1*05a0b428SJohn Marino /* @(#)s_nextafter.c 5.1 93/09/24 */
2*05a0b428SJohn Marino /*
3*05a0b428SJohn Marino * ====================================================
4*05a0b428SJohn Marino * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5*05a0b428SJohn Marino *
6*05a0b428SJohn Marino * Developed at SunPro, a Sun Microsystems, Inc. business.
7*05a0b428SJohn Marino * Permission to use, copy, modify, and distribute this
8*05a0b428SJohn Marino * software is freely granted, provided that this notice
9*05a0b428SJohn Marino * is preserved.
10*05a0b428SJohn Marino * ====================================================
11*05a0b428SJohn Marino */
12*05a0b428SJohn Marino
13*05a0b428SJohn Marino /* IEEE functions
14*05a0b428SJohn Marino * nexttowardf(x,y)
15*05a0b428SJohn Marino * return the next machine floating-point number of x in the
16*05a0b428SJohn Marino * direction toward y.
17*05a0b428SJohn Marino * This is for machines which use the same binary type for double and
18*05a0b428SJohn Marino * long double.
19*05a0b428SJohn Marino * Special cases:
20*05a0b428SJohn Marino */
21*05a0b428SJohn Marino
22*05a0b428SJohn Marino #include <math.h>
23*05a0b428SJohn Marino #include <float.h>
24*05a0b428SJohn Marino
25*05a0b428SJohn Marino #include "math_private.h"
26*05a0b428SJohn Marino
27*05a0b428SJohn Marino float
nexttowardf(float x,long double y)28*05a0b428SJohn Marino nexttowardf(float x, long double y)
29*05a0b428SJohn Marino {
30*05a0b428SJohn Marino int32_t hx,hy,ix,iy;
31*05a0b428SJohn Marino u_int32_t ly;
32*05a0b428SJohn Marino
33*05a0b428SJohn Marino GET_FLOAT_WORD(hx,x);
34*05a0b428SJohn Marino EXTRACT_WORDS(hy,ly,y);
35*05a0b428SJohn Marino ix = hx&0x7fffffff; /* |x| */
36*05a0b428SJohn Marino iy = hy&0x7fffffff; /* |y| */
37*05a0b428SJohn Marino
38*05a0b428SJohn Marino if((ix>0x7f800000) || /* x is nan */
39*05a0b428SJohn Marino ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */
40*05a0b428SJohn Marino return x+y;
41*05a0b428SJohn Marino if((long double) x==y) return y; /* x=y, return y */
42*05a0b428SJohn Marino if(ix==0) { /* x == 0 */
43*05a0b428SJohn Marino volatile float u;
44*05a0b428SJohn Marino SET_FLOAT_WORD(x,(u_int32_t)(hy&0x80000000)|1);/* return +-minsub*/
45*05a0b428SJohn Marino u = x;
46*05a0b428SJohn Marino u = u * u; /* raise underflow flag */
47*05a0b428SJohn Marino return x;
48*05a0b428SJohn Marino }
49*05a0b428SJohn Marino if(hx>=0) { /* x > 0 */
50*05a0b428SJohn Marino if(hy<0||(ix>>23)>(iy>>20)-0x380
51*05a0b428SJohn Marino || ((ix>>23)==(iy>>20)-0x380
52*05a0b428SJohn Marino && (ix&0x7fffff)>(((hy<<3)|(ly>>29))&0x7fffff))) /* x > y, x -= ulp */
53*05a0b428SJohn Marino hx -= 1;
54*05a0b428SJohn Marino else /* x < y, x += ulp */
55*05a0b428SJohn Marino hx += 1;
56*05a0b428SJohn Marino } else { /* x < 0 */
57*05a0b428SJohn Marino if(hy>=0||(ix>>23)>(iy>>20)-0x380
58*05a0b428SJohn Marino || ((ix>>23)==(iy>>20)-0x380
59*05a0b428SJohn Marino && (ix&0x7fffff)>(((hy<<3)|(ly>>29))&0x7fffff))) /* x < y, x -= ulp */
60*05a0b428SJohn Marino hx -= 1;
61*05a0b428SJohn Marino else /* x > y, x += ulp */
62*05a0b428SJohn Marino hx += 1;
63*05a0b428SJohn Marino }
64*05a0b428SJohn Marino hy = hx&0x7f800000;
65*05a0b428SJohn Marino if(hy>=0x7f800000) {
66*05a0b428SJohn Marino x = x+x; /* overflow */
67*05a0b428SJohn Marino return x;
68*05a0b428SJohn Marino }
69*05a0b428SJohn Marino if(hy<0x00800000) {
70*05a0b428SJohn Marino volatile float u = x*x; /* underflow */
71*05a0b428SJohn Marino if(u==x) {
72*05a0b428SJohn Marino SET_FLOAT_WORD(x,hx);
73*05a0b428SJohn Marino return x;
74*05a0b428SJohn Marino }
75*05a0b428SJohn Marino }
76*05a0b428SJohn Marino SET_FLOAT_WORD(x,hx);
77*05a0b428SJohn Marino return x;
78*05a0b428SJohn Marino }
79