[vm] Fix profiler in PRODUCT mode.

* Make sure to start and stop profiler as mutator pauses and resumes.
* Allow profiler to call Code::GetPrologOffset without crashing
* Make sure to emit mapping with id 0 into the perfetto output if
  necessary, otherwise Perfetto UI can't load the profile

The last item seems a bug in Perfetto UI because 0 is supposed
to mean "value not set".

TEST=tested by running _perf_witness tests

Change-Id: I57578ba3efafd2aaf83c2c41b0e0b1f36a6a6964
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/459744
Reviewed-by: Martin Kustermann <kustermann@google.com>
Commit-Queue: Slava Egorov <vegorov@google.com>

runtime/vm/dart_api_impl.cc

@@ -1577,23 +1577,23 @@ DART_EXPORT void Dart_StopProfiling() {
 }
 
 DART_EXPORT void Dart_ThreadDisableProfiling() {
-#if !defined(PRODUCT)
+#if defined(DART_INCLUDE_PROFILER)
   OSThread* os_thread = OSThread::Current();
   if (os_thread == nullptr) {
     return;
   }
   os_thread->DisableThreadInterrupts();
-#endif  // !defined(PRODUCT)
+#endif  // defined(DART_INCLUDE_PROFILER)
 }
 
 DART_EXPORT void Dart_ThreadEnableProfiling() {
-#if !defined(PRODUCT)
+#if defined(DART_INCLUDE_PROFILER)
   OSThread* os_thread = OSThread::Current();
   if (os_thread == nullptr) {
     return;
   }
   os_thread->EnableThreadInterrupts();
-#endif  // !defined(PRODUCT)
+#endif  // defined(DART_INCLUDE_PROFILER)
 }
 
 DART_EXPORT void Dart_AddSymbols(const char* dso_name,

runtime/vm/object.cc

@@ -18737,7 +18737,6 @@ void Code::SetPrologueOffset(intptr_t offset) const {
 
 intptr_t Code::GetPrologueOffset() const {
 #if defined(PRODUCT)
-  UNREACHABLE();
   return -1;
 #else
   const Object& object = Object::Handle(untag()->return_address_metadata());

runtime/vm/os_thread.h

@@ -133,6 +133,11 @@ class OSThread : public BaseThread {
   void DisableThreadInterrupts();
   void EnableThreadInterrupts();
   bool ThreadInterruptsEnabled();
+#else
+  // Used to temporarily disable or enable thread interrupts.
+  void DisableThreadInterrupts() {}
+  void EnableThreadInterrupts() {}
+  bool ThreadInterruptsEnabled() { return false; }
 #endif  // defined(DART_INCLUDE_PROFILER)
 
   // The currently executing thread, or nullptr if not yet initialized.

runtime/vm/perfetto_utils.h

@@ -308,6 +308,8 @@ class InternedDataBuilder : public ValueObject {
  private:
   using SequenceFlags = perfetto::protos::pbzero::TracePacket_SequenceFlags;
 
+  enum class UnknownMappingState { kNotNeeded, kNeeded, kEmitted };
+
  public:
   // InternedData contains multiple independent interning dictionaries which
   // are used for different attributes.
@@ -331,6 +333,12 @@ class InternedDataBuilder : public ValueObject {
 
   InternedDataBuilder() = default;
 
+  void MarkNeedUnknownMapping() {
+    if (unknown_mapping_ == UnknownMappingState::kNotNeeded) {
+      unknown_mapping_ = UnknownMappingState::kNeeded;
+    }
+  }
+
   // Emit all strings added since the last invocation of |AttachInternedDataTo|
   // into |interned_data| of the given |TracePacket|.
   //
@@ -372,6 +380,18 @@ class InternedDataBuilder : public ValueObject {
       }
     });
 
+    // Perfetto proto message definition claim that mapping iid 0 means
+    // the same as frame not having mapping information. However Perfetto UI
+    // fails to load profiles if they contain any frames without mapping iid or
+    // with 0 mapping iid - but such mapping (with 0 iid) is not present in
+    // interned mappings. To work-around this bug we simply emit an empty
+    // mapping with 0 iid if we need it.
+    if (unknown_mapping_ == UnknownMappingState::kNeeded) {
+      auto mapping = interned_data->add_mappings();
+      mapping->set_iid(0);
+      unknown_mapping_ = UnknownMappingState::kEmitted;
+    }
+
     mappings_.FlushNewlyInternedTo([interned_data](const auto& interned) {
       auto mapping = interned_data->add_mappings();
       mapping->set_iid(interned.iid);
@@ -458,6 +478,8 @@ class InternedDataBuilder : public ValueObject {
   uint32_t sequence_flags_ = SequenceFlags::SEQ_INCREMENTAL_STATE_CLEARED |
                              SequenceFlags::SEQ_NEEDS_INCREMENTAL_STATE;
 
+  UnknownMappingState unknown_mapping_ = UnknownMappingState::kNotNeeded;
+
   // These are interned in debug_annotation_string_values space.
   IdToIidMap isolate_id_to_iid_of_formatted_string_;
   IdToIidMap isolate_group_id_to_iid_of_formatted_string_;

runtime/vm/profiler_service.cc

@@ -1976,6 +1976,10 @@ void Profile::PrintProfilePerfettoImpl(
                                                             /*length=*/1);
     }
 
+    if (mapping_iid == 0) {
+      interned_data_builder.MarkNeedUnknownMapping();
+    }
+
     // Add a |Frame| to the interned data table that is linked to |function|'s
     // name and source location (through the interned data table). A Perfetto
     // |Callstack| consists of a stack of |Frame|s, so the |Callstack|s

runtime/vm/thread.cc

@@ -651,7 +651,7 @@ void Thread::ResumeThreadInternal(Thread* thread) {
   thread->set_os_thread(os_thread);
   os_thread->set_thread(thread);
   Thread::SetCurrent(thread);
-  NOT_IN_PRODUCT(os_thread->EnableThreadInterrupts());
+  os_thread->EnableThreadInterrupts();
 
 #if !defined(PRODUCT) || defined(FORCE_INCLUDE_SAMPLING_HEAP_PROFILER)
   thread->heap_sampler().Initialize();
@@ -667,7 +667,7 @@ void Thread::SuspendThreadInternal(Thread* thread, VMTag::VMTagId tag) {
 
   OSThread* os_thread = thread->os_thread();
   ASSERT(os_thread != nullptr);
-  NOT_IN_PRODUCT(os_thread->DisableThreadInterrupts());
+  os_thread->DisableThreadInterrupts();
   os_thread->set_thread(nullptr);
   OSThread::SetCurrent(os_thread);
   thread->set_os_thread(nullptr);
@@ -1711,7 +1711,7 @@ void Thread::VisitMutators(MutatorThreadVisitor* visitor) {
   });
 }
 
-#if !defined(PRODUCT)
+#if defined(DART_INCLUDE_PROFILER)
 DisableThreadInterruptsScope::DisableThreadInterruptsScope(Thread* thread)
     : StackResource(thread) {
   if (thread != nullptr) {

runtime/vm/thread.h

@@ -1782,7 +1782,7 @@ class RuntimeCallDeoptScope : public StackResource {
 void WindowsThreadCleanUp();
 #endif
 
-#if !defined(PRODUCT)
+#if defined(DART_INCLUDE_PROFILER)
 // Disable thread interrupts.
 class DisableThreadInterruptsScope : public StackResource {
  public:
@@ -1796,7 +1796,7 @@ class DisableThreadInterruptsScope : public StackResource {
       : StackResource(thread) {}
   ~DisableThreadInterruptsScope() {}
 };
-#endif  // !defined(PRODUCT)
+#endif  // defined(DART_INCLUDE_PROFILER)
 
 // Within a NoSafepointScope, the thread must not reach any safepoint. Used
 // around code that manipulates raw object pointers directly without handles.