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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 5564 | serge | 1 | /************************************************************************** |
| 2 | * |
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| 3 | * Copyright 2010 Luca Barbieri |
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| 4 | * |
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| 5 | * Permission is hereby granted, free of charge, to any person obtaining |
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| 6 | * a copy of this software and associated documentation files (the |
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| 7 | * "Software"), to deal in the Software without restriction, including |
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| 8 | * without limitation the rights to use, copy, modify, merge, publish, |
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| 9 | * distribute, sublicense, and/or sell copies of the Software, and to |
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| 10 | * permit persons to whom the Software is furnished to do so, subject to |
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| 11 | * the following conditions: |
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| 12 | * |
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| 13 | * The above copyright notice and this permission notice (including the |
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| 14 | * next paragraph) shall be included in all copies or substantial |
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| 15 | * portions of the Software. |
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| 16 | * |
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| 17 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
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| 18 | * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
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| 19 | * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. |
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| 20 | * IN NO EVENT SHALL THE COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS BE |
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| 21 | * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION |
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| 22 | * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION |
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| 23 | * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
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| 24 | * |
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| 25 | **************************************************************************/ |
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| 26 | |||
| 27 | |||
| 28 | #ifndef U_HALF_H |
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| 29 | #define U_HALF_H |
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| 30 | |||
| 31 | #include "pipe/p_compiler.h" |
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| 32 | #include "util/u_math.h" |
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| 33 | |||
| 34 | #ifdef __cplusplus |
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| 35 | extern "C" { |
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| 36 | #endif |
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| 37 | |||
| 38 | /* |
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| 39 | * References for float <-> half conversions |
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| 40 | * |
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| 41 | * http://fgiesen.wordpress.com/2012/03/28/half-to-float-done-quic/ |
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| 42 | * https://gist.github.com/2156668 |
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| 43 | * https://gist.github.com/2144712 |
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| 44 | */ |
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| 45 | |||
| 46 | static INLINE uint16_t |
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| 47 | util_float_to_half(float f) |
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| 48 | { |
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| 49 | uint32_t sign_mask = 0x80000000; |
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| 50 | uint32_t round_mask = ~0xfff; |
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| 51 | uint32_t f32inf = 0xff << 23; |
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| 52 | uint32_t f16inf = 0x1f << 23; |
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| 53 | uint32_t sign; |
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| 54 | union fi magic; |
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| 55 | union fi f32; |
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| 56 | uint16_t f16; |
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| 57 | |||
| 58 | magic.ui = 0xf << 23; |
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| 59 | |||
| 60 | f32.f = f; |
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| 61 | |||
| 62 | /* Sign */ |
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| 63 | sign = f32.ui & sign_mask; |
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| 64 | f32.ui ^= sign; |
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| 65 | |||
| 66 | if (f32.ui == f32inf) { |
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| 67 | /* Inf */ |
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| 68 | f16 = 0x7c00; |
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| 69 | } else if (f32.ui > f32inf) { |
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| 70 | /* NaN */ |
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| 71 | f16 = 0x7e00; |
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| 72 | } else { |
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| 73 | /* Number */ |
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| 74 | f32.ui &= round_mask; |
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| 75 | f32.f *= magic.f; |
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| 76 | f32.ui -= round_mask; |
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| 77 | |||
| 78 | /* |
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| 79 | * Clamp to max finite value if overflowed. |
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| 80 | * OpenGL has completely undefined rounding behavior for float to |
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| 81 | * half-float conversions, and this matches what is mandated for float |
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| 82 | * to fp11/fp10, which recommend round-to-nearest-finite too. |
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| 83 | * (d3d10 is deeply unhappy about flushing such values to infinity, and |
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| 84 | * while it also mandates round-to-zero it doesn't care nearly as much |
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| 85 | * about that.) |
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| 86 | */ |
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| 87 | if (f32.ui > f16inf) |
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| 88 | f32.ui = f16inf - 1; |
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| 89 | |||
| 90 | f16 = f32.ui >> 13; |
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| 91 | } |
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| 92 | |||
| 93 | /* Sign */ |
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| 94 | f16 |= sign >> 16; |
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| 95 | |||
| 96 | return f16; |
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| 97 | } |
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| 98 | |||
| 99 | static INLINE float |
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| 100 | util_half_to_float(uint16_t f16) |
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| 101 | { |
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| 102 | union fi infnan; |
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| 103 | union fi magic; |
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| 104 | union fi f32; |
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| 105 | |||
| 106 | infnan.ui = 0x8f << 23; |
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| 107 | infnan.f = 65536.0f; |
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| 108 | magic.ui = 0xef << 23; |
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| 109 | |||
| 110 | /* Exponent / Mantissa */ |
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| 111 | f32.ui = (f16 & 0x7fff) << 13; |
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| 112 | |||
| 113 | /* Adjust */ |
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| 114 | f32.f *= magic.f; |
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| 115 | |||
| 116 | /* Inf / NaN */ |
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| 117 | if (f32.f >= infnan.f) |
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| 118 | f32.ui |= 0xff << 23; |
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| 119 | |||
| 120 | /* Sign */ |
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| 121 | f32.ui |= (f16 & 0x8000) << 16; |
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| 122 | |||
| 123 | return f32.f; |
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| 124 | } |
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| 125 | |||
| 126 | #ifdef __cplusplus |
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| 127 | } |
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| 128 | #endif |
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| 129 | |||
| 130 | #endif /* U_HALF_H */ |
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| 131 |