xref: /illumos-gate/usr/src/lib/libm/common/Q/nextafterl.c (revision ddc0e0b5)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
24  */
25 /*
26  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
27  * Use is subject to license terms.
28  */
29 
30 #pragma weak __nextafterl = nextafterl
31 
32 #include "libm.h"
33 #include <float.h>		/* LDBL_MAX, LDBL_MIN */
34 
35 #if defined(__sparc)
36 #define	n0	0
37 #define	n1	1
38 #define	n2	2
39 #define	n3	3
40 #define	X86PDNRM1(x)
41 #define	INC(px)	{ \
42 			if (++px[n3] == 0) \
43 				if (++px[n2] == 0) \
44 					if (++px[n1] == 0) \
45 						++px[n0]; \
46 		}
47 #define	DEC(px)	{ \
48 			if (--px[n3] == 0xffffffff) \
49 				if (--px[n2] == 0xffffffff) \
50 					if (--px[n1] == 0xffffffff) \
51 						--px[n0]; \
52 		}
53 #elif defined(__x86)
54 #define	n0	2
55 #define	n1	1
56 #define	n2	0
57 #define	n3	0
58 /*
59  * if pseudo-denormal, replace by the equivalent normal
60  */
61 #define	X86PDNRM1(x)	if (XBIASED_EXP(x) == 0 && (((int *) &x)[1] & \
62 				0x80000000) != 0) \
63 				((int *) &x)[2] |= 1
64 #define	INC(px)	{ \
65 			if (++px[n2] == 0) \
66 				if ((++px[n1] & ~0x80000000) == 0) \
67 					px[n1] = 0x80000000, ++px[n0]; \
68 		}
69 #define	DEC(px)	{ \
70 			if (--px[n2] == 0xffffffff) \
71 				if (--px[n1] == 0x7fffffff) \
72 					if ((--px[n0] & 0x7fff) != 0) \
73 						px[n1] |= 0x80000000; \
74 		}
75 #endif
76 
77 long double
nextafterl(long double x,long double y)78 nextafterl(long double x, long double y) {
79 	int *px = (int *) &x;
80 	int *py = (int *) &y;
81 
82 	if (x == y)
83 		return (y);		/* C99 requirement */
84 	if (x != x || y != y)
85 		return (x * y);
86 
87 	if (ISZEROL(x)) {	/* x == 0.0 */
88 		px[n0] = py[n0] & XSGNMSK;
89 		px[n1] = px[n2] = 0;
90 		px[n3] = 1;
91 	} else {
92 		X86PDNRM1(x);
93 		if ((px[n0] & XSGNMSK) == 0) {	/* x > 0.0 */
94 			if (x > y)	/* x > y */
95 				DEC(px)
96 			else
97 				INC(px)
98 		} else {
99 			if (x < y)	/* x < y */
100 				DEC(px)
101 			else
102 				INC(px)
103 		}
104 	}
105 #ifndef lint
106 	{
107 		volatile long double dummy;
108 		int k = XBIASED_EXP(x);
109 
110 		if (k == 0)
111 			dummy = LDBL_MIN * copysignl(LDBL_MIN, x);
112 		else if (k == 0x7fff)
113 			dummy = LDBL_MAX * copysignl(LDBL_MAX, x);
114 	}
115 #endif
116 	return (x);
117 }
118