Add a CompareAndSwapUint32 variant to AtomicOperations so that it is possible to a CAS of a 32 bit …

runtime/vm/simulator_arm.cc

 // 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.
 
 #include <setjmp.h>  // NOLINT
 #include <stdlib.h>
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_ARM)
 
@@ skipping 1153 matching lines @@
     // Same effect on exclusive access state as a successful STREX.
     HasExclusiveAccessAndOpen(reinterpret_cast<uword>(address));
   } else {
     // Same effect on exclusive access state as an LDREX.
     SetExclusiveAccess(reinterpret_cast<uword>(address));
   }
   return value;
 }
 
 
+uint32_t Simulator::CompareExchangeUint32(uint32_t* address,
+                                          uint32_t compare_value,
+                                          uint32_t new_value) {
+  ASSERT(sizeof(uword) == sizeof(uint32_t));
+  return CompareExchange(address, compare_value, new_value);
+}
+
+
 // Returns the top of the stack area to enable checking for stack pointer
 // validity.
 uword Simulator::StackTop() const {
   // To be safe in potential stack underflows we leave some buffer above and
   // set the stack top.
   return StackBase() +
       (OSThread::GetSpecifiedStackSize() + OSThread::kStackSizeBuffer);
 }
 
 
@@ skipping 2702 matching lines @@
   set_register(kExceptionObjectReg, bit_cast<int32_t>(raw_exception));
   set_register(kStackTraceObjectReg, bit_cast<int32_t>(raw_stacktrace));
   buf->Longjmp();
 }
 
 }  // namespace dart
 
 #endif  // defined(USING_SIMULATOR)
 
 #endif  // defined TARGET_ARCH_ARM