src/mesa/drivers/dri/savage/savagespan.h

   1 /*
   2  * Copyright 1998-2003 VIA Technologies, Inc. All Rights Reserved.
   3  * Copyright 2001-2003 S3 Graphics, Inc. All Rights Reserved.
   4  *
   5  * Permission is hereby granted, free of charge, to any person obtaining a
   6  * copy of this software and associated documentation files (the "Software"),
   7  * to deal in the Software without restriction, including without limitation
   8  * the rights to use, copy, modify, merge, publish, distribute, sub license,
   9  * and/or sell copies of the Software, and to permit persons to whom the
  10  * Software is furnished to do so, subject to the following conditions:
  11  *
  12  * The above copyright notice and this permission notice (including the
  13  * next paragraph) shall be included in all copies or substantial portions
  14  * of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  19  * VIA, S3 GRAPHICS, AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  20  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  21  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  22  * DEALINGS IN THE SOFTWARE.
  23  */
  24
  25 #ifndef _SAVAGE_SPAN_H
  26 #define _SAVAGE_SPAN_H
  27
  28 extern void savageDDInitSpanFuncs( GLcontext *ctx );
  29
  30 /*
  31  * Savage 16-bit float depth format with zExpOffset=16:
  32  *   4 bit unsigned exponent, 12 bit mantissa
  33  *
  34  * The meaning of the mantissa is different from IEEE floatint point
  35  * formats. The same number can't be encoded with different exponents.
  36  * So no bits are wasted.
  37  *
  38  * exponent | range encoded by mantissa | accuracy or mantissa
  39  * ---------+---------------------------+---------------------
  40  *       15 | 2^-1 .. 1                 | 2^-13
  41  *       14 | 2^-2 .. 2^-1              | 2^-14
  42  *       13 | 2^-3 .. 2^-2              | 2^-15
  43  *      ... | ...                       |
  44  *        2 | 2^-14 .. 2^-13            | 2^-27
  45  *        1 | 2^-15 .. 2^-14            | 2^-27
  46  *        0 | 2^-16 .. 2^-15            | 2^-28
  47  *
  48  * Note that there is no encoding for numbers < 2^-16.
  49  */
  50 static __inline GLuint savageEncodeFloat16( GLdouble x )
  51 {
  52     GLint r = (GLint)(x * 0x10000000);
  53     GLint exp = 0;
  54     if (r < 0x1000)
  55         return 0;
  56     while (r - 0x1000 > 0x0fff) {
  57         r >>= 1;
  58         exp++;
  59     }
  60     return exp > 0xf ? 0xffff : (r - 0x1000) | (exp << 12);
  61 }
  62 static __inline GLdouble savageDecodeFloat16( GLuint x )
  63 {
  64     static const GLdouble pow2[16] = {
  65         1.0/(1<<28), 1.0/(1<<27), 1.0/(1<<26), 1.0/(1<<25),
  66         1.0/(1<<24), 1.0/(1<<23), 1.0/(1<<22), 1.0/(1<<21),
  67         1.0/(1<<20), 1.0/(1<<19), 1.0/(1<<18), 1.0/(1<<17),
  68         1.0/(1<<16), 1.0/(1<<15), 1.0/(1<<14), 1.0/(1<<13)
  69     };
  70     static const GLdouble bias[16] = {
  71         1.0/(1<<16), 1.0/(1<<15), 1.0/(1<<14), 1.0/(1<<13),
  72         1.0/(1<<12), 1.0/(1<<11), 1.0/(1<<10), 1.0/(1<< 9),
  73         1.0/(1<< 8), 1.0/(1<< 7), 1.0/(1<< 6), 1.0/(1<< 5),
  74         1.0/(1<< 4), 1.0/(1<< 3), 1.0/(1<< 2), 1.0/(1<< 1)
  75     };
  76     GLuint mant = x & 0x0fff;
  77     GLuint exp = (x >> 12) & 0xf;
  78     return bias[exp] + pow2[exp]*mant;
  79 }
  80
  81 /*
  82  * Savage 24-bit float depth format with zExpOffset=32:
  83  *   5 bit unsigned exponent, 19 bit mantissa
  84  *
  85  * Details analogous to the 16-bit format.
  86  */
  87 static __inline GLuint savageEncodeFloat24( GLdouble x )
  88 {
  89     int64_t r = (int64_t)(x * ((int64_t)1 << (19+32)));
  90     GLint exp = 0;
  91     if (r < 0x80000)
  92         return 0;
  93     while (r - 0x80000 > 0x7ffff) {
  94         r >>= 1;
  95         exp++;
  96     }
  97     return exp > 0x1f ? 0xffffff : (r - 0x80000) | (exp << 19);
  98 }
  99 #define _1 (int64_t)1
 100 static __inline GLdouble savageDecodeFloat24( GLuint x )
 101 {
 102     static const GLdouble pow2[32] = {
 103         1.0/(_1<<51), 1.0/(_1<<50), 1.0/(_1<<49), 1.0/(_1<<48),
 104         1.0/(_1<<47), 1.0/(_1<<46), 1.0/(_1<<45), 1.0/(_1<<44),
 105         1.0/(_1<<43), 1.0/(_1<<42), 1.0/(_1<<41), 1.0/(_1<<40),
 106         1.0/(_1<<39), 1.0/(_1<<38), 1.0/(_1<<37), 1.0/(_1<<36),
 107         1.0/(_1<<35), 1.0/(_1<<34), 1.0/(_1<<33), 1.0/(_1<<32),
 108         1.0/(_1<<31), 1.0/(_1<<30), 1.0/(_1<<29), 1.0/(_1<<28),
 109         1.0/(_1<<27), 1.0/(_1<<26), 1.0/(_1<<25), 1.0/(_1<<24),
 110         1.0/(_1<<23), 1.0/(_1<<22), 1.0/(_1<<21), 1.0/(_1<<20)
 111     };
 112     static const GLdouble bias[32] = {
 113         1.0/(_1<<32), 1.0/(_1<<31), 1.0/(_1<<30), 1.0/(_1<<29),
 114         1.0/(_1<<28), 1.0/(_1<<27), 1.0/(_1<<26), 1.0/(_1<<25),
 115         1.0/(_1<<24), 1.0/(_1<<23), 1.0/(_1<<22), 1.0/(_1<<21),
 116         1.0/(_1<<20), 1.0/(_1<<19), 1.0/(_1<<18), 1.0/(_1<<17),
 117         1.0/(_1<<16), 1.0/(_1<<15), 1.0/(_1<<14), 1.0/(_1<<13),
 118         1.0/(_1<<12), 1.0/(_1<<11), 1.0/(_1<<10), 1.0/(_1<< 9),
 119         1.0/(_1<< 8), 1.0/(_1<< 7), 1.0/(_1<< 6), 1.0/(_1<< 5),
 120         1.0/(_1<< 4), 1.0/(_1<< 3), 1.0/(_1<< 2), 1.0/(_1<< 1)
 121     };
 122     GLuint mant = x & 0x7ffff;
 123     GLuint exp = (x >> 19) & 0x1f;
 124     return bias[exp] + pow2[exp]*mant;
 125 }
 126 #undef _1
 127
 128 #endif