Land Ivan's change of 'Remove support for verified memory handling'

runtime/vm/verified_memory.h

-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-#ifndef VM_VERIFIED_MEMORY_H_
-#define VM_VERIFIED_MEMORY_H_
-
-#include "vm/allocation.h"
-#include "vm/flags.h"
-#include "vm/virtual_memory.h"
-
-namespace dart {
-
-#if defined(DEBUG)
-DECLARE_FLAG(bool, verified_mem);
-DECLARE_FLAG(int, verified_mem_max_reserve_mb);
-#endif
-
-
-// A wrapper around VirtualMemory for verifying that a particular class of
-// memory writes are only performed through a particular interface.
-//
-// The main use case is verifying that storing pointers into objects is only
-// performed by code aware of the GC write barrier.
-//
-// NOTE: Verification is enabled only if 'verified_mem' is true, and this flag
-// only exists in DEBUG builds.
-class VerifiedMemory : public AllStatic {
- public:
-  // Reserves a block of memory for which all methods in this class may
-  // be called. Returns NULL if out of memory.
-  static VirtualMemory* Reserve(intptr_t size) {
-    return enabled() ? ReserveInternal(size) : VirtualMemory::Reserve(size);
-  }
-
-  // Verifies that [start, start + size) has only been mutated through
-  // methods in this class (or explicitly accepted by calling Accept).
-  static void Verify(uword start, intptr_t size) {
-    if (!enabled()) return;
-    ASSERT(size <= offset());
-    ASSERT(memcmp(reinterpret_cast<void*>(start + offset()),
-                  reinterpret_cast<void*>(start),
-                  size) == 0);
-  }
-
-  // Assigns value to *ptr after verifying previous content at that location.
-  template<typename T>
-  static void Write(T* ptr, const T& value) {
-    if (enabled()) {
-      uword addr = reinterpret_cast<uword>(ptr);
-      Verify(addr, sizeof(T));
-      T* offset_ptr = reinterpret_cast<T*>(addr + offset());
-      *offset_ptr = value;
-    }
-    *ptr = value;
-  }
-
-  // Accepts the current state of [start, start + size), even if it has been
-  // mutated by other means.
-  static void Accept(uword start, intptr_t size) {
-    if (!enabled()) return;
-    ASSERT(size <= offset());
-    memmove(reinterpret_cast<void*>(start + offset()),
-            reinterpret_cast<void*>(start),
-            size);
-  }
-
- private:
-#if defined(DEBUG)
-  static bool enabled() { return FLAG_verified_mem; }
-  static intptr_t offset() { return FLAG_verified_mem_max_reserve_mb * MB; }
-  static VirtualMemory* ReserveInternal(intptr_t size);
-#else
-  // In release mode, most code in this class is optimized away.
-  static bool enabled() { return false; }
-  static intptr_t offset() { UNREACHABLE(); return -1; }
-  static VirtualMemory* ReserveInternal(intptr_t size) {
-    UNREACHABLE();
-    return NULL;
-  }
-#endif
-
-  friend class Assembler;  // To use enabled/offset when generating code.
-  friend class FlowGraphCompiler;  // To compute edge counter code size.
-  friend class Intrinsifier;  // To know whether a jump is near or far.
-};
-
-}  // namespace dart
-
-#endif  // VM_VERIFIED_MEMORY_H_