[llvm] [RISCV] Defer forming x0, x0 vsetvlis until after insertion (PR #89089)

[Luke Lau via llvm-commits]

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@@ -806,6 +784,17 @@ static VSETVLIInfo getInfoForVSETVLI(const MachineInstr &MI) {
   }
   NewInfo.setVTYPE(MI.getOperand(2).getImm());
 
+  // FIXME: store the def of AVL instead of the register in VSETVLIInfo so we
+  // don't need to peek through here with MRI.
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lukel97 wrote:

@BeMg This is the part that I'm hoping we can get rid of if we track the definition instead of the register in VSETVLIInfo. There's also something similar in `computeInfoForInstr` where we check the AVL def.

https://github.com/llvm/llvm-project/pull/89089