Variant 2: Only final-field like semantics for stable inits

Author: shipilev

src/hotspot/share/c1/c1_LIRGenerator.cpp

@@ -1677,18 +1677,7 @@ void LIRGenerator::do_StoreField(StoreField* x) {
 
   DecoratorSet decorators = IN_HEAP;
   if (is_volatile) {
-    // Volatile access, full SC.
     decorators |= MO_SEQ_CST;
-  } else if (x->field()->is_stable() && !x->field()->is_final() &&
-             is_reference_type(field_type)) {
-    // For reference @Stable fields, make sure we publish the contents
-    // safely. We need this to make sure compilers see a proper value when
-    // constant folding the access. Final @Stable fields are already
-    // handled in constructors.
-    decorators |= MO_RELEASE;
-  } else {
-    // Everything else is unordered.
-    decorators |= MO_UNORDERED;
   }
   if (needs_patching) {
     decorators |= C1_NEEDS_PATCHING;

src/hotspot/share/ci/ciInstance.cpp

@@ -78,11 +78,7 @@ ciConstant ciInstance::field_value_impl(BasicType field_btype, int offset) {
     case T_LONG:    value = ciConstant(obj->long_field(offset)); break;
     case T_OBJECT:  // fall through
     case T_ARRAY: {
-      // In case we are reading the constant off a reference @Stable field,
-      // we need to match the releasing store with this acquire. There is no easy
-      // way to know this from the offset, but it should not hurt to ask this for
-      // all reference fields.
-      oop o = obj->obj_field_acquire(offset);
+      oop o = obj->obj_field(offset);
 
       // A field will be "constant" if it is known always to be
       // a non-null reference to an instance of a particular class,

src/hotspot/share/opto/parse3.cpp

@@ -209,21 +209,7 @@ void Parse::do_put_xxx(Node* obj, ciField* field, bool is_field) {
   Node* val = type2size[bt] == 1 ? pop() : pop_pair();
 
   DecoratorSet decorators = IN_HEAP;
-
-  if (is_vol) {
-    // Volatile access, full SC.
-    decorators |= MO_SEQ_CST;
-  } else if (field->is_stable() && !field->is_final() &&
-             is_reference_type(field->layout_type())) {
-    // For reference @Stable fields, make sure we publish the contents
-    // safely. We need this to make sure compilers see a proper value when
-    // constant folding the access. Final @Stable fields are already
-    // handled in constructors.
-    decorators |= MO_RELEASE;
-  } else {
-    // Everything else is unordered.
-    decorators |= MO_UNORDERED;
-  }
+  decorators |= is_vol ? MO_SEQ_CST : MO_UNORDERED;
 
   bool is_obj = is_reference_type(bt);
 

test/hotspot/jtreg/compiler/c2/irTests/stable/StablePrimArrayTest.java

@@ -153,16 +153,16 @@ static Carrier testConstructorFullInit() {
     }
 
     @Test
-    @IR(counts = { IRNode.MEMBAR_RELEASE, "1" })
+    @IR(failOn = { IRNode.MEMBAR })
     static void testMethodEmptyInit() {
-        // Reference inits have release membars.
+        // Reference inits do not have membars.
         INIT_EMPTY_CARRIER.initEmpty();
     }
 
     @Test
-    @IR(counts = { IRNode.MEMBAR_RELEASE, "1" })
+    @IR(failOn = { IRNode.MEMBAR })
     static void testMethodFullInit() {
-        // Reference inits have release membars.
+        // Reference inits do not have membars.
         INIT_FULL_CARRIER.initFull();
     }
 

test/hotspot/jtreg/compiler/c2/irTests/stable/StableRefArrayTest.java

@@ -162,16 +162,16 @@ static Carrier testConstructorFullInit() {
     }
 
     @Test
-    @IR(counts = { IRNode.MEMBAR_RELEASE, "1" })
+    @IR(failOn = { IRNode.MEMBAR })
     static void testMethodEmptyInit() {
-        // Reference inits have release membars.
+        // Reference inits do not have membars.
         INIT_EMPTY_CARRIER.initEmpty();
     }
 
     @Test
-    @IR(counts = { IRNode.MEMBAR_RELEASE, "1" })
+    @IR(failOn = { IRNode.MEMBAR })
     static void testMethodFullInit() {
-        // Reference inits have release membars.
+        // Reference inits do not have membars.
         INIT_FULL_CARRIER.initFull();
     }
 

test/hotspot/jtreg/compiler/c2/irTests/stable/StableRefPlainTest.java

@@ -108,9 +108,9 @@ static Carrier testConstructorFullInit() {
     }
 
     @Test
-    @IR(counts = { IRNode.MEMBAR_RELEASE, "1" })
+    @IR(failOn = { IRNode.MEMBAR })
     static void testMethodInit() {
-        // Reference inits have release membars.
+        // Reference inits do not have membars.
         INIT_CARRIER.init();
     }