xref: /src/sys/arch/hppa/spmath/dfdiv.c

/*	$NetBSD: dfdiv.c,v 1.1 2002/06/05 01:04:24 fredette Exp $	*/

/*	$OpenBSD: dfdiv.c,v 1.4 2001/03/29 03:58:17 mickey Exp $	*/

/*
 * Copyright 1996 1995 by Open Software Foundation, Inc.
 *              All Rights Reserved
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation for any purpose and without fee is hereby granted,
 * provided that the above copyright notice appears in all copies and
 * that both the copyright notice and this permission notice appear in
 * supporting documentation.
 *
 * OSF DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE.
 *
 * IN NO EVENT SHALL OSF BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
 * NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */
/*
 * pmk1.1
 */
/*
 * (c) Copyright 1986 HEWLETT-PACKARD COMPANY
 *
 * To anyone who acknowledges that this file is provided "AS IS"
 * without any express or implied warranty:
 *     permission to use, copy, modify, and distribute this file
 * for any purpose is hereby granted without fee, provided that
 * the above copyright notice and this notice appears in all
 * copies, and that the name of Hewlett-Packard Company not be
 * used in advertising or publicity pertaining to distribution
 * of the software without specific, written prior permission.
 * Hewlett-Packard Company makes no representations about the
 * suitability of this software for any purpose.
 */

#include "../spmath/float.h"
#include "../spmath/dbl_float.h"

/*
 *  Double Precision Floating-point Divide
 */

int
dbl_fdiv(srcptr1,srcptr2,dstptr,status)

dbl_floating_point *srcptr1, *srcptr2, *dstptr;
unsigned int *status;
{
	register unsigned int opnd1p1, opnd1p2, opnd2p1, opnd2p2;
	register unsigned int opnd3p1, opnd3p2, resultp1, resultp2;
	register int dest_exponent, count;
	register int inexact = FALSE, guardbit = FALSE, stickybit = FALSE;
	int is_tiny;

	Dbl_copyfromptr(srcptr1,opnd1p1,opnd1p2);
	Dbl_copyfromptr(srcptr2,opnd2p1,opnd2p2);
	/*
	 * set sign bit of result
	 */
	if (Dbl_sign(opnd1p1) ^ Dbl_sign(opnd2p1))
		Dbl_setnegativezerop1(resultp1);
	else Dbl_setzerop1(resultp1);
	/*
	 * check first operand for NaN's or infinity
	 */
	if (Dbl_isinfinity_exponent(opnd1p1)) {
		if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
			if (Dbl_isnotnan(opnd2p1,opnd2p2)) {
				if (Dbl_isinfinity(opnd2p1,opnd2p2)) {
					/*
					 * invalid since both operands
					 * are infinity
					 */
					if (Is_invalidtrap_enabled())
						return(INVALIDEXCEPTION);
					Set_invalidflag();
					Dbl_makequietnan(resultp1,resultp2);
					Dbl_copytoptr(resultp1,resultp2,dstptr);
					return(NOEXCEPTION);
				}
				/*
				 * return infinity
				 */
				Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
				Dbl_copytoptr(resultp1,resultp2,dstptr);
				return(NOEXCEPTION);
			}
		}
		else {
			/*
			 * is NaN; signaling or quiet?
			 */
			if (Dbl_isone_signaling(opnd1p1)) {
				/* trap if INVALIDTRAP enabled */
				if (Is_invalidtrap_enabled())
					return(INVALIDEXCEPTION);
				/* make NaN quiet */
				Set_invalidflag();
				Dbl_set_quiet(opnd1p1);
			}
			/*
			 * is second operand a signaling NaN?
			 */
			else if (Dbl_is_signalingnan(opnd2p1)) {
				/* trap if INVALIDTRAP enabled */
				if (Is_invalidtrap_enabled())
					return(INVALIDEXCEPTION);
				/* make NaN quiet */
				Set_invalidflag();
				Dbl_set_quiet(opnd2p1);
				Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
				return(NOEXCEPTION);
			}
			/*
			 * return quiet NaN
			 */
			Dbl_copytoptr(opnd1p1,opnd1p2,dstptr);
			return(NOEXCEPTION);
		}
	}
	/*
	 * check second operand for NaN's or infinity
	 */
	if (Dbl_isinfinity_exponent(opnd2p1)) {
		if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
			/*
			 * return zero
			 */
			Dbl_setzero_exponentmantissa(resultp1,resultp2);
			Dbl_copytoptr(resultp1,resultp2,dstptr);
			return(NOEXCEPTION);
		}
		/*
		 * is NaN; signaling or quiet?
		 */
		if (Dbl_isone_signaling(opnd2p1)) {
			/* trap if INVALIDTRAP enabled */
			if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
			/* make NaN quiet */
			Set_invalidflag();
			Dbl_set_quiet(opnd2p1);
		}
		/*
		 * return quiet NaN
		 */
		Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
		return(NOEXCEPTION);
	}
	/*
	 * check for division by zero
	 */
	if (Dbl_iszero_exponentmantissa(opnd2p1,opnd2p2)) {
		if (Dbl_iszero_exponentmantissa(opnd1p1,opnd1p2)) {
			/* invalid since both operands are zero */
			if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
			Set_invalidflag();
			Dbl_makequietnan(resultp1,resultp2);
			Dbl_copytoptr(resultp1,resultp2,dstptr);
			return(NOEXCEPTION);
		}
		if (Is_divisionbyzerotrap_enabled())
			return(DIVISIONBYZEROEXCEPTION);
		Set_divisionbyzeroflag();
		Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
		Dbl_copytoptr(resultp1,resultp2,dstptr);
		return(NOEXCEPTION);
	}
	/*
	 * Generate exponent
	 */
	dest_exponent = Dbl_exponent(opnd1p1) - Dbl_exponent(opnd2p1) + DBL_BIAS;

	/*
	 * Generate mantissa
	 */
	if (Dbl_isnotzero_exponent(opnd1p1)) {
		/* set hidden bit */
		Dbl_clear_signexponent_set_hidden(opnd1p1);
	}
	else {
		/* check for zero */
		if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
			Dbl_setzero_exponentmantissa(resultp1,resultp2);
			Dbl_copytoptr(resultp1,resultp2,dstptr);
			return(NOEXCEPTION);
		}
		/* is denormalized, want to normalize */
		Dbl_clear_signexponent(opnd1p1);
		Dbl_leftshiftby1(opnd1p1,opnd1p2);
		Dbl_normalize(opnd1p1,opnd1p2,dest_exponent);
	}
	/* opnd2 needs to have hidden bit set with msb in hidden bit */
	if (Dbl_isnotzero_exponent(opnd2p1)) {
		Dbl_clear_signexponent_set_hidden(opnd2p1);
	}
	else {
		/* is denormalized; want to normalize */
		Dbl_clear_signexponent(opnd2p1);
		Dbl_leftshiftby1(opnd2p1,opnd2p2);
		while (Dbl_iszero_hiddenhigh7mantissa(opnd2p1)) {
			dest_exponent+=8;
			Dbl_leftshiftby8(opnd2p1,opnd2p2);
		}
		if (Dbl_iszero_hiddenhigh3mantissa(opnd2p1)) {
			dest_exponent+=4;
			Dbl_leftshiftby4(opnd2p1,opnd2p2);
		}
		while (Dbl_iszero_hidden(opnd2p1)) {
			dest_exponent++;
			Dbl_leftshiftby1(opnd2p1,opnd2p2);
		}
	}

	/* Divide the source mantissas */

	/*
	 * A non-restoring divide algorithm is used.
	 */
	Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
	Dbl_setzero(opnd3p1,opnd3p2);
	for (count=1; count <= DBL_P && (opnd1p1 || opnd1p2); count++) {
		Dbl_leftshiftby1(opnd1p1,opnd1p2);
		Dbl_leftshiftby1(opnd3p1,opnd3p2);
		if (Dbl_iszero_sign(opnd1p1)) {
			Dbl_setone_lowmantissap2(opnd3p2);
			Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
		}
		else {
			Twoword_add(opnd1p1, opnd1p2, opnd2p1, opnd2p2);
		}
	}
	if (count <= DBL_P) {
		Dbl_leftshiftby1(opnd3p1,opnd3p2);
		Dbl_setone_lowmantissap2(opnd3p2);
		Dbl_leftshift(opnd3p1,opnd3p2,(DBL_P-count));
		if (Dbl_iszero_hidden(opnd3p1)) {
			Dbl_leftshiftby1(opnd3p1,opnd3p2);
			dest_exponent--;
		}
	}
	else {
		if (Dbl_iszero_hidden(opnd3p1)) {
			/* need to get one more bit of result */
			Dbl_leftshiftby1(opnd1p1,opnd1p2);
			Dbl_leftshiftby1(opnd3p1,opnd3p2);
			if (Dbl_iszero_sign(opnd1p1)) {
				Dbl_setone_lowmantissap2(opnd3p2);
				Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
			}
			else {
				Twoword_add(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
			}
			dest_exponent--;
		}
		if (Dbl_iszero_sign(opnd1p1)) guardbit = TRUE;
		stickybit = Dbl_allp1(opnd1p1) || Dbl_allp2(opnd1p2);
	}
	inexact = guardbit | stickybit;

	/*
	 * round result
	 */
	if (inexact && (dest_exponent > 0 || Is_underflowtrap_enabled())) {
		Dbl_clear_signexponent(opnd3p1);
		switch (Rounding_mode()) {
			case ROUNDPLUS:
				if (Dbl_iszero_sign(resultp1))
					Dbl_increment(opnd3p1,opnd3p2);
				break;
			case ROUNDMINUS:
				if (Dbl_isone_sign(resultp1))
					Dbl_increment(opnd3p1,opnd3p2);
				break;
			case ROUNDNEAREST:
				if (guardbit && (stickybit ||
				    Dbl_isone_lowmantissap2(opnd3p2))) {
					Dbl_increment(opnd3p1,opnd3p2);
				}
		}
		if (Dbl_isone_hidden(opnd3p1)) dest_exponent++;
	}
	Dbl_set_mantissa(resultp1,resultp2,opnd3p1,opnd3p2);

	/*
	 * Test for overflow
	 */
	if (dest_exponent >= DBL_INFINITY_EXPONENT) {
		/* trap if OVERFLOWTRAP enabled */
		if (Is_overflowtrap_enabled()) {
			/*
			 * Adjust bias of result
			 */
			Dbl_setwrapped_exponent(resultp1,dest_exponent,ovfl);
			Dbl_copytoptr(resultp1,resultp2,dstptr);
			if (inexact) {
				if (Is_inexacttrap_enabled())
					return(OVERFLOWEXCEPTION | INEXACTEXCEPTION);
				else
					Set_inexactflag();
			}
			return(OVERFLOWEXCEPTION);
		}
		Set_overflowflag();
		/* set result to infinity or largest number */
		Dbl_setoverflow(resultp1,resultp2);
		inexact = TRUE;
	}
	/*
	 * Test for underflow
	 */
	else if (dest_exponent <= 0) {
		/* trap if UNDERFLOWTRAP enabled */
		if (Is_underflowtrap_enabled()) {
			/*
			 * Adjust bias of result
			 */
			Dbl_setwrapped_exponent(resultp1,dest_exponent,unfl);
			Dbl_copytoptr(resultp1,resultp2,dstptr);
			if (inexact) {
				if (Is_inexacttrap_enabled())
					return(UNDERFLOWEXCEPTION | INEXACTEXCEPTION);
				else
					Set_inexactflag();
			}
			return(UNDERFLOWEXCEPTION);
		}

		/* Determine if should set underflow flag */
		is_tiny = TRUE;
		if (dest_exponent == 0 && inexact) {
			switch (Rounding_mode()) {
			case ROUNDPLUS:
				if (Dbl_iszero_sign(resultp1)) {
					Dbl_increment(opnd3p1,opnd3p2);
					if (Dbl_isone_hiddenoverflow(opnd3p1))
						is_tiny = FALSE;
					Dbl_decrement(opnd3p1,opnd3p2);
				}
				break;
			case ROUNDMINUS:
				if (Dbl_isone_sign(resultp1)) {
					Dbl_increment(opnd3p1,opnd3p2);
					if (Dbl_isone_hiddenoverflow(opnd3p1))
						is_tiny = FALSE;
					Dbl_decrement(opnd3p1,opnd3p2);
				}
				break;
			case ROUNDNEAREST:
				if (guardbit && (stickybit ||
				    Dbl_isone_lowmantissap2(opnd3p2))) {
					Dbl_increment(opnd3p1,opnd3p2);
					if (Dbl_isone_hiddenoverflow(opnd3p1))
						is_tiny = FALSE;
					Dbl_decrement(opnd3p1,opnd3p2);
				}
				break;
			}
		}

		/*
		 * denormalize result or set to signed zero
		 */
		stickybit = inexact;
		Dbl_denormalize(opnd3p1,opnd3p2,dest_exponent,guardbit,
		 stickybit,inexact);

		/* return rounded number */
		if (inexact) {
			switch (Rounding_mode()) {
			case ROUNDPLUS:
				if (Dbl_iszero_sign(resultp1)) {
					Dbl_increment(opnd3p1,opnd3p2);
				}
				break;
			case ROUNDMINUS:
				if (Dbl_isone_sign(resultp1)) {
					Dbl_increment(opnd3p1,opnd3p2);
				}
				break;
			case ROUNDNEAREST:
				if (guardbit && (stickybit ||
				    Dbl_isone_lowmantissap2(opnd3p2))) {
					Dbl_increment(opnd3p1,opnd3p2);
				}
				break;
			}
			if (is_tiny)
				Set_underflowflag();
		}
		Dbl_set_exponentmantissa(resultp1,resultp2,opnd3p1,opnd3p2);
	}
	else Dbl_set_exponent(resultp1,dest_exponent);
	Dbl_copytoptr(resultp1,resultp2,dstptr);

	/* check for inexact */
	if (inexact) {
		if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
		else Set_inexactflag();
	}
	return(NOEXCEPTION);
}