Introduce concurrent on-stack replacement.

src/runtime-profiler.cc

 // 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 154 matching lines @@
 
   // We are not prepared to do OSR for a function that already has an
   // allocated arguments object.  The optimized code would bypass it for
   // arguments accesses, which is unsound.  Don't try OSR.
   if (shared->uses_arguments()) return;
 
   // We're using on-stack replacement: patch the unoptimized code so that
   // any back edge in any unoptimized frame will trigger on-stack
   // replacement for that frame.
   if (FLAG_trace_osr) {
-    PrintF("[patching back edges in ");
+    PrintF("[OSR - patching back edges in ");
     function->PrintName();
-    PrintF(" for on-stack replacement]\n");
+    PrintF("]\n");
   }
 
   Deoptimizer::PatchInterruptCode(isolate_, shared->code());
 }
 
 
 void RuntimeProfiler::ClearSampleBuffer() {
   memset(sampler_window_, 0, sizeof(sampler_window_));
   memset(sampler_window_weight_, 0, sizeof(sampler_window_weight_));
 }
@@ skipping 237 matching lines @@
 
 
 void RuntimeProfiler::UpdateSamplesAfterCompact(ObjectVisitor* visitor) {
   for (int i = 0; i < kSamplerWindowSize; i++) {
     visitor->VisitPointer(&sampler_window_[i]);
   }
 }
 
 
 } }  // namespace v8::internal