1 /* FPU control word bits. i387 version. 2 Copyright (C) 1993,1995-1998,2000,2001,2003 Free Software Foundation, Inc. 3 This file is part of the GNU C Library. 4 Contributed by Olaf Flebbe. 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 The GNU C Library is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 Lesser General Public License for more details. 15 16 You should have received a copy of the GNU Lesser General Public 17 License along with the GNU C Library; if not, write to the Free 18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 19 02111-1307 USA. */ 20 21 #ifndef _FPU_CONTROL_H 22 #define _FPU_CONTROL_H 1 23 24 /* Here is the dirty part. Set up your 387 through the control word 25 * (cw) register. 26 * 27 * 15-13 12 11-10 9-8 7-6 5 4 3 2 1 0 28 * | reserved | IC | RC | PC | reserved | PM | UM | OM | ZM | DM | IM 29 * 30 * IM: Invalid operation mask 31 * DM: Denormalized operand mask 32 * ZM: Zero-divide mask 33 * OM: Overflow mask 34 * UM: Underflow mask 35 * PM: Precision (inexact result) mask 36 * 37 * Mask bit is 1 means no interrupt. 38 * 39 * PC: Precision control 40 * 11 - round to extended precision 41 * 10 - round to double precision 42 * 00 - round to single precision 43 * 44 * RC: Rounding control 45 * 00 - rounding to nearest 46 * 01 - rounding down (toward - infinity) 47 * 10 - rounding up (toward + infinity) 48 * 11 - rounding toward zero 49 * 50 * IC: Infinity control 51 * That is for 8087 and 80287 only. 52 * 53 * The hardware default is 0x037f which we use. 54 */ 55 56 #include <features.h> 57 58 /* masking of interrupts */ 59 #define _FPU_MASK_IM 0x01 60 #define _FPU_MASK_DM 0x02 61 #define _FPU_MASK_ZM 0x04 62 #define _FPU_MASK_OM 0x08 63 #define _FPU_MASK_UM 0x10 64 #define _FPU_MASK_PM 0x20 65 66 /* precision control */ 67 #define _FPU_EXTENDED 0x300 /* libm requires double extended precision. */ 68 #define _FPU_DOUBLE 0x200 69 #define _FPU_SINGLE 0x0 70 71 /* rounding control */ 72 #define _FPU_RC_NEAREST 0x0 /* RECOMMENDED */ 73 #define _FPU_RC_DOWN 0x400 74 #define _FPU_RC_UP 0x800 75 #define _FPU_RC_ZERO 0xC00 76 77 #define _FPU_RESERVED 0xF0C0 /* Reserved bits in cw */ 78 79 80 /* The fdlibm code requires strict IEEE double precision arithmetic, 81 and no interrupts for exceptions, rounding to nearest. */ 82 83 #define _FPU_DEFAULT 0x037f 84 85 /* IEEE: same as above. */ 86 #define _FPU_IEEE 0x037f 87 88 /* Type of the control word. */ 89 typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__))); 90 91 /* Macros for accessing the hardware control word. 92 93 Note that the use of these macros is no sufficient anymore with 94 recent hardware. Some floating point operations are executed in 95 the SSE/SSE2 engines which have their own control and status register. */ 96 #define _FPU_GETCW(cw) __asm__ __volatile__ ("fnstcw %0" : "=m" (*&cw)) 97 #define _FPU_SETCW(cw) __asm__ __volatile__ ("fldcw %0" : : "m" (*&cw)) 98 99 /* Default control word set at startup. */ 100 extern fpu_control_t __fpu_control; 101 102 #endif /* fpu_control.h */ 103
