Performance improvement for the Dart VM runtime method

runtime/vm/benchmark_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 "vm/benchmark_test.h"
 
 #include "bin/file.h"
 
 #include "platform/assert.h"
 
@@ skipping 182 matching lines @@
               Dart_NewString("benchmark"),
               1,
               args);
   timer.Stop();
   int64_t elapsed_time = timer.TotalElapsedTime();
   benchmark->set_score(elapsed_time);
 }
 
 
 //
+// Measure time accessing internal and external strings.
+//
+BENCHMARK(DartStringAccess) {
+  const int kNumIterations = 10000000;
+  Timer timer(true, "DartStringAccess benchmark");
+  timer.Start();
+  Dart_EnterScope();
+
+  // Create strings.
+  uint8_t data8[] = { 'o', 'n', 'e', 0xFF };
+  int external_peer_data = 123;
+  Dart_Handle external_string = Dart_NewExternalString8(data8,
+                                                        ARRAY_SIZE(data8),
+                                                        &external_peer_data,
+                                                        NULL);
+  Dart_Handle internal_string = Dart_NewString("two");
+
+  // Run benchmark.
+  for (int64_t i = 0; i < kNumIterations; i++) {
+    EXPECT(Dart_IsString(internal_string));
+    EXPECT(Dart_IsString8(internal_string));
+    EXPECT(Dart_IsString16(internal_string));
+    EXPECT(!Dart_IsExternalString(internal_string));
+    EXPECT_VALID(external_string);
+    EXPECT(Dart_IsExternalString(external_string));
+    void* external_peer = NULL;
+    // 80% of benchmark is spent in the following call.

[Ivan Posva, 2012/08/29 05:59:30]

Is the 80% value still correct here?

+    EXPECT_VALID(Dart_ExternalStringGetPeer(external_string, &external_peer));
+    EXPECT_EQ(&external_peer_data, external_peer);
+  }
+
+  Dart_ExitScope();
+  timer.Stop();
+  int64_t elapsed_time = timer.TotalElapsedTime();
+  benchmark->set_score(elapsed_time);
+}
+
+
+//
 // Measure compile of all dart2js(compiler) functions.
 //
 static char* ComputeDart2JSPath(const char* arg) {
   char buffer[2048];
   char* dart2js_path = strdup(File::GetCanonicalPath(arg));
   const char* compiler_path = "%s%slib%scompiler%scompiler.dart";
   const char* path_separator = File::PathSeparator();
   ASSERT(path_separator != NULL && strlen(path_separator) == 1);
   char* ptr = strrchr(dart2js_path, *path_separator);
   while (ptr != NULL) {
@@ skipping 136 matching lines @@
   Dart_Handle cls = Dart_GetClass(lib, Dart_NewString("StackFrameTest"));
   Dart_Handle result = Dart_Invoke(cls, Dart_NewString("testMain"), 0, NULL);
   EXPECT_VALID(result);
   int64_t elapsed_time = 0;
   result = Dart_IntegerToInt64(result, &elapsed_time);
   EXPECT_VALID(result);
   benchmark->set_score(elapsed_time);
 }
 
 }  // namespace dart