[heap] Fix skip list for deserialized code objects.

R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/1816463002

Cr-Commit-Position: refs/heads/master@{#34895}

src/heap/heap.cc

@@ -1158,7 +1158,9 @@ bool Heap::ReserveSpace(Reservation* reservations) {
           if (space == NEW_SPACE) {
             allocation = new_space()->AllocateRawUnaligned(size);
           } else {
-            allocation = paged_space(space)->AllocateRawUnaligned(size);
+            // The deserializer will update the skip list.
+            allocation = paged_space(space)->AllocateRawUnaligned(
+                size, PagedSpace::IGNORE_SKIP_LIST);
           }
           HeapObject* free_space = nullptr;
           if (allocation.To(&free_space)) {

src/heap/spaces-inl.h

@@ -498,7 +498,8 @@ HeapObject* PagedSpace::AllocateLinearlyAligned(int* size_in_bytes,
 
 
 // Raw allocation.
-AllocationResult PagedSpace::AllocateRawUnaligned(int size_in_bytes) {
+AllocationResult PagedSpace::AllocateRawUnaligned(
+    int size_in_bytes, UpdateSkipList update_skip_list) {
   HeapObject* object = AllocateLinearly(size_in_bytes);
 
   if (object == NULL) {
@@ -509,7 +510,7 @@ AllocationResult PagedSpace::AllocateRawUnaligned(int size_in_bytes) {
   }
 
   if (object != NULL) {
-    if (identity() == CODE_SPACE) {
+    if (update_skip_list == UPDATE_SKIP_LIST && identity() == CODE_SPACE) {
       SkipList::Update(object->address(), size_in_bytes);
     }
     MSAN_ALLOCATED_UNINITIALIZED_MEMORY(object->address(), size_in_bytes);

src/heap/spaces.h

@@ -1200,7 +1200,14 @@ class SkipList {
     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);
+      }
     }
   }
 
@@ -2038,10 +2045,13 @@ class PagedSpace : public Space {
     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);

src/snapshot/deserializer.cc

@@ -425,6 +425,7 @@ Address Deserializer::Allocate(int space_index, int size) {
     int chunk_index = current_chunk_[space_index];
     CHECK_LE(high_water_[space_index], reservation[chunk_index].end);
 #endif
+    if (space_index == CODE_SPACE) SkipList::Update(address, size);
     return address;
   }
 }