RDFLiveness.h

//===- RDFLiveness.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
//
//===----------------------------------------------------------------------===//
//
// Recalculate the liveness information given a data flow graph.
// This includes block live-ins and kill flags.

#ifndef LLVM_CODEGEN_RDFLIVENESS_H
#define LLVM_CODEGEN_RDFLIVENESS_H

#include "RDFGraph.h"
#include "RDFRegisters.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/MC/LaneBitmask.h"
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <utility>

namespace llvm {

class MachineBasicBlock;
class MachineDominanceFrontier;
class MachineDominatorTree;
class MachineRegisterInfo;
class TargetRegisterInfo;

} // namespace llvm

namespace llvm {
namespace rdf {
namespace detail {

using NodeRef = std::pair<NodeId, LaneBitmask>;

} // namespace detail
} // namespace rdf
} // namespace llvm

namespace std {

template <> struct hash<llvm::rdf::detail::NodeRef> {
  std::size_t operator()(llvm::rdf::detail::NodeRef R) const {
    return std::hash<llvm::rdf::NodeId>{}(R.first) ^
           std::hash<llvm::LaneBitmask::Type>{}(R.second.getAsInteger());
  }
};

} // namespace std

namespace llvm {
namespace rdf {

  struct Liveness {
  public:
    // This is really a std::map, except that it provides a non-trivial
    // default constructor to the element accessed via [].
    struct LiveMapType {
      LiveMapType(const PhysicalRegisterInfo &pri) : Empty(pri) {}

      RegisterAggr &operator[] (MachineBasicBlock *B) {
        return Map.emplace(B, Empty).first->second;
      }

    private:
      RegisterAggr Empty;
      std::map<MachineBasicBlock*,RegisterAggr> Map;
    };

    using NodeRef = detail::NodeRef;
    using NodeRefSet = std::unordered_set<NodeRef>;
    using RefMap = std::unordered_map<RegisterId, NodeRefSet>;

    Liveness(MachineRegisterInfo &mri, const DataFlowGraph &g)
        : DFG(g), TRI(g.getTRI()), PRI(g.getPRI()), MDT(g.getDT()),
          MDF(g.getDF()), LiveMap(g.getPRI()), Empty(), NoRegs(g.getPRI()) {}

    NodeList getAllReachingDefs(RegisterRef RefRR, NodeAddr<RefNode*> RefA,
        bool TopShadows, bool FullChain, const RegisterAggr &DefRRs);

    NodeList getAllReachingDefs(NodeAddr<RefNode*> RefA) {
      return getAllReachingDefs(RefA.Addr->getRegRef(DFG), RefA, false,
                                false, NoRegs);
    }

    NodeList getAllReachingDefs(RegisterRef RefRR, NodeAddr<RefNode*> RefA) {
      return getAllReachingDefs(RefRR, RefA, false, false, NoRegs);
    }

    NodeSet getAllReachedUses(RegisterRef RefRR, NodeAddr<DefNode*> DefA,
        const RegisterAggr &DefRRs);

    NodeSet getAllReachedUses(RegisterRef RefRR, NodeAddr<DefNode*> DefA) {
      return getAllReachedUses(RefRR, DefA, NoRegs);
    }

    std::pair<NodeSet,bool> getAllReachingDefsRec(RegisterRef RefRR,
        NodeAddr<RefNode*> RefA, NodeSet &Visited, const NodeSet &Defs);

    NodeAddr<RefNode*> getNearestAliasedRef(RegisterRef RefRR,
        NodeAddr<InstrNode*> IA);

    LiveMapType &getLiveMap() { return LiveMap; }
    const LiveMapType &getLiveMap() const { return LiveMap; }

    const RefMap &getRealUses(NodeId P) const {
      auto F = RealUseMap.find(P);
      return F == RealUseMap.end() ? Empty : F->second;
    }

    void computePhiInfo();
    void computeLiveIns();
    void resetLiveIns();
    void resetKills();
    void resetKills(MachineBasicBlock *B);

    void trace(bool T) { Trace = T; }

  private:
    const DataFlowGraph &DFG;
    const TargetRegisterInfo &TRI;
    const PhysicalRegisterInfo &PRI;
    const MachineDominatorTree &MDT;
    const MachineDominanceFrontier &MDF;
    LiveMapType LiveMap;
    const RefMap Empty;
    const RegisterAggr NoRegs;
    bool Trace = false;

    // Cache of mapping from node ids (for RefNodes) to the containing
    // basic blocks. Not computing it each time for each node reduces
    // the liveness calculation time by a large fraction.
    DenseMap<NodeId, MachineBasicBlock *> NBMap;

    // Phi information:
    //
    // RealUseMap
    // map: NodeId -> (map: RegisterId -> NodeRefSet)
    //      phi id -> (map: register -> set of reached non-phi uses)
    DenseMap<NodeId, RefMap> RealUseMap;

    // Inverse iterated dominance frontier.
    std::map<MachineBasicBlock*,std::set<MachineBasicBlock*>> IIDF;

    // Live on entry.
    std::map<MachineBasicBlock*,RefMap> PhiLON;

    // Phi uses are considered to be located at the end of the block that
    // they are associated with. The reaching def of a phi use dominates the
    // block that the use corresponds to, but not the block that contains
    // the phi itself. To include these uses in the liveness propagation (up
    // the dominator tree), create a map: block -> set of uses live on exit.
    std::map<MachineBasicBlock*,RefMap> PhiLOX;

    MachineBasicBlock *getBlockWithRef(NodeId RN) const;
    void traverse(MachineBasicBlock *B, RefMap &LiveIn);
    void emptify(RefMap &M);

    std::pair<NodeSet,bool> getAllReachingDefsRecImpl(RegisterRef RefRR,
        NodeAddr<RefNode*> RefA, NodeSet &Visited, const NodeSet &Defs,
        unsigned Nest, unsigned MaxNest);
  };

  raw_ostream &operator<<(raw_ostream &OS, const Print<Liveness::RefMap> &P);

} // end namespace rdf

} // end namespace llvm

#endif // LLVM_CODEGEN_RDFLIVENESS_H