Well, very similar DSPF_sp_fftSPxSP() function is described in SPRU657C, SPRA947A for C67x. The former clearly states:
Real values are stored in even word positions and imaginary values in odd positions.
So, DSPLIB input data packing is inconsistent with intrinsics like _complex_mpysp(). It looks that if I use intrinsics myself I'd better keep {Im,Re}, but when it comes to DSPLIB, one have to make {Re, Im}. Is that correct? Is there any plan to provide DSPLIB consistent with intrinsics data packing?