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1 /* crc_i386.c -- Microsoft 32-bit C/C++ adaptation of crc_i386.asm
2 * Created by Rodney Brown from crc_i386.asm, modified by Chr. Spieler.
3 * Last revised: 22-Mai-1998
4 *
5 * Original coded (in crc_i386.asm) and put into the public domain
6 * by Paul Kienitz and Christian Spieler.
7 *
8 * Revised 06-Oct-96, Scott Field (sfield@microsoft.com)
9 * fixed to assemble with masm by not using .model directive which makes
10 * assumptions about segment alignment. Also,
11 * avoid using loop, and j[e]cxz where possible. Use mov + inc, rather
12 * than lodsb, and other misc. changes resulting in the following performance
13 * increases:
14 *
15 * unrolled loops NO_UNROLLED_LOOPS
16 * *8 >8 <8 *8 >8 <8
17 *
18 * +54% +42% +35% +82% +52% +25%
19 *
20 * first item in each table is input buffer length, even multiple of 8
21 * second item in each table is input buffer length, > 8
22 * third item in each table is input buffer length, < 8
23 *
24 * Revised 02-Apr-97, Chr. Spieler, based on Rodney Brown (rdb@cmutual.com.au)
25 * Incorporated Rodney Brown's 32-bit-reads optimization as found in the
26 * UNIX AS source crc_i386.S. This new code can be disabled by defining
27 * the macro symbol NO_32_BIT_LOADS.
28 *
29 * Revised 12-Oct-97, Chr. Spieler, based on Rodney Brown (rdb@cmutual.com.au)
30 * Incorporated Rodney Brown's additional tweaks for 32-bit-optimized CPUs
31 * (like the Pentium Pro, Pentium II, and probably some Pentium clones).
32 * This optimization is controlled by the macro symbol __686 and is disabled
33 * by default. (This default is based on the assumption that most users
34 * do not yet work on a Pentium Pro or Pentium II machine ...)
35 *
36 * Revised 16-Nov-97, Chr. Spieler: Made code compatible with Borland C++
37 * 32-bit, removed unneeded kludge for potentially unknown movzx mnemonic,
38 * confirmed correct working with MS VC++ (32-bit).
39 *
40 * Revised 22-Mai-98, Peter Kunath, Chr. Spieler : The 16-Nov-97 revision broke
41 * MSVC 5.0. Inside preprocessor macros, each instruction is enclosed in its
42 * own __asm {...} construct. For MSVC, a "#pragma warning" was added to
43 * shut up the "no return value" warning message.
44 *
45 * FLAT memory model assumed.
46 *
47 * The loop unrolling can be disabled by defining the macro NO_UNROLLED_LOOPS.
48 * This results in shorter code at the expense of reduced performance.
49 *
50 */
51
52 #include "zip.h"
53
54 #ifndef USE_ZLIB
55
56 #ifndef ZCONST
57 # define ZCONST const
58 #endif
59
60 /* Select wether the following inline-assember code is supported. */
61 #if (defined(_MSC_VER) && _MSC_VER >= 700)
62 #if (defined(_M_IX86) && _M_IX86 >= 300)
63 # define MSC_INLINE_ASM_32BIT_SUPPORT
64 /* Disable warning for no return value, typical of asm functions */
65 # pragma warning( disable : 4035 )
66 #endif
67 #endif
68
69 #if (defined(__BORLANDC__) && __BORLANDC__ >= 452)
70 # define MSC_INLINE_ASM_32BIT_SUPPORT
71 #endif
72
73 #ifdef MSC_INLINE_ASM_32BIT_SUPPORT
74 /* This code is intended for Microsoft C/C++ (32-bit) compatible compilers. */
75
76 /*
77 * These two (three) macros make up the loop body of the CRC32 cruncher.
78 * registers modified:
79 * eax : crc value "c"
80 * esi : pointer to next data byte (or dword) "buf++"
81 * registers read:
82 * edi : pointer to base of crc_table array
83 * scratch registers:
84 * ebx : index into crc_table array
85 * (requires upper three bytes = 0 when __686 is undefined)
86 */
87 #ifndef __686
88 #define Do_CRC { \
89 __asm { mov bl, al }; \
90 __asm { shr eax, 8 }; \
91 __asm { xor eax, [edi+ebx*4] }; }
92 #else /* __686 */
93 #define Do_CRC { \
94 __asm { movzx ebx, al }; \
95 __asm { shr eax, 8 }; \
96 __asm { xor eax, [edi+ebx*4] }; }
97 #endif /* ?__686 */
98
99 #define Do_CRC_byte { \
100 __asm { xor al, byte ptr [esi] }; \
101 __asm { inc esi }; \
102 Do_CRC; }
103
104 #ifndef NO_32_BIT_LOADS
105 #define Do_CRC_dword { \
106 __asm { xor eax, dword ptr [esi] }; \
107 __asm { add esi, 4 }; \
108 Do_CRC; \
109 Do_CRC; \
110 Do_CRC; \
111 Do_CRC; }
112 #endif /* !NO_32_BIT_LOADS */
113
114 /* ========================================================================= */
115 ulg crc32(crc, buf, len)
116 ulg crc; /* crc shift register */
117 ZCONST uch *buf; /* pointer to bytes to pump through */
118 extent len; /* number of bytes in buf[] */
119 /* Run a set of bytes through the crc shift register. If buf is a NULL
120 pointer, then initialize the crc shift register contents instead.
121 Return the current crc in either case. */
122 {
123 __asm {
124 push edx
125 push ecx
126
127 mov esi,buf ;/* 2nd arg: uch *buf */
128 sub eax,eax ;/*> if (!buf) */
129 test esi,esi ;/*> return 0; */
130 jz fine ;/*> else { */
131
132 call get_crc_table
133 mov edi,eax
134 mov eax,crc ;/* 1st arg: ulg crc */
135 #ifndef __686
136 sub ebx,ebx ;/* ebx=0; => bl usable as a dword */
137 #endif
138 mov ecx,len ;/* 3rd arg: extent len */
139 not eax ;/*> c = ~crc; */
140
141 #ifndef NO_UNROLLED_LOOPS
142 # ifndef NO_32_BIT_LOADS
143 test ecx,ecx
144 je bail
145 align_loop:
146 test esi,3 ;/* align buf pointer on next */
147 jz aligned_now ;/* dword boundary */
148 }
149 Do_CRC_byte ;
150 __asm {
151 dec ecx
152 jnz align_loop
153 aligned_now:
154 # endif /* !NO_32_BIT_LOADS */
155 mov edx,ecx ;/* save len in edx */
156 and edx,000000007H ;/* edx = len % 8 */
157 shr ecx,3 ;/* ecx = len / 8 */
158 jz No_Eights
159 ; align loop head at start of 486 internal cache line !!
160 align 16
161 Next_Eight:
162 }
163 # ifndef NO_32_BIT_LOADS
164 Do_CRC_dword ;
165 Do_CRC_dword ;
166 # else /* NO_32_BIT_LOADS */
167 Do_CRC_byte ;
168 Do_CRC_byte ;
169 Do_CRC_byte ;
170 Do_CRC_byte ;
171 Do_CRC_byte ;
172 Do_CRC_byte ;
173 Do_CRC_byte ;
174 Do_CRC_byte ;
175 # endif /* ?NO_32_BIT_LOADS */
176 __asm {
177 dec ecx
178 jnz Next_Eight
179 No_Eights:
180 mov ecx,edx
181
182 #endif /* NO_UNROLLED_LOOPS */
183 #ifndef NO_JECXZ_SUPPORT
184 jecxz bail ;/*> if (len) */
185 #else
186 test ecx,ecx ;/*> if (len) */
187 jz bail
188 #endif
189 ; align loop head at start of 486 internal cache line !!
190 align 16
191 loupe: ;/*> do { */
192 }
193 Do_CRC_byte ;/* c = CRC32(c, *buf++); */
194 __asm {
195 dec ecx ;/*> } while (--len); */
196 jnz loupe
197
198 bail: ;/*> } */
199 not eax ;/*> return ~c; */
200 fine:
201 pop ecx
202 pop edx
203 }
204 #ifdef NEED_RETURN
205 return _EAX;
206 #endif
207 }
208 #endif /* MSC_INLINE_ASM_32BIT_SUPPORT */
209 #if (defined(_MSC_VER) && _MSC_VER >= 700)
210 #if (defined(_M_IX86) && _M_IX86 >= 300)
211 /* Reenable missing return value warning */
212 # pragma warning( default : 4035 )
213 #endif
214 #endif
215 #endif /* !USE_ZLIB */