utils/Install/packzip/crc_i386.S

   1 /*
   2  * crc_i386.S, optimized CRC calculation function for Zip and UnZip, not
   3  * copyrighted by Paul Kienitz and Christian Spieler.  Last revised 12 Oct 97.
   4  *
   5  * GRR 961110:  incorporated Scott Field optimizations from win32/crc_i386.asm
   6  *              => overall 6% speedup in "unzip -tq" on 9MB zipfile (486-66)
   7  *
   8  * SPC 970402:  revised for Rodney Brown's optimizations (32-bit-wide
   9  *              aligned reads for most of the data from buffer), can be
  10  *              disabled by defining the macro NO_32_BIT_LOADS
  11  *
  12  * SPC 971012:  added Rodney Brown's additional tweaks for 32-bit-optimized
  13  *              CPUs (like the Pentium Pro, Pentium II, and probably some
  14  *              Pentium clones). This optimization is controlled by the
  15  *              preprocessor switch "__686" and is disabled by default.
  16  *              (This default is based on the assumption that most users
  17  *              do not yet work on a Pentium Pro or Pentium II machine ...)
  18  *
  19  * FLAT memory model assumed.  Calling interface:
  20  *   - args are pushed onto the stack from right to left,
  21  *   - return value is given in the EAX register,
  22  *   - all other registers (with exception of EFLAGS) are preserved. (With
  23  *     GNU C 2.7.x, %edx and %ecx are `scratch' registers, but preserving
  24  *     them nevertheless adds only 4 single byte instructions.)
  25  *
  26  * This source generates the function
  27  * ulg crc32(ulg crc, ZCONST uch *buf, ulg len).
  28  *
  29  * The loop unrolling can be disabled by defining the macro NO_UNROLLED_LOOPS.
  30  * This results in shorter code at the expense of reduced performance.
  31  */
  32
  33 /* This file is NOT used in conjunction with zlib. */
  34 #ifndef USE_ZLIB
  35
  36 /* Preprocess with -DNO_UNDERLINE if your C compiler does not prefix
  37  * external symbols with an underline character '_'.
  38  */
  39 #if defined(NO_UNDERLINE) || defined(__ELF__)
  40 #  define _crc32            crc32
  41 #  define _get_crc_table    get_crc_table
  42 #endif
  43 /* Use 16-byte alignment if your assembler supports it. Warning: gas
  44  * uses a log(x) parameter (.align 4 means 16-byte alignment). On SVR4
  45  * the parameter is a number of bytes.
  46  */
  47 #ifndef ALIGNMENT
  48 #  define ALIGNMENT .align 4,0x90
  49 #endif
  50
  51 #if defined(i386) || defined(_i386) || defined(_I386) || defined(__i386)
  52
  53 /* This version is for 386 Unix, OS/2, MSDOS in 32 bit mode (gcc & gas).
  54  * Warning: it uses the AT&T syntax: mov source,dest
  55  * This file is only optional. If you want to use the C version,
  56  * remove -DASM_CRC from CFLAGS in Makefile and set OBJA to an empty string.
  57  */
  58
  59                 .file   "crc_i386.S"
  60
  61 #if defined(NO_STD_STACKFRAME) && defined(USE_STD_STACKFRAME)
  62 #  undef USE_STACKFRAME
  63 #else
  64    /* The default is to use standard stack frame entry, because it
  65     * results in smaller code!
  66     */
  67 #  ifndef USE_STD_STACKFRAME
  68 #    define USE_STD_STACKFRAME
  69 #  endif
  70 #endif
  71
  72 #ifdef USE_STD_STACKFRAME
  73 #  define _STD_ENTRY    pushl   %ebp ; movl   %esp,%ebp
  74 #  define arg1  8(%ebp)
  75 #  define arg2  12(%ebp)
  76 #  define arg3  16(%ebp)
  77 #  define _STD_LEAVE    popl    %ebp
  78 #else /* !USE_STD_STACKFRAME */
  79 #  define _STD_ENTRY
  80 #  define arg1  24(%esp)
  81 #  define arg2  28(%esp)
  82 #  define arg3  32(%esp)
  83 #  define _STD_LEAVE
  84 #endif /* ?USE_STD_STACKFRAME */
  85
  86 /*
  87  * These two (three) macros make up the loop body of the CRC32 cruncher.
  88  * registers modified:
  89  *   eax  : crc value "c"
  90  *   esi  : pointer to next data byte (or lword) "buf++"
  91  * registers read:
  92  *   edi  : pointer to base of crc_table array
  93  * scratch registers:
  94  *   ebx  : index into crc_table array
  95  *          (requires upper three bytes = 0 when __686 is undefined)
  96  */
  97 #ifndef __686   /* optimize for 386, 486, Pentium */
  98 #define Do_CRC          /* c = (c >> 8) ^ table[c & 0xFF] */\
  99                 movb    %al, %bl                ;/* tmp = c & 0xFF  */\
 100                 shrl    $8, %eax                ;/* c = (c >> 8)    */\
 101                 xorl    (%edi, %ebx, 4), %eax   ;/* c ^= table[tmp] */
 102 #else   /* __686 : optimize for Pentium Pro and compatible CPUs */
 103 #define Do_CRC          /* c = (c >> 8) ^ table[c & 0xFF] */\
 104                 movzbl  %al, %ebx               ;/* tmp = c & 0xFF  */\
 105                 shrl    $8, %eax                ;/* c = (c >> 8)    */\
 106                 xorl    (%edi, %ebx, 4), %eax   ;/* c ^=table[tmp]  */
 107 #endif  /* ?__686 */
 108
 109 #define Do_CRC_byte     /* c = (c >> 8) ^ table[(c^*buf++)&0xFF] */\
 110                 xorb    (%esi), %al     ;/* c ^= *buf  */\
 111                 incl    %esi            ;/* buf++      */\
 112                 Do_CRC
 113
 114 #ifndef  NO_32_BIT_LOADS
 115 #define Do_CRC_lword \
 116                 xorl    (%esi), %eax    ;/* c ^= *(ulg *)buf */\
 117                 addl    $4, %esi        ;/* ((ulg *)buf)++   */\
 118                 Do_CRC \
 119                 Do_CRC \
 120                 Do_CRC \
 121                 Do_CRC
 122 #endif  /* !NO_32_BIT_LOADS */
 123
 124
 125                 .text
 126
 127                 .globl  _crc32
 128
 129 _crc32:                         /* ulg crc32(ulg crc, uch *buf, extent len) */
 130                 _STD_ENTRY
 131                 pushl   %edi
 132                 pushl   %esi
 133                 pushl   %ebx
 134                 pushl   %edx
 135                 pushl   %ecx
 136
 137                 movl    arg2, %esi           /* 2nd arg: uch *buf            */
 138                 subl    %eax, %eax           /* > if (!buf)                  */
 139                 testl   %esi, %esi           /* >   return 0;                */
 140                 jz      .L_fine              /* > else {                     */
 141                 call    _get_crc_table
 142                 movl    %eax, %edi
 143                 movl    arg1, %eax           /* 1st arg: ulg crc             */
 144 #ifndef __686
 145                 subl    %ebx, %ebx           /* ebx=0; bl usable as dword    */
 146 #endif
 147                 movl    arg3, %ecx           /* 3rd arg: extent len          */
 148                 notl    %eax                 /* >   c = ~crc;                */
 149
 150 #ifndef  NO_UNROLLED_LOOPS
 151 #  ifndef  NO_32_BIT_LOADS
 152                 testl   %ecx, %ecx
 153                 jz      .L_bail
 154                 /* Assert now have positive length */
 155 .L_align_loop:
 156                 testl   $3, %esi        /* Align buf on lword boundary */
 157                 jz      .L_aligned_now
 158                 Do_CRC_byte
 159                 decl    %ecx
 160                 jnz     .L_align_loop
 161 .L_aligned_now:
 162 #  endif  /* !NO_32_BIT_LOADS */
 163                 movl    %ecx, %edx           /* save len in edx          */
 164                 andl    $7, %edx             /* edx = len % 8            */
 165                 shrl    $3, %ecx             /* ecx = len / 8            */
 166                 jz      .L_No_Eights
 167 /*  align loop head at start of 486 internal cache line !! */
 168                 ALIGNMENT
 169 .L_Next_Eight:
 170 #  ifndef NO_32_BIT_LOADS
 171                  /* Do_CRC_lword */
 172                  xorl    (%esi), %eax    ;/* c ^= *(ulg *)buf */
 173                  addl    $4, %esi        ;/* ((ulg *)buf)++   */
 174                  Do_CRC
 175                  Do_CRC
 176                  Do_CRC
 177                  Do_CRC
 178                  /* Do_CRC_lword */
 179                  xorl    (%esi), %eax    ;/* c ^= *(ulg *)buf */
 180                  addl    $4, %esi        ;/* ((ulg *)buf)++   */
 181                  Do_CRC
 182                  Do_CRC
 183                  Do_CRC
 184                  Do_CRC
 185 #  else   /* NO_32_BIT_LOADS */
 186                  Do_CRC_byte
 187                  Do_CRC_byte
 188                  Do_CRC_byte
 189                  Do_CRC_byte
 190                  Do_CRC_byte
 191                  Do_CRC_byte
 192                  Do_CRC_byte
 193                  Do_CRC_byte
 194 #  endif  /* ?NO_32_BIT_LOADS */
 195                 decl    %ecx
 196                 jnz     .L_Next_Eight
 197
 198 .L_No_Eights:
 199                 movl    %edx, %ecx
 200 #endif /* NO_UNROLLED_LOOPS */
 201
 202 #ifndef NO_JECXZ_SUPPORT
 203                 jecxz   .L_bail              /* > if (len)                   */
 204 #else
 205                 testl   %ecx, %ecx           /* > if (len)                   */
 206                 jz      .L_bail
 207 #endif
 208 /* align loop head at start of 486 internal cache line !! */
 209                 ALIGNMENT
 210 .L_loupe:                                    /* >   do {                     */
 211                  Do_CRC_byte                 /*       c = CRC32(c, *buf++);  */
 212                 decl    %ecx                 /* >   } while (--len);         */
 213                 jnz     .L_loupe
 214
 215 .L_bail:                                     /* > }                          */
 216                 notl    %eax                 /* > return ~c;                 */
 217 .L_fine:
 218                 popl    %ecx
 219                 popl    %edx
 220                 popl    %ebx
 221                 popl    %esi
 222                 popl    %edi
 223                 _STD_LEAVE
 224                 ret
 225
 226 #else
 227  error: this asm version is for 386 only
 228 #endif /* i386 || _i386 || _I386 || __i386 */
 229
 230 #endif /* !USE_ZLIB */