sysdeps/ieee754/dbl-64/wordsize-64/s_floor.c

   1 /* Round double to integer away from zero.
   2    Copyright (C) 2011-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 2011.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 /* Based on a version which carries the following copyright:  */
  21
  22 /*
  23  * ====================================================
  24  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
  25  *
  26  * Developed at SunPro, a Sun Microsystems, Inc. business.
  27  * Permission to use, copy, modify, and distribute this
  28  * software is freely granted, provided that this notice
  29  * is preserved.
  30  * ====================================================
  31  */
  32
  33 #include <math.h>
  34 #include <math_private.h>
  35 #include <stdint.h>
  36
  37 /*
  38  * floor(x)
  39  * Return x rounded toward -inf to integral value
  40  * Method:
  41  *      Bit twiddling.
  42  * Exception:
  43  *      Inexact flag raised if x not equal to floor(x).
  44  */
  45
  46 static const double huge = 1.0e300;
  47
  48
  49 double
  50 __floor (double x)
  51 {
  52         int64_t i0;
  53         EXTRACT_WORDS64(i0,x);
  54         int32_t j0 = ((i0>>52)&0x7ff)-0x3ff;
  55         if(__builtin_expect(j0<52, 1)) {
  56             if(j0<0) {  /* raise inexact if x != 0 */
  57                 math_force_eval(huge+x);/* return 0*sign(x) if |x|<1 */
  58                 if(i0>=0) {i0=0;}
  59                 else if((i0&0x7fffffffffffffffl)!=0)
  60                   { i0=0xbff0000000000000l;}
  61             } else {
  62                 uint64_t i = (0x000fffffffffffffl)>>j0;
  63                 if((i0&i)==0) return x; /* x is integral */
  64                 math_force_eval(huge+x);        /* raise inexact flag */
  65                 if(i0<0) i0 += (0x0010000000000000l)>>j0;
  66                 i0 &= (~i);
  67             }
  68             INSERT_WORDS64(x,i0);
  69         } else if (j0==0x400)
  70             return x+x; /* inf or NaN */
  71         return x;
  72 }
  73 #ifndef __floor
  74 weak_alias (__floor, floor)
  75 # ifdef NO_LONG_DOUBLE
  76 strong_alias (__floor, __floorl)
  77 weak_alias (__floor, floorl)
  78 # endif
  79 #endif