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2 /* (C)Copyright 2007,2008, */
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36 /* -------------------------------------------------------------- */
37 /* PROLOG END TAG zYx */
38 #ifdef __SPU__
39
40 #ifndef _EXPM1F4_H_
41 #define _EXPM1F4_H_ 1
42
43 #include <spu_intrinsics.h>
44
45 #include "expf4.h"
46 #include "divf4.h"
47
48
49 #define EXPM1F4_P0 0.0000000000000000000000000e-00
50 #define EXPM1F4_P1 9.9999999999999988897769754e-01
51 #define EXPM1F4_P2 -6.5597409827762467697531701e-04
52 #define EXPM1F4_P3 2.3800889637330315679042414e-02
53 #define EXPM1F4_P4 -1.0914929910143700584950963e-05
54
55 #define EXPM1F4_Q0 1.0000000000000000000000000e-00
56 #define EXPM1F4_Q1 -5.0065597410018825019761834e-01
57 #define EXPM1F4_Q2 1.0746220997195164714721471e-01
58 #define EXPM1F4_Q3 -1.1966024153043854083566799e-02
59 #define EXPM1F4_Q4 5.9997727954467768105711878e-04
60
61
62 /*
63 * FUNCTION
64 * vector float _expm1f4(vector float x)
65 *
66 * _expm1d2 computes the exponential - 1 for each element
67 * of the input vector x.
68 *
69 * This function is intended to return accurate values, even
70 * where exp(x) - 1 would normally produce bad results due to
71 * floating-point cancellation errors.
72 *
73 */
74
_expm1f4(vector float x)75 static __inline vector float _expm1f4(vector float x)
76 {
77 vector float onef = spu_splats(1.0f);
78 vector float rangelo = spu_splats(-0.4f);
79 vector float rangehi = spu_splats(0.35f);
80 vector unsigned int use_exp;
81 vector float pr, qr;
82 vector float eresult;
83 vector float rresult;
84 vector float result;
85
86 use_exp = spu_or(spu_cmpgt(x, rangehi), spu_cmpgt(rangelo, x));
87
88 /*
89 * Calculate directly using exp(x) - 1
90 */
91 eresult = spu_sub(_expf4(x), onef);
92
93 /*
94 * For x in [-0.5,0.5], use a rational approximation.
95 * The madd's are interleaved to reduce dependency stalls. Looks
96 * like gcc is smart enough to do this on it's own... but why
97 * take the chance.
98 */
99 pr = spu_madd(x, spu_splats((float)EXPM1F4_P4), spu_splats((float)EXPM1F4_P3));
100 qr = spu_madd(x, spu_splats((float)EXPM1F4_Q4), spu_splats((float)EXPM1F4_Q3));
101 pr = spu_madd(pr, x, spu_splats((float)EXPM1F4_P2));
102 qr = spu_madd(qr, x, spu_splats((float)EXPM1F4_Q2));
103 pr = spu_madd(pr, x, spu_splats((float)EXPM1F4_P1));
104 qr = spu_madd(qr, x, spu_splats((float)EXPM1F4_Q1));
105 pr = spu_madd(pr, x, spu_splats((float)EXPM1F4_P0));
106 qr = spu_madd(qr, x, spu_splats((float)EXPM1F4_Q0));
107 rresult = _divf4(pr, qr);
108
109 /*
110 * Select either direct calculation or rational approximation.
111 */
112 result = spu_sel(rresult, eresult, use_exp);
113
114 return result;
115 }
116
117 #endif /* _EXPM1F4_H_ */
118 #endif /* __SPU__ */
119
