1 // Copyright 2016 The SwiftShader Authors. All Rights Reserved.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 //    http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 
15 #include "Half.hpp"
16 
17 namespace sw
18 {
half(float fp32)19 	half::half(float fp32)
20 	{
21 		unsigned int fp32i = *(unsigned int*)&fp32;
22 		unsigned int sign = (fp32i & 0x80000000) >> 16;
23 		unsigned int abs = fp32i & 0x7FFFFFFF;
24 
25 		if(abs > 0x47FFEFFF)   // Infinity
26 		{
27 			fp16i = sign | 0x7FFF;
28 		}
29 		else if(abs < 0x38800000)   // Denormal
30 		{
31 			unsigned int mantissa = (abs & 0x007FFFFF) | 0x00800000;
32 			int e = 113 - (abs >> 23);
33 
34 			if(e < 24)
35 			{
36 				abs = mantissa >> e;
37 			}
38 			else
39 			{
40 				abs = 0;
41 			}
42 
43 			fp16i = sign | (abs + 0x00000FFF + ((abs >> 13) & 1)) >> 13;
44 		}
45 		else
46 		{
47 			fp16i = sign | (abs + 0xC8000000 + 0x00000FFF + ((abs >> 13) & 1)) >> 13;
48 		}
49 	}
50 
operator float() const51 	half::operator float() const
52 	{
53 		unsigned int fp32i;
54 
55 		int s = (fp16i >> 15) & 0x00000001;
56 		int e = (fp16i >> 10) & 0x0000001F;
57 		int m =  fp16i        & 0x000003FF;
58 
59 		if(e == 0)
60 		{
61 			if(m == 0)
62 			{
63 				fp32i = s << 31;
64 
65 				return (float&)fp32i;
66 			}
67 			else
68 			{
69 				while(!(m & 0x00000400))
70 				{
71 					m <<= 1;
72 					e -=  1;
73 				}
74 
75 				e += 1;
76 				m &= ~0x00000400;
77 			}
78 		}
79 
80 		e = e + (127 - 15);
81 		m = m << 13;
82 
83 		fp32i = (s << 31) | (e << 23) | m;
84 
85 		return (float&)fp32i;
86 	}
87 
operator =(half h)88 	half &half::operator=(half h)
89 	{
90 		fp16i = h.fp16i;
91 
92 		return *this;
93 	}
94 
95 
operator =(float f)96 	half &half::operator=(float f)
97 	{
98 		*this = half(f);
99 
100 		return *this;
101 	}
102 }
103