source: trunk/minix/lib/zlib-1.2.3/contrib/asm686/match.S@ 9

Last change on this file since 9 was 9, checked in by Mattia Monga, 13 years ago

Minix 3.1.2a
File size: 9.0 KB
Line 
1/* match.s -- Pentium-Pro-optimized version of longest_match()
2 * Written for zlib 1.1.2
3 * Copyright (C) 1998 Brian Raiter <breadbox@muppetlabs.com>
4 *
5 * This is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License.
7 */
8
9#ifndef NO_UNDERLINE
10#define match_init _match_init
11#define longest_match _longest_match
12#endif
13
14#define MAX_MATCH (258)
15#define MIN_MATCH (3)
16#define MIN_LOOKAHEAD (MAX_MATCH + MIN_MATCH + 1)
17#define MAX_MATCH_8 ((MAX_MATCH + 7) & ~7)
18
19/* stack frame offsets */
20
21#define chainlenwmask 0 /* high word: current chain len */
22 /* low word: s->wmask */
23#define window 4 /* local copy of s->window */
24#define windowbestlen 8 /* s->window + bestlen */
25#define scanstart 16 /* first two bytes of string */
26#define scanend 12 /* last two bytes of string */
27#define scanalign 20 /* dword-misalignment of string */
28#define nicematch 24 /* a good enough match size */
29#define bestlen 28 /* size of best match so far */
30#define scan 32 /* ptr to string wanting match */
31
32#define LocalVarsSize (36)
33/* saved ebx 36 */
34/* saved edi 40 */
35/* saved esi 44 */
36/* saved ebp 48 */
37/* return address 52 */
38#define deflatestate 56 /* the function arguments */
39#define curmatch 60
40
41/* All the +zlib1222add offsets are due to the addition of fields
42 * in zlib in the deflate_state structure since the asm code was first written
43 * (if you compile with zlib 1.0.4 or older, use "zlib1222add equ (-4)").
44 * (if you compile with zlib between 1.0.5 and 1.2.2.1, use "zlib1222add equ 0").
45 * if you compile with zlib 1.2.2.2 or later , use "zlib1222add equ 8").
46 */
47
48#define zlib1222add (8)
49
50#define dsWSize (36+zlib1222add)
51#define dsWMask (44+zlib1222add)
52#define dsWindow (48+zlib1222add)
53#define dsPrev (56+zlib1222add)
54#define dsMatchLen (88+zlib1222add)
55#define dsPrevMatch (92+zlib1222add)
56#define dsStrStart (100+zlib1222add)
57#define dsMatchStart (104+zlib1222add)
58#define dsLookahead (108+zlib1222add)
59#define dsPrevLen (112+zlib1222add)
60#define dsMaxChainLen (116+zlib1222add)
61#define dsGoodMatch (132+zlib1222add)
62#define dsNiceMatch (136+zlib1222add)
63
64
65.file "match.S"
66
67.globl match_init, longest_match
68
69.text
70
71/* uInt longest_match(deflate_state *deflatestate, IPos curmatch) */
72
73longest_match:
74
75/* Save registers that the compiler may be using, and adjust %esp to */
76/* make room for our stack frame. */
77
78 pushl %ebp
79 pushl %edi
80 pushl %esi
81 pushl %ebx
82 subl $LocalVarsSize, %esp
83
84/* Retrieve the function arguments. %ecx will hold cur_match */
85/* throughout the entire function. %edx will hold the pointer to the */
86/* deflate_state structure during the function's setup (before */
87/* entering the main loop). */
88
89 movl deflatestate(%esp), %edx
90 movl curmatch(%esp), %ecx
91
92/* uInt wmask = s->w_mask; */
93/* unsigned chain_length = s->max_chain_length; */
94/* if (s->prev_length >= s->good_match) { */
95/* chain_length >>= 2; */
96/* } */
97
98 movl dsPrevLen(%edx), %eax
99 movl dsGoodMatch(%edx), %ebx
100 cmpl %ebx, %eax
101 movl dsWMask(%edx), %eax
102 movl dsMaxChainLen(%edx), %ebx
103 jl LastMatchGood
104 shrl $2, %ebx
105LastMatchGood:
106
107/* chainlen is decremented once beforehand so that the function can */
108/* use the sign flag instead of the zero flag for the exit test. */
109/* It is then shifted into the high word, to make room for the wmask */
110/* value, which it will always accompany. */
111
112 decl %ebx
113 shll $16, %ebx
114 orl %eax, %ebx
115 movl %ebx, chainlenwmask(%esp)
116
117/* if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead; */
118
119 movl dsNiceMatch(%edx), %eax
120 movl dsLookahead(%edx), %ebx
121 cmpl %eax, %ebx
122 jl LookaheadLess
123 movl %eax, %ebx
124LookaheadLess: movl %ebx, nicematch(%esp)
125
126/* register Bytef *scan = s->window + s->strstart; */
127
128 movl dsWindow(%edx), %esi
129 movl %esi, window(%esp)
130 movl dsStrStart(%edx), %ebp
131 lea (%esi,%ebp), %edi
132 movl %edi, scan(%esp)
133
134/* Determine how many bytes the scan ptr is off from being */
135/* dword-aligned. */
136
137 movl %edi, %eax
138 negl %eax
139 andl $3, %eax
140 movl %eax, scanalign(%esp)
141
142/* IPos limit = s->strstart > (IPos)MAX_DIST(s) ? */
143/* s->strstart - (IPos)MAX_DIST(s) : NIL; */
144
145 movl dsWSize(%edx), %eax
146 subl $MIN_LOOKAHEAD, %eax
147 subl %eax, %ebp
148 jg LimitPositive
149 xorl %ebp, %ebp
150LimitPositive:
151
152/* int best_len = s->prev_length; */
153
154 movl dsPrevLen(%edx), %eax
155 movl %eax, bestlen(%esp)
156
157/* Store the sum of s->window + best_len in %esi locally, and in %esi. */
158
159 addl %eax, %esi
160 movl %esi, windowbestlen(%esp)
161
162/* register ush scan_start = *(ushf*)scan; */
163/* register ush scan_end = *(ushf*)(scan+best_len-1); */
164/* Posf *prev = s->prev; */
165
166 movzwl (%edi), %ebx
167 movl %ebx, scanstart(%esp)
168 movzwl -1(%edi,%eax), %ebx
169 movl %ebx, scanend(%esp)
170 movl dsPrev(%edx), %edi
171
172/* Jump into the main loop. */
173
174 movl chainlenwmask(%esp), %edx
175 jmp LoopEntry
176
177.balign 16
178
179/* do {
180 * match = s->window + cur_match;
181 * if (*(ushf*)(match+best_len-1) != scan_end ||
182 * *(ushf*)match != scan_start) continue;
183 * [...]
184 * } while ((cur_match = prev[cur_match & wmask]) > limit
185 * && --chain_length != 0);
186 *
187 * Here is the inner loop of the function. The function will spend the
188 * majority of its time in this loop, and majority of that time will
189 * be spent in the first ten instructions.
190 *
191 * Within this loop:
192 * %ebx = scanend
193 * %ecx = curmatch
194 * %edx = chainlenwmask - i.e., ((chainlen << 16) | wmask)
195 * %esi = windowbestlen - i.e., (window + bestlen)
196 * %edi = prev
197 * %ebp = limit
198 */
199LookupLoop:
200 andl %edx, %ecx
201 movzwl (%edi,%ecx,2), %ecx
202 cmpl %ebp, %ecx
203 jbe LeaveNow
204 subl $0x00010000, %edx
205 js LeaveNow
206LoopEntry: movzwl -1(%esi,%ecx), %eax
207 cmpl %ebx, %eax
208 jnz LookupLoop
209 movl window(%esp), %eax
210 movzwl (%eax,%ecx), %eax
211 cmpl scanstart(%esp), %eax
212 jnz LookupLoop
213
214/* Store the current value of chainlen. */
215
216 movl %edx, chainlenwmask(%esp)
217
218/* Point %edi to the string under scrutiny, and %esi to the string we */
219/* are hoping to match it up with. In actuality, %esi and %edi are */
220/* both pointed (MAX_MATCH_8 - scanalign) bytes ahead, and %edx is */
221/* initialized to -(MAX_MATCH_8 - scanalign). */
222
223 movl window(%esp), %esi
224 movl scan(%esp), %edi
225 addl %ecx, %esi
226 movl scanalign(%esp), %eax
227 movl $(-MAX_MATCH_8), %edx
228 lea MAX_MATCH_8(%edi,%eax), %edi
229 lea MAX_MATCH_8(%esi,%eax), %esi
230
231/* Test the strings for equality, 8 bytes at a time. At the end,
232 * adjust %edx so that it is offset to the exact byte that mismatched.
233 *
234 * We already know at this point that the first three bytes of the
235 * strings match each other, and they can be safely passed over before
236 * starting the compare loop. So what this code does is skip over 0-3
237 * bytes, as much as necessary in order to dword-align the %edi
238 * pointer. (%esi will still be misaligned three times out of four.)
239 *
240 * It should be confessed that this loop usually does not represent
241 * much of the total running time. Replacing it with a more
242 * straightforward "rep cmpsb" would not drastically degrade
243 * performance.
244 */
245LoopCmps:
246 movl (%esi,%edx), %eax
247 xorl (%edi,%edx), %eax
248 jnz LeaveLoopCmps
249 movl 4(%esi,%edx), %eax
250 xorl 4(%edi,%edx), %eax
251 jnz LeaveLoopCmps4
252 addl $8, %edx
253 jnz LoopCmps
254 jmp LenMaximum
255LeaveLoopCmps4: addl $4, %edx
256LeaveLoopCmps: testl $0x0000FFFF, %eax
257 jnz LenLower
258 addl $2, %edx
259 shrl $16, %eax
260LenLower: subb $1, %al
261 adcl $0, %edx
262
263/* Calculate the length of the match. If it is longer than MAX_MATCH, */
264/* then automatically accept it as the best possible match and leave. */
265
266 lea (%edi,%edx), %eax
267 movl scan(%esp), %edi
268 subl %edi, %eax
269 cmpl $MAX_MATCH, %eax
270 jge LenMaximum
271
272/* If the length of the match is not longer than the best match we */
273/* have so far, then forget it and return to the lookup loop. */
274
275 movl deflatestate(%esp), %edx
276 movl bestlen(%esp), %ebx
277 cmpl %ebx, %eax
278 jg LongerMatch
279 movl windowbestlen(%esp), %esi
280 movl dsPrev(%edx), %edi
281 movl scanend(%esp), %ebx
282 movl chainlenwmask(%esp), %edx
283 jmp LookupLoop
284
285/* s->match_start = cur_match; */
286/* best_len = len; */
287/* if (len >= nice_match) break; */
288/* scan_end = *(ushf*)(scan+best_len-1); */
289
290LongerMatch: movl nicematch(%esp), %ebx
291 movl %eax, bestlen(%esp)
292 movl %ecx, dsMatchStart(%edx)
293 cmpl %ebx, %eax
294 jge LeaveNow
295 movl window(%esp), %esi
296 addl %eax, %esi
297 movl %esi, windowbestlen(%esp)
298 movzwl -1(%edi,%eax), %ebx
299 movl dsPrev(%edx), %edi
300 movl %ebx, scanend(%esp)
301 movl chainlenwmask(%esp), %edx
302 jmp LookupLoop
303
304/* Accept the current string, with the maximum possible length. */
305
306LenMaximum: movl deflatestate(%esp), %edx
307 movl $MAX_MATCH, bestlen(%esp)
308 movl %ecx, dsMatchStart(%edx)
309
310/* if ((uInt)best_len <= s->lookahead) return (uInt)best_len; */
311/* return s->lookahead; */
312
313LeaveNow:
314 movl deflatestate(%esp), %edx
315 movl bestlen(%esp), %ebx
316 movl dsLookahead(%edx), %eax
317 cmpl %eax, %ebx
318 jg LookaheadRet
319 movl %ebx, %eax
320LookaheadRet:
321
322/* Restore the stack and return from whence we came. */
323
324 addl $LocalVarsSize, %esp
325 popl %ebx
326 popl %esi
327 popl %edi
328 popl %ebp
329match_init: ret
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