DebugInfo: Partial implementation of DWARF type units.

Emit DW_TAG_type_units into the debug_info section using compile unit
headers. This is bogus/unusable by debuggers, but testable and provides
more isolated review.

Subsequent patches will include support for type unit headers and
emission into the debug_types section, as well as comdat grouping the
types based on their hash. Also the CompileUnit type will be renamed
'Unit' and relevant portions pulled out into respective CompileUnit and
TypeUnit types.

llvm-svn: 195166
diff --git a/llvm/lib/CodeGen/AsmPrinter/DIE.h b/llvm/lib/CodeGen/AsmPrinter/DIE.h
index 28a2e8e..0574a98 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DIE.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DIE.h
@@ -146,12 +146,12 @@
     const std::vector<DIE *> &getChildren() const { return Children; }
     const SmallVectorImpl<DIEValue*> &getValues() const { return Values; }
     DIE *getParent() const { return Parent; }
-    /// Climb up the parent chain to get the compile unit DIE this DIE belongs
-    /// to.
-    const DIE *getCompileUnit() const;
-    /// Similar to getCompileUnit, returns null when DIE is not added to an
+    /// Climb up the parent chain to get the compile or type unit DIE this DIE
+    /// belongs to.
+    const DIE *getUnit() const;
+    /// Similar to getUnit, returns null when DIE is not added to an
     /// owner yet.
-    const DIE *getCompileUnitOrNull() const;
+    const DIE *getUnitOrNull() const;
     void setOffset(unsigned O) { Offset = O; }
     void setSize(unsigned S) { Size = S; }