[linux-2.6-block.git] / arch / parisc / math-emu / dfdiv.c

/*
 * Linux/PA-RISC Project (http://www.parisc-linux.org/)
 *
 * Floating-point emulation code
 *  Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2, or (at your option)
 *    any later version.
 *
 *    This program 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 General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
/*
 * BEGIN_DESC
 *
 *  File:
 *	@(#)	pa/spmath/dfdiv.c		$Revision: 1.1 $
 *
 *  Purpose:
 *	Double Precision Floating-point Divide
 *
 *  External Interfaces:
 *	dbl_fdiv(srcptr1,srcptr2,dstptr,status)
 *
 *  Internal Interfaces:
 *
 *  Theory:
 *	<<please update with a overview of the operation of this file>>
 *
 * END_DESC
*/


#include "float.h"
#include "dbl_float.h"

/*
 *  Double Precision Floating-point Divide
 */

int
dbl_fdiv (dbl_floating_point * srcptr1, dbl_floating_point * srcptr2,
	  dbl_floating_point * dstptr, unsigned int *status)
{
	register unsigned int opnd1p1, opnd1p2, opnd2p1, opnd2p2;
	register unsigned int opnd3p1, opnd3p2, resultp1, resultp2;
	register int dest_exponent, count;
	register boolean inexact = FALSE, guardbit = FALSE, stickybit = FALSE;
	boolean 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);
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Linux/PA-RISC Project (http://www.parisc-linux.org/)
	3	*
	4	* Floating-point emulation code
	5	* Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
	6	*
	7	* This program is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU General Public License as published by
	9	* the Free Software Foundation; either version 2, or (at your option)
	10	* any later version.
	11	*
	12	* This program is distributed in the hope that it will be useful,
	13	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	15	* GNU General Public License for more details.
	16	*
	17	* You should have received a copy of the GNU General Public License
	18	* along with this program; if not, write to the Free Software
	19	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	20	*/
	21	/*
	22	* BEGIN_DESC
	23	*
	24	* File:
	25	* @(#) pa/spmath/dfdiv.c $Revision: 1.1 $
	26	*
	27	* Purpose:
	28	* Double Precision Floating-point Divide
	29	*
	30	* External Interfaces:
	31	* dbl_fdiv(srcptr1,srcptr2,dstptr,status)
	32	*
	33	* Internal Interfaces:
	34	*
	35	* Theory:
	36	* <<please update with a overview of the operation of this file>>
	37	*
	38	* END_DESC
	39	*/
	40
	41
	42	#include "float.h"
	43	#include "dbl_float.h"
	44
	45	/*
	46	* Double Precision Floating-point Divide
	47	*/
	48
	49	int
	50	dbl_fdiv (dbl_floating_point * srcptr1, dbl_floating_point * srcptr2,
	51	dbl_floating_point * dstptr, unsigned int *status)
	52	{
	53	register unsigned int opnd1p1, opnd1p2, opnd2p1, opnd2p2;
	54	register unsigned int opnd3p1, opnd3p2, resultp1, resultp2;
	55	register int dest_exponent, count;
	56	register boolean inexact = FALSE, guardbit = FALSE, stickybit = FALSE;
	57	boolean is_tiny;
	58
	59	Dbl_copyfromptr(srcptr1,opnd1p1,opnd1p2);
	60	Dbl_copyfromptr(srcptr2,opnd2p1,opnd2p2);
	61	/*
	62	* set sign bit of result
	63	*/
	64	if (Dbl_sign(opnd1p1) ^ Dbl_sign(opnd2p1))
65	Dbl_setnegativezerop1(resultp1);
66	else Dbl_setzerop1(resultp1);
67	/*
68	* check first operand for NaN's or infinity
69	*/
70	if (Dbl_isinfinity_exponent(opnd1p1)) {
71	if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
72	if (Dbl_isnotnan(opnd2p1,opnd2p2)) {
73	if (Dbl_isinfinity(opnd2p1,opnd2p2)) {
74	/*
75	* invalid since both operands
76	* are infinity
77	*/
78	if (Is_invalidtrap_enabled())
79	return(INVALIDEXCEPTION);
80	Set_invalidflag();
81	Dbl_makequietnan(resultp1,resultp2);
82	Dbl_copytoptr(resultp1,resultp2,dstptr);
83	return(NOEXCEPTION);
84	}
85	/*
86	* return infinity
87	*/
88	Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
89	Dbl_copytoptr(resultp1,resultp2,dstptr);
90	return(NOEXCEPTION);
91	}
92	}
93	else {
94	/*
95	* is NaN; signaling or quiet?
96	*/
97	if (Dbl_isone_signaling(opnd1p1)) {
98	/* trap if INVALIDTRAP enabled */
99	if (Is_invalidtrap_enabled())
100	return(INVALIDEXCEPTION);
101	/* make NaN quiet */
102	Set_invalidflag();
103	Dbl_set_quiet(opnd1p1);
104	}
105	/*
106	* is second operand a signaling NaN?
107	*/
108	else if (Dbl_is_signalingnan(opnd2p1)) {
109	/* trap if INVALIDTRAP enabled */
110	if (Is_invalidtrap_enabled())
111	return(INVALIDEXCEPTION);
112	/* make NaN quiet */
113	Set_invalidflag();
114	Dbl_set_quiet(opnd2p1);
115	Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
116	return(NOEXCEPTION);
117	}
118	/*
119	* return quiet NaN
120	*/
121	Dbl_copytoptr(opnd1p1,opnd1p2,dstptr);
122	return(NOEXCEPTION);
123	}
124	}
125	/*
126	* check second operand for NaN's or infinity
127	*/
128	if (Dbl_isinfinity_exponent(opnd2p1)) {
129	if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
130	/*
131	* return zero
132	*/
133	Dbl_setzero_exponentmantissa(resultp1,resultp2);
134	Dbl_copytoptr(resultp1,resultp2,dstptr);
135	return(NOEXCEPTION);
136	}
137	/*
138	* is NaN; signaling or quiet?
139	*/
140	if (Dbl_isone_signaling(opnd2p1)) {
141	/* trap if INVALIDTRAP enabled */
142	if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
143	/* make NaN quiet */
144	Set_invalidflag();
145	Dbl_set_quiet(opnd2p1);
146	}
147	/*
148	* return quiet NaN
149	*/
150	Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
151	return(NOEXCEPTION);
152	}
153	/*
154	* check for division by zero
155	*/
156	if (Dbl_iszero_exponentmantissa(opnd2p1,opnd2p2)) {
157	if (Dbl_iszero_exponentmantissa(opnd1p1,opnd1p2)) {
158	/* invalid since both operands are zero */
159	if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
160	Set_invalidflag();
161	Dbl_makequietnan(resultp1,resultp2);
162	Dbl_copytoptr(resultp1,resultp2,dstptr);
163	return(NOEXCEPTION);
164	}
165	if (Is_divisionbyzerotrap_enabled())
166	return(DIVISIONBYZEROEXCEPTION);
167	Set_divisionbyzeroflag();
168	Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
169	Dbl_copytoptr(resultp1,resultp2,dstptr);
170	return(NOEXCEPTION);
171	}
172	/*
173	* Generate exponent
174	*/
175	dest_exponent = Dbl_exponent(opnd1p1) - Dbl_exponent(opnd2p1) + DBL_BIAS;
176
177	/*
178	* Generate mantissa
179	*/
180	if (Dbl_isnotzero_exponent(opnd1p1)) {
181	/* set hidden bit */
182	Dbl_clear_signexponent_set_hidden(opnd1p1);
183	}
184	else {
185	/* check for zero */
186	if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
187	Dbl_setzero_exponentmantissa(resultp1,resultp2);
188	Dbl_copytoptr(resultp1,resultp2,dstptr);
189	return(NOEXCEPTION);
190	}
191	/* is denormalized, want to normalize */
192	Dbl_clear_signexponent(opnd1p1);
193	Dbl_leftshiftby1(opnd1p1,opnd1p2);
194	Dbl_normalize(opnd1p1,opnd1p2,dest_exponent);
195	}
196	/* opnd2 needs to have hidden bit set with msb in hidden bit */
197	if (Dbl_isnotzero_exponent(opnd2p1)) {
198	Dbl_clear_signexponent_set_hidden(opnd2p1);
199	}
200	else {
201	/* is denormalized; want to normalize */
202	Dbl_clear_signexponent(opnd2p1);
203	Dbl_leftshiftby1(opnd2p1,opnd2p2);
204	while (Dbl_iszero_hiddenhigh7mantissa(opnd2p1)) {
205	dest_exponent+=8;
206	Dbl_leftshiftby8(opnd2p1,opnd2p2);
207	}
208	if (Dbl_iszero_hiddenhigh3mantissa(opnd2p1)) {
209	dest_exponent+=4;
210	Dbl_leftshiftby4(opnd2p1,opnd2p2);
211	}
212	while (Dbl_iszero_hidden(opnd2p1)) {
213	dest_exponent++;
214	Dbl_leftshiftby1(opnd2p1,opnd2p2);
215	}
216	}
217
218	/* Divide the source mantissas */
219
220	/*
221	* A non-restoring divide algorithm is used.
222	*/
223	Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
224	Dbl_setzero(opnd3p1,opnd3p2);
225	for (count=1; count <= DBL_P && (opnd1p1 \|\| opnd1p2); count++) {
226	Dbl_leftshiftby1(opnd1p1,opnd1p2);
227	Dbl_leftshiftby1(opnd3p1,opnd3p2);
228	if (Dbl_iszero_sign(opnd1p1)) {
229	Dbl_setone_lowmantissap2(opnd3p2);
230	Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
231	}
232	else {
233	Twoword_add(opnd1p1, opnd1p2, opnd2p1, opnd2p2);
234	}
235	}
236	if (count <= DBL_P) {
237	Dbl_leftshiftby1(opnd3p1,opnd3p2);
238	Dbl_setone_lowmantissap2(opnd3p2);
239	Dbl_leftshift(opnd3p1,opnd3p2,(DBL_P-count));
240	if (Dbl_iszero_hidden(opnd3p1)) {
241	Dbl_leftshiftby1(opnd3p1,opnd3p2);
242	dest_exponent--;
243	}
244	}
245	else {
246	if (Dbl_iszero_hidden(opnd3p1)) {
247	/* need to get one more bit of result */
248	Dbl_leftshiftby1(opnd1p1,opnd1p2);
249	Dbl_leftshiftby1(opnd3p1,opnd3p2);
250	if (Dbl_iszero_sign(opnd1p1)) {
251	Dbl_setone_lowmantissap2(opnd3p2);
252	Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
253	}
254	else {
255	Twoword_add(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
256	}
257	dest_exponent--;
258	}
259	if (Dbl_iszero_sign(opnd1p1)) guardbit = TRUE;
260	stickybit = Dbl_allp1(opnd1p1) \|\| Dbl_allp2(opnd1p2);
261	}
262	inexact = guardbit \| stickybit;
263
264	/*
265	* round result
266	*/
267	if (inexact && (dest_exponent > 0 \|\| Is_underflowtrap_enabled())) {
268	Dbl_clear_signexponent(opnd3p1);
269	switch (Rounding_mode()) {
270	case ROUNDPLUS:
271	if (Dbl_iszero_sign(resultp1))
272	Dbl_increment(opnd3p1,opnd3p2);
273	break;
274	case ROUNDMINUS:
275	if (Dbl_isone_sign(resultp1))
276	Dbl_increment(opnd3p1,opnd3p2);
277	break;
278	case ROUNDNEAREST:
279	if (guardbit && (stickybit \|\|
280	Dbl_isone_lowmantissap2(opnd3p2))) {
281	Dbl_increment(opnd3p1,opnd3p2);
282	}
283	}
284	if (Dbl_isone_hidden(opnd3p1)) dest_exponent++;
285	}
286	Dbl_set_mantissa(resultp1,resultp2,opnd3p1,opnd3p2);
287
288	/*
289	* Test for overflow
290	*/
291	if (dest_exponent >= DBL_INFINITY_EXPONENT) {
292	/* trap if OVERFLOWTRAP enabled */
293	if (Is_overflowtrap_enabled()) {
294	/*
295	* Adjust bias of result
296	*/
297	Dbl_setwrapped_exponent(resultp1,dest_exponent,ovfl);
298	Dbl_copytoptr(resultp1,resultp2,dstptr);
299	if (inexact)
300	if (Is_inexacttrap_enabled())
301	return(OVERFLOWEXCEPTION \| INEXACTEXCEPTION);
302	else Set_inexactflag();
303	return(OVERFLOWEXCEPTION);
304	}
305	Set_overflowflag();
306	/* set result to infinity or largest number */
307	Dbl_setoverflow(resultp1,resultp2);
308	inexact = TRUE;
309	}
310	/*
311	* Test for underflow
312	*/
313	else if (dest_exponent <= 0) {
314	/* trap if UNDERFLOWTRAP enabled */
315	if (Is_underflowtrap_enabled()) {
316	/*
317	* Adjust bias of result
318	*/
319	Dbl_setwrapped_exponent(resultp1,dest_exponent,unfl);
320	Dbl_copytoptr(resultp1,resultp2,dstptr);
321	if (inexact)
322	if (Is_inexacttrap_enabled())
323	return(UNDERFLOWEXCEPTION \| INEXACTEXCEPTION);
324	else Set_inexactflag();
325	return(UNDERFLOWEXCEPTION);
326	}
327
328	/* Determine if should set underflow flag */
329	is_tiny = TRUE;
330	if (dest_exponent == 0 && inexact) {
331	switch (Rounding_mode()) {
332	case ROUNDPLUS:
333	if (Dbl_iszero_sign(resultp1)) {
334	Dbl_increment(opnd3p1,opnd3p2);
335	if (Dbl_isone_hiddenoverflow(opnd3p1))
336	is_tiny = FALSE;
337	Dbl_decrement(opnd3p1,opnd3p2);
338	}
339	break;
340	case ROUNDMINUS:
341	if (Dbl_isone_sign(resultp1)) {
342	Dbl_increment(opnd3p1,opnd3p2);
343	if (Dbl_isone_hiddenoverflow(opnd3p1))
344	is_tiny = FALSE;
345	Dbl_decrement(opnd3p1,opnd3p2);
346	}
347	break;
348	case ROUNDNEAREST:
349	if (guardbit && (stickybit \|\|
350	Dbl_isone_lowmantissap2(opnd3p2))) {
351	Dbl_increment(opnd3p1,opnd3p2);
352	if (Dbl_isone_hiddenoverflow(opnd3p1))
353	is_tiny = FALSE;
354	Dbl_decrement(opnd3p1,opnd3p2);
355	}
356	break;
357	}
358	}
359
360	/*
361	* denormalize result or set to signed zero
362	*/
363	stickybit = inexact;
364	Dbl_denormalize(opnd3p1,opnd3p2,dest_exponent,guardbit,
365	stickybit,inexact);
366
367	/* return rounded number */
368	if (inexact) {
369	switch (Rounding_mode()) {
370	case ROUNDPLUS:
371	if (Dbl_iszero_sign(resultp1)) {
372	Dbl_increment(opnd3p1,opnd3p2);
373	}
374	break;
375	case ROUNDMINUS:
376	if (Dbl_isone_sign(resultp1)) {
377	Dbl_increment(opnd3p1,opnd3p2);
378	}
379	break;
380	case ROUNDNEAREST:
381	if (guardbit && (stickybit \|\|
382	Dbl_isone_lowmantissap2(opnd3p2))) {
383	Dbl_increment(opnd3p1,opnd3p2);
384	}
385	break;
386	}
387	if (is_tiny) Set_underflowflag();
388	}
389	Dbl_set_exponentmantissa(resultp1,resultp2,opnd3p1,opnd3p2);
390	}
391	else Dbl_set_exponent(resultp1,dest_exponent);
392	Dbl_copytoptr(resultp1,resultp2,dstptr);
393
394	/* check for inexact */
395	if (inexact) {
396	if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
397	else Set_inexactflag();
398	}
399	return(NOEXCEPTION);
400	}