Support profiling based on linux kernel performance events.

src/platform.h

 // Copyright 2006-2008 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 239 matching lines @@
   // Safe formatting print. Ensures that str is always null-terminated.
   // Returns the number of chars written, or -1 if output was truncated.
   static int SNPrintF(Vector<char> str, const char* format, ...);
   static int VSNPrintF(Vector<char> str,
                        const char* format,
                        va_list args);
 
   static char* StrChr(char* str, int c);
   static void StrNCpy(Vector<char> dest, const char* src, size_t n);
 
-  // Support for profiler.  Can do nothing, in which case ticks
-  // occuring in shared libraries will not be properly accounted
-  // for.
+  // Support for the profiler.  Can do nothing, in which case ticks
+  // occuring in shared libraries will not be properly accounted for.
   static void LogSharedLibraryAddresses();
 
+  // Support for the profiler.  Notifies the external profiling
+  // process that a code moving garbage collection starts.  Can do
+  // nothing, in which case the code objects must not move (e.g., by
+  // using --never-compact) if accurate profiling is desired.
+  static void SignalCodeMovingGC();
+
   // The return value indicates the CPU features we are sure of because of the
   // OS.  For example MacOSX doesn't run on any x86 CPUs that don't have SSE2
   // instructions.
   // This is a little messy because the interpretation is subject to the cross
   // of the CPU and the OS.  The bits in the answer correspond to the bit
   // positions indicated by the members of the CpuFeature enum from globals.h
   static uint64_t CpuFeaturesImpliedByPlatform();
 
   // Returns the double constant NAN
   static double nan_value();
@@ skipping 302 matching lines @@
   bool active_;
   PlatformData* data_;  // Platform specific data.
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_H_