atof-vax.c

来自「基于4个mips核的noc设计」· C语言 代码 · 共 518 行

/* atof_vax.c - turn a Flonum into a VAX floating point number
   Copyright 1987, 1992, 1993, 1995, 1997, 1999, 2000
   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"

static int atof_vax_sizeof PARAMS ((int));
static int next_bits PARAMS ((int));
static void make_invalid_floating_point_number PARAMS ((LITTLENUM_TYPE *));
static int what_kind_of_float PARAMS ((int, int *, long *));
static char *atof_vax PARAMS ((char *, int, LITTLENUM_TYPE *));

/* Precision in LittleNums.  */
#define MAX_PRECISION (8)
#define H_PRECISION (8)
#define G_PRECISION (4)
#define D_PRECISION (4)
#define F_PRECISION (2)

/* Length in LittleNums of guard bits.  */
#define GUARD (2)

int flonum_gen2vax PARAMS ((int format_letter, FLONUM_TYPE * f,
			    LITTLENUM_TYPE * words));

/* Number of chars in flonum type 'letter'.  */
static int
atof_vax_sizeof (letter)
     int letter;
{
  int return_value;

  /*
   * Permitting uppercase letters is probably a bad idea.
   * Please use only lower-cased letters in case the upper-cased
   * ones become unsupported!
   */
  switch (letter)
    {
    case 'f':
    case 'F':
      return_value = 4;
      break;

    case 'd':
    case 'D':
    case 'g':
    case 'G':
      return_value = 8;
      break;

    case 'h':
    case 'H':
      return_value = 16;
      break;

    default:
      return_value = 0;
      break;
    }
  return (return_value);
}				/* atof_vax_sizeof */

static const 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
};


/* Shared between flonum_gen2vax and next_bits */
static int bits_left_in_littlenum;
static LITTLENUM_TYPE *littlenum_pointer;
static LITTLENUM_TYPE *littlenum_end;

static int
next_bits (number_of_bits)
     int number_of_bits;
{
  int return_value;

  if (littlenum_pointer < littlenum_end)
    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;
      bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS - number_of_bits;
      littlenum_pointer--;
      if (littlenum_pointer >= littlenum_end)
	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);
}

static void
make_invalid_floating_point_number (words)
     LITTLENUM_TYPE *words;
{
  *words = 0x8000;		/* Floating Reserved Operand Code */
}

static int			/* 0 means letter is OK.  */
what_kind_of_float (letter, precisionP, exponent_bitsP)
     int letter;		/* In: lowercase please. What kind of float? */
     int *precisionP;		/* Number of 16-bit words in the float.  */
     long *exponent_bitsP;	/* Number of exponent bits.  */
{
  int retval;			/* 0: OK.  */

  retval = 0;
  switch (letter)
    {
    case 'f':
      *precisionP = F_PRECISION;
      *exponent_bitsP = 8;
      break;

    case 'd':
      *precisionP = D_PRECISION;
      *exponent_bitsP = 8;
      break;

    case 'g':
      *precisionP = G_PRECISION;
      *exponent_bitsP = 11;
      break;

    case 'h':
      *precisionP = H_PRECISION;
      *exponent_bitsP = 15;
      break;

    default:
      retval = 69;
      break;
    }
  return (retval);
}

/***********************************************************************\
 *									*
 *	Warning: this returns 16-bit LITTLENUMs, because that is	*
 *	what the VAX thinks in. 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!		*
 *									*
 \***********************************************************************/

static char *				/* Return pointer past text consumed.  */
atof_vax (str, what_kind, words)
     char *str;			/* Text to convert to binary.  */
     int what_kind;		/* 'd', 'f', 'g', 'h' */
     LITTLENUM_TYPE *words;	/* Build the binary here.  */
{
  FLONUM_TYPE f;
  LITTLENUM_TYPE bits[MAX_PRECISION + MAX_PRECISION + GUARD];
  /* Extra bits for zeroed low-order bits.  */
  /* The 1st MAX_PRECISION are zeroed, */
  /* the last contain flonum bits.  */
  char *return_value;
  int precision;		/* Number of 16-bit words in the format.  */
  long exponent_bits;

  return_value = str;
  f.low = bits + MAX_PRECISION;
  f.high = NULL;
  f.leader = NULL;
  f.exponent = 0;
  f.sign = '\0';

  if (what_kind_of_float (what_kind, &precision, &exponent_bits))
    {
      return_value = NULL;	/* We lost.  */
      make_invalid_floating_point_number (words);
    }

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

      /* Use more LittleNums than seems */
      /* necessary: the highest flonum may have */
      /* 15 leading 0 bits, so could be useless.  */
      f.high = f.low + precision - 1 + GUARD;

      if (atof_generic (&return_value, ".", "eE", &f))
	{
	  make_invalid_floating_point_number (words);
	  return_value = NULL;	/* we lost */
	}
      else
	{
	  if (flonum_gen2vax (what_kind, &f, words))
	    {
	      return_value = NULL;
	    }
	}
    }
  return (return_value);
}				/* atof_vax() */

/*
 * In: a flonum, a vax floating point format.
 * Out: a vax floating-point bit pattern.
 */

int				/* 0: OK.  */
flonum_gen2vax (format_letter, f, words)
     int format_letter;		/* One of 'd' 'f' 'g' 'h'.  */
     FLONUM_TYPE *f;
     LITTLENUM_TYPE *words;	/* Deliver answer here.  */
{
  LITTLENUM_TYPE *lp;
  int precision;
  long exponent_bits;
  int return_value;		/* 0 == OK.  */

  return_value = what_kind_of_float (format_letter, &precision, &exponent_bits);

  if (return_value != 0)
    {
      make_invalid_floating_point_number (words);
    }
  else
    {
      if (f->low > f->leader)
	{
	  /* 0.0e0 seen.  */
	  memset (words, '\0', sizeof (LITTLENUM_TYPE) * precision);
	}
      else
	{
	  long exponent_1;
	  long exponent_2;
	  long exponent_3;
	  long exponent_4;
	  int exponent_skippage;
	  LITTLENUM_TYPE word1;

	  /* JF: Deal with new Nan, +Inf and -Inf codes */
	  if (f->sign != '-' && f->sign != '+')
	    {
	      make_invalid_floating_point_number (words);
	      return return_value;
	    }
	  /*
			 * All vaxen floating_point formats (so far) 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 are the next most significant bits.
			 * And so on for each other word.
			 *
			 * All this to be compatible with a KF11?? (Which is still faster
			 * than lots of vaxen I can think of, but it also has higher
			 * maintenance costs ... sigh).
			 *
			 * So we need: number of bits of exponent, number of bits of
			 * mantissa.
			 */

#ifdef NEVER			/******* This zeroing seems redundant - Dean 3may86 **********/
	  /*
			 * No matter how few bits we got back from the atof()
			 * routine, add enough zero littlenums so the rest of the
			 * code won't run out of "significant" bits in the mantissa.
			 */
	  {
	    LITTLENUM_TYPE *ltp;
	    for (ltp = f->leader + 1;
		 ltp <= f->low + precision;
		 ltp++)
	      {
		*ltp = 0;
	      }
	  }
#endif

	  bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS;
	  littlenum_pointer = f->leader;
	  littlenum_end = f->low;
	  /* Seek (and forget) 1st significant bit */
	  for (exponent_skippage = 0;
	       !next_bits (1);
	       exponent_skippage++);;

	  exponent_1 = f->exponent + f->leader + 1 - f->low;
	  /* Radix LITTLENUM_RADIX, point just higher than f->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));
	  /* Offset exponent.  */

	  if (exponent_4 & ~mask[exponent_bits])
	    {
	      /*
				 * Exponent overflow. Lose immediately.
				 */

	      make_invalid_floating_point_number (words);

	      /*
				 * We leave return_value alone: admit we read the
				 * number, but return a floating exception
				 * because we can't encode the number.
				 */
	    }
	  else
	    {
	      lp = words;

	      /* Word 1. Sign, exponent and perhaps high bits.  */
	      /* Assume 2's complement integers.  */
	      word1 = (((exponent_4 & mask[exponent_bits]) << (15 - exponent_bits))
		       | ((f->sign == '+') ? 0 : 0x8000)
		       | next_bits (15 - exponent_bits));
	      *lp++ = word1;

	      /* The rest of the words are just mantissa bits.  */
	      for (; lp < words + precision; lp++)
		{
		  *lp = next_bits (LITTLENUM_NUMBER_OF_BITS);
		}

	      if (next_bits (1))
		{
		  /*
					 * 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?
					 */

		  unsigned long carry;

		  /*
					  #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 ((word1 ^ *words) & (1 << (LITTLENUM_NUMBER_OF_BITS - 1)))
		    {
		      make_invalid_floating_point_number (words);
		      /*
						 * We leave return_value alone: admit we read the
						 * number, but return a floating exception
						 * because we can't encode the number.
						 */
		    }
		}		/* if (we needed to round up) */
	    }			/* if (exponent overflow) */
	}			/* if (0.0e0) */
    }				/* if (float_type was OK) */
  return (return_value);
}				/* flonum_gen2vax() */

/* JF this used to be in vax.c but this looks like a better place for it */

/*
 *		md_atof()
 *
 * In:	input_line_pointer->the 1st character of a floating-point
 *		number.
 *	1 letter denoting the type of statement that wants a
 *		binary floating point number returned.
 *	Address of where to build floating point literal.
 *		Assumed to be 'big enough'.
 *	Address of where to return size of literal (in chars).
 *
 * Out:	Input_line_pointer->of next char after floating number.
 *	Error message, or 0.
 *	Floating point literal.
 *	Number of chars we used for the literal.
 */

#define MAXIMUM_NUMBER_OF_LITTLENUMS (8)	/* For .hfloats.  */

char *
md_atof (what_statement_type, literalP, sizeP)
     int what_statement_type;
     char *literalP;
     int *sizeP;
{
  LITTLENUM_TYPE words[MAXIMUM_NUMBER_OF_LITTLENUMS];
  register char kind_of_float;
  register int number_of_chars;
  register LITTLENUM_TYPE *littlenumP;

  switch (what_statement_type)
    {
    case 'F':			/* .float */
    case 'f':			/* .ffloat */
      kind_of_float = 'f';
      break;

    case 'D':			/* .double */
    case 'd':			/* .dfloat */
      kind_of_float = 'd';
      break;

    case 'g':			/* .gfloat */
      kind_of_float = 'g';
      break;

    case 'h':			/* .hfloat */
      kind_of_float = 'h';
      break;

    default:
      kind_of_float = 0;
      break;
    };

  if (kind_of_float)
    {
      register LITTLENUM_TYPE *limit;

      input_line_pointer = atof_vax (input_line_pointer,
				     kind_of_float,
				     words);
      /*
       * The atof_vax() builds up 16-bit numbers.
       * Since the assembler may not be running on
       * a little-endian machine, be very careful about
       * converting words to chars.
       */
      number_of_chars = atof_vax_sizeof (kind_of_float);
      know (number_of_chars <= MAXIMUM_NUMBER_OF_LITTLENUMS * sizeof (LITTLENUM_TYPE));
      limit = words + (number_of_chars / sizeof (LITTLENUM_TYPE));
      for (littlenumP = words; littlenumP < limit; littlenumP++)
	{
	  md_number_to_chars (literalP, *littlenumP, sizeof (LITTLENUM_TYPE));
	  literalP += sizeof (LITTLENUM_TYPE);
	};
    }
  else
    {
      number_of_chars = 0;
    };

  *sizeP = number_of_chars;
  return kind_of_float ? NULL : _("Bad call to md_atof()");
}

/* end of atof-vax.c */