glibc/sysdeps/m68k/fpu_control.h

/* 68k FPU control word definitions.
   Copyright (C) 1996-2023 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library.  If not, see
   <https://www.gnu.org/licenses/>.  */

#ifndef _FPU_CONTROL_H
#define _FPU_CONTROL_H

/*
 * Motorola floating point control register bits.
 *
 * 31-16  -> reserved (read as 0, ignored on write)
 * 15     -> enable trap for BSUN exception
 * 14     -> enable trap for SNAN exception
 * 13     -> enable trap for OPERR exception
 * 12     -> enable trap for OVFL exception
 * 11     -> enable trap for UNFL exception
 * 10     -> enable trap for DZ exception
 *  9     -> enable trap for INEX2 exception (INEX on Coldfire)
 *  8     -> enable trap for INEX1 exception (IDE on Coldfire)
 *  7-6   -> Precision Control (only bit 6 is used on Coldfire)
 *  5-4   -> Rounding Control
 *  3-0   -> zero (read as 0, write as 0)
 *
 *
 * Precision Control:
 * 00 - round to extended precision
 * 01 - round to single precision
 * 10 - round to double precision
 * 11 - undefined
 *
 * Rounding Control:
 * 00 - rounding to nearest (RN)
 * 01 - rounding toward zero (RZ)
 * 10 - rounding (down)toward minus infinity (RM)
 * 11 - rounding (up) toward plus infinity (RP)
 *
 * The hardware default is 0x0000. I choose 0x5400.
 */

#include <features.h>

#if defined (__mcoldfire__) && !defined (__mcffpu__)

# define _FPU_RESERVED 0xffffffff
# define _FPU_DEFAULT  0x00000000
# define _FPU_GETCW(cw) ((cw) = 0)
# define _FPU_SETCW(cw) ((void) (cw))

#else

/* masking of interrupts */
# define _FPU_MASK_BSUN  0x8000
# define _FPU_MASK_SNAN  0x4000
# define _FPU_MASK_OPERR 0x2000
# define _FPU_MASK_OVFL  0x1000
# define _FPU_MASK_UNFL  0x0800
# define _FPU_MASK_DZ    0x0400
# define _FPU_MASK_INEX1 0x0200
# define _FPU_MASK_INEX2 0x0100

/* precision control */
# ifdef __mcoldfire__
#  define _FPU_DOUBLE   0x00
# else
#  define _FPU_EXTENDED 0x00   /* RECOMMENDED */
#  define _FPU_DOUBLE   0x80
# endif
# define _FPU_SINGLE   0x40     /* DO NOT USE */

/* rounding control */
# define _FPU_RC_NEAREST 0x00    /* RECOMMENDED */
# define _FPU_RC_ZERO    0x10
# define _FPU_RC_DOWN    0x20
# define _FPU_RC_UP      0x30

# ifdef __mcoldfire__
#  define _FPU_RESERVED 0xFFFF800F
# else
#  define _FPU_RESERVED 0xFFFF000F  /* Reserved bits in fpucr */
# endif


/* Now two recommended fpucr */

/* The fdlibm code requires no interrupts for exceptions.  Don't
   change the rounding mode, it would break long double I/O!  */
# define _FPU_DEFAULT  0x00000000

/* IEEE:  same as above, but exceptions.  We must make it non-zero so
   that __setfpucw works.  This bit will be ignored.  */
# define _FPU_IEEE     0x00000001

/* Macros for accessing the hardware control word.  */
# define _FPU_GETCW(cw) __asm__ ("fmove%.l %!, %0" : "=dm" (cw))
# define _FPU_SETCW(cw) __asm__ volatile ("fmove%.l %0, %!" : : "dm" (cw))
#endif

/* Type of the control word.  */
typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__SI__)));

/* Default control word set at startup.  */
extern fpu_control_t __fpu_control;

#endif /* _M68K_FPU_CONTROL_H */