The (negative) offset from a SymbolTableListTraits-using ilist to its container

object is always constant.  As such, evaluate it at compile time instead of storing
it as an ivar in SymbolTableListTraits.  This shrinks every SymbolTableListTraits
ilist by a word, shrinking BasicBlock from 44->40 bytes, Function from 96->88 bytes,
and Module from 60->52 bytes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36189 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/BasicBlock.h

@@ -31,6 +31,7 @@ template<> struct ilist_traits<Instruction>
   static void destroySentinel(Instruction *I) { delete I; }
   static iplist<Instruction> &getList(BasicBlock *BB);
   static ValueSymbolTable *getSymTab(BasicBlock *ItemParent);
+  static int getListOffset();
 };
 
 /// This represents a single basic block in LLVM. A basic block is simply a
@@ -194,8 +195,19 @@ public:
   /// the basic block).
   ///
   BasicBlock *splitBasicBlock(iterator I, const std::string &BBName = "");
+  
+  
+  static unsigned getInstListOffset() {
+    BasicBlock *Obj = 0;
+    return reinterpret_cast<unsigned>(&Obj->InstList);
+  }
 };
 
+inline int 
+ilist_traits<Instruction>::getListOffset() {
+  return BasicBlock::getInstListOffset();
+}
+
 } // End llvm namespace
 
 #endif

include/llvm/Function.h

@@ -37,6 +37,7 @@ template<> struct ilist_traits<BasicBlock>
   static void destroySentinel(BasicBlock *BB) { delete BB; }
   static iplist<BasicBlock> &getList(Function *F);
   static ValueSymbolTable *getSymTab(Function *ItemParent);
+  static int getListOffset();
 };
 
 template<> struct ilist_traits<Argument>
@@ -47,6 +48,7 @@ template<> struct ilist_traits<Argument>
   static void destroySentinel(Argument *A) { delete A; }
   static iplist<Argument> &getList(Function *F);
   static ValueSymbolTable *getSymTab(Function *ItemParent);
+  static int getListOffset();
 };
 
 class Function : public GlobalValue, public Annotable {
@@ -238,6 +240,15 @@ public:
   /// including any contained basic blocks.
   ///
   void dropAllReferences();
+  
+  static unsigned getBasicBlockListOffset() {
+    Function *Obj = 0;
+    return reinterpret_cast<unsigned>(&Obj->BasicBlocks);
+  }
+  static unsigned getArgumentListOffset() {
+    Function *Obj = 0;
+    return reinterpret_cast<unsigned>(&Obj->ArgumentList);
+  }
 };
 
 inline ValueSymbolTable *
@@ -250,6 +261,17 @@ ilist_traits<Argument>::getSymTab(Function *F) {
   return F ? &F->getValueSymbolTable() : 0;
 }
 
+inline int 
+ilist_traits<BasicBlock>::getListOffset() {
+  return Function::getBasicBlockListOffset();
+}
+
+inline int 
+ilist_traits<Argument>::getListOffset() {
+  return Function::getArgumentListOffset();
+}
+
+
 } // End llvm namespace
 
 #endif

include/llvm/Module.h

@@ -32,6 +32,7 @@ template<> struct ilist_traits<Function>
   static void destroySentinel(Function *F) { delete F; }
   static iplist<Function> &getList(Module *M);
   static inline ValueSymbolTable *getSymTab(Module *M);
+  static int getListOffset();
 };
 template<> struct ilist_traits<GlobalVariable>
   : public SymbolTableListTraits<GlobalVariable, Module> {
@@ -40,6 +41,7 @@ template<> struct ilist_traits<GlobalVariable>
   static void destroySentinel(GlobalVariable *GV) { delete GV; }
   static iplist<GlobalVariable> &getList(Module *M);
   static inline ValueSymbolTable *getSymTab(Module *M);
+  static int getListOffset();
 };
 
 /// A Module instance is used to store all the information related to an
@@ -313,6 +315,15 @@ public:
   /// that has "dropped all references", except operator delete.
   void dropAllReferences();
 /// @}
+
+  static unsigned getFunctionListOffset() {
+    Module *Obj = 0;
+    return reinterpret_cast<unsigned>(&Obj->FunctionList);
+  }
+  static unsigned getGlobalVariableListOffset() {
+    Module *Obj = 0;
+    return reinterpret_cast<unsigned>(&Obj->GlobalList);
+  }
 };
 
 /// An iostream inserter for modules.
@@ -331,6 +342,15 @@ ilist_traits<GlobalVariable>::getSymTab(Module *M) {
   return M ? &M->getValueSymbolTable() : 0;
 }
 
+inline int 
+ilist_traits<Function>::getListOffset() {
+  return Module::getFunctionListOffset();
+}
+
+inline int 
+ilist_traits<GlobalVariable>::getListOffset() {
+  return Module::getGlobalVariableListOffset();
+}
 
 } // End llvm namespace
 

include/llvm/SymbolTableListTraits.h

@@ -39,10 +39,15 @@ template<typename Ty> struct ilist_traits;
 template<typename ValueSubClass, typename ItemParentClass>
 class SymbolTableListTraits {
   typedef ilist_traits<ValueSubClass> TraitsClass;
-  ItemParentClass *ItemParent;
 public:
-  SymbolTableListTraits() : ItemParent(0) {}
+  SymbolTableListTraits() {}
 
+  /// getListOwner - Return the object that owns this list.  If this is a list
+  /// of instructions, it returns the BasicBlock that owns them.
+  ItemParentClass *getListOwner() {
+    return reinterpret_cast<ItemParentClass*>((char*)this-
+                                              TraitsClass::getListOffset());
+  }
   static ValueSubClass *getPrev(ValueSubClass *V) { return V->getPrev(); }
   static ValueSubClass *getNext(ValueSubClass *V) { return V->getNext(); }
   static const ValueSubClass *getPrev(const ValueSubClass *V) {
@@ -62,7 +67,6 @@ public:
                              ilist_iterator<ValueSubClass> first,
                              ilist_iterator<ValueSubClass> last);
 //private:
-  void setItemParent(ItemParentClass *IP) { ItemParent = IP; }
   template<typename TPtr>
   void setSymTabObject(TPtr *, TPtr);
 };

lib/VMCore/BasicBlock.cpp

@@ -72,8 +72,6 @@ template class SymbolTableListTraits<Instruction, BasicBlock>;
 BasicBlock::BasicBlock(const std::string &Name, Function *NewParent,
                        BasicBlock *InsertBefore)
   : Value(Type::LabelTy, Value::BasicBlockVal), Parent(0) {
-  // Initialize the instlist.
-  InstList.setItemParent(this);
 
   // Make sure that we get added to a function
   LeakDetector::addGarbageObject(this);

lib/VMCore/Function.cpp

@@ -143,8 +143,6 @@ Function::Function(const FunctionType *Ty, LinkageTypes Linkage,
   : GlobalValue(PointerType::get(Ty), Value::FunctionVal, 0, 0, Linkage, name) {
   ParamAttrs = 0;
   CallingConvention = 0;
-  BasicBlocks.setItemParent(this);
-  ArgumentList.setItemParent(this);
   SymTab = new ValueSymbolTable();
 
   assert((getReturnType()->isFirstClassType() ||getReturnType() == Type::VoidTy)

lib/VMCore/Module.cpp

@@ -64,8 +64,6 @@ template class SymbolTableListTraits<Function, Module>;
 
 Module::Module(const std::string &MID)
   : ModuleID(MID), DataLayout("") {
-  FunctionList.setItemParent(this);
-  GlobalList.setItemParent(this);
   ValSymTab = new ValueSymbolTable();
   TypeSymTab = new TypeSymbolTable();
 }

lib/VMCore/SymbolTableListTraitsImpl.h

@@ -29,19 +29,19 @@ template<typename TPtr>
 void SymbolTableListTraits<ValueSubClass,ItemParentClass>
 ::setSymTabObject(TPtr *Dest, TPtr Src) {
   // Get the old symtab and value list before doing the assignment.
-  ValueSymbolTable *OldST = TraitsClass::getSymTab(ItemParent);
+  ValueSymbolTable *OldST = TraitsClass::getSymTab(getListOwner());
 
   // Do it.
   *Dest = Src;
   
   // Get the new SymTab object.
-  ValueSymbolTable *NewST = TraitsClass::getSymTab(ItemParent);
+  ValueSymbolTable *NewST = TraitsClass::getSymTab(getListOwner());
   
   // If there is nothing to do, quick exit.
   if (OldST == NewST) return;
   
   // Move all the elements from the old symtab to the new one.
-  iplist<ValueSubClass> &ItemList = TraitsClass::getList(ItemParent);
+  iplist<ValueSubClass> &ItemList = TraitsClass::getList(getListOwner());
   if (ItemList.empty()) return;
   
   if (OldST) {
@@ -66,9 +66,10 @@ template<typename ValueSubClass, typename ItemParentClass>
 void SymbolTableListTraits<ValueSubClass,ItemParentClass>
 ::addNodeToList(ValueSubClass *V) {
   assert(V->getParent() == 0 && "Value already in a container!!");
-  V->setParent(ItemParent);
+  ItemParentClass *Owner = getListOwner();
+  V->setParent(Owner);
   if (V->hasName())
-    if (ValueSymbolTable *ST = TraitsClass::getSymTab(ItemParent))
+    if (ValueSymbolTable *ST = TraitsClass::getSymTab(Owner))
       ST->reinsertValue(V);
 }
 
@@ -77,7 +78,7 @@ void SymbolTableListTraits<ValueSubClass,ItemParentClass>
 ::removeNodeFromList(ValueSubClass *V) {
   V->setParent(0);
   if (V->hasName())
-    if (ValueSymbolTable *ST = TraitsClass::getSymTab(ItemParent))
+    if (ValueSymbolTable *ST = TraitsClass::getSymTab(getListOwner()))
       ST->removeValueName(V->getValueName());
 }
 
@@ -87,12 +88,12 @@ void SymbolTableListTraits<ValueSubClass,ItemParentClass>
                         ilist_iterator<ValueSubClass> first,
                         ilist_iterator<ValueSubClass> last) {
   // We only have to do work here if transferring instructions between BBs
-  ItemParentClass *NewIP = ItemParent, *OldIP = L2.ItemParent;
+  ItemParentClass *NewIP = getListOwner(), *OldIP = L2.getListOwner();
   if (NewIP == OldIP) return;  // No work to do at all...
 
   // We only have to update symbol table entries if we are transferring the
   // instructions to a different symtab object...
-  ValueSymbolTable *NewST = TraitsClass::getSymTab(ItemParent);
+  ValueSymbolTable *NewST = TraitsClass::getSymTab(NewIP);
   ValueSymbolTable *OldST = TraitsClass::getSymTab(OldIP);
   if (NewST != OldST) {
     for (; first != last; ++first) {