libm/powerpc/classic/s_nearbyint.c

   1 #include <limits.h>
   2 #include <math.h>
   3
   4 /*******************************************************************************
   5 *                                                                              *
   6 *     The function nearbyint rounds its double argument to integral value      *
   7 *     according to the current rounding direction and returns the result in    *
   8 *     double format.  This function does not signal inexact.                   *
   9 *                                                                              *
  10 ********************************************************************************
  11 *                                                                              *
  12 *     This function calls fabs and copysign.                                     *
  13 *                                                                              *
  14 *******************************************************************************/
  15
  16 static const double twoTo52      = 4503599627370496.0;
  17
  18 libm_hidden_proto(nearbyint)
  19 double nearbyint ( double x )
  20       {
  21         double y;
  22         double OldEnvironment;
  23
  24         y = twoTo52;
  25
  26         __asm__ ("mffs %0" : "=f" (OldEnvironment));    /* get the environement */
  27
  28       if ( fabs ( x ) >= y )                          /* huge case is exact */
  29             return x;
  30       if ( x < 0 ) y = -y;                                   /* negative case */
  31       y = ( x + y ) - y;                                    /* force rounding */
  32       if ( y == 0.0 )                        /* zero results mirror sign of x */
  33             y = copysign ( y, x );
  34 //      restore old flags
  35         __asm__ ("mtfsf 255,%0" : /*NULLOUT*/ : /*IN*/ "f" ( OldEnvironment ));
  36       return ( y );
  37         }
  38 libm_hidden_def(nearbyint)