 LookaheadRet: 440 441 /* Restore the registers and return from whence we came. */ 442 443 mov save_rsi, %rsi 444 mov save_rbx, %rbx 445 mov save_r12, %r12 446 mov save_r13, %r13 447 mov save_r14, %r14 448 mov save_r15, %r15 449 450 ret 451 452 match_init: ret 453
