Unweaken vtables as per http://llvm.org/docs/CodingStandards.html#ll_virtual_anch

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146960 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/llvm-diff/DiffConsumer.cpp b/tools/llvm-diff/DiffConsumer.cpp
index d9e1814..0528039 100644
--- a/tools/llvm-diff/DiffConsumer.cpp
+++ b/tools/llvm-diff/DiffConsumer.cpp
@@ -44,6 +44,8 @@
 }
 
 
+void Consumer::anchor() { }
+
 void DiffConsumer::printValue(Value *V, bool isL) {
   if (V->hasName()) {
     out << (isa<GlobalValue>(V) ? '@' : '%') << V->getName();
diff --git a/tools/llvm-diff/DiffConsumer.h b/tools/llvm-diff/DiffConsumer.h
index b95d427..2060fe1 100644
--- a/tools/llvm-diff/DiffConsumer.h
+++ b/tools/llvm-diff/DiffConsumer.h
@@ -29,6 +29,7 @@
 
   /// The interface for consumers of difference data.
   class Consumer {
+    virtual void anchor();
   public:
     /// Record that a local context has been entered.  Left and
     /// Right are IR "containers" of some sort which are being
diff --git a/tools/llvm-diff/DifferenceEngine.cpp b/tools/llvm-diff/DifferenceEngine.cpp
index 435cd87..e827b23 100644
--- a/tools/llvm-diff/DifferenceEngine.cpp
+++ b/tools/llvm-diff/DifferenceEngine.cpp
@@ -628,6 +628,8 @@
 
 }
 
+void DifferenceEngine::Oracle::anchor() { }
+
 void DifferenceEngine::diff(Function *L, Function *R) {
   Context C(*this, L, R);
 
diff --git a/tools/llvm-diff/DifferenceEngine.h b/tools/llvm-diff/DifferenceEngine.h
index 5b4f80b..7ea79e4 100644
--- a/tools/llvm-diff/DifferenceEngine.h
+++ b/tools/llvm-diff/DifferenceEngine.h
@@ -50,7 +50,9 @@
 
     /// An oracle for answering whether two values are equivalent as
     /// operands.
-    struct Oracle {
+    class Oracle {
+      virtual void anchor();
+    public:
       virtual bool operator()(Value *L, Value *R) = 0;
 
     protected: