mullong.c

来自「sdcc是为51等小型嵌入式cpu设计的c语言编译器支持数种不同类型的cpu」· C语言 代码 · 共 119 行

/*-------------------------------------------------------------------------
   _mullong.c - routine for multiplication of 32 bit (unsigned) long

             Written By -  Jean Louis VERN [e-mail] (1999)
             Written By -  Sandeep Dutta . [e-mail] (1999)
	     Modified for pic16 port by - Vangelis Rokas, [e-mail] (2004)

   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, 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 program; if not, write to the Free Software
   Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

   In other words, you are welcome to use, share and improve this program.
   You are forbidden to forbid anyone else to use, share and improve
   what you give them.   Help stamp out software-hoarding!
-------------------------------------------------------------------------*/

#include <sdcc-lib.h>

union bil {
        struct {unsigned char b0,b1,b2,b3 ;} b;
        struct {unsigned short lo,hi ;} i;
        unsigned long l;
        struct { unsigned char b0; unsigned short i12; unsigned char b3;} bi;
};

#define bcast(x) ((union bil near  *)&(x))

/*
                     3   2   1   0
       X             3   2   1   0
       ----------------------------
                   0.3 0.2 0.1 0.0
               1.3 1.2 1.1 1.0
           2.3 2.2 2.1 2.0
       3.3 3.2 3.1 3.0
       ----------------------------
                  |3.3|1.3|0.2|0.0|   A
                    |2.3|0.3|0.1|     B
                    |3.2|1.2|1.0|     C
                      |2.2|1.1|       D
                      |3.1|2.0|       E
                        |2.1|         F
                        |3.0|         G
                          |-------> only this side 32 x 32 -> 32
*/

long _mullong (long a, long b) _IL_REENTRANT
{
#if 0
        union bil t;

        t.i.hi = bcast(a)->b.b0 * bcast(b)->b.b2;       // A
        t.i.lo = bcast(a)->b.b0 * bcast(b)->b.b0;       // A
        t.b.b3 += bcast(a)->b.b3 *
                                  bcast(b)->b.b0;       // G
        t.b.b3 += bcast(a)->b.b2 *
                                  bcast(b)->b.b1;       // F
        t.i.hi += bcast(a)->b.b2 * bcast(b)->b.b0;      // E <- b lost in .lst
        // bcast(a)->i.hi is free !
        t.i.hi += bcast(a)->b.b1 * bcast(b)->b.b1;      // D <- b lost in .lst

        bcast(a)->bi.b3 = bcast(a)->b.b1 *
                                          bcast(b)->b.b2;
        bcast(a)->bi.i12 = bcast(a)->b.b1 *
                           bcast(b)->b.b0;              // C

        bcast(b)->bi.b3 = bcast(a)->b.b0 *
                                          bcast(b)->b.b3;
        bcast(b)->bi.i12 = bcast(a)->b.b0 *
                           bcast(b)->b.b1;              // B
        bcast(b)->bi.b0 = 0;                            // B
        bcast(a)->bi.b0 = 0;                            // C
        t.l += a;

        return t.l + b;
#else

  union bil x;
  union bil y;
  union bil t;
  union bil t1, t2;
  
	x.l = a;
	y.l = b;
	
	t.i.hi = x.b.b0 * y.b.b2;
	t.i.lo = x.b.b0 * y.b.b0;
	
	t.b.b3 += x.b.b3 * y.b.b0;
	t.b.b3 += x.b.b2 * y.b.b1;
	
	t.i.hi += x.b.b2 * y.b.b0;
	t.i.hi += x.b.b1 * y.b.b1;
	
	t1.bi.b3 = x.b.b1 * y.b.b2;
	t1.bi.i12 = x.b.b1 * y.b.b0;
	
	t2.bi.b3 = x.b.b0 * y.b.b3;
	t2.bi.i12 = x.b.b0 * y.b.b1;
	
	t1.bi.b0 = 0;
	t2.bi.b0 = 0;
	t.l += t1.l;

  return (t.l + t2.l);

#endif
}