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/TargetLibraryInfo.h"
30 #include "llvm/Analysis/ValueTracking.h"
31 #include "llvm/IR/DataLayout.h"
32 #include "llvm/IR/Function.h"
33 #include "llvm/IR/IRBuilder.h"
34 #include "llvm/IR/IntrinsicInst.h"
35 #include "llvm/IR/Intrinsics.h"
36 #include "llvm/IR/LLVMContext.h"
37 #include "llvm/IR/Metadata.h"
38 #include "llvm/IR/Module.h"
39 #include "llvm/IR/Type.h"
40 #include "llvm/ProfileData/InstrProf.h"
41 #include "llvm/Support/CommandLine.h"
42 #include "llvm/Support/Debug.h"
43 #include "llvm/Support/MathExtras.h"
44 #include "llvm/Support/raw_ostream.h"
45 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
46 #include "llvm/Transforms/Utils/Local.h"
47 #include "llvm/Transforms/Utils/ModuleUtils.h"
48 
49 using namespace llvm;
50 
51 #define DEBUG_TYPE "tsan"
52 
53 static cl::opt<bool>  ClInstrumentMemoryAccesses(
54     "tsan-instrument-memory-accesses", cl::init(true),
55     cl::desc("Instrument memory accesses"), cl::Hidden);
56 static cl::opt<bool>  ClInstrumentFuncEntryExit(
57     "tsan-instrument-func-entry-exit", cl::init(true),
58     cl::desc("Instrument function entry and exit"), cl::Hidden);
59 static cl::opt<bool>  ClInstrumentAtomics(
60     "tsan-instrument-atomics", cl::init(true),
61     cl::desc("Instrument atomics"), cl::Hidden);
62 static cl::opt<bool>  ClInstrumentMemIntrinsics(
63     "tsan-instrument-memintrinsics", cl::init(true),
64     cl::desc("Instrument memintrinsics (memset/memcpy/memmove)"), cl::Hidden);
65 
66 STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
67 STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
68 STATISTIC(NumOmittedReadsBeforeWrite,
69           "Number of reads ignored due to following writes");
70 STATISTIC(NumAccessesWithBadSize, "Number of accesses with bad size");
71 STATISTIC(NumInstrumentedVtableWrites, "Number of vtable ptr writes");
72 STATISTIC(NumInstrumentedVtableReads, "Number of vtable ptr reads");
73 STATISTIC(NumOmittedReadsFromConstantGlobals,
74           "Number of reads from constant globals");
75 STATISTIC(NumOmittedReadsFromVtable, "Number of vtable reads");
76 STATISTIC(NumOmittedNonCaptured, "Number of accesses ignored due to capturing");
77 
78 static const char *const kTsanModuleCtorName = "tsan.module_ctor";
79 static const char *const kTsanInitName = "__tsan_init";
80 
81 namespace {
82 
83 /// ThreadSanitizer: instrument the code in module to find races.
84 struct ThreadSanitizer : public FunctionPass {
85   ThreadSanitizer() : FunctionPass(ID) {}
86   const char *getPassName() const override;
87   void getAnalysisUsage(AnalysisUsage &AU) const override;
88   bool runOnFunction(Function &F) override;
89   bool doInitialization(Module &M) override;
90   static char ID;  // Pass identification, replacement for typeid.
91 
92  private:
93   void initializeCallbacks(Module &M);
94   bool instrumentLoadOrStore(Instruction *I, const DataLayout &DL);
95   bool instrumentAtomic(Instruction *I, const DataLayout &DL);
96   bool instrumentMemIntrinsic(Instruction *I);
97   void chooseInstructionsToInstrument(SmallVectorImpl<Instruction *> &Local,
98                                       SmallVectorImpl<Instruction *> &All,
99                                       const DataLayout &DL);
100   bool addrPointsToConstantData(Value *Addr);
101   int getMemoryAccessFuncIndex(Value *Addr, const DataLayout &DL);
102 
103   Type *IntptrTy;
104   IntegerType *OrdTy;
105   // Callbacks to run-time library are computed in doInitialization.
106   Function *TsanFuncEntry;
107   Function *TsanFuncExit;
108   // Accesses sizes are powers of two: 1, 2, 4, 8, 16.
109   static const size_t kNumberOfAccessSizes = 5;
110   Function *TsanRead[kNumberOfAccessSizes];
111   Function *TsanWrite[kNumberOfAccessSizes];
112   Function *TsanUnalignedRead[kNumberOfAccessSizes];
113   Function *TsanUnalignedWrite[kNumberOfAccessSizes];
114   Function *TsanAtomicLoad[kNumberOfAccessSizes];
115   Function *TsanAtomicStore[kNumberOfAccessSizes];
116   Function *TsanAtomicRMW[AtomicRMWInst::LAST_BINOP + 1][kNumberOfAccessSizes];
117   Function *TsanAtomicCAS[kNumberOfAccessSizes];
118   Function *TsanAtomicThreadFence;
119   Function *TsanAtomicSignalFence;
120   Function *TsanVptrUpdate;
121   Function *TsanVptrLoad;
122   Function *MemmoveFn, *MemcpyFn, *MemsetFn;
123   Function *TsanCtorFunction;
124 };
125 }  // namespace
126 
127 char ThreadSanitizer::ID = 0;
128 INITIALIZE_PASS_BEGIN(
129     ThreadSanitizer, "tsan",
130     "ThreadSanitizer: detects data races.",
131     false, false)
132 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
133 INITIALIZE_PASS_END(
134     ThreadSanitizer, "tsan",
135     "ThreadSanitizer: detects data races.",
136     false, false)
137 
138 const char *ThreadSanitizer::getPassName() const {
139   return "ThreadSanitizer";
140 }
141 
142 void ThreadSanitizer::getAnalysisUsage(AnalysisUsage &AU) const {
143   AU.addRequired<TargetLibraryInfoWrapperPass>();
144 }
145 
146 FunctionPass *llvm::createThreadSanitizerPass() {
147   return new ThreadSanitizer();
148 }
149 
150 void ThreadSanitizer::initializeCallbacks(Module &M) {
151   IRBuilder<> IRB(M.getContext());
152   // Initialize the callbacks.
153   TsanFuncEntry = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
154       "__tsan_func_entry", IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
155   TsanFuncExit = checkSanitizerInterfaceFunction(
156       M.getOrInsertFunction("__tsan_func_exit", IRB.getVoidTy(), nullptr));
157   OrdTy = IRB.getInt32Ty();
158   for (size_t i = 0; i < kNumberOfAccessSizes; ++i) {
159     const unsigned ByteSize = 1U << i;
160     const unsigned BitSize = ByteSize * 8;
161     std::string ByteSizeStr = utostr(ByteSize);
162     std::string BitSizeStr = utostr(BitSize);
163     SmallString<32> ReadName("__tsan_read" + ByteSizeStr);
164     TsanRead[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
165         ReadName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
166 
167     SmallString<32> WriteName("__tsan_write" + ByteSizeStr);
168     TsanWrite[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
169         WriteName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
170 
171     SmallString<64> UnalignedReadName("__tsan_unaligned_read" + ByteSizeStr);
172     TsanUnalignedRead[i] =
173         checkSanitizerInterfaceFunction(M.getOrInsertFunction(
174             UnalignedReadName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
175 
176     SmallString<64> UnalignedWriteName("__tsan_unaligned_write" + ByteSizeStr);
177     TsanUnalignedWrite[i] =
178         checkSanitizerInterfaceFunction(M.getOrInsertFunction(
179             UnalignedWriteName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
180 
181     Type *Ty = Type::getIntNTy(M.getContext(), BitSize);
182     Type *PtrTy = Ty->getPointerTo();
183     SmallString<32> AtomicLoadName("__tsan_atomic" + BitSizeStr + "_load");
184     TsanAtomicLoad[i] = checkSanitizerInterfaceFunction(
185         M.getOrInsertFunction(AtomicLoadName, Ty, PtrTy, OrdTy, nullptr));
186 
187     SmallString<32> AtomicStoreName("__tsan_atomic" + BitSizeStr + "_store");
188     TsanAtomicStore[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
189         AtomicStoreName, IRB.getVoidTy(), PtrTy, Ty, OrdTy, nullptr));
190 
191     for (int op = AtomicRMWInst::FIRST_BINOP;
192         op <= AtomicRMWInst::LAST_BINOP; ++op) {
193       TsanAtomicRMW[op][i] = nullptr;
194       const char *NamePart = nullptr;
195       if (op == AtomicRMWInst::Xchg)
196         NamePart = "_exchange";
197       else if (op == AtomicRMWInst::Add)
198         NamePart = "_fetch_add";
199       else if (op == AtomicRMWInst::Sub)
200         NamePart = "_fetch_sub";
201       else if (op == AtomicRMWInst::And)
202         NamePart = "_fetch_and";
203       else if (op == AtomicRMWInst::Or)
204         NamePart = "_fetch_or";
205       else if (op == AtomicRMWInst::Xor)
206         NamePart = "_fetch_xor";
207       else if (op == AtomicRMWInst::Nand)
208         NamePart = "_fetch_nand";
209       else
210         continue;
211       SmallString<32> RMWName("__tsan_atomic" + itostr(BitSize) + NamePart);
212       TsanAtomicRMW[op][i] = checkSanitizerInterfaceFunction(
213           M.getOrInsertFunction(RMWName, Ty, PtrTy, Ty, OrdTy, nullptr));
214     }
215 
216     SmallString<32> AtomicCASName("__tsan_atomic" + BitSizeStr +
217                                   "_compare_exchange_val");
218     TsanAtomicCAS[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
219         AtomicCASName, Ty, PtrTy, Ty, Ty, OrdTy, OrdTy, nullptr));
220   }
221   TsanVptrUpdate = checkSanitizerInterfaceFunction(
222       M.getOrInsertFunction("__tsan_vptr_update", IRB.getVoidTy(),
223                             IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), nullptr));
224   TsanVptrLoad = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
225       "__tsan_vptr_read", IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
226   TsanAtomicThreadFence = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
227       "__tsan_atomic_thread_fence", IRB.getVoidTy(), OrdTy, nullptr));
228   TsanAtomicSignalFence = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
229       "__tsan_atomic_signal_fence", IRB.getVoidTy(), OrdTy, nullptr));
230 
231   MemmoveFn = checkSanitizerInterfaceFunction(
232       M.getOrInsertFunction("memmove", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
233                             IRB.getInt8PtrTy(), IntptrTy, nullptr));
234   MemcpyFn = checkSanitizerInterfaceFunction(
235       M.getOrInsertFunction("memcpy", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
236                             IRB.getInt8PtrTy(), IntptrTy, nullptr));
237   MemsetFn = checkSanitizerInterfaceFunction(
238       M.getOrInsertFunction("memset", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
239                             IRB.getInt32Ty(), IntptrTy, nullptr));
240 }
241 
242 bool ThreadSanitizer::doInitialization(Module &M) {
243   const DataLayout &DL = M.getDataLayout();
244   IntptrTy = DL.getIntPtrType(M.getContext());
245   std::tie(TsanCtorFunction, std::ignore) = createSanitizerCtorAndInitFunctions(
246       M, kTsanModuleCtorName, kTsanInitName, /*InitArgTypes=*/{},
247       /*InitArgs=*/{});
248 
249   appendToGlobalCtors(M, TsanCtorFunction, 0);
250 
251   return true;
252 }
253 
254 static bool isVtableAccess(Instruction *I) {
255   if (MDNode *Tag = I->getMetadata(LLVMContext::MD_tbaa))
256     return Tag->isTBAAVtableAccess();
257   return false;
258 }
259 
260 // Do not instrument known races/"benign races" that come from compiler
261 // instrumentatin. The user has no way of suppressing them.
262 static bool shouldInstrumentReadWriteFromAddress(Value *Addr) {
263   // Peel off GEPs and BitCasts.
264   Addr = Addr->stripInBoundsOffsets();
265 
266   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
267     if (GV->hasSection()) {
268       StringRef SectionName = GV->getSection();
269       // Check if the global is in the PGO counters section.
270       if (SectionName.endswith(getInstrProfCountersSectionName(
271             /*AddSegment=*/false)))
272         return false;
273     }
274 
275     // Check if the global is private gcov data.
276     if (GV->getName().startswith("__llvm_gcov") ||
277         GV->getName().startswith("__llvm_gcda"))
278       return false;
279   }
280 
281   // Do not instrument acesses from different address spaces; we cannot deal
282   // with them.
283   if (Addr) {
284     Type *PtrTy = cast<PointerType>(Addr->getType()->getScalarType());
285     if (PtrTy->getPointerAddressSpace() != 0)
286       return false;
287   }
288 
289   return true;
290 }
291 
292 bool ThreadSanitizer::addrPointsToConstantData(Value *Addr) {
293   // If this is a GEP, just analyze its pointer operand.
294   if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Addr))
295     Addr = GEP->getPointerOperand();
296 
297   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
298     if (GV->isConstant()) {
299       // Reads from constant globals can not race with any writes.
300       NumOmittedReadsFromConstantGlobals++;
301       return true;
302     }
303   } else if (LoadInst *L = dyn_cast<LoadInst>(Addr)) {
304     if (isVtableAccess(L)) {
305       // Reads from a vtable pointer can not race with any writes.
306       NumOmittedReadsFromVtable++;
307       return true;
308     }
309   }
310   return false;
311 }
312 
313 // Instrumenting some of the accesses may be proven redundant.
314 // Currently handled:
315 //  - read-before-write (within same BB, no calls between)
316 //  - not captured variables
317 //
318 // We do not handle some of the patterns that should not survive
319 // after the classic compiler optimizations.
320 // E.g. two reads from the same temp should be eliminated by CSE,
321 // two writes should be eliminated by DSE, etc.
322 //
323 // 'Local' is a vector of insns within the same BB (no calls between).
324 // 'All' is a vector of insns that will be instrumented.
325 void ThreadSanitizer::chooseInstructionsToInstrument(
326     SmallVectorImpl<Instruction *> &Local, SmallVectorImpl<Instruction *> &All,
327     const DataLayout &DL) {
328   SmallSet<Value*, 8> WriteTargets;
329   // Iterate from the end.
330   for (Instruction *I : reverse(Local)) {
331     if (StoreInst *Store = dyn_cast<StoreInst>(I)) {
332       Value *Addr = Store->getPointerOperand();
333       if (!shouldInstrumentReadWriteFromAddress(Addr))
334         continue;
335       WriteTargets.insert(Addr);
336     } else {
337       LoadInst *Load = cast<LoadInst>(I);
338       Value *Addr = Load->getPointerOperand();
339       if (!shouldInstrumentReadWriteFromAddress(Addr))
340         continue;
341       if (WriteTargets.count(Addr)) {
342         // We will write to this temp, so no reason to analyze the read.
343         NumOmittedReadsBeforeWrite++;
344         continue;
345       }
346       if (addrPointsToConstantData(Addr)) {
347         // Addr points to some constant data -- it can not race with any writes.
348         continue;
349       }
350     }
351     Value *Addr = isa<StoreInst>(*I)
352         ? cast<StoreInst>(I)->getPointerOperand()
353         : cast<LoadInst>(I)->getPointerOperand();
354     if (isa<AllocaInst>(GetUnderlyingObject(Addr, DL)) &&
355         !PointerMayBeCaptured(Addr, true, true)) {
356       // The variable is addressable but not captured, so it cannot be
357       // referenced from a different thread and participate in a data race
358       // (see llvm/Analysis/CaptureTracking.h for details).
359       NumOmittedNonCaptured++;
360       continue;
361     }
362     All.push_back(I);
363   }
364   Local.clear();
365 }
366 
367 static bool isAtomic(Instruction *I) {
368   if (LoadInst *LI = dyn_cast<LoadInst>(I))
369     return LI->isAtomic() && LI->getSynchScope() == CrossThread;
370   if (StoreInst *SI = dyn_cast<StoreInst>(I))
371     return SI->isAtomic() && SI->getSynchScope() == CrossThread;
372   if (isa<AtomicRMWInst>(I))
373     return true;
374   if (isa<AtomicCmpXchgInst>(I))
375     return true;
376   if (isa<FenceInst>(I))
377     return true;
378   return false;
379 }
380 
381 bool ThreadSanitizer::runOnFunction(Function &F) {
382   // This is required to prevent instrumenting call to __tsan_init from within
383   // the module constructor.
384   if (&F == TsanCtorFunction)
385     return false;
386   initializeCallbacks(*F.getParent());
387   SmallVector<Instruction*, 8> RetVec;
388   SmallVector<Instruction*, 8> AllLoadsAndStores;
389   SmallVector<Instruction*, 8> LocalLoadsAndStores;
390   SmallVector<Instruction*, 8> AtomicAccesses;
391   SmallVector<Instruction*, 8> MemIntrinCalls;
392   bool Res = false;
393   bool HasCalls = false;
394   bool SanitizeFunction = F.hasFnAttribute(Attribute::SanitizeThread);
395   const DataLayout &DL = F.getParent()->getDataLayout();
396   const TargetLibraryInfo *TLI =
397       &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
398 
399   // Traverse all instructions, collect loads/stores/returns, check for calls.
400   for (auto &BB : F) {
401     for (auto &Inst : BB) {
402       if (isAtomic(&Inst))
403         AtomicAccesses.push_back(&Inst);
404       else if (isa<LoadInst>(Inst) || isa<StoreInst>(Inst))
405         LocalLoadsAndStores.push_back(&Inst);
406       else if (isa<ReturnInst>(Inst))
407         RetVec.push_back(&Inst);
408       else if (isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) {
409         if (CallInst *CI = dyn_cast<CallInst>(&Inst))
410           maybeMarkSanitizerLibraryCallNoBuiltin(CI, TLI);
411         if (isa<MemIntrinsic>(Inst))
412           MemIntrinCalls.push_back(&Inst);
413         HasCalls = true;
414         chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores,
415                                        DL);
416       }
417     }
418     chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores, DL);
419   }
420 
421   // We have collected all loads and stores.
422   // FIXME: many of these accesses do not need to be checked for races
423   // (e.g. variables that do not escape, etc).
424 
425   // Instrument memory accesses only if we want to report bugs in the function.
426   if (ClInstrumentMemoryAccesses && SanitizeFunction)
427     for (auto Inst : AllLoadsAndStores) {
428       Res |= instrumentLoadOrStore(Inst, DL);
429     }
430 
431   // Instrument atomic memory accesses in any case (they can be used to
432   // implement synchronization).
433   if (ClInstrumentAtomics)
434     for (auto Inst : AtomicAccesses) {
435       Res |= instrumentAtomic(Inst, DL);
436     }
437 
438   if (ClInstrumentMemIntrinsics && SanitizeFunction)
439     for (auto Inst : MemIntrinCalls) {
440       Res |= instrumentMemIntrinsic(Inst);
441     }
442 
443   // Instrument function entry/exit points if there were instrumented accesses.
444   if ((Res || HasCalls) && ClInstrumentFuncEntryExit) {
445     IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
446     Value *ReturnAddress = IRB.CreateCall(
447         Intrinsic::getDeclaration(F.getParent(), Intrinsic::returnaddress),
448         IRB.getInt32(0));
449     IRB.CreateCall(TsanFuncEntry, ReturnAddress);
450     for (auto RetInst : RetVec) {
451       IRBuilder<> IRBRet(RetInst);
452       IRBRet.CreateCall(TsanFuncExit, {});
453     }
454     Res = true;
455   }
456   return Res;
457 }
458 
459 bool ThreadSanitizer::instrumentLoadOrStore(Instruction *I,
460                                             const DataLayout &DL) {
461   IRBuilder<> IRB(I);
462   bool IsWrite = isa<StoreInst>(*I);
463   Value *Addr = IsWrite
464       ? cast<StoreInst>(I)->getPointerOperand()
465       : cast<LoadInst>(I)->getPointerOperand();
466   int Idx = getMemoryAccessFuncIndex(Addr, DL);
467   if (Idx < 0)
468     return false;
469   if (IsWrite && isVtableAccess(I)) {
470     DEBUG(dbgs() << "  VPTR : " << *I << "\n");
471     Value *StoredValue = cast<StoreInst>(I)->getValueOperand();
472     // StoredValue may be a vector type if we are storing several vptrs at once.
473     // In this case, just take the first element of the vector since this is
474     // enough to find vptr races.
475     if (isa<VectorType>(StoredValue->getType()))
476       StoredValue = IRB.CreateExtractElement(
477           StoredValue, ConstantInt::get(IRB.getInt32Ty(), 0));
478     if (StoredValue->getType()->isIntegerTy())
479       StoredValue = IRB.CreateIntToPtr(StoredValue, IRB.getInt8PtrTy());
480     // Call TsanVptrUpdate.
481     IRB.CreateCall(TsanVptrUpdate,
482                    {IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()),
483                     IRB.CreatePointerCast(StoredValue, IRB.getInt8PtrTy())});
484     NumInstrumentedVtableWrites++;
485     return true;
486   }
487   if (!IsWrite && isVtableAccess(I)) {
488     IRB.CreateCall(TsanVptrLoad,
489                    IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
490     NumInstrumentedVtableReads++;
491     return true;
492   }
493   const unsigned Alignment = IsWrite
494       ? cast<StoreInst>(I)->getAlignment()
495       : cast<LoadInst>(I)->getAlignment();
496   Type *OrigTy = cast<PointerType>(Addr->getType())->getElementType();
497   const uint32_t TypeSize = DL.getTypeStoreSizeInBits(OrigTy);
498   Value *OnAccessFunc = nullptr;
499   if (Alignment == 0 || Alignment >= 8 || (Alignment % (TypeSize / 8)) == 0)
500     OnAccessFunc = IsWrite ? TsanWrite[Idx] : TsanRead[Idx];
501   else
502     OnAccessFunc = IsWrite ? TsanUnalignedWrite[Idx] : TsanUnalignedRead[Idx];
503   IRB.CreateCall(OnAccessFunc, IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
504   if (IsWrite) NumInstrumentedWrites++;
505   else         NumInstrumentedReads++;
506   return true;
507 }
508 
509 static ConstantInt *createOrdering(IRBuilder<> *IRB, AtomicOrdering ord) {
510   uint32_t v = 0;
511   switch (ord) {
512     case AtomicOrdering::NotAtomic:
513       llvm_unreachable("unexpected atomic ordering!");
514     case AtomicOrdering::Unordered:              LLVM_FALLTHROUGH;
515     case AtomicOrdering::Monotonic:              v = 0; break;
516     // Not specified yet:
517     // case AtomicOrdering::Consume:                v = 1; break;
518     case AtomicOrdering::Acquire:                v = 2; break;
519     case AtomicOrdering::Release:                v = 3; break;
520     case AtomicOrdering::AcquireRelease:         v = 4; break;
521     case AtomicOrdering::SequentiallyConsistent: v = 5; break;
522   }
523   return IRB->getInt32(v);
524 }
525 
526 // If a memset intrinsic gets inlined by the code gen, we will miss races on it.
527 // So, we either need to ensure the intrinsic is not inlined, or instrument it.
528 // We do not instrument memset/memmove/memcpy intrinsics (too complicated),
529 // instead we simply replace them with regular function calls, which are then
530 // intercepted by the run-time.
531 // Since tsan is running after everyone else, the calls should not be
532 // replaced back with intrinsics. If that becomes wrong at some point,
533 // we will need to call e.g. __tsan_memset to avoid the intrinsics.
534 bool ThreadSanitizer::instrumentMemIntrinsic(Instruction *I) {
535   IRBuilder<> IRB(I);
536   if (MemSetInst *M = dyn_cast<MemSetInst>(I)) {
537     IRB.CreateCall(
538         MemsetFn,
539         {IRB.CreatePointerCast(M->getArgOperand(0), IRB.getInt8PtrTy()),
540          IRB.CreateIntCast(M->getArgOperand(1), IRB.getInt32Ty(), false),
541          IRB.CreateIntCast(M->getArgOperand(2), IntptrTy, false)});
542     I->eraseFromParent();
543   } else if (MemTransferInst *M = dyn_cast<MemTransferInst>(I)) {
544     IRB.CreateCall(
545         isa<MemCpyInst>(M) ? MemcpyFn : MemmoveFn,
546         {IRB.CreatePointerCast(M->getArgOperand(0), IRB.getInt8PtrTy()),
547          IRB.CreatePointerCast(M->getArgOperand(1), IRB.getInt8PtrTy()),
548          IRB.CreateIntCast(M->getArgOperand(2), IntptrTy, false)});
549     I->eraseFromParent();
550   }
551   return false;
552 }
553 
554 static Value *createIntOrPtrToIntCast(Value *V, Type* Ty, IRBuilder<> &IRB) {
555   return isa<PointerType>(V->getType()) ?
556     IRB.CreatePtrToInt(V, Ty) : IRB.CreateIntCast(V, Ty, false);
557 }
558 
559 // Both llvm and ThreadSanitizer atomic operations are based on C++11/C1x
560 // standards.  For background see C++11 standard.  A slightly older, publicly
561 // available draft of the standard (not entirely up-to-date, but close enough
562 // for casual browsing) is available here:
563 // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf
564 // The following page contains more background information:
565 // http://www.hpl.hp.com/personal/Hans_Boehm/c++mm/
566 
567 bool ThreadSanitizer::instrumentAtomic(Instruction *I, const DataLayout &DL) {
568   IRBuilder<> IRB(I);
569   if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
570     Value *Addr = LI->getPointerOperand();
571     int Idx = getMemoryAccessFuncIndex(Addr, DL);
572     if (Idx < 0)
573       return false;
574     const unsigned ByteSize = 1U << Idx;
575     const unsigned BitSize = ByteSize * 8;
576     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
577     Type *PtrTy = Ty->getPointerTo();
578     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
579                      createOrdering(&IRB, LI->getOrdering())};
580     Type *OrigTy = cast<PointerType>(Addr->getType())->getElementType();
581     if (Ty == OrigTy) {
582       Instruction *C = CallInst::Create(TsanAtomicLoad[Idx], Args);
583       ReplaceInstWithInst(I, C);
584     } else {
585       // We are loading a pointer, so we need to cast the return value.
586       Value *C = IRB.CreateCall(TsanAtomicLoad[Idx], Args);
587       Instruction *Cast = CastInst::Create(Instruction::IntToPtr, C, OrigTy);
588       ReplaceInstWithInst(I, Cast);
589     }
590   } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
591     Value *Addr = SI->getPointerOperand();
592     int Idx = getMemoryAccessFuncIndex(Addr, DL);
593     if (Idx < 0)
594       return false;
595     const unsigned ByteSize = 1U << Idx;
596     const unsigned BitSize = ByteSize * 8;
597     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
598     Type *PtrTy = Ty->getPointerTo();
599     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
600                      createIntOrPtrToIntCast(SI->getValueOperand(), Ty, IRB),
601                      createOrdering(&IRB, SI->getOrdering())};
602     CallInst *C = CallInst::Create(TsanAtomicStore[Idx], Args);
603     ReplaceInstWithInst(I, C);
604   } else if (AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(I)) {
605     Value *Addr = RMWI->getPointerOperand();
606     int Idx = getMemoryAccessFuncIndex(Addr, DL);
607     if (Idx < 0)
608       return false;
609     Function *F = TsanAtomicRMW[RMWI->getOperation()][Idx];
610     if (!F)
611       return false;
612     const unsigned ByteSize = 1U << Idx;
613     const unsigned BitSize = ByteSize * 8;
614     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
615     Type *PtrTy = Ty->getPointerTo();
616     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
617                      IRB.CreateIntCast(RMWI->getValOperand(), Ty, false),
618                      createOrdering(&IRB, RMWI->getOrdering())};
619     CallInst *C = CallInst::Create(F, Args);
620     ReplaceInstWithInst(I, C);
621   } else if (AtomicCmpXchgInst *CASI = dyn_cast<AtomicCmpXchgInst>(I)) {
622     Value *Addr = CASI->getPointerOperand();
623     int Idx = getMemoryAccessFuncIndex(Addr, DL);
624     if (Idx < 0)
625       return false;
626     const unsigned ByteSize = 1U << Idx;
627     const unsigned BitSize = ByteSize * 8;
628     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
629     Type *PtrTy = Ty->getPointerTo();
630     Value *CmpOperand =
631       createIntOrPtrToIntCast(CASI->getCompareOperand(), Ty, IRB);
632     Value *NewOperand =
633       createIntOrPtrToIntCast(CASI->getNewValOperand(), Ty, IRB);
634     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
635                      CmpOperand,
636                      NewOperand,
637                      createOrdering(&IRB, CASI->getSuccessOrdering()),
638                      createOrdering(&IRB, CASI->getFailureOrdering())};
639     CallInst *C = IRB.CreateCall(TsanAtomicCAS[Idx], Args);
640     Value *Success = IRB.CreateICmpEQ(C, CmpOperand);
641     Value *OldVal = C;
642     Type *OrigOldValTy = CASI->getNewValOperand()->getType();
643     if (Ty != OrigOldValTy) {
644       // The value is a pointer, so we need to cast the return value.
645       OldVal = IRB.CreateIntToPtr(C, OrigOldValTy);
646     }
647 
648     Value *Res =
649       IRB.CreateInsertValue(UndefValue::get(CASI->getType()), OldVal, 0);
650     Res = IRB.CreateInsertValue(Res, Success, 1);
651 
652     I->replaceAllUsesWith(Res);
653     I->eraseFromParent();
654   } else if (FenceInst *FI = dyn_cast<FenceInst>(I)) {
655     Value *Args[] = {createOrdering(&IRB, FI->getOrdering())};
656     Function *F = FI->getSynchScope() == SingleThread ?
657         TsanAtomicSignalFence : TsanAtomicThreadFence;
658     CallInst *C = CallInst::Create(F, Args);
659     ReplaceInstWithInst(I, C);
660   }
661   return true;
662 }
663 
664 int ThreadSanitizer::getMemoryAccessFuncIndex(Value *Addr,
665                                               const DataLayout &DL) {
666   Type *OrigPtrTy = Addr->getType();
667   Type *OrigTy = cast<PointerType>(OrigPtrTy)->getElementType();
668   assert(OrigTy->isSized());
669   uint32_t TypeSize = DL.getTypeStoreSizeInBits(OrigTy);
670   if (TypeSize != 8  && TypeSize != 16 &&
671       TypeSize != 32 && TypeSize != 64 && TypeSize != 128) {
672     NumAccessesWithBadSize++;
673     // Ignore all unusual sizes.
674     return -1;
675   }
676   size_t Idx = countTrailingZeros(TypeSize / 8);
677   assert(Idx < kNumberOfAccessSizes);
678   return Idx;
679 }
680