Reland of "[heap] Divide available memory upon compaction tasks"

src/objects.h

 // 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.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 4390 matching lines @@
 
   // Dispatched behavior.
   DECLARE_PRINTER(FreeSpace)
   DECLARE_VERIFIER(FreeSpace)
 
   // Layout description.
   // Size is smi tagged when it is stored.
   static const int kSizeOffset = HeapObject::kHeaderSize;
   static const int kNextOffset = POINTER_SIZE_ALIGN(kSizeOffset + kPointerSize);
 
+  // Minimum size for any free space node. Required to be power of two.
+  static const int kMinSize = 32;
+  STATIC_ASSERT(kMinSize >= (kNextOffset + kPointerSize));
+  STATIC_ASSERT(IS_POWER_OF_TWO(kMinSize));
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(FreeSpace);
 };
 
 
 // V has parameters (Type, type, TYPE, C type, element_size)
 #define TYPED_ARRAYS(V) \
   V(Uint8, uint8, UINT8, uint8_t, 1)                                           \
   V(Int8, int8, INT8, int8_t, 1)                                               \
   V(Uint16, uint16, UINT16, uint16_t, 2)                                       \
@@ skipping 6359 matching lines @@
   // (elements + properties) in the current level.
   int levelLength_;
 
   DISALLOW_COPY_AND_ASSIGN(KeyAccumulator);
 };
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_