//===- PruneUnprofitable.cpp ----------------------------------------------===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// Mark a SCoP as unfeasible if not deemed profitable to optimize.

//

//===----------------------------------------------------------------------===//

#include "polly/PruneUnprofitable.h"

#include "polly/ScopDetection.h"

#include "polly/ScopInfo.h"

#include "polly/ScopPass.h"

#include "llvm/ADT/Statistic.h"

#include "llvm/IR/DebugLoc.h"

#include "llvm/Support/Debug.h"

#include "llvm/Support/raw_ostream.h"

using namespace llvm;

using namespace polly;

#define DEBUG_TYPE "polly-prune-unprofitable"

namespace {

STATISTIC(ScopsProcessed,

          "Number of SCoPs considered for unprofitability pruning");

STATISTIC(ScopsPruned, "Number of pruned SCoPs because it they cannot be "

                       "optimized in a significant way");

STATISTIC(ScopsSurvived, "Number of SCoPs after pruning");

STATISTIC(NumPrunedLoops, "Number of pruned loops");

STATISTIC(NumPrunedBoxedLoops, "Number of pruned boxed loops");

STATISTIC(NumPrunedAffineLoops, "Number of pruned affine loops");

STATISTIC(NumLoopsInScop, "Number of loops in scops after pruning");

STATISTIC(NumBoxedLoops, "Number of boxed loops in SCoPs after pruning");

STATISTIC(NumAffineLoops, "Number of affine loops in SCoPs after pruning");

class PruneUnprofitable : public ScopPass {

private:

  void updateStatistics(Scop &S, bool Pruned) {

    auto ScopStats = S.getStatistics();

    if (Pruned) {

      ScopsPruned++;

      NumPrunedLoops += ScopStats.NumAffineLoops + ScopStats.NumBoxedLoops;

      NumPrunedBoxedLoops += ScopStats.NumBoxedLoops;

      NumPrunedAffineLoops += ScopStats.NumAffineLoops;

    } else {

      ScopsSurvived++;

      NumLoopsInScop += ScopStats.NumAffineLoops + ScopStats.NumBoxedLoops;

      NumBoxedLoops += ScopStats.NumBoxedLoops;

      NumAffineLoops += ScopStats.NumAffineLoops;

    }

  }

public:

  static char ID;

  explicit PruneUnprofitable() : ScopPass(ID) {}

  PruneUnprofitable(const PruneUnprofitable &) = delete;

  PruneUnprofitable &operator=(const PruneUnprofitable &) = delete;

  void getAnalysisUsage(AnalysisUsage &AU) const override {

    AU.addRequired<ScopInfoRegionPass>();

    AU.setPreservesAll();

  }

  bool runOnScop(Scop &S) override {

    if (PollyProcessUnprofitable) {

      LLVM_DEBUG(

          dbgs() << "NOTE: -polly-process-unprofitable active, won't prune "

                    "anything\n");

      return false;

    }

    ScopsProcessed++;

    if (!S.isProfitable(true)) {

      LLVM_DEBUG(

          dbgs() << "SCoP pruned because it probably cannot be optimized in "

                    "a significant way\n");

      S.invalidate(PROFITABLE, DebugLoc());

      updateStatistics(S, true);

    } else {

      updateStatistics(S, false);

    }

    return false;

  }

};

} // namespace

char PruneUnprofitable::ID;

Pass *polly::createPruneUnprofitablePass() { return new PruneUnprofitable(); }

INITIALIZE_PASS_BEGIN(PruneUnprofitable, "polly-prune-unprofitable",

                      "Polly - Prune unprofitable SCoPs", false, false)

INITIALIZE_PASS_END(PruneUnprofitable, "polly-prune-unprofitable",

                    "Polly - Prune unprofitable SCoPs", false, false)