[TurboFan] Don't serialize read-only heap objects

Read-only heap objects are immutable and immovable. It is safe to access
these objects directly from the heap. Not having to serialize them
reduces the time we spend on main thread especially for TurboProp.

Bug: v8:9684
Change-Id: Ibabb7076af50c9007d2a8ed57fe257406958fb6a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1955596Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65490}

src/compiler/js-heap-broker.h

@@ -18,6 +18,7 @@
 #include "src/objects/feedback-vector.h"
 #include "src/objects/function-kind.h"
 #include "src/objects/objects.h"
+#include "src/utils/address-map.h"
 #include "src/utils/ostreams.h"
 #include "src/zone/zone-containers.h"
 
@@ -84,7 +85,7 @@ class V8_EXPORT_PRIVATE JSHeapBroker {
   void InitializeAndStartSerializing(Handle<NativeContext> native_context);
 
   Isolate* isolate() const { return isolate_; }
-  Zone* zone() const { return current_zone_; }
+  Zone* zone() const { return zone_; }
   bool tracing_enabled() const { return tracing_enabled_; }
 
   enum BrokerMode { kDisabled, kSerializing, kSerialized, kRetired };
@@ -97,8 +98,9 @@ class V8_EXPORT_PRIVATE JSHeapBroker {
   void PrintRefsAnalysis() const;
 #endif  // DEBUG
 
-  // Returns nullptr iff handle unknown.
-  ObjectData* GetData(Handle<Object>) const;
+  // Retruns the handle from root index table for read only heap objects.
+  Handle<Object> GetRootHandle(Object object);
+
   // Never returns nullptr.
   ObjectData* GetOrCreateData(Handle<Object>);
   // Like the previous but wraps argument in handle first (for convenience).
@@ -193,6 +195,8 @@ class V8_EXPORT_PRIVATE JSHeapBroker {
   void IncrementTracingIndentation();
   void DecrementTracingIndentation();
 
+  RootIndexMap const& root_index_map() { return root_index_map_; }
+
  private:
   friend class HeapObjectRef;
   friend class ObjectRef;
@@ -221,17 +225,16 @@ class V8_EXPORT_PRIVATE JSHeapBroker {
   ProcessedFeedback const& ReadFeedbackForTemplateObject(
       FeedbackSource const& source);
 
-  void InitializeRefsMap();
   void CollectArrayAndObjectPrototypes();
   void SerializeTypedArrayStringTags();
 
   PerIsolateCompilerCache* compiler_cache() const { return compiler_cache_; }
 
   Isolate* const isolate_;
-  Zone* const broker_zone_;
-  Zone* current_zone_ = nullptr;
+  Zone* const zone_ = nullptr;
   base::Optional<NativeContextRef> target_native_context_;
   RefsMap* refs_;
+  RootIndexMap root_index_map_;
   ZoneUnorderedSet<Handle<JSObject>, Handle<JSObject>::hash,
                    Handle<JSObject>::equal_to>
       array_and_object_prototypes_;