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dfdiv.c revision 1.4.80.1
      1  1.4.80.1      yamt /*	$NetBSD: dfdiv.c,v 1.4.80.1 2012/04/17 00:06:26 yamt Exp $	*/
      2       1.1  fredette 
      3       1.1  fredette /*	$OpenBSD: dfdiv.c,v 1.4 2001/03/29 03:58:17 mickey Exp $	*/
      4       1.1  fredette 
      5       1.1  fredette /*
      6       1.1  fredette  * Copyright 1996 1995 by Open Software Foundation, Inc.
      7       1.1  fredette  *              All Rights Reserved
      8       1.1  fredette  *
      9       1.1  fredette  * Permission to use, copy, modify, and distribute this software and
     10       1.1  fredette  * its documentation for any purpose and without fee is hereby granted,
     11       1.1  fredette  * provided that the above copyright notice appears in all copies and
     12       1.1  fredette  * that both the copyright notice and this permission notice appear in
     13       1.1  fredette  * supporting documentation.
     14       1.1  fredette  *
     15       1.1  fredette  * OSF DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
     16       1.1  fredette  * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     17       1.1  fredette  * FOR A PARTICULAR PURPOSE.
     18       1.1  fredette  *
     19       1.1  fredette  * IN NO EVENT SHALL OSF BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
     20       1.1  fredette  * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
     21       1.1  fredette  * LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
     22       1.1  fredette  * NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
     23       1.1  fredette  * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     24       1.1  fredette  *
     25       1.1  fredette  */
     26       1.1  fredette /*
     27       1.1  fredette  * pmk1.1
     28       1.1  fredette  */
     29       1.1  fredette /*
     30       1.1  fredette  * (c) Copyright 1986 HEWLETT-PACKARD COMPANY
     31       1.1  fredette  *
     32       1.1  fredette  * To anyone who acknowledges that this file is provided "AS IS"
     33       1.1  fredette  * without any express or implied warranty:
     34       1.1  fredette  *     permission to use, copy, modify, and distribute this file
     35       1.1  fredette  * for any purpose is hereby granted without fee, provided that
     36       1.1  fredette  * the above copyright notice and this notice appears in all
     37       1.1  fredette  * copies, and that the name of Hewlett-Packard Company not be
     38       1.1  fredette  * used in advertising or publicity pertaining to distribution
     39       1.1  fredette  * of the software without specific, written prior permission.
     40       1.1  fredette  * Hewlett-Packard Company makes no representations about the
     41       1.1  fredette  * suitability of this software for any purpose.
     42       1.1  fredette  */
     43       1.2     lukem 
     44       1.2     lukem #include <sys/cdefs.h>
     45  1.4.80.1      yamt __KERNEL_RCSID(0, "$NetBSD: dfdiv.c,v 1.4.80.1 2012/04/17 00:06:26 yamt Exp $");
     46       1.1  fredette 
     47       1.1  fredette #include "../spmath/float.h"
     48       1.1  fredette #include "../spmath/dbl_float.h"
     49       1.1  fredette 
     50       1.1  fredette /*
     51       1.1  fredette  *  Double Precision Floating-point Divide
     52       1.1  fredette  */
     53       1.1  fredette 
     54       1.1  fredette int
     55  1.4.80.1      yamt dbl_fdiv(dbl_floating_point *srcptr1, dbl_floating_point *srcptr2,
     56  1.4.80.1      yamt     dbl_floating_point *dstptr, unsigned int *status)
     57       1.1  fredette {
     58       1.1  fredette 	register unsigned int opnd1p1, opnd1p2, opnd2p1, opnd2p2;
     59       1.1  fredette 	register unsigned int opnd3p1, opnd3p2, resultp1, resultp2;
     60       1.1  fredette 	register int dest_exponent, count;
     61       1.4   thorpej 	register int inexact = false, guardbit = false, stickybit = false;
     62       1.1  fredette 	int is_tiny;
     63       1.1  fredette 
     64       1.1  fredette 	Dbl_copyfromptr(srcptr1,opnd1p1,opnd1p2);
     65       1.1  fredette 	Dbl_copyfromptr(srcptr2,opnd2p1,opnd2p2);
     66       1.1  fredette 	/*
     67       1.1  fredette 	 * set sign bit of result
     68       1.1  fredette 	 */
     69       1.1  fredette 	if (Dbl_sign(opnd1p1) ^ Dbl_sign(opnd2p1))
     70       1.1  fredette 		Dbl_setnegativezerop1(resultp1);
     71       1.1  fredette 	else Dbl_setzerop1(resultp1);
     72       1.1  fredette 	/*
     73       1.1  fredette 	 * check first operand for NaN's or infinity
     74       1.1  fredette 	 */
     75       1.1  fredette 	if (Dbl_isinfinity_exponent(opnd1p1)) {
     76       1.1  fredette 		if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
     77       1.1  fredette 			if (Dbl_isnotnan(opnd2p1,opnd2p2)) {
     78       1.1  fredette 				if (Dbl_isinfinity(opnd2p1,opnd2p2)) {
     79       1.1  fredette 					/*
     80       1.1  fredette 					 * invalid since both operands
     81       1.1  fredette 					 * are infinity
     82       1.1  fredette 					 */
     83       1.1  fredette 					if (Is_invalidtrap_enabled())
     84       1.1  fredette 						return(INVALIDEXCEPTION);
     85       1.1  fredette 					Set_invalidflag();
     86       1.1  fredette 					Dbl_makequietnan(resultp1,resultp2);
     87       1.1  fredette 					Dbl_copytoptr(resultp1,resultp2,dstptr);
     88       1.1  fredette 					return(NOEXCEPTION);
     89       1.1  fredette 				}
     90       1.1  fredette 				/*
     91       1.1  fredette 				 * return infinity
     92       1.1  fredette 				 */
     93       1.1  fredette 				Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
     94       1.1  fredette 				Dbl_copytoptr(resultp1,resultp2,dstptr);
     95       1.1  fredette 				return(NOEXCEPTION);
     96       1.1  fredette 			}
     97       1.1  fredette 		}
     98       1.1  fredette 		else {
     99       1.1  fredette 			/*
    100       1.1  fredette 			 * is NaN; signaling or quiet?
    101       1.1  fredette 			 */
    102       1.1  fredette 			if (Dbl_isone_signaling(opnd1p1)) {
    103       1.1  fredette 				/* trap if INVALIDTRAP enabled */
    104       1.1  fredette 				if (Is_invalidtrap_enabled())
    105       1.1  fredette 					return(INVALIDEXCEPTION);
    106       1.1  fredette 				/* make NaN quiet */
    107       1.1  fredette 				Set_invalidflag();
    108       1.1  fredette 				Dbl_set_quiet(opnd1p1);
    109       1.1  fredette 			}
    110       1.1  fredette 			/*
    111       1.1  fredette 			 * is second operand a signaling NaN?
    112       1.1  fredette 			 */
    113       1.1  fredette 			else if (Dbl_is_signalingnan(opnd2p1)) {
    114       1.1  fredette 				/* trap if INVALIDTRAP enabled */
    115       1.1  fredette 				if (Is_invalidtrap_enabled())
    116       1.1  fredette 					return(INVALIDEXCEPTION);
    117       1.1  fredette 				/* make NaN quiet */
    118       1.1  fredette 				Set_invalidflag();
    119       1.1  fredette 				Dbl_set_quiet(opnd2p1);
    120       1.1  fredette 				Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
    121       1.1  fredette 				return(NOEXCEPTION);
    122       1.1  fredette 			}
    123       1.1  fredette 			/*
    124       1.1  fredette 			 * return quiet NaN
    125       1.1  fredette 			 */
    126       1.1  fredette 			Dbl_copytoptr(opnd1p1,opnd1p2,dstptr);
    127       1.1  fredette 			return(NOEXCEPTION);
    128       1.1  fredette 		}
    129       1.1  fredette 	}
    130       1.1  fredette 	/*
    131       1.1  fredette 	 * check second operand for NaN's or infinity
    132       1.1  fredette 	 */
    133       1.1  fredette 	if (Dbl_isinfinity_exponent(opnd2p1)) {
    134       1.1  fredette 		if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
    135       1.1  fredette 			/*
    136       1.1  fredette 			 * return zero
    137       1.1  fredette 			 */
    138       1.1  fredette 			Dbl_setzero_exponentmantissa(resultp1,resultp2);
    139       1.1  fredette 			Dbl_copytoptr(resultp1,resultp2,dstptr);
    140       1.1  fredette 			return(NOEXCEPTION);
    141       1.1  fredette 		}
    142       1.1  fredette 		/*
    143       1.1  fredette 		 * is NaN; signaling or quiet?
    144       1.1  fredette 		 */
    145       1.1  fredette 		if (Dbl_isone_signaling(opnd2p1)) {
    146       1.1  fredette 			/* trap if INVALIDTRAP enabled */
    147       1.1  fredette 			if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
    148       1.1  fredette 			/* make NaN quiet */
    149       1.1  fredette 			Set_invalidflag();
    150       1.1  fredette 			Dbl_set_quiet(opnd2p1);
    151       1.1  fredette 		}
    152       1.1  fredette 		/*
    153       1.1  fredette 		 * return quiet NaN
    154       1.1  fredette 		 */
    155       1.1  fredette 		Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
    156       1.1  fredette 		return(NOEXCEPTION);
    157       1.1  fredette 	}
    158       1.1  fredette 	/*
    159       1.1  fredette 	 * check for division by zero
    160       1.1  fredette 	 */
    161       1.1  fredette 	if (Dbl_iszero_exponentmantissa(opnd2p1,opnd2p2)) {
    162       1.1  fredette 		if (Dbl_iszero_exponentmantissa(opnd1p1,opnd1p2)) {
    163       1.1  fredette 			/* invalid since both operands are zero */
    164       1.1  fredette 			if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
    165       1.1  fredette 			Set_invalidflag();
    166       1.1  fredette 			Dbl_makequietnan(resultp1,resultp2);
    167       1.1  fredette 			Dbl_copytoptr(resultp1,resultp2,dstptr);
    168       1.1  fredette 			return(NOEXCEPTION);
    169       1.1  fredette 		}
    170       1.1  fredette 		if (Is_divisionbyzerotrap_enabled())
    171       1.1  fredette 			return(DIVISIONBYZEROEXCEPTION);
    172       1.1  fredette 		Set_divisionbyzeroflag();
    173       1.1  fredette 		Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
    174       1.1  fredette 		Dbl_copytoptr(resultp1,resultp2,dstptr);
    175       1.1  fredette 		return(NOEXCEPTION);
    176       1.1  fredette 	}
    177       1.1  fredette 	/*
    178       1.1  fredette 	 * Generate exponent
    179       1.1  fredette 	 */
    180       1.1  fredette 	dest_exponent = Dbl_exponent(opnd1p1) - Dbl_exponent(opnd2p1) + DBL_BIAS;
    181       1.1  fredette 
    182       1.1  fredette 	/*
    183       1.1  fredette 	 * Generate mantissa
    184       1.1  fredette 	 */
    185       1.1  fredette 	if (Dbl_isnotzero_exponent(opnd1p1)) {
    186       1.1  fredette 		/* set hidden bit */
    187       1.1  fredette 		Dbl_clear_signexponent_set_hidden(opnd1p1);
    188       1.1  fredette 	}
    189       1.1  fredette 	else {
    190       1.1  fredette 		/* check for zero */
    191       1.1  fredette 		if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
    192       1.1  fredette 			Dbl_setzero_exponentmantissa(resultp1,resultp2);
    193       1.1  fredette 			Dbl_copytoptr(resultp1,resultp2,dstptr);
    194       1.1  fredette 			return(NOEXCEPTION);
    195       1.1  fredette 		}
    196       1.1  fredette 		/* is denormalized, want to normalize */
    197       1.1  fredette 		Dbl_clear_signexponent(opnd1p1);
    198       1.1  fredette 		Dbl_leftshiftby1(opnd1p1,opnd1p2);
    199       1.1  fredette 		Dbl_normalize(opnd1p1,opnd1p2,dest_exponent);
    200       1.1  fredette 	}
    201       1.1  fredette 	/* opnd2 needs to have hidden bit set with msb in hidden bit */
    202       1.1  fredette 	if (Dbl_isnotzero_exponent(opnd2p1)) {
    203       1.1  fredette 		Dbl_clear_signexponent_set_hidden(opnd2p1);
    204       1.1  fredette 	}
    205       1.1  fredette 	else {
    206       1.1  fredette 		/* is denormalized; want to normalize */
    207       1.1  fredette 		Dbl_clear_signexponent(opnd2p1);
    208       1.1  fredette 		Dbl_leftshiftby1(opnd2p1,opnd2p2);
    209       1.1  fredette 		while (Dbl_iszero_hiddenhigh7mantissa(opnd2p1)) {
    210       1.1  fredette 			dest_exponent+=8;
    211       1.1  fredette 			Dbl_leftshiftby8(opnd2p1,opnd2p2);
    212       1.1  fredette 		}
    213       1.1  fredette 		if (Dbl_iszero_hiddenhigh3mantissa(opnd2p1)) {
    214       1.1  fredette 			dest_exponent+=4;
    215       1.1  fredette 			Dbl_leftshiftby4(opnd2p1,opnd2p2);
    216       1.1  fredette 		}
    217       1.1  fredette 		while (Dbl_iszero_hidden(opnd2p1)) {
    218       1.1  fredette 			dest_exponent++;
    219       1.1  fredette 			Dbl_leftshiftby1(opnd2p1,opnd2p2);
    220       1.1  fredette 		}
    221       1.1  fredette 	}
    222       1.1  fredette 
    223       1.1  fredette 	/* Divide the source mantissas */
    224       1.1  fredette 
    225       1.1  fredette 	/*
    226       1.1  fredette 	 * A non-restoring divide algorithm is used.
    227       1.1  fredette 	 */
    228       1.1  fredette 	Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
    229       1.1  fredette 	Dbl_setzero(opnd3p1,opnd3p2);
    230       1.1  fredette 	for (count=1; count <= DBL_P && (opnd1p1 || opnd1p2); count++) {
    231       1.1  fredette 		Dbl_leftshiftby1(opnd1p1,opnd1p2);
    232       1.1  fredette 		Dbl_leftshiftby1(opnd3p1,opnd3p2);
    233       1.1  fredette 		if (Dbl_iszero_sign(opnd1p1)) {
    234       1.1  fredette 			Dbl_setone_lowmantissap2(opnd3p2);
    235       1.1  fredette 			Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
    236       1.1  fredette 		}
    237       1.1  fredette 		else {
    238       1.1  fredette 			Twoword_add(opnd1p1, opnd1p2, opnd2p1, opnd2p2);
    239       1.1  fredette 		}
    240       1.1  fredette 	}
    241       1.1  fredette 	if (count <= DBL_P) {
    242       1.1  fredette 		Dbl_leftshiftby1(opnd3p1,opnd3p2);
    243       1.1  fredette 		Dbl_setone_lowmantissap2(opnd3p2);
    244       1.1  fredette 		Dbl_leftshift(opnd3p1,opnd3p2,(DBL_P-count));
    245       1.1  fredette 		if (Dbl_iszero_hidden(opnd3p1)) {
    246       1.1  fredette 			Dbl_leftshiftby1(opnd3p1,opnd3p2);
    247       1.1  fredette 			dest_exponent--;
    248       1.1  fredette 		}
    249       1.1  fredette 	}
    250       1.1  fredette 	else {
    251       1.1  fredette 		if (Dbl_iszero_hidden(opnd3p1)) {
    252       1.1  fredette 			/* need to get one more bit of result */
    253       1.1  fredette 			Dbl_leftshiftby1(opnd1p1,opnd1p2);
    254       1.1  fredette 			Dbl_leftshiftby1(opnd3p1,opnd3p2);
    255       1.1  fredette 			if (Dbl_iszero_sign(opnd1p1)) {
    256       1.1  fredette 				Dbl_setone_lowmantissap2(opnd3p2);
    257       1.1  fredette 				Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
    258       1.1  fredette 			}
    259       1.1  fredette 			else {
    260       1.1  fredette 				Twoword_add(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
    261       1.1  fredette 			}
    262       1.1  fredette 			dest_exponent--;
    263       1.1  fredette 		}
    264       1.4   thorpej 		if (Dbl_iszero_sign(opnd1p1)) guardbit = true;
    265       1.1  fredette 		stickybit = Dbl_allp1(opnd1p1) || Dbl_allp2(opnd1p2);
    266       1.1  fredette 	}
    267       1.1  fredette 	inexact = guardbit | stickybit;
    268       1.1  fredette 
    269       1.1  fredette 	/*
    270       1.1  fredette 	 * round result
    271       1.1  fredette 	 */
    272       1.1  fredette 	if (inexact && (dest_exponent > 0 || Is_underflowtrap_enabled())) {
    273       1.1  fredette 		Dbl_clear_signexponent(opnd3p1);
    274       1.1  fredette 		switch (Rounding_mode()) {
    275       1.1  fredette 			case ROUNDPLUS:
    276       1.1  fredette 				if (Dbl_iszero_sign(resultp1))
    277       1.1  fredette 					Dbl_increment(opnd3p1,opnd3p2);
    278       1.1  fredette 				break;
    279       1.1  fredette 			case ROUNDMINUS:
    280       1.1  fredette 				if (Dbl_isone_sign(resultp1))
    281       1.1  fredette 					Dbl_increment(opnd3p1,opnd3p2);
    282       1.1  fredette 				break;
    283       1.1  fredette 			case ROUNDNEAREST:
    284       1.1  fredette 				if (guardbit && (stickybit ||
    285       1.1  fredette 				    Dbl_isone_lowmantissap2(opnd3p2))) {
    286       1.1  fredette 					Dbl_increment(opnd3p1,opnd3p2);
    287       1.1  fredette 				}
    288       1.1  fredette 		}
    289       1.1  fredette 		if (Dbl_isone_hidden(opnd3p1)) dest_exponent++;
    290       1.1  fredette 	}
    291       1.1  fredette 	Dbl_set_mantissa(resultp1,resultp2,opnd3p1,opnd3p2);
    292       1.1  fredette 
    293       1.1  fredette 	/*
    294       1.1  fredette 	 * Test for overflow
    295       1.1  fredette 	 */
    296       1.1  fredette 	if (dest_exponent >= DBL_INFINITY_EXPONENT) {
    297       1.1  fredette 		/* trap if OVERFLOWTRAP enabled */
    298       1.1  fredette 		if (Is_overflowtrap_enabled()) {
    299       1.1  fredette 			/*
    300       1.1  fredette 			 * Adjust bias of result
    301       1.1  fredette 			 */
    302       1.1  fredette 			Dbl_setwrapped_exponent(resultp1,dest_exponent,ovfl);
    303       1.1  fredette 			Dbl_copytoptr(resultp1,resultp2,dstptr);
    304       1.1  fredette 			if (inexact) {
    305       1.1  fredette 				if (Is_inexacttrap_enabled())
    306       1.1  fredette 					return(OVERFLOWEXCEPTION | INEXACTEXCEPTION);
    307       1.1  fredette 				else
    308       1.1  fredette 					Set_inexactflag();
    309       1.1  fredette 			}
    310       1.1  fredette 			return(OVERFLOWEXCEPTION);
    311       1.1  fredette 		}
    312       1.1  fredette 		Set_overflowflag();
    313       1.1  fredette 		/* set result to infinity or largest number */
    314       1.1  fredette 		Dbl_setoverflow(resultp1,resultp2);
    315       1.4   thorpej 		inexact = true;
    316       1.1  fredette 	}
    317       1.1  fredette 	/*
    318       1.1  fredette 	 * Test for underflow
    319       1.1  fredette 	 */
    320       1.1  fredette 	else if (dest_exponent <= 0) {
    321       1.1  fredette 		/* trap if UNDERFLOWTRAP enabled */
    322       1.1  fredette 		if (Is_underflowtrap_enabled()) {
    323       1.1  fredette 			/*
    324       1.1  fredette 			 * Adjust bias of result
    325       1.1  fredette 			 */
    326       1.1  fredette 			Dbl_setwrapped_exponent(resultp1,dest_exponent,unfl);
    327       1.1  fredette 			Dbl_copytoptr(resultp1,resultp2,dstptr);
    328       1.1  fredette 			if (inexact) {
    329       1.1  fredette 				if (Is_inexacttrap_enabled())
    330       1.1  fredette 					return(UNDERFLOWEXCEPTION | INEXACTEXCEPTION);
    331       1.1  fredette 				else
    332       1.1  fredette 					Set_inexactflag();
    333       1.1  fredette 			}
    334       1.1  fredette 			return(UNDERFLOWEXCEPTION);
    335       1.1  fredette 		}
    336       1.1  fredette 
    337       1.1  fredette 		/* Determine if should set underflow flag */
    338       1.4   thorpej 		is_tiny = true;
    339       1.1  fredette 		if (dest_exponent == 0 && inexact) {
    340       1.1  fredette 			switch (Rounding_mode()) {
    341       1.1  fredette 			case ROUNDPLUS:
    342       1.1  fredette 				if (Dbl_iszero_sign(resultp1)) {
    343       1.1  fredette 					Dbl_increment(opnd3p1,opnd3p2);
    344       1.1  fredette 					if (Dbl_isone_hiddenoverflow(opnd3p1))
    345       1.4   thorpej 						is_tiny = false;
    346       1.1  fredette 					Dbl_decrement(opnd3p1,opnd3p2);
    347       1.1  fredette 				}
    348       1.1  fredette 				break;
    349       1.1  fredette 			case ROUNDMINUS:
    350       1.1  fredette 				if (Dbl_isone_sign(resultp1)) {
    351       1.1  fredette 					Dbl_increment(opnd3p1,opnd3p2);
    352       1.1  fredette 					if (Dbl_isone_hiddenoverflow(opnd3p1))
    353       1.4   thorpej 						is_tiny = false;
    354       1.1  fredette 					Dbl_decrement(opnd3p1,opnd3p2);
    355       1.1  fredette 				}
    356       1.1  fredette 				break;
    357       1.1  fredette 			case ROUNDNEAREST:
    358       1.1  fredette 				if (guardbit && (stickybit ||
    359       1.1  fredette 				    Dbl_isone_lowmantissap2(opnd3p2))) {
    360       1.1  fredette 					Dbl_increment(opnd3p1,opnd3p2);
    361       1.1  fredette 					if (Dbl_isone_hiddenoverflow(opnd3p1))
    362       1.4   thorpej 						is_tiny = false;
    363       1.1  fredette 					Dbl_decrement(opnd3p1,opnd3p2);
    364       1.1  fredette 				}
    365       1.1  fredette 				break;
    366       1.1  fredette 			}
    367       1.1  fredette 		}
    368       1.1  fredette 
    369       1.1  fredette 		/*
    370       1.1  fredette 		 * denormalize result or set to signed zero
    371       1.1  fredette 		 */
    372       1.1  fredette 		stickybit = inexact;
    373       1.1  fredette 		Dbl_denormalize(opnd3p1,opnd3p2,dest_exponent,guardbit,
    374       1.1  fredette 		 stickybit,inexact);
    375       1.1  fredette 
    376       1.1  fredette 		/* return rounded number */
    377       1.1  fredette 		if (inexact) {
    378       1.1  fredette 			switch (Rounding_mode()) {
    379       1.1  fredette 			case ROUNDPLUS:
    380       1.1  fredette 				if (Dbl_iszero_sign(resultp1)) {
    381       1.1  fredette 					Dbl_increment(opnd3p1,opnd3p2);
    382       1.1  fredette 				}
    383       1.1  fredette 				break;
    384       1.1  fredette 			case ROUNDMINUS:
    385       1.1  fredette 				if (Dbl_isone_sign(resultp1)) {
    386       1.1  fredette 					Dbl_increment(opnd3p1,opnd3p2);
    387       1.1  fredette 				}
    388       1.1  fredette 				break;
    389       1.1  fredette 			case ROUNDNEAREST:
    390       1.1  fredette 				if (guardbit && (stickybit ||
    391       1.1  fredette 				    Dbl_isone_lowmantissap2(opnd3p2))) {
    392       1.1  fredette 					Dbl_increment(opnd3p1,opnd3p2);
    393       1.1  fredette 				}
    394       1.1  fredette 				break;
    395       1.1  fredette 			}
    396       1.1  fredette 			if (is_tiny)
    397       1.1  fredette 				Set_underflowflag();
    398       1.1  fredette 		}
    399       1.1  fredette 		Dbl_set_exponentmantissa(resultp1,resultp2,opnd3p1,opnd3p2);
    400       1.1  fredette 	}
    401       1.1  fredette 	else Dbl_set_exponent(resultp1,dest_exponent);
    402       1.1  fredette 	Dbl_copytoptr(resultp1,resultp2,dstptr);
    403       1.1  fredette 
    404       1.1  fredette 	/* check for inexact */
    405       1.1  fredette 	if (inexact) {
    406       1.1  fredette 		if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
    407       1.1  fredette 		else Set_inexactflag();
    408       1.1  fredette 	}
    409       1.1  fredette 	return(NOEXCEPTION);
    410       1.1  fredette }
    411