1/* e_fmodf.c -- float version of e_fmod.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 */
4
5/*
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 *
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
12 * is preserved.
13 * ====================================================
14 */
15
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18
19/*
20 * __ieee754_fmodf(x,y)
21 * Return x mod y in exact arithmetic
22 * Method: shift and subtract
23 */
24
25#include "math.h"
26#include "math_private.h"
27
28static const float one = 1.0, Zero[] = {0.0, -0.0,};
29
30float
31__ieee754_fmodf(float x, float y)
32{
33 int32_t n,hx,hy,hz,ix,iy,sx,i;
34
35 GET_FLOAT_WORD(hx,x);
36 GET_FLOAT_WORD(hy,y);
37 sx = hx&0x80000000; /* sign of x */
38 hx ^=sx; /* |x| */
39 hy &= 0x7fffffff; /* |y| */
40
41 /* purge off exception values */
42 if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */
43 (hy>0x7f800000)) /* or y is NaN */
44 return (x*y)/(x*y);
45 if(hx<hy) return x; /* |x|<|y| return x */
46 if(hx==hy)
47 return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/
48
49 /* determine ix = ilogb(x) */
50 if(hx<0x00800000) { /* subnormal x */
51 for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
52 } else ix = (hx>>23)-127;
53
54 /* determine iy = ilogb(y) */
55 if(hy<0x00800000) { /* subnormal y */
56 for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1;
57 } else iy = (hy>>23)-127;
58
59 /* set up {hx,lx}, {hy,ly} and align y to x */
60 if(ix >= -126)
61 hx = 0x00800000|(0x007fffff&hx);
62 else { /* subnormal x, shift x to normal */
63 n = -126-ix;
64 hx = hx<<n;
65 }
66 if(iy >= -126)
67 hy = 0x00800000|(0x007fffff&hy);
68 else { /* subnormal y, shift y to normal */
69 n = -126-iy;
70 hy = hy<<n;
71 }
72
73 /* fix point fmod */
74 n = ix - iy;
75 while(n--) {
76 hz=hx-hy;
77 if(hz<0){hx = hx+hx;}
78 else {
79 if(hz==0) /* return sign(x)*0 */
80 return Zero[(u_int32_t)sx>>31];
81 hx = hz+hz;
82 }
83 }
84 hz=hx-hy;
85 if(hz>=0) {hx=hz;}
86
87 /* convert back to floating value and restore the sign */
88 if(hx==0) /* return sign(x)*0 */
89 return Zero[(u_int32_t)sx>>31];
90 while(hx<0x00800000) { /* normalize x */
91 hx = hx+hx;
92 iy -= 1;
93 }
94 if(iy>= -126) { /* normalize output */
95 hx = ((hx-0x00800000)|((iy+127)<<23));
96 SET_FLOAT_WORD(x,hx|sx);
97 } else { /* subnormal output */
98 n = -126 - iy;
99 hx >>= n;
100 SET_FLOAT_WORD(x,hx|sx);
101 x *= one; /* create necessary signal */
102 }
103 return x; /* exact output */
104}
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