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We stopped adding "Contributed by" or similar lines in sources in 2012 in favour of git logs and keeping the Contributors section of the glibc manual up to date. Removing these lines makes the license header a bit more consistent across files and also removes the possibility of error in attribution when license blocks or files are copied across since the contributed-by lines don't actually reflect reality in those cases. Move all "Contributed by" and similar lines (Written by, Test by, etc.) into a new file CONTRIBUTED-BY to retain record of these contributions. These contributors are also mentioned in manual/contrib.texi, so we just maintain this additional record as a courtesy to the earlier developers. The following scripts were used to filter a list of files to edit in place and to clean up the CONTRIBUTED-BY file respectively. These were not added to the glibc sources because they're not expected to be of any use in future given that this is a one time task: https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dc https://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02 Reviewed-by: Carlos O'Donell <carlos@redhat.com>
109 lines
3.5 KiB
C
109 lines
3.5 KiB
C
/* FPU control word bits. x86 version.
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Copyright (C) 1993-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _FPU_CONTROL_H
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#define _FPU_CONTROL_H 1
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/* Note that this file sets on x86-64 only the x87 FPU, it does not
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touch the SSE unit. */
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/* Here is the dirty part. Set up your 387 through the control word
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* (cw) register.
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*
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* 15-13 12 11-10 9-8 7-6 5 4 3 2 1 0
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* | reserved | IC | RC | PC | reserved | PM | UM | OM | ZM | DM | IM
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*
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* IM: Invalid operation mask
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* DM: Denormalized operand mask
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* ZM: Zero-divide mask
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* OM: Overflow mask
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* UM: Underflow mask
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* PM: Precision (inexact result) mask
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*
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* Mask bit is 1 means no interrupt.
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*
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* PC: Precision control
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* 11 - round to extended precision
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* 10 - round to double precision
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* 00 - round to single precision
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*
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* RC: Rounding control
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* 00 - rounding to nearest
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* 01 - rounding down (toward - infinity)
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* 10 - rounding up (toward + infinity)
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* 11 - rounding toward zero
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*
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* IC: Infinity control
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* That is for 8087 and 80287 only.
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*
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* The hardware default is 0x037f which we use.
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*/
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#include <features.h>
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/* masking of interrupts */
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#define _FPU_MASK_IM 0x01
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#define _FPU_MASK_DM 0x02
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#define _FPU_MASK_ZM 0x04
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#define _FPU_MASK_OM 0x08
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#define _FPU_MASK_UM 0x10
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#define _FPU_MASK_PM 0x20
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/* precision control */
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#define _FPU_EXTENDED 0x300 /* libm requires double extended precision. */
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#define _FPU_DOUBLE 0x200
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#define _FPU_SINGLE 0x0
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/* rounding control */
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#define _FPU_RC_NEAREST 0x0 /* RECOMMENDED */
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#define _FPU_RC_DOWN 0x400
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#define _FPU_RC_UP 0x800
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#define _FPU_RC_ZERO 0xC00
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#define _FPU_RESERVED 0xF0C0 /* Reserved bits in cw */
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/* The fdlibm code requires strict IEEE double precision arithmetic,
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and no interrupts for exceptions, rounding to nearest. */
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#define _FPU_DEFAULT 0x037f
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/* IEEE: same as above. */
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#define _FPU_IEEE 0x037f
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/* Type of the control word. */
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typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__)));
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/* Macros for accessing the hardware control word. "*&" is used to
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work around a bug in older versions of GCC. __volatile__ is used
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to support combination of writing the control register and reading
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it back. Without __volatile__, the old value may be used for reading
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back under compiler optimization.
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Note that the use of these macros is not sufficient anymore with
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recent hardware nor on x86-64. Some floating point operations are
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executed in the SSE/SSE2 engines which have their own control and
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status register. */
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#define _FPU_GETCW(cw) __asm__ __volatile__ ("fnstcw %0" : "=m" (*&cw))
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#define _FPU_SETCW(cw) __asm__ __volatile__ ("fldcw %0" : : "m" (*&cw))
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/* Default control word set at startup. */
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extern fpu_control_t __fpu_control;
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#endif /* fpu_control.h */
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