[turbofan] Support inline receiver allocation for class constructors.

src/compiler/js-typed-lowering.cc

 // Copyright 2014 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/code-factory.h"
 #include "src/compilation-dependencies.h"
 #include "src/compiler/access-builder.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/js-typed-lowering.h"
 #include "src/compiler/linkage.h"
@@ skipping 1393 matching lines @@
 
 
 namespace {
 
 // Maximum instance size for which allocations will be inlined.
 const int kMaxInlineInstanceSize = 64 * kPointerSize;
 
 
 // Checks whether allocation using the given constructor can be inlined.
 bool IsAllocationInlineable(Handle<JSFunction> constructor) {
-  // TODO(bmeurer): Support inlining of class constructors.
-  if (IsClassConstructor(constructor->shared()->kind())) return false;
+  // TODO(bmeurer): Further relax restrictions on inlining, i.e.
+  // instance type and maybe instance size (inobject properties
+  // are limited anyways by the runtime).

[Toon Verwaest, 2015/12/16 20:00:47]

DBC: Don't you only want to allow it for base classes with new.target == base?
We also store initial maps on subclasses, but the base class needs to get the
map from the new.target and verify it.

[Benedikt Meurer, 2015/12/16 20:29:07]

You already answered the question. I'm currently working on supporting
new.target here as well (essentially the case where target != new_target on the
Node* level), but I first had/still need to tweak some other parts of TurboFan
and the way we compile super calls to be able to actually trigger this case at
all.

   return constructor->has_initial_map() &&
          constructor->initial_map()->instance_type() == JS_OBJECT_TYPE &&
          constructor->initial_map()->instance_size() < kMaxInlineInstanceSize;
 }
 
 }  // namespace
 
 
 Reduction JSTypedLowering::ReduceJSCreate(Node* node) {
   DCHECK_EQ(IrOpcode::kJSCreate, node->opcode());
@@ skipping 1323 matching lines @@
 }
 
 
 CompilationDependencies* JSTypedLowering::dependencies() const {
   return dependencies_;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8