glibc/sysdeps/ieee754/ldbl-128/s_floorl.c

/* s_floorl.c -- long double version of s_floor.c.
 * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: $";
#endif

/*
 * floorl(x)
 * Return x rounded toward -inf to integral value
 * Method:
 *	Bit twiddling.
 */

#include <math.h>
#include <math_private.h>
#include <libm-alias-ldouble.h>

_Float128 __floorl(_Float128 x)
{
	int64_t i0,i1,j0;
	uint64_t i,j;
	GET_LDOUBLE_WORDS64(i0,i1,x);
	j0 = ((i0>>48)&0x7fff)-0x3fff;
	if(j0<48) {
	    if(j0<0) {
		/* return 0*sign(x) if |x|<1 */
		if(i0>=0) {i0=i1=0;}
		else if(((i0&0x7fffffffffffffffLL)|i1)!=0)
		    { i0=0xbfff000000000000ULL;i1=0;}
	    } else {
		i = (0x0000ffffffffffffULL)>>j0;
		if(((i0&i)|i1)==0) return x; /* x is integral */
		if(i0<0) i0 += (0x0001000000000000LL)>>j0;
		i0 &= (~i); i1=0;
	    }
	} else if (j0>111) {
	    if(j0==0x4000) return x+x;	/* inf or NaN */
	    else return x;		/* x is integral */
	} else {
	    i = -1ULL>>(j0-48);
	    if((i1&i)==0) return x;	/* x is integral */
	    if(i0<0) {
		if(j0==48) i0+=1;
		else {
		    j = i1+(1LL<<(112-j0));
		    if(j<i1) i0 +=1 ; 	/* got a carry */
		    i1=j;
		}
	    }
	    i1 &= (~i);
	}
	SET_LDOUBLE_WORDS64(x,i0,i1);
	return x;
}
libm_alias_ldouble (__floor, floor)