libquadmath/math/rintq.c

   1 /* s_rintl.c -- long double version of s_rint.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 #include "quadmath-imp.h"
  17
  18 static const __float128
  19 TWO112[2]={
  20   5.19229685853482762853049632922009600E+33L, /* 0x406F000000000000, 0 */
  21  -5.19229685853482762853049632922009600E+33L  /* 0xC06F000000000000, 0 */
  22 };
  23
  24 __float128
  25 rintq (__float128 x)
  26 {
  27         int64_t i0,j0,sx;
  28         uint64_t i,i1;
  29         __float128 w,t;
  30         GET_FLT128_WORDS64(i0,i1,x);
  31         sx = (((uint64_t)i0)>>63);
  32         j0 = ((i0>>48)&0x7fff)-0x3fff;
  33         if(j0<48) {
  34             if(j0<0) {
  35                 if(((i0&0x7fffffffffffffffLL)|i1)==0) return x;
  36                 i1 |= (i0&0x0000ffffffffffffLL);
  37                 i0 &= 0xffffe00000000000ULL;
  38                 i0 |= ((i1|-i1)>>16)&0x0000800000000000LL;
  39                 SET_FLT128_MSW64(x,i0);
  40                 w = TWO112[sx]+x;
  41                 t = w-TWO112[sx];
  42                 GET_FLT128_MSW64(i0,t);
  43                 SET_FLT128_MSW64(t,(i0&0x7fffffffffffffffLL)|(sx<<63));
  44                 return t;
  45             } else {
  46                 i = (0x0000ffffffffffffLL)>>j0;
  47                 if(((i0&i)|i1)==0) return x; /* x is integral */
  48                 i>>=1;
  49                 if(((i0&i)|i1)!=0) {
  50                     if(j0==47) i1 = 0x4000000000000000ULL; else
  51                     i0 = (i0&(~i))|((0x0000200000000000LL)>>j0);
  52                 }
  53             }
  54         } else if (j0>111) {
  55             if(j0==0x4000) return x+x;  /* inf or NaN */
  56             else return x;              /* x is integral */
  57         } else {
  58             i = -1ULL>>(j0-48);
  59             if((i1&i)==0) return x;     /* x is integral */
  60             i>>=1;
  61             if((i1&i)!=0) i1 = (i1&(~i))|((0x4000000000000000LL)>>(j0-48));
  62         }
  63         SET_FLT128_WORDS64(x,i0,i1);
  64         w = TWO112[sx]+x;
  65         return w-TWO112[sx];
  66 }