StdLib/LibC/gdtoa/ulp.c

   1 /* $NetBSD: ulp.c,v 1.2 2006/01/25 15:27:42 kleink Exp $ */
   2
   3 /****************************************************************
   4
   5 The author of this software is David M. Gay.
   6
   7 Copyright (C) 1998, 1999 by Lucent Technologies
   8 All Rights Reserved
   9
  10 Permission to use, copy, modify, and distribute this software and
  11 its documentation for any purpose and without fee is hereby
  12 granted, provided that the above copyright notice appear in all
  13 copies and that both that the copyright notice and this
  14 permission notice and warranty disclaimer appear in supporting
  15 documentation, and that the name of Lucent or any of its entities
  16 not be used in advertising or publicity pertaining to
  17 distribution of the software without specific, written prior
  18 permission.
  19
  20 LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
  21 INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
  22 IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY
  23 SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  24 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
  25 IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
  26 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
  27 THIS SOFTWARE.
  28
  29 ****************************************************************/
  30
  31 /* Please send bug reports to David M. Gay (dmg at acm dot org,
  32  * with " at " changed at "@" and " dot " changed to ".").  */
  33 #include  <LibConfig.h>
  34
  35 #include "gdtoaimp.h"
  36
  37  double
  38 ulp
  39 #ifdef KR_headers
  40   (x) double x;
  41 #else
  42   (double x)
  43 #endif
  44 {
  45   Long L;
  46   double a;
  47
  48   L = (word0(x) & Exp_mask) - (P-1)*Exp_msk1;
  49 #ifndef Sudden_Underflow
  50   if (L > 0) {
  51 #endif
  52 #ifdef IBM
  53     L |= Exp_msk1 >> 4;
  54 #endif
  55     word0(a) = (UINT32)L;
  56     word1(a) = 0;
  57 #ifndef Sudden_Underflow
  58     }
  59   else {
  60     L = (unsigned int)-L >> Exp_shift;
  61     if (L < Exp_shift) {
  62       word0(a) = 0x80000 >> L;
  63       word1(a) = 0;
  64       }
  65     else {
  66       word0(a) = 0;
  67       L -= Exp_shift;
  68       word1(a) = L >= 31 ? 1 : 1 << (31 - L);
  69       }
  70     }
  71 #endif
  72   return a;
  73   }