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