+//===----------------------------------------------------------------------===//
+// Register Units
+//===----------------------------------------------------------------------===//
+
+// Register units are used to compute register aliasing. Every register has at
+// least one register unit, but it can have more. Two registers overlap if and
+// only if they have a common register unit.
+//
+// A target with a complicated sub-register structure will typically have many
+// fewer register units than actual registers. MCRI::getNumRegUnits() returns
+// the number of register units in the target.
+
+// MCRegUnitIterator enumerates a list of register units for Reg. The list is
+// in ascending numerical order.
+class MCRegUnitIterator : public MCRegisterInfo::DiffListIterator {
+public:
+ /// MCRegUnitIterator - Create an iterator that traverses the register units
+ /// in Reg.
+ MCRegUnitIterator(unsigned Reg, const MCRegisterInfo *MCRI) {
+ // Decode the RegUnits MCRegisterDesc field.
+ unsigned RU = MCRI->get(Reg).RegUnits;
+ unsigned Scale = RU & 15;
+ unsigned Offset = RU >> 4;
+
+ // Initialize the iterator to Reg * Scale, and the List pointer to
+ // DiffLists + Offset.
+ init(Reg * Scale, MCRI->DiffLists + Offset);
+
+ // That may not be a valid unit, we need to advance by one to get the real
+ // unit number. The first differential can be 0 which would normally
+ // terminate the list, but since we know every register has at least one
+ // unit, we can allow a 0 differential here.
+ advance();
+ }
+};
+