libquadmath/math/nearbyintq.c

   1 /* nearbyintq.c -- __float128 version of s_nearbyint.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 /*
  17  * nearbyintq(x)
  18  * Return x rounded to integral value according to the prevailing
  19  * rounding mode.
  20  * Method:
  21  *      Using floating addition.
  22  * Exception:
  23  *      Inexact flag raised if x not equal to rintq(x).
  24  */
  25
  26 #include "quadmath-imp.h"
  27 #ifdef HAVE_FENV_H
  28 # include <fenv.h>
  29 # if defined HAVE_FEHOLDEXCEPT && defined HAVE_FESETENV
  30 #   define USE_FENV_H
  31 # endif
  32 #endif
  33
  34 static const __float128
  35 TWO112[2]={
  36   5.19229685853482762853049632922009600E+33Q, /* 0x406F000000000000, 0 */
  37  -5.19229685853482762853049632922009600E+33Q  /* 0xC06F000000000000, 0 */
  38 };
  39
  40 __float128
  41 nearbyintq(__float128 x)
  42 {
  43 #ifdef USE_FENV_H
  44         fenv_t env;
  45 #endif
  46         int64_t i0,j0,sx;
  47         uint64_t i,i1;
  48         __float128 w,t;
  49         GET_FLT128_WORDS64(i0,i1,x);
  50         sx = (((uint64_t)i0)>>63);
  51         j0 = ((i0>>48)&0x7fff)-0x3fff;
  52         if(j0<48) {
  53             if(j0<0) {
  54                 if(((i0&0x7fffffffffffffffLL)|i1)==0) return x;
  55                 i1 |= (i0&0x0000ffffffffffffLL);
  56                 i0 &= 0xffffe00000000000ULL;
  57                 i0 |= ((i1|-i1)>>16)&0x0000800000000000LL;
  58                 SET_FLT128_MSW64(x,i0);
  59 #ifdef USE_FENV_H
  60                 feholdexcept (&env);
  61 #endif
  62                 w = TWO112[sx]+x;
  63                 t = w-TWO112[sx];
  64 #ifdef USE_FENV_H
  65                 fesetenv (&env);
  66 #endif
  67                 GET_FLT128_MSW64(i0,t);
  68                 SET_FLT128_MSW64(t,(i0&0x7fffffffffffffffLL)|(sx<<63));
  69                 return t;
  70             } else {
  71                 i = (0x0000ffffffffffffLL)>>j0;
  72                 if(((i0&i)|i1)==0) return x; /* x is integral */
  73                 i>>=1;
  74                 if(((i0&i)|i1)!=0) {
  75                     if(j0==47) i1 = 0x4000000000000000ULL; else
  76                     i0 = (i0&(~i))|((0x0000200000000000LL)>>j0);
  77                 }
  78             }
  79         } else if (j0>111) {
  80             if(j0==0x4000) return x+x;  /* inf or NaN */
  81             else return x;              /* x is integral */
  82         } else {
  83             i = -1ULL>>(j0-48);
  84             if((i1&i)==0) return x;     /* x is integral */
  85             i>>=1;
  86             if((i1&i)!=0) i1 = (i1&(~i))|((0x4000000000000000LL)>>(j0-48));
  87         }
  88         SET_FLT128_WORDS64(x,i0,i1);
  89 #ifdef USE_FENV_H
  90         feholdexcept (&env);
  91 #endif
  92         w = TWO112[sx]+x;
  93         t = w-TWO112[sx];
  94 #ifdef USE_FENV_H
  95         fesetenv (&env);
  96 #endif
  97         return t;
  98 }