--- old/src/hotspot/share/gc/cms/cmsGC.hpp	2017-10-17 23:16:51.402789803 +0200
+++ new/src/hotspot/share/gc/cms/cmsGC.hpp	2017-10-17 23:16:50.912788612 +0200
@@ -22,8 +22,8 @@
  *
  */
 
-#ifndef SHARE_VM_GC_CMS_CMS_GC_HPP
-#define SHARE_VM_GC_CMS_CMS_GC_HPP
+#ifndef SHARE_GC_CMS_CMSGC_HPP
+#define SHARE_GC_CMS_CMSGC_HPP
 
 #include "gc/shared/gc.hpp"
 
@@ -36,4 +36,4 @@
   virtual size_t conservative_max_heap_alignment();
 };
 
-#endif // SHARE_VM_GC_CMS_CMS_GC_HPP
+#endif // SHARE_GC_CMS_CMSGC_HPP
--- old/src/hotspot/share/gc/g1/g1GC.hpp	2017-10-17 23:16:52.617792758 +0200
+++ new/src/hotspot/share/gc/g1/g1GC.hpp	2017-10-17 23:16:52.161791649 +0200
@@ -22,8 +22,8 @@
  *
  */
 
-#ifndef SHARE_VM_GC_G1_G1_GC_HPP
-#define SHARE_VM_GC_G1_G1_GC_HPP
+#ifndef SHARE_GC_G1_G1GC_HPP
+#define SHARE_GC_G1_G1GC_HPP
 
 #include "gc/shared/gc.hpp"
 
@@ -33,4 +33,4 @@
   virtual size_t conservative_max_heap_alignment();
 };
 
-#endif // SHARE_VM_GC_G1_G1_GC_HPP
+#endif // SHARE_GC_G1_G1GC_HPP
--- old/src/hotspot/share/gc/parallel/parallelGC.hpp	2017-10-17 23:16:53.783795594 +0200
+++ new/src/hotspot/share/gc/parallel/parallelGC.hpp	2017-10-17 23:16:53.315794456 +0200
@@ -22,8 +22,8 @@
  *
  */
 
-#ifndef SHARE_VM_GC_PARALLEL_PARALLEL_GC_HPP
-#define SHARE_VM_GC_PARALLEL_PARALLEL_GC_HPP
+#ifndef SHARE_GC_PARALLEL_PARALLELGC_HPP
+#define SHARE_GC_PARALLEL_PARALLELGC_HPP
 
 #include "gc/shared/gc.hpp"
 
@@ -33,4 +33,4 @@
   virtual size_t conservative_max_heap_alignment();
 };
 
-#endif // SHARE_VM_GC_CMS_PARALLEL_GC_HPP
+#endif // SHARE_GC_CMS_PARALLELGC_HPP
--- old/src/hotspot/share/gc/serial/serialGC.hpp	2017-10-17 23:16:54.979798502 +0200
+++ new/src/hotspot/share/gc/serial/serialGC.hpp	2017-10-17 23:16:54.549797457 +0200
@@ -22,8 +22,8 @@
  *
  */
 
-#ifndef SHARE_VM_GC_SERIAL_SERIAL_GC_HPP
-#define SHARE_VM_GC_SERIAL_SERIAL_GC_HPP
+#ifndef SHARE_GC_SERIAL_SERIALGC_HPP
+#define SHARE_GC_SERIAL_SERIALGC_HPP
 
 #include "gc/shared/gc.hpp"
 
@@ -32,4 +32,4 @@
   virtual size_t conservative_max_heap_alignment();
 };
 
-#endif // SHARE_VM_GC_SERIAL_SERIAL_GC_HPP
+#endif // SHARE_GC_SERIAL_SERIALGC_HPP
--- old/src/hotspot/share/gc/shared/gc.hpp	2017-10-17 23:16:56.118801272 +0200
+++ new/src/hotspot/share/gc/shared/gc.hpp	2017-10-17 23:16:55.644800119 +0200
@@ -22,28 +22,17 @@
  *
  */
 
-#ifndef SHARE_VM_GC_SHARED_GC_HPP
-#define SHARE_VM_GC_SHARED_GC_HPP
+#ifndef SHARE_GC_SHARED_GC_HPP
+#define SHARE_GC_SHARED_GC_HPP
 
 #include "memory/allocation.hpp"
 
 class GC : public CHeapObj<mtGC> {
-private:
-  static GC* _gc;
-
-  static void select_gc();
-  static void select_gc_ergonomically();
-  static bool gc_selected();
-
 public:
-  static jint initialize();
-  static bool is_initialized();
-  static GC* gc();
-
-  static void initialize_flags_global();
-
-  virtual void initialize_flags();
+  virtual void initialize_flags() {
+    // Default does nothing.
+  }
   virtual size_t conservative_max_heap_alignment() = 0;
 };
 
-#endif // SHARE_VM_GC_SHARED_GC_HPP
+#endif // SHARE_GC_SHARED_GC_HPP
--- old/src/hotspot/share/runtime/arguments.cpp	2017-10-17 23:16:57.236803991 +0200
+++ new/src/hotspot/share/runtime/arguments.cpp	2017-10-17 23:16:56.731802763 +0200
@@ -29,6 +29,7 @@
 #include "classfile/stringTable.hpp"
 #include "classfile/symbolTable.hpp"
 #include "gc/shared/gc.hpp"
+#include "gc/shared/gcFactory.hpp"
 #include "gc/shared/genCollectedHeap.hpp"
 #include "gc/shared/referenceProcessor.hpp"
 #include "gc/shared/taskqueue.hpp"
@@ -1587,7 +1588,7 @@
   // the alignments imposed by several sources: any requirements from the heap
   // itself, the collector policy and the maximum page size we may run the VM
   // with.
-  size_t heap_alignment = GC::gc()->conservative_max_heap_alignment();
+  size_t heap_alignment = GCFactory::gc()->conservative_max_heap_alignment();
   _conservative_max_heap_alignment = MAX4(heap_alignment,
                                           (size_t)os::vm_allocation_granularity(),
                                           os::max_page_size(),
@@ -1653,7 +1654,7 @@
   }
 #endif
 
-  jint gc_result = GC::initialize();
+  jint gc_result = GCFactory::initialize();
   if (gc_result != JNI_OK) {
     return gc_result;
   }
@@ -1690,9 +1691,9 @@
 
 void Arguments::set_gc_specific_flags() {
   // Set per-collector flags
-  GC::gc()->initialize_flags();
+  GCFactory::gc()->initialize_flags();
   // Set flags for all collectors.
-  GC::initialize_flags_global();
+  GCFactory::initialize_flags_global();
 }
 
 julong Arguments::limit_by_allocatable_memory(julong limit) {
--- old/src/hotspot/share/gc/shared/gc_factory.cpp	2017-10-17 23:16:59.300809011 +0200
+++ /dev/null	2017-10-04 16:47:44.101817018 +0200
@@ -1,113 +0,0 @@
-/*
- * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates.
- * 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.
- *
- */
-
-#include "precompiled.hpp"
-#include "gc/shared/gc.hpp"
-#include "gc/serial/serialGC.hpp"
-#include "runtime/globals.hpp"
-#include "runtime/globals_extension.hpp"
-#include "runtime/os.hpp"
-#include "utilities/macros.hpp"
-
-#if INCLUDE_ALL_GCS
-#include "gc/parallel/parallelGC.hpp"
-#include "gc/cms/cmsGC.hpp"
-#include "gc/g1/g1GC.hpp"
-#endif
-
-GC* GC::_gc = NULL;
-
-bool GC::gc_selected() {
-#if INCLUDE_ALL_GCS
-  return UseSerialGC || UseParallelGC || UseParallelOldGC || UseConcMarkSweepGC || UseG1GC;
-#else
-  return UseSerialGC;
-#endif // INCLUDE_ALL_GCS
-}
-
-void GC::select_gc_ergonomically() {
-#if INCLUDE_ALL_GCS
-  if (os::is_server_class_machine()) {
-    FLAG_SET_ERGO_IF_DEFAULT(bool, UseG1GC, true);
-  } else {
-    FLAG_SET_ERGO_IF_DEFAULT(bool, UseSerialGC, true);
-  }
-#else
-  UNSUPPORTED_OPTION(UseG1GC);
-  UNSUPPORTED_OPTION(UseParallelGC);
-  UNSUPPORTED_OPTION(UseParallelOldGC);
-  UNSUPPORTED_OPTION(UseConcMarkSweepGC);
-  FLAG_SET_ERGO_IF_DEFAULT(bool, UseSerialGC, true);
-#endif // INCLUDE_ALL_GCS
-}
-
-void GC::initialize_flags_global() {
-#if INCLUDE_ALL_GCS
-  if (AssumeMP && !UseSerialGC) {
-    if (FLAG_IS_DEFAULT(ParallelGCThreads) && ParallelGCThreads == 1) {
-      warning("If the number of processors is expected to increase from one, then"
-              " you should configure the number of parallel GC threads appropriately"
-              " using -XX:ParallelGCThreads=N");
-    }
-  }
-  if (MinHeapFreeRatio == 100) {
-    // Keeping the heap 100% free is hard ;-) so limit it to 99%.
-    FLAG_SET_ERGO(uintx, MinHeapFreeRatio, 99);
-  }
-
-  // If class unloading is disabled, also disable concurrent class unloading.
-  if (!ClassUnloading) {
-    FLAG_SET_CMDLINE(bool, CMSClassUnloadingEnabled, false);
-    FLAG_SET_CMDLINE(bool, ClassUnloadingWithConcurrentMark, false);
-  }
-#endif // INCLUDE_ALL_GCS
-}
-
-jint GC::initialize() {
-  assert(_gc == NULL, "GC already created");
-
-  select_gc();
-
-#if !INCLUDE_ALL_GCS
-  if (UseParallelGC || UseParallelOldGC) {
-    fatal("UseParallelGC not supported in this VM.");
-  } else if (UseG1GC) {
-    fatal("UseG1GC not supported in this VM.");
-  } else if (UseConcMarkSweepGC) {
-    fatal("UseConcMarkSweepGC not supported in this VM.");
-#else
-  if (UseParallelGC || UseParallelOldGC) {
-    _gc = new ParallelGC();
-  } else if (UseG1GC) {
-    _gc = new G1GC();
-  } else if (UseConcMarkSweepGC) {
-    _gc = new CMSGC();
-#endif
-  } else if (UseSerialGC) {
-    _gc = new SerialGC();
-  } else {
-    ShouldNotReachHere();
-  }
-  return JNI_OK;
-}
--- /dev/null	2017-10-04 16:47:44.101817018 +0200
+++ new/src/hotspot/share/gc/shared/gcFactory.cpp	2017-10-17 23:16:58.090806068 +0200
@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates.
+ * 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.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "gc/shared/gc.hpp"
+#include "gc/shared/gcFactory.hpp"
+#include "gc/serial/serialGC.hpp"
+#include "runtime/globals.hpp"
+#include "runtime/globals_extension.hpp"
+#include "runtime/java.hpp"
+#include "runtime/os.hpp"
+#include "utilities/macros.hpp"
+
+#if INCLUDE_ALL_GCS
+#include "gc/parallel/parallelGC.hpp"
+#include "gc/cms/cmsGC.hpp"
+#include "gc/g1/g1GC.hpp"
+#endif
+
+GC* GCFactory::_gc = NULL;
+
+GC* GCFactory::gc() {
+  assert(_gc != NULL, "GC not yet created");
+  return _gc;
+}
+
+bool GCFactory::is_initialized() {
+  return _gc != NULL;
+}
+
+bool GCFactory::gc_selected() {
+#if INCLUDE_ALL_GCS
+  return UseSerialGC || UseParallelGC || UseParallelOldGC || UseConcMarkSweepGC || UseG1GC;
+#else
+  return UseSerialGC;
+#endif // INCLUDE_ALL_GCS
+}
+
+void GCFactory::select_gc() {
+  if (!gc_selected()) {
+    select_gc_ergonomically();
+    if (!gc_selected()) {
+      vm_exit_during_initialization("Garbage collector not selected (default collector explicitly disabled)", NULL);
+    }
+  }
+}
+
+void GCFactory::select_gc_ergonomically() {
+#if INCLUDE_ALL_GCS
+  if (os::is_server_class_machine()) {
+    FLAG_SET_ERGO_IF_DEFAULT(bool, UseG1GC, true);
+  } else {
+    FLAG_SET_ERGO_IF_DEFAULT(bool, UseSerialGC, true);
+  }
+#else
+  UNSUPPORTED_OPTION(UseG1GC);
+  UNSUPPORTED_OPTION(UseParallelGC);
+  UNSUPPORTED_OPTION(UseParallelOldGC);
+  UNSUPPORTED_OPTION(UseConcMarkSweepGC);
+  FLAG_SET_ERGO_IF_DEFAULT(bool, UseSerialGC, true);
+#endif // INCLUDE_ALL_GCS
+}
+
+void GCFactory::initialize_flags_global() {
+#if INCLUDE_ALL_GCS
+  if (AssumeMP && !UseSerialGC) {
+    if (FLAG_IS_DEFAULT(ParallelGCThreads) && ParallelGCThreads == 1) {
+      warning("If the number of processors is expected to increase from one, then"
+              " you should configure the number of parallel GC threads appropriately"
+              " using -XX:ParallelGCThreads=N");
+    }
+  }
+  if (MinHeapFreeRatio == 100) {
+    // Keeping the heap 100% free is hard ;-) so limit it to 99%.
+    FLAG_SET_ERGO(uintx, MinHeapFreeRatio, 99);
+  }
+
+  // If class unloading is disabled, also disable concurrent class unloading.
+  if (!ClassUnloading) {
+    FLAG_SET_CMDLINE(bool, CMSClassUnloadingEnabled, false);
+    FLAG_SET_CMDLINE(bool, ClassUnloadingWithConcurrentMark, false);
+  }
+#endif // INCLUDE_ALL_GCS
+}
+
+jint GCFactory::initialize() {
+  assert(_gc == NULL, "GC already created");
+
+  select_gc();
+
+#if !INCLUDE_ALL_GCS
+  if (UseParallelGC || UseParallelOldGC) {
+    fatal("UseParallelGC not supported in this VM.");
+  } else if (UseG1GC) {
+    fatal("UseG1GC not supported in this VM.");
+  } else if (UseConcMarkSweepGC) {
+    fatal("UseConcMarkSweepGC not supported in this VM.");
+#else
+  if (UseParallelGC || UseParallelOldGC) {
+    _gc = new ParallelGC();
+  } else if (UseG1GC) {
+    _gc = new G1GC();
+  } else if (UseConcMarkSweepGC) {
+    _gc = new CMSGC();
+#endif
+  } else if (UseSerialGC) {
+    _gc = new SerialGC();
+  } else {
+    ShouldNotReachHere();
+  }
+  return JNI_OK;
+}
--- /dev/null	2017-10-04 16:47:44.101817018 +0200
+++ new/src/hotspot/share/gc/shared/gcFactory.hpp	2017-10-17 23:17:03.378818928 +0200
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates.
+ * 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.
+ *
+ */
+
+#ifndef SHARE_GC_SHARED_GCFACTORY_HPP
+#define SHARE_GC_SHARED_GCFACTORY_HPP
+
+#include "memory/allocation.hpp"
+
+class GCFactory : public AllStatic {
+private:
+  static GC* _gc;
+
+  static void select_gc();
+  static void select_gc_ergonomically();
+  static bool gc_selected();
+
+public:
+  static jint initialize();
+  static bool is_initialized();
+  static GC* gc();
+
+  static void initialize_flags_global();
+};
+
+#endif // SHARE_GC_SHARED_GCFACTORY_HPP
--- old/src/hotspot/share/gc/shared/gc.cpp	2017-10-17 23:17:05.907825078 +0200
+++ /dev/null	2017-10-04 16:47:44.101817018 +0200
@@ -1,52 +0,0 @@
-/*
- * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates.
- * 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.
- *
- */
-
-#include "precompiled.hpp"
-#include "gc/shared/gc.hpp"
-#include "runtime/globals.hpp"
-#include "runtime/globals_extension.hpp"
-#include "runtime/java.hpp"
-
-GC* GC::gc() {
-  assert(_gc != NULL, "GC not yet created");
-  return _gc;
-}
-
-bool GC::is_initialized() {
-  return _gc != NULL;
-}
-
-void GC::select_gc() {
-  if (!gc_selected()) {
-    select_gc_ergonomically();
-    if (!gc_selected()) {
-      vm_exit_during_initialization("Garbage collector not selected (default collector explicitly disabled)", NULL);
-    }
-  }
-}
-
-
-void GC::initialize_flags() {
-  // Default does nothing.
-}