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binutils-gdb/gas/config/atof-tahoe.c

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19990502 sourceware import
1999-05-03 09:29:11 +02:00
/* atof_tahoe.c - turn a string into a Tahoe floating point number
Copyright (C) 1987, 1998 Free Software Foundation, Inc.
*/
/* This is really a simplified version of atof_vax.c. I glommed it wholesale
and then shaved it down. I don't even know how it works. (Don't you find
my honesty refreshing? bowen@cs.Buffalo.EDU (Devon E Bowen)
I don't allow uppercase letters in the precision descrpitors. Ie 'f' and
'd' are allowed but 'F' and 'D' aren't */
#include "as.h"
/* Precision in LittleNums. */
#define MAX_PRECISION (4)
#define D_PRECISION (4)
#define F_PRECISION (2)
/* Precision in chars. */
#define D_PRECISION_CHARS (8)
#define F_PRECISION_CHARS (4)
/* Length in LittleNums of guard bits. */
#define GUARD (2)
static const long int 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_gen2tahoe and next_bits */
static int bits_left_in_littlenum;
static LITTLENUM_TYPE *littlenum_pointer;
static LITTLENUM_TYPE *littlenum_end;
#if __STDC__ == 1
int flonum_gen2tahoe (int format_letter, FLONUM_TYPE * f, LITTLENUM_TYPE * words);
#else /* not __STDC__ */
int flonum_gen2tahoe ();
#endif /* not __STDC__ */
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)
char letter; /* In: lowercase please. What kind of float? */
int *precisionP; /* Number of 16-bit words in the float. */
long int *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;
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! *
* *
\***********************************************************************/
char * /* Return pointer past text consumed. */
atof_tahoe (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. */
{
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 int exponent_bits;
return_value = str;
f.low = bits + MAX_PRECISION;
f.high = NULL;
f.leader = NULL;
f.exponent = NULL;
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_gen2tahoe (what_kind, &f, words))
{
return_value = NULL;
}
}
}
return (return_value);
}
/*
* In: a flonum, a Tahoe floating point format.
* Out: a Tahoe floating-point bit pattern.
*/
int /* 0: OK. */
flonum_gen2tahoe (format_letter, f, words)
char format_letter; /* One of 'd' 'f'. */
FLONUM_TYPE *f;
LITTLENUM_TYPE *words; /* Deliver answer here. */
{
LITTLENUM_TYPE *lp;
int precision;
long int 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 int exponent_1;
long int exponent_2;
long int exponent_3;
long int 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 tahoe floating_point formats 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.
*
* 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 int 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);
}
/*
* 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.
*/
char *
md_atof (what_statement_type, literalP, sizeP)
char what_statement_type;
char *literalP;
int *sizeP;
{
LITTLENUM_TYPE words[MAX_PRECISION];
register char kind_of_float;
register int number_of_chars;
register LITTLENUM_TYPE *littlenum_pointer;
switch (what_statement_type)
{
case 'f': /* .ffloat */
case 'd': /* .dfloat */
kind_of_float = what_statement_type;
break;
default:
kind_of_float = 0;
break;
};
if (kind_of_float)
{
register LITTLENUM_TYPE *limit;
input_line_pointer = atof_tahoe (input_line_pointer,
kind_of_float,
words);
/*
* The atof_tahoe() builds up 16-bit numbers.
* Since the assembler may not be running on
* a different-endian machine, be very careful about
* converting words to chars.
*/
number_of_chars = (kind_of_float == 'f' ? F_PRECISION_CHARS :
(kind_of_float == 'd' ? D_PRECISION_CHARS : 0));
know (number_of_chars <= MAX_PRECISION * sizeof (LITTLENUM_TYPE));
limit = words + (number_of_chars / sizeof (LITTLENUM_TYPE));
for (littlenum_pointer = words;
littlenum_pointer < limit;
littlenum_pointer++)
{
md_number_to_chars (literalP, *littlenum_pointer,
sizeof (LITTLENUM_TYPE));
literalP += sizeof (LITTLENUM_TYPE);
};
}
else
{
number_of_chars = 0;
};
*sizeP = number_of_chars;
return kind_of_float ? 0 : _("Bad call to md_atof()");
}
/* atof_tahoe.c */