Introduce concurrent on-stack replacement.

src/optimizing-compiler-thread.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 12 matching lines @@
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #ifndef V8_OPTIMIZING_COMPILER_THREAD_H_
 #define V8_OPTIMIZING_COMPILER_THREAD_H_
 
 #include "atomicops.h"
 #include "flags.h"
+#include "list.h"
 #include "platform.h"
 #include "platform/mutex.h"
 #include "platform/time.h"
 #include "unbound-queue-inl.h"
 
 namespace v8 {
 namespace internal {
 
 class HOptimizedGraphBuilder;
 class OptimizingCompiler;
 class SharedFunctionInfo;
 
 class OptimizingCompilerThread : public Thread {
  public:
   explicit OptimizingCompilerThread(Isolate *isolate) :
       Thread("OptimizingCompilerThread"),
 #ifdef DEBUG
       thread_id_(0),
 #endif
       isolate_(isolate),
       stop_semaphore_(OS::CreateSemaphore(0)),
-      input_queue_semaphore_(OS::CreateSemaphore(0)) {
+      input_queue_semaphore_(OS::CreateSemaphore(0)),
+      osr_candidates_(2),
+      ready_for_osr_(2),
+      osr_hits_(0),
+      osr_attempts_(0) {
     NoBarrier_Store(&stop_thread_, static_cast<AtomicWord>(CONTINUE));
     NoBarrier_Store(&queue_length_, static_cast<AtomicWord>(0));
   }
 
   void Run();
   void Stop();
   void Flush();
   void QueueForOptimization(OptimizingCompiler* optimizing_compiler);
   void InstallOptimizedFunctions();
+  OptimizingCompiler* FindReadyOSRCandidate(Handle<JSFunction> function,
+                                            uint32_t osr_pc_offset);
+  bool IsQueuedForOSR(Handle<JSFunction> function, uint32_t osr_pc_offset);
+
+  // Remove the oldest OSR candidates that are ready so that we
+  // only have |limit| left waiting.
+  void RemoveStaleOSRCandidates(int limit = kReadyForOSRLimit);
 
   inline bool IsQueueAvailable() {
     // We don't need a barrier since we have a data dependency right
     // after.
     Atomic32 current_length = NoBarrier_Load(&queue_length_);
 
     // This can be queried only from the execution thread.
     ASSERT(!IsOptimizerThread());
     // Since only the execution thread increments queue_length_ and
     // only one thread can run inside an Isolate at one time, a direct
@@ skipping 11 matching lines @@
     delete stop_semaphore_;
 #ifdef DEBUG
 #endif
   }
 
  private:
   enum StopFlag { CONTINUE, STOP, FLUSH };
 
   void FlushInputQueue(bool restore_function_code);
   void FlushOutputQueue(bool restore_function_code);
-
   void CompileNext();
 
 #ifdef DEBUG
   int thread_id_;
   Mutex thread_id_mutex_;
 #endif
 
   Isolate* isolate_;
   Semaphore* stop_semaphore_;
   Semaphore* input_queue_semaphore_;
+
+  // Queue of incoming recompilation tasks (including OSR).
   UnboundQueue<OptimizingCompiler*> input_queue_;
+  // Queue of recompilation tasks ready to be installed (excluding OSR).
   UnboundQueue<OptimizingCompiler*> output_queue_;
+  // List of all OSR related recompilation tasks (both incoming and ready ones).
+  List<OptimizingCompiler*> osr_candidates_;
+  // List of recompilation tasks ready for OSR.
+  List<OptimizingCompiler*> ready_for_osr_;
+
   Mutex install_mutex_;
   volatile AtomicWord stop_thread_;
   volatile Atomic32 queue_length_;
   TimeDelta time_spent_compiling_;
   TimeDelta time_spent_total_;
+
+  Mutex osr_list_mutex_;
+  int osr_hits_;
+  int osr_attempts_;
+
+  static const int kReadyForOSRLimit = 4;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OPTIMIZING_COMPILER_THREAD_H_