6626217: Fixed loader constraint array handling

Loader constraints track array elements, not arrays themselves.

Reviewed-by: dcubed, kevinw

hotspot/src/share/vm/ci/ciEnv.cpp

@@ -375,30 +375,6 @@ ciKlass* ciEnv::get_klass_by_name_impl(ciKlass* accessing_klass,
     return get_object(found_klass)->as_klass();
   }
 
-  // If we fail to find an array klass, look again for its element type.
-  // The element type may be available either locally or via constraints.
-  // In either case, if we can find the element type in the system dictionary,
-  // we must build an array type around it.  The CI requires array klasses
-  // to be loaded if their element klasses are loaded, except when memory
-  // is exhausted.
-  if (sym->byte_at(0) == '[' &&
-      (sym->byte_at(1) == '[' || sym->byte_at(1) == 'L')) {
-    // We have an unloaded array.
-    // Build it on the fly if the element class exists.
-    symbolOop elem_sym = oopFactory::new_symbol(sym->as_utf8()+1,
-                                                sym->utf8_length()-1,
-                                                KILL_COMPILE_ON_FATAL_(fail_type));
-    // Get element ciKlass recursively.
-    ciKlass* elem_klass =
-      get_klass_by_name_impl(accessing_klass,
-                             get_object(elem_sym)->as_symbol(),
-                             require_local);
-    if (elem_klass != NULL && elem_klass->is_loaded()) {
-      // Now make an array for it
-      return ciObjArrayKlass::make_impl(elem_klass);
-    }
-  }
-
   if (require_local)  return NULL;
   // Not yet loaded into the VM, or not governed by loader constraints.
   // Make a CI representative for it.

hotspot/src/share/vm/classfile/loaderConstraints.cpp

@@ -334,33 +334,6 @@ klassOop LoaderConstraintTable::find_constrained_klass(symbolHandle name,
   return NULL;
 }
 
-
-klassOop LoaderConstraintTable::find_constrained_elem_klass(symbolHandle name,
-                                                            symbolHandle elem_name,
-                                                            Handle loader,
-                                                            TRAPS) {
-  LoaderConstraintEntry *p = *(find_loader_constraint(name, loader));
-  if (p != NULL) {
-    assert(p->klass() == NULL, "Expecting null array klass");
-
-    // The array name has a constraint, but it will not have a class. Check
-    // each loader for an associated elem
-    for (int i = 0; i < p->num_loaders(); i++) {
-      Handle no_protection_domain;
-
-      klassOop k = SystemDictionary::find(elem_name, p->loader(i), no_protection_domain, THREAD);
-      if (k != NULL) {
-        // Return the first elem klass found.
-        return k;
-      }
-    }
-  }
-
-  // No constraints, or else no klass loaded yet.
-  return NULL;
-}
-
-
 void LoaderConstraintTable::ensure_loader_constraint_capacity(
                                                      LoaderConstraintEntry *p,
                                                     int nfree) {

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

@@ -66,9 +66,6 @@ public:
   //                                           bool is_method, TRAPS)
 
   klassOop find_constrained_klass(symbolHandle name, Handle loader);
-  klassOop find_constrained_elem_klass(symbolHandle name, symbolHandle elem_name,
-                                       Handle loader, TRAPS);
-
 
   // Class loader constraints
 

hotspot/src/share/vm/classfile/systemDictionary.cpp

@@ -2164,9 +2164,8 @@ klassOop SystemDictionary::find_constrained_instance_or_array_klass(
   // a loader constraint that would require this loader to return the
   // klass that is already loaded.
   if (FieldType::is_array(class_name())) {
-    // Array classes are hard because their klassOops are not kept in the
+    // For array classes, their klassOops are not kept in the
-    // constraint table. The array klass may be constrained, but the elem class
+    // constraint table. The element klassOops are.
-    // may not be.
     jint dimension;
     symbolOop object_key;
     BasicType t = FieldType::get_array_info(class_name(), &dimension,
@@ -2176,8 +2175,9 @@ klassOop SystemDictionary::find_constrained_instance_or_array_klass(
     } else {
       symbolHandle elem_name(THREAD, object_key);
       MutexLocker mu(SystemDictionary_lock, THREAD);
-      klass = constraints()->find_constrained_elem_klass(class_name, elem_name, class_loader, THREAD);
+      klass = constraints()->find_constrained_klass(elem_name, class_loader);
     }
+    // If element class already loaded, allocate array klass
     if (klass != NULL) {
       klass = Klass::cast(klass)->array_klass_or_null(dimension);
     }
@@ -2195,21 +2195,37 @@ bool SystemDictionary::add_loader_constraint(symbolHandle class_name,
                                              Handle class_loader1,
                                              Handle class_loader2,
                                              Thread* THREAD) {
-  unsigned int d_hash1 = dictionary()->compute_hash(class_name, class_loader1);
+  symbolHandle constraint_name;
+  if (!FieldType::is_array(class_name())) {
+    constraint_name = class_name;
+  } else {
+    // For array classes, their klassOops are not kept in the
+    // constraint table. The element classes are.
+    jint dimension;
+    symbolOop object_key;
+    BasicType t = FieldType::get_array_info(class_name(), &dimension,
+                                            &object_key, CHECK_(false));
+    // primitive types always pass
+    if (t != T_OBJECT) {
+      return true;
+    } else {
+      constraint_name = symbolHandle(THREAD, object_key);
+    }
+  }
+  unsigned int d_hash1 = dictionary()->compute_hash(constraint_name, class_loader1);
   int d_index1 = dictionary()->hash_to_index(d_hash1);
 
-  unsigned int d_hash2 = dictionary()->compute_hash(class_name, class_loader2);
+  unsigned int d_hash2 = dictionary()->compute_hash(constraint_name, class_loader2);
   int d_index2 = dictionary()->hash_to_index(d_hash2);
-
   {
   MutexLocker mu_s(SystemDictionary_lock, THREAD);
 
   // Better never do a GC while we're holding these oops
   No_Safepoint_Verifier nosafepoint;
 
-    klassOop klass1 = find_class(d_index1, d_hash1, class_name, class_loader1);
+  klassOop klass1 = find_class(d_index1, d_hash1, constraint_name, class_loader1);
-    klassOop klass2 = find_class(d_index2, d_hash2, class_name, class_loader2);
+  klassOop klass2 = find_class(d_index2, d_hash2, constraint_name, class_loader2);
-    return constraints()->add_entry(class_name, klass1, class_loader1,
+  return constraints()->add_entry(constraint_name, klass1, class_loader1,
                                   klass2, class_loader2);
   }
 }
@@ -2287,6 +2303,7 @@ symbolOop SystemDictionary::find_resolution_error(constantPoolHandle pool, int w
 // Returns the name of the type that failed a loader constraint check, or
 // NULL if no constraint failed. The returned C string needs cleaning up
 // with a ResourceMark in the caller.  No exception except OOME is thrown.
+// Arrays are not added to the loader constraint table, their elements are.
 char* SystemDictionary::check_signature_loaders(symbolHandle signature,
                                                Handle loader1, Handle loader2,
                                                bool is_method, TRAPS)  {