Newbie: Basic stuff

What does MIOperandInfo exactly mean while defining an Operand class?

e.g. here

class X86MemOperand : Operand {
let PrintMethod = printMethod;
let MIOperandInfo = (ops ptr_rc, i8imm, ptr_rc, i32imm);

This declares X86MemOperand as an "Operand", in the selection DAG sense. In the selection DAG, the type of this operand is iPTR (either i32 or i64 on x86).

MIOperandInfo specifies the number and types of MachineInstr operands (MachineOperand) that the dag operand corresponds to. See this doc (Representing X86 addressing modes in MachineInstrs):

... for a description of what each of these is.