[ignition] Reuse code-stub-assembler's context load operations.

- Remove (one version of) InterpreterAssembler::LoadContextSlot in favor of the
  identical CodeStubAssembler::LoadContextElement.
- Use CodeStubAssembler::LoadNativeContext instead of doing the load manually.

R=rmcilroy@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2470253003
Cr-Commit-Position: refs/heads/master@{#40766}

src/interpreter/interpreter-assembler.cc

@@ -104,7 +104,7 @@ Node* InterpreterAssembler::GetContextAtDepth(Node* context, Node* depth) {
   {
     cur_depth.Bind(Int32Sub(cur_depth.value(), Int32Constant(1)));
     cur_context.Bind(
-        LoadContextSlot(cur_context.value(), Context::PREVIOUS_INDEX));
+        LoadContextElement(cur_context.value(), Context::PREVIOUS_INDEX));
 
     Branch(Word32Equal(cur_depth.value(), Int32Constant(0)), &context_found,
            &context_search);
@@ -135,14 +135,14 @@ void InterpreterAssembler::GotoIfHasContextExtensionUpToDepth(Node* context,
     // contexts actually need to be checked.
 
     Node* extension_slot =
-        LoadContextSlot(cur_context.value(), Context::EXTENSION_INDEX);
+        LoadContextElement(cur_context.value(), Context::EXTENSION_INDEX);
 
     // Jump to the target if the extension slot is not a hole.
     GotoIf(WordNotEqual(extension_slot, TheHoleConstant()), target);
 
     cur_depth.Bind(Int32Sub(cur_depth.value(), Int32Constant(1)));
     cur_context.Bind(
-        LoadContextSlot(cur_context.value(), Context::PREVIOUS_INDEX));
+        LoadContextElement(cur_context.value(), Context::PREVIOUS_INDEX));
 
     GotoIf(Word32NotEqual(cur_depth.value(), Int32Constant(0)),
            &context_search);
@@ -485,11 +485,6 @@ Node* InterpreterAssembler::LoadAndUntagConstantPoolEntry(Node* index) {
   }
 }
 
-Node* InterpreterAssembler::LoadContextSlot(Node* context, int slot_index) {
-  return Load(MachineType::AnyTagged(), context,
-              IntPtrConstant(Context::SlotOffset(slot_index)));
-}
-
 Node* InterpreterAssembler::LoadContextSlot(Node* context, Node* slot_index) {
   Node* offset =
       IntPtrAdd(WordShl(slot_index, kPointerSizeLog2),

src/interpreter/interpreter-assembler.h

@@ -94,7 +94,6 @@ class V8_EXPORT_PRIVATE InterpreterAssembler : public CodeStubAssembler {
   compiler::Node* LoadAndUntagConstantPoolEntry(compiler::Node* index);
 
   // Load |slot_index| from |context|.
-  compiler::Node* LoadContextSlot(compiler::Node* context, int slot_index);
   compiler::Node* LoadContextSlot(compiler::Node* context,
                                   compiler::Node* slot_index);
   // Stores |value| into |slot_index| of |context|.

src/interpreter/interpreter.cc

@@ -497,9 +497,9 @@ void Interpreter::DoStaGlobal(Callable ic, InterpreterAssembler* assembler) {
   typedef StoreWithVectorDescriptor Descriptor;
   // Get the global object.
   Node* context = __ GetContext();
-  Node* native_context =
-      __ LoadContextSlot(context, Context::NATIVE_CONTEXT_INDEX);
-  Node* global = __ LoadContextSlot(native_context, Context::EXTENSION_INDEX);
+  Node* native_context = __ LoadNativeContext(context);
+  Node* global =
+      __ LoadContextElement(native_context, Context::EXTENSION_INDEX);
 
   // Store the global via the StoreIC.
   Node* code_target = __ HeapConstant(ic.code());
@@ -1757,8 +1757,7 @@ void Interpreter::DoCallJSRuntime(InterpreterAssembler* assembler) {
 
   // Get the function to call from the native context.
   Node* context = __ GetContext();
-  Node* native_context =
-      __ LoadContextSlot(context, Context::NATIVE_CONTEXT_INDEX);
+  Node* native_context = __ LoadNativeContext(context);
   Node* function = __ LoadContextSlot(native_context, context_index);
 
   // Call the function.