1*84d9c625SLionel Sambuc /* @(#)e_fmod.c 1.3 95/01/18 */
2*84d9c625SLionel Sambuc /*-
3*84d9c625SLionel Sambuc * ====================================================
4*84d9c625SLionel Sambuc * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5*84d9c625SLionel Sambuc *
6*84d9c625SLionel Sambuc * Developed at SunSoft, a Sun Microsystems, Inc. business.
7*84d9c625SLionel Sambuc * Permission to use, copy, modify, and distribute this
8*84d9c625SLionel Sambuc * software is freely granted, provided that this notice
9*84d9c625SLionel Sambuc * is preserved.
10*84d9c625SLionel Sambuc * ====================================================
11*84d9c625SLionel Sambuc */
12*84d9c625SLionel Sambuc
13*84d9c625SLionel Sambuc #include <sys/cdefs.h>
14*84d9c625SLionel Sambuc
15*84d9c625SLionel Sambuc #include "math.h"
16*84d9c625SLionel Sambuc #include "math_private.h"
17*84d9c625SLionel Sambuc
18*84d9c625SLionel Sambuc static const float Zero[] = {0.0, -0.0,};
19*84d9c625SLionel Sambuc
20*84d9c625SLionel Sambuc /*
21*84d9c625SLionel Sambuc * Return the IEEE remainder and set *quo to the last n bits of the
22*84d9c625SLionel Sambuc * quotient, rounded to the nearest integer. We choose n=31 because
23*84d9c625SLionel Sambuc * we wind up computing all the integer bits of the quotient anyway as
24*84d9c625SLionel Sambuc * a side-effect of computing the remainder by the shift and subtract
25*84d9c625SLionel Sambuc * method. In practice, this is far more bits than are needed to use
26*84d9c625SLionel Sambuc * remquo in reduction algorithms.
27*84d9c625SLionel Sambuc */
28*84d9c625SLionel Sambuc float
remquof(float x,float y,int * quo)29*84d9c625SLionel Sambuc remquof(float x, float y, int *quo)
30*84d9c625SLionel Sambuc {
31*84d9c625SLionel Sambuc int32_t n,hx,hy,hz,ix,iy,sx,i;
32*84d9c625SLionel Sambuc u_int32_t q,sxy;
33*84d9c625SLionel Sambuc
34*84d9c625SLionel Sambuc GET_FLOAT_WORD(hx,x);
35*84d9c625SLionel Sambuc GET_FLOAT_WORD(hy,y);
36*84d9c625SLionel Sambuc sxy = (hx ^ hy) & 0x80000000;
37*84d9c625SLionel Sambuc sx = hx&0x80000000; /* sign of x */
38*84d9c625SLionel Sambuc hx ^=sx; /* |x| */
39*84d9c625SLionel Sambuc hy &= 0x7fffffff; /* |y| */
40*84d9c625SLionel Sambuc
41*84d9c625SLionel Sambuc /* purge off exception values */
42*84d9c625SLionel Sambuc if(hy==0||hx>=0x7f800000||hy>0x7f800000) /* y=0,NaN;or x not finite */
43*84d9c625SLionel Sambuc return (x*y)/(x*y);
44*84d9c625SLionel Sambuc if(hx<hy) {
45*84d9c625SLionel Sambuc q = 0;
46*84d9c625SLionel Sambuc goto fixup; /* |x|<|y| return x or x-y */
47*84d9c625SLionel Sambuc } else if(hx==hy) {
48*84d9c625SLionel Sambuc *quo = 1;
49*84d9c625SLionel Sambuc return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/
50*84d9c625SLionel Sambuc }
51*84d9c625SLionel Sambuc
52*84d9c625SLionel Sambuc /* determine ix = ilogb(x) */
53*84d9c625SLionel Sambuc if(hx<0x00800000) { /* subnormal x */
54*84d9c625SLionel Sambuc for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
55*84d9c625SLionel Sambuc } else ix = (hx>>23)-127;
56*84d9c625SLionel Sambuc
57*84d9c625SLionel Sambuc /* determine iy = ilogb(y) */
58*84d9c625SLionel Sambuc if(hy<0x00800000) { /* subnormal y */
59*84d9c625SLionel Sambuc for (iy = -126,i=(hy<<8); i>0; i<<=1) iy -=1;
60*84d9c625SLionel Sambuc } else iy = (hy>>23)-127;
61*84d9c625SLionel Sambuc
62*84d9c625SLionel Sambuc /* set up {hx,lx}, {hy,ly} and align y to x */
63*84d9c625SLionel Sambuc if(ix >= -126)
64*84d9c625SLionel Sambuc hx = 0x00800000|(0x007fffff&hx);
65*84d9c625SLionel Sambuc else { /* subnormal x, shift x to normal */
66*84d9c625SLionel Sambuc n = -126-ix;
67*84d9c625SLionel Sambuc hx <<= n;
68*84d9c625SLionel Sambuc }
69*84d9c625SLionel Sambuc if(iy >= -126)
70*84d9c625SLionel Sambuc hy = 0x00800000|(0x007fffff&hy);
71*84d9c625SLionel Sambuc else { /* subnormal y, shift y to normal */
72*84d9c625SLionel Sambuc n = -126-iy;
73*84d9c625SLionel Sambuc hy <<= n;
74*84d9c625SLionel Sambuc }
75*84d9c625SLionel Sambuc
76*84d9c625SLionel Sambuc /* fix point fmod */
77*84d9c625SLionel Sambuc n = ix - iy;
78*84d9c625SLionel Sambuc q = 0;
79*84d9c625SLionel Sambuc while(n--) {
80*84d9c625SLionel Sambuc hz=hx-hy;
81*84d9c625SLionel Sambuc if(hz<0) hx = hx << 1;
82*84d9c625SLionel Sambuc else {hx = hz << 1; q++;}
83*84d9c625SLionel Sambuc q <<= 1;
84*84d9c625SLionel Sambuc }
85*84d9c625SLionel Sambuc hz=hx-hy;
86*84d9c625SLionel Sambuc if(hz>=0) {hx=hz;q++;}
87*84d9c625SLionel Sambuc
88*84d9c625SLionel Sambuc /* convert back to floating value and restore the sign */
89*84d9c625SLionel Sambuc if(hx==0) { /* return sign(x)*0 */
90*84d9c625SLionel Sambuc *quo = (sxy ? -q : q);
91*84d9c625SLionel Sambuc return Zero[(u_int32_t)sx>>31];
92*84d9c625SLionel Sambuc }
93*84d9c625SLionel Sambuc while(hx<0x00800000) { /* normalize x */
94*84d9c625SLionel Sambuc hx <<= 1;
95*84d9c625SLionel Sambuc iy -= 1;
96*84d9c625SLionel Sambuc }
97*84d9c625SLionel Sambuc if(iy>= -126) { /* normalize output */
98*84d9c625SLionel Sambuc hx = ((hx-0x00800000)|((iy+127)<<23));
99*84d9c625SLionel Sambuc } else { /* subnormal output */
100*84d9c625SLionel Sambuc n = -126 - iy;
101*84d9c625SLionel Sambuc hx >>= n;
102*84d9c625SLionel Sambuc }
103*84d9c625SLionel Sambuc fixup:
104*84d9c625SLionel Sambuc SET_FLOAT_WORD(x,hx);
105*84d9c625SLionel Sambuc y = fabsf(y);
106*84d9c625SLionel Sambuc if (y < 0x1p-125f) {
107*84d9c625SLionel Sambuc if (x+x>y || (x+x==y && (q & 1))) {
108*84d9c625SLionel Sambuc q++;
109*84d9c625SLionel Sambuc x-=y;
110*84d9c625SLionel Sambuc }
111*84d9c625SLionel Sambuc } else if (x>0.5f*y || (x==0.5f*y && (q & 1))) {
112*84d9c625SLionel Sambuc q++;
113*84d9c625SLionel Sambuc x-=y;
114*84d9c625SLionel Sambuc }
115*84d9c625SLionel Sambuc GET_FLOAT_WORD(hx,x);
116*84d9c625SLionel Sambuc SET_FLOAT_WORD(x,hx^sx);
117*84d9c625SLionel Sambuc q &= 0x7fffffff;
118*84d9c625SLionel Sambuc *quo = (sxy ? -q : q);
119*84d9c625SLionel Sambuc return x;
120*84d9c625SLionel Sambuc }
121