OpenCores
URL https://opencores.org/ocsvn/openrisc_me/openrisc_me/trunk

Subversion Repositories openrisc_me

[/] [openrisc/] [trunk/] [gnu-src/] [gcc-4.5.1/] [gcc/] [config/] [sh/] [divtab.c] - Blame information for rev 282

Details | Compare with Previous | View Log

Line No. Rev Author Line
1 282 jeremybenn
/* Copyright (C) 2003, 2009 Free Software Foundation, Inc.
2
 
3
This file is free software; you can redistribute it and/or modify it
4
under the terms of the GNU General Public License as published by the
5
Free Software Foundation; either version 3, or (at your option) any
6
later version.
7
 
8
This file is distributed in the hope that it will be useful, but
9
WITHOUT ANY WARRANTY; without even the implied warranty of
10
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
11
General Public License for more details.
12
 
13
Under Section 7 of GPL version 3, you are granted additional
14
permissions described in the GCC Runtime Library Exception, version
15
3.1, as published by the Free Software Foundation.
16
 
17
You should have received a copy of the GNU General Public License and
18
a copy of the GCC Runtime Library Exception along with this program;
19
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
20
<http://www.gnu.org/licenses/>.  */
21
 
22
 
23
/* Calculate division table for SH5Media integer division
24
   Contributed by Joern Rennecke
25
   joern.rennecke@superh.com  */
26
 
27
#include <stdio.h>
28
#include <math.h>
29
 
30
#define BITS 5
31
#define N_ENTRIES (1 << BITS)
32
#define CUTOFF_BITS 20
33
 
34
#define BIAS (-330)
35
 
36
double max_defect = 0.;
37
double max_defect_x;
38
 
39
double min_defect = 1e9;
40
double min_defect_x;
41
 
42
double max_defect2 = 0.;
43
double max_defect2_x;
44
 
45
double min_defect2 = 0.;
46
double min_defect2_x;
47
 
48
double min_defect3 = 01e9;
49
double min_defect3_x;
50
int min_defect3_val;
51
 
52
double max_defect3 = 0.;
53
double max_defect3_x;
54
int max_defect3_val;
55
 
56
static double note_defect3 (int val, double d2, double y2d, double x)
57
{
58
  int cutoff_val = val >> CUTOFF_BITS;
59
  double cutoff;
60
  double defect;
61
 
62
  if (val < 0)
63
    cutoff_val++;
64
  cutoff = (cutoff_val * (1<<CUTOFF_BITS) - val) * y2d;
65
  defect = cutoff + val * d2;
66
  if (val < 0)
67
    defect = - defect;
68
  if (defect > max_defect3)
69
    {
70
      max_defect3 = defect;
71
      max_defect3_x = x;
72
      max_defect3_val = val;
73
    }
74
  if (defect < min_defect3)
75
    {
76
      min_defect3 = defect;
77
      min_defect3_x = x;
78
      min_defect3_val = val;
79
    }
80
}
81
 
82
/* This function assumes 32-bit integers.  */
83
static double
84
calc_defect (double x, int constant, int factor)
85
{
86
  double y0 = (constant - (int) floor ((x * factor * 64.))) / 16384.;
87
  double y1 = 2 * y0 -y0 * y0 * (x + BIAS / (1.*(1LL<<30)));
88
  double y2d0, y2d;
89
  int y2d1;
90
  double d, d2;
91
 
92
  y1 = floor (y1 * (1024 * 1024 * 1024)) / (1024 * 1024 * 1024);
93
  d = y1 - 1 / x;
94
  if (d > max_defect)
95
    {
96
      max_defect = d;
97
      max_defect_x = x;
98
    }
99
  if (d < min_defect)
100
    {
101
      min_defect = d;
102
      min_defect_x = x;
103
    }
104
  y2d0 = floor (y1 * x * (1LL << 60-16));
105
  y2d1 = (int) (long long) y2d0;
106
  y2d = - floor ((y1 - y0 / (1<<30-14)) * y2d1) / (1LL<<44);
107
  d2 = y1 + y2d - 1/x;
108
  if (d2 > max_defect2)
109
    {
110
      max_defect2 = d2;
111
      max_defect2_x = x;
112
    }
113
  if (d2 < min_defect2)
114
    {
115
      min_defect2 = d2;
116
      min_defect2_x = x;
117
    }
118
  /* zero times anything is trivially zero.  */
119
  note_defect3 ((1 << CUTOFF_BITS) - 1, d2, y2d, x);
120
  note_defect3 (1 << CUTOFF_BITS, d2, y2d, x);
121
  note_defect3 ((1U << 31) - (1 << CUTOFF_BITS), d2, y2d, x);
122
  note_defect3 ((1U << 31) - 1, d2, y2d, x);
123
  note_defect3 (-1, d2, y2d, x);
124
  note_defect3 (-(1 << CUTOFF_BITS), d2, y2d, x);
125
  note_defect3 ((1U << 31) - (1 << CUTOFF_BITS) + 1, d2, y2d, x);
126
  note_defect3 (-(1U << 31), d2, y2d, x);
127
  return d;
128
}
129
 
130
int
131
main ()
132
{
133
  int i;
134
  unsigned char factors[N_ENTRIES];
135
  short constants[N_ENTRIES];
136
  int steps = N_ENTRIES / 2;
137
  double step = 1. / steps;
138
  double eps30 = 1. / (1024 * 1024 * 1024);
139
 
140
  for (i = 0; i < N_ENTRIES; i++)
141
    {
142
      double x_low = (i < steps ? 1. : -3.) + i * step;
143
      double x_high = x_low + step - eps30;
144
      double x_med;
145
      int factor, constant;
146
      double low_defect, med_defect, high_defect, max_defect;
147
 
148
      factor = (1./x_low- 1./x_high) / step * 256. + 0.5;
149
      if (factor == 256)
150
        factor = 255;
151
      factors[i] = factor;
152
      /* Use minimum of error function for x_med.  */
153
      x_med = sqrt (256./factor);
154
      if (x_low < 0)
155
        x_med = - x_med;
156
      low_defect = 1. / x_low + x_low * factor / 256.;
157
      high_defect = 1. / x_high + x_high * factor / 256.;
158
      med_defect = 1. / x_med + x_med * factor / 256.;
159
      max_defect
160
        = ((low_defect > high_defect) ^ (x_med < 0)) ? low_defect : high_defect;
161
      constant = (med_defect + max_defect) * 0.5 * 16384. + 0.5;
162
      if (constant < -32768 || constant > 32767)
163
        abort ();
164
      constants[i] = constant;
165
      calc_defect (x_low, constant, factor);
166
      calc_defect (x_med, constant, factor);
167
      calc_defect (x_high, constant, factor);
168
    }
169
    printf ("/* This table has been generated by divtab.c .\n");
170
    printf ("Defects for bias %d:\n", BIAS);
171
    printf ("   Max defect: %e at %e\n", max_defect, max_defect_x);
172
    printf ("   Min defect: %e at %e\n", min_defect, min_defect_x);
173
    printf ("   Max 2nd step defect: %e at %e\n", max_defect2, max_defect2_x);
174
    printf ("   Min 2nd step defect: %e at %e\n", min_defect2, min_defect2_x);
175
    printf ("   Max div defect: %e at %d:%e\n", max_defect3, max_defect3_val, max_defect3_x);
176
    printf ("   Min div defect: %e at %d:%e\n", min_defect3, min_defect3_val, min_defect3_x);
177
    printf ("   Defect at 1: %e\n",
178
            calc_defect (1., constants[0], factors[0]));
179
    printf ("   Defect at -2: %e */\n",
180
            calc_defect (-2., constants[steps], factors[steps]));
181
    printf ("\t.section\t.rodata\n");
182
    printf ("\t.balign 2\n");
183
    printf ("/* negative division constants */\n");
184
    for (i = steps; i < 2 * steps; i++)
185
      printf ("\t.word\t%d\n", constants[i]);
186
    printf ("/* negative division factors */\n");
187
    for (i = steps; i < 2*steps; i++)
188
      printf ("\t.byte\t%d\n", factors[i]);
189
    printf ("\t.skip %d\n", steps);
190
    printf ("\t.global  GLOBAL(div_table):\n");
191
    printf ("GLOBAL(div_table):\n");
192
    printf ("\t.skip %d\n", steps);
193
    printf ("/* positive division factors */\n");
194
    for (i = 0; i < steps; i++)
195
      printf ("\t.byte\t%d\n", factors[i]);
196
    printf ("/* positive division constants */\n");
197
    for (i = 0; i < steps; i++)
198
      printf ("\t.word\t%d\n", constants[i]);
199
  exit (0);
200
}

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.