Initial revision

[binutils.git] / gas / config / atof-ieee.c

/* atof_ieee.c - turn a Flonum into an IEEE floating point number
   Copyright (C) 1987, 92, 93, 94, 95, 96, 97, 1998
   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 2, 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, 59 Temple Place - Suite 330, Boston, MA
   02111-1307, USA.  */

#include "as.h"

/* Flonums returned here.  */
extern FLONUM_TYPE generic_floating_point_number;

static int next_bits PARAMS ((int));
static void unget_bits PARAMS ((int));
static void make_invalid_floating_point_number PARAMS ((LITTLENUM_TYPE *));

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)

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,
};
\f

static int bits_left_in_littlenum;
static int littlenums_left;
static LITTLENUM_TYPE *littlenum_pointer;

static int
next_bits (number_of_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 (num)
     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 (words)
     LITTLENUM_TYPE *words;
{
  as_bad (_("cannot create floating-point number"));
  words[0] = (LITTLENUM_TYPE) ((unsigned) -1) >> 1; /* Zero the leftmost bit */
  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;
}
\f
/************************************************************************\
 *      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 (str, what_kind, words)
     char *str;                 /* Text to convert to binary. */
     char what_kind;            /* 'd', 'f', 'g', 'h' */
     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 (words, precision, exponent_bits)
     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 (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')
    {
      /* +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')
    {
      /* 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])
                {
                  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;
                  while (lp < words_end)
                    *lp++ = 0;
                }
            }
          else if ((*lp & mask[prec_bits]) != mask[prec_bits])
            *lp += 1;
        }

      return return_value;
    }
  else if ((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 >= words); lp--)
        {
          carry = *lp + carry;
          *lp = carry;
          carry >>= LITTLENUM_NUMBER_OF_BITS;
        }
      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));
          /* make_invalid_floating_point_number (words); */
          /* return return_value; */
        }
    }
  return (return_value);
}

#if 0 /* unused */
/* This routine is a real kludge.  Someone really should do it better,
   but I'm too lazy, and I don't understand this stuff all too well
   anyway. (JF)  */
static void
int_to_gen (x)
     long x;
{
  char buf[20];
  char *bufp;

  sprintf (buf, "%ld", x);
  bufp = &buf[0];
  if (atof_generic (&bufp, ".", EXP_CHARS, &generic_floating_point_number))
    as_bad (_("Error converting number to floating point (Exponent overflow?)"));
}
#endif

#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));
  sprintf (sbuf, "%x %x %x %x %.14G   ", arr[0], arr[1], arr[2], arr[3], dv);
  gen_to_words (&arr[0], 2, 8);
  memcpy (&fv, &arr[0], sizeof (float));
  sprintf (sbuf + strlen (sbuf), "%x %x %.12g\n", arr[0], arr[1], fv);

  if (gen)
    {
      generic_floating_point_number = f;
    }

  return (sbuf);
}

#endif

/* end of atof-ieee.c */