// 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.

#include "source/opt/redundancy_elimination.h"

#include "source/opt/value_number_table.h"

namespace spvtools {

namespace opt {

Pass::Status RedundancyEliminationPass::Process() {

  bool modified = false;

  ValueNumberTable vnTable(context());

  for (auto& func : *get_module()) {

    if (func.IsDeclaration()) {

      continue;

    }

    // Build the dominator tree for this function. It is how the code is

    // traversed.

    DominatorTree& dom_tree =

        context()->GetDominatorAnalysis(&func)->GetDomTree();

    // Keeps track of all ids that contain a given value number. We keep

    // track of multiple values because they could have the same value, but

    // different decorations.

    std::map<uint32_t, uint32_t> value_to_ids;

    if (EliminateRedundanciesFrom(dom_tree.GetRoot(), vnTable, value_to_ids)) {

      modified = true;

    }

  }

  return (modified ? Status::SuccessWithChange : Status::SuccessWithoutChange);

}

bool RedundancyEliminationPass::EliminateRedundanciesFrom(

    DominatorTreeNode* bb, const ValueNumberTable& vnTable,

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

  bool modified = EliminateRedundanciesInBB(bb->bb_, vnTable, &value_to_ids);

  for (auto dominated_bb : bb->children_) {

    modified |= EliminateRedundanciesFrom(dominated_bb, vnTable, value_to_ids);

  }

  return modified;

}

}  // namespace opt

}  // namespace spvtools