/* atof_vax.c - turn a Flonum into a VAX floating point number
   Copyright (C) 1987-2020 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"

/* 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 (int, FLONUM_TYPE *, LITTLENUM_TYPE *);

/* Number of chars in flonum type 'letter'.  */

static unsigned int
atof_vax_sizeof (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;
}

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 (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 (LITTLENUM_TYPE *words)
{
  *words = 0x8000;		/* Floating Reserved Operand Code.  */
}


static int			/* 0 means letter is OK.  */
what_kind_of_float (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;

  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 *
atof_vax (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;
      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;
	}
      else if (flonum_gen2vax (what_kind, &f, words))
	return_value = NULL;
    }

  return return_value;
}

/* In: a flonum, a vax floating point format.
   Out: a vax floating-point bit pattern.  */

int
flonum_gen2vax (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.  */

	  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.  */
		    }
		}
	    }
	}
    }
  return return_value;
}

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

/* 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.  */

const char *
vax_md_atof (int what_statement_type,
	     char *literalP,
	     int *sizeP)
{
  LITTLENUM_TYPE words[MAXIMUM_NUMBER_OF_LITTLENUMS];
  char kind_of_float;
  unsigned int number_of_chars;
  LITTLENUM_TYPE *littlenumP;

  switch (what_statement_type)
    {
    case 'F':
    case 'f':
      kind_of_float = 'f';
      break;

    case 'D':
    case 'd':
      kind_of_float = 'd';
      break;

    case 'g':
      kind_of_float = 'g';
      break;

    case 'h':
      kind_of_float = 'h';
      break;

    default:
      kind_of_float = 0;
      break;
    };

  if (kind_of_float)
    {
      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 : _("Unrecognized or unsupported floating point constant");
}