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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