fcnvxf.c

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/*
 * Linux/PA-RISC Project (http://www.parisc-linux.org/)
 *
 * Floating-point emulation code
 *  Copyright (C) 2001 Hewlett-Packard (Paul Bame) <[email protected]>
 *
 *    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/fcnvxf.c      $Revision: 1.1 $
 *
 *  Purpose:
 *  Single Fixed-point to Single Floating-point
 *  Single Fixed-point to Double Floating-point 
 *  Double Fixed-point to Single Floating-point 
 *  Double Fixed-point to Double Floating-point 
 *
 *  External Interfaces:
 *  dbl_to_dbl_fcnvxf(srcptr,nullptr,dstptr,status)
 *  dbl_to_sgl_fcnvxf(srcptr,nullptr,dstptr,status)
 *  sgl_to_dbl_fcnvxf(srcptr,nullptr,dstptr,status)
 *  sgl_to_sgl_fcnvxf(srcptr,nullptr,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"
#include "dbl_float.h"
#include "cnv_float.h"

/*
 *  Convert single fixed-point to single floating-point format
 */

int
sgl_to_sgl_fcnvxf(
            int *srcptr,
            unsigned int *nullptr,
            sgl_floating_point *dstptr,
            unsigned int *status)
{
    register int src, dst_exponent;
    register unsigned int result = 0;

    src = *srcptr;
    /* 
     * set sign bit of result and get magnitude of source 
     */
    if (src < 0) {
        Sgl_setone_sign(result);  
        Int_negate(src);
    }
    else {
        Sgl_setzero_sign(result);
            /* Check for zero */ 
            if (src == 0) { 
                    Sgl_setzero(result); 
            *dstptr = result;
                    return(NOEXCEPTION); 
            } 
    }
    /*
     * Generate exponent and normalized mantissa
     */
    dst_exponent = 16;    /* initialize for normalization */
    /*
     * Check word for most significant bit set.  Returns
     * a value in dst_exponent indicating the bit position,
     * between -1 and 30.
     */
    Find_ms_one_bit(src,dst_exponent);
    /*  left justify source, with msb at bit position 1  */
    if (dst_exponent >= 0) src <<= dst_exponent;
    else src = 1 << 30;
    Sgl_set_mantissa(result, src >> (SGL_EXP_LENGTH-1));
    Sgl_set_exponent(result, 30+SGL_BIAS - dst_exponent);

    /* check for inexact */
    if (Int_isinexact_to_sgl(src)) {
        switch (Rounding_mode()) {
            case ROUNDPLUS: 
                if (Sgl_iszero_sign(result)) 
                    Sgl_increment(result);
                break;
            case ROUNDMINUS: 
                if (Sgl_isone_sign(result)) 
                    Sgl_increment(result);
                break;
            case ROUNDNEAREST:
                Sgl_roundnearest_from_int(src,result);
        }
        if (Is_inexacttrap_enabled()) {
            *dstptr = result;
            return(INEXACTEXCEPTION);
        }
        else Set_inexactflag();
    }
    *dstptr = result;
    return(NOEXCEPTION);
}

/*
 *  Single Fixed-point to Double Floating-point 
 */

int
sgl_to_dbl_fcnvxf(
            int *srcptr,
            unsigned int *nullptr,
            dbl_floating_point *dstptr,
            unsigned int *status)
{
    register int src, dst_exponent;
    register unsigned int resultp1 = 0, resultp2 = 0;

    src = *srcptr;
    /* 
     * set sign bit of result and get magnitude of source 
     */
    if (src < 0) {
        Dbl_setone_sign(resultp1);  
        Int_negate(src);
    }
    else {
        Dbl_setzero_sign(resultp1);
            /* Check for zero */
            if (src == 0) {
                    Dbl_setzero(resultp1,resultp2);
                    Dbl_copytoptr(resultp1,resultp2,dstptr);
                    return(NOEXCEPTION);
            }
    }
    /*
     * Generate exponent and normalized mantissa
     */
    dst_exponent = 16;    /* initialize for normalization */
    /*
     * Check word for most significant bit set.  Returns
     * a value in dst_exponent indicating the bit position,
     * between -1 and 30.
     */
    Find_ms_one_bit(src,dst_exponent);
    /*  left justify source, with msb at bit position 1  */
    if (dst_exponent >= 0) src <<= dst_exponent;
    else src = 1 << 30;
    Dbl_set_mantissap1(resultp1, src >> DBL_EXP_LENGTH - 1);
    Dbl_set_mantissap2(resultp2, src << (33-DBL_EXP_LENGTH));
    Dbl_set_exponent(resultp1, (30+DBL_BIAS) - dst_exponent);
    Dbl_copytoptr(resultp1,resultp2,dstptr);
    return(NOEXCEPTION);
}

/*
 *  Double Fixed-point to Single Floating-point 
 */

int
dbl_to_sgl_fcnvxf(
            dbl_integer *srcptr,
            unsigned int *nullptr,
            sgl_floating_point *dstptr,
            unsigned int *status)
{
    int dst_exponent, srcp1;
    unsigned int result = 0, srcp2;

    Dint_copyfromptr(srcptr,srcp1,srcp2);
    /* 
     * set sign bit of result and get magnitude of source 
     */
    if (srcp1 < 0) {
        Sgl_setone_sign(result);  
        Dint_negate(srcp1,srcp2);
    }
    else {
        Sgl_setzero_sign(result);
            /* Check for zero */
            if (srcp1 == 0 && srcp2 == 0) {
                    Sgl_setzero(result);
                    *dstptr = result;
                    return(NOEXCEPTION);
        }
        }
    /*
     * Generate exponent and normalized mantissa
     */
    dst_exponent = 16;    /* initialize for normalization */
    if (srcp1 == 0) {
        /*
         * Check word for most significant bit set.  Returns
         * a value in dst_exponent indicating the bit position,
         * between -1 and 30.
         */
        Find_ms_one_bit(srcp2,dst_exponent);
        /*  left justify source, with msb at bit position 1  */
        if (dst_exponent >= 0) {
            srcp1 = srcp2 << dst_exponent;    
            srcp2 = 0;
        }
        else {
            srcp1 = srcp2 >> 1;
            srcp2 <<= 31; 
        }
        /*
         *  since msb set is in second word, need to 
         *  adjust bit position count
         */
        dst_exponent += 32;
    }
    else {
        /*
         * Check word for most significant bit set.  Returns
         * a value in dst_exponent indicating the bit position,
         * between -1 and 30.
         *
         */
        Find_ms_one_bit(srcp1,dst_exponent);
        /*  left justify source, with msb at bit position 1  */
        if (dst_exponent > 0) {
            Variable_shift_double(srcp1,srcp2,(32-dst_exponent),
             srcp1); 
            srcp2 <<= dst_exponent;
        }
        /*
         * If dst_exponent = 0, we don't need to shift anything.
         * If dst_exponent = -1, src = - 2**63 so we won't need to 
         * shift srcp2.
         */
        else srcp1 >>= -(dst_exponent);
    }
    Sgl_set_mantissa(result, srcp1 >> SGL_EXP_LENGTH - 1);
    Sgl_set_exponent(result, (62+SGL_BIAS) - dst_exponent);

    /* check for inexact */
    if (Dint_isinexact_to_sgl(srcp1,srcp2)) {
        switch (Rounding_mode()) {
            case ROUNDPLUS: 
                if (Sgl_iszero_sign(result)) 
                    Sgl_increment(result);
                break;
            case ROUNDMINUS: 
                if (Sgl_isone_sign(result)) 
                    Sgl_increment(result);
                break;
            case ROUNDNEAREST:
                Sgl_roundnearest_from_dint(srcp1,srcp2,result);
        }
        if (Is_inexacttrap_enabled()) {
            *dstptr = result;
            return(INEXACTEXCEPTION);
        }
        else Set_inexactflag();
    }
    *dstptr = result;
    return(NOEXCEPTION);
}

/*
 *  Double Fixed-point to Double Floating-point 
 */

int
dbl_to_dbl_fcnvxf(
            dbl_integer *srcptr,
            unsigned int *nullptr,
            dbl_floating_point *dstptr,
            unsigned int *status)
{
    register int srcp1, dst_exponent;
    register unsigned int srcp2, resultp1 = 0, resultp2 = 0;

    Dint_copyfromptr(srcptr,srcp1,srcp2);
    /* 
     * set sign bit of result and get magnitude of source 
     */
    if (srcp1 < 0) {
        Dbl_setone_sign(resultp1);
        Dint_negate(srcp1,srcp2);
    }
    else {
        Dbl_setzero_sign(resultp1);
            /* Check for zero */
            if (srcp1 == 0 && srcp2 ==0) {
                    Dbl_setzero(resultp1,resultp2);
                    Dbl_copytoptr(resultp1,resultp2,dstptr);
                    return(NOEXCEPTION);
        }
        }
    /*
     * Generate exponent and normalized mantissa
     */
    dst_exponent = 16;    /* initialize for normalization */
    if (srcp1 == 0) {
        /*
         * Check word for most significant bit set.  Returns
         * a value in dst_exponent indicating the bit position,
         * between -1 and 30.
         */
        Find_ms_one_bit(srcp2,dst_exponent);
        /*  left justify source, with msb at bit position 1  */
        if (dst_exponent >= 0) {
            srcp1 = srcp2 << dst_exponent;    
            srcp2 = 0;
        }
        else {
            srcp1 = srcp2 >> 1;
            srcp2 <<= 31;
        }
        /*
         *  since msb set is in second word, need to 
         *  adjust bit position count
         */
        dst_exponent += 32;
    }
    else {
        /*
         * Check word for most significant bit set.  Returns
         * a value in dst_exponent indicating the bit position,
         * between -1 and 30.
         */
        Find_ms_one_bit(srcp1,dst_exponent);
        /*  left justify source, with msb at bit position 1  */
        if (dst_exponent > 0) {
            Variable_shift_double(srcp1,srcp2,(32-dst_exponent),
             srcp1); 
            srcp2 <<= dst_exponent;
        }
        /*
         * If dst_exponent = 0, we don't need to shift anything.
         * If dst_exponent = -1, src = - 2**63 so we won't need to 
         * shift srcp2.
         */
        else srcp1 >>= -(dst_exponent);
    }
    Dbl_set_mantissap1(resultp1, srcp1 >> (DBL_EXP_LENGTH-1));
    Shiftdouble(srcp1,srcp2,DBL_EXP_LENGTH-1,resultp2);
    Dbl_set_exponent(resultp1, (62+DBL_BIAS) - dst_exponent);

    /* check for inexact */
    if (Dint_isinexact_to_dbl(srcp2)) {
        switch (Rounding_mode()) {
            case ROUNDPLUS: 
                if (Dbl_iszero_sign(resultp1)) {
                    Dbl_increment(resultp1,resultp2);
                }
                break;
            case ROUNDMINUS: 
                if (Dbl_isone_sign(resultp1)) {
                    Dbl_increment(resultp1,resultp2);
                }
                break;
            case ROUNDNEAREST:
                Dbl_roundnearest_from_dint(srcp2,resultp1,
                resultp2);
        }
        if (Is_inexacttrap_enabled()) {
            Dbl_copytoptr(resultp1,resultp2,dstptr);
            return(INEXACTEXCEPTION);
        }
        else Set_inexactflag();
    }
    Dbl_copytoptr(resultp1,resultp2,dstptr);
    return(NOEXCEPTION);
}