- Use the simulator to do atomic operations that could also

runtime/vm/simulator_mips.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.
 
 // Declares a Simulator for MIPS instructions if we are not generating a native
 // MIPS binary. This Simulator allows us to run and debug MIPS 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 MIPS HW platform.
 
 #ifndef VM_SIMULATOR_MIPS_H_
 #define VM_SIMULATOR_MIPS_H_
 
 #ifndef VM_SIMULATOR_H_
 #error Do not include simulator_mips.h directly; use simulator.h.
 #endif
 
 #include "vm/constants_mips.h"
-#include "vm/object.h"
 
 namespace dart {
 
 class Isolate;
+class Mutex;
+class RawObject;
 class SimulatorSetjmpBuffer;
 
 class Simulator {
  public:
   static const uword kSimulatorStackUnderflowSize = 64;
 
   Simulator();
   ~Simulator();
 
   // The currently executing Simulator instance, which is associated to the
@@ skipping 68 matching lines @@
   // result on return. When fp_return is true the return value is the D0
   // floating point register. Otherwise, the return value is V1:V0.
   int64_t Call(int32_t entry,
                int32_t parameter0,
                int32_t parameter1,
                int32_t parameter2,
                int32_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);
+
   // Runtime and native call support.
   enum CallKind {
     kRuntimeCall,
     kLeafRuntimeCall,
     kLeafFloatRuntimeCall,
     kBootstrapNativeCall,
     kNativeCall
   };
   static uword RedirectExternalReference(uword function,
                                          CallKind call_kind,
@@ skipping 60 matching lines @@
   inline uint16_t ReadHU(uword addr, Instr *instr);
   inline intptr_t ReadW(uword addr, Instr* instr);
 
   inline void WriteB(uword addr, uint8_t value);
   inline void WriteH(uword addr, uint16_t value, Instr* isntr);
   inline void WriteW(uword addr, intptr_t value, Instr* instr);
 
   inline double ReadD(uword addr, Instr* instr);
   inline void WriteD(uword addr, double value, Instr* instr);
 
+  // In Dart, there is at most one thread per isolate.
+  // We keep track of 16 exclusive access address tags across all isolates.
+  // Since we cannot simulate a native context switch, which clears
+  // the exclusive access state of the local monitor, we associate the isolate
+  // requesting exclusive access to the address tag.
+  // Multiple isolates requesting exclusive access (using the LL instruction)
+  // to the same address will result in multiple address tags being created for
+  // the same address, one per isolate.
+  // At any given time, each isolate is associated to at most one address tag.
+  static Mutex* exclusive_access_lock_;
+  static const int kNumAddressTags = 16;
+  static struct AddressTag {
+    Isolate* isolate;
+    uword addr;
+  } exclusive_access_state_[kNumAddressTags];
+  static int next_address_tag_;
+
+  // Synchronization primitives support.
+  void ClearExclusive();
+  intptr_t ReadExclusiveW(uword addr, Instr* instr);
+  intptr_t WriteExclusiveW(uword addr, intptr_t value, Instr* instr);
+
+  // Set access to given address to 'exclusive state' for current isolate.
+  static void SetExclusiveAccess(uword addr);
+
+  // Returns true if the current isolate has exclusive access to given address,
+  // returns false otherwise. In either case, set access to given address to
+  // 'open state' for all isolates.
+  // If given addr is NULL, set access to 'open state' for current
+  // isolate (CLREX).
+  static bool HasExclusiveAccessAndOpen(uword addr);
+
   void DoBranch(Instr* instr, bool taken, bool likely);
   void DoBreak(Instr *instr);
 
   void DecodeSpecial(Instr* instr);
   void DecodeSpecial2(Instr* instr);
   void DecodeRegImm(Instr* instr);
   void DecodeCop1(Instr* instr);
   void InstructionDecode(Instr* instr);
 
   void Execute();
   void ExecuteDelaySlot();
 
   // Longjmp support for exceptions.
   SimulatorSetjmpBuffer* last_setjmp_buffer() {
     return last_setjmp_buffer_;
   }
   void set_last_setjmp_buffer(SimulatorSetjmpBuffer* buffer) {
     last_setjmp_buffer_ = buffer;
   }
 
   friend class SimulatorDebugger;
   friend class SimulatorSetjmpBuffer;
   DISALLOW_COPY_AND_ASSIGN(Simulator);
 };
 
 }  // namespace dart
 
 #endif  // VM_SIMULATOR_MIPS_H_