// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Linux/PA-RISC Project (http://www.parisc-linux.org/)
 *
 * Floating-point emulation code
 *  Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
 */
/*
 * BEGIN_DESC
 *
 *  File:
 *      @(#)    pa/spmath/dfmpy.c               $Revision: 1.1 $
 *
 *  Purpose:
 *      Double Precision Floating-point Multiply
 *
 *  External Interfaces:
 *      dbl_fmpy(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 Multiply
 */

int
dbl_fmpy(
            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_iszero_exponentmantissa(opnd2p1,opnd2p2)) {
                                        /* 
                                         * invalid since operands are infinity 
                                         * and zero 
                                         */
                                        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)) {
                        if (Dbl_iszero_exponentmantissa(opnd1p1,opnd1p2)) {
                                /* invalid since operands are zero & infinity */
                                if (Is_invalidtrap_enabled())
                                        return(INVALIDEXCEPTION);
                                Set_invalidflag();
                                Dbl_makequietnan(opnd2p1,opnd2p2);
                                Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
                                return(NOEXCEPTION);
                        }
                        /*
                         * return infinity
                         */
                        Dbl_setinfinity_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);
        }
        /*
         * 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, adjust exponent */
                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 {
                /* check for zero */
                if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
                        Dbl_setzero_exponentmantissa(resultp1,resultp2);
                        Dbl_copytoptr(resultp1,resultp2,dstptr);
                        return(NOEXCEPTION);
                }
                /* is denormalized; want to normalize */
                Dbl_clear_signexponent(opnd2p1);
                Dbl_leftshiftby1(opnd2p1,opnd2p2);
                Dbl_normalize(opnd2p1,opnd2p2,dest_exponent);
        }

        /* Multiply two source mantissas together */

        /* make room for guard bits */
        Dbl_leftshiftby7(opnd2p1,opnd2p2);
        Dbl_setzero(opnd3p1,opnd3p2);
        /* 
         * Four bits at a time are inspected in each loop, and a 
         * simple shift and add multiply algorithm is used. 
         */ 
        for (count=1;count<=DBL_P;count+=4) {
                stickybit |= Dlow4p2(opnd3p2);
                Dbl_rightshiftby4(opnd3p1,opnd3p2);
                if (Dbit28p2(opnd1p2)) {
                        /* Twoword_add should be an ADDC followed by an ADD. */
                        Twoword_add(opnd3p1, opnd3p2, opnd2p1<<3 | opnd2p2>>29, 
                                    opnd2p2<<3);
                }
                if (Dbit29p2(opnd1p2)) {
                        Twoword_add(opnd3p1, opnd3p2, opnd2p1<<2 | opnd2p2>>30, 
                                    opnd2p2<<2);
                }
                if (Dbit30p2(opnd1p2)) {
                        Twoword_add(opnd3p1, opnd3p2, opnd2p1<<1 | opnd2p2>>31,
                                    opnd2p2<<1);
                }
                if (Dbit31p2(opnd1p2)) {
                        Twoword_add(opnd3p1, opnd3p2, opnd2p1, opnd2p2);
                }
                Dbl_rightshiftby4(opnd1p1,opnd1p2);
        }
        if (Dbit3p1(opnd3p1)==0) {
                Dbl_leftshiftby1(opnd3p1,opnd3p2);
        }
        else {
                /* result mantissa >= 2. */
                dest_exponent++;
        }
        /* check for denormalized result */
        while (Dbit3p1(opnd3p1)==0) {
                Dbl_leftshiftby1(opnd3p1,opnd3p2);
                dest_exponent--;
        }
        /*
         * check for guard, sticky and inexact bits 
         */
        stickybit |= Dallp2(opnd3p2) << 25;
        guardbit = (Dallp2(opnd3p2) << 24) >> 31;
        inexact = guardbit | stickybit;

        /* align result mantissa */
        Dbl_rightshiftby8(opnd3p1,opnd3p2);

        /* 
         * 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) {
                                if (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);
                }
                inexact = TRUE;
                Set_overflowflag();
                /* set result to infinity or largest number */
                Dbl_setoverflow(resultp1,resultp2);
        }
        /* 
         * 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 zero or smallest 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);
        /* check for inexact */
        Dbl_copytoptr(resultp1,resultp2,dstptr);
        if (inexact) {
                if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
                else Set_inexactflag();
        }
        return(NOEXCEPTION);
}