/*

 * Copyright (c) 2004, 2010, 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.

 *

 */

#ifndef SHARE_VM_PRIMS_JNIFASTGETFIELD_HPP

#define SHARE_VM_PRIMS_JNIFASTGETFIELD_HPP

#include "memory/allocation.hpp"

#include "prims/jvm_misc.hpp"

// Basic logic of a fast version of jni_Get<Primitive>Field:

//

// (See safepoint.hpp for a description of _safepoint_counter)

//

// load _safepoint_counter into old_counter

// IF old_counter is odd THEN

//   a safepoint is going on, return jni_GetXXXField

// ELSE

//   load the primitive field value into result (speculatively)

//   load _safepoint_counter into new_counter

//   IF (old_counter == new_counter) THEN

//     no safepoint happened during the field access, return result

//   ELSE

//     a safepoint might have happened in-between, return jni_GetXXXField()

//   ENDIF

// ENDIF

//

// LoadLoad membars to maintain the load order may be necessary

// for some platforms.

//

// The fast versions don't check for pending suspension request.

// This is fine since it's totally read-only and doesn't create new race.

//

// There is a hypothetical safepoint counter wraparound. But it's not

// a practical concern.

class JNI_FastGetField : AllStatic {

 private:

  enum { LIST_CAPACITY = 40 };      // a conservative number for the number of

                                    // speculative loads on all the platforms

  static address speculative_load_pclist [];

  static address slowcase_entry_pclist   [];

  static int     count;

  static address generate_fast_get_int_field0(BasicType type);

  static address generate_fast_get_float_field0(BasicType type);

 public:

#if defined(_WINDOWS) && !defined(_WIN64)

  static GetBooleanField_t jni_fast_GetBooleanField_fp;

  static GetByteField_t    jni_fast_GetByteField_fp;

  static GetCharField_t    jni_fast_GetCharField_fp;

  static GetShortField_t   jni_fast_GetShortField_fp;

  static GetIntField_t     jni_fast_GetIntField_fp;

  static GetLongField_t    jni_fast_GetLongField_fp;

  static GetFloatField_t   jni_fast_GetFloatField_fp;

  static GetDoubleField_t  jni_fast_GetDoubleField_fp;

#endif

  static address generate_fast_get_boolean_field();

  static address generate_fast_get_byte_field();

  static address generate_fast_get_char_field();

  static address generate_fast_get_short_field();

  static address generate_fast_get_int_field();

  static address generate_fast_get_long_field();

  static address generate_fast_get_float_field();

  static address generate_fast_get_double_field();

  // If pc is in speculative_load_pclist, return the corresponding

  // slow case entry pc. Otherwise, return -1.

  // This is used by signal/exception handler to handle such case:

  // After an even safepoint counter is loaded and a fast field access

  // is about to begin, a GC kicks in and shrinks the heap. Then the

  // field access may fault. The signal/exception handler needs to

  // return to the slow case.

  //

  // The GC may decide to temporarily stuff some bad values into handles,

  // for example, for debugging purpose, in which case we need the mapping also.

  static address find_slowcase_pc(address pc);

};

#endif // SHARE_VM_PRIMS_JNIFASTGETFIELD_HPP