[llvm] [RISCV][GISel] First mask argument placed in v0 according to RISCV Ve… (PR #79343)

[Craig Topper via llvm-commits]

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@@ -48,10 +51,16 @@ struct RISCVOutgoingValueAssigner : public CallLowering::OutgoingValueAssigner {
     const DataLayout &DL = MF.getDataLayout();
     const RISCVSubtarget &Subtarget = MF.getSubtarget<RISCVSubtarget>();
 
+    std::optional<unsigned> FirstMaskArgument;
+    if (Subtarget.hasVInstructions() && !AssignedFirstMaskArg &&
+        ValVT.isVector() && ValVT.getVectorElementType() == MVT::i1) {
+      FirstMaskArgument = std::make_optional(ValNo);
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topperc wrote:

Why do we need std::make_optional? Can't we do `FirstMaskArgument = ValNo`?

https://github.com/llvm/llvm-project/pull/79343