62 lines
2 KiB
C
62 lines
2 KiB
C
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/* 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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* scalbnq (long double x, int n)
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* scalbnq(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 "quadmath-imp.h"
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static const __float128
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two114 = 2.0769187434139310514121985316880384E+34Q, /* 0x4071000000000000, 0 */
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twom114 = 4.8148248609680896326399448564623183E-35Q, /* 0x3F8D000000000000, 0 */
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huge = 1.0E+4900Q,
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tiny = 1.0E-4900Q;
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__float128 scalbnq (__float128 x, int n)
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{
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int64_t k,hx,lx;
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GET_FLT128_WORDS64(hx,lx,x);
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k = (hx>>48)&0x7fff; /* extract exponent */
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if (k==0) { /* 0 or subnormal x */
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if ((lx|(hx&0x7fffffffffffffffULL))==0) return x; /* +-0 */
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x *= two114;
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GET_FLT128_MSW64(hx,x);
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k = ((hx>>48)&0x7fff) - 114;
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}
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if (k==0x7fff) return x+x; /* NaN or Inf */
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if (n< -50000) return tiny*copysignq(tiny,x); /*underflow*/
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if (n> 50000 || k+n > 0x7ffe)
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return huge*copysignq(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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{SET_FLT128_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48)); return x;}
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if (k <= -114)
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return tiny*copysignq(tiny,x); /*underflow*/
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k += 114; /* subnormal result */
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SET_FLT128_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48));
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return x*twom114;
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}
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