IR: Remove implicit iterator conversions from lib/IR, NFC

Stop converting implicitly between iterators and pointers/references in
lib/IR.  For convenience, I've added a `getIterator()` accessor to
`ilist_node` so that callers don't need to know how to spell the
iterator class (i.e., they can use `X.getIterator()` instead of
`Function::iterator(X)`).

I'll eventually disallow these implicit conversions entirely, but
there's a lot of code, so it doesn't make sense to do it all in one
patch.  One library or so at a time.

Why?  To root out cases of `getNextNode()` and `getPrevNode()` being
used in iterator logic.  The design of `ilist` makes that invalid when
the current node could be at the back of the list, but it happens to
"work" right now because of a bug where those functions never return
`nullptr` if you're using a half-node sentinel.  Before I can fix the
function, I have to remove uses of it that rely on it misbehaving.
(Maybe the function should just be deleted anyway?  But I don't want
deleting it -- potentially a huge project -- to block fixing
ilist/iplist.)

llvm-svn: 249782

include/llvm/ADT/ilist.h

@@ -238,6 +238,8 @@ public:
     return *this;
   }
 
+  void reset(pointer NP) { NodePtr = NP; }
+
   // Accessors...
   operator pointer() const {
     return NodePtr;
@@ -469,7 +471,7 @@ public:
     this->setPrev(CurNode, New);
 
     this->addNodeToList(New);  // Notify traits that we added a node...
-    return New;
+    return iterator(New);
   }
 
   iterator insertAfter(iterator where, NodeTy *New) {
@@ -490,7 +492,7 @@ public:
     else
       Head = NextNode;
     this->setPrev(NextNode, PrevNode);
-    IT = NextNode;
+    IT.reset(NextNode);
     this->removeNodeFromList(Node);  // Notify traits that we removed a node...
 
     // Set the next/prev pointers of the current node to null.  This isn't
@@ -569,7 +571,7 @@ private:
       this->setNext(Last, PosNext);
       this->setPrev(PosNext, Last);
 
-      this->transferNodesFromList(L2, First, PosNext);
+      this->transferNodesFromList(L2, iterator(First), iterator(PosNext));
 
       // Now that everything is set, restore the pointers to the list sentinels.
       L2.setTail(L2Sentinel);

include/llvm/ADT/ilist_node.h

@@ -39,6 +39,8 @@ protected:
 template<typename NodeTy>
 struct ilist_nextprev_traits;
 
+template <typename NodeTy> class ilist_iterator;
+
 /// ilist_node - Base class that provides next/prev services for nodes
 /// that use ilist_nextprev_traits or ilist_default_traits.
 ///
@@ -56,6 +58,15 @@ protected:
   ilist_node() : Next(nullptr) {}
 
 public:
+  ilist_iterator<NodeTy> getIterator() {
+    // FIXME: Stop downcasting to create the iterator (potential UB).
+    return ilist_iterator<NodeTy>(static_cast<NodeTy *>(this));
+  }
+  ilist_iterator<const NodeTy> getIterator() const {
+    // FIXME: Stop downcasting to create the iterator (potential UB).
+    return ilist_iterator<const NodeTy>(static_cast<const NodeTy *>(this));
+  }
+
   /// @name Adjacent Node Accessors
   /// @{
 

include/llvm/IR/IRBuilder.h

@@ -75,7 +75,7 @@ public:
   /// inserted into a block.
   void ClearInsertionPoint() {
     BB = nullptr;
-    InsertPt = nullptr;
+    InsertPt.reset(nullptr);
   }
 
   BasicBlock *GetInsertBlock() const { return BB; }
@@ -93,8 +93,8 @@ public:
   /// the specified instruction.
   void SetInsertPoint(Instruction *I) {
     BB = I->getParent();
-    InsertPt = I;
-    assert(I != BB->end() && "Can't read debug loc from end()");
+    InsertPt = I->getIterator();
+    assert(InsertPt != BB->end() && "Can't read debug loc from end()");
     SetCurrentDebugLocation(I->getDebugLoc());
   }
 

include/llvm/Support/GenericDomTree.h

@@ -734,13 +734,13 @@ public:
       for (typename TraitsTy::nodes_iterator I = TraitsTy::nodes_begin(&F),
                                              E = TraitsTy::nodes_end(&F);
            I != E; ++I) {
-        if (TraitsTy::child_begin(I) == TraitsTy::child_end(I))
-          addRoot(I);
+        if (TraitsTy::child_begin(&*I) == TraitsTy::child_end(&*I))
+          addRoot(&*I);
 
         // Prepopulate maps so that we don't get iterator invalidation issues
         // later.
-        this->IDoms[I] = nullptr;
-        this->DomTreeNodes[I] = nullptr;
+        this->IDoms[&*I] = nullptr;
+        this->DomTreeNodes[&*I] = nullptr;
       }
 
       Calculate<FT, Inverse<NodeT *>>(*this, F);

lib/IR/AsmWriter.cpp

@@ -817,7 +817,7 @@ void SlotTracker::processFunction() {
   for(Function::const_arg_iterator AI = TheFunction->arg_begin(),
       AE = TheFunction->arg_end(); AI != AE; ++AI)
     if (!AI->hasName())
-      CreateFunctionSlot(AI);
+      CreateFunctionSlot(&*AI);
 
   ST_DEBUG("Inserting Instructions:\n");
 
@@ -2635,7 +2635,7 @@ void AssemblyWriter::printFunction(const Function *F) {
     Out << " {";
     // Output all of the function's basic blocks.
     for (Function::const_iterator I = F->begin(), E = F->end(); I != E; ++I)
-      printBasicBlock(I);
+      printBasicBlock(&*I);
 
     // Output the function's use-lists.
     printUseLists(F);

lib/IR/AutoUpgrade.cpp

@@ -362,7 +362,7 @@ void llvm::UpgradeIntrinsicCall(CallInst *CI, Function *NewFn) {
   Function *F = CI->getCalledFunction();
   LLVMContext &C = CI->getContext();
   IRBuilder<> Builder(C);
-  Builder.SetInsertPoint(CI->getParent(), CI);
+  Builder.SetInsertPoint(CI->getParent(), CI->getIterator());
 
   assert(F && "Intrinsic call is not direct?");
 
@@ -388,7 +388,7 @@ void llvm::UpgradeIntrinsicCall(CallInst *CI, Function *NewFn) {
                Name == "llvm.x86.avx.movnt.ps.256" ||
                Name == "llvm.x86.avx.movnt.pd.256") {
       IRBuilder<> Builder(C);
-      Builder.SetInsertPoint(CI->getParent(), CI);
+      Builder.SetInsertPoint(CI->getParent(), CI->getIterator());
 
       Module *M = F->getParent();
       SmallVector<Metadata *, 1> Elts;

lib/IR/BasicBlock.cpp

@@ -56,7 +56,7 @@ void BasicBlock::insertInto(Function *NewParent, BasicBlock *InsertBefore) {
   assert(!Parent && "Already has a parent");
 
   if (InsertBefore)
-    NewParent->getBasicBlockList().insert(InsertBefore, this);
+    NewParent->getBasicBlockList().insert(InsertBefore->getIterator(), this);
   else
     NewParent->getBasicBlockList().push_back(this);
 }
@@ -91,26 +91,26 @@ void BasicBlock::setParent(Function *parent) {
 }
 
 void BasicBlock::removeFromParent() {
-  getParent()->getBasicBlockList().remove(this);
+  getParent()->getBasicBlockList().remove(getIterator());
 }
 
 iplist<BasicBlock>::iterator BasicBlock::eraseFromParent() {
-  return getParent()->getBasicBlockList().erase(this);
+  return getParent()->getBasicBlockList().erase(getIterator());
 }
 
 /// Unlink this basic block from its current function and
 /// insert it into the function that MovePos lives in, right before MovePos.
 void BasicBlock::moveBefore(BasicBlock *MovePos) {
-  MovePos->getParent()->getBasicBlockList().splice(MovePos,
-                       getParent()->getBasicBlockList(), this);
+  MovePos->getParent()->getBasicBlockList().splice(
+      MovePos->getIterator(), getParent()->getBasicBlockList(), getIterator());
 }
 
 /// Unlink this basic block from its current function and
 /// insert it into the function that MovePos lives in, right after MovePos.
 void BasicBlock::moveAfter(BasicBlock *MovePos) {
-  Function::iterator I = MovePos;
-  MovePos->getParent()->getBasicBlockList().splice(++I,
-                                       getParent()->getBasicBlockList(), this);
+  MovePos->getParent()->getBasicBlockList().splice(
+      ++MovePos->getIterator(), getParent()->getBasicBlockList(),
+      getIterator());
 }
 
 const Module *BasicBlock::getModule() const {
@@ -196,7 +196,7 @@ BasicBlock::iterator BasicBlock::getFirstInsertionPt() {
   if (!FirstNonPHI)
     return end();
 
-  iterator InsertPt = FirstNonPHI;
+  iterator InsertPt = FirstNonPHI->getIterator();
   if (InsertPt->isEHPad()) ++InsertPt;
   return InsertPt;
 }

lib/IR/Core.cpp

@@ -1533,7 +1533,7 @@ LLVMValueRef LLVMGetFirstGlobal(LLVMModuleRef M) {
   Module::global_iterator I = Mod->global_begin();
   if (I == Mod->global_end())
     return nullptr;
-  return wrap(I);
+  return wrap(&*I);
 }
 
 LLVMValueRef LLVMGetLastGlobal(LLVMModuleRef M) {
@@ -1541,23 +1541,23 @@ LLVMValueRef LLVMGetLastGlobal(LLVMModuleRef M) {
   Module::global_iterator I = Mod->global_end();
   if (I == Mod->global_begin())
     return nullptr;
-  return wrap(--I);
+  return wrap(&*--I);
 }
 
 LLVMValueRef LLVMGetNextGlobal(LLVMValueRef GlobalVar) {
   GlobalVariable *GV = unwrap<GlobalVariable>(GlobalVar);
-  Module::global_iterator I = GV;
+  Module::global_iterator I(GV);
   if (++I == GV->getParent()->global_end())
     return nullptr;
-  return wrap(I);
+  return wrap(&*I);
 }
 
 LLVMValueRef LLVMGetPreviousGlobal(LLVMValueRef GlobalVar) {
   GlobalVariable *GV = unwrap<GlobalVariable>(GlobalVar);
-  Module::global_iterator I = GV;
+  Module::global_iterator I(GV);
   if (I == GV->getParent()->global_begin())
     return nullptr;
-  return wrap(--I);
+  return wrap(&*--I);
 }
 
 void LLVMDeleteGlobal(LLVMValueRef GlobalVar) {
@@ -1666,7 +1666,7 @@ LLVMValueRef LLVMGetFirstFunction(LLVMModuleRef M) {
   Module::iterator I = Mod->begin();
   if (I == Mod->end())
     return nullptr;
-  return wrap(I);
+  return wrap(&*I);
 }
 
 LLVMValueRef LLVMGetLastFunction(LLVMModuleRef M) {
@@ -1674,23 +1674,23 @@ LLVMValueRef LLVMGetLastFunction(LLVMModuleRef M) {
   Module::iterator I = Mod->end();
   if (I == Mod->begin())
     return nullptr;
-  return wrap(--I);
+  return wrap(&*--I);
 }
 
 LLVMValueRef LLVMGetNextFunction(LLVMValueRef Fn) {
   Function *Func = unwrap<Function>(Fn);
-  Module::iterator I = Func;
+  Module::iterator I(Func);
   if (++I == Func->getParent()->end())
     return nullptr;
-  return wrap(I);
+  return wrap(&*I);
 }
 
 LLVMValueRef LLVMGetPreviousFunction(LLVMValueRef Fn) {
   Function *Func = unwrap<Function>(Fn);
-  Module::iterator I = Func;
+  Module::iterator I(Func);
   if (I == Func->getParent()->begin())
     return nullptr;
-  return wrap(--I);
+  return wrap(&*--I);
 }
 
 void LLVMDeleteFunction(LLVMValueRef Fn) {
@@ -1785,14 +1785,14 @@ void LLVMGetParams(LLVMValueRef FnRef, LLVMValueRef *ParamRefs) {
   Function *Fn = unwrap<Function>(FnRef);
   for (Function::arg_iterator I = Fn->arg_begin(),
                               E = Fn->arg_end(); I != E; I++)
-    *ParamRefs++ = wrap(I);
+    *ParamRefs++ = wrap(&*I);
 }
 
 LLVMValueRef LLVMGetParam(LLVMValueRef FnRef, unsigned index) {
   Function::arg_iterator AI = unwrap<Function>(FnRef)->arg_begin();
   while (index --> 0)
     AI++;
-  return wrap(AI);
+  return wrap(&*AI);
 }
 
 LLVMValueRef LLVMGetParamParent(LLVMValueRef V) {
@@ -1804,7 +1804,7 @@ LLVMValueRef LLVMGetFirstParam(LLVMValueRef Fn) {
   Function::arg_iterator I = Func->arg_begin();
   if (I == Func->arg_end())
     return nullptr;
-  return wrap(I);
+  return wrap(&*I);
 }
 
 LLVMValueRef LLVMGetLastParam(LLVMValueRef Fn) {
@@ -1812,23 +1812,23 @@ LLVMValueRef LLVMGetLastParam(LLVMValueRef Fn) {
   Function::arg_iterator I = Func->arg_end();
   if (I == Func->arg_begin())
     return nullptr;
-  return wrap(--I);
+  return wrap(&*--I);
 }
 
 LLVMValueRef LLVMGetNextParam(LLVMValueRef Arg) {
   Argument *A = unwrap<Argument>(Arg);
-  Function::arg_iterator I = A;
+  Function::arg_iterator I(A);
   if (++I == A->getParent()->arg_end())
     return nullptr;
-  return wrap(I);
+  return wrap(&*I);
 }
 
 LLVMValueRef LLVMGetPreviousParam(LLVMValueRef Arg) {
   Argument *A = unwrap<Argument>(Arg);
-  Function::arg_iterator I = A;
+  Function::arg_iterator I(A);
   if (I == A->getParent()->arg_begin())
     return nullptr;
-  return wrap(--I);
+  return wrap(&*--I);
 }
 
 void LLVMAddAttribute(LLVMValueRef Arg, LLVMAttribute PA) {
@@ -1886,7 +1886,7 @@ unsigned LLVMCountBasicBlocks(LLVMValueRef FnRef) {
 void LLVMGetBasicBlocks(LLVMValueRef FnRef, LLVMBasicBlockRef *BasicBlocksRefs){
   Function *Fn = unwrap<Function>(FnRef);
   for (Function::iterator I = Fn->begin(), E = Fn->end(); I != E; I++)
-    *BasicBlocksRefs++ = wrap(I);
+    *BasicBlocksRefs++ = wrap(&*I);
 }
 
 LLVMBasicBlockRef LLVMGetEntryBasicBlock(LLVMValueRef Fn) {
@@ -1898,7 +1898,7 @@ LLVMBasicBlockRef LLVMGetFirstBasicBlock(LLVMValueRef Fn) {
   Function::iterator I = Func->begin();
   if (I == Func->end())
     return nullptr;
-  return wrap(I);
+  return wrap(&*I);
 }
 
 LLVMBasicBlockRef LLVMGetLastBasicBlock(LLVMValueRef Fn) {
@@ -1906,23 +1906,23 @@ LLVMBasicBlockRef LLVMGetLastBasicBlock(LLVMValueRef Fn) {
   Function::iterator I = Func->end();
   if (I == Func->begin())
     return nullptr;
-  return wrap(--I);
+  return wrap(&*--I);
 }
 
 LLVMBasicBlockRef LLVMGetNextBasicBlock(LLVMBasicBlockRef BB) {
   BasicBlock *Block = unwrap(BB);
-  Function::iterator I = Block;
+  Function::iterator I(Block);
   if (++I == Block->getParent()->end())
     return nullptr;
-  return wrap(I);
+  return wrap(&*I);
 }
 
 LLVMBasicBlockRef LLVMGetPreviousBasicBlock(LLVMBasicBlockRef BB) {
   BasicBlock *Block = unwrap(BB);
-  Function::iterator I = Block;
+  Function::iterator I(Block);
   if (I == Block->getParent()->begin())
     return nullptr;
-  return wrap(--I);
+  return wrap(&*--I);
 }
 
 LLVMBasicBlockRef LLVMAppendBasicBlockInContext(LLVMContextRef C,
@@ -1974,7 +1974,7 @@ LLVMValueRef LLVMGetFirstInstruction(LLVMBasicBlockRef BB) {
   BasicBlock::iterator I = Block->begin();
   if (I == Block->end())
     return nullptr;
-  return wrap(I);
+  return wrap(&*I);
 }
 
 LLVMValueRef LLVMGetLastInstruction(LLVMBasicBlockRef BB) {
@@ -1982,23 +1982,23 @@ LLVMValueRef LLVMGetLastInstruction(LLVMBasicBlockRef BB) {
   BasicBlock::iterator I = Block->end();
   if (I == Block->begin())
     return nullptr;
-  return wrap(--I);
+  return wrap(&*--I);
 }
 
 LLVMValueRef LLVMGetNextInstruction(LLVMValueRef Inst) {
   Instruction *Instr = unwrap<Instruction>(Inst);
-  BasicBlock::iterator I = Instr;
+  BasicBlock::iterator I(Instr);
   if (++I == Instr->getParent()->end())
     return nullptr;
-  return wrap(I);
+  return wrap(&*I);
 }
 
 LLVMValueRef LLVMGetPreviousInstruction(LLVMValueRef Inst) {
   Instruction *Instr = unwrap<Instruction>(Inst);
-  BasicBlock::iterator I = Instr;
+  BasicBlock::iterator I(Instr);
   if (I == Instr->getParent()->begin())
     return nullptr;
-  return wrap(--I);
+  return wrap(&*--I);
 }
 
 void LLVMInstructionEraseFromParent(LLVMValueRef Inst) {
@@ -2166,12 +2166,12 @@ void LLVMPositionBuilder(LLVMBuilderRef Builder, LLVMBasicBlockRef Block,
                          LLVMValueRef Instr) {
   BasicBlock *BB = unwrap(Block);
   Instruction *I = Instr? unwrap<Instruction>(Instr) : (Instruction*) BB->end();
-  unwrap(Builder)->SetInsertPoint(BB, I);
+  unwrap(Builder)->SetInsertPoint(BB, I->getIterator());
 }
 
 void LLVMPositionBuilderBefore(LLVMBuilderRef Builder, LLVMValueRef Instr) {
   Instruction *I = unwrap<Instruction>(Instr);
-  unwrap(Builder)->SetInsertPoint(I->getParent(), I);
+  unwrap(Builder)->SetInsertPoint(I->getParent(), I->getIterator());
 }
 
 void LLVMPositionBuilderAtEnd(LLVMBuilderRef Builder, LLVMBasicBlockRef Block) {

lib/IR/DebugInfo.cpp

@@ -336,7 +336,7 @@ bool llvm::StripDebugInfo(Module &M) {
 
   for (Module::named_metadata_iterator NMI = M.named_metadata_begin(),
          NME = M.named_metadata_end(); NMI != NME;) {
-    NamedMDNode *NMD = NMI;
+    NamedMDNode *NMD = &*NMI;
     ++NMI;
     if (NMD->getName().startswith("llvm.dbg.")) {
       NMD->eraseFromParent();

lib/IR/Function.cpp

@@ -235,11 +235,11 @@ Type *Function::getReturnType() const {
 }
 
 void Function::removeFromParent() {
-  getParent()->getFunctionList().remove(this);
+  getParent()->getFunctionList().remove(getIterator());
 }
 
 void Function::eraseFromParent() {
-  getParent()->getFunctionList().erase(this);
+  getParent()->getFunctionList().erase(getIterator());
 }
 
 //===----------------------------------------------------------------------===//

lib/IR/Globals.cpp

@@ -178,7 +178,7 @@ GlobalVariable::GlobalVariable(Module &M, Type *Ty, bool constant,
   }
 
   if (Before)
-    Before->getParent()->getGlobalList().insert(Before, this);
+    Before->getParent()->getGlobalList().insert(Before->getIterator(), this);
   else
     M.getGlobalList().push_back(this);
 }
@@ -188,11 +188,11 @@ void GlobalVariable::setParent(Module *parent) {
 }
 
 void GlobalVariable::removeFromParent() {
-  getParent()->getGlobalList().remove(this);
+  getParent()->getGlobalList().remove(getIterator());
 }
 
 void GlobalVariable::eraseFromParent() {
-  getParent()->getGlobalList().erase(this);
+  getParent()->getGlobalList().erase(getIterator());
 }
 
 void GlobalVariable::setInitializer(Constant *InitVal) {
@@ -276,11 +276,11 @@ void GlobalAlias::setParent(Module *parent) {
 }
 
 void GlobalAlias::removeFromParent() {
-  getParent()->getAliasList().remove(this);
+  getParent()->getAliasList().remove(getIterator());
 }
 
 void GlobalAlias::eraseFromParent() {
-  getParent()->getAliasList().erase(this);
+  getParent()->getAliasList().erase(getIterator());
 }
 
 void GlobalAlias::setAliasee(Constant *Aliasee) {

lib/IR/Instruction.cpp

@@ -28,7 +28,7 @@ Instruction::Instruction(Type *ty, unsigned it, Use *Ops, unsigned NumOps,
   if (InsertBefore) {
     BasicBlock *BB = InsertBefore->getParent();
     assert(BB && "Instruction to insert before is not in a basic block!");
-    BB->getInstList().insert(InsertBefore, this);
+    BB->getInstList().insert(InsertBefore->getIterator(), this);
   }
 }
 
@@ -64,31 +64,32 @@ Module *Instruction::getModule() {
 
 
 void Instruction::removeFromParent() {
-  getParent()->getInstList().remove(this);
+  getParent()->getInstList().remove(getIterator());
 }
 
 iplist<Instruction>::iterator Instruction::eraseFromParent() {
-  return getParent()->getInstList().erase(this);
+  return getParent()->getInstList().erase(getIterator());
 }
 
 /// insertBefore - Insert an unlinked instructions into a basic block
 /// immediately before the specified instruction.
 void Instruction::insertBefore(Instruction *InsertPos) {
-  InsertPos->getParent()->getInstList().insert(InsertPos, this);
+  InsertPos->getParent()->getInstList().insert(InsertPos->getIterator(), this);
 }
 
 /// insertAfter - Insert an unlinked instructions into a basic block
 /// immediately after the specified instruction.
 void Instruction::insertAfter(Instruction *InsertPos) {
-  InsertPos->getParent()->getInstList().insertAfter(InsertPos, this);
+  InsertPos->getParent()->getInstList().insertAfter(InsertPos->getIterator(),
+                                                    this);
 }
 
 /// moveBefore - Unlink this instruction from its current basic block and
 /// insert it into the basic block that MovePos lives in, right before
 /// MovePos.
 void Instruction::moveBefore(Instruction *MovePos) {
-  MovePos->getParent()->getInstList().splice(MovePos,getParent()->getInstList(),
-                                             this);
+  MovePos->getParent()->getInstList().splice(
+      MovePos->getIterator(), getParent()->getInstList(), getIterator());
 }
 
 /// Set or clear the unsafe-algebra flag on this instruction, which must be an

lib/IR/Module.cpp

@@ -277,7 +277,7 @@ NamedMDNode *Module::getOrInsertNamedMetadata(StringRef Name) {
 /// delete it.
 void Module::eraseNamedMetadata(NamedMDNode *NMD) {
   static_cast<StringMap<NamedMDNode *> *>(NamedMDSymTab)->erase(NMD->getName());
-  NamedMDList.erase(NMD);
+  NamedMDList.erase(NMD->getIterator());
 }
 
 bool Module::isValidModFlagBehavior(Metadata *MD, ModFlagBehavior &MFB) {

lib/IR/SymbolTableListTraitsImpl.h

@@ -55,7 +55,7 @@ void SymbolTableListTraits<ValueSubClass>::setSymTabObject(TPtr *Dest,
     // Add all of the items to the new symtab.
     for (auto I = ItemList.begin(); I != ItemList.end(); ++I)
       if (I->hasName())
-        NewST->reinsertValue(I);
+        NewST->reinsertValue(&*I);
   }
   
 }

lib/IR/TypeFinder.cpp

@@ -56,7 +56,7 @@ void TypeFinder::run(const Module &M, bool onlyNamed) {
     // First incorporate the arguments.
     for (Function::const_arg_iterator AI = FI->arg_begin(),
            AE = FI->arg_end(); AI != AE; ++AI)
-      incorporateValue(AI);
+      incorporateValue(&*AI);
 
     for (Function::const_iterator BB = FI->begin(), E = FI->end();
          BB != E;++BB)
@@ -85,7 +85,7 @@ void TypeFinder::run(const Module &M, bool onlyNamed) {
 
   for (Module::const_named_metadata_iterator I = M.named_metadata_begin(),
          E = M.named_metadata_end(); I != E; ++I) {
-    const NamedMDNode *NMD = I;
+    const NamedMDNode *NMD = &*I;
     for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
       incorporateMDNode(NMD->getOperand(i));
   }

lib/IR/Verifier.cpp

@@ -92,6 +92,10 @@ struct VerifierSupport {
       : OS(OS), M(nullptr), Broken(false) {}
 
 private:
+  template <class NodeTy> void Write(const ilist_iterator<NodeTy> &I) {
+    Write(&*I);
+  }
+
   void Write(const Value *V) {
     if (!V)
       return;