10 files changed, 52 insertions, 137 deletions
diff --git a/llvm/include/llvm/ADT/SparseBitVector.h b/llvm/include/llvm/ADT/SparseBitVector.h
index e6e72413da4..4e19b16f61a 100644
--- a/llvm/include/llvm/ADT/SparseBitVector.h
+++ b/llvm/include/llvm/ADT/SparseBitVector.h
@@ -245,20 +245,9 @@ public:
 };
 
 template <unsigned ElementSize>
-struct ilist_traits<SparseBitVectorElement<ElementSize> >
-  : public ilist_default_traits<SparseBitVectorElement<ElementSize> > {
-  typedef SparseBitVectorElement<ElementSize> Element;
-
-  Element *createSentinel() const { return static_cast<Element *>(&Sentinel); }
-  static void destroySentinel(Element *) {}
-
-  Element *provideInitialHead() const { return createSentinel(); }
-  Element *ensureHead(Element *) const { return createSentinel(); }
-  static void noteHead(Element *, Element *) {}
-
-private:
-  mutable ilist_half_node<Element> Sentinel;
-};
+struct ilist_sentinel_traits<SparseBitVectorElement<ElementSize>>
+    : public ilist_half_embedded_sentinel_traits<
+          SparseBitVectorElement<ElementSize>> {};
 
 template <unsigned ElementSize = 128>
 class SparseBitVector {
diff --git a/llvm/include/llvm/ADT/ilist.h b/llvm/include/llvm/ADT/ilist.h
index 6744ddd6c9b..3a431bb9536 100644
--- a/llvm/include/llvm/ADT/ilist.h
+++ b/llvm/include/llvm/ADT/ilist.h
@@ -109,10 +109,11 @@ template <typename NodeTy> class ilist_half_node;
 template <typename NodeTy> class ilist_node;
 
 /// Traits with an embedded ilist_node as a sentinel.
-///
-/// FIXME: The downcast in createSentinel() is UB.
 template <typename NodeTy> struct ilist_embedded_sentinel_traits {
   /// Get hold of the node that marks the end of the list.
+  ///
+  /// FIXME: This downcast is UB.  See llvm.org/PR26753.
+  LLVM_NO_SANITIZE("object-size")
   NodeTy *createSentinel() const {
     // Since i(p)lists always publicly derive from their corresponding traits,
     // placing a data member in this class will augment the i(p)list.  But since
@@ -134,10 +135,11 @@ private:
 };
 
 /// Trait with an embedded ilist_half_node as a sentinel.
-///
-/// FIXME: The downcast in createSentinel() is UB.
 template <typename NodeTy> struct ilist_half_embedded_sentinel_traits {
   /// Get hold of the node that marks the end of the list.
+  ///
+  /// FIXME: This downcast is UB.  See llvm.org/PR26753.
+  LLVM_NO_SANITIZE("object-size")
   NodeTy *createSentinel() const {
     // See comment in ilist_embedded_sentinel_traits::createSentinel().
     return static_cast<NodeTy *>(&Sentinel);
@@ -152,6 +154,20 @@ private:
   mutable ilist_half_node<NodeTy> Sentinel;
 };
 
+/// Traits with an embedded full node as a sentinel.
+template <typename NodeTy> struct ilist_full_embedded_sentinel_traits {
+  /// Get hold of the node that marks the end of the list.
+  NodeTy *createSentinel() const { return &Sentinel; }
+  static void destroySentinel(NodeTy *) {}
+
+  NodeTy *provideInitialHead() const { return createSentinel(); }
+  NodeTy *ensureHead(NodeTy *) const { return createSentinel(); }
+  static void noteHead(NodeTy *, NodeTy *) {}
+
+private:
+  mutable NodeTy Sentinel;
+};
+
 /// ilist_node_traits - A fragment for template traits for intrusive list
 /// that provides default node related operations.
 ///
diff --git a/llvm/include/llvm/Analysis/IVUsers.h b/llvm/include/llvm/Analysis/IVUsers.h
index 031085dddd2..16161be8db0 100644
--- a/llvm/include/llvm/Analysis/IVUsers.h
+++ b/llvm/include/llvm/Analysis/IVUsers.h
@@ -91,32 +91,9 @@ private:
   void deleted() override;
 };
 
-template<> struct ilist_traits<IVStrideUse>
-  : public ilist_default_traits<IVStrideUse> {
-  // createSentinel is used to get hold of a node that marks the end of
-  // the list...
-  // The sentinel is relative to this instance, so we use a non-static
-  // method.
-  IVStrideUse *createSentinel() const {
-    // since i(p)lists always publicly derive from the corresponding
-    // traits, placing a data member in this class will augment i(p)list.
-    // But since the NodeTy is expected to publicly derive from
-    // ilist_node<NodeTy>, there is a legal viable downcast from it
-    // to NodeTy. We use this trick to superpose i(p)list with a "ghostly"
-    // NodeTy, which becomes the sentinel. Dereferencing the sentinel is
-    // forbidden (save the ilist_node<NodeTy>) so no one will ever notice
-    // the superposition.
-    return static_cast<IVStrideUse*>(&Sentinel);
-  }
-  static void destroySentinel(IVStrideUse*) {}
-
-  IVStrideUse *provideInitialHead() const { return createSentinel(); }
-  IVStrideUse *ensureHead(IVStrideUse*) const { return createSentinel(); }
-  static void noteHead(IVStrideUse*, IVStrideUse*) {}
-
-private:
-  mutable ilist_node<IVStrideUse> Sentinel;
-};
+template <>
+struct ilist_sentinel_traits<IVStrideUse>
+    : public ilist_embedded_sentinel_traits<IVStrideUse> {};
 
 class IVUsers {
   friend class IVStrideUse;
diff --git a/llvm/include/llvm/CodeGen/MachineBasicBlock.h b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
index 2923371c100..37a7948c9ef 100644
--- a/llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -39,24 +39,17 @@ class MachineBranchProbabilityInfo;
 typedef unsigned LaneBitmask;
 
 template <>
+struct ilist_sentinel_traits<MachineInstr>
+    : public ilist_half_embedded_sentinel_traits<MachineInstr> {};
+
+template <>
 struct ilist_traits<MachineInstr> : public ilist_default_traits<MachineInstr> {
 private:
-  mutable ilist_half_node<MachineInstr> Sentinel;
-
   // this is only set by the MachineBasicBlock owning the LiveList
   friend class MachineBasicBlock;
   MachineBasicBlock* Parent;
 
 public:
-  MachineInstr *createSentinel() const {
-    return static_cast<MachineInstr*>(&Sentinel);
-  }
-  void destroySentinel(MachineInstr *) const {}
-
-  MachineInstr *provideInitialHead() const { return createSentinel(); }
-  MachineInstr *ensureHead(MachineInstr*) const { return createSentinel(); }
-  static void noteHead(MachineInstr*, MachineInstr*) {}
-
   void addNodeToList(MachineInstr* N);
   void removeNodeFromList(MachineInstr* N);
   void transferNodesFromList(ilist_traits &SrcTraits,
diff --git a/llvm/include/llvm/CodeGen/MachineFunction.h b/llvm/include/llvm/CodeGen/MachineFunction.h
index f4c3b5c9ebb..533d659d78b 100644
--- a/llvm/include/llvm/CodeGen/MachineFunction.h
+++ b/llvm/include/llvm/CodeGen/MachineFunction.h
@@ -49,23 +49,12 @@ struct MachinePointerInfo;
 struct WinEHFuncInfo;
 
 template <>
+struct ilist_sentinel_traits<MachineBasicBlock>
+    : public ilist_half_embedded_sentinel_traits<MachineBasicBlock> {};
+
+template <>
 struct ilist_traits<MachineBasicBlock>
     : public ilist_default_traits<MachineBasicBlock> {
-  mutable ilist_half_node<MachineBasicBlock> Sentinel;
-public:
-  // FIXME: This downcast is UB. See llvm.org/PR26753.
-  LLVM_NO_SANITIZE("object-size")
-  MachineBasicBlock *createSentinel() const {
-    return static_cast<MachineBasicBlock*>(&Sentinel);
-  }
-  void destroySentinel(MachineBasicBlock *) const {}
-
-  MachineBasicBlock *provideInitialHead() const { return createSentinel(); }
-  MachineBasicBlock *ensureHead(MachineBasicBlock*) const {
-    return createSentinel();
-  }
-  static void noteHead(MachineBasicBlock*, MachineBasicBlock*) {}
-
   void addNodeToList(MachineBasicBlock* MBB);
   void removeNodeFromList(MachineBasicBlock* MBB);
   void deleteNode(MachineBasicBlock *MBB);
diff --git a/llvm/include/llvm/CodeGen/SelectionDAG.h b/llvm/include/llvm/CodeGen/SelectionDAG.h
index 29cce873c2f..8a89249e92a 100644
--- a/llvm/include/llvm/CodeGen/SelectionDAG.h
+++ b/llvm/include/llvm/CodeGen/SelectionDAG.h
@@ -81,19 +81,11 @@ template<> struct FoldingSetTrait<SDVTListNode> : DefaultFoldingSetTrait<SDVTLis
   }
 };
 
-template<> struct ilist_traits<SDNode> : public ilist_default_traits<SDNode> {
-private:
-  mutable ilist_half_node<SDNode> Sentinel;
-public:
-  SDNode *createSentinel() const {
-    return static_cast<SDNode*>(&Sentinel);
-  }
-  static void destroySentinel(SDNode *) {}
-
-  SDNode *provideInitialHead() const { return createSentinel(); }
-  SDNode *ensureHead(SDNode*) const { return createSentinel(); }
-  static void noteHead(SDNode*, SDNode*) {}
+template <>
+struct ilist_sentinel_traits<SDNode>
+    : public ilist_half_embedded_sentinel_traits<SDNode> {};
 
+template <> struct ilist_traits<SDNode> : public ilist_default_traits<SDNode> {
   static void deleteNode(SDNode *) {
     llvm_unreachable("ilist_traits<SDNode> shouldn't see a deleteNode call!");
   }
diff --git a/llvm/include/llvm/CodeGen/SlotIndexes.h b/llvm/include/llvm/CodeGen/SlotIndexes.h
index 01184dc39b3..6090ecec32a 100644
--- a/llvm/include/llvm/CodeGen/SlotIndexes.h
+++ b/llvm/include/llvm/CodeGen/SlotIndexes.h
@@ -69,18 +69,12 @@ namespace llvm {
   };
 
   template <>
-  struct ilist_traits<IndexListEntry> : public ilist_default_traits<IndexListEntry> {
-  private:
-    mutable ilist_half_node<IndexListEntry> Sentinel;
-  public:
-    IndexListEntry *createSentinel() const {
-      return static_cast<IndexListEntry*>(&Sentinel);
-    }
-    void destroySentinel(IndexListEntry *) const {}
+  struct ilist_sentinel_traits<IndexListEntry>
+      : public ilist_half_embedded_sentinel_traits<IndexListEntry> {};
 
-    IndexListEntry *provideInitialHead() const { return createSentinel(); }
-    IndexListEntry *ensureHead(IndexListEntry*) const { return createSentinel(); }
-    static void noteHead(IndexListEntry*, IndexListEntry*) {}
+  template <>
+  struct ilist_traits<IndexListEntry>
+      : public ilist_default_traits<IndexListEntry> {
     void deleteNode(IndexListEntry *N) {}
 
   private:
diff --git a/llvm/include/llvm/IR/Module.h b/llvm/include/llvm/IR/Module.h
index 632b27e2d0d..ef7e4074176 100644
--- a/llvm/include/llvm/IR/Module.h
+++ b/llvm/include/llvm/IR/Module.h
@@ -37,23 +37,14 @@ class RandomNumberGenerator;
 class StructType;
 template <class PtrType> class SmallPtrSetImpl;
 
+template <>
+struct ilist_sentinel_traits<NamedMDNode>
+    : public ilist_embedded_sentinel_traits<NamedMDNode> {};
+
 template<> struct ilist_traits<NamedMDNode>
   : public ilist_default_traits<NamedMDNode> {
-  // createSentinel is used to get hold of a node that marks the end of
-  // the list...
-  NamedMDNode *createSentinel() const {
-    return static_cast<NamedMDNode*>(&Sentinel);
-  }
-  static void destroySentinel(NamedMDNode*) {}
-
-  NamedMDNode *provideInitialHead() const { return createSentinel(); }
-  NamedMDNode *ensureHead(NamedMDNode*) const { return createSentinel(); }
-  static void noteHead(NamedMDNode*, NamedMDNode*) {}
   void addNodeToList(NamedMDNode *) {}
   void removeNodeFromList(NamedMDNode *) {}
-
-private:
-  mutable ilist_node<NamedMDNode> Sentinel;
 };
 
 /// A Module instance is used to store all the information related to an
diff --git a/llvm/include/llvm/Transforms/Utils/MemorySSA.h b/llvm/include/llvm/Transforms/Utils/MemorySSA.h
index 2caa63feec6..606ecff59c5 100644
--- a/llvm/include/llvm/Transforms/Utils/MemorySSA.h
+++ b/llvm/include/llvm/Transforms/Utils/MemorySSA.h
@@ -171,23 +171,8 @@ private:
 };
 
 template <>
-struct ilist_traits<MemoryAccess> : public ilist_default_traits<MemoryAccess> {
-  /// See details of the instruction class for why this trick works
-  // FIXME: This downcast is UB. See llvm.org/PR26753.
-  LLVM_NO_SANITIZE("object-size")
-  MemoryAccess *createSentinel() const {
-    return static_cast<MemoryAccess *>(&Sentinel);
-  }
-
-  static void destroySentinel(MemoryAccess *) {}
-
-  MemoryAccess *provideInitialHead() const { return createSentinel(); }
-  MemoryAccess *ensureHead(MemoryAccess *) const { return createSentinel(); }
-  static void noteHead(MemoryAccess *, MemoryAccess *) {}
-
-private:
-  mutable ilist_half_node<MemoryAccess> Sentinel;
-};
+struct ilist_sentinel_traits<MemoryAccess>
+    : public ilist_half_embedded_sentinel_traits<MemoryAccess> {};
 
 inline raw_ostream &operator<<(raw_ostream &OS, const MemoryAccess &MA) {
   MA.print(OS);
diff --git a/llvm/lib/Support/YAMLParser.cpp b/llvm/lib/Support/YAMLParser.cpp
index 2b71c596cc4..4d5b750e266 100644
--- a/llvm/lib/Support/YAMLParser.cpp
+++ b/llvm/lib/Support/YAMLParser.cpp
@@ -149,20 +149,9 @@ struct Token : ilist_node<Token> {
 }
 
 namespace llvm {
-template<>
-struct ilist_sentinel_traits<Token> {
-  Token *createSentinel() const {
-    return &Sentinel;
-  }
-  static void destroySentinel(Token*) {}
-
-  Token *provideInitialHead() const { return createSentinel(); }
-  Token *ensureHead(Token*) const { return createSentinel(); }
-  static void noteHead(Token*, Token*) {}
-
-private:
-  mutable Token Sentinel;
-};
+template <>
+struct ilist_sentinel_traits<Token>
+    : public ilist_full_embedded_sentinel_traits<Token> {};
 
 template<>
 struct ilist_node_traits<Token> {