λ x x0 : word64 * word64 * word64 * word64 * word64,
Interp-η
(λ var : Syntax.base_type → Type,
 λ '(x10, x11, x9, x7, x5, (x18, x19, x17, x15, x13))%core,
 ((x10 + x18), (x11 + x19), (x9 + x17), (x7 + x15), (x5 + x13)))
(x, x0)%core
     : word64 * word64 * word64 * word64 * word64 → word64 * word64 * word64 * word64 * word64 → ReturnType (uint64_t * uint64_t * uint64_t * uint64_t * uint64_t)