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 {
  Derived &getDerived() { return *static_cast<Derived *>(this); }
  const Derived &getDerived() const {
    return *static_cast<const Derived *>(this);
  }

  RetTy visit(isl::schedule_node Node, Args... args) {
    assert(!Node.is_null());
    switch (isl_schedule_node_get_type(Node.get())) {
    case isl_schedule_node_domain:
      assert(isl_schedule_node_n_children(Node.get()) == 1);
      return getDerived().visitDomain(Node.as<isl::schedule_node_domain>(),
                                      std::forward<Args>(args)...);
    case isl_schedule_node_band:
      assert(isl_schedule_node_n_children(Node.get()) == 1);
      return getDerived().visitBand(Node.as<isl::schedule_node_band>(),
                                    std::forward<Args>(args)...);
    case isl_schedule_node_sequence:
      assert(isl_schedule_node_n_children(Node.get()) >= 2);
      return getDerived().visitSequence(Node.as<isl::schedule_node_sequence>(),
                                        std::forward<Args>(args)...);
    case isl_schedule_node_set:
      return getDerived().visitSet(Node.as<isl::schedule_node_set>(),
                                   std::forward<Args>(args)...);
      assert(isl_schedule_node_n_children(Node.get()) >= 2);
    case isl_schedule_node_leaf:
      assert(isl_schedule_node_n_children(Node.get()) == 0);
      return getDerived().visitLeaf(Node.as<isl::schedule_node_leaf>(),
                                    std::forward<Args>(args)...);
    case isl_schedule_node_mark:
      assert(isl_schedule_node_n_children(Node.get()) == 1);
      return getDerived().visitMark(Node.as<isl::schedule_node_mark>(),
                                    std::forward<Args>(args)...);
    case isl_schedule_node_extension:
      assert(isl_schedule_node_n_children(Node.get()) == 1);
      return getDerived().visitExtension(
          Node.as<isl::schedule_node_extension>(), std::forward<Args>(args)...);
    case isl_schedule_node_filter:
      assert(isl_schedule_node_n_children(Node.get()) == 1);
      return getDerived().visitFilter(Node.as<isl::schedule_node_filter>(),
                                      std::forward<Args>(args)...);
    default:
      llvm_unreachable("unimplemented schedule node type");
    }
  }

  RetTy visitDomain(isl::schedule_node_domain Domain, Args... args) {
    return getDerived().visitSingleChild(std::move(Domain),
                                         std::forward<Args>(args)...);
  }

  RetTy visitBand(isl::schedule_node_band Band, Args... args) {
    return getDerived().visitSingleChild(std::move(Band),
                                         std::forward<Args>(args)...);
  }

  RetTy visitSequence(isl::schedule_node_sequence Sequence, Args... args) {
    return getDerived().visitMultiChild(std::move(Sequence),
                                        std::forward<Args>(args)...);
  }

  RetTy visitSet(isl::schedule_node_set Set, Args... args) {
    return getDerived().visitMultiChild(std::move(Set),
                                        std::forward<Args>(args)...);
  }

  RetTy visitLeaf(isl::schedule_node_leaf Leaf, Args... args) {
    return getDerived().visitNode(std::move(Leaf), std::forward<Args>(args)...);
  }

  RetTy visitMark(isl::schedule_node_mark Mark, Args... args) {
    return getDerived().visitSingleChild(std::move(Mark),
                                         std::forward<Args>(args)...);
  }

  RetTy visitExtension(isl::schedule_node_extension Extension, Args... args) {
    return getDerived().visitSingleChild(std::move(Extension),
                                         std::forward<Args>(args)...);
  }

  RetTy visitFilter(isl::schedule_node_filter Filter, Args... args) {
    return getDerived().visitSingleChild(std::move(Filter),
                                         std::forward<Args>(args)...);
  }

  RetTy visitSingleChild(isl::schedule_node Node, Args... args) {
    return getDerived().visitNode(std::move(Node), std::forward<Args>(args)...);
  }

  RetTy visitMultiChild(isl::schedule_node Node, Args... args) {
    return getDerived().visitNode(std::move(Node), std::forward<Args>(args)...);
  }

  RetTy visitNode(isl::schedule_node Node, Args... args) {
    llvm_unreachable("Unimplemented other");
  }
};

/// Recursively visit all nodes of a schedule tree.
template <typename Derived, typename RetTy = void, typename... Args>
struct RecursiveScheduleTreeVisitor
    : ScheduleTreeVisitor<Derived, RetTy, Args...> {
  using BaseTy = ScheduleTreeVisitor<Derived, RetTy, Args...>;
  BaseTy &getBase() { return *this; }
  const BaseTy &getBase() const { return *this; }
  Derived &getDerived() { return *static_cast<Derived *>(this); }
  const Derived &getDerived() const {
    return *static_cast<const Derived *>(this);
  }

  /// When visiting an entire schedule tree, start at its root node.
  RetTy visit(isl::schedule Schedule, Args... args) {
    return getDerived().visit(Schedule.get_root(), std::forward<Args>(args)...);
  }

  // Necessary to allow overload resolution with the added visit(isl::schedule)
  // overload.
  RetTy visit(isl::schedule_node Node, Args... args) {
    return getBase().visit(Node, std::forward<Args>(args)...);
  }

  /// By default, recursively visit the child nodes.
  RetTy visitNode(isl::schedule_node Node, Args... args) {
    for (unsigned i : rangeIslSize(0, Node.n_children()))
      getDerived().visit(Node.child(i), std::forward<Args>(args)...);
    return RetTy();
  }
};

/// 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...> {
  Derived &getDerived() { return *static_cast<Derived *>(this); }
  const Derived &getDerived() const {
    return *static_cast<const Derived *>(this);
  }

  isl::schedule_node visitNode(isl::schedule_node Node, Args... args) {
    return getDerived().visitChildren(Node);
  }

  isl::schedule_node visitChildren(isl::schedule_node Node, Args... args) {
    if (!Node.has_children())
      return Node;

    isl::schedule_node It = Node.first_child();
    while (true) {
      It = getDerived().visit(It, std::forward<Args>(args)...);
      if (!It.has_next_sibling())
        break;
      It = It.next_sibling();
    }
    return It.parent();
  }
};

/// 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