// Copyright (c) 2018 Google LLC

//

// 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/dominator_analysis.h"

#include <unordered_set>

#include "source/opt/ir_context.h"

namespace spvtools {

namespace opt {

BasicBlock* DominatorAnalysisBase::CommonDominator(BasicBlock* b1,

                                                   BasicBlock* b2) const {

  if (!b1 || !b2) return nullptr;

  std::unordered_set<BasicBlock*> seen;

  BasicBlock* block = b1;

  while (block && seen.insert(block).second) {

    block = ImmediateDominator(block);

  }

  block = b2;

  while (block && !seen.count(block)) {

    block = ImmediateDominator(block);

  }

  return block;

}

bool DominatorAnalysisBase::Dominates(Instruction* a, Instruction* b) const {

  if (!a || !b) {

    return false;

  }

  if (a == b) {

    return true;

  }

  BasicBlock* bb_a = a->context()->get_instr_block(a);

  BasicBlock* bb_b = b->context()->get_instr_block(b);

  if (bb_a != bb_b) {

    return tree_.Dominates(bb_a, bb_b);

  }

  const Instruction* current = a;

  const Instruction* other = b;

  if (tree_.IsPostDominator()) {

    std::swap(current, other);

  }

  // We handle OpLabel instructions explicitly since they are not stored in the

  // instruction list.

  if (current->opcode() == spv::Op::OpLabel) {

    return true;

  }

  while ((current = current->NextNode())) {

    if (current == other) {

      return true;

    }

  }

  return false;

}

}  // namespace opt

}  // namespace spvtools