source: s10k/CommonLibs/zlib-1.2.8/contrib/asm686/match.S @ 1096

Last change on this file since 1096 was 1096, checked in by s10k, 19 months ago

Added zlib, quazip, basicxmlsyntaxhighlighter, conditionalsemaphore and linenumberdisplay libraries. zlib and quazip are pre-compiled, but you can compile them yourself, just delete the dll files (or equivalent binary files to your OS)

File size: 10.1 KB
Line 
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
88longest_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
127LastMatchGood:
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
146LookaheadLess:  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
172LimitPositive:
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 */
221LookupLoop:
222                andl    %edx, %ecx
223                movzwl  (%edi,%ecx,2), %ecx
224                cmpl    %ebp, %ecx
225                jbe     LeaveNow
226                subl    $0x00010000, %edx
227                js      LeaveNow
228LoopEntry:      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 */
267LoopCmps:
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
277LeaveLoopCmps4: addl    $4, %edx
278LeaveLoopCmps:  testl   $0x0000FFFF, %eax
279                jnz     LenLower
280                addl    $2, %edx
281                shrl    $16, %eax
282LenLower:       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
312LongerMatch:    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
328LenMaximum:     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
335LeaveNow:
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
342LookaheadRet:
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
357match_init:     ret
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