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 #ifndef SHARE_VM_OPTO_REPLACEDNODES_HPP
  26 #define SHARE_VM_OPTO_REPLACEDNODES_HPP
  27 
  28 #include "opto/connode.hpp"
  29 
  30 // During parsing, when a node is "improved",
  31 // GraphKit::replace_in_map() is called to update the current map so
  32 // that the improved node is used from that point
  33 // on. GraphKit::replace_in_map() doesn't operate on the callers maps
  34 // and so some optimization opportunities may be lost. The
  35 // ReplacedNodes class addresses that problem.
  36 //
  37 // A ReplacedNodes object is a list of pair of nodes. Every
  38 // SafePointNode carries a ReplacedNodes object. Every time
  39 // GraphKit::replace_in_map() is called, a new pair of nodes is pushed
  40 // on the list of replaced nodes. When control flow paths merge, their
  41 // replaced nodes are also merged. When parsing exits a method to
  42 // return to a caller, the replaced nodes on the exit path are used to
  43 // update the caller's map.
  44 class ReplacedNodes {
  45  private:
  46   class ReplacedNode {
  47   private:
  48     Node* _initial;
  49     Node* _improved;
  50   public:
  51     ReplacedNode() : _initial(NULL), _improved(NULL) {}
  52     ReplacedNode(Node* initial, Node* improved) : _initial(initial), _improved(improved) {}
  53     Node* initial() const  { return _initial; }
  54     Node* improved() const { return _improved; }
  55 
  56     bool operator==(const ReplacedNode& other) {
  57       return _initial == other._initial && _improved == other._improved;
  58     }
  59   };
  60   GrowableArray<ReplacedNode>* _replaced_nodes;
  61 
  62   void allocate_if_necessary();
  63   bool has_node(const ReplacedNode& r) const;
  64   bool has_target_node(Node* n) const;
  65 
  66  public:
  67   ReplacedNodes()
  68     : _replaced_nodes(NULL) {}
  69 
  70   void clone();
  71   void record(Node* initial, Node* improved);
  72   void transfer_from(const ReplacedNodes& other, uint idx);
  73   void reset();
  74   void apply(Node* n, uint idx);
  75   void merge_with(const ReplacedNodes& other);
  76   bool is_empty() const;
  77   void dump(outputStream *st) const;
  78   void apply(Compile* C, Node* ctl);
  79 };
  80 
  81 #endif // SHARE_VM_OPTO_REPLACEDNODES_HPP