Subversion Repositories openrisc_2011-10-31

/* Floating point routines for GDB, the GNU debugger.

   Copyright (C) 1986, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,

   1997, 1998, 1999, 2000, 2001, 2003, 2004, 2005, 2007, 2008

   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 3 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, see <http://www.gnu.org/licenses/>.  */

/* Support for converting target fp numbers into host DOUBLEST format.  */

/* XXX - This code should really be in libiberty/floatformat.c,

   however configuration issues with libiberty made this very

   difficult to do in the available time.  */

#include "defs.h"

#include "doublest.h"

#include "floatformat.h"

#include "gdb_assert.h"

#include "gdb_string.h"

#include "gdbtypes.h"

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

/* 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

/* The number of bytes that the largest floating-point type that we

   can convert to doublest will need.  */

#define FLOATFORMAT_LARGEST_BYTES 16

/* 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 (const bfd_byte *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;

  /* Caller must byte-swap words before calling this routine.  */

  gdb_assert (order == floatformat_little || order == floatformat_big);

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

  if (order == floatformat_little)

    {

      /* We start counting from the other end (i.e, from the high bytes

         rather than the low bytes).  As such, we need to be concerned

         with what happens if bit 0 doesn't start on a byte boundary.

         I.e, we need to properly handle the case where total_len is

         not evenly divisible by 8.  So we compute ``excess'' which

         represents the number of bits from the end of our starting

         byte needed to get to bit 0. */

      int excess = FLOATFORMAT_CHAR_BIT - (total_len % FLOATFORMAT_CHAR_BIT);

      cur_byte = (total_len / FLOATFORMAT_CHAR_BIT)

                 - ((start + len + excess) / FLOATFORMAT_CHAR_BIT);

      cur_bitshift = ((start + len + excess) % FLOATFORMAT_CHAR_BIT)

                     - FLOATFORMAT_CHAR_BIT;

    }

  else

    {

      cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT;

      cur_bitshift =

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

    }

  if (cur_bitshift > -FLOATFORMAT_CHAR_BIT)

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

  else

    result = 0;

  cur_bitshift += FLOATFORMAT_CHAR_BIT;

  if (order == floatformat_little)

    ++cur_byte;

  else

    --cur_byte;

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

  while (cur_bitshift < len)

    {

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

      cur_bitshift += FLOATFORMAT_CHAR_BIT;

      switch (order)

        {

        case floatformat_little:

          ++cur_byte;

          break;

        case floatformat_big:

          --cur_byte;

          break;

        }

    }

  if (len < sizeof(result) * FLOATFORMAT_CHAR_BIT)

    /* Mask out bits which are not part of the field */

    result &= ((1UL << len) - 1);

  return result;

}

/* Normalize the byte order of FROM into TO.  If no normalization is

   needed then FMT->byteorder is returned and TO is not changed;

   otherwise the format of the normalized form in TO is returned.  */

static enum floatformat_byteorders

floatformat_normalize_byteorder (const struct floatformat *fmt,

                                 const void *from, void *to)

{

  const unsigned char *swapin;

  unsigned char *swapout;

  int words;

  if (fmt->byteorder == floatformat_little

      || fmt->byteorder == floatformat_big)

    return fmt->byteorder;

  words = fmt->totalsize / FLOATFORMAT_CHAR_BIT;

  words >>= 2;

  swapout = (unsigned char *)to;

  swapin = (const unsigned char *)from;

  if (fmt->byteorder == floatformat_vax)

    {

      while (words-- > 0)

        {

          *swapout++ = swapin[1];

          *swapout++ = swapin[0];

          *swapout++ = swapin[3];

          *swapout++ = swapin[2];

          swapin += 4;

        }

      /* This may look weird, since VAX is little-endian, but it is

         easier to translate to big-endian than to little-endian.  */

      return floatformat_big;

    }

  else

    {

      gdb_assert (fmt->byteorder == floatformat_littlebyte_bigword);

      while (words-- > 0)

        {

          *swapout++ = swapin[3];

          *swapout++ = swapin[2];

          *swapout++ = swapin[1];

          *swapout++ = swapin[0];

          swapin += 4;

        }

      return floatformat_big;

    }

}

/* Convert from FMT to a DOUBLEST.

   FROM is the address of the extended float.

   Store the DOUBLEST in *TO.  */

static void

convert_floatformat_to_doublest (const struct floatformat *fmt,

                                 const void *from,

                                 DOUBLEST *to)

{

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

  DOUBLEST 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 */

  enum floatformat_byteorders order;

  unsigned char newfrom[FLOATFORMAT_LARGEST_BYTES];

  enum float_kind kind;

  gdb_assert (fmt->totalsize

              <= FLOATFORMAT_LARGEST_BYTES * FLOATFORMAT_CHAR_BIT);

  /* For non-numbers, reuse libiberty's logic to find the correct

     format.  We do not lose any precision in this case by passing

     through a double.  */

  kind = floatformat_classify (fmt, from);

  if (kind == float_infinite || kind == float_nan)

    {

      double dto;

      floatformat_to_double (fmt, from, &dto);

      *to = (DOUBLEST) dto;

      return;

    }

  order = floatformat_normalize_byteorder (fmt, ufrom, newfrom);

  if (order != fmt->byteorder)

    ufrom = newfrom;

  if (fmt->split_half)

    {

      DOUBLEST dtop, dbot;

      floatformat_to_doublest (fmt->split_half, ufrom, &dtop);

      /* Preserve the sign of 0, which is the sign of the top

         half.  */

      if (dtop == 0.0)

        {

          *to = dtop;

          return;

        }

      floatformat_to_doublest (fmt->split_half,

                             ufrom + fmt->totalsize / FLOATFORMAT_CHAR_BIT / 2,

                             &dbot);

      *to = dtop + dbot;

      return;

    }

  exponent = get_field (ufrom, order, 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 || exponent == fmt->exp_nan;

  /* Don't bias NaNs. Use minimum exponent for denorms. For simplicity,

     we don't check for zero as the exponent doesn't matter.  Note the cast

     to int; exp_bias is unsigned, so it's important to make sure the

     operation is done in signed arithmetic.  */

  if (!special_exponent)

    exponent -= fmt->exp_bias;

  else if (exponent == 0)

    exponent = 1 - 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, order, 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, order, 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 bytes 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;

  /* Caller must byte-swap words before calling this routine.  */

  gdb_assert (order == floatformat_little || order == floatformat_big);

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

  if (order == floatformat_little)

    {

      int excess = FLOATFORMAT_CHAR_BIT - (total_len % FLOATFORMAT_CHAR_BIT);

      cur_byte = (total_len / FLOATFORMAT_CHAR_BIT)

                 - ((start + len + excess) / FLOATFORMAT_CHAR_BIT);

      cur_bitshift = ((start + len + excess) % FLOATFORMAT_CHAR_BIT)

                     - FLOATFORMAT_CHAR_BIT;

    }

  else

    {

      cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT;

      cur_bitshift =

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

    }

  if (cur_bitshift > -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 (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;

    }

}

#ifdef HAVE_LONG_DOUBLE

/* Return the fractional part of VALUE, and put the exponent of VALUE in *EPTR.

   The range of the returned value is >= 0.5 and < 1.0.  This is equivalent to

   frexp, but operates on the long double data type.  */

static long double ldfrexp (long double value, int *eptr);

static long double

ldfrexp (long double value, int *eptr)

{

  long double tmp;

  int exp;

  /* Unfortunately, there are no portable functions for extracting the exponent

     of a long double, so we have to do it iteratively by multiplying or dividing

     by two until the fraction is between 0.5 and 1.0.  */

  if (value < 0.0l)

    value = -value;

  tmp = 1.0l;

  exp = 0;

  if (value >= tmp)             /* Value >= 1.0 */

    while (value >= tmp)

      {

        tmp *= 2.0l;

        exp++;

      }

  else if (value != 0.0l)       /* Value < 1.0  and > 0.0 */

    {

      while (value < tmp)

        {

          tmp /= 2.0l;

          exp--;

        }

      tmp *= 2.0l;

      exp++;

    }

  *eptr = exp;

  return value / tmp;

}

#endif /* HAVE_LONG_DOUBLE */

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

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

   restrictions.  */

static void

convert_doublest_to_floatformat (CONST struct floatformat *fmt,

                                 const DOUBLEST *from, void *to)

{

  DOUBLEST dfrom;

  int exponent;

  DOUBLEST mant;

  unsigned int mant_bits, mant_off;

  int mant_bits_left;

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

  enum floatformat_byteorders order = fmt->byteorder;

  unsigned char newto[FLOATFORMAT_LARGEST_BYTES];

  if (order != floatformat_little)

    order = floatformat_big;

  if (order != fmt->byteorder)

    uto = newto;

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

  memset (uto, 0, (fmt->totalsize + FLOATFORMAT_CHAR_BIT - 1)

                    / FLOATFORMAT_CHAR_BIT);

  if (fmt->split_half)

    {

      /* Use static volatile to ensure that any excess precision is

         removed via storing in memory, and so the top half really is

         the result of converting to double.  */

      static volatile double dtop, dbot;

      DOUBLEST dtopnv, dbotnv;

      dtop = (double) dfrom;

      /* If the rounded top half is Inf, the bottom must be 0 not NaN

         or Inf.  */

      if (dtop + dtop == dtop && dtop != 0.0)

        dbot = 0.0;

      else

        dbot = (double) (dfrom - (DOUBLEST) dtop);

      dtopnv = dtop;

      dbotnv = dbot;

      floatformat_from_doublest (fmt->split_half, &dtopnv, uto);

      floatformat_from_doublest (fmt->split_half, &dbotnv,

                               (uto

                                + fmt->totalsize / FLOATFORMAT_CHAR_BIT / 2));

      return;

    }

  if (dfrom == 0)

    return;                     /* Result is zero */

  if (dfrom != dfrom)           /* Result is NaN */

    {

      /* From is NaN */

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

                 32, 1);

      goto finalize_byteorder;

    }

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

  if (dfrom < 0)

    {

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

      dfrom = -dfrom;

    }

  if (dfrom + dfrom == dfrom && dfrom != 0.0)   /* Result is Infinity */

    {

      /* Infinity exponent is same as NaN's.  */

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

                 fmt->exp_len, fmt->exp_nan);

      /* Infinity mantissa is all zeroes.  */

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

                 fmt->man_len, 0);

      goto finalize_byteorder;

    }

#ifdef HAVE_LONG_DOUBLE

  mant = ldfrexp (dfrom, &exponent);

#else

  mant = frexp (dfrom, &exponent);

#endif

  put_field (uto, order, 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) & 0xffffffffL;

      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 (mant_bits_left == fmt->man_len

          && fmt->intbit == floatformat_intbit_no)

        {

          mant_long <<= 1;

          mant_long &= 0xffffffffL;

          /* If we are processing the top 32 mantissa bits of a doublest

             so as to convert to a float value with implied integer bit,

             we will only be putting 31 of those 32 bits into the

             final value due to the discarding of the top bit.  In the

             case of a small float value where the number of mantissa

             bits is less than 32, discarding the top bit does not alter

             the number of bits we will be adding to the result.  */

          if (mant_bits == 32)

            mant_bits -= 1;

        }

      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, order, fmt->totalsize,

                 mant_off, mant_bits, mant_long);

      mant_off += mant_bits;

      mant_bits_left -= mant_bits;

    }

 finalize_byteorder:

  /* Do we need to byte-swap the words in the result?  */

  if (order != fmt->byteorder)

    floatformat_normalize_byteorder (fmt, newto, to);

}

/* Check if VAL (which is assumed to be a floating point number whose

   format is described by FMT) is negative.  */

int

floatformat_is_negative (const struct floatformat *fmt,

                         const bfd_byte *uval)

{

  enum floatformat_byteorders order;

  unsigned char newfrom[FLOATFORMAT_LARGEST_BYTES];

  gdb_assert (fmt != NULL);

  gdb_assert (fmt->totalsize

              <= FLOATFORMAT_LARGEST_BYTES * FLOATFORMAT_CHAR_BIT);

  order = floatformat_normalize_byteorder (fmt, uval, newfrom);

  if (order != fmt->byteorder)

    uval = newfrom;

  return get_field (uval, order, fmt->totalsize, fmt->sign_start, 1);

}

/* Check if VAL is "not a number" (NaN) for FMT.  */

enum float_kind

floatformat_classify (const struct floatformat *fmt,

                      const bfd_byte *uval)

{

  long exponent;

  unsigned long mant;

  unsigned int mant_bits, mant_off;

  int mant_bits_left;

  enum floatformat_byteorders order;

  unsigned char newfrom[FLOATFORMAT_LARGEST_BYTES];

  int mant_zero;

  gdb_assert (fmt != NULL);

  gdb_assert (fmt->totalsize

              <= FLOATFORMAT_LARGEST_BYTES * FLOATFORMAT_CHAR_BIT);

  order = floatformat_normalize_byteorder (fmt, uval, newfrom);

  if (order != fmt->byteorder)

    uval = newfrom;

  exponent = get_field (uval, order, fmt->totalsize, fmt->exp_start,

                        fmt->exp_len);

  mant_bits_left = fmt->man_len;

  mant_off = fmt->man_start;

  mant_zero = 1;

  while (mant_bits_left > 0)

    {

      mant_bits = min (mant_bits_left, 32);

      mant = get_field (uval, order, fmt->totalsize, mant_off, mant_bits);

      /* If there is an explicit integer bit, mask it off.  */

      if (mant_off == fmt->man_start

          && fmt->intbit == floatformat_intbit_yes)

        mant &= ~(1 << (mant_bits - 1));

      if (mant)

        {

          mant_zero = 0;

          break;

        }

      mant_off += mant_bits;

      mant_bits_left -= mant_bits;

    }

  /* If exp_nan is not set, assume that inf, NaN, and subnormals are not

     supported.  */

  if (! fmt->exp_nan)

    {

      if (mant_zero)

        return float_zero;

      else

        return float_normal;

    }

  if (exponent == 0 && !mant_zero)

    return float_subnormal;

  if (exponent == fmt->exp_nan)

    {

      if (mant_zero)

        return float_infinite;

      else

        return float_nan;

    }

  if (mant_zero)

    return float_zero;

  return float_normal;

}

/* Convert the mantissa of VAL (which is assumed to be a floating

   point number whose format is described by FMT) into a hexadecimal

   and store it in a static string.  Return a pointer to that string.  */

const char *

floatformat_mantissa (const struct floatformat *fmt,

                      const bfd_byte *val)

{

  unsigned char *uval = (unsigned char *) val;

  unsigned long mant;

  unsigned int mant_bits, mant_off;

  int mant_bits_left;

  static char res[50];

  char buf[9];

  int len;

  enum floatformat_byteorders order;

  unsigned char newfrom[FLOATFORMAT_LARGEST_BYTES];

  gdb_assert (fmt != NULL);

  gdb_assert (fmt->totalsize

              <= FLOATFORMAT_LARGEST_BYTES * FLOATFORMAT_CHAR_BIT);

  order = floatformat_normalize_byteorder (fmt, uval, newfrom);

  if (order != fmt->byteorder)

    uval = newfrom;

  if (! fmt->exp_nan)

    return 0;

  /* Make sure we have enough room to store the mantissa.  */

  gdb_assert (sizeof res > ((fmt->man_len + 7) / 8) * 2);

  mant_off = fmt->man_start;

  mant_bits_left = fmt->man_len;

  mant_bits = (mant_bits_left % 32) > 0 ? mant_bits_left % 32 : 32;

  mant = get_field (uval, order, fmt->totalsize, mant_off, mant_bits);

  len = xsnprintf (res, sizeof res, "%lx", mant);

  mant_off += mant_bits;

  mant_bits_left -= mant_bits;

  while (mant_bits_left > 0)

    {

      mant = get_field (uval, order, fmt->totalsize, mant_off, 32);

      xsnprintf (buf, sizeof buf, "%08lx", mant);

      gdb_assert (len + strlen (buf) <= sizeof res);

      strcat (res, buf);

      mant_off += 32;

      mant_bits_left -= 32;

    }

  return res;

}

/* Convert TO/FROM target to the hosts DOUBLEST floating-point format.