Compiling an array literal should be context-independent.

src/ast/ast.cc

Index: src/ast/ast.cc
diff --git a/src/ast/ast.cc b/src/ast/ast.cc
index 530bd50aaf7e12fadf6860b241663b594c5c514c..9a4a68b14d472b40187d1cd6ba173d0cb8fc5309 100644
--- a/src/ast/ast.cc
+++ b/src/ast/ast.cc
@@ -580,11 +580,9 @@ void ArrayLiteral::BuildConstantElements(Isolate* isolate) {
   if (!constant_elements_.is_null()) return;
 
   int constants_length = values()->length();
-
-  // Allocate a fixed array to hold all the object literals.
-  Handle<JSArray> array = isolate->factory()->NewJSArray(
-      FAST_HOLEY_SMI_ELEMENTS, constants_length, constants_length,
-      INITIALIZE_ARRAY_ELEMENTS_WITH_HOLE);
+  ElementsKind kind = FAST_SMI_ELEMENTS;

[Toon Verwaest, 2016/11/08 10:18:02]

FIRST_FAST_ELEMENTS_KIND?

[Yang, 2016/11/09 07:32:23]

Done.

+  Handle<FixedArray> fixed_array =
+      isolate->factory()->NewFixedArrayWithHoles(constants_length);
 
   // Fill in the literals.
   bool is_simple = true;
@@ -615,29 +613,44 @@ void ArrayLiteral::BuildConstantElements(Isolate* isolate) {
       is_simple = false;
     }
 
-    JSObject::AddDataElement(array, array_index, boilerplate_value, NONE)
-        .Assert();
+    kind = GetMoreGeneralElementsKind(kind,
+                                      boilerplate_value->OptimalElementsKind());
+    fixed_array->set(array_index, *boilerplate_value);
   }
 
-  JSObject::ValidateElements(array);
-  Handle<FixedArrayBase> element_values(array->elements());
-
   // Simple and shallow arrays can be lazily copied, we transform the
   // elements array to a copy-on-write array.
   if (is_simple && depth_acc == 1 && array_index > 0 &&
-      array->HasFastSmiOrObjectElements()) {
-    element_values->set_map(isolate->heap()->fixed_cow_array_map());
+      IsFastSmiOrObjectElementsKind(kind)) {
+    fixed_array->set_map(isolate->heap()->fixed_cow_array_map());
+  }
+
+  Handle<FixedArrayBase> elements = fixed_array;
+
+  // In case of only double elements, copy over into a FixedDoubleArray.
+  if (IsFastDoubleElementsKind(kind)) {
+    Handle<FixedDoubleArray> fixed_double_array =
+        Handle<FixedDoubleArray>::cast(
+            isolate->factory()->NewFixedDoubleArray(constants_length));
+    for (int i = 0; i < constants_length; i++) {
+      Object* element = fixed_array->get(i);
+      if (element->IsTheHole(isolate)) {
+        DCHECK(is_holey);
+        fixed_double_array->set_the_hole(i);
+      } else {
+        fixed_double_array->set(i, element->Number());

[Toon Verwaest, 2016/11/08 10:16:54]

What about having a CopyElements on the elements accessor that doesn't take a
JSObject* from_holder but FixedArrayBase* from, that way we can use the regular
CopySmiToDoubleElements here. It would look like

if (IsFastDoubleElementsKind(kind)) {
  ElementsAccessor* accessor = ElementsAccessor::ForKind(kind);
  elements = isolate->factory()->NewFixedDoubleArray(constants_length);
  accessor->CopyElements(fixed_array, elements);
}

[Yang, 2016/11/09 07:32:23]

Done.

+      }
+    }
+    elements = fixed_double_array;
   }
 
+  if (is_holey) kind = GetHoleyElementsKind(kind);
+
   // Remember both the literal's constant values as well as the ElementsKind
   // in a 2-element FixedArray.
   Handle<FixedArray> literals = isolate->factory()->NewFixedArray(2, TENURED);
-
-  ElementsKind kind = array->GetElementsKind();
-  kind = is_holey ? GetHoleyElementsKind(kind) : GetPackedElementsKind(kind);
-
   literals->set(0, Smi::FromInt(kind));
-  literals->set(1, *element_values);
+  literals->set(1, *elements);
 
   constant_elements_ = literals;
   set_is_simple(is_simple);