Document javac code generation for casts with multiple bounds
The number checkcast instructions generated is different for JDK11,
JDK-17 and JDK-21.
Change-Id: If287f2319590d845cf1fb8cf40f5ff406ea7273b
Bug: b/337801526
diff --git a/src/test/examplesJava21/jdk21/ir/optimize/interfaces/CastWithMultipleBoundsJavacBytecodeTest.java b/src/test/examplesJava21/jdk21/ir/optimize/interfaces/CastWithMultipleBoundsJavacBytecodeTest.java
new file mode 100644
index 0000000..0b73ede
--- /dev/null
+++ b/src/test/examplesJava21/jdk21/ir/optimize/interfaces/CastWithMultipleBoundsJavacBytecodeTest.java
@@ -0,0 +1,85 @@
+// Copyright (c) 2024, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+package jdk21.ir.optimize.interfaces;
+
+import static org.junit.Assert.assertEquals;
+
+import com.android.tools.r8.TestBase;
+import com.android.tools.r8.TestParameters;
+import com.android.tools.r8.TestParametersCollection;
+import com.android.tools.r8.ToolHelper;
+import com.android.tools.r8.utils.codeinspector.CodeInspector;
+import com.android.tools.r8.utils.codeinspector.InstructionSubject;
+import java.io.Serializable;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameter;
+import org.junit.runners.Parameterized.Parameters;
+
+// This test is also present for base test module and JDK-17 to demonstrate the different javac
+// byte code.
+@RunWith(Parameterized.class)
+public class CastWithMultipleBoundsJavacBytecodeTest extends TestBase {
+
+ @Parameter(0)
+ public TestParameters parameters;
+
+ @Parameters(name = "{0}")
+ public static TestParametersCollection data() {
+ return getTestParameters().withAllRuntimesAndApiLevels().build();
+ }
+
+ @Test
+ public void testR8JavacCode() throws Exception {
+ parameters.assumeIsOrSimulateNoneRuntime();
+ // javac from JDK-21 generates the following code for getLambda with just one checkcast to
+ // the static return type:
+ //
+ // static java.io.Serializable getLambda();
+ // descriptor: ()Ljava/io/Serializable;
+ // flags: (0x0008) ACC_STATIC
+ // Code:
+ // stack=1, locals=0, args_size=0
+ // 0: invokedynamic #7, 0 // InvokeDynamic #0:run:()Ljava/lang/Runnable;
+ // 5: checkcast #11 // class java/io/Serializable
+ // 8: areturn
+ assertEquals(
+ 1,
+ new CodeInspector(ToolHelper.getClassFileForTestClass(TestClass.class))
+ .clazz(TestClass.class)
+ .uniqueMethodWithOriginalName("getLambda")
+ .streamInstructions()
+ .filter(InstructionSubject::isCheckCast)
+ .count());
+ }
+
+ @Test
+ public void testR8() throws Exception {
+ testForR8(parameters.getBackend())
+ .addInnerClassesAndStrippedOuter(getClass())
+ .addKeepMainRule(TestClass.class)
+ .setMinApi(parameters)
+ .addKeepMainRule(TestClass.class)
+ .run(parameters.getRuntime(), TestClass.class);
+ }
+
+ static class TestClass {
+ static void invokeLambda(Object o)
+ throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
+ Method runMethod = o.getClass().getMethod("run");
+ runMethod.invoke(o);
+ }
+
+ static Serializable getLambda() {
+ return (Runnable & Serializable) () -> System.out.println("base lambda");
+ }
+
+ public static void main(String[] args) throws Exception {
+ invokeLambda(getLambda());
+ }
+ }
+}
