Introduce {ConstantElementsPair} struct for type safety.

src/runtime/runtime-literals.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/runtime/runtime-utils.h"
 
 #include "src/allocation-site-scopes.h"
 #include "src/arguments.h"
 #include "src/ast/ast.h"
 #include "src/ast/compile-time-value.h"
@@ skipping 95 matching lines @@
   if (should_transform) {
     JSObject::MigrateSlowToFast(boilerplate,
                                 boilerplate->map()->unused_property_fields(),
                                 "FastLiteral");
   }
   return boilerplate;
 }
 
 static MaybeHandle<Object> CreateArrayLiteralBoilerplate(
     Isolate* isolate, Handle<LiteralsArray> literals,
-    Handle<FixedArray> elements) {
+    Handle<ConstantElementsPair> elements) {
   // Create the JSArray.
   Handle<JSFunction> constructor = isolate->array_function();
 
   PretenureFlag pretenure_flag =
       isolate->heap()->InNewSpace(*literals) ? NOT_TENURED : TENURED;
 
   Handle<JSArray> object = Handle<JSArray>::cast(
       isolate->factory()->NewJSObject(constructor, pretenure_flag));
 
   ElementsKind constant_elements_kind =
-      static_cast<ElementsKind>(Smi::cast(elements->get(0))->value());
-  Handle<FixedArrayBase> constant_elements_values(
-      FixedArrayBase::cast(elements->get(1)));
+      static_cast<ElementsKind>(elements->elements_kind());
+  Handle<FixedArrayBase> constant_elements_values(elements->constant_values());
 
   {
     DisallowHeapAllocation no_gc;
     DCHECK(IsFastElementsKind(constant_elements_kind));
     Context* native_context = isolate->context()->native_context();
     Object* map =
         native_context->get(Context::ArrayMapIndex(constant_elements_kind));
     object->set_map(Map::cast(map));
   }
 
@@ skipping 39 matching lines @@
   object->set_elements(*copied_elements_values);
   object->set_length(Smi::FromInt(copied_elements_values->length()));
 
   JSObject::ValidateElements(object);
   return object;
 }
 
 MUST_USE_RESULT static MaybeHandle<Object> CreateLiteralBoilerplate(
     Isolate* isolate, Handle<LiteralsArray> literals,
     Handle<FixedArray> array) {
-  Handle<FixedArray> elements = CompileTimeValue::GetElements(array);
+  Handle<HeapObject> elements = CompileTimeValue::GetElements(array);
   switch (CompileTimeValue::GetLiteralType(array)) {
-    case CompileTimeValue::OBJECT_LITERAL_FAST_ELEMENTS:
-      return CreateObjectLiteralBoilerplate(isolate, literals, elements, true);
-    case CompileTimeValue::OBJECT_LITERAL_SLOW_ELEMENTS:
-      return CreateObjectLiteralBoilerplate(isolate, literals, elements, false);
-    case CompileTimeValue::ARRAY_LITERAL:
-      return CreateArrayLiteralBoilerplate(isolate, literals, elements);
+    case CompileTimeValue::OBJECT_LITERAL_FAST_ELEMENTS: {
+      Handle<FixedArray> props = Handle<FixedArray>::cast(elements);
+      return CreateObjectLiteralBoilerplate(isolate, literals, props, true);
+    }
+    case CompileTimeValue::OBJECT_LITERAL_SLOW_ELEMENTS: {
+      Handle<FixedArray> props = Handle<FixedArray>::cast(elements);
+      return CreateObjectLiteralBoilerplate(isolate, literals, props, false);
+    }
+    case CompileTimeValue::ARRAY_LITERAL: {
+      Handle<ConstantElementsPair> elems =
+          Handle<ConstantElementsPair>::cast(elements);
+      return CreateArrayLiteralBoilerplate(isolate, literals, elems);
+    }
     default:
       UNREACHABLE();
       return MaybeHandle<Object>();
   }
 }
 
 
 RUNTIME_FUNCTION(Runtime_CreateRegExpLiteral) {
   HandleScope scope(isolate);
   DCHECK_EQ(4, args.length());
@@ skipping 56 matching lines @@
   AllocationSiteUsageContext usage_context(isolate, site, enable_mementos);
   usage_context.EnterNewScope();
   MaybeHandle<Object> maybe_copy =
       JSObject::DeepCopy(boilerplate, &usage_context);
   usage_context.ExitScope(site, boilerplate);
   RETURN_RESULT_OR_FAILURE(isolate, maybe_copy);
 }
 
 MUST_USE_RESULT static MaybeHandle<AllocationSite> GetLiteralAllocationSite(
     Isolate* isolate, Handle<LiteralsArray> literals, int literals_index,
-    Handle<FixedArray> elements) {
+    Handle<ConstantElementsPair> elements) {
   // Check if boilerplate exists. If not, create it first.
   Handle<Object> literal_site(literals->literal(literals_index), isolate);
   Handle<AllocationSite> site;
   if (literal_site->IsUndefined(isolate)) {
-    DCHECK(*elements != isolate->heap()->empty_fixed_array());
     Handle<Object> boilerplate;
     ASSIGN_RETURN_ON_EXCEPTION(
         isolate, boilerplate,
         CreateArrayLiteralBoilerplate(isolate, literals, elements),
         AllocationSite);
 
     AllocationSiteCreationContext creation_context(isolate);
     site = creation_context.EnterNewScope();
     if (JSObject::DeepWalk(Handle<JSObject>::cast(boilerplate),
                            &creation_context).is_null()) {
       return Handle<AllocationSite>::null();
     }
     creation_context.ExitScope(site, Handle<JSObject>::cast(boilerplate));
 
     literals->set_literal(literals_index, *site);
   } else {
     site = Handle<AllocationSite>::cast(literal_site);
   }
 
   return site;
 }
 
-
 static MaybeHandle<JSObject> CreateArrayLiteralImpl(
     Isolate* isolate, Handle<LiteralsArray> literals, int literals_index,
-    Handle<FixedArray> elements, int flags) {
+    Handle<ConstantElementsPair> elements, int flags) {
   CHECK(literals_index >= 0 && literals_index < literals->literals_count());
   Handle<AllocationSite> site;
   ASSIGN_RETURN_ON_EXCEPTION(
       isolate, site,
       GetLiteralAllocationSite(isolate, literals, literals_index, elements),
       JSObject);
 
   bool enable_mementos = (flags & ArrayLiteral::kDisableMementos) == 0;
   Handle<JSObject> boilerplate(JSObject::cast(site->transition_info()));
   AllocationSiteUsageContext usage_context(isolate, site, enable_mementos);
   usage_context.EnterNewScope();
   JSObject::DeepCopyHints hints = (flags & ArrayLiteral::kShallowElements) == 0
                                       ? JSObject::kNoHints
                                       : JSObject::kObjectIsShallow;
   MaybeHandle<JSObject> copy =
       JSObject::DeepCopy(boilerplate, &usage_context, hints);
   usage_context.ExitScope(site, boilerplate);
   return copy;
 }
 
 
 RUNTIME_FUNCTION(Runtime_CreateArrayLiteral) {
   HandleScope scope(isolate);
   DCHECK_EQ(4, args.length());
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, closure, 0);
   CONVERT_SMI_ARG_CHECKED(literals_index, 1);
-  CONVERT_ARG_HANDLE_CHECKED(FixedArray, elements, 2);
+  CONVERT_ARG_HANDLE_CHECKED(ConstantElementsPair, elements, 2);
   CONVERT_SMI_ARG_CHECKED(flags, 3);
 
   Handle<LiteralsArray> literals(closure->literals(), isolate);
   RETURN_RESULT_OR_FAILURE(
       isolate, CreateArrayLiteralImpl(isolate, literals, literals_index,
                                       elements, flags));
 }
 
 
 RUNTIME_FUNCTION(Runtime_CreateArrayLiteralStubBailout) {
   HandleScope scope(isolate);
   DCHECK_EQ(3, args.length());
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, closure, 0);
   CONVERT_SMI_ARG_CHECKED(literals_index, 1);
-  CONVERT_ARG_HANDLE_CHECKED(FixedArray, elements, 2);
+  CONVERT_ARG_HANDLE_CHECKED(ConstantElementsPair, elements, 2);
 
   Handle<LiteralsArray> literals(closure->literals(), isolate);
   RETURN_RESULT_OR_FAILURE(
       isolate,
       CreateArrayLiteralImpl(isolate, literals, literals_index, elements,
                              ArrayLiteral::kShallowElements));
 }
 
 }  // namespace internal
 }  // namespace v8