[llvm] [RISCV][VLOPT] Compute demanded VLs up front (PR #124530)

[Luke Lau via llvm-commits]

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@@ -56,6 +57,10 @@ class RISCVVLOptimizer : public MachineFunctionPass {
   std::optional<MachineOperand> checkUsers(MachineInstr &MI);
   bool tryReduceVL(MachineInstr &MI);
   bool isCandidate(const MachineInstr &MI) const;
+
+  /// For a given instruction, records what elements of it are demanded by
+  /// downstream users.
+  DenseMap<const MachineInstr *, MachineOperand> DemandedVLs;
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lukel97 wrote:

More than happy to do so! Hope this didn't come across as an optimisation/stylistic point, that wasn't my intention. 

https://github.com/llvm/llvm-project/pull/124530