8305404: Compile_lock not needed for InstanceKlass::implementor()

Reviewed-by: eosterlund, fparain

Author: coleenp

src/hotspot/share/ci/ciInstanceKlass.cpp

@@ -623,14 +623,14 @@ ciInstanceKlass* ciInstanceKlass::implementor() {
     } else {
       // Go into the VM to fetch the implementor.
       VM_ENTRY_MARK;
-      MutexLocker ml(Compile_lock);
-      Klass* k = get_instanceKlass()->implementor();
-      if (k != nullptr) {
-        if (k == get_instanceKlass()) {
+      InstanceKlass* ik = get_instanceKlass();
+      Klass* implk = ik->implementor();
+      if (implk != nullptr) {
+        if (implk == ik) {
           // More than one implementors. Use 'this' in this case.
           impl = this;
         } else {
-          impl = CURRENT_THREAD_ENV->get_instance_klass(k);
+          impl = CURRENT_THREAD_ENV->get_instance_klass(implk);
         }
       }
     }

src/hotspot/share/jvmci/jvmciCompilerToVM.cpp

@@ -450,12 +450,7 @@ C2V_VMENTRY_NULL(jobject, getImplementor, (JNIEnv* env, jobject, ARGUMENT_PAIR(k
         err_msg("Expected interface type, got %s", klass->external_name()));
   }
   InstanceKlass* iklass = InstanceKlass::cast(klass);
-  JVMCIKlassHandle handle(THREAD);
-  {
-    // Need Compile_lock around implementor()
-    MutexLocker locker(Compile_lock);
-    handle = iklass->implementor();
-  }
+  JVMCIKlassHandle handle(THREAD, iklass->implementor());
   JVMCIObject implementor = JVMCIENV->get_jvmci_type(handle, JVMCI_CHECK_NULL);
   return JVMCIENV->get_jobject(implementor);
 C2V_END