Revert r16648, r16641, r16638 and r16637.

src/platform.h

Index: src/platform.h
diff --git a/src/platform.h b/src/platform.h
index 848966ee598fea7677969161576a2322ba8d604f..ee8fb92910be295b2dc68c711be979adf7388ec6 100644
--- a/src/platform.h
+++ b/src/platform.h
@@ -219,6 +219,30 @@ class OS {
   static void PrintError(const char* format, ...);
   static void VPrintError(const char* format, va_list args);
 
+  // Allocate/Free memory used by JS heap. Pages are readable/writable, but
+  // they are not guaranteed to be executable unless 'executable' is true.
+  // Returns the address of allocated memory, or NULL if failed.
+  static void* Allocate(const size_t requested,
+                        size_t* allocated,
+                        bool is_executable);
+  static void Free(void* address, const size_t size);
+
+  // This is the granularity at which the ProtectCode(...) call can set page
+  // permissions.
+  static intptr_t CommitPageSize();
+
+  // Mark code segments non-writable.
+  static void ProtectCode(void* address, const size_t size);
+
+  // Assign memory as a guard page so that access will cause an exception.
+  static void Guard(void* address, const size_t size);
+
+  // Generate a random address to be used for hinting mmap().
+  static void* GetRandomMmapAddr();
+
+  // Get the Alignment guaranteed by Allocate().
+  static size_t AllocateAlignment();
+
   // Sleep for a number of milliseconds.
   static void Sleep(const int milliseconds);
 
@@ -279,6 +303,10 @@ class OS {
   // positions indicated by the members of the CpuFeature enum from globals.h
   static uint64_t CpuFeaturesImpliedByPlatform();
 
+  // Maximum size of the virtual memory.  0 means there is no artificial
+  // limit.
+  static intptr_t MaxVirtualMemory();
+
   // Returns the double constant NAN
   static double nan_value();
 
@@ -358,6 +386,99 @@ class OS {
   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. 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);
+
+  // Creates a single guard page at the given address.
+  bool Guard(void* address);
+
+  void Release() {
+    ASSERT(IsReserved());
+    // Notice: Order is important here. The VirtualMemory object might live
+    // inside the allocated region.
+    void* address = address_;
+    size_t size = size_;
+    Reset();
+    bool result = ReleaseRegion(address, size);
+    USE(result);
+    ASSERT(result);
+  }
+
+  // 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);
+
+  // Returns true if OS performs lazy commits, i.e. the memory allocation call
+  // defers actual physical memory allocation till the first memory access.
+  // Otherwise returns false.
+  static bool HasLazyCommits();
+
+ private:
+  void* address_;  // Start address of the virtual memory.
+  size_t size_;  // Size of the virtual memory.
+};
+
+
 // ----------------------------------------------------------------------------
 // Thread
 //