First step to cleanup the power-of-2 mess.

src/heap/mark-compact.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_HEAP_MARK_COMPACT_H_
 #define V8_HEAP_MARK_COMPACT_H_
 
+#include "src/base/bits.h"
 #include "src/heap/spaces.h"
 
 namespace v8 {
 namespace internal {
 
 // Callback function, returns whether an object is alive. The heap size
 // of the object is returned in size. It optionally updates the offset
 // to the first live object in the page (only used for old and map objects).
 typedef bool (*IsAliveFunction)(HeapObject* obj, int* size, int* offset);
 
@@ skipping 120 matching lines @@
 // Marking deque for tracing live objects.
 class MarkingDeque {
  public:
   MarkingDeque()
       : array_(NULL), top_(0), bottom_(0), mask_(0), overflowed_(false) {}
 
   void Initialize(Address low, Address high) {
     HeapObject** obj_low = reinterpret_cast<HeapObject**>(low);
     HeapObject** obj_high = reinterpret_cast<HeapObject**>(high);
     array_ = obj_low;
-    mask_ = RoundDownToPowerOf2(static_cast<int>(obj_high - obj_low)) - 1;
+    mask_ = base::bits::RoundDownToPowerOfTwo32(
+                static_cast<uint32_t>(obj_high - obj_low)) -
+            1;
     top_ = bottom_ = 0;
     overflowed_ = false;
   }
 
   inline bool IsFull() { return ((top_ + 1) & mask_) == bottom_; }
 
   inline bool IsEmpty() { return top_ == bottom_; }
 
   bool overflowed() const { return overflowed_; }
 
@@ skipping 785 matching lines @@
  private:
   MarkCompactCollector* collector_;
 };
 
 
 const char* AllocationSpaceName(AllocationSpace space);
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_MARK_COMPACT_H_