12116Sjkh/* @(#)s_rint.c 5.1 93/09/24 */
22116Sjkh/*
32116Sjkh * ====================================================
42116Sjkh * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
52116Sjkh *
62116Sjkh * Developed at SunPro, a Sun Microsystems, Inc. business.
72116Sjkh * Permission to use, copy, modify, and distribute this
88870Srgrimes * software is freely granted, provided that this notice
92116Sjkh * is preserved.
102116Sjkh * ====================================================
112116Sjkh */
122116Sjkh
13176451Sdas#include <sys/cdefs.h>
14176451Sdas__FBSDID("$FreeBSD$");
152116Sjkh
162116Sjkh/*
172116Sjkh * rint(x)
182116Sjkh * Return x rounded to integral value according to the prevailing
192116Sjkh * rounding mode.
202116Sjkh * Method:
212116Sjkh *	Using floating addition.
222116Sjkh * Exception:
232116Sjkh *	Inexact flag raised if x not equal to rint(x).
242116Sjkh */
252116Sjkh
26175309Sdas#include <float.h>
27175309Sdas
282116Sjkh#include "math.h"
292116Sjkh#include "math_private.h"
302116Sjkh
31153043Sbdestatic const double
322116SjkhTWO52[2]={
332116Sjkh  4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
342116Sjkh -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
352116Sjkh};
362116Sjkh
3797413Salfreddouble
38117912Speterrint(double x)
392116Sjkh{
402116Sjkh	int32_t i0,j0,sx;
412116Sjkh	u_int32_t i,i1;
422116Sjkh	double w,t;
432116Sjkh	EXTRACT_WORDS(i0,i1,x);
442116Sjkh	sx = (i0>>31)&1;
452116Sjkh	j0 = ((i0>>20)&0x7ff)-0x3ff;
462116Sjkh	if(j0<20) {
478870Srgrimes	    if(j0<0) {
482116Sjkh		if(((i0&0x7fffffff)|i1)==0) return x;
492116Sjkh		i1 |= (i0&0x0fffff);
502116Sjkh		i0 &= 0xfffe0000;
512116Sjkh		i0 |= ((i1|-i1)>>12)&0x80000;
522116Sjkh		SET_HIGH_WORD(x,i0);
53175480Sbde	        STRICT_ASSIGN(double,w,TWO52[sx]+x);
542116Sjkh	        t =  w-TWO52[sx];
552116Sjkh		GET_HIGH_WORD(i0,t);
562116Sjkh		SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31));
572116Sjkh	        return t;
582116Sjkh	    } else {
592116Sjkh		i = (0x000fffff)>>j0;
602116Sjkh		if(((i0&i)|i1)==0) return x; /* x is integral */
612116Sjkh		i>>=1;
622116Sjkh		if(((i0&i)|i1)!=0) {
63153042Sbde		    /*
64153042Sbde		     * Some bit is set after the 0.5 bit.  To avoid the
65153042Sbde		     * possibility of errors from double rounding in
66153042Sbde		     * w = TWO52[sx]+x, adjust the 0.25 bit to a lower
67153042Sbde		     * guard bit.  We do this for all j0<=51.  The
68153042Sbde		     * adjustment is trickiest for j0==18 and j0==19
69153042Sbde		     * since then it spans the word boundary.
70153042Sbde		     */
712116Sjkh		    if(j0==19) i1 = 0x40000000; else
72153042Sbde		    if(j0==18) i1 = 0x80000000; else
732116Sjkh		    i0 = (i0&(~i))|((0x20000)>>j0);
742116Sjkh		}
752116Sjkh	    }
762116Sjkh	} else if (j0>51) {
772116Sjkh	    if(j0==0x400) return x+x;	/* inf or NaN */
782116Sjkh	    else return x;		/* x is integral */
792116Sjkh	} else {
802116Sjkh	    i = ((u_int32_t)(0xffffffff))>>(j0-20);
812116Sjkh	    if((i1&i)==0) return x;	/* x is integral */
822116Sjkh	    i>>=1;
832116Sjkh	    if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20));
842116Sjkh	}
852116Sjkh	INSERT_WORDS(x,i0,i1);
86175480Sbde	STRICT_ASSIGN(double,w,TWO52[sx]+x);
872116Sjkh	return w-TWO52[sx];
882116Sjkh}
89175309Sdas
90175309Sdas#if (LDBL_MANT_DIG == 53)
91175309Sdas__weak_reference(rint, rintl);
92175309Sdas#endif
93