8302163: Speed up various String comparison methods with ArraysSupport.mismatch

Reviewed-by: stsypanov, rriggs, alanb

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

@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2023, 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::startsWith and other String
+ * comparison methods
+ */
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@State(Scope.Benchmark)
+@Warmup(iterations = 5, time = 1)
+@Measurement(iterations = 5, time = 1)
+@Fork(value = 3)
+public class StringComparisons {
+
+    @Param({"6", "15", "1024"})
+    public int size;
+
+    @Param({"true", "false"})
+    public boolean utf16;
+
+    public String string;
+    public String equalString;
+    public String endsWithA;
+    public String endsWithB;
+    public String startsWithA;
+
+    @Setup
+    public void setup() {
+        String c = utf16 ? "\uff11" : "c";
+        string = c.repeat(size);
+        equalString = c.repeat(size);
+        endsWithA = c.repeat(size).concat("A");
+        endsWithB = c.repeat(size).concat("B");
+        startsWithA = "A" + (c.repeat(size));
+    }
+
+    @Benchmark
+    public boolean startsWith() {
+        return endsWithA.startsWith(string);
+    }
+
+    @Benchmark
+    public boolean endsWith() {
+        return startsWithA.endsWith(string);
+    }
+
+    @Benchmark
+    public boolean regionMatches() {
+        return endsWithA.regionMatches(0, endsWithB, 0, endsWithB.length());
+    }
+
+    @Benchmark
+    public boolean regionMatchesRange() {
+        return startsWithA.regionMatches(1, endsWithB, 0, endsWithB.length() - 1);
+    }
+
+    @Benchmark
+    public boolean regionMatchesCI() {
+        return endsWithA.regionMatches(true, 0, endsWithB, 0, endsWithB.length());
+    }
+}