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Start development on 386BSD 0.0
[unix-history] / .ref-BSD-4_3_Net_2 / usr / src / usr.bin / gas / config / atof-ieee.c
/* 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
};
\f
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;
}
\f
/***********************************************************************\
* 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_skippage;
/* Forget leading zeros, forget 1st bit. */
exponent_4 = exponent_3 + ((1 << (exponent_bits - 1)) - 2);
/* Offset exponent. */
lp = words;
/* Word 1. Sign, exponent and perhaps high bits. */
word1 = (generic_floating_point_number.sign == '+') ? 0 : (1<<(LITTLENUM_NUMBER_OF_BITS-1));
/* Assume 2's complement integers. */
if(exponent_4<1 && exponent_4>=-62) {
int prec_bits;
int num_bits;
unget_bits(1);
num_bits= -exponent_4;
prec_bits=LITTLENUM_NUMBER_OF_BITS*precision-(exponent_bits+1+num_bits);
if(precision==X_PRECISION && exponent_bits==15)
prec_bits-=LITTLENUM_NUMBER_OF_BITS+1;
if(num_bits>=LITTLENUM_NUMBER_OF_BITS-exponent_bits) {
/* Bigger than one littlenum */
num_bits-=(LITTLENUM_NUMBER_OF_BITS-1)-exponent_bits;
*lp++=word1;
if(num_bits+exponent_bits+1>=precision*LITTLENUM_NUMBER_OF_BITS) {
/* Exponent overflow */
make_invalid_floating_point_number(words);
return return_value;
}
if(precision==X_PRECISION && exponent_bits==15) {
*lp++=0;
*lp++=0;
num_bits-=LITTLENUM_NUMBER_OF_BITS-1;
}
while(num_bits>=LITTLENUM_NUMBER_OF_BITS) {
num_bits-=LITTLENUM_NUMBER_OF_BITS;
*lp++=0;
}
if(num_bits)
*lp++=next_bits(LITTLENUM_NUMBER_OF_BITS-(num_bits));
} else {
if(precision==X_PRECISION && exponent_bits==15) {
*lp++=word1;
*lp++=0;
if(num_bits==LITTLENUM_NUMBER_OF_BITS) {
*lp++=0;
*lp++=next_bits(LITTLENUM_NUMBER_OF_BITS-1);
} else if(num_bits==LITTLENUM_NUMBER_OF_BITS-1)
*lp++=0;
else
*lp++=next_bits(LITTLENUM_NUMBER_OF_BITS-1-num_bits);
num_bits=0;
} else {
word1|= next_bits ((LITTLENUM_NUMBER_OF_BITS-1) - (exponent_bits+num_bits));
*lp++=word1;
}
}
while(lp<words+precision)
*lp++=next_bits(LITTLENUM_NUMBER_OF_BITS);
/* Round the mantissa up, but don't change the number */
if(next_bits(1)) {
--lp;
if(prec_bits>LITTLENUM_NUMBER_OF_BITS) {
int n = 0;
int tmp_bits;
n=0;
tmp_bits=prec_bits;
while(tmp_bits>LITTLENUM_NUMBER_OF_BITS) {
if(lp[n]!=(LITTLENUM_TYPE)-1)
break;
--n;
tmp_bits-=LITTLENUM_NUMBER_OF_BITS;
}
if(tmp_bits>LITTLENUM_NUMBER_OF_BITS || (lp[n]&mask[tmp_bits])!=mask[tmp_bits]) {
unsigned long int carry;
for (carry = 1; carry && (lp >= words); lp --) {
carry = * lp + carry;
* lp = carry;
carry >>= LITTLENUM_NUMBER_OF_BITS;
}
}
} else if((*lp&mask[prec_bits])!=mask[prec_bits])
lp++;
}
return return_value;
} else if (exponent_4 & ~ mask [exponent_bits]) {
/*
* Exponent overflow. Lose immediately.
*/
/*
* We leave return_value alone: admit we read the
* number, but return a floating exception
* because we can't encode the number.
*/
make_invalid_floating_point_number (words);
return return_value;
} else {
word1 |= (exponent_4 << ((LITTLENUM_NUMBER_OF_BITS-1) - exponent_bits))
| next_bits ((LITTLENUM_NUMBER_OF_BITS-1) - exponent_bits);
}
* lp ++ = word1;
/* X_PRECISION is special: it has 16 bits of zero in the middle,
followed by a 1 bit. */
if(exponent_bits==15 && precision==X_PRECISION) {
*lp++=0;
*lp++= 1<<(LITTLENUM_NUMBER_OF_BITS)|next_bits(LITTLENUM_NUMBER_OF_BITS-1);
}
/* The rest of the words are just mantissa bits. */
while(lp < words + precision)
*lp++ = next_bits (LITTLENUM_NUMBER_OF_BITS);
if (next_bits (1)) {
unsigned long int carry;
/*
* 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?
*/
/* #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)) ) {
/* We leave return_value alone: admit we read the
* number, but return a floating exception
* because we can't encode the number.
*/
*words&= ~ (1 << (LITTLENUM_NUMBER_OF_BITS - 1));
/* make_invalid_floating_point_number (words); */
/* return return_value; */
}
}
return (return_value);
}
/* This routine is a real kludge. Someone really should do it better, but
I'm too lazy, and I don't understand this stuff all too well anyway
(JF)
*/
void
int_to_gen(x)
long x;
{
char buf[20];
char *bufp;
sprintf(buf,"%ld",x);
bufp= &buf[0];
if(atof_generic(&bufp,".", EXP_CHARS, &generic_floating_point_number))
as_warn("Error converting number to floating point (Exponent overflow?)");
}
#ifdef TEST
char *
print_gen(gen)
FLONUM_TYPE *gen;
{
FLONUM_TYPE f;
LITTLENUM_TYPE arr[10];
double dv;
float fv;
static char sbuf[40];
if(gen) {
f=generic_floating_point_number;
generic_floating_point_number= *gen;
}
gen_to_words(&arr[0],4,11);
bcopy(&arr[0],&dv,sizeof(double));
sprintf(sbuf,"%x %x %x %x %.14G ",arr[0],arr[1],arr[2],arr[3],dv);
gen_to_words(&arr[0],2,8);
bcopy(&arr[0],&fv,sizeof(float));
sprintf(sbuf+strlen(sbuf),"%x %x %.12g\n",arr[0],arr[1],fv);
if(gen)
generic_floating_point_number=f;
return sbuf;
}
#endif
Continuous source code history from original PDP-7 UNIX to FreeBSD 2, the first fully unencumbered FreeBSD release.