Use atomic operation to read the length of a fixed array.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 2755eaecfec8e3457ba10000499b779d4e1fbf99..56a5a47d075ae1cb55ddf41e17d828dad5bce4fb 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -1030,7 +1030,8 @@ bool String::MakeExternal(v8::String::ExternalStringResource* resource) {
   self->set_resource(resource);
   if (is_internalized) self->Hash();  // Force regeneration of the hash value.
 
-  heap->AdjustLiveBytes(this->address(), new_size - size, Heap::FROM_MUTATOR);
+  heap->AdjustLiveBytes(this->address(), new_size - size,
+                        Heap::CONCURRENT_TO_SWEEPER);
   return true;
 }
 
@@ -1090,7 +1091,8 @@ bool String::MakeExternal(v8::String::ExternalOneByteStringResource* resource) {
   self->set_resource(resource);
   if (is_internalized) self->Hash();  // Force regeneration of the hash value.
 
-  heap->AdjustLiveBytes(this->address(), new_size - size, Heap::FROM_MUTATOR);
+  heap->AdjustLiveBytes(this->address(), new_size - size,
+                        Heap::CONCURRENT_TO_SWEEPER);
   return true;
 }
 
@@ -2113,7 +2115,7 @@ void JSObject::MigrateFastToFast(Handle<JSObject> object, Handle<Map> new_map) {
   // If there are properties in the new backing store, trim it to the correct
   // size and install the backing store into the object.
   if (external > 0) {
-    heap->RightTrimFixedArray<Heap::FROM_MUTATOR>(*array, inobject);
+    heap->RightTrimFixedArray<Heap::CONCURRENT_TO_SWEEPER>(*array, inobject);
     object->set_properties(*array);
   }
 
@@ -2126,7 +2128,8 @@ void JSObject::MigrateFastToFast(Handle<JSObject> object, Handle<Map> new_map) {
     Address address = object->address();
     heap->CreateFillerObjectAt(
         address + new_instance_size, instance_size_delta);
-    heap->AdjustLiveBytes(address, -instance_size_delta, Heap::FROM_MUTATOR);
+    heap->AdjustLiveBytes(address, -instance_size_delta,
+                          Heap::CONCURRENT_TO_SWEEPER);
   }
 
   // We are storing the new map using release store after creating a filler for
@@ -4638,7 +4641,7 @@ void JSObject::MigrateFastToSlow(Handle<JSObject> object,
     heap->CreateFillerObjectAt(object->address() + new_instance_size,
                                instance_size_delta);
     heap->AdjustLiveBytes(object->address(), -instance_size_delta,
-                          Heap::FROM_MUTATOR);
+                          Heap::CONCURRENT_TO_SWEEPER);
   }
 
   // We are storing the new map using release store after creating a filler for
@@ -8105,7 +8108,7 @@ Handle<PolymorphicCodeCacheHashTable> PolymorphicCodeCacheHashTable::Put(
 void FixedArray::Shrink(int new_length) {
   DCHECK(0 <= new_length && new_length <= length());
   if (new_length < length()) {
-    GetHeap()->RightTrimFixedArray<Heap::FROM_MUTATOR>(
+    GetHeap()->RightTrimFixedArray<Heap::CONCURRENT_TO_SWEEPER>(
         this, length() - new_length);
   }
 }
@@ -9468,7 +9471,7 @@ Handle<String> SeqString::Truncate(Handle<SeqString> string, int new_length) {
     // that are a multiple of pointer size.
     heap->CreateFillerObjectAt(start_of_string + new_size, delta);
   }
-  heap->AdjustLiveBytes(start_of_string, -delta, Heap::FROM_MUTATOR);
+  heap->AdjustLiveBytes(start_of_string, -delta, Heap::CONCURRENT_TO_SWEEPER);
 
   // We are storing the new length using release store after creating a filler
   // for the left-over space to avoid races with the sweeper thread.
@@ -9888,7 +9891,8 @@ void SharedFunctionInfo::EvictFromOptimizedCodeMap(Code* optimized_code,
   }
   if (dst != length) {
     // Always trim even when array is cleared because of heap verifier.
-    GetHeap()->RightTrimFixedArray<Heap::FROM_MUTATOR>(code_map, length - dst);
+    GetHeap()->RightTrimFixedArray<Heap::CONCURRENT_TO_SWEEPER>(code_map,
+                                                                length - dst);
     if (code_map->length() == kEntriesStart) ClearOptimizedCodeMap();
   }
 }
@@ -9899,7 +9903,8 @@ void SharedFunctionInfo::TrimOptimizedCodeMap(int shrink_by) {
   DCHECK(shrink_by % kEntryLength == 0);
   DCHECK(shrink_by <= code_map->length() - kEntriesStart);
   // Always trim even when array is cleared because of heap verifier.
-  GetHeap()->RightTrimFixedArray<Heap::FROM_GC>(code_map, shrink_by);
+  GetHeap()->RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>(code_map,
+                                                              shrink_by);
   if (code_map->length() == kEntriesStart) {
     ClearOptimizedCodeMap();
   }