DebugInfo: Emit only declarations (not whole definitions) of non-unit user defined types into type units

While this doesn't come up in reasonable cases currently (the only user
defined types not in type units are ones without linkage - which makes
for near-ODR violations, because it'd be a type with linkage referencing
a type without linkage - such a type can't be validly defined in more
than one TU, so arguably it shouldn't be in a type unit to begin with -
but it's a convenient way to demonstrate an issue that will become more
revalent with homed modular debug info type definitions - which also
don't need to be in type units but more legitimately so).

Precursor to the Clang change to de-type-unit (by omitting the
'identifier') types homed due to strong linkage vtables. (making that
change without this one would lead to major type duplication in type
units)

llvm-svn: 359122
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
index f19f6d0..14a1373 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
@@ -298,6 +298,9 @@
   /// allocated in the MCContext.
   Optional<MD5::MD5Result> getMD5AsBytes(const DIFile *File) const;
 
+  /// Get context owner's DIE.
+  DIE *createTypeDIE(const DICompositeType *Ty);
+
 protected:
   ~DwarfUnit();
 
@@ -314,11 +317,6 @@
     return Ref.resolve();
   }
 
-  /// If this is a named finished type then include it in the list of types for
-  /// the accelerator tables.
-  void updateAcceleratorTables(const DIScope *Context, const DIType *Ty,
-                               const DIE &TyDIE);
-
   /// Emit the common part of the header for this unit.
   void emitCommonHeader(bool UseOffsets, dwarf::UnitType UT);
 
@@ -346,6 +344,13 @@
   /// Set D as anonymous type for index which can be reused later.
   void setIndexTyDie(DIE *D) { IndexTyDie = D; }
 
+  virtual void finishNonUnitTypeDIE(DIE& D, const DICompositeType *CTy) = 0;
+
+  /// If this is a named finished type then include it in the list of types for
+  /// the accelerator tables.
+  void updateAcceleratorTables(const DIScope *Context, const DIType *Ty,
+                               const DIE &TyDIE);
+
   virtual bool isDwoUnit() const = 0;
   const MCSymbol *getCrossSectionRelativeBaseAddress() const override;
 };
@@ -358,6 +363,7 @@
   bool UsedLineTable = false;
 
   unsigned getOrCreateSourceID(const DIFile *File) override;
+  void finishNonUnitTypeDIE(DIE& D, const DICompositeType *CTy) override;
   bool isDwoUnit() const override;
 
 public:
@@ -367,9 +373,6 @@
   void setTypeSignature(uint64_t Signature) { TypeSignature = Signature; }
   void setType(const DIE *Ty) { this->Ty = Ty; }
 
-  /// Get context owner's DIE.
-  DIE *createTypeDIE(const DICompositeType *Ty);
-
   /// Emit the header for this unit, not including the initial length field.
   void emitHeader(bool UseOffsets) override;
   unsigned getHeaderSize() const override {