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/* IEEE floating point support routines, for GDB, the GNU Debugger.
Copyright (C) 1991, 1994 Free Software Foundation, Inc.
This file is part of GDB.
This program 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 of the License, or
(at your option) any later version.
This program 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 this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#include "floatformat.h"
#include <math.h> /* ldexp */
#ifdef __STDC__
#include <stddef.h>
extern void *memcpy (void *s1, const void *s2, size_t n);
extern void *memset (void *s, int c, size_t n);
#else
extern char *memcpy ();
extern char *memset ();
#endif
/* The odds that CHAR_BIT will be anything but 8 are low enough that I'm not
going to bother with trying to muck around with whether it is defined in
a system header, what we do if not, etc. */
#define FLOATFORMAT_CHAR_BIT 8
/* floatformats for IEEE single and double, big and little endian. */
const struct floatformat floatformat_ieee_single_big =
{
floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23, floatformat_intbit_no
};
const struct floatformat floatformat_ieee_single_little =
{
floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23, floatformat_intbit_no
};
const struct floatformat floatformat_ieee_double_big =
{
floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52, floatformat_intbit_no
};
const struct floatformat floatformat_ieee_double_little =
{
floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52, floatformat_intbit_no
};
const struct floatformat floatformat_i387_ext =
{
floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
floatformat_intbit_yes
};
const struct floatformat floatformat_m68881_ext =
{
/* Note that the bits from 16 to 31 are unused. */
floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64, floatformat_intbit_yes
};
const struct floatformat floatformat_i960_ext =
{
/* Note that the bits from 0 to 15 are unused. */
floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64,
floatformat_intbit_yes
};
const struct floatformat floatformat_m88110_ext =
{
floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
floatformat_intbit_yes
};
static unsigned long get_field PARAMS ((unsigned char *,
enum floatformat_byteorders,
unsigned int,
unsigned int,
unsigned int));
/* Extract a field which starts at START and is LEN bytes long. DATA and
TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */
static unsigned long
get_field (data, order, total_len, start, len)
unsigned char *data;
enum floatformat_byteorders order;
unsigned int total_len;
unsigned int start;
unsigned int len;
{
unsigned long result;
unsigned int cur_byte;
int cur_bitshift;
/* Start at the least significant part of the field. */
cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT;
if (order == floatformat_little)
cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1;
cur_bitshift =
((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT;
result = *(data + cur_byte) >> (-cur_bitshift);
cur_bitshift += FLOATFORMAT_CHAR_BIT;
if (order == floatformat_little)
++cur_byte;
else
--cur_byte;
/* Move towards the most significant part of the field. */
while (cur_bitshift < len)
{
if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT)
/* This is the last byte; zero out the bits which are not part of
this field. */
result |=
(*(data + cur_byte) & ((1 << (len - cur_bitshift)) - 1))
<< cur_bitshift;
else
result |= *(data + cur_byte) << cur_bitshift;
cur_bitshift += FLOATFORMAT_CHAR_BIT;
if (order == floatformat_little)
++cur_byte;
else
--cur_byte;
}
return result;
}
/* Convert from FMT to a double.
FROM is the address of the extended float.
Store the double in *TO. */
void
floatformat_to_double (fmt, from, to)
const struct floatformat *fmt;
char *from;
double *to;
{
unsigned char *ufrom = (unsigned char *)from;
double dto;
long exponent;
unsigned long mant;
unsigned int mant_bits, mant_off;
int mant_bits_left;
exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
fmt->exp_start, fmt->exp_len);
/* Note that if exponent indicates a NaN, we can't really do anything useful
(not knowing if the host has NaN's, or how to build one). So it will
end up as an infinity or something close; that is OK. */
mant_bits_left = fmt->man_len;
mant_off = fmt->man_start;
dto = 0.0;
exponent -= fmt->exp_bias;
/* Build the result algebraically. Might go infinite, underflow, etc;
who cares. */
while (mant_bits_left > 0)
{
int exp_bits;
exp_bits = mant_bits_left < 32 ? mant_bits_left : 32;
if (mant_bits_left == fmt->man_len
&& exp_bits == 32
&& fmt->intbit == floatformat_intbit_no)
{
/* If there is no integer bit, we need to get only 31 bits
so we have room for an integer bit that we create. */
mant_bits = 31;
}
else
mant_bits = exp_bits;
mant = get_field (ufrom, fmt->byteorder, fmt->totalsize,
mant_off, mant_bits);
if (mant_bits_left == fmt->man_len)
mant |= 0x80000000;
dto += ldexp ((double)mant, exponent - (exp_bits - 1));
exponent -= exp_bits;
mant_off += mant_bits;
mant_bits_left -= mant_bits;
}
/* Negate it if negative. */
if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
dto = -dto;
memcpy (to, &dto, sizeof (dto));
}
static void put_field PARAMS ((unsigned char *, enum floatformat_byteorders,
unsigned int,
unsigned int,
unsigned int,
unsigned long));
/* Set a field which starts at START and is LEN bytes long. DATA and
TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */
static void
put_field (data, order, total_len, start, len, stuff_to_put)
unsigned char *data;
enum floatformat_byteorders order;
unsigned int total_len;
unsigned int start;
unsigned int len;
unsigned long stuff_to_put;
{
unsigned int cur_byte;
int cur_bitshift;
/* Start at the least significant part of the field. */
cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT;
if (order == floatformat_little)
cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1;
cur_bitshift =
((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT;
*(data + cur_byte) &=
~(((1 << ((start + len) % FLOATFORMAT_CHAR_BIT)) - 1) << (-cur_bitshift));
*(data + cur_byte) |=
(stuff_to_put & ((1 << FLOATFORMAT_CHAR_BIT) - 1)) << (-cur_bitshift);
cur_bitshift += FLOATFORMAT_CHAR_BIT;
if (order == floatformat_little)
++cur_byte;
else
--cur_byte;
/* Move towards the most significant part of the field. */
while (cur_bitshift < len)
{
if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT)
{
/* This is the last byte. */
*(data + cur_byte) &=
~((1 << (len - cur_bitshift)) - 1);
*(data + cur_byte) |= (stuff_to_put >> cur_bitshift);
}
else
*(data + cur_byte) = ((stuff_to_put >> cur_bitshift)
& ((1 << FLOATFORMAT_CHAR_BIT) - 1));
cur_bitshift += FLOATFORMAT_CHAR_BIT;
if (order == floatformat_little)
++cur_byte;
else
--cur_byte;
}
}
/* The converse: convert the double *FROM to an extended float
and store where TO points. Neither FROM nor TO have any alignment
restrictions. */
void
floatformat_from_double (fmt, from, to)
CONST struct floatformat *fmt;
double *from;
char *to;
{
double dfrom;
int exponent;
double mant;
unsigned int mant_bits, mant_off;
int mant_bits_left;
unsigned char *uto = (unsigned char *)to;
memcpy (&dfrom, from, sizeof (dfrom));
memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT);
if (dfrom == 0)
return; /* Result is zero */
if (dfrom != dfrom)
{
/* From is NaN */
put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
fmt->exp_len, fmt->exp_nan);
/* Be sure it's not infinity, but NaN value is irrel */
put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start,
32, 1);
return;
}
/* If negative, set the sign bit. */
if (dfrom < 0)
{
put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1);
dfrom = -dfrom;
}
/* How to tell an infinity from an ordinary number? FIXME-someday */
mant = frexp (dfrom, &exponent);
put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, fmt->exp_len,
exponent + fmt->exp_bias - 1);
mant_bits_left = fmt->man_len;
mant_off = fmt->man_start;
while (mant_bits_left > 0)
{
unsigned long mant_long;
mant_bits = mant_bits_left < 32 ? mant_bits_left : 32;
mant *= 4294967296.0;
mant_long = (unsigned long)mant;
mant -= mant_long;
/* If the integer bit is implicit, then we need to discard it.
If we are discarding a zero, we should be (but are not) creating
a denormalized number which means adjusting the exponent
(I think). */
if (mant_bits_left == fmt->man_len
&& fmt->intbit == floatformat_intbit_no)
{
mant_long &= 0x7fffffff;
mant_bits -= 1;
}
else if (mant_bits < 32)
{
/* The bits we want are in the most significant MANT_BITS bits of
mant_long. Move them to the least significant. */
mant_long >>= 32 - mant_bits;
}
put_field (uto, fmt->byteorder, fmt->totalsize,
mant_off, mant_bits, mant_long);
mant_off += mant_bits;
mant_bits_left -= mant_bits;
}
}
#ifdef IEEE_DEBUG
/* This is to be run on a host which uses IEEE floating point. */
void
ieee_test (n)
double n;
{
double result;
char exten[16];
floatformat_to_double (&floatformat_ieee_double_big, &n, &result);
if (n != result)
printf ("Differ(to): %.20g -> %.20g\n", n, result);
floatformat_from_double (&floatformat_ieee_double_big, &n, &result);
if (n != result)
printf ("Differ(from): %.20g -> %.20g\n", n, result);
floatformat_from_double (&floatformat_m68881_ext, &n, exten);
floatformat_to_double (&floatformat_m68881_ext, exten, &result);
if (n != result)
printf ("Differ(to+from): %.20g -> %.20g\n", n, result);
#if IEEE_DEBUG > 1
/* This is to be run on a host which uses 68881 format. */
{
long double ex = *(long double *)exten;
if (ex != n)
printf ("Differ(from vs. extended): %.20g\n", n);
}
#endif
}
int
main ()
{
ieee_test (0.5);
ieee_test (256.0);
ieee_test (0.12345);
ieee_test (234235.78907234);
ieee_test (-512.0);
ieee_test (-0.004321);
return 0;
}
#endif
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