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
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
|
/* origin: FreeBSD /usr/src/lib/msun/src/e_fmodf.c */
/*
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
*/
/*
* ====================================================
* 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.
* ====================================================
*/
/*
* fmodf(x,y)
* Return x mod y in exact arithmetic
* Method: shift and subtract
*/
#include "libm.h"
static const float one = 1.0, Zero[] = {0.0, -0.0,};
float fmodf(float x, float y)
{
int32_t n,hx,hy,hz,ix,iy,sx,i;
GET_FLOAT_WORD(hx, x);
GET_FLOAT_WORD(hy, y);
sx = hx & 0x80000000; /* sign of x */
hx ^= sx; /* |x| */
hy &= 0x7fffffff; /* |y| */
/* purge off exception values */
if (hy == 0 || hx >= 0x7f800000 || /* y=0,or x not finite */
hy > 0x7f800000) /* or y is NaN */
return (x*y)/(x*y);
if (hx < hy) /* |x| < |y| */
return x;
if (hx == hy) /* |x| = |y|, return x*0 */
return Zero[(uint32_t)sx>>31];
/* determine ix = ilogb(x) */
if (hx < 0x00800000) { /* subnormal x */
for (ix = -126, i = hx<<8; i > 0; i <<= 1)
ix -= 1;
} else
ix = (hx>>23) - 127;
/* determine iy = ilogb(y) */
if (hy < 0x00800000) { /* subnormal y */
for (iy = -126, i = hy<<8; i >= 0; i <<= 1)
iy -= 1;
} else
iy = (hy>>23) - 127;
/* set up {hx,lx}, {hy,ly} and align y to x */
if (ix >= -126)
hx = 0x00800000|(0x007fffff&hx);
else { /* subnormal x, shift x to normal */
n = -126-ix;
hx = hx<<n;
}
if (iy >= -126)
hy = 0x00800000|(0x007fffff&hy);
else { /* subnormal y, shift y to normal */
n = -126-iy;
hy = hy<<n;
}
/* fix point fmod */
n = ix - iy;
while (n--) {
hz = hx-hy;
if (hz<0)
hx = hx+hx;
else {
if(hz == 0) /* return sign(x)*0 */
return Zero[(uint32_t)sx>>31];
hx = hz+hz;
}
}
hz = hx-hy;
if (hz >= 0)
hx = hz;
/* convert back to floating value and restore the sign */
if (hx == 0) /* return sign(x)*0 */
return Zero[(uint32_t)sx>>31];
while (hx < 0x00800000) { /* normalize x */
hx = hx+hx;
iy -= 1;
}
if (iy >= -126) { /* normalize output */
hx = ((hx-0x00800000)|((iy+127)<<23));
SET_FLOAT_WORD(x, hx|sx);
} else { /* subnormal output */
n = -126 - iy;
hx >>= n;
SET_FLOAT_WORD(x, hx|sx);
x *= one; /* create necessary signal */
}
return x; /* exact output */
}
|
