/src/moddable/xs/tools/fdlibm/e_fmod.c
Line | Count | Source |
1 | | |
2 | | /* |
3 | | * ==================================================== |
4 | | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
5 | | * |
6 | | * Developed at SunSoft, a Sun Microsystems, Inc. business. |
7 | | * Permission to use, copy, modify, and distribute this |
8 | | * software is freely granted, provided that this notice |
9 | | * is preserved. |
10 | | * ==================================================== |
11 | | */ |
12 | | |
13 | | /* |
14 | | * __ieee754_fmod(x,y) |
15 | | * Return x mod y in exact arithmetic |
16 | | * Method: shift and subtract |
17 | | */ |
18 | | |
19 | | #include <float.h> |
20 | | |
21 | | #include "math.h" |
22 | | #include "math_private.h" |
23 | | |
24 | | static const double one = 1.0, Zero[] = {0.0, -0.0,}; |
25 | | |
26 | | double |
27 | | __ieee754_fmod(double x, double y) |
28 | 11.2M | { |
29 | 11.2M | int32_t hx, hy, hz, ix, iy, n, sx; |
30 | 11.2M | u_int32_t lx, ly, lz; |
31 | | |
32 | 11.2M | EXTRACT_WORDS(hx,lx,x); |
33 | 11.2M | EXTRACT_WORDS(hy,ly,y); |
34 | 11.2M | sx = hx&0x80000000; /* sign of x */ |
35 | 11.2M | hx ^= sx; /* |x| */ |
36 | 11.2M | hy &= 0x7fffffff; /* |y| */ |
37 | | |
38 | | /* purge off exception values */ |
39 | 11.2M | if((hy|ly)==0||(hx>=0x7ff00000)|| /* y=0,or x not finite */ |
40 | 10.4M | ((hy|((ly|-ly)>>31))>0x7ff00000)) /* or y is NaN */ |
41 | 808k | return nan_mix_op(x, y, *)/nan_mix_op(x, y, *); |
42 | 10.4M | if(hx<=hy) { |
43 | 3.49M | if((hx<hy)||(lx<ly)) return x; /* |x|<|y| return x */ |
44 | 5.58k | if(lx==ly) |
45 | 5.43k | return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/ |
46 | 5.58k | } |
47 | | |
48 | | /* determine ix = ilogb(x) */ |
49 | 6.91M | if(hx<0x00100000) |
50 | 0 | ix = subnormal_ilogb(hx, lx); |
51 | 6.91M | else |
52 | 6.91M | ix = (hx>>20)-1023; |
53 | | |
54 | | /* determine iy = ilogb(y) */ |
55 | 6.91M | if(hy<0x00100000) |
56 | 31 | iy = subnormal_ilogb(hy, ly); |
57 | 6.91M | else |
58 | 6.91M | iy = (hy>>20)-1023; |
59 | | |
60 | | /* set up {hx,lx}, {hy,ly} and align y to x */ |
61 | 6.91M | if(ix >= -1022) |
62 | 6.91M | hx = 0x00100000|(0x000fffff&hx); |
63 | 0 | else { /* subnormal x, shift x to normal */ |
64 | 0 | n = -1022-ix; |
65 | 0 | if(n<=31) { |
66 | 0 | hx = (hx<<n)|(lx>>(32-n)); |
67 | 0 | lx <<= n; |
68 | 0 | } else { |
69 | 0 | hx = lx<<(n-32); |
70 | 0 | lx = 0; |
71 | 0 | } |
72 | 0 | } |
73 | 6.91M | if(iy >= -1022) |
74 | 6.91M | hy = 0x00100000|(0x000fffff&hy); |
75 | 31 | else { /* subnormal y, shift y to normal */ |
76 | 31 | n = -1022-iy; |
77 | 31 | if(n<=31) { |
78 | 26 | hy = (hy<<n)|(ly>>(32-n)); |
79 | 26 | ly <<= n; |
80 | 26 | } else { |
81 | 5 | hy = ly<<(n-32); |
82 | 5 | ly = 0; |
83 | 5 | } |
84 | 31 | } |
85 | | |
86 | | /* fix point fmod */ |
87 | 6.91M | n = ix - iy; |
88 | 175M | while(n--) { |
89 | 170M | hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1; |
90 | 170M | if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;} |
91 | 85.9M | else { |
92 | 85.9M | if((hz|lz)==0) /* return sign(x)*0 */ |
93 | 1.58M | return Zero[(u_int32_t)sx>>31]; |
94 | 84.3M | hx = hz+hz+(lz>>31); lx = lz+lz; |
95 | 84.3M | } |
96 | 170M | } |
97 | 5.33M | hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1; |
98 | 5.33M | if(hz>=0) {hx=hz;lx=lz;} |
99 | | |
100 | | /* convert back to floating value and restore the sign */ |
101 | 5.33M | if((hx|lx)==0) /* return sign(x)*0 */ |
102 | 649k | return Zero[(u_int32_t)sx>>31]; |
103 | 8.56M | while(hx<0x00100000) { /* normalize x */ |
104 | 3.87M | hx = hx+hx+(lx>>31); lx = lx+lx; |
105 | 3.87M | iy -= 1; |
106 | 3.87M | } |
107 | 4.68M | if(iy>= -1022) { /* normalize output */ |
108 | 4.68M | hx = ((hx-0x00100000)|((iy+1023)<<20)); |
109 | 4.68M | INSERT_WORDS(x,hx|sx,lx); |
110 | 4.68M | } else { /* subnormal output */ |
111 | 32 | n = -1022 - iy; |
112 | 32 | if(n<=20) { |
113 | 21 | lx = (lx>>n)|((u_int32_t)hx<<(32-n)); |
114 | 21 | hx >>= n; |
115 | 21 | } else if (n<=31) { |
116 | 7 | lx = (hx<<(32-n))|(lx>>n); hx = sx; |
117 | 7 | } else { |
118 | 4 | lx = hx>>(n-32); hx = sx; |
119 | 4 | } |
120 | 32 | INSERT_WORDS(x,hx|sx,lx); |
121 | 32 | x *= one; /* create necessary signal */ |
122 | 32 | } |
123 | 4.68M | return x; /* exact output */ |
124 | 5.33M | } |