src/optimizing-compiler-thread.h

// Copyright 2012 the V8 project authors. All rights reserved.
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#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 RecompileJob;
class SharedFunctionInfo;

class OptimizingCompilerThread : public Thread {
 public:
  explicit OptimizingCompilerThread(Isolate *isolate) :
      Thread("OptimizingCompilerThread"),
#ifdef DEBUG
      thread_id_(0),
#endif
      isolate_(isolate),
      stop_semaphore_(0),
      input_queue_semaphore_(0),
      osr_cursor_(0),
      osr_hits_(0),
      osr_attempts_(0) {
    NoBarrier_Store(&stop_thread_, static_cast<AtomicWord>(CONTINUE));
    NoBarrier_Store(&queue_length_, static_cast<AtomicWord>(0));
    if (FLAG_concurrent_osr) {
      osr_buffer_size_ = FLAG_concurrent_recompilation_queue_length + 4;
      osr_buffer_ = NewArray<RecompileJob*>(osr_buffer_size_);
      for (int i = 0; i < osr_buffer_size_; i++) osr_buffer_[i] = NULL;
    }
  }

  ~OptimizingCompilerThread() {
    if (FLAG_concurrent_osr) DeleteArray(osr_buffer_);
  }

  void Run();
  void Stop();
  void Flush();
  void QueueForOptimization(RecompileJob* optimizing_compiler);
  void InstallOptimizedFunctions();
  RecompileJob* FindReadyOSRCandidate(Handle<JSFunction> function,
                                      uint32_t osr_pc_offset);
  bool IsQueuedForOSR(Handle<JSFunction> function, uint32_t osr_pc_offset);

  bool IsQueuedForOSR(JSFunction* function);

  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
    // doesn't introduce a race -- queue_length_ may decreased in
    // meantime, but not increased.
    return (current_length < FLAG_concurrent_recompilation_queue_length);
  }

#ifdef DEBUG
  bool IsOptimizerThread();
#endif

 private:
  enum StopFlag { CONTINUE, STOP, FLUSH };

  void FlushInputQueue(bool restore_function_code);
  void FlushOutputQueue(bool restore_function_code);
  void FlushOsrBuffer(bool restore_function_code);
  void CompileNext();

  // Add a recompilation task for OSR to the cyclic buffer, awaiting OSR entry.
  // Tasks evicted from the cyclic buffer are discarded.
  void AddToOsrBuffer(RecompileJob* compiler);
  void AdvanceOsrCursor() {
    osr_cursor_ = (osr_cursor_ + 1) % osr_buffer_size_;
  }

#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<RecompileJob*> input_queue_;
  // Queue of recompilation tasks ready to be installed (excluding OSR).
  UnboundQueue<RecompileJob*> output_queue_;
  // Cyclic buffer of recompilation tasks for OSR.
  // TODO(yangguo): This may keep zombie tasks indefinitely, holding on to
  //                a lot of memory.  Fix this.
  RecompileJob** osr_buffer_;
  // Cursor for the cyclic buffer.
  int osr_cursor_;
  int osr_buffer_size_;

  volatile AtomicWord stop_thread_;
  volatile Atomic32 queue_length_;
  TimeDelta time_spent_compiling_;
  TimeDelta time_spent_total_;

  int osr_hits_;
  int osr_attempts_;
};

} }  // namespace v8::internal

#endif  // V8_OPTIMIZING_COMPILER_THREAD_H_