[llvm] [AMDGPU][MachineRegisterInfo] Extend the MRI live-ins check to account for Subreg (PR #126926)

[Vikash Gupta via llvm-commits]

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@@ -1020,7 +1020,7 @@ class MachineRegisterInfo {
     return LiveIns;
   }
 
-  bool isLiveIn(Register Reg) const;
+  bool isLiveIn(Register Reg, bool CheckForSubreg = false) const;
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vg0204 wrote:

Done it already for MachineFunction here itself, only apparently seen it left for machine verifier, which will require bit of work, so better to do separately. Any other place @cdevadas @arsenm you think it should be taken care. If its OK with you, I can take it up this task, atleast the supposedly apparent things!

https://github.com/llvm/llvm-project/pull/126926