Eric Lee / smarc-fsl-linux-kernel

Blame view

arch/mips/math-emu/sp_sqrt.c 2.6 KB
edit raw normal view history
1da177e4c   Linus Torvalds   Linux-2.6.12-rc2 
1
2
3
4
5
6
 
  /* IEEE754 floating point arithmetic
   * single precision square root
   */
  /*
   * MIPS floating point support
   * Copyright (C) 1994-2000 Algorithmics Ltd.
1da177e4c   Linus Torvalds   Linux-2.6.12-rc2 
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
 
   *
   * ########################################################################
   *
   *  This program is free software; you can distribute it and/or modify it
   *  under the terms of the GNU General Public License (Version 2) as
   *  published by the Free Software Foundation.
   *
   *  This program is distributed in the hope it will be useful, but WITHOUT
   *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   *  for more details.
   *
   *  You should have received a copy of the GNU General Public License along
   *  with this program; if not, write to the Free Software Foundation, Inc.,
   *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
   *
   * ########################################################################
   */
  
  
  #include "ieee754sp.h"
  
  ieee754sp ieee754sp_sqrt(ieee754sp x)
  {
  	int ix, s, q, m, t, i;
  	unsigned int r;
  	COMPXSP;
  
  	/* take care of Inf and NaN */
  
  	EXPLODEXSP;
  	CLEARCX;
  	FLUSHXSP;
  
  	/* x == INF or NAN? */
  	switch (xc) {
  	case IEEE754_CLASS_QNAN:
  		/* sqrt(Nan) = Nan */
  		return ieee754sp_nanxcpt(x, "sqrt");
  	case IEEE754_CLASS_SNAN:
  		SETCX(IEEE754_INVALID_OPERATION);
  		return ieee754sp_nanxcpt(ieee754sp_indef(), "sqrt");
  	case IEEE754_CLASS_ZERO:
  		/* sqrt(0) = 0 */
  		return x;
  	case IEEE754_CLASS_INF:
  		if (xs) {
  			/* sqrt(-Inf) = Nan */
  			SETCX(IEEE754_INVALID_OPERATION);
  			return ieee754sp_nanxcpt(ieee754sp_indef(), "sqrt");
  		}
  		/* sqrt(+Inf) = Inf */
  		return x;
  	case IEEE754_CLASS_DNORM:
  	case IEEE754_CLASS_NORM:
  		if (xs) {
  			/* sqrt(-x) = Nan */
  			SETCX(IEEE754_INVALID_OPERATION);
  			return ieee754sp_nanxcpt(ieee754sp_indef(), "sqrt");
  		}
  		break;
  	}
  
  	ix = x.bits;
  
  	/* normalize x */
  	m = (ix >> 23);
  	if (m == 0) {		/* subnormal x */
  		for (i = 0; (ix & 0x00800000) == 0; i++)
  			ix <<= 1;
  		m -= i - 1;
  	}
  	m -= 127;		/* unbias exponent */
  	ix = (ix & 0x007fffff) | 0x00800000;
  	if (m & 1)		/* odd m, double x to make it even */
  		ix += ix;
  	m >>= 1;		/* m = [m/2] */
  
  	/* generate sqrt(x) bit by bit */
  	ix += ix;
  	q = s = 0;		/* q = sqrt(x) */
  	r = 0x01000000;		/* r = moving bit from right to left */
  
  	while (r != 0) {
  		t = s + r;
  		if (t <= ix) {
  			s = t + r;
  			ix -= t;
  			q += r;
  		}
  		ix += ix;
  		r >>= 1;
  	}
  
  	if (ix != 0) {
  		SETCX(IEEE754_INEXACT);
  		switch (ieee754_csr.rm) {
  		case IEEE754_RP:
  			q += 2;
  			break;
  		case IEEE754_RN:
  			q += (q & 1);
  			break;
  		}
  	}
  	ix = (q >> 1) + 0x3f000000;
  	ix += (m << 23);
  	x.bits = ix;
  	return x;
  }