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 nexttoward = __nexttoward
31
32 /*
33 * nexttoward(x, y) delivers the next representable number after x
34 * in the direction of y. If x and y are both zero, the result is
35 * zero with the same sign as y. If either x or y is NaN, the result
36 * is NaN.
37 *
38 * If x != y and the result is infinite, overflow is raised; if
39 * x != y and the result is subnormal or zero, underflow is raised.
40 * (This is wrong, but it's what C99 apparently wants.)
41 */
42
43 #include "libm.h"
44
45 #if defined(__sparc)
46
47 static union {
48 unsigned i[2];
49 double d;
50 } C[] = {
51 0x00100000, 0,
52 0x7fe00000, 0,
53 0x7fffffff, 0xffffffff
54 };
55
56 #define tiny C[0].d
57 #define huge C[1].d
58 #define qnan C[2].d
59
60 enum fcc_type {
61 fcc_equal = 0,
62 fcc_less = 1,
63 fcc_greater = 2,
64 fcc_unordered = 3
65 };
66
67 #ifdef __sparcv9
68 #define _Q_cmp _Qp_cmp
69 #endif
70
71 extern enum fcc_type _Q_cmp(const long double *, const long double *);
72
73 double
74 __nexttoward(double x, long double y) {
75 union {
76 unsigned i[2];
77 double d;
78 } xx;
79 union {
80 unsigned i[4];
81 long double q;
82 } yy;
83 long double lx;
84 unsigned hx;
85 volatile double dummy;
86 enum fcc_type rel;
87
88 /*
89 * It would be somewhat more efficient to check for NaN and
90 * zero operands before converting x to long double and then
91 * to code the comparison in line rather than calling _Q_cmp.
92 * However, since this code probably won't get used much,
93 * I'm opting in favor of simplicity instead.
94 */
95 lx = xx.d = x;
96 hx = (xx.i[0] & ~0x80000000) | xx.i[1];
97
98 /* check for each of four possible orderings */
99 rel = _Q_cmp(&lx, &y);
100 if (rel == fcc_unordered)
101 return (qnan);
102
103 if (rel == fcc_equal) {
104 if (hx == 0) { /* x is zero; return zero with y's sign */
105 yy.q = y;
106 xx.i[0] = yy.i[0];
107 return (xx.d);
108 }
109 return (x);
110 }
111
112 if (rel == fcc_less) {
113 if (hx == 0) { /* x is zero */
114 xx.i[0] = 0;
115 xx.i[1] = 0x00000001;
116 } else if ((int)xx.i[0] >= 0) { /* x is positive */
117 if (++xx.i[1] == 0)
118 xx.i[0]++;
119 } else {
120 if (xx.i[1]-- == 0)
121 xx.i[0]--;
122 }
123 } else {
124 if (hx == 0) { /* x is zero */
125 xx.i[0] = 0x80000000;
126 xx.i[1] = 0x00000001;
127 } else if ((int)xx.i[0] >= 0) { /* x is positive */
128 if (xx.i[1]-- == 0)
129 xx.i[0]--;
130 } else {
131 if (++xx.i[1] == 0)
132 xx.i[0]++;
133 }
134 }
135
136 /* raise exceptions as needed */
137 hx = xx.i[0] & ~0x80000000;
138 if (hx == 0x7ff00000) {
139 dummy = huge;
140 dummy *= huge;
141 } else if (hx < 0x00100000) {
142 dummy = tiny;
143 dummy *= tiny;
144 }
145
146 return (xx.d);
147 }
148
149 #elif defined(__x86)
150
151 static union {
152 unsigned i[2];
153 double d;
154 } C[] = {
155 0, 0x00100000,
156 0, 0x7fe00000,
157 };
158
159 #define tiny C[0].d
160 #define huge C[1].d
161
162 double
163 __nexttoward(double x, long double y) {
164 union {
165 unsigned i[2];
166 double d;
167 } xx;
168 unsigned hx;
169 long double lx;
170 volatile double dummy;
171
172 lx = xx.d = x;
173 hx = (xx.i[1] & ~0x80000000) | xx.i[0];
174
175 /* check for each of four possible orderings */
176 if (isunordered(lx, y))
177 return ((double) (lx + y));
178
179 if (lx == y)
180 return ((double) y);
181
182 if (lx < y) {
183 if (hx == 0) { /* x is zero */
184 xx.i[0] = 0x00000001;
185 xx.i[1] = 0;
186 } else if ((int)xx.i[1] >= 0) { /* x is positive */
187 if (++xx.i[0] == 0)
188 xx.i[1]++;
189 } else {
190 if (xx.i[0]-- == 0)
191 xx.i[1]--;
192 }
193 } else {
194 if (hx == 0) { /* x is zero */
195 xx.i[0] = 0x00000001;
196 xx.i[1] = 0x80000000;
197 } else if ((int)xx.i[1] >= 0) { /* x is positive */
198 if (xx.i[0]-- == 0)
199 xx.i[1]--;
200 } else {
201 if (++xx.i[0] == 0)
202 xx.i[1]++;
203 }
204 }
205
206 /* raise exceptions as needed */
207 hx = xx.i[1] & ~0x80000000;
208 if (hx == 0x7ff00000) {
209 dummy = huge;
210 dummy *= huge;
211 } else if (hx < 0x00100000) {
212 dummy = tiny;
213 dummy *= tiny;
214 }
215
216 return (xx.d);
217 }
218
219 #else
220 #error Unknown architecture
221 #endif