Initial commit of MemorySanitizer.

Compiler pass only.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168866 91177308-0d34-0410-b5e6-96231b3b80d8

7 files changed, 1660 insertions, 0 deletions

diff --git a/include/llvm/InitializePasses.h b/include/llvm/InitializePasses.h
index bde2f2ca76..ee08fe0f79 100644
--- a/include/llvm/InitializePasses.h
+++ b/include/llvm/InitializePasses.h
@@ -111,6 +111,7 @@ void initializePathProfilerPass(PassRegistry&);
 void initializeGCOVProfilerPass(PassRegistry&);
 void initializeAddressSanitizerPass(PassRegistry&);
 void initializeAddressSanitizerModulePass(PassRegistry&);
+void initializeMemorySanitizerPass(PassRegistry&);
 void initializeThreadSanitizerPass(PassRegistry&);
 void initializeEarlyCSEPass(PassRegistry&);
 void initializeExpandISelPseudosPass(PassRegistry&);
diff --git a/include/llvm/Transforms/Instrumentation.h b/include/llvm/Transforms/Instrumentation.h
index e4c60bf8d1..57b6ab3d30 100644
--- a/include/llvm/Transforms/Instrumentation.h
+++ b/include/llvm/Transforms/Instrumentation.h
@@ -36,6 +36,8 @@ ModulePass *createGCOVProfilerPass(bool EmitNotes = true, bool EmitData = true,
 // Insert AddressSanitizer (address sanity checking) instrumentation
 FunctionPass *createAddressSanitizerFunctionPass();
 ModulePass *createAddressSanitizerModulePass();
+// Insert MemorySanitizer instrumentation (detection of uninitialized reads)
+FunctionPass *createMemorySanitizerPass();
 // Insert ThreadSanitizer (race detection) instrumentation
 FunctionPass *createThreadSanitizerPass();
 
diff --git a/lib/Transforms/Instrumentation/CMakeLists.txt b/lib/Transforms/Instrumentation/CMakeLists.txt
index 058f68c7ce..1c9e053679 100644
--- a/lib/Transforms/Instrumentation/CMakeLists.txt
+++ b/lib/Transforms/Instrumentation/CMakeLists.txt
@@ -4,6 +4,7 @@ add_llvm_library(LLVMInstrumentation
   BoundsChecking.cpp
   EdgeProfiling.cpp
   GCOVProfiling.cpp
+  MemorySanitizer.cpp
   Instrumentation.cpp
   OptimalEdgeProfiling.cpp
   PathProfiling.cpp
diff --git a/lib/Transforms/Instrumentation/Instrumentation.cpp b/lib/Transforms/Instrumentation/Instrumentation.cpp
index 46394da856..8ba102559b 100644
--- a/lib/Transforms/Instrumentation/Instrumentation.cpp
+++ b/lib/Transforms/Instrumentation/Instrumentation.cpp
@@ -27,6 +27,7 @@ void llvm::initializeInstrumentation(PassRegistry &Registry) {
   initializeGCOVProfilerPass(Registry);
   initializeOptimalEdgeProfilerPass(Registry);
   initializePathProfilerPass(Registry);
+  initializeMemorySanitizerPass(Registry);
   initializeThreadSanitizerPass(Registry);
 }
 
diff --git a/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/lib/Transforms/Instrumentation/MemorySanitizer.cpp
new file mode 100644
index 0000000000..57c5003085
--- /dev/null
+++ b/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -0,0 +1,1419 @@
+//===-- 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.
+///
+/// Status: early prototype.
+///
+/// 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).
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "msan"
+
+#include "BlackList.h"
+#include "llvm/DataLayout.h"
+#include "llvm/Function.h"
+#include "llvm/InlineAsm.h"
+#include "llvm/IntrinsicInst.h"
+#include "llvm/IRBuilder.h"
+#include "llvm/LLVMContext.h"
+#include "llvm/MDBuilder.h"
+#include "llvm/Module.h"
+#include "llvm/Type.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/ValueMap.h"
+#include "llvm/Transforms/Instrumentation.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/InstVisitor.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Instrumentation.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+using namespace llvm;
+
+static const uint64_t kShadowMask32 = 1ULL << 31;
+static const uint64_t kShadowMask64 = 1ULL << 46;
+static const uint64_t kOriginOffset32 = 1ULL << 30;
+static const uint64_t kOriginOffset64 = 1ULL << 45;
+
+// This is an important flag that makes the reports much more
+// informative at the cost of greater slowdown. Not fully implemented
+// yet.
+// FIXME: this should be a top-level clang flag, e.g.
+// -fmemory-sanitizer-full.
+static cl::opt<bool> ClTrackOrigins("msan-track-origins",
+       cl::desc("Track origins (allocation sites) of poisoned memory"),
+       cl::Hidden, cl::init(false));
+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 patter"),
+       cl::Hidden, cl::init(0xff));
+
+static cl::opt<bool> ClHandleICmp("msan-handle-icmp",
+       cl::desc("propagate shadow through ICmpEQ and ICmpNE"),
+       cl::Hidden, cl::init(true));
+
+// This flag controls whether we check the shadow of the address
+// operand of load or store. Such bugs are very rare, since load from
+// a garbage address typically results in SEGV, but still happen
+// (e.g. only lower bits of address are garbage, or the access happens
+// early at program startup where malloc-ed memory is more likely to
+// be zeroed. As of 2012-08-28 this flag adds 20% slowdown.
+static cl::opt<bool> ClCheckAccessAddress("msan-check-access-address",
+       cl::desc("report accesses through a pointer which has poisoned shadow"),
+       cl::Hidden, cl::init(true));
+
+static cl::opt<bool> ClDumpStrictInstructions("msan-dump-strict-instructions",
+       cl::desc("print out instructions with default strict semantics"),
+       cl::Hidden, cl::init(false));
+
+static cl::opt<std::string>  ClBlackListFile("msan-blacklist",
+       cl::desc("File containing the list of functions where MemorySanitizer "
+                "should not report bugs"), cl::Hidden);
+
+namespace {
+
+/// \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() : FunctionPass(ID), TD(0) { }
+  const char *getPassName() const { return "MemorySanitizer"; }
+  bool runOnFunction(Function &F);
+  bool doInitialization(Module &M);
+  static char ID;  // Pass identification, replacement for typeid.
+
+private:
+  DataLayout *TD;
+  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;
+  /// \brief Run-time helper that copies origin info for a memory range.
+  Value *MsanCopyOriginFn;
+  /// \brief Run-time helper that generates a new origin value for a stack
+  /// allocation.
+  Value *MsanSetAllocaOriginFn;
+  /// \brief Run-time helper that poisons stack on function entry.
+  Value *MsanPoisonStackFn;
+  /// \brief The actual "memmove" function.
+  Value *MemmoveFn;
+
+  /// \brief Address mask used in application-to-shadow address calculation.
+  /// ShadowAddr is computed as ApplicationAddr & ~ShadowMask.
+  uint64_t ShadowMask;
+  /// \brief Offset of the origin shadow from the "normal" shadow.
+  /// OriginAddr is computed as (ShadowAddr + OriginOffset) & ~3ULL
+  uint64_t OriginOffset;
+  /// \brief Branch weights for error reporting.
+  MDNode *ColdCallWeights;
+  /// \brief The blacklist.
+  OwningPtr<BlackList> BL;
+
+  friend class MemorySanitizerVisitor;
+  friend class VarArgAMD64Helper;
+};
+}  // namespace
+
+char MemorySanitizer::ID = 0;
+INITIALIZE_PASS(MemorySanitizer, "msan",
+                "MemorySanitizer: detects uninitialized reads.",
+                false, false)
+
+FunctionPass *llvm::createMemorySanitizerPass() {
+  return new MemorySanitizer();
+}
+
+/// \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 Module-level initialization.
+///
+/// Obtains pointers to the required runtime library functions, and
+/// inserts a call to __msan_init to the module's constructor list.
+bool MemorySanitizer::doInitialization(Module &M) {
+  TD = getAnalysisIfAvailable<DataLayout>();
+  if (!TD)
+    return false;
+  BL.reset(new BlackList(ClBlackListFile));
+  C = &(M.getContext());
+  unsigned PtrSize = TD->getPointerSizeInBits(/* AddressSpace */0);
+  switch (PtrSize) {
+    case 64:
+      ShadowMask = kShadowMask64;
+      OriginOffset = kOriginOffset64;
+      break;
+    case 32:
+      ShadowMask = kShadowMask32;
+      OriginOffset = kOriginOffset32;
+      break;
+    default:
+      report_fatal_error("unsupported pointer size");
+      break;
+  }
+
+  IRBuilder<> IRB(*C);
+  IntptrTy = IRB.getIntPtrTy(TD);
+  OriginTy = IRB.getInt32Ty();
+
+  ColdCallWeights = MDBuilder(*C).createBranchWeights(1, 1000);
+
+  // Insert a call to __msan_init/__msan_track_origins into the module's CTORs.
+  appendToGlobalCtors(M, cast<Function>(M.getOrInsertFunction(
+                      "__msan_init", IRB.getVoidTy(), NULL)), 0);
+
+  new GlobalVariable(M, IRB.getInt32Ty(), true, GlobalValue::LinkOnceODRLinkage,
+                     IRB.getInt32(ClTrackOrigins), "__msan_track_origins");
+
+  // 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(), NULL);
+
+  MsanCopyOriginFn = M.getOrInsertFunction(
+    "__msan_copy_origin", IRB.getVoidTy(), IRB.getInt8PtrTy(),
+    IRB.getInt8PtrTy(), IntptrTy, NULL);
+  MsanSetAllocaOriginFn = M.getOrInsertFunction(
+    "__msan_set_alloca_origin", IRB.getVoidTy(), IRB.getInt8PtrTy(), IntptrTy,
+    IRB.getInt8PtrTy(), NULL);
+  MsanPoisonStackFn = M.getOrInsertFunction(
+    "__msan_poison_stack", IRB.getVoidTy(), IRB.getInt8PtrTy(), IntptrTy, NULL);
+  MemmoveFn = M.getOrInsertFunction(
+    "memmove", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
+    IntptrTy, NULL);
+
+  // Create globals.
+  RetvalTLS = new GlobalVariable(
+    M, ArrayType::get(IRB.getInt64Ty(), 8), false,
+    GlobalVariable::ExternalLinkage, 0, "__msan_retval_tls", 0,
+    GlobalVariable::GeneralDynamicTLSModel);
+  RetvalOriginTLS = new GlobalVariable(
+    M, OriginTy, false, GlobalVariable::ExternalLinkage, 0,
+    "__msan_retval_origin_tls", 0, GlobalVariable::GeneralDynamicTLSModel);
+
+  ParamTLS = new GlobalVariable(
+    M, ArrayType::get(IRB.getInt64Ty(), 1000), false,
+    GlobalVariable::ExternalLinkage, 0, "__msan_param_tls", 0,
+    GlobalVariable::GeneralDynamicTLSModel);
+  ParamOriginTLS = new GlobalVariable(
+    M, ArrayType::get(OriginTy, 1000), false, GlobalVariable::ExternalLinkage,
+    0, "__msan_param_origin_tls", 0, GlobalVariable::GeneralDynamicTLSModel);
+
+  VAArgTLS = new GlobalVariable(
+    M, ArrayType::get(IRB.getInt64Ty(), 1000), false,
+    GlobalVariable::ExternalLinkage, 0, "__msan_va_arg_tls", 0,
+    GlobalVariable::GeneralDynamicTLSModel);
+  VAArgOverflowSizeTLS = new GlobalVariable(
+    M, IRB.getInt64Ty(), false, GlobalVariable::ExternalLinkage, 0,
+    "__msan_va_arg_overflow_size_tls", 0,
+    GlobalVariable::GeneralDynamicTLSModel);
+  OriginTLS = new GlobalVariable(
+    M, IRB.getInt32Ty(), false, GlobalVariable::ExternalLinkage, 0,
+    "__msan_origin_tls", 0, GlobalVariable::GeneralDynamicTLSModel);
+  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;
+};
+
+struct MemorySanitizerVisitor;
+
+VarArgHelper*
+CreateVarArgHelper(Function &Func, MemorySanitizer &Msan,
+                   MemorySanitizerVisitor &Visitor);
+
+/// 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;
+  bool InsertChecks;
+  OwningPtr<VarArgHelper> VAHelper;
+
+  // 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;
+
+  struct ShadowOriginAndInsertPoint {
+    Instruction *Shadow;
+    Instruction *Origin;
+    Instruction *OrigIns;
+    ShadowOriginAndInsertPoint(Instruction *S, Instruction *O, Instruction *I)
+      : Shadow(S), Origin(O), OrigIns(I) { }
+    ShadowOriginAndInsertPoint() : Shadow(0), Origin(0), OrigIns(0) { }
+  };
+  SmallVector<ShadowOriginAndInsertPoint, 16> InstrumentationList;
+
+  MemorySanitizerVisitor(Function &F, MemorySanitizer &MS)
+    : F(F), MS(MS), VAHelper(CreateVarArgHelper(F, MS, *this)) {
+    InsertChecks = !MS.BL->isIn(F);
+    DEBUG(if (!InsertChecks)
+            dbgs() << "MemorySanitizer is not inserting checks into '"
+                   << F.getName() << "'\n");
+  }
+
+  void materializeChecks() {
+    for (size_t i = 0, n = InstrumentationList.size(); i < n; i++) {
+      Instruction *Shadow = InstrumentationList[i].Shadow;
+      Instruction *OrigIns = InstrumentationList[i].OrigIns;
+      IRBuilder<> IRB(OrigIns);
+      DEBUG(dbgs() << "  SHAD0 : " << *Shadow << "\n");
+      Value *ConvertedShadow = convertToShadowTyNoVec(Shadow, IRB);
+      DEBUG(dbgs() << "  SHAD1 : " << *ConvertedShadow << "\n");
+      Value *Cmp = IRB.CreateICmpNE(ConvertedShadow,
+                                    getCleanShadow(ConvertedShadow), "_mscmp");
+      Instruction *CheckTerm =
+        SplitBlockAndInsertIfThen(cast<Instruction>(Cmp),
+                                  /* Unreachable */ !ClKeepGoing,
+                                  MS.ColdCallWeights);
+
+      IRB.SetInsertPoint(CheckTerm);
+      if (ClTrackOrigins) {
+        Instruction *Origin = InstrumentationList[i].Origin;
+        IRB.CreateStore(Origin ? (Value*)Origin : (Value*)IRB.getInt32(0),
+                        MS.OriginTLS);
+      }
+      CallInst *Call = IRB.CreateCall(MS.WarningFn);
+      Call->setDebugLoc(OrigIns->getDebugLoc());
+      DEBUG(dbgs() << "  CHECK: " << *Cmp << "\n");
+    }
+    DEBUG(dbgs() << "DONE:\n" << F);
+  }
+
+  /// \brief Add MemorySanitizer instrumentation to a function.
+  bool runOnFunction() {
+    if (!MS.TD) return false;
+    // 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 (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
+         DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) {
+      BasicBlock *BB = *DI;
+      visit(*BB);
+    }
+
+    // Finalize PHI nodes.
+    for (size_t i = 0, n = ShadowPHINodes.size(); i < n; i++) {
+      PHINode *PN = ShadowPHINodes[i];
+      PHINode *PNS = cast<PHINode>(getShadow(PN));
+      PHINode *PNO = ClTrackOrigins ? cast<PHINode>(getOrigin(PN)) : 0;
+      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();
+
+    materializeChecks();
+
+    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 0;
+    }
+    // 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;
+    if (VectorType *VT = dyn_cast<VectorType>(OrigTy))
+      return VectorType::getInteger(VT);
+    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 = MS.TD->getTypeStoreSizeInBits(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 shadow address that corresponds to a given application
+  /// address.
+  ///
+  /// Shadow = Addr & ~ShadowMask.
+  Value *getShadowPtr(Value *Addr, Type *ShadowTy,
+                      IRBuilder<> &IRB) {
+    Value *ShadowLong =
+      IRB.CreateAnd(IRB.CreatePointerCast(Addr, MS.IntptrTy),
+                    ConstantInt::get(MS.IntptrTy, ~MS.ShadowMask));
+    return IRB.CreateIntToPtr(ShadowLong, PointerType::get(ShadowTy, 0));
+  }
+
+  /// \brief Compute the origin address that corresponds to a given application
+  /// address.
+  ///
+  /// OriginAddr = (ShadowAddr + OriginOffset) & ~3ULL
+  ///            = Addr & (~ShadowMask & ~3ULL) + OriginOffset
+  Value *getOriginPtr(Value *Addr, IRBuilder<> &IRB) {
+    Value *ShadowLong =
+      IRB.CreateAnd(IRB.CreatePointerCast(Addr, MS.IntptrTy),
+                    ConstantInt::get(MS.IntptrTy, ~MS.ShadowMask & ~3ULL));
+    Value *Add =
+      IRB.CreateAdd(ShadowLong,
+                    ConstantInt::get(MS.IntptrTy, MS.OriginOffset));
+    return IRB.CreateIntToPtr(Add, 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 (!ClTrackOrigins) return 0;
+    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] = SV;
+  }
+
+  /// \brief Set Origin to be the origin value for V.
+  void setOrigin(Value *V, Value *Origin) {
+    if (!ClTrackOrigins) 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).
+  Value *getCleanShadow(Value *V) {
+    Type *ShadowTy = getShadowTy(V);
+    if (!ShadowTy)
+      return 0;
+    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);
+    StructType *ST = 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);
+  }
+
+  /// \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 (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()));
+        assert(Shadow && "No shadow for a value");
+      }
+      return Shadow;
+    }
+    if (UndefValue *U = dyn_cast<UndefValue>(V)) {
+      Value *AllOnes = getPoisonedShadow(getShadowTy(V));
+      DEBUG(dbgs() << "Undef: " << *U << " ==> " << *AllOnes << "\n");
+      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;
+      for (Function::arg_iterator AI = F->arg_begin(), AE = F->arg_end();
+           AI != AE; ++AI) {
+        if (!AI->getType()->isSized()) {
+          DEBUG(dbgs() << "Arg is not sized\n");
+          continue;
+        }
+        unsigned Size = AI->hasByValAttr()
+          ? MS.TD->getTypeAllocSize(AI->getType()->getPointerElementType())
+          : MS.TD->getTypeAllocSize(AI->getType());
+        if (A == AI) {
+          Value *Base = getShadowPtrForArgument(AI, EntryIRB, ArgOffset);
+          if (AI->hasByValAttr()) {
+            // ByVal pointer itself has clean shadow. We copy the actual
+            // argument shadow to the underlying memory.
+            Value *Cpy = EntryIRB.CreateMemCpy(
+              getShadowPtr(V, EntryIRB.getInt8Ty(), EntryIRB),
+              Base, Size, AI->getParamAlignment());
+            DEBUG(dbgs() << "  ByValCpy: " << *Cpy << "\n");
+            *ShadowPtr = getCleanShadow(V);
+          } else {
+            *ShadowPtr = EntryIRB.CreateLoad(Base);
+          }
+          DEBUG(dbgs() << "  ARG:    "  << *AI << " ==> " <<
+                **ShadowPtr << "\n");
+          if (ClTrackOrigins) {
+            Value* OriginPtr = getOriginPtrForArgument(AI, EntryIRB, ArgOffset);
+            setOrigin(A, EntryIRB.CreateLoad(OriginPtr));
+          }
+        }
+        ArgOffset += DataLayout::RoundUpAlignment(Size, 8);
+      }
+      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 (!ClTrackOrigins) return 0;
+    if (isa<Instruction>(V) || isa<Argument>(V)) {
+      Value *Origin = OriginMap[V];
+      if (!Origin) {
+        DEBUG(dbgs() << "NO ORIGIN: " << *V << "\n");
+        Origin = getCleanOrigin();
+      }
+      return Origin;
+    }
+    return getCleanOrigin();
+  }
+
+  /// \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 value is not fully defined.
+  void insertCheck(Value *Val, Instruction *OrigIns) {
+    assert(Val);
+    if (!InsertChecks) return;
+    Instruction *Shadow = dyn_cast_or_null<Instruction>(getShadow(Val));
+    if (!Shadow) return;
+    Type *ShadowTy = Shadow->getType();
+    assert((isa<IntegerType>(ShadowTy) || isa<VectorType>(ShadowTy)) &&
+           "Can only insert checks for integer and vector shadow types");
+    Instruction *Origin = dyn_cast_or_null<Instruction>(getOrigin(Val));
+    InstrumentationList.push_back(
+      ShadowOriginAndInsertPoint(Shadow, Origin, OrigIns));
+  }
+
+  //------------------- Visitors.
+
+  /// \brief Instrument LoadInst
+  ///
+  /// Loads the corresponding shadow and (optionally) origin.
+  /// Optionally, checks that the load address is fully defined.
+  void visitLoadInst(LoadInst &I) {
+    Type *LoadTy = I.getType();
+    assert(LoadTy->isSized() && "Load type must have size");
+    IRBuilder<> IRB(&I);
+    Type *ShadowTy = getShadowTy(&I);
+    Value *Addr = I.getPointerOperand();
+    Value *ShadowPtr = getShadowPtr(Addr, ShadowTy, IRB);
+    setShadow(&I, IRB.CreateLoad(ShadowPtr, "_msld"));
+
+    if (ClCheckAccessAddress)
+      insertCheck(I.getPointerOperand(), &I);
+
+    if (ClTrackOrigins)
+      setOrigin(&I, IRB.CreateLoad(getOriginPtr(Addr, IRB)));
+  }
+
+  /// \brief Instrument StoreInst
+  ///
+  /// Stores the corresponding shadow and (optionally) origin.
+  /// Optionally, checks that the store address is fully defined.
+  /// Volatile stores check that the value being stored is fully defined.
+  void visitStoreInst(StoreInst &I) {
+    IRBuilder<> IRB(&I);
+    Value *Val = I.getValueOperand();
+    Value *Addr = I.getPointerOperand();
+    Value *Shadow = getShadow(Val);
+    Value *ShadowPtr = getShadowPtr(Addr, Shadow->getType(), IRB);
+
+    StoreInst *NewSI = IRB.CreateStore(Shadow, ShadowPtr);
+    DEBUG(dbgs() << "  STORE: " << *NewSI << "\n");
+    // If the store is volatile, add a check.
+    if (I.isVolatile())
+      insertCheck(Val, &I);
+    if (ClCheckAccessAddress)
+      insertCheck(Addr, &I);
+
+    if (ClTrackOrigins)
+      IRB.CreateStore(getOrigin(Val), getOriginPtr(Addr, IRB));
+  }
+
+  // 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) {
+    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);
+    Valu