113 lines
2.7 KiB
C
113 lines
2.7 KiB
C
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*
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* From: @(#)s_floor.c 5.1 93/09/24
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*/
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#include <sys/cdefs.h>
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__RCSID("$NetBSD: s_floorl.c,v 1.1 2013/11/11 23:57:34 joerg Exp $");
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#if 0
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__FBSDID("$FreeBSD: head/lib/msun/src/s_floorl.c 176280 2008-02-14 15:10:34Z bde $");
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#endif
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/*
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* floorl(x)
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* Return x rounded toward -inf to integral value
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* Method:
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* Bit twiddling.
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* Exception:
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* Inexact flag raised if x not equal to floorl(x).
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*/
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#include "namespace.h"
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#include <float.h>
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#include <math.h>
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#include <stdint.h>
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#include <machine/ieee.h>
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#ifdef __HAVE_LONG_DOUBLE
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#ifdef __weak_alias
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__weak_alias(floorl, _floorl)
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#endif
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#ifdef LDBL_IMPLICIT_NBIT
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#define MANH_SIZE (EXT_FRACHBITS + 1)
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#define INC_MANH(ux, c) do { \
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uint64_t oi = ux.extu_frach; \
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ux.extu_frach += (c); \
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if (ux.extu_frach < oi) \
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ux.extu_exp++; \
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} while (0)
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#else
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#define MANH_SIZE EXT_FRACHBITS
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#define INC_MANH(ux, c) do { \
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uint64_t oi = ux.extu_frach; \
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ux.extu_frach += (c); \
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if (ux.extu_frach < oi) { \
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ux.extu_exp++; \
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ux.extu_frach |= 1llu << (EXT_FRACHBITS - 1); \
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} \
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} while (0)
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#endif
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static const long double huge = 1.0e300;
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long double
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floorl(long double x)
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{
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union ieee_ext_u ux = { .extu_ld = x, };
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int e = ux.extu_exp - LDBL_MAX_EXP + 1;
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if (e < MANH_SIZE - 1) {
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if (e < 0) { /* raise inexact if x != 0 */
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if (huge + x > 0.0)
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if (ux.extu_exp > 0 ||
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(ux.extu_frach | ux.extu_fracl) != 0)
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ux.extu_ld = ux.extu_sign ? -1.0 : 0.0;
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} else {
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uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
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if (((ux.extu_frach & m) | ux.extu_fracl) == 0)
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return (x); /* x is integral */
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if (ux.extu_sign) {
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#ifdef LDBL_IMPLICIT_NBIT
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if (e == 0)
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ux.extu_exp++;
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else
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#endif
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INC_MANH(ux, 1llu << (MANH_SIZE - e - 1));
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}
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if (huge + x > 0.0) { /* raise inexact flag */
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ux.extu_frach &= ~m;
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ux.extu_fracl = 0;
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}
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}
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} else if (e < LDBL_MANT_DIG - 1) {
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uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
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if ((ux.extu_fracl & m) == 0)
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return (x); /* x is integral */
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if (ux.extu_sign) {
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if (e == MANH_SIZE - 1)
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INC_MANH(ux, 1);
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else {
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uint64_t o = ux.extu_fracl;
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ux.extu_fracl += 1llu << (LDBL_MANT_DIG - e - 1);
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if (ux.extu_fracl < o) /* got a carry */
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INC_MANH(ux, 1);
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}
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}
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if (huge + x > 0.0) /* raise inexact flag */
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ux.extu_fracl &= ~m;
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}
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return (ux.extu_ld);
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}
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#endif /* __HAVE_LONG_DOUBLE */
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