[heap] Fix skip list for deserialized code objects.

src/heap/spaces.h

 // Copyright 2011 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.
 
 #ifndef V8_HEAP_SPACES_H_
 #define V8_HEAP_SPACES_H_
 
 #include "src/allocation.h"
 #include "src/atomic-utils.h"
 #include "src/base/atomicops.h"
@@ skipping 1182 matching lines @@
       starts_[idx] = reinterpret_cast<Address>(-1);
     }
   }
 
   Address StartFor(Address addr) { return starts_[RegionNumber(addr)]; }
 
   void AddObject(Address addr, int size) {
     int start_region = RegionNumber(addr);
     int end_region = RegionNumber(addr + size - kPointerSize);
     for (int idx = start_region; idx <= end_region; idx++) {
-      if (starts_[idx] > addr) starts_[idx] = addr;
+      if (starts_[idx] > addr) {
+        starts_[idx] = addr;
+      } else {
+        // In the first region, there may already be an object closer to the
+        // start of the region. Do not change the start in that case. If this
+        // is not the first region, you probably added overlapping objects.
+        DCHECK_EQ(start_region, idx);
+      }
     }
   }
 
   static inline int RegionNumber(Address addr) {
     return (OffsetFrom(addr) & Page::kPageAlignmentMask) >> kRegionSizeLog2;
   }
 
   static void Update(Address addr, int size) {
     Page* page = Page::FromAddress(addr);
     SkipList* list = page->skip_list();
@@ skipping 817 matching lines @@
   Address limit() { return allocation_info_.limit(); }
 
   // The allocation top address.
   Address* allocation_top_address() { return allocation_info_.top_address(); }
 
   // The allocation limit address.
   Address* allocation_limit_address() {
     return allocation_info_.limit_address();
   }
 
+  enum UpdateSkipList { UPDATE_SKIP_LIST, IGNORE_SKIP_LIST };
+
   // Allocate the requested number of bytes in the space if possible, return a
-  // failure object if not.
+  // failure object if not. Only use IGNORE_SKIP_LIST if the skip list is going
+  // to be manually updated later.
   MUST_USE_RESULT inline AllocationResult AllocateRawUnaligned(
-      int size_in_bytes);
+      int size_in_bytes, UpdateSkipList update_skip_list = UPDATE_SKIP_LIST);
 
   MUST_USE_RESULT inline AllocationResult AllocateRawUnalignedSynchronized(
       int size_in_bytes);
 
   // Allocate the requested number of bytes in the space double aligned if
   // possible, return a failure object if not.
   MUST_USE_RESULT inline AllocationResult AllocateRawAligned(
       int size_in_bytes, AllocationAlignment alignment);
 
   // Allocate the requested number of bytes in the space and consider allocation
@@ skipping 1027 matching lines @@
     count = 0;
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_SPACES_H_