Introduce instance type for transition arrays.

src/heap/heap.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/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/scopeinfo.h"
 #include "src/base/bits.h"
@@ skipping 162 matching lines @@
 #endif
 
   // Ensure old_generation_size_ is a multiple of kPageSize.
   DCHECK((max_old_generation_size_ & (Page::kPageSize - 1)) == 0);
 
   memset(roots_, 0, sizeof(roots_[0]) * kRootListLength);
   set_native_contexts_list(NULL);
   set_allocation_sites_list(Smi::FromInt(0));
   set_encountered_weak_collections(Smi::FromInt(0));
   set_encountered_weak_cells(Smi::FromInt(0));
+  set_encountered_transition_arrays(Smi::FromInt(0));
   // Put a dummy entry in the remembered pages so we can find the list the
   // minidump even if there are no real unmapped pages.
   RememberUnmappedPage(NULL, false);
 }
 
 
 intptr_t Heap::Capacity() {
   if (!HasBeenSetUp()) return 0;
 
   return new_space_.Capacity() + old_space_->Capacity() +
@@ skipping 2133 matching lines @@
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, sloppy_arguments_elements)
 
     ALLOCATE_VARSIZE_MAP(CODE_TYPE, code)
 
     ALLOCATE_MAP(CELL_TYPE, Cell::kSize, cell)
     ALLOCATE_MAP(PROPERTY_CELL_TYPE, PropertyCell::kSize, global_property_cell)
     ALLOCATE_MAP(WEAK_CELL_TYPE, WeakCell::kSize, weak_cell)
     ALLOCATE_MAP(FILLER_TYPE, kPointerSize, one_pointer_filler)
     ALLOCATE_MAP(FILLER_TYPE, 2 * kPointerSize, two_pointer_filler)
 
+    ALLOCATE_VARSIZE_MAP(TRANSITION_ARRAY_TYPE, transition_array)
 
     for (unsigned i = 0; i < arraysize(struct_table); i++) {
       const StructTable& entry = struct_table[i];
       Map* map;
       if (!AllocateMap(entry.type, entry.size).To(&map)) return false;
       roots_[entry.index] = map;
     }
 
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, hash_table)
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, ordered_hash_table)
@@ skipping 141 matching lines @@
     AllocationResult allocation = AllocateRaw(size, OLD_SPACE);
     if (!allocation.To(&result)) return allocation;
   }
   result->set_map_no_write_barrier(weak_cell_map());
   WeakCell::cast(result)->initialize(value);
   WeakCell::cast(result)->clear_next(this);
   return result;
 }
 
 
+AllocationResult Heap::AllocateTransitionArray(int capacity) {
+  DCHECK(capacity > 0);
+  HeapObject* raw_array = nullptr;
+  {
+    AllocationResult allocation = AllocateRawFixedArray(capacity, TENURED);
+    if (!allocation.To(&raw_array)) return allocation;
+  }
+  raw_array->set_map_no_write_barrier(transition_array_map());
+  TransitionArray* array = TransitionArray::cast(raw_array);
+  array->set_length(capacity);
+  MemsetPointer(array->data_start(), undefined_value(), capacity);
+  return array;
+}
+
+
 void Heap::CreateApiObjects() {
   HandleScope scope(isolate());
   Factory* factory = isolate()->factory();
   Handle<Map> new_neander_map =
       factory->NewMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
 
   // Don't use Smi-only elements optimizations for objects with the neander
   // map. There are too many cases where element values are set directly with a
   // bottleneck to trap the Smi-only -> fast elements transition, and there
   // appears to be no benefit for optimize this case.
@@ skipping 3596 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8