Subversion Repositories openrisc_2011-10-31

/* atof_ieee.c - turn a Flonum into an IEEE floating point number

   Copyright 1987, 1992, 1994, 1996, 1997, 1998, 1999, 2000, 2001, 2005,

   2007, 2009  Free Software Foundation, Inc.

   This file is part of GAS, the GNU Assembler.

   GAS 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, or (at your option)

   any later version.

   GAS 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 GAS; see the file COPYING.  If not, write to the Free

   Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA

   02110-1301, USA.  */

#include "as.h"

/* Flonums returned here.  */

extern FLONUM_TYPE generic_floating_point_number;

extern const char EXP_CHARS[];

/* Precision in LittleNums.  */

/* Don't count the gap in the m68k extended precision format.  */

#define MAX_PRECISION  5

#define F_PRECISION    2

#define D_PRECISION    4

#define X_PRECISION    5

#define P_PRECISION    5

/* Length in LittleNums of guard bits.  */

#define GUARD          2

#ifndef TC_LARGEST_EXPONENT_IS_NORMAL

#define TC_LARGEST_EXPONENT_IS_NORMAL(PRECISION) 0

#endif

static const unsigned long mask[] =

{

  0x00000000,

  0x00000001,

  0x00000003,

  0x00000007,

  0x0000000f,

  0x0000001f,

  0x0000003f,

  0x0000007f,

  0x000000ff,

  0x000001ff,

  0x000003ff,

  0x000007ff,

  0x00000fff,

  0x00001fff,

  0x00003fff,

  0x00007fff,

  0x0000ffff,

  0x0001ffff,

  0x0003ffff,

  0x0007ffff,

  0x000fffff,

  0x001fffff,

  0x003fffff,

  0x007fffff,

  0x00ffffff,

  0x01ffffff,

  0x03ffffff,

  0x07ffffff,

  0x0fffffff,

  0x1fffffff,

  0x3fffffff,

  0x7fffffff,

  0xffffffff,

};

static int bits_left_in_littlenum;

static int littlenums_left;

static LITTLENUM_TYPE *littlenum_pointer;

static int

next_bits (int number_of_bits)

{

  int return_value;

  if (!littlenums_left)

    return 0;

  if (number_of_bits >= bits_left_in_littlenum)

    {

      return_value = mask[bits_left_in_littlenum] & *littlenum_pointer;

      number_of_bits -= bits_left_in_littlenum;

      return_value <<= number_of_bits;

      if (--littlenums_left)

        {

          bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS - number_of_bits;

          --littlenum_pointer;

          return_value |=

            (*littlenum_pointer >> bits_left_in_littlenum)

            & mask[number_of_bits];

        }

    }

  else

    {

      bits_left_in_littlenum -= number_of_bits;

      return_value =

        mask[number_of_bits] & (*littlenum_pointer >> bits_left_in_littlenum);

    }

  return return_value;

}

/* Num had better be less than LITTLENUM_NUMBER_OF_BITS.  */

static void

unget_bits (int num)

{

  if (!littlenums_left)

    {

      ++littlenum_pointer;

      ++littlenums_left;

      bits_left_in_littlenum = num;

    }

  else if (bits_left_in_littlenum + num > LITTLENUM_NUMBER_OF_BITS)

    {

      bits_left_in_littlenum =

        num - (LITTLENUM_NUMBER_OF_BITS - bits_left_in_littlenum);

      ++littlenum_pointer;

      ++littlenums_left;

    }

  else

    bits_left_in_littlenum += num;

}

static void

make_invalid_floating_point_number (LITTLENUM_TYPE *words)

{

  as_bad (_("cannot create floating-point number"));

  /* Zero the leftmost bit.  */

  words[0] = (LITTLENUM_TYPE) ((unsigned) -1) >> 1;

  words[1] = (LITTLENUM_TYPE) -1;

  words[2] = (LITTLENUM_TYPE) -1;

  words[3] = (LITTLENUM_TYPE) -1;

  words[4] = (LITTLENUM_TYPE) -1;

  words[5] = (LITTLENUM_TYPE) -1;

}

/* Warning: This returns 16-bit LITTLENUMs.  It is up to the caller to

   figure out any alignment problems and to conspire for the

   bytes/word to be emitted in the right order.  Bigendians beware!  */

/* Note that atof-ieee always has X and P precisions enabled.  it is up

   to md_atof to filter them out if the target machine does not support

   them.  */

/* Returns pointer past text consumed.  */

char *

atof_ieee (char *str,                   /* Text to convert to binary.  */

           int what_kind,               /* 'd', 'f', 'x', 'p'.  */

           LITTLENUM_TYPE *words)       /* Build the binary here.  */

{

  /* Extra bits for zeroed low-order bits.

     The 1st MAX_PRECISION are zeroed, the last contain flonum bits.  */

  static LITTLENUM_TYPE bits[MAX_PRECISION + MAX_PRECISION + GUARD];

  char *return_value;

  /* Number of 16-bit words in the format.  */

  int precision;

  long exponent_bits;

  FLONUM_TYPE save_gen_flonum;

  /* We have to save the generic_floating_point_number because it

     contains storage allocation about the array of LITTLENUMs where

     the value is actually stored.  We will allocate our own array of

     littlenums below, but have to restore the global one on exit.  */

  save_gen_flonum = generic_floating_point_number;

  return_value = str;

  generic_floating_point_number.low = bits + MAX_PRECISION;

  generic_floating_point_number.high = NULL;

  generic_floating_point_number.leader = NULL;

  generic_floating_point_number.exponent = 0;

  generic_floating_point_number.sign = '\0';

  /* Use more LittleNums than seems necessary: the highest flonum may

     have 15 leading 0 bits, so could be useless.  */

  memset (bits, '\0', sizeof (LITTLENUM_TYPE) * MAX_PRECISION);

  switch (what_kind)

    {

    case 'f':

    case 'F':

    case 's':

    case 'S':

      precision = F_PRECISION;

      exponent_bits = 8;

      break;

    case 'd':

    case 'D':

    case 'r':

    case 'R':

      precision = D_PRECISION;

      exponent_bits = 11;

      break;

    case 'x':

    case 'X':

    case 'e':

    case 'E':

      precision = X_PRECISION;

      exponent_bits = 15;

      break;

    case 'p':

    case 'P':

      precision = P_PRECISION;

      exponent_bits = -1;

      break;

    default:

      make_invalid_floating_point_number (words);

      return (NULL);

    }

  generic_floating_point_number.high

    = generic_floating_point_number.low + precision - 1 + GUARD;

  if (atof_generic (&return_value, ".", EXP_CHARS,

                    &generic_floating_point_number))

    {

      make_invalid_floating_point_number (words);

      return NULL;

    }

  gen_to_words (words, precision, exponent_bits);

  /* Restore the generic_floating_point_number's storage alloc (and

     everything else).  */

  generic_floating_point_number = save_gen_flonum;

  return return_value;

}

/* Turn generic_floating_point_number into a real float/double/extended.  */

int

gen_to_words (LITTLENUM_TYPE *words, int precision, long exponent_bits)

{

  int return_value = 0;

  long exponent_1;

  long exponent_2;

  long exponent_3;

  long exponent_4;

  int exponent_skippage;

  LITTLENUM_TYPE word1;

  LITTLENUM_TYPE *lp;

  LITTLENUM_TYPE *words_end;

  words_end = words + precision;

#ifdef TC_M68K

  if (precision == X_PRECISION)

    /* On the m68k the extended precision format has a gap of 16 bits

       between the exponent and the mantissa.  */

    words_end++;

#endif

  if (generic_floating_point_number.low > generic_floating_point_number.leader)

    {

      /* 0.0e0 seen.  */

      if (generic_floating_point_number.sign == '+')

        words[0] = 0x0000;

      else

        words[0] = 0x8000;

      memset (&words[1], '\0',

              (words_end - words - 1) * sizeof (LITTLENUM_TYPE));

      return return_value;

    }

  /* NaN:  Do the right thing.  */

  if (generic_floating_point_number.sign == 0)

    {

      if (TC_LARGEST_EXPONENT_IS_NORMAL (precision))

        as_warn (_("NaNs are not supported by this target\n"));

      if (precision == F_PRECISION)

        {

          words[0] = 0x7fff;

          words[1] = 0xffff;

        }

      else if (precision == X_PRECISION)

        {

#ifdef TC_M68K

          words[0] = 0x7fff;

          words[1] = 0;

          words[2] = 0xffff;

          words[3] = 0xffff;

          words[4] = 0xffff;

          words[5] = 0xffff;

#else /* ! TC_M68K  */

#ifdef TC_I386

          words[0] = 0xffff;

          words[1] = 0xc000;

          words[2] = 0;

          words[3] = 0;

          words[4] = 0;

#else /* ! TC_I386  */

          abort ();

#endif /* ! TC_I386  */

#endif /* ! TC_M68K  */

        }

      else

        {

          words[0] = 0x7fff;

          words[1] = 0xffff;

          words[2] = 0xffff;

          words[3] = 0xffff;

        }

      return return_value;

    }

  else if (generic_floating_point_number.sign == 'P')

    {

      if (TC_LARGEST_EXPONENT_IS_NORMAL (precision))

        as_warn (_("Infinities are not supported by this target\n"));

      /* +INF:  Do the right thing.  */

      if (precision == F_PRECISION)

        {

          words[0] = 0x7f80;

          words[1] = 0;

        }

      else if (precision == X_PRECISION)

        {

#ifdef TC_M68K

          words[0] = 0x7fff;

          words[1] = 0;

          words[2] = 0;

          words[3] = 0;

          words[4] = 0;

          words[5] = 0;

#else /* ! TC_M68K  */

#ifdef TC_I386

          words[0] = 0x7fff;

          words[1] = 0x8000;

          words[2] = 0;

          words[3] = 0;

          words[4] = 0;

#else /* ! TC_I386  */

          abort ();

#endif /* ! TC_I386  */

#endif /* ! TC_M68K  */

        }

      else

        {

          words[0] = 0x7ff0;

          words[1] = 0;

          words[2] = 0;

          words[3] = 0;

        }

      return return_value;

    }

  else if (generic_floating_point_number.sign == 'N')

    {

      if (TC_LARGEST_EXPONENT_IS_NORMAL (precision))

        as_warn (_("Infinities are not supported by this target\n"));

      /* Negative INF.  */

      if (precision == F_PRECISION)

        {

          words[0] = 0xff80;

          words[1] = 0x0;

        }

      else if (precision == X_PRECISION)

        {

#ifdef TC_M68K

          words[0] = 0xffff;

          words[1] = 0;

          words[2] = 0;

          words[3] = 0;

          words[4] = 0;

          words[5] = 0;

#else /* ! TC_M68K  */

#ifdef TC_I386

          words[0] = 0xffff;

          words[1] = 0x8000;

          words[2] = 0;

          words[3] = 0;

          words[4] = 0;

#else /* ! TC_I386  */

          abort ();

#endif /* ! TC_I386  */

#endif /* ! TC_M68K  */

        }

      else

        {

          words[0] = 0xfff0;

          words[1] = 0x0;

          words[2] = 0x0;

          words[3] = 0x0;

        }

      return return_value;

    }

  /* The floating point formats we support have:

     Bit 15 is sign bit.

     Bits 14:n are excess-whatever exponent.

     Bits n-1:0 (if any) are most significant bits of fraction.

     Bits 15:0 of the next word(s) are the next most significant bits.

     So we need: number of bits of exponent, number of bits of

     mantissa.  */

  bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS;

  littlenum_pointer = generic_floating_point_number.leader;

  littlenums_left = (1

                     + generic_floating_point_number.leader

                     - generic_floating_point_number.low);

  /* Seek (and forget) 1st significant bit.  */

  for (exponent_skippage = 0; !next_bits (1); ++exponent_skippage);;

  exponent_1 = (generic_floating_point_number.exponent

                + generic_floating_point_number.leader

                + 1

                - generic_floating_point_number.low);

  /* Radix LITTLENUM_RADIX, point just higher than

     generic_floating_point_number.leader.  */

  exponent_2 = exponent_1 * LITTLENUM_NUMBER_OF_BITS;

  /* Radix 2.  */

  exponent_3 = exponent_2 - exponent_skippage;

  /* Forget leading zeros, forget 1st bit.  */

  exponent_4 = exponent_3 + ((1 << (exponent_bits - 1)) - 2);

  /* Offset exponent.  */

  lp = words;

  /* Word 1.  Sign, exponent and perhaps high bits.  */

  word1 = ((generic_floating_point_number.sign == '+')

           ? 0

           : (1 << (LITTLENUM_NUMBER_OF_BITS - 1)));

  /* Assume 2's complement integers.  */

  if (exponent_4 <= 0)

    {

      int prec_bits;

      int num_bits;

      unget_bits (1);

      num_bits = -exponent_4;

      prec_bits =

        LITTLENUM_NUMBER_OF_BITS * precision - (exponent_bits + 1 + num_bits);

#ifdef TC_I386

      if (precision == X_PRECISION && exponent_bits == 15)

        {

          /* On the i386 a denormalized extended precision float is

             shifted down by one, effectively decreasing the exponent

             bias by one.  */

          prec_bits -= 1;

          num_bits += 1;

        }

#endif

      if (num_bits >= LITTLENUM_NUMBER_OF_BITS - exponent_bits)

        {

          /* Bigger than one littlenum.  */

          num_bits -= (LITTLENUM_NUMBER_OF_BITS - 1) - exponent_bits;

          *lp++ = word1;

          if (num_bits + exponent_bits + 1

              > precision * LITTLENUM_NUMBER_OF_BITS)

            {

              /* Exponent overflow.  */

              make_invalid_floating_point_number (words);

              return return_value;

            }

#ifdef TC_M68K

          if (precision == X_PRECISION && exponent_bits == 15)

            *lp++ = 0;

#endif

          while (num_bits >= LITTLENUM_NUMBER_OF_BITS)

            {

              num_bits -= LITTLENUM_NUMBER_OF_BITS;

              *lp++ = 0;

            }

          if (num_bits)

            *lp++ = next_bits (LITTLENUM_NUMBER_OF_BITS - (num_bits));

        }

      else

        {

          if (precision == X_PRECISION && exponent_bits == 15)

            {

              *lp++ = word1;

#ifdef TC_M68K

              *lp++ = 0;

#endif

              *lp++ = next_bits (LITTLENUM_NUMBER_OF_BITS - num_bits);

            }

          else

            {

              word1 |= next_bits ((LITTLENUM_NUMBER_OF_BITS - 1)

                                  - (exponent_bits + num_bits));

              *lp++ = word1;

            }

        }

      while (lp < words_end)

        *lp++ = next_bits (LITTLENUM_NUMBER_OF_BITS);

      /* Round the mantissa up, but don't change the number.  */

      if (next_bits (1))

        {

          --lp;

          if (prec_bits >= LITTLENUM_NUMBER_OF_BITS)

            {

              int n = 0;

              int tmp_bits;

              n = 0;

              tmp_bits = prec_bits;

              while (tmp_bits > LITTLENUM_NUMBER_OF_BITS)

                {

                  if (lp[n] != (LITTLENUM_TYPE) - 1)

                    break;

                  --n;

                  tmp_bits -= LITTLENUM_NUMBER_OF_BITS;

                }

              if (tmp_bits > LITTLENUM_NUMBER_OF_BITS

                  || (lp[n] & mask[tmp_bits]) != mask[tmp_bits]

                  || (prec_bits != (precision * LITTLENUM_NUMBER_OF_BITS

                                    - exponent_bits - 1)

#ifdef TC_I386

                      /* An extended precision float with only the integer

                         bit set would be invalid.  That must be converted

                         to the smallest normalized number.  */

                      && !(precision == X_PRECISION

                           && prec_bits == (precision * LITTLENUM_NUMBER_OF_BITS

                                            - exponent_bits - 2))

#endif

                      ))

                {

                  unsigned long carry;

                  for (carry = 1; carry && (lp >= words); lp--)

                    {

                      carry = *lp + carry;

                      *lp = carry;

                      carry >>= LITTLENUM_NUMBER_OF_BITS;

                    }

                }

              else

                {

                  /* This is an overflow of the denormal numbers.  We

                     need to forget what we have produced, and instead

                     generate the smallest normalized number.  */

                  lp = words;

                  word1 = ((generic_floating_point_number.sign == '+')

                           ? 0

                           : (1 << (LITTLENUM_NUMBER_OF_BITS - 1)));

                  word1 |= (1

                            << ((LITTLENUM_NUMBER_OF_BITS - 1)

                                - exponent_bits));

                  *lp++ = word1;

#ifdef TC_I386

                  /* Set the integer bit in the extended precision format.

                     This cannot happen on the m68k where the mantissa

                     just overflows into the integer bit above.  */

                  if (precision == X_PRECISION)

                    *lp++ = 1 << (LITTLENUM_NUMBER_OF_BITS - 1);

#endif

                  while (lp < words_end)

                    *lp++ = 0;

                }

            }

          else

            *lp += 1;

        }

      return return_value;

    }

  else if ((unsigned long) exponent_4 > mask[exponent_bits]

           || (! TC_LARGEST_EXPONENT_IS_NORMAL (precision)

               && (unsigned long) exponent_4 == mask[exponent_bits]))

    {

      /* Exponent overflow.  Lose immediately.  */

      /* We leave return_value alone: admit we read the

         number, but return a floating exception

         because we can't encode the number.  */

      make_invalid_floating_point_number (words);

      return return_value;

    }

  else

    {

      word1 |= (exponent_4 << ((LITTLENUM_NUMBER_OF_BITS - 1) - exponent_bits))

        | next_bits ((LITTLENUM_NUMBER_OF_BITS - 1) - exponent_bits);

    }

  *lp++ = word1;

  /* X_PRECISION is special: on the 68k, it has 16 bits of zero in the

     middle.  Either way, it is then followed by a 1 bit.  */

  if (exponent_bits == 15 && precision == X_PRECISION)

    {

#ifdef TC_M68K

      *lp++ = 0;

#endif

      *lp++ = (1 << (LITTLENUM_NUMBER_OF_BITS - 1)

               | next_bits (LITTLENUM_NUMBER_OF_BITS - 1));

    }

  /* The rest of the words are just mantissa bits.  */

  while (lp < words_end)

    *lp++ = next_bits (LITTLENUM_NUMBER_OF_BITS);

  if (next_bits (1))

    {

      unsigned long carry;

      /* Since the NEXT bit is a 1, round UP the mantissa.

         The cunning design of these hidden-1 floats permits

         us to let the mantissa overflow into the exponent, and

         it 'does the right thing'. However, we lose if the

         highest-order bit of the lowest-order word flips.

         Is that clear?  */

      /* #if (sizeof(carry)) < ((sizeof(bits[0]) * BITS_PER_CHAR) + 2)

         Please allow at least 1 more bit in carry than is in a LITTLENUM.

         We need that extra bit to hold a carry during a LITTLENUM carry

         propagation. Another extra bit (kept 0) will assure us that we

         don't get a sticky sign bit after shifting right, and that

         permits us to propagate the carry without any masking of bits.

         #endif */

      for (carry = 1, lp--; carry; lp--)

        {

          carry = *lp + carry;

          *lp = carry;

          carry >>= LITTLENUM_NUMBER_OF_BITS;

          if (lp == words)

            break;

        }

      if (precision == X_PRECISION && exponent_bits == 15)

        {

          /* Extended precision numbers have an explicit integer bit

             that we may have to restore.  */

          if (lp == words)

            {

#ifdef TC_M68K

              /* On the m68k there is a gap of 16 bits.  We must

                 explicitly propagate the carry into the exponent.  */

              words[0] += words[1];

              words[1] = 0;

              lp++;

#endif

              /* Put back the integer bit.  */

              lp[1] |= 1 << (LITTLENUM_NUMBER_OF_BITS - 1);

            }

        }

      if ((word1 ^ *words) & (1 << (LITTLENUM_NUMBER_OF_BITS - 1)))

        {

          /* We leave return_value alone: admit we read the number,

             but return a floating exception because we can't encode

             the number.  */

          *words &= ~(1 << (LITTLENUM_NUMBER_OF_BITS - 1));

        }

    }

  return return_value;

}

#ifdef TEST

char *

print_gen (gen)

     FLONUM_TYPE *gen;

{

  FLONUM_TYPE f;

  LITTLENUM_TYPE arr[10];

  double dv;

  float fv;

  static char sbuf[40];

  if (gen)

    {

      f = generic_floating_point_number;

      generic_floating_point_number = *gen;

    }

  gen_to_words (&arr[0], 4, 11);

  memcpy (&dv, &arr[0], sizeof (double));