improve comment, maybe

Author: Joao Saffran

llvm/lib/ObjectYAML/DXContainerYAML.cpp

@@ -424,12 +424,13 @@ void MappingContextTraits<DXContainerYAML::RootParameterLocationYaml,
   IO.mapRequired("ParameterType", L.Header.Type);
   IO.mapRequired("ShaderVisibility", L.Header.Visibility);
 
+  // If a parameter type is invalid, we don't have a body to parse.
   if (!dxbc::isValidParameterType(L.Header.Type))
     return;
+
+  // parses the body of a given root parameter type
   dxbc::RootParameterType PT =
       static_cast<dxbc::RootParameterType>(L.Header.Type);
-
-  // We allow ParameterType to be invalid here.
   switch (PT) {
   case dxbc::RootParameterType::Constants32Bit: {
     DXContainerYAML::RootConstantsYaml &Constants =