[parser] Skipping inner funcs: Less scope analysis.

We don't need to save any data for top-level leaf
funcs (they contain no skippable funcs), so we
don't need scope analysis for them either.

BUG=v8:5516

Change-Id: I75700838a3df2f19da559145611c99e2c7ffd088
Reviewed-on: https://chromium-review.googlesource.com/691976
Commit-Queue: Marja Hölttä <marja@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48746}

src/ast/scopes.cc

@@ -1542,7 +1542,10 @@ void DeclarationScope::AnalyzePartially(AstNodeFactory* ast_node_factory) {
   DCHECK(!force_eager_compilation_);
   VariableProxy* unresolved = nullptr;
 
-  if (!outer_scope_->is_script_scope() || FLAG_preparser_scope_analysis) {
+  if (!outer_scope_->is_script_scope() ||
+      (FLAG_preparser_scope_analysis &&
+       produced_preparsed_scope_data_ != nullptr &&
+       produced_preparsed_scope_data_->ContainsInnerFunctions())) {
     // Try to resolve unresolved variables for this Scope and migrate those
     // which cannot be resolved inside. It doesn't make sense to try to resolve
     // them in the outer Scopes here, because they are incomplete.

src/parsing/preparsed-scope-data.cc

@@ -36,6 +36,7 @@ const size_t kUint32Size = 4;
 const size_t kUint8Size = 1;
 #endif
 
+const int kPlaceholderSize = kUint32Size;
 const int kSkippableFunctionDataSize = 4 * kUint32Size + 1 * kUint8Size;
 
 class LanguageField : public BitField<LanguageMode, 0, 1> {};
@@ -224,9 +225,9 @@ void ProducedPreParsedScopeData::SaveScopeAllocationData(
   DCHECK(previously_produced_preparsed_scope_data_.is_null());
   // The data contains a uint32 (reserved space for scope_data_start) and
   // function data items, kSkippableFunctionDataSize each.
-  DCHECK_GE(byte_data_->size(), kUint32Size);
+  DCHECK_GE(byte_data_->size(), kPlaceholderSize);
   DCHECK_LE(byte_data_->size(), std::numeric_limits<uint32_t>::max());
-  DCHECK_EQ(byte_data_->size() % kSkippableFunctionDataSize, kUint32Size);
+  DCHECK_EQ(byte_data_->size() % kSkippableFunctionDataSize, kPlaceholderSize);
 
   if (bailed_out_) {
     return;
@@ -235,7 +236,7 @@ void ProducedPreParsedScopeData::SaveScopeAllocationData(
   uint32_t scope_data_start = static_cast<uint32_t>(byte_data_->size());
 
   // If there are no skippable inner functions, we don't need to save anything.
-  if (scope_data_start == kUint32Size) {
+  if (scope_data_start == kPlaceholderSize) {
     return;
   }
 
@@ -250,6 +251,10 @@ void ProducedPreParsedScopeData::SaveScopeAllocationData(
   SaveDataForScope(scope);
 }
 
+bool ProducedPreParsedScopeData::ContainsInnerFunctions() const {
+  return byte_data_->size() > kPlaceholderSize;
+}
+
 MaybeHandle<PreParsedScopeData> ProducedPreParsedScopeData::Serialize(
     Isolate* isolate) const {
   if (!previously_produced_preparsed_scope_data_.is_null()) {
@@ -263,7 +268,7 @@ MaybeHandle<PreParsedScopeData> ProducedPreParsedScopeData::Serialize(
 
   DCHECK(!ThisOrParentBailedOut());
 
-  if (byte_data_->size() <= kUint32Size) {
+  if (byte_data_->size() <= kPlaceholderSize) {
     // The data contains only the placeholder.
     return MaybeHandle<PreParsedScopeData>();
   }
@@ -452,7 +457,7 @@ void ConsumedPreParsedScopeData::SetData(Handle<PreParsedScopeData> data) {
   DCHECK_EQ(scope_data_->ReadUint32(), kMagicValue);
 #endif
   // The first data item is scope_data_start. Skip over it.
-  scope_data_->SetPosition(kUint32Size);
+  scope_data_->SetPosition(kPlaceholderSize);
 }
 
 ProducedPreParsedScopeData*

src/parsing/preparsed-scope-data.h

@@ -142,6 +142,8 @@ class ProducedPreParsedScopeData : public ZoneObject {
   }
 #endif  // DEBUG
 
+  bool ContainsInnerFunctions() const;
+
   // If there is data (if the Scope contains skippable inner functions), move
   // the data into the heap and return a Handle to it; otherwise return a null
   // MaybeHandle.