λ x x0 : word64 * word64 * word64 * word64,
Interp-η
(λ var : Syntax.base_type → Type,
 λ '(x8, x9, x7, x5, (x14, x15, x13, x11))%core,
 ((x8 + x14), (x9 + x15), (x7 + x13), (x5 + x11)))
(x, x0)%core
     : word64 * word64 * word64 * word64 → word64 * word64 * word64 * word64 → ReturnType (uint64_t * uint64_t * uint64_t * uint64_t)