Add a unit test Benchmark_UseDartApi to measure dart api overhead.

runtime/vm/dart_api_impl_test.cc

Index: runtime/vm/dart_api_impl_test.cc
===================================================================
--- runtime/vm/dart_api_impl_test.cc	(revision 6173)
+++ runtime/vm/dart_api_impl_test.cc	(working copy)
@@ -4740,6 +4740,86 @@
   Isolate::SetInterruptCallback(saved);
 }
 
+
+// The specific api functions called here are a bit arbitrary.  We are
+// trying to get a sense of the overhead for using the dart api.
+void UseDartApi(Dart_NativeArguments args) {
+  Dart_EnterScope();
+  int count = Dart_GetNativeArgumentCount(args);
+  EXPECT_EQ(2, count);
+
+  // Get the receiver.
+  Dart_Handle recv = Dart_GetNativeArgument(args, 0);
+  EXPECT(!Dart_IsError(recv));
+
+  // Get param.
+  Dart_Handle param = Dart_GetNativeArgument(args, 1);
+  EXPECT(!Dart_IsError(param));
+  EXPECT(Dart_IsInteger(param));
+  bool fits = false;
+  Dart_Handle result = Dart_IntegerFitsIntoInt64(param, &fits);
+  EXPECT(!Dart_IsError(result) && fits);
+  int64_t value1;
+  result = Dart_IntegerToInt64(param, &value1);
+  EXPECT(!Dart_IsError(result));
+
+  // Get receiver.field.
+  Dart_Handle field_name = Dart_NewString("field");

[Anton Muhin, 2012/04/04 18:12:36]

this might be a separate issue.  and DOM bindings do not use direct field lookup
often.

[turnidge, 2012/04/04 19:40:22]

Changed the benchmark to do native field access, to be more similar to DOM
bindings.

+  Dart_Handle field_value = Dart_GetField(recv, field_name);
+  EXPECT(!Dart_IsError(field_value));
+  EXPECT(Dart_IsInteger(field_value));
+  fits = false;
+  result = Dart_IntegerFitsIntoInt64(field_value, &fits);
+  EXPECT(!Dart_IsError(result) && fits);
+  int64_t value2;
+  result = Dart_IntegerToInt64(field_value, &value2);
+  EXPECT(!Dart_IsError(result));
+  EXPECT_EQ(7, value2);
+
+  // Return param + receiver.field.
+  Dart_SetReturnValue(args, Dart_NewInteger(value1 + value2));

[Anton Muhin, 2012/04/04 18:12:36]

just in case: you may want to assert you always fit into Smi, otherwise you may
start to measure GC performance if a lot of heap ints are allocated.

[turnidge, 2012/04/04 19:40:22]

Added some range checks for param, which should keep this in a Smi.

+  Dart_ExitScope();
+}
+
+
+static Dart_NativeFunction bm_uda_lookup(Dart_Handle name, int argument_count) {
+  return reinterpret_cast<Dart_NativeFunction>(&UseDartApi);
+}
+
+
+TEST_CASE(Benchmark_UseDartApi) {
+  const char* kScriptChars =
+      "class Class {\n"
+      "  int field = 7;\n"
+      "  int method(int param) native 'Name_Does_Not_Matter';\n"
+      "}\n"
+      "\n"
+      "double benchmark(int count) {\n"
+      "  Class c = new Class();\n"
+      "  Stopwatch sw = new Stopwatch.start();\n"
+      "  for (int i = 0; i < count; i++) {\n"
+      "    c.method(i);\n"
+      "  }\n"
+      "  sw.stop();\n"
+      "  return sw.elapsedInUs() / count;\n"
+      "}\n";
+
+  Dart_Handle lib = TestCase::LoadTestScript(
+      kScriptChars,
+      reinterpret_cast<Dart_NativeEntryResolver>(bm_uda_lookup));
+  Dart_Handle args[1];
+  args[0] = Dart_NewInteger(10000);
+  Dart_Handle result = Dart_Invoke(lib,
+                                   Dart_NewString("benchmark"),
+                                   1,
+                                   args);
+  EXPECT_VALID(result);
+  EXPECT(Dart_IsDouble(result));
+  double out;
+  result = Dart_DoubleValue(result, &out);
+  fprintf(stderr, "Benchmark_UseDartApi: %f us per iteration\n", out);
+}
+
 #endif  // defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64).
 
 }  // namespace dart