atan2d2.h

Newlib 嵌入式 C库 标准实现代码

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#ifdef __SPU__
#ifndef _ATAN2D2_H_
#define _ATAN2D2_H_	1

#include <spu_intrinsics.h>

#include "divd2.h"
#include "atand2.h"

/*
 * FUNCTION
 *  vector double _atan2d2(vector double y, vector double x)
 *
 * DESCRIPTION
 *  The atan2d2 function returns a vector containing the angles
 *  whose tangets are y/x for the corresponding elements of the
 *  input vectors.
 *
 *  The reason this function exists is to use the signs of the
 *  arguments to determine the quadrant of the result. Consider
 *  sin(x)/cos(x) on the domain (-pi, pi]. Four quadrants are
 *  defined by the signs of sin and cos on this domain.
 *
 *  Special Cases:
 *	- If the corresponding elements of x and y are zero, the 
 *    resulting element is undefined.
 *
 */

static __inline vector double _atan2d2(vector double y, vector double x)
{
    vec_uchar16 dup_even  = ((vec_uchar16) { 0,1,2,3,  0,1,2,3, 8,9,10,11, 8,9,10,11 });
    vector double pi   = spu_splats(SM_PI);
    vector unsigned long long ones = spu_splats(0xFFFFFFFFFFFFFFFFull);
    vector unsigned long long quad1;
    vector unsigned long long quad4;
    vector double result;

    vector unsigned long long xlt0;
    vector unsigned long long yge0;
    vector unsigned long long ylt0;

    xlt0 = (vec_ullong2)spu_rlmaska((vec_int4)spu_shuffle(x,x,dup_even), 31);
    ylt0 = (vec_ullong2)spu_rlmaska((vec_int4)spu_shuffle(y,y,dup_even), 31);
    yge0 = spu_xor(ylt0, ones);

    quad1 = spu_and(ylt0, xlt0);
    quad4 = spu_and(yge0, xlt0);

    result = _atand2(_divd2(y,x));

    result = spu_sel(result, spu_sub(result, pi), quad1);
    result = spu_sel(result, spu_add(result, pi), quad4);

    return result;
}

#endif /* _ATAN2D2_H_ */
#endif /* __SPU__ */