/*
 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "gc/shared/barrierSetAssembler.hpp"
#include "memory/universe.hpp"
#include "utilities/globalDefinitions.hpp"

bool BarrierSetAssembler::needs_explicit_null_check(intptr_t offset) {
  // Exception handler checks the nmethod's implicit null checks table
  // only when this method returns false.
#ifdef _LP64
  if (UseCompressedOops && Universe::narrow_oop_base() != NULL) {
    assert (Universe::heap() != NULL, "java heap should be initialized");
    // The first page after heap_base is unmapped and
    // the 'offset' is equal to [heap_base + offset] for
    // narrow oop implicit null checks.
    uintptr_t base = (uintptr_t)Universe::narrow_oop_base();
    if ((uintptr_t)offset >= base) {
      // Normalize offset for the next check.
      offset = (intptr_t)(pointer_delta((void*)offset, (void*)base, 1));
    }
  }
#endif
  return offset < 0 || os::vm_page_size() <= offset;
}