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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* IEEE754 floating point arithmetic
2 * double precision: common utilities
3 */
4/*
5 * MIPS floating point support
6 * Copyright (C) 1994-2000 Algorithmics Ltd.
7 * http://www.algor.co.uk
8 *
9 * ########################################################################
10 *
11 * This program is free software; you can distribute it and/or modify it
12 * under the terms of the GNU General Public License (Version 2) as
13 * published by the Free Software Foundation.
14 *
15 * This program is distributed in the hope it will be useful, but WITHOUT
16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
17 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 * for more details.
19 *
20 * You should have received a copy of the GNU General Public License along
21 * with this program; if not, write to the Free Software Foundation, Inc.,
22 * 59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
23 *
24 * ########################################################################
25 */
26
27
28#include "ieee754dp.h"
29
30s64 ieee754dp_tlong(ieee754dp x)
31{
32 COMPXDP;
33
34 CLEARCX;
35
36 EXPLODEXDP;
37 FLUSHXDP;
38
39 switch (xc) {
40 case IEEE754_CLASS_SNAN:
41 case IEEE754_CLASS_QNAN:
42 case IEEE754_CLASS_INF:
43 SETCX(IEEE754_INVALID_OPERATION);
44 return ieee754di_xcpt(ieee754di_indef(), "dp_tlong", x);
45 case IEEE754_CLASS_ZERO:
46 return 0;
47 case IEEE754_CLASS_DNORM:
48 case IEEE754_CLASS_NORM:
49 break;
50 }
51 if (xe >= 63) {
52 /* look for valid corner case */
53 if (xe == 63 && xs && xm == DP_HIDDEN_BIT)
54 return -0x8000000000000000LL;
55 /* Set invalid. We will only use overflow for floating
56 point overflow */
57 SETCX(IEEE754_INVALID_OPERATION);
58 return ieee754di_xcpt(ieee754di_indef(), "dp_tlong", x);
59 }
60 /* oh gawd */
61 if (xe > DP_MBITS) {
62 xm <<= xe - DP_MBITS;
63 } else if (xe < DP_MBITS) {
64 u64 residue;
65 int round;
66 int sticky;
67 int odd;
68
69 if (xe < -1) {
70 residue = xm;
71 round = 0;
72 sticky = residue != 0;
73 xm = 0;
74 }
75 else {
76 /* Shifting a u64 64 times does not work,
77 * so we do it in two steps. Be aware that xe
78 * may be -1 */
79 residue = xm << (xe + 1);
80 residue <<= 63 - DP_MBITS;
81 round = (residue >> 63) != 0;
82 sticky = (residue << 1) != 0;
83 xm >>= DP_MBITS - xe;
84 }
85 odd = (xm & 0x1) != 0x0;
86 switch (ieee754_csr.rm) {
87 case IEEE754_RN:
88 if (round && (sticky || odd))
89 xm++;
90 break;
91 case IEEE754_RZ:
92 break;
93 case IEEE754_RU: /* toward +Infinity */
94 if ((round || sticky) && !xs)
95 xm++;
96 break;
97 case IEEE754_RD: /* toward -Infinity */
98 if ((round || sticky) && xs)
99 xm++;
100 break;
101 }
102 if ((xm >> 63) != 0) {
103 /* This can happen after rounding */
104 SETCX(IEEE754_INVALID_OPERATION);
105 return ieee754di_xcpt(ieee754di_indef(), "dp_tlong", x);
106 }
107 if (round || sticky)
108 SETCX(IEEE754_INEXACT);
109 }
110 if (xs)
111 return -xm;
112 else
113 return xm;
114}
115
116
117u64 ieee754dp_tulong(ieee754dp x)
118{
119 ieee754dp hb = ieee754dp_1e63();
120
121 /* what if x < 0 ?? */
122 if (ieee754dp_lt(x, hb))
123 return (u64) ieee754dp_tlong(x);
124
125 return (u64) ieee754dp_tlong(ieee754dp_sub(x, hb)) |
126 (1ULL << 63);
127}