text: //===-- AddressSanitizer.cpp - memory error detector ------------*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file is a part of AddressSanitizer, an address sanity checker.
  // Details of the algorithm:
  //  http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/Transforms/Instrumentation.h"
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/DenseSet.h"
  #include "llvm/ADT/DepthFirstIterator.h"
  #include "llvm/ADT/SmallSet.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/Statistic.h"
  #include "llvm/ADT/StringExtras.h"
  #include "llvm/ADT/Triple.h"
  #include "llvm/Analysis/MemoryBuiltins.h"
  #include "llvm/Analysis/TargetLibraryInfo.h"
  #include "llvm/Analysis/ValueTracking.h"
  #include "llvm/IR/CallSite.h"
  #include "llvm/IR/DIBuilder.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/Dominators.h"
  #include "llvm/IR/Function.h"
  #include "llvm/IR/IRBuilder.h"
  #include "llvm/IR/InlineAsm.h"
  #include "llvm/IR/InstVisitor.h"
  #include "llvm/IR/IntrinsicInst.h"
  #include "llvm/IR/LLVMContext.h"
  #include "llvm/IR/MDBuilder.h"
  #include "llvm/IR/Module.h"
  #include "llvm/IR/Type.h"
  #include "llvm/MC/MCSectionMachO.h"
  #include "llvm/Support/CommandLine.h"
  #include "llvm/Support/DataTypes.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/Endian.h"
  #include "llvm/Support/SwapByteOrder.h"
  #include "llvm/Support/raw_ostream.h"
  #include "llvm/Transforms/Scalar.h"
  #include "llvm/Transforms/Utils/ASanStackFrameLayout.h"
  #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  #include "llvm/Transforms/Utils/Cloning.h"
  #include "llvm/Transforms/Utils/Local.h"
  #include "llvm/Transforms/Utils/ModuleUtils.h"
  #include "llvm/Transforms/Utils/PromoteMemToReg.h"
  #include <algorithm>
  #include <string>
  #include <system_error>
  
  using namespace llvm;
  
  #define DEBUG_TYPE "asan"
  
  static const uint64_t kDefaultShadowScale = 3;
  static const uint64_t kDefaultShadowOffset32 = 1ULL << 29;
  static const uint64_t kIOSShadowOffset32 = 1ULL << 30;
  static const uint64_t kDefaultShadowOffset64 = 1ULL << 44;
  static const uint64_t kSmallX86_64ShadowOffset = 0x7FFF8000;  // < 2G.
  static const uint64_t kLinuxKasan_ShadowOffset64 = 0xdffffc0000000000;
  static const uint64_t kPPC64_ShadowOffset64 = 1ULL << 41;
  static const uint64_t kMIPS32_ShadowOffset32 = 0x0aaa0000;
  static const uint64_t kMIPS64_ShadowOffset64 = 1ULL << 37;
  static const uint64_t kAArch64_ShadowOffset64 = 1ULL << 36;
  static const uint64_t kFreeBSD_ShadowOffset32 = 1ULL << 30;
  static const uint64_t kFreeBSD_ShadowOffset64 = 1ULL << 46;
  static const uint64_t kWindowsShadowOffset32 = 3ULL << 28;
  
  static const size_t kMinStackMallocSize = 1 << 6;   // 64B
  static const size_t kMaxStackMallocSize = 1 << 16;  // 64K
  static const uintptr_t kCurrentStackFrameMagic = 0x41B58AB3;
  static const uintptr_t kRetiredStackFrameMagic = 0x45E0360E;
  
  static const char *const kAsanModuleCtorName = "asan.module_ctor";
  static const char *const kAsanModuleDtorName = "asan.module_dtor";
  static const uint64_t kAsanCtorAndDtorPriority = 1;
  static const char *const kAsanReportErrorTemplate = "__asan_report_";
  static const char *const kAsanRegisterGlobalsName = "__asan_register_globals";
  static const char *const kAsanUnregisterGlobalsName =
      "__asan_unregister_globals";
  static const char *const kAsanPoisonGlobalsName = "__asan_before_dynamic_init";
  static const char *const kAsanUnpoisonGlobalsName = "__asan_after_dynamic_init";
  static const char *const kAsanInitName = "__asan_init_v5";
  static const char *const kAsanPtrCmp = "__sanitizer_ptr_cmp";
  static const char *const kAsanPtrSub = "__sanitizer_ptr_sub";
  static const char *const kAsanHandleNoReturnName = "__asan_handle_no_return";
  static const int kMaxAsanStackMallocSizeClass = 10;
  static const char *const kAsanStackMallocNameTemplate = "__asan_stack_malloc_";
  static const char *const kAsanStackFreeNameTemplate = "__asan_stack_free_";
  static const char *const kAsanGenPrefix = "__asan_gen_";
  static const char *const kSanCovGenPrefix = "__sancov_gen_";
  static const char *const kAsanPoisonStackMemoryName =
      "__asan_poison_stack_memory";
  static const char *const kAsanUnpoisonStackMemoryName =
      "__asan_unpoison_stack_memory";
  
  static const char *const kAsanOptionDetectUAR =
      "__asan_option_detect_stack_use_after_return";
  
  static const char *const kAsanAllocaPoison = "__asan_alloca_poison";
  static const char *const kAsanAllocasUnpoison = "__asan_allocas_unpoison";
  
  // Accesses sizes are powers of two: 1, 2, 4, 8, 16.
  static const size_t kNumberOfAccessSizes = 5;
  
  static const unsigned kAllocaRzSize = 32;
  
  // Command-line flags.
  static cl::opt<bool> ClEnableKasan(
      "asan-kernel", cl::desc("Enable KernelAddressSanitizer instrumentation"),
      cl::Hidden, cl::init(false));
  
  // This flag may need to be replaced with -f[no-]asan-reads.
  static cl::opt<bool> ClInstrumentReads("asan-instrument-reads",
                                         cl::desc("instrument read instructions"),
                                         cl::Hidden, cl::init(true));
  static cl::opt<bool> ClInstrumentWrites(
      "asan-instrument-writes", cl::desc("instrument write instructions"),
      cl::Hidden, cl::init(true));
  static cl::opt<bool> ClInstrumentAtomics(
      "asan-instrument-atomics",
      cl::desc("instrument atomic instructions (rmw, cmpxchg)"), cl::Hidden,
      cl::init(true));
  static cl::opt<bool> ClAlwaysSlowPath(
      "asan-always-slow-path",
      cl::desc("use instrumentation with slow path for all accesses"), cl::Hidden,
      cl::init(false));
  // This flag limits the number of instructions to be instrumented
  // in any given BB. Normally, this should be set to unlimited (INT_MAX),
  // but due to http://llvm.org/bugs/show_bug.cgi?id=12652 we temporary
  // set it to 10000.
  static cl::opt<int> ClMaxInsnsToInstrumentPerBB(
      "asan-max-ins-per-bb", cl::init(10000),
      cl::desc("maximal number of instructions to instrument in any given BB"),
      cl::Hidden);
  // This flag may need to be replaced with -f[no]asan-stack.
  static cl::opt<bool> ClStack("asan-stack", cl::desc("Handle stack memory"),
                               cl::Hidden, cl::init(true));
  static cl::opt<bool> ClUseAfterReturn("asan-use-after-return",
                                        cl::desc("Check return-after-free"),
                                        cl::Hidden, cl::init(true));
  // This flag may need to be replaced with -f[no]asan-globals.
  static cl::opt<bool> ClGlobals("asan-globals",
                                 cl::desc("Handle global objects"), cl::Hidden,
                                 cl::init(true));
  static cl::opt<bool> ClInitializers("asan-initialization-order",
                                      cl::desc("Handle C++ initializer order"),
                                      cl::Hidden, cl::init(true));
  static cl::opt<bool> ClInvalidPointerPairs(
      "asan-detect-invalid-pointer-pair",
      cl::desc("Instrument <, <=, >, >=, - with pointer operands"), cl::Hidden,
      cl::init(false));
  static cl::opt<unsigned> ClRealignStack(
      "asan-realign-stack",
      cl::desc("Realign stack to the value of this flag (power of two)"),
      cl::Hidden, cl::init(32));
  static cl::opt<int> ClInstrumentationWithCallsThreshold(
      "asan-instrumentation-with-call-threshold",
      cl::desc(
          "If the function being instrumented contains more than "
          "this number of memory accesses, use callbacks instead of "
          "inline checks (-1 means never use callbacks)."),
      cl::Hidden, cl::init(7000));
  static cl::opt<std::string> ClMemoryAccessCallbackPrefix(
      "asan-memory-access-callback-prefix",
      cl::desc("Prefix for memory access callbacks"), cl::Hidden,
      cl::init("__asan_"));
  static cl::opt<bool> ClInstrumentAllocas("asan-instrument-allocas",
                                           cl::desc("instrument dynamic allocas"),
                                           cl::Hidden, cl::init(false));
  static cl::opt<bool> ClSkipPromotableAllocas(
      "asan-skip-promotable-allocas",
      cl::desc("Do not instrument promotable allocas"), cl::Hidden,
      cl::init(true));
  
  // These flags allow to change the shadow mapping.
  // The shadow mapping looks like
  //    Shadow = (Mem >> scale) + (1 << offset_log)
  static cl::opt<int> ClMappingScale("asan-mapping-scale",
                                     cl::desc("scale of asan shadow mapping"),
                                     cl::Hidden, cl::init(0));
  
  // Optimization flags. Not user visible, used mostly for testing
  // and benchmarking the tool.
  static cl::opt<bool> ClOpt("asan-opt", cl::desc("Optimize instrumentation"),
                             cl::Hidden, cl::init(true));
  static cl::opt<bool> ClOptSameTemp(
      "asan-opt-same-temp", cl::desc("Instrument the same temp just once"),
      cl::Hidden, cl::init(true));
  static cl::opt<bool> ClOptGlobals("asan-opt-globals",
                                    cl::desc("Don't instrument scalar globals"),
                                    cl::Hidden, cl::init(true));
  static cl::opt<bool> ClOptStack(
      "asan-opt-stack", cl::desc("Don't instrument scalar stack variables"),
      cl::Hidden, cl::init(false));
  
  static cl::opt<bool> ClCheckLifetime(
      "asan-check-lifetime",
      cl::desc("Use llvm.lifetime intrinsics to insert extra checks"), cl::Hidden,
      cl::init(false));
  
  static cl::opt<bool> ClDynamicAllocaStack(
      "asan-stack-dynamic-alloca",
      cl::desc("Use dynamic alloca to represent stack variables"), cl::Hidden,
      cl::init(true));
  
  static cl::opt<uint32_t> ClForceExperiment(
      "asan-force-experiment",
      cl::desc("Force optimization experiment (for testing)"), cl::Hidden,
      cl::init(0));
  
  // Debug flags.
  static cl::opt<int> ClDebug("asan-debug", cl::desc("debug"), cl::Hidden,
                              cl::init(0));
  static cl::opt<int> ClDebugStack("asan-debug-stack", cl::desc("debug stack"),
                                   cl::Hidden, cl::init(0));
  static cl::opt<std::string> ClDebugFunc("asan-debug-func", cl::Hidden,
                                          cl::desc("Debug func"));
  static cl::opt<int> ClDebugMin("asan-debug-min", cl::desc("Debug min inst"),
                                 cl::Hidden, cl::init(-1));
  static cl::opt<int> ClDebugMax("asan-debug-max", cl::desc("Debug man inst"),
                                 cl::Hidden, cl::init(-1));
  
  STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
  STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
  STATISTIC(NumOptimizedAccessesToGlobalVar,
            "Number of optimized accesses to global vars");
  STATISTIC(NumOptimizedAccessesToStackVar,
            "Number of optimized accesses to stack vars");
  
  namespace {
  /// Frontend-provided metadata for source location.
  struct LocationMetadata {
    StringRef Filename;
    int LineNo;
    int ColumnNo;
  
    LocationMetadata() : Filename(), LineNo(0), ColumnNo(0) {}
  
    bool empty() const { return Filename.empty(); }
  
    void parse(MDNode *MDN) {
      assert(MDN->getNumOperands() == 3);
      MDString *DIFilename = cast<MDString>(MDN->getOperand(0));
      Filename = DIFilename->getString();
      LineNo =
          mdconst::extract<ConstantInt>(MDN->getOperand(1))->getLimitedValue();
      ColumnNo =
          mdconst::extract<ConstantInt>(MDN->getOperand(2))->getLimitedValue();
    }
  };
  
  /// Frontend-provided metadata for global variables.
  class GlobalsMetadata {
   public:
    struct Entry {
      Entry() : SourceLoc(), Name(), IsDynInit(false), IsBlacklisted(false) {}
      LocationMetadata SourceLoc;
      StringRef Name;
      bool IsDynInit;
      bool IsBlacklisted;
    };
  
    GlobalsMetadata() : inited_(false) {}
  
    void init(Module &M) {
      assert(!inited_);
      inited_ = true;
      NamedMDNode *Globals = M.getNamedMetadata("llvm.asan.globals");
      if (!Globals) return;
      for (auto MDN : Globals->operands()) {
        // Metadata node contains the global and the fields of "Entry".
        assert(MDN->getNumOperands() == 5);
        auto *GV = mdconst::extract_or_null<GlobalVariable>(MDN->getOperand(0));
        // The optimizer may optimize away a global entirely.
        if (!GV) continue;
        // We can already have an entry for GV if it was merged with another
        // global.
        Entry &E = Entries[GV];
        if (auto *Loc = cast_or_null<MDNode>(MDN->getOperand(1)))
          E.SourceLoc.parse(Loc);
        if (auto *Name = cast_or_null<MDString>(MDN->getOperand(2)))
          E.Name = Name->getString();
        ConstantInt *IsDynInit =
            mdconst::extract<ConstantInt>(MDN->getOperand(3));
        E.IsDynInit |= IsDynInit->isOne();
        ConstantInt *IsBlacklisted =
            mdconst::extract<ConstantInt>(MDN->getOperand(4));
        E.IsBlacklisted |= IsBlacklisted->isOne();
      }
    }
  
    /// Returns metadata entry for a given global.
    Entry get(GlobalVariable *G) const {
      auto Pos = Entries.find(G);
      return (Pos != Entries.end()) ? Pos->second : Entry();
    }
  
   private:
    bool inited_;
    DenseMap<GlobalVariable *, Entry> Entries;
  };
  
  /// This struct defines the shadow mapping using the rule:
  ///   shadow = (mem >> Scale) ADD-or-OR Offset.
  struct ShadowMapping {
    int Scale;
    uint64_t Offset;
    bool OrShadowOffset;
  };
  
  static ShadowMapping getShadowMapping(Triple &TargetTriple, int LongSize,
                                        bool IsKasan) {
    bool IsAndroid = TargetTriple.getEnvironment() == llvm::Triple::Android;
    bool IsIOS = TargetTriple.isiOS();
    bool IsFreeBSD = TargetTriple.isOSFreeBSD();
    bool IsLinux = TargetTriple.isOSLinux();
    bool IsPPC64 = TargetTriple.getArch() == llvm::Triple::ppc64 ||
                   TargetTriple.getArch() == llvm::Triple::ppc64le;
    bool IsX86_64 = TargetTriple.getArch() == llvm::Triple::x86_64;
    bool IsMIPS32 = TargetTriple.getArch() == llvm::Triple::mips ||
                    TargetTriple.getArch() == llvm::Triple::mipsel;
    bool IsMIPS64 = TargetTriple.getArch() == llvm::Triple::mips64 ||
                    TargetTriple.getArch() == llvm::Triple::mips64el;
    bool IsAArch64 = TargetTriple.getArch() == llvm::Triple::aarch64;
    bool IsWindows = TargetTriple.isOSWindows();
  
    ShadowMapping Mapping;
  
    if (LongSize == 32) {
      if (IsAndroid)
        Mapping.Offset = 0;
      else if (IsMIPS32)
        Mapping.Offset = kMIPS32_ShadowOffset32;
      else if (IsFreeBSD)
        Mapping.Offset = kFreeBSD_ShadowOffset32;
      else if (IsIOS)
        Mapping.Offset = kIOSShadowOffset32;
      else if (IsWindows)
        Mapping.Offset = kWindowsShadowOffset32;
      else
        Mapping.Offset = kDefaultShadowOffset32;
    } else {  // LongSize == 64
      if (IsPPC64)
        Mapping.Offset = kPPC64_ShadowOffset64;
      else if (IsFreeBSD)
        Mapping.Offset = kFreeBSD_ShadowOffset64;
      else if (IsLinux && IsX86_64) {
        if (IsKasan)
          Mapping.Offset = kLinuxKasan_ShadowOffset64;
        else
          Mapping.Offset = kSmallX86_64ShadowOffset;
      } else if (IsMIPS64)
        Mapping.Offset = kMIPS64_ShadowOffset64;
      else if (IsAArch64)
        Mapping.Offset = kAArch64_ShadowOffset64;
      else
        Mapping.Offset = kDefaultShadowOffset64;
    }
  
    Mapping.Scale = kDefaultShadowScale;
    if (ClMappingScale) {
      Mapping.Scale = ClMappingScale;
    }
  
    // OR-ing shadow offset if more efficient (at least on x86) if the offset
    // is a power of two, but on ppc64 we have to use add since the shadow
    // offset is not necessary 1/8-th of the address space.
    Mapping.OrShadowOffset = !IsPPC64 && !(Mapping.Offset & (Mapping.Offset - 1));
  
    return Mapping;
  }
  
  static size_t RedzoneSizeForScale(int MappingScale) {
    // Redzone used for stack and globals is at least 32 bytes.
    // For scales 6 and 7, the redzone has to be 64 and 128 bytes respectively.
    return std::max(32U, 1U << MappingScale);
  }
  
  /// AddressSanitizer: instrument the code in module to find memory bugs.
  struct AddressSanitizer : public FunctionPass {
    explicit AddressSanitizer(bool CompileKernel = false)
        : FunctionPass(ID), CompileKernel(CompileKernel || ClEnableKasan) {
      initializeAddressSanitizerPass(*PassRegistry::getPassRegistry());
    }
    const char *getPassName() const override {
      return "AddressSanitizerFunctionPass";
    }
    void getAnalysisUsage(AnalysisUsage &AU) const override {
      AU.addRequired<DominatorTreeWrapperPass>();
      AU.addRequired<TargetLibraryInfoWrapperPass>();
    }
    uint64_t getAllocaSizeInBytes(AllocaInst *AI) const {
      Type *Ty = AI->getAllocatedType();
      uint64_t SizeInBytes =
          AI->getModule()->getDataLayout().getTypeAllocSize(Ty);
      return SizeInBytes;
    }
    /// Check if we want (and can) handle this alloca.
    bool isInterestingAlloca(AllocaInst &AI);
  
    // Check if we have dynamic alloca.
    bool isDynamicAlloca(AllocaInst &AI) const {
      return AI.isArrayAllocation() || !AI.isStaticAlloca();
    }
  
    /// If it is an interesting memory access, return the PointerOperand
    /// and set IsWrite/Alignment. Otherwise return nullptr.
    Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite,
                                     uint64_t *TypeSize, unsigned *Alignment);
    void instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis, Instruction *I,
                       bool UseCalls, const DataLayout &DL);
    void instrumentPointerComparisonOrSubtraction(Instruction *I);
    void instrumentAddress(Instruction *OrigIns, Instruction *InsertBefore,
                           Value *Addr, uint32_t TypeSize, bool IsWrite,
                           Value *SizeArgument, bool UseCalls, uint32_t Exp);
    void instrumentUnusualSizeOrAlignment(Instruction *I, Value *Addr,
                                          uint32_t TypeSize, bool IsWrite,
                                          Value *SizeArgument, bool UseCalls,
                                          uint32_t Exp);
    Value *createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
                             Value *ShadowValue, uint32_t TypeSize);
    Instruction *generateCrashCode(Instruction *InsertBefore, Value *Addr,
                                   bool IsWrite, size_t AccessSizeIndex,
                                   Value *SizeArgument, uint32_t Exp);
    void instrumentMemIntrinsic(MemIntrinsic *MI);
    Value *memToShadow(Value *Shadow, IRBuilder<> &IRB);
    bool runOnFunction(Function &F) override;
    bool maybeInsertAsanInitAtFunctionEntry(Function &F);
    bool doInitialization(Module &M) override;
    static char ID;  // Pass identification, replacement for typeid
  
    DominatorTree &getDominatorTree() const { return *DT; }
  
   private:
    void initializeCallbacks(Module &M);
  
    bool LooksLikeCodeInBug11395(Instruction *I);
    bool GlobalIsLinkerInitialized(GlobalVariable *G);
    bool isSafeAccess(ObjectSizeOffsetVisitor &ObjSizeVis, Value *Addr,
                      uint64_t TypeSize) const;
  
    LLVMContext *C;
    Triple TargetTriple;
    int LongSize;
    bool CompileKernel;
    Type *IntptrTy;
    ShadowMapping Mapping;
    DominatorTree *DT;
    Function *AsanCtorFunction = nullptr;
    Function *AsanInitFunction = nullptr;
    Function *AsanHandleNoReturnFunc;
    Function *AsanPtrCmpFunction, *AsanPtrSubFunction;
    // This array is indexed by AccessIsWrite, Experiment and log2(AccessSize).
    Function *AsanErrorCallback[2][2][kNumberOfAccessSizes];
    Function *AsanMemoryAccessCallback[2][2][kNumberOfAccessSizes];
    // This array is indexed by AccessIsWrite and Experiment.
    Function *AsanErrorCallbackSized[2][2];
    Function *AsanMemoryAccessCallbackSized[2][2];
    Function *AsanMemmove, *AsanMemcpy, *AsanMemset;
    InlineAsm *EmptyAsm;
    GlobalsMetadata GlobalsMD;
    DenseMap<AllocaInst *, bool> ProcessedAllocas;
  
    friend struct FunctionStackPoisoner;
  };
  
  class AddressSanitizerModule : public ModulePass {
   public:
    explicit AddressSanitizerModule(bool CompileKernel = false)
        : ModulePass(ID), CompileKernel(CompileKernel || ClEnableKasan) {}
    bool runOnModule(Module &M) override;
    static char ID;  // Pass identification, replacement for typeid
    const char *getPassName() const override { return "AddressSanitizerModule"; }
  
   private:
    void initializeCallbacks(Module &M);
  
    bool InstrumentGlobals(IRBuilder<> &IRB, Module &M);
    bool ShouldInstrumentGlobal(GlobalVariable *G);
    void poisonOneInitializer(Function &GlobalInit, GlobalValue *ModuleName);
    void createInitializerPoisonCalls(Module &M, GlobalValue *ModuleName);
    size_t MinRedzoneSizeForGlobal() const {
      return RedzoneSizeForScale(Mapping.Scale);
    }
  
    GlobalsMetadata GlobalsMD;
    bool CompileKernel;
    Type *IntptrTy;
    LLVMContext *C;
    Triple TargetTriple;
    ShadowMapping Mapping;
    Function *AsanPoisonGlobals;
    Function *AsanUnpoisonGlobals;
    Function *AsanRegisterGlobals;
    Function *AsanUnregisterGlobals;
  };
  
  // Stack poisoning does not play well with exception handling.
  // When an exception is thrown, we essentially bypass the code
  // that unpoisones the stack. This is why the run-time library has
  // to intercept __cxa_throw (as well as longjmp, etc) and unpoison the entire
  // stack in the interceptor. This however does not work inside the
  // actual function which catches the exception. Most likely because the
  // compiler hoists the load of the shadow value somewhere too high.
  // This causes asan to report a non-existing bug on 453.povray.
  // It sounds like an LLVM bug.
  struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
    Function &F;
    AddressSanitizer &ASan;
    DIBuilder DIB;
    LLVMContext *C;
    Type *IntptrTy;
    Type *IntptrPtrTy;
    ShadowMapping Mapping;
  
    SmallVector<AllocaInst *, 16> AllocaVec;
    SmallVector<Instruction *, 8> RetVec;
    unsigned StackAlignment;
  
    Function *AsanStackMallocFunc[kMaxAsanStackMallocSizeClass + 1],
        *AsanStackFreeFunc[kMaxAsanStackMallocSizeClass + 1];
    Function *AsanPoisonStackMemoryFunc, *AsanUnpoisonStackMemoryFunc;
    Function *AsanAllocaPoisonFunc, *AsanAllocasUnpoisonFunc;
  
    // Stores a place and arguments of poisoning/unpoisoning call for alloca.
    struct AllocaPoisonCall {
      IntrinsicInst *InsBefore;
      AllocaInst *AI;
      uint64_t Size;
      bool DoPoison;
    };
    SmallVector<AllocaPoisonCall, 8> AllocaPoisonCallVec;
  
    SmallVector<AllocaInst *, 1> DynamicAllocaVec;
    SmallVector<IntrinsicInst *, 1> StackRestoreVec;
    AllocaInst *DynamicAllocaLayout = nullptr;
  
    // Maps Value to an AllocaInst from which the Value is originated.
    typedef DenseMap<Value *, AllocaInst *> AllocaForValueMapTy;
    AllocaForValueMapTy AllocaForValue;
  
    bool HasNonEmptyInlineAsm;
    std::unique_ptr<CallInst> EmptyInlineAsm;
  
    FunctionStackPoisoner(Function &F, AddressSanitizer &ASan)
        : F(F),
          ASan(ASan),
          DIB(*F.getParent(), /*AllowUnresolved*/ false),
          C(ASan.C),
          IntptrTy(ASan.IntptrTy),
          IntptrPtrTy(PointerType::get(IntptrTy, 0)),
          Mapping(ASan.Mapping),
          StackAlignment(1 << Mapping.Scale),
          HasNonEmptyInlineAsm(false),
          EmptyInlineAsm(CallInst::Create(ASan.EmptyAsm)) {}
  
    bool runOnFunction() {
      if (!ClStack) return false;
      // Collect alloca, ret, lifetime instructions etc.
      for (BasicBlock *BB : depth_first(&F.getEntryBlock())) visit(*BB);
  
      if (AllocaVec.empty() && DynamicAllocaVec.empty()) return false;
  
      initializeCallbacks(*F.getParent());
  
      poisonStack();
  
      if (ClDebugStack) {
        DEBUG(dbgs() << F);
      }
      return true;
    }
  
    // Finds all Alloca instructions and puts
    // poisoned red zones around all of them.
    // Then unpoison everything back before the function returns.
    void poisonStack();
  
    void createDynamicAllocasInitStorage();
  
    // ----------------------- Visitors.
    /// \brief Collect all Ret instructions.
    void visitReturnInst(ReturnInst &RI) { RetVec.push_back(&RI); }
  
    void unpoisonDynamicAllocasBeforeInst(Instruction *InstBefore,
                                          Value *SavedStack) {
      IRBuilder<> IRB(InstBefore);
      IRB.CreateCall(AsanAllocasUnpoisonFunc,
                     {IRB.CreateLoad(DynamicAllocaLayout),
                      IRB.CreatePtrToInt(SavedStack, IntptrTy)});
    }
  
    // Unpoison dynamic allocas redzones.
    void unpoisonDynamicAllocas() {
      for (auto &Ret : RetVec)
        unpoisonDynamicAllocasBeforeInst(Ret, DynamicAllocaLayout);
  
      for (auto &StackRestoreInst : StackRestoreVec)
        unpoisonDynamicAllocasBeforeInst(StackRestoreInst,
                                         StackRestoreInst->getOperand(0));
    }
  
    // Deploy and poison redzones around dynamic alloca call. To do this, we
    // should replace this call with another one with changed parameters and
    // replace all its uses with new address, so
    //   addr = alloca type, old_size, align
    // is replaced by
    //   new_size = (old_size + additional_size) * sizeof(type)
    //   tmp = alloca i8, new_size, max(align, 32)
    //   addr = tmp + 32 (first 32 bytes are for the left redzone).
    // Additional_size is added to make new memory allocation contain not only
    // requested memory, but also left, partial and right redzones.
    void handleDynamicAllocaCall(AllocaInst *AI);
  
    /// \brief Collect Alloca instructions we want (and can) handle.
    void visitAllocaInst(AllocaInst &AI) {
      if (!ASan.isInterestingAlloca(AI)) return;
  
      StackAlignment = std::max(StackAlignment, AI.getAlignment());
      if (ASan.isDynamicAlloca(AI))
        DynamicAllocaVec.push_back(&AI);
      else
        AllocaVec.push_back(&AI);
    }
  
    /// \brief Collect lifetime intrinsic calls to check for use-after-scope
    /// errors.
    void visitIntrinsicInst(IntrinsicInst &II) {
      Intrinsic::ID ID = II.getIntrinsicID();
      if (ID == Intrinsic::stackrestore) StackRestoreVec.push_back(&II);
      if (!ClCheckLifetime) return;
      if (ID != Intrinsic::lifetime_start && ID != Intrinsic::lifetime_end)
        return;
      // Found lifetime intrinsic, add ASan instrumentation if necessary.
      ConstantInt *Size = dyn_cast<ConstantInt>(II.getArgOperand(0));
      // If size argument is undefined, don't do anything.
      if (Size->isMinusOne()) return;
      // Check that size doesn't saturate uint64_t and can
      // be stored in IntptrTy.
      const uint64_t SizeValue = Size->getValue().getLimitedValue();
      if (SizeValue == ~0ULL ||
          !ConstantInt::isValueValidForType(IntptrTy, SizeValue))
        return;
      // Find alloca instruction that corresponds to llvm.lifetime argument.
      AllocaInst *AI = findAllocaForValue(II.getArgOperand(1));
      if (!AI) return;
      bool DoPoison = (ID == Intrinsic::lifetime_end);
      AllocaPoisonCall APC = {&II, AI, SizeValue, DoPoison};
      AllocaPoisonCallVec.push_back(APC);
    }
  
    void visitCallInst(CallInst &CI) {
      HasNonEmptyInlineAsm |=
          CI.isInlineAsm() && !CI.isIdenticalTo(EmptyInlineAsm.get());
    }
  
    // ---------------------- Helpers.
    void initializeCallbacks(Module &M);
  
    bool doesDominateAllExits(const Instruction *I) const {
      for (auto Ret : RetVec) {
        if (!ASan.getDominatorTree().dominates(I, Ret)) return false;
      }
      return true;
    }
  
    /// Finds alloca where the value comes from.
    AllocaInst *findAllocaForValue(Value *V);
    void poisonRedZones(ArrayRef<uint8_t> ShadowBytes, IRBuilder<> &IRB,
                        Value *ShadowBase, bool DoPoison);
    void poisonAlloca(Value *V, uint64_t Size, IRBuilder<> &IRB, bool DoPoison);
  
    void SetShadowToStackAfterReturnInlined(IRBuilder<> &IRB, Value *ShadowBase,
                                            int Size);
    Value *createAllocaForLayout(IRBuilder<> &IRB, const ASanStackFrameLayout &L,
                                 bool Dynamic);
    PHINode *createPHI(IRBuilder<> &IRB, Value *Cond, Value *ValueIfTrue,
                       Instruction *ThenTerm, Value *ValueIfFalse);
  };
  
  }  // namespace
  
  char AddressSanitizer::ID = 0;
  INITIALIZE_PASS_BEGIN(
      AddressSanitizer, "asan",
      "AddressSanitizer: detects use-after-free and out-of-bounds bugs.", false,
      false)
  INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
  INITIALIZE_PASS_END(
      AddressSanitizer, "asan",
      "AddressSanitizer: detects use-after-free and out-of-bounds bugs.", false,
      false)
  FunctionPass *llvm::createAddressSanitizerFunctionPass(bool CompileKernel) {
    return new AddressSanitizer(CompileKernel);
  }
  
  char AddressSanitizerModule::ID = 0;
  INITIALIZE_PASS(
      AddressSanitizerModule, "asan-module",
      "AddressSanitizer: detects use-after-free and out-of-bounds bugs."
      "ModulePass",
      false, false)
  ModulePass *llvm::createAddressSanitizerModulePass(bool CompileKernel) {
    return new AddressSanitizerModule(CompileKernel);
  }
  
  static size_t TypeSizeToSizeIndex(uint32_t TypeSize) {
    size_t Res = countTrailingZeros(TypeSize / 8);
    assert(Res < kNumberOfAccessSizes);
    return Res;
  }
  
  // \brief Create a constant for Str so that we can pass it to the run-time lib.
  static GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str,
                                                      bool AllowMerging) {
    Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
    // We use private linkage for module-local strings. If they can be merged
    // with another one, we set the unnamed_addr attribute.
    GlobalVariable *GV =
        new GlobalVariable(M, StrConst->getType(), true,
                           GlobalValue::PrivateLinkage, StrConst, kAsanGenPrefix);
    if (AllowMerging) GV->setUnnamedAddr(true);
    GV->setAlignment(1);  // Strings may not be merged w/o setting align 1.
    return GV;
  }
  
  /// \brief Create a global describing a source location.
  static GlobalVariable *createPrivateGlobalForSourceLoc(Module &M,
                                                         LocationMetadata MD) {
    Constant *LocData[] = {
        createPrivateGlobalForString(M, MD.Filename, true),
        ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.LineNo),
        ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.ColumnNo),
    };
    auto LocStruct = ConstantStruct::getAnon(LocData);
    auto GV = new GlobalVariable(M, LocStruct->getType(), true,
                                 GlobalValue::PrivateLinkage, LocStruct,
                                 kAsanGenPrefix);
    GV->setUnnamedAddr(true);
    return GV;
  }
  
  static bool GlobalWasGeneratedByAsan(GlobalVariable *G) {
    return G->getName().find(kAsanGenPrefix) == 0 ||
           G->getName().find(kSanCovGenPrefix) == 0;
  }
  
  Value *AddressSanitizer::memToShadow(Value *Shadow, IRBuilder<> &IRB) {
    // Shadow >> scale
    Shadow = IRB.CreateLShr(Shadow, Mapping.Scale);
    if (Mapping.Offset == 0) return Shadow;
    // (Shadow >> scale) | offset
    if (Mapping.OrShadowOffset)
      return IRB.CreateOr(Shadow, ConstantInt::get(IntptrTy, Mapping.Offset));
    else
      return IRB.CreateAdd(Shadow, ConstantInt::get(IntptrTy, Mapping.Offset));
  }
  
  // Instrument memset/memmove/memcpy
  void AddressSanitizer::instrumentMemIntrinsic(MemIntrinsic *MI) {
    IRBuilder<> IRB(MI);
    if (isa<MemTransferInst>(MI)) {
      IRB.CreateCall(
          isa<MemMoveInst>(MI) ? AsanMemmove : AsanMemcpy,
          {IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()),
           IRB.CreatePointerCast(MI->getOperand(1), IRB.getInt8PtrTy()),
           IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false)});
    } else if (isa<MemSetInst>(MI)) {
      IRB.CreateCall(
          AsanMemset,
          {IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()),
           IRB.CreateIntCast(MI->getOperand(1), IRB.getInt32Ty(), false),
           IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false)});
    }
    MI->eraseFromParent();
  }
  
  /// Check if we want (and can) handle this alloca.
  bool AddressSanitizer::isInterestingAlloca(AllocaInst &AI) {
    auto PreviouslySeenAllocaInfo = ProcessedAllocas.find(&AI);
  
    if (PreviouslySeenAllocaInfo != ProcessedAllocas.end())
      return PreviouslySeenAllocaInfo->getSecond();
  
    bool IsInteresting =
        (AI.getAllocatedType()->isSized() &&
         // alloca() may be called with 0 size, ignore it.
         getAllocaSizeInBytes(&AI) > 0 &&
         // We are only interested in allocas not promotable to registers.
         // Promotable allocas are common under -O0.
         (!ClSkipPromotableAllocas || !isAllocaPromotable(&AI) ||
          isDynamicAlloca(AI)));
  
    ProcessedAllocas[&AI] = IsInteresting;
    return IsInteresting;
  }
  
  /// If I is an interesting memory access, return the PointerOperand
  /// and set IsWrite/Alignment. Otherwise return nullptr.
  Value *AddressSanitizer::isInterestingMemoryAccess(Instruction *I,
                                                     bool *IsWrite,
                                                     uint64_t *TypeSize,
                                                     unsigned *Alignment) {
    // Skip memory accesses inserted by another instrumentation.
    if (I->getMetadata("nosanitize")) return nullptr;
  
    Value *PtrOperand = nullptr;
    const DataLayout &DL = I->getModule()->getDataLayout();
    if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
      if (!ClInstrumentReads) return nullptr;
      *IsWrite = false;
      *TypeSize = DL.getTypeStoreSizeInBits(LI->getType());
      *Alignment = LI->getAlignment();
      PtrOperand = LI->getPointerOperand();
    } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
      if (!ClInstrumentWrites) return nullptr;
      *IsWrite = true;
      *TypeSize = DL.getTypeStoreSizeInBits(SI->getValueOperand()->getType());
      *Alignment = SI->getAlignment();
      PtrOperand = SI->getPointerOperand();
    } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
      if (!ClInstrumentAtomics) return nullptr;
      *IsWrite = true;
      *TypeSize = DL.getTypeStoreSizeInBits(RMW->getValOperand()->getType());
      *Alignment = 0;
      PtrOperand = RMW->getPointerOperand();
    } else if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) {
      if (!ClInstrumentAtomics) return nullptr;
      *IsWrite = true;
      *TypeSize = DL.getTypeStoreSizeInBits(XCHG->getCompareOperand()->getType());
      *Alignment = 0;
      PtrOperand = XCHG->getPointerOperand();
    }
  
    // Treat memory accesses to promotable allocas as non-interesting since they
    // will not cause memory violations. This greatly speeds up the instrumented
    // executable at -O0.
    if (ClSkipPromotableAllocas)
      if (auto AI = dyn_cast_or_null<AllocaInst>(PtrOperand))
        return isInterestingAlloca(*AI) ? AI : nullptr;
  
    return PtrOperand;
  }
  
  static bool isPointerOperand(Value *V) {
    return V->getType()->isPointerTy() || isa<PtrToIntInst>(V);
  }
  
  // This is a rough heuristic; it may cause both false positives and
  // false negatives. The proper implementation requires cooperation with
  // the frontend.
  static bool isInterestingPointerComparisonOrSubtraction(Instruction *I) {
    if (ICmpInst *Cmp = dyn_cast<ICmpInst>(I)) {
      if (!Cmp->isRelational()) return false;
    } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
      if (BO->getOpcode() != Instruction::Sub) return false;
    } else {
      return false;
    }
    if (!isPointerOperand(I->getOperand(0)) ||
        !isPointerOperand(I->getOperand(1)))
      return false;
    return true;
  }
  
  bool AddressSanitizer::GlobalIsLinkerInitialized(GlobalVariable *G) {
    // If a global variable does not have dynamic initialization we don't
    // have to instrument it.  However, if a global does not have initializer
    // at all, we assume it has dynamic initializer (in other TU).
    return G->hasInitializer() && !GlobalsMD.get(G).IsDynInit;
  }
  
  void AddressSanitizer::instrumentPointerComparisonOrSubtraction(
      Instruction *I) {
    IRBuilder<> IRB(I);
    Function *F = isa<ICmpInst>(I) ? AsanPtrCmpFunction : AsanPtrSubFunction;
    Value *Param[2] = {I->getOperand(0), I->getOperand(1)};
    for (int i = 0; i < 2; i++) {
      if (Param[i]->getType()->isPointerTy())
        Param[i] = IRB.CreatePointerCast(Param[i], IntptrTy);
    }
    IRB.CreateCall(F, Param);
  }
  
  void AddressSanitizer::instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis,
                                       Instruction *I, bool UseCalls,
                                       const DataLayout &DL) {
    bool IsWrite = false;
    unsigned Alignment = 0;
    uint64_t TypeSize = 0;
    Value *Addr = isInterestingMemoryAccess(I, &IsWrite, &TypeSize, &Alignment);
    assert(Addr);
  
    // Optimization experiments.
    // The experiments can be used to evaluate potential optimizations that remove
    // instrumentation (assess false negatives). Instead of completely removing
    // some instrumentation, you set Exp to a non-zero value (mask of optimization
    // experiments that want to remove instrumentation of this instruction).
    // If Exp is non-zero, this pass will emit special calls into runtime
    // (e.g. __asan_report_exp_load1 instead of __asan_report_load1). These calls
    // make runtime terminate the program in a special way (with a different
    // exit status). Then you run the new compiler on a buggy corpus, collect
    // the special terminations (ideally, you don't see them at all -- no false
    // negatives) and make the decision on the optimization.
    uint32_t Exp = ClForceExperiment;
  
    if (ClOpt && ClOptGlobals) {
      // If initialization order checking is disabled, a simple access to a
      // dynamically initialized global is always valid.
      GlobalVariable *G = dyn_cast<GlobalVariable>(GetUnderlyingObject(Addr, DL));
      if (G != NULL && (!ClInitializers || GlobalIsLinkerInitialized(G)) &&
          isSafeAccess(ObjSizeVis, Addr, TypeSize)) {
        NumOptimizedAccessesToGlobalVar++;
        return;
      }
    }
  
    if (ClOpt && ClOptStack) {
      // A direct inbounds access to a stack variable is always valid.
      if (isa<AllocaInst>(GetUnderlyingObject(Addr, DL)) &&
          isSafeAccess(ObjSizeVis, Addr, TypeSize)) {
        NumOptimizedAccessesToStackVar++;
        return;
      }
    }
  
    if (IsWrite)
      NumInstrumentedWrites++;
    else
      NumInstrumentedReads++;
  
    unsigned Granularity = 1 << Mapping.Scale;
    // Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check
    // if the data is properly aligned.
    if ((TypeSize == 8 || TypeSize == 16 || TypeSize == 32 || TypeSize == 64 ||
         TypeSize == 128) &&
        (Alignment >= Granularity || Alignment == 0 || Alignment >= TypeSize / 8))
      return instrumentAddress(I, I, Addr, TypeSize, IsWrite, nullptr, UseCalls,
                               Exp);
    instrumentUnusualSizeOrAlignment(I, Addr, TypeSize, IsWrite, nullptr,
                                     UseCalls, Exp);
  }
  
  Instruction *AddressSanitizer::generateCrashCode(Instruction *InsertBefore,
                                                   Value *Addr, bool IsWrite,
                                                   size_t AccessSizeIndex,
                                                   Value *SizeArgument,
                                                   uint32_t Exp) {
    IRBuilder<> IRB(InsertBefore);
    Value *ExpVal = Exp == 0 ? nullptr : ConstantInt::get(IRB.getInt32Ty(), Exp);
    CallInst *Call = nullptr;
    if (SizeArgument) {
      if (Exp == 0)
        Call = IRB.CreateCall(AsanErrorCallbackSized[IsWrite][0],
                              {Addr, SizeArgument});
      else
        Call = IRB.CreateCall(AsanErrorCallbackSized[IsWrite][1],
                              {Addr, SizeArgument, ExpVal});
    } else {
      if (Exp == 0)
        Call =
            IRB.CreateCall(AsanErrorCallback[IsWrite][0][AccessSizeIndex], Addr);
      else
        Call = IRB.CreateCall(AsanErrorCallback[IsWrite][1][AccessSizeIndex],
                              {Addr, ExpVal});
    }
  
    // We don't do Call->setDoesNotReturn() because the BB already has
    // UnreachableInst at the end.
    // This EmptyAsm is required to avoid callback merge.
    IRB.CreateCall(EmptyAsm, {});
    return Call;
  }
  
  Value *AddressSanitizer::createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
                                             Value *ShadowValue,
                                             uint32_t TypeSize) {
    size_t Granularity = 1 << Mapping.Scale;
    // Addr & (Granularity - 1)
    Value *LastAccessedByte =
        IRB.CreateAnd(AddrLong, ConstantInt::get(IntptrTy, Granularity - 1));
    // (Addr & (Granularity - 1)) + size - 1
    if (TypeSize / 8 > 1)
      LastAccessedByte = IRB.CreateAdd(
          LastAccessedByte, ConstantInt::get(IntptrTy, TypeSize / 8 - 1));
    // (uint8_t) ((Addr & (Granularity-1)) + size - 1)
    LastAccessedByte =
        IRB.CreateIntCast(LastAccessedByte, ShadowValue->getType(), false);
    // ((uint8_t) ((Addr & (Granularity-1)) + size - 1)) >= ShadowValue
    return IRB.CreateICmpSGE(LastAccessedByte, ShadowValue);
  }
  
  void AddressSanitizer::instrumentAddress(Instruction *OrigIns,
                                           Instruction *InsertBefore, Value *Addr,
                                           uint32_t TypeSize, bool IsWrite,
                                           Value *SizeArgument, bool UseCalls,
                                           uint32_t Exp) {
    IRBuilder<> IRB(InsertBefore);
    Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
    size_t AccessSizeIndex = TypeSizeToSizeIndex(TypeSize);
  
    if (UseCalls) {
      if (Exp == 0)
        IRB.CreateCall(AsanMemoryAccessCallback[IsWrite][0][AccessSizeIndex],
                       AddrLong);
      else
        IRB.CreateCall(AsanMemoryAccessCallback[IsWrite][1][AccessSizeIndex],
                       {AddrLong, ConstantInt::get(IRB.getInt32Ty(), Exp)});
      return;
    }
  
    Type *ShadowTy =
        IntegerType::get(*C, std::max(8U, TypeSize >> Mapping.Scale));
    Type *ShadowPtrTy = PointerType::get(ShadowTy, 0);
    Value *ShadowPtr = memToShadow(AddrLong, IRB);
    Value *CmpVal = Constant::getNullValue(ShadowTy);
    Value *ShadowValue =
        IRB.CreateLoad(IRB.CreateIntToPtr(ShadowPtr, ShadowPtrTy));
  
    Value *Cmp = IRB.CreateICmpNE(ShadowValue, CmpVal);
    size_t Granularity = 1 << Mapping.Scale;
    TerminatorInst *CrashTerm = nullptr;
  
    if (ClAlwaysSlowPath || (TypeSize < 8 * Granularity)) {
      // We use branch weights for the slow path check, to indicate that the slow
      // path is rarely taken. This seems to be the case for SPEC benchmarks.
      TerminatorInst *CheckTerm = SplitBlockAndInsertIfThen(
          Cmp, InsertBefore, false, MDBuilder(*C).createBranchWeights(1, 100000));
      assert(cast<BranchInst>(CheckTerm)->isUnconditional());
      BasicBlock *NextBB = CheckTerm->getSuccessor(0);
      IRB.SetInsertPoint(CheckTerm);
      Value *Cmp2 = createSlowPathCmp(IRB, AddrLong, ShadowValue, TypeSize);
      BasicBlock *CrashBlock =
          BasicBlock::Create(*C, "", NextBB->getParent(), NextBB);
      CrashTerm = new UnreachableInst(*C, CrashBlock);
      BranchInst *NewTerm = BranchInst::Create(CrashBlock, NextBB, Cmp2);
      ReplaceInstWithInst(CheckTerm, NewTerm);
    } else {
      CrashTerm = SplitBlockAndInsertIfThen(Cmp, InsertBefore, true);
    }
  
    Instruction *Crash = generateCrashCode(CrashTerm, AddrLong, IsWrite,
                                           AccessSizeIndex, SizeArgument, Exp);
    Crash->setDebugLoc(OrigIns->getDebugLoc());
  }
  
  // Instrument unusual size or unusual alignment.
  // We can not do it with a single check, so we do 1-byte check for the first
  // and the last bytes. We call __asan_report_*_n(addr, real_size) to be able
  // to report the actual access size.
  void AddressSanitizer::instrumentUnusualSizeOrAlignment(
      Instruction *I, Value *Addr, uint32_t TypeSize, bool IsWrite,
      Value *SizeArgument, bool UseCalls, uint32_t Exp) {
    IRBuilder<> IRB(I);
    Value *Size = ConstantInt::get(IntptrTy, TypeSize / 8);
    Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
    if (UseCalls) {
      if (Exp == 0)
        IRB.CreateCall(AsanMemoryAccessCallbackSized[IsWrite][0],
                       {AddrLong, Size});
      else
        IRB.CreateCall(AsanMemoryAccessCallbackSized[IsWrite][1],
                       {AddrLong, Size, ConstantInt::get(IRB.getInt32Ty(), Exp)});
    } else {
      Value *LastByte = IRB.CreateIntToPtr(
          IRB.CreateAdd(AddrLong, ConstantInt::get(IntptrTy, TypeSize / 8 - 1)),
          Addr->getType());
      instrumentAddress(I, I, Addr, 8, IsWrite, Size, false, Exp);
      instrumentAddress(I, I, LastByte, 8, IsWrite, Size, false, Exp);
    }
  }
  
  void AddressSanitizerModule::poisonOneInitializer(Function &GlobalInit,
                                                    GlobalValue *ModuleName) {
    // Set up the arguments to our poison/unpoison functions.
    IRBuilder<> IRB(GlobalInit.begin()->getFirstInsertionPt());
  
    // Add a call to poison all external globals before the given function starts.
    Value *ModuleNameAddr = ConstantExpr::getPointerCast(ModuleName, IntptrTy);
    IRB.CreateCall(AsanPoisonGlobals, ModuleNameAddr);
  
    // Add calls to unpoison all globals before each return instruction.
    for (auto &BB : GlobalInit.getBasicBlockList())
      if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator()))
        CallInst::Create(AsanUnpoisonGlobals, "", RI);
  }
  
  void AddressSanitizerModule::createInitializerPoisonCalls(
      Module &M, GlobalValue *ModuleName) {
    GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
  
    ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
    for (Use &OP : CA->operands()) {
      if (isa<ConstantAggregateZero>(OP)) continue;
      ConstantStruct *CS = cast<ConstantStruct>(OP);
  
      // Must have a function or null ptr.
      if (Function *F = dyn_cast<Function>(CS->getOperand(1))) {
        if (F->getName() == kAsanModuleCtorName) continue;
        ConstantInt *Priority = dyn_cast<ConstantInt>(CS->getOperand(0));
        // Don't instrument CTORs that will run before asan.module_ctor.
        if (Priority->getLimitedValue() <= kAsanCtorAndDtorPriority) continue;
        poisonOneInitializer(*F, ModuleName);
      }
    }
  }
  
  bool AddressSanitizerModule::ShouldInstrumentGlobal(GlobalVariable *G) {
    Type *Ty = cast<PointerType>(G->getType())->getElementType();
    DEBUG(dbgs() << "GLOBAL: " << *G << "\n");
  
    if (GlobalsMD.get(G).IsBlacklisted) return false;
    if (!Ty->isSized()) return false;
    if (!G->hasInitializer()) return false;
    if (GlobalWasGeneratedByAsan(G)) return false;  // Our own global.
    // Touch only those globals that will not be defined in other modules.
    // Don't handle ODR linkage types and COMDATs since other modules may be built
    // without ASan.
    if (G->getLinkage() != GlobalVariable::ExternalLinkage &&
        G->getLinkage() != GlobalVariable::PrivateLinkage &&
        G->getLinkage() != GlobalVariable::InternalLinkage)
      return false;
    if (G->hasComdat()) return false;
    // Two problems with thread-locals:
    //   - The address of the main thread's copy can't be computed at link-time.
    //   - Need to poison all copies, not just the main thread's one.
    if (G->isThreadLocal()) return false;
    // For now, just ignore this Global if the alignment is large.
    if (G->getAlignment() > MinRedzoneSizeForGlobal()) return false;
  
    if (G->hasSection()) {
      StringRef Section(G->getSection());
  
      // Globals from llvm.metadata aren't emitted, do not instrument them.
      if (Section == "llvm.metadata") return false;
  
      // Callbacks put into the CRT initializer/terminator sections
      // should not be instrumented.
      // See https://code.google.com/p/address-sanitizer/issues/detail?id=305
      // and http://msdn.microsoft.com/en-US/en-en/library/bb918180(v=vs.120).aspx
      if (Section.startswith(".CRT")) {
        DEBUG(dbgs() << "Ignoring a global initializer callback: " << *G << "\n");
        return false;
      }
  
      if (TargetTriple.isOSBinFormatMachO()) {
        StringRef ParsedSegment, ParsedSection;
        unsigned TAA = 0, StubSize = 0;
        bool TAAParsed;
        std::string ErrorCode = MCSectionMachO::ParseSectionSpecifier(
            Section, ParsedSegment, ParsedSection, TAA, TAAParsed, StubSize);
        if (!ErrorCode.empty()) {
          assert(false && "Invalid section specifier.");
          return false;
        }
  
        // Ignore the globals from the __OBJC section. The ObjC runtime assumes
        // those conform to /usr/lib/objc/runtime.h, so we can't add redzones to
        // them.
        if (ParsedSegment == "__OBJC" ||
            (ParsedSegment == "__DATA" && ParsedSection.startswith("__objc_"))) {
          DEBUG(dbgs() << "Ignoring ObjC runtime global: " << *G << "\n");
          return false;
        }
        // See http://code.google.com/p/address-sanitizer/issues/detail?id=32
        // Constant CFString instances are compiled in the following way:
        //  -- the string buffer is emitted into
        //     __TEXT,__cstring,cstring_literals
        //  -- the constant NSConstantString structure referencing that buffer
        //     is placed into __DATA,__cfstring
        // Therefore there's no point in placing redzones into __DATA,__cfstring.
        // Moreover, it causes the linker to crash on OS X 10.7
        if (ParsedSegment == "__DATA" && ParsedSection == "__cfstring") {
          DEBUG(dbgs() << "Ignoring CFString: " << *G << "\n");
          return false;
        }
        // The linker merges the contents of cstring_literals and removes the
        // trailing zeroes.
        if (ParsedSegment == "__TEXT" && (TAA & MachO::S_CSTRING_LITERALS)) {
          DEBUG(dbgs() << "Ignoring a cstring literal: " << *G << "\n");
          return false;
        }
      }
    }
  
    return true;
  }
  
  void AddressSanitizerModule::initializeCallbacks(Module &M) {
    IRBuilder<> IRB(*C);
    // Declare our poisoning and unpoisoning functions.
    AsanPoisonGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
        kAsanPoisonGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr));
    AsanPoisonGlobals->setLinkage(Function::ExternalLinkage);
    AsanUnpoisonGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
        kAsanUnpoisonGlobalsName, IRB.getVoidTy(), nullptr));
    AsanUnpoisonGlobals->setLinkage(Function::ExternalLinkage);
    // Declare functions that register/unregister globals.
    AsanRegisterGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
        kAsanRegisterGlobalsName, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
    AsanRegisterGlobals->setLinkage(Function::ExternalLinkage);
    AsanUnregisterGlobals = checkSanitizerInterfaceFunction(
        M.getOrInsertFunction(kAsanUnregisterGlobalsName, IRB.getVoidTy(),
                              IntptrTy, IntptrTy, nullptr));
    AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage);
  }
  
  // This function replaces all global variables with new variables that have
  // trailing redzones. It also creates a function that poisons
  // redzones and inserts this function into llvm.global_ctors.
  bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
    GlobalsMD.init(M);
  
    SmallVector<GlobalVariable *, 16> GlobalsToChange;
  
    for (auto &G : M.globals()) {
      if (ShouldInstrumentGlobal(&G)) GlobalsToChange.push_back(&G);
    }
  
    size_t n = GlobalsToChange.size();
    if (n == 0) return false;
  
    // A global is described by a structure
    //   size_t beg;
    //   size_t size;
    //   size_t size_with_redzone;
    //   const char *name;
    //   const char *module_name;
    //   size_t has_dynamic_init;
    //   void *source_location;
    // We initialize an array of such structures and pass it to a run-time call.
    StructType *GlobalStructTy =
        StructType::get(IntptrTy, IntptrTy, IntptrTy, IntptrTy, IntptrTy,
                        IntptrTy, IntptrTy, nullptr);
    SmallVector<Constant *, 16> Initializers(n);
  
    bool HasDynamicallyInitializedGlobals = false;
  
    // We shouldn't merge same module names, as this string serves as unique
    // module ID in runtime.
    GlobalVariable *ModuleName = createPrivateGlobalForString(
        M, M.getModuleIdentifier(), /*AllowMerging*/ false);
  
    auto &DL = M.getDataLayout();
    for (size_t i = 0; i < n; i++) {
      static const uint64_t kMaxGlobalRedzone = 1 << 18;
      GlobalVariable *G = GlobalsToChange[i];
  
      auto MD = GlobalsMD.get(G);
      // Create string holding the global name (use global name from metadata
      // if it's available, otherwise just write the name of global variable).
      GlobalVariable *Name = createPrivateGlobalForString(
          M, MD.Name.empty() ? G->getName() : MD.Name,
          /*AllowMerging*/ true);
  
      PointerType *PtrTy = cast<PointerType>(G->getType());
      Type *Ty = PtrTy->getElementType();
      uint64_t SizeInBytes = DL.getTypeAllocSize(Ty);
      uint64_t MinRZ = MinRedzoneSizeForGlobal();
      // MinRZ <= RZ <= kMaxGlobalRedzone
      // and trying to make RZ to be ~ 1/4 of SizeInBytes.
      uint64_t RZ = std::max(
          MinRZ, std::min(kMaxGlobalRedzone, (SizeInBytes / MinRZ / 4) * MinRZ));
      uint64_t RightRedzoneSize = RZ;
      // Round up to MinRZ
      if (SizeInBytes % MinRZ) RightRedzoneSize += MinRZ - (SizeInBytes % MinRZ);
      assert(((RightRedzoneSize + SizeInBytes) % MinRZ) == 0);
      Type *RightRedZoneTy = ArrayType::get(IRB.getInt8Ty(), RightRedzoneSize);
  
      StructType *NewTy = StructType::get(Ty, RightRedZoneTy, nullptr);
      Constant *NewInitializer =
          ConstantStruct::get(NewTy, G->getInitializer(),
                              Constant::getNullValue(RightRedZoneTy), nullptr);
  
      // Create a new global variable with enough space for a redzone.
      GlobalValue::LinkageTypes Linkage = G->getLinkage();
      if (G->isConstant() && Linkage == GlobalValue::PrivateLinkage)
        Linkage = GlobalValue::InternalLinkage;
      GlobalVariable *NewGlobal =
          new GlobalVariable(M, NewTy, G->isConstant(), Linkage, NewInitializer,
                             "", G, G->getThreadLocalMode());
      NewGlobal->copyAttributesFrom(G);
      NewGlobal->setAlignment(MinRZ);
  
      Value *Indices2[2];
      Indices2[0] = IRB.getInt32(0);
      Indices2[1] = IRB.getInt32(0);
  
      G->replaceAllUsesWith(
          ConstantExpr::getGetElementPtr(NewTy, NewGlobal, Indices2, true));
      NewGlobal->takeName(G);
      G->eraseFromParent();
  
      Constant *SourceLoc;
      if (!MD.SourceLoc.empty()) {
        auto SourceLocGlobal = createPrivateGlobalForSourceLoc(M, MD.SourceLoc);
        SourceLoc = ConstantExpr::getPointerCast(SourceLocGlobal, IntptrTy);
      } else {
        SourceLoc = ConstantInt::get(IntptrTy, 0);
      }
  
      Initializers[i] = ConstantStruct::get(
          GlobalStructTy, ConstantExpr::getPointerCast(NewGlobal, IntptrTy),
          ConstantInt::get(IntptrTy, SizeInBytes),
          ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize),
          ConstantExpr::getPointerCast(Name, IntptrTy),
          ConstantExpr::getPointerCast(ModuleName, IntptrTy),
          ConstantInt::get(IntptrTy, MD.IsDynInit), SourceLoc, nullptr);
  
      if (ClInitializers && MD.IsDynInit) HasDynamicallyInitializedGlobals = true;
  
      DEBUG(dbgs() << "NEW GLOBAL: " << *NewGlobal << "\n");
    }
  
    ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
    GlobalVariable *AllGlobals = new GlobalVariable(
        M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
        ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");
  
    // Create calls for poisoning before initializers run and unpoisoning after.
    if (HasDynamicallyInitializedGlobals)
      createInitializerPoisonCalls(M, ModuleName);
    IRB.CreateCall(AsanRegisterGlobals,
                   {IRB.CreatePointerCast(AllGlobals, IntptrTy),
                    ConstantInt::get(IntptrTy, n)});
  
    // We also need to unregister globals at the end, e.g. when a shared library
    // gets closed.
    Function *AsanDtorFunction =
        Function::Create(FunctionType::get(Type::getVoidTy(*C), false),
                         GlobalValue::InternalLinkage, kAsanModuleDtorName, &M);
    BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction);
    IRBuilder<> IRB_Dtor(ReturnInst::Create(*C, AsanDtorBB));
    IRB_Dtor.CreateCall(AsanUnregisterGlobals,
                        {IRB.CreatePointerCast(AllGlobals, IntptrTy),
                         ConstantInt::get(IntptrTy, n)});
    appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority);
  
    DEBUG(dbgs() << M);
    return true;
  }
  
  bool AddressSanitizerModule::runOnModule(Module &M) {
    C = &(M.getContext());
    int LongSize = M.getDataLayout().getPointerSizeInBits();
    IntptrTy = Type::getIntNTy(*C, LongSize);
    TargetTriple = Triple(M.getTargetTriple());
    Mapping = getShadowMapping(TargetTriple, LongSize, CompileKernel);
    initializeCallbacks(M);
  
    bool Changed = false;
  
    // TODO(glider): temporarily disabled globals instrumentation for KASan.
    if (ClGlobals && !CompileKernel) {
      Function *CtorFunc = M.getFunction(kAsanModuleCtorName);
      assert(CtorFunc);
      IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator());
      Changed |= InstrumentGlobals(IRB, M);
    }
  
    return Changed;
  }
  
  void AddressSanitizer::initializeCallbacks(Module &M) {
    IRBuilder<> IRB(*C);
    // Create __asan_report* callbacks.
    // IsWrite, TypeSize and Exp are encoded in the function name.
    for (int Exp = 0; Exp < 2; Exp++) {
      for (size_t AccessIsWrite = 0; AccessIsWrite <= 1; AccessIsWrite++) {
        const std::string TypeStr = AccessIsWrite ? "store" : "load";
        const std::string ExpStr = Exp ? "exp_" : "";
        const std::string SuffixStr = CompileKernel ? "N" : "_n";
        const std::string EndingStr = CompileKernel ? "_noabort" : "";
        const Type *ExpType = Exp ? Type::getInt32Ty(*C) : nullptr;
        // TODO(glider): for KASan builds add _noabort to error reporting
        // functions and make them actually noabort (remove the UnreachableInst).
        AsanErrorCallbackSized[AccessIsWrite][Exp] =
            checkSanitizerInterfaceFunction(M.getOrInsertFunction(
                kAsanReportErrorTemplate + ExpStr + TypeStr + SuffixStr,
                IRB.getVoidTy(), IntptrTy, IntptrTy, ExpType, nullptr));
        AsanMemoryAccessCallbackSized[AccessIsWrite][Exp] =
            checkSanitizerInterfaceFunction(M.getOrInsertFunction(
                ClMemoryAccessCallbackPrefix + ExpStr + TypeStr + "N" + EndingStr,
                IRB.getVoidTy(), IntptrTy, IntptrTy, ExpType, nullptr));
        for (size_t AccessSizeIndex = 0; AccessSizeIndex < kNumberOfAccessSizes;
             AccessSizeIndex++) {
          const std::string Suffix = TypeStr + itostr(1 << AccessSizeIndex);
          AsanErrorCallback[AccessIsWrite][Exp][AccessSizeIndex] =
              checkSanitizerInterfaceFunction(M.getOrInsertFunction(
                  kAsanReportErrorTemplate + ExpStr + Suffix,
                  IRB.getVoidTy(), IntptrTy, ExpType, nullptr));
          AsanMemoryAccessCallback[AccessIsWrite][Exp][AccessSizeIndex] =
              checkSanitizerInterfaceFunction(M.getOrInsertFunction(
                  ClMemoryAccessCallbackPrefix + ExpStr + Suffix + EndingStr,
                  IRB.getVoidTy(), IntptrTy, ExpType, nullptr));
        }
      }
    }
  
    const std::string MemIntrinCallbackPrefix =
        CompileKernel ? std::string("") : ClMemoryAccessCallbackPrefix;
    AsanMemmove = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
        MemIntrinCallbackPrefix + "memmove", IRB.getInt8PtrTy(),
        IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy, nullptr));
    AsanMemcpy = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
        MemIntrinCallbackPrefix + "memcpy", IRB.getInt8PtrTy(),
        IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy, nullptr));
    AsanMemset = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
        MemIntrinCallbackPrefix + "memset", IRB.getInt8PtrTy(),
        IRB.getInt8PtrTy(), IRB.getInt32Ty(), IntptrTy, nullptr));
  
    AsanHandleNoReturnFunc = checkSanitizerInterfaceFunction(
        M.getOrInsertFunction(kAsanHandleNoReturnName, IRB.getVoidTy(), nullptr));
  
    AsanPtrCmpFunction = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
        kAsanPtrCmp, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
    AsanPtrSubFunction = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
        kAsanPtrSub, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
    // We insert an empty inline asm after __asan_report* to avoid callback merge.
    EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
                              StringRef(""), StringRef(""),
                              /*hasSideEffects=*/true);
  }
  
  // virtual
  bool AddressSanitizer::doInitialization(Module &M) {
    // Initialize the private fields. No one has accessed them before.
  
    GlobalsMD.init(M);
  
    C = &(M.getContext());
    LongSize = M.getDataLayout().getPointerSizeInBits();
    IntptrTy = Type::getIntNTy(*C, LongSize);
    TargetTriple = Triple(M.getTargetTriple());
  
    if (!CompileKernel) {
      std::tie(AsanCtorFunction, AsanInitFunction) =
          createSanitizerCtorAndInitFunctions(M, kAsanModuleCtorName, kAsanInitName,
                                              /*InitArgTypes=*/{},
                                              /*InitArgs=*/{});
      appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndDtorPriority);
    }
    Mapping = getShadowMapping(TargetTriple, LongSize, CompileKernel);
    return true;
  }
  
  bool AddressSanitizer::maybeInsertAsanInitAtFunctionEntry(Function &F) {
    // For each NSObject descendant having a +load method, this method is invoked
    // by the ObjC runtime before any of the static constructors is called.
    // Therefore we need to instrument such methods with a call to __asan_init
    // at the beginning in order to initialize our runtime before any access to
    // the shadow memory.
    // We cannot just ignore these methods, because they may call other
    // instrumented functions.
    if (F.getName().find(" load]") != std::string::npos) {
      IRBuilder<> IRB(F.begin()->begin());
      IRB.CreateCall(AsanInitFunction, {});
      return true;
    }
    return false;
  }
  
  bool AddressSanitizer::runOnFunction(Function &F) {
    if (&F == AsanCtorFunction) return false;
    if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage) return false;
    DEBUG(dbgs() << "ASAN instrumenting:\n" << F << "\n");
    initializeCallbacks(*F.getParent());
  
    DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
  
    // If needed, insert __asan_init before checking for SanitizeAddress attr.
    maybeInsertAsanInitAtFunctionEntry(F);
  
    if (!F.hasFnAttribute(Attribute::SanitizeAddress)) return false;
  
    if (!ClDebugFunc.empty() && ClDebugFunc != F.getName()) return false;
  
    // We want to instrument every address only once per basic block (unless there
    // are calls between uses).
    SmallSet<Value *, 16> TempsToInstrument;
    SmallVector<Instruction *, 16> ToInstrument;
    SmallVector<Instruction *, 8> NoReturnCalls;
    SmallVector<BasicBlock *, 16> AllBlocks;
    SmallVector<Instruction *, 16> PointerComparisonsOrSubtracts;
    int NumAllocas = 0;
    bool IsWrite;
    unsigned Alignment;
    uint64_t TypeSize;
  
    // Fill the set of memory operations to instrument.
    for (auto &BB : F) {
      AllBlocks.push_back(&BB);
      TempsToInstrument.clear();
      int NumInsnsPerBB = 0;
      for (auto &Inst : BB) {
        if (LooksLikeCodeInBug11395(&Inst)) return false;
        if (Value *Addr = isInterestingMemoryAccess(&Inst, &IsWrite, &TypeSize,
                                                    &Alignment)) {
          if (ClOpt && ClOptSameTemp) {
            if (!TempsToInstrument.insert(Addr).second)
              continue;  // We've seen this temp in the current BB.
          }
        } else if (ClInvalidPointerPairs &&
                   isInterestingPointerComparisonOrSubtraction(&Inst)) {
          PointerComparisonsOrSubtracts.push_back(&Inst);
          continue;
        } else if (isa<MemIntrinsic>(Inst)) {
          // ok, take it.
        } else {
          if (isa<AllocaInst>(Inst)) NumAllocas++;
          CallSite CS(&Inst);
          if (CS) {
            // A call inside BB.
            TempsToInstrument.clear();
            if (CS.doesNotReturn()) NoReturnCalls.push_back(CS.getInstruction());
          }
          continue;
        }
        ToInstrument.push_back(&Inst);
        NumInsnsPerBB++;
        if (NumInsnsPerBB >= ClMaxInsnsToInstrumentPerBB) break;
      }
    }
  
    bool UseCalls =
        CompileKernel ||
        (ClInstrumentationWithCallsThreshold >= 0 &&
         ToInstrument.size() > (unsigned)ClInstrumentationWithCallsThreshold);
    const TargetLibraryInfo *TLI =
        &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
    const DataLayout &DL = F.getParent()->getDataLayout();
    ObjectSizeOffsetVisitor ObjSizeVis(DL, TLI, F.getContext(),
                                       /*RoundToAlign=*/true);
  
    // Instrument.
    int NumInstrumented = 0;
    for (auto Inst : ToInstrument) {
      if (ClDebugMin < 0 || ClDebugMax < 0 ||
          (NumInstrumented >= ClDebugMin && NumInstrumented <= ClDebugMax)) {
        if (isInterestingMemoryAccess(Inst, &IsWrite, &TypeSize, &Alignment))
          instrumentMop(ObjSizeVis, Inst, UseCalls,
                        F.getParent()->getDataLayout());
        else
          instrumentMemIntrinsic(cast<MemIntrinsic>(Inst));
      }
      NumInstrumented++;
    }
  
    FunctionStackPoisoner FSP(F, *this);
    bool ChangedStack = FSP.runOnFunction();
  
    // We must unpoison the stack before every NoReturn call (throw, _exit, etc).
    // See e.g. http://code.google.com/p/address-sanitizer/issues/detail?id=37
    for (auto CI : NoReturnCalls) {
      IRBuilder<> IRB(CI);
      IRB.CreateCall(AsanHandleNoReturnFunc, {});
    }
  
    for (auto Inst : PointerComparisonsOrSubtracts) {
      instrumentPointerComparisonOrSubtraction(Inst);
      NumInstrumented++;
    }
  
    bool res = NumInstrumented > 0 || ChangedStack || !NoReturnCalls.empty();
  
    DEBUG(dbgs() << "ASAN done instrumenting: " << res << " " << F << "\n");
  
    return res;
  }
  
  // Workaround for bug 11395: we don't want to instrument stack in functions
  // with large assembly blobs (32-bit only), otherwise reg alloc may crash.
  // FIXME: remove once the bug 11395 is fixed.
  bool AddressSanitizer::LooksLikeCodeInBug11395(Instruction *I) {
    if (LongSize != 32) return false;
    CallInst *CI = dyn_cast<CallInst>(I);
    if (!CI || !CI->isInlineAsm()) return false;
    if (CI->getNumArgOperands() <= 5) return false;
    // We have inline assembly with quite a few arguments.
    return true;
  }
  
  void FunctionStackPoisoner::initializeCallbacks(Module &M) {
    IRBuilder<> IRB(*C);
    for (int i = 0; i <= kMaxAsanStackMallocSizeClass; i++) {
      std::string Suffix = itostr(i);
      AsanStackMallocFunc[i] = checkSanitizerInterfaceFunction(
          M.getOrInsertFunction(kAsanStackMallocNameTemplate + Suffix, IntptrTy,
                                IntptrTy, nullptr));
      AsanStackFreeFunc[i] = checkSanitizerInterfaceFunction(
          M.getOrInsertFunction(kAsanStackFreeNameTemplate + Suffix,
                                IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
    }
    AsanPoisonStackMemoryFunc = checkSanitizerInterfaceFunction(
        M.getOrInsertFunction(kAsanPoisonStackMemoryName, IRB.getVoidTy(),
                              IntptrTy, IntptrTy, nullptr));
    AsanUnpoisonStackMemoryFunc = checkSanitizerInterfaceFunction(
        M.getOrInsertFunction(kAsanUnpoisonStackMemoryName, IRB.getVoidTy(),
                              IntptrTy, IntptrTy, nullptr));
    AsanAllocaPoisonFunc = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
        kAsanAllocaPoison, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
    AsanAllocasUnpoisonFunc =
        checkSanitizerInterfaceFunction(M.getOrInsertFunction(
            kAsanAllocasUnpoison, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
  }
  
  void FunctionStackPoisoner::poisonRedZones(ArrayRef<uint8_t> ShadowBytes,
                                             IRBuilder<> &IRB, Value *ShadowBase,
                                             bool DoPoison) {
    size_t n = ShadowBytes.size();
    size_t i = 0;
    // We need to (un)poison n bytes of stack shadow. Poison as many as we can
    // using 64-bit stores (if we are on 64-bit arch), then poison the rest
    // with 32-bit stores, then with 16-byte stores, then with 8-byte stores.
    for (size_t LargeStoreSizeInBytes = ASan.LongSize / 8;
         LargeStoreSizeInBytes != 0; LargeStoreSizeInBytes /= 2) {
      for (; i + LargeStoreSizeInBytes - 1 < n; i += LargeStoreSizeInBytes) {
        uint64_t Val = 0;
        for (size_t j = 0; j < LargeStoreSizeInBytes; j++) {
          if (F.getParent()->getDataLayout().isLittleEndian())
            Val |= (uint64_t)ShadowBytes[i + j] << (8 * j);
          else
            Val = (Val << 8) | ShadowBytes[i + j];
        }
        if (!Val) continue;
        Value *Ptr = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
        Type *StoreTy = Type::getIntNTy(*C, LargeStoreSizeInBytes * 8);
        Value *Poison = ConstantInt::get(StoreTy, DoPoison ? Val : 0);
        IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, StoreTy->getPointerTo()));
      }
    }
  }
  
  // Fake stack allocator (asan_fake_stack.h) has 11 size classes
  // for every power of 2 from kMinStackMallocSize to kMaxAsanStackMallocSizeClass
  static int StackMallocSizeClass(uint64_t LocalStackSize) {
    assert(LocalStackSize <= kMaxStackMallocSize);
    uint64_t MaxSize = kMinStackMallocSize;
    for (int i = 0;; i++, MaxSize *= 2)
      if (LocalStackSize <= MaxSize) return i;
    llvm_unreachable("impossible LocalStackSize");
  }
  
  // Set Size bytes starting from ShadowBase to kAsanStackAfterReturnMagic.
  // We can not use MemSet intrinsic because it may end up calling the actual
  // memset. Size is a multiple of 8.
  // Currently this generates 8-byte stores on x86_64; it may be better to
  // generate wider stores.
  void FunctionStackPoisoner::SetShadowToStackAfterReturnInlined(
      IRBuilder<> &IRB, Value *ShadowBase, int Size) {
    assert(!(Size % 8));
  
    // kAsanStackAfterReturnMagic is 0xf5.
    const uint64_t kAsanStackAfterReturnMagic64 = 0xf5f5f5f5f5f5f5f5ULL;
  
    for (int i = 0; i < Size; i += 8) {
      Value *p = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
      IRB.CreateStore(
          ConstantInt::get(IRB.getInt64Ty(), kAsanStackAfterReturnMagic64),
          IRB.CreateIntToPtr(p, IRB.getInt64Ty()->getPointerTo()));
    }
  }
  
  static DebugLoc getFunctionEntryDebugLocation(Function &F) {
    for (const auto &Inst : F.getEntryBlock())
      if (!isa<AllocaInst>(Inst)) return Inst.getDebugLoc();
    return DebugLoc();
  }
  
  PHINode *FunctionStackPoisoner::createPHI(IRBuilder<> &IRB, Value *Cond,
                                            Value *ValueIfTrue,
                                            Instruction *ThenTerm,
                                            Value *ValueIfFalse) {
    PHINode *PHI = IRB.CreatePHI(IntptrTy, 2);
    BasicBlock *CondBlock = cast<Instruction>(Cond)->getParent();
    PHI->addIncoming(ValueIfFalse, CondBlock);
    BasicBlock *ThenBlock = ThenTerm->getParent();
    PHI->addIncoming(ValueIfTrue, ThenBlock);
    return PHI;
  }
  
  Value *FunctionStackPoisoner::createAllocaForLayout(
      IRBuilder<> &IRB, const ASanStackFrameLayout &L, bool Dynamic) {
    AllocaInst *Alloca;
    if (Dynamic) {
      Alloca = IRB.CreateAlloca(IRB.getInt8Ty(),
                                ConstantInt::get(IRB.getInt64Ty(), L.FrameSize),
                                "MyAlloca");
    } else {
      Alloca = IRB.CreateAlloca(ArrayType::get(IRB.getInt8Ty(), L.FrameSize),
                                nullptr, "MyAlloca");
      assert(Alloca->isStaticAlloca());
    }
    assert((ClRealignStack & (ClRealignStack - 1)) == 0);
    size_t FrameAlignment = std::max(L.FrameAlignment, (size_t)ClRealignStack);
    Alloca->setAlignment(FrameAlignment);
    return IRB.CreatePointerCast(Alloca, IntptrTy);
  }
  
  void FunctionStackPoisoner::createDynamicAllocasInitStorage() {
    BasicBlock &FirstBB = *F.begin();
    IRBuilder<> IRB(dyn_cast<Instruction>(FirstBB.begin()));
    DynamicAllocaLayout = IRB.CreateAlloca(IntptrTy, nullptr);
    IRB.CreateStore(Constant::getNullValue(IntptrTy), DynamicAllocaLayout);
    DynamicAllocaLayout->setAlignment(32);
  }
  
  void FunctionStackPoisoner::poisonStack() {
    assert(AllocaVec.size() > 0 || DynamicAllocaVec.size() > 0);
  
    if (ClInstrumentAllocas && DynamicAllocaVec.size() > 0) {
      // Handle dynamic allocas.
      createDynamicAllocasInitStorage();
      for (auto &AI : DynamicAllocaVec) handleDynamicAllocaCall(AI);
  
      unpoisonDynamicAllocas();
    }
  
    if (AllocaVec.size() == 0) return;
  
    int StackMallocIdx = -1;
    DebugLoc EntryDebugLocation = getFunctionEntryDebugLocation(F);
  
    Instruction *InsBefore = AllocaVec[0];
    IRBuilder<> IRB(InsBefore);
    IRB.SetCurrentDebugLocation(EntryDebugLocation);
  
    SmallVector<ASanStackVariableDescription, 16> SVD;
    SVD.reserve(AllocaVec.size());
    for (AllocaInst *AI : AllocaVec) {
      ASanStackVariableDescription D = {AI->getName().data(),
                                        ASan.getAllocaSizeInBytes(AI),
                                        AI->getAlignment(), AI, 0};
      SVD.push_back(D);
    }
    // Minimal header size (left redzone) is 4 pointers,
    // i.e. 32 bytes on 64-bit platforms and 16 bytes in 32-bit platforms.
    size_t MinHeaderSize = ASan.LongSize / 2;
    ASanStackFrameLayout L;
    ComputeASanStackFrameLayout(SVD, 1UL << Mapping.Scale, MinHeaderSize, &L);
    DEBUG(dbgs() << L.DescriptionString << " --- " << L.FrameSize << "\n");
    uint64_t LocalStackSize = L.FrameSize;
    bool DoStackMalloc = ClUseAfterReturn && !ASan.CompileKernel &&
                         LocalStackSize <= kMaxStackMallocSize;
    // Don't do dynamic alloca in presence of inline asm: too often it makes
    // assumptions on which registers are available. Don't do stack malloc in the
    // presence of inline asm on 32-bit platforms for the same reason.
    bool DoDynamicAlloca = ClDynamicAllocaStack && !HasNonEmptyInlineAsm;
    DoStackMalloc &= !HasNonEmptyInlineAsm || ASan.LongSize != 32;
  
    Value *StaticAlloca =
        DoDynamicAlloca ? nullptr : createAllocaForLayout(IRB, L, false);
  
    Value *FakeStack;
    Value *LocalStackBase;
  
    if (DoStackMalloc) {
      // void *FakeStack = __asan_option_detect_stack_use_after_return
      //     ? __asan_stack_malloc_N(LocalStackSize)
      //     : nullptr;
      // void *LocalStackBase = (FakeStack) ? FakeStack : alloca(LocalStackSize);
      Constant *OptionDetectUAR = F.getParent()->getOrInsertGlobal(
          kAsanOptionDetectUAR, IRB.getInt32Ty());
      Value *UARIsEnabled =
          IRB.CreateICmpNE(IRB.CreateLoad(OptionDetectUAR),
                           Constant::getNullValue(IRB.getInt32Ty()));
      Instruction *Term =
          SplitBlockAndInsertIfThen(UARIsEnabled, InsBefore, false);
      IRBuilder<> IRBIf(Term);
      IRBIf.SetCurrentDebugLocation(EntryDebugLocation);
      StackMallocIdx = StackMallocSizeClass(LocalStackSize);
      assert(StackMallocIdx <= kMaxAsanStackMallocSizeClass);
      Value *FakeStackValue =
          IRBIf.CreateCall(AsanStackMallocFunc[StackMallocIdx],
                           ConstantInt::get(IntptrTy, LocalStackSize));
      IRB.SetInsertPoint(InsBefore);
      IRB.SetCurrentDebugLocation(EntryDebugLocation);
      FakeStack = createPHI(IRB, UARIsEnabled, FakeStackValue, Term,
                            ConstantInt::get(IntptrTy, 0));
  
      Value *NoFakeStack =
          IRB.CreateICmpEQ(FakeStack, Constant::getNullValue(IntptrTy));
      Term = SplitBlockAndInsertIfThen(NoFakeStack, InsBefore, false);
      IRBIf.SetInsertPoint(Term);
      IRBIf.SetCurrentDebugLocation(EntryDebugLocation);
      Value *AllocaValue =
          DoDynamicAlloca ? createAllocaForLayout(IRBIf, L, true) : StaticAlloca;
      IRB.SetInsertPoint(InsBefore);
      IRB.SetCurrentDebugLocation(EntryDebugLocation);
      LocalStackBase = createPHI(IRB, NoFakeStack, AllocaValue, Term, FakeStack);
    } else {
      // void *FakeStack = nullptr;
      // void *LocalStackBase = alloca(LocalStackSize);
      FakeStack = ConstantInt::get(IntptrTy, 0);
      LocalStackBase =
          DoDynamicAlloca ? createAllocaForLayout(IRB, L, true) : StaticAlloca;
    }
  
    // Insert poison calls for lifetime intrinsics for alloca.
    bool HavePoisonedAllocas = false;
    for (const auto &APC : AllocaPoisonCallVec) {
      assert(APC.InsBefore);
      assert(APC.AI);
      IRBuilder<> IRB(APC.InsBefore);
      poisonAlloca(APC.AI, APC.Size, IRB, APC.DoPoison);
      HavePoisonedAllocas |= APC.DoPoison;
    }
  
    // Replace Alloca instructions with base+offset.
    for (const auto &Desc : SVD) {
      AllocaInst *AI = Desc.AI;
      Value *NewAllocaPtr = IRB.CreateIntToPtr(
          IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy, Desc.Offset)),
          AI->getType());
      replaceDbgDeclareForAlloca(AI, NewAllocaPtr, DIB, /*Deref=*/true);
      AI->replaceAllUsesWith(NewAllocaPtr);
    }
  
    // The left-most redzone has enough space for at least 4 pointers.
    // Write the Magic value to redzone[0].
    Value *BasePlus0 = IRB.CreateIntToPtr(LocalStackBase, IntptrPtrTy);
    IRB.CreateStore(ConstantInt::get(IntptrTy, kCurrentStackFrameMagic),
                    BasePlus0);
    // Write the frame description constant to redzone[1].
    Value *BasePlus1 = IRB.CreateIntToPtr(
        IRB.CreateAdd(LocalStackBase,
                      ConstantInt::get(IntptrTy, ASan.LongSize / 8)),
        IntptrPtrTy);
    GlobalVariable *StackDescriptionGlobal =
        createPrivateGlobalForString(*F.getParent(), L.DescriptionString,
                                     /*AllowMerging*/ true);
    Value *Description = IRB.CreatePointerCast(StackDescriptionGlobal, IntptrTy);
    IRB.CreateStore(Description, BasePlus1);
    // Write the PC to redzone[2].
    Value *BasePlus2 = IRB.CreateIntToPtr(
        IRB.CreateAdd(LocalStackBase,
                      ConstantInt::get(IntptrTy, 2 * ASan.LongSize / 8)),
        IntptrPtrTy);
    IRB.CreateStore(IRB.CreatePointerCast(&F, IntptrTy), BasePlus2);
  
    // Poison the stack redzones at the entry.
    Value *ShadowBase = ASan.memToShadow(LocalStackBase, IRB);
    poisonRedZones(L.ShadowBytes, IRB, ShadowBase, true);
  
    // (Un)poison the stack before all ret instructions.
    for (auto Ret : RetVec) {
      IRBuilder<> IRBRet(Ret);
      // Mark the current frame as retired.
      IRBRet.CreateStore(ConstantInt::get(IntptrTy, kRetiredStackFrameMagic),
                         BasePlus0);
      if (DoStackMalloc) {
        assert(StackMallocIdx >= 0);
        // if FakeStack != 0  // LocalStackBase == FakeStack
        //     // In use-after-return mode, poison the whole stack frame.
        //     if StackMallocIdx <= 4
        //         // For small sizes inline the whole thing:
        //         memset(ShadowBase, kAsanStackAfterReturnMagic, ShadowSize);
        //         **SavedFlagPtr(FakeStack) = 0
        //     else
        //         __asan_stack_free_N(FakeStack, LocalStackSize)
        // else
        //     <This is not a fake stack; unpoison the redzones>
        Value *Cmp =
            IRBRet.CreateICmpNE(FakeStack, Constant::getNullValue(IntptrTy));
        TerminatorInst *ThenTerm, *ElseTerm;
        SplitBlockAndInsertIfThenElse(Cmp, Ret, &ThenTerm, &ElseTerm);
  
        IRBuilder<> IRBPoison(ThenTerm);
        if (StackMallocIdx <= 4) {
          int ClassSize = kMinStackMallocSize << StackMallocIdx;
          SetShadowToStackAfterReturnInlined(IRBPoison, ShadowBase,
                                             ClassSize >> Mapping.Scale);
          Value *SavedFlagPtrPtr = IRBPoison.CreateAdd(
              FakeStack,
              ConstantInt::get(IntptrTy, ClassSize - ASan.LongSize / 8));
          Value *SavedFlagPtr = IRBPoison.CreateLoad(
              IRBPoison.CreateIntToPtr(SavedFlagPtrPtr, IntptrPtrTy));
          IRBPoison.CreateStore(
              Constant::getNullValue(IRBPoison.getInt8Ty()),
              IRBPoison.CreateIntToPtr(SavedFlagPtr, IRBPoison.getInt8PtrTy()));
        } else {
          // For larger frames call __asan_stack_free_*.
          IRBPoison.CreateCall(
              AsanStackFreeFunc[StackMallocIdx],
              {FakeStack, ConstantInt::get(IntptrTy, LocalStackSize)});
        }
  
        IRBuilder<> IRBElse(ElseTerm);
        poisonRedZones(L.ShadowBytes, IRBElse, ShadowBase, false);
      } else if (HavePoisonedAllocas) {
        // If we poisoned some allocas in llvm.lifetime analysis,
        // unpoison whole stack frame now.
        poisonAlloca(LocalStackBase, LocalStackSize, IRBRet, false);
      } else {
        poisonRedZones(L.ShadowBytes, IRBRet, ShadowBase, false);
      }
    }
  
    // We are done. Remove the old unused alloca instructions.
    for (auto AI : AllocaVec) AI->eraseFromParent();
  }
  
  void FunctionStackPoisoner::poisonAlloca(Value *V, uint64_t Size,
                                           IRBuilder<> &IRB, bool DoPoison) {
    // For now just insert the call to ASan runtime.
    Value *AddrArg = IRB.CreatePointerCast(V, IntptrTy);
    Value *SizeArg = ConstantInt::get(IntptrTy, Size);
    IRB.CreateCall(
        DoPoison ? AsanPoisonStackMemoryFunc : AsanUnpoisonStackMemoryFunc,
        {AddrArg, SizeArg});
  }
  
  // Handling llvm.lifetime intrinsics for a given %alloca:
  // (1) collect all llvm.lifetime.xxx(%size, %value) describing the alloca.
  // (2) if %size is constant, poison memory for llvm.lifetime.end (to detect
  //     invalid accesses) and unpoison it for llvm.lifetime.start (the memory
  //     could be poisoned by previous llvm.lifetime.end instruction, as the
  //     variable may go in and out of scope several times, e.g. in loops).
  // (3) if we poisoned at least one %alloca in a function,
  //     unpoison the whole stack frame at function exit.
  
  AllocaInst *FunctionStackPoisoner::findAllocaForValue(Value *V) {
    if (AllocaInst *AI = dyn_cast<AllocaInst>(V))
      // We're intested only in allocas we can handle.
      return ASan.isInterestingAlloca(*AI) ? AI : nullptr;
    // See if we've already calculated (or started to calculate) alloca for a
    // given value.
    AllocaForValueMapTy::iterator I = AllocaForValue.find(V);
    if (I != AllocaForValue.end()) return I->second;
    // Store 0 while we're calculating alloca for value V to avoid
    // infinite recursion if the value references itself.
    AllocaForValue[V] = nullptr;
    AllocaInst *Res = nullptr;
    if (CastInst *CI = dyn_cast<CastInst>(V))
      Res = findAllocaForValue(CI->getOperand(0));
    else if (PHINode *PN = dyn_cast<PHINode>(V)) {
      for (Value *IncValue : PN->incoming_values()) {
        // Allow self-referencing phi-nodes.
        if (IncValue == PN) continue;
        AllocaInst *IncValueAI = findAllocaForValue(IncValue);
        // AI for incoming values should exist and should all be equal.
        if (IncValueAI == nullptr || (Res != nullptr && IncValueAI != Res))
          return nullptr;
        Res = IncValueAI;
      }
    }
    if (Res) AllocaForValue[V] = Res;
    return Res;
  }
  
  void FunctionStackPoisoner::handleDynamicAllocaCall(AllocaInst *AI) {
    IRBuilder<> IRB(AI);
  
    const unsigned Align = std::max(kAllocaRzSize, AI->getAlignment());
    const uint64_t AllocaRedzoneMask = kAllocaRzSize - 1;
  
    Value *Zero = Constant::getNullValue(IntptrTy);
    Value *AllocaRzSize = ConstantInt::get(IntptrTy, kAllocaRzSize);
    Value *AllocaRzMask = ConstantInt::get(IntptrTy, AllocaRedzoneMask);
  
    // Since we need to extend alloca with additional memory to locate
    // redzones, and OldSize is number of allocated blocks with
    // ElementSize size, get allocated memory size in bytes by
    // OldSize * ElementSize.
    const unsigned ElementSize =
        F.getParent()->getDataLayout().getTypeAllocSize(AI->getAllocatedType());
    Value *OldSize =
        IRB.CreateMul(IRB.CreateIntCast(AI->getArraySize(), IntptrTy, false),
                      ConstantInt::get(IntptrTy, ElementSize));
  
    // PartialSize = OldSize % 32
    Value *PartialSize = IRB.CreateAnd(OldSize, AllocaRzMask);
  
    // Misalign = kAllocaRzSize - PartialSize;
    Value *Misalign = IRB.CreateSub(AllocaRzSize, PartialSize);
  
    // PartialPadding = Misalign != kAllocaRzSize ? Misalign : 0;
    Value *Cond = IRB.CreateICmpNE(Misalign, AllocaRzSize);
    Value *PartialPadding = IRB.CreateSelect(Cond, Misalign, Zero);
  
    // AdditionalChunkSize = Align + PartialPadding + kAllocaRzSize
    // Align is added to locate left redzone, PartialPadding for possible
    // partial redzone and kAllocaRzSize for right redzone respectively.
    Value *AdditionalChunkSize = IRB.CreateAdd(
        ConstantInt::get(IntptrTy, Align + kAllocaRzSize), PartialPadding);
  
    Value *NewSize = IRB.CreateAdd(OldSize, AdditionalChunkSize);
  
    // Insert new alloca with new NewSize and Align params.
    AllocaInst *NewAlloca = IRB.CreateAlloca(IRB.getInt8Ty(), NewSize);
    NewAlloca->setAlignment(Align);
  
    // NewAddress = Address + Align
    Value *NewAddress = IRB.CreateAdd(IRB.CreatePtrToInt(NewAlloca, IntptrTy),
                                      ConstantInt::get(IntptrTy, Align));
  
    // Insert __asan_alloca_poison call for new created alloca.
    IRB.CreateCall(AsanAllocaPoisonFunc, {NewAddress, OldSize});
  
    // Store the last alloca's address to DynamicAllocaLayout. We'll need this
    // for unpoisoning stuff.
    IRB.CreateStore(IRB.CreatePtrToInt(NewAlloca, IntptrTy), DynamicAllocaLayout);
  
    Value *NewAddressPtr = IRB.CreateIntToPtr(NewAddress, AI->getType());
  
    // Replace all uses of AddessReturnedByAlloca with NewAddressPtr.
    AI->replaceAllUsesWith(NewAddressPtr);
  
    // We are done. Erase old alloca from parent.
    AI->eraseFromParent();
  }
  
  // isSafeAccess returns true if Addr is always inbounds with respect to its
  // base object. For example, it is a field access or an array access with
  // constant inbounds index.
  bool AddressSanitizer::isSafeAccess(ObjectSizeOffsetVisitor &ObjSizeVis,
                                      Value *Addr, uint64_t TypeSize) const {
    SizeOffsetType SizeOffset = ObjSizeVis.compute(Addr);
    if (!ObjSizeVis.bothKnown(SizeOffset)) return false;
    uint64_t Size = SizeOffset.first.getZExtValue();
    int64_t Offset = SizeOffset.second.getSExtValue();
    // Three checks are required to ensure safety:
    // . Offset >= 0  (since the offset is given from the base ptr)
    // . Size >= Offset  (unsigned)
    // . Size - Offset >= NeededSize  (unsigned)
    return Offset >= 0 && Size >= uint64_t(Offset) &&
           Size - uint64_t(Offset) >= TypeSize / 8;
  }
  