tand2.h

Newlib 嵌入式 C库 标准实现代码

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/* PROLOG END TAG zYx                                              */
#ifdef __SPU__
#ifndef _TAND2_H_
#define _TAND2_H_	1

#include <spu_intrinsics.h>

#include "cos_sin.h"
#include "divd2.h"

/*
 * FUNCTION
 *	vector double _tand2(vector double angle)
 *
 * DESCRIPTION
 *	The _tand2 function computes the tangent of a vector of "angle"s 
 *      (expressed in radians) to an accuracy of double precision floating 
 *      point.
 *
 */
static __inline vector double _tand2(vector double angle)
{
  vec_int4    octant;
  vec_ullong2 select;
  vec_double2 cos, sin;
  vec_double2 num, den;
  vec_double2 toggle_sign, answer;

  /* Range reduce the input angle x into the range -PI/4 to PI/4
   * by performing simple modulus.
   */
  MOD_PI_OVER_FOUR(angle, octant);

  /* Compute the cosine and sine of the range reduced input.
   */
  COMPUTE_COS_SIN(angle, cos, sin);

  /* For each SIMD element, select the numerator, denominator, and sign
   * correction depending upon the octant of the original angle.
   *
   *   octants      angles     numerator denominator sign toggle 
   *   -------   ------------  --------- ----------- -----------
   *     0          0 to 45      sin        cos          no      
   *    1,2        45 to 135     cos        sin         no,yes
   *    3,4       135 to 225     sin        cos         yes,no
   *    5,6       225 to 315     cos        sin         no,yes
   *     7        315 to 360     sin        cos          yes
   */ 
  octant = spu_shuffle(octant, octant, ((vec_uchar16) {
					  0,1, 2, 3, 0,1, 2, 3,
					    8,9,10,11, 8,9,10,11 }));

  toggle_sign = spu_and((vec_double2)spu_sl(octant, 30),
    (vec_double2) spu_splats(0x8000000000000000ULL));

  select = (vec_ullong2)spu_cmpeq(spu_and(octant, 2), 0);
  num = spu_sel(cos, sin, select);
  den = spu_sel(sin, cos, select);

  answer = spu_xor(_divd2(num, den), toggle_sign);

  return (answer);
}

#endif /* _TAND2_H_ */
#endif /* __SPU__ */