1  /* s_scalblnl.c -- long double version of s_scalbn.c.
       2   */
       3  
       4  /* @(#)s_scalbn.c 5.1 93/09/24 */
       5  /*
       6   * ====================================================
       7   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
       8   *
       9   * Developed at SunPro, a Sun Microsystems, Inc. business.
      10   * Permission to use, copy, modify, and distribute this
      11   * software is freely granted, provided that this notice
      12   * is preserved.
      13   * ====================================================
      14   */
      15  
      16  #if defined(LIBM_SCCS) && !defined(lint)
      17  static char rcsid[] = "$NetBSD: $";
      18  #endif
      19  
      20  /*
      21   * scalblnl (long double x, long int n)
      22   * scalblnl(x,n) returns x* 2**n  computed by  exponent
      23   * manipulation rather than by actually performing an
      24   * exponentiation or a multiplication.
      25   */
      26  
      27  #include <math.h>
      28  #include <math_private.h>
      29  
      30  static const _Float128
      31  two114 = L(2.0769187434139310514121985316880384E+34), /* 0x4071000000000000, 0 */
      32  twom114 = L(4.8148248609680896326399448564623183E-35), /* 0x3F8D000000000000, 0 */
      33  huge   = L(1.0E+4900),
      34  tiny   = L(1.0E-4900);
      35  
      36  _Float128 __scalblnl (_Float128 x, long int n)
      37  {
      38  	int64_t k,hx,lx;
      39  	GET_LDOUBLE_WORDS64(hx,lx,x);
      40          k = (hx>>48)&0x7fff;		/* extract exponent */
      41          if (k==0) {				/* 0 or subnormal x */
      42              if ((lx|(hx&0x7fffffffffffffffULL))==0) return x; /* +-0 */
      43  	    x *= two114;
      44  	    GET_LDOUBLE_MSW64(hx,x);
      45  	    k = ((hx>>48)&0x7fff) - 114;
      46  	}
      47          if (k==0x7fff) return x+x;		/* NaN or Inf */
      48  	if (n< -50000) return tiny*copysignl(tiny,x); /*underflow*/
      49          if (n> 50000 || k+n > 0x7ffe)
      50  	  return huge*copysignl(huge,x); /* overflow  */
      51  	/* Now k and n are bounded we know that k = k+n does not
      52  	   overflow.  */
      53          k = k+n;
      54          if (k > 0) 				/* normal result */
      55  	    {SET_LDOUBLE_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48)); return x;}
      56          if (k <= -114)
      57  	  return tiny*copysignl(tiny,x); 	/*underflow*/
      58          k += 114;				/* subnormal result */
      59  	SET_LDOUBLE_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48));
      60          return x*twom114;
      61  }