gnu/usr.bin/gzip/match.S

/* match.s -- optional optimized asm version of longest match in deflate.c
 * Copyright (C) 1992-1993 Jean-loup Gailly
 * This is free software; you can redistribute it and/or modify it under the
 * terms of the GNU General Public License, see the file COPYING.
 *
 * The 68020 version has been written by Francesco Potorti` <pot@cnuce.cnr.it>
 * with adaptations by Carsten Steger <stegerc@informatik.tu-muenchen.de>,
 * Andreas Schwab <schwab@lamothe.informatik.uni-dortmund.de> and
 * Kristoffer Eriksson <ske@pkmab.se>
 */

/* $Id: match.S,v 0.14 1993/06/11 18:33:24 jloup Exp $ */

/* Preprocess with -DNO_UNDERLINE if your C compiler does not prefix
 * external symbols with an underline character '_'.
 */
#ifdef NO_UNDERLINE
#  define _prev             prev
#  define _window           window
#  define _match_start      match_start
#  define _prev_length      prev_length
#  define _good_match       good_match
#  define _nice_match       nice_match
#  define _strstart         strstart
#  define _max_chain_length max_chain_length

#  define _match_init       match_init
#  define _longest_match    longest_match
#endif

#ifdef DYN_ALLOC
  error: DYN_ALLOC not yet supported in match.s
#endif

#if defined(i386) || defined(_I386)

/* This version is for 386 Unix or OS/2 in 32 bit mode.
 * Warning: it uses the AT&T syntax: mov source,dest
 * This file is only optional. If you want to force the C version,
 * add -DNO_ASM to CFLAGS in Makefile and set OBJA to an empty string.
 * If you have reduced WSIZE in gzip.h, then change its value below.
 * This version assumes static allocation of the arrays (-DDYN_ALLOC not used).
 */

        .file   "match.S"

#define MAX_MATCH       258
#define MAX_MATCH2      $128 /* MAX_MATCH/2-1 */
#define MIN_MATCH       3
#define    WSIZE        $32768
#define MAX_DIST        WSIZE - MAX_MATCH - MIN_MATCH - 1

        .globl  _match_init
        .globl  _longest_match

        .text

_match_init:
        ret

/*-----------------------------------------------------------------------
 * Set match_start to the longest match starting at the given string and
 * return its length. Matches shorter or equal to prev_length are discarded,
 * in which case the result is equal to prev_length and match_start is
 * garbage.
 * IN assertions: cur_match is the head of the hash chain for the current
 *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
 */

_longest_match: /* int longest_match(cur_match) */

#define cur_match   20(%esp)
     /* return address */               /* esp+16 */
        push    %ebp                    /* esp+12 */
        push    %edi                    /* esp+8  */
        push    %esi                    /* esp+4  */
        push    %ebx                    /* esp    */

/*
 *      match        equ esi
 *      scan         equ edi
 *      chain_length equ ebp
 *      best_len     equ ebx
 *      limit        equ edx
 */
        mov     cur_match,%esi
        mov     _max_chain_length,%ebp /* chain_length = max_chain_length */
        mov     _strstart,%edi
        mov     %edi,%edx
        sub     MAX_DIST,%edx          /* limit = strstart-MAX_DIST */
        jae     limit_ok
        sub     %edx,%edx              /* limit = NIL */
limit_ok:
        add     $2+_window,%edi        /* edi = offset(window+strstart+2) */
        mov     _prev_length,%ebx      /* best_len = prev_length */
        movw    -3(%ebx,%edi),%ax      /* ax = scan[best_len-1..best_len] */
        movw    -2(%edi),%cx           /* cx = scan[0..1] */
        cmp     _good_match,%ebx       /* do we have a good match already? */
        jb      do_scan
        shr     $2,%ebp                /* chain_length >>= 2 */
        jmp     do_scan

        .align  4
long_loop:
/* at this point, edi == scan+2, esi == cur_match */
        movw    -3(%ebx,%edi),%ax       /* ax = scan[best_len-1..best_len] */
        movw     -2(%edi),%cx           /* cx = scan[0..1] */
short_loop:
/*
 * at this point, di == scan+2, si == cur_match,
 * ax = scan[best_len-1..best_len] and cx = scan[0..1]
 */
        and     WSIZE-1, %esi
        movw    _prev(%esi,%esi),%si    /* cur_match = prev[cur_match] */
                                        /* top word of esi is still 0 */
        cmp     %edx,%esi               /* cur_match <= limit ? */
        jbe     the_end
        dec     %ebp                    /* --chain_length */
        jz      the_end
do_scan:
        cmpw    _window-1(%ebx,%esi),%ax/* check match at best_len-1 */
        jne     short_loop
        cmpw    _window(%esi),%cx       /* check min_match_length match */
        jne     short_loop

        lea     _window+2(%esi),%esi    /* si = match */
        mov     %edi,%eax               /* ax = scan+2 */
        mov     MAX_MATCH2,%ecx         /* scan for at most MAX_MATCH bytes */
        rep;    cmpsw                   /* loop until mismatch */
        je      maxmatch                /* match of length MAX_MATCH? */
mismatch:
        movb    -2(%edi),%cl        /* mismatch on first or second byte? */
        subb    -2(%esi),%cl        /* cl = 0 if first bytes equal */
        xchg    %edi,%eax           /* edi = scan+2, eax = end of scan */
        sub     %edi,%eax           /* eax = len */
        sub     %eax,%esi           /* esi = cur_match + 2 + offset(window) */
        sub     $2+_window,%esi     /* esi = cur_match */
        subb    $1,%cl              /* set carry if cl == 0 (cannot use DEC) */
        adc     $0,%eax             /* eax = carry ? len+1 : len */
        cmp     %ebx,%eax           /* len > best_len ? */
        jle     long_loop
        mov     %esi,_match_start       /* match_start = cur_match */
        mov     %eax,%ebx               /* ebx = best_len = len */
        cmp     _nice_match,%eax        /* len >= nice_match ? */
        jl      long_loop
the_end:
        mov     %ebx,%eax               /* result = eax = best_len */
        pop     %ebx
        pop     %esi
        pop     %edi
        pop     %ebp
        ret
maxmatch:
        cmpsb
        jmp     mismatch

#else

/* ======================== 680x0 version ================================= */

#if defined(m68k)||defined(mc68k)||defined(__mc68000__)||defined(__MC68000__)
#  ifndef mc68000
#    define mc68000
#  endif
#endif

#if defined(__mc68020__) || defined(__MC68020__) || defined(sysV68)
#  ifndef mc68020
#    define mc68020
#  endif
#endif

#if defined(mc68020) || defined(mc68000)

#if (defined(mc68020) || defined(NeXT)) && !defined(UNALIGNED_OK)
#  define UNALIGNED_OK
#endif

#ifdef sysV68  /* Try Motorola Delta style */

#  define GLOBAL(symbol)        global  symbol
#  define TEXT                  text
#  define FILE(filename)        file    filename
#  define invert_maybe(src,dst) dst,src
#  define imm(data)             &data
#  define reg(register)         %register

#  define addl                  add.l
#  define addql                 addq.l
#  define blos                  blo.b
#  define bhis                  bhi.b
#  define bras                  bra.b
#  define clrl                  clr.l
#  define cmpmb                 cmpm.b
#  define cmpw                  cmp.w
#  define cmpl                  cmp.l
#  define lslw                  lsl.w
#  define lsrl                  lsr.l
#  define movel                 move.l
#  define movew                 move.w
#  define moveb                 move.b
#  define moveml                movem.l
#  define subl                  sub.l
#  define subw                  sub.w
#  define subql                 subq.l

#  define IndBase(bd,An)        (bd,An)
#  define IndBaseNdxl(bd,An,Xn) (bd,An,Xn.l)
#  define IndBaseNdxw(bd,An,Xn) (bd,An,Xn.w)
#  define predec(An)            -(An)
#  define postinc(An)           (An)+

#else /* default style (Sun 3, NeXT, Amiga, Atari) */

#  define GLOBAL(symbol)        .globl  symbol
#  define TEXT                  .text
#  define FILE(filename)        .even
#  define invert_maybe(src,dst) src,dst
#  if defined(sun) || defined(mc68k)
#    define imm(data)           #data
#  else
#    define imm(data)           \#data
#  endif
#  define reg(register)         register

#  define blos                  bcss
#  if defined(sun) || defined(mc68k)
#    define movel               movl
#    define movew               movw
#    define moveb               movb
#  endif
#  define IndBase(bd,An)        An@(bd)
#  define IndBaseNdxl(bd,An,Xn) An@(bd,Xn:l)
#  define IndBaseNdxw(bd,An,Xn) An@(bd,Xn:w)
#  define predec(An)            An@-
#  define postinc(An)           An@+

#endif  /* styles */

#define Best_Len        reg(d0)         /* unsigned */
#define Cur_Match       reg(d1)         /* Ipos */
#define Loop_Counter    reg(d2)         /* int */
#define Scan_Start      reg(d3)         /* unsigned short */
#define Scan_End        reg(d4)         /* unsigned short */
#define Limit           reg(d5)         /* IPos */
#define Chain_Length    reg(d6)         /* unsigned */
#define Scan_Test       reg(d7)
#define Scan            reg(a0)         /* *uch */
#define Match           reg(a1)         /* *uch */
#define Prev_Address    reg(a2)         /* *Pos */
#define Scan_Ini        reg(a3)         /* *uch */
#define Match_Ini       reg(a4)         /* *uch */
#define Stack_Pointer   reg(sp)

#define MAX_MATCH       258
#define MIN_MATCH       3
#define WSIZE           32768
#define MAX_DIST        (WSIZE - MAX_MATCH - MIN_MATCH - 1)

        GLOBAL  (_match_init)
        GLOBAL  (_longest_match)

        TEXT

        FILE    ("match.S")

_match_init:
        rts

/*-----------------------------------------------------------------------
 * Set match_start to the longest match starting at the given string and
 * return its length. Matches shorter or equal to prev_length are discarded,
 * in which case the result is equal to prev_length and match_start is
 * garbage.
 * IN assertions: cur_match is the head of the hash chain for the current
 *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
 */

/* int longest_match (cur_match) */

#ifdef UNALIGNED_OK
#  define pushreg       15928           /* d2-d6/a2-a4 */
#  define popreg        7292
#else
#  define pushreg       16184           /* d2-d7/a2-a4 */
#  define popreg        7420
#endif

_longest_match:
        movel   IndBase(4,Stack_Pointer),Cur_Match
        moveml  imm(pushreg),predec(Stack_Pointer)
        movel   _max_chain_length,Chain_Length
        movel   _prev_length,Best_Len
        movel   imm(_prev),Prev_Address
        movel   imm(_window+MIN_MATCH),Match_Ini
        movel   _strstart,Limit
        movel   Match_Ini,Scan_Ini
        addl    Limit,Scan_Ini
        subw    imm(MAX_DIST),Limit
        bhis    L__limit_ok
        clrl    Limit
L__limit_ok:
        cmpl    invert_maybe(_good_match,Best_Len)
        blos    L__length_ok
        lsrl    imm(2),Chain_Length
L__length_ok:
        subql   imm(1),Chain_Length
#ifdef UNALIGNED_OK
        movew   IndBase(-MIN_MATCH,Scan_Ini),Scan_Start
        movew   IndBaseNdxw(-MIN_MATCH-1,Scan_Ini,Best_Len),Scan_End
#else
        moveb   IndBase(-MIN_MATCH,Scan_Ini),Scan_Start
        lslw    imm(8),Scan_Start
        moveb   IndBase(-MIN_MATCH+1,Scan_Ini),Scan_Start
        moveb   IndBaseNdxw(-MIN_MATCH-1,Scan_Ini,Best_Len),Scan_End
        lslw    imm(8),Scan_End
        moveb   IndBaseNdxw(-MIN_MATCH,Scan_Ini,Best_Len),Scan_End
#endif
        bras    L__do_scan

L__long_loop:
#ifdef UNALIGNED_OK
        movew   IndBaseNdxw(-MIN_MATCH-1,Scan_Ini,Best_Len),Scan_End
#else
        moveb   IndBaseNdxw(-MIN_MATCH-1,Scan_Ini,Best_Len),Scan_End
        lslw    imm(8),Scan_End
        moveb   IndBaseNdxw(-MIN_MATCH,Scan_Ini,Best_Len),Scan_End
#endif

L__short_loop:
        lslw    imm(1),Cur_Match
        movew   IndBaseNdxl(0,Prev_Address,Cur_Match),Cur_Match
        cmpw    invert_maybe(Limit,Cur_Match)
        dbls    Chain_Length,L__do_scan
        bras    L__return

L__do_scan:
        movel   Match_Ini,Match
        addl    Cur_Match,Match
#ifdef UNALIGNED_OK
        cmpw    invert_maybe(IndBaseNdxw(-MIN_MATCH-1,Match,Best_Len),Scan_End)
        bne     L__short_loop
        cmpw    invert_maybe(IndBase(-MIN_MATCH,Match),Scan_Start)
        bne     L__short_loop
#else
        moveb   IndBaseNdxw(-MIN_MATCH-1,Match,Best_Len),Scan_Test
        lslw    imm(8),Scan_Test
        moveb   IndBaseNdxw(-MIN_MATCH,Match,Best_Len),Scan_Test
        cmpw    invert_maybe(Scan_Test,Scan_End)
        bne     L__short_loop
        moveb   IndBase(-MIN_MATCH,Match),Scan_Test
        lslw    imm(8),Scan_Test
        moveb   IndBase(-MIN_MATCH+1,Match),Scan_Test
        cmpw    invert_maybe(Scan_Test,Scan_Start)
        bne     L__short_loop
#endif

        movew   imm((MAX_MATCH-MIN_MATCH+1)-1),Loop_Counter
        movel   Scan_Ini,Scan
L__scan_loop:
        cmpmb   postinc(Match),postinc(Scan)
        dbne    Loop_Counter,L__scan_loop

        subl    Scan_Ini,Scan
        addql   imm(MIN_MATCH-1),Scan
        cmpl    invert_maybe(Best_Len,Scan)
        bls     L__short_loop
        movel   Scan,Best_Len
        movel   Cur_Match,_match_start
        cmpl    invert_maybe(_nice_match,Best_Len)
        blos    L__long_loop
L__return:
        moveml  postinc(Stack_Pointer),imm(popreg)
        rts

#else
 error: this asm version is for 386 or 680x0 only
#endif /* mc68000 || mc68020 */
#endif /* i386 || _I386   */