Reland "Disable the CompilerDispatcher if we don't have idle time"

src/compiler-dispatcher/compiler-dispatcher.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler-dispatcher/compiler-dispatcher.h"
 
 #include "include/v8-platform.h"
 #include "include/v8.h"
 #include "src/base/platform/time.h"
 #include "src/cancelable-task.h"
@@ skipping 92 matching lines @@
       max_stack_size_(max_stack_size),
       tracer_(new CompilerDispatcherTracer(isolate_)),
       idle_task_scheduled_(false) {}
 
 CompilerDispatcher::~CompilerDispatcher() {
   // To avoid crashing in unit tests due to unfished jobs.
   AbortAll(BlockingBehavior::kBlock);
 }
 
 bool CompilerDispatcher::Enqueue(Handle<SharedFunctionInfo> function) {
+  if (!IsEnabled()) return false;
+
   // We only handle functions (no eval / top-level code / wasm) that are
   // attached to a script.
   if (!function->script()->IsScript() || !function->is_function() ||
       function->asm_function() || function->native()) {
     return false;
   }
 
   if (IsEnqueued(function)) return true;
   std::unique_ptr<CompilerDispatcherJob> job(new CompilerDispatcherJob(
       isolate_, tracer_.get(), function, max_stack_size_));
   std::pair<int, int> key(Script::cast(function->script())->id(),
                           function->function_literal_id());
   jobs_.insert(std::make_pair(key, std::move(job)));
   ScheduleIdleTaskIfNeeded();
   return true;
 }
 
+bool CompilerDispatcher::IsEnabled() const {
+  v8::Isolate* v8_isolate = reinterpret_cast<v8::Isolate*>(isolate_);
+  return FLAG_compiler_dispatcher && platform_->IdleTasksEnabled(v8_isolate);
+}
+
 bool CompilerDispatcher::IsEnqueued(Handle<SharedFunctionInfo> function) const {
   return GetJobFor(function) != jobs_.end();
 }
 
 bool CompilerDispatcher::FinishNow(Handle<SharedFunctionInfo> function) {
   JobMap::const_iterator job = GetJobFor(function);
   CHECK(job != jobs_.end());
 
   // TODO(jochen): Check if there's an in-flight background task working on this
   // job.
@@ skipping 36 matching lines @@
                           shared->function_literal_id());
   auto range = jobs_.equal_range(key);
   for (auto job = range.first; job != range.second; ++job) {
     if (job->second->IsAssociatedWith(shared)) return job;
   }
   return jobs_.end();
 }
 
 void CompilerDispatcher::ScheduleIdleTaskIfNeeded() {
   v8::Isolate* v8_isolate = reinterpret_cast<v8::Isolate*>(isolate_);
-  if (!platform_->IdleTasksEnabled(v8_isolate)) return;
+  DCHECK(platform_->IdleTasksEnabled(v8_isolate));
   if (idle_task_scheduled_) return;
   if (jobs_.empty()) return;
   idle_task_scheduled_ = true;
   platform_->CallIdleOnForegroundThread(v8_isolate,
                                         new IdleTask(isolate_, this));
 }
 
 void CompilerDispatcher::DoIdleWork(double deadline_in_seconds) {
   idle_task_scheduled_ = false;
 
@@ skipping 28 matching lines @@
       // iterator).
       DoNextStepOnMainThread(isolate_, job->second.get(),
                              ExceptionHandling::kSwallow);
     }
   }
   if (jobs_.size() > too_long_jobs) ScheduleIdleTaskIfNeeded();
 }
 
 }  // namespace internal
 }  // namespace v8