Add templatized GlobalHandles::Create method

The old method always returned a Handle<Object>, requiring an explicit
cast in the caller. This CL makes it return Handle<T> if called with a
T* as parameter.

Also, remove now redundant casts from callers.

R=bmeurer@chromium.org

Change-Id: I13cfb2f2e812e8582a9a1d9d6c8a5a24f40d0e79
Reviewed-on: https://chromium-review.googlesource.com/458376
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44012}

src/compiler-dispatcher/compiler-dispatcher-job.cc

@@ -68,10 +68,8 @@ CompilerDispatcherJob::CompilerDispatcherJob(Isolate* isolate,
     : status_(CompileJobStatus::kInitial),
       isolate_(isolate),
       tracer_(tracer),
-      context_(Handle<Context>::cast(
-          isolate_->global_handles()->Create(isolate->context()))),
-      shared_(Handle<SharedFunctionInfo>::cast(
-          isolate_->global_handles()->Create(*shared))),
+      context_(isolate_->global_handles()->Create(isolate->context())),
+      shared_(isolate_->global_handles()->Create(*shared)),
       max_stack_size_(max_stack_size),
       trace_compiler_dispatcher_jobs_(FLAG_trace_compiler_dispatcher_jobs) {
   DCHECK(!shared_->is_toplevel());
@@ -94,10 +92,8 @@ CompilerDispatcherJob::CompilerDispatcherJob(
     : status_(CompileJobStatus::kAnalyzed),
       isolate_(isolate),
       tracer_(tracer),
-      context_(Handle<Context>::cast(
-          isolate_->global_handles()->Create(isolate->context()))),
-      shared_(Handle<SharedFunctionInfo>::cast(
-          isolate_->global_handles()->Create(*shared))),
+      context_(isolate_->global_handles()->Create(isolate->context())),
+      shared_(isolate_->global_handles()->Create(*shared)),
       max_stack_size_(max_stack_size),
       parse_info_(new ParseInfo(shared_)),
       parse_zone_(parse_zone),
@@ -158,8 +154,7 @@ void CompilerDispatcherJob::PrepareToParseOnMainThread() {
     if (isolate_->heap()->lo_space()->Contains(*source)) {
       // We need to globalize the handle to the flattened string here, in
       // case it's not referenced from anywhere else.
-      source_ =
-          Handle<String>::cast(isolate_->global_handles()->Create(*source));
+      source_ = isolate_->global_handles()->Create(*source);
       DisallowHeapAllocation no_allocation;
       String::FlatContent content = source->GetFlatContent();
       DCHECK(content.IsFlat());
@@ -205,8 +200,7 @@ void CompilerDispatcherJob::PrepareToParseOnMainThread() {
                     ->NewExternalStringFromTwoByte(resource)
                     .ToHandleChecked();
     }
-    wrapper_ =
-        Handle<String>::cast(isolate_->global_handles()->Create(*wrapper));
+    wrapper_ = isolate_->global_handles()->Create(*wrapper);
 
     character_stream_.reset(
         ScannerStream::For(wrapper_, shared_->start_position() - offset,

src/debug/debug.cc

@@ -423,8 +423,7 @@ void Debug::Iterate(ObjectVisitor* v) {
 DebugInfoListNode::DebugInfoListNode(DebugInfo* debug_info): next_(NULL) {
   // Globalize the request debug info object and make it weak.
   GlobalHandles* global_handles = debug_info->GetIsolate()->global_handles();
-  debug_info_ =
-      Handle<DebugInfo>::cast(global_handles->Create(debug_info)).location();
+  debug_info_ = global_handles->Create(debug_info).location();
 }
 
 
@@ -464,8 +463,7 @@ bool Debug::Load() {
   // Fail if no context could be created.
   if (context.is_null()) return false;
 
-  debug_context_ = Handle<Context>::cast(
-      isolate_->global_handles()->Create(*context));
+  debug_context_ = isolate_->global_handles()->Create(*context);
 
   feature_tracker()->Track(DebugFeatureTracker::kActive);
 
@@ -2369,7 +2367,7 @@ JavaScriptDebugDelegate::JavaScriptDebugDelegate(Isolate* isolate,
                                                  Handle<Object> data)
     : LegacyDebugDelegate(isolate) {
   GlobalHandles* global_handles = isolate->global_handles();
-  listener_ = Handle<JSFunction>::cast(global_handles->Create(*listener));
+  listener_ = global_handles->Create(*listener);
   data_ = global_handles->Create(*data);
 }
 

src/global-handles.h

@@ -5,6 +5,8 @@
 #ifndef V8_GLOBAL_HANDLES_H_
 #define V8_GLOBAL_HANDLES_H_
 
+#include <type_traits>
+
 #include "include/v8.h"
 #include "include/v8-profiler.h"
 
@@ -52,6 +54,14 @@ class GlobalHandles {
   // Creates a new global handle that is alive until Destroy is called.
   Handle<Object> Create(Object* value);
 
+  template <typename T>
+  Handle<T> Create(T* value) {
+    static_assert(std::is_base_of<Object, T>::value, "static type violation");
+    // The compiler should only pick this method if T is not Object.
+    static_assert(!std::is_same<Object, T>::value, "compiler error");
+    return Handle<T>::cast(Create(static_cast<Object*>(value)));
+  }
+
   // Copy a global handle
   static Handle<Object> CopyGlobal(Object** location);
 

src/isolate.cc

@@ -1846,8 +1846,7 @@ bool Isolate::OptionalRescheduleException(bool is_bottom_call) {
 void Isolate::PushPromise(Handle<JSObject> promise) {
   ThreadLocalTop* tltop = thread_local_top();
   PromiseOnStack* prev = tltop->promise_on_stack_;
-  Handle<JSObject> global_promise =
-      Handle<JSObject>::cast(global_handles()->Create(*promise));
+  Handle<JSObject> global_promise = global_handles()->Create(*promise);
   tltop->promise_on_stack_ = new PromiseOnStack(global_promise, prev);
 }
 

src/profiler/allocation-tracker.cc

@@ -302,8 +302,7 @@ AllocationTracker::UnresolvedLocation::UnresolvedLocation(
     Script* script, int start, FunctionInfo* info)
     : start_position_(start),
       info_(info) {
-  script_ = Handle<Script>::cast(
-      script->GetIsolate()->global_handles()->Create(script));
+  script_ = script->GetIsolate()->global_handles()->Create(script);
   GlobalHandles::MakeWeak(reinterpret_cast<Object**>(script_.location()), this,
                           &HandleWeakScript, v8::WeakCallbackType::kParameter);
 }

src/value-serializer.cc

@@ -922,8 +922,8 @@ ValueDeserializer::ValueDeserializer(Isolate* isolate,
       position_(data.start()),
       end_(data.start() + data.length()),
       pretenure_(data.length() > kPretenureThreshold ? TENURED : NOT_TENURED),
-      id_map_(Handle<FixedArray>::cast(isolate->global_handles()->Create(
-          isolate_->heap()->empty_fixed_array()))) {}
+      id_map_(isolate->global_handles()->Create(
+          isolate_->heap()->empty_fixed_array())) {}
 
 ValueDeserializer::~ValueDeserializer() {
   GlobalHandles::Destroy(Handle<Object>::cast(id_map_).location());
@@ -1052,9 +1052,8 @@ bool ValueDeserializer::ReadRawBytes(size_t length, const void** data) {
 void ValueDeserializer::TransferArrayBuffer(
     uint32_t transfer_id, Handle<JSArrayBuffer> array_buffer) {
   if (array_buffer_transfer_map_.is_null()) {
-    array_buffer_transfer_map_ =
-        Handle<SeededNumberDictionary>::cast(isolate_->global_handles()->Create(
-            *SeededNumberDictionary::New(isolate_, 0)));
+    array_buffer_transfer_map_ = isolate_->global_handles()->Create(
+        *SeededNumberDictionary::New(isolate_, 0));
   }
   Handle<SeededNumberDictionary> dictionary =
       array_buffer_transfer_map_.ToHandleChecked();
@@ -1064,8 +1063,8 @@ void ValueDeserializer::TransferArrayBuffer(
                                           not_a_prototype_holder);
   if (!new_dictionary.is_identical_to(dictionary)) {
     GlobalHandles::Destroy(Handle<Object>::cast(dictionary).location());
-    array_buffer_transfer_map_ = Handle<SeededNumberDictionary>::cast(
-        isolate_->global_handles()->Create(*new_dictionary));
+    array_buffer_transfer_map_ =
+        isolate_->global_handles()->Create(*new_dictionary);
   }
 }
 
@@ -1877,8 +1876,7 @@ void ValueDeserializer::AddObjectWithID(uint32_t id,
   // If the dictionary was reallocated, update the global handle.
   if (!new_array.is_identical_to(id_map_)) {
     GlobalHandles::Destroy(Handle<Object>::cast(id_map_).location());
-    id_map_ = Handle<FixedArray>::cast(
-        isolate_->global_handles()->Create(*new_array));
+    id_map_ = isolate_->global_handles()->Create(*new_array);
   }
 }