4 files changed, 33 insertions, 0 deletions
diff --git a/llvm/include/llvm/Analysis/TypeMetadataUtils.h b/llvm/include/llvm/Analysis/TypeMetadataUtils.h
index 82cf8efeea5..43ce26147c2 100644
--- a/llvm/include/llvm/Analysis/TypeMetadataUtils.h
+++ b/llvm/include/llvm/Analysis/TypeMetadataUtils.h
@@ -50,6 +50,8 @@ void findDevirtualizableCallsForTypeCheckedLoad(
     SmallVectorImpl<Instruction *> &LoadedPtrs,
     SmallVectorImpl<Instruction *> &Preds, bool &HasNonCallUses,
     const CallInst *CI, DominatorTree &DT);
+
+Constant *getPointerAtOffset(Constant *I, uint64_t Offset, Module &M);
 }
 
 #endif
diff --git a/llvm/include/llvm/IR/FixedMetadataKinds.def b/llvm/include/llvm/IR/FixedMetadataKinds.def
index 1ad17093a71..0e1ffef5867 100644
--- a/llvm/include/llvm/IR/FixedMetadataKinds.def
+++ b/llvm/include/llvm/IR/FixedMetadataKinds.def
@@ -40,3 +40,4 @@ LLVM_FIXED_MD_KIND(MD_access_group, "llvm.access.group", 25)
 LLVM_FIXED_MD_KIND(MD_callback, "callback", 26)
 LLVM_FIXED_MD_KIND(MD_preserve_access_index, "llvm.preserve.access.index", 27)
 LLVM_FIXED_MD_KIND(MD_misexpect, "misexpect", 28)
+LLVM_FIXED_MD_KIND(MD_vcall_visibility, "vcall_visibility", 29)
diff --git a/llvm/include/llvm/IR/GlobalObject.h b/llvm/include/llvm/IR/GlobalObject.h
index 739ef75dd8b..ce81eb9f071 100644
--- a/llvm/include/llvm/IR/GlobalObject.h
+++ b/llvm/include/llvm/IR/GlobalObject.h
@@ -28,6 +28,20 @@ class MDNode;
 class Metadata;
 
 class GlobalObject : public GlobalValue {
+public:
+  // VCallVisibility - values for visibility metadata attached to vtables. This
+  // describes the scope in which a virtual call could end up being dispatched
+  // through this vtable.
+  enum VCallVisibility {
+    // Type is potentially visible to external code.
+    VCallVisibilityPublic = 0,
+    // Type is only visible to code which will be in the current Module after
+    // LTO internalization.
+    VCallVisibilityLinkageUnit = 1,
+    // Type is only visible to code in the current Module.
+    VCallVisibilityTranslationUnit = 2,
+  };
+
 protected:
   GlobalObject(Type *Ty, ValueTy VTy, Use *Ops, unsigned NumOps,
                LinkageTypes Linkage, const Twine &Name,
@@ -164,6 +178,8 @@ public:
   void copyMetadata(const GlobalObject *Src, unsigned Offset);
 
   void addTypeMetadata(unsigned Offset, Metadata *TypeID);
+  void addVCallVisibilityMetadata(VCallVisibility Visibility);
+  VCallVisibility getVCallVisibility() const;
 
 protected:
   void copyAttributesFrom(const GlobalObject *Src);
diff --git a/llvm/include/llvm/Transforms/IPO/GlobalDCE.h b/llvm/include/llvm/Transforms/IPO/GlobalDCE.h
index c434484d1ae..0a6851849e7 100644
--- a/llvm/include/llvm/Transforms/IPO/GlobalDCE.h
+++ b/llvm/include/llvm/Transforms/IPO/GlobalDCE.h
@@ -43,11 +43,25 @@ private:
   /// Comdat -> Globals in that Comdat section.
   std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers;
 
+  /// !type metadata -> set of (vtable, offset) pairs
+  DenseMap<Metadata *, SmallSet<std::pair<GlobalVariable *, uint64_t>, 4>>
+      TypeIdMap;
+
+  // Global variables which are vtables, and which we have enough information
+  // about to safely do dead virtual function elimination.
+  SmallPtrSet<GlobalValue *, 32> VFESafeVTables;
+
   void UpdateGVDependencies(GlobalValue &GV);
   void MarkLive(GlobalValue &GV,
                 SmallVectorImpl<GlobalValue *> *Updates = nullptr);
   bool RemoveUnusedGlobalValue(GlobalValue &GV);
 
+  // Dead virtual function elimination.
+  void AddVirtualFunctionDependencies(Module &M);
+  void ScanVTables(Module &M);
+  void ScanTypeCheckedLoadIntrinsics(Module &M);
+  void ScanVTableLoad(Function *Caller, Metadata *TypeId, uint64_t CallOffset);
+
   void ComputeDependencies(Value *V, SmallPtrSetImpl<GlobalValue *> &U);
 };