private static void CgTableAccessExp(FuncInfo fi, TableAccessExp node, int a)
{
var b = fi.AllocReg();
CgExp(fi, node.PrefixExp, b, 1);
var c = fi.AllocReg();
CgExp(fi, node.KeyExp, c, 1);
fi.EmitGetTable(a, b, c);
fi.FreeRegs(2);
}