xref: /openbmc/linux/arch/mips/math-emu/dp_tint.c (revision 22246614)
1 /* 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 <linux/kernel.h>
29 #include "ieee754dp.h"
30 
31 int ieee754dp_tint(ieee754dp x)
32 {
33 	COMPXDP;
34 
35 	CLEARCX;
36 
37 	EXPLODEXDP;
38 	FLUSHXDP;
39 
40 	switch (xc) {
41 	case IEEE754_CLASS_SNAN:
42 	case IEEE754_CLASS_QNAN:
43 	case IEEE754_CLASS_INF:
44 		SETCX(IEEE754_INVALID_OPERATION);
45 		return ieee754si_xcpt(ieee754si_indef(), "dp_tint", x);
46 	case IEEE754_CLASS_ZERO:
47 		return 0;
48 	case IEEE754_CLASS_DNORM:
49 	case IEEE754_CLASS_NORM:
50 		break;
51 	}
52 	if (xe > 31) {
53 		/* Set invalid. We will only use overflow for floating
54 		   point overflow */
55 		SETCX(IEEE754_INVALID_OPERATION);
56 		return ieee754si_xcpt(ieee754si_indef(), "dp_tint", x);
57 	}
58 	/* oh gawd */
59 	if (xe > DP_MBITS) {
60 		xm <<= xe - DP_MBITS;
61 	} else if (xe < DP_MBITS) {
62 		u64 residue;
63 		int round;
64 		int sticky;
65 		int odd;
66 
67 		if (xe < -1) {
68 			residue = xm;
69 			round = 0;
70 			sticky = residue != 0;
71 			xm = 0;
72 		}
73 		else {
74 			residue = xm << (64 - DP_MBITS + xe);
75 			round = (residue >> 63) != 0;
76 			sticky = (residue << 1) != 0;
77 			xm >>= DP_MBITS - xe;
78 		}
79 		/* Note: At this point upper 32 bits of xm are guaranteed
80 		   to be zero */
81 		odd = (xm & 0x1) != 0x0;
82 		switch (ieee754_csr.rm) {
83 		case IEEE754_RN:
84 			if (round && (sticky || odd))
85 				xm++;
86 			break;
87 		case IEEE754_RZ:
88 			break;
89 		case IEEE754_RU:	/* toward +Infinity */
90 			if ((round || sticky) && !xs)
91 				xm++;
92 			break;
93 		case IEEE754_RD:	/* toward -Infinity */
94 			if ((round || sticky) && xs)
95 				xm++;
96 			break;
97 		}
98 		/* look for valid corner case 0x80000000 */
99 		if ((xm >> 31) != 0 && (xs == 0 || xm != 0x80000000)) {
100 			/* This can happen after rounding */
101 			SETCX(IEEE754_INVALID_OPERATION);
102 			return ieee754si_xcpt(ieee754si_indef(), "dp_tint", x);
103 		}
104 		if (round || sticky)
105 			SETCX(IEEE754_INEXACT);
106 	}
107 	if (xs)
108 		return -xm;
109 	else
110 		return xm;
111 }
112 
113 
114 unsigned int ieee754dp_tuns(ieee754dp x)
115 {
116 	ieee754dp hb = ieee754dp_1e31();
117 
118 	/* what if x < 0 ?? */
119 	if (ieee754dp_lt(x, hb))
120 		return (unsigned) ieee754dp_tint(x);
121 
122 	return (unsigned) ieee754dp_tint(ieee754dp_sub(x, hb)) |
123 	    ((unsigned) 1 << 31);
124 }
125