Only swap undefined for the global object if necessary in the prologue

src/compiler.cc

 // Copyright 2012 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.h"
 
 #include <algorithm>
 
 #include "src/ast-numbering.h"
 #include "src/bootstrapper.h"
@@ skipping 196 matching lines @@
         function()->feedback_vector_spec());
   }
 }
 
 
 bool CompilationInfo::is_simple_parameter_list() {
   return scope()->is_simple_parameter_list();
 }
 
 
+bool CompilationInfo::MayUseThis() const {
+  return scope()->uses_this() || scope()->inner_uses_this() ||
+         scope()->calls_sloppy_eval();
+}
+
+
 int CompilationInfo::TraceInlinedFunction(Handle<SharedFunctionInfo> shared,
                                           SourcePosition position,
                                           int parent_id) {
   DCHECK(track_positions_);
 
   int inline_id = static_cast<int>(inlined_function_infos_.size());
   InlinedFunctionInfo info(parent_id, position, UnboundScript::kNoScriptId,
       shared->start_position());
   if (!shared->script()->IsUndefined()) {
     Handle<Script> script(Script::cast(shared->script()));
@@ skipping 1313 matching lines @@
 }
 
 
 #if DEBUG
 void CompilationInfo::PrintAstForTesting() {
   PrintF("--- Source from AST ---\n%s\n",
          PrettyPrinter(isolate(), zone()).PrintProgram(function()));
 }
 #endif
 } }  // namespace v8::internal