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atof-ieee.c
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1991-01-24
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/* atof_ieee.c - turn a Flonum into an IEEE floating point number
Copyright (C) 1987 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 1, 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, 675 Mass Ave, Cambridge, MA 02139, USA. */
#include "flonum.h"
#ifdef USG
#define bzero(s,n) memset(s,0,n)
#define bcopy(from,to,n) memcpy((to),(from),(n))
#endif
extern FLONUM_TYPE generic_floating_point_number; /* Flonums returned here. */
#define NULL (0)
extern char EXP_CHARS[];
/* Precision in LittleNums. */
#define MAX_PRECISION (6)
#define F_PRECISION (2)
#define D_PRECISION (4)
#define X_PRECISION (6)
#define P_PRECISION (6)
/* Length in LittleNums of guard bits. */
#define GUARD (2)
static unsigned 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
};
static int bits_left_in_littlenum;
static int littlenums_left;
static LITTLENUM_TYPE * littlenum_pointer;
static int
next_bits (number_of_bits)
int number_of_bits;
{
int return_value;
if(!littlenums_left)
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;
if(--littlenums_left) {
bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS - number_of_bits;
littlenum_pointer --;
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);
}
/* Num had better be less than LITTLENUM_NUMBER_OF_BITS */
static int
unget_bits(num)
{
if(!littlenums_left) {
++littlenum_pointer;
++littlenums_left;
bits_left_in_littlenum=num;
} else if(bits_left_in_littlenum+num>LITTLENUM_NUMBER_OF_BITS) {
bits_left_in_littlenum= num-(LITTLENUM_NUMBER_OF_BITS-bits_left_in_littlenum);
++littlenum_pointer;
++littlenums_left;
} else
bits_left_in_littlenum+=num;
}
static void
make_invalid_floating_point_number (words)
LITTLENUM_TYPE * words;
{
as_warn("cannot create floating-point number");
words[0]= ((unsigned)-1)>>1; /* Zero the leftmost bit */
words[1]= -1;
words[2]= -1;
words[3]= -1;
words[4]= -1;
words[5]= -1;
}
/***********************************************************************\
* Warning: this returns 16-bit LITTLENUMs. 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! *
* *
\***********************************************************************/
/* Note that atof-ieee always has X and P precisions enabled. it is up
to md_atof to filter them out if the target machine does not support
them. */
char * /* Return pointer past text consumed. */
atof_ieee (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. */
{
static 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;
generic_floating_point_number.low = bits + MAX_PRECISION;
generic_floating_point_number.high = NULL;
generic_floating_point_number.leader = NULL;
generic_floating_point_number.exponent = NULL;
generic_floating_point_number.sign = '\0';
/* Use more LittleNums than seems */
/* necessary: the highest flonum may have */
/* 15 leading 0 bits, so could be useless. */
bzero (bits, sizeof(LITTLENUM_TYPE) * MAX_PRECISION);
switch(what_kind) {
case 'f':
case 'F':
case 's':
case 'S':
precision = F_PRECISION;
exponent_bits = 8;
break;
case 'd':
case 'D':
case 'r':
case 'R':
precision = D_PRECISION;
exponent_bits = 11;
break;
case 'x':
case 'X':
case 'e':
case 'E':
precision = X_PRECISION;
exponent_bits = 15;
break;
case 'p':
case 'P':
precision = P_PRECISION;
exponent_bits= -1;
break;
default:
make_invalid_floating_point_number (words);
return NULL;
}
generic_floating_point_number.high = generic_floating_point_number.low + precision - 1 + GUARD;
if (atof_generic (& return_value, ".", EXP_CHARS, & generic_floating_point_number)) {
/* as_warn("Error converting floating point number (Exponent overflow?)"); */
make_invalid_floating_point_number (words);
return NULL;
}
gen_to_words(words, precision, exponent_bits);
return return_value;
}
/* Turn generic_floating_point_number into a real float/double/extended */
gen_to_words(words,precision,exponent_bits)
LITTLENUM_TYPE *words;
long int exponent_bits;
int precision;
{
int return_value=0;
long int exponent_1;
long int exponent_2;
long int exponent_3;
long int exponent_4;
int exponent_skippage;
LITTLENUM_TYPE word1;
LITTLENUM_TYPE * lp;
if (generic_floating_point_number.low > generic_floating_point_number.leader) {
/* 0.0e0 seen. */
if(generic_floating_point_number.sign=='+')
words[0]=0x0000;
else
words[0]=0x8000;
bzero (&words[1], sizeof(LITTLENUM_TYPE) * (precision-1));
return return_value;
}
/* NaN: Do the right thing */
if(generic_floating_point_number.sign==0) {
if(precision==F_PRECISION) {
words[0]=0x7fff;
words[1]=0xffff;
} else {
words[0]=0x7fff;
words[1]=0xffff;
words[2]=0xffff;
words[3]=0xffff;
}
return return_value;
} else if(generic_floating_point_number.sign=='P') {
/* +INF: Do the right thing */
if(precision==F_PRECISION) {
words[0]=0x7f80;
words[1]=0;
} else {
words[0]=0x7ff0;
words[1]=0;
words[2]=0;
words[3]=0;
}
return return_value;
} else if(generic_floating_point_number.sign=='N') {
/* Negative INF */
if(precision==F_PRECISION) {
words[0]=0xff80;
words[1]=0x0;
} else {
words[0]=0xfff0;
words[1]=0x0;
words[2]=0x0;
words[3]=0x0;
}
return return_value;
}
/*
* The floating point formats we support 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(s) are the next most significant bits.
*
* So we need: number of bits of exponent, number of bits of
* mantissa.
*/
bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS;
littlenum_pointer = generic_floating_point_number.leader;
littlenums_left = 1+generic_floating_point_number.leader - generic_floating_point_number.low;
/* Seek (and forget) 1st significant bit */
for (exponent_skippage = 0;! next_bits(1); exponent_skippage ++)
;
exponent_1 = generic_floating_point_number.exponent + generic_floating_point_number.leader + 1 -
generic_floating_point_number.low;
/* Radix LITTLENUM_RADIX, point just higher than generic_floating_point_number.leader. */
exponent_2 = exponent_1 * LITTLENUM_NUMBER_OF_BITS;
/* Radix 2. */
exponent_3 = exponent_2 - exponent_skipp