/*
 * ====================================================
 * 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.
 * ====================================================
 *
 * From: @(#)s_floor.c 5.1 93/09/24
 */

#include <sys/cdefs.h>
__RCSID("$NetBSD: s_floorl.c,v 1.1 2013/11/11 23:57:34 joerg Exp $");
#if 0
__FBSDID("$FreeBSD: head/lib/msun/src/s_floorl.c 176280 2008-02-14 15:10:34Z bde $");
#endif

/*
 * floorl(x)
 * Return x rounded toward -inf to integral value
 * Method:
 *      Bit twiddling.
 * Exception:
 *      Inexact flag raised if x not equal to floorl(x).
 */
#include "namespace.h"

#include <float.h>
#include <math.h>
#include <stdint.h>
#include <machine/ieee.h>

#ifdef __HAVE_LONG_DOUBLE

#ifdef __weak_alias
__weak_alias(floorl, _floorl)
#endif

#ifdef LDBL_IMPLICIT_NBIT
#define MANH_SIZE       (EXT_FRACHBITS + 1)
#define INC_MANH(ux, c) do {                                    \
        uint64_t oi = ux.extu_frach;                            \
        ux.extu_frach += (c);                                   \
        if (ux.extu_frach < oi)                                 \
                ux.extu_exp++;                                  \
} while (0)
#else
#define MANH_SIZE       EXT_FRACHBITS
#define INC_MANH(ux, c) do {                                    \
        uint64_t oi = ux.extu_frach;                            \
        ux.extu_frach += (c);                                   \
        if (ux.extu_frach < oi) {                               \
                ux.extu_exp++;                                  \
                ux.extu_frach |= 1llu << (EXT_FRACHBITS - 1);   \
        }                                                       \
} while (0)
#endif

static const long double huge = 1.0e300;

long double
floorl(long double x)
{
        union ieee_ext_u ux = { .extu_ld = x, };
        int e = ux.extu_exp - LDBL_MAX_EXP + 1;

        if (e < MANH_SIZE - 1) {
                if (e < 0) {                    /* raise inexact if x != 0 */
                        if (huge + x > 0.0)
                                if (ux.extu_exp > 0 ||
                                    (ux.extu_frach | ux.extu_fracl) != 0)
                                        ux.extu_ld = ux.extu_sign ? -1.0 : 0.0;
                } else {
                        uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
                        if (((ux.extu_frach & m) | ux.extu_fracl) == 0)
                                return (x);     /* x is integral */
                        if (ux.extu_sign) {
#ifdef LDBL_IMPLICIT_NBIT
                                if (e == 0)
                                        ux.extu_exp++;
                                else
#endif
                                INC_MANH(ux, 1llu << (MANH_SIZE - e - 1));
                        }
                        if (huge + x > 0.0) {   /* raise inexact flag */
                                ux.extu_frach &= ~m;
                                ux.extu_fracl = 0;
                        }
                }
        } else if (e < LDBL_MANT_DIG - 1) {
                uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
                if ((ux.extu_fracl & m) == 0)
                        return (x);     /* x is integral */
                if (ux.extu_sign) {
                        if (e == MANH_SIZE - 1)
                                INC_MANH(ux, 1);
                        else {
                                uint64_t o = ux.extu_fracl;
                                ux.extu_fracl += 1llu << (LDBL_MANT_DIG - e - 1);
                                if (ux.extu_fracl < o)  /* got a carry */
                                        INC_MANH(ux, 1);
                        }
                }
                if (huge + x > 0.0)             /* raise inexact flag */
                        ux.extu_fracl &= ~m;
        }
        return (ux.extu_ld);
}

#endif /* __HAVE_LONG_DOUBLE */