kc3-lang/libquadmath/math/scalbnq.c

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• Hash : 4f659ab9
  Author : Thomas de Grivel
  Date : 2025-11-02T19:33:45
  

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• math/scalbnq.c

• /* s_scalbnl.c -- long double version of s_scalbn.c.
   * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
   */
  
  /* @(#)s_scalbn.c 5.1 93/09/24 */
  /*
   * ====================================================
   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   *
   * Developed at SunPro, a Sun Microsystems, Inc. business.
   * Permission to use, copy, modify, and distribute this
   * software is freely granted, provided that this notice
   * is preserved.
   * ====================================================
   */
  
  #if defined(LIBM_SCCS) && !defined(lint)
  static char rcsid[] = "$NetBSD: $";
  #endif
  
  /*
   * scalbnq (long double x, int n)
   * scalbnq(x,n) returns x* 2**n  computed by  exponent
   * manipulation rather than by actually performing an
   * exponentiation or a multiplication.
   */
  
  #include "quadmath-imp.h"
  
  static const __float128
  two114 = 2.0769187434139310514121985316880384E+34Q, /* 0x4071000000000000, 0 */
  twom114 = 4.8148248609680896326399448564623183E-35Q, /* 0x3F8D000000000000, 0 */
  huge   = 1.0E+4900Q,
  tiny   = 1.0E-4900Q;
  
  __float128 scalbnq (__float128 x, int n)
  {
  	int64_t k,hx,lx;
  	GET_FLT128_WORDS64(hx,lx,x);
          k = (hx>>48)&0x7fff;		/* extract exponent */
          if (k==0) {				/* 0 or subnormal x */
              if ((lx|(hx&0x7fffffffffffffffULL))==0) return x; /* +-0 */
  	    x *= two114;
  	    GET_FLT128_MSW64(hx,x);
  	    k = ((hx>>48)&0x7fff) - 114;
  	}
          if (k==0x7fff) return x+x;		/* NaN or Inf */
  	if (n< -50000) return tiny*copysignq(tiny,x); /*underflow*/
          if (n> 50000 || k+n > 0x7ffe)
  	  return huge*copysignq(huge,x); /* overflow  */
  	/* Now k and n are bounded we know that k = k+n does not
  	   overflow.  */
          k = k+n;
          if (k > 0) 				/* normal result */
  	    {SET_FLT128_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48)); return x;}
          if (k <= -114)
  	  return tiny*copysignq(tiny,x); 	/*underflow*/
          k += 114;				/* subnormal result */
  	SET_FLT128_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48));
          return x*twom114;
  }
  

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