virtual ~TargetRegisterInfo();
public:
- enum { // Define some target independent constants
- /// NoRegister - This physical register is not a real target register. It
- /// is useful as a sentinel.
- NoRegister = 0
- };
+ // Register numbers can represent physical registers, virtual registers, and
+ // sometimes stack slots. The unsigned values are divided into these ranges:
+ //
+ // 0 Not a register, can be used as a sentinel.
+ // [1;2^30) Physical registers assigned by TableGen.
+ // [2^30;2^31) Stack slots. (Rarely used.)
+ // [2^31;2^32) Virtual registers assigned by MachineRegisterInfo.
+ //
+ // Further sentinels can be allocated from the small negative integers.
+ // DenseMapInfo<unsigned> uses -1u and -2u.
/// isStackSlot - Sometimes it is useful the be able to store a non-negative
/// frame index in a variable that normally holds a register. isStackSlot()