1 /* @(#)s_nextafter.c 5.1 93/09/24 */
2 /*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
11 */
12
13 #include <math.h>
14
15 #include "math_private.h"
16
17 float
nexttowardf(float x,long double y)18 nexttowardf(float x, long double y)
19 {
20 int32_t hx,ix;
21 int64_t hy,iy;
22 u_int64_t ly;
23
24 GET_FLOAT_WORD(hx,x);
25 GET_LDOUBLE_WORDS64(hy,ly,y);
26 ix = hx&0x7fffffff; /* |x| */
27 iy = hy&0x7fffffffffffffffLL; /* |y| */
28
29 if((ix>0x7f800000) || /* x is nan */
30 ((iy>=0x7fff000000000000LL)&&((iy-0x7fff000000000000LL)|ly)!=0))
31 /* y is nan */
32 return x+y;
33 if((long double) x==y) return y; /* x=y, return y */
34 if(ix==0) { /* x == 0 */
35 volatile float u;
36 SET_FLOAT_WORD(x,(u_int32_t)((hy>>32)&0x80000000)|1);/* return +-minsub*/
37 u = x;
38 u = u * u; /* raise underflow flag */
39 return x;
40 }
41 if(hx>=0) { /* x > 0 */
42 if(hy<0||(ix>>23)>(iy>>48)-0x3f80
43 || ((ix>>23)==(iy>>48)-0x3f80
44 && (ix&0x7fffff)>((hy>>25)&0x7fffff))) {/* x > y, x -= ulp */
45 hx -= 1;
46 } else { /* x < y, x += ulp */
47 hx += 1;
48 }
49 } else { /* x < 0 */
50 if(hy>=0||(ix>>23)>(iy>>48)-0x3f80
51 || ((ix>>23)==(iy>>48)-0x3f80
52 && (ix&0x7fffff)>((hy>>25)&0x7fffff))) {/* x < y, x -= ulp */
53 hx -= 1;
54 } else { /* x > y, x += ulp */
55 hx += 1;
56 }
57 }
58 hy = hx&0x7f800000;
59 if(hy>=0x7f800000) return x+x; /* overflow */
60 if(hy<0x00800000) {
61 volatile float u = x*x; /* underflow */
62 }
63 SET_FLOAT_WORD(x,hx);
64 return x;
65 }
66