ceph/src/Beast/test/zlib/zlib-1.2.8/contrib/asm686/match.S

   1 /* match.S -- x86 assembly version of the zlib longest_match() function.
   2  * Optimized for the Intel 686 chips (PPro and later).
   3  *
   4  * Copyright (C) 1998, 2007 Brian Raiter <breadbox@muppetlabs.com>
   5  *
   6  * This software is provided 'as-is', without any express or implied
   7  * warranty.  In no event will the author be held liable for any damages
   8  * arising from the use of this software.
   9  *
  10  * Permission is granted to anyone to use this software for any purpose,
  11  * including commercial applications, and to alter it and redistribute it
  12  * freely, subject to the following restrictions:
  13  *
  14  * 1. The origin of this software must not be misrepresented; you must not
  15  *    claim that you wrote the original software. If you use this software
  16  *    in a product, an acknowledgment in the product documentation would be
  17  *    appreciated but is not required.
  18  * 2. Altered source versions must be plainly marked as such, and must not be
  19  *    misrepresented as being the original software.
  20  * 3. This notice may not be removed or altered from any source distribution.
  21  */
  22
  23 #ifndef NO_UNDERLINE
  24 #define match_init      _match_init
  25 #define longest_match   _longest_match
  26 #endif
  27
  28 #define MAX_MATCH       (258)
  29 #define MIN_MATCH       (3)
  30 #define MIN_LOOKAHEAD   (MAX_MATCH + MIN_MATCH + 1)
  31 #define MAX_MATCH_8     ((MAX_MATCH + 7) & ~7)
  32
  33 /* stack frame offsets */
  34
  35 #define chainlenwmask           0       /* high word: current chain len */
  36                                         /* low word: s->wmask           */
  37 #define window                  4       /* local copy of s->window      */
  38 #define windowbestlen           8       /* s->window + bestlen          */
  39 #define scanstart               16      /* first two bytes of string    */
  40 #define scanend                 12      /* last two bytes of string     */
  41 #define scanalign               20      /* dword-misalignment of string */
  42 #define nicematch               24      /* a good enough match size     */
  43 #define bestlen                 28      /* size of best match so far    */
  44 #define scan                    32      /* ptr to string wanting match  */
  45
  46 #define LocalVarsSize           (36)
  47 /*      saved ebx               36 */
  48 /*      saved edi               40 */
  49 /*      saved esi               44 */
  50 /*      saved ebp               48 */
  51 /*      return address          52 */
  52 #define deflatestate            56      /* the function arguments       */
  53 #define curmatch                60
  54
  55 /* All the +zlib1222add offsets are due to the addition of fields
  56  *  in zlib in the deflate_state structure since the asm code was first written
  57  * (if you compile with zlib 1.0.4 or older, use "zlib1222add equ (-4)").
  58  * (if you compile with zlib between 1.0.5 and 1.2.2.1, use "zlib1222add equ 0").
  59  * if you compile with zlib 1.2.2.2 or later , use "zlib1222add equ 8").
  60  */
  61
  62 #define zlib1222add             (8)
  63
  64 #define dsWSize                 (36+zlib1222add)
  65 #define dsWMask                 (44+zlib1222add)
  66 #define dsWindow                (48+zlib1222add)
  67 #define dsPrev                  (56+zlib1222add)
  68 #define dsMatchLen              (88+zlib1222add)
  69 #define dsPrevMatch             (92+zlib1222add)
  70 #define dsStrStart              (100+zlib1222add)
  71 #define dsMatchStart            (104+zlib1222add)
  72 #define dsLookahead             (108+zlib1222add)
  73 #define dsPrevLen               (112+zlib1222add)
  74 #define dsMaxChainLen           (116+zlib1222add)
  75 #define dsGoodMatch             (132+zlib1222add)
  76 #define dsNiceMatch             (136+zlib1222add)
  77
  78
  79 .file "match.S"
  80
  81 .globl  match_init, longest_match
  82
  83 .text
  84
  85 /* uInt longest_match(deflate_state *deflatestate, IPos curmatch) */
  86 .cfi_sections   .debug_frame
  87
  88 longest_match:
  89
  90 .cfi_startproc
  91 /* Save registers that the compiler may be using, and adjust %esp to    */
  92 /* make room for our stack frame.                                       */
  93
  94                 pushl   %ebp
  95                 .cfi_def_cfa_offset 8
  96                 .cfi_offset ebp, -8
  97                 pushl   %edi
  98                 .cfi_def_cfa_offset 12
  99                 pushl   %esi
 100                 .cfi_def_cfa_offset 16
 101                 pushl   %ebx
 102                 .cfi_def_cfa_offset 20
 103                 subl    $LocalVarsSize, %esp
 104                 .cfi_def_cfa_offset LocalVarsSize+20
 105
 106 /* Retrieve the function arguments. %ecx will hold cur_match            */
 107 /* throughout the entire function. %edx will hold the pointer to the    */
 108 /* deflate_state structure during the function's setup (before          */
 109 /* entering the main loop).                                             */
 110
 111                 movl    deflatestate(%esp), %edx
 112                 movl    curmatch(%esp), %ecx
 113
 114 /* uInt wmask = s->w_mask;                                              */
 115 /* unsigned chain_length = s->max_chain_length;                         */
 116 /* if (s->prev_length >= s->good_match) {                               */
 117 /*     chain_length >>= 2;                                              */
 118 /* }                                                                    */
 119
 120                 movl    dsPrevLen(%edx), %eax
 121                 movl    dsGoodMatch(%edx), %ebx
 122                 cmpl    %ebx, %eax
 123                 movl    dsWMask(%edx), %eax
 124                 movl    dsMaxChainLen(%edx), %ebx
 125                 jl      LastMatchGood
 126                 shrl    $2, %ebx
 127 LastMatchGood:
 128
 129 /* chainlen is decremented once beforehand so that the function can     */
 130 /* use the sign flag instead of the zero flag for the exit test.        */
 131 /* It is then shifted into the high word, to make room for the wmask    */
 132 /* value, which it will always accompany.                               */
 133
 134                 decl    %ebx
 135                 shll    $16, %ebx
 136                 orl     %eax, %ebx
 137                 movl    %ebx, chainlenwmask(%esp)
 138
 139 /* if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;      */
 140
 141                 movl    dsNiceMatch(%edx), %eax
 142                 movl    dsLookahead(%edx), %ebx
 143                 cmpl    %eax, %ebx
 144                 jl      LookaheadLess
 145                 movl    %eax, %ebx
 146 LookaheadLess:  movl    %ebx, nicematch(%esp)
 147
 148 /* register Bytef *scan = s->window + s->strstart;                      */
 149
 150                 movl    dsWindow(%edx), %esi
 151                 movl    %esi, window(%esp)
 152                 movl    dsStrStart(%edx), %ebp
 153                 lea     (%esi,%ebp), %edi
 154                 movl    %edi, scan(%esp)
 155
 156 /* Determine how many bytes the scan ptr is off from being              */
 157 /* dword-aligned.                                                       */
 158
 159                 movl    %edi, %eax
 160                 negl    %eax
 161                 andl    $3, %eax
 162                 movl    %eax, scanalign(%esp)
 163
 164 /* IPos limit = s->strstart > (IPos)MAX_DIST(s) ?                       */
 165 /*     s->strstart - (IPos)MAX_DIST(s) : NIL;                           */
 166
 167                 movl    dsWSize(%edx), %eax
 168                 subl    $MIN_LOOKAHEAD, %eax
 169                 subl    %eax, %ebp
 170                 jg      LimitPositive
 171                 xorl    %ebp, %ebp
 172 LimitPositive:
 173
 174 /* int best_len = s->prev_length;                                       */
 175
 176                 movl    dsPrevLen(%edx), %eax
 177                 movl    %eax, bestlen(%esp)
 178
 179 /* Store the sum of s->window + best_len in %esi locally, and in %esi.  */
 180
 181                 addl    %eax, %esi
 182                 movl    %esi, windowbestlen(%esp)
 183
 184 /* register ush scan_start = *(ushf*)scan;                              */
 185 /* register ush scan_end   = *(ushf*)(scan+best_len-1);                 */
 186 /* Posf *prev = s->prev;                                                */
 187
 188                 movzwl  (%edi), %ebx
 189                 movl    %ebx, scanstart(%esp)
 190                 movzwl  -1(%edi,%eax), %ebx
 191                 movl    %ebx, scanend(%esp)
 192                 movl    dsPrev(%edx), %edi
 193
 194 /* Jump into the main loop.                                             */
 195
 196                 movl    chainlenwmask(%esp), %edx
 197                 jmp     LoopEntry
 198
 199 .balign 16
 200
 201 /* do {
 202  *     match = s->window + cur_match;
 203  *     if (*(ushf*)(match+best_len-1) != scan_end ||
 204  *         *(ushf*)match != scan_start) continue;
 205  *     [...]
 206  * } while ((cur_match = prev[cur_match & wmask]) > limit
 207  *          && --chain_length != 0);
 208  *
 209  * Here is the inner loop of the function. The function will spend the
 210  * majority of its time in this loop, and majority of that time will
 211  * be spent in the first ten instructions.
 212  *
 213  * Within this loop:
 214  * %ebx = scanend
 215  * %ecx = curmatch
 216  * %edx = chainlenwmask - i.e., ((chainlen << 16) | wmask)
 217  * %esi = windowbestlen - i.e., (window + bestlen)
 218  * %edi = prev
 219  * %ebp = limit
 220  */
 221 LookupLoop:
 222                 andl    %edx, %ecx
 223                 movzwl  (%edi,%ecx,2), %ecx
 224                 cmpl    %ebp, %ecx
 225                 jbe     LeaveNow
 226                 subl    $0x00010000, %edx
 227                 js      LeaveNow
 228 LoopEntry:      movzwl  -1(%esi,%ecx), %eax
 229                 cmpl    %ebx, %eax
 230                 jnz     LookupLoop
 231                 movl    window(%esp), %eax
 232                 movzwl  (%eax,%ecx), %eax
 233                 cmpl    scanstart(%esp), %eax
 234                 jnz     LookupLoop
 235
 236 /* Store the current value of chainlen.                                 */
 237
 238                 movl    %edx, chainlenwmask(%esp)
 239
 240 /* Point %edi to the string under scrutiny, and %esi to the string we   */
 241 /* are hoping to match it up with. In actuality, %esi and %edi are      */
 242 /* both pointed (MAX_MATCH_8 - scanalign) bytes ahead, and %edx is      */
 243 /* initialized to -(MAX_MATCH_8 - scanalign).                           */
 244
 245                 movl    window(%esp), %esi
 246                 movl    scan(%esp), %edi
 247                 addl    %ecx, %esi
 248                 movl    scanalign(%esp), %eax
 249                 movl    $(-MAX_MATCH_8), %edx
 250                 lea     MAX_MATCH_8(%edi,%eax), %edi
 251                 lea     MAX_MATCH_8(%esi,%eax), %esi
 252
 253 /* Test the strings for equality, 8 bytes at a time. At the end,
 254  * adjust %edx so that it is offset to the exact byte that mismatched.
 255  *
 256  * We already know at this point that the first three bytes of the
 257  * strings match each other, and they can be safely passed over before
 258  * starting the compare loop. So what this code does is skip over 0-3
 259  * bytes, as much as necessary in order to dword-align the %edi
 260  * pointer. (%esi will still be misaligned three times out of four.)
 261  *
 262  * It should be confessed that this loop usually does not represent
 263  * much of the total running time. Replacing it with a more
 264  * straightforward "rep cmpsb" would not drastically degrade
 265  * performance.
 266  */
 267 LoopCmps:
 268                 movl    (%esi,%edx), %eax
 269                 xorl    (%edi,%edx), %eax
 270                 jnz     LeaveLoopCmps
 271                 movl    4(%esi,%edx), %eax
 272                 xorl    4(%edi,%edx), %eax
 273                 jnz     LeaveLoopCmps4
 274                 addl    $8, %edx
 275                 jnz     LoopCmps
 276                 jmp     LenMaximum
 277 LeaveLoopCmps4: addl    $4, %edx
 278 LeaveLoopCmps:  testl   $0x0000FFFF, %eax
 279                 jnz     LenLower
 280                 addl    $2, %edx
 281                 shrl    $16, %eax
 282 LenLower:       subb    $1, %al
 283                 adcl    $0, %edx
 284
 285 /* Calculate the length of the match. If it is longer than MAX_MATCH,   */
 286 /* then automatically accept it as the best possible match and leave.   */
 287
 288                 lea     (%edi,%edx), %eax
 289                 movl    scan(%esp), %edi
 290                 subl    %edi, %eax
 291                 cmpl    $MAX_MATCH, %eax
 292                 jge     LenMaximum
 293
 294 /* If the length of the match is not longer than the best match we      */
 295 /* have so far, then forget it and return to the lookup loop.           */
 296
 297                 movl    deflatestate(%esp), %edx
 298                 movl    bestlen(%esp), %ebx
 299                 cmpl    %ebx, %eax
 300                 jg      LongerMatch
 301                 movl    windowbestlen(%esp), %esi
 302                 movl    dsPrev(%edx), %edi
 303                 movl    scanend(%esp), %ebx
 304                 movl    chainlenwmask(%esp), %edx
 305                 jmp     LookupLoop
 306
 307 /*         s->match_start = cur_match;                                  */
 308 /*         best_len = len;                                              */
 309 /*         if (len >= nice_match) break;                                */
 310 /*         scan_end = *(ushf*)(scan+best_len-1);                        */
 311
 312 LongerMatch:    movl    nicematch(%esp), %ebx
 313                 movl    %eax, bestlen(%esp)
 314                 movl    %ecx, dsMatchStart(%edx)
 315                 cmpl    %ebx, %eax
 316                 jge     LeaveNow
 317                 movl    window(%esp), %esi
 318                 addl    %eax, %esi
 319                 movl    %esi, windowbestlen(%esp)
 320                 movzwl  -1(%edi,%eax), %ebx
 321                 movl    dsPrev(%edx), %edi
 322                 movl    %ebx, scanend(%esp)
 323                 movl    chainlenwmask(%esp), %edx
 324                 jmp     LookupLoop
 325
 326 /* Accept the current string, with the maximum possible length.         */
 327
 328 LenMaximum:     movl    deflatestate(%esp), %edx
 329                 movl    $MAX_MATCH, bestlen(%esp)
 330                 movl    %ecx, dsMatchStart(%edx)
 331
 332 /* if ((uInt)best_len <= s->lookahead) return (uInt)best_len;           */
 333 /* return s->lookahead;                                                 */
 334
 335 LeaveNow:
 336                 movl    deflatestate(%esp), %edx
 337                 movl    bestlen(%esp), %ebx
 338                 movl    dsLookahead(%edx), %eax
 339                 cmpl    %eax, %ebx
 340                 jg      LookaheadRet
 341                 movl    %ebx, %eax
 342 LookaheadRet:
 343
 344 /* Restore the stack and return from whence we came.                    */
 345
 346                 addl    $LocalVarsSize, %esp
 347                 .cfi_def_cfa_offset 20
 348                 popl    %ebx
 349                 .cfi_def_cfa_offset 16
 350                 popl    %esi
 351                 .cfi_def_cfa_offset 12
 352                 popl    %edi
 353                 .cfi_def_cfa_offset 8
 354                 popl    %ebp
 355                 .cfi_def_cfa_offset 4
 356 .cfi_endproc
 357 match_init:     ret