148 lines
3.5 KiB
C
148 lines
3.5 KiB
C
/* s_frexpl.c -- long double version of s_frexp.c.
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*/
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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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#if defined(LIBM_SCCS) && !defined(lint)
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static char rcsid[] = "$NetBSD: $";
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#endif
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/*
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* for non-zero x
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* x = frexpl(arg,&exp);
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* return a long double fp quantity x such that 0.5 <= |x| <1.0
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* and the corresponding binary exponent "exp". That is
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* arg = x*2^exp.
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* If arg is inf, 0.0, or NaN, then frexpl(arg,&exp) returns arg
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* with *exp=0.
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*/
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#include <math.h>
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#include <math_private.h>
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#include <math_ldbl_opt.h>
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long double __frexpl(long double x, int *eptr)
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{
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uint64_t hx, lx, ix, ixl;
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int64_t explo, expon;
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double xhi, xlo;
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ldbl_unpack (x, &xhi, &xlo);
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EXTRACT_WORDS64 (hx, xhi);
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EXTRACT_WORDS64 (lx, xlo);
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ixl = 0x7fffffffffffffffULL & lx;
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ix = 0x7fffffffffffffffULL & hx;
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expon = 0;
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if (ix >= 0x7ff0000000000000ULL || ix == 0)
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{
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/* 0,inf,nan. */
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*eptr = expon;
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return x + x;
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}
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expon = ix >> 52;
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if (expon == 0)
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{
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/* Denormal high double, the low double must be 0.0. */
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int cnt;
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/* Normalize. */
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if (sizeof (ix) == sizeof (long))
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cnt = __builtin_clzl (ix);
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else if ((ix >> 32) != 0)
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cnt = __builtin_clzl ((long) (ix >> 32));
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else
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cnt = __builtin_clzl ((long) ix) + 32;
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cnt = cnt - 12;
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expon -= cnt;
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ix <<= cnt + 1;
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}
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expon -= 1022;
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ix &= 0x000fffffffffffffULL;
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hx &= 0x8000000000000000ULL;
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hx |= (1022LL << 52) | ix;
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if (ixl != 0)
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{
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/* If the high double is an exact power of two and the low
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double has the opposite sign, then the exponent calculated
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from the high double is one too big. */
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if (ix == 0
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&& (int64_t) (hx ^ lx) < 0)
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{
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hx += 1LL << 52;
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expon -= 1;
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}
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explo = ixl >> 52;
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if (explo == 0)
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{
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/* The low double started out as a denormal. Normalize its
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mantissa and adjust the exponent. */
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int cnt;
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if (sizeof (ixl) == sizeof (long))
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cnt = __builtin_clzl (ixl);
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else if ((ixl >> 32) != 0)
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cnt = __builtin_clzl ((long) (ixl >> 32));
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else
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cnt = __builtin_clzl ((long) ixl) + 32;
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cnt = cnt - 12;
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explo -= cnt;
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ixl <<= cnt + 1;
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}
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/* With variable precision we can't assume much about the
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magnitude of the returned low double. It may even be a
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denormal. */
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explo -= expon;
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ixl &= 0x000fffffffffffffULL;
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lx &= 0x8000000000000000ULL;
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if (explo <= 0)
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{
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/* Handle denormal low double. */
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if (explo > -52)
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{
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ixl |= 1LL << 52;
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ixl >>= 1 - explo;
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}
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else
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{
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ixl = 0;
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lx = 0;
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if ((hx & 0x7ff0000000000000ULL) == (1023LL << 52))
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{
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/* Oops, the adjustment we made above for values a
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little smaller than powers of two turned out to
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be wrong since the returned low double will be
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zero. This can happen if the input was
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something weird like 0x1p1000 - 0x1p-1000. */
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hx -= 1LL << 52;
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expon += 1;
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}
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}
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explo = 0;
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}
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lx |= (explo << 52) | ixl;
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}
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INSERT_WORDS64 (xhi, hx);
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INSERT_WORDS64 (xlo, lx);
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x = ldbl_pack (xhi, xlo);
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*eptr = expon;
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return x;
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}
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#if IS_IN (libm)
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long_double_symbol (libm, __frexpl, frexpl);
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#else
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long_double_symbol (libc, __frexpl, frexpl);
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#endif
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