text: // 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
  //       with the distribution.
  //     * Neither the name of Google Inc. nor the names of its
  //       contributors may be used to endorse or promote products derived
  //       from this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // 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.
  
  #include "optimizing-compiler-thread.h"
  
  #include "v8.h"
  
  #include "full-codegen.h"
  #include "hydrogen.h"
  #include "isolate.h"
  #include "v8threads.h"
  
  namespace v8 {
  namespace internal {
  
  OptimizingCompilerThread::~OptimizingCompilerThread() {
    ASSERT_EQ(0, input_queue_length_);
    DeleteArray(input_queue_);
    if (FLAG_concurrent_osr) {
  #ifdef DEBUG
      for (int i = 0; i < osr_buffer_capacity_; i++) {
        CHECK_EQ(NULL, osr_buffer_[i]);
      }
  #endif
      DeleteArray(osr_buffer_);
    }
  }
  
  
  void OptimizingCompilerThread::Run() {
  #ifdef DEBUG
    { LockGuard<Mutex> lock_guard(&thread_id_mutex_);
      thread_id_ = ThreadId::Current().ToInteger();
    }
  #endif
    Isolate::SetIsolateThreadLocals(isolate_, NULL);
    DisallowHeapAllocation no_allocation;
    DisallowHandleAllocation no_handles;
    DisallowHandleDereference no_deref;
  
    ElapsedTimer total_timer;
    if (FLAG_trace_concurrent_recompilation) total_timer.Start();
  
    while (true) {
      input_queue_semaphore_.Wait();
      Logger::TimerEventScope timer(
          isolate_, Logger::TimerEventScope::v8_recompile_concurrent);
  
      if (FLAG_concurrent_recompilation_delay != 0) {
        OS::Sleep(FLAG_concurrent_recompilation_delay);
      }
  
      switch (static_cast<StopFlag>(Acquire_Load(&stop_thread_))) {
        case CONTINUE:
          break;
        case STOP:
          if (FLAG_trace_concurrent_recompilation) {
            time_spent_total_ = total_timer.Elapsed();
          }
          stop_semaphore_.Signal();
          return;
        case FLUSH:
          // The main thread is blocked, waiting for the stop semaphore.
          { AllowHandleDereference allow_handle_dereference;
            FlushInputQueue(true);
          }
          Release_Store(&stop_thread_, static_cast<AtomicWord>(CONTINUE));
          stop_semaphore_.Signal();
          // Return to start of consumer loop.
          continue;
      }
  
      ElapsedTimer compiling_timer;
      if (FLAG_trace_concurrent_recompilation) compiling_timer.Start();
  
      CompileNext();
  
      if (FLAG_trace_concurrent_recompilation) {
        time_spent_compiling_ += compiling_timer.Elapsed();
      }
    }
  }
  
  
  OptimizedCompileJob* OptimizingCompilerThread::NextInput() {
    LockGuard<Mutex> access_input_queue_(&input_queue_mutex_);
    if (input_queue_length_ == 0) return NULL;
    OptimizedCompileJob* job = input_queue_[InputQueueIndex(0)];
    ASSERT_NE(NULL, job);
    input_queue_shift_ = InputQueueIndex(1);
    input_queue_length_--;
    return job;
  }
  
  
  void OptimizingCompilerThread::CompileNext() {
    OptimizedCompileJob* job = NextInput();
    ASSERT_NE(NULL, job);
  
    // The function may have already been optimized by OSR.  Simply continue.
    OptimizedCompileJob::Status status = job->OptimizeGraph();
    USE(status);   // Prevent an unused-variable error in release mode.
    ASSERT(status != OptimizedCompileJob::FAILED);
  
    // The function may have already been optimized by OSR.  Simply continue.
    // Use a mutex to make sure that functions marked for install
    // are always also queued.
    output_queue_.Enqueue(job);
    isolate_->stack_guard()->RequestInstallCode();
  }
  
  
  static void DisposeOptimizedCompileJob(OptimizedCompileJob* job,
                                         bool restore_function_code) {
    // The recompile job is allocated in the CompilationInfo's zone.
    CompilationInfo* info = job->info();
    if (restore_function_code) {
      if (info->is_osr()) {
        if (!job->IsWaitingForInstall()) {
          // Remove stack check that guards OSR entry on original code.
          Handle<Code> code = info->unoptimized_code();
          uint32_t offset = code->TranslateAstIdToPcOffset(info->osr_ast_id());
          BackEdgeTable::RemoveStackCheck(code, offset);
        }
      } else {
        Handle<JSFunction> function = info->closure();
        function->ReplaceCode(function->shared()->code());
      }
    }
    delete info;
  }
  
  
  void OptimizingCompilerThread::FlushInputQueue(bool restore_function_code) {
    OptimizedCompileJob* job;
    while ((job = NextInput())) {
      // This should not block, since we have one signal on the input queue
      // semaphore corresponding to each element in the input queue.
      input_queue_semaphore_.Wait();
      // OSR jobs are dealt with separately.
      if (!job->info()->is_osr()) {
        DisposeOptimizedCompileJob(job, restore_function_code);
      }
    }
  }
  
  
  void OptimizingCompilerThread::FlushOutputQueue(bool restore_function_code) {
    OptimizedCompileJob* job;
    while (output_queue_.Dequeue(&job)) {
      // OSR jobs are dealt with separately.
      if (!job->info()->is_osr()) {
        DisposeOptimizedCompileJob(job, restore_function_code);
      }
    }
  }
  
  
  void OptimizingCompilerThread::FlushOsrBuffer(bool restore_function_code) {
    for (int i = 0; i < osr_buffer_capacity_; i++) {
      if (osr_buffer_[i] != NULL) {
        DisposeOptimizedCompileJob(osr_buffer_[i], restore_function_code);
        osr_buffer_[i] = NULL;
      }
    }
  }
  
  
  void OptimizingCompilerThread::Flush() {
    ASSERT(!IsOptimizerThread());
    Release_Store(&stop_thread_, static_cast<AtomicWord>(FLUSH));
    if (FLAG_block_concurrent_recompilation) Unblock();
    input_queue_semaphore_.Signal();
    stop_semaphore_.Wait();
    FlushOutputQueue(true);
    if (FLAG_concurrent_osr) FlushOsrBuffer(true);
    if (FLAG_trace_concurrent_recompilation) {
      PrintF("  ** Flushed concurrent recompilation queues.\n");
    }
  }
  
  
  void OptimizingCompilerThread::Stop() {
    ASSERT(!IsOptimizerThread());
    Release_Store(&stop_thread_, static_cast<AtomicWord>(STOP));
    if (FLAG_block_concurrent_recompilation) Unblock();
    input_queue_semaphore_.Signal();
    stop_semaphore_.Wait();
  
    if (FLAG_concurrent_recompilation_delay != 0) {
      // At this point the optimizing compiler thread's event loop has stopped.
      // There is no need for a mutex when reading input_queue_length_.
      while (input_queue_length_ > 0) CompileNext();
      InstallOptimizedFunctions();
    } else {
      FlushInputQueue(false);
      FlushOutputQueue(false);
    }
  
    if (FLAG_concurrent_osr) FlushOsrBuffer(false);
  
    if (FLAG_trace_concurrent_recompilation) {
      double percentage = time_spent_compiling_.PercentOf(time_spent_total_);
      PrintF("  ** Compiler thread did %.2f%% useful work\n", percentage);
    }
  
    if ((FLAG_trace_osr || FLAG_trace_concurrent_recompilation) &&
        FLAG_concurrent_osr) {
      PrintF("[COSR hit rate %d / %d]\n", osr_hits_, osr_attempts_);
    }
  
    Join();
  }
  
  
  void OptimizingCompilerThread::InstallOptimizedFunctions() {
    ASSERT(!IsOptimizerThread());
    HandleScope handle_scope(isolate_);
  
    OptimizedCompileJob* job;
    while (output_queue_.Dequeue(&job)) {
      CompilationInfo* info = job->info();
      Handle<JSFunction> function(*info->closure());
      if (info->is_osr()) {
        if (FLAG_trace_osr) {
          PrintF("[COSR - ");
          info->closure()->PrintName();
          PrintF(" is ready for install and entry at AST id %d]\n",
                 info->osr_ast_id().ToInt());
        }
        job->WaitForInstall();
        // Remove stack check that guards OSR entry on original code.
        Handle<Code> code = info->unoptimized_code();
        uint32_t offset = code->TranslateAstIdToPcOffset(info->osr_ast_id());
        BackEdgeTable::RemoveStackCheck(code, offset);
      } else {
        Handle<Code> code = Compiler::GetConcurrentlyOptimizedCode(job);
        function->ReplaceCode(
            code.is_null() ? function->shared()->code() : *code);
      }
    }
  }
  
  
  void OptimizingCompilerThread::QueueForOptimization(OptimizedCompileJob* job) {
    ASSERT(IsQueueAvailable());
    ASSERT(!IsOptimizerThread());
    CompilationInfo* info = job->info();
    if (info->is_osr()) {
      osr_attempts_++;
      AddToOsrBuffer(job);
      // Add job to the front of the input queue.
      LockGuard<Mutex> access_input_queue(&input_queue_mutex_);
      ASSERT_LT(input_queue_length_, input_queue_capacity_);
      // Move shift_ back by one.
      input_queue_shift_ = InputQueueIndex(input_queue_capacity_ - 1);
      input_queue_[InputQueueIndex(0)] = job;
      input_queue_length_++;
    } else {
      // Add job to the back of the input queue.
      LockGuard<Mutex> access_input_queue(&input_queue_mutex_);
      ASSERT_LT(input_queue_length_, input_queue_capacity_);
      input_queue_[InputQueueIndex(input_queue_length_)] = job;
      input_queue_length_++;
    }
    if (FLAG_block_concurrent_recompilation) {
      blocked_jobs_++;
    } else {
      input_queue_semaphore_.Signal();
    }
  }
  
  
  void OptimizingCompilerThread::Unblock() {
    ASSERT(!IsOptimizerThread());
    while (blocked_jobs_ > 0) {
      input_queue_semaphore_.Signal();
      blocked_jobs_--;
    }
  }
  
  
  OptimizedCompileJob* OptimizingCompilerThread::FindReadyOSRCandidate(
      Handle<JSFunction> function, BailoutId osr_ast_id) {
    ASSERT(!IsOptimizerThread());
    for (int i = 0; i < osr_buffer_capacity_; i++) {
      OptimizedCompileJob* current = osr_buffer_[i];
      if (current != NULL &&
          current->IsWaitingForInstall() &&
          current->info()->HasSameOsrEntry(function, osr_ast_id)) {
        osr_hits_++;
        osr_buffer_[i] = NULL;
        return current;
      }
    }
    return NULL;
  }
  
  
  bool OptimizingCompilerThread::IsQueuedForOSR(Handle<JSFunction> function,
                                                BailoutId osr_ast_id) {
    ASSERT(!IsOptimizerThread());
    for (int i = 0; i < osr_buffer_capacity_; i++) {
      OptimizedCompileJob* current = osr_buffer_[i];
      if (current != NULL &&
          current->info()->HasSameOsrEntry(function, osr_ast_id)) {
        return !current->IsWaitingForInstall();
      }
    }
    return false;
  }
  
  
  bool OptimizingCompilerThread::IsQueuedForOSR(JSFunction* function) {
    ASSERT(!IsOptimizerThread());
    for (int i = 0; i < osr_buffer_capacity_; i++) {
      OptimizedCompileJob* current = osr_buffer_[i];
      if (current != NULL && *current->info()->closure() == function) {
        return !current->IsWaitingForInstall();
      }
    }
    return false;
  }
  
  
  void OptimizingCompilerThread::AddToOsrBuffer(OptimizedCompileJob* job) {
    ASSERT(!IsOptimizerThread());
    // Find the next slot that is empty or has a stale job.
    OptimizedCompileJob* stale = NULL;
    while (true) {
      stale = osr_buffer_[osr_buffer_cursor_];
      if (stale == NULL || stale->IsWaitingForInstall()) break;
      osr_buffer_cursor_ = (osr_buffer_cursor_ + 1) % osr_buffer_capacity_;
    }
  
    // Add to found slot and dispose the evicted job.
    if (stale != NULL) {
      ASSERT(stale->IsWaitingForInstall());
      CompilationInfo* info = stale->info();
      if (FLAG_trace_osr) {
        PrintF("[COSR - Discarded ");
        info->closure()->PrintName();
        PrintF(", AST id %d]\n", info->osr_ast_id().ToInt());
      }
      DisposeOptimizedCompileJob(stale, false);
    }
    osr_buffer_[osr_buffer_cursor_] = job;
    osr_buffer_cursor_ = (osr_buffer_cursor_ + 1) % osr_buffer_capacity_;
  }
  
  
  #ifdef DEBUG
  bool OptimizingCompilerThread::IsOptimizerThread(Isolate* isolate) {
    return isolate->concurrent_recompilation_enabled() &&
           isolate->optimizing_compiler_thread()->IsOptimizerThread();
  }
  
  
  bool OptimizingCompilerThread::IsOptimizerThread() {
    LockGuard<Mutex> lock_guard(&thread_id_mutex_);
    return ThreadId::Current().ToInteger() == thread_id_;
  }
  #endif
  
  
  } }  // namespace v8::internal
  