gcc/ada/arit64.c

   1 /****************************************************************************
   2  *                                                                          *
   3  *                         GNAT COMPILER COMPONENTS                         *
   4  *                                                                          *
   5  *                             A R I T 6 4 . C                              *
   6  *                                                                          *
   7  *                          C Implementation File                           *
   8  *                                                                          *
   9  *         Copyright (C) 2009, Free Software Foundation, Inc.               *
  10  *                                                                          *
  11  * GNAT is free software;  you can  redistribute it  and/or modify it under *
  12  * terms of the  GNU General Public License as published  by the Free Soft- *
  13  * ware  Foundation;  either version 3,  or (at your option) any later ver- *
  14  * sion.  GNAT is distributed in the hope that it will be useful, but WITH- *
  15  * OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY *
  16  * or FITNESS FOR A PARTICULAR PURPOSE.                                     *
  17  *                                                                          *
  18  * As a special exception under Section 7 of GPL version 3, you are granted *
  19  * additional permissions described in the GCC Runtime Library Exception,   *
  20  * version 3.1, as published by the Free Software Foundation.               *
  21  *                                                                          *
  22  * You should have received a copy of the GNU General Public License and    *
  23  * a copy of the GCC Runtime Library Exception along with this program;     *
  24  * see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    *
  25  * <http://www.gnu.org/licenses/>.                                          *
  26  *                                                                          *
  27  * GNAT was originally developed  by the GNAT team at  New York University. *
  28  * Extensive contributions were provided by Ada Core Technologies Inc.      *
  29  *                                                                          *
  30  ****************************************************************************/
  31
  32 extern void __gnat_rcheck_10(char *file, int line)
  33   __attribute__ ((__noreturn__));
  34
  35 long long int __gnat_mulv64 (long long int x, long long int y)
  36 {
  37   unsigned neg = (x >= 0) ^ (y >= 0);
  38   long long unsigned xa = x >= 0 ? (long long unsigned) x
  39                                  : -(long long unsigned) x;
  40   long long unsigned ya = y >= 0 ? (long long unsigned) y
  41                                  : -(long long unsigned) y;
  42   unsigned xhi = (unsigned) (xa >> 32);
  43   unsigned yhi = (unsigned) (ya >> 32);
  44   unsigned xlo = (unsigned) xa;
  45   unsigned ylo = (unsigned) ya;
  46   long long unsigned mid
  47     = xhi ? (long long unsigned) xhi * (long long unsigned) ylo
  48          : (long long unsigned) yhi * (long long unsigned) xlo;
  49   long long unsigned low = (long long unsigned) xlo * (long long unsigned) ylo;
  50
  51   if ((xhi && yhi) ||  mid + (low  >> 32) > 0x7fffffff + neg)
  52     __gnat_rcheck_10 (__FILE__, __LINE__);
  53
  54   low += ((long long unsigned) (unsigned) mid) << 32;
  55
  56   return (long long int) (neg ? -low : low);
  57 }