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39 /* -------------------------------------------------------------- */
40 /* PROLOG END TAG zYx */
41 #ifdef __SPU__
42 #ifndef _SCALBNF4_H_
43 #define _SCALBNF4_H_ 1
44
45 #include <spu_intrinsics.h>
46
47 /*
48 * FUNCTION
49 * vector float _scalbnf4(vector float x, vector signed int exp)
50 *
51 * DESCRIPTION
52 * The _scalbnf4 function returns a vector containing each element of x
53 * multiplied by 2^n computed efficiently. This function is computed
54 * without the assistance of any floating point operations and as such
55 * does not set any floating point exceptions.
56 *
57 * Special Cases:
58 * - if the exponent is 0, then x is either 0 or a subnormal, and the
59 * result will be returned as 0.
60 * - if the result if underflows, it will be returned as 0.
61 * - if the result overflows, it will be returned as FLT_MAX.
62 *
63 */
_scalbnf4(vector float x,vector signed int exp)64 static __inline vector float _scalbnf4(vector float x, vector signed int exp)
65 {
66 vec_int4 x_exp;
67 vec_uint4 zero;
68 vec_uint4 overflow;
69 vec_uint4 exp_mask = (vec_uint4)spu_splats(0x7F800000);
70 vec_float4 out;
71
72 /* Extract exponent from x. If the exponent is 0, then
73 * x is either 0 or a denorm and x*2^exp is a zero.
74 */
75 x_exp = spu_and(spu_rlmask((vec_int4)x, -23), 0xFF);
76 zero = spu_cmpeq(x_exp, 0);
77
78 /* Compute the expected exponent and determine if the
79 * result is within range.
80 */
81 x_exp = spu_add(exp, x_exp);
82
83 /* Check for zero or overflow of result.
84 * Note: set high bit of flags = 0, since we have to
85 * return -0 when x = -0
86 */
87 zero = spu_rlmask(spu_orc(zero, spu_cmpgt(x_exp, 0)), -1);
88 overflow = spu_rlmask(spu_cmpgt(x_exp, 255), -1);
89
90 /* Merge the expect exponent with x's mantissa. Zero the
91 * result if underflow and force to max if overflow.
92 */
93 out = spu_sel(x, (vec_float4)spu_rl(x_exp, 23), exp_mask);
94 out = spu_andc(out, (vec_float4)zero);
95 out = spu_or(out, (vec_float4)overflow);
96
97 return out;
98 }
99
100 #endif /* _SCALBNF4_H_ */
101 #endif /* __SPU__ */
102
