8215017: Improve String::equals warmup characteristics

Reviewed-by: jlaskey

test/micro/org/openjdk/bench/java/lang/StringEquals.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package org.openjdk.bench.java.lang;
+
+import org.openjdk.jmh.annotations.*;
+import java.util.concurrent.TimeUnit;
+
+/*
+ * This benchmark naively explores String::equals performance
+ */
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@State(Scope.Benchmark)
+public class StringEquals {
+
+    public String test = new String("0123456789");
+    public String test2 = new String("tgntogjnrognagronagroangroarngorngaorng");
+    public String test3 = new String(test); // equal to test, but not same
+    public String test4 = new String("0123\u01FF");
+    public String test5 = new String(test4); // equal to test4, but not same
+    public String test6 = new String("0123456780");
+    public String test7 = new String("0123\u01FE");
+
+    @Benchmark
+    public boolean different() {
+        return test.equals(test2);
+    }
+
+    @Benchmark
+    public boolean equal() {
+        return test.equals(test3);
+    }
+
+    @Benchmark
+    public boolean almostEqual() {
+        return test.equals(test6);
+    }
+
+    @Benchmark
+    public boolean almostEqualUTF16() {
+        return test4.equals(test7);
+    }
+
+    @Benchmark
+    public boolean differentCoders() {
+        return test.equals(test4);
+    }
+
+    @Benchmark
+    public boolean equalsUTF16() {
+        return test5.equals(test4);
+    }
+}
+