[llvm] [NFC] Refactoring DXContainerYaml Root Parameter representation (PR #138318)

[via llvm-commits]

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@@ -316,14 +319,22 @@ void MappingTraits<llvm::DXContainerYAML::RootParameterYamlDesc>::mapping(
   IO.mapRequired("ShaderVisibility", P.Visibility);
 
   switch (P.Type) {
-  case llvm::to_underlying(dxbc::RootParameterType::Constants32Bit):
-    IO.mapRequired("Constants", P.Constants);
-    break;
+  case llvm::to_underlying(dxbc::RootParameterType::Constants32Bit): {
+    DXContainerYAML::RootConstantsYaml Constants;
+    if (IO.outputting())
+      Constants = std::get<DXContainerYAML::RootConstantsYaml>(P.Data);
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joaosaffran wrote:

`DXContainerYaml` handles both serialization and deserialization of yaml files. `IO.outputting()` is a way for me to know which one is happening. Since parameter data is using a variant, the yaml serialization doesn't have a native way of handling that. Therefore, this is a custom logic to read and write the correct parameters data to and from YAML. I think this is still a NFC, since I am just keeping the existing functionality.

https://github.com/llvm/llvm-project/pull/138318