1
2
3
4
5
6
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
|
/* origin: FreeBSD /usr/src/lib/msun/src/s_floor.c */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/*
* floor(x)
* Return x rounded toward -inf to integral value
* Method:
* Bit twiddling.
* Exception:
* Inexact flag raised if x not equal to floor(x).
*/
#include "libm.h"
static const double huge = 1.0e300;
double floor(double x)
{
int32_t i0,i1,j0;
uint32_t i,j;
EXTRACT_WORDS(i0, i1, x);
// FIXME: signed shift
j0 = ((i0>>20)&0x7ff) - 0x3ff;
if (j0 < 20) {
if (j0 < 0) { /* |x| < 1 */
/* raise inexact if x != 0 */
if (huge+x > 0.0) {
if (i0 >= 0) { /* x >= 0 */
i0 = i1 = 0;
} else if (((i0&0x7fffffff)|i1) != 0) {
i0 = 0xbff00000;
i1 = 0;
}
}
} else {
i = 0x000fffff>>j0;
if (((i0&i)|i1) == 0)
return x; /* x is integral */
/* raise inexact flag */
if (huge+x > 0.0) {
if (i0 < 0)
i0 += 0x00100000>>j0;
i0 &= ~i;
i1=0;
}
}
} else if (j0 > 51) {
if (j0 == 0x400)
return x+x; /* inf or NaN */
else
return x; /* x is integral */
} else {
i = ((uint32_t)(0xffffffff))>>(j0-20);
if ((i1&i) == 0)
return x; /* x is integral */
/* raise inexact flag */
if (huge+x > 0.0) {
if (i0 < 0) {
if (j0 == 20)
i0+=1;
else {
j = i1+(1<<(52-j0));
if (j < i1)
i0 += 1; /* got a carry */
i1 = j;
}
}
i1 &= ~i;
}
}
INSERT_WORDS(x, i0, i1);
return x;
}
|
