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62 lines
1.8 KiB
C
62 lines
1.8 KiB
C
/* s_scalbnl.c -- long double version of s_scalbn.c.
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* Conversion to long double by Ulrich Drepper,
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* Cygnus Support, drepper@cygnus.com.
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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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/*
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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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static const long double
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two64 = 1.8446744073709551616e19L,
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twom64 = 5.421010862427522170037e-20L,
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huge = 1.0e+4900L,
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tiny = 1.0e-4900L;
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long double
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__scalbnl (long double x, int n)
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{
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int32_t k,es,hx,lx;
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GET_LDOUBLE_WORDS(es,hx,lx,x);
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k = es&0x7fff; /* extract exponent */
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if (__builtin_expect(k==0, 0)) { /* 0 or subnormal x */
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if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
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x *= two64;
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GET_LDOUBLE_EXP(hx,x);
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k = (hx&0x7fff) - 64;
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}
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if (__builtin_expect(k==0x7fff, 0)) return x+x; /* NaN or Inf */
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if (__builtin_expect(n< -50000, 0))
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return tiny*__copysignl(tiny,x);
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if (__builtin_expect(n> 50000 || k+n > 0x7ffe, 0))
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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 (__builtin_expect(k > 0, 1)) /* normal result */
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{SET_LDOUBLE_EXP(x,(es&0x8000)|k); return x;}
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if (k <= -64)
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return tiny*__copysignl(tiny,x); /*underflow*/
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k += 64; /* subnormal result */
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SET_LDOUBLE_EXP(x,(es&0x8000)|k);
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return x*twom64;
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}
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weak_alias (__scalbnl, scalbnl)
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