Reduce boot-up memory use of V8.

src/serialize.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 594 matching lines @@
       ASSERT_EQ(kLargeCode, space_index);
       new_allocation =
           lo_space->AllocateRaw(size, EXECUTABLE)->ToObjectUnchecked();
     }
     HeapObject* new_object = HeapObject::cast(new_allocation);
     // Record all large objects in the same space.
     address = new_object->address();
     pages_[LO_SPACE].Add(address);
   }
   last_object_address_ = address;
+  ASSERT(address >= Page::FromAddress(address)->ObjectAreaStart());
   return address;
 }
 
 
 // This returns the address of an object that has been described in the
 // snapshot as being offset bytes back in a particular space.
 HeapObject* Deserializer::GetAddressFromEnd(int space) {
   int offset = source_->GetInt();
   ASSERT(!SpaceIsLarge(space));
   offset <<= kObjectAlignmentBits;
-  return HeapObject::FromAddress(high_water_[space] - offset);
+  Address address = high_water_[space] - offset;
+  // This assert will fail if kMinimumSpaceSizes is too small for a space,
+  // because we rely on the fact that all allocation is linear when the VM
+  // is very young.
+  ASSERT(address >= Page::FromAddress(address)->ObjectAreaStart());
+  return HeapObject::FromAddress(address);
 }
 
 
 // This returns the address of an object that has been described in the
 // snapshot as being offset bytes into a particular space.
 HeapObject* Deserializer::GetAddressFromStart(int space) {
   int offset = source_->GetInt();
   if (SpaceIsLarge(space)) {
     // Large spaces have one object per 'page'.
     return HeapObject::FromAddress(pages_[LO_SPACE][offset]);
@@ skipping 1012 matching lines @@
       fullness_[space] = RoundUp(fullness_[space], Page::kPageSize);
     }
   }
   int allocation_address = fullness_[space];
   fullness_[space] = allocation_address + size;
   return allocation_address;
 }
 
 
 } }  // namespace v8::internal