test/langtools/tools/javac/StringConcat/TestIndyStringConcat.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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import jdk.test.lib.compiler.CompilerUtils;
import toolbox.ToolBox;

import java.lang.classfile.BootstrapMethodEntry;
import java.lang.classfile.ClassFile;
import java.lang.classfile.ClassModel;
import java.lang.classfile.CodeElement;
import java.lang.classfile.CodeModel;
import java.lang.classfile.MethodModel;
import java.lang.classfile.constantpool.MethodHandleEntry;
import java.lang.classfile.instruction.InvokeDynamicInstruction;
import java.nio.file.Path;

/*
 * @test
 * @bug     8148483 8151516 8151223
 * @summary Test that StringConcat is working for JDK >= 9
 * @library /tools/lib /test/lib
 * @run main TestIndyStringConcat
 */
public class TestIndyStringConcat {

    private static final String SOURCE = """
            public class IndyStringConcat {
                static String other;

                public static String test() {
                    return "Foo" + other;
                }
            }
            """;

    public static void main(String[] args) throws Exception {
        Path src = Path.of("src");
        ToolBox toolBox = new ToolBox();
        toolBox.writeJavaFiles(src, SOURCE);

        int errors = 0;
        errors += test(false, "java8", "-source", "8", "-target", "8");
        errors += test(false, "inline", "-XDstringConcat=inline");
        errors += test(true, "indy", "-XDstringConcat=indy");
        errors += test(true, "indyWithConstants", "-XDstringConcat=indyWithConstants");

        if (errors > 0) {
            throw new AssertionError(errors + " cases failed");
        }
    }

    public static int test(boolean expected, String label, String... args) throws Exception {
        Path src = Path.of("src");
        Path out = Path.of(label);
        CompilerUtils.compile(src, out, args);
        if (hasStringConcatFactoryCall(out.resolve("IndyStringConcat.class"), "test") != expected) {
            System.err.println("Expected " + expected + " failed for case " + label);
            return 1;
        }
        return 0;
    }

    public static boolean hasStringConcatFactoryCall(Path file, String methodName) throws Exception {
        ClassModel classFile = ClassFile.of().parse(file);

        for (MethodModel method : classFile.methods()) {
            if (method.methodName().equalsString(methodName)) {
                CodeModel code = method.code().orElseThrow();
                for (CodeElement i : code.elementList()) {
                    if (i instanceof InvokeDynamicInstruction indy) {
                        BootstrapMethodEntry bsmSpec = indy.invokedynamic().bootstrap();
                        MethodHandleEntry bsmInfo = bsmSpec.bootstrapMethod();
                        if (bsmInfo.reference().owner().asInternalName().equals("java/lang/invoke/StringConcatFactory")) {
                            return true;
                        }
                    }
                }
            }
        }
        return false;
    }

}