/*	$OpenBSD: fenv.c,v 1.1 2011/04/28 17:34:23 martynas Exp $	*/

/*
 * Copyright (c) 2011 Martynas Venckus <martynas@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/cdefs.h>

#include <fenv.h>

union u {
	unsigned long long fpsr;
	unsigned int bits[2];
};

/*
 * The following constant represents the default floating-point environment
 * (that is, the one installed at program startup) and has type pointer to
 * const-qualified fenv_t.
 *
 * It can be used as an argument to the functions within the <fenv.h> header
 * that manage the floating-point environment, namely fesetenv() and
 * feupdateenv().
 */
fenv_t __fe_dfl_env = 0;

/*
 * The feclearexcept() function clears the supported floating-point exceptions
 * represented by `excepts'.
 */
int
feclearexcept(int excepts)
{
	volatile union u u;

	excepts &= FE_ALL_EXCEPT;

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	/* Clear the requested floating-point exceptions */
	u.bits[0] &= ~(excepts << _MASK_SHIFT);

	/* Load the floating-point status register */
	__asm__ __volatile__ ("fldd 0(%0), %%fr0" : : "r" (&u.fpsr));

	return (0);
}

/*
 * The fegetexceptflag() function stores an implementation-defined
 * representation of the states of the floating-point status flags indicated by
 * the argument excepts in the object pointed to by the argument flagp.
 */
int
fegetexceptflag(fexcept_t *flagp, int excepts)
{
	volatile union u u;

	excepts &= FE_ALL_EXCEPT;

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	/* Store the results in flagp */
	*flagp = (u.bits[0] >> _MASK_SHIFT) & excepts;

	return (0);
}

/*
 * The feraiseexcept() function raises the supported floating-point exceptions
 * represented by the argument `excepts'.
 */
int
feraiseexcept(int excepts)
{
	volatile double d;

	excepts &= FE_ALL_EXCEPT;

	/*
	 * With a compiler that supports the FENV_ACCESS pragma
	 * properly, simple expressions like '0.0 / 0.0' should
	 * be sufficient to generate traps.  Unfortunately, we
	 * need to bring a volatile variable into the equation
	 * to prevent incorrect optimizations.
	 */
	if (excepts & FE_INVALID) {
		d = 0.0;
		d = 0.0 / d;
	}
	if (excepts & FE_DIVBYZERO) {
		d = 0.0;
		d = 1.0 / d;
	}
	if (excepts & FE_OVERFLOW) {
		d = 0x1.ffp1023;
		d *= 2.0;
	}
	if (excepts & FE_UNDERFLOW) {
		d = 0x1p-1022;
		d /= 0x1p1023;
	}
	if (excepts & FE_INEXACT) {
		d = 0x1p-1022;
		d += 1.0;
	}
	__asm__ __volatile__ ("fldd 0(%%sr0,%%sp), %0" : "=f" (d));

	return (0);
}

/*
 * This function sets the floating-point status flags indicated by the argument
 * `excepts' to the states stored in the object pointed to by `flagp'. It does
 * NOT raise any floating-point exceptions, but only sets the state of the flags.
 */
int
fesetexceptflag(const fexcept_t *flagp, int excepts)
{
	volatile union u u;

	excepts &= FE_ALL_EXCEPT;

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	/* Set the requested status flags */
	u.bits[0] &= ~(excepts << _MASK_SHIFT);
	u.bits[0] |= (*flagp & excepts) << _MASK_SHIFT;

	/* Load the floating-point status register */
	__asm__ __volatile__ ("fldd 0(%0), %%fr0" : : "r" (&u.fpsr));

	return (0);
}

/*
 * The fetestexcept() function determines which of a specified subset of the
 * floating-point exception flags are currently set. The `excepts' argument
 * specifies the floating-point status flags to be queried.
 */
int
fetestexcept(int excepts)
{
	volatile union u u;

	excepts &= FE_ALL_EXCEPT;

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	return ((u.bits[0] >> _MASK_SHIFT) & excepts);
}

/*
 * The fegetround() function gets the current rounding direction.
 */
int
fegetround(void)
{
	volatile union u u;

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	return (u.bits[0] & _ROUND_MASK);
}

/*
 * The fesetround() function establishes the rounding direction represented by
 * its argument `round'. If the argument is not equal to the value of a rounding
 * direction macro, the rounding direction is not changed.
 */
int
fesetround(int round)
{
	volatile union u u;

	/* Check whether requested rounding direction is supported */
	if (round & ~_ROUND_MASK)
		return (-1);

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	/* Set the rounding direction */
	u.bits[0] &= ~_ROUND_MASK;
	u.bits[0] |= round;

	/* Load the floating-point status register */
	__asm__ __volatile__ ("fldd 0(%0), %%fr0" : : "r" (&u.fpsr));

	return (0);
}

/*
 * The fegetenv() function attempts to store the current floating-point
 * environment in the object pointed to by envp.
 */
int
fegetenv(fenv_t *envp)
{
	volatile union u u;

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	*envp = u.bits[0];

	return (0);
}

/*
 * The feholdexcept() function saves the current floating-point environment
 * in the object pointed to by envp, clears the floating-point status flags, and
 * then installs a non-stop (continue on floating-point exceptions) mode, if
 * available, for all floating-point exceptions.
 */
int
feholdexcept(fenv_t *envp)
{
	volatile union u u;

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	*envp = u.bits[0];

	/* Clear exception flags in FPSR */
	u.bits[0] &= ~(FE_ALL_EXCEPT << _MASK_SHIFT);

	/* Mask all exceptions */
	u.bits[0] &= ~FE_ALL_EXCEPT;
	__asm__ __volatile__ ("fldd 0(%0), %%fr0" : : "r" (&u.fpsr));

	return (0);
}

/*
 * The fesetenv() function attempts to establish the floating-point environment
 * represented by the object pointed to by envp. The argument `envp' points
 * to an object set by a call to fegetenv() or feholdexcept(), or equal a
 * floating-point environment macro. The fesetenv() function does not raise
 * floating-point exceptions, but only installs the state of the floating-point
 * status flags represented through its argument.
 */
int
fesetenv(const fenv_t *envp)
{
	volatile union u u;

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	/* Set the requested flags */
	u.bits[0] &= ~(FE_ALL_EXCEPT | _ROUND_MASK |
	    (FE_ALL_EXCEPT << _MASK_SHIFT));
	u.bits[0] |= *envp & (FE_ALL_EXCEPT | _ROUND_MASK |
	    (FE_ALL_EXCEPT << _MASK_SHIFT));

	/* Load the floating-point status register */
	__asm__ __volatile__ ("fldd 0(%0), %%fr0" : : "r" (&u.fpsr));

	return (0);
}

/*
 * The feupdateenv() function saves the currently raised floating-point
 * exceptions in its automatic storage, installs the floating-point environment
 * represented by the object pointed to by `envp', and then raises the saved
 * floating-point exceptions. The argument `envp' shall point to an object set
 * by a call to feholdexcept() or fegetenv(), or equal a floating-point
 * environment macro.
 */
int
feupdateenv(const fenv_t *envp)
{
	volatile union u u;

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	/* Install new floating-point environment */
	fesetenv(envp);

	/* Raise any previously accumulated exceptions */
	feraiseexcept(u.bits[0] >> _MASK_SHIFT);

	return (0);
}

/*
 * The following functions are extentions to the standard
 */
int
feenableexcept(int mask)
{
	volatile union u u;
	unsigned int omask;

	mask &= FE_ALL_EXCEPT;

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	omask = u.bits[0] & FE_ALL_EXCEPT;
	u.bits[0] |= mask;

	/* Load the floating-point status register */
	__asm__ __volatile__ ("fldd 0(%0), %%fr0" : : "r" (&u.fpsr));

	return (omask);

}

int
fedisableexcept(int mask)
{
	volatile union u u;
	unsigned int omask;

	mask &= FE_ALL_EXCEPT;

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	omask = u.bits[0] & FE_ALL_EXCEPT;
	u.bits[0] &= ~mask;

	/* Load the floating-point status register */
	__asm__ __volatile__ ("fldd 0(%0), %%fr0" : : "r" (&u.fpsr));

	return (omask);
}

int
fegetexcept(void)
{
	volatile union u u;

	/* Store the current floating-point status register */
	__asm__ __volatile__ ("fstd %%fr0, 0(%1)" : "=m" (u.fpsr) :
	    "r" (&u.fpsr));

	return (u.bits[0] & FE_ALL_EXCEPT);
}