[turbofan] Set elements kind to holey if constructing array of possibly non-zero length.

src/compiler/js-create-lowering.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/js-create-lowering.h"
 
 #include "src/allocation-site-scopes.h"
 #include "src/code-factory.h"
 #include "src/compilation-dependencies.h"
 #include "src/compiler/access-builder.h"
@@ skipping 455 matching lines @@
   Node* context = NodeProperties::GetContextInput(node);
   Node* effect = NodeProperties::GetEffectInput(node);
   Node* control = NodeProperties::GetControlInput(node);
 
   // Extract transition and tenuring feedback from the {site} and add
   // appropriate code dependencies on the {site} if deoptimization is
   // enabled.
   PretenureFlag pretenure = site->GetPretenureMode();
   ElementsKind elements_kind = site->GetElementsKind();
   DCHECK(IsFastElementsKind(elements_kind));
+  if (NodeProperties::GetType(length)->Max() > 0) {

[Jarin, 2016/07/06 04:39:59]

Not sure whether we should thread through the type cache just to be able to say
!GetType(length)->Is(cache_.kSingletonZero). WDYT?

+    elements_kind = GetHoleyElementsKind(elements_kind);
+  }
   dependencies()->AssumeTenuringDecision(site);
   dependencies()->AssumeTransitionStable(site);
 
   // Retrieve the initial map for the array from the appropriate native context.
   Node* native_context = effect = graph()->NewNode(
       javascript()->LoadContext(0, Context::NATIVE_CONTEXT_INDEX, true),
       context, context, effect);
   Node* js_array_map = effect = graph()->NewNode(
       javascript()->LoadContext(0, Context::ArrayMapIndex(elements_kind), true),
       native_context, native_context, effect);
@@ skipping 641 matching lines @@
   return jsgraph()->simplified();
 }
 
 MachineOperatorBuilder* JSCreateLowering::machine() const {
   return jsgraph()->machine();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8