--- a/src/hotspot/share/gc/cms/cmsArguments.cpp	Wed Mar 28 11:38:47 2018 +0200
+++ b/src/hotspot/share/gc/cms/cmsArguments.cpp	Wed Mar 28 11:38:47 2018 +0200
@@ -80,8 +80,8 @@
 // sparc/solaris for certain applications, but would gain from
 // further optimization and tuning efforts, and would almost
 // certainly gain from analysis of platform and environment.
-void CMSArguments::initialize_flags() {
-  GCArguments::initialize_flags();
+void CMSArguments::initialize() {
+  GCArguments::initialize();
   assert(!UseSerialGC && !UseParallelOldGC && !UseParallelGC, "Error");
   assert(UseConcMarkSweepGC, "CMS is expected to be on here");
 

--- a/src/hotspot/share/gc/cms/cmsArguments.hpp	Wed Mar 28 11:38:47 2018 +0200
+++ b/src/hotspot/share/gc/cms/cmsArguments.hpp	Wed Mar 28 11:38:47 2018 +0200
@@ -34,7 +34,7 @@
   void disable_adaptive_size_policy(const char* collector_name);
   void set_parnew_gc_flags();
 public:
-  virtual void initialize_flags();
+  virtual void initialize();
   virtual size_t conservative_max_heap_alignment();
   virtual CollectedHeap* create_heap();
 };

--- a/src/hotspot/share/gc/g1/g1Arguments.cpp	Wed Mar 28 11:38:47 2018 +0200
+++ b/src/hotspot/share/gc/g1/g1Arguments.cpp	Wed Mar 28 11:38:47 2018 +0200
@@ -72,8 +72,8 @@
   }
 }
 
-void G1Arguments::initialize_flags() {
-  GCArguments::initialize_flags();
+void G1Arguments::initialize() {
+  GCArguments::initialize();
   assert(UseG1GC, "Error");
   FLAG_SET_DEFAULT(ParallelGCThreads, Abstract_VM_Version::parallel_worker_threads());
   if (ParallelGCThreads == 0) {

--- a/src/hotspot/share/gc/g1/g1Arguments.hpp	Wed Mar 28 11:38:47 2018 +0200
+++ b/src/hotspot/share/gc/g1/g1Arguments.hpp	Wed Mar 28 11:38:47 2018 +0200
@@ -38,7 +38,7 @@
   static void parse_verification_type(const char* type);
 
 public:
-  virtual void initialize_flags();
+  virtual void initialize();
   virtual size_t conservative_max_heap_alignment();
   virtual CollectedHeap* create_heap();
 };

--- a/src/hotspot/share/gc/parallel/parallelArguments.cpp	Wed Mar 28 11:38:47 2018 +0200
+++ b/src/hotspot/share/gc/parallel/parallelArguments.cpp	Wed Mar 28 11:38:47 2018 +0200
@@ -38,8 +38,8 @@
   return CollectorPolicy::compute_heap_alignment();
 }
 
-void ParallelArguments::initialize_flags() {
-  GCArguments::initialize_flags();
+void ParallelArguments::initialize() {
+  GCArguments::initialize();
   assert(UseParallelGC || UseParallelOldGC, "Error");
   // Enable ParallelOld unless it was explicitly disabled (cmd line or rc file).
   if (FLAG_IS_DEFAULT(UseParallelOldGC)) {

--- a/src/hotspot/share/gc/parallel/parallelArguments.hpp	Wed Mar 28 11:38:47 2018 +0200
+++ b/src/hotspot/share/gc/parallel/parallelArguments.hpp	Wed Mar 28 11:38:47 2018 +0200
@@ -31,7 +31,7 @@
 
 class ParallelArguments : public GCArguments {
 public:
-  virtual void initialize_flags();
+  virtual void initialize();
   virtual size_t conservative_max_heap_alignment();
   virtual CollectedHeap* create_heap();
 };

--- a/src/hotspot/share/gc/shared/collectedHeap.hpp	Wed Mar 28 11:38:47 2018 +0200
+++ b/src/hotspot/share/gc/shared/collectedHeap.hpp	Wed Mar 28 11:38:47 2018 +0200
@@ -187,6 +187,7 @@
 
  public:
   enum Name {
+    None,
     Serial,
     Parallel,
     CMS,

--- a/src/hotspot/share/gc/shared/gcArguments.cpp	Wed Mar 28 11:38:47 2018 +0200
+++ b/src/hotspot/share/gc/shared/gcArguments.cpp	Wed Mar 28 11:38:47 2018 +0200
@@ -25,68 +25,12 @@
 
 #include "precompiled.hpp"
 #include "gc/shared/gcArguments.hpp"
-#include "gc/serial/serialArguments.hpp"
-#include "logging/log.hpp"
-#include "memory/allocation.inline.hpp"
 #include "runtime/arguments.hpp"
 #include "runtime/globals.hpp"
 #include "runtime/globals_extension.hpp"
-#include "runtime/java.hpp"
-#include "runtime/os.hpp"
-#include "utilities/defaultStream.hpp"
 #include "utilities/macros.hpp"
 
-#if INCLUDE_ALL_GCS
-#include "gc/parallel/parallelArguments.hpp"
-#include "gc/cms/cmsArguments.hpp"
-#include "gc/g1/g1Arguments.hpp"
-#endif
-
-GCArguments* GCArguments::_instance = NULL;
-
-GCArguments* GCArguments::arguments() {
-  assert(is_initialized(), "Heap factory not yet created");
-  return _instance;
-}
-
-bool GCArguments::is_initialized() {
-  return _instance != NULL;
-}
-
-bool GCArguments::gc_selected() {
-#if INCLUDE_ALL_GCS
-  return UseSerialGC || UseParallelGC || UseParallelOldGC || UseConcMarkSweepGC || UseG1GC;
-#else
-  return UseSerialGC;
-#endif // INCLUDE_ALL_GCS
-}
-
-void GCArguments::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 GCArguments::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 GCArguments::initialize_flags() {
+void GCArguments::initialize() {
 #if INCLUDE_ALL_GCS
   if (MinHeapFreeRatio == 100) {
     // Keeping the heap 100% free is hard ;-) so limit it to 99%.
@@ -100,34 +44,3 @@
   }
 #endif // INCLUDE_ALL_GCS
 }
-
-jint GCArguments::initialize() {
-  assert(!is_initialized(), "GC arguments already initialized");
-
-  select_gc();
-
-#if !INCLUDE_ALL_GCS
-  if (UseParallelGC || UseParallelOldGC) {
-    jio_fprintf(defaultStream::error_stream(), "UseParallelGC not supported in this VM.\n");
-    return JNI_ERR;
-  } else if (UseG1GC) {
-    jio_fprintf(defaultStream::error_stream(), "UseG1GC not supported in this VM.\n");
-    return JNI_ERR;
-  } else if (UseConcMarkSweepGC) {
-    jio_fprintf(defaultStream::error_stream(), "UseConcMarkSweepGC not supported in this VM.\n");
-    return JNI_ERR;
-#else
-  if (UseParallelGC || UseParallelOldGC) {
-    _instance = new ParallelArguments();
-  } else if (UseG1GC) {
-    _instance = new G1Arguments();
-  } else if (UseConcMarkSweepGC) {
-    _instance = new CMSArguments();
-#endif
-  } else if (UseSerialGC) {
-    _instance = new SerialArguments();
-  } else {
-    ShouldNotReachHere();
-  }
-  return JNI_OK;
-}

--- a/src/hotspot/share/gc/shared/gcArguments.hpp	Wed Mar 28 11:38:47 2018 +0200
+++ b/src/hotspot/share/gc/shared/gcArguments.hpp	Wed Mar 28 11:38:47 2018 +0200
@@ -30,27 +30,14 @@
 
 class CollectedHeap;
 
-class GCArguments : public CHeapObj<mtGC> {
-private:
-  static GCArguments* _instance;
-
-  static void select_gc();
-  static void select_gc_ergonomically();
-  static bool gc_selected();
-
+class GCArguments {
 protected:
   template <class Heap, class Policy>
   CollectedHeap* create_heap_with_policy();
 
 public:
-  static jint initialize();
-  static bool is_initialized();
-  static GCArguments* arguments();
-
-  virtual void initialize_flags();
-
+  virtual void initialize();
   virtual size_t conservative_max_heap_alignment() = 0;
-
   virtual CollectedHeap* create_heap() = 0;
 };
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/gcConfig.cpp	Wed Mar 28 11:38:47 2018 +0200
@@ -0,0 +1,178 @@
+/*
+ * 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.
+ *
+ * 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/serial/serialArguments.hpp"
+#include "gc/shared/gcConfig.hpp"
+#include "runtime/java.hpp"
+#include "runtime/os.hpp"
+#include "utilities/macros.hpp"
+#if INCLUDE_ALL_GCS
+#include "gc/parallel/parallelArguments.hpp"
+#include "gc/cms/cmsArguments.hpp"
+#include "gc/g1/g1Arguments.hpp"
+#endif // INCLUDE_ALL_GCS
+
+struct SupportedGC {
+  bool&               _flag;
+  CollectedHeap::Name _name;
+  GCArguments&        _arguments;
+
+  SupportedGC(bool& flag, CollectedHeap::Name name, GCArguments& arguments) :
+      _flag(flag), _name(name), _arguments(arguments) {}
+};
+
+static SerialArguments   serialArguments;
+#if INCLUDE_ALL_GCS
+static ParallelArguments parallelArguments;
+static CMSArguments      cmsArguments;
+static G1Arguments       g1Arguments;
+#endif // INCLUDE_ALL_GCS
+
+// Table of supported GCs, for translating between command
+// line flag, CollectedHeap::Name and GCArguments instance.
+static const SupportedGC SupportedGCs[] = {
+  SupportedGC(UseSerialGC,        CollectedHeap::Serial,   serialArguments),
+#if INCLUDE_ALL_GCS
+  SupportedGC(UseParallelGC,      CollectedHeap::Parallel, parallelArguments),
+  SupportedGC(UseParallelOldGC,   CollectedHeap::Parallel, parallelArguments),
+  SupportedGC(UseConcMarkSweepGC, CollectedHeap::CMS,      cmsArguments),
+  SupportedGC(UseG1GC,            CollectedHeap::G1,       g1Arguments),
+#endif // INCLUDE_ALL_GCS
+};
+
+GCArguments* GCConfig::_arguments = NULL;
+bool GCConfig::_gc_selected_ergonomically = false;
+
+void GCConfig::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
+}
+
+bool GCConfig::is_no_gc_selected() {
+  for (size_t i = 0; i < ARRAY_SIZE(SupportedGCs); i++) {
+    if (SupportedGCs[i]._flag) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+bool GCConfig::is_exactly_one_gc_selected() {
+  CollectedHeap::Name selected = CollectedHeap::None;
+
+  for (size_t i = 0; i < ARRAY_SIZE(SupportedGCs); i++) {
+    if (SupportedGCs[i]._flag) {
+      if (SupportedGCs[i]._name == selected || selected == CollectedHeap::None) {
+        // Selected
+        selected = SupportedGCs[i]._name;
+      } else {
+        // More than one selected
+        return false;
+      }
+    }
+  }
+
+  return selected != CollectedHeap::None;
+}
+
+GCArguments* GCConfig::select_gc() {
+  if (is_no_gc_selected()) {
+    // Try select GC ergonomically
+    select_gc_ergonomically();
+
+    if (is_no_gc_selected()) {
+      // Failed to select GC ergonomically
+      vm_exit_during_initialization("Garbage collector not selected "
+                                    "(default collector explicitly disabled)", NULL);
+    }
+
+    // Succeeded to select GC ergonomically
+    _gc_selected_ergonomically = true;
+  }
+
+  if (is_exactly_one_gc_selected()) {
+    // Exacly one GC selected
+    for (size_t i = 0; i < ARRAY_SIZE(SupportedGCs); i++) {
+      if (SupportedGCs[i]._flag) {
+        return &SupportedGCs[i]._arguments;
+      }
+    }
+  }
+
+  // More than one GC selected
+  vm_exit_during_initialization("Multiple garbage collectors selected", NULL);
+
+  return NULL;
+}
+
+void GCConfig::initialize() {
+  assert(_arguments == NULL, "Already initialized");
+  _arguments = select_gc();
+}
+
+bool GCConfig::is_gc_supported(CollectedHeap::Name name) {
+  for (size_t i = 0; i < ARRAY_SIZE(SupportedGCs); i++) {
+    if (SupportedGCs[i]._name == name) {
+      // Supported
+      return true;
+    }
+  }
+
+  // Not supported
+  return false;
+}
+
+bool GCConfig::is_gc_selected(CollectedHeap::Name name) {
+  for (size_t i = 0; i < ARRAY_SIZE(SupportedGCs); i++) {
+    if (SupportedGCs[i]._name == name && SupportedGCs[i]._flag) {
+      // Selected
+      return true;
+    }
+  }
+
+  // Not selected
+  return false;
+}
+
+bool GCConfig::is_gc_selected_ergonomically() {
+  return _gc_selected_ergonomically;
+}
+
+GCArguments* GCConfig::arguments() {
+  assert(_arguments != NULL, "Not initialized");
+  return _arguments;
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/gcConfig.hpp	Wed Mar 28 11:38:47 2018 +0200
@@ -0,0 +1,54 @@
+/*
+ * 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.
+ *
+ * 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_GCCONFIG_HPP
+#define SHARE_GC_SHARED_GCCONFIG_HPP
+
+#include "gc/shared/collectedHeap.hpp"
+#include "memory/allocation.hpp"
+
+class GCArguments;
+
+class GCConfig : public AllStatic {
+private:
+  static GCArguments* _arguments;
+  static bool         _gc_selected_ergonomically;
+
+  static bool is_no_gc_selected();
+  static bool is_exactly_one_gc_selected();
+
+  static void select_gc_ergonomically();
+  static GCArguments* select_gc();
+
+public:
+  static void initialize();
+
+  static bool is_gc_supported(CollectedHeap::Name name);
+  static bool is_gc_selected(CollectedHeap::Name name);
+  static bool is_gc_selected_ergonomically();
+
+  static GCArguments* arguments();
+};
+
+#endif // SHARE_GC_SHARED_GCCONFIG_HPP

--- a/src/hotspot/share/memory/universe.cpp	Wed Mar 28 11:38:47 2018 +0200
+++ b/src/hotspot/share/memory/universe.cpp	Wed Mar 28 11:38:47 2018 +0200
@@ -35,6 +35,7 @@
 #include "gc/shared/cardTableBarrierSet.hpp"
 #include "gc/shared/collectedHeap.inline.hpp"
 #include "gc/shared/gcArguments.hpp"
+#include "gc/shared/gcConfig.hpp"
 #include "gc/shared/gcLocker.hpp"
 #include "gc/shared/generation.hpp"
 #include "gc/shared/gcTraceTime.inline.hpp"
@@ -745,8 +746,7 @@
 
 CollectedHeap* Universe::create_heap() {
   assert(_collectedHeap == NULL, "Heap already created");
-  assert(GCArguments::is_initialized(), "GC must be initialized here");
-  return GCArguments::arguments()->create_heap();
+  return GCConfig::arguments()->create_heap();
 }
 
 // Choose the heap base address and oop encoding mode

--- a/src/hotspot/share/runtime/arguments.cpp	Wed Mar 28 11:38:47 2018 +0200
+++ b/src/hotspot/share/runtime/arguments.cpp	Wed Mar 28 11:38:47 2018 +0200
@@ -30,6 +30,7 @@
 #include "classfile/stringTable.hpp"
 #include "classfile/symbolTable.hpp"
 #include "gc/shared/gcArguments.hpp"
+#include "gc/shared/gcConfig.hpp"
 #include "gc/shared/genCollectedHeap.hpp"
 #include "gc/shared/referenceProcessor.hpp"
 #include "gc/shared/taskqueue.hpp"
@@ -1749,7 +1750,7 @@
   // 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 = GCArguments::arguments()->conservative_max_heap_alignment();
+  size_t heap_alignment = GCConfig::arguments()->conservative_max_heap_alignment();
   _conservative_max_heap_alignment = MAX4(heap_alignment,
                                           (size_t)os::vm_allocation_granularity(),
                                           os::max_page_size(),
@@ -1815,10 +1816,7 @@
   }
 #endif
 
-  jint gc_result = GCArguments::initialize();
-  if (gc_result != JNI_OK) {
-    return gc_result;
-  }
+  GCConfig::initialize();
 
 #if COMPILER2_OR_JVMCI
   // Shared spaces work fine with other GCs but causes bytecode rewriting
@@ -2176,26 +2174,6 @@
 }
 #endif //INCLUDE_JVMCI
 
-// Check consistency of GC selection
-bool Arguments::check_gc_consistency() {
-  // Ensure that the user has not selected conflicting sets
-  // of collectors.
-  uint i = 0;
-  if (UseSerialGC)                       i++;
-  if (UseConcMarkSweepGC)                i++;
-  if (UseParallelGC || UseParallelOldGC) i++;
-  if (UseG1GC)                           i++;
-  if (i > 1) {
-    jio_fprintf(defaultStream::error_stream(),
-                "Conflicting collector combinations in option list; "
-                "please refer to the release notes for the combinations "
-                "allowed\n");
-    return false;
-  }
-
-  return true;
-}
-
 // Check the consistency of vm_init_args
 bool Arguments::check_vm_args_consistency() {
   // Method for adding checks for flag consistency.
@@ -2225,8 +2203,6 @@
     FLAG_SET_DEFAULT(UseGCOverheadLimit, false);
   }
 
-  status = status && check_gc_consistency();
-
   // CMS space iteration, which FLSVerifyAllHeapreferences entails,
   // insists that we hold the requisite locks so that the iteration is
   // MT-safe. For the verification at start-up and shut-down, we don't
@@ -4241,11 +4217,6 @@
 
   set_shared_spaces_flags();
 
-  // Check the GC selections again.
-  if (!check_gc_consistency()) {
-    return JNI_EINVAL;
-  }
-
   if (TieredCompilation) {
     set_tiered_flags();
   } else {
@@ -4278,7 +4249,7 @@
   // Set heap size based on available physical memory
   set_heap_size();
 
-  GCArguments::arguments()->initialize_flags();
+  GCConfig::arguments()->initialize();
 
   // Initialize Metaspace flags and alignments
   Metaspace::ergo_initialize();

--- a/test/hotspot/jtreg/serviceability/sa/TestIntConstant.java	Wed Mar 28 11:38:47 2018 +0200
+++ b/test/hotspot/jtreg/serviceability/sa/TestIntConstant.java	Wed Mar 28 11:38:47 2018 +0200
@@ -110,7 +110,7 @@
             // with names and the values derived from enums and #define preprocessor
             // macros in hotspot.
             String[] defaultOutputStrings =
-                {"CollectedHeap::G1 3",
+                {"CollectedHeap::G1 4",
                  "RUNNABLE 2",
                  "Deoptimization::Reason_class_check 4",
                  "InstanceKlass::_misc_is_anonymous 32",