Store embed-script flag as metadata into snapshot blob.

R=vogelheim@chromium.org

Review URL: https://codereview.chromium.org/848023002

Cr-Commit-Position: refs/heads/master@{#26049}

src/api.cc

@@ -229,11 +229,13 @@ StartupData V8::CreateSnapshotDataBlob(char* custom_source) {
     Isolate::Scope isolate_scope(isolate);
     i::Isolate* internal_isolate = reinterpret_cast<i::Isolate*>(isolate);
     Persistent<Context> context;
+    i::Snapshot::Metadata metadata;
     {
       HandleScope handle_scope(isolate);
       Handle<Context> new_context = Context::New(isolate);
       context.Reset(isolate, new_context);
       if (custom_source != NULL) {
+        metadata.set_embeds_script(true);
         Context::Scope context_scope(new_context);
         if (!RunExtraCode(isolate, custom_source)) context.Reset();
       }
@@ -264,7 +266,8 @@ StartupData V8::CreateSnapshotDataBlob(char* custom_source) {
       i::SnapshotData sd(snapshot_sink, ser);
       i::SnapshotData csd(context_sink, context_ser);
 
-      result = i::Snapshot::CreateSnapshotBlob(sd.RawData(), csd.RawData());
+      result = i::Snapshot::CreateSnapshotBlob(sd.RawData(), csd.RawData(),
+                                               metadata);
     }
   }
   isolate->Dispose();

src/bootstrapper.cc

@@ -2578,6 +2578,11 @@ bool Genesis::ConfigureApiObject(Handle<JSObject> object,
 
 void Genesis::TransferNamedProperties(Handle<JSObject> from,
                                       Handle<JSObject> to) {
+  // If JSObject::AddProperty asserts due to already existing property,
+  // it is likely due to both global objects sharing property name(s).
+  // Merging those two global objects is impossible.
+  // The global template must not create properties that already exist
+  // in the snapshotted global object.
   if (from->HasFastProperties()) {
     Handle<DescriptorArray> descs =
         Handle<DescriptorArray>(from->map()->instance_descriptors());

src/heap/spaces.cc

@@ -10,6 +10,7 @@
 #include "src/heap/mark-compact.h"
 #include "src/macro-assembler.h"
 #include "src/msan.h"
+#include "src/snapshot.h"
 
 namespace v8 {
 namespace internal {
@@ -1044,6 +1045,8 @@ bool PagedSpace::Expand() {
 
 
 intptr_t PagedSpace::SizeOfFirstPage() {
+  // If the snapshot contains a custom script, all size guarantees are off.
+  if (Snapshot::EmbedsScript()) return AreaSize();
   // If using an ool constant pool then transfer the constant pool allowance
   // from the code space to the old pointer space.
   static const int constant_pool_delta = FLAG_enable_ool_constant_pool ? 48 : 0;

src/snapshot-common.cc

@@ -19,6 +19,21 @@ bool Snapshot::HaveASnapshotToStartFrom() {
 }
 
 
+#ifdef DEBUG
+bool Snapshot::SnapshotIsValid(v8::StartupData* snapshot_blob) {
+  return !Snapshot::ExtractStartupData(snapshot_blob).is_empty() &&
+         !Snapshot::ExtractContextData(snapshot_blob).is_empty();
+}
+#endif  // DEBUG
+
+
+bool Snapshot::EmbedsScript() {
+  if (!HaveASnapshotToStartFrom()) return false;
+  const v8::StartupData blob = SnapshotBlob();
+  return ExtractMetadata(&blob).embeds_script();
+}
+
+
 bool Snapshot::Initialize(Isolate* isolate) {
   if (!HaveASnapshotToStartFrom()) return false;
   base::ElapsedTimer timer;
@@ -54,6 +69,9 @@ MaybeHandle<Context> Snapshot::NewContextFromSnapshot(
   Handle<Object> result;
   if (!maybe_context.ToHandle(&result)) return MaybeHandle<Context>();
   CHECK(result->IsContext());
+  // If the snapshot does not contain a custom script, we need to update
+  // the global object for exactly one context.
+  CHECK(EmbedsScript() || (*outdated_contexts_out)->length() == 1);
   if (FLAG_profile_deserialization) {
     double ms = timer.Elapsed().InMillisecondsF();
     int bytes = context_data.length();
@@ -65,28 +83,37 @@ MaybeHandle<Context> Snapshot::NewContextFromSnapshot(
 
 v8::StartupData Snapshot::CreateSnapshotBlob(
     const Vector<const byte> startup_data,
-    const Vector<const byte> context_data) {
+    const Vector<const byte> context_data, Snapshot::Metadata metadata) {
   int startup_length = startup_data.length();
   int context_length = context_data.length();
-  int context_offset = kIntSize + startup_length;
+  int context_offset = ContextOffset(startup_length);
+
   int length = context_offset + context_length;
   char* data = new char[length];
 
-  memcpy(data, &startup_length, kIntSize);
-  memcpy(data + kIntSize, startup_data.begin(), startup_length);
+  memcpy(data + kMetadataOffset, &metadata.RawValue(), kInt32Size);
+  memcpy(data + kStartupLengthOffset, &startup_length, kInt32Size);
+  memcpy(data + kStartupDataOffset, startup_data.begin(), startup_length);
   memcpy(data + context_offset, context_data.begin(), context_length);
   v8::StartupData result = {data, length};
   return result;
 }
 
 
+Snapshot::Metadata Snapshot::ExtractMetadata(const v8::StartupData* data) {
+  uint32_t raw;
+  memcpy(&raw, data->data + kMetadataOffset, kInt32Size);
+  return Metadata(raw);
+}
+
+
 Vector<const byte> Snapshot::ExtractStartupData(const v8::StartupData* data) {
   DCHECK_LT(kIntSize, data->raw_size);
   int startup_length;
-  memcpy(&startup_length, data->data, kIntSize);
+  memcpy(&startup_length, data->data + kStartupLengthOffset, kInt32Size);
   DCHECK_LT(startup_length, data->raw_size);
   const byte* startup_data =
-      reinterpret_cast<const byte*>(data->data + kIntSize);
+      reinterpret_cast<const byte*>(data->data + kStartupDataOffset);
   return Vector<const byte>(startup_data, startup_length);
 }
 
@@ -94,8 +121,8 @@ Vector<const byte> Snapshot::ExtractStartupData(const v8::StartupData* data) {
 Vector<const byte> Snapshot::ExtractContextData(const v8::StartupData* data) {
   DCHECK_LT(kIntSize, data->raw_size);
   int startup_length;
-  memcpy(&startup_length, data->data, kIntSize);
-  int context_offset = kIntSize + startup_length;
+  memcpy(&startup_length, data->data + kStartupLengthOffset, kIntSize);
+  int context_offset = ContextOffset(startup_length);
   const byte* context_data =
       reinterpret_cast<const byte*>(data->data + context_offset);
   DCHECK_LT(context_offset, data->raw_size);

src/snapshot-external.cc

@@ -26,9 +26,7 @@ void SetSnapshotFromFile(StartupData* snapshot_blob) {
   DCHECK(snapshot_blob->data);
   DCHECK(snapshot_blob->raw_size > 0);
   DCHECK(!external_startup_blob.data);
-  // Validate snapshot blob.
-  DCHECK(!Snapshot::ExtractStartupData(snapshot_blob).is_empty());
-  DCHECK(!Snapshot::ExtractContextData(snapshot_blob).is_empty());
+  DCHECK(Snapshot::SnapshotIsValid(snapshot_blob));
   external_startup_blob = *snapshot_blob;
 }
 

src/snapshot.h

@@ -12,6 +12,21 @@ namespace internal {
 
 class Snapshot : public AllStatic {
  public:
+  class Metadata {
+   public:
+    explicit Metadata(uint32_t data = 0) : data_(data) {}
+    bool embeds_script() { return EmbedsScriptBits::decode(data_); }
+    void set_embeds_script(bool v) {
+      data_ = EmbedsScriptBits::update(data_, v);
+    }
+
+    uint32_t& RawValue() { return data_; }
+
+   private:
+    class EmbedsScriptBits : public BitField<bool, 0, 1> {};
+    uint32_t data_;
+  };
+
   // Initialize the Isolate from the internal snapshot. Returns false if no
   // snapshot could be found.
   static bool Initialize(Isolate* isolate);
@@ -21,17 +36,32 @@ class Snapshot : public AllStatic {
 
   static bool HaveASnapshotToStartFrom();
 
+  static bool EmbedsScript();
+
   // To be implemented by the snapshot source.
   static const v8::StartupData SnapshotBlob();
 
   static v8::StartupData CreateSnapshotBlob(
       const Vector<const byte> startup_data,
-      const Vector<const byte> context_data);
+      const Vector<const byte> context_data, Metadata metadata);
+
+#ifdef DEBUG
+  static bool SnapshotIsValid(v8::StartupData* snapshot_blob);
+#endif  // DEBUG
 
+ private:
   static Vector<const byte> ExtractStartupData(const v8::StartupData* data);
   static Vector<const byte> ExtractContextData(const v8::StartupData* data);
+  static Metadata ExtractMetadata(const v8::StartupData* data);
+
+  static const int kMetadataOffset = 0;
+  static const int kStartupLengthOffset = kMetadataOffset + kInt32Size;
+  static const int kStartupDataOffset = kStartupLengthOffset + kInt32Size;
+
+  static int ContextOffset(int startup_length) {
+    return kStartupDataOffset + startup_length;
+  }
 
- private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(Snapshot);
 };