JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2014, 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 "precompiled.hpp"
#include "opto/opaquenode.hpp"
#include "opto/phaseX.hpp"

//=============================================================================
// Do not allow value-numbering
uint Opaque1Node::hash() const { return NO_HASH; }
bool Opaque1Node::cmp( const Node &n ) const {
  return (&n == this);          // Always fail except on self
}

//------------------------------Identity---------------------------------------
// If _major_progress, then more loop optimizations follow.  Do NOT remove
// the opaque Node until no more loop ops can happen.  Note the timing of
// _major_progress; it's set in the major loop optimizations THEN comes the
// call to IterGVN and any chance of hitting this code.  Hence there's no
// phase-ordering problem with stripping Opaque1 in IGVN followed by some
// more loop optimizations that require it.
Node* Opaque1Node::Identity(PhaseGVN* phase) {
  return phase->C->major_progress() ? this : in(1);
}

//=============================================================================
// A node to prevent unwanted optimizations.  Allows constant folding.  Stops
// value-numbering, most Ideal calls or Identity functions.  This Node is
// specifically designed to prevent the pre-increment value of a loop trip
// counter from being live out of the bottom of the loop (hence causing the
// pre- and post-increment values both being live and thus requiring an extra
// temp register and an extra move).  If we "accidentally" optimize through
// this kind of a Node, we'll get slightly pessimal, but correct, code.  Thus
// it's OK to be slightly sloppy on optimizations here.

// Do not allow value-numbering
uint Opaque2Node::hash() const { return NO_HASH; }
bool Opaque2Node::cmp( const Node &n ) const {
  return (&n == this);          // Always fail except on self
}

const Type* Opaque4Node::Value(PhaseGVN* phase) const {
  return phase->type(in(1));
}

//=============================================================================

uint ProfileBooleanNode::hash() const { return NO_HASH; }
bool ProfileBooleanNode::cmp( const Node &n ) const {
  return (&n == this);
}


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