Implement lowering of JSStoreContext to machine operators.

src/compiler/js-generic-lowering.cc

Index: src/compiler/js-generic-lowering.cc
diff --git a/src/compiler/js-generic-lowering.cc b/src/compiler/js-generic-lowering.cc
index 3526715638ad6ff90af8f164c6d1d89498e037c3..f87006f08b4c4a5d8267099cd10ad9efa0e36580 100644
--- a/src/compiler/js-generic-lowering.cc
+++ b/src/compiler/js-generic-lowering.cc
@@ -388,9 +388,19 @@ Node* JSGenericLowering::LowerJSLoadContext(Node* node) {
 
 Node* JSGenericLowering::LowerJSStoreContext(Node* node) {
   ContextAccess access = OpParameter<ContextAccess>(node);
-  PatchInsertInput(node, 1, SmiConstant(access.depth()));
-  PatchInsertInput(node, 2, SmiConstant(access.index()));
-  ReplaceWithRuntimeCall(node, Runtime::kStoreContextRelative, 4);
+  // TODO(mstarzinger): Use simplified operators instead of machine operators
+  // here so that load/store optimization can be applied afterwards.
+  for (int i = 0; i < access.depth(); ++i) {
+    node->ReplaceInput(
+        0, graph()->NewNode(
+               machine()->Load(kMachineTagged),
+               NodeProperties::GetValueInput(node, 0),
+               Int32Constant(Context::SlotOffset(Context::PREVIOUS_INDEX)),
+               NodeProperties::GetEffectInput(node)));
+  }
+  node->ReplaceInput(2, NodeProperties::GetValueInput(node, 1));
+  node->ReplaceInput(1, Int32Constant(Context::SlotOffset(access.index())));
+  PatchOperator(node, machine()->Store(kMachineTagged, kFullWriteBarrier));
   return node;
 }