[llvm] [RISCV][NFC] Add helpers for RVV register classes (PR #84144)

[Craig Topper via llvm-commits]

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@@ -278,21 +278,7 @@ class RVVRegisterRegAlloc : public RegisterRegAllocBase<RVVRegisterRegAlloc> {
 
 static bool onlyAllocateRVVReg(const TargetRegisterInfo &TRI,
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topperc wrote:

Was TRI an unused argument before?

https://github.com/llvm/llvm-project/pull/84144