FCLoopSplit[exp, {q1, q2, ...}] separates exp into the following four pieces:
terms that are free of loop integrals
terms with scalar loop integrals
terms with tensor loop integrals, where all loop momenta are contracted
terms with tensor loop integrals, where at least some loop momenta have free indices
The result is returned as a list with the 4 above elements.
FVD[q, \[Mu]] FAD[{q, m}]
FCLoopSplit[%, {q}]\frac{q^{\mu }}{q^2-m^2}
\left\{0,0,0,\frac{q^{\mu }}{q^2-m^2}\right\}
x + GSD[p + q] FAD[{q, m}]
FCLoopSplit[%, {q}]\frac{\gamma \cdot (p+q)}{q^2-m^2}+x
\left\{x,\frac{\gamma \cdot p}{q^2-m^2},0,\frac{\gamma \cdot q}{q^2-m^2}\right\}