real.c

gcc库的原代码,对编程有很大帮助.

	abort ();
#endif
	}
#endif
      ediv (d2, d1, v);	/* d1/d2 */
      break;

    case MIN_EXPR:		/* min (d1,d2) */
      if (ecmp (d1, d2) < 0)
	emov (d1, v);
      else
	emov (d2, v);
      break;

    case MAX_EXPR:		/* max (d1,d2) */
      if (ecmp (d1, d2) > 0)
	emov (d1, v);
      else
	emov (d2, v);
      break;
    default:
      emov (ezero, v);
      break;
    }
PUT_REAL (v, value);
}


/* Truncate REAL_VALUE_TYPE toward zero to signed HOST_WIDE_INT.
   implements REAL_VALUE_RNDZINT (x) (etrunci (x)).  */

REAL_VALUE_TYPE 
etrunci (x)
     REAL_VALUE_TYPE x;
{
  unsigned EMUSHORT f[NE], g[NE];
  REAL_VALUE_TYPE r;
  HOST_WIDE_INT l;

  GET_REAL (&x, g);
#ifdef NANS
  if (eisnan (g))
    return (x);
#endif
  eifrac (g, &l, f);
  ltoe (&l, g);
  PUT_REAL (g, &r);
  return (r);
}


/* Truncate REAL_VALUE_TYPE toward zero to unsigned HOST_WIDE_INT;
   implements REAL_VALUE_UNSIGNED_RNDZINT (x) (etruncui (x)).  */

REAL_VALUE_TYPE 
etruncui (x)
     REAL_VALUE_TYPE x;
{
  unsigned EMUSHORT f[NE], g[NE];
  REAL_VALUE_TYPE r;
  unsigned HOST_WIDE_INT l;

  GET_REAL (&x, g);
#ifdef NANS
  if (eisnan (g))
    return (x);
#endif
  euifrac (g, &l, f);
  ultoe (&l, g);
  PUT_REAL (g, &r);
  return (r);
}


/* This is the REAL_VALUE_ATOF function.  It converts a decimal string to
   binary, rounding off as indicated by the machine_mode argument.  Then it
   promotes the rounded value to REAL_VALUE_TYPE.  */

REAL_VALUE_TYPE 
ereal_atof (s, t)
     char *s;
     enum machine_mode t;
{
  unsigned EMUSHORT tem[NE], e[NE];
  REAL_VALUE_TYPE r;

  switch (t)
    {
    case HFmode:
    case SFmode:
      asctoe24 (s, tem);
      e24toe (tem, e);
      break;
    case DFmode:
      asctoe53 (s, tem);
      e53toe (tem, e);
      break;
    case XFmode:
      asctoe64 (s, tem);
      e64toe (tem, e);
      break;
    case TFmode:
      asctoe113 (s, tem);
      e113toe (tem, e);
      break;
    default:
      asctoe (s, e);
    }
  PUT_REAL (e, &r);
  return (r);
}


/* Expansion of REAL_NEGATE.  */

REAL_VALUE_TYPE 
ereal_negate (x)
     REAL_VALUE_TYPE x;
{
  unsigned EMUSHORT e[NE];
  REAL_VALUE_TYPE r;

  GET_REAL (&x, e);
  eneg (e);
  PUT_REAL (e, &r);
  return (r);
}


/* Round real toward zero to HOST_WIDE_INT;
   implements REAL_VALUE_FIX (x).  */

HOST_WIDE_INT
efixi (x)
     REAL_VALUE_TYPE x;
{
  unsigned EMUSHORT f[NE], g[NE];
  HOST_WIDE_INT l;

  GET_REAL (&x, f);
#ifdef NANS
  if (eisnan (f))
    {
      warning ("conversion from NaN to int");
      return (-1);
    }
#endif
  eifrac (f, &l, g);
  return l;
}

/* Round real toward zero to unsigned HOST_WIDE_INT
   implements  REAL_VALUE_UNSIGNED_FIX (x).
   Negative input returns zero.  */

unsigned HOST_WIDE_INT
efixui (x)
     REAL_VALUE_TYPE x;
{
  unsigned EMUSHORT f[NE], g[NE];
  unsigned HOST_WIDE_INT l;

  GET_REAL (&x, f);
#ifdef NANS
  if (eisnan (f))
    {
      warning ("conversion from NaN to unsigned int");
      return (-1);
    }
#endif
  euifrac (f, &l, g);
  return l;
}


/* REAL_VALUE_FROM_INT macro.  */

void 
ereal_from_int (d, i, j)
     REAL_VALUE_TYPE *d;
     HOST_WIDE_INT i, j;
{
  unsigned EMUSHORT df[NE], dg[NE];
  HOST_WIDE_INT low, high;
  int sign;

  sign = 0;
  low = i;
  if ((high = j) < 0)
    {
      sign = 1;
      /* complement and add 1 */
      high = ~high;
      if (low)
	low = -low;
      else
	high += 1;
    }
  eldexp (eone, HOST_BITS_PER_WIDE_INT, df);
  ultoe ((unsigned HOST_WIDE_INT *) &high, dg);
  emul (dg, df, dg);
  ultoe ((unsigned HOST_WIDE_INT *) &low, df);
  eadd (df, dg, dg);
  if (sign)
    eneg (dg);
  PUT_REAL (dg, d);
}


/* REAL_VALUE_FROM_UNSIGNED_INT macro.   */

void 
ereal_from_uint (d, i, j)
     REAL_VALUE_TYPE *d;
     unsigned HOST_WIDE_INT i, j;
{
  unsigned EMUSHORT df[NE], dg[NE];
  unsigned HOST_WIDE_INT low, high;

  low = i;
  high = j;
  eldexp (eone, HOST_BITS_PER_WIDE_INT, df);
  ultoe (&high, dg);
  emul (dg, df, dg);
  ultoe (&low, df);
  eadd (df, dg, dg);
  PUT_REAL (dg, d);
}


/* REAL_VALUE_TO_INT macro.  */

void 
ereal_to_int (low, high, rr)
     HOST_WIDE_INT *low, *high;
     REAL_VALUE_TYPE rr;
{
  unsigned EMUSHORT d[NE], df[NE], dg[NE], dh[NE];
  int s;

  GET_REAL (&rr, d);
#ifdef NANS
  if (eisnan (d))
    {
      warning ("conversion from NaN to int");
      *low = -1;
      *high = -1;
      return;
    }
#endif
  /* convert positive value */
  s = 0;
  if (eisneg (d))
    {
      eneg (d);
      s = 1;
    }
  eldexp (eone, HOST_BITS_PER_WIDE_INT, df);
  ediv (df, d, dg);		/* dg = d / 2^32 is the high word */
  euifrac (dg, (unsigned HOST_WIDE_INT *) high, dh);
  emul (df, dh, dg);		/* fractional part is the low word */
  euifrac (dg, (unsigned HOST_WIDE_INT *)low, dh);
  if (s)
    {
      /* complement and add 1 */
      *high = ~(*high);
      if (*low)
	*low = -(*low);
      else
	*high += 1;
    }
}


/* REAL_VALUE_LDEXP macro.  */

REAL_VALUE_TYPE
ereal_ldexp (x, n)
     REAL_VALUE_TYPE x;
     int n;
{
  unsigned EMUSHORT e[NE], y[NE];
  REAL_VALUE_TYPE r;

  GET_REAL (&x, e);
#ifdef NANS
  if (eisnan (e))
    return (x);
#endif
  eldexp (e, n, y);
  PUT_REAL (y, &r);
  return (r);
}

/* These routines are conditionally compiled because functions
   of the same names may be defined in fold-const.c.  */

#ifdef REAL_ARITHMETIC

/* Check for infinity in a REAL_VALUE_TYPE. */

int
target_isinf (x)
     REAL_VALUE_TYPE x;
{
  unsigned EMUSHORT e[NE];

#ifdef INFINITY
  GET_REAL (&x, e);
  return (eisinf (e));
#else
  return 0;
#endif
}

/* Check whether a REAL_VALUE_TYPE item is a NaN. */

int
target_isnan (x)
     REAL_VALUE_TYPE x;
{
  unsigned EMUSHORT e[NE];

#ifdef NANS
  GET_REAL (&x, e);
  return (eisnan (e));
#else
  return (0);
#endif
}


/* Check for a negative REAL_VALUE_TYPE number.
   This just checks the sign bit, so that -0 counts as negative. */

int
target_negative (x)
     REAL_VALUE_TYPE x;
{
  return ereal_isneg (x);
}

/* Expansion of REAL_VALUE_TRUNCATE.
   The result is in floating point, rounded to nearest or even.  */

REAL_VALUE_TYPE
real_value_truncate (mode, arg)
     enum machine_mode mode;
     REAL_VALUE_TYPE arg;
{
  unsigned EMUSHORT e[NE], t[NE];
  REAL_VALUE_TYPE r;

  GET_REAL (&arg, e);
#ifdef NANS
  if (eisnan (e))
    return (arg);
#endif
  eclear (t);
  switch (mode)
    {
    case TFmode:
      etoe113 (e, t);
      e113toe (t, t);
      break;

    case XFmode:
      etoe64 (e, t);
      e64toe (t, t);
      break;

    case DFmode:
      etoe53 (e, t);
      e53toe (t, t);
      break;

    case HFmode:
    case SFmode:
      etoe24 (e, t);
      e24toe (t, t);
      break;

    case SImode:
      r = etrunci (arg);
      return (r);

    /* If an unsupported type was requested, presume that
       the machine files know something useful to do with
       the unmodified value.  */

    default:
      return (arg);
    }
  PUT_REAL (t, &r);
  return (r);
}

#endif /* REAL_ARITHMETIC defined */

/* Used for debugging--print the value of R in human-readable format
   on stderr.  */

void
debug_real (r)
     REAL_VALUE_TYPE r;
{
  char dstr[30];

  REAL_VALUE_TO_DECIMAL (r, "%.20g", dstr);
  fprintf (stderr, "%s", dstr);
}  


/* The following routines convert REAL_VALUE_TYPE to the various floating
   point formats that are meaningful to supported computers.

   The results are returned in 32-bit pieces, each piece stored in a `long'.  
   This is so they can be printed by statements like
 
      fprintf (file, "%lx, %lx", L[0],  L[1]);

   that will work on both narrow- and wide-word host computers.  */

/* Convert R to a 128-bit long double precision value.  The output array L
   contains four 32-bit pieces of the result, in the order they would appear
   in memory.  */

void 
etartdouble (r, l)
     REAL_VALUE_TYPE r;
     long l[];
{
  unsigned EMUSHORT e[NE];

  GET_REAL (&r, e);
  etoe113 (e, e);
  endian (e, l, TFmode);
}

/* Convert R to a double extended precision value.  The output array L
   contains three 32-bit pieces of the result, in the order they would
   appear in memory.  */

void 
etarldouble (r, l)
     REAL_VALUE_TYPE r;
     long l[];
{
  unsigned EMUSHORT e[NE];

  GET_REAL (&r, e);
  etoe64 (e, e);
  endian (e, l, XFmode);
}

/* Convert R to a double precision value.  The output array L contains two
   32-bit pieces of the result, in the order they would appear in memory.  */

void 
etardouble (r, l)
     REAL_VALUE_TYPE r;
     long l[];
{
  unsigned EMUSHORT e[NE];

  GET_REAL (&r, e);
  etoe53 (e, e);
  endian (e, l, DFmode);
}

/* Convert R to a single precision float value stored in the least-significant
   bits of a `long'.  */

long
etarsingle (r)
     REAL_VALUE_TYPE r;
{
  unsigned EMUSHORT e[NE];
  long l;

  GET_REAL (&r, e);
  etoe24 (e, e);
  endian (e, &l, SFmode);
  return ((long) l);
}

/* Convert X to a decimal ASCII string S for output to an assembly
   language file.  Note, there is no standard way to spell infinity or
   a NaN, so these values may require special treatment in the tm.h
   macros.  */

void
ereal_to_decimal (x, s)
     REAL_VALUE_TYPE x;
     char *s;
{
  unsigned EMUSHORT e[NE];

  GET_REAL (&x, e);
  etoasc (e, s, 20);
}

/* Compare X and Y.  Return 1 if X > Y, 0 if X == Y, -1 if X < Y,
   or -2 if either is a NaN.   */

int
ereal_cmp (x, y)
     REAL_VALUE_TYPE x, y;
{
  unsigned EMUSHORT ex[NE], ey[NE];

  GET_REAL (&x, ex);
  GET_REAL (&y, ey);
  return (ecmp (ex, ey));
}

/*  Return 1 if the sign bit of X is set, else return 0.  */

int
ereal_isneg (x)
     REAL_VALUE_TYPE x;
{
  unsigned EMUSHORT ex[NE];

  GET_REAL (&x, ex);
  return (eisneg (ex));
}

/* End of REAL_ARITHMETIC interface */

/*
  Extended precision IEEE binary floating point arithmetic routines

  Numbers are stored in C language as arrays of 16-bit unsigned
  short integers.  The arguments of the routines are pointers to
  the arrays.

  External e type data structure, similar to Intel 8087 chip
  temporary real format but possibly with a larger significand:

	NE-1 significand words	(least significant word first,
				 most significant bit is normally set)
	exponent		(value = EXONE for 1.0,
				top bit is the sign)


  Internal exploded e-type data structure of a number (a "word" is 16 bits):

  ei[0]	sign word	(0 for positive, 0xffff for negative)
  ei[1]	biased exponent	(value = EXONE for the number 1.0)
  ei[2]	high guard word	(always zero after normalization)
  ei[3]
  to ei[NI-2]	significand	(NI-4 significand words,
 				 most significant word first,
 				 most significant bit is set)
  ei[NI-1]	low guard word	(0x8000 bit is rounding place)
 
 
 
 		Routines for external format e-type numbers
 
 	asctoe (string, e)	ASCII string to extended double e type
 	asctoe64 (string, &d)	ASCII string to long double
 	asctoe53 (string, &d)	ASCII string to double
 	asctoe24 (string, &f)	ASCII string to single
 	asctoeg (string, e, prec) ASCII string to specified precision
 	e24toe (&f, e)		IEEE single precision to e type
 	e53toe (&d, e)		IEEE double precision to e type
 	e64toe (&d, e)		IEEE long double precision to e type
 	e113toe (&d, e)		128-bit long double precision to e type
 	eabs (e)			absolute value
 	eadd (a, b, c)		c = b + a
 	eclear (e)		e = 0
 	ecmp (a, b)		Returns 1 if a > b, 0 if a == b,
 				-1 if a < b, -2 if either a or b is a NaN.
 	ediv (a, b, c)		c = b / a
 	efloor (a, b)		truncate to integer, toward -infinity
 	efrexp (a, exp, s)	extract exponent and significand
 	eifrac (e, &l, frac)    e to HOST_WIDE_INT and e type fraction
 	euifrac (e, &l, frac)   e to unsigned HOST_WIDE_INT and e type fraction
 	einfin (e)		set e to infinity, leaving its sign alone
 	eldexp (a, n, b)	multiply by 2**n