log1pd2.h

Newlib 嵌入式 C库 标准实现代码

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#ifdef __SPU__
#ifndef _LOG1PD2_H_
#define _LOG1PD2_H_	1

#include <spu_intrinsics.h>
#include "simdmath.h"

#include "logd2.h"
#include "divd2.h"



#define LOG1PD2_P0 0.0000000000000000000000000e+00
#define LOG1PD2_P1 1.0000000000000000000000000e+00
#define LOG1PD2_P2 2.3771612265431403265836252e+00
#define LOG1PD2_P3 2.0034423569559494104908026e+00
#define LOG1PD2_P4 7.1309327316770110272159400e-01
#define LOG1PD2_P5 9.8219761968547217301228613e-02
#define LOG1PD2_P6 3.4385125174546914139650511e-03

#define LOG1PD2_Q0 1.0000000000000000000000000e+00
#define LOG1PD2_Q1 2.8771612265431403265836252e+00
#define LOG1PD2_Q2 3.1086896368941925317130881e+00
#define LOG1PD2_Q3 1.5583843494335058998956356e+00
#define LOG1PD2_Q4 3.6047236436186669283898709e-01
#define LOG1PD2_Q5 3.2620075387969869884496887e-02
#define LOG1PD2_Q6 6.8047193336239690346356479e-04


/*
 * FUNCTION
 *	vector double _log1pd2(vector double x)
 *
 * DESCRIPTION
 *	The function _log1pd2 computes the natural logarithm of x + 1 
 *	for each of the double word elements of x.
 *
 */

static __inline vector double _log1pd2(vector double x) 
{
  vector double oned  = spu_splats(1.0);
  vector double rangehi = spu_splats(0.35);
  vector double rangelo = spu_splats(0.0);
  vector unsigned long long use_log;
  vector double pr, qr;
  vector double eresult;
  vector double rresult;
  vector double result;

  /* Compiler Bug. Replace xbug with x when spu_cmp*() doesn't 
   * modify it's arguments! */
  volatile vector double xbug = x;
  use_log = spu_or(spu_cmpgt(xbug, rangehi), spu_cmpgt(rangelo, xbug));

  /*
   * Calculate directly using log(x+1)
   */
  eresult = _logd2(spu_add(x, oned));

  /*
   * For x in [0.0,0.35], use a rational approximation.
   */
  pr = spu_madd(x, spu_splats(LOG1PD2_P6), spu_splats(LOG1PD2_P5));
  qr = spu_madd(x, spu_splats(LOG1PD2_Q6), spu_splats(LOG1PD2_Q5));
  pr = spu_madd(pr, x, spu_splats(LOG1PD2_P4));
  qr = spu_madd(qr, x, spu_splats(LOG1PD2_Q4));
  pr = spu_madd(pr, x, spu_splats(LOG1PD2_P3));
  qr = spu_madd(qr, x, spu_splats(LOG1PD2_Q3));
  pr = spu_madd(pr, x, spu_splats(LOG1PD2_P2));
  qr = spu_madd(qr, x, spu_splats(LOG1PD2_Q2));
  pr = spu_madd(pr, x, spu_splats(LOG1PD2_P1));
  qr = spu_madd(qr, x, spu_splats(LOG1PD2_Q1));
  pr = spu_madd(pr, x, spu_splats(LOG1PD2_P0));
  qr = spu_madd(qr, x, spu_splats(LOG1PD2_Q0));
  rresult = _divd2(pr, qr);

  /*
   * Select either direct calculation or rational approximation.
   */
  result = spu_sel(rresult, eresult, use_log);

  return result;
}

#endif /* _LOG1PD2_H_ */
#endif /* __SPU__ */