[llvm] [llvm][CodeGen] Update checking method of loop-carried phi in window scheduler (PR #96288)

[Matt Arsenault via llvm-commits]

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@@ -192,22 +192,36 @@ bool WindowScheduler::initialize() {
     return false;
   }
   // Check each MI in MBB.
-  SmallVector<Register, 8> PhiDefs;
+  SmallSet<Register, 8> PrevDefs;
+  SmallSet<Register, 8> PrevUses;
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arsenm wrote:

These sets aren't used outside of the lambda. Just make the lambda a helper function with these used locally? 

https://github.com/llvm/llvm-project/pull/96288