From ace94df55831d8c075f7fae3624b0fd41c850d4c Mon Sep 17 00:00:00 2001
From: yangguo <yangguo@chromium.org>
Date: Fri, 16 Jan 2015 14:22:13 -0800
Subject: [PATCH] Use back reference map to find references to global proxy.

R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/825933004

Cr-Commit-Position: refs/heads/master@{#26114}
---
 src/serialize.cc | 20 +++++++++-----------
 src/serialize.h  | 14 +++++++++++---
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/src/serialize.cc b/src/serialize.cc
index 085f4e5..140902f 100644
--- a/src/serialize.cc
+++ b/src/serialize.cc
@@ -1405,7 +1405,7 @@ void PartialSerializer::Serialize(Object** o) {
   if ((*o)->IsContext()) {
     Context* context = Context::cast(*o);
     global_object_ = context->global_object();
-    global_proxy_ = context->global_proxy();
+    back_reference_map()->AddGlobalProxy(context->global_proxy());
   }
   VisitPointer(o);
   SerializeOutdatedContextsAsFixedArray();
@@ -1562,8 +1562,14 @@ bool Serializer::SerializeKnownObject(HeapObject* obj, HowToCode how_to_code,
       FlushSkip(skip);
       if (FLAG_trace_serializer) PrintF(" Encoding source object\n");
       DCHECK(how_to_code == kPlain && where_to_point == kStartOfObject);
-      sink_->Put(kAttachedReference + how_to_code + where_to_point, "Source");
-      sink_->PutInt(kSourceObjectReference, "kSourceObjectIndex");
+      sink_->Put(kAttachedReference + kPlain + kStartOfObject, "Source");
+      sink_->PutInt(kSourceObjectReference, "kSourceObjectReference");
+    } else if (back_reference.is_global_proxy()) {
+      FlushSkip(skip);
+      if (FLAG_trace_serializer) PrintF(" Encoding global proxy\n");
+      DCHECK(how_to_code == kPlain && where_to_point == kStartOfObject);
+      sink_->Put(kAttachedReference + kPlain + kStartOfObject, "Global Proxy");
+      sink_->PutInt(kGlobalProxyReference, "kGlobalProxyReference");
     } else {
       if (FLAG_trace_serializer) {
         PrintF(" Encoding back reference to: ");
@@ -1696,14 +1702,6 @@ void PartialSerializer::SerializeObject(HeapObject* obj, HowToCode how_to_code,
 
   FlushSkip(skip);
 
-  if (obj == global_proxy_) {
-    FlushSkip(skip);
-    DCHECK(how_to_code == kPlain && where_to_point == kStartOfObject);
-    sink_->Put(kAttachedReference + how_to_code + where_to_point, "Reference");
-    sink_->PutInt(kGlobalProxyReference, "kGlobalProxyReferenceIndex");
-    return;
-  }
-
   // Object has not yet been serialized.  Serialize it here.
   ObjectSerializer serializer(this, obj, sink_, how_to_code, where_to_point);
   serializer.Serialize();
diff --git a/src/serialize.h b/src/serialize.h
index 53dc6eb..cc267aa 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -193,6 +193,10 @@ class BackReference {
 
   static BackReference SourceReference() { return BackReference(kSourceValue); }
 
+  static BackReference GlobalProxyReference() {
+    return BackReference(kGlobalProxyValue);
+  }
+
   static BackReference LargeObjectReference(uint32_t index) {
     return BackReference(SpaceBits::encode(LO_SPACE) |
                          ChunkOffsetBits::encode(index));
@@ -209,6 +213,7 @@ class BackReference {
 
   bool is_valid() const { return bitfield_ != kInvalidValue; }
   bool is_source() const { return bitfield_ == kSourceValue; }
+  bool is_global_proxy() const { return bitfield_ == kGlobalProxyValue; }
 
   AllocationSpace space() const {
     DCHECK(is_valid());
@@ -235,6 +240,7 @@ class BackReference {
  private:
   static const uint32_t kInvalidValue = 0xFFFFFFFF;
   static const uint32_t kSourceValue = 0xFFFFFFFE;
+  static const uint32_t kGlobalProxyValue = 0xFFFFFFFD;
   static const int kChunkOffsetSize = kPageSizeBits - kObjectAlignmentBits;
   static const int kChunkIndexSize = 32 - kChunkOffsetSize - kSpaceTagSize;
 
@@ -278,6 +284,10 @@ class BackReferenceMap : public AddressMapBase {
     Add(string, BackReference::SourceReference());
   }
 
+  void AddGlobalProxy(HeapObject* global_proxy) {
+    Add(global_proxy, BackReference::GlobalProxyReference());
+  }
+
  private:
   DisallowHeapAllocation no_allocation_;
   HashMap* map_;
@@ -751,8 +761,7 @@ class PartialSerializer : public Serializer {
       : Serializer(isolate, sink),
         startup_serializer_(startup_snapshot_serializer),
         outdated_contexts_(0),
-        global_object_(NULL),
-        global_proxy_(NULL) {
+        global_object_(NULL) {
     InitializeCodeAddressMap();
   }
 
@@ -781,7 +790,6 @@ class PartialSerializer : public Serializer {
   Serializer* startup_serializer_;
   List<BackReference> outdated_contexts_;
   Object* global_object_;
-  Object* global_proxy_;
   DISALLOW_COPY_AND_ASSIGN(PartialSerializer);
 };
 
-- 
2.7.4