ART: Added benchmark for string dex cache

Added a benchmark for the string dex cache, measures how long the fast
path takes. In order to account for potential optimizations, I have
separated it into two different functions, one of which is called from a
loop so the code is no longer in the loop. Please subtract ~1.5ns from
the runtime per iteration as a result.

Change-Id: I77803ebf83b18b806288349e1e5b3d26ac215d84

1 files changed, 32 insertions, 0 deletions

diff --git a/benchmarks/src/benchmarks/StringDexCacheBenchmark.java b/benchmarks/src/benchmarks/StringDexCacheBenchmark.java
new file mode 100644
index 0000000000..ce72b4d90a
--- /dev/null
+++ b/benchmarks/src/benchmarks/StringDexCacheBenchmark.java
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package benchmarks;
+
+/**
+ * How long does it take to access a string in the dex cache?
+ */
+public class StringDexCacheBenchmark {
+    public int timeStringDexCacheAccess(int reps) {
+        int v = 0;
+        for (int rep = 0; rep < reps; ++rep) {
+          // Deliberately obscured to make optimizations less likely.
+          String s = (rep >= 0) ? "hello, world!" : null;
+          v += s.length();
+        }
+        return v;
+    }
+}