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Annotation of gforth/engine/dblsub.c, revision 1.1

1.1     ! anton       1: /* some routines for double-cell arithmetic
        !             2:    only used if BUGGY_LONG_LONG
        !             3: 
        !             4:    Copyright (C) 1996 Free Software Foundation, Inc.
        !             5:  * Copyright (C) 1995  Dirk Uwe Zoller
        !             6:  *
        !             7:  * This library is free software; you can redistribute it and/or
        !             8:  * modify it under the terms of the GNU Library General Public
        !             9:  * License as published by the Free Software Foundation; either
        !            10:  * version 2 of the License, or (at your option) any later version.
        !            11:  *
        !            12:  * This library is distributed in the hope that it will be useful,
        !            13:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
        !            14:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
        !            15:  * See the GNU Library General Public License for more details.
        !            16:  *
        !            17:  * You should have received a copy of the GNU Library General Public
        !            18:  * License along with this library; if not, write to the Free
        !            19:  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
        !            20: 
        !            21:  This has been adapted from pfe-0.9.14
        !            22:  */
        !            23: 
        !            24: #include "config.h"
        !            25: #include "forth.h"
        !            26: 
        !            27: /* !! a bit machine dependent */
        !            28: #define HALFCELL_BITS  (CELL_BITS/2)
        !            29: #define UH(x)          (((UCell)(x))>>HALFCELL_BITS)
        !            30: #define LH(x)          ((x)&((~(UCell)0)>>HALFCELL_BITS))
        !            31: #define L2U(x)         (((UCell)(x))<<HALFCELL_BITS)
        !            32: #define HIGHBIT(x)     (((UCell)(x))>>(CELL_BITS-1))
        !            33: #define UD2D(ud)       ({UDCell _ud=(ud); (DCell){_ud.hi,_ud.lo};})
        !            34: #define D2UD(d)                ({DCell _d=(d); (UDCell){_d.hi,_d.lo};})
        !            35: 
        !            36: DCell dnegate(DCell d1)
        !            37: {
        !            38:   DCell res;
        !            39: 
        !            40:   res.hi = ~d1.hi + (d1.lo==0);
        !            41:   res.lo = -d1.lo;
        !            42:   return res;
        !            43: }
        !            44: 
        !            45: UDCell ummul (UCell a, UCell b)        /* unsigned multiply, mixed precision */
        !            46: {
        !            47:   UDCell res;
        !            48:   UCell m,ul,lu,uu;
        !            49: 
        !            50:   res.lo = a*b;
        !            51: /*ll = LH(a)*LH(b); dead code */
        !            52:   ul = UH(a)*LH(b);
        !            53:   lu = LH(a)*UH(b);
        !            54:   uu = UH(a)*UH(b);
        !            55:   m = ul+lu;
        !            56:   res.hi = (uu
        !            57:            + L2U(m<ul) /* the carry of ul+lu */
        !            58:            + UH(m)
        !            59:            + (res.lo<L2U(m)) /* the carry of ll+L2U(m) */
        !            60:            );
        !            61:   return res;
        !            62: }
        !            63: 
        !            64: DCell mmul (Cell a, Cell b)            /* signed multiply, mixed precision */
        !            65: {
        !            66:   DCell res;
        !            67: 
        !            68:   res = UD2D(ummul (a, b));
        !            69:   if (a < 0)
        !            70:     res.hi -= b;
        !            71:   if (b < 0)
        !            72:     res.hi -= a;
        !            73:   return res;
        !            74: }
        !            75: 
        !            76: UDCell umdiv (UDCell u, UCell v)
        !            77: /* Divide unsigned double by single precision using shifts and subtracts.
        !            78:    Return quotient in lo, remainder in hi. */
        !            79: {
        !            80:   int i = CELL_BITS, c = 0;
        !            81:   UCell q = 0, h = u.hi, l = u.lo;
        !            82:   UDCell res;
        !            83: 
        !            84:   for (;;)
        !            85:     {
        !            86:       if (c || h >= v)
        !            87:        {
        !            88:          q++;
        !            89:          h -= v;
        !            90:        }
        !            91:       if (--i < 0)
        !            92:        break;
        !            93:       c = HIGHBIT (h);
        !            94:       h <<= 1;
        !            95:       h += HIGHBIT (l);
        !            96:       l <<= 1;
        !            97:       q <<= 1;
        !            98:     }
        !            99:   res.hi = h;
        !           100:   res.lo = q;
        !           101:   return res;
        !           102: }
        !           103: 
        !           104: DCell smdiv (DCell num, Cell denom)    /* symmetric divide procedure, mixed prec */
        !           105: {
        !           106:   DCell res;
        !           107:   Cell numsign=num.hi;
        !           108:   Cell denomsign=denom;
        !           109: 
        !           110:   if (numsign < 0)
        !           111:     num = dnegate (num);
        !           112:   if (denomsign < 0)
        !           113:     denom = -denom;
        !           114:   res = UD2D(umdiv (D2UD(num), denom));
        !           115:   if ((numsign^denomsign)<0)
        !           116:     res.lo = -res.lo;
        !           117:   if (numsign<0)
        !           118:     res.hi = -res.hi;
        !           119:   return res;
        !           120: }
        !           121: 
        !           122: DCell fmdiv (DCell num, Cell denom)    /* floored divide procedure, mixed prec */
        !           123: {
        !           124:   /* I have this technique from Andrew Haley */
        !           125:   DCell res;
        !           126:   Cell denomsign=denom;
        !           127: 
        !           128:   if (denom < 0) {
        !           129:     denom = -denom;
        !           130:     num = dnegate(num);
        !           131:   }
        !           132:   if (num.hi < 0)
        !           133:     num.hi += denom;
        !           134:   res = UD2D(umdiv(D2UD(num),denom));
        !           135:   if (denomsign<0)
        !           136:     res.hi = -res.hi;
        !           137:   return res;
        !           138: }