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1 | /* Software floating-point emulation. |
2 | Truncate bfloat16 into IEEE half. | |
3 | Copyright (C) 2022-2024 Free Software Foundation, Inc. | |
4 | This file is part of the GNU C Library. | |
5 | ||
6 | The GNU C Library is free software; you can redistribute it and/or | |
7 | modify it under the terms of the GNU Lesser General Public | |
8 | License as published by the Free Software Foundation; either | |
9 | version 2.1 of the License, or (at your option) any later version. | |
10 | ||
11 | In addition to the permissions in the GNU Lesser General Public | |
12 | License, the Free Software Foundation gives you unlimited | |
13 | permission to link the compiled version of this file into | |
14 | combinations with other programs, and to distribute those | |
15 | combinations without any restriction coming from the use of this | |
16 | file. (The Lesser General Public License restrictions do apply in | |
17 | other respects; for example, they cover modification of the file, | |
18 | and distribution when not linked into a combine executable.) | |
19 | ||
20 | The GNU C Library is distributed in the hope that it will be useful, | |
21 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
22 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
23 | Lesser General Public License for more details. | |
24 | ||
25 | You should have received a copy of the GNU Lesser General Public | |
26 | License along with the GNU C Library; if not, see | |
27 | <http://www.gnu.org/licenses/>. */ | |
28 | ||
29 | #include "soft-fp.h" | |
30 | #include "half.h" | |
31 | #include "brain.h" | |
32 | #include "single.h" | |
33 | ||
34 | /* BFtype and HFtype are unordered, neither is a superset or subset | |
35 | of each other. Convert BFtype to SFtype (lossless) and then | |
36 | truncate to HFtype. */ | |
37 | ||
38 | HFtype | |
39 | __truncbfhf2 (BFtype a) | |
40 | { | |
41 | FP_DECL_EX; | |
42 | FP_DECL_H (A); | |
43 | FP_DECL_S (B); | |
44 | FP_DECL_B (R); | |
45 | SFtype b; | |
46 | HFtype r; | |
47 | ||
48 | FP_INIT_ROUNDMODE; | |
49 | /* Optimize BFtype to SFtype conversion to simple left shift | |
50 | by 16 if possible, we don't need to raise exceptions on sNaN | |
51 | here as the SFtype to HFtype truncation should do that too. */ | |
52 | if (sizeof (BFtype) == 2 | |
53 | && sizeof (unsigned short) == 2 | |
54 | && sizeof (SFtype) == 4 | |
55 | && sizeof (unsigned int) == 4) | |
56 | { | |
57 | union { BFtype a; unsigned short b; } u1; | |
58 | union { SFtype a; unsigned int b; } u2; | |
59 | u1.a = a; | |
60 | u2.b = (u1.b << 8) << 8; | |
61 | b = u2.a; | |
62 | } | |
63 | else | |
64 | { | |
65 | FP_UNPACK_RAW_B (A, a); | |
66 | FP_EXTEND (S, B, 1, 1, B, A); | |
67 | FP_PACK_RAW_S (b, B); | |
68 | } | |
69 | FP_UNPACK_SEMIRAW_S (B, b); | |
70 | FP_TRUNC (H, S, 1, 1, R, B); | |
71 | FP_PACK_SEMIRAW_H (r, R); | |
72 | FP_HANDLE_EXCEPTIONS; | |
73 | ||
74 | return r; | |
75 | } |