/*      $NetBSD: dfsqrt.c,v 1.6 2016/02/29 18:22:06 christos Exp $      */

/*      $OpenBSD: dfsqrt.c,v 1.5 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 <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: dfsqrt.c,v 1.6 2016/02/29 18:22:06 christos Exp $");

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

/*
 *  Double Floating-point Square Root
 */

/*ARGSUSED*/
int
dbl_fsqrt(dbl_floating_point *srcptr, dbl_floating_point *dstptr,
    unsigned int *status)
{
        register unsigned int srcp1, srcp2, resultp1, resultp2;
        register unsigned int newbitp1, newbitp2, sump1, sump2;
        register int src_exponent;
        register int guardbit = false, even_exponent;

        Dbl_copyfromptr(srcptr,srcp1,srcp2);
        /*
         * check source operand for NaN or infinity
         */
        if ((src_exponent = Dbl_exponent(srcp1)) == DBL_INFINITY_EXPONENT) {
                /*
                 * is signaling NaN?
                 */
                if (Dbl_isone_signaling(srcp1)) {
                        /* trap if INVALIDTRAP enabled */
                        if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
                        /* make NaN quiet */
                        Set_invalidflag();
                        Dbl_set_quiet(srcp1);
                }
                /*
                 * Return quiet NaN or positive infinity.
                 *  Fall thru to negative test if negative infinity.
                 */
                if (Dbl_iszero_sign(srcp1) ||
                    Dbl_isnotzero_mantissa(srcp1,srcp2)) {
                        Dbl_copytoptr(srcp1,srcp2,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * check for zero source operand
         */
        if (Dbl_iszero_exponentmantissa(srcp1,srcp2)) {
                Dbl_copytoptr(srcp1,srcp2,dstptr);
                return(NOEXCEPTION);
        }

        /*
         * check for negative source operand
         */
        if (Dbl_isone_sign(srcp1)) {
                /* trap if INVALIDTRAP enabled */
                if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
                /* make NaN quiet */
                Set_invalidflag();
                Dbl_makequietnan(srcp1,srcp2);
                Dbl_copytoptr(srcp1,srcp2,dstptr);
                return(NOEXCEPTION);
        }

        /*
         * Generate result
         */
        if (src_exponent > 0) {
                even_exponent = Dbl_hidden(srcp1);
                Dbl_clear_signexponent_set_hidden(srcp1);
        }
        else {
                /* normalize operand */
                Dbl_clear_signexponent(srcp1);
                src_exponent++;
                Dbl_normalize(srcp1,srcp2,src_exponent);
                even_exponent = src_exponent & 1;
        }
        if (even_exponent) {
                /* exponent is even */
                /* Add comment here.  Explain why odd exponent needs correction */
                Dbl_leftshiftby1(srcp1,srcp2);
        }
        /*
         * Add comment here.  Explain following algorithm.
         *
         * Trust me, it works.
         *
         */
        Dbl_setzero(resultp1,resultp2);
        Dbl_allp1(newbitp1) = 1 << (DBL_P - 32);
        Dbl_setzero_mantissap2(newbitp2);
        while (Dbl_isnotzero(newbitp1,newbitp2) && Dbl_isnotzero(srcp1,srcp2)) {
                Dbl_addition(resultp1,resultp2,newbitp1,newbitp2,sump1,sump2);
                if(Dbl_isnotgreaterthan(sump1,sump2,srcp1,srcp2)) {
                        Dbl_leftshiftby1(newbitp1,newbitp2);
                        /* update result */
                        Dbl_addition(resultp1,resultp2,newbitp1,newbitp2,
                         resultp1,resultp2);
                        Dbl_subtract(srcp1,srcp2,sump1,sump2,srcp1,srcp2);
                        Dbl_rightshiftby2(newbitp1,newbitp2);
                }
                else {
                        Dbl_rightshiftby1(newbitp1,newbitp2);
                }
                Dbl_leftshiftby1(srcp1,srcp2);
        }
        /* correct exponent for pre-shift */
        if (even_exponent) {
                Dbl_rightshiftby1(resultp1,resultp2);
        }

        /* check for inexact */
        if (Dbl_isnotzero(srcp1,srcp2)) {
                if (!even_exponent && Dbl_islessthan(resultp1,resultp2,srcp1,srcp2)) {
                        Dbl_increment(resultp1,resultp2);
                }
                guardbit = Dbl_lowmantissap2(resultp2);
                Dbl_rightshiftby1(resultp1,resultp2);

                /*  now round result  */
                switch (Rounding_mode()) {
                case ROUNDPLUS:
                     Dbl_increment(resultp1,resultp2);
                     break;
                case ROUNDNEAREST:
                     /* stickybit is always true, so guardbit
                      * is enough to determine rounding */
                     if (guardbit) {
                            Dbl_increment(resultp1,resultp2);
                     }
                     break;
                }
                /* increment result exponent by 1 if mantissa overflowed */
                if (Dbl_isone_hiddenoverflow(resultp1)) src_exponent+=2;

                if (Is_inexacttrap_enabled()) {
                        Dbl_set_exponent(resultp1,
                         ((src_exponent-DBL_BIAS)>>1)+DBL_BIAS);
                        Dbl_copytoptr(resultp1,resultp2,dstptr);
                        return(INEXACTEXCEPTION);
                }
                else Set_inexactflag();
        }
        else {
                Dbl_rightshiftby1(resultp1,resultp2);
        }
        Dbl_set_exponent(resultp1,((src_exponent-DBL_BIAS)>>1)+DBL_BIAS);
        Dbl_copytoptr(resultp1,resultp2,dstptr);
        return(NOEXCEPTION);
}