LoopFusionUtils.h

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//===- LoopFusionUtils.h - Loop fusion utilities ----------------*- C++ -*-===//
//
// Part of the MLIR 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
//
//===----------------------------------------------------------------------===//
//
// This header file defines prototypes for various loop fusion utility
// methods: these are not passes by themselves but are used either by passes,
// optimization sequences, or in turn by other transformation utilities.
//
//===----------------------------------------------------------------------===//

#ifndef MLIR_TRANSFORMS_LOOP_FUSION_UTILS_H
#define MLIR_TRANSFORMS_LOOP_FUSION_UTILS_H

#include "mlir/Support/LLVM.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"

namespace mlir {
class AffineForOp;
struct ComputationSliceState;
class Operation;

// TODO(andydavis) Extend this module to include utility functions for querying
// fusion cost/storage reduction, and for performing the loop fusion
// transformation.

struct FusionResult {
  enum ResultEnum {
    Success,
    FailPrecondition,     // Failed precondition for fusion. (e.g. same block).
    FailBlockDependence,  // Fusion would violate another dependence in block.
    FailFusionDependence, // Fusion would reverse dependences between loops.
    FailComputationSlice, // Unable to compute src loop computation slice.
  } value;
  FusionResult(ResultEnum v) : value(v) {}
};

FusionResult canFuseLoops(AffineForOp srcForOp, AffineForOp dstForOp,
                          unsigned dstLoopDepth,
                          ComputationSliceState *srcSlice);

struct LoopNestStats {
  DenseMap<Operation *, SmallVector<AffineForOp, 2>> loopMap;
  DenseMap<Operation *, uint64_t> opCountMap;
  DenseMap<Operation *, uint64_t> tripCountMap;
};

// TODO(andydavis) Consider moving this to LoopUtils.
bool getLoopNestStats(AffineForOp forOp, LoopNestStats *stats);

// TODO(andydavis) Improve this cost model.
int64_t getComputeCost(AffineForOp forOp, LoopNestStats &stats);

// TODO(andydavis) Improve this cost model.
bool getFusionComputeCost(AffineForOp srcForOp, LoopNestStats &srcStats,
                          AffineForOp dstForOp, LoopNestStats &dstStats,
                          ComputationSliceState *slice, int64_t *computeCost);

} // end namespace mlir

#endif // MLIR_TRANSFORMS_LOOP_FUSION_UTILS_H