Debug Info: Use identifier to reference DIType in base type field of

ptr_to_member.

We introduce a new class DITypeRef that represents a reference to a DIType.
It wraps around a Value*, which can be either an identifier in MDString
or an actual MDNode. The class has a helper function "resolve" that
finds the actual MDNode for a given DITypeRef.

We specialize getFieldAs to return a field that is a reference to a
DIType. To correctly access the base type field of ptr_to_member,
getClassType now calls getFieldAs<DITypeRef> to return a DITypeRef.

Also add a typedef for DITypeIdentifierMap and a helper
generateDITypeIdentifierMap in DebugInfo.h. In DwarfDebug.cpp, we keep
a DITypeIdentifierMap and call generateDITypeIdentifierMap to actually
populate the map.

Verifier is updated accordingly.

llvm-svn: 190081

1 files changed, 13 insertions, 1 deletions

diff --git a/llvm/lib/IR/DIBuilder.cpp b/llvm/lib/IR/DIBuilder.cpp
index 51e296383e0..2ff10b593ed 100644
--- a/llvm/lib/IR/DIBuilder.cpp
+++ b/llvm/lib/IR/DIBuilder.cpp
@@ -75,6 +75,18 @@ void DIBuilder::finalize() {
   DIType(TempImportedModules).replaceAllUsesWith(IMs);
 }
 
+/// Use the type identifier instead of the actual MDNode if possible,
+/// to help type uniquing. This function returns the identifier if it
+/// exists for the given type, otherwise returns the MDNode.
+static Value *getTypeIdentifier(DIType T) {
+  if (!T.isCompositeType())
+    return T;
+  DICompositeType DTy(T);
+  if (!DTy.getIdentifier())
+    return T;
+  return DTy.getIdentifier();
+}
+
 /// getNonCompileUnitScope - If N is compile unit return NULL otherwise return
 /// N.
 static MDNode *getNonCompileUnitScope(MDNode *N) {
@@ -322,7 +334,7 @@ DIDerivedType DIBuilder::createMemberPointerType(DIType PointeeTy,
     ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
     ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Flags
     PointeeTy,
-    Base
+    getTypeIdentifier(Base)
   };
   return DIDerivedType(MDNode::get(VMContext, Elts));
 }