Fix optimizer bug with external strings.

runtime/vm/dart_api_impl_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/builtin.h"
 #include "vm/compiler.h"
 #include "include/dart_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 #include "include/dart_tools_api.h"
@@ skipping 8939 matching lines @@
   EXPECT_VALID(result);
   bool value = false;
   result = Dart_BooleanValue(result, &value);
   EXPECT_VALID(result);
   EXPECT(value);
 
   FLAG_support_externalizable_strings = saved_flag;
 }
 
 
+TEST_CASE(ExternalStringLoadElimination) {
+  const bool saved_flag = FLAG_support_externalizable_strings;
+  FLAG_support_externalizable_strings = true;
+
+  const char* kScriptChars =
+      "class A {\n"
+      "  static change_str(String s) native 'A_change_str';\n"
+      "}\n"
+      "double_char0(str) {\n"
+      "  return str.codeUnitAt(0) + str.codeUnitAt(0);\n"
+      "}\n"
+      "main() {\n"
+      "  var externalA = 'AA' + 'AA';\n"
+      "  A.change_str(externalA);\n"
+      "  for (var i = 0; i < 10000; i++) double_char0(externalA);\n"
+      "  var result = double_char0(externalA);\n"
+      "  return result == 130;\n"
+      "}\n";
+  Dart_Handle lib =
+      TestCase::LoadTestScript(kScriptChars,
+                               &ExternalStringDeoptimize_native_lookup);
+  Dart_Handle result = Dart_Invoke(lib,
+                                   NewString("main"),
+                                   0,
+                                   NULL);
+  EXPECT_VALID(result);
+  bool value = false;
+  result = Dart_BooleanValue(result, &value);
+  EXPECT_VALID(result);
+  EXPECT(value);
+
+  FLAG_support_externalizable_strings = saved_flag;
+}
+
+
 TEST_CASE(ExternalStringGuardFieldDeoptimize) {
   const bool saved_flag = FLAG_support_externalizable_strings;
   FLAG_support_externalizable_strings = true;
 
   const char* kScriptChars =
       "const strA = 'AAAA';\n"
       "class A {\n"
       "  static change_str(String s) native 'A_change_str';\n"
       "}\n"
       "class G { var f = 'A'; }\n"
@@ skipping 1076 matching lines @@
   result = Dart_Invoke(lib,
                        NewString("foozoo"),
                        0,
                        NULL);
   EXPECT(Dart_IsError(result));
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart