Switch the type field in DIVariable and DIGlobalVariable over to DITypeRefs.
This allows us to catch more opportunities for ODR-based type uniquing
during LTO.
Paired commit with CFE which updates some testcases to verify the new
DIBuilder behavior.

llvm-svn: 204106
diff --git a/llvm/lib/IR/DebugInfo.cpp b/llvm/lib/IR/DebugInfo.cpp
index d69138e..afeeb7b 100644
--- a/llvm/lib/IR/DebugInfo.cpp
+++ b/llvm/lib/IR/DebugInfo.cpp
@@ -541,10 +541,11 @@
 
   if (getDisplayName().empty())
     return false;
-  // Make sure context @ field 2 and type @ field 8 are MDNodes.
+  // Make sure context @ field 2 is an MDNode.
   if (!fieldIsMDNode(DbgNode, 2))
     return false;
-  if (!fieldIsMDNode(DbgNode, 8))
+  // Make sure that type @ field 8 is a DITypeRef.
+  if (!fieldIsTypeRef(DbgNode, 8))
     return false;
   // Make sure StaticDataMemberDeclaration @ field 12 is MDNode.
   if (!fieldIsMDNode(DbgNode, 12))
@@ -558,10 +559,11 @@
   if (!isVariable())
     return false;
 
-  // Make sure context @ field 1 and type @ field 5 are MDNodes.
+  // Make sure context @ field 1 is an MDNode.
   if (!fieldIsMDNode(DbgNode, 1))
     return false;
-  if (!fieldIsMDNode(DbgNode, 5))
+  // Make sure that type @ field 5 is a DITypeRef.
+  if (!fieldIsTypeRef(DbgNode, 5))
     return false;
   return DbgNode->getNumOperands() >= 8;
 }
@@ -999,7 +1001,7 @@
         DIGlobalVariable DIG(GVs.getElement(i));
         if (addGlobalVariable(DIG)) {
           processScope(DIG.getContext());
-          processType(DIG.getType());
+          processType(DIG.getType().resolve(TypeIdentifierMap));
         }
       }
       DIArray SPs = CU.getSubprograms();
@@ -1133,7 +1135,7 @@
   if (!NodesSeen.insert(DV))
     return;
   processScope(DIVariable(N).getContext());
-  processType(DIVariable(N).getType());
+  processType(DIVariable(N).getType().resolve(TypeIdentifierMap));
 }
 
 void DebugInfoFinder::processValue(const Module &M, const DbgValueInst *DVI) {
@@ -1149,7 +1151,7 @@
   if (!NodesSeen.insert(DV))
     return;
   processScope(DIVariable(N).getContext());
-  processType(DIVariable(N).getType());
+  processType(DIVariable(N).getType().resolve(TypeIdentifierMap));
 }
 
 /// addType - Add type into Tys.