xref: /illumos-gate/usr/src/lib/libc/sparc/fp/_Q_scl.c (revision 7c478bd9)
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, Version 1.0 only
6  * (the "License").  You may not use this file except in compliance
7  * with the License.
8  *
9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10  * or http://www.opensolaris.org/os/licensing.
11  * See the License for the specific language governing permissions
12  * and limitations under the License.
13  *
14  * When distributing Covered Code, include this CDDL HEADER in each
15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16  * If applicable, add the following below this CDDL HEADER, with the
17  * fields enclosed by brackets "[]" replaced with your own identifying
18  * information: Portions Copyright [yyyy] [name of copyright owner]
19  *
20  * CDDL HEADER END
21  */
22 /*
23  * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 #pragma ident	"%Z%%M%	%I%	%E% SMI"
28 
29 #if !defined(sparc) && !defined(__sparc)
30 #error This code is for SPARC only
31 #endif
32 
33 /*
34  * _Q_scl(x, n) sets *x = *x * 2^n.
35  *
36  * This routine tacitly assumes the result will be either zero
37  * or normal, so there is no need to raise any exceptions.
38  */
39 void
_Q_scl(long double * x,int n)40 _Q_scl(long double *x, int n)
41 {
42 	union {
43 		unsigned int	i[4];
44 		long double	q;
45 	} xx;
46 	int	hx;
47 
48 	xx.q = *x;
49 	hx = xx.i[0] & ~0x80000000;
50 
51 	if (hx < 0x10000) { /* x is zero or subnormal */
52 		if ((hx | xx.i[1] | xx.i[2] | xx.i[3]) == 0)
53 			return;
54 
55 		/* normalize x */
56 		while (hx == 0 && xx.i[1] < 0x10000) {
57 			hx = xx.i[1];
58 			xx.i[1] = xx.i[2];
59 			xx.i[2] = xx.i[3];
60 			xx.i[3] = 0;
61 			n -= 32;
62 		}
63 		while (hx < 0x10000) {
64 			hx = (hx << 1) | (xx.i[1] >> 31);
65 			xx.i[1] = (xx.i[1] << 1) | (xx.i[2] >> 31);
66 			xx.i[2] = (xx.i[2] << 1) | (xx.i[3] >> 31);
67 			xx.i[3] <<= 1;
68 			n--;
69 		}
70 		xx.i[0] = hx | (xx.i[0] & 0x80000000);
71 	}
72 
73 	if ((hx >> 16) + n < 1) {
74 		/* for subnormal result, just deliver zero */
75 		xx.i[0] = xx.i[0] & 0x80000000;
76 		xx.i[1] = xx.i[2] = xx.i[3] = 0;
77 	} else
78 		xx.i[0] += (n << 16);
79 	*x = xx.q;
80 }
81 
82 static const union {
83 	int		i[4];
84 	long double	q;
85 } consts[2] = {
86 	{ 0x7ffe0000, 0, 0, 0 },
87 	{ 0x00010000, 0, 0, 0 }
88 };
89 
90 /*
91  * _Q_scle(x, n) sets *x = *x * 2^n, raising overflow or underflow
92  * as appropriate.
93  *
94  * This routine tacitly assumes the argument is either zero or normal.
95  */
96 void
_Q_scle(long double * x,int n)97 _Q_scle(long double *x, int n)
98 {
99 	union {
100 		unsigned int	i[4];
101 		long double	q;
102 	} xx;
103 	int	hx;
104 
105 	xx.q = *x;
106 	hx = (xx.i[0] >> 16) & 0x7fff;
107 
108 	if (hx == 0) /* x must be zero */
109 		return;
110 
111 	hx += n;
112 	if (hx >= 0x7fff) { /* overflow */
113 		xx.i[0] = 0x7ffe0000 | (xx.i[0] & 0x80000000);
114 		xx.i[1] = xx.i[2] = xx.i[3] = 0;
115 		xx.q *= consts[0].q;
116 	} else if (hx < 1) { /* possible underflow */
117 		if (hx < -112) {
118 			xx.i[0] = 0x00010000 | (xx.i[0] & 0x80000000);
119 			xx.i[1] = xx.i[2] = xx.i[3] = 0;
120 		} else {
121 			xx.i[0] = (0x3ffe0000 + (hx << 16)) |
122 				(xx.i[0] & 0x8000ffff);
123 		}
124 		xx.q *= consts[1].q;
125 	} else
126 		xx.i[0] += (n << 16);
127 
128 	*x = xx.q;
129 }
130