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