[GR-45212] Missing barriers in CompilerToVM.readFieldValue for Reference.referent

PullRequest: labsjdk-ce-17/110

Author: tkrodriguez

src/hotspot/share/jvmci/jvmciCompilerToVM.cpp

@@ -2097,14 +2097,14 @@ static jobject read_field_value(Handle obj, long displacement, jchar type_char,
   // folding Unsafe.get* methods with volatile semantics.
 
   switch (basic_type) {
-    case T_BOOLEAN: value = obj->bool_field_acquire(displacement);  break;
-    case T_BYTE:    value = obj->byte_field_acquire(displacement);  break;
-    case T_SHORT:   value = obj->short_field_acquire(displacement); break;
-    case T_CHAR:    value = obj->char_field_acquire(displacement);  break;
+    case T_BOOLEAN: value = HeapAccess<MO_SEQ_CST>::load(obj->field_addr_of_type<jboolean>(displacement)); break;
+    case T_BYTE:    value = HeapAccess<MO_SEQ_CST>::load(obj->field_addr_of_type<jbyte>(displacement));    break;
+    case T_SHORT:   value = HeapAccess<MO_SEQ_CST>::load(obj->field_addr_of_type<jshort>(displacement));   break;
+    case T_CHAR:    value = HeapAccess<MO_SEQ_CST>::load(obj->field_addr_of_type<jchar>(displacement));    break;
     case T_FLOAT:
-    case T_INT:     value = obj->int_field_acquire(displacement);   break;
+    case T_INT:     value = HeapAccess<MO_SEQ_CST>::load(obj->field_addr_of_type<jint>(displacement));     break;
     case T_DOUBLE:
-    case T_LONG:    value = obj->long_field_acquire(displacement);  break;
+    case T_LONG:    value = HeapAccess<MO_SEQ_CST>::load(obj->field_addr_of_type<jlong>(displacement));    break;
 
     case T_OBJECT: {
       if (displacement == java_lang_Class::component_mirror_offset() && java_lang_Class::is_instance(obj()) &&
@@ -2114,7 +2114,9 @@ static jobject read_field_value(Handle obj, long displacement, jchar type_char,
         return JVMCIENV->get_jobject(JVMCIENV->get_JavaConstant_NULL_POINTER());
       }
 
-      oop value = obj->obj_field_acquire(displacement);
+      // Perform the read including any barriers required to make the reference strongly reachable
+      // since it will be wrapped as a JavaConstant.
+      oop value = obj->obj_field_access<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>(displacement);
 
       if (value == nullptr) {
         return JVMCIENV->get_jobject(JVMCIENV->get_JavaConstant_NULL_POINTER());

src/hotspot/share/jvmci/jvmciRuntime.cpp

@@ -941,7 +941,9 @@ int JVMCIRuntime::release_cleared_oop_handles() {
       // Example: to_release: 2
 
       // Bulk release the handles with a null referent
+    if (to_release != 0) {
       object_handles()->release(_oop_handles.adr_at(num_alive), to_release);
+    }
 
       // Truncate oop handles to only those with a non-null referent
       JVMCI_event_1("compacted oop handles in JVMCI runtime %d from %d to %d", _id, _oop_handles.length(), num_alive);

src/hotspot/share/oops/oop.hpp

@@ -117,6 +117,10 @@ class oopDesc {
   // field addresses in oop
   inline void* field_addr(int offset) const;
 
+  // Backport of templating version of field_addr
+  template<typename T>
+  inline T* field_addr_of_type(int offset) const;
+
   // Need this as public for garbage collection.
   template <class T> inline T* obj_field_addr(int offset) const;
 

src/hotspot/share/oops/oop.inline.hpp

@@ -211,6 +211,9 @@ void*    oopDesc::field_addr(int offset)     const { return reinterpret_cast<voi
 template <class T>
 T*       oopDesc::obj_field_addr(int offset) const { return (T*) field_addr(offset); }
 
+template<typename T>
+T*       oopDesc::field_addr_of_type(int offset)     const { return reinterpret_cast<T*>(cast_from_oop<intptr_t>(as_oop()) + offset); }
+
 template <typename T>
 size_t   oopDesc::field_offset(T* p) const { return pointer_delta((void*)p, (void*)this, 1); }