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Reminder to my future self to not over-optimize complex conjugate multiply.

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Jared Boone 2015-12-28 10:12:40 -08:00
parent b8726b6ecf
commit dc86db5b87
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3
firmware/common/utility_m4.hpp
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@ -40,6 +40,9 @@ static inline complex32_t multiply_conjugate_s16_s32(const complex16_t::rep_type
// multiply: (a + bj) * (c + dj) = (ac - bd) + (bc + ad)j // multiply: (a + bj) * (c + dj) = (ac - bd) + (bc + ad)j
// conjugate-multiply: (ac + bd) + (bc - ad)j // conjugate-multiply: (ac + bd) + (bc - ad)j
//return { a.real() * b.real() + a.imag() * b.imag(), a.imag() * b.real() - a.real() * b.imag() }; //return { a.real() * b.real() + a.imag() * b.imag(), a.imag() * b.real() - a.real() * b.imag() };
// NOTE: Did not use combination of SMUAD and SMUSDX because of non-saturating arithmetic.
// const int32_t r = __SMUAD(a, b);
// const int32_t i = __SMUSDX(b, a);
const int32_t rr = __SMULBB(a, b); const int32_t rr = __SMULBB(a, b);
const int32_t ii = __SMULTT(a, b); const int32_t ii = __SMULTT(a, b);
const int32_t r = __QADD(rr, ii); const int32_t r = __QADD(rr, ii);