text: // Copyright 2020 The XLS Authors
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //      http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  // Dead Code Elimination.
  //
  #ifndef XLS_PASSES_DCE_PASS_H_
  #define XLS_PASSES_DCE_PASS_H_
  
  #include "absl/status/statusor.h"
  #include "xls/ir/function.h"
  #include "xls/passes/passes.h"
  
  namespace xls {
  
  // class DeadCodeEliminationPass iterates up from a functions result
  // nodes and marks all visited node. After that, all unvisited nodes
  // are considered dead.
  class DeadCodeEliminationPass : public FunctionBasePass {
   public:
    DeadCodeEliminationPass()
        : FunctionBasePass("dce", "Dead Code Elimination") {}
    ~DeadCodeEliminationPass() override {}
  
   protected:
    // Iterate all nodes, mark and eliminate the unvisited nodes.
    absl::StatusOr<bool> RunOnFunctionBaseInternal(
        FunctionBase* f, const PassOptions& options,
        PassResults* results) const override;
  };
  
  }  // namespace xls
  
  #endif  // XLS_PASSES_DCE_PASS_H_
  