1 /*

     2  * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    24 

    25 #include "precompiled.hpp"

    26 #include "opto/opaquenode.hpp"

    27 #include "opto/phaseX.hpp"

    28 

    29 //=============================================================================

    30 // Do not allow value-numbering

    31 uint Opaque1Node::hash() const { return NO_HASH; }

    32 uint Opaque1Node::cmp( const Node &n ) const {

    33   return (&n == this);          // Always fail except on self

    34 }

    35 

    36 //------------------------------Identity---------------------------------------

    37 // If _major_progress, then more loop optimizations follow.  Do NOT remove

    38 // the opaque Node until no more loop ops can happen.  Note the timing of

    39 // _major_progress; it's set in the major loop optimizations THEN comes the

    40 // call to IterGVN and any chance of hitting this code.  Hence there's no

    41 // phase-ordering problem with stripping Opaque1 in IGVN followed by some

    42 // more loop optimizations that require it.

    43 Node *Opaque1Node::Identity( PhaseTransform *phase ) {

    44   return phase->C->major_progress() ? this : in(1);

    45 }

    46 

    47 //=============================================================================

    48 // A node to prevent unwanted optimizations.  Allows constant folding.  Stops

    49 // value-numbering, most Ideal calls or Identity functions.  This Node is

    50 // specifically designed to prevent the pre-increment value of a loop trip

    51 // counter from being live out of the bottom of the loop (hence causing the

    52 // pre- and post-increment values both being live and thus requiring an extra

    53 // temp register and an extra move).  If we "accidentally" optimize through

    54 // this kind of a Node, we'll get slightly pessimal, but correct, code.  Thus

    55 // it's OK to be slightly sloppy on optimizations here.

    56 

    57 // Do not allow value-numbering

    58 uint Opaque2Node::hash() const { return NO_HASH; }

    59 uint Opaque2Node::cmp( const Node &n ) const {

    60   return (&n == this);          // Always fail except on self

    61 }

    62 

    63