8317975: [JVMCI] assert(pointee != nullptr) failed: invariant

Reviewed-by: never, thartmann

Author: Doug Simon

src/hotspot/share/jvmci/jvmciCompilerToVM.cpp

@@ -2436,6 +2436,16 @@ C2V_VMENTRY_0(jint, arrayIndexScale, (JNIEnv* env, jobject, jchar type_char))
   return type2aelembytes(type);
 C2V_END
 
+C2V_VMENTRY(void, clearOopHandle, (JNIEnv* env, jobject, jlong oop_handle))
+  if (oop_handle == 0L) {
+    JVMCI_THROW(NullPointerException);
+  }
+  // Assert before nulling out, for better debugging.
+  assert(JVMCIRuntime::is_oop_handle(oop_handle), "precondition");
+  oop* oop_ptr = (oop*) oop_handle;
+  NativeAccess<>::oop_store(oop_ptr, (oop) nullptr);
+C2V_END
+
 C2V_VMENTRY(void, releaseClearedOopHandles, (JNIEnv* env, jobject))
   JVMCIENV->runtime()->release_cleared_oop_handles();
 C2V_END
@@ -3260,6 +3270,7 @@ JNINativeMethod CompilerToVM::methods[] = {
   {CC "readArrayElement",                             CC "(" OBJECTCONSTANT "I)Ljava/lang/Object;",                                         FN_PTR(readArrayElement)},
   {CC "arrayBaseOffset",                              CC "(C)I",                                                                            FN_PTR(arrayBaseOffset)},
   {CC "arrayIndexScale",                              CC "(C)I",                                                                            FN_PTR(arrayIndexScale)},
+  {CC "clearOopHandle",                               CC "(J)V",                                                                            FN_PTR(clearOopHandle)},
   {CC "releaseClearedOopHandles",                     CC "()V",                                                                             FN_PTR(releaseClearedOopHandles)},
   {CC "registerNativeMethods",                        CC "(" CLASS ")[J",                                                                   FN_PTR(registerNativeMethods)},
   {CC "isCurrentThreadAttached",                      CC "()Z",                                                                             FN_PTR(isCurrentThreadAttached)},

src/hotspot/share/jvmci/jvmciRuntime.cpp

@@ -887,6 +887,13 @@ jlong JVMCIRuntime::make_oop_handle(const Handle& obj) {
   return reinterpret_cast<jlong>(ptr);
 }
 
+#ifdef ASSERT
+bool JVMCIRuntime::is_oop_handle(jlong handle) {
+  const oop* ptr = (oop*) handle;
+  return object_handles()->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY;
+}
+#endif
+
 int JVMCIRuntime::release_and_clear_oop_handles() {
   guarantee(_num_attached_threads == cannot_be_attached, "only call during JVMCI runtime shutdown");
   int released = release_cleared_oop_handles();

src/hotspot/share/jvmci/jvmciRuntime.hpp

@@ -317,11 +317,12 @@ class JVMCIRuntime: public CHeapObj<mtJVMCI> {
   // used when creating an IndirectHotSpotObjectConstantImpl in the
   // shared library JavaVM.
   jlong make_oop_handle(const Handle& obj);
+#ifdef ASSERT
+  static bool is_oop_handle(jlong handle);
+#endif
 
   // Releases all the non-null entries in _oop_handles whose referent is null.
   // Returns the number of handles released by this call.
-  // The method also resets _last_found_oop_handle_index to -1
-  // and _null_oop_handles to 0.
   int release_cleared_oop_handles();
 
   // Allocation and management of metadata handles.

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/CompilerToVM.java

@@ -1300,6 +1300,11 @@ boolean isTrustedForIntrinsics(HotSpotResolvedObjectTypeImpl klass) {
 
     native boolean isTrustedForIntrinsics(HotSpotResolvedObjectTypeImpl klass, long klassPointer);
 
+    /**
+     * Clears the oop handle in {@code handle}.
+     */
+    native void clearOopHandle(long handle);
+
     /**
      * Releases all oop handles whose referent is null.
      */

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/IndirectHotSpotObjectConstantImpl.java

@@ -155,10 +155,11 @@ void clear(Object scopeDescription) {
 
     /**
      * Sets the referent of {@code handle} to 0 so that it will be reclaimed when calling
-     * {@link CompilerToVM#releaseClearedOopHandles}.
+     * {@link CompilerToVM#releaseClearedOopHandles}. This must be done with a VM call so
+     * that the JNI handle is cleared at a safepoint.
      */
     static void clearHandle(long handle) {
-        UNSAFE.putLong(handle, 0);
+        runtime().compilerToVm.clearOopHandle(handle);
     }
 
     @Override