[tsan] Do not report errors in __destroy_helper_block_

[zaks.anna]

Summary

There is a synchronization point between the reference count of a block dropping to zero and it's destruction, which TSan does not observe. Do not report errors in the compiler-emitted block destroy method and everything called from it.

This is similar to https://reviews.llvm.org/D25857

cfe/trunk/lib/CodeGen/CodeGenFunction.cpp

static bool endsWithReturn(const Decl* F) {
   if (auto *CS = dyn_cast_or_null<CompoundStmt>(Body)) {
     auto LastStmt = CS->body_rbegin();
     if (LastStmt != CS->body_rend())
       return isa<ReturnStmt>(*LastStmt);
   }
   return false;
 }
 
+static void markAsIgnoreThreadCheckingAtRuntime(llvm::Function *Fn) {
+  Fn->addFnAttr("sanitize_thread_no_checking_at_run_time");
+  Fn->removeFnAttr(llvm::Attribute::SanitizeThread);
+}
+
 void CodeGenFunction::StartFunction(GlobalDecl GD,
                                     QualType RetTy,
                                     llvm::Function *Fn,
                                     const CGFunctionInfo &FnInfo,
                                     const FunctionArgList &Args,
                                     SourceLocation Loc,
                                     SourceLocation StartLoc) {
   assert(!CurFn &&
void CodeGenFunction::StartFunction(GlobalDecl GD,
   if (SanOpts.has(SanitizerKind::Thread))
     Fn->addFnAttr(llvm::Attribute::SanitizeThread);
   if (SanOpts.has(SanitizerKind::Memory))
     Fn->addFnAttr(llvm::Attribute::SanitizeMemory);
   if (SanOpts.has(SanitizerKind::SafeStack))
     Fn->addFnAttr(llvm::Attribute::SafeStack);
 
   // Ignore TSan memory acesses from within ObjC/ObjC++ dealloc, initialize,
-  // .cxx_destruct and all of their calees at run time.
+  // .cxx_destruct, __destroy_helper_block_ and all of their calees at run time.
   if (SanOpts.has(SanitizerKind::Thread)) {
     if (const auto *OMD = dyn_cast_or_null<ObjCMethodDecl>(D)) {
       IdentifierInfo *II = OMD->getSelector().getIdentifierInfoForSlot(0);
       if (OMD->getMethodFamily() == OMF_dealloc ||
           OMD->getMethodFamily() == OMF_initialize ||
           (OMD->getSelector().isUnarySelector() && II->isStr(".cxx_destruct"))) {
-        Fn->addFnAttr("sanitize_thread_no_checking_at_run_time");
-        Fn->removeFnAttr(llvm::Attribute::SanitizeThread);
+        markAsIgnoreThreadCheckingAtRuntime(Fn);
       }
+    } else if (const auto *FD = dyn_cast_or_null<FunctionDecl>(D)) {
+      IdentifierInfo *II = FD->getIdentifier();
+      if (II && II->isStr("__destroy_helper_block_"))
+        markAsIgnoreThreadCheckingAtRuntime(Fn);
     }
   }
 
   // Apply xray attributes to the function (as a string, for now)
   if (D && ShouldXRayInstrumentFunction()) {
     if (const auto *XRayAttr = D->getAttr<XRayInstrumentAttr>()) {
       if (XRayAttr->alwaysXRayInstrument())
         Fn->addFnAttr("function-instrument", "xray-always");

cfe/trunk/test/CodeGen/sanitize-thread-no-checking-at-run-time.m

-// RUN: %clang_cc1 -triple x86_64-apple-darwin -x objective-c++ -emit-llvm -o - %s | FileCheck -check-prefix=WITHOUT %s
-// RUN: %clang_cc1 -triple x86_64-apple-darwin -x objective-c++ -emit-llvm -o - %s -fsanitize=thread | FileCheck -check-prefix=TSAN %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -x objective-c++ -fblocks -emit-llvm -o - %s | FileCheck -check-prefix=WITHOUT %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -x objective-c++ -fblocks -emit-llvm -o - %s -fsanitize=thread | FileCheck -check-prefix=TSAN %s
+
+// WITHOUT-NOT: "sanitize_thread_no_checking_at_run_time"
 
 __attribute__((objc_root_class))
 @interface NSObject
 - (void)dealloc;
 @end
 
 class NeedCleanup {
 public:

 @implementation MyObject
 + (void)initialize {
 }
 - (void)dealloc {
   [super dealloc];
 }
 @end
 
-// WITHOUT-NOT: "sanitize_thread_no_checking_at_run_time"
-
 // TSAN: initialize{{.*}}) [[ATTR:#[0-9]+]]
 // TSAN: dealloc{{.*}}) [[ATTR:#[0-9]+]]
 // TSAN: cxx_destruct{{.*}}) [[ATTR:#[0-9]+]]
+
+void test2(id x) {
+  extern void test2_helper(id (^)(void));
+  test2_helper(^{ return x; });
+// TSAN: define internal void @__destroy_helper_block_(i8*) [[ATTR:#[0-9]+]]
+}
+
 // TSAN: attributes [[ATTR]] = { noinline nounwind {{.*}} "sanitize_thread_no_checking_at_run_time" {{.*}} }