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llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
Benjamin Kramer 47d60da931 Make helper functions static. NFC. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265653 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-07 10:10:09 +00:00

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//===-- ThreadSanitizer.cpp - race detector -------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is a part of ThreadSanitizer, a race detector.
//
// The tool is under development, for the details about previous versions see
// http://code.google.com/p/data-race-test
//
// The instrumentation phase is quite simple:
// - Insert calls to run-time library before every memory access.
// - Optimizations may apply to avoid instrumenting some of the accesses.
// - Insert calls at function entry/exit.
// The rest is handled by the run-time library.
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Instrumentation.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/CaptureTracking.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/ProfileData/InstrProf.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
using namespace llvm;
#define DEBUG_TYPE "tsan"
static cl::opt<bool> ClInstrumentMemoryAccesses(
"tsan-instrument-memory-accesses", cl::init(true),
cl::desc("Instrument memory accesses"), cl::Hidden);
static cl::opt<bool> ClInstrumentFuncEntryExit(
"tsan-instrument-func-entry-exit", cl::init(true),
cl::desc("Instrument function entry and exit"), cl::Hidden);
static cl::opt<bool> ClInstrumentAtomics(
"tsan-instrument-atomics", cl::init(true),
cl::desc("Instrument atomics"), cl::Hidden);
static cl::opt<bool> ClInstrumentMemIntrinsics(
"tsan-instrument-memintrinsics", cl::init(true),
cl::desc("Instrument memintrinsics (memset/memcpy/memmove)"), cl::Hidden);
STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
STATISTIC(NumOmittedReadsBeforeWrite,
"Number of reads ignored due to following writes");
STATISTIC(NumAccessesWithBadSize, "Number of accesses with bad size");
STATISTIC(NumInstrumentedVtableWrites, "Number of vtable ptr writes");
STATISTIC(NumInstrumentedVtableReads, "Number of vtable ptr reads");
STATISTIC(NumOmittedReadsFromConstantGlobals,
"Number of reads from constant globals");
STATISTIC(NumOmittedReadsFromVtable, "Number of vtable reads");
STATISTIC(NumOmittedNonCaptured, "Number of accesses ignored due to capturing");
static const char *const kTsanModuleCtorName = "tsan.module_ctor";
static const char *const kTsanInitName = "__tsan_init";
namespace {
/// ThreadSanitizer: instrument the code in module to find races.
struct ThreadSanitizer : public FunctionPass {
ThreadSanitizer() : FunctionPass(ID) {}
const char *getPassName() const override;
bool runOnFunction(Function &F) override;
bool doInitialization(Module &M) override;
static char ID; // Pass identification, replacement for typeid.
private:
void initializeCallbacks(Module &M);
bool instrumentLoadOrStore(Instruction *I, const DataLayout &DL);
bool instrumentAtomic(Instruction *I, const DataLayout &DL);
bool instrumentMemIntrinsic(Instruction *I);
void chooseInstructionsToInstrument(SmallVectorImpl<Instruction *> &Local,
SmallVectorImpl<Instruction *> &All,
const DataLayout &DL);
bool addrPointsToConstantData(Value *Addr);
int getMemoryAccessFuncIndex(Value *Addr, const DataLayout &DL);
Type *IntptrTy;
IntegerType *OrdTy;
// Callbacks to run-time library are computed in doInitialization.
Function *TsanFuncEntry;
Function *TsanFuncExit;
// Accesses sizes are powers of two: 1, 2, 4, 8, 16.
static const size_t kNumberOfAccessSizes = 5;
Function *TsanRead[kNumberOfAccessSizes];
Function *TsanWrite[kNumberOfAccessSizes];
Function *TsanUnalignedRead[kNumberOfAccessSizes];
Function *TsanUnalignedWrite[kNumberOfAccessSizes];
Function *TsanAtomicLoad[kNumberOfAccessSizes];
Function *TsanAtomicStore[kNumberOfAccessSizes];
Function *TsanAtomicRMW[AtomicRMWInst::LAST_BINOP + 1][kNumberOfAccessSizes];
Function *TsanAtomicCAS[kNumberOfAccessSizes];
Function *TsanAtomicThreadFence;
Function *TsanAtomicSignalFence;
Function *TsanVptrUpdate;
Function *TsanVptrLoad;
Function *MemmoveFn, *MemcpyFn, *MemsetFn;
Function *TsanCtorFunction;
};
} // namespace
char ThreadSanitizer::ID = 0;
INITIALIZE_PASS(ThreadSanitizer, "tsan",
"ThreadSanitizer: detects data races.",
false, false)
const char *ThreadSanitizer::getPassName() const {
return "ThreadSanitizer";
}
FunctionPass *llvm::createThreadSanitizerPass() {
return new ThreadSanitizer();
}
void ThreadSanitizer::initializeCallbacks(Module &M) {
IRBuilder<> IRB(M.getContext());
// Initialize the callbacks.
TsanFuncEntry = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
"__tsan_func_entry", IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
TsanFuncExit = checkSanitizerInterfaceFunction(
M.getOrInsertFunction("__tsan_func_exit", IRB.getVoidTy(), nullptr));
OrdTy = IRB.getInt32Ty();
for (size_t i = 0; i < kNumberOfAccessSizes; ++i) {
const unsigned ByteSize = 1U << i;
const unsigned BitSize = ByteSize * 8;
std::string ByteSizeStr = utostr(ByteSize);
std::string BitSizeStr = utostr(BitSize);
SmallString<32> ReadName("__tsan_read" + ByteSizeStr);
TsanRead[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
ReadName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
SmallString<32> WriteName("__tsan_write" + ByteSizeStr);
TsanWrite[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
WriteName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
SmallString<64> UnalignedReadName("__tsan_unaligned_read" + ByteSizeStr);
TsanUnalignedRead[i] =
checkSanitizerInterfaceFunction(M.getOrInsertFunction(
UnalignedReadName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
SmallString<64> UnalignedWriteName("__tsan_unaligned_write" + ByteSizeStr);
TsanUnalignedWrite[i] =
checkSanitizerInterfaceFunction(M.getOrInsertFunction(
UnalignedWriteName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
Type *Ty = Type::getIntNTy(M.getContext(), BitSize);
Type *PtrTy = Ty->getPointerTo();
SmallString<32> AtomicLoadName("__tsan_atomic" + BitSizeStr + "_load");
TsanAtomicLoad[i] = checkSanitizerInterfaceFunction(
M.getOrInsertFunction(AtomicLoadName, Ty, PtrTy, OrdTy, nullptr));
SmallString<32> AtomicStoreName("__tsan_atomic" + BitSizeStr + "_store");
TsanAtomicStore[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
AtomicStoreName, IRB.getVoidTy(), PtrTy, Ty, OrdTy, nullptr));
for (int op = AtomicRMWInst::FIRST_BINOP;
op <= AtomicRMWInst::LAST_BINOP; ++op) {
TsanAtomicRMW[op][i] = nullptr;
const char *NamePart = nullptr;
if (op == AtomicRMWInst::Xchg)
NamePart = "_exchange";
else if (op == AtomicRMWInst::Add)
NamePart = "_fetch_add";
else if (op == AtomicRMWInst::Sub)
NamePart = "_fetch_sub";
else if (op == AtomicRMWInst::And)
NamePart = "_fetch_and";
else if (op == AtomicRMWInst::Or)
NamePart = "_fetch_or";
else if (op == AtomicRMWInst::Xor)
NamePart = "_fetch_xor";
else if (op == AtomicRMWInst::Nand)
NamePart = "_fetch_nand";
else
continue;
SmallString<32> RMWName("__tsan_atomic" + itostr(BitSize) + NamePart);
TsanAtomicRMW[op][i] = checkSanitizerInterfaceFunction(
M.getOrInsertFunction(RMWName, Ty, PtrTy, Ty, OrdTy, nullptr));
}
SmallString<32> AtomicCASName("__tsan_atomic" + BitSizeStr +
"_compare_exchange_val");
TsanAtomicCAS[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
AtomicCASName, Ty, PtrTy, Ty, Ty, OrdTy, OrdTy, nullptr));
}
TsanVptrUpdate = checkSanitizerInterfaceFunction(
M.getOrInsertFunction("__tsan_vptr_update", IRB.getVoidTy(),
IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), nullptr));
TsanVptrLoad = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
"__tsan_vptr_read", IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
TsanAtomicThreadFence = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
"__tsan_atomic_thread_fence", IRB.getVoidTy(), OrdTy, nullptr));
TsanAtomicSignalFence = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
"__tsan_atomic_signal_fence", IRB.getVoidTy(), OrdTy, nullptr));
MemmoveFn = checkSanitizerInterfaceFunction(
M.getOrInsertFunction("memmove", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
IRB.getInt8PtrTy(), IntptrTy, nullptr));
MemcpyFn = checkSanitizerInterfaceFunction(
M.getOrInsertFunction("memcpy", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
IRB.getInt8PtrTy(), IntptrTy, nullptr));
MemsetFn = checkSanitizerInterfaceFunction(
M.getOrInsertFunction("memset", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
IRB.getInt32Ty(), IntptrTy, nullptr));
}
bool ThreadSanitizer::doInitialization(Module &M) {
const DataLayout &DL = M.getDataLayout();
IntptrTy = DL.getIntPtrType(M.getContext());
std::tie(TsanCtorFunction, std::ignore) = createSanitizerCtorAndInitFunctions(
M, kTsanModuleCtorName, kTsanInitName, /*InitArgTypes=*/{},
/*InitArgs=*/{});
appendToGlobalCtors(M, TsanCtorFunction, 0);
return true;
}
static bool isVtableAccess(Instruction *I) {
if (MDNode *Tag = I->getMetadata(LLVMContext::MD_tbaa))
return Tag->isTBAAVtableAccess();
return false;
}
// Do not instrument known races/"benign races" that come from compiler
// instrumentatin. The user has no way of suppressing them.
static bool shouldInstrumentReadWriteFromAddress(Value *Addr) {
// Peel off GEPs and BitCasts.
Addr = Addr->stripInBoundsOffsets();
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
if (GV->hasSection()) {
StringRef SectionName = GV->getSection();
// Check if the global is in the PGO counters section.
if (SectionName.endswith(getInstrProfCountersSectionName(
/*AddSegment=*/false)))
return false;
}
}
return true;
}
bool ThreadSanitizer::addrPointsToConstantData(Value *Addr) {
// If this is a GEP, just analyze its pointer operand.
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Addr))
Addr = GEP->getPointerOperand();
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
if (GV->isConstant()) {
// Reads from constant globals can not race with any writes.
NumOmittedReadsFromConstantGlobals++;
return true;
}
} else if (LoadInst *L = dyn_cast<LoadInst>(Addr)) {
if (isVtableAccess(L)) {
// Reads from a vtable pointer can not race with any writes.
NumOmittedReadsFromVtable++;
return true;
}
}
return false;
}
// Instrumenting some of the accesses may be proven redundant.
// Currently handled:
// - read-before-write (within same BB, no calls between)
// - not captured variables
//
// We do not handle some of the patterns that should not survive
// after the classic compiler optimizations.
// E.g. two reads from the same temp should be eliminated by CSE,
// two writes should be eliminated by DSE, etc.
//
// 'Local' is a vector of insns within the same BB (no calls between).
// 'All' is a vector of insns that will be instrumented.
void ThreadSanitizer::chooseInstructionsToInstrument(
SmallVectorImpl<Instruction *> &Local, SmallVectorImpl<Instruction *> &All,
const DataLayout &DL) {
SmallSet<Value*, 8> WriteTargets;
// Iterate from the end.
for (SmallVectorImpl<Instruction*>::reverse_iterator It = Local.rbegin(),
E = Local.rend(); It != E; ++It) {
Instruction *I = *It;
if (StoreInst *Store = dyn_cast<StoreInst>(I)) {
Value *Addr = Store->getPointerOperand();
if (!shouldInstrumentReadWriteFromAddress(Addr))
continue;
WriteTargets.insert(Addr);
} else {
LoadInst *Load = cast<LoadInst>(I);
Value *Addr = Load->getPointerOperand();
if (!shouldInstrumentReadWriteFromAddress(Addr))
continue;
if (WriteTargets.count(Addr)) {
// We will write to this temp, so no reason to analyze the read.
NumOmittedReadsBeforeWrite++;
continue;
}
if (addrPointsToConstantData(Addr)) {
// Addr points to some constant data -- it can not race with any writes.
continue;
}
}
Value *Addr = isa<StoreInst>(*I)
? cast<StoreInst>(I)->getPointerOperand()
: cast<LoadInst>(I)->getPointerOperand();
if (isa<AllocaInst>(GetUnderlyingObject(Addr, DL)) &&
!PointerMayBeCaptured(Addr, true, true)) {
// The variable is addressable but not captured, so it cannot be
// referenced from a different thread and participate in a data race
// (see llvm/Analysis/CaptureTracking.h for details).
NumOmittedNonCaptured++;
continue;
}
All.push_back(I);
}
Local.clear();
}
static bool isAtomic(Instruction *I) {
if (LoadInst *LI = dyn_cast<LoadInst>(I))
return LI->isAtomic() && LI->getSynchScope() == CrossThread;
if (StoreInst *SI = dyn_cast<StoreInst>(I))
return SI->isAtomic() && SI->getSynchScope() == CrossThread;
if (isa<AtomicRMWInst>(I))
return true;
if (isa<AtomicCmpXchgInst>(I))
return true;
if (isa<FenceInst>(I))
return true;
return false;
}
bool ThreadSanitizer::runOnFunction(Function &F) {
// This is required to prevent instrumenting call to __tsan_init from within
// the module constructor.
if (&F == TsanCtorFunction)
return false;
initializeCallbacks(*F.getParent());
SmallVector<Instruction*, 8> RetVec;
SmallVector<Instruction*, 8> AllLoadsAndStores;
SmallVector<Instruction*, 8> LocalLoadsAndStores;
SmallVector<Instruction*, 8> AtomicAccesses;
SmallVector<Instruction*, 8> MemIntrinCalls;
bool Res = false;
bool HasCalls = false;
bool SanitizeFunction = F.hasFnAttribute(Attribute::SanitizeThread);
const DataLayout &DL = F.getParent()->getDataLayout();
// Traverse all instructions, collect loads/stores/returns, check for calls.
for (auto &BB : F) {
for (auto &Inst : BB) {
if (isAtomic(&Inst))
AtomicAccesses.push_back(&Inst);
else if (isa<LoadInst>(Inst) || isa<StoreInst>(Inst))
LocalLoadsAndStores.push_back(&Inst);
else if (isa<ReturnInst>(Inst))
RetVec.push_back(&Inst);
else if (isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) {
if (isa<MemIntrinsic>(Inst))
MemIntrinCalls.push_back(&Inst);
HasCalls = true;
chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores,
DL);
}
}
chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores, DL);
}
// We have collected all loads and stores.
// FIXME: many of these accesses do not need to be checked for races
// (e.g. variables that do not escape, etc).
// Instrument memory accesses only if we want to report bugs in the function.
if (ClInstrumentMemoryAccesses && SanitizeFunction)
for (auto Inst : AllLoadsAndStores) {
Res |= instrumentLoadOrStore(Inst, DL);
}
// Instrument atomic memory accesses in any case (they can be used to
// implement synchronization).
if (ClInstrumentAtomics)
for (auto Inst : AtomicAccesses) {
Res |= instrumentAtomic(Inst, DL);
}
if (ClInstrumentMemIntrinsics && SanitizeFunction)
for (auto Inst : MemIntrinCalls) {
Res |= instrumentMemIntrinsic(Inst);
}
// Instrument function entry/exit points if there were instrumented accesses.
if ((Res || HasCalls) && ClInstrumentFuncEntryExit) {
IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
Value *ReturnAddress = IRB.CreateCall(
Intrinsic::getDeclaration(F.getParent(), Intrinsic::returnaddress),
IRB.getInt32(0));
IRB.CreateCall(TsanFuncEntry, ReturnAddress);
for (auto RetInst : RetVec) {
IRBuilder<> IRBRet(RetInst);
IRBRet.CreateCall(TsanFuncExit, {});
}
Res = true;
}
return Res;
}
bool ThreadSanitizer::instrumentLoadOrStore(Instruction *I,
const DataLayout &DL) {
IRBuilder<> IRB(I);
bool IsWrite = isa<StoreInst>(*I);
Value *Addr = IsWrite
? cast<StoreInst>(I)->getPointerOperand()
: cast<LoadInst>(I)->getPointerOperand();
int Idx = getMemoryAccessFuncIndex(Addr, DL);
if (Idx < 0)
return false;
if (IsWrite && isVtableAccess(I)) {
DEBUG(dbgs() << " VPTR : " << *I << "\n");
Value *StoredValue = cast<StoreInst>(I)->getValueOperand();
// StoredValue may be a vector type if we are storing several vptrs at once.
// In this case, just take the first element of the vector since this is
// enough to find vptr races.
if (isa<VectorType>(StoredValue->getType()))
StoredValue = IRB.CreateExtractElement(
StoredValue, ConstantInt::get(IRB.getInt32Ty(), 0));
if (StoredValue->getType()->isIntegerTy())
StoredValue = IRB.CreateIntToPtr(StoredValue, IRB.getInt8PtrTy());
// Call TsanVptrUpdate.
IRB.CreateCall(TsanVptrUpdate,
{IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()),
IRB.CreatePointerCast(StoredValue, IRB.getInt8PtrTy())});
NumInstrumentedVtableWrites++;
return true;
}
if (!IsWrite && isVtableAccess(I)) {
IRB.CreateCall(TsanVptrLoad,
IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
NumInstrumentedVtableReads++;
return true;
}
const unsigned Alignment = IsWrite
? cast<StoreInst>(I)->getAlignment()
: cast<LoadInst>(I)->getAlignment();
Type *OrigTy = cast<PointerType>(Addr->getType())->getElementType();
const uint32_t TypeSize = DL.getTypeStoreSizeInBits(OrigTy);
Value *OnAccessFunc = nullptr;
if (Alignment == 0 || Alignment >= 8 || (Alignment % (TypeSize / 8)) == 0)
OnAccessFunc = IsWrite ? TsanWrite[Idx] : TsanRead[Idx];
else
OnAccessFunc = IsWrite ? TsanUnalignedWrite[Idx] : TsanUnalignedRead[Idx];
IRB.CreateCall(OnAccessFunc, IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
if (IsWrite) NumInstrumentedWrites++;
else NumInstrumentedReads++;
return true;
}
static ConstantInt *createOrdering(IRBuilder<> *IRB, AtomicOrdering ord) {
uint32_t v = 0;
switch (ord) {
case AtomicOrdering::NotAtomic:
llvm_unreachable("unexpected atomic ordering!");
case AtomicOrdering::Unordered: // Fall-through.
case AtomicOrdering::Monotonic: v = 0; break;
// Not specified yet:
// case AtomicOrdering::Consume: v = 1; break;
case AtomicOrdering::Acquire: v = 2; break;
case AtomicOrdering::Release: v = 3; break;
case AtomicOrdering::AcquireRelease: v = 4; break;
case AtomicOrdering::SequentiallyConsistent: v = 5; break;
}
return IRB->getInt32(v);
}
// If a memset intrinsic gets inlined by the code gen, we will miss races on it.
// So, we either need to ensure the intrinsic is not inlined, or instrument it.
// We do not instrument memset/memmove/memcpy intrinsics (too complicated),
// instead we simply replace them with regular function calls, which are then
// intercepted by the run-time.
// Since tsan is running after everyone else, the calls should not be
// replaced back with intrinsics. If that becomes wrong at some point,
// we will need to call e.g. __tsan_memset to avoid the intrinsics.
bool ThreadSanitizer::instrumentMemIntrinsic(Instruction *I) {
IRBuilder<> IRB(I);
if (MemSetInst *M = dyn_cast<MemSetInst>(I)) {
IRB.CreateCall(
MemsetFn,
{IRB.CreatePointerCast(M->getArgOperand(0), IRB.getInt8PtrTy()),
IRB.CreateIntCast(M->getArgOperand(1), IRB.getInt32Ty(), false),
IRB.CreateIntCast(M->getArgOperand(2), IntptrTy, false)});
I->eraseFromParent();
} else if (MemTransferInst *M = dyn_cast<MemTransferInst>(I)) {
IRB.CreateCall(
isa<MemCpyInst>(M) ? MemcpyFn : MemmoveFn,
{IRB.CreatePointerCast(M->getArgOperand(0), IRB.getInt8PtrTy()),
IRB.CreatePointerCast(M->getArgOperand(1), IRB.getInt8PtrTy()),
IRB.CreateIntCast(M->getArgOperand(2), IntptrTy, false)});
I->eraseFromParent();
}
return false;
}
static Value *createIntOrPtrToIntCast(Value *V, Type* Ty, IRBuilder<> &IRB) {
return isa<PointerType>(V->getType()) ?
IRB.CreatePtrToInt(V, Ty) : IRB.CreateIntCast(V, Ty, false);
}
// Both llvm and ThreadSanitizer atomic operations are based on C++11/C1x
// standards. For background see C++11 standard. A slightly older, publicly
// available draft of the standard (not entirely up-to-date, but close enough
// for casual browsing) is available here:
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf
// The following page contains more background information:
// http://www.hpl.hp.com/personal/Hans_Boehm/c++mm/
bool ThreadSanitizer::instrumentAtomic(Instruction *I, const DataLayout &DL) {
IRBuilder<> IRB(I);
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
Value *Addr = LI->getPointerOperand();
int Idx = getMemoryAccessFuncIndex(Addr, DL);
if (Idx < 0)
return false;
const unsigned ByteSize = 1U << Idx;
const unsigned BitSize = ByteSize * 8;
Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
Type *PtrTy = Ty->getPointerTo();
Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
createOrdering(&IRB, LI->getOrdering())};
Type *OrigTy = cast<PointerType>(Addr->getType())->getElementType();
if (Ty == OrigTy) {
Instruction *C = CallInst::Create(TsanAtomicLoad[Idx], Args);
ReplaceInstWithInst(I, C);
} else {
// We are loading a pointer, so we need to cast the return value.
Value *C = IRB.CreateCall(TsanAtomicLoad[Idx], Args);
Instruction *Cast = CastInst::Create(Instruction::IntToPtr, C, OrigTy);
ReplaceInstWithInst(I, Cast);
}
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
Value *Addr = SI->getPointerOperand();
int Idx = getMemoryAccessFuncIndex(Addr, DL);
if (Idx < 0)
return false;
const unsigned ByteSize = 1U << Idx;
const unsigned BitSize = ByteSize * 8;
Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
Type *PtrTy = Ty->getPointerTo();
Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
createIntOrPtrToIntCast(SI->getValueOperand(), Ty, IRB),
createOrdering(&IRB, SI->getOrdering())};
CallInst *C = CallInst::Create(TsanAtomicStore[Idx], Args);
ReplaceInstWithInst(I, C);
} else if (AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(I)) {
Value *Addr = RMWI->getPointerOperand();
int Idx = getMemoryAccessFuncIndex(Addr, DL);
if (Idx < 0)
return false;
Function *F = TsanAtomicRMW[RMWI->getOperation()][Idx];
if (!F)
return false;
const unsigned ByteSize = 1U << Idx;
const unsigned BitSize = ByteSize * 8;
Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
Type *PtrTy = Ty->getPointerTo();
Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
IRB.CreateIntCast(RMWI->getValOperand(), Ty, false),
createOrdering(&IRB, RMWI->getOrdering())};
CallInst *C = CallInst::Create(F, Args);
ReplaceInstWithInst(I, C);
} else if (AtomicCmpXchgInst *CASI = dyn_cast<AtomicCmpXchgInst>(I)) {
Value *Addr = CASI->getPointerOperand();
int Idx = getMemoryAccessFuncIndex(Addr, DL);
if (Idx < 0)
return false;
const unsigned ByteSize = 1U << Idx;
const unsigned BitSize = ByteSize * 8;
Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
Type *PtrTy = Ty->getPointerTo();
Value *CmpOperand =
createIntOrPtrToIntCast(CASI->getCompareOperand(), Ty, IRB);
Value *NewOperand =
createIntOrPtrToIntCast(CASI->getNewValOperand(), Ty, IRB);
Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
CmpOperand,
NewOperand,
createOrdering(&IRB, CASI->getSuccessOrdering()),
createOrdering(&IRB, CASI->getFailureOrdering())};
CallInst *C = IRB.CreateCall(TsanAtomicCAS[Idx], Args);
Value *Success = IRB.CreateICmpEQ(C, CmpOperand);
Value *OldVal = C;
Type *OrigOldValTy = CASI->getNewValOperand()->getType();
if (Ty != OrigOldValTy) {
// The value is a pointer, so we need to cast the return value.
OldVal = IRB.CreateIntToPtr(C, OrigOldValTy);
}
Value *Res =
IRB.CreateInsertValue(UndefValue::get(CASI->getType()), OldVal, 0);
Res = IRB.CreateInsertValue(Res, Success, 1);
I->replaceAllUsesWith(Res);
I->eraseFromParent();
} else if (FenceInst *FI = dyn_cast<FenceInst>(I)) {
Value *Args[] = {createOrdering(&IRB, FI->getOrdering())};
Function *F = FI->getSynchScope() == SingleThread ?
TsanAtomicSignalFence : TsanAtomicThreadFence;
CallInst *C = CallInst::Create(F, Args);
ReplaceInstWithInst(I, C);
}
return true;
}
int ThreadSanitizer::getMemoryAccessFuncIndex(Value *Addr,
const DataLayout &DL) {
Type *OrigPtrTy = Addr->getType();
Type *OrigTy = cast<PointerType>(OrigPtrTy)->getElementType();
assert(OrigTy->isSized());
uint32_t TypeSize = DL.getTypeStoreSizeInBits(OrigTy);
if (TypeSize != 8 && TypeSize != 16 &&
TypeSize != 32 && TypeSize != 64 && TypeSize != 128) {
NumAccessesWithBadSize++;
// Ignore all unusual sizes.
return -1;
}
size_t Idx = countTrailingZeros(TypeSize / 8);
assert(Idx < kNumberOfAccessSizes);
return Idx;
}
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