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39 /* -------------------------------------------------------------- */
40 /* PROLOG END TAG zYx */
41 #ifdef __SPU__
42 #ifndef _POWF4_H_
43 #define _POWF4_H_ 1
44
45 #include <spu_intrinsics.h>
46 #include <vec_types.h>
47
48 #include "exp2f4.h"
49 #include "log2f4.h"
50
51 /*
52 * FUNCTION
53 * vector float _powf4(vector float x, vector float y)
54 *
55 * DESCRIPTION
56 * The _powf4 function computes x raised to the power y for the set of
57 * vectors. The powf4 function is computed as by decomposing
58 * the problem into:
59 *
60 * x^y = 2^(y*log2(x))
61 *
62 */
_powf4(vector float x,vector float y)63 static __inline vector float _powf4(vector float x, vector float y)
64 {
65 vec_uint4 y_exp;
66 vec_uint4 y_mantissa;
67 vec_uint4 mant_shift;
68 vec_uint4 y_is_int;
69 vec_uint4 y_is_odd;
70 vec_uint4 x_sign_bit;
71 vec_uint4 zero = (vec_uint4)spu_splats(0);
72 vec_uint4 bit0 = (vec_uint4)spu_splats(0x80000000);
73 vec_int4 error = spu_splats(-1);
74 vec_float4 out;
75
76 y_exp = spu_and(spu_rlmask((vec_uint4)y, -23), 0x000000FF);
77
78 /* Need the implied bit in the mantissa to catch
79 * y = 1 case later
80 */
81 y_mantissa = spu_or(spu_sl((vec_uint4)y, (unsigned int)8), bit0);
82
83 x_sign_bit = spu_and((vec_uint4)x, bit0);
84
85 /* We are going to shift the mantissa over enough to
86 * determine if we have an integer.
87 */
88 mant_shift = spu_add(y_exp, -127);
89
90
91 /* Leave the lowest-order integer bit of mantissa on the
92 * high end so we can see if the integer is odd.
93 */
94 y_mantissa = spu_sl(y_mantissa, mant_shift);
95
96 y_is_int = spu_cmpeq(spu_andc(y_mantissa, bit0), 0);
97 y_is_int = spu_and(y_is_int, spu_cmpgt(y_exp, 126));
98
99 y_is_odd = spu_and(spu_cmpeq(y_mantissa, bit0), y_is_int);
100
101 out = _exp2f4(spu_mul(y, _log2f4(spu_andc(x, (vec_float4)bit0))));
102
103 /* x < 0 is only ok when y integer
104 */
105 out = spu_sel(out, (vec_float4)error,
106 spu_andc(spu_cmpeq(x_sign_bit, bit0), y_is_int));
107
108 /* Preserve the sign of x if y is an odd integer
109 */
110 out = spu_sel(out, spu_or(out, (vec_float4)x_sign_bit), y_is_odd);
111
112 /* x = anything, y = +/- 0, returns 1
113 */
114 out = spu_sel(out, spu_splats(1.0f), spu_cmpabseq(y, (vec_float4)zero));
115
116 return(out);
117 }
118
119 #endif /* _POWF4_H_ */
120 #endif /* __SPU__ */
121
