text: /*
   * ====================================================
   * Copyright (C) 1998, 2002 by Red Hat Inc. All rights reserved.
   *
   * Permission to use, copy, modify, and distribute this
   * software is freely granted, provided that this notice
   * is preserved.
   * ====================================================
   */
  
  #if !defined(_SOFT_FLOAT)
  
  /*
  Fast version of pow using Intel float instructions.
  
     double _f_pow (double x, double y);
  
  Function calculates x to power of y.
  The function optimizes the case where x is >0.0 and y is finite.
  In such a case, there is no error checking or setting of errno.
  All other cases defer to normal pow() function which will
  set errno as normal.
  */
  
  #include <math.h>
  #include <ieeefp.h>
  #include "f_math.h"
  
  double _f_pow (double x, double y)
  {
    /* following sequence handles the majority of cases for pow() */
    if (x > 0.0 && check_finite(y))
      {
        double result;
        /* calculate x ** y as 2 ** (y log2(x)).  On Intel, can only
           raise 2 to an integer or a small fraction, thus, we have
           to perform two steps 2**integer portion * 2**fraction. */
        asm ("fyl2x; fld %%st; frndint; fsub %%st,%%st(1);"\
             "fxch; fchs; f2xm1; fld1; faddp; fxch; fld1; fscale; fstp %%st(1);"\
             "fmulp" : "=t" (result) : "0" (x), "u" (y) : "st(1)" );
        return result;
      }
    else /* all other strange cases, defer to normal pow() */
      return pow (x,y);
  }
  
  #endif
  