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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 _EXPM1D2_H_
41 #define _EXPM1D2_H_ 1
42
43 #include <spu_intrinsics.h>
44
45 #include "expd2.h"
46 #include "divd2.h"
47
48 #define EXPM1_P0 0.0000000000000000000000000e+00
49 #define EXPM1_P1 1.0000000000000000000000000e+00
50 #define EXPM1_P2 9.7234232565378004697204117e-04
51 #define EXPM1_P3 3.3328278237299953368211192e-02
52 #define EXPM1_P4 3.1156225044634678993365345e-05
53 #define EXPM1_P5 2.1352206553343212164751408e-04
54 #define EXPM1_P6 1.6975135794626144795757452e-07
55 #define EXPM1_P7 2.7686287801334994383131629e-07
56 #define EXPM1_P8 1.1186114936216450015354379e-10
57
58 #define EXPM1_Q0 1.0000000000000000000000000e+00
59 #define EXPM1_Q1 -4.9902765767434620336473472e-01
60 #define EXPM1_Q2 1.1617544040780639069687652e-01
61 #define EXPM1_Q3 -1.6551954366467523660499950e-02
62 #define EXPM1_Q4 1.5864115838972218334307351e-03
63 #define EXPM1_Q5 -1.0534540477401370666288988e-04
64 #define EXPM1_Q6 4.7650003993592160620959043e-06
65 #define EXPM1_Q7 -1.3529198871087017840776265e-07
66 #define EXPM1_Q8 1.8635779407675460757658020e-09
67
68 /*
69 * FUNCTION
70 * vector double _expm1d2(vector double x)
71 *
72 * DESCRIPTION
73 * _expm1d2 computes the exponential - 1 for each element
74 * of the input vector x.
75 *
76 * This function is intended to return accurate values, even
77 * where exp(x) - 1 would normally produce bad results due to
78 * floating-point cancellation errors.
79 *
80 */
81
_expm1d2(vector double x)82 static __inline vector double _expm1d2(vector double x)
83 {
84 vector double oned = spu_splats(1.0);
85 vector double range = spu_splats(1.0625);
86 vector unsigned long long use_exp;
87 vector double pr, qr;
88 vector double eresult;
89 vector double rresult;
90 vector double result;
91
92 /* Compiler Bug. Replace xbug with x when spu_cmp*() doesn't
93 * modify it's arguments! */
94 volatile vector double xbug = x;
95 use_exp = spu_cmpabsgt(xbug, range);
96
97 /*
98 * Calculate directly using exp(x) - 1
99 */
100 eresult = spu_sub(_expd2(x), oned);
101
102 /*
103 * For x in [-1.0625,1.0625], use a rational approximation.
104 * The madd's are interleaved to reduce dependency stalls. Looks
105 * like gcc is smart enough to do this on it's own... but why
106 * take the chance.
107 */
108 pr = spu_madd(x, spu_splats(EXPM1_P8), spu_splats(EXPM1_P7));
109 qr = spu_madd(x, spu_splats(EXPM1_Q8), spu_splats(EXPM1_Q7));
110 pr = spu_madd(pr, x, spu_splats(EXPM1_P6));
111 qr = spu_madd(qr, x, spu_splats(EXPM1_Q6));
112 pr = spu_madd(pr, x, spu_splats(EXPM1_P5));
113 qr = spu_madd(qr, x, spu_splats(EXPM1_Q5));
114 pr = spu_madd(pr, x, spu_splats(EXPM1_P4));
115 qr = spu_madd(qr, x, spu_splats(EXPM1_Q4));
116 pr = spu_madd(pr, x, spu_splats(EXPM1_P3));
117 qr = spu_madd(qr, x, spu_splats(EXPM1_Q3));
118 pr = spu_madd(pr, x, spu_splats(EXPM1_P2));
119 qr = spu_madd(qr, x, spu_splats(EXPM1_Q2));
120 pr = spu_madd(pr, x, spu_splats(EXPM1_P1));
121 qr = spu_madd(qr, x, spu_splats(EXPM1_Q1));
122 pr = spu_madd(pr, x, spu_splats(EXPM1_P0));
123 qr = spu_madd(qr, x, spu_splats(EXPM1_Q0));
124 rresult = _divd2(pr, qr);
125
126 /*
127 * Select either direct calculation or rational approximation.
128 */
129 result = spu_sel(rresult, eresult, use_exp);
130
131 return result;
132 }
133
134 #endif /* _EXPM1D2_H_ */
135 #endif /* __SPU__ */
136
