ISK
if (!ISK(reg) && reg >= fs->nactvar) {
if (ISK(c)) { /* is 'c' a constant? */
lua_assert(!ISK(GETARG_B(inst)));
ISK(GETARG_B(i)) ? k+INDEXK(GETARG_B(i)) : base+GETARG_B(i))
ISK(GETARG_C(i)) ? k+INDEXK(GETARG_C(i)) : base+GETARG_C(i))