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| 63 | pj | 1 | /* FPU control word bits. i387 version. |
| 2 | Copyright (C) 1993,1995,1996,1997,1998,2000,2001 Free Software Foundation, Inc. |
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| 3 | This file is part of the GNU C Library. |
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| 4 | Contributed by Olaf Flebbe. |
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| 5 | |||
| 6 | The GNU C Library is free software; you can redistribute it and/or |
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| 7 | modify it under the terms of the GNU Lesser General Public |
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| 8 | License as published by the Free Software Foundation; either |
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| 9 | version 2.1 of the License, or (at your option) any later version. |
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| 10 | |||
| 11 | The GNU C Library is distributed in the hope that it will be useful, |
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| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 14 | Lesser General Public License for more details. |
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| 15 | |||
| 16 | You should have received a copy of the GNU Lesser General Public |
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| 17 | License along with the GNU C Library; if not, write to the Free |
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| 18 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
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| 19 | 02111-1307 USA. */ |
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| 20 | |||
| 21 | #ifndef _FPU_CONTROL_H |
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| 22 | #define _FPU_CONTROL_H 1 |
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| 23 | |||
| 24 | /* Here is the dirty part. Set up your 387 through the control word |
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| 25 | * (cw) register. |
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| 26 | * |
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| 27 | * 15-13 12 11-10 9-8 7-6 5 4 3 2 1 0 |
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| 28 | * | reserved | IC | RC | PC | reserved | PM | UM | OM | ZM | DM | IM |
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| 29 | * |
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| 30 | * IM: Invalid operation mask |
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| 31 | * DM: Denormalized operand mask |
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| 32 | * ZM: Zero-divide mask |
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| 33 | * OM: Overflow mask |
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| 34 | * UM: Underflow mask |
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| 35 | * PM: Precision (inexact result) mask |
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| 36 | * |
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| 37 | * Mask bit is 1 means no interrupt. |
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| 38 | * |
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| 39 | * PC: Precision control |
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| 40 | * 11 - round to extended precision |
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| 41 | * 10 - round to double precision |
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| 42 | * 00 - round to single precision |
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| 43 | * |
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| 44 | * RC: Rounding control |
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| 45 | * 00 - rounding to nearest |
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| 46 | * 01 - rounding down (toward - infinity) |
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| 47 | * 10 - rounding up (toward + infinity) |
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| 48 | * 11 - rounding toward zero |
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| 49 | * |
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| 50 | * IC: Infinity control |
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| 51 | * That is for 8087 and 80287 only. |
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| 52 | * |
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| 53 | * The hardware default is 0x037f which we use. |
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| 54 | */ |
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| 55 | |||
| 56 | #include <features.h> |
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| 57 | |||
| 58 | /* masking of interrupts */ |
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| 59 | #define _FPU_MASK_IM 0x01 |
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| 60 | #define _FPU_MASK_DM 0x02 |
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| 61 | #define _FPU_MASK_ZM 0x04 |
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| 62 | #define _FPU_MASK_OM 0x08 |
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| 63 | #define _FPU_MASK_UM 0x10 |
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| 64 | #define _FPU_MASK_PM 0x20 |
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| 65 | |||
| 66 | /* precision control */ |
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| 67 | #define _FPU_EXTENDED 0x300 /* libm requires double extended precision. */ |
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| 68 | #define _FPU_DOUBLE 0x200 |
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| 69 | #define _FPU_SINGLE 0x0 |
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| 70 | |||
| 71 | /* rounding control */ |
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| 72 | #define _FPU_RC_NEAREST 0x0 /* RECOMMENDED */ |
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| 73 | #define _FPU_RC_DOWN 0x400 |
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| 74 | #define _FPU_RC_UP 0x800 |
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| 75 | #define _FPU_RC_ZERO 0xC00 |
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| 76 | |||
| 77 | #define _FPU_RESERVED 0xF0C0 /* Reserved bits in cw */ |
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| 78 | |||
| 79 | |||
| 80 | /* The fdlibm code requires strict IEEE double precision arithmetic, |
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| 81 | and no interrupts for exceptions, rounding to nearest. */ |
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| 82 | |||
| 83 | #define _FPU_DEFAULT 0x037f |
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| 84 | |||
| 85 | /* IEEE: same as above. */ |
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| 86 | #define _FPU_IEEE 0x037f |
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| 87 | |||
| 88 | /* Type of the control word. */ |
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| 89 | typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__))); |
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| 90 | |||
| 91 | /* Macros for accessing the hardware control word. */ |
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| 92 | #define _FPU_GETCW(cw) __asm__ ("fnstcw %0" : "=m" (*&cw)) |
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| 93 | #define _FPU_SETCW(cw) __asm__ ("fldcw %0" : : "m" (*&cw)) |
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| 94 | |||
| 95 | /* Default control word set at startup. */ |
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| 96 | extern fpu_control_t __fpu_control; |
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| 97 | |||
| 98 | #endif /* fpu_control.h */ |