x86/opusdsp: implement FMA3 accelerated postfilter and deemphasis
58893 decicycles in deemphasis_c, 130548 runs, 524 skips
9475 decicycles in deemphasis_fma3, 130686 runs, 386 skips -> 6.21x speedup
24866 decicycles in postfilter_c, 65386 runs, 150 skips
5268 decicycles in postfilter_fma3, 65505 runs, 31 skips -> 4.72x speedup
Total decoder speedup: ~14%
Deemphasis SIMD based on the following unrolling:
const float c1 = CELT_EMPH_COEFF, c2 = c1*c1, c3 = c2*c1, c4 = c3*c1;
float state = coeff;
for (int i = 0; i < len; i += 4) {
y[0] = x[0] + c1*state;
y[1] = x[1] + c2*state + c1*x[0];
y[2] = x[2] + c3*state + c1*x[1] + c2*x[0];
y[3] = x[3] + c4*state + c1*x[2] + c2*x[1] + c3*x[0];
state = y[3];
y += 4;
x += 4;
}
Lynne