1 /* @(#)s_rint.c 5.1 93/09/24 */
2 /* $FreeBSD: head/lib/msun/src/s_rint.c 176451 2008-02-22 02:30:36Z das $ */
4 * ====================================================
5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 * Developed at SunPro, a Sun Microsystems, Inc. business.
8 * Permission to use, copy, modify, and distribute this
9 * software is freely granted, provided that this notice
11 * ====================================================
16 * Return x rounded to integral value according to the prevailing
19 * Using floating addition.
21 * Inexact flag raised if x not equal to rint(x).
27 #include "math_private.h"
31 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
32 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
41 EXTRACT_WORDS(i0,i1,x);
43 j0 = ((i0>>20)&0x7ff)-0x3ff;
46 if(((i0&0x7fffffff)|i1)==0) return x;
49 i0 |= ((i1|-i1)>>12)&0x80000;
51 STRICT_ASSIGN(double,w,TWO52[sx]+x);
54 SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31));
58 if(((i0&i)|i1)==0) return x; /* x is integral */
62 * Some bit is set after the 0.5 bit. To avoid the
63 * possibility of errors from double rounding in
64 * w = TWO52[sx]+x, adjust the 0.25 bit to a lower
65 * guard bit. We do this for all j0<=51. The
66 * adjustment is trickiest for j0==18 and j0==19
67 * since then it spans the word boundary.
69 if(j0==19) i1 = 0x40000000; else
70 if(j0==18) i1 = 0x80000000; else
71 i0 = (i0&(~i))|((0x20000)>>j0);
75 if(j0==0x400) return x+x; /* inf or NaN */
76 else return x; /* x is integral */
78 i = ((u_int32_t)(0xffffffff))>>(j0-20);
79 if((i1&i)==0) return x; /* x is integral */
81 if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20));
83 INSERT_WORDS(x,i0,i1);
84 STRICT_ASSIGN(double,w,TWO52[sx]+x);
88 #if (LDBL_MANT_DIG == 53)
89 __weak_reference(rint, rintl);