Subversion Repositories shark

Rev

Details | Last modification | View Log | RSS feed

Rev Author Line No. Line
55 pj 1 
/* $Id: mmath.c,v 1.1 2003-02-28 11:42:03 pj Exp $ */
2 
 
3 
/*
4 
 * Mesa 3-D graphics library
5 
 * Version:  3.5
6 
 *
7 
 * Copyright (C) 1999-2001  Brian Paul   All Rights Reserved.
8 
 *
9 
 * Permission is hereby granted, free of charge, to any person obtaining a
10 
 * copy of this software and associated documentation files (the "Software"),
11 
 * to deal in the Software without restriction, including without limitation
12 
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
13 
 * and/or sell copies of the Software, and to permit persons to whom the
14 
 * Software is furnished to do so, subject to the following conditions:
15 
 *
16 
 * The above copyright notice and this permission notice shall be included
17 
 * in all copies or substantial portions of the Software.
18 
 *
19 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
20 
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
21 
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
22 
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
23 
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
24 
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25 
 */
26 
 
27 
 
28 
#include "glheader.h"
29 
#include "mmath.h"
30 
 
31 
 
32 
static int in_fast_math;
33 
 
34 
/*
35 
 * A High Speed, Low Precision Square Root
36 
 * by Paul Lalonde and Robert Dawson
37 
 * from "Graphics Gems", Academic Press, 1990
38 
 */
39 
 
40 
/*
41 
 * SPARC implementation of a fast square root by table
42 
 * lookup.
43 
 * SPARC floating point format is as follows:
44 
 *
45 
 * BIT 31       30      23      22      0
46 
 *     sign     exponent        mantissa
47 
 */
48 
static short sqrttab[0x100];    /* declare table of square roots */
49 
 
50 
static void init_sqrt(void)
51 
{
52 
#ifdef FAST_MATH
53 
   unsigned short i;
54 
   fi_type fi;     /* to access the bits of a float in  C quickly  */
55 
                   /* we use a union defined in glheader.h         */
56 
 
57 
   for(i=0; i<= 0x7f; i++) {
58 
      fi.i = 0;
59 
 
60 
      /*
61 
       * Build a float with the bit pattern i as mantissa
62 
       * and an exponent of 0, stored as 127
63 
       */
64 
 
65 
      fi.i = (i << 16) | (127 << 23);
66 
      fi.f = _mesa_sqrt(fi.f);
67 
 
68 
      /*
69 
       * Take the square root then strip the first 7 bits of
70 
       * the mantissa into the table
71 
       */
72 
 
73 
      sqrttab[i] = (fi.i & 0x7fffff) >> 16;
74 
 
75 
      /*
76 
       * Repeat the process, this time with an exponent of
77 
       * 1, stored as 128
78 
       */
79 
 
80 
      fi.i = 0;
81 
      fi.i = (i << 16) | (128 << 23);
82 
      fi.f = sqrt(fi.f);
83 
      sqrttab[i+0x80] = (fi.i & 0x7fffff) >> 16;
84 
   }
85 
#else
86 
   (void) sqrttab;  /* silence compiler warnings */
87 
#endif /*FAST_MATH*/
88 
}
89 
 
90 
 
91 
float gl_sqrt( float x )
92 
{
93 
#ifdef FAST_MATH
94 
   fi_type num;
95 
                                /* to access the bits of a float in C
96 
                                 * we use a union from glheader.h     */
97 
 
98 
   short e;                     /* the exponent */
99 
   if (x == 0.0F) return 0.0F;  /* check for square root of 0 */
100 
   num.f = x;
101 
   e = (num.i >> 23) - 127;     /* get the exponent - on a SPARC the */
102 
                                /* exponent is stored with 127 added */
103 
   num.i &= 0x7fffff;           /* leave only the mantissa */
104 
   if (e & 0x01) num.i |= 0x800000;
105 
                                /* the exponent is odd so we have to */
106 
                                /* look it up in the second half of  */
107 
                                /* the lookup table, so we set the   */
108 
                                /* high bit                                */
109 
   e >>= 1;                     /* divide the exponent by two */
110 
                                /* note that in C the shift */
111 
                                /* operators are sign preserving */
112 
                                /* for signed operands */
113 
   /* Do the table lookup, based on the quaternary mantissa,
114 
    * then reconstruct the result back into a float
115 
    */
116 
   num.i = ((sqrttab[num.i >> 16]) << 16) | ((e + 127) << 23);
117 
   return num.f;
118 
#else
119 
   return (GLfloat) _mesa_sqrt(x);
120 
#endif
121 
}
122 
 
123 
 
124 
/* ubyte -> float conversion */
125 
float _mesa_ubyte_to_float_color_tab[256];
126 
 
127 
 
128 
/*
129 
 * Initialize tables, etc for fast math functions.
130 
 */
131 
void
132 
_mesa_init_math(void)
133 
{
134 
   static GLboolean initialized = GL_FALSE;
135 
 
136 
   if (!initialized) {
137 
      int i;
138 
      for (i = 0; i < 256; i++) {
139 
         _mesa_ubyte_to_float_color_tab[i] = (float) i / 255.0F;
140 
      }
141 
 
142 
      init_sqrt();
143 
 
144 
      initialized = GL_TRUE;
145 
      in_fast_math = 0;
146 
 
147 
#if defined(_FPU_GETCW) && defined(_FPU_SETCW)
148 
      {
149 
         const char *debug = _mesa_getenv("MESA_DEBUG");
150 
         if (debug && _mesa_strcmp(debug, "FP")==0) {
151 
            /* die on FP exceptions */
152 
            fpu_control_t mask;
153 
            _FPU_GETCW(mask);
154 
            mask &= ~(_FPU_MASK_IM | _FPU_MASK_DM | _FPU_MASK_ZM
155 
                      | _FPU_MASK_OM | _FPU_MASK_UM);
156 
            _FPU_SETCW(mask);
157 
         }
158 
      }
159 
#endif
160 
   }
161 
}
162 
 
163 
 
164 
 
165 
/*
166 
 * Return number of bits set in given GLuint.
167 
 */
168 
GLuint
169 
_mesa_bitcount(GLuint n)
170 
{
171 
   GLuint bits;
172 
   for (bits = 0; n > 0; n = n >> 1) {
173 
      if (n & 1) {
174 
         bits++;
175 
      }
176 
   }
177 
   return bits;
178 
}