text: /*
   * Copyright (C) 2011, 2014 Apple Inc. All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
   * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
   * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
   */
  
  #pragma once
  
  #if ENABLE(DFG_JIT)
  
  #include "DFGCommon.h"
  
  namespace JSC { namespace DFG {
  
  class Graph;
  
  // Block-local common subexpression elimination. It uses clobberize() for heap
  // modeling, which is quite precise. This phase is known to produce big wins on
  // a few benchmarks, and is relatively cheap to run.
  //
  // Note that this phase also gets rid of Identity nodes, which means that it's
  // currently not an optional phase. Basically, DFG IR doesn't have use-lists,
  // so there is no instantaneous replaceAllUsesWith operation. Instead, you turn
  // a node into an Identity and wait for CSE to clean it up.
  bool performLocalCSE(Graph&);
  
  // Same, but global. Only works for SSA. This will find common subexpressions
  // both in the same block and in any block that dominates the current block. It
  // has no limits on how far it will look for load-elimination opportunities.
  bool performGlobalCSE(Graph&);
  
  } } // namespace JSC::DFG
  
  #endif // ENABLE(DFG_JIT)
  