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/* IEEE floating point support routines, for GDB, the GNU Debugger.

   Copyright (C) 1991, 1994, 1999 Free Software Foundation, Inc.

This file is part of GDB.

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 of the License, 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.  */

#include "floatformat.h"

#include <math.h>               /* ldexp */

#ifdef __STDC__

#include <stddef.h>

extern void *memcpy (void *s1, const void *s2, size_t n);

extern void *memset (void *s, int c, size_t n);

#else

extern char *memcpy ();

extern char *memset ();

#endif

/* The odds that CHAR_BIT will be anything but 8 are low enough that I'm not

   going to bother with trying to muck around with whether it is defined in

   a system header, what we do if not, etc.  */

#define FLOATFORMAT_CHAR_BIT 8

/* floatformats for IEEE single and double, big and little endian.  */

const struct floatformat floatformat_ieee_single_big =

{

  floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23, floatformat_intbit_no

};

const struct floatformat floatformat_ieee_single_little =

{

  floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23, floatformat_intbit_no

};

const struct floatformat floatformat_ieee_double_big =

{

  floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52, floatformat_intbit_no

};

const struct floatformat floatformat_ieee_double_little =

{

  floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52, floatformat_intbit_no

};

/* floatformat for IEEE double, little endian byte order, with big endian word

   ordering, as on the ARM.  */

const struct floatformat floatformat_ieee_double_littlebyte_bigword =

{

  floatformat_littlebyte_bigword, 64, 0, 1, 11, 1023, 2047, 12, 52, floatformat_intbit_no

};

const struct floatformat floatformat_i387_ext =

{

  floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,

  floatformat_intbit_yes

};

const struct floatformat floatformat_m68881_ext =

{

  /* Note that the bits from 16 to 31 are unused.  */

  floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64, floatformat_intbit_yes

};

const struct floatformat floatformat_i960_ext =

{

  /* Note that the bits from 0 to 15 are unused.  */

  floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64,

  floatformat_intbit_yes

};

const struct floatformat floatformat_m88110_ext =

{

#ifdef HARRIS_FLOAT_FORMAT

  /* Harris uses raw format 128 bytes long, but the number is just an ieee

     double, and the last 64 bits are wasted. */

  floatformat_big,128, 0, 1, 11,  0x3ff,  0x7ff, 12, 52,

  floatformat_intbit_no

#else

  floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,

  floatformat_intbit_yes

#endif /* HARRIS_FLOAT_FORMAT */

};

const struct floatformat floatformat_arm_ext =

{

  /* Bits 1 to 16 are unused.  */

  floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64,

  floatformat_intbit_yes

};

static unsigned long get_field PARAMS ((unsigned char *,

                                        enum floatformat_byteorders,

                                        unsigned int,

                                        unsigned int,

                                        unsigned int));

/* Extract a field which starts at START and is LEN bytes long.  DATA and

   TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER.  */

static unsigned long

get_field (data, order, total_len, start, len)

     unsigned char *data;

     enum floatformat_byteorders order;

     unsigned int total_len;

     unsigned int start;

     unsigned int len;

{

  unsigned long result;

  unsigned int cur_byte;

  int cur_bitshift;

  /* Start at the least significant part of the field.  */

  cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT;

  if (order == floatformat_little)

    cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1;

  cur_bitshift =

    ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT;

  result = *(data + cur_byte) >> (-cur_bitshift);

  cur_bitshift += FLOATFORMAT_CHAR_BIT;

  if (order == floatformat_little)

    ++cur_byte;

  else

    --cur_byte;

  /* Move towards the most significant part of the field.  */

  while ((unsigned int) cur_bitshift < len)

    {

      if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT)

        /* This is the last byte; zero out the bits which are not part of

           this field.  */

        result |=

          (*(data + cur_byte) & ((1 << (len - cur_bitshift)) - 1))

            << cur_bitshift;

      else

        result |= *(data + cur_byte) << cur_bitshift;

      cur_bitshift += FLOATFORMAT_CHAR_BIT;

      if (order == floatformat_little)

        ++cur_byte;

      else

        --cur_byte;

    }

  return result;

}

#ifndef min

#define min(a, b) ((a) < (b) ? (a) : (b))

#endif

/* Convert from FMT to a double.

   FROM is the address of the extended float.

   Store the double in *TO.  */

void

floatformat_to_double (fmt, from, to)

     const struct floatformat *fmt;

     char *from;

     double *to;

{

  unsigned char *ufrom = (unsigned char *)from;

  double dto;

  long exponent;

  unsigned long mant;

  unsigned int mant_bits, mant_off;

  int mant_bits_left;

  int special_exponent;         /* It's a NaN, denorm or zero */

  exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,

                        fmt->exp_start, fmt->exp_len);

  /* Note that if exponent indicates a NaN, we can't really do anything useful

     (not knowing if the host has NaN's, or how to build one).  So it will

     end up as an infinity or something close; that is OK.  */

  mant_bits_left = fmt->man_len;

  mant_off = fmt->man_start;

  dto = 0.0;

  special_exponent = exponent == 0 || (unsigned long) exponent == fmt->exp_nan;

  /* Don't bias zero's, denorms or NaNs.  */

  if (!special_exponent)

    exponent -= fmt->exp_bias;

  /* Build the result algebraically.  Might go infinite, underflow, etc;

     who cares. */

  /* If this format uses a hidden bit, explicitly add it in now.  Otherwise,

     increment the exponent by one to account for the integer bit.  */

  if (!special_exponent)

    {

      if (fmt->intbit == floatformat_intbit_no)

        dto = ldexp (1.0, exponent);

      else

        exponent++;

    }

  while (mant_bits_left > 0)

    {

      mant_bits = min (mant_bits_left, 32);

      mant = get_field (ufrom, fmt->byteorder, fmt->totalsize,

                         mant_off, mant_bits);

      dto += ldexp ((double)mant, exponent - mant_bits);

      exponent -= mant_bits;

      mant_off += mant_bits;

      mant_bits_left -= mant_bits;

    }

  /* Negate it if negative.  */

  if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))

    dto = -dto;

  *to = dto;

}

static void put_field PARAMS ((unsigned char *, enum floatformat_byteorders,

                               unsigned int,

                               unsigned int,

                               unsigned int,

                               unsigned long));

/* Set a field which starts at START and is LEN bytes long.  DATA and

   TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER.  */

static void

put_field (data, order, total_len, start, len, stuff_to_put)

     unsigned char *data;

     enum floatformat_byteorders order;

     unsigned int total_len;

     unsigned int start;

     unsigned int len;

     unsigned long stuff_to_put;

{

  unsigned int cur_byte;

  int cur_bitshift;

  /* Start at the least significant part of the field.  */

  cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT;

  if (order == floatformat_little)

    cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1;

  cur_bitshift =

    ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT;

  *(data + cur_byte) &=

    ~(((1 << ((start + len) % FLOATFORMAT_CHAR_BIT)) - 1) << (-cur_bitshift));

  *(data + cur_byte) |=

    (stuff_to_put & ((1 << FLOATFORMAT_CHAR_BIT) - 1)) << (-cur_bitshift);

  cur_bitshift += FLOATFORMAT_CHAR_BIT;

  if (order == floatformat_little)

    ++cur_byte;

  else

    --cur_byte;

  /* Move towards the most significant part of the field.  */

  while ((unsigned int) cur_bitshift < len)

    {

      if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT)

        {

          /* This is the last byte.  */

          *(data + cur_byte) &=

            ~((1 << (len - cur_bitshift)) - 1);

          *(data + cur_byte) |= (stuff_to_put >> cur_bitshift);

        }

      else

        *(data + cur_byte) = ((stuff_to_put >> cur_bitshift)

                              & ((1 << FLOATFORMAT_CHAR_BIT) - 1));

      cur_bitshift += FLOATFORMAT_CHAR_BIT;

      if (order == floatformat_little)

        ++cur_byte;

      else

        --cur_byte;

    }

}

/* The converse: convert the double *FROM to an extended float

   and store where TO points.  Neither FROM nor TO have any alignment

   restrictions.  */

void

floatformat_from_double (fmt, from, to)

     const struct floatformat *fmt;

     double *from;

     char *to;

{

  double dfrom;

  int exponent;

  double mant;

  unsigned int mant_bits, mant_off;

  int mant_bits_left;

  unsigned char *uto = (unsigned char *)to;

  memcpy (&dfrom, from, sizeof (dfrom));

  memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT);

  if (dfrom == 0)

    return;                     /* Result is zero */

  if (dfrom != dfrom)

    {

      /* From is NaN */

      put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,

                 fmt->exp_len, fmt->exp_nan);

      /* Be sure it's not infinity, but NaN value is irrel */

      put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start,

                 32, 1);

      return;

    }

  /* If negative, set the sign bit.  */

  if (dfrom < 0)

    {

      put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1);

      dfrom = -dfrom;

    }

  /* How to tell an infinity from an ordinary number?  FIXME-someday */

  mant = frexp (dfrom, &exponent);

  put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, fmt->exp_len,

             exponent + fmt->exp_bias - 1);

  mant_bits_left = fmt->man_len;

  mant_off = fmt->man_start;

  while (mant_bits_left > 0)

    {

      unsigned long mant_long;

      mant_bits = mant_bits_left < 32 ? mant_bits_left : 32;

      mant *= 4294967296.0;

      mant_long = (unsigned long)mant;

      mant -= mant_long;

      /* If the integer bit is implicit, then we need to discard it.

         If we are discarding a zero, we should be (but are not) creating

         a denormalized number which means adjusting the exponent

         (I think).  */

      if ((unsigned int) mant_bits_left == fmt->man_len

          && fmt->intbit == floatformat_intbit_no)

        {

          mant_long &= 0x7fffffff;

          mant_bits -= 1;

        }

      else if (mant_bits < 32)

        {

          /* The bits we want are in the most significant MANT_BITS bits of

             mant_long.  Move them to the least significant.  */

          mant_long >>= 32 - mant_bits;

        }

      put_field (uto, fmt->byteorder, fmt->totalsize,

                 mant_off, mant_bits, mant_long);

      mant_off += mant_bits;

      mant_bits_left -= mant_bits;

    }

}

#ifdef IEEE_DEBUG

/* This is to be run on a host which uses IEEE floating point.  */

void

ieee_test (n)

     double n;

{

  double result;

  char exten[16];

  floatformat_to_double (&floatformat_ieee_double_big, &n, &result);

  if (n != result)

    printf ("Differ(to): %.20g -> %.20g\n", n, result);

  floatformat_from_double (&floatformat_ieee_double_big, &n, &result);

  if (n != result)

    printf ("Differ(from): %.20g -> %.20g\n", n, result);

  floatformat_from_double (&floatformat_m68881_ext, &n, exten);

  floatformat_to_double (&floatformat_m68881_ext, exten, &result);

  if (n != result)

    printf ("Differ(to+from): %.20g -> %.20g\n", n, result);

#if IEEE_DEBUG > 1

  /* This is to be run on a host which uses 68881 format.  */

  {

    long double ex = *(long double *)exten;

    if (ex != n)

      printf ("Differ(from vs. extended): %.20g\n", n);

  }

#endif

}

int

main ()

{

  ieee_test (0.5);

  ieee_test (256.0);

  ieee_test (0.12345);

  ieee_test (234235.78907234);

  ieee_test (-512.0);

  ieee_test (-0.004321);

  return 0;

}

#endif