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
35extern "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
46static INLINE uint16_t
47util_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
91static INLINE float
92util_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