Create a internal, global native context used only for generated code stubs

src/snapshot/serialize.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/platform/platform.h"
 #include "src/bootstrapper.h"
@@ skipping 557 matching lines @@
   {
     DisallowHeapAllocation no_gc;
     isolate_->heap()->IterateSmiRoots(this);
     isolate_->heap()->IterateStrongRoots(this, VISIT_ONLY_STRONG);
     isolate_->heap()->RepairFreeListsAfterDeserialization();
     isolate_->heap()->IterateWeakRoots(this, VISIT_ALL);
     DeserializeDeferredObjects();
   }
 
   isolate_->heap()->set_native_contexts_list(
-      isolate_->heap()->undefined_value());
+      isolate_->heap()->code_stub_context());
 
   // The allocation site list is build during root iteration, but if no sites
   // were encountered then it needs to be initialized to undefined.
   if (isolate_->heap()->allocation_sites_list() == Smi::FromInt(0)) {
     isolate_->heap()->set_allocation_sites_list(
         isolate_->heap()->undefined_value());
   }
 
   // Update data pointers to the external strings containing natives sources.
   for (int i = 0; i < Natives::GetBuiltinsCount(); i++) {
     Object* source = isolate_->heap()->natives_source_cache()->get(i);
     if (!source->IsUndefined()) {
       ExternalOneByteString::cast(source)->update_data_cache();
     }
   }
 
+  for (int i = 0; i < CodeStubNatives::GetBuiltinsCount(); i++) {
+    Object* source = isolate_->heap()->code_stub_natives_source_cache()->get(i);
+    if (!source->IsUndefined()) {
+      ExternalOneByteString::cast(source)->update_data_cache();
+    }
+  }
+
   FlushICacheForNewCodeObjects();
 
   // Issue code events for newly deserialized code objects.
   LOG_CODE_EVENT(isolate_, LogCodeObjects());
   LOG_CODE_EVENT(isolate_, LogCompiledFunctions());
 }
 
 
 MaybeHandle<Object> Deserializer::DeserializePartial(
     Isolate* isolate, Handle<JSGlobalProxy> global_proxy,
@@ skipping 573 matching lines @@
         int index = source_.Get();
         Vector<const char> source_vector = Natives::GetScriptSource(index);
         NativesExternalStringResource* resource =
             new NativesExternalStringResource(source_vector.start(),
                                               source_vector.length());
         Object* resource_obj = reinterpret_cast<Object*>(resource);
         UnalignedCopy(current++, &resource_obj);
         break;
       }
 
+      case kCodeStubNativesStringResource: {
+        DCHECK(!isolate_->heap()->deserialization_complete());
+        int index = source_.Get();

[Yang, 2015/07/08 08:32:54]

This duplicate code could be refactored into a helper function that takes a
Vector<const char>. Or you could handle both cases at once and then choose the
script source depending on the value of |data|.

[danno, 2015/07/08 20:25:59]

Done.

+        Vector<const char> source_vector =
+            CodeStubNatives::GetScriptSource(index);
+        NativesExternalStringResource* resource =
+            new NativesExternalStringResource(source_vector.start(),
+                                              source_vector.length());
+        Object* resource_obj = reinterpret_cast<Object*>(resource);
+        UnalignedCopy(current++, &resource_obj);
+        break;
+      }
+
       // Deserialize raw data of variable length.
       case kVariableRawData: {
         int size_in_bytes = source_.GetInt();
         byte* raw_data_out = reinterpret_cast<byte*>(current);
         source_.CopyRaw(raw_data_out, size_in_bytes);
         break;
       }
 
       case kVariableRepeat: {
         int repeats = source_.GetInt();
@@ skipping 214 matching lines @@
     }
   }
 }
 
 
 void PartialSerializer::Serialize(Object** o) {
   if ((*o)->IsContext()) {
     Context* context = Context::cast(*o);
     global_object_ = context->global_object();
     back_reference_map()->AddGlobalProxy(context->global_proxy());
+    if (context->IsNativeContext()) {
+      context->set(Context::NEXT_CONTEXT_LINK,

[Yang, 2015/07/08 08:32:54]

Some comment here would be great.

[danno, 2015/07/08 20:25:59]

Done.

+                   isolate_->heap()->undefined_value());
+      DCHECK(!context->global_object()->IsUndefined());
+      DCHECK(!context->builtins()->IsUndefined());
+    }
   }
   VisitPointer(o);
   SerializeDeferredObjects();
   SerializeOutdatedContextsAsFixedArray();
   Pad();
 }
 
 
 void PartialSerializer::SerializeOutdatedContextsAsFixedArray() {
   int length = outdated_contexts_.length();
@@ skipping 184 matching lines @@
       PutBackReference(obj, back_reference);
     }
     return true;
   }
   return false;
 }
 
 
 void StartupSerializer::SerializeObject(HeapObject* obj, HowToCode how_to_code,
                                         WhereToPoint where_to_point, int skip) {
-  DCHECK(!obj->IsJSFunction());
+#if DEBUG
+  // Make sure that all contexts are derived from the code-stub context

[Yang, 2015/07/08 08:32:54]

... all *functions* are derived ...

[danno, 2015/07/08 20:25:59]

Done.

+  if (obj->IsJSFunction()) {
+    Context* current = JSFunction::cast(obj)->context();

[Yang, 2015/07/08 08:32:54]

Can you replace this with

DCHECK(!obj->IsJSFunction() || obj->GetCreationContext() ==
isolate()->heap()->code_stub_context())

There is a small difference between the creation context and the function
context, but the native context of the latter should be the same. Either way you
save yourself that explicit context walk.

[danno, 2015/07/08 20:25:59]

Done.

+    while (current != isolate()->heap()->code_stub_context()) {
+      current = current->previous();
+    }
+    DCHECK_EQ(isolate()->heap()->code_stub_context(), current);
+  }
+#endif
 
   int root_index = root_index_map_.Lookup(obj);
   // We can only encode roots as such if it has already been serialized.
   // That applies to root indices below the wave front.
   if (root_index != RootIndexMap::kInvalidRootIndex &&
       root_index < root_index_wave_front_) {
     PutRoot(root_index, obj, how_to_code, where_to_point, skip);
     return;
   }
 
@@ skipping 502 matching lines @@
       typedef v8::String::ExternalOneByteStringResource Resource;
       const Resource* resource = string->resource();
       if (resource == *resource_pointer) {
         sink_->Put(kNativesStringResource, "NativesStringResource");
         sink_->PutSection(i, "NativesStringResourceEnd");
         bytes_processed_so_far_ += sizeof(resource);
         return;
       }
     }
   }
+  for (int i = 0; i < CodeStubNatives::GetBuiltinsCount(); i++) {

[Yang, 2015/07/08 08:32:54]

Could you refactor this duplicate code into a helper function that takes the
cache and the builtins count as arguments?

[danno, 2015/07/08 20:25:59]

Done.

+    Object* source =
+        serializer_->isolate()->heap()->code_stub_natives_source_cache()->get(
+            i);
+    if (!source->IsUndefined()) {
+      ExternalOneByteString* string = ExternalOneByteString::cast(source);
+      typedef v8::String::ExternalOneByteStringResource Resource;
+      const Resource* resource = string->resource();
+      if (resource == *resource_pointer) {
+        sink_->Put(kCodeStubNativesStringResource,
+                   "CodeStubNativesStringResource");
+        sink_->PutSection(i, "CodeStubNativesStringResourceEnd");
+        bytes_processed_so_far_ += sizeof(resource);
+        return;
+      }
+    }
+  }
   // One of the strings in the natives cache should match the resource.  We
   // don't expect any other kinds of external strings here.
   UNREACHABLE();
 }
 
 
 Address Serializer::ObjectSerializer::PrepareCode() {
   // To make snapshots reproducible, we make a copy of the code object
   // and wipe all pointers in the copy, which we then serialize.
   Code* original = Code::cast(object_);
@@ skipping 590 matching lines @@
   SerializedCodeData* scd = new SerializedCodeData(cached_data);
   SanityCheckResult r = scd->SanityCheck(isolate, source);
   if (r == CHECK_SUCCESS) return scd;
   cached_data->Reject();
   source->GetIsolate()->counters()->code_cache_reject_reason()->AddSample(r);
   delete scd;
   return NULL;
 }
 }  // namespace internal
 }  // namespace v8