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/* some routines for double-cell arithmetic
only used if BUGGY_LONG_LONG
Copyright (C) 1996 Free Software Foundation, Inc.
* Copyright (C) 1995 Dirk Uwe Zoller
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
This has been adapted from pfe-0.9.14
*/
#include "config.h"
#include "forth.h"
/* !! a bit machine dependent */
#define HALFCELL_BITS (CELL_BITS/2)
#define UH(x) (((UCell)(x))>>HALFCELL_BITS)
#define LH(x) ((x)&((~(UCell)0)>>HALFCELL_BITS))
#define L2U(x) (((UCell)(x))<<HALFCELL_BITS)
#define HIGHBIT(x) (((UCell)(x))>>(CELL_BITS-1))
#define UD2D(ud) ({UDCell _ud=(ud); (DCell){_ud.hi,_ud.lo};})
#define D2UD(d) ({DCell _d=(d); (UDCell){_d.hi,_d.lo};})
DCell dnegate(DCell d1)
{
DCell res;
res.hi = ~d1.hi + (d1.lo==0);
res.lo = -d1.lo;
return res;
}
UDCell ummul (UCell a, UCell b) /* unsigned multiply, mixed precision */
{
UDCell res;
UCell m,ul,lu,uu;
res.lo = a*b;
/*ll = LH(a)*LH(b); dead code */
ul = UH(a)*LH(b);
lu = LH(a)*UH(b);
uu = UH(a)*UH(b);
m = ul+lu;
res.hi = (uu
+ L2U(m<ul) /* the carry of ul+lu */
+ UH(m)
+ (res.lo<L2U(m)) /* the carry of ll+L2U(m) */
);
return res;
}
DCell mmul (Cell a, Cell b) /* signed multiply, mixed precision */
{
DCell res;
res = UD2D(ummul (a, b));
if (a < 0)
res.hi -= b;
if (b < 0)
res.hi -= a;
return res;
}
UDCell umdiv (UDCell u, UCell v)
/* Divide unsigned double by single precision using shifts and subtracts.
Return quotient in lo, remainder in hi. */
{
int i = CELL_BITS, c = 0;
UCell q = 0, h = u.hi, l = u.lo;
UDCell res;
for (;;)
{
if (c || h >= v)
{
q++;
h -= v;
}
if (--i < 0)
break;
c = HIGHBIT (h);
h <<= 1;
h += HIGHBIT (l);
l <<= 1;
q <<= 1;
}
res.hi = h;
res.lo = q;
return res;
}
DCell smdiv (DCell num, Cell denom) /* symmetric divide procedure, mixed prec */
{
DCell res;
Cell numsign=num.hi;
Cell denomsign=denom;
if (numsign < 0)
num = dnegate (num);
if (denomsign < 0)
denom = -denom;
res = UD2D(umdiv (D2UD(num), denom));
if ((numsign^denomsign)<0)
res.lo = -res.lo;
if (numsign<0)
res.hi = -res.hi;
return res;
}
DCell fmdiv (DCell num, Cell denom) /* floored divide procedure, mixed prec */
{
/* I have this technique from Andrew Haley */
DCell res;
Cell denomsign=denom;
if (denom < 0) {
denom = -denom;
num = dnegate(num);
}
if (num.hi < 0)
num.hi += denom;
res = UD2D(umdiv(D2UD(num),denom));
if (denomsign<0)
res.hi = -res.hi;
return res;
}
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