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 #ifdef __STDC__
  35 static const long double one = 1.0;
  36 #else
  37 static long double one = 1.0;
  38 #endif
  39
  40 #ifdef __STDC__
  41         long double __modfl(long double x, long double *iptr)
  42 #else
  43         long double __modfl(x, iptr)
  44         long double x,*iptr;
  45 #endif
  46 {
  47         int64_t i0,i1,j0;
  48         u_int64_t i;
  49         GET_LDOUBLE_WORDS64(i0,i1,x);
  50         i1 &= 0x000fffffffffffffLL;
  51         j0 = ((i0>>52)&0x7ff)-0x3ff;    /* exponent of x */
  52         if(j0<52) {                     /* integer part in high x */
  53             if(j0<0) {                  /* |x|<1 */
  54                 /* *iptr = +-0 */
  55                 SET_LDOUBLE_WORDS64(*iptr,i0&0x8000000000000000ULL,0);
  56                 return x;
  57             } else {
  58                 i = (0x000fffffffffffffLL)>>j0;
  59                 if(((i0&i)|(i1&0x7fffffffffffffffLL))==0) {             /* x is integral */
  60                     *iptr = x;
  61                     /* return +-0 */
  62                     SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
  63                     return x;
  64                 } else {
  65                     SET_LDOUBLE_WORDS64(*iptr,i0&(~i),0);
  66                     return x - *iptr;
  67                 }
  68             }
  69         } else if (j0>103) {            /* no fraction part */
  70             *iptr = x*one;
  71             /* We must handle NaNs separately.  */
  72             if (j0 == 0x400 && ((i0 & 0x000fffffffffffffLL) | i1))
  73               return x*one;
  74             /* return +-0 */
  75             SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
  76             return x;
  77         } else {                        /* fraction part in low x */
  78             i = -1ULL>>(j0-52);
  79             if((i1&i)==0) {             /* x is integral */
  80                 *iptr = x;
  81                 /* return +-0 */
  82                 SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
  83                 return x;
  84             } else {
  85                 SET_LDOUBLE_WORDS64(*iptr,i0,i1&(~i));
  86                 return x - *iptr;
  87             }
  88         }
  89 }
  90 #ifdef IS_IN_libm
  91 long_double_symbol (libm, __modfl, modfl);
  92 #else
  93 long_double_symbol (libc, __modfl, modfl);
  94 #endif