[DebugInfo] Introduce DIEExpr variant of DIEValue to hold MCExpr values

This partially reverts r185202 and restores DIELabel to hold plain
MCSymbol references.  Instead, we add a new subclass DIEExpr of
DIEValue that can hold generic MCExpr references.

This is in preparation for supporting debug info for TLS variables
on PowerPC, where we need to describe the variable location using
a more complex expression than just MCSymbolRefExpr.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185458 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h b/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
index 3a95195..7fbf4af 100644
--- a/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
+++ b/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
@@ -218,11 +218,14 @@
   ///
   void addLocalString(DIE *Die, unsigned Attribute, const StringRef Str);
 
+  /// addExpr - Add a Dwarf expression attribute data and value.
+  ///
+  void addExpr(DIE *Die, unsigned Attribute, unsigned Form,
+               const MCExpr *Expr);
+
   /// addLabel - Add a Dwarf label attribute data and value.
   ///
   void addLabel(DIE *Die, unsigned Attribute, unsigned Form,
-                const MCSymbolRefExpr *Label);
-  void addLabel(DIE *Die, unsigned Attribute, unsigned Form,
                 const MCSymbol *Label);
 
   /// addLabelAddress - Add a dwarf label attribute data and value using