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

/*	$NetBSD: sfmpy.c,v 1.1.4.2 2002/07/14 17:47:48 gehenna Exp $	*/

/*	$OpenBSD: sfmpy.c,v 1.4 2001/03/29 03:58:19 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/sgl_float.h"

/*
 *  Single Precision Floating-point Multiply
 */
int
sgl_fmpy(srcptr1,srcptr2,dstptr,status)

sgl_floating_point *srcptr1, *srcptr2, *dstptr;
unsigned int *status;
{
	register unsigned int opnd1, opnd2, opnd3, result;
	register int dest_exponent, count;
	register int inexact = FALSE, guardbit = FALSE, stickybit = FALSE;
	int is_tiny;

	opnd1 = *srcptr1;
	opnd2 = *srcptr2;
	/*
	 * set sign bit of result
	 */
	if (Sgl_sign(opnd1) ^ Sgl_sign(opnd2)) Sgl_setnegativezero(result);
	else Sgl_setzero(result);
	/*
	 * check first operand for NaN's or infinity
	 */
	if (Sgl_isinfinity_exponent(opnd1)) {
		if (Sgl_iszero_mantissa(opnd1)) {
			if (Sgl_isnotnan(opnd2)) {
				if (Sgl_iszero_exponentmantissa(opnd2)) {
					/*
					 * invalid since operands are infinity
					 * and zero
					 */
					if (Is_invalidtrap_enabled())
						return(INVALIDEXCEPTION);
					Set_invalidflag();
					Sgl_makequietnan(result);
					*dstptr = result;
					return(NOEXCEPTION);
				}
				/*
				 * return infinity
				 */
				Sgl_setinfinity_exponentmantissa(result);
				*dstptr = result;
				return(NOEXCEPTION);
			}
		}
		else {
			/*
			 * is NaN; signaling or quiet?
			 */
			if (Sgl_isone_signaling(opnd1)) {
				/* trap if INVALIDTRAP enabled */
				if (Is_invalidtrap_enabled())
					return(INVALIDEXCEPTION);
				/* make NaN quiet */
				Set_invalidflag();
				Sgl_set_quiet(opnd1);
			}
			/*
			 * is second operand a signaling NaN?
			 */
			else if (Sgl_is_signalingnan(opnd2)) {
				/* trap if INVALIDTRAP enabled */
				if (Is_invalidtrap_enabled())
					return(INVALIDEXCEPTION);
				/* make NaN quiet */
				Set_invalidflag();
				Sgl_set_quiet(opnd2);
				*dstptr = opnd2;
				return(NOEXCEPTION);
			}
			/*
			 * return quiet NaN
			 */
			*dstptr = opnd1;
			return(NOEXCEPTION);
		}
	}
	/*
	 * check second operand for NaN's or infinity
	 */
	if (Sgl_isinfinity_exponent(opnd2)) {
		if (Sgl_iszero_mantissa(opnd2)) {
			if (Sgl_iszero_exponentmantissa(opnd1)) {
				/* invalid since operands are zero & infinity */
				if (Is_invalidtrap_enabled())
					return(INVALIDEXCEPTION);
				Set_invalidflag();
				Sgl_makequietnan(opnd2);
				*dstptr = opnd2;
				return(NOEXCEPTION);
			}
			/*
			 * return infinity
			 */
			Sgl_setinfinity_exponentmantissa(result);
			*dstptr = result;
			return(NOEXCEPTION);
		}
		/*
		 * is NaN; signaling or quiet?
		 */
		if (Sgl_isone_signaling(opnd2)) {
			/* trap if INVALIDTRAP enabled */
			if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);

			/* make NaN quiet */
			Set_invalidflag();
			Sgl_set_quiet(opnd2);
		}
		/*
		 * return quiet NaN
		 */
		*dstptr = opnd2;
		return(NOEXCEPTION);
	}
	/*
	 * Generate exponent
	 */
	dest_exponent = Sgl_exponent(opnd1) + Sgl_exponent(opnd2) - SGL_BIAS;

	/*
	 * Generate mantissa
	 */
	if (Sgl_isnotzero_exponent(opnd1)) {
		/* set hidden bit */
		Sgl_clear_signexponent_set_hidden(opnd1);
	}
	else {
		/* check for zero */
		if (Sgl_iszero_mantissa(opnd1)) {
			Sgl_setzero_exponentmantissa(result);
			*dstptr = result;
			return(NOEXCEPTION);
		}
		/* is denormalized, adjust exponent */
		Sgl_clear_signexponent(opnd1);
		Sgl_leftshiftby1(opnd1);
		Sgl_normalize(opnd1,dest_exponent);
	}
	/* opnd2 needs to have hidden bit set with msb in hidden bit */
	if (Sgl_isnotzero_exponent(opnd2)) {
		Sgl_clear_signexponent_set_hidden(opnd2);
	}
	else {
		/* check for zero */
		if (Sgl_iszero_mantissa(opnd2)) {
			Sgl_setzero_exponentmantissa(result);
			*dstptr = result;
			return(NOEXCEPTION);
		}
		/* is denormalized; want to normalize */
		Sgl_clear_signexponent(opnd2);
		Sgl_leftshiftby1(opnd2);
		Sgl_normalize(opnd2,dest_exponent);
	}

	/* Multiply two source mantissas together */

	Sgl_leftshiftby4(opnd2);     /* make room for guard bits */
	Sgl_setzero(opnd3);
	/*
	 * Four bits at a time are inspected in each loop, and a
	 * simple shift and add multiply algorithm is used.
	 */
	for (count=1;count<SGL_P;count+=4) {
		stickybit |= Slow4(opnd3);
		Sgl_rightshiftby4(opnd3);
		if (Sbit28(opnd1)) Sall(opnd3) += (Sall(opnd2) << 3);
		if (Sbit29(opnd1)) Sall(opnd3) += (Sall(opnd2) << 2);
		if (Sbit30(opnd1)) Sall(opnd3) += (Sall(opnd2) << 1);
		if (Sbit31(opnd1)) Sall(opnd3) += Sall(opnd2);
		Sgl_rightshiftby4(opnd1);
	}
	/* make sure result is left-justified */
	if (Sgl_iszero_sign(opnd3)) {
		Sgl_leftshiftby1(opnd3);
	}
	else {
		/* result mantissa >= 2. */
		dest_exponent++;
	}
	/* check for denormalized result */
	while (Sgl_iszero_sign(opnd3)) {
		Sgl_leftshiftby1(opnd3);
		dest_exponent--;
	}
	/*
	 * check for guard, sticky and inexact bits
	 */
	stickybit |= Sgl_all(opnd3) << (SGL_BITLENGTH - SGL_EXP_LENGTH + 1);
	guardbit = Sbit24(opnd3);
	inexact = guardbit | stickybit;

	/* re-align mantissa */
	Sgl_rightshiftby8(opnd3);

	/*
	 * round result
	 */
	if (inexact && (dest_exponent>0 || Is_underflowtrap_enabled())) {
		Sgl_clear_signexponent(opnd3);
		switch (Rounding_mode()) {
			case ROUNDPLUS:
				if (Sgl_iszero_sign(result))
					Sgl_increment(opnd3);
				break;
			case ROUNDMINUS:
				if (Sgl_isone_sign(result))
					Sgl_increment(opnd3);
				break;
			case ROUNDNEAREST:
				if (guardbit &&
				    (stickybit || Sgl_isone_lowmantissa(opnd3)))
					Sgl_increment(opnd3);
				break;
		}
		if (Sgl_isone_hidden(opnd3)) dest_exponent++;
	}
	Sgl_set_mantissa(result,opnd3);

	/*
	 * Test for overflow
	 */
	if (dest_exponent >= SGL_INFINITY_EXPONENT) {
		/* trap if OVERFLOWTRAP enabled */
		if (Is_overflowtrap_enabled()) {
			/*
			 * Adjust bias of result
			 */
			Sgl_setwrapped_exponent(result,dest_exponent,ovfl);
			*dstptr = result;
			if (inexact) {
			    if (Is_inexacttrap_enabled())
				return(OVERFLOWEXCEPTION | INEXACTEXCEPTION);
			    else Set_inexactflag();
			}
			return(OVERFLOWEXCEPTION);
		}
		inexact = TRUE;
		Set_overflowflag();
		/* set result to infinity or largest number */
		Sgl_setoverflow(result);
	}
	/*
	 * Test for underflow
	 */
	else if (dest_exponent <= 0) {
		/* trap if UNDERFLOWTRAP enabled */
		if (Is_underflowtrap_enabled()) {
			/*
			 * Adjust bias of result
			 */
			Sgl_setwrapped_exponent(result,dest_exponent,unfl);
			*dstptr = result;
			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 (Sgl_iszero_sign(result)) {
					Sgl_increment(opnd3);
					if (Sgl_isone_hiddenoverflow(opnd3))
						is_tiny = FALSE;
					Sgl_decrement(opnd3);
				}
				break;
			case ROUNDMINUS:
				if (Sgl_isone_sign(result)) {
					Sgl_increment(opnd3);
					if (Sgl_isone_hiddenoverflow(opnd3))
						is_tiny = FALSE;
					Sgl_decrement(opnd3);
				}
				break;
			case ROUNDNEAREST:
				if (guardbit && (stickybit ||
				    Sgl_isone_lowmantissa(opnd3))) {
					Sgl_increment(opnd3);
					if (Sgl_isone_hiddenoverflow(opnd3))
						is_tiny = FALSE;
					Sgl_decrement(opnd3);
				}
				break;
			}
		}

		/*
		 * denormalize result or set to signed zero
		 */
		stickybit = inexact;
		Sgl_denormalize(opnd3,dest_exponent,guardbit,stickybit,inexact);

		/* return zero or smallest number */
		if (inexact) {
			switch (Rounding_mode()) {
			case ROUNDPLUS:
				if (Sgl_iszero_sign(result))
					Sgl_increment(opnd3);
				break;
			case ROUNDMINUS:
				if (Sgl_isone_sign(result))
					Sgl_increment(opnd3);
				break;
			case ROUNDNEAREST:
				if (guardbit && (stickybit ||
				    Sgl_isone_lowmantissa(opnd3)))
					Sgl_increment(opnd3);
				break;
			}
		if (is_tiny) Set_underflowflag();
		}
		Sgl_set_exponentmantissa(result,opnd3);
	}
	else Sgl_set_exponent(result,dest_exponent);
	*dstptr = result;

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