amiga/match.a

   1 ; match.a -- optional optimized asm version of longest match in deflate.c
   2 ; Copyright (C) 1992-1993 Jean-loup Gailly
   3 ; This is free software; you can redistribute it and/or modify it under the
   4 ; terms of the GNU General Public License, see the file COPYING.
   5
   6 ; Adapted for the Amiga by Carsten Steger <stegerc@informatik.tu-muenchen.de>
   7 ; using the code in match.S.
   8 ; The major change in this code consists of removing all unaligned
   9 ; word accesses, because they cause 68000-based Amigas to crash.
  10 ; For maximum speed, UNALIGNED_OK can be defined in Makefile.sasc.
  11 ; The program will then only run on 68020-based Amigas, though.
  12 ;
  13 ; This code will run with registerized parameters too, unless SAS
  14 ; changes parameter passing conventions between new releases of SAS/C.
  15
  16
  17 Cur_Match       reg     d0      ; Must be in d0!
  18 Best_Len        reg     d1
  19 Loop_Counter    reg     d2
  20 Scan_Start      reg     d3
  21 Scan_End        reg     d4
  22 Limit           reg     d5
  23 Chain_Length    reg     d6
  24 Scan_Test       reg     d7
  25 Scan            reg     a0
  26 Match           reg     a1
  27 Prev_Address    reg     a2
  28 Scan_Ini        reg     a3
  29 Match_Ini       reg     a4
  30
  31 MAX_MATCH       equ     258
  32 MIN_MATCH       equ     3
  33 WSIZE           equ     32768
  34 MAX_DIST        equ     WSIZE-MAX_MATCH-MIN_MATCH-1
  35
  36
  37         xref    _max_chain_length
  38         xref    _prev_length
  39         xref    _prev
  40         xref    _window
  41         xref    _strstart
  42         xref    _good_match
  43         xref    _match_start
  44         xref    _nice_match
  45
  46
  47         section match,code
  48
  49         xdef    _match_init
  50         xdef    @match_init
  51         xdef    _longest_match
  52         xdef    @longest_match
  53
  54
  55 _match_init:
  56 @match_init:
  57         rts
  58
  59
  60 _longest_match:
  61         move.l  4(sp),Cur_Match
  62 @longest_match:
  63         ifd     UNALIGNED_OK
  64         movem.l d2-d6/a2-a4,-(sp)
  65         else
  66         movem.l d2-d7/a2-a4,-(sp)
  67         endc
  68         move.l  _max_chain_length,Chain_Length
  69         move.l  _prev_length,Best_Len
  70         lea     _prev,Prev_Address
  71         lea     _window+MIN_MATCH,Match_Ini
  72         move.l  _strstart,Limit
  73         move.l  Match_Ini,Scan_Ini
  74         add.l   Limit,Scan_Ini
  75         subi.w  #MAX_DIST,Limit
  76         bhi.b   limit_ok
  77         moveq   #0,Limit
  78 limit_ok:
  79         cmp.l   _good_match,Best_Len
  80         bcs.b   length_ok
  81         lsr.l   #2,Chain_Length
  82 length_ok:
  83         subq.l  #1,Chain_Length
  84
  85         ifd     UNALIGNED_OK
  86
  87         move.w  -MIN_MATCH(Scan_Ini),Scan_Start
  88         move.w  -MIN_MATCH-1(Scan_Ini,Best_Len),Scan_End
  89
  90         else
  91
  92         move.b  -MIN_MATCH(Scan_Ini),Scan_Start
  93         lsl.w   #8,Scan_Start
  94         move.b  -MIN_MATCH+1(Scan_Ini),Scan_Start
  95         move.b  -MIN_MATCH-1(Scan_Ini,Best_Len),Scan_End
  96         lsl.w   #8,Scan_End
  97         move.b  -MIN_MATCH(Scan_Ini,Best_Len),Scan_End
  98
  99         endc
 100
 101         bra.b   do_scan
 102
 103 long_loop:
 104
 105         ifd     UNALIGNED_OK
 106
 107         move.w  -MIN_MATCH-1(Scan_Ini,Best_Len),Scan_End
 108
 109         else
 110
 111         move.b  -MIN_MATCH-1(Scan_Ini,Best_Len),Scan_End
 112         lsl.w   #8,Scan_End
 113         move.b  -MIN_MATCH(Scan_Ini,Best_Len),Scan_End
 114
 115         endc
 116
 117 short_loop:
 118         lsl.w   #1,Cur_Match
 119         move.w  0(Prev_Address,Cur_Match),Cur_Match
 120         cmp.w   Limit,Cur_Match
 121         dbls    Chain_Length,do_scan
 122         bra.b   return
 123
 124 do_scan:
 125         move.l  Match_Ini,Match
 126         add.l   Cur_Match,Match
 127
 128         ifd     UNALIGNED_OK
 129
 130         cmp.w   -MIN_MATCH-1(Match,Best_Len),Scan_End
 131         bne.b   short_loop
 132         cmp.w   -MIN_MATCH(Match),Scan_Start
 133         bne.b   short_loop
 134
 135         else
 136
 137         move.b  -MIN_MATCH-1(Match,Best_Len),Scan_Test
 138         lsl.w   #8,Scan_Test
 139         move.b  -MIN_MATCH(Match,Best_Len),Scan_Test
 140         cmp.w   Scan_Test,Scan_End
 141         bne.b   short_loop
 142         move.b  -MIN_MATCH(Match),Scan_Test
 143         lsl.w   #8,Scan_Test
 144         move.b  -MIN_MATCH+1(Match),Scan_Test
 145         cmp.w   Scan_Test,Scan_Start
 146         bne.b   short_loop
 147
 148         endc
 149
 150         move.w  #(MAX_MATCH-MIN_MATCH),Loop_Counter
 151         move.l  Scan_Ini,Scan
 152 scan_loop:
 153         cmpm.b  (Match)+,(Scan)+
 154         dbne    Loop_Counter,scan_loop
 155
 156         sub.l   Scan_Ini,Scan
 157         addq.l  #(MIN_MATCH-1),Scan
 158         cmp.l   Best_Len,Scan
 159         bls.b   short_loop
 160         move.l  Scan,Best_Len
 161         move.l  Cur_Match,_match_start
 162         cmp.l   _nice_match,Best_Len
 163         bcs.b   long_loop
 164 return:
 165         move.l  Best_Len,d0
 166         ifd     UNALIGNED_OK
 167         movem.l (sp)+,d2-d6/a2-a4
 168         else
 169         movem.l (sp)+,d2-d7/a2-a4
 170         endc
 171         rts
 172
 173         end