1 /* Adapted for Newlib, 2009. (Allow for int < 32 bits; return *quo=0 during
2 * errors to make test scripts easier.) */
3 /* @(#)e_fmod.c 1.3 95/01/18 */
4 /*-
5 * ====================================================
6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 *
8 * Developed at SunSoft, 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 #include <math.h>
16 #include "fdlibm.h"
17
18 /* For quotient, return either all 31 bits that can from calculation (using
19 * int32_t), or as many as can fit into an int that is smaller than 32 bits. */
20 #if INT_MAX > 0x7FFFFFFFL
21 #define QUO_MASK 0x7FFFFFFF
22 # else
23 #define QUO_MASK INT_MAX
24 #endif
25
26 static const float Zero[] = {0.0, -0.0,};
27
28 /*
29 * Return the IEEE remainder and set *quo to the last n bits of the
30 * quotient, rounded to the nearest integer. We choose n=31--if that many fit--
31 * we wind up computing all the integer bits of the quotient anyway as
32 * a side-effect of computing the remainder by the shift and subtract
33 * method. In practice, this is far more bits than are needed to use
34 * remquo in reduction algorithms.
35 */
36 float
remquof(float x,float y,int * quo)37 remquof(float x, float y, int *quo)
38 {
39 __int32_t n,hx,hy,hz,ix,iy,sx,i;
40 __uint32_t q,sxy;
41
42 GET_FLOAT_WORD(hx,x);
43 GET_FLOAT_WORD(hy,y);
44 sxy = (hx ^ hy) & 0x80000000;
45 sx = hx&0x80000000; /* sign of x */
46 hx ^=sx; /* |x| */
47 hy &= 0x7fffffff; /* |y| */
48
49 /* purge off exception values */
50 if(hy==0||hx>=0x7f800000||hy>0x7f800000) { /* y=0,NaN;or x not finite */
51 *quo = 0; /* Not necessary, but return consistent value */
52 return (x*y)/(x*y);
53 }
54 if(hx<hy) {
55 q = 0;
56 goto fixup; /* |x|<|y| return x or x-y */
57 } else if(hx==hy) {
58 *quo = (sxy ? -1 : 1);
59 return Zero[(__uint32_t)sx>>31]; /* |x|=|y| return x*0*/
60 }
61
62 /* determine ix = ilogb(x) */
63 if(hx<0x00800000) { /* subnormal x */
64 for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
65 } else ix = (hx>>23)-127;
66
67 /* determine iy = ilogb(y) */
68 if(hy<0x00800000) { /* subnormal y */
69 for (iy = -126,i=(hy<<8); i>0; i<<=1) iy -=1;
70 } else iy = (hy>>23)-127;
71
72 /* set up {hx,lx}, {hy,ly} and align y to x */
73 if(ix >= -126)
74 hx = 0x00800000|(0x007fffff&hx);
75 else { /* subnormal x, shift x to normal */
76 n = -126-ix;
77 hx <<= n;
78 }
79 if(iy >= -126)
80 hy = 0x00800000|(0x007fffff&hy);
81 else { /* subnormal y, shift y to normal */
82 n = -126-iy;
83 hy <<= n;
84 }
85
86 /* fix point fmod */
87 n = ix - iy;
88 q = 0;
89 while(n--) {
90 hz=hx-hy;
91 if(hz<0) hx = hx << 1;
92 else {hx = hz << 1; q++;}
93 q <<= 1;
94 }
95 hz=hx-hy;
96 if(hz>=0) {hx=hz;q++;}
97
98 /* convert back to floating value and restore the sign */
99 if(hx==0) { /* return sign(x)*0 */
100 *quo = (sxy ? -q : q);
101 return Zero[(__uint32_t)sx>>31];
102 }
103 while(hx<0x00800000) { /* normalize x */
104 hx <<= 1;
105 iy -= 1;
106 }
107 if(iy>= -126) { /* normalize output */
108 hx = ((hx-0x00800000)|((iy+127)<<23));
109 } else { /* subnormal output */
110 n = -126 - iy;
111 hx >>= n;
112 }
113 fixup:
114 SET_FLOAT_WORD(x,hx);
115 y = fabsf(y);
116 if (y < 0x1p-125f) {
117 if (x+x>y || (x+x==y && (q & 1))) {
118 q++;
119 x-=y;
120 }
121 } else if (x>0.5f*y || (x==0.5f*y && (q & 1))) {
122 q++;
123 x-=y;
124 }
125 GET_FLOAT_WORD(hx,x);
126 SET_FLOAT_WORD(x,hx^sx);
127 q &= 0x7fffffff;
128 *quo = (sxy ? -q : q);
129 return x;
130 }
131
132 _MATH_ALIAS_f_ffI(remquo)
133
