define ATOMICOPS_COMPILER_BARRIER in platform.h

src/platform.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 26 matching lines @@
 // the platform dependent classes could have been implemented using abstract
 // superclasses with virtual methods and having specializations for each
 // platform. This design was rejected because it was more complicated and
 // slower. It would require factory methods for selecting the right
 // implementation and the overhead of virtual methods for performance
 // sensitive like mutex locking/unlocking.
 
 #ifndef V8_PLATFORM_H_
 #define V8_PLATFORM_H_
 
+#define ATOMICOPS_COMPILER_BARRIER() __asm__ __volatile__("" : : : "memory")
+
 #ifdef __sun
 # ifndef signbit
 int signbit(double x);
 # endif
 #endif
 
 // GCC specific stuff
 #ifdef __GNUC__
 
 // Needed for va_list on at least MinGW and Android.
@@ skipping 700 matching lines @@
   Atomic32 active_;
   PlatformData* data_;  // Platform specific data.
   int samples_taken_;  // Counts stack samples taken.
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_H_