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
16/*
17 * __ieee754_fmodf(x,y)
18 * Return x mod y in exact arithmetic
19 * Method: shift and subtract
20 */
21
22#include <math.h>
23#include <math_private.h>
24#include <libm-alias-finite.h>
25
26static const float one = 1.0, Zero[] = {0.0, -0.0,};
27
28float
29__ieee754_fmodf (float x, float y)
30{
31 int32_t n,hx,hy,hz,ix,iy,sx,i;
32
33 GET_FLOAT_WORD(hx,x);
34 GET_FLOAT_WORD(hy,y);
35 sx = hx&0x80000000; /* sign of x */
36 hx ^=sx; /* |x| */
37 hy &= 0x7fffffff; /* |y| */
38
39 /* purge off exception values */
40 if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */
41 (hy>0x7f800000)) /* or y is NaN */
42 return (x*y)/(x*y);
43 if(hx<hy) return x; /* |x|<|y| return x */
44 if(hx==hy)
45 return Zero[(uint32_t)sx>>31]; /* |x|=|y| return x*0*/
46
47 /* determine ix = ilogb(x) */
48 if(hx<0x00800000) { /* subnormal x */
49 for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
50 } else ix = (hx>>23)-127;
51
52 /* determine iy = ilogb(y) */
53 if(hy<0x00800000) { /* subnormal y */
54 for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1;
55 } else iy = (hy>>23)-127;
56
57 /* set up {hx,lx}, {hy,ly} and align y to x */
58 if(ix >= -126)
59 hx = 0x00800000|(0x007fffff&hx);
60 else { /* subnormal x, shift x to normal */
61 n = -126-ix;
62 hx = hx<<n;
63 }
64 if(iy >= -126)
65 hy = 0x00800000|(0x007fffff&hy);
66 else { /* subnormal y, shift y to normal */
67 n = -126-iy;
68 hy = hy<<n;
69 }
70
71 /* fix point fmod */
72 n = ix - iy;
73 while(n--) {
74 hz=hx-hy;
75 if(hz<0){hx = hx+hx;}
76 else {
77 if(hz==0) /* return sign(x)*0 */
78 return Zero[(uint32_t)sx>>31];
79 hx = hz+hz;
80 }
81 }
82 hz=hx-hy;
83 if(hz>=0) {hx=hz;}
84
85 /* convert back to floating value and restore the sign */
86 if(hx==0) /* return sign(x)*0 */
87 return Zero[(uint32_t)sx>>31];
88 while(hx<0x00800000) { /* normalize x */
89 hx = hx+hx;
90 iy -= 1;
91 }
92 if(iy>= -126) { /* normalize output */
93 hx = ((hx-0x00800000)|((iy+127)<<23));
94 SET_FLOAT_WORD(x,hx|sx);
95 } else { /* subnormal output */
96 n = -126 - iy;
97 hx >>= n;
98 SET_FLOAT_WORD(x,hx|sx);
99 x *= one; /* create necessary signal */
100 }
101 return x; /* exact output */
102}
103libm_alias_finite (__ieee754_fmodf, __fmodf)
104