Use the space freed up by sparc and zaurus to import LLVM.

ok hackroom@

1 files changed, 3322 insertions, 0 deletions

diff --git a/gnu/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/gnu/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
new file mode 100644
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+++ b/gnu/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -0,0 +1,3322 @@
+//===-- MemorySanitizer.cpp - detector of uninitialized reads -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \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.
+
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Instrumentation.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/InlineAsm.h"
+#include "llvm/IR/InstVisitor.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Type.h"
+#include "llvm/IR/ValueMap.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+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;
+
+/// \brief 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));
+
+// 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));
+
+// 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));
+
+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;
+};
+
+// 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 = {
+  0x004000000000,  // AndMask
+  0,               // XorMask (not used)
+  0,               // ShadowBase (not used)
+  0x002000000000,  // OriginBase
+};
+
+// ppc64 Linux
+static const MemoryMapParams Linux_PowerPC64_MemoryMapParams = {
+  0x200000000000,  // 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
+};
+
+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,
+};
+
+/// \brief An instrumentation pass implementing detection of uninitialized
+/// reads.
+///
+/// MemorySanitizer: instrument the code in module to find
+/// uninitialized reads.
+class MemorySanitizer : public FunctionPass {
+ public:
+  MemorySanitizer(int TrackOrigins = 0)
+      : FunctionPass(ID),
+        TrackOrigins(std::max(TrackOrigins, (int)ClTrackOrigins)),
+        WarningFn(nullptr) {}
+  const char *getPassName() const override { return "MemorySanitizer"; }
+  bool runOnFunction(Function &F) override;
+  bool doInitialization(Module &M) override;
+  static char ID;  // Pass identification, replacement for typeid.
+
+ private:
+  void initializeCallbacks(Module &M);
+
+  /// \brief Track origins (allocation points) of uninitialized values.
+  int TrackOrigins;
+
+  LLVMContext *C;
+  Type *IntptrTy;
+  Type *OriginTy;
+  /// \brief Thread-local shadow storage for function parameters.
+  GlobalVariable *ParamTLS;
+  /// \brief Thread-local origin storage for function parameters.
+  GlobalVariable *ParamOriginTLS;
+  /// \brief Thread-local shadow storage for function return value.
+  GlobalVariable *RetvalTLS;
+  /// \brief Thread-local origin storage for function return value.
+  GlobalVariable *RetvalOriginTLS;
+  /// \brief Thread-local shadow storage for in-register va_arg function
+  /// parameters (x86_64-specific).
+  GlobalVariable *VAArgTLS;
+  /// \brief Thread-local shadow storage for va_arg overflow area
+  /// (x86_64-specific).
+  GlobalVariable *VAArgOverflowSizeTLS;
+  /// \brief Thread-local space used to pass origin value to the UMR reporting
+  /// function.
+  GlobalVariable *OriginTLS;
+
+  /// \brief The run-time callback to print a warning.
+  Value *WarningFn;
+  // These arrays are indexed by log2(AccessSize).
+  Value *MaybeWarningFn[kNumberOfAccessSizes];
+  Value *MaybeStoreOriginFn[kNumberOfAccessSizes];
+
+  /// \brief Run-time helper that generates a new origin value for a stack
+  /// allocation.
+  Value *MsanSetAllocaOrigin4Fn;
+  /// \brief Run-time helper that poisons stack on function entry.
+  Value *MsanPoisonStackFn;
+  /// \brief Run-time helper that records a store (or any event) of an
+  /// uninitialized value and returns an updated origin id encoding this info.
+  Value *MsanChainOriginFn;
+  /// \brief MSan runtime replacements for memmove, memcpy and memset.
+  Value *MemmoveFn, *MemcpyFn, *MemsetFn;
+
+  /// \brief Memory map parameters used in application-to-shadow calculation.
+  const MemoryMapParams *MapParams;
+
+  MDNode *ColdCallWeights;
+  /// \brief Branch weights for origin store.
+  MDNode *OriginStoreWeights;
+  /// \brief An empty volatile inline asm that prevents callback merge.
+  InlineAsm *EmptyAsm;
+  Function *MsanCtorFunction;
+
+  friend struct MemorySanitizerVisitor;
+  friend struct VarArgAMD64Helper;
+  friend struct VarArgMIPS64Helper;
+  friend struct VarArgAArch64Helper;
+};
+} // anonymous namespace
+
+char MemorySanitizer::ID = 0;
+INITIALIZE_PASS(MemorySanitizer, "msan",
+                "MemorySanitizer: detects uninitialized reads.",
+                false, false)
+
+FunctionPass *llvm::createMemorySanitizerPass(int TrackOrigins) {
+  return new MemorySanitizer(TrackOrigins);
+}
+
+/// \brief 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, "");
+}
+
+/// \brief Insert extern declaration of runtime-provided functions and globals.
+void MemorySanitizer::initializeCallbacks(Module &M) {
+  // Only do this once.
+  if (WarningFn)
+    return;
+
+  IRBuilder<> IRB(*C);
+  // Create the callback.
+  // FIXME: this function should have "Cold" calling conv,
+  // which is not yet implemented.
+  StringRef WarningFnName = ClKeepGoing ? "__msan_warning"
+                                        : "__msan_warning_noreturn";
+  WarningFn = M.getOrInsertFunction(WarningFnName, IRB.getVoidTy(), nullptr);
+
+  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(), nullptr);
+
+    FunctionName = "__msan_maybe_store_origin_" + itostr(AccessSize);
+    MaybeStoreOriginFn[AccessSizeIndex] = M.getOrInsertFunction(
+        FunctionName, IRB.getVoidTy(), IRB.getIntNTy(AccessSize * 8),
+        IRB.getInt8PtrTy(), IRB.getInt32Ty(), nullptr);
+  }
+
+  MsanSetAllocaOrigin4Fn = M.getOrInsertFunction(
+    "__msan_set_alloca_origin4", IRB.getVoidTy(), IRB.getInt8PtrTy(), IntptrTy,
+    IRB.getInt8PtrTy(), IntptrTy, nullptr);
+  MsanPoisonStackFn =
+      M.getOrInsertFunction("__msan_poison_stack", IRB.getVoidTy(),
+                            IRB.getInt8PtrTy(), IntptrTy, nullptr);
+  MsanChainOriginFn = M.getOrInsertFunction(
+    "__msan_chain_origin", IRB.getInt32Ty(), IRB.getInt32Ty(), nullptr);
+  MemmoveFn = M.getOrInsertFunction(
+    "__msan_memmove", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
+    IRB.getInt8PtrTy(), IntptrTy, nullptr);
+  MemcpyFn = M.getOrInsertFunction(
+    "__msan_memcpy", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
+    IntptrTy, nullptr);
+  MemsetFn = M.getOrInsertFunction(
+    "__msan_memset", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IRB.getInt32Ty(),
+    IntptrTy, nullptr);
+
+  // Create globals.
+  RetvalTLS = new GlobalVariable(
+    M, ArrayType::get(IRB.getInt64Ty(), kRetvalTLSSize / 8), false,
+    GlobalVariable::ExternalLinkage, nullptr, "__msan_retval_tls", nullptr,
+    GlobalVariable::InitialExecTLSModel);
+  RetvalOriginTLS = new GlobalVariable(
+    M, OriginTy, false, GlobalVariable::ExternalLinkage, nullptr,
+    "__msan_retval_origin_tls", nullptr, GlobalVariable::InitialExecTLSModel);
+
+  ParamTLS = new GlobalVariable(
+    M, ArrayType::get(IRB.getInt64Ty(), kParamTLSSize / 8), false,
+    GlobalVariable::ExternalLinkage, nullptr, "__msan_param_tls", nullptr,
+    GlobalVariable::InitialExecTLSModel);
+  ParamOriginTLS = new GlobalVariable(
+    M, ArrayType::get(OriginTy, kParamTLSSize / 4), false,
+    GlobalVariable::ExternalLinkage, nullptr, "__msan_param_origin_tls",
+    nullptr, GlobalVariable::InitialExecTLSModel);
+
+  VAArgTLS = new GlobalVariable(
+    M, ArrayType::get(IRB.getInt64Ty(), kParamTLSSize / 8), false,
+    GlobalVariable::ExternalLinkage, nullptr, "__msan_va_arg_tls", nullptr,
+    GlobalVariable::InitialExecTLSModel);
+  VAArgOverflowSizeTLS = new GlobalVariable(
+    M, IRB.getInt64Ty(), false, GlobalVariable::ExternalLinkage, nullptr,
+    "__msan_va_arg_overflow_size_tls", nullptr,
+    GlobalVariable::InitialExecTLSModel);
+  OriginTLS = new GlobalVariable(
+    M, IRB.getInt32Ty(), false, GlobalVariable::ExternalLinkage, nullptr,
+    "__msan_origin_tls", nullptr, GlobalVariable::InitialExecTLSModel);
+
+  // 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);
+}
+
+/// \brief Module-level initialization.
+///
+/// inserts a call to __msan_init to the module's constructor list.
+bool MemorySanitizer::doInitialization(Module &M) {
+  auto &DL = M.getDataLayout();
+
+  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::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);
+
+  std::tie(MsanCtorFunction, std::ignore) =
+      createSanitizerCtorAndInitFunctions(M, kMsanModuleCtorName, kMsanInitName,
+                                          /*InitArgTypes=*/{},
+                                          /*InitArgs=*/{});
+
+  appendToGlobalCtors(M, MsanCtorFunction, 0);
+
+  if (TrackOrigins)
+    new GlobalVariable(M, IRB.getInt32Ty(), true, GlobalValue::WeakODRLinkage,
+                       IRB.getInt32(TrackOrigins), "__msan_track_origins");
+
+  if (ClKeepGoing)
+    new GlobalVariable(M, IRB.getInt32Ty(), true, GlobalValue::WeakODRLinkage,
+                       IRB.getInt32(ClKeepGoing), "__msan_keep_going");
+
+  return true;
+}
+
+namespace {
+
+/// \brief 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 {
+  /// \brief Visit a CallSite.
+  virtual void visitCallSite(CallSite &CS, IRBuilder<> &IRB) = 0;
+
+  /// \brief Visit a va_start call.
+  virtual void visitVAStartInst(VAStartInst &I) = 0;
+
+  /// \brief Visit a va_copy call.
+  virtual void visitVACopyInst(VACopyInst &I) = 0;
+
+  /// \brief Finalize function instrumentation.
+  ///
+  /// This method is called after visiting all interesting (see above)
+  /// instructions in a function.
+  virtual void finalizeInstrumentation() = 0;
+
+  virtual ~VarArgHelper() {}
+};
+
+struct MemorySanitizerVisitor;
+
+VarArgHelper*
+CreateVarArgHelper(Function &Func, MemorySanitizer &Msan,
+                   MemorySanitizerVisitor &Visitor);
+
+unsigned TypeSizeToSizeIndex(unsigned TypeSize) {
+  if (TypeSize <= 8) return 0;
+  return Log2_32_Ceil(TypeSize / 8);
+}
+
+/// 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;
+
+  // 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;
+  SmallVector<Instruction*, 16> StoreList;
+
+  MemorySanitizerVisitor(Function &F, MemorySanitizer &MS)
+      : F(F), MS(MS), VAHelper(CreateVarArgHelper(F, MS, *this)) {
+    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");
+
+    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));
+  }
+
+  /// \brief 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(nullptr, OriginPtr, i) : OriginPtr;
+      IRB.CreateAlignedStore(Origin, GEP, CurrentAlignment);
+      CurrentAlignment = kMinOriginAlignment;
+    }
+  }
+
+  void storeOrigin(IRBuilder<> &IRB, Value *Addr, Value *Shadow, Value *Origin,
+                   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),
+                  getOriginPtr(Addr, IRB, Alignment), 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),
+                      getOriginPtr(Addr, IRB, Alignment), StoreSize,
+                      OriginAlignment);
+        return;
+      }
+
+      unsigned TypeSizeInBits =
+          DL.getTypeSizeInBits(ConvertedShadow->getType());
+      unsigned SizeIndex = TypeSizeToSizeIndex(TypeSizeInBits);
+      if (AsCall && SizeIndex < kNumberOfAccessSizes) {
+        Value *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),
+                    getOriginPtr(Addr, IRBNew, Alignment), StoreSize,
+                    OriginAlignment);
+      }
+    }
+  }
+
+  void materializeStores(bool InstrumentWithCalls) {
+    for (auto Inst : StoreList) {
+      StoreInst &SI = *dyn_cast<StoreInst>(Inst);
+
+      IRBuilder<> IRB(&SI);
+      Value *Val = SI.getValueOperand();
+      Value *Addr = SI.getPointerOperand();
+      Value *Shadow = SI.isAtomic() ? getCleanShadow(Val) : getShadow(Val);
+      Value *ShadowPtr = getShadowPtr(Addr, Shadow->getType(), IRB);
+
+      StoreInst *NewSI =
+          IRB.CreateAlignedStore(Shadow, ShadowPtr, SI.getAlignment());
+      DEBUG(dbgs() << "  STORE: " << *NewSI << "\n");
+      (void)NewSI;
+
+      if (ClCheckAccessAddress) insertShadowCheck(Addr, &SI);
+
+      if (SI.isAtomic()) SI.setOrdering(addReleaseOrdering(SI.getOrdering()));
+
+      if (MS.TrackOrigins && !SI.isAtomic())
+        storeOrigin(IRB, Addr, Shadow, getOrigin(Val), SI.getAlignment(),
+                    InstrumentWithCalls);
+    }
+  }
+
+  void materializeOneCheck(Instruction *OrigIns, Value *Shadow, Value *Origin,
+                           bool AsCall) {
+    IRBuilder<> IRB(OrigIns);
+    DEBUG(dbgs() << "  SHAD0 : " << *Shadow << "\n");
+    Value *ConvertedShadow = convertToShadowTyNoVec(Shadow, IRB);
+    DEBUG(dbgs() << "  SHAD1 : " << *ConvertedShadow << "\n");
+
+    Constant *ConstantShadow = dyn_cast_or_null<Constant>(ConvertedShadow);
+    if (ConstantShadow) {
+      if (ClCheckConstantShadow && !ConstantShadow->isZeroValue()) {
+        if (MS.TrackOrigins) {
+          IRB.CreateStore(Origin ? (Value *)Origin : (Value *)IRB.getInt32(0),
+                          MS.OriginTLS);
+        }
+        IRB.CreateCall(MS.WarningFn, {});
+        IRB.CreateCall(MS.EmptyAsm, {});
+        // FIXME: Insert UnreachableInst if !ClKeepGoing?
+        // This may invalidate some of the following checks and needs to be done
+        // at the very end.
+      }
+      return;
+    }
+
+    const DataLayout &DL = OrigIns->getModule()->getDataLayout();
+
+    unsigned TypeSizeInBits = DL.getTypeSizeInBits(ConvertedShadow->getType());
+    unsigned SizeIndex = TypeSizeToSizeIndex(TypeSizeInBits);
+    if (AsCall && SizeIndex < kNumberOfAccessSizes) {
+      Value *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 */ !ClKeepGoing, MS.ColdCallWeights);
+
+      IRB.SetInsertPoint(CheckTerm);
+      if (MS.TrackOrigins) {
+        IRB.CreateStore(Origin ? (Value *)Origin : (Value *)IRB.getInt32(0),
+                        MS.OriginTLS);
+      }
+      IRB.CreateCall(MS.WarningFn, {});
+      IRB.CreateCall(MS.EmptyAsm, {});
+      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);
+    }
+    DEBUG(dbgs() << "DONE:\n" << F);
+  }
+
+  /// \brief Add MemorySanitizer instrumentation to a function.
+  bool runOnFunction() {
+    MS.initializeCallbacks(*F.getParent());
+
+    // 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(&F.getEntryBlock()))
+      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();
+
+    bool InstrumentWithCalls = ClInstrumentationWithCallThreshold >= 0 &&
+                               InstrumentationList.size() + StoreList.size() >
+                                   (unsigned)ClInstrumentationWithCallThreshold;
+
+    // Delayed instrumentation of StoreInst.
+    // This may add new checks to be inserted later.
+    materializeStores(InstrumentWithCalls);
+
+    // Insert shadow value checks.
+    materializeChecks(InstrumentWithCalls);
+
+    return true;
+  }
+
+  /// \brief Compute the shadow type that corresponds to a given Value.
+  Type *getShadowTy(Value *V) {
+    return getShadowTy(V->getType());
+  }
+
+  /// \brief 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());
+      DEBUG(dbgs() << "getShadowTy: " << *ST << " ===> " << *Res << "\n");
+      return Res;
+    }
+    uint32_t TypeSize = DL.getTypeSizeInBits(OrigTy);
+    return IntegerType::get(*MS.C, TypeSize);
+  }
+
+  /// \brief Flatten a vector type.
+  Type *getShadowTyNoVec(Type *ty) {
+    if (VectorType *vt = dyn_cast<VectorType>(ty))
+      return IntegerType::get(*MS.C, vt->getBitWidth());
+    return ty;
+  }
+
+  /// \brief 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);
+  }
+
+  /// \brief 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;
+  }
+
+  /// \brief Compute the shadow address that corresponds to a given application
+  /// address.
+  ///
+  /// Shadow = ShadowBase + Offset
+  Value *getShadowPtr(Value *Addr, Type *ShadowTy,
+                      IRBuilder<> &IRB) {
+    Value *ShadowLong = getShadowPtrOffset(Addr, IRB);
+    uint64_t ShadowBase = MS.MapParams->ShadowBase;
+    if (ShadowBase != 0)
+      ShadowLong =
+        IRB.CreateAdd(ShadowLong,
+                      ConstantInt::get(MS.IntptrTy, ShadowBase));
+    return IRB.CreateIntToPtr(ShadowLong, PointerType::get(ShadowTy, 0));
+  }
+
+  /// \brief Compute the origin address that corresponds to a given application
+  /// address.
+  ///
+  /// OriginAddr = (OriginBase + Offset) & ~3ULL
+  Value *getOriginPtr(Value *Addr, IRBuilder<> &IRB, unsigned Alignment) {
+    Value *OriginLong = getShadowPtrOffset(Addr, IRB);
+    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));
+    }
+    return IRB.CreateIntToPtr(OriginLong,
+                              PointerType::get(IRB.getInt32Ty(), 0));
+  }
+
+  /// \brief 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);
+    Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
+    return IRB.CreateIntToPtr(Base, PointerType::get(getShadowTy(A), 0),
+                              "_msarg");
+  }
+
+  /// \brief 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);
+    Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
+    return IRB.CreateIntToPtr(Base, PointerType::get(MS.OriginTy, 0),
+                              "_msarg_o");
+  }
+
+  /// \brief Compute the shadow address for a retval.
+  Value *getShadowPtrForRetval(Value *A, IRBuilder<> &IRB) {
+    Value *Base = IRB.CreatePointerCast(MS.RetvalTLS, MS.IntptrTy);
+    return IRB.CreateIntToPtr(Base, PointerType::get(getShadowTy(A), 0),
+                              "_msret");
+  }
+
+  /// \brief 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;
+  }
+
+  /// \brief 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);
+  }
+
+  /// \brief 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");
+    DEBUG(dbgs() << "ORIGIN: " << *V << "  ==> " << *Origin << "\n");
+    OriginMap[V] = Origin;
+  }
+
+  /// \brief 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) {
+    Type *ShadowTy = getShadowTy(V);
+    if (!ShadowTy)
+      return nullptr;
+    return Constant::getNullValue(ShadowTy);
+  }
+
+  /// \brief 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");
+  }
+
+  /// \brief Create a dirty shadow for a given value.
+  Constant *getPoisonedShadow(Value *V) {
+    Type *ShadowTy = getShadowTy(V);
+    if (!ShadowTy)
+      return nullptr;
+    return getPoisonedShadow(ShadowTy);
+  }
+
+  /// \brief Create a clean (zero) origin.
+  Value *getCleanOrigin() {
+    return Constant::getNullValue(MS.OriginTy);
+  }
+
+  /// \brief 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)) {
+      // For instructions the shadow is already stored in the map.
+      Value *Shadow = ShadowMap[V];
+      if (!Shadow) {
+        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);
+      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(F->getEntryBlock().getFirstNonPHI());
+      unsigned ArgOffset = 0;
+      const DataLayout &DL = F->getParent()->getDataLayout();
+      for (auto &FArg : F->args()) {
+        if (!FArg.getType()->isSized()) {
+          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);
+            }
+            if (Overflow) {
+              // ParamTLS overflow.
+              EntryIRB.CreateMemSet(
+                  getShadowPtr(V, EntryIRB.getInt8Ty(), EntryIRB),
+                  Constant::getNullValue(EntryIRB.getInt8Ty()), Size, ArgAlign);
+            } else {
+              unsigned CopyAlign = std::min(ArgAlign, kShadowTLSAlignment);
+              Value *Cpy = EntryIRB.CreateMemCpy(
+                  getShadowPtr(V, EntryIRB.getInt8Ty(), EntryIRB), Base, Size,
+                  CopyAlign);
+              DEBUG(dbgs() << "  ByValCpy: " << *Cpy << "\n");
+              (void)Cpy;
+            }
+            *ShadowPtr = getCleanShadow(V);
+          } else {
+            if (Overflow) {
+              // ParamTLS overflow.
+              *ShadowPtr = getCleanShadow(V);
+            } else {
+              *ShadowPtr =
+                  EntryIRB.CreateAlignedLoad(Base, kShadowTLSAlignment);
+            }
+          }
+          DEBUG(dbgs() << "  ARG:    "  << FArg << " ==> " <<
+                **ShadowPtr << "\n");
+          if (MS.TrackOrigins && !Overflow) {
+            Value *OriginPtr =
+                getOriginPtrForArgument(&FArg, EntryIRB, ArgOffset);
+            setOrigin(A, EntryIRB.CreateLoad(OriginPtr));
+          } else {
+            setOrigin(A, getCleanOrigin());
+          }
+        }
+        ArgOffset += RoundUpToAlignment(Size, kShadowTLSAlignment);
+      }
+      assert(*ShadowPtr && "Could not find shadow for an argument");
+      return *ShadowPtr;
+    }
+    // For everything else the shadow is zero.
+    return getCleanShadow(V);
+  }
+
+  /// \brief Get the shadow for i-th argument of the instruction I.
+  Value *getShadow(Instruction *I, int i) {
+    return getShadow(I->getOperand(i));
+  }
+
+  /// \brief 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()");
+    Value *Origin = OriginMap[V];
+    assert(Origin && "Missing origin");
+    return Origin;
+  }
+
+  /// \brief Get the origin for i-th argument of the instruction I.
+  Value *getOrigin(Instruction *I, int i) {
+    return getOrigin(I->getOperand(i));
+  }
+
+  /// \brief 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));
+  }
+
+  /// \brief 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 NotAtomic:
+        return NotAtomic;
+      case Unordered:
+      case Monotonic:
+      case Release:
+        return Release;
+      case Acquire:
+      case AcquireRelease:
+        return AcquireRelease;
+      case SequentiallyConsistent:
+        return SequentiallyConsistent;
+    }
+    llvm_unreachable("Unknown ordering");
+  }
+
+  AtomicOrdering addAcquireOrdering(AtomicOrdering a) {
+    switch (a) {
+      case NotAtomic:
+        return NotAtomic;
+      case Unordered:
+      case Monotonic:
+      case Acquire:
+        return Acquire;
+      case Release:
+      case AcquireRelease:
+        return AcquireRelease;
+      case SequentiallyConsistent:
+        return SequentiallyConsistent;
+    }
+    llvm_unreachable("Unknown ordering");
+  }
+
+  // ------------------- Visitors.
+
+  /// \brief 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");
+    IRBuilder<> IRB(I.getNextNode());
+    Type *ShadowTy = getShadowTy(&I);
+    Value *Addr = I.getPointerOperand();
+    if (PropagateShadow && !I.getMetadata("nosanitize")) {
+      Value *ShadowPtr = getShadowPtr(Addr, ShadowTy, IRB);
+      setShadow(&I,
+                IRB.CreateAlignedLoad(ShadowPtr, I.getAlignment(), "_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 Alignment = I.getAlignment();
+        unsigned OriginAlignment = std::max(kMinOriginAlignment, Alignment);
+        setOrigin(&I, IRB.CreateAlignedLoad(getOriginPtr(Addr, IRB, Alignment),
+                                            OriginAlignment));
+      } else {
+        setOrigin(&I, getCleanOrigin());
+      }
+    }
+  }
+
+  /// \brief 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);
+  }
+
+  void handleCASOrRMW(Instruction &I) {
+    assert(isa<AtomicRMWInst>(I) || isa<AtomicCmpXchgInst>(I));
+
+    IRBuilder<> IRB(&I);
+    Value *Addr = I.getOperand(0);
+    Value *ShadowPtr = getShadowPtr(Addr, I.getType(), IRB);
+
+    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); }
+
+  /// \brief 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, IRB.CreateOr(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, IRB.CreateOr(V1S2, S1V2)));
+    setOriginForNaryOp(I);
+  }
+
+  /// \brief 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;
+    Value *Origin;
+    IRBuilder<> &IRB;
+    MemorySanitizerVisitor *MSV;
+
+  public:
+    Combiner(MemorySanitizerVisitor *MSV, IRBuilder<> &IRB) :
+      Shadow(nullptr), Origin(nullptr), IRB(IRB), MSV(MSV) {}
+
+    /// \brief 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;
+    }
+
+    /// \brief 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);
+    }
+
+    /// \brief 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);
+      }
+    }
+  };
+
+  typedef Combiner<true> ShadowAndOriginCombiner;
+  typedef Combiner<false> OriginCombiner;
+
+  /// \brief 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();
+  }
+
+  /// \brief 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();
+    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);
+    size_t srcSizeInBits = VectorOrPrimitiveTypeSizeInBits(srcTy);
+    size_t dstSizeInBits = VectorOrPrimitiveTypeSizeInBits(dstTy);
+    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.
+  }
+
+  /// \brief 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);
+  }
+
+  /// \brief 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);
+  }
+
+  // \brief 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))) {
+          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)) {
+        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 handleDiv(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) { handleDiv(I); }
+  void visitSDiv(BinaryOperator &I) { handleDiv(I); }
+  void visitFDiv(BinaryOperator &I) { handleDiv(I); }
+  void visitURem(BinaryOperator &I) { handleDiv(I); }
+  void visitSRem(BinaryOperator &I) { handleDiv(I); }
+  void visitFRem(BinaryOperator &I) { handleDiv(I); }
+
+  /// \brief 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);
+  }
+
+  /// \brief 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));
+    }
+  }
+
+  /// \brief 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);
+    }
+  }
+
+  /// \brief 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);
+  }
+
+  /// \brief 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); }
+
+  /// \brief 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);
+  }
+
+  /// \brief 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 = getShadowPtr(Addr, Shadow->getType(), IRB);
+
+    // We don't know the pointer alignment (could be unaligned SSE store!).
+    // Have to assume to worst case.
+    IRB.CreateAlignedStore(Shadow, ShadowPtr, 1);
+
+    if (ClCheckAccessAddress)
+      insertShadowCheck(Addr, &I);
+
+    // FIXME: use ClStoreCleanOrigin
+    // FIXME: factor out common code from materializeStores
+    if (MS.TrackOrigins)
+      IRB.CreateStore(getOrigin(&I, 1), getOriginPtr(Addr, IRB, 1));
+    return true;
+  }
+
+  /// \brief 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);
+    if (PropagateShadow) {
+      Value *ShadowPtr = getShadowPtr(Addr, ShadowTy, IRB);
+      // We don't know the pointer alignment (could be unaligned SSE load!).
+      // Have to assume to worst case.
+      setShadow(&I, IRB.CreateAlignedLoad(ShadowPtr, 1, "_msld"));
+    } else {
+      setShadow(&I, getCleanShadow(&I));
+    }
+
+    if (ClCheckAccessAddress)
+      insertShadowCheck(Addr, &I);
+
+    if (MS.TrackOrigins) {
+      if (PropagateShadow)
+        setOrigin(&I, IRB.CreateLoad(getOriginPtr(Addr, IRB, 1)));
+      else
+        setOrigin(&I, getCleanOrigin());
+    }
+    return true;
+  }
+
+  /// \brief 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;
+  }
+
+  /// \brief 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 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));
+  }
+
+  // \brief 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");
+    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);
+  }
+
+  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);
+  }
+
+  // \brief 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.getCalledValue(),
+                                  {IRB.CreateBitCast(S1, V1->getType()), V2});
+    Shift = IRB.CreateBitCast(Shift, getShadowTy(&I));
+    setShadow(&I, IRB.CreateOr(Shift, S2Conv));
+    setOriginForNaryOp(I);
+  }
+
+  // \brief Get an X86_MMX-sized vector type.
+  Type *getMMXVectorTy(unsigned EltSizeInBits) {
+    const unsigned X86_MMXSizeInBits = 64;
+    return VectorType::get(IntegerType::get(*MS.C, EltSizeInBits),
+                           X86_MMXSizeInBits / EltSizeInBits);
+  }
+
+  // \brief Returns a signed counterpart for an (un)signed-saturate-and-pack
+  // intrinsic.
+  Intrinsic::ID getSignedPackIntrinsic(Intrinsic::ID id) {
+    switch (id) {
+      case llvm::Intrinsic::x86_sse2_packsswb_128:
+      case llvm::Intrinsic::x86_sse2_packuswb_128:
+        return llvm::Intrinsic::x86_sse2_packsswb_128;
+
+      case llvm::Intrinsic::x86_sse2_packssdw_128:
+      case llvm::Intrinsic::x86_sse41_packusdw:
+        return llvm::Intrinsic::x86_sse2_packssdw_128;
+
+      case llvm::Intrinsic::x86_avx2_packsswb:
+      case llvm::Intrinsic::x86_avx2_packuswb:
+        return llvm::Intrinsic::x86_avx2_packsswb;
+
+      case llvm::Intrinsic::x86_avx2_packssdw:
+      case llvm::Intrinsic::x86_avx2_packusdw:
+        return llvm::Intrinsic::x86_avx2_packssdw;
+
+      case llvm::Intrinsic::x86_mmx_packsswb:
+      case llvm::Intrinsic::x86_mmx_packuswb:
+        return llvm::Intrinsic::x86_mmx_packsswb;
+
+      case llvm::Intrinsic::x86_mmx_packssdw:
+        return llvm::Intrinsic::x86_mmx_packssdw;
+      default:
+        llvm_unreachable("unexpected intrinsic id");
+    }
+  }
+
+  // \brief 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, llvm::Constant::getNullValue(T)), T);
+    Value *S2_ext = IRB.CreateSExt(
+        IRB.CreateICmpNE(S2, llvm::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);
+  }
+
+  // \brief 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);
+  }
+
+  // \brief 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);
+  }
+
+  void visitIntrinsicInst(IntrinsicInst &I) {
+    switch (I.getIntrinsicID()) {
+    case llvm::Intrinsic::bswap:
+      handleBswap(I);
+      break;
+    case llvm::Intrinsic::x86_avx512_cvtsd2usi64:
+    case llvm::Intrinsic::x86_avx512_cvtsd2usi:
+    case llvm::Intrinsic::x86_avx512_cvtss2usi64:
+    case llvm::Intrinsic::x86_avx512_cvtss2usi:
+    case llvm::Intrinsic::x86_avx512_cvttss2usi64:
+    case llvm::Intrinsic::x86_avx512_cvttss2usi:
+    case llvm::Intrinsic::x86_avx512_cvttsd2usi64:
+    case llvm::Intrinsic::x86_avx512_cvttsd2usi:
+    case llvm::Intrinsic::x86_avx512_cvtusi2sd:
+    case llvm::Intrinsic::x86_avx512_cvtusi2ss:
+    case llvm::Intrinsic::x86_avx512_cvtusi642sd:
+    case llvm::Intrinsic::x86_avx512_cvtusi642ss:
+    case llvm::Intrinsic::x86_sse2_cvtsd2si64:
+    case llvm::Intrinsic::x86_sse2_cvtsd2si:
+    case llvm::Intrinsic::x86_sse2_cvtsd2ss:
+    case llvm::Intrinsic::x86_sse2_cvtsi2sd:
+    case llvm::Intrinsic::x86_sse2_cvtsi642sd:
+    case llvm::Intrinsic::x86_sse2_cvtss2sd:
+    case llvm::Intrinsic::x86_sse2_cvttsd2si64:
+    case llvm::Intrinsic::x86_sse2_cvttsd2si:
+    case llvm::Intrinsic::x86_sse_cvtsi2ss:
+    case llvm::Intrinsic::x86_sse_cvtsi642ss:
+    case llvm::Intrinsic::x86_sse_cvtss2si64:
+    case llvm::Intrinsic::x86_sse_cvtss2si:
+    case llvm::Intrinsic::x86_sse_cvttss2si64:
+    case llvm::Intrinsic::x86_sse_cvttss2si:
+      handleVectorConvertIntrinsic(I, 1);
+      break;
+    case llvm::Intrinsic::x86_sse2_cvtdq2pd:
+    case llvm::Intrinsic::x86_sse2_cvtps2pd:
+    case llvm::Intrinsic::x86_sse_cvtps2pi:
+    case llvm::Intrinsic::x86_sse_cvttps2pi:
+      handleVectorConvertIntrinsic(I, 2);
+      break;
+    case llvm::Intrinsic::x86_avx2_psll_w:
+    case llvm::Intrinsic::x86_avx2_psll_d:
+    case llvm::Intrinsic::x86_avx2_psll_q:
+    case llvm::Intrinsic::x86_avx2_pslli_w:
+    case llvm::Intrinsic::x86_avx2_pslli_d:
+    case llvm::Intrinsic::x86_avx2_pslli_q:
+    case llvm::Intrinsic::x86_avx2_psrl_w:
+    case llvm::Intrinsic::x86_avx2_psrl_d:
+    case llvm::Intrinsic::x86_avx2_psrl_q:
+    case llvm::Intrinsic::x86_avx2_psra_w:
+    case llvm::Intrinsic::x86_avx2_psra_d:
+    case llvm::Intrinsic::x86_avx2_psrli_w:
+    case llvm::Intrinsic::x86_avx2_psrli_d:
+    case llvm::Intrinsic::x86_avx2_psrli_q:
+    case llvm::Intrinsic::x86_avx2_psrai_w:
+    case llvm::Intrinsic::x86_avx2_psrai_d:
+    case llvm::Intrinsic::x86_sse2_psll_w:
+    case llvm::Intrinsic::x86_sse2_psll_d:
+    case llvm::Intrinsic::x86_sse2_psll_q:
+    case llvm::Intrinsic::x86_sse2_pslli_w:
+    case llvm::Intrinsic::x86_sse2_pslli_d:
+    case llvm::Intrinsic::x86_sse2_pslli_q:
+    case llvm::Intrinsic::x86_sse2_psrl_w:
+    case llvm::Intrinsic::x86_sse2_psrl_d:
+    case llvm::Intrinsic::x86_sse2_psrl_q:
+    case llvm::Intrinsic::x86_sse2_psra_w:
+    case llvm::Intrinsic::x86_sse2_psra_d:
+    case llvm::Intrinsic::x86_sse2_psrli_w:
+    case llvm::Intrinsic::x86_sse2_psrli_d:
+    case llvm::Intrinsic::x86_sse2_psrli_q:
+    case llvm::Intrinsic::x86_sse2_psrai_w:
+    case llvm::Intrinsic::x86_sse2_psrai_d:
+    case llvm::Intrinsic::x86_mmx_psll_w:
+    case llvm::Intrinsic::x86_mmx_psll_d:
+    case llvm::Intrinsic::x86_mmx_psll_q:
+    case llvm::Intrinsic::x86_mmx_pslli_w:
+    case llvm::Intrinsic::x86_mmx_pslli_d:
+    case llvm::Intrinsic::x86_mmx_pslli_q:
+    case llvm::Intrinsic::x86_mmx_psrl_w:
+    case llvm::Intrinsic::x86_mmx_psrl_d:
+    case llvm::Intrinsic::x86_mmx_psrl_q:
+    case llvm::Intrinsic::x86_mmx_psra_w:
+    case llvm::Intrinsic::x86_mmx_psra_d:
+    case llvm::Intrinsic::x86_mmx_psrli_w:
+    case llvm::Intrinsic::x86_mmx_psrli_d:
+    case llvm::Intrinsic::x86_mmx_psrli_q:
+    case llvm::Intrinsic::x86_mmx_psrai_w:
+    case llvm::Intrinsic::x86_mmx_psrai_d:
+      handleVectorShiftIntrinsic(I, /* Variable */ false);
+      break;
+    case llvm::Intrinsic::x86_avx2_psllv_d:
+    case llvm::Intrinsic::x86_avx2_psllv_d_256:
+    case llvm::Intrinsic::x86_avx2_psllv_q:
+    case llvm::Intrinsic::x86_avx2_psllv_q_256:
+    case llvm::Intrinsic::x86_avx2_psrlv_d:
+    case llvm::Intrinsic::x86_avx2_psrlv_d_256:
+    case llvm::Intrinsic::x86_avx2_psrlv_q:
+    case llvm::Intrinsic::x86_avx2_psrlv_q_256:
+    case llvm::Intrinsic::x86_avx2_psrav_d:
+    case llvm::Intrinsic::x86_avx2_psrav_d_256:
+      handleVectorShiftIntrinsic(I, /* Variable */ true);
+      break;
+
+    case llvm::Intrinsic::x86_sse2_packsswb_128:
+    case llvm::Intrinsic::x86_sse2_packssdw_128:
+    case llvm::Intrinsic::x86_sse2_packuswb_128:
+    case llvm::Intrinsic::x86_sse41_packusdw:
+    case llvm::Intrinsic::x86_avx2_packsswb:
+    case llvm::Intrinsic::x86_avx2_packssdw:
+    case llvm::Intrinsic::x86_avx2_packuswb:
+    case llvm::Intrinsic::x86_avx2_packusdw:
+      handleVectorPackIntrinsic(I);
+      break;
+
+    case llvm::Intrinsic::x86_mmx_packsswb:
+    case llvm::Intrinsic::x86_mmx_packuswb:
+      handleVectorPackIntrinsic(I, 16);
+      break;
+
+    case llvm::Intrinsic::x86_mmx_packssdw:
+      handleVectorPackIntrinsic(I, 32);
+      break;
+
+    case llvm::Intrinsic::x86_mmx_psad_bw:
+    case llvm::Intrinsic::x86_sse2_psad_bw:
+    case llvm::Intrinsic::x86_avx2_psad_bw:
+      handleVectorSadIntrinsic(I);
+      break;
+
+    case llvm::Intrinsic::x86_sse2_pmadd_wd:
+    case llvm::Intrinsic::x86_avx2_pmadd_wd:
+    case llvm::Intrinsic::x86_ssse3_pmadd_ub_sw_128:
+    case llvm::Intrinsic::x86_avx2_pmadd_ub_sw:
+      handleVectorPmaddIntrinsic(I);
+      break;
+
+    case llvm::Intrinsic::x86_ssse3_pmadd_ub_sw:
+      handleVectorPmaddIntrinsic(I, 8);
+      break;
+
+    case llvm::Intrinsic::x86_mmx_pmadd_wd:
+      handleVectorPmaddIntrinsic(I, 16);
+      break;
+
+    default:
+      if (!handleUnknownIntrinsic(I))
+        visitInstruction(I);
+      break;
+    }
+  }
+
+  void visitCallSite(CallSite CS) {
+    Instruction &I = *CS.getInstruction();
+    assert((CS.isCall() || CS.isInvoke()) && "Unknown type of CallSite");
+    if (CS.isCall()) {
+      CallInst *Call = cast<CallInst>(&I);
+
+      // For inline asm, 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 (Call->isInlineAsm()) {
+        visitInstruction(I);
+        return;
+      }
+
+      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(AttributeSet::FunctionIndex,
+                               AttributeSet::get(Func->getContext(),
+                                                 AttributeSet::FunctionIndex,
+                                                 B));
+      }
+    }
+    IRBuilder<> IRB(&I);
+
+    unsigned ArgOffset = 0;
+    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()) {
+        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);
+      DEBUG(dbgs() << "  Arg#" << i << ": " << *A <<
+            " Shadow: " << *ArgShadow << "\n");
+      bool ArgIsInitialized = false;
+      const DataLayout &DL = F.getParent()->getDataLayout();
+      if (CS.paramHasAttr(i + 1, 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 + 1);
+        unsigned Alignment = std::min(ParamAlignment, kShadowTLSAlignment);
+        Store = IRB.CreateMemCpy(ArgShadowBase,
+                                 getShadowPtr(A, Type::getInt8Ty(*MS.C), IRB),
+                                 Size, Alignment);
+      } 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);
+      DEBUG(dbgs() << "  Param:" << *Store << "\n");
+      ArgOffset += RoundUpToAlignment(Size, 8);
+    }
+    DEBUG(dbgs() << "  done with call args\n");
+
+    FunctionType *FT =
+      cast<FunctionType>(CS.getCalledValue()->getType()->getContainedType(0));
+    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;
+      }
+      NextInsn = NormalDest->getFirstInsertionPt();
+      assert(NextInsn != NormalDest->end() &&
+             "Could not find insertion point for retval shadow load");
+    }
+    IRBuilder<> IRBAfter(&*NextInsn);
+    Value *RetvalShadow =
+      IRBAfter.CreateAlignedLoad(getShadowPtrForRetval(&I, IRBAfter),
+                                 kShadowTLSAlignment, "_msret");
+    setShadow(&I, RetvalShadow);
+    if (MS.TrackOrigins)
+      setOrigin(&I, IRBAfter.CreateLoad(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);
+      // FIXME: make it conditional if ClStoreCleanOrigin==0
+      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"));
+  }
+
+  void visitAllocaInst(AllocaInst &I) {
+    setShadow(&I, getCleanShadow(&I));
+    setOrigin(&I, getCleanOrigin());
+    IRBuilder<> IRB(I.getNextNode());
+    const DataLayout &DL = F.getParent()->getDataLayout();
+    uint64_t Size = DL.getTypeAllocSize(I.getAllocatedType());
+    if (PoisonStack && ClPoisonStackWithCall) {
+      IRB.CreateCall(MS.MsanPoisonStackFn,
+                     {IRB.CreatePointerCast(&I, IRB.getInt8PtrTy()),
+                      ConstantInt::get(MS.IntptrTy, Size)});
+    } else {
+      Value *ShadowBase = getShadowPtr(&I, Type::getInt8PtrTy(*MS.C), IRB);
+      Value *PoisonValue = IRB.getInt8(PoisonStack ? ClPoisonStackPattern : 0);
+      IRB.CreateMemSet(ShadowBase, PoisonValue, Size, I.getAlignment());
+    }
+
+    if (PoisonStack && MS.TrackOrigins) {
+      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();
+      Value *Descr =
+          createPrivateNonConstGlobalForString(*F.getParent(),
+                                               StackDescription.str());
+
+      IRB.CreateCall(MS.MsanSetAllocaOrigin4Fn,
+                     {IRB.CreatePointerCast(&I, IRB.getInt8PtrTy()),
+                      ConstantInt::get(MS.IntptrTy, Size),
+                      IRB.CreatePointerCast(Descr, IRB.getInt8PtrTy()),
+                      IRB.CreatePointerCast(&F, MS.IntptrTy)});
+    }
+  }
+
+  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), IRB.CreateOr(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 http://code.google.com/p/memory-sanitizer/issues/detail?id=1
+    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();
+    DEBUG(dbgs() << "ExtractValue:  " << I << "\n");
+    Value *AggShadow = getShadow(Agg);
+    DEBUG(dbgs() << "   AggShadow:  " << *AggShadow << "\n");
+    Value *ResShadow = IRB.CreateExtractValue(AggShadow, I.getIndices());
+    DEBUG(dbgs() << "   ResShadow:  " << *ResShadow << "\n");
+    setShadow(&I, ResShadow);
+    setOriginForNaryOp(I);
+  }
+
+  void visitInsertValueInst(InsertValueInst &I) {
+    IRBuilder<> IRB(&I);
+    DEBUG(dbgs() << "InsertValue:  " << I << "\n");
+    Value *AggShadow = getShadow(I.getAggregateOperand());
+    Value *InsShadow = getShadow(I.getInsertedValueOperand());
+    DEBUG(dbgs() << "   AggShadow:  " << *AggShadow << "\n");
+    DEBUG(dbgs() << "   InsShadow:  " << *InsShadow << "\n");
+    Value *Res = IRB.CreateInsertValue(AggShadow, InsShadow, I.getIndices());
+    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) {
+    DEBUG(dbgs() << "Resume: " << I << "\n");
+    // Nothing to do here.
+  }
+
+  void visitCleanupReturnInst(CleanupReturnInst &CRI) {
+    DEBUG(dbgs() << "CleanupReturn: " << CRI << "\n");
+    // Nothing to do here.
+  }
+
+  void visitCatchReturnInst(CatchReturnInst &CRI) {
+    DEBUG(dbgs() << "CatchReturn: " << CRI << "\n");
+    // Nothing to do here.
+  }
+
+  void visitInstruction(Instruction &I) {
+    // Everything else: stop propagating and check for poisoned shadow.
+    if (ClDumpStrictInstructions)
+      dumpInst(I);
+    DEBUG(dbgs() << "DEFAULT: " << I << "\n");
+    for (size_t i = 0, n = I.getNumOperands(); i < n; i++)
+      insertShadowCheck(I.getOperand(i), &I);
+    setShadow(&I, getCleanShadow(&I));
+    setOrigin(&I, getCleanOrigin());
+  }
+};
+
+/// \brief 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 AMD64FpEndOffset = 176;
+
+  Function &F;
+  MemorySanitizer &MS;
+  MemorySanitizerVisitor &MSV;
+  Value *VAArgTLSCopy;
+  Value *VAArgOverflowSize;
+
+  SmallVector<CallInst*, 16> VAStartInstrumentationList;
+
+  VarArgAMD64Helper(Function &F, MemorySanitizer &MS,
+                    MemorySanitizerVisitor &MSV)
+    : F(F), MS(MS), MSV(MSV), VAArgTLSCopy(nullptr),
+      VAArgOverflowSize(nullptr) {}
+
+  enum ArgKind { AK_GeneralPurpose, AK_FloatingPoint, AK_Memory };
+
+  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 IsByVal = CS.paramHasAttr(ArgNo + 1, Attribute::ByVal);
+      if (IsByVal) {
+        // ByVal arguments always go to the overflow area.
+        assert(A->getType()->isPointerTy());
+        Type *RealTy = A->getType()->getPointerElementType();
+        uint64_t ArgSize = DL.getTypeAllocSize(RealTy);
+        Value *Base = getShadowPtrForVAArgument(RealTy, IRB, OverflowOffset);
+        OverflowOffset += RoundUpToAlignment(ArgSize, 8);
+        IRB.CreateMemCpy(Base, MSV.getShadowPtr(A, IRB.getInt8Ty(), IRB),
+                         ArgSize, kShadowTLSAlignment);
+      } else {
+        ArgKind AK = classifyArgument(A);
+        if (AK == AK_GeneralPurpose && GpOffset >= AMD64GpEndOffset)
+          AK = AK_Memory;
+        if (AK == AK_FloatingPoint && FpOffset >= AMD64FpEndOffset)
+          AK = AK_Memory;
+        Value *Base;
+        switch (AK) {
+          case AK_GeneralPurpose:
+            Base = getShadowPtrForVAArgument(A->getType(), IRB, GpOffset);
+            GpOffset += 8;
+            break;
+          case AK_FloatingPoint:
+            Base = getShadowPtrForVAArgument(A->getType(), IRB, FpOffset);
+            FpOffset += 16;
+            break;
+          case AK_Memory:
+            uint64_t ArgSize = DL.getTypeAllocSize(A->getType());
+            Base = getShadowPtrForVAArgument(A->getType(), IRB, OverflowOffset);
+            OverflowOffset += RoundUpToAlignment(ArgSize, 8);
+        }
+        IRB.CreateAlignedStore(MSV.getShadow(A), Base, kShadowTLSAlignment);
+      }
+    }
+    Constant *OverflowSize =
+      ConstantInt::get(IRB.getInt64Ty(), OverflowOffset - AMD64FpEndOffset);
+    IRB.CreateStore(OverflowSize, MS.VAArgOverflowSizeTLS);
+  }
+
+  /// \brief Compute the shadow address for a given va_arg.
+  Value *getShadowPtrForVAArgument(Type *Ty, IRBuilder<> &IRB,
+                                   int ArgOffset) {
+    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 {
+    if (F.getCallingConv() == CallingConv::X86_64_Win64)
+      return;
+    IRBuilder<> IRB(&I);
+    VAStartInstrumentationList.push_back(&I);
+    Value *VAListTag = I.getArgOperand(0);
+    Value *ShadowPtr = MSV.getShadowPtr(VAListTag, IRB.getInt8Ty(), IRB);
+
+    // Unpoison the whole __va_list_tag.
+    // FIXME: magic ABI constants.
+    IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
+                     /* size */24, /* alignment */8, false);
+  }
+
+  void visitVACopyInst(VACopyInst &I) override {
+    if (F.getCallingConv() == CallingConv::X86_64_Win64)
+      return;
+    IRBuilder<> IRB(&I);
+    Value *VAListTag = I.getArgOperand(0);
+    Value *ShadowPtr = MSV.getShadowPtr(VAListTag, IRB.getInt8Ty(), IRB);
+
+    // Unpoison the whole __va_list_tag.
+    // FIXME: magic ABI constants.
+    IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
+                     /* size */24, /* alignment */8, false);
+  }
+
+  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(F.getEntryBlock().getFirstNonPHI());
+      VAArgOverflowSize = IRB.CreateLoad(MS.VAArgOverflowSizeTLS);
+      Value *CopySize =
+        IRB.CreateAdd(ConstantInt::get(MS.IntptrTy, AMD64FpEndOffset),
+                      VAArgOverflowSize);
+      VAArgTLSCopy = IRB.CreateAlloca(Type::getInt8Ty(*MS.C), CopySize);
+      IRB.CreateMemCpy(VAArgTLSCopy, MS.VAArgTLS, CopySize, 8);
+    }
+
+    // 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);
+
+      Value *RegSaveAreaPtrPtr =
+        IRB.CreateIntToPtr(
+          IRB.CreateAdd(IRB.CreatePtrToInt(VAListTag, MS.IntptrTy),
+                        ConstantInt::get(MS.IntptrTy, 16)),
+          Type::getInt64PtrTy(*MS.C));
+      Value *RegSaveAreaPtr = IRB.CreateLoad(RegSaveAreaPtrPtr);
+      Value *RegSaveAreaShadowPtr =
+        MSV.getShadowPtr(RegSaveAreaPtr, IRB.getInt8Ty(), IRB);
+      IRB.CreateMemCpy(RegSaveAreaShadowPtr, VAArgTLSCopy,
+                       AMD64FpEndOffset, 16);
+
+      Value *OverflowArgAreaPtrPtr =
+        IRB.CreateIntToPtr(
+          IRB.CreateAdd(IRB.CreatePtrToInt(VAListTag, MS.IntptrTy),
+                        ConstantInt::get(MS.IntptrTy, 8)),
+          Type::getInt64PtrTy(*MS.C));
+      Value *OverflowArgAreaPtr = IRB.CreateLoad(OverflowArgAreaPtrPtr);
+      Value *OverflowArgAreaShadowPtr =
+        MSV.getShadowPtr(OverflowArgAreaPtr, IRB.getInt8Ty(), IRB);
+      Value *SrcPtr = IRB.CreateConstGEP1_32(IRB.getInt8Ty(), VAArgTLSCopy,
+                                             AMD64FpEndOffset);
+      IRB.CreateMemCpy(OverflowArgAreaShadowPtr, SrcPtr, VAArgOverflowSize, 16);
+    }
+  }
+};
+
+/// \brief MIPS64-specific implementation of VarArgHelper.
+struct VarArgMIPS64Helper : public VarArgHelper {
+  Function &F;
+  MemorySanitizer &MS;
+  MemorySanitizerVisitor &MSV;
+  Value *VAArgTLSCopy;
+  Value *VAArgSize;
+
+  SmallVector<CallInst*, 16> VAStartInstrumentationList;
+
+  VarArgMIPS64Helper(Function &F, MemorySanitizer &MS,
+                    MemorySanitizerVisitor &MSV)
+    : F(F), MS(MS), MSV(MSV), VAArgTLSCopy(nullptr),
+      VAArgSize(nullptr) {}
+
+  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) {
+      llvm::Triple TargetTriple(F.getParent()->getTargetTriple());
+      Value *A = *ArgIt;
+      Value *Base;
+      uint64_t ArgSize = DL.getTypeAllocSize(A->getType());
+      if (TargetTriple.getArch() == llvm::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);
+      VAArgOffset += ArgSize;
+      VAArgOffset = RoundUpToAlignment(VAArgOffset, 8);
+      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);
+  }
+
+  /// \brief Compute the shadow address for a given va_arg.
+  Value *getShadowPtrForVAArgument(Type *Ty, IRBuilder<> &IRB,
+                                   int ArgOffset) {
+    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 = MSV.getShadowPtr(VAListTag, IRB.getInt8Ty(), IRB);
+    IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
+                     /* size */8, /* alignment */8, false);
+  }
+
+  void visitVACopyInst(VACopyInst &I) override {
+    IRBuilder<> IRB(&I);
+    Value *VAListTag = I.getArgOperand(0);
+    Value *ShadowPtr = MSV.getShadowPtr(VAListTag, IRB.getInt8Ty(), IRB);
+    // Unpoison the whole __va_list_tag.
+    // FIXME: magic ABI constants.
+    IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
+                     /* size */8, /* alignment */8, false);
+  }
+
+  void finalizeInstrumentation() override {
+    assert(!VAArgSize && !VAArgTLSCopy &&
+           "finalizeInstrumentation called twice");
+    IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
+    VAArgSize = IRB.CreateLoad(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, MS.VAArgTLS, CopySize, 8);
+    }
+
+    // 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);
+      Value *RegSaveAreaPtrPtr =
+        IRB.CreateIntToPtr(IRB.CreatePtrToInt(VAListTag, MS.IntptrTy),
+                        Type::getInt64PtrTy(*MS.C));
+      Value *RegSaveAreaPtr = IRB.CreateLoad(RegSaveAreaPtrPtr);
+      Value *RegSaveAreaShadowPtr =
+      MSV.getShadowPtr(RegSaveAreaPtr, IRB.getInt8Ty(), IRB);
+      IRB.CreateMemCpy(RegSaveAreaShadowPtr, VAArgTLSCopy, CopySize, 8);
+    }
+  }
+};
+
+
+/// \brief AArch64-specific implementation of VarArgHelper.
+struct VarArgAArch64Helper : public VarArgHelper {
+  static const unsigned kAArch64GrArgSize = 56;
+  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 + 8;
+  static const unsigned AArch64VrEndOffset = AArch64VrBegOffset
+                                             + kAArch64VrArgSize;
+  static const unsigned AArch64VAEndOffset = AArch64VrEndOffset;
+
+  Function &F;
+  MemorySanitizer &MS;
+  MemorySanitizerVisitor &MSV;
+  Value *VAArgTLSCopy;
+  Value *VAArgOverflowSize;
+
+  SmallVector<CallInst*, 16> VAStartInstrumentationList;
+
+  VarArgAArch64Helper(Function &F, MemorySanitizer &MS,
+                    MemorySanitizerVisitor &MSV)
+    : F(F), MS(MS), MSV(MSV), VAArgTLSCopy(nullptr),
+      VAArgOverflowSize(nullptr) {}
+
+  enum ArgKind { AK_GeneralPurpose, AK_FloatingPoint, AK_Memory };
+
+  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() + 1, End = CS.arg_end();
+         ArgIt != End; ++ArgIt) {
+      Value *A = *ArgIt;
+      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);
+          GrOffset += 8;
+          break;
+        case AK_FloatingPoint:
+          Base = getShadowPtrForVAArgument(A->getType(), IRB, VrOffset);
+          VrOffset += 16;
+          break;
+        case AK_Memory:
+          uint64_t ArgSize = DL.getTypeAllocSize(A->getType());
+          Base = getShadowPtrForVAArgument(A->getType(), IRB, OverflowOffset);
+          OverflowOffset += RoundUpToAlignment(ArgSize, 8);
+          break;
+      }
+      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,
+                                   int ArgOffset) {
+    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 = MSV.getShadowPtr(VAListTag, IRB.getInt8Ty(), IRB);
+    // Unpoison the whole __va_list_tag.
+    // FIXME: magic ABI constants (size of va_list).
+    IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
+                     /* size */32, /* alignment */8, false);
+  }
+
+  void visitVACopyInst(VACopyInst &I) override {
+    IRBuilder<> IRB(&I);
+    Value *VAListTag = I.getArgOperand(0);
+    Value *ShadowPtr = MSV.getShadowPtr(VAListTag, IRB.getInt8Ty(), IRB);
+    // Unpoison the whole __va_list_tag.
+    // FIXME: magic ABI constants (size of va_list).
+    IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
+                     /* size */32, /* alignment */8, 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(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(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(F.getEntryBlock().getFirstNonPHI());
+      VAArgOverflowSize = IRB.CreateLoad(MS.VAArgOverflowSizeTLS);
+      Value *CopySize =
+        IRB.CreateAdd(ConstantInt::get(MS.IntptrTy, AArch64VAEndOffset),
+                      VAArgOverflowSize);
+      VAArgTLSCopy = IRB.CreateAlloca(Type::getInt8Ty(*MS.C), CopySize);
+      IRB.CreateMemCpy(VAArgTLSCopy, MS.VAArgTLS, CopySize, 8);
+    }
+
+    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.getShadowPtr(GrRegSaveAreaPtr, IRB.getInt8Ty(), IRB);
+
+      Value *GrSrcPtr = IRB.CreateInBoundsGEP(IRB.getInt8Ty(), VAArgTLSCopy,
+                                              GrRegSaveAreaShadowPtrOff);
+      Value *GrCopySize = IRB.CreateSub(GrArgSize, GrRegSaveAreaShadowPtrOff);
+
+      IRB.CreateMemCpy(GrRegSaveAreaShadowPtr, GrSrcPtr, GrCopySize, 8);
+
+      // Again, but for FP/SIMD values.
+      Value *VrRegSaveAreaShadowPtrOff =
+          IRB.CreateAdd(VrArgSize, VrOffSaveArea);
+
+      Value *VrRegSaveAreaShadowPtr =
+        MSV.getShadowPtr(VrRegSaveAreaPtr, IRB.getInt8Ty(), IRB);
+
+      Value *VrSrcPtr = IRB.CreateInBoundsGEP(
+        IRB.getInt8Ty(),
+        IRB.CreateInBoundsGEP(IRB.getInt8Ty(), VAArgTLSCopy,
+                              IRB.getInt32(AArch64VrBegOffset)),
+        VrRegSaveAreaShadowPtrOff);
+      Value *VrCopySize = IRB.CreateSub(VrArgSize, VrRegSaveAreaShadowPtrOff);
+
+      IRB.CreateMemCpy(VrRegSaveAreaShadowPtr, VrSrcPtr, VrCopySize, 8);
+
+      // And finally for remaining arguments.
+      Value *StackSaveAreaShadowPtr =
+        MSV.getShadowPtr(StackSaveAreaPtr, IRB.getInt8Ty(), IRB);
+
+      Value *StackSrcPtr =
+        IRB.CreateInBoundsGEP(IRB.getInt8Ty(), VAArgTLSCopy,
+                              IRB.getInt32(AArch64VAEndOffset));
+
+      IRB.CreateMemCpy(StackSaveAreaShadowPtr, StackSrcPtr,
+                       VAArgOverflowSize, 16);
+    }
+  }
+};
+
+/// \brief 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 {}
+};
+
+VarArgHelper *CreateVarArgHelper(Function &Func, MemorySanitizer &Msan,
+                                 MemorySanitizerVisitor &Visitor) {
+  // VarArg handling is only implemented on AMD64. False positives are possible
+  // on other platforms.
+  llvm::Triple TargetTriple(Func.getParent()->getTargetTriple());
+  if (TargetTriple.getArch() == llvm::Triple::x86_64)
+    return new VarArgAMD64Helper(Func, Msan, Visitor);
+  else if (TargetTriple.getArch() == llvm::Triple::mips64 ||
+           TargetTriple.getArch() == llvm::Triple::mips64el)
+    return new VarArgMIPS64Helper(Func, Msan, Visitor);
+  else if (TargetTriple.getArch() == llvm::Triple::aarch64)
+    return new VarArgAArch64Helper(Func, Msan, Visitor);
+  else
+    return new VarArgNoOpHelper(Func, Msan, Visitor);
+}
+
+} // anonymous namespace
+
+bool MemorySanitizer::runOnFunction(Function &F) {
+  if (&F == MsanCtorFunction)
+    return false;
+  MemorySanitizerVisitor Visitor(F, *this);
+
+  // Clear out readonly/readnone attributes.
+  AttrBuilder B;
+  B.addAttribute(Attribute::ReadOnly)
+    .addAttribute(Attribute::ReadNone);
+  F.removeAttributes(AttributeSet::FunctionIndex,
+                     AttributeSet::get(F.getContext(),
+                                       AttributeSet::FunctionIndex, B));
+
+  return Visitor.runOnFunction();
+}