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