llvm/mlir/lib/Dialect/Affine/Transforms/LoopTiling.cpp

//===- LoopTiling.cpp --- Loop tiling pass ------------------------------*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file implements a pass to tile loop nests.
//
//===----------------------------------------------------------------------===//

#include "mlir/Dialect/Affine/Passes.h"

#include "mlir/Dialect/Affine/Analysis/AffineAnalysis.h"
#include "mlir/Dialect/Affine/Analysis/AffineStructures.h"
#include "mlir/Dialect/Affine/Analysis/LoopAnalysis.h"
#include "mlir/Dialect/Affine/Analysis/Utils.h"
#include "mlir/Dialect/Affine/IR/AffineOps.h"
#include "mlir/Dialect/Affine/IR/AffineValueMap.h"
#include "mlir/Dialect/Affine/LoopUtils.h"
#include "mlir/Dialect/Affine/Utils.h"
#include "mlir/Dialect/Func/IR/FuncOps.h"
#include "mlir/IR/Builders.h"
#include "mlir/IR/IRMapping.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include <optional>

namespace mlir {
namespace affine {
#define GEN_PASS_DEF_AFFINELOOPTILING
#include "mlir/Dialect/Affine/Passes.h.inc"
} // namespace affine
} // namespace mlir

usingnamespacemlir;
usingnamespacemlir::affine;

#define DEBUG_TYPE …

namespace {

/// A pass to perform loop tiling on all suitable loop nests of a Function.
struct LoopTiling : public affine::impl::AffineLoopTilingBase<LoopTiling> { … };

} // namespace

/// Creates a pass to perform loop tiling on all suitable loop nests of a
/// Function.
std::unique_ptr<OperationPass<func::FuncOp>>
mlir::affine::createLoopTilingPass(uint64_t cacheSizeBytes) { … }
std::unique_ptr<OperationPass<func::FuncOp>>
mlir::affine::createLoopTilingPass() { … }

/// Reduces each tile size to the largest divisor of the corresponding trip
/// count (if the trip count is known).
static void adjustToDivisorsOfTripCounts(ArrayRef<AffineForOp> band,
                                         SmallVectorImpl<unsigned> *tileSizes) { … }

// Returns tile sizes to use. Checks CL options; if none are specified, sets it
// based on a simple model that looks at the memory footprint and determines
// tile sizes assuming identity accesses / 1:1 tile size proportional footprint
// along each of the dimensions being tiled.
// TODO: evolve this model. Tile size determination is a large area
// to play with in general.
void LoopTiling::getTileSizes(ArrayRef<AffineForOp> band,
                              SmallVectorImpl<unsigned> *tileSizes) { … }

void LoopTiling::runOnOperation() { … }

constexpr unsigned LoopTiling::kDefaultTileSize;