Introduce {ConstantElementsPair} struct for type safety.

src/compiler/bytecode-graph-builder.cc

 // Copyright 2015 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/bytecode-graph-builder.h"
 
 #include "src/ast/ast.h"
 #include "src/ast/scopes.h"
 #include "src/compilation-info.h"
 #include "src/compiler/compiler-source-position-table.h"
@@ skipping 1182 matching lines @@
       Handle<String>::cast(bytecode_iterator().GetConstantForIndexOperand(0));
   int literal_index = bytecode_iterator().GetIndexOperand(1);
   int literal_flags = bytecode_iterator().GetFlagOperand(2);
   Node* literal = NewNode(javascript()->CreateLiteralRegExp(
                               constant_pattern, literal_flags, literal_index),
                           GetFunctionClosure());
   environment()->BindAccumulator(literal, Environment::kAttachFrameState);
 }
 
 void BytecodeGraphBuilder::VisitCreateArrayLiteral() {
-  Handle<FixedArray> constant_elements = Handle<FixedArray>::cast(
-      bytecode_iterator().GetConstantForIndexOperand(0));
+  Handle<ConstantElementsPair> constant_elements =
+      Handle<ConstantElementsPair>::cast(
+          bytecode_iterator().GetConstantForIndexOperand(0));
   int literal_index = bytecode_iterator().GetIndexOperand(1);
   int bytecode_flags = bytecode_iterator().GetFlagOperand(2);
   int literal_flags =
       interpreter::CreateArrayLiteralFlags::FlagsBits::decode(bytecode_flags);
   // Disable allocation site mementos. Only unoptimized code will collect
   // feedback about allocation site. Once the code is optimized we expect the
   // data to converge. So, we disable allocation site mementos in optimized
   // code. We can revisit this when we have data to the contrary.
   literal_flags |= ArrayLiteral::kDisableMementos;
   // TODO(mstarzinger): Thread through number of elements. The below number is
   // only an estimate and does not match {ArrayLiteral::values::length}.
-  int number_of_elements =
-      FixedArrayBase::cast(constant_elements->get(1))->length();
+  int number_of_elements = constant_elements->constant_values()->length();
   Node* literal = NewNode(
       javascript()->CreateLiteralArray(constant_elements, literal_flags,
                                        literal_index, number_of_elements),
       GetFunctionClosure());
   environment()->BindAccumulator(literal, Environment::kAttachFrameState);
 }
 
 void BytecodeGraphBuilder::VisitCreateObjectLiteral() {
   PrepareEagerCheckpoint();
   Handle<FixedArray> constant_properties = Handle<FixedArray>::cast(
@@ skipping 1032 matching lines @@
         it->source_position().ScriptOffset(), start_position_.InliningId()));
     it->Advance();
   } else {
     DCHECK_GT(it->code_offset(), offset);
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8