1 /* $NetBSD: s_nexttowardf.c,v 1.5 2024/05/05 14:06:47 riastradh Exp $ */
2
3 /*
4 * ====================================================
5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 *
7 * Developed at SunPro, a Sun Microsystems, Inc. business.
8 * Permission to use, copy, modify, and distribute this
9 * software is freely granted, provided that this notice
10 * is preserved.
11 * ====================================================
12 */
13
14 #include <sys/cdefs.h>
15 #if 0
16 __FBSDID("$FreeBSD: src/lib/msun/src/s_nexttowardf.c,v 1.3 2011/02/10 07:38:38 das Exp $");
17 #else
18 __RCSID("$NetBSD: s_nexttowardf.c,v 1.5 2024/05/05 14:06:47 riastradh Exp $");
19 #endif
20
21 #include <string.h>
22 #include <float.h>
23 #include <machine/ieee.h>
24
25 #include "math.h"
26 #include "math_private.h"
27
28 /*
29 * On ports where long double is just double, reuse the ieee_double_u
30 * union as if it were ieee_ext_u -- broken-down components of (long)
31 * double values.
32 */
33 #ifndef __HAVE_LONG_DOUBLE
34 #define ieee_ext_u ieee_double_u
35 #define extu_ld dblu_d
36 #define extu_ext dblu_dbl
37 #define ext_sign dbl_sign
38 #define ext_exp dbl_exp
39 #define ext_frach dbl_frach
40 #define ext_fracl dbl_fracl
41 #define EXT_EXP_INFNAN DBL_EXP_INFNAN
42 #define LDBL_NBIT 0
43 #endif
44
45 /*
46 * XXX We should arrange to define LDBL_NBIT unconditionally in the
47 * appropriate MD header file.
48 */
49 #ifdef LDBL_IMPLICIT_NBIT
50 #define LDBL_NBIT 0
51 #endif
52
53 float
nexttowardf(float x,long double y)54 nexttowardf(float x, long double y)
55 {
56 volatile float t;
57 int32_t hx,ix;
58 union ieee_ext_u uy;
59
60 GET_FLOAT_WORD(hx,x);
61 ix = hx&0x7fffffff; /* |x| */
62
63 memset(&uy, 0, sizeof(uy));
64 uy.extu_ld = y;
65 uy.extu_ext.ext_frach &= ~LDBL_NBIT;
66
67 if((ix>0x7f800000) ||
68 (uy.extu_ext.ext_exp == EXT_EXP_INFNAN &&
69 (uy.extu_ext.ext_frach | uy.extu_ext.ext_fracl) != 0))
70 return x+y; /* x or y is nan */
71 if(x==y) return (float)y; /* x=y, return y */
72 if(ix==0) { /* x == 0 */
73 SET_FLOAT_WORD(x,(uy.extu_ext.ext_sign<<31)|1);/* return +-minsubnormal */
74 t = x*x;
75 if(t==x) return t; else return x; /* raise underflow flag */
76 }
77 if((hx >= 0) ^ (x < y)) /* x -= ulp */
78 hx -= 1;
79 else /* x += ulp */
80 hx += 1;
81 ix = hx&0x7f800000;
82 if(ix>=0x7f800000) return x+x; /* overflow */
83 if(ix<0x00800000) { /* underflow */
84 t = x*x;
85 if(t!=x) { /* raise underflow flag */
86 SET_FLOAT_WORD(x,hx);
87 return x;
88 }
89 }
90 SET_FLOAT_WORD(x,hx);
91 return x;
92 }
93