[stubs] Add LoadFixedArrayElements with int index

src/builtins/builtins-string.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/builtins/builtins.h"
 #include "src/builtins/builtins-utils.h"
 
 #include "src/code-factory.h"
 #include "src/regexp/regexp-utils.h"
 
@@ skipping 1263 matching lines @@
   typedef compiler::Node Node;
   CodeStubAssembler assembler(state);
 
   Node* receiver = assembler.Parameter(0);
   Node* context = assembler.Parameter(3);
 
   Node* string = assembler.ToThisString(context, receiver,
                                         "String.prototype[Symbol.iterator]");
 
   Node* native_context = assembler.LoadNativeContext(context);
-  Node* map = assembler.LoadFixedArrayElement(
-      native_context,
-      assembler.IntPtrConstant(Context::STRING_ITERATOR_MAP_INDEX), 0,
-      CodeStubAssembler::INTPTR_PARAMETERS);
+  Node* map = assembler.LoadContextElement(native_context,
+                                           Context::STRING_ITERATOR_MAP_INDEX);
   Node* iterator = assembler.Allocate(JSStringIterator::kSize);
   assembler.StoreMapNoWriteBarrier(iterator, map);
   assembler.StoreObjectFieldRoot(iterator, JSValue::kPropertiesOffset,
                                  Heap::kEmptyFixedArrayRootIndex);
   assembler.StoreObjectFieldRoot(iterator, JSObject::kElementsOffset,
                                  Heap::kEmptyFixedArrayRootIndex);
   assembler.StoreObjectFieldNoWriteBarrier(
       iterator, JSStringIterator::kStringOffset, string);
   Node* index = assembler.SmiConstant(Smi::kZero);
   assembler.StoreObjectFieldNoWriteBarrier(
@@ skipping 135 matching lines @@
     assembler.StoreObjectFieldNoWriteBarrier(
         iterator, JSStringIterator::kNextIndexOffset,
         assembler.SmiAdd(position, length));
     var_done.Bind(assembler.BooleanConstant(false));
     assembler.Goto(&return_result);
   }
 
   assembler.Bind(&return_result);
   {
     Node* native_context = assembler.LoadNativeContext(context);
-    Node* map = assembler.LoadFixedArrayElement(
-        native_context,
-        assembler.IntPtrConstant(Context::ITERATOR_RESULT_MAP_INDEX), 0,
-        CodeStubAssembler::INTPTR_PARAMETERS);
+    Node* map = assembler.LoadContextElement(
+        native_context, Context::ITERATOR_RESULT_MAP_INDEX);
     Node* result = assembler.Allocate(JSIteratorResult::kSize);
     assembler.StoreMapNoWriteBarrier(result, map);
     assembler.StoreObjectFieldRoot(result, JSIteratorResult::kPropertiesOffset,
                                    Heap::kEmptyFixedArrayRootIndex);
     assembler.StoreObjectFieldRoot(result, JSIteratorResult::kElementsOffset,
                                    Heap::kEmptyFixedArrayRootIndex);
     assembler.StoreObjectFieldNoWriteBarrier(
         result, JSIteratorResult::kValueOffset, var_value.value());
     assembler.StoreObjectFieldNoWriteBarrier(
         result, JSIteratorResult::kDoneOffset, var_done.value());
     assembler.Return(result);
   }
 
   assembler.Bind(&throw_bad_receiver);
   {
     // The {receiver} is not a valid JSGeneratorObject.
     Node* result = assembler.CallRuntime(
         Runtime::kThrowIncompatibleMethodReceiver, context,
         assembler.HeapConstant(assembler.factory()->NewStringFromAsciiChecked(
             "String Iterator.prototype.next", TENURED)),
         iterator);
     assembler.Return(result);  // Never reached.
   }
 }
 
 }  // namespace internal
 }  // namespace v8