// Copyright (c) 2017 Google Inc.

//

// 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.

#ifndef SOURCE_OPT_REDUNDANCY_ELIMINATION_H_

#define SOURCE_OPT_REDUNDANCY_ELIMINATION_H_

#include <map>

#include "source/opt/ir_context.h"

#include "source/opt/local_redundancy_elimination.h"

#include "source/opt/pass.h"

#include "source/opt/value_number_table.h"

namespace spvtools {

namespace opt {

// This pass implements total redundancy elimination.  This is the same as

// local redundancy elimination except it looks across basic block boundaries.

// An instruction, inst, is totally redundant if there is another instruction

// that dominates inst, and also computes the same value.

class RedundancyEliminationPass : public LocalRedundancyEliminationPass {

 public:

  const char* name() const override { return "redundancy-elimination"; }

  Status Process() override;

 protected:

  // Removes for all total redundancies in the function starting at |bb|.

  //

  // |vnTable| must have computed a value number for every result id defined

  // in the function containing |bb|.

  //

  // |value_to_ids| is a map from value number to ids.  If {vn, id} is in

  // |value_to_ids| then vn is the value number of id, and the definition of id

  // dominates |bb|.

  //

  // Returns true if at least one instruction is deleted.

  bool EliminateRedundanciesFrom(DominatorTreeNode* bb,

                                 const ValueNumberTable& vnTable,

                                 std::map<uint32_t, uint32_t> value_to_ids);

};

}  // namespace opt

}  // namespace spvtools

#endif  // SOURCE_OPT_REDUNDANCY_ELIMINATION_H_