[llvm] [CodeGen][MachineLICM] Use RegUnits in HoistRegionPostRA (PR #94608)

[Matt Arsenault via llvm-commits]

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@@ -540,22 +556,22 @@ void MachineLICMBase::HoistRegionPostRA(MachineLoop *CurLoop,
     // FIXME: That means a reload that're reused in successor block(s) will not
     // be LICM'ed.
     for (const auto &LI : BB->liveins()) {
-      for (MCRegAliasIterator AI(LI.PhysReg, TRI, true); AI.isValid(); ++AI)
-        PhysRegDefs.set(*AI);
+      for (MCRegUnitIterator RUI(LI.PhysReg, TRI); RUI.isValid(); ++RUI)
+        RUDefs.set(*RUI);
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arsenm wrote:

I'm not sure exactly when lane liveins are introduced, or how they interact with aliases. This is another reason that tracking liveins by regunits would be easier to understand 

https://github.com/llvm/llvm-project/pull/94608