[IR] De-virtualize ~Value to save a vptr

[rnk]

Summary

Implements PR889

Removing the virtual table pointer from Value saves 1% of RSS when doing
LTO of llc on Linux. The impact on time was positive, but too noisy to
conclusively say that performance improved. Here is a link to the
spreadsheet with the original data:

https://docs.google.com/spreadsheets/d/1F4FHir0qYnV0MEp2sYYp_BuvnJgWlWPhWOwZ6LbW7W4/edit?usp=sharing

This change makes it invalid to directly delete a Value, User, or
Instruction pointer. Instead, such code can be rewritten to a null check
and a call Value::deleteValue(). Value objects tend to have their
lifetimes managed through iplist, so for the most part, this isn't a big deal.
However, there are some places where
LLVM deletes values, and those places had to be migrated to deleteValue.
I have also created llvm::unique_value, which has a custom deleter, so
it can be used in place of std::unique_ptr<Value>.

I had to add the "ValueCallbacks" escape hatch for MemorySSA, which
derives from User outside of lib/IR. Code in IR cannot include MemorySSA
headers or call the MemoryAccess object destructors without introducing
a circular dependency, so we need some level of indirection.
Unfortunately, no class derived from User may have any virtual methods,
because adding a virtual method would break User::getHungOffOperands(),
which assumes that it can find the use list immediately prior to the
User object. I've added a static_assert to the appropriate OperandTraits
templates to help people avoid this trap.

[george.burgess.iv]

Thanks for working on this!

I think we need some way of checking this at compile time, because developers are going to trip over this

#define NO_VIRTUALS_ALLOWED(cls) static_assert(!std::is_polymorphic<cls>::value, #cls " is not allowed to have virtual methods");

class Value /* ... */ { /* ... */ };
NO_VIRTUALS_ALLOWED(Value);

class BasicBlock : public Value, /* ... */ { /* ... */ };
NO_VIRTUALS_ALLOWED(BasicBlock);

might be a good starting point. Can't think of a way to make it automagically apply to subclasses, though.

include/llvm/IR/DerivedUser.h

28 ↗

(On Diff #92713)

"instead inherit from DerivedUser instead"?

[rnk]

• rebase

[rnk]

• rebase after committing GlobalValue and TerminatorInst changes

[rnk]

PTAL, I think this is the final form of this patch. I couldn't come up with a cleaner way to allow MemorySSA to retain it's virtual methods. Trust me, I tried.

Then again, extending the Value/User hierarchy isn't really a supported use case. If we want to let people reuse the use/def list machinery with less work, we can tackle that separately from this change.

[pcc]

llvm/include/llvm/IR/DerivedUser.h

42

Can "ValueCallbacks" just be a function pointer?

[rnk]

llvm/include/llvm/IR/DerivedUser.h

42

It could be, but I had the idea that MemorySSA might prefer to add virtual methods here instead of doing switch dispatch like I ended up doing. Whatever dannyb/gbiv prefer, I'll do that.

[george.burgess.iv]

llvm/include/llvm/IR/DerivedUser.h

42

We don't have that many virtual methods in Memory*, so I'd be perfectly happy with switch dispatch. If that changes, looks straightforward to swap back to this approach.

(If we take the ValueCallbacks route, though, please make deleteValue and VCallbacks const)

[chandlerc]

Have you checked Polly and Clang for changes needed there? Detailed comments below.

llvm/include/llvm/IR/DerivedUser.h

10–14

Given that this header just defines a class, maybe just move all the comments to the class doxygen and nuke the intro section?

27–29

I'd personally like some moderately strong discouragement of using this and indicate that if we find another way to extend use/def chains it may go away. I just don't want folks outside the project designing things on top of this extension point and then being in a really bad spot if we ever get rid of it.

42

+1 for me FWIW.

llvm/include/llvm/IR/GlobalValue.h

179

Redundant public.

llvm/include/llvm/IR/Instruction.def

192–193

I guess you should match the weird formatting of this file for this patch. We should probably come back and clean up all of this formatting ,but seems weird to deviate here.

llvm/include/llvm/IR/Instruction.h

59

Make this a doxygen comment?

llvm/include/llvm/IR/User.h

96

Add whitespace before the protected?

llvm/include/llvm/IR/Value.def

61

Leave a FIXME comment here to document that this isn't ideal but we don't have any better idea?

llvm/include/llvm/IR/Value.h

209–214

Move this up to the protected region with the constructor?

Also, the trailing comment doesn't seem to add value at this point.

216

No blank line here.

[rnk]

llvm/include/llvm/IR/Instruction.h

59

The intention of these trailing comments is to make it so they show up in diagnostic notes when users try to delete a Value*. It looks like this:

C:\src\llvm-project\llvm\unittests\IR\InstructionsTest.cpp(410,10):  error: calling a protected destructor of class 'llvm::Instruction'
  delete I;
         ^
C:\src\llvm-project\llvm\include\llvm/IR/Instruction.h(59,3):  note: declared protected here
  ~Instruction(); // Use deleteValue() to delete a generic Instruction.
  ^
1 error generated.

llvm/include/llvm/IR/User.h

96

Done, I also added the trailing comment so it shows up in notes. People don't often delete a User directly, though.

llvm/include/llvm/IR/Value.h

209–214

See example where it shows up in diagnostic notes but the doxygen one doesn't.

[rnk]

• Address Chandler's comments

[rnk]

In D31261#756987, @chandlerc wrote:

Have you checked Polly and Clang for changes needed there? Detailed comments below.

check-polly and check-clang pass for me.

[chandlerc]

LGTM with some nits! Totally awesome.

llvm/include/llvm/IR/Instruction.h

54–58

Sink this public region down to coalesce it with the one right below the protected detsructor?

59

Neat!

It'd be awesome if there were a non-comment way of doing this, but hey... =]

llvm/include/llvm/IR/User.h

96

Maybe move the public constructor above down so that we don't have the 2 public regions split by a protected one?

llvm/include/llvm/IR/Value.h

208

Redundant public:.

[rnk]

Thanks! Time to find out if this breaks something. :)

[rnk]

• Adjust access specifiers

llvm/include/llvm/Analysis/MemorySSA.h

 #include "llvm/ADT/ilist.h"
 #include "llvm/ADT/ilist_node.h"
 #include "llvm/ADT/iterator.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/MemoryLocation.h"
 #include "llvm/Analysis/PHITransAddr.h"
 #include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/DerivedUser.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/OperandTraits.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IR/Use.h"
 #include "llvm/IR/User.h"
 #include "llvm/IR/Value.h"
 #include "llvm/Pass.h"

 template <class T> class memoryaccess_def_iterator_base;
 using memoryaccess_def_iterator = memoryaccess_def_iterator_base<MemoryAccess>;
 using const_memoryaccess_def_iterator =
     memoryaccess_def_iterator_base<const MemoryAccess>;
 
 // \brief The base for all memory accesses. All memory accesses in a block are
 // linked together using an intrusive list.
 class MemoryAccess
-    : public User,
+    : public DerivedUser,
       public ilist_node<MemoryAccess, ilist_tag<MSSAHelpers::AllAccessTag>>,
       public ilist_node<MemoryAccess, ilist_tag<MSSAHelpers::DefsOnlyTag>> {
 public:
   using AllAccessType =
       ilist_node<MemoryAccess, ilist_tag<MSSAHelpers::AllAccessTag>>;
   using DefsOnlyType =
       ilist_node<MemoryAccess, ilist_tag<MSSAHelpers::DefsOnlyTag>>;
 
   // Methods for support type inquiry through isa, cast, and
   // dyn_cast
   static inline bool classof(const Value *V) {
     unsigned ID = V->getValueID();
     return ID == MemoryUseVal || ID == MemoryPhiVal || ID == MemoryDefVal;
   }
 
   MemoryAccess(const MemoryAccess &) = delete;
   MemoryAccess &operator=(const MemoryAccess &) = delete;
-  ~MemoryAccess() override;
 
   void *operator new(size_t, unsigned) = delete;
   void *operator new(size_t) = delete;
 
   BasicBlock *getBlock() const { return Block; }
 
-  virtual void print(raw_ostream &OS) const = 0;
-  virtual void dump() const;
+  void print(raw_ostream &OS) const;
+  void dump() const;
 
   /// \brief The user iterators for a memory access
   typedef user_iterator iterator;
   typedef const_user_iterator const_iterator;
 
   /// \brief This iterator walks over all of the defs in a given
   /// MemoryAccess. For MemoryPhi nodes, this walks arguments. For
   /// MemoryUse/MemoryDef, this walks the defining access.
protected:
   friend class MemoryPhi;
 
   /// \brief Used by MemorySSA to change the block of a MemoryAccess when it is
   /// moved.
   void setBlock(BasicBlock *BB) { Block = BB; }
 
   /// \brief Used for debugging and tracking things about MemoryAccesses.
   /// Guaranteed unique among MemoryAccesses, no guarantees otherwise.
-  virtual unsigned getID() const = 0;
+  inline unsigned getID() const;
 
-  MemoryAccess(LLVMContext &C, unsigned Vty, BasicBlock *BB,
+  MemoryAccess(LLVMContext &C, unsigned Vty, ValueCallbacks *VC, BasicBlock *BB,
                unsigned NumOperands)
-      : User(Type::getVoidTy(C), Vty, nullptr, NumOperands), Block(BB) {}
+      : DerivedUser(Type::getVoidTy(C), Vty, nullptr, NumOperands, VC),
+        Block(BB) {}
 
 private:
   BasicBlock *Block;
 };
 
 inline raw_ostream &operator<<(raw_ostream &OS, const MemoryAccess &MA) {
   MA.print(OS);
   return OS;
public:
   MemoryAccess *getDefiningAccess() const { return getOperand(0); }
 
   static inline bool classof(const Value *MA) {
     return MA->getValueID() == MemoryUseVal || MA->getValueID() == MemoryDefVal;
   }
 
   // Sadly, these have to be public because they are needed in some of the
   // iterators.
-  virtual bool isOptimized() const = 0;
-  virtual MemoryAccess *getOptimized() const = 0;
-  virtual void setOptimized(MemoryAccess *) = 0;
+  inline bool isOptimized() const;
+  inline MemoryAccess *getOptimized() const;
+  inline void setOptimized(MemoryAccess *);
 
   /// \brief Reset the ID of what this MemoryUse was optimized to, causing it to
   /// be rewalked by the walker if necessary.
   /// This really should only be called by tests.
-  virtual void resetOptimized() = 0;
+  inline void resetOptimized();
 
 protected:
   friend class MemorySSA;
   friend class MemorySSAUpdater;
   MemoryUseOrDef(LLVMContext &C, MemoryAccess *DMA, unsigned Vty,
-                 Instruction *MI, BasicBlock *BB)
-      : MemoryAccess(C, Vty, BB, 1), MemoryInst(MI) {
+                 ValueCallbacks *VC, Instruction *MI, BasicBlock *BB)
+      : MemoryAccess(C, Vty, VC, BB, 1), MemoryInst(MI) {
     setDefiningAccess(DMA);
   }
   void setDefiningAccess(MemoryAccess *DMA, bool Optimized = false) {
     if (!Optimized) {
       setOperand(0, DMA);
       return;
     }
     setOptimized(DMA);

 /// In particular, the set of Instructions that will be represented by
 /// MemoryUse's is exactly the set of Instructions for which
 /// AliasAnalysis::getModRefInfo returns "Ref".
 class MemoryUse final : public MemoryUseOrDef {
 public:
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(MemoryAccess);
 
   MemoryUse(LLVMContext &C, MemoryAccess *DMA, Instruction *MI, BasicBlock *BB)
-      : MemoryUseOrDef(C, DMA, MemoryUseVal, MI, BB), OptimizedID(0) {}
+      : MemoryUseOrDef(C, DMA, MemoryUseVal, getValueCallbacks(), MI, BB),
+        OptimizedID(0) {}
 
   // allocate space for exactly one operand
   void *operator new(size_t s) { return User::operator new(s, 1); }
   void *operator new(size_t, unsigned) = delete;
 
   static inline bool classof(const Value *MA) {
     return MA->getValueID() == MemoryUseVal;
   }
 
-  void print(raw_ostream &OS) const override;
+  void print(raw_ostream &OS) const;
 
-  virtual void setOptimized(MemoryAccess *DMA) override {
+  void setOptimized(MemoryAccess *DMA) {
     OptimizedID = DMA->getID();
     setOperand(0, DMA);
   }
 
-  virtual bool isOptimized() const override {
+  bool isOptimized() const {
     return getDefiningAccess() && OptimizedID == getDefiningAccess()->getID();
   }
 
-  virtual MemoryAccess *getOptimized() const override {
+  MemoryAccess *getOptimized() const {
     return getDefiningAccess();
   }
-  virtual void resetOptimized() override {
+  void resetOptimized() {
     OptimizedID = INVALID_MEMORYACCESS_ID;
   }
 
 protected:
   friend class MemorySSA;
 
-  unsigned getID() const override {
-    llvm_unreachable("MemoryUses do not have IDs");
-  }
-
 private:
+  ValueCallbacks *getValueCallbacks();
+
   unsigned int OptimizedID;
 };
 
 template <>
 struct OperandTraits<MemoryUse> : public FixedNumOperandTraits<MemoryUse, 1> {};
 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(MemoryUse, MemoryAccess)
 
 /// \brief Represents a read-write access to memory, whether it is a must-alias,
 /// or a may-alias.
 ///
 /// In particular, the set of Instructions that will be represented by
 /// MemoryDef's is exactly the set of Instructions for which
 /// AliasAnalysis::getModRefInfo returns "Mod" or "ModRef".
 /// Note that, in order to provide def-def chains, all defs also have a use
 /// associated with them. This use points to the nearest reaching
 /// MemoryDef/MemoryPhi.
 class MemoryDef final : public MemoryUseOrDef {
 public:
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(MemoryAccess);
 
   MemoryDef(LLVMContext &C, MemoryAccess *DMA, Instruction *MI, BasicBlock *BB,
             unsigned Ver)
-      : MemoryUseOrDef(C, DMA, MemoryDefVal, MI, BB), ID(Ver),
-        Optimized(nullptr), OptimizedID(INVALID_MEMORYACCESS_ID) {}
+      : MemoryUseOrDef(C, DMA, MemoryDefVal, getValueCallbacks(), MI, BB),
+        ID(Ver), Optimized(nullptr), OptimizedID(INVALID_MEMORYACCESS_ID) {}
 
   // allocate space for exactly one operand
   void *operator new(size_t s) { return User::operator new(s, 1); }
   void *operator new(size_t, unsigned) = delete;
 
   static inline bool classof(const Value *MA) {
     return MA->getValueID() == MemoryDefVal;
   }
 
-  virtual void setOptimized(MemoryAccess *MA) override {
+  void setOptimized(MemoryAccess *MA) {
     Optimized = MA;
     OptimizedID = getDefiningAccess()->getID();
   }
-  virtual MemoryAccess *getOptimized() const override { return Optimized; }
-  virtual bool isOptimized() const override {
+  MemoryAccess *getOptimized() const { return Optimized; }
+  bool isOptimized() const {
     return getOptimized() && getDefiningAccess() &&
            OptimizedID == getDefiningAccess()->getID();
   }
-  virtual void resetOptimized() override {
+  void resetOptimized() {
     OptimizedID = INVALID_MEMORYACCESS_ID;
   }
 
-  void print(raw_ostream &OS) const override;
+  void print(raw_ostream &OS) const;
 
-protected:
   friend class MemorySSA;
 
-  unsigned getID() const override { return ID; }
+  unsigned getID() const { return ID; }
 
 private:
+  ValueCallbacks *getValueCallbacks();
+
   const unsigned ID;
   MemoryAccess *Optimized;
   unsigned int OptimizedID;
 };
 
 template <>
 struct OperandTraits<MemoryDef> : public FixedNumOperandTraits<MemoryDef, 1> {};
 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(MemoryDef, MemoryAccess)
class MemoryPhi final : public MemoryAccess {
   // allocate space for exactly zero operands
   void *operator new(size_t s) { return User::operator new(s); }
 
 public:
   /// Provide fast operand accessors
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(MemoryAccess);
 
   MemoryPhi(LLVMContext &C, BasicBlock *BB, unsigned Ver, unsigned NumPreds = 0)
-      : MemoryAccess(C, MemoryPhiVal, BB, 0), ID(Ver), ReservedSpace(NumPreds) {
+      : MemoryAccess(C, MemoryPhiVal, getValueCallbacks(), BB, 0), ID(Ver),
+        ReservedSpace(NumPreds) {
     allocHungoffUses(ReservedSpace);
   }
 
   void *operator new(size_t, unsigned) = delete;
 
   // Block iterator interface. This provides access to the list of incoming
   // basic blocks, which parallels the list of incoming values.
   typedef BasicBlock **block_iterator;
Value *getIncomingValueForBlock(const BasicBlock *BB) const {
     assert(Idx >= 0 && "Invalid basic block argument!");
     return getIncomingValue(Idx);
   }
 
   static inline bool classof(const Value *V) {
     return V->getValueID() == MemoryPhiVal;
   }
 
-  void print(raw_ostream &OS) const override;
+  void print(raw_ostream &OS) const;
+
+  unsigned getID() const { return ID; }
 
 protected:
   friend class MemorySSA;
 
   /// \brief this is more complicated than the generic
   /// User::allocHungoffUses, because we have to allocate Uses for the incoming
   /// values and pointers to the incoming blocks, all in one allocation.
   void allocHungoffUses(unsigned N) {
     User::allocHungoffUses(N, /* IsPhi */ true);
   }
 
-  unsigned getID() const final { return ID; }
-
 private:
   // For debugging only
   const unsigned ID;
   unsigned ReservedSpace;
 
   /// \brief This grows the operand list in response to a push_back style of
   /// operation.  This grows the number of ops by 1.5 times.
   void growOperands() {
     unsigned E = getNumOperands();
     // 2 op PHI nodes are VERY common, so reserve at least enough for that.
     ReservedSpace = std::max(E + E / 2, 2u);
     growHungoffUses(ReservedSpace, /* IsPhi */ true);
   }
+
+  ValueCallbacks *getValueCallbacks();
 };
 
+inline unsigned MemoryAccess::getID() const {
+  assert((isa<MemoryDef>(this) || isa<MemoryPhi>(this)) &&
+         "only memory defs and phis have ids");
+  if (const auto *MD = dyn_cast<MemoryDef>(this))
+    return MD->getID();
+  return cast<MemoryPhi>(this)->getID();
+}
+
+inline bool MemoryUseOrDef::isOptimized() const {
+  if (const auto *MD = dyn_cast<MemoryDef>(this))
+    return MD->isOptimized();
+  return cast<MemoryUse>(this)->isOptimized();
+}
+
+inline MemoryAccess *MemoryUseOrDef::getOptimized() const {
+  if (const auto *MD = dyn_cast<MemoryDef>(this))
+    return MD->getOptimized();
+  return cast<MemoryUse>(this)->getOptimized();
+}
+
+inline void MemoryUseOrDef::setOptimized(MemoryAccess *MA) {
+  if (auto *MD = dyn_cast<MemoryDef>(this))
+    MD->setOptimized(MA);
+  else
+    cast<MemoryUse>(this)->setOptimized(MA);
+}
+
+inline void MemoryUseOrDef::resetOptimized() {
+  if (auto *MD = dyn_cast<MemoryDef>(this))
+    MD->resetOptimized();
+  else
+    cast<MemoryUse>(this)->resetOptimized();
+}
+
+
 template <> struct OperandTraits<MemoryPhi> : public HungoffOperandTraits<2> {};
 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(MemoryPhi, MemoryAccess)
 
 class MemorySSAWalker;
 
 /// \brief Encapsulates MemorySSA, including all data associated with memory
 /// accesses.
 class MemorySSA {

llvm/include/llvm/IR/Argument.h

 namespace llvm {
 
 /// This class represents an incoming formal argument to a Function. A formal
 /// argument, since it is ``formal'', does not contain an actual value but
 /// instead represents the type, argument number, and attributes of an argument
 /// for a specific function. When used in the body of said function, the
 /// argument of course represents the value of the actual argument that the
 /// function was called with.
-class Argument : public Value {
-  virtual void anchor();
+class Argument final : public Value {
   Function *Parent;
   unsigned ArgNo;
 
   friend class Function;
   void setParent(Function *parent);
 
 public:
   /// Argument constructor.

llvm/include/llvm/IR/BasicBlock.h

 ///
 /// A well formed basic block is formed of a list of non-terminating
 /// instructions followed by a single TerminatorInst instruction.
 /// TerminatorInst's may not occur in the middle of basic blocks, and must
 /// terminate the blocks. The BasicBlock class allows malformed basic blocks to
 /// occur because it may be useful in the intermediate stage of constructing or
 /// modifying a program. However, the verifier will ensure that basic blocks
 /// are "well formed".
-class BasicBlock : public Value, // Basic blocks are data objects also
+class BasicBlock final : public Value, // Basic blocks are data objects also
                          public ilist_node_with_parent<BasicBlock, Function> {
 public:
   using InstListType = SymbolTableList<Instruction>;
 
 private:
   friend class BlockAddress;
   friend class SymbolTableListTraits<BasicBlock>;
 
   InstListType InstList;
   Function *Parent;
 
   void setParent(Function *parent);
 
   /// \brief Constructor.
   ///
   /// If the function parameter is specified, the basic block is automatically
   /// inserted at either the end of the function (if InsertBefore is null), or
   /// before the specified basic block.
   explicit BasicBlock(LLVMContext &C, const Twine &Name = "",
                       Function *Parent = nullptr,
                       BasicBlock *InsertBefore = nullptr);
 
 public:
   BasicBlock(const BasicBlock &) = delete;
   BasicBlock &operator=(const BasicBlock &) = delete;
-  ~BasicBlock() override;
+  ~BasicBlock();
 
   /// \brief Get the context in which this basic block lives.
   LLVMContext &getContext() const;
 
   /// Instruction iterators...
   using iterator = InstListType::iterator;
   using const_iterator = InstListType::const_iterator;
   using reverse_iterator = InstListType::reverse_iterator;

llvm/include/llvm/IR/Constant.h

 ///
 /// Note that Constants are immutable (once created they never change)
 /// and are fully shared by structural equivalence.  This means that two
 /// structurally equivalent constants will always have the same address.
 /// Constants are created on demand as needed and never deleted: thus clients
 /// don't have to worry about the lifetime of the objects.
 /// @brief LLVM Constant Representation
 class Constant : public User {
-  void anchor() override;
-
 protected:
   Constant(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps)
     : User(ty, vty, Ops, NumOps) {}
 
 public:
   void operator=(const Constant &) = delete;
   Constant(const Constant &) = delete;
 

llvm/include/llvm/IR/Constants.h

 /// Base class for constants with no operands.
 ///
 /// These constants have no operands; they represent their data directly.
 /// Since they can be in use by unrelated modules (and are never based on
 /// GlobalValues), it never makes sense to RAUW them.
 class ConstantData : public Constant {
   friend class Constant;
 
-  void anchor() override;
-
   Value *handleOperandChangeImpl(Value *From, Value *To) {
     llvm_unreachable("Constant data does not have operands!");
   }
 
 protected:
   explicit ConstantData(Type *Ty, ValueTy VT) : Constant(Ty, VT, nullptr, 0) {}
 
   void *operator new(size_t s) { return User::operator new(s, 0); }

 /// @brief Class for constant integers.
 class ConstantInt final : public ConstantData {
   friend class Constant;
 
   APInt Val;
 
   ConstantInt(IntegerType *Ty, const APInt& V);
 
-  void anchor() override;
   void destroyConstantImpl();
 
 public:
   ConstantInt(const ConstantInt &) = delete;
 
   static ConstantInt *getTrue(LLVMContext &Context);
   static ConstantInt *getFalse(LLVMContext &Context);
   static Constant *getTrue(Type *Ty);

 ///
 class ConstantFP final : public ConstantData {
   friend class Constant;
 
   APFloat Val;
 
   ConstantFP(Type *Ty, const APFloat& V);
 
-  void anchor() override;
   void destroyConstantImpl();
 
 public:
   ConstantFP(const ConstantFP &) = delete;
 
   /// Floating point negation must be implemented with f(x) = -0.0 - x. This
   /// method returns the negative zero constant for floating point or vector
   /// floating point types; for all other types, it returns the null value.
class ConstantDataSequential : public ConstantData {
   /// the same StringMap bucket, linked up.
   ConstantDataSequential *Next;
 
   void destroyConstantImpl();
 
 protected:
   explicit ConstantDataSequential(Type *ty, ValueTy VT, const char *Data)
       : ConstantData(ty, VT), DataElements(Data), Next(nullptr) {}
-  ~ConstantDataSequential() override { delete Next; }
+  ~ConstantDataSequential() { delete Next; }
 
   static Constant *getImpl(StringRef Bytes, Type *Ty);
 
 public:
   ConstantDataSequential(const ConstantDataSequential &) = delete;
 
   /// Return true if a ConstantDataSequential can be formed with a vector or
   /// array of the specified element type.
class ConstantDataArray final : public ConstantDataSequential {
   explicit ConstantDataArray(Type *ty, const char *Data)
       : ConstantDataSequential(ty, ConstantDataArrayVal, Data) {}
 
   /// Allocate space for exactly zero operands.
   void *operator new(size_t s) {
     return User::operator new(s, 0);
   }
 
-  void anchor() override;
-
 public:
   ConstantDataArray(const ConstantDataArray &) = delete;
 
   void *operator new(size_t, unsigned) = delete;
 
   /// get() constructors - Return a constant with array type with an element
   /// count and element type matching the ArrayRef passed in.  Note that this
   /// can return a ConstantAggregateZero object.
class ConstantDataVector final : public ConstantDataSequential {
   explicit ConstantDataVector(Type *ty, const char *Data)
       : ConstantDataSequential(ty, ConstantDataVectorVal, Data) {}
 
   // allocate space for exactly zero operands.
   void *operator new(size_t s) {
     return User::operator new(s, 0);
   }
 
-  void anchor() override;
-
 public:
   ConstantDataVector(const ConstantDataVector &) = delete;
 
   void *operator new(size_t, unsigned) = delete;
 
   /// get() constructors - Return a constant with vector type with an element
   /// count and element type matching the ArrayRef passed in.  Note that this
   /// can return a ConstantAggregateZero object.

llvm/include/llvm/IR/DerivedUser.h

+//===-- DerivedUser.h - Base for non-IR Users -------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the DerivedUser class, which is an extension point for the
+// Value class hierarchy. Generally speaking, Value is the base of a closed
+// class hierarchy that can't be extended by code outside of lib/IR. This class
+// creates a loophole that allows classes outside of lib/IR to extend User to
+// leverage its use/def list machinery.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_DERIVEDUSER_H
+#define LLVM_IR_DERIVEDUSER_H
+
+#include "llvm/IR/User.h"
+
+namespace llvm {
+
+class ValueCallbacks;
+
+/// Extension point for the Value hierarchy. All classes outside of lib/IR
+/// that wish to inherit from User should instead inherit from DerivedUser
+/// instead.
+class DerivedUser : public User {
+  friend Value;
+  ValueCallbacks *VCallbacks;
+
+public:
+  DerivedUser(Type *Ty, unsigned VK, Use *U, unsigned NumOps,
+              ValueCallbacks *VC)
+      : User(Ty, VK, U, NumOps), VCallbacks(VC) {}
+};
+
+/// Interface implemented for DerivedUser subclasses implemented outside of
+/// lib/IR.
+class ValueCallbacks {
+public:
+  virtual ~ValueCallbacks(); // Satisfy -Wweak-vtables and -Wnon-virtual-dtor.
+  virtual void deleteValue(Value *DV) = 0;
+};
+
+} // namespace llvm
+
+#endif // LLVM_IR_DERIVEDUSER_H

llvm/include/llvm/IR/Function.h

private:
   /// the module.
   ///
   Function(FunctionType *Ty, LinkageTypes Linkage,
            const Twine &N = "", Module *M = nullptr);
 
 public:
   Function(const Function&) = delete;
   void operator=(const Function&) = delete;
-  ~Function() override;
+  ~Function();
 
   static Function *Create(FunctionType *Ty, LinkageTypes Linkage,
                           const Twine &N = "", Module *M = nullptr) {
     return new Function(Ty, Linkage, N, M);
   }
 
   // Provide fast operand accessors.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);

llvm/include/llvm/IR/GlobalValue.h

protected:
 
   Module *Parent;             // The containing module.
 
   // Used by SymbolTableListTraits.
   void setParent(Module *parent) {
     Parent = parent;
   }
 
+  ~GlobalValue() {
+    removeDeadConstantUsers();   // remove any dead constants using this.
+  }
+
 public:
   enum ThreadLocalMode {
     NotThreadLocal = 0,
     GeneralDynamicTLSModel,
     LocalDynamicTLSModel,
     InitialExecTLSModel,
     LocalExecTLSModel
   };
 
   GlobalValue(const GlobalValue &) = delete;
 
-  ~GlobalValue() override {
-    removeDeadConstantUsers();   // remove any dead constants using this.
-  }
-
+public:
   unsigned getAlignment() const;
 
   enum class UnnamedAddr {
     None,
     Local,
     Global,
   };
 

llvm/include/llvm/IR/GlobalVariable.h

public:
   GlobalVariable(Module &M, Type *Ty, bool isConstant,
                  LinkageTypes Linkage, Constant *Initializer,
                  const Twine &Name = "", GlobalVariable *InsertBefore = nullptr,
                  ThreadLocalMode = NotThreadLocal, unsigned AddressSpace = 0,
                  bool isExternallyInitialized = false);
   GlobalVariable(const GlobalVariable &) = delete;
   GlobalVariable &operator=(const GlobalVariable &) = delete;
 
-  ~GlobalVariable() override {
+  ~GlobalVariable() {
     dropAllReferences();
 
     // FIXME: needed by operator delete
     setGlobalVariableNumOperands(1);
   }
 
   // allocate space for exactly one operand
   void *operator new(size_t s) {

llvm/include/llvm/IR/InlineAsm.h

 #include <vector>
 
 namespace llvm {
 
 class FunctionType;
 class PointerType;
 template <class ConstantClass> class ConstantUniqueMap;
 
-class InlineAsm : public Value {
+class InlineAsm final : public Value {
 public:
   enum AsmDialect {
     AD_ATT,
     AD_Intel
   };
 
 private:
   friend struct InlineAsmKeyType;
   friend class ConstantUniqueMap<InlineAsm>;
 
   std::string AsmString, Constraints;
   FunctionType *FTy;
   bool HasSideEffects;
   bool IsAlignStack;
   AsmDialect Dialect;
 
   InlineAsm(FunctionType *Ty, const std::string &AsmString,
             const std::string &Constraints, bool hasSideEffects,
             bool isAlignStack, AsmDialect asmDialect);
-  ~InlineAsm() override;
 
   /// When the ConstantUniqueMap merges two types and makes two InlineAsms
   /// identical, it destroys one of them with this method.
   void destroyConstant();
 
 public:
   InlineAsm(const InlineAsm &) = delete;
   InlineAsm &operator=(const InlineAsm &) = delete;

llvm/include/llvm/IR/InstrTypes.h

TerminatorInst(Type *Ty, Instruction::TermOps iType,
                  Use *Ops, unsigned NumOps,
                  Instruction *InsertBefore = nullptr)
     : Instruction(Ty, iType, Ops, NumOps, InsertBefore) {}
 
   TerminatorInst(Type *Ty, Instruction::TermOps iType,
                  Use *Ops, unsigned NumOps, BasicBlock *InsertAtEnd)
     : Instruction(Ty, iType, Ops, NumOps, InsertAtEnd) {}
 
-  // Out of line virtual method, so the vtable, etc has a home.
-  ~TerminatorInst() override;
-
 public:
   /// Return the number of successors that this terminator has.
   unsigned getNumSuccessors() const;
 
   /// Return the specified successor.
   BasicBlock *getSuccessor(unsigned idx) const;
 
   /// Update the specified successor to point at the provided block.

 public:
   // allocate space for exactly one operand
   void *operator new(size_t s) {
     return User::operator new(s, 1);
   }
 
   void *operator new(size_t, unsigned) = delete;
 
-  // Out of line virtual method, so the vtable, etc has a home.
-  ~UnaryInstruction() override;
-
   /// Transparently provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
   // Methods for support type inquiry through isa, cast, and dyn_cast:
   static inline bool classof(const Instruction *I) {
     return I->getOpcode() == Instruction::Alloca ||
            I->getOpcode() == Instruction::Load ||
            I->getOpcode() == Instruction::VAArg ||

 
 /// This is the base class for all instructions that perform data
 /// casts. It is simply provided so that instruction category testing
 /// can be performed with code like:
 ///
 /// if (isa<CastInst>(Instr)) { ... }
 /// @brief Base class of casting instructions.
 class CastInst : public UnaryInstruction {
-  void anchor() override;
-
 protected:
   /// @brief Constructor with insert-before-instruction semantics for subclasses
   CastInst(Type *Ty, unsigned iType, Value *S,
            const Twine &NameStr = "", Instruction *InsertBefore = nullptr)
     : UnaryInstruction(Ty, iType, S, InsertBefore) {
     setName(NameStr);
   }
   /// @brief Constructor with insert-at-end-of-block semantics for subclasses
protected:
   CmpInst(Type *ty, Instruction::OtherOps op, Predicate pred,
           Value *LHS, Value *RHS, const Twine &Name = "",
           Instruction *InsertBefore = nullptr);
 
   CmpInst(Type *ty, Instruction::OtherOps op, Predicate pred,
           Value *LHS, Value *RHS, const Twine &Name,
           BasicBlock *InsertAtEnd);
 
-  void anchor() override; // Out of line virtual method.
-
 public:
   CmpInst() = delete;
 
   // allocate space for exactly two operands
   void *operator new(size_t s) {
     return User::operator new(s, 2);
   }
 

llvm/include/llvm/IR/Instruction.h

 
 namespace llvm {
 
 class BasicBlock;
 class FastMathFlags;
 class MDNode;
 struct AAMDNodes;
 
+template <> struct ilist_alloc_traits<Instruction> {
+  static inline void deleteNode(Instruction *V);
+};
+
 class Instruction : public User,
                     public ilist_node_with_parent<Instruction, BasicBlock> {
   BasicBlock *Parent;
   DebugLoc DbgLoc;                         // 'dbg' Metadata cache.
 
   enum {
     /// This is a bit stored in the SubClassData field which indicates whether
     /// this instruction has metadata attached to it or not.
     HasMetadataBit = 1 << 15
   };
 
 public:
   Instruction(const Instruction &) = delete;
   Instruction &operator=(const Instruction &) = delete;
 
-  // Out of line virtual method, so the vtable, etc has a home.
-  ~Instruction() override;
+protected:
+  ~Instruction(); // Use deleteValue() to delete a generic Instruction.
 
+public:
   /// Specialize the methods defined in Value, as we know that an instruction
   /// can only be used by other instructions.
   Instruction       *user_back()       { return cast<Instruction>(*user_begin());}
   const Instruction *user_back() const { return cast<Instruction>(*user_begin());}
 
   inline const BasicBlock *getParent() const { return Parent; }
   inline       BasicBlock *getParent()       { return Parent; }
 
protected:
   Instruction(Type *Ty, unsigned iType, Use *Ops, unsigned NumOps,
               BasicBlock *InsertAtEnd);
 
 private:
   /// Create a copy of this instruction.
   Instruction *cloneImpl() const;
 };
 
+inline void ilist_alloc_traits<Instruction>::deleteNode(Instruction *V) {
+  V->deleteValue();
+}
+
 } // end namespace llvm
 
 #endif // LLVM_IR_INSTRUCTION_H

llvm/include/llvm/IR/Instruction.def

 #else
 #define HANDLE_OTHER_INST(num, opcode, Class) HANDLE_INST(num, opcode, Class)
 #endif
 #endif
 #ifndef LAST_OTHER_INST
 #define LAST_OTHER_INST(num)
 #endif
 
+#ifndef HANDLE_USER_INST
+#define HANDLE_USER_INST(num, opc, Class) HANDLE_OTHER_INST(num, opc, Class)
+#endif
+
 // Terminator Instructions - These instructions are used to terminate a basic
 // block of the program.   Every basic block must end with one of these
 // instructions for it to be a well formed basic block.
 //
  FIRST_TERM_INST  ( 1)
 HANDLE_TERM_INST  ( 1, Ret           , ReturnInst)
 HANDLE_TERM_INST  ( 2, Br            , BranchInst)
 HANDLE_TERM_INST  ( 3, Switch        , SwitchInst)

 
 // Other operators...
  FIRST_OTHER_INST(51)
 HANDLE_OTHER_INST(51, ICmp   , ICmpInst   )  // Integer comparison instruction
 HANDLE_OTHER_INST(52, FCmp   , FCmpInst   )  // Floating point comparison instr.
 HANDLE_OTHER_INST(53, PHI    , PHINode    )  // PHI node instruction
 HANDLE_OTHER_INST(54, Call   , CallInst   )  // Call a function
 HANDLE_OTHER_INST(55, Select , SelectInst )  // select instruction
-HANDLE_OTHER_INST(56, UserOp1, Instruction)  // May be used internally in a pass
-HANDLE_OTHER_INST(57, UserOp2, Instruction)  // Internal to passes only
+HANDLE_USER_INST(56, UserOp1, Instruction)  // May be used internally in a pass
+HANDLE_USER_INST(57, UserOp2, Instruction)  // Internal to passes only
 HANDLE_OTHER_INST(58, VAArg  , VAArgInst  )  // vaarg instruction
 HANDLE_OTHER_INST(59, ExtractElement, ExtractElementInst)// extract from vector
 HANDLE_OTHER_INST(60, InsertElement, InsertElementInst)  // insert into vector
 HANDLE_OTHER_INST(61, ShuffleVector, ShuffleVectorInst)  // shuffle two vectors.
 HANDLE_OTHER_INST(62, ExtractValue, ExtractValueInst)// extract from aggregate
 HANDLE_OTHER_INST(63, InsertValue, InsertValueInst)  // insert into aggregate
 HANDLE_OTHER_INST(64, LandingPad, LandingPadInst)  // Landing pad instruction.
   LAST_OTHER_INST(64)

 #undef  FIRST_FUNCLETPAD_INST
 #undef HANDLE_FUNCLETPAD_INST
 #undef   LAST_FUNCLETPAD_INST
 
 #undef  FIRST_OTHER_INST
 #undef HANDLE_OTHER_INST
 #undef   LAST_OTHER_INST
 
+#undef HANDLE_USER_INST
+
 #ifdef HANDLE_INST
 #undef HANDLE_INST
 #endif

llvm/include/llvm/IR/Instructions.h

public:
   AllocaInst(Type *Ty, unsigned AddrSpace,
              const Twine &Name, BasicBlock *InsertAtEnd);
 
   AllocaInst(Type *Ty, unsigned AddrSpace, Value *ArraySize, unsigned Align,
              const Twine &Name = "", Instruction *InsertBefore = nullptr);
   AllocaInst(Type *Ty, unsigned AddrSpace, Value *ArraySize, unsigned Align,
              const Twine &Name, BasicBlock *InsertAtEnd);
 
-  // Out of line virtual method, so the vtable, etc. has a home.
-  ~AllocaInst() override;
-
   /// Return true if there is an allocation size parameter to the allocation
   /// instruction that is not 1.
   bool isArrayAllocation() const;
 
   /// Get the number of elements allocated. For a simple allocation of a single
   /// element, this will return a constant 1 value.
   const Value *getArraySize() const { return getOperand(0); }
   Value *getArraySize() { return getOperand(0); }

 
 /// an instruction for type-safe pointer arithmetic to
 /// access elements of arrays and structs
 ///
 class GetElementPtrInst : public Instruction {
   Type *SourceElementType;
   Type *ResultElementType;
 
-  void anchor() override;
-
   GetElementPtrInst(const GetElementPtrInst &GEPI);
   void init(Value *Ptr, ArrayRef<Value *> IdxList, const Twine &NameStr);
 
   /// Constructors - Create a getelementptr instruction with a base pointer an
   /// list of indices. The first ctor can optionally insert before an existing
   /// instruction, the second appends the new instruction to the specified
   /// BasicBlock.
   inline GetElementPtrInst(Type *PointeeType, Value *Ptr,

 //                               ICmpInst Class
 //===----------------------------------------------------------------------===//
 
 /// This instruction compares its operands according to the predicate given
 /// to the constructor. It only operates on integers or pointers. The operands
 /// must be identical types.
 /// Represent an integer comparison operator.
 class ICmpInst: public CmpInst {
-  void anchor() override;
-
   void AssertOK() {
     assert(getPredicate() >= CmpInst::FIRST_ICMP_PREDICATE &&
            getPredicate() <= CmpInst::LAST_ICMP_PREDICATE &&
            "Invalid ICmp predicate value");
     assert(getOperand(0)->getType() == getOperand(1)->getType() &&
           "Both operands to ICmp instruction are not of the same type!");
     // Check that the operands are the right type
     assert((getOperand(0)->getType()->isIntOrIntVectorTy() ||

 
 protected:
   // Note: Instruction needs to be a friend here to call cloneImpl.
   friend class Instruction;
 
   CallInst *cloneImpl() const;
 
 public:
-  ~CallInst() override;
-
   static CallInst *Create(Value *Func, ArrayRef<Value *> Args,
                           ArrayRef<OperandBundleDef> Bundles = None,
                           const Twine &NameStr = "",
                           Instruction *InsertBefore = nullptr) {
     return Create(cast<FunctionType>(
                       cast<PointerType>(Func->getType())->getElementType()),
                   Func, Args, Bundles, NameStr, InsertBefore);
   }
PHINode(Type *Ty, unsigned NumReservedValues, const Twine &NameStr,
     setName(NameStr);
     allocHungoffUses(ReservedSpace);
   }
 
   void *operator new(size_t s) {
     return User::operator new(s);
   }
 
-  void anchor() override;
-
 protected:
   // Note: Instruction needs to be a friend here to call cloneImpl.
   friend class Instruction;
 
   PHINode *cloneImpl() const;
 
   // allocHungoffUses - this is more complicated than the generic
   // User::allocHungoffUses, because we have to allocate Uses for the incoming

 
 protected:
   // Note: Instruction needs to be a friend here to call cloneImpl.
   friend class Instruction;
 
   ReturnInst *cloneImpl() const;
 
 public:
-  ~ReturnInst() override;
-
   static ReturnInst* Create(LLVMContext &C, Value *retVal = nullptr,
                             Instruction *InsertBefore = nullptr) {
     return new(!!retVal) ReturnInst(C, retVal, InsertBefore);
   }
 
   static ReturnInst* Create(LLVMContext &C, Value *retVal,
                             BasicBlock *InsertAtEnd) {
     return new(!!retVal) ReturnInst(C, retVal, InsertAtEnd);

llvm/include/llvm/IR/Metadata.h

 /// reference \a LocalAsMetadata.
 class MetadataAsValue : public Value {
   friend class ReplaceableMetadataImpl;
   friend class LLVMContextImpl;
 
   Metadata *MD;
 
   MetadataAsValue(Type *Ty, Metadata *MD);
-  ~MetadataAsValue() override;
 
   /// \brief Drop use of metadata (during teardown).
   void dropUse() { MD = nullptr; }
 
 public:
+  ~MetadataAsValue();
+
   static MetadataAsValue *get(LLVMContext &Context, Metadata *MD);
   static MetadataAsValue *getIfExists(LLVMContext &Context, Metadata *MD);
   Metadata *getMetadata() const { return MD; }
 
   static bool classof(const Value *V) {
     return V->getValueID() == MetadataAsValueVal;
   }
 

llvm/include/llvm/IR/OperandTraits.h

 
 /// FixedNumOperandTraits - determine the allocation regime of the Use array
 /// when it is a prefix to the User object, and the number of Use objects is
 /// known at compile time.
 
 template <typename SubClass, unsigned ARITY>
 struct FixedNumOperandTraits {
   static Use *op_begin(SubClass* U) {
+    static_assert(
+        !std::is_polymorphic<SubClass>::value,
+        "adding virtual methods to subclasses of User breaks use lists");
     return reinterpret_cast<Use*>(U) - ARITY;
   }
   static Use *op_end(SubClass* U) {
     return reinterpret_cast<Use*>(U);
   }
   static unsigned operands(const User*) {
     return ARITY;
   }

 
 /// VariadicOperandTraits - determine the allocation regime of the Use array
 /// when it is a prefix to the User object, and the number of Use objects is
 /// only known at allocation time.
 
 template <typename SubClass, unsigned MINARITY = 0>
 struct VariadicOperandTraits {
   static Use *op_begin(SubClass* U) {
+    static_assert(
+        !std::is_polymorphic<SubClass>::value,
+        "adding virtual methods to subclasses of User breaks use lists");
     return reinterpret_cast<Use*>(U) - static_cast<User*>(U)->getNumOperands();
   }
   static Use *op_end(SubClass* U) {
     return reinterpret_cast<Use*>(U);
   }
   static unsigned operands(const User *U) {
     return U->getNumOperands();
   }

llvm/include/llvm/IR/Operator.h

 #include "llvm/Support/Casting.h"
 #include <cstddef>
 
 namespace llvm {
 
 /// This is a utility class that provides an abstraction for the common
 /// functionality between Instructions and ConstantExprs.
 class Operator : public User {
-protected:
-  // NOTE: Cannot use = delete because it's not legal to delete
-  // an overridden method that's not deleted in the base class. Cannot leave
-  // this unimplemented because that leads to an ODR-violation.
-  ~Operator() override;
-
 public:
   // The Operator class is intended to be used as a utility, and is never itself
   // instantiated.
   Operator() = delete;
+  ~Operator() = delete;
 
   void *operator new(size_t, unsigned) = delete;
   void *operator new(size_t s) = delete;
 
   /// Return the opcode for this Instruction or ConstantExpr.
   unsigned getOpcode() const {
     if (const Instruction *I = dyn_cast<Instruction>(this))
       return I->getOpcode();

llvm/include/llvm/IR/User.h

 /// Customizes operand-related allocators and accessors.
 template <class>
 struct OperandTraits;
 
 class User : public Value {
   template <unsigned>
   friend struct HungoffOperandTraits;
 
-  virtual void anchor();
-
   LLVM_ATTRIBUTE_ALWAYS_INLINE inline static void *
   allocateFixedOperandUser(size_t, unsigned, unsigned);
 
 protected:
   /// Allocate a User with an operand pointer co-allocated.
   ///
   /// This is used for subclasses which need to allocate a variable number
   /// of operands, ie, 'hung off uses'.
protected:
   void allocHungoffUses(unsigned N, bool IsPhi = false);
 
   /// \brief Grow the number of hung off uses.  Note that allocHungoffUses
   /// should be called if there are no uses.
   void growHungoffUses(unsigned N, bool IsPhi = false);
 
 public:
   User(const User &) = delete;
-  ~User() override = default;
+protected:
+  ~User() = default;
 
+public:
   /// \brief Free memory allocated for User and Use objects.
   void operator delete(void *Usr);
   /// \brief Placement delete - required by std, but never called.
   void operator delete(void*, unsigned) {
     llvm_unreachable("Constructor throws?");
   }
   /// \brief Placement delete - required by std, but never called.
   void operator delete(void*, unsigned, bool) {

llvm/include/llvm/IR/Value.h

 
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/IR/Use.h"
 #include "llvm/Support/CBindingWrapping.h"
 #include "llvm/Support/Casting.h"
 #include "llvm-c/Types.h"
 #include <cassert>
 #include <iterator>
+#include <memory>
 
 namespace llvm {
 
 class APInt;
 class Argument;
 class BasicBlock;
 class Constant;
 class ConstantData;

 /// have a name and they belong to some Module.  Setting the name on the Value
 /// automatically updates the module's symbol table.
 ///
 /// Every value has a "use list" that keeps track of which other Values are
 /// using this Value.  A Value can also have an arbitrary number of ValueHandle
 /// objects that watch it and listen to RAUW and Destroy events.  See
 /// llvm/IR/ValueHandle.h for details.
 class Value {
+  // The least-significant bit of the first word of Value *must* be zero:
+  //   http://www.llvm.org/docs/ProgrammersManual.html#the-waymarking-algorithm
   Type *VTy;
   Use *UseList;
 
   friend class ValueAsMetadata; // Allow access to IsUsedByMD.
   friend class ValueHandleBase;
 
   const unsigned char SubclassID;   // Subclass identifier (for isa/dyn_cast)
   unsigned char HasValueHandle : 1; // Has a ValueHandle pointing to this?
private:
   };
 
 protected:
   Value(Type *Ty, unsigned scid);
 
 public:
   Value(const Value &) = delete;
   void operator=(const Value &) = delete;
-  virtual ~Value();
+
+protected:
+  /// Value's destructor should be virtual by design, but that would require
+  /// that Value and all of its subclasses have a vtable that effectively
+  /// duplicates the information in the value ID. As a size optimization, the
+  /// destructor has been protected, and the caller should manually call
+  /// deleteValue.
+  ~Value(); // Use deleteValue() to delete a generic Value.
+public:
+
+  /// Delete a pointer to a generic Value.
+  void deleteValue();
 
   /// \brief Support for debugging, callable in GDB: V->dump()
   void dump() const;
 
   /// \brief Implement operator<< on Value.
   /// @{
   void print(raw_ostream &O, bool IsForDebug = false) const;
   void print(raw_ostream &O, ModuleSlotTracker &MST,
private:
   template <class Compare>
   static void mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp);
 
 protected:
   unsigned short getSubclassDataFromValue() const { return SubclassData; }
   void setValueSubclassData(unsigned short D) { SubclassData = D; }
 };
 
+struct ValueDeleter { void operator()(Value *V) { V->deleteValue(); } };
+
+/// Use this instead of std::unique_ptr<Value> or std::unique_ptr<Instruction>.
+/// Those don't work because Value and Instruction's destructors are protected,
+/// aren't virtual, and won't destroy the complete object.
+typedef std::unique_ptr<Value, ValueDeleter> unique_value;
+
 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
   V.print(OS);
   return OS;
 }
 
 void Use::set(Value *V) {
   if (Val) removeFromList();
   Val = V;

llvm/include/llvm/IR/Value.def

 // NOTE: NO INCLUDE GUARD DESIRED!
 
 // Provide definitions of macros so that users of this file do not have to
 // define everything to use it...
 //
 #if !(defined HANDLE_GLOBAL_VALUE || defined HANDLE_CONSTANT ||                \
       defined HANDLE_INSTRUCTION || defined HANDLE_INLINE_ASM_VALUE ||         \
       defined HANDLE_METADATA_VALUE || defined HANDLE_VALUE ||                 \
-      defined HANDLE_CONSTANT_MARKER)
+      defined HANDLE_CONSTANT_MARKER || defined HANDLE_MEMORY_VALUE)
 #error "Missing macro definition of HANDLE_VALUE*"
 #endif
 
+#ifndef HANDLE_MEMORY_VALUE
+#define HANDLE_MEMORY_VALUE(ValueName) HANDLE_VALUE(ValueName)
+#endif
+
 #ifndef HANDLE_GLOBAL_VALUE
 #define HANDLE_GLOBAL_VALUE(ValueName) HANDLE_CONSTANT(ValueName)
 #endif
 
 #ifndef HANDLE_CONSTANT
 #define HANDLE_CONSTANT(ValueName) HANDLE_VALUE(ValueName)
 #endif
 

 #endif
 
 #ifndef HANDLE_CONSTANT_MARKER
 #define HANDLE_CONSTANT_MARKER(MarkerName, ValueName)
 #endif
 
 HANDLE_VALUE(Argument)
 HANDLE_VALUE(BasicBlock)
-HANDLE_VALUE(MemoryUse)
-HANDLE_VALUE(MemoryDef)
-HANDLE_VALUE(MemoryPhi)
+
+HANDLE_MEMORY_VALUE(MemoryUse)
+HANDLE_MEMORY_VALUE(MemoryDef)
+HANDLE_MEMORY_VALUE(MemoryPhi)
 
 HANDLE_GLOBAL_VALUE(Function)
 HANDLE_GLOBAL_VALUE(GlobalAlias)
 HANDLE_GLOBAL_VALUE(GlobalIFunc)
 HANDLE_GLOBAL_VALUE(GlobalVariable)
 HANDLE_CONSTANT(BlockAddress)
 HANDLE_CONSTANT(ConstantExpr)
 

 
 HANDLE_CONSTANT_MARKER(ConstantFirstVal, Function)
 HANDLE_CONSTANT_MARKER(ConstantLastVal, ConstantTokenNone)
 HANDLE_CONSTANT_MARKER(ConstantDataFirstVal, UndefValue)
 HANDLE_CONSTANT_MARKER(ConstantDataLastVal, ConstantTokenNone)
 HANDLE_CONSTANT_MARKER(ConstantAggregateFirstVal, ConstantArray)
 HANDLE_CONSTANT_MARKER(ConstantAggregateLastVal, ConstantVector)
 
+#undef HANDLE_MEMORY_VALUE
 #undef HANDLE_GLOBAL_VALUE
 #undef HANDLE_CONSTANT
 #undef HANDLE_INSTRUCTION
 #undef HANDLE_METADATA_VALUE
 #undef HANDLE_INLINE_ASM_VALUE
 #undef HANDLE_VALUE
 #undef HANDLE_CONSTANT_MARKER

llvm/lib/Analysis/MemorySSA.cpp

if (MemoryPhi *MP = dyn_cast<MemoryPhi>(Dominatee.getUser())) {
     return locallyDominates(Dominator, cast<MemoryAccess>(Dominatee));
   }
   // If it's not a PHI node use, the normal dominates can already handle it.
   return dominates(Dominator, cast<MemoryAccess>(Dominatee.getUser()));
 }
 
 const static char LiveOnEntryStr[] = "liveOnEntry";
 
+void MemoryAccess::print(raw_ostream &OS) const {
+  switch (getValueID()) {
+  case MemoryPhiVal: return static_cast<const MemoryPhi *>(this)->print(OS);
+  case MemoryDefVal: return static_cast<const MemoryDef *>(this)->print(OS);
+  case MemoryUseVal: return static_cast<const MemoryUse *>(this)->print(OS);
+  }
+  llvm_unreachable("invalid value id");
+}
+
 void MemoryDef::print(raw_ostream &OS) const {
   MemoryAccess *UO = getDefiningAccess();
 
   OS << getID() << " = MemoryDef(";
   if (UO && UO->getID())
     OS << UO->getID();
   else
     OS << LiveOnEntryStr;
if (unsigned ID = MA->getID())
       OS << ID;
     else
       OS << LiveOnEntryStr;
     OS << '}';
   }
   OS << ')';
 }
 
-MemoryAccess::~MemoryAccess() {}
-
 void MemoryUse::print(raw_ostream &OS) const {
   MemoryAccess *UO = getDefiningAccess();
   OS << "MemoryUse(";
   if (UO && UO->getID())
     OS << UO->getID();
   else
     OS << LiveOnEntryStr;
   OS << ')';

 
 MemoryAccess *DoNothingMemorySSAWalker::getClobberingMemoryAccess(
     MemoryAccess *StartingAccess, const MemoryLocation &) {
   if (auto *Use = dyn_cast<MemoryUseOrDef>(StartingAccess))
     return Use->getDefiningAccess();
   return StartingAccess;
 }
 } // namespace llvm
+
+// Stamp out value callbacks to delete Memory SSA Value objects.
+#define DEFINE_MEMORY_VALUE_CALLBACKS(Class)                                   \
+  namespace {                                                                  \
+  class Class##Callbacks : public ValueCallbacks {                             \
+  public:                                                                      \
+    void deleteValue(Value *V) override { delete static_cast<Class *>(V); }    \
+  };                                                                           \
+  } /* end namespace */                                                        \
+  ValueCallbacks *llvm::Class::getValueCallbacks() {                           \
+    static Class##Callbacks CB;                                                \
+    return &CB;                                                                \
+  }
+DEFINE_MEMORY_VALUE_CALLBACKS(MemoryPhi)
+DEFINE_MEMORY_VALUE_CALLBACKS(MemoryDef)
+DEFINE_MEMORY_VALUE_CALLBACKS(MemoryUse)
+#undef DEFINE_MEMORY_VALUE_CALLBACKS

llvm/lib/AsmParser/LLParser.cpp

 LLParser::PerFunctionState::~PerFunctionState() {
   // If there were any forward referenced non-basicblock values, delete them.
 
   for (const auto &P : ForwardRefVals) {
     if (isa<BasicBlock>(P.second.first))
       continue;
     P.second.first->replaceAllUsesWith(
         UndefValue::get(P.second.first->getType()));
-    delete P.second.first;
+    P.second.first->deleteValue();
   }
 
   for (const auto &P : ForwardRefValIDs) {
     if (isa<BasicBlock>(P.second.first))
       continue;
     P.second.first->replaceAllUsesWith(
         UndefValue::get(P.second.first->getType()));
-    delete P.second.first;
+    P.second.first->deleteValue();
   }
 }
 
 bool LLParser::PerFunctionState::FinishFunction() {
   if (!ForwardRefVals.empty())
     return P.Error(ForwardRefVals.begin()->second.second,
                    "use of undefined value '%" + ForwardRefVals.begin()->first +
                    "'");
if (NameStr.empty()) {
     auto FI = ForwardRefValIDs.find(NameID);
     if (FI != ForwardRefValIDs.end()) {
       Value *Sentinel = FI->second.first;
       if (Sentinel->getType() != Inst->getType())
         return P.Error(NameLoc, "instruction forward referenced with type '" +
                        getTypeString(FI->second.first->getType()) + "'");
 
       Sentinel->replaceAllUsesWith(Inst);
-      delete Sentinel;
+      Sentinel->deleteValue();
       ForwardRefValIDs.erase(FI);
     }
 
     NumberedVals.push_back(Inst);
     return false;
   }
 
   // Otherwise, the instruction had a name.  Resolve forward refs and set it.
   auto FI = ForwardRefVals.find(NameStr);
   if (FI != ForwardRefVals.end()) {
     Value *Sentinel = FI->second.first;
     if (Sentinel->getType() != Inst->getType())
       return P.Error(NameLoc, "instruction forward referenced with type '" +
                      getTypeString(FI->second.first->getType()) + "'");
 
     Sentinel->replaceAllUsesWith(Inst);
-    delete Sentinel;
+    Sentinel->deleteValue();
     ForwardRefVals.erase(FI);
   }
 
   // Set the name on the instruction.
   Inst->setName(NameStr);
 
   if (Inst->getName() != NameStr)
     return P.Error(NameLoc, "multiple definition of local value named '" +

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

case bitc::FUNC_CODE_OPERAND_BUNDLE: {
       OperandBundles.emplace_back(BundleTags[Record[0]], std::move(Inputs));
       continue;
     }
     }
 
     // Add instruction to end of current BB.  If there is no current BB, reject
     // this file.
     if (!CurBB) {
-      delete I;
+      I->deleteValue();
       return error("Invalid instruction with no BB");
     }
     if (!OperandBundles.empty()) {
-      delete I;
+      I->deleteValue();
       return error("Operand bundles found with no consumer");
     }
     CurBB->getInstList().push_back(I);
 
     // If this was a terminator instruction, move to the next block.
     if (isa<TerminatorInst>(I)) {
       ++CurBBNo;
       CurBB = CurBBNo < FunctionBBs.size() ? FunctionBBs[CurBBNo] : nullptr;

llvm/lib/Bitcode/Reader/ValueList.cpp

void BitcodeReaderValueList::assignValue(Value *V, unsigned Idx) {
   // efficiency.
   if (Constant *PHC = dyn_cast<Constant>(&*OldV)) {
     ResolveConstants.push_back(std::make_pair(PHC, Idx));
     OldV = V;
   } else {
     // If there was a forward reference to this value, replace it.
     Value *PrevVal = OldV;
     OldV->replaceAllUsesWith(V);
-    delete PrevVal;
+    PrevVal->deleteValue();
   }
 }
 
 Constant *BitcodeReaderValueList::getConstantFwdRef(unsigned Idx, Type *Ty) {
   if (Idx >= size())
     resize(Idx + 1);
 
   if (Value *V = ValuePtrs[Idx]) {
while (!Placeholder->use_empty()) {
 
       UserC->replaceAllUsesWith(NewC);
       UserC->destroyConstant();
       NewOps.clear();
     }
 
     // Update all ValueHandles, they should be the only users at this point.
     Placeholder->replaceAllUsesWith(RealVal);
-    delete Placeholder;
+    Placeholder->deleteValue();
   }
 }

llvm/lib/CodeGen/CodeGenPrepare.cpp

for (Function::iterator I = F.begin(); I != F.end(); ) {
       if (ModifiedDTOnIteration)
         break;
     }
     if (EnableTypePromotionMerge && !ValToSExtendedUses.empty())
       MadeChange |= mergeSExts(F);
 
     // Really free removed instructions during promotion.
     for (Instruction *I : RemovedInsts)
-      delete I;
+      I->deleteValue();
 
     EverMadeChange |= MadeChange;
   }
 
   SunkAddrs.clear();
 
   if (!DisableBranchOpts) {
     MadeChange = false;

llvm/lib/IR/Constants.cpp

 #include <algorithm>
 
 using namespace llvm;
 
 //===----------------------------------------------------------------------===//
 //                              Constant Class
 //===----------------------------------------------------------------------===//
 
-void Constant::anchor() { }
-
-void ConstantData::anchor() {}
-
 bool Constant::isNegativeZeroValue() const {
   // Floating point values have an explicit -0.0 value.
   if (const ConstantFP *CFP = dyn_cast<ConstantFP>(this))
     return CFP->isZero() && CFP->isNegative();
 
   // Equivalent for a vector of -0.0's.
   if (const ConstantDataVector *CV = dyn_cast<ConstantDataVector>(this))
     if (ConstantFP *SplatCFP = dyn_cast_or_null<ConstantFP>(CV->getSplatValue()))

 }
 
 
 
 //===----------------------------------------------------------------------===//
 //                                ConstantInt
 //===----------------------------------------------------------------------===//
 
-void ConstantInt::anchor() { }
-
 ConstantInt::ConstantInt(IntegerType *Ty, const APInt &V)
     : ConstantData(Ty, ConstantIntVal), Val(V) {
   assert(V.getBitWidth() == Ty->getBitWidth() && "Invalid constant for type");
 }
 
 ConstantInt *ConstantInt::getTrue(LLVMContext &Context) {
   LLVMContextImpl *pImpl = Context.pImpl;
   if (!pImpl->TheTrueVal)
if (Ty->isX86_FP80Ty())
     return &APFloat::x87DoubleExtended();
   else if (Ty->isFP128Ty())
     return &APFloat::IEEEquad();
 
   assert(Ty->isPPC_FP128Ty() && "Unknown FP format");
   return &APFloat::PPCDoubleDouble();
 }
 
-void ConstantFP::anchor() { }
-
 Constant *ConstantFP::get(Type *Ty, double V) {
   LLVMContext &Context = Ty->getContext();
 
   APFloat FV(V);
   bool ignored;
   FV.convert(*TypeToFloatSemantics(Ty->getScalarType()),
              APFloat::rmNearestTiesToEven, &ignored);
   Constant *C = get(Context, FV);

 
 Type *GetElementPtrConstantExpr::getResultElementType() const {
   return ResElementTy;
 }
 
 //===----------------------------------------------------------------------===//
 //                       ConstantData* implementations
 
-void ConstantDataArray::anchor() {}
-void ConstantDataVector::anchor() {}
-
 Type *ConstantDataSequential::getElementType() const {
   return getType()->getElementType();
 }
 
 StringRef ConstantDataSequential::getRawDataValues() const {
   return StringRef(DataElements, getNumElements()*getElementByteSize());
 }
 

llvm/lib/IR/ConstantsContext.h

 
 #define DEBUG_TYPE "ir"
 
 namespace llvm {
 
 /// UnaryConstantExpr - This class is private to Constants.cpp, and is used
 /// behind the scenes to implement unary constant exprs.
 class UnaryConstantExpr : public ConstantExpr {
-  void anchor() override;
-
 public:
   UnaryConstantExpr(unsigned Opcode, Constant *C, Type *Ty)
     : ConstantExpr(Ty, Opcode, &Op<0>(), 1) {
     Op<0>() = C;
   }
 
   // allocate space for exactly one operand
   void *operator new(size_t s) {
     return User::operator new(s, 1);
   }
 
   void *operator new(size_t, unsigned) = delete;
 
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 };
 
 /// BinaryConstantExpr - This class is private to Constants.cpp, and is used
 /// behind the scenes to implement binary constant exprs.
 class BinaryConstantExpr : public ConstantExpr {
-  void anchor() override;
-
 public:
   BinaryConstantExpr(unsigned Opcode, Constant *C1, Constant *C2,
                      unsigned Flags)
     : ConstantExpr(C1->getType(), Opcode, &Op<0>(), 2) {
     Op<0>() = C1;
     Op<1>() = C2;
     SubclassOptionalData = Flags;
   }
 
   // allocate space for exactly two operands
   void *operator new(size_t s) {
     return User::operator new(s, 2);
   }
 
   void *operator new(size_t, unsigned) = delete;
 
   /// Transparently provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 };
 
 /// SelectConstantExpr - This class is private to Constants.cpp, and is used
 /// behind the scenes to implement select constant exprs.
 class SelectConstantExpr : public ConstantExpr {
-  void anchor() override;
-
 public:
   SelectConstantExpr(Constant *C1, Constant *C2, Constant *C3)
     : ConstantExpr(C2->getType(), Instruction::Select, &Op<0>(), 3) {
     Op<0>() = C1;
     Op<1>() = C2;
     Op<2>() = C3;
   }
 
   // allocate space for exactly three operands
   void *operator new(size_t s) {
     return User::operator new(s, 3);
   }
 
   void *operator new(size_t, unsigned) = delete;
 
   /// Transparently provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 };
 
 /// ExtractElementConstantExpr - This class is private to
 /// Constants.cpp, and is used behind the scenes to implement
 /// extractelement constant exprs.
 class ExtractElementConstantExpr : public ConstantExpr {
-  void anchor() override;
-
 public:
   ExtractElementConstantExpr(Constant *C1, Constant *C2)
     : ConstantExpr(cast<VectorType>(C1->getType())->getElementType(),
                    Instruction::ExtractElement, &Op<0>(), 2) {
     Op<0>() = C1;
     Op<1>() = C2;
   }
 
   // allocate space for exactly two operands
   void *operator new(size_t s) {
     return User::operator new(s, 2);
   }
 
   void *operator new(size_t, unsigned) = delete;
 
   /// Transparently provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 };
 
 /// InsertElementConstantExpr - This class is private to
 /// Constants.cpp, and is used behind the scenes to implement
 /// insertelement constant exprs.
 class InsertElementConstantExpr : public ConstantExpr {
-  void anchor() override;
-
 public:
   InsertElementConstantExpr(Constant *C1, Constant *C2, Constant *C3)
     : ConstantExpr(C1->getType(), Instruction::InsertElement,
                    &Op<0>(), 3) {
     Op<0>() = C1;
     Op<1>() = C2;
     Op<2>() = C3;
   }
 
   // allocate space for exactly three operands
   void *operator new(size_t s) {
     return User::operator new(s, 3);
   }
 
   void *operator new(size_t, unsigned) = delete;
 
   /// Transparently provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 };
 
 /// ShuffleVectorConstantExpr - This class is private to
 /// Constants.cpp, and is used behind the scenes to implement
 /// shufflevector constant exprs.
 class ShuffleVectorConstantExpr : public ConstantExpr {
-  void anchor() override;
-
 public:
   ShuffleVectorConstantExpr(Constant *C1, Constant *C2, Constant *C3)
   : ConstantExpr(VectorType::get(
                    cast<VectorType>(C1->getType())->getElementType(),
                    cast<VectorType>(C3->getType())->getNumElements()),
                  Instruction::ShuffleVector,
                  &Op<0>(), 3) {
     Op<0>() = C1;
public:
   /// Transparently provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 };
 
 /// ExtractValueConstantExpr - This class is private to
 /// Constants.cpp, and is used behind the scenes to implement
 /// extractvalue constant exprs.
 class ExtractValueConstantExpr : public ConstantExpr {
-  void anchor() override;
-
 public:
   ExtractValueConstantExpr(Constant *Agg, ArrayRef<unsigned> IdxList,
                            Type *DestTy)
       : ConstantExpr(DestTy, Instruction::ExtractValue, &Op<0>(), 1),
         Indices(IdxList.begin(), IdxList.end()) {
     Op<0>() = Agg;
   }
 
static bool classof(const Value *V) {
     return isa<ConstantExpr>(V) && classof(cast<ConstantExpr>(V));
   }
 };
 
 /// InsertValueConstantExpr - This class is private to
 /// Constants.cpp, and is used behind the scenes to implement
 /// insertvalue constant exprs.
 class InsertValueConstantExpr : public ConstantExpr {
-  void anchor() override;
-
 public:
   InsertValueConstantExpr(Constant *Agg, Constant *Val,
                           ArrayRef<unsigned> IdxList, Type *DestTy)
       : ConstantExpr(DestTy, Instruction::InsertValue, &Op<0>(), 2),
         Indices(IdxList.begin(), IdxList.end()) {
     Op<0>() = Agg;
     Op<1>() = Val;
   }

 /// used behind the scenes to implement getelementpr constant exprs.
 class GetElementPtrConstantExpr : public ConstantExpr {
   Type *SrcElementTy;
   Type *ResElementTy;
 
   GetElementPtrConstantExpr(Type *SrcElementTy, Constant *C,
                             ArrayRef<Constant *> IdxList, Type *DestTy);
 
-  void anchor() override;
-
 public:
   static GetElementPtrConstantExpr *Create(Type *SrcElementTy, Constant *C,
                                            ArrayRef<Constant *> IdxList,
                                            Type *DestTy, unsigned Flags) {
     GetElementPtrConstantExpr *Result = new (IdxList.size() + 1)
         GetElementPtrConstantExpr(SrcElementTy, C, IdxList, DestTy);
     Result->SubclassOptionalData = Flags;
     return Result;
static bool classof(const Value *V) {
     return isa<ConstantExpr>(V) && classof(cast<ConstantExpr>(V));
   }
 };
 
 // CompareConstantExpr - This class is private to Constants.cpp, and is used
 // behind the scenes to implement ICmp and FCmp constant expressions. This is
 // needed in order to store the predicate value for these instructions.
 class CompareConstantExpr : public ConstantExpr {
-  void anchor() override;
-
 public:
   unsigned short predicate;
   CompareConstantExpr(Type *ty, Instruction::OtherOps opc,
                       unsigned short pred,  Constant* LHS, Constant* RHS)
     : ConstantExpr(ty, opc, &Op<0>(), 2), predicate(pred) {
     Op<0>() = LHS;
     Op<1>() = RHS;
   }

llvm/lib/IR/Function.cpp

 // Explicit instantiations of SymbolTableListTraits since some of the methods
 // are not in the public header file...
 template class llvm::SymbolTableListTraits<BasicBlock>;
 
 //===----------------------------------------------------------------------===//
 // Argument Implementation
 //===----------------------------------------------------------------------===//
 
-void Argument::anchor() {}
-
 Argument::Argument(Type *Ty, const Twine &Name, Function *Par, unsigned ArgNo)
     : Value(Ty, Value::ArgumentVal), Parent(Par), ArgNo(ArgNo) {
   setName(Name);
 }
 
 void Argument::setParent(Function *parent) {
   Parent = parent;
 }

llvm/lib/IR/InlineAsm.cpp

: Value(PointerType::getUnqual(FTy), Value::InlineAsmVal),
       AsmString(asmString), Constraints(constraints), FTy(FTy),
       HasSideEffects(hasSideEffects), IsAlignStack(isAlignStack),
       Dialect(asmDialect) {
   // Do various checks on the constraint string and type.
   assert(Verify(getFunctionType(), constraints) &&
          "Function type not legal for constraints!");
 }
 
-// Implement the first virtual method in this class in this file so the
-// InlineAsm vtable is emitted here.
-InlineAsm::~InlineAsm() = default;
-
 InlineAsm *InlineAsm::get(FunctionType *FTy, StringRef AsmString,
                           StringRef Constraints, bool hasSideEffects,
                           bool isAlignStack, AsmDialect asmDialect) {
   InlineAsmKeyType Key(AsmString, Constraints, FTy, hasSideEffects,
                        isAlignStack, asmDialect);
   LLVMContextImpl *pImpl = FTy->getContext().pImpl;
   return pImpl->InlineAsms.getOrCreate(PointerType::getUnqual(FTy), Key);
 }

llvm/lib/IR/Instruction.cpp

Instruction::Instruction(Type *ty, unsigned it, Use *Ops, unsigned NumOps,
                          BasicBlock *InsertAtEnd)
   : User(ty, Value::InstructionVal + it, Ops, NumOps), Parent(nullptr) {
 
   // append this instruction into the basic block
   assert(InsertAtEnd && "Basic block to append to may not be NULL!");
   InsertAtEnd->getInstList().push_back(this);
 }
 
-
-// Out of line virtual method, so the vtable, etc has a home.
 Instruction::~Instruction() {
   assert(!Parent && "Instruction still linked in the program!");
   if (hasMetadataHashEntry())
     clearMetadataHashEntries();
 }
 
 
 void Instruction::setParent(BasicBlock *P) {

llvm/lib/IR/Instructions.cpp

return isCall()
     ? cast<CallInst>(II)->op_end() - 1 // Skip Callee
     : cast<InvokeInst>(II)->op_end() - 3; // Skip BB, BB, Callee
 }
 
 //===----------------------------------------------------------------------===//
 //                            TerminatorInst Class
 //===----------------------------------------------------------------------===//
 
-// Out of line virtual method, so the vtable, etc has a home.
-TerminatorInst::~TerminatorInst() {
-}
-
 unsigned TerminatorInst::getNumSuccessors() const {
   switch (getOpcode()) {
 #define HANDLE_TERM_INST(N, OPC, CLASS)                                        \
   case Instruction::OPC:                                                       \
     return static_cast<const CLASS *>(this)->getNumSuccessorsV();
 #include "llvm/IR/Instruction.def"
   default:
     break;

 #include "llvm/IR/Instruction.def"
   default:
     break;
   }
   llvm_unreachable("not a terminator");
 }
 
 //===----------------------------------------------------------------------===//
-//                           UnaryInstruction Class
-//===----------------------------------------------------------------------===//
-
-// Out of line virtual method, so the vtable, etc has a home.
-UnaryInstruction::~UnaryInstruction() {
-}
-
-//===----------------------------------------------------------------------===//
 //                              SelectInst Class
 //===----------------------------------------------------------------------===//
 
 /// areInvalidOperands - Return a string if the specified operands are invalid
 /// for a select operation, otherwise return null.
 const char *SelectInst::areInvalidOperands(Value *Op0, Value *Op1, Value *Op2) {
   if (Op1->getType() != Op2->getType())
     return "both values to select must have same type";
const char *SelectInst::areInvalidOperands(Value *Op0, Value *Op1, Value *Op2) {
   return nullptr;
 }
 
 
 //===----------------------------------------------------------------------===//
 //                               PHINode Class
 //===----------------------------------------------------------------------===//
 
-void PHINode::anchor() {}
-
 PHINode::PHINode(const PHINode &PN)
     : Instruction(PN.getType(), Instruction::PHI, nullptr, PN.getNumOperands()),
       ReservedSpace(PN.getNumOperands()) {
   allocHungoffUses(PN.getNumOperands());
   std::copy(PN.op_begin(), PN.op_end(), op_begin());
   std::copy(PN.block_begin(), PN.block_end(), block_begin());
   SubclassOptionalData = PN.SubclassOptionalData;
 }
void LandingPadInst::addClause(Constant *Val) {
   setNumHungOffUseOperands(getNumOperands() + 1);
   getOperandList()[OpNo] = Val;
 }
 
 //===----------------------------------------------------------------------===//
 //                        CallInst Implementation
 //===----------------------------------------------------------------------===//
 
-CallInst::~CallInst() {
-}
-
 void CallInst::init(FunctionType *FTy, Value *Func, ArrayRef<Value *> Args,
                     ArrayRef<OperandBundleDef> Bundles, const Twine &NameStr) {
   this->FTy = FTy;
   assert(getNumOperands() == Args.size() + CountBundleInputs(Bundles) + 1 &&
          "NumOperands not set up?");
   Op<-1>() = Func;
 
 #ifndef NDEBUG

 void ReturnInst::setSuccessorV(unsigned idx, BasicBlock *NewSucc) {
   llvm_unreachable("ReturnInst has no successors!");
 }
 
 BasicBlock *ReturnInst::getSuccessorV(unsigned idx) const {
   llvm_unreachable("ReturnInst has no successors!");
 }
 
-ReturnInst::~ReturnInst() {
-}
-
 //===----------------------------------------------------------------------===//
 //                        ResumeInst Implementation
 //===----------------------------------------------------------------------===//
 
 ResumeInst::ResumeInst(const ResumeInst &RI)
   : TerminatorInst(Type::getVoidTy(RI.getContext()), Instruction::Resume,
                    OperandTraits<ResumeInst>::op_begin(this), 1) {
   Op<0>() = RI.Op<0>();
AllocaInst::AllocaInst(Type *Ty, unsigned AddrSpace, Value *ArraySize,
   : UnaryInstruction(PointerType::get(Ty, AddrSpace), Alloca,
                      getAISize(Ty->getContext(), ArraySize), InsertAtEnd),
       AllocatedType(Ty) {
   setAlignment(Align);
   assert(!Ty->isVoidTy() && "Cannot allocate void!");
   setName(Name);
 }
 
-// Out of line virtual method, so the vtable, etc has a home.
-AllocaInst::~AllocaInst() {
-}
-
 void AllocaInst::setAlignment(unsigned Align) {
   assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
   assert(Align <= MaximumAlignment &&
          "Alignment is greater than MaximumAlignment!");
   setInstructionSubclassData((getSubclassDataFromInstruction() & ~31) |
                              (Log2_32(Align) + 1));
   assert(getAlignment() == Align && "Alignment representation error!");
 }
FenceInst::FenceInst(LLVMContext &C, AtomicOrdering Ordering,
   setOrdering(Ordering);
   setSynchScope(SynchScope);
 }
 
 //===----------------------------------------------------------------------===//
 //                       GetElementPtrInst Implementation
 //===----------------------------------------------------------------------===//
 
-void GetElementPtrInst::anchor() {}
-
 void GetElementPtrInst::init(Value *Ptr, ArrayRef<Value *> IdxList,
                              const Twine &Name) {
   assert(getNumOperands() == 1 + IdxList.size() &&
          "NumOperands not initialized?");
   Op<0>() = Ptr;
   std::copy(IdxList.begin(), IdxList.end(), op_begin() + 1);
   setName(Name);
 }
float FPMathOperator::getFPAccuracy() const {
   return Accuracy->getValueAPF().convertToFloat();
 }
 
 
 //===----------------------------------------------------------------------===//
 //                                CastInst Class
 //===----------------------------------------------------------------------===//
 
-void CastInst::anchor() {}
-
 // Just determine if this cast only deals with integral->integral conversion.
 bool CastInst::isIntegerCast() const {
   switch (getOpcode()) {
     default: return false;
     case Instruction::ZExt:
     case Instruction::SExt:
     case Instruction::Trunc:
       return true;

 ) : CastInst(Ty, AddrSpaceCast, S, Name, InsertAtEnd) {
   assert(castIsValid(getOpcode(), S, Ty) && "Illegal AddrSpaceCast");
 }
 
 //===----------------------------------------------------------------------===//
 //                               CmpInst Classes
 //===----------------------------------------------------------------------===//
 
-void CmpInst::anchor() {}
-
 CmpInst::CmpInst(Type *ty, OtherOps op, Predicate predicate, Value *LHS,
                  Value *RHS, const Twine &Name, Instruction *InsertBefore)
   : Instruction(ty, op,
                 OperandTraits<CmpInst>::op_begin(this),
                 OperandTraits<CmpInst>::operands(this),
                 InsertBefore) {
     Op<0>() = LHS;
     Op<1>() = RHS;
StringRef CmpInst::getPredicateName(Predicate Pred) {
   case ICmpInst::ICMP_SLE:   return "sle";
   case ICmpInst::ICMP_UGT:   return "ugt";
   case ICmpInst::ICMP_UGE:   return "uge";
   case ICmpInst::ICMP_ULT:   return "ult";
   case ICmpInst::ICMP_ULE:   return "ule";
   }
 }
 
-void ICmpInst::anchor() {}
-
 ICmpInst::Predicate ICmpInst::getSignedPredicate(Predicate pred) {
   switch (pred) {
     default: llvm_unreachable("Unknown icmp predicate!");
     case ICMP_EQ: case ICMP_NE: 
     case ICMP_SGT: case ICMP_SLT: case ICMP_SGE: case ICMP_SLE: 
        return pred;
     case ICMP_UGT: return ICMP_SGT;
     case ICMP_ULT: return ICMP_SLT;

llvm/lib/IR/LLVMContextImpl.cpp

 }
 
 uint32_t LLVMContextImpl::getOperandBundleTagID(StringRef Tag) const {
   auto I = BundleTagCache.find(Tag);
   assert(I != BundleTagCache.end() && "Unknown tag!");
   return I->second;
 }
 
-// ConstantsContext anchors
-void UnaryConstantExpr::anchor() { }
-
-void BinaryConstantExpr::anchor() { }
-
-void SelectConstantExpr::anchor() { }
-
-void ExtractElementConstantExpr::anchor() { }
-
-void InsertElementConstantExpr::anchor() { }
-
-void ShuffleVectorConstantExpr::anchor() { }
-
-void ExtractValueConstantExpr::anchor() { }
-
-void InsertValueConstantExpr::anchor() { }
-
-void GetElementPtrConstantExpr::anchor() { }
-
-void CompareConstantExpr::anchor() { }
-
 /// Singleton instance of the OptBisect class.
 ///
 /// This singleton is accessed via the LLVMContext::getOptBisect() function.  It
 /// provides a mechanism to disable passes and individual optimizations at
 /// compile time based on a command line option (-opt-bisect-limit) in order to
 /// perform a bisecting search for optimization-related problems.
 ///
 /// Even if multiple LLVMContext objects are created, they will all return the
 /// same instance of OptBisect in order to provide a single bisect count.  Any
 /// code that uses the OptBisect object should be serialized when bisection is
 /// enabled in order to enable a consistent bisect count.
 static ManagedStatic<OptBisect> OptBisector;
 
 OptBisect &LLVMContextImpl::getOptBisect() {
   return *OptBisector;
 }

llvm/lib/IR/User.cpp

 
 namespace llvm {
 class BasicBlock;
 
 //===----------------------------------------------------------------------===//
 //                                 User Class
 //===----------------------------------------------------------------------===//
 
-void User::anchor() {}
-
 void User::replaceUsesOfWith(Value *From, Value *To) {
   if (From == To) return;   // Duh what?
 
   assert((!isa<Constant>(this) || isa<GlobalValue>(this)) &&
          "Cannot call User::replaceUsesOfWith on a constant!");
 
   for (unsigned i = 0, E = getNumOperands(); i != E; ++i)
     if (getOperand(i) == From) {  // Is This operand is pointing to oldval?
void User::operator delete(void *Usr) {
   } else {
     Use *Storage = static_cast<Use *>(Usr) - Obj->NumUserOperands;
     Use::zap(Storage, Storage + Obj->NumUserOperands,
              /* Delete */ false);
     ::operator delete(Storage);
   }
 }
 
-//===----------------------------------------------------------------------===//
-//                             Operator Class
-//===----------------------------------------------------------------------===//
-
-Operator::~Operator() {
-  llvm_unreachable("should never destroy an Operator");
-}
-
 } // End llvm namespace

llvm/lib/IR/Value.cpp

 #include "LLVMContextImpl.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/DerivedUser.h"
 #include "llvm/IR/GetElementPtrTypeIterator.h"
 #include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/Statepoint.h"
 #include "llvm/IR/ValueHandle.h"
Value::Value(Type *ty, unsigned scid)
   // constructed.
   if (SubclassID == Instruction::Call || SubclassID == Instruction::Invoke)
     assert((VTy->isFirstClassType() || VTy->isVoidTy() || VTy->isStructTy()) &&
            "invalid CallInst type!");
   else if (SubclassID != BasicBlockVal &&
            (SubclassID < ConstantFirstVal || SubclassID > ConstantLastVal))
     assert((VTy->isFirstClassType() || VTy->isVoidTy()) &&
            "Cannot create non-first-class values except for constants!");
-  static_assert(sizeof(Value) == 3 * sizeof(void *) + 2 * sizeof(unsigned),
+  static_assert(sizeof(Value) == 2 * sizeof(void *) + 2 * sizeof(unsigned),
                 "Value too big");
 }
 
 Value::~Value() {
   // Notify all ValueHandles (if present) that this value is going away.
   if (HasValueHandle)
     ValueHandleBase::ValueIsDeleted(this);
   if (isUsedByMetadata())

 #endif
   assert(use_empty() && "Uses remain when a value is destroyed!");
 
   // If this value is named, destroy the name.  This should not be in a symtab
   // at this point.
   destroyValueName();
 }
 
+void Value::deleteValue() {
+  switch (getValueID()) {
+#define HANDLE_VALUE(Name)                                                     \
+  case Value::Name##Val:                                                       \
+    delete static_cast<Name *>(this);                                          \
+    break;
+#define HANDLE_MEMORY_VALUE(Name)                                              \
+  case Value::Name##Val:                                                       \
+    static_cast<DerivedUser *>(this)->VCallbacks->deleteValue(this);           \
+    break;
+#define HANDLE_INSTRUCTION(Name)  /* nothing */
+#include "llvm/IR/Value.def"
+
+#define HANDLE_INST(N, OPC, CLASS)                                             \
+  case Value::InstructionVal + Instruction::OPC:                               \
+    delete static_cast<CLASS *>(this);                                         \
+    break;
+#define HANDLE_USER_INST(N, OPC, CLASS)
+#include "llvm/IR/Instruction.def"
+
+  default:
+    llvm_unreachable("attempting to delete unknown value kind");
+  }
+}
+
 void Value::destroyValueName() {
   ValueName *Name = getValueName();
   if (Name)
     Name->Destroy();
   setValueName(nullptr);
 }
 
 bool Value::hasNUses(unsigned N) const {
for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
       default:
         break;
       }
 #endif
 }
 
 // Pin the vtable to this file.
 void CallbackVH::anchor() {}
+
+// Pin the vtable to this file.
+ValueCallbacks::~ValueCallbacks() {}

llvm/lib/Target/Hexagon/HexagonLoopIdiomRecognition.cpp

for (Value *V : Clones) {
     Instruction *U = cast<Instruction>(V);
     if (!U->getParent())
       U->dropAllReferences();
   }
 
   for (Value *V : Clones) {
     Instruction *U = cast<Instruction>(V);
     if (!U->getParent())
-      delete U;
+      U->deleteValue();
   }
 }
 
 
 bool Simplifier::Context::equal(const Instruction *I,
                                 const Instruction *J) const {
   if (I == J)
     return true;

llvm/lib/Transforms/Scalar/GVN.cpp

if (isCriticalEdge(PREPred->getTerminator(), SuccNum)) {
       toSplit.push_back(std::make_pair(PREPred->getTerminator(), SuccNum));
       return false;
     }
     // We need to insert somewhere, so let's give it a shot
     PREInstr = CurInst->clone();
     if (!performScalarPREInsertion(PREInstr, PREPred, ValNo)) {
       // If we failed insertion, make sure we remove the instruction.
       DEBUG(verifyRemoved(PREInstr));
-      delete PREInstr;
+      PREInstr->deleteValue();
       return false;
     }
   }
 
   // Either we should have filled in the PRE instruction, or we should
   // not have needed insertions.
   assert (PREInstr != nullptr || NumWithout == 0);
 

llvm/lib/Transforms/Scalar/JumpThreading.cpp

for (; BI != BB->end(); ++BI) {
     // If this instruction can be simplified after the operands are updated,
     // just use the simplified value instead.  This frequently happens due to
     // phi translation.
     if (Value *IV = SimplifyInstruction(
             New,
             {BB->getModule()->getDataLayout(), TLI, nullptr, nullptr, New})) {
       ValueMapping[&*BI] = IV;
       if (!New->mayHaveSideEffects()) {
-        delete New;
+        New->deleteValue();
         New = nullptr;
       }
     } else {
       ValueMapping[&*BI] = New;
     }
     if (New) {
       // Otherwise, insert the new instruction into the block.
       New->setName(BI->getName());

llvm/lib/Transforms/Scalar/LoopRotation.cpp

while (I != E) {
     // otherwise simplifyable.  This commonly occurs because the entry from PHI
     // nodes allows icmps and other instructions to fold.
     Value *V = SimplifyInstruction(C, SQ);
     if (V && LI->replacementPreservesLCSSAForm(C, V)) {
       // If so, then delete the temporary instruction and stick the folded value
       // in the map.
       ValueMap[Inst] = V;
       if (!C->mayHaveSideEffects()) {
-        delete C;
+        C->deleteValue();
         C = nullptr;
       }
     } else {
       ValueMap[Inst] = C;
     }
     if (C) {
       // Otherwise, stick the new instruction into the new block!
       C->setName(Inst->getName());

llvm/lib/Transforms/Scalar/Reassociate.cpp

for (unsigned i = 0; i != Ops.size(); ++i) {
             Ops.erase(Ops.begin()+j);
           }
         }
         --i;
       }
     }
 
     // No need for extra uses anymore.
-    delete DummyInst;
+    DummyInst->deleteValue();
 
     unsigned NumAddedValues = NewMulOps.size();
     Value *V = EmitAddTreeOfValues(I, NewMulOps);
 
     // Now that we have inserted the add tree, optimize it. This allows us to
     // handle cases that require multiple factoring steps, such as this:
     // A*A*B + A*A*C   -->   A*(A*B+A*C)   -->   A*(A*(B+C))
     assert(NumAddedValues > 1 && "Each occurrence should contribute a value");

llvm/lib/Transforms/Scalar/SROA.cpp

if (IsSplit) {
       // the computed value, and then replace the placeholder with LI, leaving
       // LI only used for this computation.
       Value *Placeholder =
           new LoadInst(UndefValue::get(LI.getType()->getPointerTo(AS)));
       V = insertInteger(DL, IRB, Placeholder, V, NewBeginOffset - BeginOffset,
                         "insert");
       LI.replaceAllUsesWith(V);
       Placeholder->replaceAllUsesWith(&LI);
-      delete Placeholder;
+      Placeholder->deleteValue();
     } else {
       LI.replaceAllUsesWith(V);
     }
 
     Pass.DeadInsts.insert(&LI);
     deleteIfTriviallyDead(OldOp);
     DEBUG(dbgs() << "          to: " << *V << "\n");
     return !LI.isVolatile() && !IsPtrAdjusted;

llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp

bool StraightLineStrengthReduce::runOnFunction(Function &F) {
 
   // Delete all unlink instructions.
   for (auto *UnlinkedInst : UnlinkedInstructions) {
     for (unsigned I = 0, E = UnlinkedInst->getNumOperands(); I != E; ++I) {
       Value *Op = UnlinkedInst->getOperand(I);
       UnlinkedInst->setOperand(I, nullptr);
       RecursivelyDeleteTriviallyDeadInstructions(Op);
     }
-    delete UnlinkedInst;
+    UnlinkedInst->deleteValue();
   }
   bool Ret = !UnlinkedInstructions.empty();
   UnlinkedInstructions.clear();
   return Ret;
 }

llvm/lib/Transforms/Utils/CloneFunction.cpp

if (!isa<PHINode>(NewInst)) {
               SimplifyInstruction(NewInst, BB->getModule()->getDataLayout())) {
         // On the off-chance that this simplifies to an instruction in the old
         // function, map it back into the new function.
         if (Value *MappedV = VMap.lookup(V))
           V = MappedV;
 
         if (!NewInst->mayHaveSideEffects()) {
           VMap[&*II] = V;
-          delete NewInst;
+          NewInst->deleteValue();
           continue;
         }
       }
     }
 
     if (II->hasName())
       NewInst->setName(II->getName()+NameSuffix);
     VMap[&*II] = NewInst; // Add instruction map to value.

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) {
           *i = PI->second;
       }
 
       // Check for trivial simplification.
       if (Value *V = SimplifyInstruction(N, {DL, nullptr, nullptr, AC})) {
         if (!BBI->use_empty())
           TranslateMap[&*BBI] = V;
         if (!N->mayHaveSideEffects()) {
-          delete N; // Instruction folded away, don't need actual inst
+          N->deleteValue(); // Instruction folded away, don't need actual inst
           N = nullptr;
         }
       } else {
         if (!BBI->use_empty())
           TranslateMap[&*BBI] = N;
       }
       // Insert the new instruction into its new home.
       if (N)

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

private:
   /// It's like Instruction::eraseFromParent() except that the actual deletion
   /// is delayed until BoUpSLP is destructed.
   /// This is required to ensure that there are no incorrect collisions in the
   /// AliasCache, which can happen if a new instruction is allocated at the
   /// same address as a previously deleted instruction.
   void eraseInstruction(Instruction *I) {
     I->removeFromParent();
     I->dropAllReferences();
-    DeletedInstructions.push_back(std::unique_ptr<Instruction>(I));
+    DeletedInstructions.emplace_back(I);
   }
 
   /// Temporary store for deleted instructions. Instructions will be deleted
   /// eventually when the BoUpSLP is destructed.
-  SmallVector<std::unique_ptr<Instruction>, 8> DeletedInstructions;
+  SmallVector<unique_value, 8> DeletedInstructions;
 
   /// A list of values that need to extracted out of the tree.
   /// This list holds pairs of (Internal Scalar : External User). External User
   /// can be nullptr, it means that this Internal Scalar will be used later,
   /// after vectorization.
   UserList ExternalUses;
 
   /// Values used only by @llvm.assume calls.

llvm/unittests/IR/ConstantsTest.cpp

TEST(ConstantsTest, PointerCast) {
   // Make sure that addrspacecast of null is not folded away.
   EXPECT_NE(Constant::getNullValue(Int32PtrTy),
             ConstantExpr::getAddrSpaceCast(NullInt32Ptr0, Int32Ptr1Ty));
 
   EXPECT_NE(Constant::getNullValue(Int32Ptr1Ty),
             ConstantExpr::getAddrSpaceCast(NullInt32Ptr1, Int32PtrTy));
 }
 
-#define CHECK(x, y) {                                             \
-    std::string __s;                                              \
-    raw_string_ostream __o(__s);                                  \
-    Instruction *__I = cast<ConstantExpr>(x)->getAsInstruction();  \
-    __I->print(__o);                 \
-    delete __I;               \
-    __o.flush();                                                  \
-    EXPECT_EQ(std::string("  <badref> = " y), __s);               \
+#define CHECK(x, y)                                                            \
+  {                                                                            \
+    std::string __s;                                                           \
+    raw_string_ostream __o(__s);                                               \
+    Instruction *__I = cast<ConstantExpr>(x)->getAsInstruction();              \
+    __I->print(__o);                                                           \
+    __I->deleteValue();                                                        \
+    __o.flush();                                                               \
+    EXPECT_EQ(std::string("  <badref> = " y), __s);                            \
   }
 
 TEST(ConstantsTest, AsInstructionsTest) {
   LLVMContext Context;
   std::unique_ptr<Module> M(new Module("MyModule", Context));
 
   Type *Int64Ty = Type::getInt64Ty(Context);
   Type *Int32Ty = Type::getInt32Ty(Context);

llvm/unittests/IR/InstructionsTest.cpp

TEST(InstructionsTest, FPMathOperator) {
   IRBuilder<> Builder(Context);
   MDBuilder MDHelper(Context);
   Instruction *I = Builder.CreatePHI(Builder.getDoubleTy(), 0);
   MDNode *MD1 = MDHelper.createFPMath(1.0);
   Value *V1 = Builder.CreateFAdd(I, I, "", MD1);
   EXPECT_TRUE(isa<FPMathOperator>(V1));
   FPMathOperator *O1 = cast<FPMathOperator>(V1);
   EXPECT_EQ(O1->getFPAccuracy(), 1.0);
-  delete V1;
-  delete I;
+  V1->deleteValue();
+  I->deleteValue();
 }
 
 
 TEST(InstructionsTest, isEliminableCastPair) {
   LLVMContext C;
 
   Type* Int16Ty = Type::getInt16Ty(C);
   Type* Int32Ty = Type::getInt32Ty(C);

llvm/unittests/IR/MetadataTest.cpp

TEST_F(MDNodeTest, Delete) {
   Instruction *I = new BitCastInst(C, Type::getInt32Ty(Context));
 
   Metadata *const V = LocalAsMetadata::get(I);
   MDNode *n = MDNode::get(Context, V);
   TrackingMDRef wvh(n);
 
   EXPECT_EQ(n, wvh);
 
-  delete I;
+  I->deleteValue();
 }
 
 TEST_F(MDNodeTest, SelfReference) {
   // !0 = !{!0}
   // !1 = !{!0}
   {
     auto Temp = MDNode::getTemporary(Context, None);
     Metadata *Args[] = {Temp.get()};

llvm/unittests/Transforms/Utils/Cloning.cpp

protected:
   T *clone(T *V1) {
     Value *V2 = V1->clone();
     Orig.insert(V1);
     Clones.insert(V2);
     return cast<T>(V2);
   }
 
   void eraseClones() {
-    DeleteContainerPointers(Clones);
+    for (Value *V : Clones)
+      V->deleteValue();
+    Clones.clear();
   }
 
   void TearDown() override {
     eraseClones();
-    DeleteContainerPointers(Orig);
-    delete V;
+    for (Value *V : Orig)
+      V->deleteValue();
+    Orig.clear();
+    if (V)
+      V->deleteValue();
   }
 
   SmallPtrSet<Value *, 4> Orig;   // Erase on exit
   SmallPtrSet<Value *, 4> Clones; // Erase in eraseClones
 
   LLVMContext context;
   Value *V;
 };