WIP: HLSL: add structuredbuffer pass by reference in fn params

This PR adds the ability to pass structuredbuffer types by reference
as function parameters.

It also changes the representation of structuredbuffers from anonymous
blocks with named members, to named blocks with pseudonymous members.
That should not be an externally visible change.

hlsl/hlslParseHelper.h

@@ -180,6 +180,9 @@ public:
     void initFlattening() { flattenLevel.push_back(0); flattenOffset.push_back(0); }
     void finalizeFlattening() { flattenLevel.pop_back(); flattenOffset.pop_back(); }
 
+    // Share struct buffer deep types
+    void shareStructBufferType(TType&);
+
 protected:
     struct TFlattenData {
         TFlattenData() : nextBinding(TQualifier::layoutBindingEnd) { }
@@ -248,6 +251,14 @@ protected:
     bool isSamplerMethod(const TString& name) const;
     bool isStructBufferMethod(const TString& name) const;
 
+    TType* getStructBufferContentType(const TType& type) const;
+    bool isStructBufferType(const TType& type) const { return getStructBufferContentType(type) != nullptr; }
+    TIntermTyped* indexStructBufferContent(const TSourceLoc& loc, TIntermTyped* buffer) const;
+
+    // Return true if this type is a reference.  This is not currently a type method in case that's
+    // a language specific answer.
+    bool isReference(const TType& type) const { return isStructBufferType(type); }
+
     // Pass through to base class after remembering builtin mappings.
     using TParseContextBase::trackLinkage;
     void trackLinkage(TSymbol& variable) override;
@@ -330,6 +341,9 @@ protected:
     // Structure splitting data:
     TMap<int, TVariable*>              splitIoVars;  // variables with the builtin interstage IO removed, indexed by unique ID.
 
+    // Structuredbuffer shared types.  Typically there are only a few.
+    TVector<TType*> structBufferTypes;
+
     // The builtin interstage IO map considers e.g, EvqPosition on input and output separately, so that we
     // can build the linkage correctly if position appears on both sides.  Otherwise, multiple positions
     // are considered identical.