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36 /* -------------------------------------------------------------- */
37 /* PROLOG END TAG zYx */
38 #ifdef __SPU__
39
40 #ifndef _LOGBF4_H_
41 #define _LOGBF4_H_ 1
42
43 #include <spu_intrinsics.h>
44 #include <vec_types.h>
45
46 /*
47 * FUNCTION
48 * vector float _logbf4(vector float x)
49 *
50 * DESCRIPTION
51 * The _logbf4 function returns a vector float that contains the exponent
52 * of the corresponding elements of the input vector x. The exponent is
53 * defined by:
54 * x = frac * FLT_RADIX^exp, with frac in [1, FLT_RADIX).
55 *
56 * Special Cases:
57 * x = 0, result is undefined.
58 * x = NaN, result is NaN.
59 * x = infinity, +infinity is returned.
60 *
61 */
_logbf4(vector float x)62 static __inline vector float _logbf4(vector float x)
63 {
64 vec_uint4 lzero = (vector unsigned int) {0, 0, 0, 0};
65 vec_uint4 exp_mask = (vector unsigned int) {0xFF, 0xFF, 0xFF, 0xFF};
66 vec_int4 exp_shift = (vector signed int) { -23, -23, -23, -23};
67 vec_int4 exp_bias = (vector signed int) {-127, -127, -127, -127};
68 vec_uint4 sign_mask = (vector unsigned int) {0x80000000, 0x80000000,
69 0x80000000, 0x80000000};
70 vec_uint4 linf = (vector unsigned int) {0x7F800000, 0x7F800000,
71 0x7F800000, 0x7F800000};
72 vec_uint4 lminf = (vector unsigned int) {0xFF800000, 0xFF800000,
73 0xFF800000, 0xFF800000};
74 vec_uint4 exp;
75 vec_uint4 xabs;
76 vec_float4 exp_unbias;
77
78
79 xabs = spu_andc((vec_uint4)x, sign_mask);
80
81 exp = spu_and(spu_rlmask((vec_uint4)x, exp_shift), exp_mask);
82 exp_unbias = spu_convtf(spu_add((vec_int4)exp, exp_bias), 0);
83
84 /* Zero */
85 exp_unbias = spu_sel(exp_unbias, (vec_float4)lminf, (vec_uint4)spu_cmpeq(xabs, lzero));
86
87 /* NaN */
88 exp_unbias = spu_sel(exp_unbias, x, (vec_uint4)spu_cmpgt(xabs, linf));
89
90 /* Infinite */
91 exp_unbias = spu_sel(exp_unbias, (vec_float4)linf, (vec_uint4)spu_cmpeq(xabs, linf));
92
93 return (exp_unbias);
94 }
95
96 #endif /* _LOGBF4_H_ */
97
98 #endif /* __SPU__ */
99
