Added few more stubs so that control reaches to DestroyDevice().
[mesa.git] / src / util / half_float.c
1 /*
2 * Mesa 3-D graphics library
3 *
4 * Copyright (C) 1999-2007 Brian Paul All Rights Reserved.
5 * Copyright 2015 Philip Taylor <philip@zaynar.co.uk>
6 * Copyright 2018 Advanced Micro Devices, Inc.
7 * Copyright (C) 2018-2019 Intel Corporation
8 *
9 * Permission is hereby granted, free of charge, to any person obtaining a
10 * copy of this software and associated documentation files (the "Software"),
11 * to deal in the Software without restriction, including without limitation
12 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
13 * and/or sell copies of the Software, and to permit persons to whom the
14 * Software is furnished to do so, subject to the following conditions:
15 *
16 * The above copyright notice and this permission notice shall be included
17 * in all copies or substantial portions of the Software.
18 *
19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
20 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
21 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
22 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
23 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
24 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
25 * OTHER DEALINGS IN THE SOFTWARE.
26 */
27
28 #include <math.h>
29 #include <assert.h>
30 #include "half_float.h"
31 #include "util/u_half.h"
32 #include "rounding.h"
33 #include "softfloat.h"
34 #include "macros.h"
35
36 typedef union { float f; int32_t i; uint32_t u; } fi_type;
37
38 /**
39 * Convert a 4-byte float to a 2-byte half float.
40 *
41 * Not all float32 values can be represented exactly as a float16 value. We
42 * round such intermediate float32 values to the nearest float16. When the
43 * float32 lies exactly between to float16 values, we round to the one with
44 * an even mantissa.
45 *
46 * This rounding behavior has several benefits:
47 * - It has no sign bias.
48 *
49 * - It reproduces the behavior of real hardware: opcode F32TO16 in Intel's
50 * GPU ISA.
51 *
52 * - By reproducing the behavior of the GPU (at least on Intel hardware),
53 * compile-time evaluation of constant packHalf2x16 GLSL expressions will
54 * result in the same value as if the expression were executed on the GPU.
55 */
56 uint16_t
57 _mesa_float_to_half(float val)
58 {
59 const fi_type fi = {val};
60 const int flt_m = fi.i & 0x7fffff;
61 const int flt_e = (fi.i >> 23) & 0xff;
62 const int flt_s = (fi.i >> 31) & 0x1;
63 int s, e, m = 0;
64 uint16_t result;
65
66 /* sign bit */
67 s = flt_s;
68
69 /* handle special cases */
70 if ((flt_e == 0) && (flt_m == 0)) {
71 /* zero */
72 /* m = 0; - already set */
73 e = 0;
74 }
75 else if ((flt_e == 0) && (flt_m != 0)) {
76 /* denorm -- denorm float maps to 0 half */
77 /* m = 0; - already set */
78 e = 0;
79 }
80 else if ((flt_e == 0xff) && (flt_m == 0)) {
81 /* infinity */
82 /* m = 0; - already set */
83 e = 31;
84 }
85 else if ((flt_e == 0xff) && (flt_m != 0)) {
86 /* NaN */
87 m = 1;
88 e = 31;
89 }
90 else {
91 /* regular number */
92 const int new_exp = flt_e - 127;
93 if (new_exp < -14) {
94 /* The float32 lies in the range (0.0, min_normal16) and is rounded
95 * to a nearby float16 value. The result will be either zero, subnormal,
96 * or normal.
97 */
98 e = 0;
99 m = _mesa_lroundevenf((1 << 24) * fabsf(fi.f));
100 }
101 else if (new_exp > 15) {
102 /* map this value to infinity */
103 /* m = 0; - already set */
104 e = 31;
105 }
106 else {
107 /* The float32 lies in the range
108 * [min_normal16, max_normal16 + max_step16)
109 * and is rounded to a nearby float16 value. The result will be
110 * either normal or infinite.
111 */
112 e = new_exp + 15;
113 m = _mesa_lroundevenf(flt_m / (float) (1 << 13));
114 }
115 }
116
117 assert(0 <= m && m <= 1024);
118 if (m == 1024) {
119 /* The float32 was rounded upwards into the range of the next exponent,
120 * so bump the exponent. This correctly handles the case where f32
121 * should be rounded up to float16 infinity.
122 */
123 ++e;
124 m = 0;
125 }
126
127 result = (s << 15) | (e << 10) | m;
128 return result;
129 }
130
131 uint16_t
132 _mesa_float_to_float16_rtz(float val)
133 {
134 return _mesa_float_to_half_rtz(val);
135 }
136
137 /**
138 * Convert a 2-byte half float to a 4-byte float.
139 * Based on code from:
140 * http://www.opengl.org/discussion_boards/ubb/Forum3/HTML/008786.html
141 */
142 float
143 _mesa_half_to_float(uint16_t val)
144 {
145 return util_half_to_float(val);
146 }
147
148 /**
149 * Convert 0.0 to 0x00, 1.0 to 0xff.
150 * Values outside the range [0.0, 1.0] will give undefined results.
151 */
152 uint8_t _mesa_half_to_unorm8(uint16_t val)
153 {
154 const int m = val & 0x3ff;
155 const int e = (val >> 10) & 0x1f;
156 ASSERTED const int s = (val >> 15) & 0x1;
157
158 /* v = round_to_nearest(1.mmmmmmmmmm * 2^(e-15) * 255)
159 * = round_to_nearest((1.mmmmmmmmmm * 255) * 2^(e-15))
160 * = round_to_nearest((1mmmmmmmmmm * 255) * 2^(e-25))
161 * = round_to_zero((1mmmmmmmmmm * 255) * 2^(e-25) + 0.5)
162 * = round_to_zero(((1mmmmmmmmmm * 255) * 2^(e-24) + 1) / 2)
163 *
164 * This happens to give the correct answer for zero/subnormals too
165 */
166 assert(s == 0 && val <= FP16_ONE); /* check 0 <= this <= 1 */
167 /* (implies e <= 15, which means the bit-shifts below are safe) */
168
169 uint32_t v = ((1 << 10) | m) * 255;
170 v = ((v >> (24 - e)) + 1) >> 1;
171 return v;
172 }
173
174 /**
175 * Takes a uint16_t, divides by 65536, converts the infinite-precision
176 * result to fp16 with round-to-zero. Used by the ASTC decoder.
177 */
178 uint16_t _mesa_uint16_div_64k_to_half(uint16_t v)
179 {
180 /* Zero or subnormal. Set the mantissa to (v << 8) and return. */
181 if (v < 4)
182 return v << 8;
183
184 /* Count the leading 0s in the uint16_t */
185 #ifdef HAVE___BUILTIN_CLZ
186 int n = __builtin_clz(v) - 16;
187 #else
188 int n = 16;
189 for (int i = 15; i >= 0; i--) {
190 if (v & (1 << i)) {
191 n = 15 - i;
192 break;
193 }
194 }
195 #endif
196
197 /* Shift the mantissa up so bit 16 is the hidden 1 bit,
198 * mask it off, then shift back down to 10 bits
199 */
200 int m = ( ((uint32_t)v << (n + 1)) & 0xffff ) >> 6;
201
202 /* (0{n} 1 X{15-n}) * 2^-16
203 * = 1.X * 2^(15-n-16)
204 * = 1.X * 2^(14-n - 15)
205 * which is the FP16 form with e = 14 - n
206 */
207 int e = 14 - n;
208
209 assert(e >= 1 && e <= 30);
210 assert(m >= 0 && m < 0x400);
211
212 return (e << 10) | m;
213 }