xref: /openbsd-src/lib/libm/src/ld128/s_nextafterl.c (revision 2f2c00629eff6a304ebffb255fc56f4fa7a1833b)

/* @(#)s_nextafter.c 5.1 93/09/24 */
/*
 * ====================================================
 * 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.
 * ====================================================
 */

/* 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"

long double
nextafterl(long double x, long double y)
{
	int64_t hx,hy,ix,iy;
	u_int64_t lx,ly;

	GET_LDOUBLE_WORDS64(hx,lx,x);
	GET_LDOUBLE_WORDS64(hy,ly,y);
	ix = hx&0x7fffffffffffffffLL;		/* |x| */
	iy = hy&0x7fffffffffffffffLL;		/* |y| */

	if(((ix>=0x7fff000000000000LL)&&((ix-0x7fff000000000000LL)|lx)!=0) ||   /* x is nan */
	   ((iy>=0x7fff000000000000LL)&&((iy-0x7fff000000000000LL)|ly)!=0))     /* y is nan */
	   return x+y;
	if(x==y) return y;		/* x=y, return y */
	if((ix|lx)==0) {			/* x == 0 */
	    volatile long double u;
	    SET_LDOUBLE_WORDS64(x,hy&0x8000000000000000ULL,1);/* return +-minsubnormal */
	    u = x;
	    u = u * u;				/* raise underflow flag */
	    return x;
	}
	if(hx>=0) {			/* x > 0 */
	    if(hx>hy||((hx==hy)&&(lx>ly))) {	/* x > y, x -= ulp */
		if(lx==0) hx--;
		lx--;
	    } else {				/* x < y, x += ulp */
		lx++;
		if(lx==0) hx++;
	    }
	} else {				/* x < 0 */
	    if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
		if(lx==0) hx--;
		lx--;
	    } else {				/* x > y, x += ulp */
		lx++;
		if(lx==0) hx++;
	    }
	}
	hy = hx&0x7fff000000000000LL;
	if(hy==0x7fff000000000000LL) return x+x;/* overflow  */
	if(hy==0) {
	    volatile long double u = x*x;	/* underflow */
	}
	SET_LDOUBLE_WORDS64(x,hx,lx);
	return x;
}
DEF_STD(nextafterl);
MAKE_UNUSED_CLONE(nexttowardl, nextafterl);