v8/src/optimizing-compiler-thread.cc

// Copyright 2012 the V8 project authors. All rights reserved.
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#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
  { ScopedLock lock(thread_id_mutex_);
    thread_id_ = ThreadId::Current().ToInteger();
  }
#endif
  Isolate::SetIsolateThreadLocals(isolate_, NULL);
  DisallowHeapAllocation no_allocation;
  DisallowHandleAllocation no_handles;
  DisallowHandleDereference no_deref;

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


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

  // The function may have already been optimized by OSR.  Simply continue.
  OptimizingCompiler::Status status = optimizing_compiler->OptimizeGraph();
  USE(status);   // Prevent an unused-variable error in release mode.
  ASSERT(status != OptimizingCompiler::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.
  ScopedLock mark_and_queue(install_mutex_);
  { Heap::RelocationLock relocation_lock(isolate_->heap());
    AllowHandleDereference ahd;
    optimizing_compiler->info()->closure()->MarkForInstallingRecompiledCode();
  }
  output_queue_.Enqueue(optimizing_compiler);
}


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

  if (FLAG_parallel_recompilation_delay != 0) {
    // 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();
  } else {
    OptimizingCompiler* optimizing_compiler;
    // The optimizing compiler is allocated in the CompilationInfo's zone.
    while (input_queue_.Dequeue(&optimizing_compiler)) {
      delete optimizing_compiler->info();
    }
    while (output_queue_.Dequeue(&optimizing_compiler)) {
      delete optimizing_compiler->info();
    }
  }

  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);
  }

  Join();
}


void OptimizingCompilerThread::InstallOptimizedFunctions() {
  ASSERT(!IsOptimizerThread());
  HandleScope handle_scope(isolate_);
  OptimizingCompiler* compiler;
  while (true) {
    { // Memory barrier to ensure marked functions are queued.
      ScopedLock marked_and_queued(install_mutex_);
      if (!output_queue_.Dequeue(&compiler)) return;
    }
    Compiler::InstallOptimizedCode(compiler);
  }
}


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


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


} }  // namespace v8::internal