compiler/optimizing/load_store_analysis.cc

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * 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 "load_store_analysis.h"

namespace art {

// A cap for the number of heap locations to prevent pathological time/space consumption.
// The number of heap locations for most of the methods stays below this threshold.
constexpr size_t kMaxNumberOfHeapLocations = 32;

void LoadStoreAnalysis::Run() {
  for (HBasicBlock* block : graph_->GetReversePostOrder()) {
    heap_location_collector_.VisitBasicBlock(block);
  }

  if (heap_location_collector_.GetNumberOfHeapLocations() > kMaxNumberOfHeapLocations) {
    // Bail out if there are too many heap locations to deal with.
    heap_location_collector_.CleanUp();
    return;
  }
  if (!heap_location_collector_.HasHeapStores()) {
    // Without heap stores, this pass would act mostly as GVN on heap accesses.
    heap_location_collector_.CleanUp();
    return;
  }
  if (heap_location_collector_.HasVolatile() || heap_location_collector_.HasMonitorOps()) {
    // Don't do load/store elimination if the method has volatile field accesses or
    // monitor operations, for now.
    // TODO: do it right.
    heap_location_collector_.CleanUp();
    return;
  }

  heap_location_collector_.BuildAliasingMatrix();
}

}  // namespace art