text: //===- MemorySanitizer.cpp - detector of uninitialized reads --------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  /// \file
  /// This file is a part of MemorySanitizer, a detector of uninitialized
  /// reads.
  ///
  /// The algorithm of the tool is similar to Memcheck
  /// (http://goo.gl/QKbem). We associate a few shadow bits with every
  /// byte of the application memory, poison the shadow of the malloc-ed
  /// or alloca-ed memory, load the shadow bits on every memory read,
  /// propagate the shadow bits through some of the arithmetic
  /// instruction (including MOV), store the shadow bits on every memory
  /// write, report a bug on some other instructions (e.g. JMP) if the
  /// associated shadow is poisoned.
  ///
  /// But there are differences too. The first and the major one:
  /// compiler instrumentation instead of binary instrumentation. This
  /// gives us much better register allocation, possible compiler
  /// optimizations and a fast start-up. But this brings the major issue
  /// as well: msan needs to see all program events, including system
  /// calls and reads/writes in system libraries, so we either need to
  /// compile *everything* with msan or use a binary translation
  /// component (e.g. DynamoRIO) to instrument pre-built libraries.
  /// Another difference from Memcheck is that we use 8 shadow bits per
  /// byte of application memory and use a direct shadow mapping. This
  /// greatly simplifies the instrumentation code and avoids races on
  /// shadow updates (Memcheck is single-threaded so races are not a
  /// concern there. Memcheck uses 2 shadow bits per byte with a slow
  /// path storage that uses 8 bits per byte).
  ///
  /// The default value of shadow is 0, which means "clean" (not poisoned).
  ///
  /// Every module initializer should call __msan_init to ensure that the
  /// shadow memory is ready. On error, __msan_warning is called. Since
  /// parameters and return values may be passed via registers, we have a
  /// specialized thread-local shadow for return values
  /// (__msan_retval_tls) and parameters (__msan_param_tls).
  ///
  ///                           Origin tracking.
  ///
  /// MemorySanitizer can track origins (allocation points) of all uninitialized
  /// values. This behavior is controlled with a flag (msan-track-origins) and is
  /// disabled by default.
  ///
  /// Origins are 4-byte values created and interpreted by the runtime library.
  /// They are stored in a second shadow mapping, one 4-byte value for 4 bytes
  /// of application memory. Propagation of origins is basically a bunch of
  /// "select" instructions that pick the origin of a dirty argument, if an
  /// instruction has one.
  ///
  /// Every 4 aligned, consecutive bytes of application memory have one origin
  /// value associated with them. If these bytes contain uninitialized data
  /// coming from 2 different allocations, the last store wins. Because of this,
  /// MemorySanitizer reports can show unrelated origins, but this is unlikely in
  /// practice.
  ///
  /// Origins are meaningless for fully initialized values, so MemorySanitizer
  /// avoids storing origin to memory when a fully initialized value is stored.
  /// This way it avoids needless overwritting origin of the 4-byte region on
  /// a short (i.e. 1 byte) clean store, and it is also good for performance.
  ///
  ///                            Atomic handling.
  ///
  /// Ideally, every atomic store of application value should update the
  /// corresponding shadow location in an atomic way. Unfortunately, atomic store
  /// of two disjoint locations can not be done without severe slowdown.
  ///
  /// Therefore, we implement an approximation that may err on the safe side.
  /// In this implementation, every atomically accessed location in the program
  /// may only change from (partially) uninitialized to fully initialized, but
  /// not the other way around. We load the shadow _after_ the application load,
  /// and we store the shadow _before_ the app store. Also, we always store clean
  /// shadow (if the application store is atomic). This way, if the store-load
  /// pair constitutes a happens-before arc, shadow store and load are correctly
  /// ordered such that the load will get either the value that was stored, or
  /// some later value (which is always clean).
  ///
  /// This does not work very well with Compare-And-Swap (CAS) and
  /// Read-Modify-Write (RMW) operations. To follow the above logic, CAS and RMW
  /// must store the new shadow before the app operation, and load the shadow
  /// after the app operation. Computers don't work this way. Current
  /// implementation ignores the load aspect of CAS/RMW, always returning a clean
  /// value. It implements the store part as a simple atomic store by storing a
  /// clean shadow.
  ///
  ///                      Instrumenting inline assembly.
  ///
  /// For inline assembly code LLVM has little idea about which memory locations
  /// become initialized depending on the arguments. It can be possible to figure
  /// out which arguments are meant to point to inputs and outputs, but the
  /// actual semantics can be only visible at runtime. In the Linux kernel it's
  /// also possible that the arguments only indicate the offset for a base taken
  /// from a segment register, so it's dangerous to treat any asm() arguments as
  /// pointers. We take a conservative approach generating calls to
  ///   __msan_instrument_asm_store(ptr, size)
  /// , which defer the memory unpoisoning to the runtime library.
  /// The latter can perform more complex address checks to figure out whether
  /// it's safe to touch the shadow memory.
  /// Like with atomic operations, we call __msan_instrument_asm_store() before
  /// the assembly call, so that changes to the shadow memory will be seen by
  /// other threads together with main memory initialization.
  ///
  ///                  KernelMemorySanitizer (KMSAN) implementation.
  ///
  /// The major differences between KMSAN and MSan instrumentation are:
  ///  - KMSAN always tracks the origins and implies msan-keep-going=true;
  ///  - KMSAN allocates shadow and origin memory for each page separately, so
  ///    there are no explicit accesses to shadow and origin in the
  ///    instrumentation.
  ///    Shadow and origin values for a particular X-byte memory location
  ///    (X=1,2,4,8) are accessed through pointers obtained via the
  ///      __msan_metadata_ptr_for_load_X(ptr)
  ///      __msan_metadata_ptr_for_store_X(ptr)
  ///    functions. The corresponding functions check that the X-byte accesses
  ///    are possible and returns the pointers to shadow and origin memory.
  ///    Arbitrary sized accesses are handled with:
  ///      __msan_metadata_ptr_for_load_n(ptr, size)
  ///      __msan_metadata_ptr_for_store_n(ptr, size);
  ///  - TLS variables are stored in a single per-task struct. A call to a
  ///    function __msan_get_context_state() returning a pointer to that struct
  ///    is inserted into every instrumented function before the entry block;
  ///  - __msan_warning() takes a 32-bit origin parameter;
  ///  - local variables are poisoned with __msan_poison_alloca() upon function
  ///    entry and unpoisoned with __msan_unpoison_alloca() before leaving the
  ///    function;
  ///  - the pass doesn't declare any global variables or add global constructors
  ///    to the translation unit.
  ///
  /// Also, KMSAN currently ignores uninitialized memory passed into inline asm
  /// calls, making sure we're on the safe side wrt. possible false positives.
  ///
  ///  KernelMemorySanitizer only supports X86_64 at the moment.
  ///
  //===----------------------------------------------------------------------===//
  
  #include "llvm/Transforms/Instrumentation/MemorySanitizer.h"
  #include "llvm/ADT/APInt.h"
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/DepthFirstIterator.h"
  #include "llvm/ADT/SmallSet.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringExtras.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/ADT/Triple.h"
  #include "llvm/Analysis/TargetLibraryInfo.h"
  #include "llvm/IR/Argument.h"
  #include "llvm/IR/Attributes.h"
  #include "llvm/IR/BasicBlock.h"
  #include "llvm/IR/CallSite.h"
  #include "llvm/IR/CallingConv.h"
  #include "llvm/IR/Constant.h"
  #include "llvm/IR/Constants.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/DerivedTypes.h"
  #include "llvm/IR/Function.h"
  #include "llvm/IR/GlobalValue.h"
  #include "llvm/IR/GlobalVariable.h"
  #include "llvm/IR/IRBuilder.h"
  #include "llvm/IR/InlineAsm.h"
  #include "llvm/IR/InstVisitor.h"
  #include "llvm/IR/InstrTypes.h"
  #include "llvm/IR/Instruction.h"
  #include "llvm/IR/Instructions.h"
  #include "llvm/IR/IntrinsicInst.h"
  #include "llvm/IR/Intrinsics.h"
  #include "llvm/IR/LLVMContext.h"
  #include "llvm/IR/MDBuilder.h"
  #include "llvm/IR/Module.h"
  #include "llvm/IR/Type.h"
  #include "llvm/IR/Value.h"
  #include "llvm/IR/ValueMap.h"
  #include "llvm/Pass.h"
  #include "llvm/Support/AtomicOrdering.h"
  #include "llvm/Support/Casting.h"
  #include "llvm/Support/CommandLine.h"
  #include "llvm/Support/Compiler.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/MathExtras.h"
  #include "llvm/Support/raw_ostream.h"
  #include "llvm/Transforms/Instrumentation.h"
  #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  #include "llvm/Transforms/Utils/Local.h"
  #include "llvm/Transforms/Utils/ModuleUtils.h"
  #include <algorithm>
  #include <cassert>
  #include <cstddef>
  #include <cstdint>
  #include <memory>
  #include <string>
  #include <tuple>
  
  using namespace llvm;
  
  #define DEBUG_TYPE "msan"
  
  static const unsigned kOriginSize = 4;
  static const unsigned kMinOriginAlignment = 4;
  static const unsigned kShadowTLSAlignment = 8;
  
  // These constants must be kept in sync with the ones in msan.h.
  static const unsigned kParamTLSSize = 800;
  static const unsigned kRetvalTLSSize = 800;
  
  // Accesses sizes are powers of two: 1, 2, 4, 8.
  static const size_t kNumberOfAccessSizes = 4;
  
  /// Track origins of uninitialized values.
  ///
  /// Adds a section to MemorySanitizer report that points to the allocation
  /// (stack or heap) the uninitialized bits came from originally.
  static cl::opt<int> ClTrackOrigins("msan-track-origins",
         cl::desc("Track origins (allocation sites) of poisoned memory"),
         cl::Hidden, cl::init(0));
  
  static cl::opt<bool> ClKeepGoing("msan-keep-going",
         cl::desc("keep going after reporting a UMR"),
         cl::Hidden, cl::init(false));
  
  static cl::opt<bool> ClPoisonStack("msan-poison-stack",
         cl::desc("poison uninitialized stack variables"),
         cl::Hidden, cl::init(true));
  
  static cl::opt<bool> ClPoisonStackWithCall("msan-poison-stack-with-call",
         cl::desc("poison uninitialized stack variables with a call"),
         cl::Hidden, cl::init(false));
  
  static cl::opt<int> ClPoisonStackPattern("msan-poison-stack-pattern",
         cl::desc("poison uninitialized stack variables with the given pattern"),
         cl::Hidden, cl::init(0xff));
  
  static cl::opt<bool> ClPoisonUndef("msan-poison-undef",
         cl::desc("poison undef temps"),
         cl::Hidden, cl::init(true));
  
  static cl::opt<bool> ClHandleICmp("msan-handle-icmp",
         cl::desc("propagate shadow through ICmpEQ and ICmpNE"),
         cl::Hidden, cl::init(true));
  
  static cl::opt<bool> ClHandleICmpExact("msan-handle-icmp-exact",
         cl::desc("exact handling of relational integer ICmp"),
         cl::Hidden, cl::init(false));
  
  static cl::opt<bool> ClHandleLifetimeIntrinsics(
      "msan-handle-lifetime-intrinsics",
      cl::desc(
          "when possible, poison scoped variables at the beginning of the scope "
          "(slower, but more precise)"),
      cl::Hidden, cl::init(true));
  
  // When compiling the Linux kernel, we sometimes see false positives related to
  // MSan being unable to understand that inline assembly calls may initialize
  // local variables.
  // This flag makes the compiler conservatively unpoison every memory location
  // passed into an assembly call. Note that this may cause false positives.
  // Because it's impossible to figure out the array sizes, we can only unpoison
  // the first sizeof(type) bytes for each type* pointer.
  // The instrumentation is only enabled in KMSAN builds, and only if
  // -msan-handle-asm-conservative is on. This is done because we may want to
  // quickly disable assembly instrumentation when it breaks.
  static cl::opt<bool> ClHandleAsmConservative(
      "msan-handle-asm-conservative",
      cl::desc("conservative handling of inline assembly"), cl::Hidden,
      cl::init(true));
  
  // This flag controls whether we check the shadow of the address
  // operand of load or store. Such bugs are very rare, since load from
  // a garbage address typically results in SEGV, but still happen
  // (e.g. only lower bits of address are garbage, or the access happens
  // early at program startup where malloc-ed memory is more likely to
  // be zeroed. As of 2012-08-28 this flag adds 20% slowdown.
  static cl::opt<bool> ClCheckAccessAddress("msan-check-access-address",
         cl::desc("report accesses through a pointer which has poisoned shadow"),
         cl::Hidden, cl::init(true));
  
  static cl::opt<bool> ClDumpStrictInstructions("msan-dump-strict-instructions",
         cl::desc("print out instructions with default strict semantics"),
         cl::Hidden, cl::init(false));
  
  static cl::opt<int> ClInstrumentationWithCallThreshold(
      "msan-instrumentation-with-call-threshold",
      cl::desc(
          "If the function being instrumented requires more than "
          "this number of checks and origin stores, use callbacks instead of "
          "inline checks (-1 means never use callbacks)."),
      cl::Hidden, cl::init(3500));
  
  static cl::opt<bool>
      ClEnableKmsan("msan-kernel",
                    cl::desc("Enable KernelMemorySanitizer instrumentation"),
                    cl::Hidden, cl::init(false));
  
  // This is an experiment to enable handling of cases where shadow is a non-zero
  // compile-time constant. For some unexplainable reason they were silently
  // ignored in the instrumentation.
  static cl::opt<bool> ClCheckConstantShadow("msan-check-constant-shadow",
         cl::desc("Insert checks for constant shadow values"),
         cl::Hidden, cl::init(false));
  
  // This is off by default because of a bug in gold:
  // https://sourceware.org/bugzilla/show_bug.cgi?id=19002
  static cl::opt<bool> ClWithComdat("msan-with-comdat",
         cl::desc("Place MSan constructors in comdat sections"),
         cl::Hidden, cl::init(false));
  
  // These options allow to specify custom memory map parameters
  // See MemoryMapParams for details.
  static cl::opt<uint64_t> ClAndMask("msan-and-mask",
                                     cl::desc("Define custom MSan AndMask"),
                                     cl::Hidden, cl::init(0));
  
  static cl::opt<uint64_t> ClXorMask("msan-xor-mask",
                                     cl::desc("Define custom MSan XorMask"),
                                     cl::Hidden, cl::init(0));
  
  static cl::opt<uint64_t> ClShadowBase("msan-shadow-base",
                                        cl::desc("Define custom MSan ShadowBase"),
                                        cl::Hidden, cl::init(0));
  
  static cl::opt<uint64_t> ClOriginBase("msan-origin-base",
                                        cl::desc("Define custom MSan OriginBase"),
                                        cl::Hidden, cl::init(0));
  
  static const char *const kMsanModuleCtorName = "msan.module_ctor";
  static const char *const kMsanInitName = "__msan_init";
  
  namespace {
  
  // Memory map parameters used in application-to-shadow address calculation.
  // Offset = (Addr & ~AndMask) ^ XorMask
  // Shadow = ShadowBase + Offset
  // Origin = OriginBase + Offset
  struct MemoryMapParams {
    uint64_t AndMask;
    uint64_t XorMask;
    uint64_t ShadowBase;
    uint64_t OriginBase;
  };
  
  struct PlatformMemoryMapParams {
    const MemoryMapParams *bits32;
    const MemoryMapParams *bits64;
  };
  
  } // end anonymous namespace
  
  // i386 Linux
  static const MemoryMapParams Linux_I386_MemoryMapParams = {
    0x000080000000,  // AndMask
    0,               // XorMask (not used)
    0,               // ShadowBase (not used)
    0x000040000000,  // OriginBase
  };
  
  // x86_64 Linux
  static const MemoryMapParams Linux_X86_64_MemoryMapParams = {
  #ifdef MSAN_LINUX_X86_64_OLD_MAPPING
    0x400000000000,  // AndMask
    0,               // XorMask (not used)
    0,               // ShadowBase (not used)
    0x200000000000,  // OriginBase
  #else
    0,               // AndMask (not used)
    0x500000000000,  // XorMask
    0,               // ShadowBase (not used)
    0x100000000000,  // OriginBase
  #endif
  };
  
  // mips64 Linux
  static const MemoryMapParams Linux_MIPS64_MemoryMapParams = {
    0,               // AndMask (not used)
    0x008000000000,  // XorMask
    0,               // ShadowBase (not used)
    0x002000000000,  // OriginBase
  };
  
  // ppc64 Linux
  static const MemoryMapParams Linux_PowerPC64_MemoryMapParams = {
    0xE00000000000,  // AndMask
    0x100000000000,  // XorMask
    0x080000000000,  // ShadowBase
    0x1C0000000000,  // OriginBase
  };
  
  // aarch64 Linux
  static const MemoryMapParams Linux_AArch64_MemoryMapParams = {
    0,               // AndMask (not used)
    0x06000000000,   // XorMask
    0,               // ShadowBase (not used)
    0x01000000000,   // OriginBase
  };
  
  // i386 FreeBSD
  static const MemoryMapParams FreeBSD_I386_MemoryMapParams = {
    0x000180000000,  // AndMask
    0x000040000000,  // XorMask
    0x000020000000,  // ShadowBase
    0x000700000000,  // OriginBase
  };
  
  // x86_64 FreeBSD
  static const MemoryMapParams FreeBSD_X86_64_MemoryMapParams = {
    0xc00000000000,  // AndMask
    0x200000000000,  // XorMask
    0x100000000000,  // ShadowBase
    0x380000000000,  // OriginBase
  };
  
  // x86_64 NetBSD
  static const MemoryMapParams NetBSD_X86_64_MemoryMapParams = {
    0,               // AndMask
    0x500000000000,  // XorMask
    0,               // ShadowBase
    0x100000000000,  // OriginBase
  };
  
  static const PlatformMemoryMapParams Linux_X86_MemoryMapParams = {
    &Linux_I386_MemoryMapParams,
    &Linux_X86_64_MemoryMapParams,
  };
  
  static const PlatformMemoryMapParams Linux_MIPS_MemoryMapParams = {
    nullptr,
    &Linux_MIPS64_MemoryMapParams,
  };
  
  static const PlatformMemoryMapParams Linux_PowerPC_MemoryMapParams = {
    nullptr,
    &Linux_PowerPC64_MemoryMapParams,
  };
  
  static const PlatformMemoryMapParams Linux_ARM_MemoryMapParams = {
    nullptr,
    &Linux_AArch64_MemoryMapParams,
  };
  
  static const PlatformMemoryMapParams FreeBSD_X86_MemoryMapParams = {
    &FreeBSD_I386_MemoryMapParams,
    &FreeBSD_X86_64_MemoryMapParams,
  };
  
  static const PlatformMemoryMapParams NetBSD_X86_MemoryMapParams = {
    nullptr,
    &NetBSD_X86_64_MemoryMapParams,
  };
  
  namespace {
  
  /// Instrument functions of a module to detect uninitialized reads.
  ///
  /// Instantiating MemorySanitizer inserts the msan runtime library API function
  /// declarations into the module if they don't exist already. Instantiating
  /// ensures the __msan_init function is in the list of global constructors for
  /// the module.
  class MemorySanitizer {
  public:
    MemorySanitizer(Module &M, MemorySanitizerOptions Options) {
      this->CompileKernel =
          ClEnableKmsan.getNumOccurrences() > 0 ? ClEnableKmsan : Options.Kernel;
      if (ClTrackOrigins.getNumOccurrences() > 0)
        this->TrackOrigins = ClTrackOrigins;
      else
        this->TrackOrigins = this->CompileKernel ? 2 : Options.TrackOrigins;
      this->Recover = ClKeepGoing.getNumOccurrences() > 0
                          ? ClKeepGoing
                          : (this->CompileKernel | Options.Recover);
      initializeModule(M);
    }
  
    // MSan cannot be moved or copied because of MapParams.
    MemorySanitizer(MemorySanitizer &&) = delete;
    MemorySanitizer &operator=(MemorySanitizer &&) = delete;
    MemorySanitizer(const MemorySanitizer &) = delete;
    MemorySanitizer &operator=(const MemorySanitizer &) = delete;
  
    bool sanitizeFunction(Function &F, TargetLibraryInfo &TLI);
  
  private:
    friend struct MemorySanitizerVisitor;
    friend struct VarArgAMD64Helper;
    friend struct VarArgMIPS64Helper;
    friend struct VarArgAArch64Helper;
    friend struct VarArgPowerPC64Helper;
  
    void initializeModule(Module &M);
    void initializeCallbacks(Module &M);
    void createKernelApi(Module &M);
    void createUserspaceApi(Module &M);
  
    /// True if we're compiling the Linux kernel.
    bool CompileKernel;
    /// Track origins (allocation points) of uninitialized values.
    int TrackOrigins;
    bool Recover;
  
    LLVMContext *C;
    Type *IntptrTy;
    Type *OriginTy;
  
    // XxxTLS variables represent the per-thread state in MSan and per-task state
    // in KMSAN.
    // For the userspace these point to thread-local globals. In the kernel land
    // they point to the members of a per-task struct obtained via a call to
    // __msan_get_context_state().
  
    /// Thread-local shadow storage for function parameters.
    Value *ParamTLS;
  
    /// Thread-local origin storage for function parameters.
    Value *ParamOriginTLS;
  
    /// Thread-local shadow storage for function return value.
    Value *RetvalTLS;
  
    /// Thread-local origin storage for function return value.
    Value *RetvalOriginTLS;
  
    /// Thread-local shadow storage for in-register va_arg function
    /// parameters (x86_64-specific).
    Value *VAArgTLS;
  
    /// Thread-local shadow storage for in-register va_arg function
    /// parameters (x86_64-specific).
    Value *VAArgOriginTLS;
  
    /// Thread-local shadow storage for va_arg overflow area
    /// (x86_64-specific).
    Value *VAArgOverflowSizeTLS;
  
    /// Thread-local space used to pass origin value to the UMR reporting
    /// function.
    Value *OriginTLS;
  
    /// Are the instrumentation callbacks set up?
    bool CallbacksInitialized = false;
  
    /// The run-time callback to print a warning.
    FunctionCallee WarningFn;
  
    // These arrays are indexed by log2(AccessSize).
    FunctionCallee MaybeWarningFn[kNumberOfAccessSizes];
    FunctionCallee MaybeStoreOriginFn[kNumberOfAccessSizes];
  
    /// Run-time helper that generates a new origin value for a stack
    /// allocation.
    FunctionCallee MsanSetAllocaOrigin4Fn;
  
    /// Run-time helper that poisons stack on function entry.
    FunctionCallee MsanPoisonStackFn;
  
    /// Run-time helper that records a store (or any event) of an
    /// uninitialized value and returns an updated origin id encoding this info.
    FunctionCallee MsanChainOriginFn;
  
    /// MSan runtime replacements for memmove, memcpy and memset.
    FunctionCallee MemmoveFn, MemcpyFn, MemsetFn;
  
    /// KMSAN callback for task-local function argument shadow.
    StructType *MsanContextStateTy;
    FunctionCallee MsanGetContextStateFn;
  
    /// Functions for poisoning/unpoisoning local variables
    FunctionCallee MsanPoisonAllocaFn, MsanUnpoisonAllocaFn;
  
    /// Each of the MsanMetadataPtrXxx functions returns a pair of shadow/origin
    /// pointers.
    FunctionCallee MsanMetadataPtrForLoadN, MsanMetadataPtrForStoreN;
    FunctionCallee MsanMetadataPtrForLoad_1_8[4];
    FunctionCallee MsanMetadataPtrForStore_1_8[4];
    FunctionCallee MsanInstrumentAsmStoreFn;
  
    /// Helper to choose between different MsanMetadataPtrXxx().
    FunctionCallee getKmsanShadowOriginAccessFn(bool isStore, int size);
  
    /// Memory map parameters used in application-to-shadow calculation.
    const MemoryMapParams *MapParams;
  
    /// Custom memory map parameters used when -msan-shadow-base or
    // -msan-origin-base is provided.
    MemoryMapParams CustomMapParams;
  
    MDNode *ColdCallWeights;
  
    /// Branch weights for origin store.
    MDNode *OriginStoreWeights;
  
    /// An empty volatile inline asm that prevents callback merge.
    InlineAsm *EmptyAsm;
  
    Function *MsanCtorFunction;
  };
  
  /// A legacy function pass for msan instrumentation.
  ///
  /// Instruments functions to detect unitialized reads.
  struct MemorySanitizerLegacyPass : public FunctionPass {
    // Pass identification, replacement for typeid.
    static char ID;
  
    MemorySanitizerLegacyPass(MemorySanitizerOptions Options = {})
        : FunctionPass(ID), Options(Options) {}
    StringRef getPassName() const override { return "MemorySanitizerLegacyPass"; }
  
    void getAnalysisUsage(AnalysisUsage &AU) const override {
      AU.addRequired<TargetLibraryInfoWrapperPass>();
    }
  
    bool runOnFunction(Function &F) override {
      return MSan->sanitizeFunction(
          F, getAnalysis<TargetLibraryInfoWrapperPass>().getTLI());
    }
    bool doInitialization(Module &M) override;
  
    Optional<MemorySanitizer> MSan;
    MemorySanitizerOptions Options;
  };
  
  } // end anonymous namespace
  
  PreservedAnalyses MemorySanitizerPass::run(Function &F,
                                             FunctionAnalysisManager &FAM) {
    MemorySanitizer Msan(*F.getParent(), Options);
    if (Msan.sanitizeFunction(F, FAM.getResult<TargetLibraryAnalysis>(F)))
      return PreservedAnalyses::none();
    return PreservedAnalyses::all();
  }
  
  char MemorySanitizerLegacyPass::ID = 0;
  
  INITIALIZE_PASS_BEGIN(MemorySanitizerLegacyPass, "msan",
                        "MemorySanitizer: detects uninitialized reads.", false,
                        false)
  INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
  INITIALIZE_PASS_END(MemorySanitizerLegacyPass, "msan",
                      "MemorySanitizer: detects uninitialized reads.", false,
                      false)
  
  FunctionPass *
  llvm::createMemorySanitizerLegacyPassPass(MemorySanitizerOptions Options) {
    return new MemorySanitizerLegacyPass(Options);
  }
  
  /// Create a non-const global initialized with the given string.
  ///
  /// Creates a writable global for Str so that we can pass it to the
  /// run-time lib. Runtime uses first 4 bytes of the string to store the
  /// frame ID, so the string needs to be mutable.
  static GlobalVariable *createPrivateNonConstGlobalForString(Module &M,
                                                              StringRef Str) {
    Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
    return new GlobalVariable(M, StrConst->getType(), /*isConstant=*/false,
                              GlobalValue::PrivateLinkage, StrConst, "");
  }
  
  /// Create KMSAN API callbacks.
  void MemorySanitizer::createKernelApi(Module &M) {
    IRBuilder<> IRB(*C);
  
    // These will be initialized in insertKmsanPrologue().
    RetvalTLS = nullptr;
    RetvalOriginTLS = nullptr;
    ParamTLS = nullptr;
    ParamOriginTLS = nullptr;
    VAArgTLS = nullptr;
    VAArgOriginTLS = nullptr;
    VAArgOverflowSizeTLS = nullptr;
    // OriginTLS is unused in the kernel.
    OriginTLS = nullptr;
  
    // __msan_warning() in the kernel takes an origin.
    WarningFn = M.getOrInsertFunction("__msan_warning", IRB.getVoidTy(),
                                      IRB.getInt32Ty());
    // Requests the per-task context state (kmsan_context_state*) from the
    // runtime library.
    MsanContextStateTy = StructType::get(
        ArrayType::get(IRB.getInt64Ty(), kParamTLSSize / 8),
        ArrayType::get(IRB.getInt64Ty(), kRetvalTLSSize / 8),
        ArrayType::get(IRB.getInt64Ty(), kParamTLSSize / 8),
        ArrayType::get(IRB.getInt64Ty(), kParamTLSSize / 8), /* va_arg_origin */
        IRB.getInt64Ty(), ArrayType::get(OriginTy, kParamTLSSize / 4), OriginTy,
        OriginTy);
    MsanGetContextStateFn = M.getOrInsertFunction(
        "__msan_get_context_state", PointerType::get(MsanContextStateTy, 0));
  
    Type *RetTy = StructType::get(PointerType::get(IRB.getInt8Ty(), 0),
                                  PointerType::get(IRB.getInt32Ty(), 0));
  
    for (int ind = 0, size = 1; ind < 4; ind++, size <<= 1) {
      std::string name_load =
          "__msan_metadata_ptr_for_load_" + std::to_string(size);
      std::string name_store =
          "__msan_metadata_ptr_for_store_" + std::to_string(size);
      MsanMetadataPtrForLoad_1_8[ind] = M.getOrInsertFunction(
          name_load, RetTy, PointerType::get(IRB.getInt8Ty(), 0));
      MsanMetadataPtrForStore_1_8[ind] = M.getOrInsertFunction(
          name_store, RetTy, PointerType::get(IRB.getInt8Ty(), 0));
    }
  
    MsanMetadataPtrForLoadN = M.getOrInsertFunction(
        "__msan_metadata_ptr_for_load_n", RetTy,
        PointerType::get(IRB.getInt8Ty(), 0), IRB.getInt64Ty());
    MsanMetadataPtrForStoreN = M.getOrInsertFunction(
        "__msan_metadata_ptr_for_store_n", RetTy,
        PointerType::get(IRB.getInt8Ty(), 0), IRB.getInt64Ty());
  
    // Functions for poisoning and unpoisoning memory.
    MsanPoisonAllocaFn =
        M.getOrInsertFunction("__msan_poison_alloca", IRB.getVoidTy(),
                              IRB.getInt8PtrTy(), IntptrTy, IRB.getInt8PtrTy());
    MsanUnpoisonAllocaFn = M.getOrInsertFunction(
        "__msan_unpoison_alloca", IRB.getVoidTy(), IRB.getInt8PtrTy(), IntptrTy);
  }
  
  static Constant *getOrInsertGlobal(Module &M, StringRef Name, Type *Ty) {
    return M.getOrInsertGlobal(Name, Ty, [&] {
      return new GlobalVariable(M, Ty, false, GlobalVariable::ExternalLinkage,
                                nullptr, Name, nullptr,
                                GlobalVariable::InitialExecTLSModel);
    });
  }
  
  /// Insert declarations for userspace-specific functions and globals.
  void MemorySanitizer::createUserspaceApi(Module &M) {
    IRBuilder<> IRB(*C);
    // Create the callback.
    // FIXME: this function should have "Cold" calling conv,
    // which is not yet implemented.
    StringRef WarningFnName = Recover ? "__msan_warning"
                                      : "__msan_warning_noreturn";
    WarningFn = M.getOrInsertFunction(WarningFnName, IRB.getVoidTy());
  
    // Create the global TLS variables.
    RetvalTLS =
        getOrInsertGlobal(M, "__msan_retval_tls",
                          ArrayType::get(IRB.getInt64Ty(), kRetvalTLSSize / 8));
  
    RetvalOriginTLS = getOrInsertGlobal(M, "__msan_retval_origin_tls", OriginTy);
  
    ParamTLS =
        getOrInsertGlobal(M, "__msan_param_tls",
                          ArrayType::get(IRB.getInt64Ty(), kParamTLSSize / 8));
  
    ParamOriginTLS =
        getOrInsertGlobal(M, "__msan_param_origin_tls",
                          ArrayType::get(OriginTy, kParamTLSSize / 4));
  
    VAArgTLS =
        getOrInsertGlobal(M, "__msan_va_arg_tls",
                          ArrayType::get(IRB.getInt64Ty(), kParamTLSSize / 8));
  
    VAArgOriginTLS =
        getOrInsertGlobal(M, "__msan_va_arg_origin_tls",
                          ArrayType::get(OriginTy, kParamTLSSize / 4));
  
    VAArgOverflowSizeTLS =
        getOrInsertGlobal(M, "__msan_va_arg_overflow_size_tls", IRB.getInt64Ty());
    OriginTLS = getOrInsertGlobal(M, "__msan_origin_tls", IRB.getInt32Ty());
  
    for (size_t AccessSizeIndex = 0; AccessSizeIndex < kNumberOfAccessSizes;
         AccessSizeIndex++) {
      unsigned AccessSize = 1 << AccessSizeIndex;
      std::string FunctionName = "__msan_maybe_warning_" + itostr(AccessSize);
      MaybeWarningFn[AccessSizeIndex] = M.getOrInsertFunction(
          FunctionName, IRB.getVoidTy(), IRB.getIntNTy(AccessSize * 8),
          IRB.getInt32Ty());
  
      FunctionName = "__msan_maybe_store_origin_" + itostr(AccessSize);
      MaybeStoreOriginFn[AccessSizeIndex] = M.getOrInsertFunction(
          FunctionName, IRB.getVoidTy(), IRB.getIntNTy(AccessSize * 8),
          IRB.getInt8PtrTy(), IRB.getInt32Ty());
    }
  
    MsanSetAllocaOrigin4Fn = M.getOrInsertFunction(
      "__msan_set_alloca_origin4", IRB.getVoidTy(), IRB.getInt8PtrTy(), IntptrTy,
      IRB.getInt8PtrTy(), IntptrTy);
    MsanPoisonStackFn =
        M.getOrInsertFunction("__msan_poison_stack", IRB.getVoidTy(),
                              IRB.getInt8PtrTy(), IntptrTy);
  }
  
  /// Insert extern declaration of runtime-provided functions and globals.
  void MemorySanitizer::initializeCallbacks(Module &M) {
    // Only do this once.
    if (CallbacksInitialized)
      return;
  
    IRBuilder<> IRB(*C);
    // Initialize callbacks that are common for kernel and userspace
    // instrumentation.
    MsanChainOriginFn = M.getOrInsertFunction(
      "__msan_chain_origin", IRB.getInt32Ty(), IRB.getInt32Ty());
    MemmoveFn = M.getOrInsertFunction(
      "__msan_memmove", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
      IRB.getInt8PtrTy(), IntptrTy);
    MemcpyFn = M.getOrInsertFunction(
      "__msan_memcpy", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
      IntptrTy);
    MemsetFn = M.getOrInsertFunction(
      "__msan_memset", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IRB.getInt32Ty(),
      IntptrTy);
    // We insert an empty inline asm after __msan_report* to avoid callback merge.
    EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
                              StringRef(""), StringRef(""),
                              /*hasSideEffects=*/true);
  
    MsanInstrumentAsmStoreFn =
        M.getOrInsertFunction("__msan_instrument_asm_store", IRB.getVoidTy(),
                              PointerType::get(IRB.getInt8Ty(), 0), IntptrTy);
  
    if (CompileKernel) {
      createKernelApi(M);
    } else {
      createUserspaceApi(M);
    }
    CallbacksInitialized = true;
  }
  
  FunctionCallee MemorySanitizer::getKmsanShadowOriginAccessFn(bool isStore,
                                                               int size) {
    FunctionCallee *Fns =
        isStore ? MsanMetadataPtrForStore_1_8 : MsanMetadataPtrForLoad_1_8;
    switch (size) {
    case 1:
      return Fns[0];
    case 2:
      return Fns[1];
    case 4:
      return Fns[2];
    case 8:
      return Fns[3];
    default:
      return nullptr;
    }
  }
  
  /// Module-level initialization.
  ///
  /// inserts a call to __msan_init to the module's constructor list.
  void MemorySanitizer::initializeModule(Module &M) {
    auto &DL = M.getDataLayout();
  
    bool ShadowPassed = ClShadowBase.getNumOccurrences() > 0;
    bool OriginPassed = ClOriginBase.getNumOccurrences() > 0;
    // Check the overrides first
    if (ShadowPassed || OriginPassed) {
      CustomMapParams.AndMask = ClAndMask;
      CustomMapParams.XorMask = ClXorMask;
      CustomMapParams.ShadowBase = ClShadowBase;
      CustomMapParams.OriginBase = ClOriginBase;
      MapParams = &CustomMapParams;
    } else {
      Triple TargetTriple(M.getTargetTriple());
      switch (TargetTriple.getOS()) {
        case Triple::FreeBSD:
          switch (TargetTriple.getArch()) {
            case Triple::x86_64:
              MapParams = FreeBSD_X86_MemoryMapParams.bits64;
              break;
            case Triple::x86:
              MapParams = FreeBSD_X86_MemoryMapParams.bits32;
              break;
            default:
              report_fatal_error("unsupported architecture");
          }
          break;
        case Triple::NetBSD:
          switch (TargetTriple.getArch()) {
            case Triple::x86_64:
              MapParams = NetBSD_X86_MemoryMapParams.bits64;
              break;
            default:
              report_fatal_error("unsupported architecture");
          }
          break;
        case Triple::Linux:
          switch (TargetTriple.getArch()) {
            case Triple::x86_64:
              MapParams = Linux_X86_MemoryMapParams.bits64;
              break;
            case Triple::x86:
              MapParams = Linux_X86_MemoryMapParams.bits32;
              break;
            case Triple::mips64:
            case Triple::mips64el:
              MapParams = Linux_MIPS_MemoryMapParams.bits64;
              break;
            case Triple::ppc64:
            case Triple::ppc64le:
              MapParams = Linux_PowerPC_MemoryMapParams.bits64;
              break;
            case Triple::aarch64:
            case Triple::aarch64_be:
              MapParams = Linux_ARM_MemoryMapParams.bits64;
              break;
            default:
              report_fatal_error("unsupported architecture");
          }
          break;
        default:
          report_fatal_error("unsupported operating system");
      }
    }
  
    C = &(M.getContext());
    IRBuilder<> IRB(*C);
    IntptrTy = IRB.getIntPtrTy(DL);
    OriginTy = IRB.getInt32Ty();
  
    ColdCallWeights = MDBuilder(*C).createBranchWeights(1, 1000);
    OriginStoreWeights = MDBuilder(*C).createBranchWeights(1, 1000);
  
    if (!CompileKernel) {
      std::tie(MsanCtorFunction, std::ignore) =
          getOrCreateSanitizerCtorAndInitFunctions(
              M, kMsanModuleCtorName, kMsanInitName,
              /*InitArgTypes=*/{},
              /*InitArgs=*/{},
              // This callback is invoked when the functions are created the first
              // time. Hook them into the global ctors list in that case:
              [&](Function *Ctor, FunctionCallee) {
                if (!ClWithComdat) {
                  appendToGlobalCtors(M, Ctor, 0);
                  return;
                }
                Comdat *MsanCtorComdat = M.getOrInsertComdat(kMsanModuleCtorName);
                Ctor->setComdat(MsanCtorComdat);
                appendToGlobalCtors(M, Ctor, 0, Ctor);
              });
  
      if (TrackOrigins)
        M.getOrInsertGlobal("__msan_track_origins", IRB.getInt32Ty(), [&] {
          return new GlobalVariable(
              M, IRB.getInt32Ty(), true, GlobalValue::WeakODRLinkage,
              IRB.getInt32(TrackOrigins), "__msan_track_origins");
        });
  
      if (Recover)
        M.getOrInsertGlobal("__msan_keep_going", IRB.getInt32Ty(), [&] {
          return new GlobalVariable(M, IRB.getInt32Ty(), true,
                                    GlobalValue::WeakODRLinkage,
                                    IRB.getInt32(Recover), "__msan_keep_going");
        });
  }
  }
  
  bool MemorySanitizerLegacyPass::doInitialization(Module &M) {
    MSan.emplace(M, Options);
    return true;
  }
  
  namespace {
  
  /// A helper class that handles instrumentation of VarArg
  /// functions on a particular platform.
  ///
  /// Implementations are expected to insert the instrumentation
  /// necessary to propagate argument shadow through VarArg function
  /// calls. Visit* methods are called during an InstVisitor pass over
  /// the function, and should avoid creating new basic blocks. A new
  /// instance of this class is created for each instrumented function.
  struct VarArgHelper {
    virtual ~VarArgHelper() = default;
  
    /// Visit a CallSite.
    virtual void visitCallSite(CallSite &CS, IRBuilder<> &IRB) = 0;
  
    /// Visit a va_start call.
    virtual void visitVAStartInst(VAStartInst &I) = 0;
  
    /// Visit a va_copy call.
    virtual void visitVACopyInst(VACopyInst &I) = 0;
  
    /// Finalize function instrumentation.
    ///
    /// This method is called after visiting all interesting (see above)
    /// instructions in a function.
    virtual void finalizeInstrumentation() = 0;
  };
  
  struct MemorySanitizerVisitor;
  
  } // end anonymous namespace
  
  static VarArgHelper *CreateVarArgHelper(Function &Func, MemorySanitizer &Msan,
                                          MemorySanitizerVisitor &Visitor);
  
  static unsigned TypeSizeToSizeIndex(unsigned TypeSize) {
    if (TypeSize <= 8) return 0;
    return Log2_32_Ceil((TypeSize + 7) / 8);
  }
  
  namespace {
  
  /// This class does all the work for a given function. Store and Load
  /// instructions store and load corresponding shadow and origin
  /// values. Most instructions propagate shadow from arguments to their
  /// return values. Certain instructions (most importantly, BranchInst)
  /// test their argument shadow and print reports (with a runtime call) if it's
  /// non-zero.
  struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
    Function &F;
    MemorySanitizer &MS;
    SmallVector<PHINode *, 16> ShadowPHINodes, OriginPHINodes;
    ValueMap<Value*, Value*> ShadowMap, OriginMap;
    std::unique_ptr<VarArgHelper> VAHelper;
    const TargetLibraryInfo *TLI;
    BasicBlock *ActualFnStart;
  
    // The following flags disable parts of MSan instrumentation based on
    // blacklist contents and command-line options.
    bool InsertChecks;
    bool PropagateShadow;
    bool PoisonStack;
    bool PoisonUndef;
    bool CheckReturnValue;
  
    struct ShadowOriginAndInsertPoint {
      Value *Shadow;
      Value *Origin;
      Instruction *OrigIns;
  
      ShadowOriginAndInsertPoint(Value *S, Value *O, Instruction *I)
        : Shadow(S), Origin(O), OrigIns(I) {}
    };
    SmallVector<ShadowOriginAndInsertPoint, 16> InstrumentationList;
    bool InstrumentLifetimeStart = ClHandleLifetimeIntrinsics;
    SmallSet<AllocaInst *, 16> AllocaSet;
    SmallVector<std::pair<IntrinsicInst *, AllocaInst *>, 16> LifetimeStartList;
    SmallVector<StoreInst *, 16> StoreList;
  
    MemorySanitizerVisitor(Function &F, MemorySanitizer &MS,
                           const TargetLibraryInfo &TLI)
        : F(F), MS(MS), VAHelper(CreateVarArgHelper(F, MS, *this)), TLI(&TLI) {
      bool SanitizeFunction = F.hasFnAttribute(Attribute::SanitizeMemory);
      InsertChecks = SanitizeFunction;
      PropagateShadow = SanitizeFunction;
      PoisonStack = SanitizeFunction && ClPoisonStack;
      PoisonUndef = SanitizeFunction && ClPoisonUndef;
      // FIXME: Consider using SpecialCaseList to specify a list of functions that
      // must always return fully initialized values. For now, we hardcode "main".
      CheckReturnValue = SanitizeFunction && (F.getName() == "main");
  
      MS.initializeCallbacks(*F.getParent());
      if (MS.CompileKernel)
        ActualFnStart = insertKmsanPrologue(F);
      else
        ActualFnStart = &F.getEntryBlock();
  
      LLVM_DEBUG(if (!InsertChecks) dbgs()
                 << "MemorySanitizer is not inserting checks into '"
                 << F.getName() << "'\n");
    }
  
    Value *updateOrigin(Value *V, IRBuilder<> &IRB) {
      if (MS.TrackOrigins <= 1) return V;
      return IRB.CreateCall(MS.MsanChainOriginFn, V);
    }
  
    Value *originToIntptr(IRBuilder<> &IRB, Value *Origin) {
      const DataLayout &DL = F.getParent()->getDataLayout();
      unsigned IntptrSize = DL.getTypeStoreSize(MS.IntptrTy);
      if (IntptrSize == kOriginSize) return Origin;
      assert(IntptrSize == kOriginSize * 2);
      Origin = IRB.CreateIntCast(Origin, MS.IntptrTy, /* isSigned */ false);
      return IRB.CreateOr(Origin, IRB.CreateShl(Origin, kOriginSize * 8));
    }
  
    /// Fill memory range with the given origin value.
    void paintOrigin(IRBuilder<> &IRB, Value *Origin, Value *OriginPtr,
                     unsigned Size, unsigned Alignment) {
      const DataLayout &DL = F.getParent()->getDataLayout();
      unsigned IntptrAlignment = DL.getABITypeAlignment(MS.IntptrTy);
      unsigned IntptrSize = DL.getTypeStoreSize(MS.IntptrTy);
      assert(IntptrAlignment >= kMinOriginAlignment);
      assert(IntptrSize >= kOriginSize);
  
      unsigned Ofs = 0;
      unsigned CurrentAlignment = Alignment;
      if (Alignment >= IntptrAlignment && IntptrSize > kOriginSize) {
        Value *IntptrOrigin = originToIntptr(IRB, Origin);
        Value *IntptrOriginPtr =
            IRB.CreatePointerCast(OriginPtr, PointerType::get(MS.IntptrTy, 0));
        for (unsigned i = 0; i < Size / IntptrSize; ++i) {
          Value *Ptr = i ? IRB.CreateConstGEP1_32(MS.IntptrTy, IntptrOriginPtr, i)
                         : IntptrOriginPtr;
          IRB.CreateAlignedStore(IntptrOrigin, Ptr, CurrentAlignment);
          Ofs += IntptrSize / kOriginSize;
          CurrentAlignment = IntptrAlignment;
        }
      }
  
      for (unsigned i = Ofs; i < (Size + kOriginSize - 1) / kOriginSize; ++i) {
        Value *GEP =
            i ? IRB.CreateConstGEP1_32(MS.OriginTy, OriginPtr, i) : OriginPtr;
        IRB.CreateAlignedStore(Origin, GEP, CurrentAlignment);
        CurrentAlignment = kMinOriginAlignment;
      }
    }
  
    void storeOrigin(IRBuilder<> &IRB, Value *Addr, Value *Shadow, Value *Origin,
                     Value *OriginPtr, unsigned Alignment, bool AsCall) {
      const DataLayout &DL = F.getParent()->getDataLayout();
      unsigned OriginAlignment = std::max(kMinOriginAlignment, Alignment);
      unsigned StoreSize = DL.getTypeStoreSize(Shadow->getType());
      if (Shadow->getType()->isAggregateType()) {
        paintOrigin(IRB, updateOrigin(Origin, IRB), OriginPtr, StoreSize,
                    OriginAlignment);
      } else {
        Value *ConvertedShadow = convertToShadowTyNoVec(Shadow, IRB);
        Constant *ConstantShadow = dyn_cast_or_null<Constant>(ConvertedShadow);
        if (ConstantShadow) {
          if (ClCheckConstantShadow && !ConstantShadow->isZeroValue())
            paintOrigin(IRB, updateOrigin(Origin, IRB), OriginPtr, StoreSize,
                        OriginAlignment);
          return;
        }
  
        unsigned TypeSizeInBits =
            DL.getTypeSizeInBits(ConvertedShadow->getType());
        unsigned SizeIndex = TypeSizeToSizeIndex(TypeSizeInBits);
        if (AsCall && SizeIndex < kNumberOfAccessSizes && !MS.CompileKernel) {
          FunctionCallee Fn = MS.MaybeStoreOriginFn[SizeIndex];
          Value *ConvertedShadow2 = IRB.CreateZExt(
              ConvertedShadow, IRB.getIntNTy(8 * (1 << SizeIndex)));
          IRB.CreateCall(Fn, {ConvertedShadow2,
                              IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()),
                              Origin});
        } else {
          Value *Cmp = IRB.CreateICmpNE(
              ConvertedShadow, getCleanShadow(ConvertedShadow), "_mscmp");
          Instruction *CheckTerm = SplitBlockAndInsertIfThen(
              Cmp, &*IRB.GetInsertPoint(), false, MS.OriginStoreWeights);
          IRBuilder<> IRBNew(CheckTerm);
          paintOrigin(IRBNew, updateOrigin(Origin, IRBNew), OriginPtr, StoreSize,
                      OriginAlignment);
        }
      }
    }
  
    void materializeStores(bool InstrumentWithCalls) {
      for (StoreInst *SI : StoreList) {
        IRBuilder<> IRB(SI);
        Value *Val = SI->getValueOperand();
        Value *Addr = SI->getPointerOperand();
        Value *Shadow = SI->isAtomic() ? getCleanShadow(Val) : getShadow(Val);
        Value *ShadowPtr, *OriginPtr;
        Type *ShadowTy = Shadow->getType();
        unsigned Alignment = SI->getAlignment();
        unsigned OriginAlignment = std::max(kMinOriginAlignment, Alignment);
        std::tie(ShadowPtr, OriginPtr) =
            getShadowOriginPtr(Addr, IRB, ShadowTy, Alignment, /*isStore*/ true);
  
        StoreInst *NewSI = IRB.CreateAlignedStore(Shadow, ShadowPtr, Alignment);
        LLVM_DEBUG(dbgs() << "  STORE: " << *NewSI << "\n");
        (void)NewSI;
  
        if (SI->isAtomic())
          SI->setOrdering(addReleaseOrdering(SI->getOrdering()));
  
        if (MS.TrackOrigins && !SI->isAtomic())
          storeOrigin(IRB, Addr, Shadow, getOrigin(Val), OriginPtr,
                      OriginAlignment, InstrumentWithCalls);
      }
    }
  
    /// Helper function to insert a warning at IRB's current insert point.
    void insertWarningFn(IRBuilder<> &IRB, Value *Origin) {
      if (!Origin)
        Origin = (Value *)IRB.getInt32(0);
      if (MS.CompileKernel) {
        IRB.CreateCall(MS.WarningFn, Origin);
      } else {
        if (MS.TrackOrigins) {
          IRB.CreateStore(Origin, MS.OriginTLS);
        }
        IRB.CreateCall(MS.WarningFn, {});
      }
      IRB.CreateCall(MS.EmptyAsm, {});
      // FIXME: Insert UnreachableInst if !MS.Recover?
      // This may invalidate some of the following checks and needs to be done
      // at the very end.
    }
  
    void materializeOneCheck(Instruction *OrigIns, Value *Shadow, Value *Origin,
                             bool AsCall) {
      IRBuilder<> IRB(OrigIns);
      LLVM_DEBUG(dbgs() << "  SHAD0 : " << *Shadow << "\n");
      Value *ConvertedShadow = convertToShadowTyNoVec(Shadow, IRB);
      LLVM_DEBUG(dbgs() << "  SHAD1 : " << *ConvertedShadow << "\n");
  
      Constant *ConstantShadow = dyn_cast_or_null<Constant>(ConvertedShadow);
      if (ConstantShadow) {
        if (ClCheckConstantShadow && !ConstantShadow->isZeroValue()) {
          insertWarningFn(IRB, Origin);
        }
        return;
      }
  
      const DataLayout &DL = OrigIns->getModule()->getDataLayout();
  
      unsigned TypeSizeInBits = DL.getTypeSizeInBits(ConvertedShadow->getType());
      unsigned SizeIndex = TypeSizeToSizeIndex(TypeSizeInBits);
      if (AsCall && SizeIndex < kNumberOfAccessSizes && !MS.CompileKernel) {
        FunctionCallee Fn = MS.MaybeWarningFn[SizeIndex];
        Value *ConvertedShadow2 =
            IRB.CreateZExt(ConvertedShadow, IRB.getIntNTy(8 * (1 << SizeIndex)));
        IRB.CreateCall(Fn, {ConvertedShadow2, MS.TrackOrigins && Origin
                                                  ? Origin
                                                  : (Value *)IRB.getInt32(0)});
      } else {
        Value *Cmp = IRB.CreateICmpNE(ConvertedShadow,
                                      getCleanShadow(ConvertedShadow), "_mscmp");
        Instruction *CheckTerm = SplitBlockAndInsertIfThen(
            Cmp, OrigIns,
            /* Unreachable */ !MS.Recover, MS.ColdCallWeights);
  
        IRB.SetInsertPoint(CheckTerm);
        insertWarningFn(IRB, Origin);
        LLVM_DEBUG(dbgs() << "  CHECK: " << *Cmp << "\n");
      }
    }
  
    void materializeChecks(bool InstrumentWithCalls) {
      for (const auto &ShadowData : InstrumentationList) {
        Instruction *OrigIns = ShadowData.OrigIns;
        Value *Shadow = ShadowData.Shadow;
        Value *Origin = ShadowData.Origin;
        materializeOneCheck(OrigIns, Shadow, Origin, InstrumentWithCalls);
      }
      LLVM_DEBUG(dbgs() << "DONE:\n" << F);
    }
  
    BasicBlock *insertKmsanPrologue(Function &F) {
      BasicBlock *ret =
          SplitBlock(&F.getEntryBlock(), F.getEntryBlock().getFirstNonPHI());
      IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
      Value *ContextState = IRB.CreateCall(MS.MsanGetContextStateFn, {});
      Constant *Zero = IRB.getInt32(0);
      MS.ParamTLS = IRB.CreateGEP(MS.MsanContextStateTy, ContextState,
                                  {Zero, IRB.getInt32(0)}, "param_shadow");
      MS.RetvalTLS = IRB.CreateGEP(MS.MsanContextStateTy, ContextState,
                                   {Zero, IRB.getInt32(1)}, "retval_shadow");
      MS.VAArgTLS = IRB.CreateGEP(MS.MsanContextStateTy, ContextState,
                                  {Zero, IRB.getInt32(2)}, "va_arg_shadow");
      MS.VAArgOriginTLS = IRB.CreateGEP(MS.MsanContextStateTy, ContextState,
                                        {Zero, IRB.getInt32(3)}, "va_arg_origin");
      MS.VAArgOverflowSizeTLS =
          IRB.CreateGEP(MS.MsanContextStateTy, ContextState,
                        {Zero, IRB.getInt32(4)}, "va_arg_overflow_size");
      MS.ParamOriginTLS = IRB.CreateGEP(MS.MsanContextStateTy, ContextState,
                                        {Zero, IRB.getInt32(5)}, "param_origin");
      MS.RetvalOriginTLS =
          IRB.CreateGEP(MS.MsanContextStateTy, ContextState,
                        {Zero, IRB.getInt32(6)}, "retval_origin");
      return ret;
    }
  
    /// Add MemorySanitizer instrumentation to a function.
    bool runOnFunction() {
      // In the presence of unreachable blocks, we may see Phi nodes with
      // incoming nodes from such blocks. Since InstVisitor skips unreachable
      // blocks, such nodes will not have any shadow value associated with them.
      // It's easier to remove unreachable blocks than deal with missing shadow.
      removeUnreachableBlocks(F);
  
      // Iterate all BBs in depth-first order and create shadow instructions
      // for all instructions (where applicable).
      // For PHI nodes we create dummy shadow PHIs which will be finalized later.
      for (BasicBlock *BB : depth_first(ActualFnStart))
        visit(*BB);
  
      // Finalize PHI nodes.
      for (PHINode *PN : ShadowPHINodes) {
        PHINode *PNS = cast<PHINode>(getShadow(PN));
        PHINode *PNO = MS.TrackOrigins ? cast<PHINode>(getOrigin(PN)) : nullptr;
        size_t NumValues = PN->getNumIncomingValues();
        for (size_t v = 0; v < NumValues; v++) {
          PNS->addIncoming(getShadow(PN, v), PN->getIncomingBlock(v));
          if (PNO) PNO->addIncoming(getOrigin(PN, v), PN->getIncomingBlock(v));
        }
      }
  
      VAHelper->finalizeInstrumentation();
  
      // Poison llvm.lifetime.start intrinsics, if we haven't fallen back to
      // instrumenting only allocas.
      if (InstrumentLifetimeStart) {
        for (auto Item : LifetimeStartList) {
          instrumentAlloca(*Item.second, Item.first);
          AllocaSet.erase(Item.second);
        }
      }
      // Poison the allocas for which we didn't instrument the corresponding
      // lifetime intrinsics.
      for (AllocaInst *AI : AllocaSet)
        instrumentAlloca(*AI);
  
      bool InstrumentWithCalls = ClInstrumentationWithCallThreshold >= 0 &&
                                 InstrumentationList.size() + StoreList.size() >
                                     (unsigned)ClInstrumentationWithCallThreshold;
  
      // Insert shadow value checks.
      materializeChecks(InstrumentWithCalls);
  
      // Delayed instrumentation of StoreInst.
      // This may not add new address checks.
      materializeStores(InstrumentWithCalls);
  
      return true;
    }
  
    /// Compute the shadow type that corresponds to a given Value.
    Type *getShadowTy(Value *V) {
      return getShadowTy(V->getType());
    }
  
    /// Compute the shadow type that corresponds to a given Type.
    Type *getShadowTy(Type *OrigTy) {
      if (!OrigTy->isSized()) {
        return nullptr;
      }
      // For integer type, shadow is the same as the original type.
      // This may return weird-sized types like i1.
      if (IntegerType *IT = dyn_cast<IntegerType>(OrigTy))
        return IT;
      const DataLayout &DL = F.getParent()->getDataLayout();
      if (VectorType *VT = dyn_cast<VectorType>(OrigTy)) {
        uint32_t EltSize = DL.getTypeSizeInBits(VT->getElementType());
        return VectorType::get(IntegerType::get(*MS.C, EltSize),
                               VT->getNumElements());
      }
      if (ArrayType *AT = dyn_cast<ArrayType>(OrigTy)) {
        return ArrayType::get(getShadowTy(AT->getElementType()),
                              AT->getNumElements());
      }
      if (StructType *ST = dyn_cast<StructType>(OrigTy)) {
        SmallVector<Type*, 4> Elements;
        for (unsigned i = 0, n = ST->getNumElements(); i < n; i++)
          Elements.push_back(getShadowTy(ST->getElementType(i)));
        StructType *Res = StructType::get(*MS.C, Elements, ST->isPacked());
        LLVM_DEBUG(dbgs() << "getShadowTy: " << *ST << " ===> " << *Res << "\n");
        return Res;
      }
      uint32_t TypeSize = DL.getTypeSizeInBits(OrigTy);
      return IntegerType::get(*MS.C, TypeSize);
    }
  
    /// Flatten a vector type.
    Type *getShadowTyNoVec(Type *ty) {
      if (VectorType *vt = dyn_cast<VectorType>(ty))
        return IntegerType::get(*MS.C, vt->getBitWidth());
      return ty;
    }
  
    /// Convert a shadow value to it's flattened variant.
    Value *convertToShadowTyNoVec(Value *V, IRBuilder<> &IRB) {
      Type *Ty = V->getType();
      Type *NoVecTy = getShadowTyNoVec(Ty);
      if (Ty == NoVecTy) return V;
      return IRB.CreateBitCast(V, NoVecTy);
    }
  
    /// Compute the integer shadow offset that corresponds to a given
    /// application address.
    ///
    /// Offset = (Addr & ~AndMask) ^ XorMask
    Value *getShadowPtrOffset(Value *Addr, IRBuilder<> &IRB) {
      Value *OffsetLong = IRB.CreatePointerCast(Addr, MS.IntptrTy);
  
      uint64_t AndMask = MS.MapParams->AndMask;
      if (AndMask)
        OffsetLong =
            IRB.CreateAnd(OffsetLong, ConstantInt::get(MS.IntptrTy, ~AndMask));
  
      uint64_t XorMask = MS.MapParams->XorMask;
      if (XorMask)
        OffsetLong =
            IRB.CreateXor(OffsetLong, ConstantInt::get(MS.IntptrTy, XorMask));
      return OffsetLong;
    }
  
    /// Compute the shadow and origin addresses corresponding to a given
    /// application address.
    ///
    /// Shadow = ShadowBase + Offset
    /// Origin = (OriginBase + Offset) & ~3ULL
    std::pair<Value *, Value *> getShadowOriginPtrUserspace(Value *Addr,
                                                            IRBuilder<> &IRB,
                                                            Type *ShadowTy,
                                                            unsigned Alignment) {
      Value *ShadowOffset = getShadowPtrOffset(Addr, IRB);
      Value *ShadowLong = ShadowOffset;
      uint64_t ShadowBase = MS.MapParams->ShadowBase;
      if (ShadowBase != 0) {
        ShadowLong =
          IRB.CreateAdd(ShadowLong,
                        ConstantInt::get(MS.IntptrTy, ShadowBase));
      }
      Value *ShadowPtr =
          IRB.CreateIntToPtr(ShadowLong, PointerType::get(ShadowTy, 0));
      Value *OriginPtr = nullptr;
      if (MS.TrackOrigins) {
        Value *OriginLong = ShadowOffset;
        uint64_t OriginBase = MS.MapParams->OriginBase;
        if (OriginBase != 0)
          OriginLong = IRB.CreateAdd(OriginLong,
                                     ConstantInt::get(MS.IntptrTy, OriginBase));
        if (Alignment < kMinOriginAlignment) {
          uint64_t Mask = kMinOriginAlignment - 1;
          OriginLong =
              IRB.CreateAnd(OriginLong, ConstantInt::get(MS.IntptrTy, ~Mask));
        }
        OriginPtr =
            IRB.CreateIntToPtr(OriginLong, PointerType::get(MS.OriginTy, 0));
      }
      return std::make_pair(ShadowPtr, OriginPtr);
    }
  
    std::pair<Value *, Value *>
    getShadowOriginPtrKernel(Value *Addr, IRBuilder<> &IRB, Type *ShadowTy,
                             unsigned Alignment, bool isStore) {
      Value *ShadowOriginPtrs;
      const DataLayout &DL = F.getParent()->getDataLayout();
      int Size = DL.getTypeStoreSize(ShadowTy);
  
      FunctionCallee Getter = MS.getKmsanShadowOriginAccessFn(isStore, Size);
      Value *AddrCast =
          IRB.CreatePointerCast(Addr, PointerType::get(IRB.getInt8Ty(), 0));
      if (Getter) {
        ShadowOriginPtrs = IRB.CreateCall(Getter, AddrCast);
      } else {
        Value *SizeVal = ConstantInt::get(MS.IntptrTy, Size);
        ShadowOriginPtrs = IRB.CreateCall(isStore ? MS.MsanMetadataPtrForStoreN
                                                  : MS.MsanMetadataPtrForLoadN,
                                          {AddrCast, SizeVal});
      }
      Value *ShadowPtr = IRB.CreateExtractValue(ShadowOriginPtrs, 0);
      ShadowPtr = IRB.CreatePointerCast(ShadowPtr, PointerType::get(ShadowTy, 0));
      Value *OriginPtr = IRB.CreateExtractValue(ShadowOriginPtrs, 1);
  
      return std::make_pair(ShadowPtr, OriginPtr);
    }
  
    std::pair<Value *, Value *> getShadowOriginPtr(Value *Addr, IRBuilder<> &IRB,
                                                   Type *ShadowTy,
                                                   unsigned Alignment,
                                                   bool isStore) {
      std::pair<Value *, Value *> ret;
      if (MS.CompileKernel)
        ret = getShadowOriginPtrKernel(Addr, IRB, ShadowTy, Alignment, isStore);
      else
        ret = getShadowOriginPtrUserspace(Addr, IRB, ShadowTy, Alignment);
      return ret;
    }
  
    /// Compute the shadow address for a given function argument.
    ///
    /// Shadow = ParamTLS+ArgOffset.
    Value *getShadowPtrForArgument(Value *A, IRBuilder<> &IRB,
                                   int ArgOffset) {
      Value *Base = IRB.CreatePointerCast(MS.ParamTLS, MS.IntptrTy);
      if (ArgOffset)
        Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
      return IRB.CreateIntToPtr(Base, PointerType::get(getShadowTy(A), 0),
                                "_msarg");
    }
  
    /// Compute the origin address for a given function argument.
    Value *getOriginPtrForArgument(Value *A, IRBuilder<> &IRB,
                                   int ArgOffset) {
      if (!MS.TrackOrigins)
        return nullptr;
      Value *Base = IRB.CreatePointerCast(MS.ParamOriginTLS, MS.IntptrTy);
      if (ArgOffset)
        Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
      return IRB.CreateIntToPtr(Base, PointerType::get(MS.OriginTy, 0),
                                "_msarg_o");
    }
  
    /// Compute the shadow address for a retval.
    Value *getShadowPtrForRetval(Value *A, IRBuilder<> &IRB) {
      return IRB.CreatePointerCast(MS.RetvalTLS,
                                   PointerType::get(getShadowTy(A), 0),
                                   "_msret");
    }
  
    /// Compute the origin address for a retval.
    Value *getOriginPtrForRetval(IRBuilder<> &IRB) {
      // We keep a single origin for the entire retval. Might be too optimistic.
      return MS.RetvalOriginTLS;
    }
  
    /// Set SV to be the shadow value for V.
    void setShadow(Value *V, Value *SV) {
      assert(!ShadowMap.count(V) && "Values may only have one shadow");
      ShadowMap[V] = PropagateShadow ? SV : getCleanShadow(V);
    }
  
    /// Set Origin to be the origin value for V.
    void setOrigin(Value *V, Value *Origin) {
      if (!MS.TrackOrigins) return;
      assert(!OriginMap.count(V) && "Values may only have one origin");
      LLVM_DEBUG(dbgs() << "ORIGIN: " << *V << "  ==> " << *Origin << "\n");
      OriginMap[V] = Origin;
    }
  
    Constant *getCleanShadow(Type *OrigTy) {
      Type *ShadowTy = getShadowTy(OrigTy);
      if (!ShadowTy)
        return nullptr;
      return Constant::getNullValue(ShadowTy);
    }
  
    /// Create a clean shadow value for a given value.
    ///
    /// Clean shadow (all zeroes) means all bits of the value are defined
    /// (initialized).
    Constant *getCleanShadow(Value *V) {
      return getCleanShadow(V->getType());
    }
  
    /// Create a dirty shadow of a given shadow type.
    Constant *getPoisonedShadow(Type *ShadowTy) {
      assert(ShadowTy);
      if (isa<IntegerType>(ShadowTy) || isa<VectorType>(ShadowTy))
        return Constant::getAllOnesValue(ShadowTy);
      if (ArrayType *AT = dyn_cast<ArrayType>(ShadowTy)) {
        SmallVector<Constant *, 4> Vals(AT->getNumElements(),
                                        getPoisonedShadow(AT->getElementType()));
        return ConstantArray::get(AT, Vals);
      }
      if (StructType *ST = dyn_cast<StructType>(ShadowTy)) {
        SmallVector<Constant *, 4> Vals;
        for (unsigned i = 0, n = ST->getNumElements(); i < n; i++)
          Vals.push_back(getPoisonedShadow(ST->getElementType(i)));
        return ConstantStruct::get(ST, Vals);
      }
      llvm_unreachable("Unexpected shadow type");
    }
  
    /// Create a dirty shadow for a given value.
    Constant *getPoisonedShadow(Value *V) {
      Type *ShadowTy = getShadowTy(V);
      if (!ShadowTy)
        return nullptr;
      return getPoisonedShadow(ShadowTy);
    }
  
    /// Create a clean (zero) origin.
    Value *getCleanOrigin() {
      return Constant::getNullValue(MS.OriginTy);
    }
  
    /// Get the shadow value for a given Value.
    ///
    /// This function either returns the value set earlier with setShadow,
    /// or extracts if from ParamTLS (for function arguments).
    Value *getShadow(Value *V) {
      if (!PropagateShadow) return getCleanShadow(V);
      if (Instruction *I = dyn_cast<Instruction>(V)) {
        if (I->getMetadata("nosanitize"))
          return getCleanShadow(V);
        // For instructions the shadow is already stored in the map.
        Value *Shadow = ShadowMap[V];
        if (!Shadow) {
          LLVM_DEBUG(dbgs() << "No shadow: " << *V << "\n" << *(I->getParent()));
          (void)I;
          assert(Shadow && "No shadow for a value");
        }
        return Shadow;
      }
      if (UndefValue *U = dyn_cast<UndefValue>(V)) {
        Value *AllOnes = PoisonUndef ? getPoisonedShadow(V) : getCleanShadow(V);
        LLVM_DEBUG(dbgs() << "Undef: " << *U << " ==> " << *AllOnes << "\n");
        (void)U;
        return AllOnes;
      }
      if (Argument *A = dyn_cast<Argument>(V)) {
        // For arguments we compute the shadow on demand and store it in the map.
        Value **ShadowPtr = &ShadowMap[V];
        if (*ShadowPtr)
          return *ShadowPtr;
        Function *F = A->getParent();
        IRBuilder<> EntryIRB(ActualFnStart->getFirstNonPHI());
        unsigned ArgOffset = 0;
        const DataLayout &DL = F->getParent()->getDataLayout();
        for (auto &FArg : F->args()) {
          if (!FArg.getType()->isSized()) {
            LLVM_DEBUG(dbgs() << "Arg is not sized\n");
            continue;
          }
          unsigned Size =
              FArg.hasByValAttr()
                  ? DL.getTypeAllocSize(FArg.getType()->getPointerElementType())
                  : DL.getTypeAllocSize(FArg.getType());
          if (A == &FArg) {
            bool Overflow = ArgOffset + Size > kParamTLSSize;
            Value *Base = getShadowPtrForArgument(&FArg, EntryIRB, ArgOffset);
            if (FArg.hasByValAttr()) {
              // ByVal pointer itself has clean shadow. We copy the actual
              // argument shadow to the underlying memory.
              // Figure out maximal valid memcpy alignment.
              unsigned ArgAlign = FArg.getParamAlignment();
              if (ArgAlign == 0) {
                Type *EltType = A->getType()->getPointerElementType();
                ArgAlign = DL.getABITypeAlignment(EltType);
              }
              Value *CpShadowPtr =
                  getShadowOriginPtr(V, EntryIRB, EntryIRB.getInt8Ty(), ArgAlign,
                                     /*isStore*/ true)
                      .first;
              // TODO(glider): need to copy origins.
              if (Overflow) {
                // ParamTLS overflow.
                EntryIRB.CreateMemSet(
                    CpShadowPtr, Constant::getNullValue(EntryIRB.getInt8Ty()),
                    Size, ArgAlign);
              } else {
                unsigned CopyAlign = std::min(ArgAlign, kShadowTLSAlignment);
                Value *Cpy = EntryIRB.CreateMemCpy(CpShadowPtr, CopyAlign, Base,
                                                   CopyAlign, Size);
                LLVM_DEBUG(dbgs() << "  ByValCpy: " << *Cpy << "\n");
                (void)Cpy;
              }
              *ShadowPtr = getCleanShadow(V);
            } else {
              if (Overflow) {
                // ParamTLS overflow.
                *ShadowPtr = getCleanShadow(V);
              } else {
                *ShadowPtr = EntryIRB.CreateAlignedLoad(getShadowTy(&FArg), Base,
                                                        kShadowTLSAlignment);
              }
            }
            LLVM_DEBUG(dbgs()
                       << "  ARG:    " << FArg << " ==> " << **ShadowPtr << "\n");
            if (MS.TrackOrigins && !Overflow) {
              Value *OriginPtr =
                  getOriginPtrForArgument(&FArg, EntryIRB, ArgOffset);
              setOrigin(A, EntryIRB.CreateLoad(MS.OriginTy, OriginPtr));
            } else {
              setOrigin(A, getCleanOrigin());
            }
          }
          ArgOffset += alignTo(Size, kShadowTLSAlignment);
        }
        assert(*ShadowPtr && "Could not find shadow for an argument");
        return *ShadowPtr;
      }
      // For everything else the shadow is zero.
      return getCleanShadow(V);
    }
  
    /// Get the shadow for i-th argument of the instruction I.
    Value *getShadow(Instruction *I, int i) {
      return getShadow(I->getOperand(i));
    }
  
    /// Get the origin for a value.
    Value *getOrigin(Value *V) {
      if (!MS.TrackOrigins) return nullptr;
      if (!PropagateShadow) return getCleanOrigin();
      if (isa<Constant>(V)) return getCleanOrigin();
      assert((isa<Instruction>(V) || isa<Argument>(V)) &&
             "Unexpected value type in getOrigin()");
      if (Instruction *I = dyn_cast<Instruction>(V)) {
        if (I->getMetadata("nosanitize"))
          return getCleanOrigin();
      }
      Value *Origin = OriginMap[V];
      assert(Origin && "Missing origin");
      return Origin;
    }
  
    /// Get the origin for i-th argument of the instruction I.
    Value *getOrigin(Instruction *I, int i) {
      return getOrigin(I->getOperand(i));
    }
  
    /// Remember the place where a shadow check should be inserted.
    ///
    /// This location will be later instrumented with a check that will print a
    /// UMR warning in runtime if the shadow value is not 0.
    void insertShadowCheck(Value *Shadow, Value *Origin, Instruction *OrigIns) {
      assert(Shadow);
      if (!InsertChecks) return;
  #ifndef NDEBUG
      Type *ShadowTy = Shadow->getType();
      assert((isa<IntegerType>(ShadowTy) || isa<VectorType>(ShadowTy)) &&
             "Can only insert checks for integer and vector shadow types");
  #endif
      InstrumentationList.push_back(
          ShadowOriginAndInsertPoint(Shadow, Origin, OrigIns));
    }
  
    /// Remember the place where a shadow check should be inserted.
    ///
    /// This location will be later instrumented with a check that will print a
    /// UMR warning in runtime if the value is not fully defined.
    void insertShadowCheck(Value *Val, Instruction *OrigIns) {
      assert(Val);
      Value *Shadow, *Origin;
      if (ClCheckConstantShadow) {
        Shadow = getShadow(Val);
        if (!Shadow) return;
        Origin = getOrigin(Val);
      } else {
        Shadow = dyn_cast_or_null<Instruction>(getShadow(Val));
        if (!Shadow) return;
        Origin = dyn_cast_or_null<Instruction>(getOrigin(Val));
      }
      insertShadowCheck(Shadow, Origin, OrigIns);
    }
  
    AtomicOrdering addReleaseOrdering(AtomicOrdering a) {
      switch (a) {
        case AtomicOrdering::NotAtomic:
          return AtomicOrdering::NotAtomic;
        case AtomicOrdering::Unordered:
        case AtomicOrdering::Monotonic:
        case AtomicOrdering::Release:
          return AtomicOrdering::Release;
        case AtomicOrdering::Acquire:
        case AtomicOrdering::AcquireRelease:
          return AtomicOrdering::AcquireRelease;
        case AtomicOrdering::SequentiallyConsistent:
          return AtomicOrdering::SequentiallyConsistent;
      }
      llvm_unreachable("Unknown ordering");
    }
  
    AtomicOrdering addAcquireOrdering(AtomicOrdering a) {
      switch (a) {
        case AtomicOrdering::NotAtomic:
          return AtomicOrdering::NotAtomic;
        case AtomicOrdering::Unordered:
        case AtomicOrdering::Monotonic:
        case AtomicOrdering::Acquire:
          return AtomicOrdering::Acquire;
        case AtomicOrdering::Release:
        case AtomicOrdering::AcquireRelease:
          return AtomicOrdering::AcquireRelease;
        case AtomicOrdering::SequentiallyConsistent:
          return AtomicOrdering::SequentiallyConsistent;
      }
      llvm_unreachable("Unknown ordering");
    }
  
    // ------------------- Visitors.
    using InstVisitor<MemorySanitizerVisitor>::visit;
    void visit(Instruction &I) {
      if (!I.getMetadata("nosanitize"))
        InstVisitor<MemorySanitizerVisitor>::visit(I);
    }
  
    /// Instrument LoadInst
    ///
    /// Loads the corresponding shadow and (optionally) origin.
    /// Optionally, checks that the load address is fully defined.
    void visitLoadInst(LoadInst &I) {
      assert(I.getType()->isSized() && "Load type must have size");
      assert(!I.getMetadata("nosanitize"));
      IRBuilder<> IRB(I.getNextNode());
      Type *ShadowTy = getShadowTy(&I);
      Value *Addr = I.getPointerOperand();
      Value *ShadowPtr, *OriginPtr;
      unsigned Alignment = I.getAlignment();
      if (PropagateShadow) {
        std::tie(ShadowPtr, OriginPtr) =
            getShadowOriginPtr(Addr, IRB, ShadowTy, Alignment, /*isStore*/ false);
        setShadow(&I,
                  IRB.CreateAlignedLoad(ShadowTy, ShadowPtr, Alignment, "_msld"));
      } else {
        setShadow(&I, getCleanShadow(&I));
      }
  
      if (ClCheckAccessAddress)
        insertShadowCheck(I.getPointerOperand(), &I);
  
      if (I.isAtomic())
        I.setOrdering(addAcquireOrdering(I.getOrdering()));
  
      if (MS.TrackOrigins) {
        if (PropagateShadow) {
          unsigned OriginAlignment = std::max(kMinOriginAlignment, Alignment);
          setOrigin(
              &I, IRB.CreateAlignedLoad(MS.OriginTy, OriginPtr, OriginAlignment));
        } else {
          setOrigin(&I, getCleanOrigin());
        }
      }
    }
  
    /// Instrument StoreInst
    ///
    /// Stores the corresponding shadow and (optionally) origin.
    /// Optionally, checks that the store address is fully defined.
    void visitStoreInst(StoreInst &I) {
      StoreList.push_back(&I);
      if (ClCheckAccessAddress)
        insertShadowCheck(I.getPointerOperand(), &I);
    }
  
    void handleCASOrRMW(Instruction &I) {
      assert(isa<AtomicRMWInst>(I) || isa<AtomicCmpXchgInst>(I));
  
      IRBuilder<> IRB(&I);
      Value *Addr = I.getOperand(0);
      Value *ShadowPtr = getShadowOriginPtr(Addr, IRB, I.getType(),
                                            /*Alignment*/ 1, /*isStore*/ true)
                             .first;
  
      if (ClCheckAccessAddress)
        insertShadowCheck(Addr, &I);
  
      // Only test the conditional argument of cmpxchg instruction.
      // The other argument can potentially be uninitialized, but we can not
      // detect this situation reliably without possible false positives.
      if (isa<AtomicCmpXchgInst>(I))
        insertShadowCheck(I.getOperand(1), &I);
  
      IRB.CreateStore(getCleanShadow(&I), ShadowPtr);
  
      setShadow(&I, getCleanShadow(&I));
      setOrigin(&I, getCleanOrigin());
    }
  
    void visitAtomicRMWInst(AtomicRMWInst &I) {
      handleCASOrRMW(I);
      I.setOrdering(addReleaseOrdering(I.getOrdering()));
    }
  
    void visitAtomicCmpXchgInst(AtomicCmpXchgInst &I) {
      handleCASOrRMW(I);
      I.setSuccessOrdering(addReleaseOrdering(I.getSuccessOrdering()));
    }
  
    // Vector manipulation.
    void visitExtractElementInst(ExtractElementInst &I) {
      insertShadowCheck(I.getOperand(1), &I);
      IRBuilder<> IRB(&I);
      setShadow(&I, IRB.CreateExtractElement(getShadow(&I, 0), I.getOperand(1),
                "_msprop"));
      setOrigin(&I, getOrigin(&I, 0));
    }
  
    void visitInsertElementInst(InsertElementInst &I) {
      insertShadowCheck(I.getOperand(2), &I);
      IRBuilder<> IRB(&I);
      setShadow(&I, IRB.CreateInsertElement(getShadow(&I, 0), getShadow(&I, 1),
                I.getOperand(2), "_msprop"));
      setOriginForNaryOp(I);
    }
  
    void visitShuffleVectorInst(ShuffleVectorInst &I) {
      insertShadowCheck(I.getOperand(2), &I);
      IRBuilder<> IRB(&I);
      setShadow(&I, IRB.CreateShuffleVector(getShadow(&I, 0), getShadow(&I, 1),
                I.getOperand(2), "_msprop"));
      setOriginForNaryOp(I);
    }
  
    // Casts.
    void visitSExtInst(SExtInst &I) {
      IRBuilder<> IRB(&I);
      setShadow(&I, IRB.CreateSExt(getShadow(&I, 0), I.getType(), "_msprop"));
      setOrigin(&I, getOrigin(&I, 0));
    }
  
    void visitZExtInst(ZExtInst &I) {
      IRBuilder<> IRB(&I);
      setShadow(&I, IRB.CreateZExt(getShadow(&I, 0), I.getType(), "_msprop"));
      setOrigin(&I, getOrigin(&I, 0));
    }
  
    void visitTruncInst(TruncInst &I) {
      IRBuilder<> IRB(&I);
      setShadow(&I, IRB.CreateTrunc(getShadow(&I, 0), I.getType(), "_msprop"));
      setOrigin(&I, getOrigin(&I, 0));
    }
  
    void visitBitCastInst(BitCastInst &I) {
      // Special case: if this is the bitcast (there is exactly 1 allowed) between
      // a musttail call and a ret, don't instrument. New instructions are not
      // allowed after a musttail call.
      if (auto *CI = dyn_cast<CallInst>(I.getOperand(0)))
        if (CI->isMustTailCall())
          return;
      IRBuilder<> IRB(&I);
      setShadow(&I, IRB.CreateBitCast(getShadow(&I, 0), getShadowTy(&I)));
      setOrigin(&I, getOrigin(&I, 0));
    }
  
    void visitPtrToIntInst(PtrToIntInst &I) {
      IRBuilder<> IRB(&I);
      setShadow(&I, IRB.CreateIntCast(getShadow(&I, 0), getShadowTy(&I), false,
               "_msprop_ptrtoint"));
      setOrigin(&I, getOrigin(&I, 0));
    }
  
    void visitIntToPtrInst(IntToPtrInst &I) {
      IRBuilder<> IRB(&I);
      setShadow(&I, IRB.CreateIntCast(getShadow(&I, 0), getShadowTy(&I), false,
               "_msprop_inttoptr"));
      setOrigin(&I, getOrigin(&I, 0));
    }
  
    void visitFPToSIInst(CastInst& I) { handleShadowOr(I); }
    void visitFPToUIInst(CastInst& I) { handleShadowOr(I); }
    void visitSIToFPInst(CastInst& I) { handleShadowOr(I); }
    void visitUIToFPInst(CastInst& I) { handleShadowOr(I); }
    void visitFPExtInst(CastInst& I) { handleShadowOr(I); }
    void visitFPTruncInst(CastInst& I) { handleShadowOr(I); }
  
    /// Propagate shadow for bitwise AND.
    ///
    /// This code is exact, i.e. if, for example, a bit in the left argument
    /// is defined and 0, then neither the value not definedness of the
    /// corresponding bit in B don't affect the resulting shadow.
    void visitAnd(BinaryOperator &I) {
      IRBuilder<> IRB(&I);
      //  "And" of 0 and a poisoned value results in unpoisoned value.
      //  1&1 => 1;     0&1 => 0;     p&1 => p;
      //  1&0 => 0;     0&0 => 0;     p&0 => 0;
      //  1&p => p;     0&p => 0;     p&p => p;
      //  S = (S1 & S2) | (V1 & S2) | (S1 & V2)
      Value *S1 = getShadow(&I, 0);
      Value *S2 = getShadow(&I, 1);
      Value *V1 = I.getOperand(0);
      Value *V2 = I.getOperand(1);
      if (V1->getType() != S1->getType()) {
        V1 = IRB.CreateIntCast(V1, S1->getType(), false);
        V2 = IRB.CreateIntCast(V2, S2->getType(), false);
      }
      Value *S1S2 = IRB.CreateAnd(S1, S2);
      Value *V1S2 = IRB.CreateAnd(V1, S2);
      Value *S1V2 = IRB.CreateAnd(S1, V2);
      setShadow(&I, IRB.CreateOr({S1S2, V1S2, S1V2}));
      setOriginForNaryOp(I);
    }
  
    void visitOr(BinaryOperator &I) {
      IRBuilder<> IRB(&I);
      //  "Or" of 1 and a poisoned value results in unpoisoned value.
      //  1|1 => 1;     0|1 => 1;     p|1 => 1;
      //  1|0 => 1;     0|0 => 0;     p|0 => p;
      //  1|p => 1;     0|p => p;     p|p => p;
      //  S = (S1 & S2) | (~V1 & S2) | (S1 & ~V2)
      Value *S1 = getShadow(&I, 0);
      Value *S2 = getShadow(&I, 1);
      Value *V1 = IRB.CreateNot(I.getOperand(0));
      Value *V2 = IRB.CreateNot(I.getOperand(1));
      if (V1->getType() != S1->getType()) {
        V1 = IRB.CreateIntCast(V1, S1->getType(), false);
        V2 = IRB.CreateIntCast(V2, S2->getType(), false);
      }
      Value *S1S2 = IRB.CreateAnd(S1, S2);
      Value *V1S2 = IRB.CreateAnd(V1, S2);
      Value *S1V2 = IRB.CreateAnd(S1, V2);
      setShadow(&I, IRB.CreateOr({S1S2, V1S2, S1V2}));
      setOriginForNaryOp(I);
    }
  
    /// Default propagation of shadow and/or origin.
    ///
    /// This class implements the general case of shadow propagation, used in all
    /// cases where we don't know and/or don't care about what the operation
    /// actually does. It converts all input shadow values to a common type
    /// (extending or truncating as necessary), and bitwise OR's them.
    ///
    /// This is much cheaper than inserting checks (i.e. requiring inputs to be
    /// fully initialized), and less prone to false positives.
    ///
    /// This class also implements the general case of origin propagation. For a
    /// Nary operation, result origin is set to the origin of an argument that is
    /// not entirely initialized. If there is more than one such arguments, the
    /// rightmost of them is picked. It does not matter which one is picked if all
    /// arguments are initialized.
    template <bool CombineShadow>
    class Combiner {
      Value *Shadow = nullptr;
      Value *Origin = nullptr;
      IRBuilder<> &IRB;
      MemorySanitizerVisitor *MSV;
  
    public:
      Combiner(MemorySanitizerVisitor *MSV, IRBuilder<> &IRB)
          : IRB(IRB), MSV(MSV) {}
  
      /// Add a pair of shadow and origin values to the mix.
      Combiner &Add(Value *OpShadow, Value *OpOrigin) {
        if (CombineShadow) {
          assert(OpShadow);
          if (!Shadow)
            Shadow = OpShadow;
          else {
            OpShadow = MSV->CreateShadowCast(IRB, OpShadow, Shadow->getType());
            Shadow = IRB.CreateOr(Shadow, OpShadow, "_msprop");
          }
        }
  
        if (MSV->MS.TrackOrigins) {
          assert(OpOrigin);
          if (!Origin) {
            Origin = OpOrigin;
          } else {
            Constant *ConstOrigin = dyn_cast<Constant>(OpOrigin);
            // No point in adding something that might result in 0 origin value.
            if (!ConstOrigin || !ConstOrigin->isNullValue()) {
              Value *FlatShadow = MSV->convertToShadowTyNoVec(OpShadow, IRB);
              Value *Cond =
                  IRB.CreateICmpNE(FlatShadow, MSV->getCleanShadow(FlatShadow));
              Origin = IRB.CreateSelect(Cond, OpOrigin, Origin);
            }
          }
        }
        return *this;
      }
  
      /// Add an application value to the mix.
      Combiner &Add(Value *V) {
        Value *OpShadow = MSV->getShadow(V);
        Value *OpOrigin = MSV->MS.TrackOrigins ? MSV->getOrigin(V) : nullptr;
        return Add(OpShadow, OpOrigin);
      }
  
      /// Set the current combined values as the given instruction's shadow
      /// and origin.
      void Done(Instruction *I) {
        if (CombineShadow) {
          assert(Shadow);
          Shadow = MSV->CreateShadowCast(IRB, Shadow, MSV->getShadowTy(I));
          MSV->setShadow(I, Shadow);
        }
        if (MSV->MS.TrackOrigins) {
          assert(Origin);
          MSV->setOrigin(I, Origin);
        }
      }
    };
  
    using ShadowAndOriginCombiner = Combiner<true>;
    using OriginCombiner = Combiner<false>;
  
    /// Propagate origin for arbitrary operation.
    void setOriginForNaryOp(Instruction &I) {
      if (!MS.TrackOrigins) return;
      IRBuilder<> IRB(&I);
      OriginCombiner OC(this, IRB);
      for (Instruction::op_iterator OI = I.op_begin(); OI != I.op_end(); ++OI)
        OC.Add(OI->get());
      OC.Done(&I);
    }
  
    size_t VectorOrPrimitiveTypeSizeInBits(Type *Ty) {
      assert(!(Ty->isVectorTy() && Ty->getScalarType()->isPointerTy()) &&
             "Vector of pointers is not a valid shadow type");
      return Ty->isVectorTy() ?
        Ty->getVectorNumElements() * Ty->getScalarSizeInBits() :
        Ty->getPrimitiveSizeInBits();
    }
  
    /// Cast between two shadow types, extending or truncating as
    /// necessary.
    Value *CreateShadowCast(IRBuilder<> &IRB, Value *V, Type *dstTy,
                            bool Signed = false) {
      Type *srcTy = V->getType();
      size_t srcSizeInBits = VectorOrPrimitiveTypeSizeInBits(srcTy);
      size_t dstSizeInBits = VectorOrPrimitiveTypeSizeInBits(dstTy);
      if (srcSizeInBits > 1 && dstSizeInBits == 1)
        return IRB.CreateICmpNE(V, getCleanShadow(V));
  
      if (dstTy->isIntegerTy() && srcTy->isIntegerTy())
        return IRB.CreateIntCast(V, dstTy, Signed);
      if (dstTy->isVectorTy() && srcTy->isVectorTy() &&
          dstTy->getVectorNumElements() == srcTy->getVectorNumElements())
        return IRB.CreateIntCast(V, dstTy, Signed);
      Value *V1 = IRB.CreateBitCast(V, Type::getIntNTy(*MS.C, srcSizeInBits));
      Value *V2 =
        IRB.CreateIntCast(V1, Type::getIntNTy(*MS.C, dstSizeInBits), Signed);
      return IRB.CreateBitCast(V2, dstTy);
      // TODO: handle struct types.
    }
  
    /// Cast an application value to the type of its own shadow.
    Value *CreateAppToShadowCast(IRBuilder<> &IRB, Value *V) {
      Type *ShadowTy = getShadowTy(V);
      if (V->getType() == ShadowTy)
        return V;
      if (V->getType()->isPtrOrPtrVectorTy())
        return IRB.CreatePtrToInt(V, ShadowTy);
      else
        return IRB.CreateBitCast(V, ShadowTy);
    }
  
    /// Propagate shadow for arbitrary operation.
    void handleShadowOr(Instruction &I) {
      IRBuilder<> IRB(&I);
      ShadowAndOriginCombiner SC(this, IRB);
      for (Instruction::op_iterator OI = I.op_begin(); OI != I.op_end(); ++OI)
        SC.Add(OI->get());
      SC.Done(&I);
    }
  
    void visitFNeg(UnaryOperator &I) { handleShadowOr(I); }
  
    // Handle multiplication by constant.
    //
    // Handle a special case of multiplication by constant that may have one or
    // more zeros in the lower bits. This makes corresponding number of lower bits
    // of the result zero as well. We model it by shifting the other operand
    // shadow left by the required number of bits. Effectively, we transform
    // (X * (A * 2**B)) to ((X << B) * A) and instrument (X << B) as (Sx << B).
    // We use multiplication by 2**N instead of shift to cover the case of
    // multiplication by 0, which may occur in some elements of a vector operand.
    void handleMulByConstant(BinaryOperator &I, Constant *ConstArg,
                             Value *OtherArg) {
      Constant *ShadowMul;
      Type *Ty = ConstArg->getType();
      if (Ty->isVectorTy()) {
        unsigned NumElements = Ty->getVectorNumElements();
        Type *EltTy = Ty->getSequentialElementType();
        SmallVector<Constant *, 16> Elements;
        for (unsigned Idx = 0; Idx < NumElements; ++Idx) {
          if (ConstantInt *Elt =
                  dyn_cast<ConstantInt>(ConstArg->getAggregateElement(Idx))) {
            const APInt &V = Elt->getValue();
            APInt V2 = APInt(V.getBitWidth(), 1) << V.countTrailingZeros();
            Elements.push_back(ConstantInt::get(EltTy, V2));
          } else {
            Elements.push_back(ConstantInt::get(EltTy, 1));
          }
        }
        ShadowMul = ConstantVector::get(Elements);
      } else {
        if (ConstantInt *Elt = dyn_cast<ConstantInt>(ConstArg)) {
          const APInt &V = Elt->getValue();
          APInt V2 = APInt(V.getBitWidth(), 1) << V.countTrailingZeros();
          ShadowMul = ConstantInt::get(Ty, V2);
        } else {
          ShadowMul = ConstantInt::get(Ty, 1);
        }
      }
  
      IRBuilder<> IRB(&I);
      setShadow(&I,
                IRB.CreateMul(getShadow(OtherArg), ShadowMul, "msprop_mul_cst"));
      setOrigin(&I, getOrigin(OtherArg));
    }
  
    void visitMul(BinaryOperator &I) {
      Constant *constOp0 = dyn_cast<Constant>(I.getOperand(0));
      Constant *constOp1 = dyn_cast<Constant>(I.getOperand(1));
      if (constOp0 && !constOp1)
        handleMulByConstant(I, constOp0, I.getOperand(1));
      else if (constOp1 && !constOp0)
        handleMulByConstant(I, constOp1, I.getOperand(0));
      else
        handleShadowOr(I);
    }
  
    void visitFAdd(BinaryOperator &I) { handleShadowOr(I); }
    void visitFSub(BinaryOperator &I) { handleShadowOr(I); }
    void visitFMul(BinaryOperator &I) { handleShadowOr(I); }
    void visitAdd(BinaryOperator &I) { handleShadowOr(I); }
    void visitSub(BinaryOperator &I) { handleShadowOr(I); }
    void visitXor(BinaryOperator &I) { handleShadowOr(I); }
  
    void handleIntegerDiv(Instruction &I) {
      IRBuilder<> IRB(&I);
      // Strict on the second argument.
      insertShadowCheck(I.getOperand(1), &I);
      setShadow(&I, getShadow(&I, 0));
      setOrigin(&I, getOrigin(&I, 0));
    }
  
    void visitUDiv(BinaryOperator &I) { handleIntegerDiv(I); }
    void visitSDiv(BinaryOperator &I) { handleIntegerDiv(I); }
    void visitURem(BinaryOperator &I) { handleIntegerDiv(I); }
    void visitSRem(BinaryOperator &I) { handleIntegerDiv(I); }
  
    // Floating point division is side-effect free. We can not require that the
    // divisor is fully initialized and must propagate shadow. See PR37523.
    void visitFDiv(BinaryOperator &I) { handleShadowOr(I); }
    void visitFRem(BinaryOperator &I) { handleShadowOr(I); }
  
    /// Instrument == and != comparisons.
    ///
    /// Sometimes the comparison result is known even if some of the bits of the
    /// arguments are not.
    void handleEqualityComparison(ICmpInst &I) {
      IRBuilder<> IRB(&I);
      Value *A = I.getOperand(0);
      Value *B = I.getOperand(1);
      Value *Sa = getShadow(A);
      Value *Sb = getShadow(B);
  
      // Get rid of pointers and vectors of pointers.
      // For ints (and vectors of ints), types of A and Sa match,
      // and this is a no-op.
      A = IRB.CreatePointerCast(A, Sa->getType());
      B = IRB.CreatePointerCast(B, Sb->getType());
  
      // A == B  <==>  (C = A^B) == 0
      // A != B  <==>  (C = A^B) != 0
      // Sc = Sa | Sb
      Value *C = IRB.CreateXor(A, B);
      Value *Sc = IRB.CreateOr(Sa, Sb);
      // Now dealing with i = (C == 0) comparison (or C != 0, does not matter now)
      // Result is defined if one of the following is true
      // * there is a defined 1 bit in C
      // * C is fully defined
      // Si = !(C & ~Sc) && Sc
      Value *Zero = Constant::getNullValue(Sc->getType());
      Value *MinusOne = Constant::getAllOnesValue(Sc->getType());
      Value *Si =
        IRB.CreateAnd(IRB.CreateICmpNE(Sc, Zero),
                      IRB.CreateICmpEQ(
                        IRB.CreateAnd(IRB.CreateXor(Sc, MinusOne), C), Zero));
      Si->setName("_msprop_icmp");
      setShadow(&I, Si);
      setOriginForNaryOp(I);
    }
  
    /// Build the lowest possible value of V, taking into account V's
    ///        uninitialized bits.
    Value *getLowestPossibleValue(IRBuilder<> &IRB, Value *A, Value *Sa,
                                  bool isSigned) {
      if (isSigned) {
        // Split shadow into sign bit and other bits.
        Value *SaOtherBits = IRB.CreateLShr(IRB.CreateShl(Sa, 1), 1);
        Value *SaSignBit = IRB.CreateXor(Sa, SaOtherBits);
        // Maximise the undefined shadow bit, minimize other undefined bits.
        return
          IRB.CreateOr(IRB.CreateAnd(A, IRB.CreateNot(SaOtherBits)), SaSignBit);
      } else {
        // Minimize undefined bits.
        return IRB.CreateAnd(A, IRB.CreateNot(Sa));
      }
    }
  
    /// Build the highest possible value of V, taking into account V's
    ///        uninitialized bits.
    Value *getHighestPossibleValue(IRBuilder<> &IRB, Value *A, Value *Sa,
                                  bool isSigned) {
      if (isSigned) {
        // Split shadow into sign bit and other bits.
        Value *SaOtherBits = IRB.CreateLShr(IRB.CreateShl(Sa, 1), 1);
        Value *SaSignBit = IRB.CreateXor(Sa, SaOtherBits);
        // Minimise the undefined shadow bit, maximise other undefined bits.
        return
          IRB.CreateOr(IRB.CreateAnd(A, IRB.CreateNot(SaSignBit)), SaOtherBits);
      } else {
        // Maximize undefined bits.
        return IRB.CreateOr(A, Sa);
      }
    }
  
    /// Instrument relational comparisons.
    ///
    /// This function does exact shadow propagation for all relational
    /// comparisons of integers, pointers and vectors of those.
    /// FIXME: output seems suboptimal when one of the operands is a constant
    void handleRelationalComparisonExact(ICmpInst &I) {
      IRBuilder<> IRB(&I);
      Value *A = I.getOperand(0);
      Value *B = I.getOperand(1);
      Value *Sa = getShadow(A);
      Value *Sb = getShadow(B);
  
      // Get rid of pointers and vectors of pointers.
      // For ints (and vectors of ints), types of A and Sa match,
      // and this is a no-op.
      A = IRB.CreatePointerCast(A, Sa->getType());
      B = IRB.CreatePointerCast(B, Sb->getType());
  
      // Let [a0, a1] be the interval of possible values of A, taking into account
      // its undefined bits. Let [b0, b1] be the interval of possible values of B.
      // Then (A cmp B) is defined iff (a0 cmp b1) == (a1 cmp b0).
      bool IsSigned = I.isSigned();
      Value *S1 = IRB.CreateICmp(I.getPredicate(),
                                 getLowestPossibleValue(IRB, A, Sa, IsSigned),
                                 getHighestPossibleValue(IRB, B, Sb, IsSigned));
      Value *S2 = IRB.CreateICmp(I.getPredicate(),
                                 getHighestPossibleValue(IRB, A, Sa, IsSigned),
                                 getLowestPossibleValue(IRB, B, Sb, IsSigned));
      Value *Si = IRB.CreateXor(S1, S2);
      setShadow(&I, Si);
      setOriginForNaryOp(I);
    }
  
    /// Instrument signed relational comparisons.
    ///
    /// Handle sign bit tests: x<0, x>=0, x<=-1, x>-1 by propagating the highest
    /// bit of the shadow. Everything else is delegated to handleShadowOr().
    void handleSignedRelationalComparison(ICmpInst &I) {
      Constant *constOp;
      Value *op = nullptr;
      CmpInst::Predicate pre;
      if ((constOp = dyn_cast<Constant>(I.getOperand(1)))) {
        op = I.getOperand(0);
        pre = I.getPredicate();
      } else if ((constOp = dyn_cast<Constant>(I.getOperand(0)))) {
        op = I.getOperand(1);
        pre = I.getSwappedPredicate();
      } else {
        handleShadowOr(I);
        return;
      }
  
      if ((constOp->isNullValue() &&
           (pre == CmpInst::ICMP_SLT || pre == CmpInst::ICMP_SGE)) ||
          (constOp->isAllOnesValue() &&
           (pre == CmpInst::ICMP_SGT || pre == CmpInst::ICMP_SLE))) {
        IRBuilder<> IRB(&I);
        Value *Shadow = IRB.CreateICmpSLT(getShadow(op), getCleanShadow(op),
                                          "_msprop_icmp_s");
        setShadow(&I, Shadow);
        setOrigin(&I, getOrigin(op));
      } else {
        handleShadowOr(I);
      }
    }
  
    void visitICmpInst(ICmpInst &I) {
      if (!ClHandleICmp) {
        handleShadowOr(I);
        return;
      }
      if (I.isEquality()) {
        handleEqualityComparison(I);
        return;
      }
  
      assert(I.isRelational());
      if (ClHandleICmpExact) {
        handleRelationalComparisonExact(I);
        return;
      }
      if (I.isSigned()) {
        handleSignedRelationalComparison(I);
        return;
      }
  
      assert(I.isUnsigned());
      if ((isa<Constant>(I.getOperand(0)) || isa<Constant>(I.getOperand(1)))) {
        handleRelationalComparisonExact(I);
        return;
      }
  
      handleShadowOr(I);
    }
  
    void visitFCmpInst(FCmpInst &I) {
      handleShadowOr(I);
    }
  
    void handleShift(BinaryOperator &I) {
      IRBuilder<> IRB(&I);
      // If any of the S2 bits are poisoned, the whole thing is poisoned.
      // Otherwise perform the same shift on S1.
      Value *S1 = getShadow(&I, 0);
      Value *S2 = getShadow(&I, 1);
      Value *S2Conv = IRB.CreateSExt(IRB.CreateICmpNE(S2, getCleanShadow(S2)),
                                     S2->getType());
      Value *V2 = I.getOperand(1);
      Value *Shift = IRB.CreateBinOp(I.getOpcode(), S1, V2);
      setShadow(&I, IRB.CreateOr(Shift, S2Conv));
      setOriginForNaryOp(I);
    }
  
    void visitShl(BinaryOperator &I) { handleShift(I); }
    void visitAShr(BinaryOperator &I) { handleShift(I); }
    void visitLShr(BinaryOperator &I) { handleShift(I); }
  
    /// Instrument llvm.memmove
    ///
    /// At this point we don't know if llvm.memmove will be inlined or not.
    /// If we don't instrument it and it gets inlined,
    /// our interceptor will not kick in and we will lose the memmove.
    /// If we instrument the call here, but it does not get inlined,
    /// we will memove the shadow twice: which is bad in case
    /// of overlapping regions. So, we simply lower the intrinsic to a call.
    ///
    /// Similar situation exists for memcpy and memset.
    void visitMemMoveInst(MemMoveInst &I) {
      IRBuilder<> IRB(&I);
      IRB.CreateCall(
          MS.MemmoveFn,
          {IRB.CreatePointerCast(I.getArgOperand(0), IRB.getInt8PtrTy()),
           IRB.CreatePointerCast(I.getArgOperand(1), IRB.getInt8PtrTy()),
           IRB.CreateIntCast(I.getArgOperand(2), MS.IntptrTy, false)});
      I.eraseFromParent();
    }
  
    // Similar to memmove: avoid copying shadow twice.
    // This is somewhat unfortunate as it may slowdown small constant memcpys.
    // FIXME: consider doing manual inline for small constant sizes and proper
    // alignment.
    void visitMemCpyInst(MemCpyInst &I) {
      IRBuilder<> IRB(&I);
      IRB.CreateCall(
          MS.MemcpyFn,
          {IRB.CreatePointerCast(I.getArgOperand(0), IRB.getInt8PtrTy()),
           IRB.CreatePointerCast(I.getArgOperand(1), IRB.getInt8PtrTy()),
           IRB.CreateIntCast(I.getArgOperand(2), MS.IntptrTy, false)});
      I.eraseFromParent();
    }
  
    // Same as memcpy.
    void visitMemSetInst(MemSetInst &I) {
      IRBuilder<> IRB(&I);
      IRB.CreateCall(
          MS.MemsetFn,
          {IRB.CreatePointerCast(I.getArgOperand(0), IRB.getInt8PtrTy()),
           IRB.CreateIntCast(I.getArgOperand(1), IRB.getInt32Ty(), false),
           IRB.CreateIntCast(I.getArgOperand(2), MS.IntptrTy, false)});
      I.eraseFromParent();
    }
  
    void visitVAStartInst(VAStartInst &I) {
      VAHelper->visitVAStartInst(I);
    }
  
    void visitVACopyInst(VACopyInst &I) {
      VAHelper->visitVACopyInst(I);
    }
  
    /// Handle vector store-like intrinsics.
    ///
    /// Instrument intrinsics that look like a simple SIMD store: writes memory,
    /// has 1 pointer argument and 1 vector argument, returns void.
    bool handleVectorStoreIntrinsic(IntrinsicInst &I) {
      IRBuilder<> IRB(&I);
      Value* Addr = I.getArgOperand(0);
      Value *Shadow = getShadow(&I, 1);
      Value *ShadowPtr, *OriginPtr;
  
      // We don't know the pointer alignment (could be unaligned SSE store!).
      // Have to assume to worst case.
      std::tie(ShadowPtr, OriginPtr) = getShadowOriginPtr(
          Addr, IRB, Shadow->getType(), /*Alignment*/ 1, /*isStore*/ true);
      IRB.CreateAlignedStore(Shadow, ShadowPtr, 1);
  
      if (ClCheckAccessAddress)
        insertShadowCheck(Addr, &I);
  
      // FIXME: factor out common code from materializeStores
      if (MS.TrackOrigins) IRB.CreateStore(getOrigin(&I, 1), OriginPtr);
      return true;
    }
  
    /// Handle vector load-like intrinsics.
    ///
    /// Instrument intrinsics that look like a simple SIMD load: reads memory,
    /// has 1 pointer argument, returns a vector.
    bool handleVectorLoadIntrinsic(IntrinsicInst &I) {
      IRBuilder<> IRB(&I);
      Value *Addr = I.getArgOperand(0);
  
      Type *ShadowTy = getShadowTy(&I);
      Value *ShadowPtr, *OriginPtr;
      if (PropagateShadow) {
        // We don't know the pointer alignment (could be unaligned SSE load!).
        // Have to assume to worst case.
        unsigned Alignment = 1;
        std::tie(ShadowPtr, OriginPtr) =
            getShadowOriginPtr(Addr, IRB, ShadowTy, Alignment, /*isStore*/ false);
        setShadow(&I,
                  IRB.CreateAlignedLoad(ShadowTy, ShadowPtr, Alignment, "_msld"));
      } else {
        setShadow(&I, getCleanShadow(&I));
      }
  
      if (ClCheckAccessAddress)
        insertShadowCheck(Addr, &I);
  
      if (MS.TrackOrigins) {
        if (PropagateShadow)
          setOrigin(&I, IRB.CreateLoad(MS.OriginTy, OriginPtr));
        else
          setOrigin(&I, getCleanOrigin());
      }
      return true;
    }
  
    /// Handle (SIMD arithmetic)-like intrinsics.
    ///
    /// Instrument intrinsics with any number of arguments of the same type,
    /// equal to the return type. The type should be simple (no aggregates or
    /// pointers; vectors are fine).
    /// Caller guarantees that this intrinsic does not access memory.
    bool maybeHandleSimpleNomemIntrinsic(IntrinsicInst &I) {
      Type *RetTy = I.getType();
      if (!(RetTy->isIntOrIntVectorTy() ||
            RetTy->isFPOrFPVectorTy() ||
            RetTy->isX86_MMXTy()))
        return false;
  
      unsigned NumArgOperands = I.getNumArgOperands();
  
      for (unsigned i = 0; i < NumArgOperands; ++i) {
        Type *Ty = I.getArgOperand(i)->getType();
        if (Ty != RetTy)
          return false;
      }
  
      IRBuilder<> IRB(&I);
      ShadowAndOriginCombiner SC(this, IRB);
      for (unsigned i = 0; i < NumArgOperands; ++i)
        SC.Add(I.getArgOperand(i));
      SC.Done(&I);
  
      return true;
    }
  
    /// Heuristically instrument unknown intrinsics.
    ///
    /// The main purpose of this code is to do something reasonable with all
    /// random intrinsics we might encounter, most importantly - SIMD intrinsics.
    /// We recognize several classes of intrinsics by their argument types and
    /// ModRefBehaviour and apply special intrumentation when we are reasonably
    /// sure that we know what the intrinsic does.
    ///
    /// We special-case intrinsics where this approach fails. See llvm.bswap
    /// handling as an example of that.
    bool handleUnknownIntrinsic(IntrinsicInst &I) {
      unsigned NumArgOperands = I.getNumArgOperands();
      if (NumArgOperands == 0)
        return false;
  
      if (NumArgOperands == 2 &&
          I.getArgOperand(0)->getType()->isPointerTy() &&
          I.getArgOperand(1)->getType()->isVectorTy() &&
          I.getType()->isVoidTy() &&
          !I.onlyReadsMemory()) {
        // This looks like a vector store.
        return handleVectorStoreIntrinsic(I);
      }
  
      if (NumArgOperands == 1 &&
          I.getArgOperand(0)->getType()->isPointerTy() &&
          I.getType()->isVectorTy() &&
          I.onlyReadsMemory()) {
        // This looks like a vector load.
        return handleVectorLoadIntrinsic(I);
      }
  
      if (I.doesNotAccessMemory())
        if (maybeHandleSimpleNomemIntrinsic(I))
          return true;
  
      // FIXME: detect and handle SSE maskstore/maskload
      return false;
    }
  
    void handleLifetimeStart(IntrinsicInst &I) {
      if (!PoisonStack)
        return;
      DenseMap<Value *, AllocaInst *> AllocaForValue;
      AllocaInst *AI =
          llvm::findAllocaForValue(I.getArgOperand(1), AllocaForValue);
      if (!AI)
        InstrumentLifetimeStart = false;
      LifetimeStartList.push_back(std::make_pair(&I, AI));
    }
  
    void handleBswap(IntrinsicInst &I) {
      IRBuilder<> IRB(&I);
      Value *Op = I.getArgOperand(0);
      Type *OpType = Op->getType();
      Function *BswapFunc = Intrinsic::getDeclaration(
        F.getParent(), Intrinsic::bswap, makeArrayRef(&OpType, 1));
      setShadow(&I, IRB.CreateCall(BswapFunc, getShadow(Op)));
      setOrigin(&I, getOrigin(Op));
    }
  
    // Instrument vector convert instrinsic.
    //
    // This function instruments intrinsics like cvtsi2ss:
    // %Out = int_xxx_cvtyyy(%ConvertOp)
    // or
    // %Out = int_xxx_cvtyyy(%CopyOp, %ConvertOp)
    // Intrinsic converts \p NumUsedElements elements of \p ConvertOp to the same
    // number \p Out elements, and (if has 2 arguments) copies the rest of the
    // elements from \p CopyOp.
    // In most cases conversion involves floating-point value which may trigger a
    // hardware exception when not fully initialized. For this reason we require
    // \p ConvertOp[0:NumUsedElements] to be fully initialized and trap otherwise.
    // We copy the shadow of \p CopyOp[NumUsedElements:] to \p
    // Out[NumUsedElements:]. This means that intrinsics without \p CopyOp always
    // return a fully initialized value.
    void handleVectorConvertIntrinsic(IntrinsicInst &I, int NumUsedElements) {
      IRBuilder<> IRB(&I);
      Value *CopyOp, *ConvertOp;
  
      switch (I.getNumArgOperands()) {
      case 3:
        assert(isa<ConstantInt>(I.getArgOperand(2)) && "Invalid rounding mode");
        LLVM_FALLTHROUGH;
      case 2:
        CopyOp = I.getArgOperand(0);
        ConvertOp = I.getArgOperand(1);
        break;
      case 1:
        ConvertOp = I.getArgOperand(0);
        CopyOp = nullptr;
        break;
      default:
        llvm_unreachable("Cvt intrinsic with unsupported number of arguments.");
      }
  
      // The first *NumUsedElements* elements of ConvertOp are converted to the
      // same number of output elements. The rest of the output is copied from
      // CopyOp, or (if not available) filled with zeroes.
      // Combine shadow for elements of ConvertOp that are used in this operation,
      // and insert a check.
      // FIXME: consider propagating shadow of ConvertOp, at least in the case of
      // int->any conversion.
      Value *ConvertShadow = getShadow(ConvertOp);
      Value *AggShadow = nullptr;
      if (ConvertOp->getType()->isVectorTy()) {
        AggShadow = IRB.CreateExtractElement(
            ConvertShadow, ConstantInt::get(IRB.getInt32Ty(), 0));
        for (int i = 1; i < NumUsedElements; ++i) {
          Value *MoreShadow = IRB.CreateExtractElement(
              ConvertShadow, ConstantInt::get(IRB.getInt32Ty(), i));
          AggShadow = IRB.CreateOr(AggShadow, MoreShadow);
        }
      } else {
        AggShadow = ConvertShadow;
      }
      assert(AggShadow->getType()->isIntegerTy());
      insertShadowCheck(AggShadow, getOrigin(ConvertOp), &I);
  
      // Build result shadow by zero-filling parts of CopyOp shadow that come from
      // ConvertOp.
      if (CopyOp) {
        assert(CopyOp->getType() == I.getType());
        assert(CopyOp->getType()->isVectorTy());
        Value *ResultShadow = getShadow(CopyOp);
        Type *EltTy = ResultShadow->getType()->getVectorElementType();
        for (int i = 0; i < NumUsedElements; ++i) {
          ResultShadow = IRB.CreateInsertElement(
              ResultShadow, ConstantInt::getNullValue(EltTy),
              ConstantInt::get(IRB.getInt32Ty(), i));
        }
        setShadow(&I, ResultShadow);
        setOrigin(&I, getOrigin(CopyOp));
      } else {
        setShadow(&I, getCleanShadow(&I));
        setOrigin(&I, getCleanOrigin());
      }
    }
  
    // Given a scalar or vector, extract lower 64 bits (or less), and return all
    // zeroes if it is zero, and all ones otherwise.
    Value *Lower64ShadowExtend(IRBuilder<> &IRB, Value *S, Type *T) {
      if (S->getType()->isVectorTy())
        S = CreateShadowCast(IRB, S, IRB.getInt64Ty(), /* Signed */ true);
      assert(S->getType()->getPrimitiveSizeInBits() <= 64);
      Value *S2 = IRB.CreateICmpNE(S, getCleanShadow(S));
      return CreateShadowCast(IRB, S2, T, /* Signed */ true);
    }
  
    // Given a vector, extract its first element, and return all
    // zeroes if it is zero, and all ones otherwise.
    Value *LowerElementShadowExtend(IRBuilder<> &IRB, Value *S, Type *T) {
      Value *S1 = IRB.CreateExtractElement(S, (uint64_t)0);
      Value *S2 = IRB.CreateICmpNE(S1, getCleanShadow(S1));
      return CreateShadowCast(IRB, S2, T, /* Signed */ true);
    }
  
    Value *VariableShadowExtend(IRBuilder<> &IRB, Value *S) {
      Type *T = S->getType();
      assert(T->isVectorTy());
      Value *S2 = IRB.CreateICmpNE(S, getCleanShadow(S));
      return IRB.CreateSExt(S2, T);
    }
  
    // Instrument vector shift instrinsic.
    //
    // This function instruments intrinsics like int_x86_avx2_psll_w.
    // Intrinsic shifts %In by %ShiftSize bits.
    // %ShiftSize may be a vector. In that case the lower 64 bits determine shift
    // size, and the rest is ignored. Behavior is defined even if shift size is
    // greater than register (or field) width.
    void handleVectorShiftIntrinsic(IntrinsicInst &I, bool Variable) {
      assert(I.getNumArgOperands() == 2);
      IRBuilder<> IRB(&I);
      // If any of the S2 bits are poisoned, the whole thing is poisoned.
      // Otherwise perform the same shift on S1.
      Value *S1 = getShadow(&I, 0);
      Value *S2 = getShadow(&I, 1);
      Value *S2Conv = Variable ? VariableShadowExtend(IRB, S2)
                               : Lower64ShadowExtend(IRB, S2, getShadowTy(&I));
      Value *V1 = I.getOperand(0);
      Value *V2 = I.getOperand(1);
      Value *Shift = IRB.CreateCall(I.getFunctionType(), I.getCalledValue(),
                                    {IRB.CreateBitCast(S1, V1->getType()), V2});
      Shift = IRB.CreateBitCast(Shift, getShadowTy(&I));
      setShadow(&I, IRB.CreateOr(Shift, S2Conv));
      setOriginForNaryOp(I);
    }
  
    // Get an X86_MMX-sized vector type.
    Type *getMMXVectorTy(unsigned EltSizeInBits) {
      const unsigned X86_MMXSizeInBits = 64;
      assert(EltSizeInBits != 0 && (X86_MMXSizeInBits % EltSizeInBits) == 0 &&
             "Illegal MMX vector element size");
      return VectorType::get(IntegerType::get(*MS.C, EltSizeInBits),
                             X86_MMXSizeInBits / EltSizeInBits);
    }
  
    // Returns a signed counterpart for an (un)signed-saturate-and-pack
    // intrinsic.
    Intrinsic::ID getSignedPackIntrinsic(Intrinsic::ID id) {
      switch (id) {
        case Intrinsic::x86_sse2_packsswb_128:
        case Intrinsic::x86_sse2_packuswb_128:
          return Intrinsic::x86_sse2_packsswb_128;
  
        case Intrinsic::x86_sse2_packssdw_128:
        case Intrinsic::x86_sse41_packusdw:
          return Intrinsic::x86_sse2_packssdw_128;
  
        case Intrinsic::x86_avx2_packsswb:
        case Intrinsic::x86_avx2_packuswb:
          return Intrinsic::x86_avx2_packsswb;
  
        case Intrinsic::x86_avx2_packssdw:
        case Intrinsic::x86_avx2_packusdw:
          return Intrinsic::x86_avx2_packssdw;
  
        case Intrinsic::x86_mmx_packsswb:
        case Intrinsic::x86_mmx_packuswb:
          return Intrinsic::x86_mmx_packsswb;
  
        case Intrinsic::x86_mmx_packssdw:
          return Intrinsic::x86_mmx_packssdw;
        default:
          llvm_unreachable("unexpected intrinsic id");
      }
    }
  
    // Instrument vector pack instrinsic.
    //
    // This function instruments intrinsics like x86_mmx_packsswb, that
    // packs elements of 2 input vectors into half as many bits with saturation.
    // Shadow is propagated with the signed variant of the same intrinsic applied
    // to sext(Sa != zeroinitializer), sext(Sb != zeroinitializer).
    // EltSizeInBits is used only for x86mmx arguments.
    void handleVectorPackIntrinsic(IntrinsicInst &I, unsigned EltSizeInBits = 0) {
      assert(I.getNumArgOperands() == 2);
      bool isX86_MMX = I.getOperand(0)->getType()->isX86_MMXTy();
      IRBuilder<> IRB(&I);
      Value *S1 = getShadow(&I, 0);
      Value *S2 = getShadow(&I, 1);
      assert(isX86_MMX || S1->getType()->isVectorTy());
  
      // SExt and ICmpNE below must apply to individual elements of input vectors.
      // In case of x86mmx arguments, cast them to appropriate vector types and
      // back.
      Type *T = isX86_MMX ? getMMXVectorTy(EltSizeInBits) : S1->getType();
      if (isX86_MMX) {
        S1 = IRB.CreateBitCast(S1, T);
        S2 = IRB.CreateBitCast(S2, T);
      }
      Value *S1_ext = IRB.CreateSExt(
          IRB.CreateICmpNE(S1, Constant::getNullValue(T)), T);
      Value *S2_ext = IRB.CreateSExt(
          IRB.CreateICmpNE(S2, Constant::getNullValue(T)), T);
      if (isX86_MMX) {
        Type *X86_MMXTy = Type::getX86_MMXTy(*MS.C);
        S1_ext = IRB.CreateBitCast(S1_ext, X86_MMXTy);
        S2_ext = IRB.CreateBitCast(S2_ext, X86_MMXTy);
      }
  
      Function *ShadowFn = Intrinsic::getDeclaration(
          F.getParent(), getSignedPackIntrinsic(I.getIntrinsicID()));
  
      Value *S =
          IRB.CreateCall(ShadowFn, {S1_ext, S2_ext}, "_msprop_vector_pack");
      if (isX86_MMX) S = IRB.CreateBitCast(S, getShadowTy(&I));
      setShadow(&I, S);
      setOriginForNaryOp(I);
    }
  
    // Instrument sum-of-absolute-differencies intrinsic.
    void handleVectorSadIntrinsic(IntrinsicInst &I) {
      const unsigned SignificantBitsPerResultElement = 16;
      bool isX86_MMX = I.getOperand(0)->getType()->isX86_MMXTy();
      Type *ResTy = isX86_MMX ? IntegerType::get(*MS.C, 64) : I.getType();
      unsigned ZeroBitsPerResultElement =
          ResTy->getScalarSizeInBits() - SignificantBitsPerResultElement;
  
      IRBuilder<> IRB(&I);
      Value *S = IRB.CreateOr(getShadow(&I, 0), getShadow(&I, 1));
      S = IRB.CreateBitCast(S, ResTy);
      S = IRB.CreateSExt(IRB.CreateICmpNE(S, Constant::getNullValue(ResTy)),
                         ResTy);
      S = IRB.CreateLShr(S, ZeroBitsPerResultElement);
      S = IRB.CreateBitCast(S, getShadowTy(&I));
      setShadow(&I, S);
      setOriginForNaryOp(I);
    }
  
    // Instrument multiply-add intrinsic.
    void handleVectorPmaddIntrinsic(IntrinsicInst &I,
                                    unsigned EltSizeInBits = 0) {
      bool isX86_MMX = I.getOperand(0)->getType()->isX86_MMXTy();
      Type *ResTy = isX86_MMX ? getMMXVectorTy(EltSizeInBits * 2) : I.getType();
      IRBuilder<> IRB(&I);
      Value *S = IRB.CreateOr(getShadow(&I, 0), getShadow(&I, 1));
      S = IRB.CreateBitCast(S, ResTy);
      S = IRB.CreateSExt(IRB.CreateICmpNE(S, Constant::getNullValue(ResTy)),
                         ResTy);
      S = IRB.CreateBitCast(S, getShadowTy(&I));
      setShadow(&I, S);
      setOriginForNaryOp(I);
    }
  
    // Instrument compare-packed intrinsic.
    // Basically, an or followed by sext(icmp ne 0) to end up with all-zeros or
    // all-ones shadow.
    void handleVectorComparePackedIntrinsic(IntrinsicInst &I) {
      IRBuilder<> IRB(&I);
      Type *ResTy = getShadowTy(&I);
      Value *S0 = IRB.CreateOr(getShadow(&I, 0), getShadow(&I, 1));
      Value *S = IRB.CreateSExt(
          IRB.CreateICmpNE(S0, Constant::getNullValue(ResTy)), ResTy);
      setShadow(&I, S);
      setOriginForNaryOp(I);
    }
  
    // Instrument compare-scalar intrinsic.
    // This handles both cmp* intrinsics which return the result in the first
    // element of a vector, and comi* which return the result as i32.
    void handleVectorCompareScalarIntrinsic(IntrinsicInst &I) {
      IRBuilder<> IRB(&I);
      Value *S0 = IRB.CreateOr(getShadow(&I, 0), getShadow(&I, 1));
      Value *S = LowerElementShadowExtend(IRB, S0, getShadowTy(&I));
      setShadow(&I, S);
      setOriginForNaryOp(I);
    }
  
    void handleStmxcsr(IntrinsicInst &I) {
      IRBuilder<> IRB(&I);
      Value* Addr = I.getArgOperand(0);
      Type *Ty = IRB.getInt32Ty();
      Value *ShadowPtr =
          getShadowOriginPtr(Addr, IRB, Ty, /*Alignment*/ 1, /*isStore*/ true)
              .first;
  
      IRB.CreateStore(getCleanShadow(Ty),
                      IRB.CreatePointerCast(ShadowPtr, Ty->getPointerTo()));
  
      if (ClCheckAccessAddress)
        insertShadowCheck(Addr, &I);
    }
  
    void handleLdmxcsr(IntrinsicInst &I) {
      if (!InsertChecks) return;
  
      IRBuilder<> IRB(&I);
      Value *Addr = I.getArgOperand(0);
      Type *Ty = IRB.getInt32Ty();
      unsigned Alignment = 1;
      Value *ShadowPtr, *OriginPtr;
      std::tie(ShadowPtr, OriginPtr) =
          getShadowOriginPtr(Addr, IRB, Ty, Alignment, /*isStore*/ false);
  
      if (ClCheckAccessAddress)
        insertShadowCheck(Addr, &I);
  
      Value *Shadow = IRB.CreateAlignedLoad(Ty, ShadowPtr, Alignment, "_ldmxcsr");
      Value *Origin = MS.TrackOrigins ? IRB.CreateLoad(MS.OriginTy, OriginPtr)
                                      : getCleanOrigin();
      insertShadowCheck(Shadow, Origin, &I);
    }
  
    void handleMaskedStore(IntrinsicInst &I) {
      IRBuilder<> IRB(&I);
      Value *V = I.getArgOperand(0);
      Value *Addr = I.getArgOperand(1);
      unsigned Align = cast<ConstantInt>(I.getArgOperand(2))->getZExtValue();
      Value *Mask = I.getArgOperand(3);
      Value *Shadow = getShadow(V);
  
      Value *ShadowPtr;
      Value *OriginPtr;
      std::tie(ShadowPtr, OriginPtr) = getShadowOriginPtr(
          Addr, IRB, Shadow->getType(), Align, /*isStore*/ true);
  
      if (ClCheckAccessAddress) {
        insertShadowCheck(Addr, &I);
        // Uninitialized mask is kind of like uninitialized address, but not as
        // scary.
        insertShadowCheck(Mask, &I);
      }
  
      IRB.CreateMaskedStore(Shadow, ShadowPtr, Align, Mask);
  
      if (MS.TrackOrigins) {
        auto &DL = F.getParent()->getDataLayout();
        paintOrigin(IRB, getOrigin(V), OriginPtr,
                    DL.getTypeStoreSize(Shadow->getType()),
                    std::max(Align, kMinOriginAlignment));
      }
    }
  
    bool handleMaskedLoad(IntrinsicInst &I) {
      IRBuilder<> IRB(&I);
      Value *Addr = I.getArgOperand(0);
      unsigned Align = cast<ConstantInt>(I.getArgOperand(1))->getZExtValue();
      Value *Mask = I.getArgOperand(2);
      Value *PassThru = I.getArgOperand(3);
  
      Type *ShadowTy = getShadowTy(&I);
      Value *ShadowPtr, *OriginPtr;
      if (PropagateShadow) {
        std::tie(ShadowPtr, OriginPtr) =
            getShadowOriginPtr(Addr, IRB, ShadowTy, Align, /*isStore*/ false);
        setShadow(&I, IRB.CreateMaskedLoad(ShadowPtr, Align, Mask,
                                           getShadow(PassThru), "_msmaskedld"));
      } else {
        setShadow(&I, getCleanShadow(&I));
      }
  
      if (ClCheckAccessAddress) {
        insertShadowCheck(Addr, &I);
        insertShadowCheck(Mask, &I);
      }
  
      if (MS.TrackOrigins) {
        if (PropagateShadow) {
          // Choose between PassThru's and the loaded value's origins.
          Value *MaskedPassThruShadow = IRB.CreateAnd(
              getShadow(PassThru), IRB.CreateSExt(IRB.CreateNeg(Mask), ShadowTy));
  
          Value *Acc = IRB.CreateExtractElement(
              MaskedPassThruShadow, ConstantInt::get(IRB.getInt32Ty(), 0));
          for (int i = 1, N = PassThru->getType()->getVectorNumElements(); i < N;
               ++i) {
            Value *More = IRB.CreateExtractElement(
                MaskedPassThruShadow, ConstantInt::get(IRB.getInt32Ty(), i));
            Acc = IRB.CreateOr(Acc, More);
          }
  
          Value *Origin = IRB.CreateSelect(
              IRB.CreateICmpNE(Acc, Constant::getNullValue(Acc->getType())),
              getOrigin(PassThru), IRB.CreateLoad(MS.OriginTy, OriginPtr));
  
          setOrigin(&I, Origin);
        } else {
          setOrigin(&I, getCleanOrigin());
        }
      }
      return true;
    }
  
    // Instrument BMI / BMI2 intrinsics.
    // All of these intrinsics are Z = I(X, Y)
    // where the types of all operands and the result match, and are either i32 or i64.
    // The following instrumentation happens to work for all of them:
    //   Sz = I(Sx, Y) | (sext (Sy != 0))
    void handleBmiIntrinsic(IntrinsicInst &I) {
      IRBuilder<> IRB(&I);
      Type *ShadowTy = getShadowTy(&I);
  
      // If any bit of the mask operand is poisoned, then the whole thing is.
      Value *SMask = getShadow(&I, 1);
      SMask = IRB.CreateSExt(IRB.CreateICmpNE(SMask, getCleanShadow(ShadowTy)),
                             ShadowTy);
      // Apply the same intrinsic to the shadow of the first operand.
      Value *S = IRB.CreateCall(I.getCalledFunction(),
                                {getShadow(&I, 0), I.getOperand(1)});
      S = IRB.CreateOr(SMask, S);
      setShadow(&I, S);
      setOriginForNaryOp(I);
    }
  
    void visitIntrinsicInst(IntrinsicInst &I) {
      switch (I.getIntrinsicID()) {
      case Intrinsic::lifetime_start:
        handleLifetimeStart(I);
        break;
      case Intrinsic::bswap:
        handleBswap(I);
        break;
      case Intrinsic::masked_store:
        handleMaskedStore(I);
        break;
      case Intrinsic::masked_load:
        handleMaskedLoad(I);
        break;
      case Intrinsic::x86_sse_stmxcsr:
        handleStmxcsr(I);
        break;
      case Intrinsic::x86_sse_ldmxcsr:
        handleLdmxcsr(I);
        break;
      case Intrinsic::x86_avx512_vcvtsd2usi64:
      case Intrinsic::x86_avx512_vcvtsd2usi32:
      case Intrinsic::x86_avx512_vcvtss2usi64:
      case Intrinsic::x86_avx512_vcvtss2usi32:
      case Intrinsic::x86_avx512_cvttss2usi64:
      case Intrinsic::x86_avx512_cvttss2usi:
      case Intrinsic::x86_avx512_cvttsd2usi64:
      case Intrinsic::x86_avx512_cvttsd2usi:
      case Intrinsic::x86_avx512_cvtusi2ss:
      case Intrinsic::x86_avx512_cvtusi642sd:
      case Intrinsic::x86_avx512_cvtusi642ss:
      case Intrinsic::x86_sse2_cvtsd2si64:
      case Intrinsic::x86_sse2_cvtsd2si:
      case Intrinsic::x86_sse2_cvtsd2ss:
      case Intrinsic::x86_sse2_cvttsd2si64:
      case Intrinsic::x86_sse2_cvttsd2si:
      case Intrinsic::x86_sse_cvtss2si64:
      case Intrinsic::x86_sse_cvtss2si:
      case Intrinsic::x86_sse_cvttss2si64:
      case Intrinsic::x86_sse_cvttss2si:
        handleVectorConvertIntrinsic(I, 1);
        break;
      case Intrinsic::x86_sse_cvtps2pi:
      case Intrinsic::x86_sse_cvttps2pi:
        handleVectorConvertIntrinsic(I, 2);
        break;
  
      case Intrinsic::x86_avx512_psll_w_512:
      case Intrinsic::x86_avx512_psll_d_512:
      case Intrinsic::x86_avx512_psll_q_512:
      case Intrinsic::x86_avx512_pslli_w_512:
      case Intrinsic::x86_avx512_pslli_d_512:
      case Intrinsic::x86_avx512_pslli_q_512:
      case Intrinsic::x86_avx512_psrl_w_512:
      case Intrinsic::x86_avx512_psrl_d_512:
      case Intrinsic::x86_avx512_psrl_q_512:
      case Intrinsic::x86_avx512_psra_w_512:
      case Intrinsic::x86_avx512_psra_d_512:
      case Intrinsic::x86_avx512_psra_q_512:
      case Intrinsic::x86_avx512_psrli_w_512:
      case Intrinsic::x86_avx512_psrli_d_512:
      case Intrinsic::x86_avx512_psrli_q_512:
      case Intrinsic::x86_avx512_psrai_w_512:
      case Intrinsic::x86_avx512_psrai_d_512:
      case Intrinsic::x86_avx512_psrai_q_512:
      case Intrinsic::x86_avx512_psra_q_256:
      case Intrinsic::x86_avx512_psra_q_128:
      case Intrinsic::x86_avx512_psrai_q_256:
      case Intrinsic::x86_avx512_psrai_q_128:
      case Intrinsic::x86_avx2_psll_w:
      case Intrinsic::x86_avx2_psll_d:
      case Intrinsic::x86_avx2_psll_q:
      case Intrinsic::x86_avx2_pslli_w:
      case Intrinsic::x86_avx2_pslli_d:
      case Intrinsic::x86_avx2_pslli_q:
      case Intrinsic::x86_avx2_psrl_w:
      case Intrinsic::x86_avx2_psrl_d:
      case Intrinsic::x86_avx2_psrl_q:
      case Intrinsic::x86_avx2_psra_w:
      case Intrinsic::x86_avx2_psra_d:
      case Intrinsic::x86_avx2_psrli_w:
      case Intrinsic::x86_avx2_psrli_d:
      case Intrinsic::x86_avx2_psrli_q:
      case Intrinsic::x86_avx2_psrai_w:
      case Intrinsic::x86_avx2_psrai_d:
      case Intrinsic::x86_sse2_psll_w:
      case Intrinsic::x86_sse2_psll_d:
      case Intrinsic::x86_sse2_psll_q:
      case Intrinsic::x86_sse2_pslli_w:
      case Intrinsic::x86_sse2_pslli_d:
      case Intrinsic::x86_sse2_pslli_q:
      case Intrinsic::x86_sse2_psrl_w:
      case Intrinsic::x86_sse2_psrl_d:
      case Intrinsic::x86_sse2_psrl_q:
      case Intrinsic::x86_sse2_psra_w:
      case Intrinsic::x86_sse2_psra_d:
      case Intrinsic::x86_sse2_psrli_w:
      case Intrinsic::x86_sse2_psrli_d:
      case Intrinsic::x86_sse2_psrli_q:
      case Intrinsic::x86_sse2_psrai_w:
      case Intrinsic::x86_sse2_psrai_d:
      case Intrinsic::x86_mmx_psll_w:
      case Intrinsic::x86_mmx_psll_d:
      case Intrinsic::x86_mmx_psll_q:
      case Intrinsic::x86_mmx_pslli_w:
      case Intrinsic::x86_mmx_pslli_d:
      case Intrinsic::x86_mmx_pslli_q:
      case Intrinsic::x86_mmx_psrl_w:
      case Intrinsic::x86_mmx_psrl_d:
      case Intrinsic::x86_mmx_psrl_q:
      case Intrinsic::x86_mmx_psra_w:
      case Intrinsic::x86_mmx_psra_d:
      case Intrinsic::x86_mmx_psrli_w:
      case Intrinsic::x86_mmx_psrli_d:
      case Intrinsic::x86_mmx_psrli_q:
      case Intrinsic::x86_mmx_psrai_w:
      case Intrinsic::x86_mmx_psrai_d:
        handleVectorShiftIntrinsic(I, /* Variable */ false);
        break;
      case Intrinsic::x86_avx2_psllv_d:
      case Intrinsic::x86_avx2_psllv_d_256:
      case Intrinsic::x86_avx512_psllv_d_512:
      case Intrinsic::x86_avx2_psllv_q:
      case Intrinsic::x86_avx2_psllv_q_256:
      case Intrinsic::x86_avx512_psllv_q_512:
      case Intrinsic::x86_avx2_psrlv_d:
      case Intrinsic::x86_avx2_psrlv_d_256:
      case Intrinsic::x86_avx512_psrlv_d_512:
      case Intrinsic::x86_avx2_psrlv_q:
      case Intrinsic::x86_avx2_psrlv_q_256:
      case Intrinsic::x86_avx512_psrlv_q_512:
      case Intrinsic::x86_avx2_psrav_d:
      case Intrinsic::x86_avx2_psrav_d_256:
      case Intrinsic::x86_avx512_psrav_d_512:
      case Intrinsic::x86_avx512_psrav_q_128:
      case Intrinsic::x86_avx512_psrav_q_256:
      case Intrinsic::x86_avx512_psrav_q_512:
        handleVectorShiftIntrinsic(I, /* Variable */ true);
        break;
  
      case Intrinsic::x86_sse2_packsswb_128:
      case Intrinsic::x86_sse2_packssdw_128:
      case Intrinsic::x86_sse2_packuswb_128:
      case Intrinsic::x86_sse41_packusdw:
      case Intrinsic::x86_avx2_packsswb:
      case Intrinsic::x86_avx2_packssdw:
      case Intrinsic::x86_avx2_packuswb:
      case Intrinsic::x86_avx2_packusdw:
        handleVectorPackIntrinsic(I);
        break;
  
      case Intrinsic::x86_mmx_packsswb:
      case Intrinsic::x86_mmx_packuswb:
        handleVectorPackIntrinsic(I, 16);
        break;
  
      case Intrinsic::x86_mmx_packssdw:
        handleVectorPackIntrinsic(I, 32);
        break;
  
      case Intrinsic::x86_mmx_psad_bw:
      case Intrinsic::x86_sse2_psad_bw:
      case Intrinsic::x86_avx2_psad_bw:
        handleVectorSadIntrinsic(I);
        break;
  
      case Intrinsic::x86_sse2_pmadd_wd:
      case Intrinsic::x86_avx2_pmadd_wd:
      case Intrinsic::x86_ssse3_pmadd_ub_sw_128:
      case Intrinsic::x86_avx2_pmadd_ub_sw:
        handleVectorPmaddIntrinsic(I);
        break;
  
      case Intrinsic::x86_ssse3_pmadd_ub_sw:
        handleVectorPmaddIntrinsic(I, 8);
        break;
  
      case Intrinsic::x86_mmx_pmadd_wd:
        handleVectorPmaddIntrinsic(I, 16);
        break;
  
      case Intrinsic::x86_sse_cmp_ss:
      case Intrinsic::x86_sse2_cmp_sd:
      case Intrinsic::x86_sse_comieq_ss:
      case Intrinsic::x86_sse_comilt_ss:
      case Intrinsic::x86_sse_comile_ss:
      case Intrinsic::x86_sse_comigt_ss:
      case Intrinsic::x86_sse_comige_ss:
      case Intrinsic::x86_sse_comineq_ss:
      case Intrinsic::x86_sse_ucomieq_ss:
      case Intrinsic::x86_sse_ucomilt_ss:
      case Intrinsic::x86_sse_ucomile_ss:
      case Intrinsic::x86_sse_ucomigt_ss:
      case Intrinsic::x86_sse_ucomige_ss:
      case Intrinsic::x86_sse_ucomineq_ss:
      case Intrinsic::x86_sse2_comieq_sd:
      case Intrinsic::x86_sse2_comilt_sd:
      case Intrinsic::x86_sse2_comile_sd:
      case Intrinsic::x86_sse2_comigt_sd:
      case Intrinsic::x86_sse2_comige_sd:
      case Intrinsic::x86_sse2_comineq_sd:
      case Intrinsic::x86_sse2_ucomieq_sd:
      case Intrinsic::x86_sse2_ucomilt_sd:
      case Intrinsic::x86_sse2_ucomile_sd:
      case Intrinsic::x86_sse2_ucomigt_sd:
      case Intrinsic::x86_sse2_ucomige_sd:
      case Intrinsic::x86_sse2_ucomineq_sd:
        handleVectorCompareScalarIntrinsic(I);
        break;
  
      case Intrinsic::x86_sse_cmp_ps:
      case Intrinsic::x86_sse2_cmp_pd:
        // FIXME: For x86_avx_cmp_pd_256 and x86_avx_cmp_ps_256 this function
        // generates reasonably looking IR that fails in the backend with "Do not
        // know how to split the result of this operator!".
        handleVectorComparePackedIntrinsic(I);
        break;
  
      case Intrinsic::x86_bmi_bextr_32:
      case Intrinsic::x86_bmi_bextr_64:
      case Intrinsic::x86_bmi_bzhi_32:
      case Intrinsic::x86_bmi_bzhi_64:
      case Intrinsic::x86_bmi_pdep_32:
      case Intrinsic::x86_bmi_pdep_64:
      case Intrinsic::x86_bmi_pext_32:
      case Intrinsic::x86_bmi_pext_64:
        handleBmiIntrinsic(I);
        break;
  
      case Intrinsic::is_constant:
        // The result of llvm.is.constant() is always defined.
        setShadow(&I, getCleanShadow(&I));
        setOrigin(&I, getCleanOrigin());
        break;
  
      default:
        if (!handleUnknownIntrinsic(I))
          visitInstruction(I);
        break;
      }
    }
  
    void visitCallSite(CallSite CS) {
      Instruction &I = *CS.getInstruction();
      assert(!I.getMetadata("nosanitize"));
      assert((CS.isCall() || CS.isInvoke() || CS.isCallBr()) &&
             "Unknown type of CallSite");
      if (CS.isCallBr() || (CS.isCall() && cast<CallInst>(&I)->isInlineAsm())) {
        // For inline asm (either a call to asm function, or callbr instruction),
        // do the usual thing: check argument shadow and mark all outputs as
        // clean. Note that any side effects of the inline asm that are not
        // immediately visible in its constraints are not handled.
        if (ClHandleAsmConservative && MS.CompileKernel)
          visitAsmInstruction(I);
        else
          visitInstruction(I);
        return;
      }
      if (CS.isCall()) {
        CallInst *Call = cast<CallInst>(&I);
        assert(!isa<IntrinsicInst>(&I) && "intrinsics are handled elsewhere");
  
        // We are going to insert code that relies on the fact that the callee
        // will become a non-readonly function after it is instrumented by us. To
        // prevent this code from being optimized out, mark that function
        // non-readonly in advance.
        if (Function *Func = Call->getCalledFunction()) {
          // Clear out readonly/readnone attributes.
          AttrBuilder B;
          B.addAttribute(Attribute::ReadOnly)
            .addAttribute(Attribute::ReadNone);
          Func->removeAttributes(AttributeList::FunctionIndex, B);
        }
  
        maybeMarkSanitizerLibraryCallNoBuiltin(Call, TLI);
      }
      IRBuilder<> IRB(&I);
  
      unsigned ArgOffset = 0;
      LLVM_DEBUG(dbgs() << "  CallSite: " << I << "\n");
      for (CallSite::arg_iterator ArgIt = CS.arg_begin(), End = CS.arg_end();
           ArgIt != End; ++ArgIt) {
        Value *A = *ArgIt;
        unsigned i = ArgIt - CS.arg_begin();
        if (!A->getType()->isSized()) {
          LLVM_DEBUG(dbgs() << "Arg " << i << " is not sized: " << I << "\n");
          continue;
        }
        unsigned Size = 0;
        Value *Store = nullptr;
        // Compute the Shadow for arg even if it is ByVal, because
        // in that case getShadow() will copy the actual arg shadow to
        // __msan_param_tls.
        Value *ArgShadow = getShadow(A);
        Value *ArgShadowBase = getShadowPtrForArgument(A, IRB, ArgOffset);
        LLVM_DEBUG(dbgs() << "  Arg#" << i << ": " << *A
                          << " Shadow: " << *ArgShadow << "\n");
        bool ArgIsInitialized = false;
        const DataLayout &DL = F.getParent()->getDataLayout();
        if (CS.paramHasAttr(i, Attribute::ByVal)) {
          assert(A->getType()->isPointerTy() &&
                 "ByVal argument is not a pointer!");
          Size = DL.getTypeAllocSize(A->getType()->getPointerElementType());
          if (ArgOffset + Size > kParamTLSSize) break;
          unsigned ParamAlignment = CS.getParamAlignment(i);
          unsigned Alignment = std::min(ParamAlignment, kShadowTLSAlignment);
          Value *AShadowPtr =
              getShadowOriginPtr(A, IRB, IRB.getInt8Ty(), Alignment,
                                 /*isStore*/ false)
                  .first;
  
          Store = IRB.CreateMemCpy(ArgShadowBase, Alignment, AShadowPtr,
                                   Alignment, Size);
          // TODO(glider): need to copy origins.
        } else {
          Size = DL.getTypeAllocSize(A->getType());
          if (ArgOffset + Size > kParamTLSSize) break;
          Store = IRB.CreateAlignedStore(ArgShadow, ArgShadowBase,
                                         kShadowTLSAlignment);
          Constant *Cst = dyn_cast<Constant>(ArgShadow);
          if (Cst && Cst->isNullValue()) ArgIsInitialized = true;
        }
        if (MS.TrackOrigins && !ArgIsInitialized)
          IRB.CreateStore(getOrigin(A),
                          getOriginPtrForArgument(A, IRB, ArgOffset));
        (void)Store;
        assert(Size != 0 && Store != nullptr);
        LLVM_DEBUG(dbgs() << "  Param:" << *Store << "\n");
        ArgOffset += alignTo(Size, 8);
      }
      LLVM_DEBUG(dbgs() << "  done with call args\n");
  
      FunctionType *FT = CS.getFunctionType();
      if (FT->isVarArg()) {
        VAHelper->visitCallSite(CS, IRB);
      }
  
      // Now, get the shadow for the RetVal.
      if (!I.getType()->isSized()) return;
      // Don't emit the epilogue for musttail call returns.
      if (CS.isCall() && cast<CallInst>(&I)->isMustTailCall()) return;
      IRBuilder<> IRBBefore(&I);
      // Until we have full dynamic coverage, make sure the retval shadow is 0.
      Value *Base = getShadowPtrForRetval(&I, IRBBefore);
      IRBBefore.CreateAlignedStore(getCleanShadow(&I), Base, kShadowTLSAlignment);
      BasicBlock::iterator NextInsn;
      if (CS.isCall()) {
        NextInsn = ++I.getIterator();
        assert(NextInsn != I.getParent()->end());
      } else {
        BasicBlock *NormalDest = cast<InvokeInst>(&I)->getNormalDest();
        if (!NormalDest->getSinglePredecessor()) {
          // FIXME: this case is tricky, so we are just conservative here.
          // Perhaps we need to split the edge between this BB and NormalDest,
          // but a naive attempt to use SplitEdge leads to a crash.
          setShadow(&I, getCleanShadow(&I));
          setOrigin(&I, getCleanOrigin());
          return;
        }
        // FIXME: NextInsn is likely in a basic block that has not been visited yet.
        // Anything inserted there will be instrumented by MSan later!
        NextInsn = NormalDest->getFirstInsertionPt();
        assert(NextInsn != NormalDest->end() &&
               "Could not find insertion point for retval shadow load");
      }
      IRBuilder<> IRBAfter(&*NextInsn);
      Value *RetvalShadow = IRBAfter.CreateAlignedLoad(
          getShadowTy(&I), getShadowPtrForRetval(&I, IRBAfter),
          kShadowTLSAlignment, "_msret");
      setShadow(&I, RetvalShadow);
      if (MS.TrackOrigins)
        setOrigin(&I, IRBAfter.CreateLoad(MS.OriginTy,
                                          getOriginPtrForRetval(IRBAfter)));
    }
  
    bool isAMustTailRetVal(Value *RetVal) {
      if (auto *I = dyn_cast<BitCastInst>(RetVal)) {
        RetVal = I->getOperand(0);
      }
      if (auto *I = dyn_cast<CallInst>(RetVal)) {
        return I->isMustTailCall();
      }
      return false;
    }
  
    void visitReturnInst(ReturnInst &I) {
      IRBuilder<> IRB(&I);
      Value *RetVal = I.getReturnValue();
      if (!RetVal) return;
      // Don't emit the epilogue for musttail call returns.
      if (isAMustTailRetVal(RetVal)) return;
      Value *ShadowPtr = getShadowPtrForRetval(RetVal, IRB);
      if (CheckReturnValue) {
        insertShadowCheck(RetVal, &I);
        Value *Shadow = getCleanShadow(RetVal);
        IRB.CreateAlignedStore(Shadow, ShadowPtr, kShadowTLSAlignment);
      } else {
        Value *Shadow = getShadow(RetVal);
        IRB.CreateAlignedStore(Shadow, ShadowPtr, kShadowTLSAlignment);
        if (MS.TrackOrigins)
          IRB.CreateStore(getOrigin(RetVal), getOriginPtrForRetval(IRB));
      }
    }
  
    void visitPHINode(PHINode &I) {
      IRBuilder<> IRB(&I);
      if (!PropagateShadow) {
        setShadow(&I, getCleanShadow(&I));
        setOrigin(&I, getCleanOrigin());
        return;
      }
  
      ShadowPHINodes.push_back(&I);
      setShadow(&I, IRB.CreatePHI(getShadowTy(&I), I.getNumIncomingValues(),
                                  "_msphi_s"));
      if (MS.TrackOrigins)
        setOrigin(&I, IRB.CreatePHI(MS.OriginTy, I.getNumIncomingValues(),
                                    "_msphi_o"));
    }
  
    Value *getLocalVarDescription(AllocaInst &I) {
      SmallString<2048> StackDescriptionStorage;
      raw_svector_ostream StackDescription(StackDescriptionStorage);
      // We create a string with a description of the stack allocation and
      // pass it into __msan_set_alloca_origin.
      // It will be printed by the run-time if stack-originated UMR is found.
      // The first 4 bytes of the string are set to '----' and will be replaced
      // by __msan_va_arg_overflow_size_tls at the first call.
      StackDescription << "----" << I.getName() << "@" << F.getName();
      return createPrivateNonConstGlobalForString(*F.getParent(),
                                                  StackDescription.str());
    }
  
    void poisonAllocaUserspace(AllocaInst &I, IRBuilder<> &IRB, Value *Len) {
      if (PoisonStack && ClPoisonStackWithCall) {
        IRB.CreateCall(MS.MsanPoisonStackFn,
                       {IRB.CreatePointerCast(&I, IRB.getInt8PtrTy()), Len});
      } else {
        Value *ShadowBase, *OriginBase;
        std::tie(ShadowBase, OriginBase) =
            getShadowOriginPtr(&I, IRB, IRB.getInt8Ty(), 1, /*isStore*/ true);
  
        Value *PoisonValue = IRB.getInt8(PoisonStack ? ClPoisonStackPattern : 0);
        IRB.CreateMemSet(ShadowBase, PoisonValue, Len, I.getAlignment());
      }
  
      if (PoisonStack && MS.TrackOrigins) {
        Value *Descr = getLocalVarDescription(I);
        IRB.CreateCall(MS.MsanSetAllocaOrigin4Fn,
                       {IRB.CreatePointerCast(&I, IRB.getInt8PtrTy()), Len,
                        IRB.CreatePointerCast(Descr, IRB.getInt8PtrTy()),
                        IRB.CreatePointerCast(&F, MS.IntptrTy)});
      }
    }
  
    void poisonAllocaKmsan(AllocaInst &I, IRBuilder<> &IRB, Value *Len) {
      Value *Descr = getLocalVarDescription(I);
      if (PoisonStack) {
        IRB.CreateCall(MS.MsanPoisonAllocaFn,
                       {IRB.CreatePointerCast(&I, IRB.getInt8PtrTy()), Len,
                        IRB.CreatePointerCast(Descr, IRB.getInt8PtrTy())});
      } else {
        IRB.CreateCall(MS.MsanUnpoisonAllocaFn,
                       {IRB.CreatePointerCast(&I, IRB.getInt8PtrTy()), Len});
      }
    }
  
    void instrumentAlloca(AllocaInst &I, Instruction *InsPoint = nullptr) {
      if (!InsPoint)
        InsPoint = &I;
      IRBuilder<> IRB(InsPoint->getNextNode());
      const DataLayout &DL = F.getParent()->getDataLayout();
      uint64_t TypeSize = DL.getTypeAllocSize(I.getAllocatedType());
      Value *Len = ConstantInt::get(MS.IntptrTy, TypeSize);
      if (I.isArrayAllocation())
        Len = IRB.CreateMul(Len, I.getArraySize());
  
      if (MS.CompileKernel)
        poisonAllocaKmsan(I, IRB, Len);
      else
        poisonAllocaUserspace(I, IRB, Len);
    }
  
    void visitAllocaInst(AllocaInst &I) {
      setShadow(&I, getCleanShadow(&I));
      setOrigin(&I, getCleanOrigin());
      // We'll get to this alloca later unless it's poisoned at the corresponding
      // llvm.lifetime.start.
      AllocaSet.insert(&I);
    }
  
    void visitSelectInst(SelectInst& I) {
      IRBuilder<> IRB(&I);
      // a = select b, c, d
      Value *B = I.getCondition();
      Value *C = I.getTrueValue();
      Value *D = I.getFalseValue();
      Value *Sb = getShadow(B);
      Value *Sc = getShadow(C);
      Value *Sd = getShadow(D);
  
      // Result shadow if condition shadow is 0.
      Value *Sa0 = IRB.CreateSelect(B, Sc, Sd);
      Value *Sa1;
      if (I.getType()->isAggregateType()) {
        // To avoid "sign extending" i1 to an arbitrary aggregate type, we just do
        // an extra "select". This results in much more compact IR.
        // Sa = select Sb, poisoned, (select b, Sc, Sd)
        Sa1 = getPoisonedShadow(getShadowTy(I.getType()));
      } else {
        // Sa = select Sb, [ (c^d) | Sc | Sd ], [ b ? Sc : Sd ]
        // If Sb (condition is poisoned), look for bits in c and d that are equal
        // and both unpoisoned.
        // If !Sb (condition is unpoisoned), simply pick one of Sc and Sd.
  
        // Cast arguments to shadow-compatible type.
        C = CreateAppToShadowCast(IRB, C);
        D = CreateAppToShadowCast(IRB, D);
  
        // Result shadow if condition shadow is 1.
        Sa1 = IRB.CreateOr({IRB.CreateXor(C, D), Sc, Sd});
      }
      Value *Sa = IRB.CreateSelect(Sb, Sa1, Sa0, "_msprop_select");
      setShadow(&I, Sa);
      if (MS.TrackOrigins) {
        // Origins are always i32, so any vector conditions must be flattened.
        // FIXME: consider tracking vector origins for app vectors?
        if (B->getType()->isVectorTy()) {
          Type *FlatTy = getShadowTyNoVec(B->getType());
          B = IRB.CreateICmpNE(IRB.CreateBitCast(B, FlatTy),
                                  ConstantInt::getNullValue(FlatTy));
          Sb = IRB.CreateICmpNE(IRB.CreateBitCast(Sb, FlatTy),
                                        ConstantInt::getNullValue(FlatTy));
        }
        // a = select b, c, d
        // Oa = Sb ? Ob : (b ? Oc : Od)
        setOrigin(
            &I, IRB.CreateSelect(Sb, getOrigin(I.getCondition()),
                                 IRB.CreateSelect(B, getOrigin(I.getTrueValue()),
                                                  getOrigin(I.getFalseValue()))));
      }
    }
  
    void visitLandingPadInst(LandingPadInst &I) {
      // Do nothing.
      // See https://github.com/google/sanitizers/issues/504
      setShadow(&I, getCleanShadow(&I));
      setOrigin(&I, getCleanOrigin());
    }
  
    void visitCatchSwitchInst(CatchSwitchInst &I) {
      setShadow(&I, getCleanShadow(&I));
      setOrigin(&I, getCleanOrigin());
    }
  
    void visitFuncletPadInst(FuncletPadInst &I) {
      setShadow(&I, getCleanShadow(&I));
      setOrigin(&I, getCleanOrigin());
    }
  
    void visitGetElementPtrInst(GetElementPtrInst &I) {
      handleShadowOr(I);
    }
  
    void visitExtractValueInst(ExtractValueInst &I) {
      IRBuilder<> IRB(&I);
      Value *Agg = I.getAggregateOperand();
      LLVM_DEBUG(dbgs() << "ExtractValue:  " << I << "\n");
      Value *AggShadow = getShadow(Agg);
      LLVM_DEBUG(dbgs() << "   AggShadow:  " << *AggShadow << "\n");
      Value *ResShadow = IRB.CreateExtractValue(AggShadow, I.getIndices());
      LLVM_DEBUG(dbgs() << "   ResShadow:  " << *ResShadow << "\n");
      setShadow(&I, ResShadow);
      setOriginForNaryOp(I);
    }
  
    void visitInsertValueInst(InsertValueInst &I) {
      IRBuilder<> IRB(&I);
      LLVM_DEBUG(dbgs() << "InsertValue:  " << I << "\n");
      Value *AggShadow = getShadow(I.getAggregateOperand());
      Value *InsShadow = getShadow(I.getInsertedValueOperand());
      LLVM_DEBUG(dbgs() << "   AggShadow:  " << *AggShadow << "\n");
      LLVM_DEBUG(dbgs() << "   InsShadow:  " << *InsShadow << "\n");
      Value *Res = IRB.CreateInsertValue(AggShadow, InsShadow, I.getIndices());
      LLVM_DEBUG(dbgs() << "   Res:        " << *Res << "\n");
      setShadow(&I, Res);
      setOriginForNaryOp(I);
    }
  
    void dumpInst(Instruction &I) {
      if (CallInst *CI = dyn_cast<CallInst>(&I)) {
        errs() << "ZZZ call " << CI->getCalledFunction()->getName() << "\n";
      } else {
        errs() << "ZZZ " << I.getOpcodeName() << "\n";
      }
      errs() << "QQQ " << I << "\n";
    }
  
    void visitResumeInst(ResumeInst &I) {
      LLVM_DEBUG(dbgs() << "Resume: " << I << "\n");
      // Nothing to do here.
    }
  
    void visitCleanupReturnInst(CleanupReturnInst &CRI) {
      LLVM_DEBUG(dbgs() << "CleanupReturn: " << CRI << "\n");
      // Nothing to do here.
    }
  
    void visitCatchReturnInst(CatchReturnInst &CRI) {
      LLVM_DEBUG(dbgs() << "CatchReturn: " << CRI << "\n");
      // Nothing to do here.
    }
  
    void instrumentAsmArgument(Value *Operand, Instruction &I, IRBuilder<> &IRB,
                               const DataLayout &DL, bool isOutput) {
      // For each assembly argument, we check its value for being initialized.
      // If the argument is a pointer, we assume it points to a single element
      // of the corresponding type (or to a 8-byte word, if the type is unsized).
      // Each such pointer is instrumented with a call to the runtime library.
      Type *OpType = Operand->getType();
      // Check the operand value itself.
      insertShadowCheck(Operand, &I);
      if (!OpType->isPointerTy() || !isOutput) {
        assert(!isOutput);
        return;
      }
      Type *ElType = OpType->getPointerElementType();
      if (!ElType->isSized())
        return;
      int Size = DL.getTypeStoreSize(ElType);
      Value *Ptr = IRB.CreatePointerCast(Operand, IRB.getInt8PtrTy());
      Value *SizeVal = ConstantInt::get(MS.IntptrTy, Size);
      IRB.CreateCall(MS.MsanInstrumentAsmStoreFn, {Ptr, SizeVal});
    }
  
    /// Get the number of output arguments returned by pointers.
    int getNumOutputArgs(InlineAsm *IA, CallBase *CB) {
      int NumRetOutputs = 0;
      int NumOutputs = 0;
      Type *RetTy = dyn_cast<Value>(CB)->getType();
      if (!RetTy->isVoidTy()) {
        // Register outputs are returned via the CallInst return value.
        StructType *ST = dyn_cast_or_null<StructType>(RetTy);
        if (ST)
          NumRetOutputs = ST->getNumElements();
        else
          NumRetOutputs = 1;
      }
      InlineAsm::ConstraintInfoVector Constraints = IA->ParseConstraints();
      for (size_t i = 0, n = Constraints.size(); i < n; i++) {
        InlineAsm::ConstraintInfo Info = Constraints[i];
        switch (Info.Type) {
        case InlineAsm::isOutput:
          NumOutputs++;
          break;
        default:
          break;
        }
      }
      return NumOutputs - NumRetOutputs;
    }
  
    void visitAsmInstruction(Instruction &I) {
      // Conservative inline assembly handling: check for poisoned shadow of
      // asm() arguments, then unpoison the result and all the memory locations
      // pointed to by those arguments.
      // An inline asm() statement in C++ contains lists of input and output
      // arguments used by the assembly code. These are mapped to operands of the
      // CallInst as follows:
      //  - nR register outputs ("=r) are returned by value in a single structure
      //  (SSA value of the CallInst);
      //  - nO other outputs ("=m" and others) are returned by pointer as first
      // nO operands of the CallInst;
      //  - nI inputs ("r", "m" and others) are passed to CallInst as the
      // remaining nI operands.
      // The total number of asm() arguments in the source is nR+nO+nI, and the
      // corresponding CallInst has nO+nI+1 operands (the last operand is the
      // function to be called).
      const DataLayout &DL = F.getParent()->getDataLayout();
      CallBase *CB = dyn_cast<CallBase>(&I);
      IRBuilder<> IRB(&I);
      InlineAsm *IA = cast<InlineAsm>(CB->getCalledValue());
      int OutputArgs = getNumOutputArgs(IA, CB);
      // The last operand of a CallInst is the function itself.
      int NumOperands = CB->getNumOperands() - 1;
  
      // Check input arguments. Doing so before unpoisoning output arguments, so
      // that we won't overwrite uninit values before checking them.
      for (int i = OutputArgs; i < NumOperands; i++) {
        Value *Operand = CB->getOperand(i);
        instrumentAsmArgument(Operand, I, IRB, DL, /*isOutput*/ false);
      }
      // Unpoison output arguments. This must happen before the actual InlineAsm
      // call, so that the shadow for memory published in the asm() statement
      // remains valid.
      for (int i = 0; i < OutputArgs; i++) {
        Value *Operand = CB->getOperand(i);
        instrumentAsmArgument(Operand, I, IRB, DL, /*isOutput*/ true);
      }
  
      setShadow(&I, getCleanShadow(&I));
      setOrigin(&I, getCleanOrigin());
    }
  
    void visitInstruction(Instruction &I) {
      // Everything else: stop propagating and check for poisoned shadow.
      if (ClDumpStrictInstructions)
        dumpInst(I);
      LLVM_DEBUG(dbgs() << "DEFAULT: " << I << "\n");
      for (size_t i = 0, n = I.getNumOperands(); i < n; i++) {
        Value *Operand = I.getOperand(i);
        if (Operand->getType()->isSized())
          insertShadowCheck(Operand, &I);
      }
      setShadow(&I, getCleanShadow(&I));
      setOrigin(&I, getCleanOrigin());
    }
  };
  
  /// AMD64-specific implementation of VarArgHelper.
  struct VarArgAMD64Helper : public VarArgHelper {
    // An unfortunate workaround for asymmetric lowering of va_arg stuff.
    // See a comment in visitCallSite for more details.
    static const unsigned AMD64GpEndOffset = 48;  // AMD64 ABI Draft 0.99.6 p3.5.7
    static const unsigned AMD64FpEndOffsetSSE = 176;
    // If SSE is disabled, fp_offset in va_list is zero.
    static const unsigned AMD64FpEndOffsetNoSSE = AMD64GpEndOffset;
  
    unsigned AMD64FpEndOffset;
    Function &F;
    MemorySanitizer &MS;
    MemorySanitizerVisitor &MSV;
    Value *VAArgTLSCopy = nullptr;
    Value *VAArgTLSOriginCopy = nullptr;
    Value *VAArgOverflowSize = nullptr;
  
    SmallVector<CallInst*, 16> VAStartInstrumentationList;
  
    enum ArgKind { AK_GeneralPurpose, AK_FloatingPoint, AK_Memory };
  
    VarArgAMD64Helper(Function &F, MemorySanitizer &MS,
                      MemorySanitizerVisitor &MSV)
        : F(F), MS(MS), MSV(MSV) {
      AMD64FpEndOffset = AMD64FpEndOffsetSSE;
      for (const auto &Attr : F.getAttributes().getFnAttributes()) {
        if (Attr.isStringAttribute() &&
            (Attr.getKindAsString() == "target-features")) {
          if (Attr.getValueAsString().contains("-sse"))
            AMD64FpEndOffset = AMD64FpEndOffsetNoSSE;
          break;
        }
      }
    }
  
    ArgKind classifyArgument(Value* arg) {
      // A very rough approximation of X86_64 argument classification rules.
      Type *T = arg->getType();
      if (T->isFPOrFPVectorTy() || T->isX86_MMXTy())
        return AK_FloatingPoint;
      if (T->isIntegerTy() && T->getPrimitiveSizeInBits() <= 64)
        return AK_GeneralPurpose;
      if (T->isPointerTy())
        return AK_GeneralPurpose;
      return AK_Memory;
    }
  
    // For VarArg functions, store the argument shadow in an ABI-specific format
    // that corresponds to va_list layout.
    // We do this because Clang lowers va_arg in the frontend, and this pass
    // only sees the low level code that deals with va_list internals.
    // A much easier alternative (provided that Clang emits va_arg instructions)
    // would have been to associate each live instance of va_list with a copy of
    // MSanParamTLS, and extract shadow on va_arg() call in the argument list
    // order.
    void visitCallSite(CallSite &CS, IRBuilder<> &IRB) override {
      unsigned GpOffset = 0;
      unsigned FpOffset = AMD64GpEndOffset;
      unsigned OverflowOffset = AMD64FpEndOffset;
      const DataLayout &DL = F.getParent()->getDataLayout();
      for (CallSite::arg_iterator ArgIt = CS.arg_begin(), End = CS.arg_end();
           ArgIt != End; ++ArgIt) {
        Value *A = *ArgIt;
        unsigned ArgNo = CS.getArgumentNo(ArgIt);
        bool IsFixed = ArgNo < CS.getFunctionType()->getNumParams();
        bool IsByVal = CS.paramHasAttr(ArgNo, Attribute::ByVal);
        if (IsByVal) {
          // ByVal arguments always go to the overflow area.
          // Fixed arguments passed through the overflow area will be stepped
          // over by va_start, so don't count them towards the offset.
          if (IsFixed)
            continue;
          assert(A->getType()->isPointerTy());
          Type *RealTy = A->getType()->getPointerElementType();
          uint64_t ArgSize = DL.getTypeAllocSize(RealTy);
          Value *ShadowBase = getShadowPtrForVAArgument(
              RealTy, IRB, OverflowOffset, alignTo(ArgSize, 8));
          Value *OriginBase = nullptr;
          if (MS.TrackOrigins)
            OriginBase = getOriginPtrForVAArgument(RealTy, IRB, OverflowOffset);
          OverflowOffset += alignTo(ArgSize, 8);
          if (!ShadowBase)
            continue;
          Value *ShadowPtr, *OriginPtr;
          std::tie(ShadowPtr, OriginPtr) =
              MSV.getShadowOriginPtr(A, IRB, IRB.getInt8Ty(), kShadowTLSAlignment,
                                     /*isStore*/ false);
  
          IRB.CreateMemCpy(ShadowBase, kShadowTLSAlignment, ShadowPtr,
                           kShadowTLSAlignment, ArgSize);
          if (MS.TrackOrigins)
            IRB.CreateMemCpy(OriginBase, kShadowTLSAlignment, OriginPtr,
                             kShadowTLSAlignment, ArgSize);
        } else {
          ArgKind AK = classifyArgument(A);
          if (AK == AK_GeneralPurpose && GpOffset >= AMD64GpEndOffset)
            AK = AK_Memory;
          if (AK == AK_FloatingPoint && FpOffset >= AMD64FpEndOffset)
            AK = AK_Memory;
          Value *ShadowBase, *OriginBase = nullptr;
          switch (AK) {
            case AK_GeneralPurpose:
              ShadowBase =
                  getShadowPtrForVAArgument(A->getType(), IRB, GpOffset, 8);
              if (MS.TrackOrigins)
                OriginBase =
                    getOriginPtrForVAArgument(A->getType(), IRB, GpOffset);
              GpOffset += 8;
              break;
            case AK_FloatingPoint:
              ShadowBase =
                  getShadowPtrForVAArgument(A->getType(), IRB, FpOffset, 16);
              if (MS.TrackOrigins)
                OriginBase =
                    getOriginPtrForVAArgument(A->getType(), IRB, FpOffset);
              FpOffset += 16;
              break;
            case AK_Memory:
              if (IsFixed)
                continue;
              uint64_t ArgSize = DL.getTypeAllocSize(A->getType());
              ShadowBase =
                  getShadowPtrForVAArgument(A->getType(), IRB, OverflowOffset, 8);
              if (MS.TrackOrigins)
                OriginBase =
                    getOriginPtrForVAArgument(A->getType(), IRB, OverflowOffset);
              OverflowOffset += alignTo(ArgSize, 8);
          }
          // Take fixed arguments into account for GpOffset and FpOffset,
          // but don't actually store shadows for them.
          // TODO(glider): don't call get*PtrForVAArgument() for them.
          if (IsFixed)
            continue;
          if (!ShadowBase)
            continue;
          Value *Shadow = MSV.getShadow(A);
          IRB.CreateAlignedStore(Shadow, ShadowBase, kShadowTLSAlignment);
          if (MS.TrackOrigins) {
            Value *Origin = MSV.getOrigin(A);
            unsigned StoreSize = DL.getTypeStoreSize(Shadow->getType());
            MSV.paintOrigin(IRB, Origin, OriginBase, StoreSize,
                            std::max(kShadowTLSAlignment, kMinOriginAlignment));
          }
        }
      }
      Constant *OverflowSize =
        ConstantInt::get(IRB.getInt64Ty(), OverflowOffset - AMD64FpEndOffset);
      IRB.CreateStore(OverflowSize, MS.VAArgOverflowSizeTLS);
    }
  
    /// Compute the shadow address for a given va_arg.
    Value *getShadowPtrForVAArgument(Type *Ty, IRBuilder<> &IRB,
                                     unsigned ArgOffset, unsigned ArgSize) {
      // Make sure we don't overflow __msan_va_arg_tls.
      if (ArgOffset + ArgSize > kParamTLSSize)
        return nullptr;
      Value *Base = IRB.CreatePointerCast(MS.VAArgTLS, MS.IntptrTy);
      Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
      return IRB.CreateIntToPtr(Base, PointerType::get(MSV.getShadowTy(Ty), 0),
                                "_msarg_va_s");
    }
  
    /// Compute the origin address for a given va_arg.
    Value *getOriginPtrForVAArgument(Type *Ty, IRBuilder<> &IRB, int ArgOffset) {
      Value *Base = IRB.CreatePointerCast(MS.VAArgOriginTLS, MS.IntptrTy);
      // getOriginPtrForVAArgument() is always called after
      // getShadowPtrForVAArgument(), so __msan_va_arg_origin_tls can never
      // overflow.
      Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
      return IRB.CreateIntToPtr(Base, PointerType::get(MS.OriginTy, 0),
                                "_msarg_va_o");
    }
  
    void unpoisonVAListTagForInst(IntrinsicInst &I) {
      IRBuilder<> IRB(&I);
      Value *VAListTag = I.getArgOperand(0);
      Value *ShadowPtr, *OriginPtr;
      unsigned Alignment = 8;
      std::tie(ShadowPtr, OriginPtr) =
          MSV.getShadowOriginPtr(VAListTag, IRB, IRB.getInt8Ty(), Alignment,
                                 /*isStore*/ true);
  
      // Unpoison the whole __va_list_tag.
      // FIXME: magic ABI constants.
      IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
                       /* size */ 24, Alignment, false);
      // We shouldn't need to zero out the origins, as they're only checked for
      // nonzero shadow.
    }
  
    void visitVAStartInst(VAStartInst &I) override {
      if (F.getCallingConv() == CallingConv::Win64)
        return;
      VAStartInstrumentationList.push_back(&I);
      unpoisonVAListTagForInst(I);
    }
  
    void visitVACopyInst(VACopyInst &I) override {
      if (F.getCallingConv() == CallingConv::Win64) return;
      unpoisonVAListTagForInst(I);
    }
  
    void finalizeInstrumentation() override {
      assert(!VAArgOverflowSize && !VAArgTLSCopy &&
             "finalizeInstrumentation called twice");
      if (!VAStartInstrumentationList.empty()) {
        // If there is a va_start in this function, make a backup copy of
        // va_arg_tls somewhere in the function entry block.
        IRBuilder<> IRB(MSV.ActualFnStart->getFirstNonPHI());
        VAArgOverflowSize =
            IRB.CreateLoad(IRB.getInt64Ty(), MS.VAArgOverflowSizeTLS);
        Value *CopySize =
          IRB.CreateAdd(ConstantInt::get(MS.IntptrTy, AMD64FpEndOffset),
                        VAArgOverflowSize);
        VAArgTLSCopy = IRB.CreateAlloca(Type::getInt8Ty(*MS.C), CopySize);
        IRB.CreateMemCpy(VAArgTLSCopy, 8, MS.VAArgTLS, 8, CopySize);
        if (MS.TrackOrigins) {
          VAArgTLSOriginCopy = IRB.CreateAlloca(Type::getInt8Ty(*MS.C), CopySize);
          IRB.CreateMemCpy(VAArgTLSOriginCopy, 8, MS.VAArgOriginTLS, 8, CopySize);
        }
      }
  
      // Instrument va_start.
      // Copy va_list shadow from the backup copy of the TLS contents.
      for (size_t i = 0, n = VAStartInstrumentationList.size(); i < n; i++) {
        CallInst *OrigInst = VAStartInstrumentationList[i];
        IRBuilder<> IRB(OrigInst->getNextNode());
        Value *VAListTag = OrigInst->getArgOperand(0);
  
        Type *RegSaveAreaPtrTy = Type::getInt64PtrTy(*MS.C);
        Value *RegSaveAreaPtrPtr = IRB.CreateIntToPtr(
            IRB.CreateAdd(IRB.CreatePtrToInt(VAListTag, MS.IntptrTy),
                          ConstantInt::get(MS.IntptrTy, 16)),
            PointerType::get(RegSaveAreaPtrTy, 0));
        Value *RegSaveAreaPtr =
            IRB.CreateLoad(RegSaveAreaPtrTy, RegSaveAreaPtrPtr);
        Value *RegSaveAreaShadowPtr, *RegSaveAreaOriginPtr;
        unsigned Alignment = 16;
        std::tie(RegSaveAreaShadowPtr, RegSaveAreaOriginPtr) =
            MSV.getShadowOriginPtr(RegSaveAreaPtr, IRB, IRB.getInt8Ty(),
                                   Alignment, /*isStore*/ true);
        IRB.CreateMemCpy(RegSaveAreaShadowPtr, Alignment, VAArgTLSCopy, Alignment,
                         AMD64FpEndOffset);
        if (MS.TrackOrigins)
          IRB.CreateMemCpy(RegSaveAreaOriginPtr, Alignment, VAArgTLSOriginCopy,
                           Alignment, AMD64FpEndOffset);
        Type *OverflowArgAreaPtrTy = Type::getInt64PtrTy(*MS.C);
        Value *OverflowArgAreaPtrPtr = IRB.CreateIntToPtr(
            IRB.CreateAdd(IRB.CreatePtrToInt(VAListTag, MS.IntptrTy),
                          ConstantInt::get(MS.IntptrTy, 8)),
            PointerType::get(OverflowArgAreaPtrTy, 0));
        Value *OverflowArgAreaPtr =
            IRB.CreateLoad(OverflowArgAreaPtrTy, OverflowArgAreaPtrPtr);
        Value *OverflowArgAreaShadowPtr, *OverflowArgAreaOriginPtr;
        std::tie(OverflowArgAreaShadowPtr, OverflowArgAreaOriginPtr) =
            MSV.getShadowOriginPtr(OverflowArgAreaPtr, IRB, IRB.getInt8Ty(),
                                   Alignment, /*isStore*/ true);
        Value *SrcPtr = IRB.CreateConstGEP1_32(IRB.getInt8Ty(), VAArgTLSCopy,
                                               AMD64FpEndOffset);
        IRB.CreateMemCpy(OverflowArgAreaShadowPtr, Alignment, SrcPtr, Alignment,
                         VAArgOverflowSize);
        if (MS.TrackOrigins) {
          SrcPtr = IRB.CreateConstGEP1_32(IRB.getInt8Ty(), VAArgTLSOriginCopy,
                                          AMD64FpEndOffset);
          IRB.CreateMemCpy(OverflowArgAreaOriginPtr, Alignment, SrcPtr, Alignment,
                           VAArgOverflowSize);
        }
      }
    }
  };
  
  /// MIPS64-specific implementation of VarArgHelper.
  struct VarArgMIPS64Helper : public VarArgHelper {
    Function &F;
    MemorySanitizer &MS;
    MemorySanitizerVisitor &MSV;
    Value *VAArgTLSCopy = nullptr;
    Value *VAArgSize = nullptr;
  
    SmallVector<CallInst*, 16> VAStartInstrumentationList;
  
    VarArgMIPS64Helper(Function &F, MemorySanitizer &MS,
                      MemorySanitizerVisitor &MSV) : F(F), MS(MS), MSV(MSV) {}
  
    void visitCallSite(CallSite &CS, IRBuilder<> &IRB) override {
      unsigned VAArgOffset = 0;
      const DataLayout &DL = F.getParent()->getDataLayout();
      for (CallSite::arg_iterator ArgIt = CS.arg_begin() +
           CS.getFunctionType()->getNumParams(), End = CS.arg_end();
           ArgIt != End; ++ArgIt) {
        Triple TargetTriple(F.getParent()->getTargetTriple());
        Value *A = *ArgIt;
        Value *Base;
        uint64_t ArgSize = DL.getTypeAllocSize(A->getType());
        if (TargetTriple.getArch() == Triple::mips64) {
          // Adjusting the shadow for argument with size < 8 to match the placement
          // of bits in big endian system
          if (ArgSize < 8)
            VAArgOffset += (8 - ArgSize);
        }
        Base = getShadowPtrForVAArgument(A->getType(), IRB, VAArgOffset, ArgSize);
        VAArgOffset += ArgSize;
        VAArgOffset = alignTo(VAArgOffset, 8);
        if (!Base)
          continue;
        IRB.CreateAlignedStore(MSV.getShadow(A), Base, kShadowTLSAlignment);
      }
  
      Constant *TotalVAArgSize = ConstantInt::get(IRB.getInt64Ty(), VAArgOffset);
      // Here using VAArgOverflowSizeTLS as VAArgSizeTLS to avoid creation of
      // a new class member i.e. it is the total size of all VarArgs.
      IRB.CreateStore(TotalVAArgSize, MS.VAArgOverflowSizeTLS);
    }
  
    /// Compute the shadow address for a given va_arg.
    Value *getShadowPtrForVAArgument(Type *Ty, IRBuilder<> &IRB,
                                     unsigned ArgOffset, unsigned ArgSize) {
      // Make sure we don't overflow __msan_va_arg_tls.
      if (ArgOffset + ArgSize > kParamTLSSize)
        return nullptr;
      Value *Base = IRB.CreatePointerCast(MS.VAArgTLS, MS.IntptrTy);
      Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
      return IRB.CreateIntToPtr(Base, PointerType::get(MSV.getShadowTy(Ty), 0),
                                "_msarg");
    }
  
    void visitVAStartInst(VAStartInst &I) override {
      IRBuilder<> IRB(&I);
      VAStartInstrumentationList.push_back(&I);
      Value *VAListTag = I.getArgOperand(0);
      Value *ShadowPtr, *OriginPtr;
      unsigned Alignment = 8;
      std::tie(ShadowPtr, OriginPtr) = MSV.getShadowOriginPtr(
          VAListTag, IRB, IRB.getInt8Ty(), Alignment, /*isStore*/ true);
      IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
                       /* size */ 8, Alignment, false);
    }
  
    void visitVACopyInst(VACopyInst &I) override {
      IRBuilder<> IRB(&I);
      VAStartInstrumentationList.push_back(&I);
      Value *VAListTag = I.getArgOperand(0);
      Value *ShadowPtr, *OriginPtr;
      unsigned Alignment = 8;
      std::tie(ShadowPtr, OriginPtr) = MSV.getShadowOriginPtr(
          VAListTag, IRB, IRB.getInt8Ty(), Alignment, /*isStore*/ true);
      IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
                       /* size */ 8, Alignment, false);
    }
  
    void finalizeInstrumentation() override {
      assert(!VAArgSize && !VAArgTLSCopy &&
             "finalizeInstrumentation called twice");
      IRBuilder<> IRB(MSV.ActualFnStart->getFirstNonPHI());
      VAArgSize = IRB.CreateLoad(IRB.getInt64Ty(), MS.VAArgOverflowSizeTLS);
      Value *CopySize = IRB.CreateAdd(ConstantInt::get(MS.IntptrTy, 0),
                                      VAArgSize);
  
      if (!VAStartInstrumentationList.empty()) {
        // If there is a va_start in this function, make a backup copy of
        // va_arg_tls somewhere in the function entry block.
        VAArgTLSCopy = IRB.CreateAlloca(Type::getInt8Ty(*MS.C), CopySize);
        IRB.CreateMemCpy(VAArgTLSCopy, 8, MS.VAArgTLS, 8, CopySize);
      }
  
      // Instrument va_start.
      // Copy va_list shadow from the backup copy of the TLS contents.
      for (size_t i = 0, n = VAStartInstrumentationList.size(); i < n; i++) {
        CallInst *OrigInst = VAStartInstrumentationList[i];
        IRBuilder<> IRB(OrigInst->getNextNode());
        Value *VAListTag = OrigInst->getArgOperand(0);
        Type *RegSaveAreaPtrTy = Type::getInt64PtrTy(*MS.C);
        Value *RegSaveAreaPtrPtr =
            IRB.CreateIntToPtr(IRB.CreatePtrToInt(VAListTag, MS.IntptrTy),
                               PointerType::get(RegSaveAreaPtrTy, 0));
        Value *RegSaveAreaPtr =
            IRB.CreateLoad(RegSaveAreaPtrTy, RegSaveAreaPtrPtr);
        Value *RegSaveAreaShadowPtr, *RegSaveAreaOriginPtr;
        unsigned Alignment = 8;
        std::tie(RegSaveAreaShadowPtr, RegSaveAreaOriginPtr) =
            MSV.getShadowOriginPtr(RegSaveAreaPtr, IRB, IRB.getInt8Ty(),
                                   Alignment, /*isStore*/ true);
        IRB.CreateMemCpy(RegSaveAreaShadowPtr, Alignment, VAArgTLSCopy, Alignment,
                         CopySize);
      }
    }
  };
  
  /// AArch64-specific implementation of VarArgHelper.
  struct VarArgAArch64Helper : public VarArgHelper {
    static const unsigned kAArch64GrArgSize = 64;
    static const unsigned kAArch64VrArgSize = 128;
  
    static const unsigned AArch64GrBegOffset = 0;
    static const unsigned AArch64GrEndOffset = kAArch64GrArgSize;
    // Make VR space aligned to 16 bytes.
    static const unsigned AArch64VrBegOffset = AArch64GrEndOffset;
    static const unsigned AArch64VrEndOffset = AArch64VrBegOffset
                                               + kAArch64VrArgSize;
    static const unsigned AArch64VAEndOffset = AArch64VrEndOffset;
  
    Function &F;
    MemorySanitizer &MS;
    MemorySanitizerVisitor &MSV;
    Value *VAArgTLSCopy = nullptr;
    Value *VAArgOverflowSize = nullptr;
  
    SmallVector<CallInst*, 16> VAStartInstrumentationList;
  
    enum ArgKind { AK_GeneralPurpose, AK_FloatingPoint, AK_Memory };
  
    VarArgAArch64Helper(Function &F, MemorySanitizer &MS,
                      MemorySanitizerVisitor &MSV) : F(F), MS(MS), MSV(MSV) {}
  
    ArgKind classifyArgument(Value* arg) {
      Type *T = arg->getType();
      if (T->isFPOrFPVectorTy())
        return AK_FloatingPoint;
      if ((T->isIntegerTy() && T->getPrimitiveSizeInBits() <= 64)
          || (T->isPointerTy()))
        return AK_GeneralPurpose;
      return AK_Memory;
    }
  
    // The instrumentation stores the argument shadow in a non ABI-specific
    // format because it does not know which argument is named (since Clang,
    // like x86_64 case, lowers the va_args in the frontend and this pass only
    // sees the low level code that deals with va_list internals).
    // The first seven GR registers are saved in the first 56 bytes of the
    // va_arg tls arra, followers by the first 8 FP/SIMD registers, and then
    // the remaining arguments.
    // Using constant offset within the va_arg TLS array allows fast copy
    // in the finalize instrumentation.
    void visitCallSite(CallSite &CS, IRBuilder<> &IRB) override {
      unsigned GrOffset = AArch64GrBegOffset;
      unsigned VrOffset = AArch64VrBegOffset;
      unsigned OverflowOffset = AArch64VAEndOffset;
  
      const DataLayout &DL = F.getParent()->getDataLayout();
      for (CallSite::arg_iterator ArgIt = CS.arg_begin(), End = CS.arg_end();
           ArgIt != End; ++ArgIt) {
        Value *A = *ArgIt;
        unsigned ArgNo = CS.getArgumentNo(ArgIt);
        bool IsFixed = ArgNo < CS.getFunctionType()->getNumParams();
        ArgKind AK = classifyArgument(A);
        if (AK == AK_GeneralPurpose && GrOffset >= AArch64GrEndOffset)
          AK = AK_Memory;
        if (AK == AK_FloatingPoint && VrOffset >= AArch64VrEndOffset)
          AK = AK_Memory;
        Value *Base;
        switch (AK) {
          case AK_GeneralPurpose:
            Base = getShadowPtrForVAArgument(A->getType(), IRB, GrOffset, 8);
            GrOffset += 8;
            break;
          case AK_FloatingPoint:
            Base = getShadowPtrForVAArgument(A->getType(), IRB, VrOffset, 8);
            VrOffset += 16;
            break;
          case AK_Memory:
            // Don't count fixed arguments in the overflow area - va_start will
            // skip right over them.
            if (IsFixed)
              continue;
            uint64_t ArgSize = DL.getTypeAllocSize(A->getType());
            Base = getShadowPtrForVAArgument(A->getType(), IRB, OverflowOffset,
                                             alignTo(ArgSize, 8));
            OverflowOffset += alignTo(ArgSize, 8);
            break;
        }
        // Count Gp/Vr fixed arguments to their respective offsets, but don't
        // bother to actually store a shadow.
        if (IsFixed)
          continue;
        if (!Base)
          continue;
        IRB.CreateAlignedStore(MSV.getShadow(A), Base, kShadowTLSAlignment);
      }
      Constant *OverflowSize =
        ConstantInt::get(IRB.getInt64Ty(), OverflowOffset - AArch64VAEndOffset);
      IRB.CreateStore(OverflowSize, MS.VAArgOverflowSizeTLS);
    }
  
    /// Compute the shadow address for a given va_arg.
    Value *getShadowPtrForVAArgument(Type *Ty, IRBuilder<> &IRB,
                                     unsigned ArgOffset, unsigned ArgSize) {
      // Make sure we don't overflow __msan_va_arg_tls.
      if (ArgOffset + ArgSize > kParamTLSSize)
        return nullptr;
      Value *Base = IRB.CreatePointerCast(MS.VAArgTLS, MS.IntptrTy);
      Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
      return IRB.CreateIntToPtr(Base, PointerType::get(MSV.getShadowTy(Ty), 0),
                                "_msarg");
    }
  
    void visitVAStartInst(VAStartInst &I) override {
      IRBuilder<> IRB(&I);
      VAStartInstrumentationList.push_back(&I);
      Value *VAListTag = I.getArgOperand(0);
      Value *ShadowPtr, *OriginPtr;
      unsigned Alignment = 8;
      std::tie(ShadowPtr, OriginPtr) = MSV.getShadowOriginPtr(
          VAListTag, IRB, IRB.getInt8Ty(), Alignment, /*isStore*/ true);
      IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
                       /* size */ 32, Alignment, false);
    }
  
    void visitVACopyInst(VACopyInst &I) override {
      IRBuilder<> IRB(&I);
      VAStartInstrumentationList.push_back(&I);
      Value *VAListTag = I.getArgOperand(0);
      Value *ShadowPtr, *OriginPtr;
      unsigned Alignment = 8;
      std::tie(ShadowPtr, OriginPtr) = MSV.getShadowOriginPtr(
          VAListTag, IRB, IRB.getInt8Ty(), Alignment, /*isStore*/ true);
      IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
                       /* size */ 32, Alignment, false);
    }
  
    // Retrieve a va_list field of 'void*' size.
    Value* getVAField64(IRBuilder<> &IRB, Value *VAListTag, int offset) {
      Value *SaveAreaPtrPtr =
        IRB.CreateIntToPtr(
          IRB.CreateAdd(IRB.CreatePtrToInt(VAListTag, MS.IntptrTy),
                        ConstantInt::get(MS.IntptrTy, offset)),
          Type::getInt64PtrTy(*MS.C));
      return IRB.CreateLoad(Type::getInt64Ty(*MS.C), SaveAreaPtrPtr);
    }
  
    // Retrieve a va_list field of 'int' size.
    Value* getVAField32(IRBuilder<> &IRB, Value *VAListTag, int offset) {
      Value *SaveAreaPtr =
        IRB.CreateIntToPtr(
          IRB.CreateAdd(IRB.CreatePtrToInt(VAListTag, MS.IntptrTy),
                        ConstantInt::get(MS.IntptrTy, offset)),
          Type::getInt32PtrTy(*MS.C));
      Value *SaveArea32 = IRB.CreateLoad(IRB.getInt32Ty(), SaveAreaPtr);
      return IRB.CreateSExt(SaveArea32, MS.IntptrTy);
    }
  
    void finalizeInstrumentation() override {
      assert(!VAArgOverflowSize && !VAArgTLSCopy &&
             "finalizeInstrumentation called twice");
      if (!VAStartInstrumentationList.empty()) {
        // If there is a va_start in this function, make a backup copy of
        // va_arg_tls somewhere in the function entry block.
        IRBuilder<> IRB(MSV.ActualFnStart->getFirstNonPHI());
        VAArgOverflowSize =
            IRB.CreateLoad(IRB.getInt64Ty(), MS.VAArgOverflowSizeTLS);
        Value *CopySize =
          IRB.CreateAdd(ConstantInt::get(MS.IntptrTy, AArch64VAEndOffset),
                        VAArgOverflowSize);
        VAArgTLSCopy = IRB.CreateAlloca(Type::getInt8Ty(*MS.C), CopySize);
        IRB.CreateMemCpy(VAArgTLSCopy, 8, MS.VAArgTLS, 8, CopySize);
      }
  
      Value *GrArgSize = ConstantInt::get(MS.IntptrTy, kAArch64GrArgSize);
      Value *VrArgSize = ConstantInt::get(MS.IntptrTy, kAArch64VrArgSize);
  
      // Instrument va_start, copy va_list shadow from the backup copy of
      // the TLS contents.
      for (size_t i = 0, n = VAStartInstrumentationList.size(); i < n; i++) {
        CallInst *OrigInst = VAStartInstrumentationList[i];
        IRBuilder<> IRB(OrigInst->getNextNode());
  
        Value *VAListTag = OrigInst->getArgOperand(0);
  
        // The variadic ABI for AArch64 creates two areas to save the incoming
        // argument registers (one for 64-bit general register xn-x7 and another
        // for 128-bit FP/SIMD vn-v7).
        // We need then to propagate the shadow arguments on both regions
        // 'va::__gr_top + va::__gr_offs' and 'va::__vr_top + va::__vr_offs'.
        // The remaning arguments are saved on shadow for 'va::stack'.
        // One caveat is it requires only to propagate the non-named arguments,
        // however on the call site instrumentation 'all' the arguments are
        // saved. So to copy the shadow values from the va_arg TLS array
        // we need to adjust the offset for both GR and VR fields based on
        // the __{gr,vr}_offs value (since they are stores based on incoming
        // named arguments).
  
        // Read the stack pointer from the va_list.
        Value *StackSaveAreaPtr = getVAField64(IRB, VAListTag, 0);
  
        // Read both the __gr_top and __gr_off and add them up.
        Value *GrTopSaveAreaPtr = getVAField64(IRB, VAListTag, 8);
        Value *GrOffSaveArea = getVAField32(IRB, VAListTag, 24);
  
        Value *GrRegSaveAreaPtr = IRB.CreateAdd(GrTopSaveAreaPtr, GrOffSaveArea);
  
        // Read both the __vr_top and __vr_off and add them up.
        Value *VrTopSaveAreaPtr = getVAField64(IRB, VAListTag, 16);
        Value *VrOffSaveArea = getVAField32(IRB, VAListTag, 28);
  
        Value *VrRegSaveAreaPtr = IRB.CreateAdd(VrTopSaveAreaPtr, VrOffSaveArea);
  
        // It does not know how many named arguments is being used and, on the
        // callsite all the arguments were saved.  Since __gr_off is defined as
        // '0 - ((8 - named_gr) * 8)', the idea is to just propagate the variadic
        // argument by ignoring the bytes of shadow from named arguments.
        Value *GrRegSaveAreaShadowPtrOff =
          IRB.CreateAdd(GrArgSize, GrOffSaveArea);
  
        Value *GrRegSaveAreaShadowPtr =
            MSV.getShadowOriginPtr(GrRegSaveAreaPtr, IRB, IRB.getInt8Ty(),
                                   /*Alignment*/ 8, /*isStore*/ true)
                .first;
  
        Value *GrSrcPtr = IRB.CreateInBoundsGEP(IRB.getInt8Ty(), VAArgTLSCopy,
                                                GrRegSaveAreaShadowPtrOff);
        Value *GrCopySize = IRB.CreateSub(GrArgSize, GrRegSaveAreaShadowPtrOff);
  
        IRB.CreateMemCpy(GrRegSaveAreaShadowPtr, 8, GrSrcPtr, 8, GrCopySize);
  
        // Again, but for FP/SIMD values.
        Value *VrRegSaveAreaShadowPtrOff =
            IRB.CreateAdd(VrArgSize, VrOffSaveArea);
  
        Value *VrRegSaveAreaShadowPtr =
            MSV.getShadowOriginPtr(VrRegSaveAreaPtr, IRB, IRB.getInt8Ty(),
                                   /*Alignment*/ 8, /*isStore*/ true)
                .first;
  
        Value *VrSrcPtr = IRB.CreateInBoundsGEP(
          IRB.getInt8Ty(),
          IRB.CreateInBoundsGEP(IRB.getInt8Ty(), VAArgTLSCopy,
                                IRB.getInt32(AArch64VrBegOffset)),
          VrRegSaveAreaShadowPtrOff);
        Value *VrCopySize = IRB.CreateSub(VrArgSize, VrRegSaveAreaShadowPtrOff);
  
        IRB.CreateMemCpy(VrRegSaveAreaShadowPtr, 8, VrSrcPtr, 8, VrCopySize);
  
        // And finally for remaining arguments.
        Value *StackSaveAreaShadowPtr =
            MSV.getShadowOriginPtr(StackSaveAreaPtr, IRB, IRB.getInt8Ty(),
                                   /*Alignment*/ 16, /*isStore*/ true)
                .first;
  
        Value *StackSrcPtr =
          IRB.CreateInBoundsGEP(IRB.getInt8Ty(), VAArgTLSCopy,
                                IRB.getInt32(AArch64VAEndOffset));
  
        IRB.CreateMemCpy(StackSaveAreaShadowPtr, 16, StackSrcPtr, 16,
                         VAArgOverflowSize);
      }
    }
  };
  
  /// PowerPC64-specific implementation of VarArgHelper.
  struct VarArgPowerPC64Helper : public VarArgHelper {
    Function &F;
    MemorySanitizer &MS;
    MemorySanitizerVisitor &MSV;
    Value *VAArgTLSCopy = nullptr;
    Value *VAArgSize = nullptr;
  
    SmallVector<CallInst*, 16> VAStartInstrumentationList;
  
    VarArgPowerPC64Helper(Function &F, MemorySanitizer &MS,
                      MemorySanitizerVisitor &MSV) : F(F), MS(MS), MSV(MSV) {}
  
    void visitCallSite(CallSite &CS, IRBuilder<> &IRB) override {
      // For PowerPC, we need to deal with alignment of stack arguments -
      // they are mostly aligned to 8 bytes, but vectors and i128 arrays
      // are aligned to 16 bytes, byvals can be aligned to 8 or 16 bytes,
      // and QPX vectors are aligned to 32 bytes.  For that reason, we
      // compute current offset from stack pointer (which is always properly
      // aligned), and offset for the first vararg, then subtract them.
      unsigned VAArgBase;
      Triple TargetTriple(F.getParent()->getTargetTriple());
      // Parameter save area starts at 48 bytes from frame pointer for ABIv1,
      // and 32 bytes for ABIv2.  This is usually determined by target
      // endianness, but in theory could be overriden by function attribute.
      // For simplicity, we ignore it here (it'd only matter for QPX vectors).
      if (TargetTriple.getArch() == Triple::ppc64)
        VAArgBase = 48;
      else
        VAArgBase = 32;
      unsigned VAArgOffset = VAArgBase;
      const DataLayout &DL = F.getParent()->getDataLayout();
      for (CallSite::arg_iterator ArgIt = CS.arg_begin(), End = CS.arg_end();
           ArgIt != End; ++ArgIt) {
        Value *A = *ArgIt;
        unsigned ArgNo = CS.getArgumentNo(ArgIt);
        bool IsFixed = ArgNo < CS.getFunctionType()->getNumParams();
        bool IsByVal = CS.paramHasAttr(ArgNo, Attribute::ByVal);
        if (IsByVal) {
          assert(A->getType()->isPointerTy());
          Type *RealTy = A->getType()->getPointerElementType();
          uint64_t ArgSize = DL.getTypeAllocSize(RealTy);
          uint64_t ArgAlign = CS.getParamAlignment(ArgNo);
          if (ArgAlign < 8)
            ArgAlign = 8;
          VAArgOffset = alignTo(VAArgOffset, ArgAlign);
          if (!IsFixed) {
            Value *Base = getShadowPtrForVAArgument(
                RealTy, IRB, VAArgOffset - VAArgBase, ArgSize);
            if (Base) {
              Value *AShadowPtr, *AOriginPtr;
              std::tie(AShadowPtr, AOriginPtr) =
                  MSV.getShadowOriginPtr(A, IRB, IRB.getInt8Ty(),
                                         kShadowTLSAlignment, /*isStore*/ false);
  
              IRB.CreateMemCpy(Base, kShadowTLSAlignment, AShadowPtr,
                               kShadowTLSAlignment, ArgSize);
            }
          }
          VAArgOffset += alignTo(ArgSize, 8);
        } else {
          Value *Base;
          uint64_t ArgSize = DL.getTypeAllocSize(A->getType());
          uint64_t ArgAlign = 8;
          if (A->getType()->isArrayTy()) {
            // Arrays are aligned to element size, except for long double
            // arrays, which are aligned to 8 bytes.
            Type *ElementTy = A->getType()->getArrayElementType();
            if (!ElementTy->isPPC_FP128Ty())
              ArgAlign = DL.getTypeAllocSize(ElementTy);
          } else if (A->getType()->isVectorTy()) {
            // Vectors are naturally aligned.
            ArgAlign = DL.getTypeAllocSize(A->getType());
          }
          if (ArgAlign < 8)
            ArgAlign = 8;
          VAArgOffset = alignTo(VAArgOffset, ArgAlign);
          if (DL.isBigEndian()) {
            // Adjusting the shadow for argument with size < 8 to match the placement
            // of bits in big endian system
            if (ArgSize < 8)
              VAArgOffset += (8 - ArgSize);
          }
          if (!IsFixed) {
            Base = getShadowPtrForVAArgument(A->getType(), IRB,
                                             VAArgOffset - VAArgBase, ArgSize);
            if (Base)
              IRB.CreateAlignedStore(MSV.getShadow(A), Base, kShadowTLSAlignment);
          }
          VAArgOffset += ArgSize;
          VAArgOffset = alignTo(VAArgOffset, 8);
        }
        if (IsFixed)
          VAArgBase = VAArgOffset;
      }
  
      Constant *TotalVAArgSize = ConstantInt::get(IRB.getInt64Ty(),
                                                  VAArgOffset - VAArgBase);
      // Here using VAArgOverflowSizeTLS as VAArgSizeTLS to avoid creation of
      // a new class member i.e. it is the total size of all VarArgs.
      IRB.CreateStore(TotalVAArgSize, MS.VAArgOverflowSizeTLS);
    }
  
    /// Compute the shadow address for a given va_arg.
    Value *getShadowPtrForVAArgument(Type *Ty, IRBuilder<> &IRB,
                                     unsigned ArgOffset, unsigned ArgSize) {
      // Make sure we don't overflow __msan_va_arg_tls.
      if (ArgOffset + ArgSize > kParamTLSSize)
        return nullptr;
      Value *Base = IRB.CreatePointerCast(MS.VAArgTLS, MS.IntptrTy);
      Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
      return IRB.CreateIntToPtr(Base, PointerType::get(MSV.getShadowTy(Ty), 0),
                                "_msarg");
    }
  
    void visitVAStartInst(VAStartInst &I) override {
      IRBuilder<> IRB(&I);
      VAStartInstrumentationList.push_back(&I);
      Value *VAListTag = I.getArgOperand(0);
      Value *ShadowPtr, *OriginPtr;
      unsigned Alignment = 8;
      std::tie(ShadowPtr, OriginPtr) = MSV.getShadowOriginPtr(
          VAListTag, IRB, IRB.getInt8Ty(), Alignment, /*isStore*/ true);
      IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
                       /* size */ 8, Alignment, false);
    }
  
    void visitVACopyInst(VACopyInst &I) override {
      IRBuilder<> IRB(&I);
      Value *VAListTag = I.getArgOperand(0);
      Value *ShadowPtr, *OriginPtr;
      unsigned Alignment = 8;
      std::tie(ShadowPtr, OriginPtr) = MSV.getShadowOriginPtr(
          VAListTag, IRB, IRB.getInt8Ty(), Alignment, /*isStore*/ true);
      // Unpoison the whole __va_list_tag.
      // FIXME: magic ABI constants.
      IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
                       /* size */ 8, Alignment, false);
    }
  
    void finalizeInstrumentation() override {
      assert(!VAArgSize && !VAArgTLSCopy &&
             "finalizeInstrumentation called twice");
      IRBuilder<> IRB(MSV.ActualFnStart->getFirstNonPHI());
      VAArgSize = IRB.CreateLoad(IRB.getInt64Ty(), MS.VAArgOverflowSizeTLS);
      Value *CopySize = IRB.CreateAdd(ConstantInt::get(MS.IntptrTy, 0),
                                      VAArgSize);
  
      if (!VAStartInstrumentationList.empty()) {
        // If there is a va_start in this function, make a backup copy of
        // va_arg_tls somewhere in the function entry block.
        VAArgTLSCopy = IRB.CreateAlloca(Type::getInt8Ty(*MS.C), CopySize);
        IRB.CreateMemCpy(VAArgTLSCopy, 8, MS.VAArgTLS, 8, CopySize);
      }
  
      // Instrument va_start.
      // Copy va_list shadow from the backup copy of the TLS contents.
      for (size_t i = 0, n = VAStartInstrumentationList.size(); i < n; i++) {
        CallInst *OrigInst = VAStartInstrumentationList[i];
        IRBuilder<> IRB(OrigInst->getNextNode());
        Value *VAListTag = OrigInst->getArgOperand(0);
        Type *RegSaveAreaPtrTy = Type::getInt64PtrTy(*MS.C);
        Value *RegSaveAreaPtrPtr =
            IRB.CreateIntToPtr(IRB.CreatePtrToInt(VAListTag, MS.IntptrTy),
                               PointerType::get(RegSaveAreaPtrTy, 0));
        Value *RegSaveAreaPtr =
            IRB.CreateLoad(RegSaveAreaPtrTy, RegSaveAreaPtrPtr);
        Value *RegSaveAreaShadowPtr, *RegSaveAreaOriginPtr;
        unsigned Alignment = 8;
        std::tie(RegSaveAreaShadowPtr, RegSaveAreaOriginPtr) =
            MSV.getShadowOriginPtr(RegSaveAreaPtr, IRB, IRB.getInt8Ty(),
                                   Alignment, /*isStore*/ true);
        IRB.CreateMemCpy(RegSaveAreaShadowPtr, Alignment, VAArgTLSCopy, Alignment,
                         CopySize);
      }
    }
  };
  
  /// A no-op implementation of VarArgHelper.
  struct VarArgNoOpHelper : public VarArgHelper {
    VarArgNoOpHelper(Function &F, MemorySanitizer &MS,
                     MemorySanitizerVisitor &MSV) {}
  
    void visitCallSite(CallSite &CS, IRBuilder<> &IRB) override {}
  
    void visitVAStartInst(VAStartInst &I) override {}
  
    void visitVACopyInst(VACopyInst &I) override {}
  
    void finalizeInstrumentation() override {}
  };
  
  } // end anonymous namespace
  
  static VarArgHelper *CreateVarArgHelper(Function &Func, MemorySanitizer &Msan,
                                          MemorySanitizerVisitor &Visitor) {
    // VarArg handling is only implemented on AMD64. False positives are possible
    // on other platforms.
    Triple TargetTriple(Func.getParent()->getTargetTriple());
    if (TargetTriple.getArch() == Triple::x86_64)
      return new VarArgAMD64Helper(Func, Msan, Visitor);
    else if (TargetTriple.isMIPS64())
      return new VarArgMIPS64Helper(Func, Msan, Visitor);
    else if (TargetTriple.getArch() == Triple::aarch64)
      return new VarArgAArch64Helper(Func, Msan, Visitor);
    else if (TargetTriple.getArch() == Triple::ppc64 ||
             TargetTriple.getArch() == Triple::ppc64le)
      return new VarArgPowerPC64Helper(Func, Msan, Visitor);
    else
      return new VarArgNoOpHelper(Func, Msan, Visitor);
  }
  
  bool MemorySanitizer::sanitizeFunction(Function &F, TargetLibraryInfo &TLI) {
    if (!CompileKernel && (&F == MsanCtorFunction))
      return false;
    MemorySanitizerVisitor Visitor(F, *this, TLI);
  
    // Clear out readonly/readnone attributes.
    AttrBuilder B;
    B.addAttribute(Attribute::ReadOnly)
      .addAttribute(Attribute::ReadNone)
      .addAttribute(Attribute::ArgMemOnly)
      .addAttribute(Attribute::InaccessibleMemOnly)
      .addAttribute(Attribute::InaccessibleMemOrArgMemOnly);
    F.removeAttributes(AttributeList::FunctionIndex, B);
  
    return Visitor.runOnFunction();
  }
  