sysdeps/ieee754/ldbl-128ibm/s_modfl.c

   1 /* s_modfl.c -- long double version of s_modf.c.
   2  * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #if defined(LIBM_SCCS) && !defined(lint)
  17 static char rcsid[] = "$NetBSD: $";
  18 #endif
  19
  20 /*
  21  * modfl(long double x, long double *iptr)
  22  * return fraction part of x, and return x's integral part in *iptr.
  23  * Method:
  24  *      Bit twiddling.
  25  *
  26  * Exception:
  27  *      No exception.
  28  */
  29
  30 #include <math.h>
  31 #include <math_private.h>
  32 #include <math_ldbl_opt.h>
  33
  34 static const long double one = 1.0;
  35
  36 long double __modfl(long double x, long double *iptr)
  37 {
  38         int64_t i0,i1,j0;
  39         u_int64_t i;
  40         double xhi, xlo;
  41
  42         ldbl_unpack (x, &xhi, &xlo);
  43         EXTRACT_WORDS64 (i0, xhi);
  44         EXTRACT_WORDS64 (i1, xlo);
  45         i1 &= 0x000fffffffffffffLL;
  46         j0 = ((i0>>52)&0x7ff)-0x3ff;    /* exponent of x */
  47         if(j0<52) {                     /* integer part in high x */
  48             if(j0<0) {                  /* |x|<1 */
  49                 /* *iptr = +-0 */
  50                 INSERT_WORDS64 (xhi, i0&0x8000000000000000ULL);
  51                 *iptr = xhi;
  52                 return x;
  53             } else {
  54                 i = (0x000fffffffffffffLL)>>j0;
  55                 if(((i0&i)|(i1&0x7fffffffffffffffLL))==0) {             /* x is integral */
  56                     *iptr = x;
  57                     /* return +-0 */
  58                     INSERT_WORDS64 (xhi, i0&0x8000000000000000ULL);
  59                     x = xhi;
  60                     return x;
  61                 } else {
  62                     INSERT_WORDS64 (xhi, i0&(~i));
  63                     *iptr = xhi;
  64                     return x - *iptr;
  65                 }
  66             }
  67         } else if (j0>103) {            /* no fraction part */
  68             *iptr = x*one;
  69             /* We must handle NaNs separately.  */
  70             if ((i0 & 0x7fffffffffffffffLL) > 0x7ff0000000000000LL)
  71               return x*one;
  72             /* return +-0 */
  73             INSERT_WORDS64 (xhi, i0&0x8000000000000000ULL);
  74             x = xhi;
  75             return x;
  76         } else {                        /* fraction part in low x */
  77             i = -1ULL>>(j0-52);
  78             if((i1&i)==0) {             /* x is integral */
  79                 *iptr = x;
  80                 /* return +-0 */
  81                 INSERT_WORDS64 (xhi, i0&0x8000000000000000ULL);
  82                 x = xhi;
  83                 return x;
  84             } else {
  85                 INSERT_WORDS64 (xhi, i0);
  86                 INSERT_WORDS64 (xlo, i1&(~i));
  87                 *iptr = ldbl_pack (xhi, xlo);
  88                 return x - *iptr;
  89             }
  90         }
  91 }
  92 #if IS_IN (libm)
  93 long_double_symbol (libm, __modfl, modfl);
  94 #else
  95 long_double_symbol (libc, __modfl, modfl);
  96 #endif