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37 /* PROLOG END TAG zYx */
38
39 #ifdef __SPU__
40
41 #ifndef _ATAND2_H_
42 #define _ATAND2_H_ 1
43
44 #include <spu_intrinsics.h>
45
46 #include "simdmath.h"
47 #include "recipd2.h"
48 #include "logd2.h"
49 #include "acosd2.h"
50 #include "asind2.h"
51 #include "sqrtd2.h"
52
53 /*
54 * FUNCTION
55 * vector double _atand2(vector double x)
56 *
57 * DESCRIPTION
58 * The _atand2 function computes the arc tangent of a vector of values x.
59 *
60 * The arc tangent function is computed using the following relations:
61 * [0, 1] : arcsin(x1/sqrt(spu_add(x1squ + 1 )));
62 * (1, infinity] : PI/2 + atanf(-1/x)
63 * [-infinity, 0) : -arcsin(|x|)
64 *
65 */
66
_atand2(vector double x)67 static __inline vector double _atand2(vector double x)
68 {
69 vector double signbit = spu_splats(-0.0);
70 vector double oned = spu_splats(1.0);
71 vector double pi2 = spu_splats(SM_PI_2);
72 vector double xabs, x1;
73 vector double result;
74 vector unsigned long long gt1;
75
76 xabs = spu_andc(x, signbit);
77 gt1 = spu_cmpgt(xabs, oned);
78
79 /*
80 * For x > 1, use the relation:
81 * atan(x) = pi/2 - atan(1/x), x>1
82 */
83 x1 = spu_sel(xabs, _recipd2(xabs), gt1);
84
85 vector double x1squ = spu_mul(x1, x1);
86
87 result = _asind2(_divd2(x1, _sqrtd2(spu_add(x1squ, oned))));
88
89 /*
90 * For x > 1, use the relation: atan(x) = pi/2 - atan(1/x), x>1
91 */
92 result = spu_sel(result, spu_sub(pi2, result), gt1);
93
94 /*
95 * Antisymmetric function - preserve sign of x in result.
96 */
97 result = spu_sel(result, x, (vec_ullong2)signbit);
98
99 return (result);
100 }
101
102 #endif /* _ATAND2_H_ */
103 #endif /* __SPU__ */
104
