// 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/sfmpy.c               $Revision: 1.1 $
 *
 *  Purpose:
 *      Single Precision Floating-point Multiply
 *
 *  External Interfaces:
 *      sgl_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 "sgl_float.h"

/*
 *  Single Precision Floating-point Multiply
 */

int
sgl_fmpy(
    sgl_floating_point *srcptr1,
    sgl_floating_point *srcptr2,
    sgl_floating_point *dstptr,
    unsigned int *status)
{
        register unsigned int opnd1, opnd2, opnd3, result;
        register int dest_exponent, count;
        register boolean inexact = FALSE, guardbit = FALSE, stickybit = FALSE;
        boolean 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) {
                                if (stickybit || Sgl_isone_lowmantissa(opnd3))
                                Sgl_increment(opnd3);
                                }
                }
                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);
}