C++ GlobalVariable::hasDefinitiveInitializer方法代码示例

SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalVariable(GlobalVariable &GV){
  if (!GV.hasDefinitiveInitializer())
    return unknown();

  APInt Size(IntTyBits, TD->getTypeAllocSize(GV.getType()->getElementType()));
  return std::make_pair(align(Size, GV.getAlignment()), Zero);
}

 bool runOnModule(Module &M) override {
   // function pointer initialized at compile time
   for (Module::global_iterator G = M.global_begin(); G != M.global_end(); G++) {
     GlobalVariable *gv = &*G;
     if (!gv->hasDefinitiveInitializer())
       continue;
     Constant *initor = gv->getInitializer();
     if (constantFunctionPointerName(initor) || constantTravel(initor))
       errs() << *gv << "\n";
   }
   // function pointer initialized at runtime
   for (Module::iterator F = M.begin(); F != M.end(); F++) {
     for (inst_iterator I = inst_begin(F); I != inst_end(F); I++) {
       if (StoreInst *si = dyn_cast<StoreInst>(&*I)) {
         Value *val = si->getValueOperand();
         if (constantFunctionPointerName(val))
           errs() << *I << "\n";
       } else if (CallInst *ci = dyn_cast<CallInst>(&*I)) {
         for (unsigned i = 0; i < ci->getNumArgOperands(); i++) {
           Value *operand = ci->getArgOperand(i);
           if (constantFunctionPointerName(operand))
             errs() << *I << "\n";
         }
       } else if (ReturnInst *ri = dyn_cast<ReturnInst>(&*I)) {
         Value *ret = ri->getReturnValue();
         if (constantFunctionPointerName(ret))
           errs() << *I << "\n";
       }
     }
   }
   return false;
 }

static void initialiseStore(ShadowBB* BB) {

  for(uint32_t i = 0, ilim = GlobalIHP->heap.size(); i != ilim; ++i) {

    AllocData& AD = GlobalIHP->heap[i];
    ImprovedValSetSingle* Init = new ImprovedValSetSingle();

    if(AD.allocValue.isGV()) {

      GlobalVariable* G = AD.allocValue.getGV()->G;

      if(GlobalIHP->useGlobalInitialisers && G->hasDefinitiveInitializer()) {

	Constant* I = G->getInitializer();
	if(isa<ConstantAggregateZero>(I)) {

	  Init->SetType = ValSetTypeScalarSplat;
	  Type* I8 = Type::getInt8Ty(BB->invar->BB->getContext());
	  Constant* I8Z = Constant::getNullValue(I8);
	  Init->insert(ImprovedVal(I8Z));

	}
	else {

	  std::pair<ValSetType, ImprovedVal> InitIV = getValPB(I);
	  (*Init) = ImprovedValSetSingle(InitIV.second, InitIV.first);

	}

      }
      else {

	// Start off overdef, and known-older-than-specialisation.
	Init->SetType = ValSetTypeOldOverdef;

      }

    }
    else {

      // All non-GVs initialise to an old value.
      Init->SetType = ValSetTypeOldOverdef;

    }

    LocStore* LS = BB->getWritableStoreFor(AD.allocValue, 0, AD.storeSize, true);
    release_assert(LS && "Non-writable location in initialiseStore?");
    LS->store->dropReference();
    LS->store = Init;

  }

}

bool ObjCARCAPElim::runOnModule(Module &M) {
  if (!EnableARCOpts)
    return false;

  // If nothing in the Module uses ARC, don't do anything.
  if (!ModuleHasARC(M))
    return false;

  // Find the llvm.global_ctors variable, as the first step in
  // identifying the global constructors. In theory, unnecessary autorelease
  // pools could occur anywhere, but in practice it's pretty rare. Global
  // ctors are a place where autorelease pools get inserted automatically,
  // so it's pretty common for them to be unnecessary, and it's pretty
  // profitable to eliminate them.
  GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
  if (!GV)
    return false;

  assert(GV->hasDefinitiveInitializer() &&
         "llvm.global_ctors is uncooperative!");

  bool Changed = false;

  // Dig the constructor functions out of GV's initializer.
  ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
  for (User::op_iterator OI = Init->op_begin(), OE = Init->op_end();
       OI != OE; ++OI) {
    Value *Op = *OI;
    // llvm.global_ctors is an array of three-field structs where the second
    // members are constructor functions.
    Function *F = dyn_cast<Function>(cast<ConstantStruct>(Op)->getOperand(1));
    // If the user used a constructor function with the wrong signature and
    // it got bitcasted or whatever, look the other way.
    if (!F)
      continue;
    // Only look at function definitions.
    if (F->isDeclaration())
      continue;
    // Only look at functions with one basic block.
    if (std::next(F->begin()) != F->end())
      continue;
    // Ok, a single-block constructor function definition. Try to optimize it.
    Changed |= OptimizeBB(F->begin());
  }

  return Changed;
}

// doInitialization - Initializes the vector of functions that have been
// annotated with the noinline attribute.
bool SimpleInliner::doInitialization(CallGraph &CG) {
  CA.setTargetData(getAnalysisIfAvailable<TargetData>());

  Module &M = CG.getModule();

  for (Module::iterator I = M.begin(), E = M.end();
       I != E; ++I)
    if (!I->isDeclaration() && I->hasFnAttr(Attribute::NoInline))
      NeverInline.insert(I);

  // Get llvm.noinline
  GlobalVariable *GV = M.getNamedGlobal("llvm.noinline");

  if (GV == 0)
    return false;

  // Don't crash on invalid code
  if (!GV->hasDefinitiveInitializer())
    return false;

  const ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());

  if (InitList == 0)
    return false;

  // Iterate over each element and add to the NeverInline set
  for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {

    // Get Source
    const Constant *Elt = InitList->getOperand(i);

    if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(Elt))
      if (CE->getOpcode() == Instruction::BitCast)
        Elt = CE->getOperand(0);

    // Insert into set of functions to never inline
    if (const Function *F = dyn_cast<Function>(Elt))
      NeverInline.insert(F);
  }

  return false;
}

/// Return the value that would be computed by a load from P after the stores
/// reflected by 'memory' have been performed.  If we can't decide, return null.
Constant *Evaluator::ComputeLoadResult(Constant *P) {
  // If this memory location has been recently stored, use the stored value: it
  // is the most up-to-date.
  DenseMap<Constant*, Constant*>::const_iterator I = MutatedMemory.find(P);
  if (I != MutatedMemory.end()) return I->second;

  // Access it.
  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
    if (GV->hasDefinitiveInitializer())
      return GV->getInitializer();
    return nullptr;
  }

  // Handle a constantexpr getelementptr.
  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
    if (CE->getOpcode() == Instruction::GetElementPtr &&
        isa<GlobalVariable>(CE->getOperand(0))) {
      GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
      if (GV->hasDefinitiveInitializer())
        return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
    }

  return nullptr;  // don't know how to evaluate.
}

bool ConstantMerge::runOnModule(Module &M) {
  TD = getAnalysisIfAvailable<TargetData>();

  // Find all the globals that are marked "used".  These cannot be merged.
  SmallPtrSet<const GlobalValue*, 8> UsedGlobals;
  FindUsedValues(M.getGlobalVariable("llvm.used"), UsedGlobals);
  FindUsedValues(M.getGlobalVariable("llvm.compiler.used"), UsedGlobals);
  
  // Map unique <constants, has-unknown-alignment> pairs to globals.  We don't
  // want to merge globals of unknown alignment with those of explicit
  // alignment.  If we have TargetData, we always know the alignment.
  DenseMap<PointerIntPair<Constant*, 1, bool>, GlobalVariable*> CMap;

  // Replacements - This vector contains a list of replacements to perform.
  SmallVector<std::pair<GlobalVariable*, GlobalVariable*>, 32> Replacements;

  bool MadeChange = false;

  // Iterate constant merging while we are still making progress.  Merging two
  // constants together may allow us to merge other constants together if the
  // second level constants have initializers which point to the globals that
  // were just merged.
  while (1) {

    // First: Find the canonical constants others will be merged with.
    for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
         GVI != E; ) {
      GlobalVariable *GV = GVI++;

      // If this GV is dead, remove it.
      GV->removeDeadConstantUsers();
      if (GV->use_empty() && GV->hasLocalLinkage()) {
        GV->eraseFromParent();
        continue;
      }

      // Only process constants with initializers in the default address space.
      if (!GV->isConstant() || !GV->hasDefinitiveInitializer() ||
          GV->getType()->getAddressSpace() != 0 || GV->hasSection() ||
          // Don't touch values marked with attribute(used).
          UsedGlobals.count(GV))
        continue;

      // This transformation is legal for weak ODR globals in the sense it
      // doesn't change semantics, but we really don't want to perform it
      // anyway; it's likely to pessimize code generation, and some tools
      // (like the Darwin linker in cases involving CFString) don't expect it.
      if (GV->isWeakForLinker())
        continue;

      Constant *Init = GV->getInitializer();

      // Check to see if the initializer is already known.
      PointerIntPair<Constant*, 1, bool> Pair(Init, hasKnownAlignment(GV));
      GlobalVariable *&Slot = CMap[Pair];

      // If this is the first constant we find or if the old one is local,
      // replace with the current one. If the current is externally visible
      // it cannot be replace, but can be the canonical constant we merge with.
      if (Slot == 0 || IsBetterCannonical(*GV, *Slot))
        Slot = GV;
    }

    // Second: identify all globals that can be merged together, filling in
    // the Replacements vector.  We cannot do the replacement in this pass
    // because doing so may cause initializers of other globals to be rewritten,
    // invalidating the Constant* pointers in CMap.
    for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
         GVI != E; ) {
      GlobalVariable *GV = GVI++;

      // Only process constants with initializers in the default address space.
      if (!GV->isConstant() || !GV->hasDefinitiveInitializer() ||
          GV->getType()->getAddressSpace() != 0 || GV->hasSection() ||
          // Don't touch values marked with attribute(used).
          UsedGlobals.count(GV))
        continue;

      // We can only replace constant with local linkage.
      if (!GV->hasLocalLinkage())
        continue;

      Constant *Init = GV->getInitializer();

      // Check to see if the initializer is already known.
      PointerIntPair<Constant*, 1, bool> Pair(Init, hasKnownAlignment(GV));
      GlobalVariable *Slot = CMap[Pair];

      if (!Slot || Slot == GV)
        continue;

      if (!Slot->hasUnnamedAddr() && !GV->hasUnnamedAddr())
        continue;

      if (!GV->hasUnnamedAddr())
        Slot->setUnnamedAddr(false);

      // Make all uses of the duplicate constant use the canonical version.
      Replacements.push_back(std::make_pair(GV, Slot));
    }
//.........这里部分代码省略.........

bool ConstantMerge::runOnModule(Module &M) {
  // Find all the globals that are marked "used".  These cannot be merged.
  SmallPtrSet<const GlobalValue*, 8> UsedGlobals;
  FindUsedValues(M.getGlobalVariable("llvm.used"), UsedGlobals);
  FindUsedValues(M.getGlobalVariable("llvm.compiler.used"), UsedGlobals);
  
  // Map unique constant/section pairs to globals.  We don't want to merge
  // globals in different sections.
  DenseMap<Constant*, GlobalVariable*> CMap;

  // Replacements - This vector contains a list of replacements to perform.
  SmallVector<std::pair<GlobalVariable*, GlobalVariable*>, 32> Replacements;

  bool MadeChange = false;

  // Iterate constant merging while we are still making progress.  Merging two
  // constants together may allow us to merge other constants together if the
  // second level constants have initializers which point to the globals that
  // were just merged.
  while (1) {
    // First pass: identify all globals that can be merged together, filling in
    // the Replacements vector.  We cannot do the replacement in this pass
    // because doing so may cause initializers of other globals to be rewritten,
    // invalidating the Constant* pointers in CMap.
    //
    for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
         GVI != E; ) {
      GlobalVariable *GV = GVI++;
      
      // If this GV is dead, remove it.
      GV->removeDeadConstantUsers();
      if (GV->use_empty() && GV->hasLocalLinkage()) {
        GV->eraseFromParent();
        continue;
      }
      
      // Only process constants with initializers in the default addres space.
      if (!GV->isConstant() ||!GV->hasDefinitiveInitializer() ||
          GV->getType()->getAddressSpace() != 0 || !GV->getSection().empty() ||
          // Don't touch values marked with attribute(used).
          UsedGlobals.count(GV))
        continue;
      
      
      
      Constant *Init = GV->getInitializer();

      // Check to see if the initializer is already known.
      GlobalVariable *&Slot = CMap[Init];

      if (Slot == 0) {    // Nope, add it to the map.
        Slot = GV;
      } else if (GV->hasLocalLinkage()) {    // Yup, this is a duplicate!
        // Make all uses of the duplicate constant use the canonical version.
        Replacements.push_back(std::make_pair(GV, Slot));
      }
    }

    if (Replacements.empty())
      return MadeChange;
    CMap.clear();

    // Now that we have figured out which replacements must be made, do them all
    // now.  This avoid invalidating the pointers in CMap, which are unneeded
    // now.
    for (unsigned i = 0, e = Replacements.size(); i != e; ++i) {
      // Eliminate any uses of the dead global.
      Replacements[i].first->replaceAllUsesWith(Replacements[i].second);

      // Delete the global value from the module.
      Replacements[i].first->eraseFromParent();
    }

    NumMerged += Replacements.size();
    Replacements.clear();
  }
}