[llvm] [AMDGPU] Constrain use LiveMask by the operand's LaneMask for RP calculation. (PR #111452)

[Matt Arsenault via llvm-commits]

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@@ -265,13 +265,14 @@ class GCNDownwardRPTracker : public GCNRPTracker {
                const LiveRegSet *LiveRegsCopy = nullptr);
 };
 
-LaneBitmask getLiveLaneMask(unsigned Reg,
-                            SlotIndex SI,
+LaneBitmask getLiveLaneMask(unsigned Reg, SlotIndex SI,
                             const LiveIntervals &LIS,
-                            const MachineRegisterInfo &MRI);
+                            const MachineRegisterInfo &MRI,
+                            LaneBitmask Mask = LaneBitmask::getAll());
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arsenm wrote:

Parameter name could be more specific, and should be documented. 

https://github.com/llvm/llvm-project/pull/111452