Stack allocate lexical locals + hoist stack slots

test/mjsunit/es6/block-scoping-top-level.js

+// 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.
+
+// Flags: --min-preparse-length=0
+'use strict';
+
+let xxx = 1;
+let f = undefined;
+{
+  let inner_x = xxx;
+  f = function() { return inner_x; };
+}
+
+assertSame(1, f());
+
+xxx = 42;
+{
+  f = function() { return inner_x1; };
+  let inner_x1 = xxx;
+}
+
+assertSame(42, f());
+
+xxx = 31;
+{
+  let inner_x1 = xxx;
+  try {
+    throw new Error();
+  } catch (e) {
+    f = function() { return inner_x1; };
+  }
+}
+assertSame(31, f());