Subversion Repositories openrisc_2011-10-31

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

   Copyright 1991, 1994, 1999, 2000, 2003, 2005, 2006

   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., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */

/* This is needed to pick up the NAN macro on some systems.  */

#define _GNU_SOURCE

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include <math.h>

#ifdef HAVE_STRING_H

#include <string.h>

#endif

/* On some platforms, <float.h> provides DBL_QNAN.  */

#ifdef STDC_HEADERS

#include <float.h>

#endif

#include "ansidecl.h"

#include "libiberty.h"

#include "floatformat.h"

#ifndef INFINITY

#ifdef HUGE_VAL

#define INFINITY HUGE_VAL

#else

#define INFINITY (1.0 / 0.0)

#endif

#endif

#ifndef NAN

#ifdef DBL_QNAN

#define NAN DBL_QNAN

#else

#define NAN (0.0 / 0.0)

#endif

#endif

static unsigned long get_field (const unsigned char *,

                                enum floatformat_byteorders,

                                unsigned int,

                                unsigned int,

                                unsigned int);

static int floatformat_always_valid (const struct floatformat *fmt,

                                     const void *from);

static int

floatformat_always_valid (const struct floatformat *fmt ATTRIBUTE_UNUSED,

                          const void *from ATTRIBUTE_UNUSED)

{

  return 1;

}

/* 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,

  "floatformat_ieee_single_big",

  floatformat_always_valid

};

const struct floatformat floatformat_ieee_single_little =

{

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

  floatformat_intbit_no,

  "floatformat_ieee_single_little",

  floatformat_always_valid

};

const struct floatformat floatformat_ieee_double_big =

{

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

  floatformat_intbit_no,

  "floatformat_ieee_double_big",

  floatformat_always_valid

};

const struct floatformat floatformat_ieee_double_little =

{

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

  floatformat_intbit_no,

  "floatformat_ieee_double_little",

  floatformat_always_valid

};

/* 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,

  "floatformat_ieee_double_littlebyte_bigword",

  floatformat_always_valid

};

/* floatformat for VAX.  Not quite IEEE, but close enough.  */

const struct floatformat floatformat_vax_f =

{

  floatformat_vax, 32, 0, 1, 8, 129, 0, 9, 23,

  floatformat_intbit_no,

  "floatformat_vax_f",

  floatformat_always_valid

};

const struct floatformat floatformat_vax_d =

{

  floatformat_vax, 64, 0, 1, 8, 129, 0, 9, 55,

  floatformat_intbit_no,

  "floatformat_vax_d",

  floatformat_always_valid

};

const struct floatformat floatformat_vax_g =

{

  floatformat_vax, 64, 0, 1, 11, 1025, 0, 12, 52,

  floatformat_intbit_no,

  "floatformat_vax_g",

  floatformat_always_valid

};

static int floatformat_i387_ext_is_valid (const struct floatformat *fmt,

                                          const void *from);

static int

floatformat_i387_ext_is_valid (const struct floatformat *fmt, const void *from)

{

  /* In the i387 double-extended format, if the exponent is all ones,

     then the integer bit must be set.  If the exponent is neither 0

     nor ~0, the intbit must also be set.  Only if the exponent is

     zero can it be zero, and then it must be zero.  */

  unsigned long exponent, int_bit;

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

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

                        fmt->exp_start, fmt->exp_len);

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

                       fmt->man_start, 1);

  if ((exponent == 0) != (int_bit == 0))

    return 0;

  else

    return 1;

}

const struct floatformat floatformat_i387_ext =

{

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

  floatformat_intbit_yes,

  "floatformat_i387_ext",

  floatformat_i387_ext_is_valid

};

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,

  "floatformat_m68881_ext",

  floatformat_always_valid

};

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,

  "floatformat_i960_ext",

  floatformat_always_valid

};

const struct floatformat floatformat_m88110_ext =

{

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

  floatformat_intbit_yes,

  "floatformat_m88110_ext",

  floatformat_always_valid

};

const struct floatformat floatformat_m88110_harris_ext =

{

  /* 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,

  "floatformat_m88110_ext_harris",

  floatformat_always_valid

};

const struct floatformat floatformat_arm_ext_big =

{

  /* Bits 1 to 16 are unused.  */

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

  floatformat_intbit_yes,

  "floatformat_arm_ext_big",

  floatformat_always_valid

};

const struct floatformat floatformat_arm_ext_littlebyte_bigword =

{

  /* Bits 1 to 16 are unused.  */

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

  floatformat_intbit_yes,

  "floatformat_arm_ext_littlebyte_bigword",

  floatformat_always_valid

};

const struct floatformat floatformat_ia64_spill_big =

{

  floatformat_big, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,

  floatformat_intbit_yes,

  "floatformat_ia64_spill_big",

  floatformat_always_valid

};

const struct floatformat floatformat_ia64_spill_little =

{

  floatformat_little, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,

  floatformat_intbit_yes,

  "floatformat_ia64_spill_little",

  floatformat_always_valid

};

const struct floatformat floatformat_ia64_quad_big =

{

  floatformat_big, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,

  floatformat_intbit_no,

  "floatformat_ia64_quad_big",

  floatformat_always_valid

};

const struct floatformat floatformat_ia64_quad_little =

{

  floatformat_little, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,

  floatformat_intbit_no,

  "floatformat_ia64_quad_little",

  floatformat_always_valid

};

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

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

static unsigned long

get_field (const 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 (const struct floatformat *fmt,

                       const void *from, double *to)

{

  const unsigned char *ufrom = (const 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);

  /* If the exponent indicates a NaN, we don't have information to

     decide what to do.  So we handle it like IEEE, except that we

     don't try to preserve the type of NaN.  FIXME.  */

  if ((unsigned long) exponent == fmt->exp_nan)

    {

      int nan;

      mant_off = fmt->man_start;

      mant_bits_left = fmt->man_len;

      nan = 0;

      while (mant_bits_left > 0)

        {

          mant_bits = min (mant_bits_left, 32);

          if (get_field (ufrom, fmt->byteorder, fmt->totalsize,

                         mant_off, mant_bits) != 0)

            {

              /* This is a NaN.  */

              nan = 1;

              break;

            }

          mant_off += mant_bits;

          mant_bits_left -= mant_bits;

        }

      /* On certain systems (such as GNU/Linux), the use of the

         INFINITY macro below may generate a warning that can not be

         silenced due to a bug in GCC (PR preprocessor/11931).  The

         preprocessor fails to recognise the __extension__ keyword in

         conjunction with the GNU/C99 extension for hexadecimal

         floating point constants and will issue a warning when

         compiling with -pedantic.  */

      if (nan)

        dto = NAN;

      else

        dto = INFINITY;

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

        dto = -dto;

      *to = dto;

      return;

    }

  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);

      /* Handle denormalized numbers.  FIXME: What should we do for

         non-IEEE formats?  */

      if (special_exponent && exponent == 0 && mant != 0)

        dto += ldexp ((double)mant,

                      (- fmt->exp_bias

                       - mant_bits

                       - (mant_off - fmt->man_start)

                       + 1));

      else

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

      if (exponent != 0)

        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 (unsigned char *, enum floatformat_byteorders,

                       unsigned int,

                       unsigned int,

                       unsigned int,

                       unsigned long);

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

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

static void

put_field (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 (const struct floatformat *fmt,

                         const double *from, void *to)

{

  double dfrom;

  int exponent;

  double mant;

  unsigned int mant_bits, mant_off;

  int mant_bits_left;

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

  dfrom = *from;

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

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

  if (dfrom < 0)

    {

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

      dfrom = -dfrom;

    }

  if (dfrom == 0)

    {

      /* 0.0.  */

      return;

    }

  if (dfrom != dfrom)

    {

      /* 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 irrelevant.  */

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

                 32, 1);

      return;

    }

  if (dfrom + dfrom == dfrom)

    {

      /* This can only happen for an infinite value (or zero, which we

         already handled above).  */

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

                 fmt->exp_len, fmt->exp_nan);

      return;

    }

  mant = frexp (dfrom, &exponent);

  if (exponent + fmt->exp_bias - 1 > 0)

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

               fmt->exp_len, exponent + fmt->exp_bias - 1);

  else

    {

      /* Handle a denormalized number.  FIXME: What should we do for

         non-IEEE formats?  */

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

                 fmt->exp_len, 0);

      mant = ldexp (mant, 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, and we are not creating a

         denormalized number, then we need to discard it.  */

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

          && fmt->intbit == floatformat_intbit_no

          && exponent + fmt->exp_bias - 1 > 0)

        {

          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;

    }

}

/* Return non-zero iff the data at FROM is a valid number in format FMT.  */

int

floatformat_is_valid (const struct floatformat *fmt, const void *from)

{

  return fmt->is_valid (fmt, from);

}

#ifdef IEEE_DEBUG

#include <stdio.h>

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

void

ieee_test (double n)

{

  double result;

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

  if ((n != result && (! isnan (n) || ! isnan (result)))

      || (n < 0 && result >= 0)

      || (n >= 0 && result < 0))

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

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

  if ((n != result && (! isnan (n) || ! isnan (result)))

      || (n < 0 && result >= 0)

      || (n >= 0 && result < 0))

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

#if 0

  {

    char exten[16];

    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);

  }

#endif

#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 (void)

{

  ieee_test (0.0);

  ieee_test (0.5);

  ieee_test (256.0);

  ieee_test (0.12345);

  ieee_test (234235.78907234);

  ieee_test (-512.0);

  ieee_test (-0.004321);

  ieee_test (1.2E-70);

  ieee_test (1.2E-316);

  ieee_test (4.9406564584124654E-324);

  ieee_test (- 4.9406564584124654E-324);

  ieee_test (- 0.0);

  ieee_test (- INFINITY);

  ieee_test (- NAN);

  ieee_test (INFINITY);

  ieee_test (NAN);

  return 0;

}

#endif