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

runtime/vm/simulator_arm64.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.
 
 // Declares a Simulator for ARM64 instructions if we are not generating a native
 // ARM64 binary. This Simulator allows us to run and debug ARM64 code generation
 // on regular desktop machines.
 // Dart calls into generated code by "calling" the InvokeDartCode stub,
 // which will start execution in the Simulator or forwards to the real entry
 // on a ARM64 HW platform.
@@ skipping 84 matching lines @@
                int64_t parameter2,
                int64_t parameter3,
                bool fp_return = false,
                bool fp_args = false);
 
   // Implementation of atomic compare and exchange in the same synchronization
   // domain as other synchronization primitive instructions (e.g. ldrex, strex).
   static uword CompareExchange(uword* address,
                                uword compare_value,
                                uword new_value);
+  static uint32_t CompareExchangeUint32(uint32_t* address,
+                                        uint32_t compare_value,
+                                        uint32_t new_value);
 
   // Runtime and native call support.
   enum CallKind {
     kRuntimeCall,
     kLeafRuntimeCall,
     kLeafFloatRuntimeCall,
     kBootstrapNativeCall,
     kNativeCall
   };
   static uword RedirectExternalReference(uword function,
@@ skipping 154 matching lines @@
   }
 
   friend class SimulatorDebugger;
   friend class SimulatorSetjmpBuffer;
   DISALLOW_COPY_AND_ASSIGN(Simulator);
 };
 
 }  // namespace dart
 
 #endif  // VM_SIMULATOR_ARM64_H_