getCMode
lua_assert(getCMode(o) != OpArgN || c == 0);
lua_assert(getCMode(o) == OpArgN);
#define RC(i) check_exp(getCMode(GET_OPCODE(i)) == OpArgR, base+GETARG_C(i))
#define RKC(i) check_exp(getCMode(GET_OPCODE(i)) == OpArgK, \