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cell-binutils  2.17cvs20070401
Defines | Functions | Variables
atof-ieee.c File Reference
#include "as.h"

Go to the source code of this file.

Defines

#define MAX_PRECISION   5
#define F_PRECISION   2
#define D_PRECISION   4
#define X_PRECISION   5
#define P_PRECISION   5
#define GUARD   2
#define TC_LARGEST_EXPONENT_IS_NORMAL(PRECISION)   0

Functions

static int next_bits (int number_of_bits)
static void unget_bits (int num)
static void make_invalid_floating_point_number (LITTLENUM_TYPE *words)
char * atof_ieee (char *str, int what_kind, LITTLENUM_TYPE *words)
int gen_to_words (LITTLENUM_TYPE *words, int precision, long exponent_bits)

Variables

FLONUM_TYPE generic_floating_point_number
const char EXP_CHARS []
static const unsigned long mask []
static int bits_left_in_littlenum
static int littlenums_left
static LITTLENUM_TYPElittlenum_pointer

Define Documentation

#define D_PRECISION   4

Definition at line 32 of file atof-ieee.c.

#define F_PRECISION   2

Definition at line 31 of file atof-ieee.c.

#define GUARD   2

Definition at line 37 of file atof-ieee.c.

#define MAX_PRECISION   5

Definition at line 30 of file atof-ieee.c.

#define P_PRECISION   5

Definition at line 34 of file atof-ieee.c.

#define TC_LARGEST_EXPONENT_IS_NORMAL (   PRECISION)    0

Definition at line 40 of file atof-ieee.c.

#define X_PRECISION   5

Definition at line 33 of file atof-ieee.c.


Function Documentation

char* atof_ieee ( char *  str,
int  what_kind,
LITTLENUM_TYPE words 
)

Definition at line 162 of file atof-ieee.c.

{
  /* 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;
}

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

Definition at line 252 of file atof-ieee.c.

{
  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;
}

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static void make_invalid_floating_point_number ( LITTLENUM_TYPE words) [static]

Definition at line 139 of file atof-ieee.c.

{
  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;
}

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static int next_bits ( int  number_of_bits) [static]

Definition at line 85 of file atof-ieee.c.

{
  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;
}

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static void unget_bits ( int  num) [static]

Definition at line 119 of file atof-ieee.c.

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Variable Documentation

Definition at line 80 of file atof-ieee.c.

const char EXP_CHARS[]

Definition at line 223 of file tc-alpha.c.

Definition at line 180 of file expr.c.

Definition at line 82 of file atof-ieee.c.

int littlenums_left [static]

Definition at line 81 of file atof-ieee.c.

const unsigned long mask[] [static]

Definition at line 43 of file atof-ieee.c.