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99 lines
2.8 KiB
C
99 lines
2.8 KiB
C
/* s_scalbnl.c -- long double version of s_scalbn.c.
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* Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
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*/
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/* @(#)s_scalbn.c 5.1 93/09/24 */
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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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* scalbnl (long double x, int n)
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* scalbnl(x,n) returns x* 2**n computed by exponent
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* manipulation rather than by actually performing an
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* exponentiation or a multiplication.
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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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static const long double
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twolm54 = 5.55111512312578270212e-17, /* 0x3C90000000000000, 0 */
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huge = 1.0E+300L,
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tiny = 1.0E-300L;
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static const double
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two54 = 1.80143985094819840000e+16, /* 0x4350000000000000 */
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twom54 = 5.55111512312578270212e-17; /* 0x3C90000000000000 */
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long double __scalbnl (long double x, int n)
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{
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int64_t k,l,hx,lx;
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union { int64_t i; double d; } u;
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GET_LDOUBLE_WORDS64(hx,lx,x);
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k = (hx>>52)&0x7ff; /* extract exponent */
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l = (lx>>52)&0x7ff;
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if (k==0) { /* 0 or subnormal x */
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if (((hx|lx)&0x7fffffffffffffffULL)==0) return x; /* +-0 */
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u.i = hx;
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u.d *= two54;
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hx = u.i;
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k = ((hx>>52)&0x7ff) - 54;
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}
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else if (k==0x7ff) return x+x; /* NaN or Inf */
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if (n< -50000) return tiny*__copysignl(tiny,x); /*underflow */
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if (n> 50000 || k+n > 0x7fe)
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return huge*__copysignl(huge,x); /* overflow */
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/* Now k and n are bounded we know that k = k+n does not
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overflow. */
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k = k+n;
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if (k > 0) { /* normal result */
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hx = (hx&0x800fffffffffffffULL)|(k<<52);
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if ((lx & 0x7fffffffffffffffULL) == 0) { /* low part +-0 */
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SET_LDOUBLE_WORDS64(x,hx,lx);
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return x;
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}
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if (l == 0) { /* low part subnormal */
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u.i = lx;
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u.d *= two54;
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lx = u.i;
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l = ((lx>>52)&0x7ff) - 54;
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}
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l = l + n;
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if (l > 0)
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lx = (lx&0x800fffffffffffffULL)|(l<<52);
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else if (l <= -54)
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lx = (lx&0x8000000000000000ULL);
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else {
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l += 54;
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u.i = (lx&0x800fffffffffffffULL)|(l<<52);
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u.d *= twom54;
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lx = u.i;
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}
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SET_LDOUBLE_WORDS64(x,hx,lx);
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return x;
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}
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if (k <= -54)
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return tiny*__copysignl(tiny,x); /*underflow*/
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k += 54; /* subnormal result */
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lx &= 0x8000000000000000ULL;
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SET_LDOUBLE_WORDS64(x,(hx&0x800fffffffffffffULL)|(k<<52),lx);
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return x*twolm54;
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}
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#ifdef IS_IN_libm
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long_double_symbol (libm, __scalbnl, scalbnl);
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#else
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long_double_symbol (libc, __scalbnl, scalbnl);
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#endif
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