1//===-- ThreadSanitizer.cpp - race detector -------------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file is a part of ThreadSanitizer, a race detector.
11//
12// The tool is under development, for the details about previous versions see
13// http://code.google.com/p/data-race-test
14//
15// The instrumentation phase is quite simple:
16//   - Insert calls to run-time library before every memory access.
17//      - Optimizations may apply to avoid instrumenting some of the accesses.
18//   - Insert calls at function entry/exit.
19// The rest is handled by the run-time library.
20//===----------------------------------------------------------------------===//
21
22#include "llvm/Transforms/Instrumentation.h"
23#include "llvm/ADT/SmallSet.h"
24#include "llvm/ADT/SmallString.h"
25#include "llvm/ADT/SmallVector.h"
26#include "llvm/ADT/Statistic.h"
27#include "llvm/ADT/StringExtras.h"
28#include "llvm/Analysis/CaptureTracking.h"
29#include "llvm/Analysis/ValueTracking.h"
30#include "llvm/IR/DataLayout.h"
31#include "llvm/IR/Function.h"
32#include "llvm/IR/IRBuilder.h"
33#include "llvm/IR/IntrinsicInst.h"
34#include "llvm/IR/Intrinsics.h"
35#include "llvm/IR/LLVMContext.h"
36#include "llvm/IR/Metadata.h"
37#include "llvm/IR/Module.h"
38#include "llvm/IR/Type.h"
39#include "llvm/Support/CommandLine.h"
40#include "llvm/Support/Debug.h"
41#include "llvm/Support/MathExtras.h"
42#include "llvm/Support/raw_ostream.h"
43#include "llvm/Transforms/Utils/BasicBlockUtils.h"
44#include "llvm/Transforms/Utils/ModuleUtils.h"
45
46using namespace llvm;
47
48#define DEBUG_TYPE "tsan"
49
50static cl::opt<bool>  ClInstrumentMemoryAccesses(
51    "tsan-instrument-memory-accesses", cl::init(true),
52    cl::desc("Instrument memory accesses"), cl::Hidden);
53static cl::opt<bool>  ClInstrumentFuncEntryExit(
54    "tsan-instrument-func-entry-exit", cl::init(true),
55    cl::desc("Instrument function entry and exit"), cl::Hidden);
56static cl::opt<bool>  ClInstrumentAtomics(
57    "tsan-instrument-atomics", cl::init(true),
58    cl::desc("Instrument atomics"), cl::Hidden);
59static cl::opt<bool>  ClInstrumentMemIntrinsics(
60    "tsan-instrument-memintrinsics", cl::init(true),
61    cl::desc("Instrument memintrinsics (memset/memcpy/memmove)"), cl::Hidden);
62
63STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
64STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
65STATISTIC(NumOmittedReadsBeforeWrite,
66          "Number of reads ignored due to following writes");
67STATISTIC(NumAccessesWithBadSize, "Number of accesses with bad size");
68STATISTIC(NumInstrumentedVtableWrites, "Number of vtable ptr writes");
69STATISTIC(NumInstrumentedVtableReads, "Number of vtable ptr reads");
70STATISTIC(NumOmittedReadsFromConstantGlobals,
71          "Number of reads from constant globals");
72STATISTIC(NumOmittedReadsFromVtable, "Number of vtable reads");
73STATISTIC(NumOmittedNonCaptured, "Number of accesses ignored due to capturing");
74
75namespace {
76
77/// ThreadSanitizer: instrument the code in module to find races.
78struct ThreadSanitizer : public FunctionPass {
79  ThreadSanitizer() : FunctionPass(ID) {}
80  const char *getPassName() const override;
81  bool runOnFunction(Function &F) override;
82  bool doInitialization(Module &M) override;
83  static char ID;  // Pass identification, replacement for typeid.
84
85 private:
86  void initializeCallbacks(Module &M);
87  bool instrumentLoadOrStore(Instruction *I, const DataLayout &DL);
88  bool instrumentAtomic(Instruction *I, const DataLayout &DL);
89  bool instrumentMemIntrinsic(Instruction *I);
90  void chooseInstructionsToInstrument(SmallVectorImpl<Instruction *> &Local,
91                                      SmallVectorImpl<Instruction *> &All,
92                                      const DataLayout &DL);
93  bool addrPointsToConstantData(Value *Addr);
94  int getMemoryAccessFuncIndex(Value *Addr, const DataLayout &DL);
95
96  Type *IntptrTy;
97  IntegerType *OrdTy;
98  // Callbacks to run-time library are computed in doInitialization.
99  Function *TsanFuncEntry;
100  Function *TsanFuncExit;
101  // Accesses sizes are powers of two: 1, 2, 4, 8, 16.
102  static const size_t kNumberOfAccessSizes = 5;
103  Function *TsanRead[kNumberOfAccessSizes];
104  Function *TsanWrite[kNumberOfAccessSizes];
105  Function *TsanUnalignedRead[kNumberOfAccessSizes];
106  Function *TsanUnalignedWrite[kNumberOfAccessSizes];
107  Function *TsanAtomicLoad[kNumberOfAccessSizes];
108  Function *TsanAtomicStore[kNumberOfAccessSizes];
109  Function *TsanAtomicRMW[AtomicRMWInst::LAST_BINOP + 1][kNumberOfAccessSizes];
110  Function *TsanAtomicCAS[kNumberOfAccessSizes];
111  Function *TsanAtomicThreadFence;
112  Function *TsanAtomicSignalFence;
113  Function *TsanVptrUpdate;
114  Function *TsanVptrLoad;
115  Function *MemmoveFn, *MemcpyFn, *MemsetFn;
116};
117}  // namespace
118
119char ThreadSanitizer::ID = 0;
120INITIALIZE_PASS(ThreadSanitizer, "tsan",
121    "ThreadSanitizer: detects data races.",
122    false, false)
123
124const char *ThreadSanitizer::getPassName() const {
125  return "ThreadSanitizer";
126}
127
128FunctionPass *llvm::createThreadSanitizerPass() {
129  return new ThreadSanitizer();
130}
131
132void ThreadSanitizer::initializeCallbacks(Module &M) {
133  IRBuilder<> IRB(M.getContext());
134  // Initialize the callbacks.
135  TsanFuncEntry = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
136      "__tsan_func_entry", IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
137  TsanFuncExit = checkSanitizerInterfaceFunction(
138      M.getOrInsertFunction("__tsan_func_exit", IRB.getVoidTy(), nullptr));
139  OrdTy = IRB.getInt32Ty();
140  for (size_t i = 0; i < kNumberOfAccessSizes; ++i) {
141    const size_t ByteSize = 1 << i;
142    const size_t BitSize = ByteSize * 8;
143    SmallString<32> ReadName("__tsan_read" + itostr(ByteSize));
144    TsanRead[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
145        ReadName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
146
147    SmallString<32> WriteName("__tsan_write" + itostr(ByteSize));
148    TsanWrite[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
149        WriteName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
150
151    SmallString<64> UnalignedReadName("__tsan_unaligned_read" +
152        itostr(ByteSize));
153    TsanUnalignedRead[i] =
154        checkSanitizerInterfaceFunction(M.getOrInsertFunction(
155            UnalignedReadName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
156
157    SmallString<64> UnalignedWriteName("__tsan_unaligned_write" +
158        itostr(ByteSize));
159    TsanUnalignedWrite[i] =
160        checkSanitizerInterfaceFunction(M.getOrInsertFunction(
161            UnalignedWriteName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
162
163    Type *Ty = Type::getIntNTy(M.getContext(), BitSize);
164    Type *PtrTy = Ty->getPointerTo();
165    SmallString<32> AtomicLoadName("__tsan_atomic" + itostr(BitSize) +
166                                   "_load");
167    TsanAtomicLoad[i] = checkSanitizerInterfaceFunction(
168        M.getOrInsertFunction(AtomicLoadName, Ty, PtrTy, OrdTy, nullptr));
169
170    SmallString<32> AtomicStoreName("__tsan_atomic" + itostr(BitSize) +
171                                    "_store");
172    TsanAtomicStore[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
173        AtomicStoreName, IRB.getVoidTy(), PtrTy, Ty, OrdTy, nullptr));
174
175    for (int op = AtomicRMWInst::FIRST_BINOP;
176        op <= AtomicRMWInst::LAST_BINOP; ++op) {
177      TsanAtomicRMW[op][i] = nullptr;
178      const char *NamePart = nullptr;
179      if (op == AtomicRMWInst::Xchg)
180        NamePart = "_exchange";
181      else if (op == AtomicRMWInst::Add)
182        NamePart = "_fetch_add";
183      else if (op == AtomicRMWInst::Sub)
184        NamePart = "_fetch_sub";
185      else if (op == AtomicRMWInst::And)
186        NamePart = "_fetch_and";
187      else if (op == AtomicRMWInst::Or)
188        NamePart = "_fetch_or";
189      else if (op == AtomicRMWInst::Xor)
190        NamePart = "_fetch_xor";
191      else if (op == AtomicRMWInst::Nand)
192        NamePart = "_fetch_nand";
193      else
194        continue;
195      SmallString<32> RMWName("__tsan_atomic" + itostr(BitSize) + NamePart);
196      TsanAtomicRMW[op][i] = checkSanitizerInterfaceFunction(
197          M.getOrInsertFunction(RMWName, Ty, PtrTy, Ty, OrdTy, nullptr));
198    }
199
200    SmallString<32> AtomicCASName("__tsan_atomic" + itostr(BitSize) +
201                                  "_compare_exchange_val");
202    TsanAtomicCAS[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
203        AtomicCASName, Ty, PtrTy, Ty, Ty, OrdTy, OrdTy, nullptr));
204  }
205  TsanVptrUpdate = checkSanitizerInterfaceFunction(
206      M.getOrInsertFunction("__tsan_vptr_update", IRB.getVoidTy(),
207                            IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), nullptr));
208  TsanVptrLoad = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
209      "__tsan_vptr_read", IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
210  TsanAtomicThreadFence = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
211      "__tsan_atomic_thread_fence", IRB.getVoidTy(), OrdTy, nullptr));
212  TsanAtomicSignalFence = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
213      "__tsan_atomic_signal_fence", IRB.getVoidTy(), OrdTy, nullptr));
214
215  MemmoveFn = checkSanitizerInterfaceFunction(
216      M.getOrInsertFunction("memmove", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
217                            IRB.getInt8PtrTy(), IntptrTy, nullptr));
218  MemcpyFn = checkSanitizerInterfaceFunction(
219      M.getOrInsertFunction("memcpy", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
220                            IRB.getInt8PtrTy(), IntptrTy, nullptr));
221  MemsetFn = checkSanitizerInterfaceFunction(
222      M.getOrInsertFunction("memset", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
223                            IRB.getInt32Ty(), IntptrTy, nullptr));
224}
225
226bool ThreadSanitizer::doInitialization(Module &M) {
227  const DataLayout &DL = M.getDataLayout();
228
229  // Always insert a call to __tsan_init into the module's CTORs.
230  IRBuilder<> IRB(M.getContext());
231  IntptrTy = IRB.getIntPtrTy(DL);
232  Value *TsanInit = M.getOrInsertFunction("__tsan_init",
233                                          IRB.getVoidTy(), nullptr);
234  appendToGlobalCtors(M, cast<Function>(TsanInit), 0);
235
236  return true;
237}
238
239static bool isVtableAccess(Instruction *I) {
240  if (MDNode *Tag = I->getMetadata(LLVMContext::MD_tbaa))
241    return Tag->isTBAAVtableAccess();
242  return false;
243}
244
245bool ThreadSanitizer::addrPointsToConstantData(Value *Addr) {
246  // If this is a GEP, just analyze its pointer operand.
247  if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Addr))
248    Addr = GEP->getPointerOperand();
249
250  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
251    if (GV->isConstant()) {
252      // Reads from constant globals can not race with any writes.
253      NumOmittedReadsFromConstantGlobals++;
254      return true;
255    }
256  } else if (LoadInst *L = dyn_cast<LoadInst>(Addr)) {
257    if (isVtableAccess(L)) {
258      // Reads from a vtable pointer can not race with any writes.
259      NumOmittedReadsFromVtable++;
260      return true;
261    }
262  }
263  return false;
264}
265
266// Instrumenting some of the accesses may be proven redundant.
267// Currently handled:
268//  - read-before-write (within same BB, no calls between)
269//  - not captured variables
270//
271// We do not handle some of the patterns that should not survive
272// after the classic compiler optimizations.
273// E.g. two reads from the same temp should be eliminated by CSE,
274// two writes should be eliminated by DSE, etc.
275//
276// 'Local' is a vector of insns within the same BB (no calls between).
277// 'All' is a vector of insns that will be instrumented.
278void ThreadSanitizer::chooseInstructionsToInstrument(
279    SmallVectorImpl<Instruction *> &Local, SmallVectorImpl<Instruction *> &All,
280    const DataLayout &DL) {
281  SmallSet<Value*, 8> WriteTargets;
282  // Iterate from the end.
283  for (SmallVectorImpl<Instruction*>::reverse_iterator It = Local.rbegin(),
284       E = Local.rend(); It != E; ++It) {
285    Instruction *I = *It;
286    if (StoreInst *Store = dyn_cast<StoreInst>(I)) {
287      WriteTargets.insert(Store->getPointerOperand());
288    } else {
289      LoadInst *Load = cast<LoadInst>(I);
290      Value *Addr = Load->getPointerOperand();
291      if (WriteTargets.count(Addr)) {
292        // We will write to this temp, so no reason to analyze the read.
293        NumOmittedReadsBeforeWrite++;
294        continue;
295      }
296      if (addrPointsToConstantData(Addr)) {
297        // Addr points to some constant data -- it can not race with any writes.
298        continue;
299      }
300    }
301    Value *Addr = isa<StoreInst>(*I)
302        ? cast<StoreInst>(I)->getPointerOperand()
303        : cast<LoadInst>(I)->getPointerOperand();
304    if (isa<AllocaInst>(GetUnderlyingObject(Addr, DL)) &&
305        !PointerMayBeCaptured(Addr, true, true)) {
306      // The variable is addressable but not captured, so it cannot be
307      // referenced from a different thread and participate in a data race
308      // (see llvm/Analysis/CaptureTracking.h for details).
309      NumOmittedNonCaptured++;
310      continue;
311    }
312    All.push_back(I);
313  }
314  Local.clear();
315}
316
317static bool isAtomic(Instruction *I) {
318  if (LoadInst *LI = dyn_cast<LoadInst>(I))
319    return LI->isAtomic() && LI->getSynchScope() == CrossThread;
320  if (StoreInst *SI = dyn_cast<StoreInst>(I))
321    return SI->isAtomic() && SI->getSynchScope() == CrossThread;
322  if (isa<AtomicRMWInst>(I))
323    return true;
324  if (isa<AtomicCmpXchgInst>(I))
325    return true;
326  if (isa<FenceInst>(I))
327    return true;
328  return false;
329}
330
331bool ThreadSanitizer::runOnFunction(Function &F) {
332  initializeCallbacks(*F.getParent());
333  SmallVector<Instruction*, 8> RetVec;
334  SmallVector<Instruction*, 8> AllLoadsAndStores;
335  SmallVector<Instruction*, 8> LocalLoadsAndStores;
336  SmallVector<Instruction*, 8> AtomicAccesses;
337  SmallVector<Instruction*, 8> MemIntrinCalls;
338  bool Res = false;
339  bool HasCalls = false;
340  bool SanitizeFunction = F.hasFnAttribute(Attribute::SanitizeThread);
341  const DataLayout &DL = F.getParent()->getDataLayout();
342
343  // Traverse all instructions, collect loads/stores/returns, check for calls.
344  for (auto &BB : F) {
345    for (auto &Inst : BB) {
346      if (isAtomic(&Inst))
347        AtomicAccesses.push_back(&Inst);
348      else if (isa<LoadInst>(Inst) || isa<StoreInst>(Inst))
349        LocalLoadsAndStores.push_back(&Inst);
350      else if (isa<ReturnInst>(Inst))
351        RetVec.push_back(&Inst);
352      else if (isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) {
353        if (isa<MemIntrinsic>(Inst))
354          MemIntrinCalls.push_back(&Inst);
355        HasCalls = true;
356        chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores,
357                                       DL);
358      }
359    }
360    chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores, DL);
361  }
362
363  // We have collected all loads and stores.
364  // FIXME: many of these accesses do not need to be checked for races
365  // (e.g. variables that do not escape, etc).
366
367  // Instrument memory accesses only if we want to report bugs in the function.
368  if (ClInstrumentMemoryAccesses && SanitizeFunction)
369    for (auto Inst : AllLoadsAndStores) {
370      Res |= instrumentLoadOrStore(Inst, DL);
371    }
372
373  // Instrument atomic memory accesses in any case (they can be used to
374  // implement synchronization).
375  if (ClInstrumentAtomics)
376    for (auto Inst : AtomicAccesses) {
377      Res |= instrumentAtomic(Inst, DL);
378    }
379
380  if (ClInstrumentMemIntrinsics && SanitizeFunction)
381    for (auto Inst : MemIntrinCalls) {
382      Res |= instrumentMemIntrinsic(Inst);
383    }
384
385  // Instrument function entry/exit points if there were instrumented accesses.
386  if ((Res || HasCalls) && ClInstrumentFuncEntryExit) {
387    IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
388    Value *ReturnAddress = IRB.CreateCall(
389        Intrinsic::getDeclaration(F.getParent(), Intrinsic::returnaddress),
390        IRB.getInt32(0));
391    IRB.CreateCall(TsanFuncEntry, ReturnAddress);
392    for (auto RetInst : RetVec) {
393      IRBuilder<> IRBRet(RetInst);
394      IRBRet.CreateCall(TsanFuncExit);
395    }
396    Res = true;
397  }
398  return Res;
399}
400
401bool ThreadSanitizer::instrumentLoadOrStore(Instruction *I,
402                                            const DataLayout &DL) {
403  IRBuilder<> IRB(I);
404  bool IsWrite = isa<StoreInst>(*I);
405  Value *Addr = IsWrite
406      ? cast<StoreInst>(I)->getPointerOperand()
407      : cast<LoadInst>(I)->getPointerOperand();
408  int Idx = getMemoryAccessFuncIndex(Addr, DL);
409  if (Idx < 0)
410    return false;
411  if (IsWrite && isVtableAccess(I)) {
412    DEBUG(dbgs() << "  VPTR : " << *I << "\n");
413    Value *StoredValue = cast<StoreInst>(I)->getValueOperand();
414    // StoredValue may be a vector type if we are storing several vptrs at once.
415    // In this case, just take the first element of the vector since this is
416    // enough to find vptr races.
417    if (isa<VectorType>(StoredValue->getType()))
418      StoredValue = IRB.CreateExtractElement(
419          StoredValue, ConstantInt::get(IRB.getInt32Ty(), 0));
420    if (StoredValue->getType()->isIntegerTy())
421      StoredValue = IRB.CreateIntToPtr(StoredValue, IRB.getInt8PtrTy());
422    // Call TsanVptrUpdate.
423    IRB.CreateCall2(TsanVptrUpdate,
424                    IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()),
425                    IRB.CreatePointerCast(StoredValue, IRB.getInt8PtrTy()));
426    NumInstrumentedVtableWrites++;
427    return true;
428  }
429  if (!IsWrite && isVtableAccess(I)) {
430    IRB.CreateCall(TsanVptrLoad,
431                   IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
432    NumInstrumentedVtableReads++;
433    return true;
434  }
435  const unsigned Alignment = IsWrite
436      ? cast<StoreInst>(I)->getAlignment()
437      : cast<LoadInst>(I)->getAlignment();
438  Type *OrigTy = cast<PointerType>(Addr->getType())->getElementType();
439  const uint32_t TypeSize = DL.getTypeStoreSizeInBits(OrigTy);
440  Value *OnAccessFunc = nullptr;
441  if (Alignment == 0 || Alignment >= 8 || (Alignment % (TypeSize / 8)) == 0)
442    OnAccessFunc = IsWrite ? TsanWrite[Idx] : TsanRead[Idx];
443  else
444    OnAccessFunc = IsWrite ? TsanUnalignedWrite[Idx] : TsanUnalignedRead[Idx];
445  IRB.CreateCall(OnAccessFunc, IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
446  if (IsWrite) NumInstrumentedWrites++;
447  else         NumInstrumentedReads++;
448  return true;
449}
450
451static ConstantInt *createOrdering(IRBuilder<> *IRB, AtomicOrdering ord) {
452  uint32_t v = 0;
453  switch (ord) {
454    case NotAtomic: llvm_unreachable("unexpected atomic ordering!");
455    case Unordered:              // Fall-through.
456    case Monotonic:              v = 0; break;
457    // case Consume:                v = 1; break;  // Not specified yet.
458    case Acquire:                v = 2; break;
459    case Release:                v = 3; break;
460    case AcquireRelease:         v = 4; break;
461    case SequentiallyConsistent: v = 5; break;
462  }
463  return IRB->getInt32(v);
464}
465
466// If a memset intrinsic gets inlined by the code gen, we will miss races on it.
467// So, we either need to ensure the intrinsic is not inlined, or instrument it.
468// We do not instrument memset/memmove/memcpy intrinsics (too complicated),
469// instead we simply replace them with regular function calls, which are then
470// intercepted by the run-time.
471// Since tsan is running after everyone else, the calls should not be
472// replaced back with intrinsics. If that becomes wrong at some point,
473// we will need to call e.g. __tsan_memset to avoid the intrinsics.
474bool ThreadSanitizer::instrumentMemIntrinsic(Instruction *I) {
475  IRBuilder<> IRB(I);
476  if (MemSetInst *M = dyn_cast<MemSetInst>(I)) {
477    IRB.CreateCall3(MemsetFn,
478      IRB.CreatePointerCast(M->getArgOperand(0), IRB.getInt8PtrTy()),
479      IRB.CreateIntCast(M->getArgOperand(1), IRB.getInt32Ty(), false),
480      IRB.CreateIntCast(M->getArgOperand(2), IntptrTy, false));
481    I->eraseFromParent();
482  } else if (MemTransferInst *M = dyn_cast<MemTransferInst>(I)) {
483    IRB.CreateCall3(isa<MemCpyInst>(M) ? MemcpyFn : MemmoveFn,
484      IRB.CreatePointerCast(M->getArgOperand(0), IRB.getInt8PtrTy()),
485      IRB.CreatePointerCast(M->getArgOperand(1), IRB.getInt8PtrTy()),
486      IRB.CreateIntCast(M->getArgOperand(2), IntptrTy, false));
487    I->eraseFromParent();
488  }
489  return false;
490}
491
492// Both llvm and ThreadSanitizer atomic operations are based on C++11/C1x
493// standards.  For background see C++11 standard.  A slightly older, publicly
494// available draft of the standard (not entirely up-to-date, but close enough
495// for casual browsing) is available here:
496// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf
497// The following page contains more background information:
498// http://www.hpl.hp.com/personal/Hans_Boehm/c++mm/
499
500bool ThreadSanitizer::instrumentAtomic(Instruction *I, const DataLayout &DL) {
501  IRBuilder<> IRB(I);
502  if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
503    Value *Addr = LI->getPointerOperand();
504    int Idx = getMemoryAccessFuncIndex(Addr, DL);
505    if (Idx < 0)
506      return false;
507    const size_t ByteSize = 1 << Idx;
508    const size_t BitSize = ByteSize * 8;
509    Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
510    Type *PtrTy = Ty->getPointerTo();
511    Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
512                     createOrdering(&IRB, LI->getOrdering())};
513    CallInst *C = CallInst::Create(TsanAtomicLoad[Idx], Args);
514    ReplaceInstWithInst(I, C);
515
516  } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
517    Value *Addr = SI->getPointerOperand();
518    int Idx = getMemoryAccessFuncIndex(Addr, DL);
519    if (Idx < 0)
520      return false;
521    const size_t ByteSize = 1 << Idx;
522    const size_t BitSize = ByteSize * 8;
523    Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
524    Type *PtrTy = Ty->getPointerTo();
525    Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
526                     IRB.CreateIntCast(SI->getValueOperand(), Ty, false),
527                     createOrdering(&IRB, SI->getOrdering())};
528    CallInst *C = CallInst::Create(TsanAtomicStore[Idx], Args);
529    ReplaceInstWithInst(I, C);
530  } else if (AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(I)) {
531    Value *Addr = RMWI->getPointerOperand();
532    int Idx = getMemoryAccessFuncIndex(Addr, DL);
533    if (Idx < 0)
534      return false;
535    Function *F = TsanAtomicRMW[RMWI->getOperation()][Idx];
536    if (!F)
537      return false;
538    const size_t ByteSize = 1 << Idx;
539    const size_t BitSize = ByteSize * 8;
540    Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
541    Type *PtrTy = Ty->getPointerTo();
542    Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
543                     IRB.CreateIntCast(RMWI->getValOperand(), Ty, false),
544                     createOrdering(&IRB, RMWI->getOrdering())};
545    CallInst *C = CallInst::Create(F, Args);
546    ReplaceInstWithInst(I, C);
547  } else if (AtomicCmpXchgInst *CASI = dyn_cast<AtomicCmpXchgInst>(I)) {
548    Value *Addr = CASI->getPointerOperand();
549    int Idx = getMemoryAccessFuncIndex(Addr, DL);
550    if (Idx < 0)
551      return false;
552    const size_t ByteSize = 1 << Idx;
553    const size_t BitSize = ByteSize * 8;
554    Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
555    Type *PtrTy = Ty->getPointerTo();
556    Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
557                     IRB.CreateIntCast(CASI->getCompareOperand(), Ty, false),
558                     IRB.CreateIntCast(CASI->getNewValOperand(), Ty, false),
559                     createOrdering(&IRB, CASI->getSuccessOrdering()),
560                     createOrdering(&IRB, CASI->getFailureOrdering())};
561    CallInst *C = IRB.CreateCall(TsanAtomicCAS[Idx], Args);
562    Value *Success = IRB.CreateICmpEQ(C, CASI->getCompareOperand());
563
564    Value *Res = IRB.CreateInsertValue(UndefValue::get(CASI->getType()), C, 0);
565    Res = IRB.CreateInsertValue(Res, Success, 1);
566
567    I->replaceAllUsesWith(Res);
568    I->eraseFromParent();
569  } else if (FenceInst *FI = dyn_cast<FenceInst>(I)) {
570    Value *Args[] = {createOrdering(&IRB, FI->getOrdering())};
571    Function *F = FI->getSynchScope() == SingleThread ?
572        TsanAtomicSignalFence : TsanAtomicThreadFence;
573    CallInst *C = CallInst::Create(F, Args);
574    ReplaceInstWithInst(I, C);
575  }
576  return true;
577}
578
579int ThreadSanitizer::getMemoryAccessFuncIndex(Value *Addr,
580                                              const DataLayout &DL) {
581  Type *OrigPtrTy = Addr->getType();
582  Type *OrigTy = cast<PointerType>(OrigPtrTy)->getElementType();
583  assert(OrigTy->isSized());
584  uint32_t TypeSize = DL.getTypeStoreSizeInBits(OrigTy);
585  if (TypeSize != 8  && TypeSize != 16 &&
586      TypeSize != 32 && TypeSize != 64 && TypeSize != 128) {
587    NumAccessesWithBadSize++;
588    // Ignore all unusual sizes.
589    return -1;
590  }
591  size_t Idx = countTrailingZeros(TypeSize / 8);
592  assert(Idx < kNumberOfAccessSizes);
593  return Idx;
594}
595