newlib/winsup/mingw/mingwex/math/cephes_emath.c

/* This file is extracted from S L Moshier's  ioldoubl.c,
 * modified for use in MinGW 
 *
 * Extended precision arithmetic functions for long double I/O.
 * This program has been placed in the public domain.
 */

   

/*
 * Revision history:
 *
 *  5 Jan 84	PDP-11 assembly language version
 *  6 Dec 86	C language version
 * 30 Aug 88	100 digit version, improved rounding
 * 15 May 92    80-bit long double support
 *
 * Author:  S. L. Moshier.
 *
 * 6 Oct 02	Modified for MinGW by inlining utility routines,
 * 		removing global variables and splitting out strtold
 *		from _IO_ldtoa and _IO_ldtostr.
 *  
 *		Danny Smith <dannysmith@users.sourceforge.net>
 * 
 */


#include "cephes_emath.h"

/*
 * The constants are for 64 bit precision.
 */


/* Move in external format number,
 * converting it to internal format.
 */
void __emovi(const short unsigned int * __restrict__ a,
		  short unsigned int * __restrict__ b)
{
register const unsigned short *p;
register unsigned short *q;
int i;

q = b;
p = a + (NE-1);	/* point to last word of external number */
/* get the sign bit */
if( *p & 0x8000 )
	*q++ = 0xffff;
else
	*q++ = 0;
/* get the exponent */
*q = *p--;
*q++ &= 0x7fff;	/* delete the sign bit */
#ifdef INFINITY
if( (*(q-1) & 0x7fff) == 0x7fff )
	{
#ifdef NANS
	if( __eisnan(a) )
		{
		*q++ = 0;
		for( i=3; i<NI; i++ )
			*q++ = *p--;
		return;
		}
#endif
	for( i=2; i<NI; i++ )
		*q++ = 0;
	return;
	}
#endif
/* clear high guard word */
*q++ = 0;
/* move in the significand */
for( i=0; i<NE-1; i++ )
	*q++ = *p--;
/* clear low guard word */
*q = 0;
}


/*
;	Add significands
;	x + y replaces y
*/

void __eaddm(const short unsigned int * __restrict__ x,
		  short unsigned int * __restrict__ y)
{
register unsigned long a;
int i;
unsigned int carry;

x += NI-1;
y += NI-1;
carry = 0;
for( i=M; i<NI; i++ )
	{
	a = (unsigned long )(*x) + (unsigned long )(*y) + carry;
	if( a & 0x10000 )
		carry = 1;
	else
		carry = 0;
	*y = (unsigned short )a;
	--x;
	--y;
	}
}

/*
;	Subtract significands
;	y - x replaces y
*/

void __esubm(const short unsigned int * __restrict__ x,
		  short unsigned int * __restrict__ y)
{
unsigned long a;
int i;
unsigned int carry;

x += NI-1;
y += NI-1;
carry = 0;
for( i=M; i<NI; i++ )
	{
	a = (unsigned long )(*y) - (unsigned long )(*x) - carry;
	if( a & 0x10000 )
		carry = 1;
	else
		carry = 0;
	*y = (unsigned short )a;
	--x;
	--y;
	}
}


/* Multiply significand of e-type number b
by 16-bit quantity a, e-type result to c. */

static void __m16m(short unsigned int a,
		 short unsigned int *  __restrict__ b,
		 short unsigned int *  __restrict__ c)
{
register unsigned short *pp;
register unsigned long carry;
unsigned short *ps;
unsigned short p[NI];
unsigned long aa, m;
int i;

aa = a;
pp = &p[NI-2];
*pp++ = 0;
*pp = 0;
ps = &b[NI-1];

for( i=M+1; i<NI; i++ )
	{
	if( *ps == 0 )
		{
		--ps;
		--pp;
		*(pp-1) = 0;
		}
	else
		{
		m = (unsigned long) aa * *ps--;
		carry = (m & 0xffff) + *pp;
		*pp-- = (unsigned short )carry;
		carry = (carry >> 16) + (m >> 16) + *pp;
		*pp = (unsigned short )carry;
		*(pp-1) = carry >> 16;
		}
	}
for( i=M; i<NI; i++ )
	c[i] = p[i];
}


/* Divide significands. Neither the numerator nor the denominator
is permitted to have its high guard word nonzero.  */


int __edivm(short unsigned int * __restrict__ den,
		 short unsigned int * __restrict__ num)
{
int i;
register unsigned short *p;
unsigned long tnum;
unsigned short j, tdenm, tquot;
unsigned short tprod[NI+1];
unsigned short equot[NI];

p = &equot[0];
*p++ = num[0];
*p++ = num[1];

for( i=M; i<NI; i++ )
	{
	*p++ = 0;
	}
__eshdn1( num );
tdenm = den[M+1];
for( i=M; i<NI; i++ )
	{
	/* Find trial quotient digit (the radix is 65536). */
	tnum = (((unsigned long) num[M]) << 16) + num[M+1];

	/* Do not execute the divide instruction if it will overflow. */
        if( (tdenm * 0xffffUL) < tnum )
		tquot = 0xffff;
	else
		tquot = tnum / tdenm;

		/* Prove that the divide worked. */
/*
	tcheck = (unsigned long )tquot * tdenm;
	if( tnum - tcheck > tdenm )
		tquot = 0xffff;
*/
	/* Multiply denominator by trial quotient digit. */
	__m16m( tquot, den, tprod );
	/* The quotient digit may have been overestimated. */
	if( __ecmpm( tprod, num ) > 0 )
		{
		tquot -= 1;
		__esubm( den, tprod );
		if( __ecmpm( tprod, num ) > 0 )
			{
			tquot -= 1;
			__esubm( den, tprod );
			}
		}
	__esubm( tprod, num );
	equot[i] = tquot;
	__eshup6(num);
	}
/* test for nonzero remainder after roundoff bit */
p = &num[M];
j = 0;
for( i=M; i<NI; i++ )
	{
	j |= *p++;
	}
if( j )
	j = 1;

for( i=0; i<NI; i++ )
	num[i] = equot[i];

return( (int )j );
}



/* Multiply significands */
int __emulm(const short unsigned int * __restrict__ a,
		 short unsigned int * __restrict__ b)
{
const unsigned short *p;
unsigned short *q;
unsigned short pprod[NI];
unsigned short equot[NI];
unsigned short j;
int i;

equot[0] = b[0];
equot[1] = b[1];
for( i=M; i<NI; i++ )
	equot[i] = 0;

j = 0;
p = &a[NI-1];
q = &equot[NI-1];
for( i=M+1; i<NI; i++ )
	{
	if( *p == 0 )
		{
		--p;
		}
	else
		{
		__m16m( *p--, b, pprod );
		__eaddm(pprod, equot);
		}
	j |= *q;
	__eshdn6(equot);
	}

for( i=0; i<NI; i++ )
	b[i] = equot[i];

/* return flag for lost nonzero bits */
return( (int)j );
}



/*
 * Normalize and round off.
 *
 * The internal format number to be rounded is "s".
 * Input "lost" indicates whether the number is exact.
 * This is the so-called sticky bit.
 *
 * Input "subflg" indicates whether the number was obtained
 * by a subtraction operation.  In that case if lost is nonzero
 * then the number is slightly smaller than indicated.
 *
 * Input "exp" is the biased exponent, which may be negative.
 * the exponent field of "s" is ignored but is replaced by
 * "exp" as adjusted by normalization and rounding.
 *
 * Input "rcntrl" is the rounding control.
 *
 * Input "rnprc" is precison control (64 or NBITS).
 */

void __emdnorm(short unsigned int *s, int lost, int subflg, long int exp, int rcntrl, int rndprc)
{
int i, j;
unsigned short r;
int rw = NI-1; /* low guard word */
int re = NI-2;
const unsigned short rmsk = 0xffff;
const unsigned short rmbit = 0x8000;
#if NE == 6
unsigned short rbit[NI] = {0,0,0,0,0,0,0,1,0};
#else
unsigned short rbit[NI] = {0,0,0,0,0,0,0,0,0,0,0,1,0};
#endif

/* Normalize */
j = __enormlz( s );

/* a blank significand could mean either zero or infinity. */
#ifndef INFINITY
if( j > NBITS )
	{
	__ecleazs( s );
	return;
	}
#endif
exp -= j;
#ifndef INFINITY
if( exp >= 32767L )
	goto overf;
#else
if( (j > NBITS) && (exp < 32767L) )
	{
	__ecleazs( s );
	return;
	}
#endif
if( exp < 0L )
	{
	if( exp > (long )(-NBITS-1) )
		{
		j = (int )exp;
		i = __eshift( s, j );
		if( i )
			lost = 1;
		}
	else
		{
		__ecleazs( s );
		return;
		}
	}
/* Round off, unless told not to by rcntrl. */
if( rcntrl == 0 )
	goto mdfin;
if (rndprc == 64)
  {
    rw = 7;
    re = 6;
    rbit[NI-2] = 0;
    rbit[6] = 1;
  }

/* Shift down 1 temporarily if the data structure has an implied
 * most significant bit and the number is denormal.
 * For rndprc = 64 or NBITS, there is no implied bit.
 * But Intel long double denormals lose one bit of significance even so.
 */
#if IBMPC
if( (exp <= 0) && (rndprc != NBITS) )
#else
if( (exp <= 0) && (rndprc != 64) && (rndprc != NBITS) )
#endif
	{
	lost |= s[NI-1] & 1;
	__eshdn1(s);
	}
/* Clear out all bits below the rounding bit,
 * remembering in r if any were nonzero.
 */
r = s[rw] & rmsk;
if( rndprc < NBITS )
	{
	i = rw + 1;
	while( i < NI )
		{
		if( s[i] )
			r |= 1;
		s[i] = 0;
		++i;
		}
	}
s[rw] &= ~rmsk;
if( (r & rmbit) != 0 )
	{
	if( r == rmbit )
		{
		if( lost == 0 )
			{ /* round to even */
			if( (s[re] & 1) == 0 )
				goto mddone;
			}
		else
			{
			if( subflg != 0 )
				goto mddone;
			}
		}
	__eaddm( rbit, s );
	}
mddone:
#if IBMPC
if( (exp <= 0) && (rndprc != NBITS) )
#else
if( (exp <= 0) && (rndprc != 64) && (rndprc != NBITS) )
#endif
	{
	__eshup1(s);
	}
if( s[2] != 0 )
	{ /* overflow on roundoff */
	__eshdn1(s);
	exp += 1;
	}
mdfin:
s[NI-1] = 0;
if( exp >= 32767L )
	{
#ifndef INFINITY
overf:
#endif
#ifdef INFINITY
	s[1] = 32767;
	for( i=2; i<NI-1; i++ )
		s[i] = 0;
#else
	s[1] = 32766;
	s[2] = 0;
	for( i=M+1; i<NI-1; i++ )
		s[i] = 0xffff;
	s[NI-1] = 0;
	if( (rndprc < 64) || (rndprc == 113) )
		s[rw] &= ~rmsk;
#endif
	return;
	}
if( exp < 0 )
	s[1] = 0;
else
	s[1] = (unsigned short )exp;
}


/*
;	Multiply.
;
;	unsigned short a[NE], b[NE], c[NE];
;	emul( a, b, c );	c = b * a
*/
void __emul(const short unsigned int *a,
		 const short unsigned int *b,
		 short unsigned int *c)
{
unsigned short ai[NI], bi[NI];
int i, j;
long lt, lta, ltb;

#ifdef NANS
/* NaN times anything is the same NaN. */
if( __eisnan(a) )
	{
	__emov(a,c);
	return;
	}
if( __eisnan(b) )
	{
	__emov(b,c);
	return;
	}
/* Zero times infinity is a NaN. */
if( (__eisinf(a) && __eiiszero(b))
	|| (__eisinf(b) && __eiiszero(a)) )
	{
	mtherr( "emul", DOMAIN );
	__enan_NBITS( c );
	return;
	}
#endif
/* Infinity times anything else is infinity. */
#ifdef INFINITY
if( __eisinf(a) || __eisinf(b) )
	{
	if( __eisneg(a) ^ __eisneg(b) )
		*(c+(NE-1)) = 0x8000;
	else
		*(c+(NE-1)) = 0;
	__einfin(c);
	return;
	}
#endif
__emovi( a, ai );
__emovi( b, bi );
lta = ai[E];
ltb = bi[E];
if( ai[E] == 0 )
	{
	for( i=1; i<NI-1; i++ )
		{
		if( ai[i] != 0 )
			{
			lta -= __enormlz( ai );
			goto mnzer1;
			}
		}
	__eclear(c);
	return;
	}
mnzer1:

if( bi[E] == 0 )
	{
	for( i=1; i<NI-1; i++ )
		{
		if( bi[i] != 0 )
			{
			ltb -= __enormlz( bi );
			goto mnzer2;
			}
		}
	__eclear(c);
	return;
	}
mnzer2:

/* Multiply significands */
j = __emulm( ai, bi );
/* calculate exponent */
lt = lta + ltb - (EXONE - 1);
__emdnorm( bi, j, 0, lt, 64, NBITS );
/* calculate sign of product */
if( ai[0] == bi[0] )
	bi[0] = 0;
else
	bi[0] = 0xffff;
__emovo( bi, c );
}


/* move out internal format to ieee long double */
void __toe64(short unsigned int *a, short unsigned int *b)
{
register unsigned short *p, *q;
unsigned short i;

#ifdef NANS
if( __eiisnan(a) )
	{
	__enan_64( b );
	return;
	}
#endif
#ifdef IBMPC
/* Shift Intel denormal significand down 1.  */
if( a[E] == 0 )
  __eshdn1(a);
#endif
p = a;
#ifdef MIEEE
q = b;
#else
q = b + 4; /* point to output exponent */
#if 1
/* NOTE: if data type is 96 bits wide, clear the last word here. */
*(q+1)= 0;
#endif
#endif

/* combine sign and exponent */
i = *p++;
#ifdef MIEEE
if( i )
	*q++ = *p++ | 0x8000;
else
	*q++ = *p++;
*q++ = 0;
#else
if( i )
	*q-- = *p++ | 0x8000;
else
	*q-- = *p++;
#endif
/* skip over guard word */
++p;
/* move the significand */
#ifdef MIEEE
for( i=0; i<4; i++ )
	*q++ = *p++;
#else
#ifdef INFINITY
if (__eiisinf (a))
        {
	/* Intel long double infinity.  */
	*q-- = 0x8000;
	*q-- = 0;
	*q-- = 0;
	*q = 0;
	return;
	}
#endif
for( i=0; i<4; i++ )
	*q-- = *p++;
#endif
}


/* Compare two e type numbers.
 *
 * unsigned short a[NE], b[NE];
 * ecmp( a, b );
 *
 *  returns +1 if a > b
 *           0 if a == b
 *          -1 if a < b
 *          -2 if either a or b is a NaN.
 */
int __ecmp(const short unsigned int * __restrict__ a,
		const short unsigned int *  __restrict__ b)
{
unsigned short ai[NI], bi[NI];
register unsigned short *p, *q;
register int i;
int msign;

#ifdef NANS
if (__eisnan (a)  || __eisnan (b))
	return( -2 );
#endif
__emovi( a, ai );
p = ai;
__emovi( b, bi );
q = bi;

if( *p != *q )
	{ /* the signs are different */
/* -0 equals + 0 */
	for( i=1; i<NI-1; i++ )
		{
		if( ai[i] != 0 )
			goto nzro;
		if( bi[i] != 0 )
			goto nzro;
		}
	return(0);
nzro:
	if( *p == 0 )
		return( 1 );
	else
		return( -1 );
	}
/* both are the same sign */
if( *p == 0 )
	msign = 1;
else
	msign = -1;
i = NI-1;
do
	{
	if( *p++ != *q++ )
		{
		goto diff;
		}
	}
while( --i > 0 );

return(0);	/* equality */



diff:

if( *(--p) > *(--q) )
	return( msign );		/* p is bigger */
else
	return( -msign );	/* p is littler */
}

/*
;	Shift significand
;
;	Shifts significand area up or down by the number of bits
;	given by the variable sc.
*/
int __eshift(short unsigned int *x, int sc)
{
unsigned short lost;
unsigned short *p;

if( sc == 0 )
	return( 0 );

lost = 0;
p = x + NI-1;

if( sc < 0 )
	{
	sc = -sc;
	while( sc >= 16 )
		{
		lost |= *p;	/* remember lost bits */
		__eshdn6(x);
		sc -= 16;
		}

	while( sc >= 8 )
		{
		lost |= *p & 0xff;
		__eshdn8(x);
		sc -= 8;
		}

	while( sc > 0 )
		{
		lost |= *p & 1;
		__eshdn1(x);
		sc -= 1;
		}
	}
else
	{
	while( sc >= 16 )
		{
		__eshup6(x);
		sc -= 16;
		}

	while( sc >= 8 )
		{
		__eshup8(x);
		sc -= 8;
		}

	while( sc > 0 )
		{
		__eshup1(x);
		sc -= 1;
		}
	}
if( lost )
	lost = 1;
return( (int )lost );
}



/*
;	normalize
;
; Shift normalizes the significand area pointed to by argument
; shift count (up = positive) is returned.
*/
int __enormlz(short unsigned int *x)
{
register unsigned short *p;
int sc;

sc = 0;
p = &x[M];
if( *p != 0 )
	goto normdn;
++p;
if( *p & 0x8000 )
	return( 0 );	/* already normalized */
while( *p == 0 )
	{
	__eshup6(x);
	sc += 16;
/* With guard word, there are NBITS+16 bits available.
 * return true if all are zero.
 */
	if( sc > NBITS )
		return( sc );
	}
/* see if high byte is zero */
while( (*p & 0xff00) == 0 )
	{
	__eshup8(x);
	sc += 8;
	}
/* now shift 1 bit at a time */
while( (*p  & 0x8000) == 0)
	{
	__eshup1(x);
	sc += 1;
	if( sc > (NBITS+16) )
		{
		mtherr( "enormlz", UNDERFLOW );
		return( sc );
		}
	}
return( sc );

/* Normalize by shifting down out of the high guard word
   of the significand */
normdn:

if( *p & 0xff00 )
	{
	__eshdn8(x);
	sc -= 8;
	}
while( *p != 0 )
	{
	__eshdn1(x);
	sc -= 1;

	if( sc < -NBITS )
		{
		mtherr( "enormlz", OVERFLOW );
		return( sc );
		}
	}
return( sc );
}


/* Move internal format number out,
 * converting it to external format.
 */
void __emovo(const short unsigned int * __restrict__ a,
		  short unsigned int * __restrict__ b)
{
register const unsigned short *p;
register unsigned short *q;
unsigned short i;

p = a;
q = b + (NE-1); /* point to output exponent */
/* combine sign and exponent */
i = *p++;
if( i )
	*q-- = *p++ | 0x8000;
else
	*q-- = *p++;
#ifdef INFINITY
if( *(p-1) == 0x7fff )
	{
#ifdef NANS
	if( __eiisnan(a) )
		{
		__enan_NBITS( b );
		return;
		}
#endif
	__einfin(b);
	return;
	}
#endif
/* skip over guard word */
++p;
/* move the significand */
for( i=0; i<NE-1; i++ )
	*q-- = *p++;
}


#if USE_LDTOA


void __eiremain(short unsigned int *den, short unsigned int *num,
	 short unsigned int *equot )
{
long ld, ln;
unsigned short j;

ld = den[E];
ld -= __enormlz( den );
ln = num[E];
ln -= __enormlz( num );
__ecleaz( equot );
while( ln >= ld )
	{
	if( __ecmpm(den,num) <= 0 )
		{
		__esubm(den, num);
		j = 1;
		}
	else
		{
		j = 0;
		}
	__eshup1(equot);
	equot[NI-1] |= j;
	__eshup1(num);
	ln -= 1;
	}
__emdnorm( num, 0, 0, ln, 0, NBITS );
}


void __eadd1(const short unsigned int *  __restrict__ a,
		  const short unsigned int *  __restrict__ b,
		  short unsigned int *  __restrict__ c,
		  int subflg)
{
unsigned short ai[NI], bi[NI], ci[NI];
int i, lost, j, k;
long lt, lta, ltb;

#ifdef INFINITY
if( __eisinf(a) )
	{
	__emov(a,c);
	if( subflg )
		__eneg(c);
	return;
	}
if( __eisinf(b) )
	{
	__emov(b,c);
	return;
	}
#endif
__emovi( a, ai );
__emovi( b, bi );
if( sub )
	ai[0] = ~ai[0];

/* compare exponents */
lta = ai[E];
ltb = bi[E];
lt = lta - ltb;
if( lt > 0L )
	{	/* put the larger number in bi */
	__emovz( bi, ci );
	__emovz( ai, bi );
	__emovz( ci, ai );
	ltb = bi[E];
	lt = -lt;
	}
lost = 0;
if( lt != 0L )
	{
	if( lt < (long )(-NBITS-1) )
		goto done;	/* answer same as larger addend */
	k = (int )lt;
	lost = __eshift( ai, k ); /* shift the smaller number down */
	}
else
	{
/* exponents were the same, so must compare significands */
	i = __ecmpm( ai, bi );
	if( i == 0 )
		{ /* the numbers are identical in magnitude */
		/* if different signs, result is zero */
		if( ai[0] != bi[0] )
			{
			__eclear(c);
			return;
			}
		/* if same sign, result is double */
		/* double denomalized tiny number */
		if( (bi[E] == 0) && ((bi[3] & 0x8000) == 0) )
			{
			__eshup1( bi );
			goto done;
			}
		/* add 1 to exponent unless both are zero! */
		for( j=1; j<NI-1; j++ )
			{
			if( bi[j] != 0 )
				{
/* This could overflow, but let emovo take care of that. */
				ltb += 1;
				break;
				}
			}
		bi[E] = (unsigned short )ltb;
		goto done;
		}
	if( i > 0 )
		{	/* put the larger number in bi */
		__emovz( bi, ci );
		__emovz( ai, bi );
		__emovz( ci, ai );
		}
	}
if( ai[0] == bi[0] )
	{
	__eaddm( ai, bi );
	subflg = 0;
	}
else
	{
	__esubm( ai, bi );
	subflg = 1;
	}
__emdnorm( bi, lost, subflg, ltb, 64, NBITS);

done:
__emovo( bi, c );
}


/* y = largest integer not greater than x
 * (truncated toward minus infinity)
 *
 * unsigned short x[NE], y[NE]
 *
 * efloor( x, y );
 */


void __efloor(short unsigned int *x, short unsigned int *y)
{
register unsigned short *p;
int e, expon, i;
unsigned short f[NE];
const unsigned short bmask[] = {
0xffff,
0xfffe,
0xfffc,
0xfff8,
0xfff0,
0xffe0,
0xffc0,
0xff80,
0xff00,
0xfe00,
0xfc00,
0xf800,
0xf000,
0xe000,
0xc000,
0x8000,
0x0000,
};

__emov( x, f ); /* leave in external format */
expon = (int )f[NE-1];
e = (expon & 0x7fff) - (EXONE - 1);
if( e <= 0 )
	{
	__eclear(y);
	goto isitneg;
	}
/* number of bits to clear out */
e = NBITS - e;
__emov( f, y );
if( e <= 0 )
	return;

p = &y[0];
while( e >= 16 )
	{
	*p++ = 0;
	e -= 16;
	}
/* clear the remaining bits */
*p &= bmask[e];
/* truncate negatives toward minus infinity */
isitneg:

if( (unsigned short )expon & (unsigned short )0x8000 )
	{
	for( i=0; i<NE-1; i++ )
		{
		if( f[i] != y[i] )
			{
			__esub( __eone, y, y );
			break;
			}
		}
	}
}

/*
;	Subtract external format numbers.
;
;	unsigned short a[NE], b[NE], c[NE];
;	esub( a, b, c );	 c = b - a
*/


void __esub(const short unsigned int *  a,
		 const short unsigned int *  b,
		 short unsigned int *  c)
{

#ifdef NANS
if( __eisnan(a) )
	{
	__emov (a, c);
	return;
	}
if( __eisnan(b) )
	{
	__emov(b,c);
	return;
	}
/* Infinity minus infinity is a NaN.
 * Test for subtracting infinities of the same sign.
 */
if( __eisinf(a) && __eisinf(b) && ((__eisneg (a) ^ __eisneg (b)) == 0))
	{
	mtherr( "esub", DOMAIN );
	__enan_NBITS( c );
	return;
	}
#endif
__eadd1( a, b, c, 1 );
}



/*
;	Divide.
;
;	unsigned short a[NI], b[NI], c[NI];
;	ediv( a, b, c );	c = b / a
*/

void __ediv(const short unsigned int *a,
		 const short unsigned int *b,
		 short unsigned int *c)
{
unsigned short ai[NI], bi[NI];
int i;
long lt, lta, ltb;

#ifdef NANS
/* Return any NaN input. */
if( __eisnan(a) )
	{
	__emov(a,c);
	return;
	}
if( __eisnan(b) )
	{
	__emov(b,c);
	return;
	}
/* Zero over zero, or infinity over infinity, is a NaN. */
if( (__eiszero(a) && __eiszero(b))
	|| (__eisinf (a) && __eisinf (b)) )
	{
	mtherr( "ediv", DOMAIN );
	__enan_NBITS( c );
	return;
	}
#endif
/* Infinity over anything else is infinity. */
#ifdef INFINITY
if( __eisinf(b) )
	{
	if( __eisneg(a) ^ __eisneg(b) )
		*(c+(NE-1)) = 0x8000;
	else
		*(c+(NE-1)) = 0;
	__einfin(c);
	return;
	}
if( __eisinf(a) )
	{
	__eclear(c);
	return;
	}
#endif
__emovi( a, ai );
__emovi( b, bi );
lta = ai[E];
ltb = bi[E];
if( bi[E] == 0 )
	{ /* See if numerator is zero. */
	for( i=1; i<NI-1; i++ )
		{
		if( bi[i] != 0 )
			{
			ltb -= __enormlz( bi );
			goto dnzro1;
			}
		}
	__eclear(c);
	return;
	}
dnzro1:

if( ai[E] == 0 )
	{	/* possible divide by zero */
	for( i=1; i<NI-1; i++ )
		{
		if( ai[i] != 0 )
			{
			lta -= __enormlz( ai );
			goto dnzro2;
			}
		}
	if( ai[0] == bi[0] )
		*(c+(NE-1)) = 0;
	else
		*(c+(NE-1)) = 0x8000;
	__einfin(c);
	mtherr( "ediv", SING );
	return;
	}
dnzro2:

i = __edivm( ai, bi );
/* calculate exponent */
lt = ltb - lta + EXONE;
__emdnorm( bi, i, 0, lt, 64, NBITS );
/* set the sign */
if( ai[0] == bi[0] )
	bi[0] = 0;
else
	bi[0] = 0Xffff;
__emovo( bi, c );
}

void __e64toe(short unsigned int *pe, short unsigned int *y)
{
unsigned short yy[NI];
unsigned short *p, *q, *e;
int i;

e = pe;
p = yy;
for( i=0; i<NE-5; i++ )
	*p++ = 0;
#ifdef IBMPC
for( i=0; i<5; i++ )
	*p++ = *e++;
#endif
#ifdef DEC
for( i=0; i<5; i++ )
	*p++ = *e++;
#endif
#ifdef MIEEE
p = &yy[0] + (NE-1);
*p-- = *e++;
++e;
for( i=0; i<4; i++ )
	*p-- = *e++;
#endif

#ifdef IBMPC
/* For Intel long double, shift denormal significand up 1
   -- but only if the top significand bit is zero.  */
if((yy[NE-1] & 0x7fff) == 0 && (yy[NE-2] & 0x8000) == 0)
  {
    unsigned short temp[NI+1];
    __emovi(yy, temp);
    __eshup1(temp);
    __emovo(temp,y);
    return;
  }
#endif
#ifdef INFINITY
/* Point to the exponent field.  */
p = &yy[NE-1];
if( *p == 0x7fff )
	{
#ifdef NANS
#ifdef IBMPC
	for( i=0; i<4; i++ )
		{
		if((i != 3 && pe[i] != 0)
		   /* Check for Intel long double infinity pattern.  */
		   || (i == 3 && pe[i] != 0x8000))
			{
			__enan_NBITS( y );
			return;
			}
		}
#else
	for( i=1; i<=4; i++ )
		{
		if( pe[i] != 0 )
			{
			__enan_NBITS( y );
			return;
			}
		}
#endif
#endif /* NANS */
	__eclear( y );
	__einfin( y );
	if( *p & 0x8000 )
		__eneg(y);
	return;
	}
#endif
p = yy;
q = y;
for( i=0; i<NE; i++ )
	*q++ = *p++;
}

#endif /* USE_LDTOA */