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/*
* ====================================================
* 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
*/
#ifndef lint
static char rcsid[] = "$FreeBSD$";
#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 <float.h>
#include <math.h>
#include <stdint.h>
#include "fpmath.h"
#ifdef LDBL_IMPLICIT_NBIT
#define MANH_SIZE (LDBL_MANH_SIZE + 1)
#define INC_MANH(u, c) do { \
uint64_t o = u.bits.manh; \
u.bits.manh += (c); \
if (u.bits.manh < o) \
u.bits.exp++; \
} while (0)
#else
#define MANH_SIZE LDBL_MANH_SIZE
#define INC_MANH(u, c) do { \
uint64_t o = u.bits.manh; \
u.bits.manh += (c); \
if (u.bits.manh < o) { \
u.bits.exp++; \
u.bits.manh |= 1llu << (LDBL_MANH_SIZE - 1); \
} \
} while (0)
#endif
static const long double huge = 1.0e300;
long double
floorl(long double x)
{
union IEEEl2bits u = { .e = x };
int e = u.bits.exp - LDBL_MAX_EXP + 1;
if (e < MANH_SIZE - 1) {
if (e < 0) { /* raise inexact if x != 0 */
if (huge + x > 0.0)
if (u.bits.exp > 0 ||
(u.bits.manh | u.bits.manl) != 0)
u.e = u.bits.sign ? -1.0 : 0.0;
} else {
uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
if (((u.bits.manh & m) | u.bits.manl) == 0)
return (x); /* x is integral */
if (u.bits.sign) {
#ifdef LDBL_IMPLICIT_NBIT
if (e == 0)
u.bits.exp++;
else
#endif
INC_MANH(u, 1llu << (MANH_SIZE - e - 1));
}
if (huge + x > 0.0) { /* raise inexact flag */
u.bits.manh &= ~m;
u.bits.manl = 0;
}
}
} else if (e < LDBL_MANT_DIG - 1) {
uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
if ((u.bits.manl & m) == 0)
return (x); /* x is integral */
if (u.bits.sign) {
if (e == MANH_SIZE - 1)
INC_MANH(u, 1);
else {
uint64_t o = u.bits.manl;
u.bits.manl += 1llu << (LDBL_MANT_DIG - e - 1);
if (u.bits.manl < o) /* got a carry */
INC_MANH(u, 1);
}
}
if (huge + x > 0.0) /* raise inexact flag */
u.bits.manl &= ~m;
}
return (u.e);
}
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