/*
 * Copyright (c) 2014, 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.
 */

import sun.hotspot.WhiteBox;
import sun.hotspot.code.NMethod;
import com.oracle.java.testlibrary.Platform;

import java.lang.reflect.Method;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.util.function.BiFunction;

/*
 * @test NullCheckDroppingsTest
 * @bug 8054492
 * @summary "Casting can result in redundant null checks in generated code"
 * @library /testlibrary /testlibrary/whitebox /testlibrary/com/oracle/java/testlibrary
 * @build NullCheckDroppingsTest
 * @run main ClassFileInstaller sun.hotspot.WhiteBox
 *                              sun.hotspot.WhiteBox$WhiteBoxPermission
 * @run main ClassFileInstaller com.oracle.java.testlibrary.Platform
 * @run main/othervm -Xbootclasspath/a:. -XX:+IgnoreUnrecognizedVMOptions -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
 *                   -Xmixed -XX:-BackgroundCompilation -XX:-TieredCompilation -XX:CompileThreshold=1000
 *                   -XX:CompileCommand=exclude,NullCheckDroppingsTest::main NullCheckDroppingsTest
 */

public class NullCheckDroppingsTest {

  private static final WhiteBox WHITE_BOX = WhiteBox.getWhiteBox();

  static final BiFunction<Class, Object, Object> fCast = (c, o) -> c.cast(o);

  static final MethodHandle SET_SSINK;
  static final MethodHandle MH_CAST;

  static {
      try {
          SET_SSINK = MethodHandles.lookup().findSetter(NullCheckDroppingsTest.class, "ssink", String.class);
          MH_CAST = MethodHandles.lookup().findVirtual(Class.class,
                                                       "cast",
                                                       MethodType.methodType(Object.class, Object.class));
      }
      catch (Exception e) {
          throw new Error(e);
      }
  }  

  static volatile String svalue = "A";
  static volatile String snull = null;

  String ssink;

  public static void main(String[] args) throws Exception {
  
      // Only test C2 in Server VM
      if (!Platform.isServer()) {
          return;
      }
      // Make sure background compilation is disabled
      if (WHITE_BOX.getBooleanVMFlag("BackgroundCompilation")) {
          throw new RuntimeException("Background compilation enabled");
      }
      // Make sure Tiered compilation is disabled
      if (WHITE_BOX.getBooleanVMFlag("TieredCompilation")) {
          throw new RuntimeException("Tiered compilation enabled");
      }
      
      Method testOne   = NullCheckDroppingsTest.class.getDeclaredMethod("testLoopOne", String.class);
      Method testTwo   = NullCheckDroppingsTest.class.getDeclaredMethod("testLoopTwo", String.class);
      Method testThree = NullCheckDroppingsTest.class.getDeclaredMethod("testLoopThree", String.class);
      Method testFour  = NullCheckDroppingsTest.class.getDeclaredMethod("testLoopFour", String.class);
  
      NullCheckDroppingsTest t = new NullCheckDroppingsTest();

      // Ensure testLoopOne is compiled
      for (int i = 0; i < 3000; i++) {
          t.testLoopOne(svalue);
          t.testLoopTwo(svalue);
          t.testLoopThree(svalue);
          t.testLoopFour(svalue);
      }
      NMethod nm = getNMethod(testOne);
      // This should cause a de-optimisation
      // if testLoopOne is compiled with a null-check.
      t.testLoopOne(snull);
      checkDeoptimization(testOne, nm);

      nm = getNMethod(testTwo);
      t.testLoopTwo(snull);
      checkDeoptimization(testTwo, nm);
      
      nm = getNMethod(testThree);
      t.testLoopThree(snull);
      checkDeoptimization(testThree, nm);
      
      nm = getNMethod(testFour);
      t.testLoopFour(snull);
      checkDeoptimization(testFour, nm);
  }

  void testLoopOne(String s) {
      try {
          ssink = String.class.cast(s);
      } catch (Throwable t) {
          throw new Error(t);
      }
  }

  void testLoopTwo(String s) {
      try {
          ssink = (String) (Object) MH_CAST.invokeExact(String.class, (Object) s);;
      } catch (Throwable t) {
          throw new Error(t);
      }
  }

  void testLoopThree(String s) {
      try {
          SET_SSINK.invokeExact(this, s);
      } catch (Throwable t) {
          throw new Error(t);
      }
  }

  void testLoopFour(String s) {
      try {
          ssink = (String) fCast.apply(String.class, s);
      } catch (Throwable t) {
          throw new Error(t);
      }
  }
  
  static NMethod getNMethod(Method test) throws Exception {
      // Because background compilation is disabled, method should now be compiled
      if (!WHITE_BOX.isMethodCompiled(test)) {
          throw new RuntimeException(test + " not compiled");
      }

      NMethod nm = NMethod.get(test, false); // not OSR nmethod
      if (nm == null) {
          throw new RuntimeException(test + " missing nmethod?");
      }
      if (nm.comp_level != 4) {
          throw new RuntimeException(test + " compiled by not C2: " + nm);
      }
      return nm;
  }
  
  static void checkDeoptimization(Method test, NMethod nmOrig) throws Exception {
      // Ensure no deoptimization (intrinsic Class.cast() works).
      if (!WHITE_BOX.isMethodCompiled(test)) {
          throw new RuntimeException(test + " deoptimized");
      }

      // Ensure no recompilation.
      NMethod nm = NMethod.get(test, false); // not OSR nmethod
      if (nm == null) {
          throw new RuntimeException(test + " missing nmethod?");
      }
      if (nm.comp_level != 4) {
          throw new RuntimeException(test + " compiled by not C2: " + nm);
      }
      if (nm.compile_id != nmOrig.compile_id) {
          throw new RuntimeException(test + " was recompiled: old nmethod=" + nmOrig + ", new nmethod=" + nm);
      } 
  }
}