src/optimizing-compiler-thread.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
//       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 "hydrogen.h"
#include "isolate.h"
#include "v8threads.h"

namespace v8 {
namespace internal {


void OptimizingCompilerThread::Run() {
#ifdef DEBUG
  thread_id_ = ThreadId::Current().ToInteger();
#endif
  Isolate::SetIsolateThreadLocals(isolate_, NULL);

  int64_t epoch = 0;
  if (FLAG_trace_parallel_recompilation) epoch = OS::Ticks();

  while (true) {
    input_queue_semaphore_->Wait();
    Logger::TimerEventScope timer(
        isolate_, Logger::TimerEventScope::v8_recompile_parallel);

    if (FLAG_parallel_recompilation_delay != 0) {
      OS::Sleep(FLAG_parallel_recompilation_delay);
    }

    if (Acquire_Load(&stop_thread_)) {
      stop_semaphore_->Signal();
      if (FLAG_trace_parallel_recompilation) {
        time_spent_total_ = OS::Ticks() - epoch;
      }
      return;
    }

    int64_t compiling_start = 0;
    if (FLAG_trace_parallel_recompilation) compiling_start = OS::Ticks();

    CompileNext();

    if (!FLAG_manual_parallel_recompilation) {
      isolate_->stack_guard()->RequestCodeReadyEvent();
    } else {
      // In manual mode, do not trigger a code ready event.
      // Instead, wait for the optimized functions to be installed manually.
      output_queue_semaphore_->Signal();
    }

    if (FLAG_trace_parallel_recompilation) {
      time_spent_compiling_ += OS::Ticks() - compiling_start;
    }
  }
}


void OptimizingCompilerThread::CompileNext() {
  Heap::RelocationLock relocation_lock(isolate_->heap());
  OptimizingCompiler* optimizing_compiler = NULL;
  input_queue_.Dequeue(&optimizing_compiler);
  Barrier_AtomicIncrement(&queue_length_, static_cast<Atomic32>(-1));

  // Function may have been optimized meanwhile by OSR.
  if (FLAG_use_osr &&
      optimizing_compiler->info()->closure()->IsOptimized()) {
    return;
  }

  OptimizingCompiler::Status status = optimizing_compiler->OptimizeGraph();
  ASSERT(status != OptimizingCompiler::FAILED);
  // Prevent an unused-variable error in release mode.
  USE(status);

  output_queue_.Enqueue(optimizing_compiler);
}


void OptimizingCompilerThread::Stop() {
  Release_Store(&stop_thread_, static_cast<AtomicWord>(true));
  input_queue_semaphore_->Signal();
  stop_semaphore_->Wait();

  if (FLAG_parallel_recompilation_delay != 0) {
    // Execution ended before we managed to compile and install the remaining
    // functions in the queue.  We still want to do that for debugging though.
    // At this point the optimizing thread already stopped, so we finish
    // processing the queue in the main thread.
    InstallOptimizedFunctions();
    // Barrier when loading queue length is not necessary since the write
    // happens in CompileNext on the same thread.
    while (NoBarrier_Load(&queue_length_) > 0) {
      CompileNext();
      InstallOptimizedFunctions();
    }
  }

  if (FLAG_trace_parallel_recompilation) {
    double compile_time = static_cast<double>(time_spent_compiling_);
    double total_time = static_cast<double>(time_spent_total_);
    double percentage = (compile_time * 100) / total_time;
    PrintF("  ** Compiler thread did %.2f%% useful work\n", percentage);
  }
}


void OptimizingCompilerThread::InstallOptimizedFunctions() {
  HandleScope handle_scope(isolate_);
  int functions_installed = 0;
  while (!output_queue_.IsEmpty()) {
    if (FLAG_manual_parallel_recompilation) {
      output_queue_semaphore_->Wait();
    }
    OptimizingCompiler* compiler = NULL;
    output_queue_.Dequeue(&compiler);
    Compiler::InstallOptimizedCode(compiler);
    functions_installed++;
  }
  if (FLAG_trace_parallel_recompilation && functions_installed != 0) {
    PrintF("  ** Installed %d function(s).\n", functions_installed);
  }
}


Handle<SharedFunctionInfo>
    OptimizingCompilerThread::InstallNextOptimizedFunction() {
  ASSERT(FLAG_manual_parallel_recompilation ||
         FLAG_parallel_recompilation_delay != 0);
  output_queue_semaphore_->Wait();
  OptimizingCompiler* compiler = NULL;
  output_queue_.Dequeue(&compiler);
  // Copy a handle from deferred handle scope to the normal handle scope.
  Handle<SharedFunctionInfo> shared(*compiler->info()->shared_info());
  Compiler::InstallOptimizedCode(compiler);
  return shared;
}


void OptimizingCompilerThread::QueueForOptimization(
    OptimizingCompiler* optimizing_compiler) {
  ASSERT(IsQueueAvailable());
  Barrier_AtomicIncrement(&queue_length_, static_cast<Atomic32>(1));
  input_queue_.Enqueue(optimizing_compiler);
  input_queue_semaphore_->Signal();
}

#ifdef DEBUG
bool OptimizingCompilerThread::IsOptimizerThread() {
  if (!FLAG_parallel_recompilation) return false;
  return ThreadId::Current().ToInteger() == thread_id_;
}
#endif


} }  // namespace v8::internal