1 /* @(#)e_fmod.c 5.1 93/09/24 */
2 /*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunPro, 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 #include <LibConfig.h>
13 #include <sys/EfiCdefs.h>
14 #if defined(LIBM_SCCS) && !defined(lint)
15 __RCSID("$NetBSD: e_fmod.c,v 1.11 2002/05/26 22:01:49 wiz Exp $");
16 #endif
17
18 /*
19 * __ieee754_fmod(x,y)
20 * Return x mod y in exact arithmetic
21 * Method: shift and subtract
22 */
23
24 #include "math.h"
25 #include "math_private.h"
26
27 #if defined(_MSC_VER) /* Handle Microsoft VC++ compiler specifics. */
28 // unary minus operator applied to unsigned type, result still unsigned
29 #pragma warning ( disable : 4146 )
30 #endif
31
32 static const double one = 1.0, Zero[] = {0.0, -0.0,};
33
34 double
__ieee754_fmod(double x,double y)35 __ieee754_fmod(double x, double y)
36 {
37 int32_t n,hx,hy,hz,ix,iy,sx,i;
38 u_int32_t lx,ly,lz;
39
40 EXTRACT_WORDS(hx,lx,x);
41 EXTRACT_WORDS(hy,ly,y);
42 sx = hx&0x80000000; /* sign of x */
43 hx ^=sx; /* |x| */
44 hy &= 0x7fffffff; /* |y| */
45
46 /* purge off exception values */
47 if((hy|ly)==0||(hx>=0x7ff00000)|| /* y=0,or x not finite */
48 ((hy|((ly|-ly)>>31))>0x7ff00000)) /* or y is NaN */
49 return (x*y)/(x*y);
50 if(hx<=hy) {
51 if((hx<hy)||(lx<ly)) return x; /* |x|<|y| return x */
52 if(lx==ly)
53 return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/
54 }
55
56 /* determine ix = ilogb(x) */
57 if(hx<0x00100000) { /* subnormal x */
58 if(hx==0) {
59 for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;
60 } else {
61 for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;
62 }
63 } else ix = (hx>>20)-1023;
64
65 /* determine iy = ilogb(y) */
66 if(hy<0x00100000) { /* subnormal y */
67 if(hy==0) {
68 for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;
69 } else {
70 for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;
71 }
72 } else iy = (hy>>20)-1023;
73
74 /* set up {hx,lx}, {hy,ly} and align y to x */
75 if(ix >= -1022)
76 hx = 0x00100000|(0x000fffff&hx);
77 else { /* subnormal x, shift x to normal */
78 n = -1022-ix;
79 if(n<=31) {
80 hx = (hx<<n)|(lx>>(32-n));
81 lx <<= n;
82 } else {
83 hx = lx<<(n-32);
84 lx = 0;
85 }
86 }
87 if(iy >= -1022)
88 hy = 0x00100000|(0x000fffff&hy);
89 else { /* subnormal y, shift y to normal */
90 n = -1022-iy;
91 if(n<=31) {
92 hy = (hy<<n)|(ly>>(32-n));
93 ly <<= n;
94 } else {
95 hy = ly<<(n-32);
96 ly = 0;
97 }
98 }
99
100 /* fix point fmod */
101 n = ix - iy;
102 while(n--) {
103 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
104 if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}
105 else {
106 if((hz|lz)==0) /* return sign(x)*0 */
107 return Zero[(u_int32_t)sx>>31];
108 hx = hz+hz+(lz>>31); lx = lz+lz;
109 }
110 }
111 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
112 if(hz>=0) {hx=hz;lx=lz;}
113
114 /* convert back to floating value and restore the sign */
115 if((hx|lx)==0) /* return sign(x)*0 */
116 return Zero[(u_int32_t)sx>>31];
117 while(hx<0x00100000) { /* normalize x */
118 hx = hx+hx+(lx>>31); lx = lx+lx;
119 iy -= 1;
120 }
121 if(iy>= -1022) { /* normalize output */
122 hx = ((hx-0x00100000)|((iy+1023)<<20));
123 INSERT_WORDS(x,hx|sx,lx);
124 } else { /* subnormal output */
125 n = -1022 - iy;
126 if(n<=20) {
127 lx = (lx>>n)|((u_int32_t)hx<<(32-n));
128 hx >>= n;
129 } else if (n<=31) {
130 lx = (hx<<(32-n))|(lx>>n); hx = sx;
131 } else {
132 lx = hx>>(n-32); hx = sx;
133 }
134 INSERT_WORDS(x,hx|sx,lx);
135 x *= one; /* create necessary signal */
136 }
137 return x; /* exact output */
138 }
139