1*05a0b428SJohn Marino /* @(#)s_rint.c 5.1 93/09/24 */
2*05a0b428SJohn Marino /*
3*05a0b428SJohn Marino * ====================================================
4*05a0b428SJohn Marino * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5*05a0b428SJohn Marino *
6*05a0b428SJohn Marino * Developed at SunPro, a Sun Microsystems, Inc. business.
7*05a0b428SJohn Marino * Permission to use, copy, modify, and distribute this
8*05a0b428SJohn Marino * software is freely granted, provided that this notice
9*05a0b428SJohn Marino * is preserved.
10*05a0b428SJohn Marino * ====================================================
11*05a0b428SJohn Marino */
12*05a0b428SJohn Marino
13*05a0b428SJohn Marino /*
14*05a0b428SJohn Marino * rint(x)
15*05a0b428SJohn Marino * Return x rounded to integral value according to the prevailing
16*05a0b428SJohn Marino * rounding mode.
17*05a0b428SJohn Marino * Method:
18*05a0b428SJohn Marino * Using floating addition.
19*05a0b428SJohn Marino * Exception:
20*05a0b428SJohn Marino * Inexact flag raised if x not equal to rint(x).
21*05a0b428SJohn Marino */
22*05a0b428SJohn Marino
23*05a0b428SJohn Marino #include <float.h>
24*05a0b428SJohn Marino #include <math.h>
25*05a0b428SJohn Marino
26*05a0b428SJohn Marino #include "math_private.h"
27*05a0b428SJohn Marino
28*05a0b428SJohn Marino static const double
29*05a0b428SJohn Marino TWO52[2]={
30*05a0b428SJohn Marino 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
31*05a0b428SJohn Marino -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
32*05a0b428SJohn Marino };
33*05a0b428SJohn Marino
34*05a0b428SJohn Marino double
rint(double x)35*05a0b428SJohn Marino rint(double x)
36*05a0b428SJohn Marino {
37*05a0b428SJohn Marino int32_t i0,jj0,sx;
38*05a0b428SJohn Marino u_int32_t i,i1;
39*05a0b428SJohn Marino double t;
40*05a0b428SJohn Marino volatile double w; /* clip extra precision */
41*05a0b428SJohn Marino EXTRACT_WORDS(i0,i1,x);
42*05a0b428SJohn Marino sx = (i0>>31)&1;
43*05a0b428SJohn Marino jj0 = ((i0>>20)&0x7ff)-0x3ff;
44*05a0b428SJohn Marino if(jj0<20) {
45*05a0b428SJohn Marino if(jj0<0) {
46*05a0b428SJohn Marino if(((i0&0x7fffffff)|i1)==0) return x;
47*05a0b428SJohn Marino i1 |= (i0&0x0fffff);
48*05a0b428SJohn Marino i0 &= 0xfffe0000;
49*05a0b428SJohn Marino i0 |= ((i1|-i1)>>12)&0x80000;
50*05a0b428SJohn Marino SET_HIGH_WORD(x,i0);
51*05a0b428SJohn Marino w = TWO52[sx]+x;
52*05a0b428SJohn Marino t = w-TWO52[sx];
53*05a0b428SJohn Marino GET_HIGH_WORD(i0,t);
54*05a0b428SJohn Marino SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31));
55*05a0b428SJohn Marino return t;
56*05a0b428SJohn Marino } else {
57*05a0b428SJohn Marino i = (0x000fffff)>>jj0;
58*05a0b428SJohn Marino if(((i0&i)|i1)==0) return x; /* x is integral */
59*05a0b428SJohn Marino i>>=1;
60*05a0b428SJohn Marino if(((i0&i)|i1)!=0) {
61*05a0b428SJohn Marino if(jj0==19) i1 = 0x40000000; else
62*05a0b428SJohn Marino i0 = (i0&(~i))|((0x20000)>>jj0);
63*05a0b428SJohn Marino }
64*05a0b428SJohn Marino }
65*05a0b428SJohn Marino } else if (jj0>51) {
66*05a0b428SJohn Marino if(jj0==0x400) return x+x; /* inf or NaN */
67*05a0b428SJohn Marino else return x; /* x is integral */
68*05a0b428SJohn Marino } else {
69*05a0b428SJohn Marino i = ((u_int32_t)(0xffffffff))>>(jj0-20);
70*05a0b428SJohn Marino if((i1&i)==0) return x; /* x is integral */
71*05a0b428SJohn Marino i>>=1;
72*05a0b428SJohn Marino if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(jj0-20));
73*05a0b428SJohn Marino }
74*05a0b428SJohn Marino INSERT_WORDS(x,i0,i1);
75*05a0b428SJohn Marino w = TWO52[sx]+x;
76*05a0b428SJohn Marino return w-TWO52[sx];
77*05a0b428SJohn Marino }
78*05a0b428SJohn Marino
79*05a0b428SJohn Marino #if LDBL_MANT_DIG == DBL_MANT_DIG
80*05a0b428SJohn Marino __strong_alias(rintl, rint);
81*05a0b428SJohn Marino #endif /* LDBL_MANT_DIG == DBL_MANT_DIG */
82