1*2fe8fb19SBen Gras /* @(#)s_rint.c 5.1 93/09/24 */
2*2fe8fb19SBen Gras /*
3*2fe8fb19SBen Gras * ====================================================
4*2fe8fb19SBen Gras * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5*2fe8fb19SBen Gras *
6*2fe8fb19SBen Gras * Developed at SunPro, a Sun Microsystems, Inc. business.
7*2fe8fb19SBen Gras * Permission to use, copy, modify, and distribute this
8*2fe8fb19SBen Gras * software is freely granted, provided that this notice
9*2fe8fb19SBen Gras * is preserved.
10*2fe8fb19SBen Gras * ====================================================
11*2fe8fb19SBen Gras */
12*2fe8fb19SBen Gras
13*2fe8fb19SBen Gras #include <sys/cdefs.h>
14*2fe8fb19SBen Gras #if defined(LIBM_SCCS) && !defined(lint)
15*2fe8fb19SBen Gras __RCSID("$NetBSD: s_rint.c,v 1.12 2008/04/25 22:21:53 christos Exp $");
16*2fe8fb19SBen Gras #endif
17*2fe8fb19SBen Gras
18*2fe8fb19SBen Gras /*
19*2fe8fb19SBen Gras * rint(x)
20*2fe8fb19SBen Gras * Return x rounded to integral value according to the prevailing
21*2fe8fb19SBen Gras * rounding mode.
22*2fe8fb19SBen Gras * Method:
23*2fe8fb19SBen Gras * Using floating addition.
24*2fe8fb19SBen Gras * Exception:
25*2fe8fb19SBen Gras * Inexact flag raised if x not equal to rint(x).
26*2fe8fb19SBen Gras */
27*2fe8fb19SBen Gras
28*2fe8fb19SBen Gras #include "math.h"
29*2fe8fb19SBen Gras #include "math_private.h"
30*2fe8fb19SBen Gras
31*2fe8fb19SBen Gras static const double
32*2fe8fb19SBen Gras TWO52[2]={
33*2fe8fb19SBen Gras 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
34*2fe8fb19SBen Gras -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
35*2fe8fb19SBen Gras };
36*2fe8fb19SBen Gras
37*2fe8fb19SBen Gras double
rint(double x)38*2fe8fb19SBen Gras rint(double x)
39*2fe8fb19SBen Gras {
40*2fe8fb19SBen Gras int32_t i0,jj0,sx;
41*2fe8fb19SBen Gras u_int32_t i,i1;
42*2fe8fb19SBen Gras double w,t;
43*2fe8fb19SBen Gras EXTRACT_WORDS(i0,i1,x);
44*2fe8fb19SBen Gras sx = (i0>>31)&1;
45*2fe8fb19SBen Gras jj0 = ((i0>>20)&0x7ff)-0x3ff;
46*2fe8fb19SBen Gras if(jj0<20) {
47*2fe8fb19SBen Gras if(jj0<0) {
48*2fe8fb19SBen Gras if(((i0&0x7fffffff)|i1)==0) return x;
49*2fe8fb19SBen Gras i1 |= (i0&0x0fffff);
50*2fe8fb19SBen Gras i0 &= 0xfffe0000;
51*2fe8fb19SBen Gras i0 |= ((i1|-i1)>>12)&0x80000;
52*2fe8fb19SBen Gras SET_HIGH_WORD(x,i0);
53*2fe8fb19SBen Gras w = TWO52[sx]+x;
54*2fe8fb19SBen Gras t = w-TWO52[sx];
55*2fe8fb19SBen Gras GET_HIGH_WORD(i0,t);
56*2fe8fb19SBen Gras SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31));
57*2fe8fb19SBen Gras return t;
58*2fe8fb19SBen Gras } else {
59*2fe8fb19SBen Gras i = (0x000fffff)>>jj0;
60*2fe8fb19SBen Gras if(((i0&i)|i1)==0) return x; /* x is integral */
61*2fe8fb19SBen Gras i>>=1;
62*2fe8fb19SBen Gras if(((i0&i)|i1)!=0) {
63*2fe8fb19SBen Gras if(jj0==19) i1 = 0x40000000; else
64*2fe8fb19SBen Gras i0 = (i0&(~i))|((0x20000)>>jj0);
65*2fe8fb19SBen Gras }
66*2fe8fb19SBen Gras }
67*2fe8fb19SBen Gras } else if (jj0>51) {
68*2fe8fb19SBen Gras if(jj0==0x400) return x+x; /* inf or NaN */
69*2fe8fb19SBen Gras else return x; /* x is integral */
70*2fe8fb19SBen Gras } else {
71*2fe8fb19SBen Gras i = ((u_int32_t)(0xffffffff))>>(jj0-20);
72*2fe8fb19SBen Gras if((i1&i)==0) return x; /* x is integral */
73*2fe8fb19SBen Gras i>>=1;
74*2fe8fb19SBen Gras if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(jj0-20));
75*2fe8fb19SBen Gras }
76*2fe8fb19SBen Gras INSERT_WORDS(x,i0,i1);
77*2fe8fb19SBen Gras w = TWO52[sx]+x;
78*2fe8fb19SBen Gras return w-TWO52[sx];
79*2fe8fb19SBen Gras }
80