Safe and efficient stack-limit based interrupt checking in C++.

runtime/vm/atomic_win.h

 // Copyright (c) 2013, 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_ATOMIC_WIN_H_
 #define VM_ATOMIC_WIN_H_
 
 #if !defined VM_ATOMIC_H_
 #error Do not include atomic_win.h directly. Use atomic.h instead.
 #endif
@@ skipping 10 matching lines @@
       InterlockedIncrement64(reinterpret_cast<LONGLONG*>(p))) - 1;
 #elif defined(TARGET_ARCH_IA32)
   return static_cast<uintptr_t>(
       InterlockedIncrement(reinterpret_cast<LONG*>(p))) - 1;
 #else
   UNIMPLEMENTED();
 #endif
 }
 
 
+inline intptr_t AtomicOperations::FetchAndAdd(intptr_t* p, intptr_t delta) {
+#if defined(TARGET_ARCH_X64)
+  return static_cast<intptr_t>(
+      InterlockedAdd64(reinterpret_cast<LONGLONG*>(p), delta)) - 1;

[Ivan Posva, 2015/08/07 20:55:46]

What does the -1 mean here?

[koda, 2015/08/07 21:05:22]

Fixed to 'delta' (InterlockedAdd returns the value *after*).

+#elif defined(TARGET_ARCH_IA32)
+  return static_cast<intptr_t>(
+      InterlockedAdd(reinterpret_cast<LONG*>(p), delta)) - 1;
+#else
+  UNIMPLEMENTED();
+#endif
+}
+
+
 #if !defined(USING_SIMULATOR)
 inline uword AtomicOperations::CompareAndSwapWord(uword* ptr,
                                                   uword old_value,
                                                   uword new_value) {
 #if defined(TARGET_ARCH_X64)
   return static_cast<uword>(
       InterlockedCompareExchange64(reinterpret_cast<LONGLONG*>(ptr),
                                    static_cast<LONGLONG>(new_value),
                                    static_cast<LONGLONG>(old_value)));
 #elif defined(TARGET_ARCH_IA32)
   return static_cast<uword>(
       InterlockedCompareExchange(reinterpret_cast<LONG*>(ptr),
                                  static_cast<LONG>(new_value),
                                  static_cast<LONG>(old_value)));
 #else
   UNIMPLEMENTED();
 #endif
 }
 #endif  // !defined(USING_SIMULATOR)
 
+
+inline uword AtomicOperations::LoadRelaxed(uword* ptr) {
+  // TODO(koda): Consider using C++11 <atomic> to avoid the barrier on more
+  // compilers/platforms.
+  return FetchAndAdd(reinterpret_cast<intptr_t*>(ptr), 0);
+}
+
 }  // namespace dart
 
 #endif  // VM_ATOMIC_WIN_H_