glibc/sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c

/* s_nextafterl.c -- long double version of s_nextafter.c.
 * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: $";
#endif

/* IEEE functions
 *	nextafterl(x,y)
 *	return the next machine floating-point number of x in the
 *	direction toward y.
 *   Special cases:
 */

#include <math.h>
#include <math_private.h>
#include <math_ldbl_opt.h>

long double __nextafterl(long double x, long double y)
{
	int64_t hx,hy,ihx,ihy;
	uint64_t lx;
	double xhi, xlo, yhi;

	ldbl_unpack (x, &xhi, &xlo);
	EXTRACT_WORDS64 (hx, xhi);
	EXTRACT_WORDS64 (lx, xlo);
	yhi = ldbl_high (y);
	EXTRACT_WORDS64 (hy, yhi);
	ihx = hx&0x7fffffffffffffffLL;		/* |hx| */
	ihy = hy&0x7fffffffffffffffLL;		/* |hy| */

	if((ihx>0x7ff0000000000000LL) ||	/* x is nan */
	   (ihy>0x7ff0000000000000LL))		/* y is nan */
	    return x+y; /* signal the nan */
	if(x==y)
	    return y;		/* x=y, return y */
	if(ihx == 0) {				/* x == 0 */
	    long double u;			/* return +-minsubnormal */
	    hy = (hy & 0x8000000000000000ULL) | 1;
	    INSERT_WORDS64 (yhi, hy);
	    x = yhi;
	    u = math_opt_barrier (x);
	    u = u * u;
	    math_force_eval (u);		/* raise underflow flag */
	    return x;
	}

	long double u;
	if(x > y) {	/* x > y, x -= ulp */
	    /* This isn't the largest magnitude correctly rounded
	       long double as you can see from the lowest mantissa
	       bit being zero.  It is however the largest magnitude
	       long double with a 106 bit mantissa, and nextafterl
	       is insane with variable precision.  So to make
	       nextafterl sane we assume 106 bit precision.  */
	    if((hx==0xffefffffffffffffLL)&&(lx==0xfc8ffffffffffffeLL))
	      return x+x;	/* overflow, return -inf */
	    if (hx >= 0x7ff0000000000000LL) {
	      u = 0x1.fffffffffffff7ffffffffffff8p+1023L;
	      return u;
	    }
	    if(ihx <= 0x0360000000000000LL) {  /* x <= LDBL_MIN */
	      u = math_opt_barrier (x);
	      x -= __LDBL_DENORM_MIN__;
	      if (ihx < 0x0360000000000000LL
		  || (hx > 0 && (int64_t) lx <= 0)
		  || (hx < 0 && (int64_t) lx > 1)) {
		u = u * u;
		math_force_eval (u);		/* raise underflow flag */
	      }
	      return x;
	    }
	    if (ihx < 0x06a0000000000000LL) { /* ulp will denormal */
	      INSERT_WORDS64 (yhi, hx & (0x7ffLL<<52));
	      u = yhi;
	      u *= 0x1.0000000000000p-105L;
	    } else {
	      INSERT_WORDS64 (yhi, (hx & (0x7ffLL<<52))-(0x069LL<<52));
	      u = yhi;
	    }
	    return x - u;
	} else {				/* x < y, x += ulp */
	    if((hx==0x7fefffffffffffffLL)&&(lx==0x7c8ffffffffffffeLL))
	      return x+x;	/* overflow, return +inf */
	    if ((uint64_t) hx >= 0xfff0000000000000ULL) {
	      u = -0x1.fffffffffffff7ffffffffffff8p+1023L;
	      return u;
	    }
	    if(ihx <= 0x0360000000000000LL) {  /* x <= LDBL_MIN */
	      u = math_opt_barrier (x);
	      x += __LDBL_DENORM_MIN__;
	      if (ihx < 0x0360000000000000LL
		  || (hx > 0 && (int64_t) lx < 0 && lx != 0x8000000000000001LL)
		  || (hx < 0 && (int64_t) lx >= 0)) {
		u = u * u;
		math_force_eval (u);		/* raise underflow flag */
	      }
	      if (x == 0.0L)	/* handle negative __LDBL_DENORM_MIN__ case */
		x = -0.0L;
	      return x;
	    }
	    if (ihx < 0x06a0000000000000LL) { /* ulp will denormal */
	      INSERT_WORDS64 (yhi, hx & (0x7ffLL<<52));
	      u = yhi;
	      u *= 0x1.0000000000000p-105L;
	    } else {
	      INSERT_WORDS64 (yhi, (hx & (0x7ffLL<<52))-(0x069LL<<52));
	      u = yhi;
	    }
	    return x + u;
	}
}
strong_alias (__nextafterl, __nexttowardl)
long_double_symbol (libm, __nextafterl, nextafterl);
long_double_symbol (libm, __nexttowardl, nexttowardl);