1 /*
2 * Copyright © 2014 Intel Corporation
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 */
23 #include "brw_reg.h"
24
25 union fu {
26 float f;
27 unsigned u;
28 struct {
29 unsigned mantissa:23;
30 unsigned exponent:8;
31 unsigned sign:1;
32 } s;
33 };
34
35 int
brw_float_to_vf(float f)36 brw_float_to_vf(float f)
37 {
38 union fu fu = { .f = f };
39
40 /* ±0.0f is special cased. */
41 if (f == 0.0f)
42 return fu.s.sign << 7;
43
44 unsigned mantissa = fu.s.mantissa >> (23 - 4);
45 unsigned exponent = fu.s.exponent - (127 - 3);
46 unsigned vf = (fu.s.sign << 7) | (exponent << 4) | mantissa;
47
48 /* 0.125 would have had the same representation as 0.0, so reject it. */
49 if ((vf & 0x7f) == 0)
50 return -1;
51
52 /* Make sure the mantissa fits in 4-bits and the exponent in 3-bits. */
53 if (fu.u & 0x7ffff || exponent > 7)
54 return -1;
55
56 return vf;
57 }
58
59 float
brw_vf_to_float(unsigned char vf)60 brw_vf_to_float(unsigned char vf)
61 {
62 union fu fu;
63
64 /* ±0.0f is special cased. */
65 if (vf == 0x00 || vf == 0x80) {
66 fu.u = vf << 24;
67 return fu.f;
68 }
69
70 fu.s.sign = vf >> 7;
71 fu.s.exponent = ((vf & 0x70) >> 4) + (127 - 3);
72 fu.s.mantissa = (vf & 0xf) << (23 - 4);
73
74 return fu.f;
75 }
76