C++ Constant::isNullValue方法代码示例

/// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP
/// constant expression, do so.
static Constant *SymbolicallyEvaluateGEP(Constant** Ops, unsigned NumOps,
                                         const Type *ResultTy,
                                         const TargetData *TD) {
  Constant *Ptr = Ops[0];
  if (!cast<PointerType>(Ptr->getType())->getElementType()->isSized())
    return 0;
  
  if (TD && Ptr->isNullValue()) {
    // If this is a constant expr gep that is effectively computing an
    // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
    bool isFoldableGEP = true;
    for (unsigned i = 1; i != NumOps; ++i)
      if (!isa<ConstantInt>(Ops[i])) {
        isFoldableGEP = false;
        break;
      }
    if (isFoldableGEP) {
      uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
                                             (Value**)Ops+1, NumOps-1);
      Constant *C = ConstantInt::get(TD->getIntPtrType(), Offset);
      return ConstantExpr::getIntToPtr(C, ResultTy);
    }
  }
  
  return 0;
}

/// runStaticConstructorsDestructors - This method is used to execute all of
/// the static constructors or destructors for a module, depending on the
/// value of isDtors.
void ExecutionEngine::runStaticConstructorsDestructors(Module *module, bool isDtors) {
  const char *Name = isDtors ? "llvm.global_dtors" : "llvm.global_ctors";
  
  // Execute global ctors/dtors for each module in the program.
  
 GlobalVariable *GV = module->getNamedGlobal(Name);

 // If this global has internal linkage, or if it has a use, then it must be
 // an old-style (llvmgcc3) static ctor with __main linked in and in use.  If
 // this is the case, don't execute any of the global ctors, __main will do
 // it.
 if (!GV || GV->isDeclaration() || GV->hasLocalLinkage()) return;
 
 // Should be an array of '{ int, void ()* }' structs.  The first value is
 // the init priority, which we ignore.
 ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
 if (!InitList) return;
 for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
   if (ConstantStruct *CS = 
       dyn_cast<ConstantStruct>(InitList->getOperand(i))) {
     if (CS->getNumOperands() != 2) return; // Not array of 2-element structs.
   
     Constant *FP = CS->getOperand(1);
     if (FP->isNullValue())
       break;  // Found a null terminator, exit.
   
     if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
       if (CE->isCast())
         FP = CE->getOperand(0);
     if (Function *F = dyn_cast<Function>(FP)) {
       // Execute the ctor/dtor function!
       runFunction(F, std::vector<GenericValue>());
     }
   }
}

// Instrument memset/memmove/memcpy
bool AddressSanitizer::instrumentMemIntrinsic(AsanFunctionContext &AFC,
                                              MemIntrinsic *MI) {
  Value *Dst = MI->getDest();
  MemTransferInst *MemTran = dyn_cast<MemTransferInst>(MI);
  Value *Src = MemTran ? MemTran->getSource() : 0;
  Value *Length = MI->getLength();

  Constant *ConstLength = dyn_cast<Constant>(Length);
  Instruction *InsertBefore = MI;
  if (ConstLength) {
    if (ConstLength->isNullValue()) return false;
  } else {
    // The size is not a constant so it could be zero -- check at run-time.
    IRBuilder<> IRB(InsertBefore);

    Value *Cmp = IRB.CreateICmpNE(Length,
                                  Constant::getNullValue(Length->getType()));
    InsertBefore = splitBlockAndInsertIfThen(Cmp, false);
  }

  instrumentMemIntrinsicParam(AFC, MI, Dst, Length, InsertBefore, true);
  if (Src)
    instrumentMemIntrinsicParam(AFC, MI, Src, Length, InsertBefore, false);
  return true;
}

/// allocateIDATA - allocate an initialized global into an existing
/// or new section and return that section.
const MCSection *
PIC16TargetObjectFile::allocateIDATA(const GlobalVariable *GV) const{
  assert(GV->hasInitializer() && "This global doesn't need space");
  Constant *C = GV->getInitializer();
  assert(!C->isNullValue() && "initialized globals has zero initializer");
  assert(GV->getType()->getAddressSpace() == PIC16ISD::RAM_SPACE &&
         "can allocate initialized RAM data only");

  // Find how much space this global needs.
  const TargetData *TD = TM->getTargetData();
  const Type *Ty = C->getType(); 
  unsigned ValSize = TD->getTypeAllocSize(Ty);
 
  // Go through all IDATA Sections and assign this variable
  // to the first available section having enough space.
  PIC16Section *Found = NULL;
  for (unsigned i = 0; i < IDATASections_.size(); i++) {
    if (DataBankSize - IDATASections_[i]->getSize() >= ValSize) {
      Found = IDATASections_[i]; 
      break;
    }
  }

  // No IDATA section spacious enough was found. Crate a new one.
  if (!Found) {
    std::string name = PAN::getIdataSectionName(IDATASections_.size());
    Found = getPIC16DataSection(name.c_str(), IDATA);
  }
  
  // Insert the GV into this IDATA.
  Found->Items.push_back(GV);
  Found->setSize(Found->getSize() + ValSize);
  return Found;
} 

static void addTryBlockMapEntry(WinEHFuncInfo &FuncInfo, int TryLow,
                                int TryHigh, int CatchHigh,
                                ArrayRef<const CatchPadInst *> Handlers) {
  WinEHTryBlockMapEntry TBME;
  TBME.TryLow = TryLow;
  TBME.TryHigh = TryHigh;
  TBME.CatchHigh = CatchHigh;
  assert(TBME.TryLow <= TBME.TryHigh);
  for (const CatchPadInst *CPI : Handlers) {
    WinEHHandlerType HT;
    Constant *TypeInfo = cast<Constant>(CPI->getArgOperand(0));
    if (TypeInfo->isNullValue())
      HT.TypeDescriptor = nullptr;
    else
      HT.TypeDescriptor = cast<GlobalVariable>(TypeInfo->stripPointerCasts());
    HT.Adjectives = cast<ConstantInt>(CPI->getArgOperand(1))->getZExtValue();
    HT.Handler = CPI->getParent();
    if (auto *AI =
            dyn_cast<AllocaInst>(CPI->getArgOperand(2)->stripPointerCasts()))
      HT.CatchObj.Alloca = AI;
    else
      HT.CatchObj.Alloca = nullptr;
    TBME.HandlerArray.push_back(HT);
  }
  FuncInfo.TryBlockMap.push_back(TBME);
}

void ControlFlowIntegrity::PatchDtorFunctions(void) {
  GlobalVariable *global_dtors = _M.getNamedGlobal("llvm.global_dtors");

  // check for dtor section
  if (!global_dtors || !global_dtors->getOperand(0)) {
    return;
  }

  Constant *c = global_dtors->getInitializer();
  if (!c)
    report_fatal_error("llvm.global_dtors without initializer!", false);

  ConstantArray *CA = dyn_cast<ConstantArray>(c);
  if (!CA)
    report_fatal_error("Cast to ConstantArray failed", true);

  for (Value *Op : ValueOpRange(*CA)) {
    ConstantStruct *CS = dyn_cast<ConstantStruct>(Op);
    if (!CS)
      report_fatal_error("Cast to ConstantStruct failed", true);

    Constant *FP = CS->getOperand(1);
    if (FP->isNullValue())
      break; // found a NULL termintator, stop here

    Function *F = dyn_cast_or_null<Function>(FP);
    if (F == NULL) {
      // Strip off constant expression cast
      ConstantExpr *CE = dyn_cast<ConstantExpr>(FP);
      if (!CE)
        report_fatal_error("Cast to ConstantExpr failed", true);
      if (CE->isCast()) {
        FP = CE->getOperand(0);
      }
      F = dyn_cast_or_null<Function>(FP);
    }

    if (!F)
      report_fatal_error("Cast to Function failed", true);

    // set visibility to hidden (do not export), unless it is already
    // local (for ex. static), in which case we have to make it non-static
    if (F->hasLocalLinkage()) {
      F->setLinkage(llvm::GlobalValue::ExternalLinkage);
    }
    F->setVisibility(GlobalValue::HiddenVisibility);

    _FiniFunctions.insert(F->getName());
  }

  if (global_dtors->getNumUses() > 0)
    report_fatal_error("llvm.global_dtors uses count is > 0!", false);

  global_dtors->removeFromParent();

}

Constant *ShadowStackGC::GetFrameMap(Function &F) {
  // doInitialization creates the abstract type of this value.
  Type *VoidPtr = Type::getInt8PtrTy(F.getContext());

  // Truncate the ShadowStackDescriptor if some metadata is null.
  unsigned NumMeta = 0;
  SmallVector<Constant*, 16> Metadata;
  for (unsigned I = 0; I != Roots.size(); ++I) {
    Constant *C = cast<Constant>(Roots[I].first->getArgOperand(1));
    if (!C->isNullValue())
      NumMeta = I + 1;
    Metadata.push_back(ConstantExpr::getBitCast(C, VoidPtr));
  }
  Metadata.resize(NumMeta);

  Type *Int32Ty = Type::getInt32Ty(F.getContext());
  
  Constant *BaseElts[] = {
    ConstantInt::get(Int32Ty, Roots.size(), false),
    ConstantInt::get(Int32Ty, NumMeta, false),
  };

  Constant *DescriptorElts[] = {
    ConstantStruct::get(FrameMapTy, BaseElts),
    ConstantArray::get(ArrayType::get(VoidPtr, NumMeta), Metadata)
  };

  Type *EltTys[] = { DescriptorElts[0]->getType(),DescriptorElts[1]->getType()};
  StructType *STy = StructType::create(EltTys, "gc_map."+utostr(NumMeta));
  
  Constant *FrameMap = ConstantStruct::get(STy, DescriptorElts);

  // FIXME: Is this actually dangerous as WritingAnLLVMPass.html claims? Seems
  //        that, short of multithreaded LLVM, it should be safe; all that is
  //        necessary is that a simple Module::iterator loop not be invalidated.
  //        Appending to the GlobalVariable list is safe in that sense.
  //
  //        All of the output passes emit globals last. The ExecutionEngine
  //        explicitly supports adding globals to the module after
  //        initialization.
  //
  //        Still, if it isn't deemed acceptable, then this transformation needs
  //        to be a ModulePass (which means it cannot be in the 'llc' pipeline
  //        (which uses a FunctionPassManager (which segfaults (not asserts) if
  //        provided a ModulePass))).
  Constant *GV = new GlobalVariable(*F.getParent(), FrameMap->getType(), true,
                                    GlobalVariable::InternalLinkage,
                                    FrameMap, "__gc_" + F.getName());

  Constant *GEPIndices[2] = {
                          ConstantInt::get(Type::getInt32Ty(F.getContext()), 0),
                          ConstantInt::get(Type::getInt32Ty(F.getContext()), 0)
                          };
  return ConstantExpr::getGetElementPtr(GV, GEPIndices);
}

static void addConditions(CallSite CS, const ConditionsTy &Conditions) {
  for (auto &Cond : Conditions) {
    Value *Arg = Cond.first->getOperand(0);
    Constant *ConstVal = cast<Constant>(Cond.first->getOperand(1));
    if (Cond.second == ICmpInst::ICMP_EQ)
      setConstantInArgument(CS, Arg, ConstVal);
    else if (ConstVal->getType()->isPointerTy() && ConstVal->isNullValue()) {
      assert(Cond.second == ICmpInst::ICMP_NE);
      addNonNullAttribute(CS, Arg);
    }
  }
}

// what a hack
static Function *getStubFunctionForCtorList(Module *m,
                                            GlobalVariable *gv, 
                                            std::string name) {
  assert(!gv->isDeclaration() && !gv->hasInternalLinkage() &&
         "do not support old LLVM style constructor/destructor lists");

  std::vector<Type *> nullary;

  Function *fn = Function::Create(FunctionType::get(Type::getVoidTy(m->getContext()),
						    nullary, false),
				  GlobalVariable::InternalLinkage, 
				  name,
                              m);
  BasicBlock *bb = BasicBlock::Create(m->getContext(), "entry", fn);
  
  // From lli:
  // Should be an array of '{ int, void ()* }' structs.  The first value is
  // the init priority, which we ignore.
  ConstantArray *arr = dyn_cast<ConstantArray>(gv->getInitializer());
  if (arr) {
    for (unsigned i=0; i<arr->getNumOperands(); i++) {
      ConstantStruct *cs = cast<ConstantStruct>(arr->getOperand(i));
#if LLVM_VERSION_CODE >= LLVM_VERSION(3, 5)
      // There is a third *optional* element in global_ctor elements (``i8
      // @data``).
      assert((cs->getNumOperands() == 2 || cs->getNumOperands() == 3) &&
             "unexpected element in ctor initializer list");
#else
      assert(cs->getNumOperands()==2 && "unexpected element in ctor initializer list");
#endif
      Constant *fp = cs->getOperand(1);      
      if (!fp->isNullValue()) {
        if (llvm::ConstantExpr *ce = dyn_cast<llvm::ConstantExpr>(fp))
          fp = ce->getOperand(0);

        if (Function *f = dyn_cast<Function>(fp)) {
	  CallInst::Create(f, "", bb);
        } else {
          assert(0 && "unable to get function pointer from ctor initializer list");
        }
      }
    }
  }
  
  ReturnInst::Create(m->getContext(), bb);

  return fn;
}

static bool isSuitableForBSS(const GlobalVariable *GV) {
  Constant *C = GV->getInitializer();

  // Must have zero initializer.
  if (!C->isNullValue())
    return false;

  // Leave constant zeros in readonly constant sections, so they can be shared.
  if (GV->isConstant())
    return false;

  // If the global has an explicit section specified, don't put it in BSS.
  if (!GV->getSection().empty())
    return false;

  // If -nozero-initialized-in-bss is specified, don't ever use BSS.
  if (NoZerosInBSS)
    return false;

  // Otherwise, put it in BSS!
  return true;
}

static void RemoveFunctionReferences(Module *M, const char* Name) {
  auto *UsedVar = M->getGlobalVariable(Name, true);
  if (!UsedVar || !UsedVar->hasInitializer()) return;
  if (isa<ConstantAggregateZero>(UsedVar->getInitializer())) {
    assert(UsedVar->use_empty());
    UsedVar->eraseFromParent();
    return;
  }
  auto *OldUsedVal = cast<ConstantArray>(UsedVar->getInitializer());
  std::vector<Constant*> Used;
  for(Value *V : OldUsedVal->operand_values()) {
    Constant *Op = cast<Constant>(V->stripPointerCasts());
    if(!Op->isNullValue()) {
      Used.push_back(cast<Constant>(V));
    }
  }
  auto *NewValElemTy = OldUsedVal->getType()->getElementType();
  auto *NewValTy = ArrayType::get(NewValElemTy, Used.size());
  auto *NewUsedVal = ConstantArray::get(NewValTy, Used);
  UsedVar->mutateType(NewUsedVal->getType()->getPointerTo());
  UsedVar->setInitializer(NewUsedVal);
}

void MemoryInstrumenter::lowerGlobalCtors(Module &M) {
  // Find llvm.global_ctors.
  GlobalVariable *GV = M.getNamedGlobal("llvm.global_ctors");
  if (!GV)
    return;
  assert(!GV->isDeclaration() && !GV->hasLocalLinkage());

  // Should be an array of '{ int, void ()* }' structs.  The first value is
  // the init priority, which must be 65535 if the bitcode is generated using
  // clang.
  if (ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer())) {
    for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
      ConstantStruct *CS =
        dyn_cast<ConstantStruct>(InitList->getOperand(i));
      assert(CS);
      assert(CS->getNumOperands() == 2);

      // Get the priority.
      ConstantInt *Priority = dyn_cast<ConstantInt>(CS->getOperand(0));
      assert(Priority);
      // TODO: For now, we assume all priorities must be 65535.
      assert(Priority->equalsInt(65535));

      // Get the constructor function.
      Constant *FP = CS->getOperand(1);
      if (FP->isNullValue())
        break;  // Found a null terminator, exit.

      // Explicitly call the constructor at the main entry.
      CallInst::Create(FP, "", Main->begin()->getFirstNonPHI());
    }
  }

  // Clear the global_ctors array.
  // Use eraseFromParent() instead of removeFromParent().
  GV->eraseFromParent();
}

static LazyValueInfo::Tristate
getPredicateResult(unsigned Pred, Constant *C, LVILatticeVal &Result,
                   const DataLayout *DL, TargetLibraryInfo *TLI) {

  // If we know the value is a constant, evaluate the conditional.
  Constant *Res = nullptr;
  if (Result.isConstant()) {
    Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, DL,
                                          TLI);
    if (ConstantInt *ResCI = dyn_cast<ConstantInt>(Res))
      return ResCI->isZero() ? LazyValueInfo::False : LazyValueInfo::True;
    return LazyValueInfo::Unknown;
  }

  if (Result.isConstantRange()) {
    ConstantInt *CI = dyn_cast<ConstantInt>(C);
    if (!CI) return LazyValueInfo::Unknown;

    ConstantRange CR = Result.getConstantRange();
    if (Pred == ICmpInst::ICMP_EQ) {
      if (!CR.contains(CI->getValue()))
        return LazyValueInfo::False;

      if (CR.isSingleElement() && CR.contains(CI->getValue()))
        return LazyValueInfo::True;
    } else if (Pred == ICmpInst::ICMP_NE) {
      if (!CR.contains(CI->getValue()))
        return LazyValueInfo::True;

      if (CR.isSingleElement() && CR.contains(CI->getValue()))
        return LazyValueInfo::False;
    }

    // Handle more complex predicates.
    ConstantRange TrueValues =
        ICmpInst::makeConstantRange((ICmpInst::Predicate)Pred, CI->getValue());
    if (TrueValues.contains(CR))
      return LazyValueInfo::True;
    if (TrueValues.inverse().contains(CR))
      return LazyValueInfo::False;
    return LazyValueInfo::Unknown;
  }

  if (Result.isNotConstant()) {
    // If this is an equality comparison, we can try to fold it knowing that
    // "V != C1".
    if (Pred == ICmpInst::ICMP_EQ) {
      // !C1 == C -> false iff C1 == C.
      Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
                                            Result.getNotConstant(), C, DL,
                                            TLI);
      if (Res->isNullValue())
        return LazyValueInfo::False;
    } else if (Pred == ICmpInst::ICMP_NE) {
      // !C1 != C -> true iff C1 == C.
      Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
                                            Result.getNotConstant(), C, DL,
                                            TLI);
      if (Res->isNullValue())
        return LazyValueInfo::True;
    }
    return LazyValueInfo::Unknown;
  }

  return LazyValueInfo::Unknown;
}

bool ReduceCrashingFunctions::TestFuncs(std::vector<Function*> &Funcs) {
  // If main isn't present, claim there is no problem.
  if (KeepMain && std::find(Funcs.begin(), Funcs.end(),
                            BD.getProgram()->getFunction("main")) ==
                      Funcs.end())
    return false;

  // Clone the program to try hacking it apart...
  ValueToValueMapTy VMap;
  Module *M = CloneModule(BD.getProgram(), VMap);

  // Convert list to set for fast lookup...
  std::set<Function*> Functions;
  for (unsigned i = 0, e = Funcs.size(); i != e; ++i) {
    Function *CMF = cast<Function>(VMap[Funcs[i]]);
    assert(CMF && "Function not in module?!");
    assert(CMF->getFunctionType() == Funcs[i]->getFunctionType() && "wrong ty");
    assert(CMF->getName() == Funcs[i]->getName() && "wrong name");
    Functions.insert(CMF);
  }

  outs() << "Checking for crash with only these functions: ";
  PrintFunctionList(Funcs);
  outs() << ": ";
  if (!ReplaceFuncsWithNull) {
    // Loop over and delete any functions which we aren't supposed to be playing
    // with...
    for (Function &I : *M)
      if (!I.isDeclaration() && !Functions.count(&I))
        DeleteFunctionBody(&I);
  } else {
    std::vector<GlobalValue*> ToRemove;
    // First, remove aliases to functions we're about to purge.
    for (GlobalAlias &Alias : M->aliases()) {
      Constant *Root = Alias.getAliasee()->stripPointerCasts();
      Function *F = dyn_cast<Function>(Root);
      if (F) {
        if (Functions.count(F))
          // We're keeping this function.
          continue;
      } else if (Root->isNullValue()) {
        // This referenced a globalalias that we've already replaced,
        // so we still need to replace this alias.
      } else if (!F) {
        // Not a function, therefore not something we mess with.
        continue;
      }

      PointerType *Ty = cast<PointerType>(Alias.getType());
      Constant *Replacement = ConstantPointerNull::get(Ty);
      Alias.replaceAllUsesWith(Replacement);
      ToRemove.push_back(&Alias);
    }

    for (Function &I : *M) {
      if (!I.isDeclaration() && !Functions.count(&I)) {
        PointerType *Ty = cast<PointerType>(I.getType());
        Constant *Replacement = ConstantPointerNull::get(Ty);
        I.replaceAllUsesWith(Replacement);
        ToRemove.push_back(&I);
      }
    }

    for (auto *F : ToRemove) {
      F->eraseFromParent();
    }

    // Finally, remove any null members from any global intrinsic.
    RemoveFunctionReferences(M, "llvm.used");
    RemoveFunctionReferences(M, "llvm.compiler.used");
  }
  // Try running the hacked up program...
  if (TestFn(BD, M)) {
    BD.setNewProgram(M);        // It crashed, keep the trimmed version...

    // Make sure to use function pointers that point into the now-current
    // module.
    Funcs.assign(Functions.begin(), Functions.end());
    return true;
  }
  delete M;
  return false;
}

//
// Method: postOrderInline()
//
// Description:
//  This methods does a post order traversal of the call graph and performs
//  bottom-up inlining of the DSGraphs.
//
void
BUDataStructures::postOrderInline (Module & M) {
  // Variables used for Tarjan SCC-finding algorithm.  These are passed into
  // the recursive function used to find SCCs.
  std::vector<const Function*> Stack;
  std::map<const Function*, unsigned> ValMap;
  unsigned NextID = 1;


  // Do post order traversal on the global ctors. Use this information to update
  // the globals graph.
  const char *Name = "llvm.global_ctors";
  GlobalVariable *GV = M.getNamedGlobal(Name);
  if (GV && !(GV->isDeclaration()) && !(GV->hasLocalLinkage())) {
    // Should be an array of '{ int, void ()* }' structs.  The first value is
    // the init priority, which we ignore.
    ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
    if (InitList) {
      for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
        if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))) {
          if (CS->getNumOperands() != 2)
            break; // Not array of 2-element structs.
          Constant *FP = CS->getOperand(1);
          if (FP->isNullValue())
            break;  // Found a null terminator, exit.

          if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
            if (CE->isCast())
              FP = CE->getOperand(0);
          Function *F = dyn_cast<Function>(FP);
          if (F && !F->isDeclaration() && !ValMap.count(F)) {
            calculateGraphs(F, Stack, NextID, ValMap);
            CloneAuxIntoGlobal(getDSGraph(*F));
          }
        }
      GlobalsGraph->removeTriviallyDeadNodes();
      GlobalsGraph->maskIncompleteMarkers();

      // Mark external globals incomplete.
      GlobalsGraph->markIncompleteNodes(DSGraph::IgnoreGlobals);
      GlobalsGraph->computeExternalFlags(DSGraph::DontMarkFormalsExternal);
      GlobalsGraph->computeIntPtrFlags();

      //
      // Create equivalence classes for aliasing globals so that we only need to
      // record one global per DSNode.
      //
      formGlobalECs();
      // propogte information calculated
      // from the globals graph to the other graphs.
      for (Module::iterator F = M.begin(); F != M.end(); ++F) {
        if (!(F->isDeclaration())){
          DSGraph *Graph  = getDSGraph(*F);
          cloneGlobalsInto(Graph, DSGraph::DontCloneCallNodes |
                           DSGraph::DontCloneAuxCallNodes);
          Graph->buildCallGraph(callgraph, GlobalFunctionList, filterCallees);
          Graph->maskIncompleteMarkers();
          Graph->markIncompleteNodes(DSGraph::MarkFormalArgs |
                                     DSGraph::IgnoreGlobals);
          Graph->computeExternalFlags(DSGraph::DontMarkFormalsExternal);
          Graph->computeIntPtrFlags();
        }
      }
    }
  }

  //
  // Start the post order traversal with the main() function.  If there is no
  // main() function, don't worry; we'll have a separate traversal for inlining
  // graphs for functions not reachable from main().
  //
  Function *MainFunc = M.getFunction ("main");
  if (MainFunc && !MainFunc->isDeclaration()) {
    calculateGraphs(MainFunc, Stack, NextID, ValMap);
    CloneAuxIntoGlobal(getDSGraph(*MainFunc));
  }

  //
  // Calculate the graphs for any functions that are unreachable from main...
  //
  for (Function &F : M)
    if (!F.isDeclaration() && !ValMap.count(&F)) {
      if (MainFunc)
        DEBUG(errs() << debugname << ": Function unreachable from main: "
        << F.getName() << "\n");
      calculateGraphs(&F, Stack, NextID, ValMap);     // Calculate all graphs.
      CloneAuxIntoGlobal(getDSGraph(F));

      // Mark this graph as processed.  Do this by finding all functions
      // in the graph that map to it, and mark them visited.
      // Note that this really should be handled neatly by calculateGraphs
      // itself, not here.  However this catches the worst offenders.
      DSGraph *G = getDSGraph(F);
//.........这里部分代码省略.........