Move aligned allocation to the platform files.

src/platform.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 318 matching lines @@
   }
   static const int kMinComplexMemCopy = 256;
 #endif  // V8_TARGET_ARCH_IA32
 
  private:
   static const int msPerSecond = 1000;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(OS);
 };
 
-
+// Represents and controls an area of reserved memory.
+// Control of the reserved memory can be assigned to another VirtualMemory
+// object by assignment or copy-contructing. This removes the reserved memory
+// from the original object.
 class VirtualMemory {
  public:
+  // Empty VirtualMemory object, controlling no reserved memory.
+  VirtualMemory();
+
   // Reserves virtual memory with size.
   explicit VirtualMemory(size_t size);
+
+  // Reserves virtual memory containing an area of the given size that
+  // is aligned per alignment. This may not be at the position returned
+  // by address().
+  VirtualMemory(size_t size, size_t alignment);
+
+  // Releases the reserved memory, if any, controlled by this VirtualMemory
+  // object.
   ~VirtualMemory();
 
   // Returns whether the memory has been reserved.
   bool IsReserved();
 
+  // Initialize or resets an embedded VirtualMemory object.
+  void Reset();
+
   // Returns the start address of the reserved memory.
+  // If the memory was reserved with an alignment, this address is not
+  // necessarily aligned. The user might need to round it up to a multiple of
+  // the alignment to get the start of the aligned block.
   void* address() {
     ASSERT(IsReserved());
     return address_;
   }
 
-  // Returns the size of the reserved memory.
+  // Returns the size of the reserved memory. The returned value is only
+  // meaningful when IsReserved() returns true.
+  // If the memory was reserved with an alignment, this size may be larger
+  // than the requested size.
   size_t size() { return size_; }
 
   // Commits real memory. Returns whether the operation succeeded.
   bool Commit(void* address, size_t size, bool is_executable);
 
   // Uncommit real memory.  Returns whether the operation succeeded.
   bool Uncommit(void* address, size_t size);
 
+  void Release() {
+    ASSERT(IsReserved());
+    // Notice: Order is somportant here. The VirtualMemory object might live
+    // inside the allocated region.
+    void* address = address_;
+    size_t size = size_;
+    Reset();
+    ReleaseRegion(address, size);
+  }
+
+  // Assign control of the reserved region to a different VirtualMemory object.
+  // The old object is no longer functional (IsReserved() returns false).
+  void TakeControl(VirtualMemory* from) {
+    ASSERT(!IsReserved());
+    address_ = from->address_;
+    size_ = from->size_;
+    from->Reset();
+  }
+
   static void* ReserveRegion(size_t size);
 
   static bool CommitRegion(void* base, size_t size, bool is_executable);
 
   static bool UncommitRegion(void* base, size_t size);
 
+  // Must be called with a base pointer that has been returned by ReserveRegion
+  // and the same size it was reserved with.
   static bool ReleaseRegion(void* base, size_t size);
 
  private:
   void* address_;  // Start address of the virtual memory.
   size_t size_;  // Size of the virtual memory.
 };
 
+
 // ----------------------------------------------------------------------------
 // Thread
 //
 // Thread objects are used for creating and running threads. When the start()
 // method is called the new thread starts running the run() method in the new
 // thread. The Thread object should not be deallocated before the thread has
 // terminated.
 
 class Thread {
  public:
@@ skipping 282 matching lines @@
   Atomic32 active_;
   PlatformData* data_;  // Platform specific data.
   int samples_taken_;  // Counts stack samples taken.
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_H_