[IR] Avoid UB in SymbolTableListTraits

Author: dtcxzyw

llvm/include/llvm/IR/SymbolTableListTraits.h

@@ -73,18 +73,14 @@ class SymbolTableListTraits : public ilist_alloc_traits<ValueSubClass> {
 public:
   SymbolTableListTraits() = default;
 
+  void setListOwner(ItemParentClass *Par) { ListOwner = Par; }
+
 private:
+  ItemParentClass *ListOwner;
+
   /// getListOwner - Return the object that owns this list.  If this is a list
   /// of instructions, it returns the BasicBlock that owns them.
-  ItemParentClass *getListOwner() {
-    size_t Offset = reinterpret_cast<size_t>(
-        &((ItemParentClass *)nullptr->*ItemParentClass::getSublistAccess(
-                                           static_cast<ValueSubClass *>(
-                                               nullptr))));
-    ListTy *Anchor = static_cast<ListTy *>(this);
-    return reinterpret_cast<ItemParentClass*>(reinterpret_cast<char*>(Anchor)-
-                                              Offset);
-  }
+  ItemParentClass *getListOwner() { return ListOwner; }
 
   static ListTy &getList(ItemParentClass *Par) {
     return Par->*(Par->getSublistAccess((ValueSubClass*)nullptr));

llvm/lib/IR/BasicBlock.cpp

@@ -187,7 +187,7 @@ BasicBlock::BasicBlock(LLVMContext &C, const Twine &Name, Function *NewParent,
                        BasicBlock *InsertBefore)
     : Value(Type::getLabelTy(C), Value::BasicBlockVal),
       IsNewDbgInfoFormat(UseNewDbgInfoFormat), Parent(nullptr) {
-
+  InstList.setListOwner(this);
   if (NewParent)
     insertInto(NewParent, InsertBefore);
   else

llvm/lib/IR/Function.cpp

@@ -495,6 +495,7 @@ Function::Function(FunctionType *Ty, LinkageTypes Linkage, unsigned AddrSpace,
       NumArgs(Ty->getNumParams()), IsNewDbgInfoFormat(UseNewDbgInfoFormat) {
   assert(FunctionType::isValidReturnType(getReturnType()) &&
          "invalid return type");
+  BasicBlocks.setListOwner(this);
   setGlobalObjectSubClassData(0);
 
   // We only need a symbol table for a function if the context keeps value names

llvm/lib/IR/Module.cpp

@@ -75,6 +75,10 @@ Module::Module(StringRef MID, LLVMContext &C)
       ModuleID(std::string(MID)), SourceFileName(std::string(MID)),
       IsNewDbgInfoFormat(UseNewDbgInfoFormat) {
   Context.addModule(this);
+  GlobalList.setListOwner(this);
+  FunctionList.setListOwner(this);
+  AliasList.setListOwner(this);
+  IFuncList.setListOwner(this);
 }
 
 Module &Module::operator=(Module &&Other) {