sources/third_party/shaderc/third_party/spirv-tools/source/opt/compact_ids_pass.cpp

// 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 "compact_ids_pass.h"

#include <cassert>
#include <unordered_map>

namespace spvtools {
namespace opt {

using ir::Instruction;
using ir::Operand;

Pass::Status CompactIdsPass::Process(ir::Module* module) {
  bool modified = false;
  std::unordered_map<uint32_t, uint32_t> result_id_mapping;

  module->ForEachInst([&result_id_mapping, &modified] (Instruction* inst) {
    auto operand = inst->begin();
    while (operand != inst->end()) {
      if (spvIsIdType(operand->type)) {
        assert(operand->words.size() == 1);
        uint32_t& id = operand->words[0];
        auto it = result_id_mapping.find(id);
        if (it == result_id_mapping.end()) {
          const uint32_t new_id =
              static_cast<uint32_t>(result_id_mapping.size()) + 1;
          const auto insertion_result = result_id_mapping.emplace(id, new_id);
          it = insertion_result.first;
          assert(insertion_result.second);
        }
        if (id != it->second) {
          modified = true;
          id = it->second;
        }
      }
      ++operand;
    }
  }, true);

  return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange;
}

}  // namespace opt
}  // namespace spvtools