cosd2.h

Newlib 嵌入式 C库 标准实现代码

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#ifdef __SPU__

#ifndef _COSD2_H_
#define _COSD2_H_	1

#include <spu_intrinsics.h>

#include "cos_sin.h"

/*
 * FUNCTION
 *	vector double _cosd2(vector double angle)
 *
 * DESCRIPTION
 *	_cosd2 computes the cosine of a vector of angles (expressed 
 *	in radians) to an accuracy of a double precision floating point.
 */
static __inline vector double _cosd2(vector double angle)
{
  vec_int4    octant;
  vec_ullong2 select;
  vec_double2 cos, sin;
  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 which result (cos or sin) to use
   * with a sign correction depending upon the octant of the original
   * angle (Maclaurin series).
   *
   *   octants      angles     select  sign toggle 
   *   -------   ------------  ------  -----------
   *     0          0 to 45     cos        no      
   *    1,2        45 to 135    sin        yes
   *    3,4       135 to 225    cos        yes
   *    5,6       225 to 315    sin        no
   *     7        315 to 360    cos        no
   */ 
  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 = (vec_double2)spu_sl(spu_and(spu_add(octant, 2), 4), ((vec_uint4) { 29,32,29,32 }));
  select = (vec_ullong2)spu_cmpeq(spu_and(octant, 2), 0);

  answer = spu_xor(spu_sel(sin, cos, select), toggle_sign);

  return (answer);
}

#endif /* _COSD2_H_ */
#endif /* __SPU__ */