OpenLibm/ld80/s_nexttoward.c

87 lines
2.2 KiB
C
Raw Normal View History

/* @(#)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
* nexttoward(x,y)
* return the next machine floating-point number of x in the
* direction toward y.
* Special cases:
*/
#include <float.h>
#include <openlibm_math.h>
#include "math_private.h"
double
nexttoward(double x, long double y)
{
int32_t hx,ix,iy;
u_int32_t lx,hy,ly,esy;
EXTRACT_WORDS(hx,lx,x);
GET_LDOUBLE_WORDS(esy,hy,ly,y);
ix = hx&0x7fffffff; /* |x| */
iy = esy&0x7fff; /* |y| */
if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
((iy>=0x7fff)&&(hy|ly)!=0)) /* y is nan */
return x+y;
if((long double) x==y) return y; /* x=y, return y */
if((ix|lx)==0) { /* x == 0 */
volatile double u;
INSERT_WORDS(x,(esy&0x8000)<<16,1); /* return +-minsub */
u = x;
u = u * u; /* raise underflow flag */
return x;
}
if(hx>=0) { /* x > 0 */
if (esy>=0x8000||((ix>>20)&0x7ff)>iy-0x3c00
|| (((ix>>20)&0x7ff)==iy-0x3c00
&& (((hx<<11)|(lx>>21))>(hy&0x7fffffff)
|| (((hx<<11)|(lx>>21))==(hy&0x7fffffff)
&& (lx<<11)>ly)))) { /* x > y, x -= ulp */
if(lx==0) hx -= 1;
lx -= 1;
} else { /* x < y, x += ulp */
lx += 1;
if(lx==0) hx += 1;
}
} else { /* x < 0 */
if (esy<0x8000||((ix>>20)&0x7ff)>iy-0x3c00
|| (((ix>>20)&0x7ff)==iy-0x3c00
&& (((hx<<11)|(lx>>21))>(hy&0x7fffffff)
|| (((hx<<11)|(lx>>21))==(hy&0x7fffffff)
&& (lx<<11)>ly)))) {/* x < y, x -= ulp */
if(lx==0) hx -= 1;
lx -= 1;
} else { /* x > y, x += ulp */
lx += 1;
if(lx==0) hx += 1;
}
}
hy = hx&0x7ff00000;
if(hy>=0x7ff00000) {
x = x+x; /* overflow */
return x;
}
if(hy<0x00100000) {
volatile double u = x*x; /* underflow */
if(u==x) {
INSERT_WORDS(x,hx,lx);
return x;
}
}
INSERT_WORDS(x,hx,lx);
return x;
}