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3ee947b1 | 1 | /* FPU control word bits. x86 version. |
6d7e8eda | 2 | Copyright (C) 1993-2023 Free Software Foundation, Inc. |
c7c8ca97 | 3 | This file is part of the GNU C Library. |
c7c8ca97 AJ |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
59ba27a6 | 16 | License along with the GNU C Library; if not, see |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
c7c8ca97 AJ |
18 | |
19 | #ifndef _FPU_CONTROL_H | |
20 | #define _FPU_CONTROL_H 1 | |
21 | ||
22 | /* Note that this file sets on x86-64 only the x87 FPU, it does not | |
23 | touch the SSE unit. */ | |
24 | ||
25 | /* Here is the dirty part. Set up your 387 through the control word | |
26 | * (cw) register. | |
27 | * | |
28 | * 15-13 12 11-10 9-8 7-6 5 4 3 2 1 0 | |
29 | * | reserved | IC | RC | PC | reserved | PM | UM | OM | ZM | DM | IM | |
30 | * | |
31 | * IM: Invalid operation mask | |
32 | * DM: Denormalized operand mask | |
33 | * ZM: Zero-divide mask | |
34 | * OM: Overflow mask | |
35 | * UM: Underflow mask | |
36 | * PM: Precision (inexact result) mask | |
37 | * | |
38 | * Mask bit is 1 means no interrupt. | |
39 | * | |
40 | * PC: Precision control | |
41 | * 11 - round to extended precision | |
42 | * 10 - round to double precision | |
43 | * 00 - round to single precision | |
44 | * | |
45 | * RC: Rounding control | |
46 | * 00 - rounding to nearest | |
47 | * 01 - rounding down (toward - infinity) | |
48 | * 10 - rounding up (toward + infinity) | |
49 | * 11 - rounding toward zero | |
50 | * | |
51 | * IC: Infinity control | |
52 | * That is for 8087 and 80287 only. | |
53 | * | |
54 | * The hardware default is 0x037f which we use. | |
55 | */ | |
56 | ||
57 | #include <features.h> | |
58 | ||
59 | /* masking of interrupts */ | |
60 | #define _FPU_MASK_IM 0x01 | |
61 | #define _FPU_MASK_DM 0x02 | |
62 | #define _FPU_MASK_ZM 0x04 | |
63 | #define _FPU_MASK_OM 0x08 | |
64 | #define _FPU_MASK_UM 0x10 | |
65 | #define _FPU_MASK_PM 0x20 | |
66 | ||
67 | /* precision control */ | |
68 | #define _FPU_EXTENDED 0x300 /* libm requires double extended precision. */ | |
69 | #define _FPU_DOUBLE 0x200 | |
70 | #define _FPU_SINGLE 0x0 | |
71 | ||
72 | /* rounding control */ | |
73 | #define _FPU_RC_NEAREST 0x0 /* RECOMMENDED */ | |
74 | #define _FPU_RC_DOWN 0x400 | |
75 | #define _FPU_RC_UP 0x800 | |
76 | #define _FPU_RC_ZERO 0xC00 | |
77 | ||
78 | #define _FPU_RESERVED 0xF0C0 /* Reserved bits in cw */ | |
79 | ||
80 | ||
81 | /* The fdlibm code requires strict IEEE double precision arithmetic, | |
82 | and no interrupts for exceptions, rounding to nearest. */ | |
83 | ||
84 | #define _FPU_DEFAULT 0x037f | |
85 | ||
86 | /* IEEE: same as above. */ | |
87 | #define _FPU_IEEE 0x037f | |
88 | ||
89 | /* Type of the control word. */ | |
90 | typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__))); | |
91 | ||
3ee947b1 L |
92 | /* Macros for accessing the hardware control word. "*&" is used to |
93 | work around a bug in older versions of GCC. __volatile__ is used | |
94 | to support combination of writing the control register and reading | |
95 | it back. Without __volatile__, the old value may be used for reading | |
96 | back under compiler optimization. | |
97 | ||
98 | Note that the use of these macros is not sufficient anymore with | |
99 | recent hardware nor on x86-64. Some floating point operations are | |
100 | executed in the SSE/SSE2 engines which have their own control and | |
101 | status register. */ | |
102 | #define _FPU_GETCW(cw) __asm__ __volatile__ ("fnstcw %0" : "=m" (*&cw)) | |
103 | #define _FPU_SETCW(cw) __asm__ __volatile__ ("fldcw %0" : : "m" (*&cw)) | |
c7c8ca97 AJ |
104 | |
105 | /* Default control word set at startup. */ | |
106 | extern fpu_control_t __fpu_control; | |
107 | ||
108 | #endif /* fpu_control.h */ |