1 /*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 */
11
12 /*
13 * __ieee754_fmodf(x,y)
14 * Return x mod y in exact arithmetic
15 * Method: shift and subtract
16 */
17
18 #include "bsd_privatef.h"
19
bsd__ieee754_fmodf(float x,float y)20 float bsd__ieee754_fmodf(float x, float y)
21 {
22 int32_t n,hx,hy,hz,ix,iy,sx,i;
23
24 GET_FLOAT_WORD(hx,x);
25 GET_FLOAT_WORD(hy,y);
26 sx = hx&0x80000000; /* sign of x */
27 hx ^=sx; /* |x| */
28 hy &= 0x7fffffff; /* |y| */
29
30 /* purge off exception values */
31 if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */
32 (hy>0x7f800000)) /* or y is NaN */
33 return (x*y)/(x*y);
34 if(hx<hy) return x; /* |x|<|y| return x */
35 if(hx==hy)
36 return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/
37
38 /* determine ix = ilogb(x) */
39 if(hx<0x00800000) { /* subnormal x */
40 for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
41 } else ix = (hx>>23)-127;
42
43 /* determine iy = ilogb(y) */
44 if(hy<0x00800000) { /* subnormal y */
45 for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1;
46 } else iy = (hy>>23)-127;
47
48 /* set up {hx,lx}, {hy,ly} and align y to x */
49 if(ix >= -126)
50 hx = 0x00800000|(0x007fffff&hx);
51 else { /* subnormal x, shift x to normal */
52 n = -126-ix;
53 hx = hx<<n;
54 }
55 if(iy >= -126)
56 hy = 0x00800000|(0x007fffff&hy);
57 else { /* subnormal y, shift y to normal */
58 n = -126-iy;
59 hy = hy<<n;
60 }
61
62 /* fix point fmod */
63 n = ix - iy;
64 while(n--) {
65 hz=hx-hy;
66 if(hz<0){hx = hx+hx;}
67 else {
68 if(hz==0) /* return sign(x)*0 */
69 return Zero[(u_int32_t)sx>>31];
70 hx = hz+hz;
71 }
72 }
73 hz=hx-hy;
74 if(hz>=0) {hx=hz;}
75
76 /* convert back to floating value and restore the sign */
77 if(hx==0) /* return sign(x)*0 */
78 return Zero[(u_int32_t)sx>>31];
79 while(hx<0x00800000) { /* normalize x */
80 hx = hx+hx;
81 iy -= 1;
82 }
83 if(iy>= -126) { /* normalize output */
84 hx = ((hx-0x00800000)|((iy+127)<<23));
85 SET_FLOAT_WORD(x,hx|sx);
86 } else { /* subnormal output */
87 n = -126 - iy;
88 hx >>= n;
89 SET_FLOAT_WORD(x,hx|sx);
90 x *= one; /* create necessary signal */
91 }
92 return x; /* exact output */
93 }
94