8004318: JEP-171: Support Unsafe fences intrinsics

Summary: Add three memory-ordering intrinsics to the sun.misc.Unsafe class.
Reviewed-by: twisti, kvn
Contributed-by: NAleksey Shipilev <aleksey.shipilev@oracle.com>

hotspot/src/share/vm/c1/c1_GraphBuilder.cpp

@@ -3442,6 +3442,11 @@ bool GraphBuilder::try_inline_intrinsics(ciMethod* callee) {
       preserves_state = true;
       break;
 
+    case vmIntrinsics::_loadFence :
+    case vmIntrinsics::_storeFence:
+    case vmIntrinsics::_fullFence :
+      break;
+
     default                       : return false; // do not inline
   }
   // create intrinsic node

hotspot/src/share/vm/c1/c1_LIRGenerator.cpp

@@ -2977,6 +2977,16 @@ void LIRGenerator::do_Intrinsic(Intrinsic* x) {
     do_CompareAndSwap(x, longType);
     break;
 
+  case vmIntrinsics::_loadFence :
+    if (os::is_MP()) __ membar_acquire();
+    break;
+  case vmIntrinsics::_storeFence:
+    if (os::is_MP()) __ membar_release();
+    break;
+  case vmIntrinsics::_fullFence :
+    if (os::is_MP()) __ membar();
+    break;
+
   case vmIntrinsics::_Reference_get:
     do_Reference_get(x);
     break;

hotspot/src/share/vm/classfile/vmSymbols.hpp

@@ -756,6 +756,15 @@
   do_intrinsic(_unpark,                   sun_misc_Unsafe,        unpark_name, unpark_signature,                 F_RN)  \
    do_name(     unpark_name,                                     "unpark")                                              \
    do_alias(    unpark_signature,                               /*(LObject;)V*/ object_void_signature)                  \
+  do_intrinsic(_loadFence,                sun_misc_Unsafe,        loadFence_name, loadFence_signature,           F_RN)  \
+   do_name(     loadFence_name,                                  "loadFence")                                           \
+   do_alias(    loadFence_signature,                              void_method_signature)                                \
+  do_intrinsic(_storeFence,               sun_misc_Unsafe,        storeFence_name, storeFence_signature,         F_RN)  \
+   do_name(     storeFence_name,                                 "storeFence")                                          \
+   do_alias(    storeFence_signature,                             void_method_signature)                                \
+  do_intrinsic(_fullFence,                sun_misc_Unsafe,        fullFence_name, fullFence_signature,           F_RN)  \
+   do_name(     fullFence_name,                                  "fullFence")                                           \
+   do_alias(    fullFence_signature,                              void_method_signature)                                \
                                                                                                                         \
   /* unsafe memory references (there are a lot of them...) */                                                           \
   do_signature(getObject_signature,       "(Ljava/lang/Object;J)Ljava/lang/Object;")                                    \

hotspot/src/share/vm/opto/library_call.cpp

@@ -282,6 +282,7 @@ class LibraryCallKit : public GraphKit {
   typedef enum { LS_xadd, LS_xchg, LS_cmpxchg } LoadStoreKind;
   bool inline_unsafe_load_store(BasicType type,  LoadStoreKind kind);
   bool inline_unsafe_ordered_store(BasicType type);
+  bool inline_unsafe_fence(vmIntrinsics::ID id);
   bool inline_fp_conversions(vmIntrinsics::ID id);
   bool inline_number_methods(vmIntrinsics::ID id);
   bool inline_reference_get();
@@ -334,6 +335,9 @@ CallGenerator* Compile::make_vm_intrinsic(ciMethod* m, bool is_virtual) {
     case vmIntrinsics::_getAndSetInt:
     case vmIntrinsics::_getAndSetLong:
     case vmIntrinsics::_getAndSetObject:
+    case vmIntrinsics::_loadFence:
+    case vmIntrinsics::_storeFence:
+    case vmIntrinsics::_fullFence:
       break;  // InlineNatives does not control String.compareTo
     case vmIntrinsics::_Reference_get:
       break;  // InlineNatives does not control Reference.get
@@ -732,6 +736,10 @@ bool LibraryCallKit::try_to_inline() {
   case vmIntrinsics::_getAndSetLong:            return inline_unsafe_load_store(T_LONG,   LS_xchg);
   case vmIntrinsics::_getAndSetObject:          return inline_unsafe_load_store(T_OBJECT, LS_xchg);
 
+  case vmIntrinsics::_loadFence:
+  case vmIntrinsics::_storeFence:
+  case vmIntrinsics::_fullFence:                return inline_unsafe_fence(intrinsic_id());
+
   case vmIntrinsics::_currentThread:            return inline_native_currentThread();
   case vmIntrinsics::_isInterrupted:            return inline_native_isInterrupted();
 
@@ -2840,6 +2848,26 @@ bool LibraryCallKit::inline_unsafe_ordered_store(BasicType type) {
   return true;
 }
 
+bool LibraryCallKit::inline_unsafe_fence(vmIntrinsics::ID id) {
+  // Regardless of form, don't allow previous ld/st to move down,
+  // then issue acquire, release, or volatile mem_bar.
+  insert_mem_bar(Op_MemBarCPUOrder);
+  switch(id) {
+    case vmIntrinsics::_loadFence:
+      insert_mem_bar(Op_MemBarAcquire);
+      return true;
+    case vmIntrinsics::_storeFence:
+      insert_mem_bar(Op_MemBarRelease);
+      return true;
+    case vmIntrinsics::_fullFence:
+      insert_mem_bar(Op_MemBarVolatile);
+      return true;
+    default:
+      fatal_unexpected_iid(id);
+      return false;
+  }
+}
+
 //----------------------------inline_unsafe_allocate---------------------------
 // public native Object sun.mics.Unsafe.allocateInstance(Class<?> cls);
 bool LibraryCallKit::inline_unsafe_allocate() {

hotspot/src/share/vm/prims/unsafe.cpp

@@ -468,6 +468,21 @@ UNSAFE_ENTRY(void, Unsafe_SetOrderedLong(JNIEnv *env, jobject unsafe, jobject ob
 #endif
 UNSAFE_END
 
+UNSAFE_ENTRY(void, Unsafe_LoadFence(JNIEnv *env, jobject unsafe))
+  UnsafeWrapper("Unsafe_LoadFence");
+  OrderAccess::acquire();
+UNSAFE_END
+
+UNSAFE_ENTRY(void, Unsafe_StoreFence(JNIEnv *env, jobject unsafe))
+  UnsafeWrapper("Unsafe_StoreFence");
+  OrderAccess::release();
+UNSAFE_END
+
+UNSAFE_ENTRY(void, Unsafe_FullFence(JNIEnv *env, jobject unsafe))
+  UnsafeWrapper("Unsafe_FullFence");
+  OrderAccess::fence();
+UNSAFE_END
+
 ////// Data in the C heap.
 
 // Note:  These do not throw NullPointerException for bad pointers.
@@ -1550,6 +1565,9 @@ static JNINativeMethod methods[] = {
     {CC"putOrderedObject",   CC"("OBJ"J"OBJ")V",         FN_PTR(Unsafe_SetOrderedObject)},
     {CC"putOrderedInt",      CC"("OBJ"JI)V",             FN_PTR(Unsafe_SetOrderedInt)},
     {CC"putOrderedLong",     CC"("OBJ"JJ)V",             FN_PTR(Unsafe_SetOrderedLong)},
+    {CC"loadFence",          CC"()V",                    FN_PTR(Unsafe_LoadFence)},
+    {CC"storeFence",         CC"()V",                    FN_PTR(Unsafe_StoreFence)},
+    {CC"fullFence",          CC"()V",                    FN_PTR(Unsafe_FullFence)},
     {CC"park",               CC"(ZJ)V",                  FN_PTR(Unsafe_Park)},
     {CC"unpark",             CC"("OBJ")V",               FN_PTR(Unsafe_Unpark)}