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      1 // Copyright 2012 the V8 project authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef V8_OPTIMIZING_COMPILE_DISPATCHER_H_
      6 #define V8_OPTIMIZING_COMPILE_DISPATCHER_H_
      7 
      8 #include <queue>
      9 
     10 #include "src/base/atomicops.h"
     11 #include "src/base/platform/condition-variable.h"
     12 #include "src/base/platform/mutex.h"
     13 #include "src/base/platform/platform.h"
     14 #include "src/flags.h"
     15 #include "src/list.h"
     16 
     17 namespace v8 {
     18 namespace internal {
     19 
     20 class HOptimizedGraphBuilder;
     21 class OptimizedCompileJob;
     22 class SharedFunctionInfo;
     23 
     24 class OptimizingCompileDispatcher {
     25  public:
     26   explicit OptimizingCompileDispatcher(Isolate* isolate)
     27       : isolate_(isolate),
     28         input_queue_capacity_(FLAG_concurrent_recompilation_queue_length),
     29         input_queue_length_(0),
     30         input_queue_shift_(0),
     31         osr_buffer_capacity_(FLAG_concurrent_recompilation_queue_length + 4),
     32         osr_buffer_cursor_(0),
     33         osr_hits_(0),
     34         osr_attempts_(0),
     35         blocked_jobs_(0),
     36         ref_count_(0),
     37         recompilation_delay_(FLAG_concurrent_recompilation_delay) {
     38     base::NoBarrier_Store(&mode_, static_cast<base::AtomicWord>(COMPILE));
     39     input_queue_ = NewArray<OptimizedCompileJob*>(input_queue_capacity_);
     40     if (FLAG_concurrent_osr) {
     41       // Allocate and mark OSR buffer slots as empty.
     42       osr_buffer_ = NewArray<OptimizedCompileJob*>(osr_buffer_capacity_);
     43       for (int i = 0; i < osr_buffer_capacity_; i++) osr_buffer_[i] = NULL;
     44     }
     45   }
     46 
     47   ~OptimizingCompileDispatcher();
     48 
     49   void Run();
     50   void Stop();
     51   void Flush();
     52   void QueueForOptimization(OptimizedCompileJob* optimizing_compiler);
     53   void Unblock();
     54   void InstallOptimizedFunctions();
     55   OptimizedCompileJob* FindReadyOSRCandidate(Handle<JSFunction> function,
     56                                              BailoutId osr_ast_id);
     57   bool IsQueuedForOSR(Handle<JSFunction> function, BailoutId osr_ast_id);
     58 
     59   bool IsQueuedForOSR(JSFunction* function);
     60 
     61   inline bool IsQueueAvailable() {
     62     base::LockGuard<base::Mutex> access_input_queue(&input_queue_mutex_);
     63     return input_queue_length_ < input_queue_capacity_;
     64   }
     65 
     66   inline void AgeBufferedOsrJobs() {
     67     // Advance cursor of the cyclic buffer to next empty slot or stale OSR job.
     68     // Dispose said OSR job in the latter case.  Calling this on every GC
     69     // should make sure that we do not hold onto stale jobs indefinitely.
     70     AddToOsrBuffer(NULL);
     71   }
     72 
     73   static bool Enabled() { return FLAG_concurrent_recompilation; }
     74 
     75  private:
     76   class CompileTask;
     77 
     78   enum ModeFlag { COMPILE, FLUSH };
     79 
     80   void FlushOutputQueue(bool restore_function_code);
     81   void FlushOsrBuffer(bool restore_function_code);
     82   void CompileNext(OptimizedCompileJob* job);
     83   OptimizedCompileJob* NextInput(bool check_if_flushing = false);
     84 
     85   // Add a recompilation task for OSR to the cyclic buffer, awaiting OSR entry.
     86   // Tasks evicted from the cyclic buffer are discarded.
     87   void AddToOsrBuffer(OptimizedCompileJob* compiler);
     88 
     89   inline int InputQueueIndex(int i) {
     90     int result = (i + input_queue_shift_) % input_queue_capacity_;
     91     DCHECK_LE(0, result);
     92     DCHECK_LT(result, input_queue_capacity_);
     93     return result;
     94   }
     95 
     96   Isolate* isolate_;
     97 
     98   // Circular queue of incoming recompilation tasks (including OSR).
     99   OptimizedCompileJob** input_queue_;
    100   int input_queue_capacity_;
    101   int input_queue_length_;
    102   int input_queue_shift_;
    103   base::Mutex input_queue_mutex_;
    104 
    105   // Queue of recompilation tasks ready to be installed (excluding OSR).
    106   std::queue<OptimizedCompileJob*> output_queue_;
    107   // Used for job based recompilation which has multiple producers on
    108   // different threads.
    109   base::Mutex output_queue_mutex_;
    110 
    111   // Cyclic buffer of recompilation tasks for OSR.
    112   OptimizedCompileJob** osr_buffer_;
    113   int osr_buffer_capacity_;
    114   int osr_buffer_cursor_;
    115 
    116   volatile base::AtomicWord mode_;
    117 
    118   int osr_hits_;
    119   int osr_attempts_;
    120 
    121   int blocked_jobs_;
    122 
    123   int ref_count_;
    124   base::Mutex ref_count_mutex_;
    125   base::ConditionVariable ref_count_zero_;
    126 
    127   // Copy of FLAG_concurrent_recompilation_delay that will be used from the
    128   // background thread.
    129   //
    130   // Since flags might get modified while the background thread is running, it
    131   // is not safe to access them directly.
    132   int recompilation_delay_;
    133 };
    134 }  // namespace internal
    135 }  // namespace v8
    136 
    137 #endif  // V8_OPTIMIZING_COMPILE_DISPATCHER_H_
    138