libgfortran/runtime/normalize.c

   1 /* Nelper routines to convert from integer to real.
   2    Copyright 2004 Free Software Foundation, Inc.
   3    Contributed by Paul Brook.
   4
   5 This file is part of the GNU Fortran 95 runtime library (libgfortran).
   6
   7 Libgfortran is free software; you can redistribute it and/or
   8 modify it under the terms of the GNU General Public
   9 License as published by the Free Software Foundation; either
  10 version 2 of the License, or (at your option) any later version.
  11
  12 In addition to the permissions in the GNU General Public License, the
  13 Free Software Foundation gives you unlimited permission to link the
  14 compiled version of this file into combinations with other programs,
  15 and to distribute those combinations without any restriction coming
  16 from the use of this file.  (The General Public License restrictions
  17 do apply in other respects; for example, they cover modification of
  18 the file, and distribution when not linked into a combine
  19 executable.)
  20
  21 Ligbfortran is distributed in the hope that it will be useful,
  22 but WITHOUT ANY WARRANTY; without even the implied warranty of
  23 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  24 GNU General Public License for more details.
  25
  26 You should have received a copy of the GNU General Public
  27 License along with libgfortran; see the file COPYING.  If not,
  28 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  29 Boston, MA 02111-1307, USA.  */
  30 #include <math.h>
  31 #include "libgfortran.h"
  32
  33 /* These routines can be sensitive to excess precision, so should really be
  34    compiled with -ffloat-store.  */
  35
  36 /* Return the largest value less than one representable in a REAL*4.  */
  37
  38 static inline GFC_REAL_4
  39 almostone_r4 ()
  40 {
  41 #ifdef HAVE_NEXTAFTERF
  42   return nextafterf (1.0f, 0.0f);
  43 #else
  44   /* The volatile is a hack to prevent excess precision on x86.  */
  45   static volatile GFC_REAL_4 val = 0.0f;
  46   GFC_REAL_4 x;
  47
  48   if (val != 0.0f)
  49     return val;
  50
  51   val = 0.9999f;
  52   do
  53     {
  54       x = val;
  55       val = (val + 1.0f) / 2.0f;
  56     }
  57   while (val > x && val < 1.0f);
  58   if (val == 1.0f)
  59     val = x;
  60   return val;
  61 #endif
  62 }
  63
  64
  65 /* Return the largest value less than one representable in a REAL*8.  */
  66
  67 static inline GFC_REAL_8
  68 almostone_r8 ()
  69 {
  70 #ifdef HAVE_NEXTAFTER
  71   return nextafter (1.0, 0.0);
  72 #else
  73   static volatile GFC_REAL_8 val = 0.0;
  74   GFC_REAL_8 x;
  75
  76   if (val != 0.0)
  77     return val;
  78
  79   val = 0.9999;
  80   do
  81     {
  82       x = val;
  83       val = (val + 1.0) / 2.0;
  84     }
  85   while (val > x && val < 1.0);
  86   if (val == 1.0)
  87     val = x;
  88   return val;
  89 #endif
  90 }
  91
  92
  93 /* Convert an unsigned integer in the range [0..x] into a
  94    real the range [0..1).  */
  95
  96 GFC_REAL_4
  97 normalize_r4_i4 (GFC_UINTEGER_4 i, GFC_UINTEGER_4 x)
  98 {
  99   GFC_REAL_4 r;
 100
 101   r = (GFC_REAL_4) i / (GFC_REAL_4) x;
 102   if (r == 1.0f)
 103     r = almostone_r4 ();
 104   return r;
 105 }
 106
 107
 108 /* Convert an unsigned integer in the range [0..x] into a
 109    real the range [0..1).  */
 110
 111 GFC_REAL_8
 112 normalize_r8_i8 (GFC_UINTEGER_8 i, GFC_UINTEGER_8 x)
 113 {
 114   GFC_REAL_8 r;
 115
 116   r = (GFC_REAL_8) i / (GFC_REAL_8) x;
 117   if (r == 1.0)
 118     r = almostone_r8 ();
 119   return r;
 120 }