JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
 * Copyright 2007, 2008, 2010 Red Hat, Inc.
 * 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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#ifndef CPU_ZERO_JAVAFRAMEANCHOR_ZERO_HPP
#define CPU_ZERO_JAVAFRAMEANCHOR_ZERO_HPP

 private:
  ZeroFrame* volatile _last_Java_fp;

 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)
  // Note that whenever _last_Java_sp != NULL other anchor fields
  // must be valid.  The profiler apparently depends on this.

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

  void copy(JavaFrameAnchor* src) {
    set(src->_last_Java_sp, src->_last_Java_pc, src->_last_Java_fp);
  }

  void set(intptr_t* sp, address pc, ZeroFrame* fp) {
    // 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 != sp)
      _last_Java_sp = NULL;

    _last_Java_fp = fp;
    _last_Java_pc = pc;
    // Must be last so profiler will always see valid frame if
    // has_last_frame() is true
    _last_Java_sp = sp;
  }

  bool walkable() {
    return true;
  }

  void make_walkable(JavaThread* thread) {
    // nothing to do
  }

  intptr_t* last_Java_sp() const {

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