[llvm] GlobalISel lane masks merging (PR #73337)

[Matt Arsenault via llvm-commits]

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@@ -158,9 +153,9 @@ Register MachineSSAUpdater::GetValueInMiddleOfBlock(MachineBasicBlock *BB,
     if (ExistingValueOnly)
       return Register();
     // Insert an implicit_def to represent an undef value.
-    MachineInstr *NewDef = InsertNewDef(TargetOpcode::IMPLICIT_DEF,
-                                        BB, BB->getFirstTerminator(),
-                                        VRC, MRI, TII);
+    MachineInstr *NewDef =
+        InsertNewDef(TargetOpcode::IMPLICIT_DEF, BB, BB->getFirstTerminator(),
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arsenm wrote:

Should really use G_IMPLICIT_DEF if it's a generic virtual register 

https://github.com/llvm/llvm-project/pull/73337