1 | /* e_fmodf.c -- float version of e_fmod.c. |
2 | */ |
3 | |
4 | /* |
5 | * ==================================================== |
6 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
7 | * |
8 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
9 | * Permission to use, copy, modify, and distribute this |
10 | * software is freely granted, provided that this notice |
11 | * is preserved. |
12 | * ==================================================== |
13 | */ |
14 | |
15 | /* |
16 | * __ieee754_fmodf(x,y) |
17 | * Return x mod y in exact arithmetic |
18 | * Method: shift and subtract |
19 | */ |
20 | |
21 | #include <math.h> |
22 | #include <math_private.h> |
23 | #include <libm-alias-finite.h> |
24 | |
25 | static const float one = 1.0, Zero[] = {0.0, -0.0,}; |
26 | |
27 | float |
28 | __ieee754_fmodf (float x, float y) |
29 | { |
30 | int32_t n,hx,hy,hz,ix,iy,sx,i; |
31 | |
32 | GET_FLOAT_WORD(hx,x); |
33 | GET_FLOAT_WORD(hy,y); |
34 | sx = hx&0x80000000; /* sign of x */ |
35 | hx ^=sx; /* |x| */ |
36 | hy &= 0x7fffffff; /* |y| */ |
37 | |
38 | /* purge off exception values */ |
39 | if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */ |
40 | (hy>0x7f800000)) /* or y is NaN */ |
41 | return (x*y)/(x*y); |
42 | if(hx<hy) return x; /* |x|<|y| return x */ |
43 | if(hx==hy) |
44 | return Zero[(uint32_t)sx>>31]; /* |x|=|y| return x*0*/ |
45 | |
46 | /* determine ix = ilogb(x) */ |
47 | if(hx<0x00800000) { /* subnormal x */ |
48 | for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; |
49 | } else ix = (hx>>23)-127; |
50 | |
51 | /* determine iy = ilogb(y) */ |
52 | if(hy<0x00800000) { /* subnormal y */ |
53 | for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1; |
54 | } else iy = (hy>>23)-127; |
55 | |
56 | /* set up {hx,lx}, {hy,ly} and align y to x */ |
57 | if(ix >= -126) |
58 | hx = 0x00800000|(0x007fffff&hx); |
59 | else { /* subnormal x, shift x to normal */ |
60 | n = -126-ix; |
61 | hx = hx<<n; |
62 | } |
63 | if(iy >= -126) |
64 | hy = 0x00800000|(0x007fffff&hy); |
65 | else { /* subnormal y, shift y to normal */ |
66 | n = -126-iy; |
67 | hy = hy<<n; |
68 | } |
69 | |
70 | /* fix point fmod */ |
71 | n = ix - iy; |
72 | while(n--) { |
73 | hz=hx-hy; |
74 | if(hz<0){hx = hx+hx;} |
75 | else { |
76 | if(hz==0) /* return sign(x)*0 */ |
77 | return Zero[(uint32_t)sx>>31]; |
78 | hx = hz+hz; |
79 | } |
80 | } |
81 | hz=hx-hy; |
82 | if(hz>=0) {hx=hz;} |
83 | |
84 | /* convert back to floating value and restore the sign */ |
85 | if(hx==0) /* return sign(x)*0 */ |
86 | return Zero[(uint32_t)sx>>31]; |
87 | while(hx<0x00800000) { /* normalize x */ |
88 | hx = hx+hx; |
89 | iy -= 1; |
90 | } |
91 | if(iy>= -126) { /* normalize output */ |
92 | hx = ((hx-0x00800000)|((iy+127)<<23)); |
93 | SET_FLOAT_WORD(x,hx|sx); |
94 | } else { /* subnormal output */ |
95 | n = -126 - iy; |
96 | hx >>= n; |
97 | SET_FLOAT_WORD(x,hx|sx); |
98 | x *= one; /* create necessary signal */ |
99 | } |
100 | return x; /* exact output */ |
101 | } |
102 | libm_alias_finite (__ieee754_fmodf, __fmodf) |
103 | |