C++ global_iterator::setInitializer方法代码示例

/// SplitFunctionsOutOfModule - Given a module and a list of functions in the
/// module, split the functions OUT of the specified module, and place them in
/// the new module.
Module *
llvm::SplitFunctionsOutOfModule(Module *M,
                                const std::vector<Function*> &F,
                                DenseMap<const Value*, Value*> &ValueMap) {
  // Make sure functions & globals are all external so that linkage
  // between the two modules will work.
  for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
    I->setLinkage(GlobalValue::ExternalLinkage);
  for (Module::global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I) {
    if (I->hasName() && I->getName()[0] == '\01')
      I->setName(I->getName().substr(1));
    I->setLinkage(GlobalValue::ExternalLinkage);
  }

  DenseMap<const Value*, Value*> NewValueMap;
  Module *New = CloneModule(M, NewValueMap);

  // Make sure global initializers exist only in the safe module (CBE->.so)
  for (Module::global_iterator I = New->global_begin(), E = New->global_end();
       I != E; ++I)
    I->setInitializer(0);  // Delete the initializer to make it external

  // Remove the Test functions from the Safe module
  std::set<Function *> TestFunctions;
  for (unsigned i = 0, e = F.size(); i != e; ++i) {
    Function *TNOF = cast<Function>(ValueMap[F[i]]);
    DEBUG(errs() << "Removing function ");
    DEBUG(WriteAsOperand(errs(), TNOF, false));
    DEBUG(errs() << "\n");
    TestFunctions.insert(cast<Function>(NewValueMap[TNOF]));
    DeleteFunctionBody(TNOF);       // Function is now external in this module!
  }

  
  // Remove the Safe functions from the Test module
  for (Module::iterator I = New->begin(), E = New->end(); I != E; ++I)
    if (!TestFunctions.count(I))
      DeleteFunctionBody(I);
  

  // Make sure that there is a global ctor/dtor array in both halves of the
  // module if they both have static ctor/dtor functions.
  SplitStaticCtorDtor("llvm.global_ctors", M, New, NewValueMap);
  SplitStaticCtorDtor("llvm.global_dtors", M, New, NewValueMap);
  
  return New;
}

bool StripExternals::runOnModule(Module &M) {
  bool Changed = false;

  for (Module::iterator I = M.begin(); I != M.end(); ) {
    if (I->hasAvailableExternallyLinkage()) {
      assert(!I->isDeclaration()&&"Declarations can't be available_externally");
      Changed = true;
      ++NumFunctions;
      if (I->use_empty()) {
        DEBUG(errs() << "Deleting function: " << *I);
        Module::iterator todelete = I;
        ++I;
        todelete->eraseFromParent();
        continue;
      } else {
        I->deleteBody();
        DEBUG(errs() << "Deleted function body: " << *I);
      }
    }
    ++I;
  }

  for (Module::global_iterator I = M.global_begin();
       I != M.global_end(); ) {
    if (I->hasAvailableExternallyLinkage()) {
      assert(!I->isDeclaration()&&"Declarations can't be available_externally");
      Changed = true;
      ++NumVariables;
      if (I->use_empty()) {
        DEBUG(errs() << "Deleting global: " << *I);
        Module::global_iterator todelete = I;
        ++I;
        todelete->eraseFromParent();
        continue;
      } else {
        I->setInitializer(0);
        I->setLinkage(GlobalValue::ExternalLinkage);
        DEBUG(errs() << "Deleted initializer: " << *I);
      }
    }
    ++I;
  }

  return Changed;
}

bool
ReduceCrashingGlobalVariables::TestGlobalVariables(
                              std::vector<GlobalVariable*> &GVs) {
  // Clone the program to try hacking it apart...
  ValueMap<const Value*, Value*> VMap;
  Module *M = CloneModule(BD.getProgram(), VMap);

  // Convert list to set for fast lookup...
  std::set<GlobalVariable*> GVSet;

  for (unsigned i = 0, e = GVs.size(); i != e; ++i) {
    GlobalVariable* CMGV = cast<GlobalVariable>(VMap[GVs[i]]);
    assert(CMGV && "Global Variable not in module?!");
    GVSet.insert(CMGV);
  }

  outs() << "Checking for crash with only these global variables: ";
  PrintGlobalVariableList(GVs);
  outs() << ": ";

  // Loop over and delete any global variables which we aren't supposed to be
  // playing with...
  for (Module::global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I)
    if (I->hasInitializer() && !GVSet.count(I)) {
      I->setInitializer(0);
      I->setLinkage(GlobalValue::ExternalLinkage);
    }

  // Try running the hacked up program...
  if (TestFn(BD, M)) {
    BD.setNewProgram(M);        // It crashed, keep the trimmed version...

    // Make sure to use global variable pointers that point into the now-current
    // module.
    GVs.assign(GVSet.begin(), GVSet.end());
    return true;
  }

  delete M;
  return false;
}

static int runCompilePasses(Module *ModuleRef,
                            unsigned ModuleIndex,
                            ThreadedFunctionQueue *FuncQueue,
                            const Triple &TheTriple,
                            TargetMachine &Target,
                            StringRef ProgramName,
                            raw_pwrite_stream &OS){
  PNaClABIErrorReporter ABIErrorReporter;

  if (SplitModuleCount > 1 || ExternalizeAll) {
    // Add function and global names, and give them external linkage.
    // This relies on LLVM's consistent auto-generation of names, we could
    // maybe do our own in case something changes there.
    for (Function &F : *ModuleRef) {
      if (!F.hasName())
        F.setName("Function");
      if (F.hasInternalLinkage())
        F.setLinkage(GlobalValue::ExternalLinkage);
    }
    for (Module::global_iterator GI = ModuleRef->global_begin(),
         GE = ModuleRef->global_end();
         GI != GE; ++GI) {
      if (!GI->hasName())
        GI->setName("Global");
      if (GI->hasInternalLinkage())
        GI->setLinkage(GlobalValue::ExternalLinkage);
    }
    if (ModuleIndex > 0) {
      // Remove the initializers for all global variables, turning them into
      // declarations.
      for (Module::global_iterator GI = ModuleRef->global_begin(),
          GE = ModuleRef->global_end();
          GI != GE; ++GI) {
        assert(GI->hasInitializer() && "Global variable missing initializer");
        Constant *Init = GI->getInitializer();
        GI->setInitializer(nullptr);
        if (Init->getNumUses() == 0)
          Init->destroyConstant();
      }
    }
  }

  // Make all non-weak symbols hidden for better code. We cannot do
  // this for weak symbols. The linker complains when some weak
  // symbols are not resolved.
  for (Function &F : *ModuleRef) {
    if (!F.isWeakForLinker() && !F.hasLocalLinkage())
      F.setVisibility(GlobalValue::HiddenVisibility);
  }
  for (Module::global_iterator GI = ModuleRef->global_begin(),
           GE = ModuleRef->global_end();
       GI != GE; ++GI) {
    if (!GI->isWeakForLinker() && !GI->hasLocalLinkage())
      GI->setVisibility(GlobalValue::HiddenVisibility);
  }

  // Build up all of the passes that we want to do to the module.
  std::unique_ptr<legacy::PassManagerBase> PM;
  if (LazyBitcode)
    PM.reset(new legacy::FunctionPassManager(ModuleRef));
  else
    PM.reset(new legacy::PassManager());

  // Add the target data from the target machine, if it exists, or the module.
  if (const DataLayout *DL = Target.getDataLayout())
    ModuleRef->setDataLayout(*DL);

  // For conformance with llc, we let the user disable LLVM IR verification with
  // -disable-verify. Unlike llc, when LLVM IR verification is enabled we only
  // run it once, before PNaCl ABI verification.
  if (!NoVerify)
    PM->add(createVerifierPass());

  // Add the ABI verifier pass before the analysis and code emission passes.
  if (PNaClABIVerify)
    PM->add(createPNaClABIVerifyFunctionsPass(&ABIErrorReporter));

  // Add the intrinsic resolution pass. It assumes ABI-conformant code.
  PM->add(createResolvePNaClIntrinsicsPass());

  // Add an appropriate TargetLibraryInfo pass for the module's triple.
  TargetLibraryInfoImpl TLII(TheTriple);

  // The -disable-simplify-libcalls flag actually disables all builtin optzns.
  if (DisableSimplifyLibCalls)
    TLII.disableAllFunctions();
  PM->add(new TargetLibraryInfoWrapperPass(TLII));

  // Allow subsequent passes and the backend to better optimize instructions
  // that were simplified for PNaCl's ABI. This pass uses the TargetLibraryInfo
  // above.
  PM->add(createBackendCanonicalizePass());

  // Ask the target to add backend passes as necessary. We explicitly ask it
  // not to add the verifier pass because we added it earlier.
  if (Target.addPassesToEmitFile(*PM, OS, FileType,
                                 /* DisableVerify */ true)) {
    errs() << ProgramName
    << ": target does not support generation of this file type!\n";
    return 1;
//.........这里部分代码省略.........

/// DebugACrash - Given a predicate that determines whether a component crashes
/// on a program, try to destructively reduce the program while still keeping
/// the predicate true.
static bool DebugACrash(BugDriver &BD,
                        bool (*TestFn)(const BugDriver &, Module *),
                        std::string &Error) {
  // See if we can get away with nuking some of the global variable initializers
  // in the program...
  if (!NoGlobalRM &&
      BD.getProgram()->global_begin() != BD.getProgram()->global_end()) {
    // Now try to reduce the number of global variable initializers in the
    // module to something small.
    Module *M = CloneModule(BD.getProgram());
    bool DeletedInit = false;

    for (Module::global_iterator I = M->global_begin(), E = M->global_end();
         I != E; ++I)
      if (I->hasInitializer()) {
        I->setInitializer(nullptr);
        I->setLinkage(GlobalValue::ExternalLinkage);
        DeletedInit = true;
      }

    if (!DeletedInit) {
      delete M;  // No change made...
    } else {
      // See if the program still causes a crash...
      outs() << "\nChecking to see if we can delete global inits: ";

      if (TestFn(BD, M)) {      // Still crashes?
        BD.setNewProgram(M);
        outs() << "\n*** Able to remove all global initializers!\n";
      } else {                  // No longer crashes?
        outs() << "  - Removing all global inits hides problem!\n";
        delete M;

        std::vector<GlobalVariable*> GVs;

        for (Module::global_iterator I = BD.getProgram()->global_begin(),
               E = BD.getProgram()->global_end(); I != E; ++I)
          if (I->hasInitializer())
            GVs.push_back(&*I);

        if (GVs.size() > 1 && !BugpointIsInterrupted) {
          outs() << "\n*** Attempting to reduce the number of global "
                    << "variables in the testcase\n";

          unsigned OldSize = GVs.size();
          ReduceCrashingGlobalVariables(BD, TestFn).reduceList(GVs, Error);
          if (!Error.empty())
            return true;

          if (GVs.size() < OldSize)
            BD.EmitProgressBitcode(BD.getProgram(), "reduced-global-variables");
        }
      }
    }
  }

  // Now try to reduce the number of functions in the module to something small.
  std::vector<Function*> Functions;
  for (Function &F : *BD.getProgram())
    if (!F.isDeclaration())
      Functions.push_back(&F);

  if (Functions.size() > 1 && !BugpointIsInterrupted) {
    outs() << "\n*** Attempting to reduce the number of functions "
      "in the testcase\n";

    unsigned OldSize = Functions.size();
    ReduceCrashingFunctions(BD, TestFn).reduceList(Functions, Error);

    if (Functions.size() < OldSize)
      BD.EmitProgressBitcode(BD.getProgram(), "reduced-function");
  }

  // Attempt to delete entire basic blocks at a time to speed up
  // convergence... this actually works by setting the terminator of the blocks
  // to a return instruction then running simplifycfg, which can potentially
  // shrinks the code dramatically quickly
  //
  if (!DisableSimplifyCFG && !BugpointIsInterrupted) {
    std::vector<const BasicBlock*> Blocks;
    for (Function &F : *BD.getProgram())
      for (BasicBlock &BB : F)
        Blocks.push_back(&BB);
    unsigned OldSize = Blocks.size();
    ReduceCrashingBlocks(BD, TestFn).reduceList(Blocks, Error);
    if (Blocks.size() < OldSize)
      BD.EmitProgressBitcode(BD.getProgram(), "reduced-blocks");
  }

  // Attempt to delete instructions using bisection. This should help out nasty
  // cases with large basic blocks where the problem is at one end.
  if (!BugpointIsInterrupted) {
    std::vector<const Instruction*> Insts;
    for (const Function &F : *BD.getProgram())
      for (const BasicBlock &BB : F)
        for (const Instruction &I : BB)
          if (!isa<TerminatorInst>(&I))
//.........这里部分代码省略.........

/// SplitFunctionsOutOfModule - Given a module and a list of functions in the
/// module, split the functions OUT of the specified module, and place them in
/// the new module.
Module *
llvm::SplitFunctionsOutOfModule(Module *M,
                                const std::vector<Function*> &F,
                                ValueToValueMapTy &VMap) {
  // Make sure functions & globals are all external so that linkage
  // between the two modules will work.
  for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
    I->setLinkage(GlobalValue::ExternalLinkage);
  for (Module::global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I) {
    if (I->hasName() && I->getName()[0] == '\01')
      I->setName(I->getName().substr(1));
    I->setLinkage(GlobalValue::ExternalLinkage);
  }

  ValueToValueMapTy NewVMap;
  Module *New = CloneModule(M, NewVMap);

  // Remove the Test functions from the Safe module
  std::set<Function *> TestFunctions;
  for (unsigned i = 0, e = F.size(); i != e; ++i) {
    Function *TNOF = cast<Function>(VMap[F[i]]);
    DEBUG(errs() << "Removing function ");
    DEBUG(WriteAsOperand(errs(), TNOF, false));
    DEBUG(errs() << "\n");
    TestFunctions.insert(cast<Function>(NewVMap[TNOF]));
    DeleteFunctionBody(TNOF);       // Function is now external in this module!
  }

  
  // Remove the Safe functions from the Test module
  for (Module::iterator I = New->begin(), E = New->end(); I != E; ++I)
    if (!TestFunctions.count(I))
      DeleteFunctionBody(I);
  

  // Try to split the global initializers evenly
  for (Module::global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I) {
    GlobalVariable *GV = cast<GlobalVariable>(NewVMap[I]);
    if (Function *TestFn = globalInitUsesExternalBA(I)) {
      if (Function *SafeFn = globalInitUsesExternalBA(GV)) {
        errs() << "*** Error: when reducing functions, encountered "
                  "the global '";
        WriteAsOperand(errs(), GV, false);
        errs() << "' with an initializer that references blockaddresses "
                  "from safe function '" << SafeFn->getName()
               << "' and from test function '" << TestFn->getName() << "'.\n";
        exit(1);
      }
      I->setInitializer(0);  // Delete the initializer to make it external
    } else {
      // If we keep it in the safe module, then delete it in the test module
      GV->setInitializer(0);
    }
  }

  // Make sure that there is a global ctor/dtor array in both halves of the
  // module if they both have static ctor/dtor functions.
  SplitStaticCtorDtor("llvm.global_ctors", M, New, NewVMap);
  SplitStaticCtorDtor("llvm.global_dtors", M, New, NewVMap);
  
  return New;
}

bool GlobalDCE::runOnModule(Module &M) {
  bool Changed = false;
  
  // Loop over the module, adding globals which are obviously necessary.
  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
    Changed |= RemoveUnusedGlobalValue(*I);
    // Functions with external linkage are needed if they have a body
    if (!I->isDiscardableIfUnused() &&
        !I->isDeclaration() && !I->hasAvailableExternallyLinkage())
      GlobalIsNeeded(I);
  }

  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
       I != E; ++I) {
    Changed |= RemoveUnusedGlobalValue(*I);
    // Externally visible & appending globals are needed, if they have an
    // initializer.
    if (!I->isDiscardableIfUnused() &&
        !I->isDeclaration() && !I->hasAvailableExternallyLinkage())
      GlobalIsNeeded(I);
  }

  for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
       I != E; ++I) {
    Changed |= RemoveUnusedGlobalValue(*I);
    // Externally visible aliases are needed.
    if (!I->isDiscardableIfUnused())
      GlobalIsNeeded(I);
  }

  // Now that all globals which are needed are in the AliveGlobals set, we loop
  // through the program, deleting those which are not alive.
  //

  // The first pass is to drop initializers of global variables which are dead.
  std::vector<GlobalVariable*> DeadGlobalVars;   // Keep track of dead globals
  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
       I != E; ++I)
    if (!AliveGlobals.count(I)) {
      DeadGlobalVars.push_back(I);         // Keep track of dead globals
      I->setInitializer(0);
    }

  // The second pass drops the bodies of functions which are dead...
  std::vector<Function*> DeadFunctions;
  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
    if (!AliveGlobals.count(I)) {
      DeadFunctions.push_back(I);         // Keep track of dead globals
      if (!I->isDeclaration())
        I->deleteBody();
    }

  // The third pass drops targets of aliases which are dead...
  std::vector<GlobalAlias*> DeadAliases;
  for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); I != E;
       ++I)
    if (!AliveGlobals.count(I)) {
      DeadAliases.push_back(I);
      I->setAliasee(0);
    }

  if (!DeadFunctions.empty()) {
    // Now that all interferences have been dropped, delete the actual objects
    // themselves.
    for (unsigned i = 0, e = DeadFunctions.size(); i != e; ++i) {
      RemoveUnusedGlobalValue(*DeadFunctions[i]);
      M.getFunctionList().erase(DeadFunctions[i]);
    }
    NumFunctions += DeadFunctions.size();
    Changed = true;
  }

  if (!DeadGlobalVars.empty()) {
    for (unsigned i = 0, e = DeadGlobalVars.size(); i != e; ++i) {
      RemoveUnusedGlobalValue(*DeadGlobalVars[i]);
      M.getGlobalList().erase(DeadGlobalVars[i]);
    }
    NumVariables += DeadGlobalVars.size();
    Changed = true;
  }

  // Now delete any dead aliases.
  if (!DeadAliases.empty()) {
    for (unsigned i = 0, e = DeadAliases.size(); i != e; ++i) {
      RemoveUnusedGlobalValue(*DeadAliases[i]);
      M.getAliasList().erase(DeadAliases[i]);
    }
    NumAliases += DeadAliases.size();
    Changed = true;
  }

  // Make sure that all memory is released
  AliveGlobals.clear();

  return Changed;
}