[llvm] [AMDGPU] Update LiveVariables in SILowerControlFlow::combineMasks (PR #217844)

[Arseniy Obolenskiy via llvm-commits]

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@@ -636,10 +638,29 @@ void SILowerControlFlow::combineMasks(MachineInstr &MI) {
     return;
 
   Register Reg = MI.getOperand(OpToReplace).getReg();
+  MachineInstr *Def = MRI->getUniqueVRegDef(Reg);
   MI.removeOperand(OpToReplace);
   MI.addOperand(*KeepOp);
-  if (MRI->use_empty(Reg))
-    MRI->getUniqueVRegDef(Reg)->eraseFromParent();
+
+  // The fold moves the last use of Reg and of the Def sources onto MI.
+  SmallSet<Register, 4> RecomputeLV;
+  if (LV) {
+    RecomputeLV.insert(Reg);
+    for (const MachineOperand &Op : Def->all_uses())
+      if (Op.getReg().isVirtual())
+        RecomputeLV.insert(Op.getReg());
+  }
+
+  if (MRI->use_empty(Reg)) {
+    if (OuterNext == Def->getIterator())
+      ++OuterNext;
+    Def->eraseFromParent();
+  }
+
+  if (LV)
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aobolensk wrote:

Done

https://github.com/llvm/llvm-project/pull/217844