[turboshaft] performance tweak: source positions only if needed

Change-Id: I2a35ae0d07bcd5c570bcaae8ae6ef886a5b5e926
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3852484Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83185}

src/compiler/compiler-source-position-table.cc

@@ -32,11 +32,16 @@ SourcePositionTable::SourcePositionTable(Graph* graph)
 
 void SourcePositionTable::AddDecorator() {
   DCHECK_NULL(decorator_);
+  if (!enabled_) return;
   decorator_ = graph_->zone()->New<Decorator>(this);
   graph_->AddDecorator(decorator_);
 }
 
 void SourcePositionTable::RemoveDecorator() {
+  if (!enabled_) {
+    DCHECK_NULL(decorator_);
+    return;
+  }
   DCHECK_NOT_NULL(decorator_);
   graph_->RemoveDecorator(decorator_);
   decorator_ = nullptr;
@@ -51,6 +56,7 @@ SourcePosition SourcePositionTable::GetSourcePosition(NodeId id) const {
 
 void SourcePositionTable::SetSourcePosition(Node* node,
                                             SourcePosition position) {
+  DCHECK(IsEnabled());
   table_.Set(node, position);
 }
 

src/compiler/compiler-source-position-table.h

@@ -57,6 +57,10 @@ class V8_EXPORT_PRIVATE SourcePositionTable final
   }
   SourcePosition GetCurrentPosition() const { return current_position_; }
 
+  void Disable() { enabled_ = false; }
+
+  bool IsEnabled() const { return enabled_; }
+
   void PrintJson(std::ostream& os) const;
 
  private:
@@ -70,6 +74,7 @@ class V8_EXPORT_PRIVATE SourcePositionTable final
   Decorator* decorator_;
   SourcePosition current_position_;
   NodeAuxData<SourcePosition, UnknownSourcePosition> table_;
+  bool enabled_ = true;
 };
 
 }  // namespace compiler

src/compiler/pipeline.cc

@@ -2799,7 +2799,9 @@ void PipelineImpl::InitializeHeapBroker() {
     TurboCfgFile tcf(isolate());
     tcf << AsC1VCompilation(info());
   }
-
+  if (data->info()->bytecode_array()->SourcePositionTable().DataSize() == 0) {
+    data->source_positions()->Disable();
+  }
   data->source_positions()->AddDecorator();
   if (data->info()->trace_turbo_json()) {
     data->node_origins()->AddDecorator();

src/compiler/turboshaft/graph-builder.cc

@@ -224,7 +224,7 @@ base::Optional<BailoutReason> GraphBuilder::Run() {
     DCHECK_NULL(assembler.current_block());
   }
 
-  if (source_positions) {
+  if (source_positions->IsEnabled()) {
     for (OpIndex index : assembler.graph().AllOperationIndices()) {
       compiler::NodeId origin =
           assembler.graph().operation_origins()[index].DecodeTurbofanNodeId();

src/compiler/turboshaft/recreate-schedule.cc

@@ -156,7 +156,7 @@ void ScheduleBuilder::ProcessOperation(const Operation& op) {
   OpIndex index = input_graph.Index(op);
   DCHECK_LT(index.id(), nodes.size());
   nodes[index.id()] = node;
-  if (source_positions && node) {
+  if (source_positions->IsEnabled() && node) {
     source_positions->SetSourcePosition(node,
                                         input_graph.source_positions()[index]);
   }

test/cctest/test-cpu-profiler.cc

@@ -1247,6 +1247,8 @@ static void TickLines(bool optimize) {
   i::Isolate* isolate = CcTest::i_isolate();
   i::Factory* factory = isolate->factory();
   i::HandleScope scope(isolate);
+  // Ensure that source positions are collected everywhere.
+  isolate->SetIsProfiling(true);
 
   base::EmbeddedVector<char, 512> script;
   base::EmbeddedVector<char, 64> prepare_opt;
@@ -1850,6 +1852,8 @@ TEST(Inlining) {
   v8::Local<v8::Context> env = CcTest::NewContext({PROFILER_EXTENSION_ID});
   v8::Context::Scope context_scope(env);
   ProfilerHelper helper(env);
+  // Ensure that source positions are collected everywhere.
+  CcTest::i_isolate()->SetIsProfiling(true);
 
   CompileRun(inlining_test_source);
   v8::Local<v8::Function> function = GetFunction(env, "start");