llvm/polly/include/polly/ScheduleTreeTransform.h

//===- polly/ScheduleTreeTransform.h ----------------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Make changes to isl's schedule tree data structure.
//
//===----------------------------------------------------------------------===//

#ifndef POLLY_SCHEDULETREETRANSFORM_H
#define POLLY_SCHEDULETREETRANSFORM_H

#include "polly/Support/ISLTools.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/Support/ErrorHandling.h"
#include "isl/isl-noexceptions.h"
#include <cassert>

namespace polly {
struct BandAttr;

/// This class defines a simple visitor class that may be used for
/// various schedule tree analysis purposes.
template <typename Derived, typename RetTy = void, typename... Args>
struct ScheduleTreeVisitor { … };

/// Recursively visit all nodes of a schedule tree.
template <typename Derived, typename RetTy = void, typename... Args>
struct RecursiveScheduleTreeVisitor
    : ScheduleTreeVisitor<Derived, RetTy, Args...> { … };

/// Recursively visit all nodes of a schedule tree while allowing changes.
///
/// The visit methods return an isl::schedule_node that is used to continue
/// visiting the tree. Structural changes such as returning a different node
/// will confuse the visitor.
template <typename Derived, typename... Args>
struct ScheduleNodeRewriter
    : public RecursiveScheduleTreeVisitor<Derived, isl::schedule_node,
                                          Args...> { … };

/// Is this node the marker for its parent band?
bool isBandMark(const isl::schedule_node &Node);

/// Extract the BandAttr from a band's wrapping marker. Can also pass the band
/// itself and this methods will try to find its wrapping mark. Returns nullptr
/// if the band has not BandAttr.
BandAttr *getBandAttr(isl::schedule_node MarkOrBand);

/// Hoist all domains from extension into the root domain node, such that there
/// are no more extension nodes (which isl does not support for some
/// operations). This assumes that domains added by to extension nodes do not
/// overlap.
isl::schedule hoistExtensionNodes(isl::schedule Sched);

/// Replace the AST band @p BandToUnroll by a sequence of all its iterations.
///
/// The implementation enumerates all points in the partial schedule and creates
/// an ISL sequence node for each point. The number of iterations must be a
/// constant.
isl::schedule applyFullUnroll(isl::schedule_node BandToUnroll);

/// Replace the AST band @p BandToUnroll by a partially unrolled equivalent.
isl::schedule applyPartialUnroll(isl::schedule_node BandToUnroll, int Factor);

/// Loop-distribute the band @p BandToFission as much as possible.
isl::schedule applyMaxFission(isl::schedule_node BandToFission);

/// Build the desired set of partial tile prefixes.
///
/// We build a set of partial tile prefixes, which are prefixes of the vector
/// loop that have exactly VectorWidth iterations.
///
/// 1. Drop all constraints involving the dimension that represents the
///    vector loop.
/// 2. Constrain the last dimension to get a set, which has exactly VectorWidth
///    iterations.
/// 3. Subtract loop domain from it, project out the vector loop dimension and
///    get a set that contains prefixes, which do not have exactly VectorWidth
///    iterations.
/// 4. Project out the vector loop dimension of the set that was build on the
///    first step and subtract the set built on the previous step to get the
///    desired set of prefixes.
///
/// @param ScheduleRange A range of a map, which describes a prefix schedule
///                      relation.
isl::set getPartialTilePrefixes(isl::set ScheduleRange, int VectorWidth);

/// Create an isl::union_set, which describes the isolate option based on
/// IsolateDomain.
///
/// @param IsolateDomain An isl::set whose @p OutDimsNum last dimensions should
///                      belong to the current band node.
/// @param OutDimsNum    A number of dimensions that should belong to
///                      the current band node.
isl::union_set getIsolateOptions(isl::set IsolateDomain, unsigned OutDimsNum);

/// Create an isl::union_set, which describes the specified option for the
/// dimension of the current node.
///
/// @param Ctx    An isl::ctx, which is used to create the isl::union_set.
/// @param Option The name of the option.
isl::union_set getDimOptions(isl::ctx Ctx, const char *Option);

/// Tile a schedule node.
///
/// @param Node            The node to tile.
/// @param Identifier      An name that identifies this kind of tiling and
///                        that is used to mark the tiled loops in the
///                        generated AST.
/// @param TileSizes       A vector of tile sizes that should be used for
///                        tiling.
/// @param DefaultTileSize A default tile size that is used for dimensions
///                        that are not covered by the TileSizes vector.
isl::schedule_node tileNode(isl::schedule_node Node, const char *Identifier,
                            llvm::ArrayRef<int> TileSizes, int DefaultTileSize);

/// Tile a schedule node and unroll point loops.
///
/// @param Node            The node to register tile.
/// @param TileSizes       A vector of tile sizes that should be used for
///                        tiling.
/// @param DefaultTileSize A default tile size that is used for dimensions
isl::schedule_node applyRegisterTiling(isl::schedule_node Node,
                                       llvm::ArrayRef<int> TileSizes,
                                       int DefaultTileSize);

/// Apply greedy fusion. That is, fuse any loop that is possible to be fused
/// top-down.
///
/// @param Sched  Sched tree to fuse all the loops in.
/// @param Deps   Validity constraints that must be preserved.
isl::schedule applyGreedyFusion(isl::schedule Sched,
                                const isl::union_map &Deps);

} // namespace polly

#endif // POLLY_SCHEDULETREETRANSFORM_H