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37 /* PROLOG END TAG zYx */
38
39 #ifdef __SPU__
40 #ifndef _LOG1PF4_H_
41 #define _LOG1PF4_H_ 1
42
43 #include <spu_intrinsics.h>
44 #include "simdmath.h"
45
46 #include "logf4.h"
47 #include "divf4.h"
48
49 /*
50 * FUNCTION
51 * vector float _log1pf4(vector float x)
52 *
53 * DESCRIPTION
54 * The function _log1pf4 computes the natural logarithm of x + 1
55 * for each of the float word elements of x.
56 *
57 *
58 */
59
60 #define LOG1PF4_P0 0.0000000000000000000000000e+00f
61 #define LOG1PF4_P1 1.0000000000000000000000000e+00f
62 #define LOG1PF4_P2 1.4220868022897381610647471e+00f
63 #define LOG1PF4_P3 5.4254553902256308361984338e-01f
64 #define LOG1PF4_P4 4.5971908823142115796400731e-02f
65
66 #define LOG1PF4_Q0 1.0000000000000000000000000e+00f
67 #define LOG1PF4_Q1 1.9220868007537357247116461e+00f
68 #define LOG1PF4_Q2 1.1702556461286610645089468e+00f
69 #define LOG1PF4_Q3 2.4040413392943396631018516e-01f
70 #define LOG1PF4_Q4 1.0637426466449625625521058e-02f
71
72
_log1pf4(vector float x)73 static __inline vector float _log1pf4(vector float x)
74 {
75 vector float onef = spu_splats(1.0f);
76 vector float range = spu_splats(0.35f);
77 vector unsigned int use_log;
78 vector float pr, qr;
79 vector float eresult;
80 vector float rresult;
81 vector float result;
82
83 use_log = spu_cmpabsgt(x, range);
84
85 /*
86 * Calculate directly using log(x+1)
87 */
88 eresult = _logf4(spu_add(x, onef));
89
90 /*
91 * For x in [-0.35,0.35], use a rational approximation.
92 */
93 pr = spu_madd(x, spu_splats((float)LOG1PF4_P4), spu_splats((float)LOG1PF4_P3));
94 qr = spu_madd(x, spu_splats((float)LOG1PF4_Q4), spu_splats((float)LOG1PF4_Q3));
95 pr = spu_madd(pr, x, spu_splats((float)LOG1PF4_P2));
96 qr = spu_madd(qr, x, spu_splats((float)LOG1PF4_Q2));
97 pr = spu_madd(pr, x, spu_splats((float)LOG1PF4_P1));
98 qr = spu_madd(qr, x, spu_splats((float)LOG1PF4_Q1));
99 pr = spu_madd(pr, x, spu_splats((float)LOG1PF4_P0));
100 qr = spu_madd(qr, x, spu_splats((float)LOG1PF4_Q0));
101 rresult = _divf4(pr, qr);
102
103 /*
104 * Select either direct calculation or rational approximation.
105 */
106 result = spu_sel(rresult, eresult, use_log);
107
108 return result;
109 }
110
111 #endif /* _LOG1PF4_H_ */
112 #endif /* __SPU__ */
113
