8202035: Archive the set of ModuleDescriptor and ModuleReference objects for observable system modules with unnamed initial module

Support system module archiving with unnamed initial module at dump time.

Co-authored-by: Alan Bateman <alan.bateman@oracle.com>
Reviewed-by: erikj, coleenp, mchung, iklam, ccheung

src/java.base/share/classes/jdk/internal/misc/VM.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2018, 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
@@ -413,4 +413,15 @@ public class VM {
         initialize();
     }
     private static native void initialize();
+
+    /**
+     * Initialize archived static fields in the given Class using archived
+     * values from CDS dump time. Also initialize the classes of objects in
+     * the archived graph referenced by those fields.
+     *
+     * Those static fields remain as uninitialized if there is no mapped CDS
+     * java heap data or there is any error during initialization of the
+     * object class in the archived graph.
+     */
+    public static native void initializeFromArchive(Class<?> c);
 }

src/java.base/share/classes/jdk/internal/module/ArchivedModuleGraph.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2018, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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 jdk.internal.module;
+
+import java.lang.module.ModuleFinder;
+import java.util.Objects;
+import jdk.internal.misc.VM;
+
+/**
+ * Used by ModuleBootstrap to obtain the archived system modules and finder.
+ */
+final class ArchivedModuleGraph {
+    private static String archivedMainModule;
+    private static SystemModules archivedSystemModules;
+    private static ModuleFinder archivedModuleFinder;
+
+    private final SystemModules systemModules;
+    private final ModuleFinder finder;
+
+    private ArchivedModuleGraph(SystemModules modules, ModuleFinder finder) {
+        this.systemModules = modules;
+        this.finder = finder;
+    }
+
+    SystemModules systemModules() {
+        return systemModules;
+    }
+
+    ModuleFinder finder() {
+        return finder;
+    }
+
+    // A factory method that ModuleBootstrap can use to obtain the
+    // ArchivedModuleGraph.
+    static ArchivedModuleGraph get(String mainModule) {
+        if (Objects.equals(mainModule, archivedMainModule)
+                && archivedSystemModules != null
+                && archivedModuleFinder != null) {
+            return new ArchivedModuleGraph(archivedSystemModules,
+                                           archivedModuleFinder);
+        } else {
+            return null;
+        }
+    }
+
+    // Used at CDS dump time
+    static void archive(String mainModule, SystemModules systemModules,
+                        ModuleFinder finder) {
+        if (archivedMainModule != null)
+            throw new UnsupportedOperationException();
+        archivedMainModule = mainModule;
+        archivedSystemModules = systemModules;
+        archivedModuleFinder = finder;
+    }
+
+    static {
+        VM.initializeFromArchive(ArchivedModuleGraph.class);
+    }
+}

src/java.base/share/classes/jdk/internal/module/ModuleBootstrap.java

@@ -54,6 +54,7 @@ import jdk.internal.loader.BuiltinClassLoader;
 import jdk.internal.misc.JavaLangAccess;
 import jdk.internal.misc.JavaLangModuleAccess;
 import jdk.internal.misc.SharedSecrets;
+import jdk.internal.misc.VM;
 import jdk.internal.perf.PerfCounter;
 
 /**
@@ -172,23 +173,45 @@ public final class ModuleBootstrap {
         boolean haveModulePath = (appModulePath != null || upgradeModulePath != null);
         boolean needResolution = true;
 
-        if (!haveModulePath && addModules.isEmpty() && limitModules.isEmpty()) {
-            systemModules = SystemModuleFinders.systemModules(mainModule);
-            if (systemModules != null && !isPatched && (traceOutput == null)) {
-                needResolution = false;
-            }
-        }
-        if (systemModules == null) {
-            // all system modules are observable
-            systemModules = SystemModuleFinders.allSystemModules();
-        }
-        if (systemModules != null) {
-            // images build
-            systemModuleFinder = SystemModuleFinders.of(systemModules);
+        // If the java heap was archived at CDS dump time and the environment
+        // at dump time matches the current environment then use the archived
+        // system modules and finder.
+        ArchivedModuleGraph archivedModuleGraph = ArchivedModuleGraph.get(mainModule);
+        if (archivedModuleGraph != null
+                && !haveModulePath
+                && addModules.isEmpty()
+                && limitModules.isEmpty()
+                && !isPatched) {
+            systemModules = archivedModuleGraph.systemModules();
+            systemModuleFinder = archivedModuleGraph.finder();
+            needResolution = (traceOutput != null);
         } else {
-            // exploded build or testing
-            systemModules = new ExplodedSystemModules();
-            systemModuleFinder = SystemModuleFinders.ofSystem();
+            boolean canArchive = false;
+            if (!haveModulePath && addModules.isEmpty() && limitModules.isEmpty()) {
+                systemModules = SystemModuleFinders.systemModules(mainModule);
+                if (systemModules != null && !isPatched) {
+                    needResolution = (traceOutput != null);
+                    canArchive = true;
+                }
+            }
+            if (systemModules == null) {
+                // all system modules are observable
+                systemModules = SystemModuleFinders.allSystemModules();
+            }
+            if (systemModules != null) {
+                // images build
+                systemModuleFinder = SystemModuleFinders.of(systemModules);
+            } else {
+                // exploded build or testing
+                systemModules = new ExplodedSystemModules();
+                systemModuleFinder = SystemModuleFinders.ofSystem();
+            }
+
+            // Module graph can be archived at CDS dump time. Only allow the
+            // unnamed module case for now.
+            if (canArchive && (mainModule == null)) {
+                ArchivedModuleGraph.archive(mainModule, systemModules, systemModuleFinder);
+            }
         }
 
         Counters.add("jdk.module.boot.1.systemModulesTime", t1);