Ensure double alignment when deserializing.

src/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 789 matching lines @@
   }
   return obj;
 }
 
 
 // This routine writes the new object into the pointer provided and then
 // returns true if the new object was in young space and false otherwise.
 // The reason for this strange interface is that otherwise the object is
 // written very late, which means the FreeSpace map is not set up by the
 // time we need to use it to mark the space at the end of a page free.
-void Deserializer::ReadObject(int space_number,
-                              Object** write_back) {
-  int size = source_->GetInt() << kObjectAlignmentBits;
-  Address address = Allocate(space_number, size);
-  HeapObject* obj = HeapObject::FromAddress(address);
+void Deserializer::ReadObject(int space_number, Object** write_back) {
+  Address address;
+  HeapObject* obj;
+  int next_int = source_->GetInt();
+
+  bool double_align = false;
+#ifndef V8_HOST_ARCH_64_BIT
+  double_align = next_int == kDoubleAlignmentSentinel;
+  if (double_align) next_int = source_->GetInt();
+#endif
+
+  DCHECK_NE(kDoubleAlignmentSentinel, next_int);
+  int size = next_int << kObjectAlignmentBits;
+  int reserved_size = size + (double_align ? kPointerSize : 0);
+  address = Allocate(space_number, reserved_size);
+  obj = HeapObject::FromAddress(address);
+  if (double_align) {
+    obj = isolate_->heap()->DoubleAlignForDeserialization(obj, reserved_size);
+    address = obj->address();
+  }
+
   isolate_->heap()->OnAllocationEvent(obj, size);
   Object** current = reinterpret_cast<Object**>(address);
   Object** limit = current + (size >> kPointerSizeLog2);
   if (FLAG_log_snapshot_positions) {
     LOG(isolate_, SnapshotPositionEvent(address, source_->position()));
   }
   ReadData(current, limit, space_number, address);
 
   // TODO(mvstanton): consider treating the heap()->allocation_sites_list()
   // as a (weak) root. If this root is relocated correctly,
@@ skipping 717 matching lines @@
     sink_->PutInt(skip, "SkipDistanceFromSerializeObject");
   }
   // Object has not yet been serialized.  Serialize it here.
   ObjectSerializer serializer(this, obj, sink_, how_to_code, where_to_point);
   serializer.Serialize();
 }
 
 
 void Serializer::ObjectSerializer::SerializePrologue(AllocationSpace space,
                                                      int size, Map* map) {
+  int reserved_size = size;
+
   sink_->Put(kNewObject + reference_representation_ + space,
              "ObjectSerialization");
-  sink_->PutInt(size >> kObjectAlignmentBits, "Size in words");
+  // Objects on the large object space are always double-aligned.
+  if (space != LO_SPACE && object_->NeedsToEnsureDoubleAlignment()) {
+    sink_->PutInt(kDoubleAlignmentSentinel, "double align next object");
+    // Add wriggle room for double alignment padding.
+    reserved_size += kPointerSize;
+  }
+  int encoded_size = size >> kObjectAlignmentBits;
+  DCHECK_NE(kDoubleAlignmentSentinel, encoded_size);
+  sink_->PutInt(encoded_size, "Size in words");
 
   if (serializer_->code_address_map_) {
     const char* code_name =
         serializer_->code_address_map_->Lookup(object_->address());
     LOG(serializer_->isolate_,
         CodeNameEvent(object_->address(), sink_->Position(), code_name));
     LOG(serializer_->isolate_,
         SnapshotPositionEvent(object_->address(), sink_->Position()));
   }
 
   // Mark this object as already serialized.
   BackReference back_reference;
   if (space == LO_SPACE) {
     if (object_->IsCode()) {
       sink_->Put(EXECUTABLE, "executable large object");
     } else {
       sink_->Put(NOT_EXECUTABLE, "not executable large object");
     }
     back_reference = serializer_->AllocateLargeObject(size);
   } else {
-    back_reference = serializer_->Allocate(space, size);
+    back_reference = serializer_->Allocate(space, reserved_size);
   }
   serializer_->back_reference_map()->Add(object_, back_reference);
 
   // Serialize the map (first word of the object).
   serializer_->SerializeObject(map, kPlain, kStartOfObject, 0);
 }
 
 
 void Serializer::ObjectSerializer::SerializeExternalString() {
   // Instead of serializing this as an external string, we serialize
@@ skipping 325 matching lines @@
 
 BackReference Serializer::AllocateLargeObject(int size) {
   // Large objects are allocated one-by-one when deserializing. We do not
   // have to keep track of multiple chunks.
   large_objects_total_size_ += size;
   return BackReference::LargeObjectReference(seen_large_objects_index_++);
 }
 
 
 BackReference Serializer::Allocate(AllocationSpace space, int size) {
-  CHECK(space >= 0 && space < kNumberOfPreallocatedSpaces);
+  DCHECK(space >= 0 && space < kNumberOfPreallocatedSpaces);
   DCHECK(size > 0 && size <= static_cast<int>(max_chunk_size(space)));
   uint32_t new_chunk_size = pending_chunk_[space] + size;
   if (new_chunk_size > max_chunk_size(space)) {
     // The new chunk size would not fit onto a single page. Complete the
     // current chunk and start a new one.
     completed_chunks_[space].Add(pending_chunk_[space]);
     pending_chunk_[space] = 0;
     new_chunk_size = size;
   }
   uint32_t offset = pending_chunk_[space];
@@ skipping 389 matching lines @@
 bool SerializedCodeData::IsSane(String* source) {
   return GetHeaderValue(kCheckSumOffset) == CheckSum(source) &&
          PayloadLength() >= SharedFunctionInfo::kSize;
 }
 
 
 int SerializedCodeData::CheckSum(String* string) {
   return Version::Hash() ^ string->length();
 }
 } }  // namespace v8::internal