1  /* s_scalbnf.c -- float version of s_scalbn.c.
       2   */
       3  
       4  /*
       5   * ====================================================
       6   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
       7   *
       8   * Developed at SunPro, a Sun Microsystems, Inc. business.
       9   * Permission to use, copy, modify, and distribute this
      10   * software is freely granted, provided that this notice
      11   * is preserved.
      12   * ====================================================
      13   */
      14  
      15  #include <math.h>
      16  #include <math_private.h>
      17  
      18  static const float
      19  two25   =  3.355443200e+07,	/* 0x4c000000 */
      20  twom25  =  2.9802322388e-08,	/* 0x33000000 */
      21  huge   = 1.0e+30,
      22  tiny   = 1.0e-30;
      23  
      24  float
      25  __scalbnf (float x, int n)
      26  {
      27  	int32_t k,ix;
      28  	GET_FLOAT_WORD(ix,x);
      29  	k = (ix&0x7f800000)>>23;		/* extract exponent */
      30  	if (__builtin_expect(k==0, 0)) {	/* 0 or subnormal x */
      31  	    if ((ix&0x7fffffff)==0) return x; /* +-0 */
      32  	    x *= two25;
      33  	    GET_FLOAT_WORD(ix,x);
      34  	    k = ((ix&0x7f800000)>>23) - 25;
      35  	    }
      36  	if (__builtin_expect(k==0xff, 0)) return x+x;	/* NaN or Inf */
      37  	if (__builtin_expect(n< -50000, 0))
      38  	  return tiny*copysignf(tiny,x);	/*underflow*/
      39  	if (__builtin_expect(n> 50000 || k+n > 0xfe, 0))
      40  	  return huge*copysignf(huge,x); /* overflow  */
      41  	/* Now k and n are bounded we know that k = k+n does not
      42  	   overflow.  */
      43  	k = k+n;
      44  	if (__builtin_expect(k > 0, 1))		/* normal result */
      45  	    {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
      46  	if (k <= -25)
      47  	    return tiny*copysignf(tiny,x);	/*underflow*/
      48  	k += 25;				/* subnormal result */
      49  	SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
      50  	return x*twom25;
      51  }