tsan: properly instrument unaligned accesses

If a memory access is unaligned, emit __tsan_unaligned_read/write
callbacks instead of __tsan_read/write.
Required to change semantics of __tsan_unaligned_read/write to not do the user memory.
But since they were unused (other than through __sanitizer_unaligned_load/store) this is fine.
Fixes long standing issue 17:
https://code.google.com/p/thread-sanitizer/issues/detail?id=17

llvm-svn: 227231

1 files changed, 22 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
index 1b86ae5acf7..e9999c486fa 100644
--- a/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
@@ -99,6 +99,8 @@ struct ThreadSanitizer : public FunctionPass {
   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];
@@ -150,6 +152,16 @@ void ThreadSanitizer::initializeCallbacks(Module &M) {
     TsanWrite[i] = checkInterfaceFunction(M.getOrInsertFunction(
         WriteName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
 
+    SmallString<64> UnalignedReadName("__tsan_unaligned_read" +
+        itostr(ByteSize));
+    TsanUnalignedRead[i] = checkInterfaceFunction(M.getOrInsertFunction(
+        UnalignedReadName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
+
+    SmallString<64> UnalignedWriteName("__tsan_unaligned_write" +
+        itostr(ByteSize));
+    TsanUnalignedWrite[i] = checkInterfaceFunction(M.getOrInsertFunction(
+        UnalignedWriteName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
+
     Type *Ty = Type::getIntNTy(M.getContext(), BitSize);
     Type *PtrTy = Ty->getPointerTo();
     SmallString<32> AtomicLoadName("__tsan_atomic" + itostr(BitSize) +
@@ -412,7 +424,16 @@ bool ThreadSanitizer::instrumentLoadOrStore(Instruction *I) {
     NumInstrumentedVtableReads++;
     return true;
   }
-  Value *OnAccessFunc = IsWrite ? TsanWrite[Idx] : TsanRead[Idx];
+  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++;