xref: /titanic_41/usr/src/lib/libm/common/m9x/modfl.c (revision 9ea11b96f9f71eef4f1bd2062ea054451a32a216)
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 modfl = __modfl
31 
32 #include "libm.h"
33 
34 #if defined(__sparc)
35 
36 long double
37 __modfl(long double x, long double *iptr) {
38 	union {
39 		unsigned i[4];
40 		long double q;
41 	} xx, yy;
42 	unsigned hx, s;
43 
44 	xx.q = x;
45 	hx = xx.i[0] & ~0x80000000;
46 
47 	if (hx >= 0x406f0000) {	/* x is NaN, infinite, or integral */
48 		*iptr = x;
49 		if (hx < 0x7fff0000 || (hx == 0x7fff0000 &&
50 			(xx.i[1] | xx.i[2] | xx.i[3]) == 0)) {
51 			xx.i[0] &= 0x80000000;
52 			xx.i[1] = xx.i[2] = xx.i[3] = 0;
53 		}
54 		return (xx.q);
55 	}
56 
57 	if (hx < 0x3fff0000) {	/* |x| < 1 */
58 		xx.i[0] &= 0x80000000;
59 		xx.i[1] = xx.i[2] = xx.i[3] = 0;
60 		*iptr = xx.q;
61 		return (x);
62 	}
63 
64 	/* split x at the binary point */
65 	s = xx.i[0] & 0x80000000;
66 	if (hx < 0x40100000) {
67 		yy.i[0] = xx.i[0] & ~((1 << (0x400f - (hx >> 16))) - 1);
68 		yy.i[1] = yy.i[2] = yy.i[3] = 0;
69 	} else if (hx < 0x40300000) {
70 		yy.i[0] = xx.i[0];
71 		yy.i[1] = xx.i[1] & ~((1 << (0x402f - (hx >> 16))) - 1);
72 		yy.i[2] = yy.i[3] = 0;
73 	} else if (hx < 0x40500000) {
74 		yy.i[0] = xx.i[0];
75 		yy.i[1] = xx.i[1];
76 		yy.i[2] = xx.i[2] & ~((1 << (0x404f - (hx >> 16))) - 1);
77 		yy.i[3] = 0;
78 	} else {
79 		yy.i[0] = xx.i[0];
80 		yy.i[1] = xx.i[1];
81 		yy.i[2] = xx.i[2];
82 		yy.i[3] = xx.i[3] & ~((1 << (0x406f - (hx >> 16))) - 1);
83 	}
84 	*iptr = yy.q;
85 
86 	/*
87 	 * we could implement the following more efficiently than by using
88 	 * software emulation of fsubq, but we'll do it this way for now
89 	 * (and hope hardware support becomes commonplace)
90 	 */
91 	xx.q -= yy.q;
92 	xx.i[0] = (xx.i[0] & ~0x80000000) | s;	/* keep sign of x */
93 	return (xx.q);
94 }
95 
96 #elif defined(__x86)
97 
98 long double
99 __modfl(long double x, long double *iptr) {
100 	union {
101 		unsigned i[3];
102 		long double e;
103 	} xx, yy;
104 	unsigned hx, s;
105 
106 	/*
107 	 * It might be faster to use one of the x86 fpops instead of
108 	 * the following.
109 	 */
110 	xx.e = x;
111 	hx = xx.i[2] & 0x7fff;
112 
113 	if (hx >= 0x403e) {	/* x is NaN, infinite, or integral */
114 		*iptr = x;
115 		if (hx < 0x7fff || (hx == 0x7fff &&
116 			((xx.i[1] << 1) | xx.i[0]) == 0)) {
117 			xx.i[2] &= 0x8000;
118 			xx.i[1] = xx.i[0] = 0;
119 		}
120 		return (xx.e);
121 	}
122 
123 	if (hx < 0x3fff) {	/* |x| < 1 */
124 		xx.i[2] &= 0x8000;
125 		xx.i[1] = xx.i[0] = 0;
126 		*iptr = xx.e;
127 		return (x);
128 	}
129 
130 	/* split x at the binary point */
131 	s = xx.i[2] & 0x8000;
132 	yy.i[2] = xx.i[2];
133 	if (hx < 0x401f) {
134 		yy.i[1] = xx.i[1] & ~((1 << (0x401e - hx)) - 1);
135 		yy.i[0] = 0;
136 	} else {
137 		yy.i[1] = xx.i[1];
138 		yy.i[0] = xx.i[0] & ~((1 << (0x403e - hx)) - 1);
139 	}
140 	*iptr = yy.e;
141 	xx.e -= yy.e;
142 	xx.i[2] = (xx.i[2] & ~0x8000) | s;	/* keep sign of x */
143 	return (xx.e);
144 }
145 
146 #else
147 #error Unknown architecture
148 #endif
149