JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2008, 2019, 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
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 * questions.
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 */

#ifndef CPU_ARM_JAVAFRAMEANCHOR_ARM_HPP
#define CPU_ARM_JAVAFRAMEANCHOR_ARM_HPP

private:

  // FP value associated with _last_Java_sp:
  intptr_t* volatile        _last_Java_fp;           // pointer is volatile not what it points to

public:
  // Each arch must define reset, save, restore
  // These are used by objects that only care about:
  //  1 - initializing a new state (thread creation, javaCalls)
  //  2 - saving a current state (javaCalls)
  //  3 - restoring an old state (javaCalls)

  void clear(void) {
    // clearing _last_Java_sp must be first
    _last_Java_sp = NULL;
    // fence?
    _last_Java_fp = NULL;
    _last_Java_pc = NULL;
  }

  void copy(JavaFrameAnchor* src) {
    // In order to make sure the transition state is valid for "this"
    // We must clear _last_Java_sp before copying the rest of the new data
    //
    // Hack Alert: Temporary bugfix for 4717480/4721647
    // To act like previous version (pd_cache_state) don't NULL _last_Java_sp
    // unless the value is changing
    //
    if (_last_Java_sp != src->_last_Java_sp)
      _last_Java_sp = NULL;

    _last_Java_fp = src->_last_Java_fp;
    _last_Java_pc = src->_last_Java_pc;
    // Must be last so profiler will always see valid frame if has_last_frame() is true
    _last_Java_sp = src->_last_Java_sp;
  }

  // Always walkable
  bool walkable(void) { return true; }
  // Never any thing to do since we are always walkable and can find address of return addresses
  void make_walkable(JavaThread* thread) { }

  intptr_t* last_Java_sp(void) const             { return _last_Java_sp; }

  address last_Java_pc(void)                     { return _last_Java_pc; }

private:

  static ByteSize last_Java_fp_offset()          { return byte_offset_of(JavaFrameAnchor, _last_Java_fp); }

public:


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