[handles] Branch hints and force-inline in HandleScope

Force-inline the HandleScope constructor and destructor, and
add branch hints for two commonly-mispredicted branches. This
moves the overall JetStream2/cdjs score by roughly 4% on d8. I
suspect no change will be visible in chromium builds (with PGO).

Bug: v8:12196
Change-Id: I0fd7b67aa554876d2dad2d706b874df21dbb72e2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3270542
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77836}

src/execution/isolate.h

@@ -1199,7 +1199,7 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
     return descriptor_lookup_cache_;
   }
 
-  HandleScopeData* handle_scope_data() { return &handle_scope_data_; }
+  V8_INLINE HandleScopeData* handle_scope_data() { return &handle_scope_data_; }
 
   HandleScopeImplementer* handle_scope_implementer() const {
     DCHECK(handle_scope_implementer_);

src/handles/handles-inl.h

@@ -95,7 +95,7 @@ HandleScope::HandleScope(HandleScope&& other) V8_NOEXCEPT
 }
 
 HandleScope::~HandleScope() {
-  if (isolate_ == nullptr) return;
+  if (V8_UNLIKELY(isolate_ == nullptr)) return;
   CloseScope(isolate_, prev_next_, prev_limit_);
 }
 
@@ -123,7 +123,7 @@ void HandleScope::CloseScope(Isolate* isolate, Address* prev_next,
   std::swap(current->next, prev_next);
   current->level--;
   Address* limit = prev_next;
-  if (current->limit != prev_limit) {
+  if (V8_UNLIKELY(current->limit != prev_limit)) {
     current->limit = prev_limit;
     limit = prev_limit;
     DeleteExtensions(isolate);

src/handles/handles.h

@@ -199,7 +199,7 @@ inline std::ostream& operator<<(std::ostream& os, Handle<T> handle);
 // for which the handle scope has been deleted is undefined.
 class V8_NODISCARD HandleScope {
  public:
-  explicit inline HandleScope(Isolate* isolate);
+  explicit V8_INLINE HandleScope(Isolate* isolate);
   inline HandleScope(HandleScope&& other) V8_NOEXCEPT;
   HandleScope(const HandleScope&) = delete;
   HandleScope& operator=(const HandleScope&) = delete;
@@ -213,7 +213,7 @@ class V8_NODISCARD HandleScope {
   void* operator new(size_t size) = delete;
   void operator delete(void* size_t) = delete;
 
-  inline ~HandleScope();
+  V8_INLINE ~HandleScope();
 
   inline HandleScope& operator=(HandleScope&& other) V8_NOEXCEPT;
 
@@ -253,8 +253,8 @@ class V8_NODISCARD HandleScope {
   Address* prev_limit_;
 
   // Close the handle scope resetting limits to a previous state.
-  static inline void CloseScope(Isolate* isolate, Address* prev_next,
-                                Address* prev_limit);
+  static V8_INLINE void CloseScope(Isolate* isolate, Address* prev_next,
+                                   Address* prev_limit);
 
   // Extend the handle scope making room for more handles.
   V8_EXPORT_PRIVATE static Address* Extend(Isolate* isolate);