[maglev] Add a skeleton MaglevConcurrentDispatcher impl

A dispatcher that currently does nothing, installed on the Isolate.

The implementation is close to the baseline concurrent compiler; but
boilerplate is short enough that a common base class is not worth the
additional complexity.

Bug: v8:7700
Change-Id: Ia34781e24cb6b1f72e5560fb0afe107bb0486092
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3497690
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79353}

BUILD.gn

@@ -3470,6 +3470,7 @@ v8_header_set("v8_internal_headers") {
       "src/maglev/maglev-code-generator.h",
       "src/maglev/maglev-compilation-data.h",
       "src/maglev/maglev-compiler.h",
+      "src/maglev/maglev-concurrent-dispatcher.h",
       "src/maglev/maglev-graph-builder.h",
       "src/maglev/maglev-graph-labeller.h",
       "src/maglev/maglev-graph-printer.h",
@@ -4493,6 +4494,7 @@ v8_source_set("v8_base_without_compiler") {
       "src/maglev/maglev-code-generator.cc",
       "src/maglev/maglev-compilation-data.cc",
       "src/maglev/maglev-compiler.cc",
+      "src/maglev/maglev-concurrent-dispatcher.cc",
       "src/maglev/maglev-graph-builder.cc",
       "src/maglev/maglev-graph-printer.cc",
       "src/maglev/maglev-ir.cc",

src/DEPS

@@ -53,6 +53,7 @@ include_rules = [
   "+src/interpreter/setup-interpreter.h",
   "-src/maglev",
   "+src/maglev/maglev.h",
+  "+src/maglev/maglev-concurrent-dispatcher.h",
   "-src/regexp",
   "+src/regexp/regexp.h",
   "+src/regexp/regexp-flags.h",

src/execution/isolate.cc

@@ -75,6 +75,7 @@
 #include "src/logging/log.h"
 #include "src/logging/metrics.h"
 #include "src/logging/runtime-call-stats-scope.h"
+#include "src/maglev/maglev-concurrent-dispatcher.h"
 #include "src/numbers/hash-seed-inl.h"
 #include "src/objects/backing-store.h"
 #include "src/objects/call-site-info-inl.h"
@@ -3366,10 +3367,15 @@ void Isolate::Deinit() {
     cancelable_task_manager()->CancelAndWait();
   }
 
-  // Cancel all baseline compiler tasks.
+  // Cancel all compiler tasks.
   delete baseline_batch_compiler_;
   baseline_batch_compiler_ = nullptr;
 
+#ifdef V8_ENABLE_MAGLEV
+  delete maglev_concurrent_dispatcher_;
+  maglev_concurrent_dispatcher_ = nullptr;
+#endif  // V8_ENABLE_MAGLEV
+
   if (lazy_compile_dispatcher_) {
     lazy_compile_dispatcher_->AbortAll();
     lazy_compile_dispatcher_.reset();
@@ -3877,6 +3883,9 @@ bool Isolate::Init(SnapshotData* startup_snapshot_data,
         this, V8::GetCurrentPlatform(), FLAG_stack_size);
   }
   baseline_batch_compiler_ = new baseline::BaselineBatchCompiler(this);
+#ifdef V8_ENABLE_MAGLEV
+  maglev_concurrent_dispatcher_ = new maglev::MaglevConcurrentDispatcher(this);
+#endif  // V8_ENABLE_MAGLEV
 
 #if USE_SIMULATOR
   simulator_data_ = new SimulatorData;

src/execution/isolate.h

@@ -87,6 +87,10 @@ namespace heap {
 class HeapTester;
 }  // namespace heap
 
+namespace maglev {
+class MaglevConcurrentDispatcher;
+}  // namespace maglev
+
 class AddressToIndexHashMap;
 class AstStringConstants;
 class Bootstrapper;
@@ -103,11 +107,11 @@ class Deoptimizer;
 class DescriptorLookupCache;
 class EmbeddedFileWriterInterface;
 class EternalHandles;
+class GlobalHandles;
+class GlobalSafepoint;
 class HandleScopeImplementer;
 class HeapObjectToIndexHashMap;
 class HeapProfiler;
-class GlobalHandles;
-class GlobalSafepoint;
 class InnerPointerToCodeCache;
 class LazyCompileDispatcher;
 class LocalIsolate;
@@ -121,7 +125,6 @@ class PersistentHandlesList;
 class ReadOnlyArtifacts;
 class RegExpStack;
 class RootVisitor;
-class TieringManager;
 class SetupIsolateDelegate;
 class Simulator;
 class SnapshotData;
@@ -130,6 +133,7 @@ class StubCache;
 class ThreadManager;
 class ThreadState;
 class ThreadVisitor;  // Defined in v8threads.h
+class TieringManager;
 class TracingCpuProfilerImpl;
 class UnicodeCache;
 struct ManagedPtrDestructor;
@@ -1463,11 +1467,18 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
   bool IsDeferredHandle(Address* location);
 #endif  // DEBUG
 
-  baseline::BaselineBatchCompiler* baseline_batch_compiler() {
+  baseline::BaselineBatchCompiler* baseline_batch_compiler() const {
     DCHECK_NOT_NULL(baseline_batch_compiler_);
     return baseline_batch_compiler_;
   }
 
+#ifdef V8_ENABLE_MAGLEV
+  maglev::MaglevConcurrentDispatcher* maglev_concurrent_dispatcher() {
+    DCHECK_NOT_NULL(maglev_concurrent_dispatcher_);
+    return maglev_concurrent_dispatcher_;
+  }
+#endif  // V8_ENABLE_MAGLEV
+
   bool concurrent_recompilation_enabled() {
     // Thread is only available with flag enabled.
     DCHECK(optimizing_compile_dispatcher_ == nullptr ||
@@ -1733,10 +1744,6 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
     return lazy_compile_dispatcher_.get();
   }
 
-  baseline::BaselineBatchCompiler* baseline_batch_compiler() const {
-    return baseline_batch_compiler_;
-  }
-
   bool IsInAnyContext(Object object, uint32_t index);
 
   void ClearKeptObjects();
@@ -2218,6 +2225,9 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
 
   std::unique_ptr<LazyCompileDispatcher> lazy_compile_dispatcher_;
   baseline::BaselineBatchCompiler* baseline_batch_compiler_ = nullptr;
+#ifdef V8_ENABLE_MAGLEV
+  maglev::MaglevConcurrentDispatcher* maglev_concurrent_dispatcher_ = nullptr;
+#endif  // V8_ENABLE_MAGLEV
 
   using InterruptEntry = std::pair<InterruptCallback, void*>;
   std::queue<InterruptEntry> api_interrupts_queue_;

src/maglev/maglev-concurrent-dispatcher.cc

@@ -0,0 +1,81 @@
+// Copyright 2022 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/maglev/maglev-concurrent-dispatcher.h"
+
+#include "src/flags/flags.h"
+#include "src/objects/js-function.h"
+#include "src/utils/locked-queue-inl.h"
+
+namespace v8 {
+namespace internal {
+namespace maglev {
+
+class MaglevConcurrentDispatcher::Job final {
+ public:
+  explicit Job(Handle<JSFunction> function) : function_(function) {}
+
+  void Install(Isolate* isolate) { UNIMPLEMENTED(); }
+
+ private:
+  const Handle<JSFunction> function_;
+};
+
+class MaglevConcurrentDispatcher::JobTask final : public v8::JobTask {
+ public:
+  explicit JobTask(MaglevConcurrentDispatcher* dispatcher)
+      : dispatcher_(dispatcher) {}
+
+  void Run(JobDelegate* delegate) override {}
+
+  size_t GetMaxConcurrency(size_t) const override {
+    return incoming_queue()->size();
+  }
+
+ private:
+  QueueT* incoming_queue() const { return &dispatcher_->incoming_queue_; }
+  QueueT* outgoing_queue() const { return &dispatcher_->outgoing_queue_; }
+
+  MaglevConcurrentDispatcher* const dispatcher_;
+  const Handle<JSFunction> function_;
+};
+
+MaglevConcurrentDispatcher::MaglevConcurrentDispatcher(Isolate* isolate)
+    : isolate_(isolate) {
+  if (FLAG_concurrent_recompilation && FLAG_maglev) {
+    job_handle_ = V8::GetCurrentPlatform()->PostJob(
+        TaskPriority::kUserVisible, std::make_unique<JobTask>(this));
+    DCHECK(is_enabled());
+  } else {
+    DCHECK(!is_enabled());
+  }
+}
+
+MaglevConcurrentDispatcher::~MaglevConcurrentDispatcher() {
+  if (is_enabled() && job_handle_->IsValid()) {
+    // Wait for the job handle to complete, so that we know the queue
+    // pointers are safe.
+    job_handle_->Cancel();
+  }
+}
+
+void MaglevConcurrentDispatcher::EnqueueJob(Handle<JSFunction> function) {
+  DCHECK(is_enabled());
+  // TODO(v8:7700): RCS.
+  // RCS_SCOPE(isolate_, RuntimeCallCounterId::kCompileMaglev);
+  incoming_queue_.Enqueue(std::make_unique<Job>(function));
+  job_handle_->NotifyConcurrencyIncrease();
+}
+
+void MaglevConcurrentDispatcher::ProcessFinishedJobs() {
+  while (!outgoing_queue_.IsEmpty()) {
+    std::unique_ptr<Job> job;
+    outgoing_queue_.Dequeue(&job);
+    job->Install(isolate_);
+  }
+}
+
+}  // namespace maglev
+}  // namespace internal
+}  // namespace v8

src/maglev/maglev-concurrent-dispatcher.h

@@ -0,0 +1,54 @@
+// Copyright 2022 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.
+
+#ifndef V8_MAGLEV_MAGLEV_CONCURRENT_DISPATCHER_H_
+#define V8_MAGLEV_MAGLEV_CONCURRENT_DISPATCHER_H_
+
+#ifdef V8_ENABLE_MAGLEV
+
+#include <memory>
+
+#include "src/utils/locked-queue.h"
+
+namespace v8 {
+namespace internal {
+
+class Isolate;
+
+namespace maglev {
+
+class MaglevConcurrentDispatcher final {
+  class Job;
+  class JobTask;
+
+  // TODO(jgruber): There's no reason to use locking queues here, we only use
+  // them for simplicity - consider replacing with lock-free data structures.
+  using QueueT = LockedQueue<std::unique_ptr<Job>>;
+
+ public:
+  explicit MaglevConcurrentDispatcher(Isolate* isolate);
+  ~MaglevConcurrentDispatcher();
+
+  // Called from the main thread.
+  void EnqueueJob(Handle<JSFunction> function);
+
+  // Called from the main thread.
+  void ProcessFinishedJobs();
+
+  bool is_enabled() const { return static_cast<bool>(job_handle_); }
+
+ private:
+  Isolate* const isolate_;
+  std::unique_ptr<JobHandle> job_handle_;
+  QueueT incoming_queue_;
+  QueueT outgoing_queue_;
+};
+
+}  // namespace maglev
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_ENABLE_MAGLEV
+
+#endif  // V8_MAGLEV_MAGLEV_CONCURRENT_DISPATCHER_H_