jdk/test/hotspot/jtreg/compiler/runtime/TestDontCompileHugeMethods.java

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/**
 * @test
 * @bug 8366118 8367613
 * @summary Check that a huge method is not compiled under -XX:+DontCompileHugeMethods.
 * @library /test/lib
 * @run main compiler.runtime.TestDontCompileHugeMethods
 */
package compiler.runtime;

import jdk.test.lib.JDKToolLauncher;
import jdk.test.lib.Utils;
import jdk.test.lib.process.OutputAnalyzer;
import jdk.test.lib.process.ProcessTools;

import java.io.IOException;
import java.io.Writer;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

public class TestDontCompileHugeMethods {

    private static final String HUGE_SWITCH_CLASS_NAME = "HugeSwitch";

    private static void generateClass(Writer writer) throws IOException {
        writer.write("""
            public class HugeSwitch {
              private static int hugeSwitch(int x) {
                switch (x) {
            """);
        for (int i = 0; i < 2000; i++) {
            writer.write("      case " + i + ": return " + i + " + 1;\n");
        }
        writer.write("""
                  default:
                    return 0;
                }
              }
              private static int shortMethod(int x) {
                if (x % 3 == 0) {
                  return x - 1;
                }
                return x + 1;
              }
              public static void main(String[] args) {
                int val = 0;
                for (int i = 0; i < 100000; i++) {
                  val += hugeSwitch(shortMethod(i));
                }
                System.out.println(val);
              }
            }
            """);
    }

    private static void compileClass(Path workDir, Path sourceFile) throws Exception {
        JDKToolLauncher javac = JDKToolLauncher.create("javac").addToolArg("-d")
            .addToolArg(workDir.toAbsolutePath().toString()).addToolArg("-cp")
            .addToolArg(Utils.TEST_CLASS_PATH).addToolArg(sourceFile.toAbsolutePath().toString());

        OutputAnalyzer output = ProcessTools.executeProcess(javac.getCommand());
        output.shouldHaveExitValue(0);
    }

    private static void generateAndCompileClass(Path workDir) throws Exception {
        Path sourceFile = workDir.resolve(HUGE_SWITCH_CLASS_NAME + ".java");
        try (Writer writer = Files.newBufferedWriter(sourceFile)) {
            generateClass(writer);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        compileClass(workDir, sourceFile);
    }

    private static void runTest(Path workDir, List jvmArgs) throws Exception {
        ArrayList<String> command = new ArrayList<>();
        // Disable inlining for shortMethod().
        // Otherwise under "-Xcomp -XX:TieredStopAtLevel=1", shortMethod() is inlined into main(),
        // and is not directly executed or compiled.
        command.add("-XX:CompileCommand=dontinline,HugeSwitch::shortMethod");
        command.add("-XX:+PrintCompilation");
        command.add("-Xbatch");
        command.addAll(jvmArgs);
        command.add("-cp");
        command.add(workDir.toAbsolutePath().toString());
        command.add(HUGE_SWITCH_CLASS_NAME);
        ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(command);
        OutputAnalyzer analyzer = new OutputAnalyzer(pb.start());
        analyzer.shouldHaveExitValue(0);
        analyzer.shouldContain("   HugeSwitch::shortMethod (");
        analyzer.shouldNotContain("   HugeSwitch::hugeSwitch (");
    }

    public static void main(String[] args) throws Exception {
        Path workDir = Paths.get("");
        generateAndCompileClass(workDir);

        runTest(workDir, List.of());
        runTest(workDir, List.of("-XX:-TieredCompilation"));
    }
}