utils/Install/sfxzip/crc_i386.asm

   1 ; crc_i386.asm, optimized CRC calculation function for Zip and UnZip, not
   2 ; copyrighted by Paul Kienitz and Christian Spieler.  Last revised 25 Mar 98.
   3 ;
   4 ; Revised 06-Oct-96, Scott Field (sfield@microsoft.com)
   5 ;   fixed to assemble with masm by not using .model directive which makes
   6 ;   assumptions about segment alignment.  Also,
   7 ;   avoid using loop, and j[e]cxz where possible.  Use mov + inc, rather
   8 ;   than lodsb, and other misc. changes resulting in the following performance
   9 ;   increases:
  10 ;
  11 ;      unrolled loops                NO_UNROLLED_LOOPS
  12 ;      *8    >8      <8              *8      >8      <8
  13 ;
  14 ;      +54%  +42%    +35%            +82%    +52%    +25%
  15 ;
  16 ;   first item in each table is input buffer length, even multiple of 8
  17 ;   second item in each table is input buffer length, > 8
  18 ;   third item in each table is input buffer length, < 8
  19 ;
  20 ; Revised 02-Apr-97, Chr. Spieler, based on Rodney Brown (rdb@cmutual.com.au)
  21 ;   Incorporated Rodney Brown's 32-bit-reads optimization as found in the
  22 ;   UNIX AS source crc_i386.S. This new code can be disabled by defining
  23 ;   the macro symbol NO_32_BIT_LOADS.
  24 ;
  25 ; Revised 12-Oct-97, Chr. Spieler, based on Rodney Brown (rdb@cmutual.com.au)
  26 ;   Incorporated Rodney Brown's additional tweaks for 32-bit-optimized CPUs
  27 ;   (like the Pentium Pro, Pentium II, and probably some Pentium clones).
  28 ;   This optimization is controlled by the macro symbol __686 and is disabled
  29 ;   by default. (This default is based on the assumption that most users
  30 ;   do not yet work on a Pentium Pro or Pentium II machine ...)
  31 ;
  32 ; FLAT memory model assumed.
  33 ;
  34 ; The loop unrolling can be disabled by defining the macro NO_UNROLLED_LOOPS.
  35 ; This results in shorter code at the expense of reduced performance.
  36 ;
  37 ; Revised 25-Mar-98, Cosmin Truta (cosmint@cs.ubbcluj.ro)
  38 ;   Working without .model directive caused tasm32 version 5.0 to produce
  39 ;   bad object code. The optimized alignments can be optionally disabled
  40 ;   by defining NO_ALIGN, thus allowing to use .model flat. There is no need
  41 ;   to define this macro if using other version of tasm.
  42 ;
  43 ;==============================================================================
  44 ;
  45 ; Do NOT assemble this source if external crc32 routine from zlib gets used.
  46 ;
  47     IFNDEF USE_ZLIB
  48 ;
  49         .386p
  50         name    crc_i386
  51
  52     IFDEF NO_ALIGN
  53         .model flat
  54     ENDIF
  55
  56 extrn   _get_crc_table:near    ; ZCONST ulg near *get_crc_table(void);
  57
  58 ;
  59     IFNDEF NO_STD_STACKFRAME
  60         ; Use a `standard' stack frame setup on routine entry and exit.
  61         ; Actually, this option is set as default, because it results
  62         ; in smaller code !!
  63 STD_ENTRY       MACRO
  64                 push    ebp
  65                 mov     ebp,esp
  66         ENDM
  67
  68         Arg1    EQU     08H[ebp]
  69         Arg2    EQU     0CH[ebp]
  70         Arg3    EQU     10H[ebp]
  71
  72 STD_LEAVE       MACRO
  73                 pop     ebp
  74         ENDM
  75
  76     ELSE  ; NO_STD_STACKFRAME
  77
  78 STD_ENTRY       MACRO
  79         ENDM
  80
  81         Arg1    EQU     18H[esp]
  82         Arg2    EQU     1CH[esp]
  83         Arg3    EQU     20H[esp]
  84
  85 STD_LEAVE       MACRO
  86         ENDM
  87
  88     ENDIF ; ?NO_STD_STACKFRAME
  89
  90 ; These two (three) macros make up the loop body of the CRC32 cruncher.
  91 ; registers modified:
  92 ;   eax  : crc value "c"
  93 ;   esi  : pointer to next data byte (or dword) "buf++"
  94 ; registers read:
  95 ;   edi  : pointer to base of crc_table array
  96 ; scratch registers:
  97 ;   ebx  : index into crc_table array
  98 ;          (requires upper three bytes = 0 when __686 is undefined)
  99     IFNDEF  __686 ; optimize for 386, 486, Pentium
 100 Do_CRC  MACRO
 101                 mov     bl,al                ; tmp = c & 0xFF
 102                 shr     eax,8                ; c = (c >> 8)
 103                 xor     eax,[edi+ebx*4]      ;  ^ table[tmp]
 104         ENDM
 105     ELSE ; __686 : optimize for Pentium Pro, Pentium II and compatible CPUs
 106 Do_CRC  MACRO
 107                 movzx   ebx,al               ; tmp = c & 0xFF
 108                 shr     eax,8                ; c = (c >> 8)
 109                 xor     eax,[edi+ebx*4]      ;  ^ table[tmp]
 110         ENDM
 111     ENDIF ; ?__686
 112 Do_CRC_byte     MACRO
 113                 xor     al, byte ptr [esi]   ; c ^= *buf
 114                 inc     esi                  ; buf++
 115                 Do_CRC                       ; c = (c >> 8) ^ table[c & 0xFF]
 116         ENDM
 117     IFNDEF  NO_32_BIT_LOADS
 118 Do_CRC_dword    MACRO
 119                 xor     eax, dword ptr [esi] ; c ^= *(ulg *)buf
 120                 add     esi, 4               ; ((ulg *)buf)++
 121                 Do_CRC
 122                 Do_CRC
 123                 Do_CRC
 124                 Do_CRC
 125         ENDM
 126     ENDIF ; !NO_32_BIT_LOADS
 127
 128     IFNDEF NO_ALIGN
 129 _TEXT   segment use32 para public 'CODE'
 130     ELSE
 131 _TEXT   segment use32
 132     ENDIF
 133         assume  CS: _TEXT
 134
 135         public  _crc32
 136 _crc32          proc    near  ; ulg crc32(ulg crc, ZCONST uch *buf, extent len)
 137                 STD_ENTRY
 138                 push    edi
 139                 push    esi
 140                 push    ebx
 141                 push    edx
 142                 push    ecx
 143
 144                 mov     esi,Arg2             ; 2nd arg: uch *buf
 145                 sub     eax,eax              ;> if (!buf)
 146                 test    esi,esi              ;>   return 0;
 147                 jz      fine                 ;> else {
 148
 149                 call    _get_crc_table
 150                 mov     edi,eax
 151                 mov     eax,Arg1             ; 1st arg: ulg crc
 152     IFNDEF __686
 153                 sub     ebx,ebx              ; ebx=0; make bl usable as a dword
 154     ENDIF
 155                 mov     ecx,Arg3             ; 3rd arg: extent len
 156                 not     eax                  ;>   c = ~crc;
 157
 158     IFNDEF  NO_UNROLLED_LOOPS
 159     IFNDEF  NO_32_BIT_LOADS
 160                 test    ecx,ecx
 161                 je      bail
 162 align_loop:
 163                 test    esi,3                ; align buf pointer on next
 164                 jz      SHORT aligned_now    ;  dword boundary
 165                 Do_CRC_byte
 166                 dec     ecx
 167                 jnz     align_loop
 168 aligned_now:
 169     ENDIF ; !NO_32_BIT_LOADS
 170                 mov     edx,ecx              ; save len in edx
 171                 and     edx,000000007H       ; edx = len % 8
 172                 shr     ecx,3                ; ecx = len / 8
 173                 jz      SHORT No_Eights
 174     IFNDEF NO_ALIGN
 175 ; align loop head at start of 486 internal cache line !!
 176                 align   16
 177     ENDIF
 178 Next_Eight:
 179     IFNDEF  NO_32_BIT_LOADS
 180                 Do_CRC_dword
 181                 Do_CRC_dword
 182     ELSE ; NO_32_BIT_LOADS
 183                 Do_CRC_byte
 184                 Do_CRC_byte
 185                 Do_CRC_byte
 186                 Do_CRC_byte
 187                 Do_CRC_byte
 188                 Do_CRC_byte
 189                 Do_CRC_byte
 190                 Do_CRC_byte
 191     ENDIF ; ?NO_32_BIT_LOADS
 192                 dec     ecx
 193                 jnz     Next_Eight
 194 No_Eights:
 195                 mov     ecx,edx
 196
 197     ENDIF ; NO_UNROLLED_LOOPS
 198     IFNDEF  NO_JECXZ_SUPPORT
 199                 jecxz   bail                 ;>   if (len)
 200     ELSE
 201                 test    ecx,ecx              ;>   if (len)
 202                 jz      SHORT bail
 203     ENDIF
 204     IFNDEF NO_ALIGN
 205 ; align loop head at start of 486 internal cache line !!
 206                 align   16
 207     ENDIF
 208 loupe:                                       ;>     do {
 209                 Do_CRC_byte                  ;        c = CRC32(c, *buf++);
 210                 dec     ecx                  ;>     } while (--len);
 211                 jnz     loupe
 212
 213 bail:                                        ;> }
 214                 not     eax                  ;> return ~c;
 215 fine:
 216                 pop     ecx
 217                 pop     edx
 218                 pop     ebx
 219                 pop     esi
 220                 pop     edi
 221                 STD_LEAVE
 222                 ret
 223 _crc32          endp
 224
 225 _TEXT   ends
 226 ;
 227     ENDIF ; !USE_ZLIB
 228 ;
 229 end