[llvm] [RISCV][VLOpt] Reorganize visit order and worklist management (PR #123973)

[Philip Reames via llvm-commits]

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@@ -1292,53 +1292,60 @@ std::optional<MachineOperand> RISCVVLOptimizer::checkUsers(MachineInstr &MI) {
   return CommonVL;
 }
 
-bool RISCVVLOptimizer::tryReduceVL(MachineInstr &OrigMI) {
-  SetVector<MachineInstr *> Worklist;
-  Worklist.insert(&OrigMI);
+bool RISCVVLOptimizer::tryReduceVL(MachineInstr &MI) {
+  LLVM_DEBUG(dbgs() << "Trying to reduce VL for " << MI << "\n");
 
-  bool MadeChange = false;
-  while (!Worklist.empty()) {
-    MachineInstr &MI = *Worklist.pop_back_val();
-    LLVM_DEBUG(dbgs() << "Trying to reduce VL for " << MI << "\n");
+  if (!isVectorRegClass(MI.getOperand(0).getReg(), MRI))
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preames wrote:

There's a bit more cleanup on some the workload invariants here.  I'm planning a separate patch.  

https://github.com/llvm/llvm-project/pull/123973