xref: /llvm-project-15.0.7/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp (revision b7760210)

//===-- 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/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallSet.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/Instrumentation.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 <iomanip>
#include <limits>
#include <sstream>
#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 kDefaultShadowOffset64 = 1ULL << 44;
static const uint64_t kDynamicShadowSentinel = ~(uint64_t)0;
static const uint64_t kIOSShadowOffset32 = 1ULL << 30;
static const uint64_t kIOSSimShadowOffset32 = 1ULL << 30;
static const uint64_t kIOSSimShadowOffset64 = kDefaultShadowOffset64;
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 kSystemZ_ShadowOffset64 = 1ULL << 52;
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 kPS4CPU_ShadowOffset64 = 1ULL << 40;
static const uint64_t kWindowsShadowOffset32 = 3ULL << 28;
// The shadow memory space is dynamically allocated.
static const uint64_t kWindowsShadowOffset64 = kDynamicShadowSentinel;

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 kAsanRegisterImageGlobalsName =
  "__asan_register_image_globals";
static const char *const kAsanUnregisterImageGlobalsName =
  "__asan_unregister_image_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";
static const char *const kAsanVersionCheckName =
    "__asan_version_mismatch_check_v8";
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 kODRGenPrefix = "__odr_asan_gen_";
static const char *const kSanCovGenPrefix = "__sancov_gen_";
static const char *const kAsanSetShadowPrefix = "__asan_set_shadow_";
static const char *const kAsanPoisonStackMemoryName =
    "__asan_poison_stack_memory";
static const char *const kAsanUnpoisonStackMemoryName =
    "__asan_unpoison_stack_memory";
static const char *const kAsanGlobalsRegisteredFlagName =
    "__asan_globals_registered";

static const char *const kAsanOptionDetectUseAfterReturn =
    "__asan_option_detect_stack_use_after_return";

static const char *const kAsanShadowMemoryDynamicAddress =
    "__asan_shadow_memory_dynamic_address";

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));
static cl::opt<bool> ClRecover(
    "asan-recover",
    cl::desc("Enable recovery mode (continue-after-error)."),
    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));
static cl::opt<bool> ClForceDynamicShadow(
    "asan-force-dynamic-shadow",
    cl::desc("Load shadow address into a local variable for each function"),
    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<uint32_t> ClMaxInlinePoisoningSize(
    "asan-max-inline-poisoning-size",
    cl::desc(
        "Inline shadow poisoning for blocks up to the given size in bytes."),
    cl::Hidden, cl::init(64));
static cl::opt<bool> ClUseAfterReturn("asan-use-after-return",
                                      cl::desc("Check stack-use-after-return"),
                                      cl::Hidden, cl::init(true));
static cl::opt<bool> ClUseAfterScope("asan-use-after-scope",
                                     cl::desc("Check stack-use-after-scope"),
                                     cl::Hidden, cl::init(false));
// 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>
    ClInstrumentDynamicAllocas("asan-instrument-dynamic-allocas",
                               cl::desc("instrument dynamic allocas"),
                               cl::Hidden, cl::init(true));
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) + offset
static cl::opt<int> ClMappingScale("asan-mapping-scale",
                                   cl::desc("scale of asan shadow mapping"),
                                   cl::Hidden, cl::init(0));
static cl::opt<unsigned long long> ClMappingOffset(
    "asan-mapping-offset",
    cl::desc("offset of asan shadow mapping [EXPERIMENTAL]"), 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> 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));

static cl::opt<bool>
    ClUsePrivateAliasForGlobals("asan-use-private-alias",
                                cl::desc("Use private aliases for global"
                                         " variables"),
                                cl::Hidden, cl::init(false));

static cl::opt<bool>
    ClUseMachOGlobalsSection("asan-globals-live-support",
                             cl::desc("Use linker features to support dead "
                                      "code stripping of globals "
                                      "(Mach-O only)"),
                             cl::Hidden, cl::init(true));

// 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 max 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 reset() {
    inited_ = false;
    Entries.clear();
  }

  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.isAndroid();
  bool IsIOS = TargetTriple.isiOS() || TargetTriple.isWatchOS();
  bool IsFreeBSD = TargetTriple.isOSFreeBSD();
  bool IsPS4CPU = TargetTriple.isPS4CPU();
  bool IsLinux = TargetTriple.isOSLinux();
  bool IsPPC64 = TargetTriple.getArch() == llvm::Triple::ppc64 ||
                 TargetTriple.getArch() == llvm::Triple::ppc64le;
  bool IsSystemZ = TargetTriple.getArch() == llvm::Triple::systemz;
  bool IsX86 = TargetTriple.getArch() == llvm::Triple::x86;
  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) {
    // Android is always PIE, which means that the beginning of the address
    // space is always available.
    if (IsAndroid)
      Mapping.Offset = 0;
    else if (IsMIPS32)
      Mapping.Offset = kMIPS32_ShadowOffset32;
    else if (IsFreeBSD)
      Mapping.Offset = kFreeBSD_ShadowOffset32;
    else if (IsIOS)
      // If we're targeting iOS and x86, the binary is built for iOS simulator.
      Mapping.Offset = IsX86 ? kIOSSimShadowOffset32 : kIOSShadowOffset32;
    else if (IsWindows)
      Mapping.Offset = kWindowsShadowOffset32;
    else
      Mapping.Offset = kDefaultShadowOffset32;
  } else {  // LongSize == 64
    if (IsPPC64)
      Mapping.Offset = kPPC64_ShadowOffset64;
    else if (IsSystemZ)
      Mapping.Offset = kSystemZ_ShadowOffset64;
    else if (IsFreeBSD)
      Mapping.Offset = kFreeBSD_ShadowOffset64;
    else if (IsPS4CPU)
      Mapping.Offset = kPS4CPU_ShadowOffset64;
    else if (IsLinux && IsX86_64) {
      if (IsKasan)
        Mapping.Offset = kLinuxKasan_ShadowOffset64;
      else
        Mapping.Offset = kSmallX86_64ShadowOffset;
    } else if (IsWindows && IsX86_64) {
      Mapping.Offset = kWindowsShadowOffset64;
    } else if (IsMIPS64)
      Mapping.Offset = kMIPS64_ShadowOffset64;
    else if (IsIOS)
      // If we're targeting iOS and x86, the binary is built for iOS simulator.
      // We are using dynamic shadow offset on the 64-bit devices.
      Mapping.Offset =
        IsX86_64 ? kIOSSimShadowOffset64 : kDynamicShadowSentinel;
    else if (IsAArch64)
      Mapping.Offset = kAArch64_ShadowOffset64;
    else
      Mapping.Offset = kDefaultShadowOffset64;
  }

  if (ClForceDynamicShadow) {
    Mapping.Offset = kDynamicShadowSentinel;
  }

  Mapping.Scale = kDefaultShadowScale;
  if (ClMappingScale.getNumOccurrences() > 0) {
    Mapping.Scale = ClMappingScale;
  }

  if (ClMappingOffset.getNumOccurrences() > 0) {
    Mapping.Offset = ClMappingOffset;
  }

  // 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.  On SystemZ,
  // we could OR the constant in a single instruction, but it's more
  // efficient to load it once and use indexed addressing.
  Mapping.OrShadowOffset = !IsAArch64 && !IsPPC64 && !IsSystemZ && !IsPS4CPU &&
                           !(Mapping.Offset & (Mapping.Offset - 1)) &&
                           Mapping.Offset != kDynamicShadowSentinel;

  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, bool Recover = false,
                            bool UseAfterScope = false)
      : FunctionPass(ID), CompileKernel(CompileKernel || ClEnableKasan),
        Recover(Recover || ClRecover),
        UseAfterScope(UseAfterScope || ClUseAfterScope),
        LocalDynamicShadow(nullptr) {
    initializeAddressSanitizerPass(*PassRegistry::getPassRegistry());
  }
  StringRef getPassName() const override {
    return "AddressSanitizerFunctionPass";
  }
  void getAnalysisUsage(AnalysisUsage &AU) const override {
    AU.addRequired<DominatorTreeWrapperPass>();
    AU.addRequired<TargetLibraryInfoWrapperPass>();
  }
  uint64_t getAllocaSizeInBytes(const AllocaInst &AI) const {
    uint64_t ArraySize = 1;
    if (AI.isArrayAllocation()) {
      const ConstantInt *CI = dyn_cast<ConstantInt>(AI.getArraySize());
      assert(CI && "non-constant array size");
      ArraySize = CI->getZExtValue();
    }
    Type *Ty = AI.getAllocatedType();
    uint64_t SizeInBytes =
        AI.getModule()->getDataLayout().getTypeAllocSize(Ty);
    return SizeInBytes * ArraySize;
  }
  /// Check if we want (and can) handle this alloca.
  bool isInterestingAlloca(const AllocaInst &AI);

  /// If it is an interesting memory access, return the PointerOperand
  /// and set IsWrite/Alignment. Otherwise return nullptr.
  /// MaybeMask is an output parameter for the mask Value, if we're looking at a
  /// masked load/store.
  Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite,
                                   uint64_t *TypeSize, unsigned *Alignment,
                                   Value **MaybeMask = nullptr);
  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,
                                        Instruction *InsertBefore, 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);
  void maybeInsertDynamicShadowAtFunctionEntry(Function &F);
  void markEscapedLocalAllocas(Function &F);
  bool doInitialization(Module &M) override;
  bool doFinalization(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;

  /// Helper to cleanup per-function state.
  struct FunctionStateRAII {
    AddressSanitizer *Pass;
    FunctionStateRAII(AddressSanitizer *Pass) : Pass(Pass) {
      assert(Pass->ProcessedAllocas.empty() &&
             "last pass forgot to clear cache");
      assert(!Pass->LocalDynamicShadow);
    }
    ~FunctionStateRAII() {
      Pass->LocalDynamicShadow = nullptr;
      Pass->ProcessedAllocas.clear();
    }
  };

  LLVMContext *C;
  Triple TargetTriple;
  int LongSize;
  bool CompileKernel;
  bool Recover;
  bool UseAfterScope;
  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;
  Value *LocalDynamicShadow;
  GlobalsMetadata GlobalsMD;
  DenseMap<const AllocaInst *, bool> ProcessedAllocas;

  friend struct FunctionStackPoisoner;
};

class AddressSanitizerModule : public ModulePass {
 public:
  explicit AddressSanitizerModule(bool CompileKernel = false,
                                  bool Recover = false)
      : ModulePass(ID), CompileKernel(CompileKernel || ClEnableKasan),
        Recover(Recover || ClRecover) {}
  bool runOnModule(Module &M) override;
  static char ID;  // Pass identification, replacement for typeid
  StringRef getPassName() const override { return "AddressSanitizerModule"; }

private:
  void initializeCallbacks(Module &M);

  bool InstrumentGlobals(IRBuilder<> &IRB, Module &M);
  void InstrumentGlobalsCOFF(IRBuilder<> &IRB, Module &M,
                             ArrayRef<GlobalVariable *> ExtendedGlobals,
                             ArrayRef<Constant *> MetadataInitializers);
  void InstrumentGlobalsMachO(IRBuilder<> &IRB, Module &M,
                              ArrayRef<GlobalVariable *> ExtendedGlobals,
                              ArrayRef<Constant *> MetadataInitializers);
  void
  InstrumentGlobalsWithMetadataArray(IRBuilder<> &IRB, Module &M,
                                     ArrayRef<GlobalVariable *> ExtendedGlobals,
                                     ArrayRef<Constant *> MetadataInitializers);

  GlobalVariable *CreateMetadataGlobal(Module &M, Constant *Initializer,
                                       StringRef OriginalName);
  void SetComdatForGlobalMetadata(GlobalVariable *G, GlobalVariable *Metadata);
  IRBuilder<> CreateAsanModuleDtor(Module &M);

  bool ShouldInstrumentGlobal(GlobalVariable *G);
  bool ShouldUseMachOGlobalsSection() const;
  StringRef getGlobalMetadataSection() const;
  void poisonOneInitializer(Function &GlobalInit, GlobalValue *ModuleName);
  void createInitializerPoisonCalls(Module &M, GlobalValue *ModuleName);
  size_t MinRedzoneSizeForGlobal() const {
    return RedzoneSizeForScale(Mapping.Scale);
  }

  GlobalsMetadata GlobalsMD;
  bool CompileKernel;
  bool Recover;
  Type *IntptrTy;
  LLVMContext *C;
  Triple TargetTriple;
  ShadowMapping Mapping;
  Function *AsanPoisonGlobals;
  Function *AsanUnpoisonGlobals;
  Function *AsanRegisterGlobals;
  Function *AsanUnregisterGlobals;
  Function *AsanRegisterImageGlobals;
  Function *AsanUnregisterImageGlobals;
};

// 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<AllocaInst *, 16> StaticAllocasToMoveUp;
  SmallVector<Instruction *, 8> RetVec;
  unsigned StackAlignment;

  Function *AsanStackMallocFunc[kMaxAsanStackMallocSizeClass + 1],
      *AsanStackFreeFunc[kMaxAsanStackMallocSizeClass + 1];
  Function *AsanSetShadowFunc[0x100] = {};
  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> DynamicAllocaPoisonCallVec;
  SmallVector<AllocaPoisonCall, 8> StaticAllocaPoisonCallVec;

  SmallVector<AllocaInst *, 1> DynamicAllocaVec;
  SmallVector<IntrinsicInst *, 1> StackRestoreVec;
  AllocaInst *DynamicAllocaLayout = nullptr;
  IntrinsicInst *LocalEscapeCall = nullptr;

  // Maps Value to an AllocaInst from which the Value is originated.
  typedef DenseMap<Value *, AllocaInst *> AllocaForValueMapTy;
  AllocaForValueMapTy AllocaForValue;

  bool HasNonEmptyInlineAsm = false;
  bool HasReturnsTwiceCall = false;
  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),
        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());

    processDynamicAllocas();
    processStaticAllocas();

    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 processStaticAllocas();
  void processDynamicAllocas();

  void createDynamicAllocasInitStorage();

  // ----------------------- Visitors.
  /// \brief Collect all Ret instructions.
  void visitReturnInst(ReturnInst &RI) { RetVec.push_back(&RI); }

  /// \brief Collect all Resume instructions.
  void visitResumeInst(ResumeInst &RI) { RetVec.push_back(&RI); }

  /// \brief Collect all CatchReturnInst instructions.
  void visitCleanupReturnInst(CleanupReturnInst &CRI) { RetVec.push_back(&CRI); }

  void unpoisonDynamicAllocasBeforeInst(Instruction *InstBefore,
                                        Value *SavedStack) {
    IRBuilder<> IRB(InstBefore);
    Value *DynamicAreaPtr = IRB.CreatePtrToInt(SavedStack, IntptrTy);
    // When we insert _asan_allocas_unpoison before @llvm.stackrestore, we
    // need to adjust extracted SP to compute the address of the most recent
    // alloca. We have a special @llvm.get.dynamic.area.offset intrinsic for
    // this purpose.
    if (!isa<ReturnInst>(InstBefore)) {
      Function *DynamicAreaOffsetFunc = Intrinsic::getDeclaration(
          InstBefore->getModule(), Intrinsic::get_dynamic_area_offset,
          {IntptrTy});

      Value *DynamicAreaOffset = IRB.CreateCall(DynamicAreaOffsetFunc, {});

      DynamicAreaPtr = IRB.CreateAdd(IRB.CreatePtrToInt(SavedStack, IntptrTy),
                                     DynamicAreaOffset);
    }

    IRB.CreateCall(AsanAllocasUnpoisonFunc,
                   {IRB.CreateLoad(DynamicAllocaLayout), DynamicAreaPtr});
  }

  // 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)) {
      if (AI.isStaticAlloca()) {
        // Skip over allocas that are present *before* the first instrumented
        // alloca, we don't want to move those around.
        if (AllocaVec.empty())
          return;

        StaticAllocasToMoveUp.push_back(&AI);
      }
      return;
    }

    StackAlignment = std::max(StackAlignment, AI.getAlignment());
    if (!AI.isStaticAlloca())
      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 (ID == Intrinsic::localescape) LocalEscapeCall = &II;
    if (!ASan.UseAfterScope)
      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 || !ASan.isInterestingAlloca(*AI))
      return;
    bool DoPoison = (ID == Intrinsic::lifetime_end);
    AllocaPoisonCall APC = {&II, AI, SizeValue, DoPoison};
    if (AI->isStaticAlloca())
      StaticAllocaPoisonCallVec.push_back(APC);
    else if (ClInstrumentDynamicAllocas)
      DynamicAllocaPoisonCallVec.push_back(APC);
  }

  void visitCallSite(CallSite CS) {
    Instruction *I = CS.getInstruction();
    if (CallInst *CI = dyn_cast<CallInst>(I)) {
      HasNonEmptyInlineAsm |=
          CI->isInlineAsm() && !CI->isIdenticalTo(EmptyInlineAsm.get());
      HasReturnsTwiceCall |= CI->canReturnTwice();
    }
  }

  // ---------------------- 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);

  // Copies bytes from ShadowBytes into shadow memory for indexes where
  // ShadowMask is not zero. If ShadowMask[i] is zero, we assume that
  // ShadowBytes[i] is constantly zero and doesn't need to be overwritten.
  void copyToShadow(ArrayRef<uint8_t> ShadowMask, ArrayRef<uint8_t> ShadowBytes,
                    IRBuilder<> &IRB, Value *ShadowBase);
  void copyToShadow(ArrayRef<uint8_t> ShadowMask, ArrayRef<uint8_t> ShadowBytes,
                    size_t Begin, size_t End, IRBuilder<> &IRB,
                    Value *ShadowBase);
  void copyToShadowInline(ArrayRef<uint8_t> ShadowMask,
                          ArrayRef<uint8_t> ShadowBytes, size_t Begin,
                          size_t End, IRBuilder<> &IRB, Value *ShadowBase);

  void poisonAlloca(Value *V, uint64_t Size, IRBuilder<> &IRB, bool DoPoison);

  Value *createAllocaForLayout(IRBuilder<> &IRB, const ASanStackFrameLayout &L,
                               bool Dynamic);
  PHINode *createPHI(IRBuilder<> &IRB, Value *Cond, Value *ValueIfTrue,
                     Instruction *ThenTerm, Value *ValueIfFalse);
};

} // anonymous 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_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_END(
    AddressSanitizer, "asan",
    "AddressSanitizer: detects use-after-free and out-of-bounds bugs.", false,
    false)
FunctionPass *llvm::createAddressSanitizerFunctionPass(bool CompileKernel,
                                                       bool Recover,
                                                       bool UseAfterScope) {
  assert(!CompileKernel || Recover);
  return new AddressSanitizer(CompileKernel, Recover, UseAfterScope);
}

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,
                                                   bool Recover) {
  assert(!CompileKernel || Recover);
  return new AddressSanitizerModule(CompileKernel, Recover);
}

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(GlobalValue::UnnamedAddr::Global);
  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(GlobalValue::UnnamedAddr::Global);
  return GV;
}

/// \brief Check if \p G has been created by a trusted compiler pass.
static bool GlobalWasGeneratedByCompiler(GlobalVariable *G) {
  // Do not instrument asan globals.
  if (G->getName().startswith(kAsanGenPrefix) ||
      G->getName().startswith(kSanCovGenPrefix) ||
      G->getName().startswith(kODRGenPrefix))
    return true;

  // Do not instrument gcov counter arrays.
  if (G->getName() == "__llvm_gcov_ctr")
    return true;

  return false;
}

Value *AddressSanitizer::memToShadow(Value *Shadow, IRBuilder<> &IRB) {
  // Shadow >> scale
  Shadow = IRB.CreateLShr(Shadow, Mapping.Scale);
  if (Mapping.Offset == 0) return Shadow;
  // (Shadow >> scale) | offset
  Value *ShadowBase;
  if (LocalDynamicShadow)
    ShadowBase = LocalDynamicShadow;
  else
    ShadowBase = ConstantInt::get(IntptrTy, Mapping.Offset);
  if (Mapping.OrShadowOffset)
    return IRB.CreateOr(Shadow, ShadowBase);
  else
    return IRB.CreateAdd(Shadow, ShadowBase);
}

// 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(const 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.
       ((!AI.isStaticAlloca()) || getAllocaSizeInBytes(AI) > 0) &&
       // We are only interested in allocas not promotable to registers.
       // Promotable allocas are common under -O0.
       (!ClSkipPromotableAllocas || !isAllocaPromotable(&AI)) &&
       // inalloca allocas are not treated as static, and we don't want
       // dynamic alloca instrumentation for them as well.
       !AI.isUsedWithInAlloca() &&
       // swifterror allocas are register promoted by ISel
       !AI.isSwiftError());

  ProcessedAllocas[&AI] = IsInteresting;
  return IsInteresting;
}

Value *AddressSanitizer::isInterestingMemoryAccess(Instruction *I,
                                                   bool *IsWrite,
                                                   uint64_t *TypeSize,
                                                   unsigned *Alignment,
                                                   Value **MaybeMask) {
  // Skip memory accesses inserted by another instrumentation.
  if (I->getMetadata("nosanitize")) return nullptr;

  // Do not instrument the load fetching the dynamic shadow address.
  if (LocalDynamicShadow == I)
    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();
  } else if (auto CI = dyn_cast<CallInst>(I)) {
    auto *F = dyn_cast<Function>(CI->getCalledValue());
    if (F && (F->getName().startswith("llvm.masked.load.") ||
              F->getName().startswith("llvm.masked.store."))) {
      unsigned OpOffset = 0;
      if (F->getName().startswith("llvm.masked.store.")) {
        if (!ClInstrumentWrites)
          return nullptr;
        // Masked store has an initial operand for the value.
        OpOffset = 1;
        *IsWrite = true;
      } else {
        if (!ClInstrumentReads)
          return nullptr;
        *IsWrite = false;
      }

      auto BasePtr = CI->getOperand(0 + OpOffset);
      auto Ty = cast<PointerType>(BasePtr->getType())->getElementType();
      *TypeSize = DL.getTypeStoreSizeInBits(Ty);
      if (auto AlignmentConstant =
              dyn_cast<ConstantInt>(CI->getOperand(1 + OpOffset)))
        *Alignment = (unsigned)AlignmentConstant->getZExtValue();
      else
        *Alignment = 1; // No alignment guarantees. We probably got Undef
      if (MaybeMask)
        *MaybeMask = CI->getOperand(2 + OpOffset);
      PtrOperand = BasePtr;
    }
  }

  if (PtrOperand) {
    // Do not instrument acesses from different address spaces; we cannot deal
    // with them.
    Type *PtrTy = cast<PointerType>(PtrOperand->getType()->getScalarType());
    if (PtrTy->getPointerAddressSpace() != 0)
      return nullptr;

    // Ignore swifterror addresses.
    // swifterror memory addresses are mem2reg promoted by instruction
    // selection. As such they cannot have regular uses like an instrumentation
    // function and it makes no sense to track them as memory.
    if (PtrOperand->isSwiftError())
      return nullptr;
  }

  // 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;
  }
  return isPointerOperand(I->getOperand(0)) &&
         isPointerOperand(I->getOperand(1));
}

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 (Value *&i : Param) {
    if (i->getType()->isPointerTy())
      i = IRB.CreatePointerCast(i, IntptrTy);
  }
  IRB.CreateCall(F, Param);
}

static void doInstrumentAddress(AddressSanitizer *Pass, Instruction *I,
                                Instruction *InsertBefore, Value *Addr,
                                unsigned Alignment, unsigned Granularity,
                                uint32_t TypeSize, bool IsWrite,
                                Value *SizeArgument, bool UseCalls,
                                uint32_t Exp) {
  // 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 Pass->instrumentAddress(I, InsertBefore, Addr, TypeSize, IsWrite,
                                   nullptr, UseCalls, Exp);
  Pass->instrumentUnusualSizeOrAlignment(I, InsertBefore, Addr, TypeSize,
                                         IsWrite, nullptr, UseCalls, Exp);
}

static void instrumentMaskedLoadOrStore(AddressSanitizer *Pass,
                                        const DataLayout &DL, Type *IntptrTy,
                                        Value *Mask, Instruction *I,
                                        Value *Addr, unsigned Alignment,
                                        unsigned Granularity, uint32_t TypeSize,
                                        bool IsWrite, Value *SizeArgument,
                                        bool UseCalls, uint32_t Exp) {
  auto *VTy = cast<PointerType>(Addr->getType())->getElementType();
  uint64_t ElemTypeSize = DL.getTypeStoreSizeInBits(VTy->getScalarType());
  unsigned Num = VTy->getVectorNumElements();
  auto Zero = ConstantInt::get(IntptrTy, 0);
  for (unsigned Idx = 0; Idx < Num; ++Idx) {
    Value *InstrumentedAddress = nullptr;
    Instruction *InsertBefore = I;
    if (auto *Vector = dyn_cast<ConstantVector>(Mask)) {
      // dyn_cast as we might get UndefValue
      if (auto *Masked = dyn_cast<ConstantInt>(Vector->getOperand(Idx))) {
        if (Masked->isNullValue())
          // Mask is constant false, so no instrumentation needed.
          continue;
        // If we have a true or undef value, fall through to doInstrumentAddress
        // with InsertBefore == I
      }
    } else {
      IRBuilder<> IRB(I);
      Value *MaskElem = IRB.CreateExtractElement(Mask, Idx);
      TerminatorInst *ThenTerm = SplitBlockAndInsertIfThen(MaskElem, I, false);
      InsertBefore = ThenTerm;
    }

    IRBuilder<> IRB(InsertBefore);
    InstrumentedAddress =
        IRB.CreateGEP(Addr, {Zero, ConstantInt::get(IntptrTy, Idx)});
    doInstrumentAddress(Pass, I, InsertBefore, InstrumentedAddress, Alignment,
                        Granularity, ElemTypeSize, IsWrite, SizeArgument,
                        UseCalls, Exp);
  }
}

void AddressSanitizer::instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis,
                                     Instruction *I, bool UseCalls,
                                     const DataLayout &DL) {
  bool IsWrite = false;
  unsigned Alignment = 0;
  uint64_t TypeSize = 0;
  Value *MaybeMask = nullptr;
  Value *Addr =
      isInterestingMemoryAccess(I, &IsWrite, &TypeSize, &Alignment, &MaybeMask);
  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 && (!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;
  if (MaybeMask) {
    instrumentMaskedLoadOrStore(this, DL, IntptrTy, MaybeMask, I, Addr,
                                Alignment, Granularity, TypeSize, IsWrite,
                                nullptr, UseCalls, Exp);
  } else {
    doInstrumentAddress(this, I, I, Addr, Alignment, Granularity, 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 = static_cast<size_t>(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 = 1ULL << 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);
    if (Recover) {
      CrashTerm = SplitBlockAndInsertIfThen(Cmp2, CheckTerm, false);
    } else {
      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, !Recover);
  }

  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, Instruction *InsertBefore, Value *Addr, uint32_t TypeSize,
    bool IsWrite, Value *SizeArgument, bool UseCalls, uint32_t Exp) {
  IRBuilder<> IRB(InsertBefore);
  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, InsertBefore, Addr, 8, IsWrite, Size, false, Exp);
    instrumentAddress(I, InsertBefore, 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.front(),
                  GlobalInit.front().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 = G->getValueType();
  DEBUG(dbgs() << "GLOBAL: " << *G << "\n");

  if (GlobalsMD.get(G).IsBlacklisted) return false;
  if (!Ty->isSized()) return false;
  if (!G->hasInitializer()) return false;
  if (GlobalWasGeneratedByCompiler(G)) return false; // Our own globals.
  // 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;
    // Do not instrument globals from special LLVM sections.
    if (Section.find("__llvm") != StringRef::npos || Section.find("__LLVM") != StringRef::npos) return false;

    // Do not instrument function pointers to initialization and termination
    // routines: dynamic linker will not properly handle redzones.
    if (Section.startswith(".preinit_array") ||
        Section.startswith(".init_array") ||
        Section.startswith(".fini_array")) {
      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);
      assert(ErrorCode.empty() && "Invalid section specifier.");

      // 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;
}

// On Mach-O platforms, we emit global metadata in a separate section of the
// binary in order to allow the linker to properly dead strip. This is only
// supported on recent versions of ld64.
bool AddressSanitizerModule::ShouldUseMachOGlobalsSection() const {
  if (!ClUseMachOGlobalsSection)
    return false;

  if (!TargetTriple.isOSBinFormatMachO())
    return false;

  if (TargetTriple.isMacOSX() && !TargetTriple.isMacOSXVersionLT(10, 11))
    return true;
  if (TargetTriple.isiOS() /* or tvOS */ && !TargetTriple.isOSVersionLT(9))
    return true;
  if (TargetTriple.isWatchOS() && !TargetTriple.isOSVersionLT(2))
    return true;

  return false;
}

StringRef AddressSanitizerModule::getGlobalMetadataSection() const {
  switch (TargetTriple.getObjectFormat()) {
  case Triple::COFF:  return ".ASAN$GL";
  case Triple::ELF:   return "asan_globals";
  case Triple::MachO: return "__DATA,__asan_globals,regular";
  default: break;
  }
  llvm_unreachable("unsupported object format");
}

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);

  // Declare the functions that find globals in a shared object and then invoke
  // the (un)register function on them.
  AsanRegisterImageGlobals =
      checkSanitizerInterfaceFunction(M.getOrInsertFunction(
          kAsanRegisterImageGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr));
  AsanRegisterImageGlobals->setLinkage(Function::ExternalLinkage);

  AsanUnregisterImageGlobals =
      checkSanitizerInterfaceFunction(M.getOrInsertFunction(
          kAsanUnregisterImageGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr));
  AsanUnregisterImageGlobals->setLinkage(Function::ExternalLinkage);
}

// Put the metadata and the instrumented global in the same group. This ensures
// that the metadata is discarded if the instrumented global is discarded.
void AddressSanitizerModule::SetComdatForGlobalMetadata(
    GlobalVariable *G, GlobalVariable *Metadata) {
  Module &M = *G->getParent();
  Comdat *C = G->getComdat();
  if (!C) {
    if (!G->hasName()) {
      // If G is unnamed, it must be internal. Give it an artificial name
      // so we can put it in a comdat.
      assert(G->hasLocalLinkage());
      G->setName(Twine(kAsanGenPrefix) + "_anon_global");
    }
    C = M.getOrInsertComdat(G->getName());
    // Make this IMAGE_COMDAT_SELECT_NODUPLICATES on COFF.
    if (TargetTriple.isOSBinFormatCOFF())
      C->setSelectionKind(Comdat::NoDuplicates);
    G->setComdat(C);
  }

  assert(G->hasComdat());
  Metadata->setComdat(G->getComdat());
}

// Create a separate metadata global and put it in the appropriate ASan
// global registration section.
GlobalVariable *
AddressSanitizerModule::CreateMetadataGlobal(Module &M, Constant *Initializer,
                                             StringRef OriginalName) {
  GlobalVariable *Metadata =
      new GlobalVariable(M, Initializer->getType(), false,
                         GlobalVariable::InternalLinkage, Initializer,
                         Twine("__asan_global_") +
                             GlobalValue::getRealLinkageName(OriginalName));
  Metadata->setSection(getGlobalMetadataSection());
  return Metadata;
}

IRBuilder<> AddressSanitizerModule::CreateAsanModuleDtor(Module &M) {
  Function *AsanDtorFunction =
      Function::Create(FunctionType::get(Type::getVoidTy(*C), false),
                       GlobalValue::InternalLinkage, kAsanModuleDtorName, &M);
  BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction);
  appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority);

  return IRBuilder<>(ReturnInst::Create(*C, AsanDtorBB));
}

void AddressSanitizerModule::InstrumentGlobalsCOFF(
    IRBuilder<> &IRB, Module &M, ArrayRef<GlobalVariable *> ExtendedGlobals,
    ArrayRef<Constant *> MetadataInitializers) {
  assert(ExtendedGlobals.size() == MetadataInitializers.size());
  auto &DL = M.getDataLayout();

  for (size_t i = 0; i < ExtendedGlobals.size(); i++) {
    Constant *Initializer = MetadataInitializers[i];
    GlobalVariable *G = ExtendedGlobals[i];
    GlobalVariable *Metadata =
        CreateMetadataGlobal(M, Initializer, G->getName());

    // The MSVC linker always inserts padding when linking incrementally. We
    // cope with that by aligning each struct to its size, which must be a power
    // of two.
    unsigned SizeOfGlobalStruct = DL.getTypeAllocSize(Initializer->getType());
    assert(isPowerOf2_32(SizeOfGlobalStruct) &&
           "global metadata will not be padded appropriately");
    Metadata->setAlignment(SizeOfGlobalStruct);

    SetComdatForGlobalMetadata(G, Metadata);
  }
}

void AddressSanitizerModule::InstrumentGlobalsMachO(
    IRBuilder<> &IRB, Module &M, ArrayRef<GlobalVariable *> ExtendedGlobals,
    ArrayRef<Constant *> MetadataInitializers) {
  assert(ExtendedGlobals.size() == MetadataInitializers.size());

  // On recent Mach-O platforms, use a structure which binds the liveness of
  // the global variable to the metadata struct. Keep the list of "Liveness" GV
  // created to be added to llvm.compiler.used
  StructType *LivenessTy = StructType::get(IntptrTy, IntptrTy, nullptr);
  SmallVector<GlobalValue *, 16> LivenessGlobals(ExtendedGlobals.size());

  for (size_t i = 0; i < ExtendedGlobals.size(); i++) {
    Constant *Initializer = MetadataInitializers[i];
    GlobalVariable *G = ExtendedGlobals[i];
    GlobalVariable *Metadata =
        CreateMetadataGlobal(M, Initializer, G->getName());

    // On recent Mach-O platforms, we emit the global metadata in a way that
    // allows the linker to properly strip dead globals.
    auto LivenessBinder = ConstantStruct::get(
        LivenessTy, Initializer->getAggregateElement(0u),
        ConstantExpr::getPointerCast(Metadata, IntptrTy), nullptr);
    GlobalVariable *Liveness = new GlobalVariable(
        M, LivenessTy, false, GlobalVariable::InternalLinkage, LivenessBinder,
        Twine("__asan_binder_") + G->getName());
    Liveness->setSection("__DATA,__asan_liveness,regular,live_support");
    LivenessGlobals[i] = Liveness;
  }

  // Update llvm.compiler.used, adding the new liveness globals. This is
  // needed so that during LTO these variables stay alive. The alternative
  // would be to have the linker handling the LTO symbols, but libLTO
  // current API does not expose access to the section for each symbol.
  if (!LivenessGlobals.empty())
    appendToCompilerUsed(M, LivenessGlobals);

  // RegisteredFlag serves two purposes. First, we can pass it to dladdr()
  // to look up the loaded image that contains it. Second, we can store in it
  // whether registration has already occurred, to prevent duplicate
  // registration.
  //
  // common linkage ensures that there is only one global per shared library.
  GlobalVariable *RegisteredFlag = new GlobalVariable(
      M, IntptrTy, false, GlobalVariable::CommonLinkage,
      ConstantInt::get(IntptrTy, 0), kAsanGlobalsRegisteredFlagName);
  RegisteredFlag->setVisibility(GlobalVariable::HiddenVisibility);

  IRB.CreateCall(AsanRegisterImageGlobals,
                 {IRB.CreatePointerCast(RegisteredFlag, IntptrTy)});

  // We also need to unregister globals at the end, e.g., when a shared library
  // gets closed.
  IRBuilder<> IRB_Dtor = CreateAsanModuleDtor(M);
  IRB_Dtor.CreateCall(AsanUnregisterImageGlobals,
                      {IRB.CreatePointerCast(RegisteredFlag, IntptrTy)});
}

void AddressSanitizerModule::InstrumentGlobalsWithMetadataArray(
    IRBuilder<> &IRB, Module &M, ArrayRef<GlobalVariable *> ExtendedGlobals,
    ArrayRef<Constant *> MetadataInitializers) {
  assert(ExtendedGlobals.size() == MetadataInitializers.size());
  unsigned N = ExtendedGlobals.size();
  assert(N > 0);

  // On platforms that don't have a custom metadata section, we emit an array
  // of global metadata structures.
  ArrayType *ArrayOfGlobalStructTy =
      ArrayType::get(MetadataInitializers[0]->getType(), N);
  auto AllGlobals = new GlobalVariable(
      M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
      ConstantArray::get(ArrayOfGlobalStructTy, MetadataInitializers), "");

  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.
  IRBuilder<> IRB_Dtor = CreateAsanModuleDtor(M);
  IRB_Dtor.CreateCall(AsanUnregisterGlobals,
                      {IRB.CreatePointerCast(AllGlobals, IntptrTy),
                       ConstantInt::get(IntptrTy, N)});
}

// 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;

  auto &DL = M.getDataLayout();

  // 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;
  //   size_t odr_indicator;
  // 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, IntptrTy, nullptr);
  SmallVector<GlobalVariable *, 16> NewGlobals(n);
  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);

  for (size_t i = 0; i < n; i++) {
    static const uint64_t kMaxGlobalRedzone = 1 << 18;
    GlobalVariable *G = GlobalsToChange[i];

    auto MD = GlobalsMD.get(G);
    StringRef NameForGlobal = G->getName();
    // 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() ? NameForGlobal : MD.Name,
        /*AllowMerging*/ true);

    Type *Ty = G->getValueType();
    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);

    // Move null-terminated C strings to "__asan_cstring" section on Darwin.
    if (TargetTriple.isOSBinFormatMachO() && !G->hasSection() &&
        G->isConstant()) {
      auto Seq = dyn_cast<ConstantDataSequential>(G->getInitializer());
      if (Seq && Seq->isCString())
        NewGlobal->setSection("__TEXT,__asan_cstring,regular");
    }

    // Transfer the debug info.  The payload starts at offset zero so we can
    // copy the debug info over as is.
    SmallVector<DIGlobalVariableExpression *, 1> GVs;
    G->getDebugInfo(GVs);
    for (auto *GV : GVs)
      NewGlobal->addDebugInfo(GV);

    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();
    NewGlobals[i] = NewGlobal;

    Constant *SourceLoc;
    if (!MD.SourceLoc.empty()) {
      auto SourceLocGlobal = createPrivateGlobalForSourceLoc(M, MD.SourceLoc);
      SourceLoc = ConstantExpr::getPointerCast(SourceLocGlobal, IntptrTy);
    } else {
      SourceLoc = ConstantInt::get(IntptrTy, 0);
    }

    Constant *ODRIndicator = ConstantExpr::getNullValue(IRB.getInt8PtrTy());
    GlobalValue *InstrumentedGlobal = NewGlobal;

    bool CanUsePrivateAliases =
        TargetTriple.isOSBinFormatELF() || TargetTriple.isOSBinFormatMachO() ||
        TargetTriple.isOSBinFormatWasm();
    if (CanUsePrivateAliases && ClUsePrivateAliasForGlobals) {
      // Create local alias for NewGlobal to avoid crash on ODR between
      // instrumented and non-instrumented libraries.
      auto *GA = GlobalAlias::create(GlobalValue::InternalLinkage,
                                     NameForGlobal + M.getName(), NewGlobal);

      // With local aliases, we need to provide another externally visible
      // symbol __odr_asan_XXX to detect ODR violation.
      auto *ODRIndicatorSym =
          new GlobalVariable(M, IRB.getInt8Ty(), false, Linkage,
                             Constant::getNullValue(IRB.getInt8Ty()),
                             kODRGenPrefix + NameForGlobal, nullptr,
                             NewGlobal->getThreadLocalMode());

      // Set meaningful attributes for indicator symbol.
      ODRIndicatorSym->setVisibility(NewGlobal->getVisibility());
      ODRIndicatorSym->setDLLStorageClass(NewGlobal->getDLLStorageClass());
      ODRIndicatorSym->setAlignment(1);
      ODRIndicator = ODRIndicatorSym;
      InstrumentedGlobal = GA;
    }

    Constant *Initializer = ConstantStruct::get(
        GlobalStructTy,
        ConstantExpr::getPointerCast(InstrumentedGlobal, IntptrTy),
        ConstantInt::get(IntptrTy, SizeInBytes),
        ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize),
        ConstantExpr::getPointerCast(Name, IntptrTy),
        ConstantExpr::getPointerCast(ModuleName, IntptrTy),
        ConstantInt::get(IntptrTy, MD.IsDynInit), SourceLoc,
        ConstantExpr::getPointerCast(ODRIndicator, IntptrTy), nullptr);

    if (ClInitializers && MD.IsDynInit) HasDynamicallyInitializedGlobals = true;

    DEBUG(dbgs() << "NEW GLOBAL: " << *NewGlobal << "\n");

    Initializers[i] = Initializer;
  }

  if (TargetTriple.isOSBinFormatCOFF()) {
    InstrumentGlobalsCOFF(IRB, M, NewGlobals, Initializers);
  } else if (ShouldUseMachOGlobalsSection()) {
    InstrumentGlobalsMachO(IRB, M, NewGlobals, Initializers);
  } else {
    InstrumentGlobalsWithMetadataArray(IRB, M, NewGlobals, Initializers);
  }

  // Create calls for poisoning before initializers run and unpoisoning after.
  if (HasDynamicallyInitializedGlobals)
    createInitializerPoisonCalls(M, ModuleName);

  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 = Recover ? "_noabort" : "";
      Type *ExpType = Exp ? Type::getInt32Ty(*C) : nullptr;
      AsanErrorCallbackSized[AccessIsWrite][Exp] =
          checkSanitizerInterfaceFunction(M.getOrInsertFunction(
              kAsanReportErrorTemplate + ExpStr + TypeStr + SuffixStr + EndingStr,
              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(1ULL << AccessSizeIndex);
        AsanErrorCallback[AccessIsWrite][Exp][AccessSizeIndex] =
            checkSanitizerInterfaceFunction(M.getOrInsertFunction(
                kAsanReportErrorTemplate + ExpStr + Suffix + EndingStr,
                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=*/{}, kAsanVersionCheckName);
    appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndDtorPriority);
  }
  Mapping = getShadowMapping(TargetTriple, LongSize, CompileKernel);
  return true;
}

bool AddressSanitizer::doFinalization(Module &M) {
  GlobalsMD.reset();
  return false;
}

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.front(), F.front().begin());
    IRB.CreateCall(AsanInitFunction, {});
    return true;
  }
  return false;
}

void AddressSanitizer::maybeInsertDynamicShadowAtFunctionEntry(Function &F) {
  // Generate code only when dynamic addressing is needed.
  if (Mapping.Offset != kDynamicShadowSentinel)
    return;

  IRBuilder<> IRB(&F.front().front());
  Value *GlobalDynamicAddress = F.getParent()->getOrInsertGlobal(
      kAsanShadowMemoryDynamicAddress, IntptrTy);
  LocalDynamicShadow = IRB.CreateLoad(GlobalDynamicAddress);
}

void AddressSanitizer::markEscapedLocalAllocas(Function &F) {
  // Find the one possible call to llvm.localescape and pre-mark allocas passed
  // to it as uninteresting. This assumes we haven't started processing allocas
  // yet. This check is done up front because iterating the use list in
  // isInterestingAlloca would be algorithmically slower.
  assert(ProcessedAllocas.empty() && "must process localescape before allocas");

  // Try to get the declaration of llvm.localescape. If it's not in the module,
  // we can exit early.
  if (!F.getParent()->getFunction("llvm.localescape")) return;

  // Look for a call to llvm.localescape call in the entry block. It can't be in
  // any other block.
  for (Instruction &I : F.getEntryBlock()) {
    IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I);
    if (II && II->getIntrinsicID() == Intrinsic::localescape) {
      // We found a call. Mark all the allocas passed in as uninteresting.
      for (Value *Arg : II->arg_operands()) {
        AllocaInst *AI = dyn_cast<AllocaInst>(Arg->stripPointerCasts());
        assert(AI && AI->isStaticAlloca() &&
               "non-static alloca arg to localescape");
        ProcessedAllocas[AI] = false;
      }
      break;
    }
  }
}

bool AddressSanitizer::runOnFunction(Function &F) {
  if (&F == AsanCtorFunction) return false;
  if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage) return false;
  if (!ClDebugFunc.empty() && ClDebugFunc == F.getName()) return false;
  if (F.getName().startswith("__asan_")) return false;

  bool FunctionModified = false;

  // If needed, insert __asan_init before checking for SanitizeAddress attr.
  // This function needs to be called even if the function body is not
  // instrumented.
  if (maybeInsertAsanInitAtFunctionEntry(F))
    FunctionModified = true;

  // Leave if the function doesn't need instrumentation.
  if (!F.hasFnAttribute(Attribute::SanitizeAddress)) return FunctionModified;

  DEBUG(dbgs() << "ASAN instrumenting:\n" << F << "\n");

  initializeCallbacks(*F.getParent());
  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();

  FunctionStateRAII CleanupObj(this);

  maybeInsertDynamicShadowAtFunctionEntry(F);

  // We can't instrument allocas used with llvm.localescape. Only static allocas
  // can be passed to that intrinsic.
  markEscapedLocalAllocas(F);

  // 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;
  const TargetLibraryInfo *TLI =
      &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();

  // 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;
      Value *MaybeMask = nullptr;
      if (Value *Addr = isInterestingMemoryAccess(&Inst, &IsWrite, &TypeSize,
                                                  &Alignment, &MaybeMask)) {
        if (ClOpt && ClOptSameTemp) {
          // If we have a mask, skip instrumentation if we've already
          // instrumented the full object. But don't add to TempsToInstrument
          // because we might get another load/store with a different mask.
          if (MaybeMask) {
            if (TempsToInstrument.count(Addr))
              continue; // We've seen this (whole) temp in the current BB.
          } else {
            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());
        }
        if (CallInst *CI = dyn_cast<CallInst>(&Inst))
          maybeMarkSanitizerLibraryCallNoBuiltin(CI, TLI);
        continue;
      }
      ToInstrument.push_back(&Inst);
      NumInsnsPerBB++;
      if (NumInsnsPerBB >= ClMaxInsnsToInstrumentPerBB) break;
    }
  }

  bool UseCalls =
      CompileKernel ||
      (ClInstrumentationWithCallsThreshold >= 0 &&
       ToInstrument.size() > (unsigned)ClInstrumentationWithCallsThreshold);
  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++;
  }

  if (NumInstrumented > 0 || ChangedStack || !NoReturnCalls.empty())
    FunctionModified = true;

  DEBUG(dbgs() << "ASAN done instrumenting: " << FunctionModified << " "
               << F << "\n");

  return FunctionModified;
}

// 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));
  }
  if (ASan.UseAfterScope) {
    AsanPoisonStackMemoryFunc = checkSanitizerInterfaceFunction(
        M.getOrInsertFunction(kAsanPoisonStackMemoryName, IRB.getVoidTy(),
                              IntptrTy, IntptrTy, nullptr));
    AsanUnpoisonStackMemoryFunc = checkSanitizerInterfaceFunction(
        M.getOrInsertFunction(kAsanUnpoisonStackMemoryName, IRB.getVoidTy(),
                              IntptrTy, IntptrTy, nullptr));
  }

  for (size_t Val : {0x00, 0xf1, 0xf2, 0xf3, 0xf5, 0xf8}) {
    std::ostringstream Name;
    Name << kAsanSetShadowPrefix;
    Name << std::setw(2) << std::setfill('0') << std::hex << Val;
    AsanSetShadowFunc[Val] =
        checkSanitizerInterfaceFunction(M.getOrInsertFunction(
            Name.str(), 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::copyToShadowInline(ArrayRef<uint8_t> ShadowMask,
                                               ArrayRef<uint8_t> ShadowBytes,
                                               size_t Begin, size_t End,
                                               IRBuilder<> &IRB,
                                               Value *ShadowBase) {
  if (Begin >= End)
    return;

  const size_t LargestStoreSizeInBytes =
      std::min<size_t>(sizeof(uint64_t), ASan.LongSize / 8);

  const bool IsLittleEndian = F.getParent()->getDataLayout().isLittleEndian();

  // Poison given range in shadow using larges store size with out leading and
  // trailing zeros in ShadowMask. Zeros never change, so they need neither
  // poisoning nor up-poisoning. Still we don't mind if some of them get into a
  // middle of a store.
  for (size_t i = Begin; i < End;) {
    if (!ShadowMask[i]) {
      assert(!ShadowBytes[i]);
      ++i;
      continue;
    }

    size_t StoreSizeInBytes = LargestStoreSizeInBytes;
    // Fit store size into the range.
    while (StoreSizeInBytes > End - i)
      StoreSizeInBytes /= 2;

    // Minimize store size by trimming trailing zeros.
    for (size_t j = StoreSizeInBytes - 1; j && !ShadowMask[i + j]; --j) {
      while (j <= StoreSizeInBytes / 2)
        StoreSizeInBytes /= 2;
    }

    uint64_t Val = 0;
    for (size_t j = 0; j < StoreSizeInBytes; j++) {
      if (IsLittleEndian)
        Val |= (uint64_t)ShadowBytes[i + j] << (8 * j);
      else
        Val = (Val << 8) | ShadowBytes[i + j];
    }

    Value *Ptr = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
    Value *Poison = IRB.getIntN(StoreSizeInBytes * 8, Val);
    IRB.CreateAlignedStore(
        Poison, IRB.CreateIntToPtr(Ptr, Poison->getType()->getPointerTo()), 1);

    i += StoreSizeInBytes;
  }
}

void FunctionStackPoisoner::copyToShadow(ArrayRef<uint8_t> ShadowMask,
                                         ArrayRef<uint8_t> ShadowBytes,
                                         IRBuilder<> &IRB, Value *ShadowBase) {
  copyToShadow(ShadowMask, ShadowBytes, 0, ShadowMask.size(), IRB, ShadowBase);
}

void FunctionStackPoisoner::copyToShadow(ArrayRef<uint8_t> ShadowMask,
                                         ArrayRef<uint8_t> ShadowBytes,
                                         size_t Begin, size_t End,
                                         IRBuilder<> &IRB, Value *ShadowBase) {
  assert(ShadowMask.size() == ShadowBytes.size());
  size_t Done = Begin;
  for (size_t i = Begin, j = Begin + 1; i < End; i = j++) {
    if (!ShadowMask[i]) {
      assert(!ShadowBytes[i]);
      continue;
    }
    uint8_t Val = ShadowBytes[i];
    if (!AsanSetShadowFunc[Val])
      continue;

    // Skip same values.
    for (; j < End && ShadowMask[j] && Val == ShadowBytes[j]; ++j) {
    }

    if (j - i >= ClMaxInlinePoisoningSize) {
      copyToShadowInline(ShadowMask, ShadowBytes, Done, i, IRB, ShadowBase);
      IRB.CreateCall(AsanSetShadowFunc[Val],
                     {IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i)),
                      ConstantInt::get(IntptrTy, j - i)});
      Done = j;
    }
  }

  copyToShadowInline(ShadowMask, ShadowBytes, Done, End, IRB, ShadowBase);
}

// 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");
}

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::processDynamicAllocas() {
  if (!ClInstrumentDynamicAllocas || DynamicAllocaVec.empty()) {
    assert(DynamicAllocaPoisonCallVec.empty());
    return;
  }

  // Insert poison calls for lifetime intrinsics for dynamic allocas.
  for (const auto &APC : DynamicAllocaPoisonCallVec) {
    assert(APC.InsBefore);
    assert(APC.AI);
    assert(ASan.isInterestingAlloca(*APC.AI));
    assert(!APC.AI->isStaticAlloca());

    IRBuilder<> IRB(APC.InsBefore);
    poisonAlloca(APC.AI, APC.Size, IRB, APC.DoPoison);
    // Dynamic allocas will be unpoisoned unconditionally below in
    // unpoisonDynamicAllocas.
    // Flag that we need unpoison static allocas.
  }

  // Handle dynamic allocas.
  createDynamicAllocasInitStorage();
  for (auto &AI : DynamicAllocaVec)
    handleDynamicAllocaCall(AI);
  unpoisonDynamicAllocas();
}

void FunctionStackPoisoner::processStaticAllocas() {
  if (AllocaVec.empty()) {
    assert(StaticAllocaPoisonCallVec.empty());
    return;
  }

  int StackMallocIdx = -1;
  DebugLoc EntryDebugLocation;
  if (auto SP = F.getSubprogram())
    EntryDebugLocation = DebugLoc::get(SP->getScopeLine(), 0, SP);

  Instruction *InsBefore = AllocaVec[0];
  IRBuilder<> IRB(InsBefore);
  IRB.SetCurrentDebugLocation(EntryDebugLocation);

  // Make sure non-instrumented allocas stay in the entry block. Otherwise,
  // debug info is broken, because only entry-block allocas are treated as
  // regular stack slots.
  auto InsBeforeB = InsBefore->getParent();
  assert(InsBeforeB == &F.getEntryBlock());
  for (auto *AI : StaticAllocasToMoveUp)
    if (AI->getParent() == InsBeforeB)
      AI->moveBefore(InsBefore);

  // If we have a call to llvm.localescape, keep it in the entry block.
  if (LocalEscapeCall) LocalEscapeCall->moveBefore(InsBefore);

  SmallVector<ASanStackVariableDescription, 16> SVD;
  SVD.reserve(AllocaVec.size());
  for (AllocaInst *AI : AllocaVec) {
    ASanStackVariableDescription D = {AI->getName().data(),
                                      ASan.getAllocaSizeInBytes(*AI),
                                      0,
                                      AI->getAlignment(),
                                      AI,
                                      0,
                                      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;
  const ASanStackFrameLayout &L =
      ComputeASanStackFrameLayout(SVD, 1ULL << Mapping.Scale, MinHeaderSize);

  // Build AllocaToSVDMap for ASanStackVariableDescription lookup.
  DenseMap<const AllocaInst *, ASanStackVariableDescription *> AllocaToSVDMap;
  for (auto &Desc : SVD)
    AllocaToSVDMap[Desc.AI] = &Desc;

  // Update SVD with information from lifetime intrinsics.
  for (const auto &APC : StaticAllocaPoisonCallVec) {
    assert(APC.InsBefore);
    assert(APC.AI);
    assert(ASan.isInterestingAlloca(*APC.AI));
    assert(APC.AI->isStaticAlloca());

    ASanStackVariableDescription &Desc = *AllocaToSVDMap[APC.AI];
    Desc.LifetimeSize = Desc.Size;
    if (const DILocation *FnLoc = EntryDebugLocation.get()) {
      if (const DILocation *LifetimeLoc = APC.InsBefore->getDebugLoc().get()) {
        if (LifetimeLoc->getFile() == FnLoc->getFile())
          if (unsigned Line = LifetimeLoc->getLine())
            Desc.Line = std::min(Desc.Line ? Desc.Line : Line, Line);
      }
    }
  }

  auto DescriptionString = ComputeASanStackFrameDescription(SVD);
  DEBUG(dbgs() << DescriptionString << " --- " << L.FrameSize << "\n");
  uint64_t LocalStackSize = L.FrameSize;
  bool DoStackMalloc = ClUseAfterReturn && !ASan.CompileKernel &&
                       LocalStackSize <= kMaxStackMallocSize;
  bool DoDynamicAlloca = ClDynamicAllocaStack;
  // Don't do dynamic alloca or stack malloc if:
  // 1) There is inline asm: too often it makes assumptions on which registers
  //    are available.
  // 2) There is a returns_twice call (typically setjmp), which is
  //    optimization-hostile, and doesn't play well with introduced indirect
  //    register-relative calculation of local variable addresses.
  DoDynamicAlloca &= !HasNonEmptyInlineAsm && !HasReturnsTwiceCall;
  DoStackMalloc &= !HasNonEmptyInlineAsm && !HasReturnsTwiceCall;

  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 *OptionDetectUseAfterReturn = F.getParent()->getOrInsertGlobal(
        kAsanOptionDetectUseAfterReturn, IRB.getInt32Ty());
    Value *UseAfterReturnIsEnabled =
        IRB.CreateICmpNE(IRB.CreateLoad(OptionDetectUseAfterReturn),
                         Constant::getNullValue(IRB.getInt32Ty()));
    Instruction *Term =
        SplitBlockAndInsertIfThen(UseAfterReturnIsEnabled, 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, UseAfterReturnIsEnabled, 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;
  }

  // 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(), 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);

  const auto &ShadowAfterScope = GetShadowBytesAfterScope(SVD, L);

  // Poison the stack red zones at the entry.
  Value *ShadowBase = ASan.memToShadow(LocalStackBase, IRB);
  // As mask we must use most poisoned case: red zones and after scope.
  // As bytes we can use either the same or just red zones only.
  copyToShadow(ShadowAfterScope, ShadowAfterScope, IRB, ShadowBase);

  if (!StaticAllocaPoisonCallVec.empty()) {
    const auto &ShadowInScope = GetShadowBytes(SVD, L);

    // Poison static allocas near lifetime intrinsics.
    for (const auto &APC : StaticAllocaPoisonCallVec) {
      const ASanStackVariableDescription &Desc = *AllocaToSVDMap[APC.AI];
      assert(Desc.Offset % L.Granularity == 0);
      size_t Begin = Desc.Offset / L.Granularity;
      size_t End = Begin + (APC.Size + L.Granularity - 1) / L.Granularity;

      IRBuilder<> IRB(APC.InsBefore);
      copyToShadow(ShadowAfterScope,
                   APC.DoPoison ? ShadowAfterScope : ShadowInScope, Begin, End,
                   IRB, ShadowBase);
    }
  }

  SmallVector<uint8_t, 64> ShadowClean(ShadowAfterScope.size(), 0);
  SmallVector<uint8_t, 64> ShadowAfterReturn;

  // (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;
        ShadowAfterReturn.resize(ClassSize / L.Granularity,
                                 kAsanStackUseAfterReturnMagic);
        copyToShadow(ShadowAfterReturn, ShadowAfterReturn, IRBPoison,
                     ShadowBase);
        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);
      copyToShadow(ShadowAfterScope, ShadowClean, IRBElse, ShadowBase);
    } else {
      copyToShadow(ShadowAfterScope, ShadowClean, IRBRet, ShadowBase);
    }
  }

  // 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 interested 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;
    }
  } else if (GetElementPtrInst *EP = dyn_cast<GetElementPtrInst>(V)) {
    Res = findAllocaForValue(EP->getPointerOperand());
  } else {
    DEBUG(dbgs() << "Alloca search canceled on unknown instruction: " << *V << "\n");
  }
  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;
}