text: /* @(#)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.
   * ====================================================
   */
  
  #ifndef lint
  static char rcsid[] = "$FreeBSD: releng/11.1/lib/msun/src/s_scalbn.c 143264 2005-03-07 21:27:37Z das $";
  #endif
  
  /*
   * scalbn (double x, int n)
   * scalbn(x,n) returns x* 2**n  computed by  exponent
   * manipulation rather than by actually performing an
   * exponentiation or a multiplication.
   */
  
  #include <sys/cdefs.h>
  #include <float.h>
  
  #include "math.h"
  #include "math_private.h"
  
  static const double
  two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
  twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
  huge   = 1.0e+300,
  tiny   = 1.0e-300;
  
  double
  scalbn (double x, int n)
  {
  	int32_t k,hx,lx;
  	EXTRACT_WORDS(hx,lx,x);
          k = (hx&0x7ff00000)>>20;		/* extract exponent */
          if (k==0) {				/* 0 or subnormal x */
              if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
  	    x *= two54;
  	    GET_HIGH_WORD(hx,x);
  	    k = ((hx&0x7ff00000)>>20) - 54;
              if (n< -50000) return tiny*x; 	/*underflow*/
  	    }
          if (k==0x7ff) return x+x;		/* NaN or Inf */
          k = k+n;
          if (k >  0x7fe) return huge*copysign(huge,x); /* overflow  */
          if (k > 0) 				/* normal result */
  	    {SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;}
          if (k <= -54)
              if (n > 50000) 	/* in case integer overflow in n+k */
  		return huge*copysign(huge,x);	/*overflow*/
  	    else return tiny*copysign(tiny,x); 	/*underflow*/
          k += 54;				/* subnormal result */
  	SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));
          return x*twom54;
  }
  
  #if (LDBL_MANT_DIG == 53)
  __weak_reference(scalbn, ldexpl);
  __weak_reference(scalbn, scalbnl);
  #endif
  