[llvm] [RISCV] Add TSFlag for reading past VL behaviour. NFCI (PR #149704)

[Pengcheng Wang via llvm-commits]

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@@ -1315,7 +1287,8 @@ RISCVVLOptimizer::getMinimumVLForUser(const MachineOperand &UserOp) const {
     return std::nullopt;
   }
 
-  if (mayReadPastVL(UserMI)) {
+  if (RISCVII::readsPastVL(
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wangpc-pp wrote:

Can we add this bit to RVVPseudo so that we don't need to convert the opcode to MC opcode first?

https://github.com/llvm/llvm-project/pull/149704