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fcnvxf.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/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);
}

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