// Copyright (c) 2018 The Khronos Group Inc.

// Copyright (c) 2018 Valve Corporation

// Copyright (c) 2018 LunarG 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_DEAD_INSERT_ELIM_PASS_H_

#define SOURCE_OPT_DEAD_INSERT_ELIM_PASS_H_

#include <algorithm>

#include <map>

#include <unordered_map>

#include <unordered_set>

#include <utility>

#include <vector>

#include "source/opt/basic_block.h"

#include "source/opt/def_use_manager.h"

#include "source/opt/ir_context.h"

#include "source/opt/mem_pass.h"

#include "source/opt/module.h"

namespace spvtools {

namespace opt {

// See optimizer.hpp for documentation.

class DeadInsertElimPass : public MemPass {

 public:

  DeadInsertElimPass() = default;

  const char* name() const override { return "eliminate-dead-inserts"; }

  Status Process() override;

  IRContext::Analysis GetPreservedAnalyses() override {

    return IRContext::kAnalysisDefUse |

           IRContext::kAnalysisInstrToBlockMapping |

           IRContext::kAnalysisDecorations | IRContext::kAnalysisCombinators |

           IRContext::kAnalysisCFG | IRContext::kAnalysisDominatorAnalysis |

           IRContext::kAnalysisNameMap | IRContext::kAnalysisConstants |

           IRContext::kAnalysisTypes;

  }

 private:

  // Return the number of subcomponents in the composite type |typeId|.

  // Return 0 if not a composite type or number of components is not a

  // 32-bit constant.

  uint32_t NumComponents(Instruction* typeInst);

  // Mark all inserts in instruction chain ending at |insertChain| with

  // indices that intersect with extract indices |extIndices| starting with

  // index at |extOffset|. Chains are composed solely of Inserts and Phis.

  // Mark all inserts in chain if |extIndices| is nullptr.

  void MarkInsertChain(Instruction* insertChain,

                       std::vector<uint32_t>* extIndices, uint32_t extOffset,

                       std::unordered_set<uint32_t>* visited_phis);

  // Perform EliminateDeadInsertsOnePass(|func|) until no modification is

  // made. Return true if modified.

  bool EliminateDeadInserts(Function* func);

  // DCE all dead struct, matrix and vector inserts in |func|. An insert is

  // dead if the value it inserts is never used. Replace any reference to the

  // insert with its original composite. Return true if modified. Dead inserts

  // in dependence cycles are not currently eliminated. Dead inserts into

  // arrays are not currently eliminated.

  bool EliminateDeadInsertsOnePass(Function* func);

  // Return true if all extensions in this module are allowed by this pass.

  bool AllExtensionsSupported() const;

  // Live inserts

  std::unordered_set<uint32_t> liveInserts_;

  // Visited phis as insert chain is traversed; used to avoid infinite loop

  std::unordered_map<uint32_t, bool> visitedPhis_;

};

}  // namespace opt

}  // namespace spvtools

#endif  // SOURCE_OPT_DEAD_INSERT_ELIM_PASS_H_