[llvm] [RISCV][GISEL] Add support for scalable vector types in lowerReturnVal (PR #71587)

[Matt Arsenault via llvm-commits]

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@@ -301,6 +301,27 @@ struct RISCVCallReturnHandler : public RISCVIncomingValueHandler {
 RISCVCallLowering::RISCVCallLowering(const RISCVTargetLowering &TLI)
     : CallLowering(&TLI) {}
 
+/// Return true if scalable vector with ScalarTy is legal for lowering.
+static bool isLegalElementTypeForRVV(Type *EltTy,
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arsenm wrote:

Why do you need to filter the IR like this? I would hope anything unhandled would naturally fail and hit the fallback 

https://github.com/llvm/llvm-project/pull/71587