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 "source/opt/compact_ids_pass.h"

#include <cassert>
#include <unordered_map>

#include "source/opt/ir_context.h"

namespace spvtools {
namespace opt {
namespace {

// Returns the remapped id of |id| from |result_id_mapping|. If the remapped
// id does not exist, adds a new one to |result_id_mapping| and returns it.
uint32_t GetRemappedId(
    std::unordered_map<uint32_t, uint32_t>* result_id_mapping, uint32_t id) {
  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);
  }
  return it->second;
}

}  // namespace

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

  context()->module()->ForEachInst(
      [&result_id_mapping, &modified](Instruction* inst) {
        auto operand = inst->begin();
        while (operand != inst->end()) {
          const auto type = operand->type;
          if (spvIsIdType(type)) {
            assert(operand->words.size() == 1);
            uint32_t& id = operand->words[0];
            uint32_t new_id = GetRemappedId(&result_id_mapping, id);
            if (id != new_id) {
              modified = true;
              id = new_id;
              // Update data cached in the instruction object.
              if (type == SPV_OPERAND_TYPE_RESULT_ID) {
                inst->SetResultId(id);
              } else if (type == SPV_OPERAND_TYPE_TYPE_ID) {
                inst->SetResultType(id);
              }
            }
          }
          ++operand;
        }

        uint32_t scope_id = inst->GetDebugScope().GetLexicalScope();
        if (scope_id != kNoDebugScope) {
          uint32_t new_id = GetRemappedId(&result_id_mapping, scope_id);
          if (scope_id != new_id) {
            inst->UpdateLexicalScope(new_id);
            modified = true;
          }
        }
        uint32_t inlinedat_id = inst->GetDebugInlinedAt();
        if (inlinedat_id != kNoInlinedAt) {
          uint32_t new_id = GetRemappedId(&result_id_mapping, inlinedat_id);
          if (inlinedat_id != new_id) {
            inst->UpdateDebugInlinedAt(new_id);
            modified = true;
          }
        }
      },
      true);

  if (modified) {
    context()->module()->SetIdBound(
        static_cast<uint32_t>(result_id_mapping.size() + 1));
    // There are ids in the feature manager that could now be invalid
    context()->ResetFeatureManager();
  }

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

}  // namespace opt
}  // namespace spvtools