xref: /illumos-gate/usr/src/lib/libm/common/m9x/modfl.c (revision 25c28e83beb90e7c80452a7c818c5e6f73a07dc8)
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 #if defined(ELFOBJ)
31 #pragma weak modfl = __modfl
32 #endif
33 
34 #include "libm.h"
35 
36 #if defined(__sparc)
37 
38 long double
39 __modfl(long double x, long double *iptr) {
40 	union {
41 		unsigned i[4];
42 		long double q;
43 	} xx, yy;
44 	unsigned hx, s;
45 
46 	xx.q = x;
47 	hx = xx.i[0] & ~0x80000000;
48 
49 	if (hx >= 0x406f0000) {	/* x is NaN, infinite, or integral */
50 		*iptr = x;
51 		if (hx < 0x7fff0000 || (hx == 0x7fff0000 &&
52 			(xx.i[1] | xx.i[2] | xx.i[3]) == 0)) {
53 			xx.i[0] &= 0x80000000;
54 			xx.i[1] = xx.i[2] = xx.i[3] = 0;
55 		}
56 		return (xx.q);
57 	}
58 
59 	if (hx < 0x3fff0000) {	/* |x| < 1 */
60 		xx.i[0] &= 0x80000000;
61 		xx.i[1] = xx.i[2] = xx.i[3] = 0;
62 		*iptr = xx.q;
63 		return (x);
64 	}
65 
66 	/* split x at the binary point */
67 	s = xx.i[0] & 0x80000000;
68 	if (hx < 0x40100000) {
69 		yy.i[0] = xx.i[0] & ~((1 << (0x400f - (hx >> 16))) - 1);
70 		yy.i[1] = yy.i[2] = yy.i[3] = 0;
71 	} else if (hx < 0x40300000) {
72 		yy.i[0] = xx.i[0];
73 		yy.i[1] = xx.i[1] & ~((1 << (0x402f - (hx >> 16))) - 1);
74 		yy.i[2] = yy.i[3] = 0;
75 	} else if (hx < 0x40500000) {
76 		yy.i[0] = xx.i[0];
77 		yy.i[1] = xx.i[1];
78 		yy.i[2] = xx.i[2] & ~((1 << (0x404f - (hx >> 16))) - 1);
79 		yy.i[3] = 0;
80 	} else {
81 		yy.i[0] = xx.i[0];
82 		yy.i[1] = xx.i[1];
83 		yy.i[2] = xx.i[2];
84 		yy.i[3] = xx.i[3] & ~((1 << (0x406f - (hx >> 16))) - 1);
85 	}
86 	*iptr = yy.q;
87 
88 	/*
89 	 * we could implement the following more efficiently than by using
90 	 * software emulation of fsubq, but we'll do it this way for now
91 	 * (and hope hardware support becomes commonplace)
92 	 */
93 	xx.q -= yy.q;
94 	xx.i[0] = (xx.i[0] & ~0x80000000) | s;	/* keep sign of x */
95 	return (xx.q);
96 }
97 
98 #elif defined(__x86)
99 
100 long double
101 __modfl(long double x, long double *iptr) {
102 	union {
103 		unsigned i[3];
104 		long double e;
105 	} xx, yy;
106 	unsigned hx, s;
107 
108 	/*
109 	 * It might be faster to use one of the x86 fpops instead of
110 	 * the following.
111 	 */
112 	xx.e = x;
113 	hx = xx.i[2] & 0x7fff;
114 
115 	if (hx >= 0x403e) {	/* x is NaN, infinite, or integral */
116 		*iptr = x;
117 		if (hx < 0x7fff || (hx == 0x7fff &&
118 			((xx.i[1] << 1) | xx.i[0]) == 0)) {
119 			xx.i[2] &= 0x8000;
120 			xx.i[1] = xx.i[0] = 0;
121 		}
122 		return (xx.e);
123 	}
124 
125 	if (hx < 0x3fff) {	/* |x| < 1 */
126 		xx.i[2] &= 0x8000;
127 		xx.i[1] = xx.i[0] = 0;
128 		*iptr = xx.e;
129 		return (x);
130 	}
131 
132 	/* split x at the binary point */
133 	s = xx.i[2] & 0x8000;
134 	yy.i[2] = xx.i[2];
135 	if (hx < 0x401f) {
136 		yy.i[1] = xx.i[1] & ~((1 << (0x401e - hx)) - 1);
137 		yy.i[0] = 0;
138 	} else {
139 		yy.i[1] = xx.i[1];
140 		yy.i[0] = xx.i[0] & ~((1 << (0x403e - hx)) - 1);
141 	}
142 	*iptr = yy.e;
143 	xx.e -= yy.e;
144 	xx.i[2] = (xx.i[2] & ~0x8000) | s;	/* keep sign of x */
145 	return (xx.e);
146 }
147 
148 #else
149 #error Unknown architecture
150 #endif
151