lib/CodeGen/AggressiveAntiDepBreaker.h

   1 //==- llvm/CodeGen/AggressiveAntiDepBreaker.h - Anti-Dep Support -*- C++ -*-==//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements the AggressiveAntiDepBreaker class, which
  10 // implements register anti-dependence breaking during post-RA
  11 // scheduling. It attempts to break all anti-dependencies within a
  12 // block.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #ifndef LLVM_LIB_CODEGEN_AGGRESSIVEANTIDEPBREAKER_H
  17 #define LLVM_LIB_CODEGEN_AGGRESSIVEANTIDEPBREAKER_H
  18
  19 #include "AntiDepBreaker.h"
  20 #include "llvm/ADT/BitVector.h"
  21 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  22 #include "llvm/Support/Compiler.h"
  23 #include <map>
  24 #include <set>
  25 #include <vector>
  26
  27 namespace llvm {
  28
  29 class MachineBasicBlock;
  30 class MachineFunction;
  31 class MachineInstr;
  32 class MachineOperand;
  33 class MachineRegisterInfo;
  34 class RegisterClassInfo;
  35 class TargetInstrInfo;
  36 class TargetRegisterClass;
  37 class TargetRegisterInfo;
  38
  39   /// Contains all the state necessary for anti-dep breaking.
  40 class LLVM_LIBRARY_VISIBILITY AggressiveAntiDepState {
  41   public:
  42     /// Information about a register reference within a liverange
  43     struct RegisterReference {
  44       /// The registers operand
  45       MachineOperand *Operand;
  46
  47       /// The register class
  48       const TargetRegisterClass *RC;
  49     };
  50
  51   private:
  52     /// Number of non-virtual target registers (i.e. TRI->getNumRegs()).
  53     const unsigned NumTargetRegs;
  54
  55     /// Implements a disjoint-union data structure to
  56     /// form register groups. A node is represented by an index into
  57     /// the vector. A node can "point to" itself to indicate that it
  58     /// is the parent of a group, or point to another node to indicate
  59     /// that it is a member of the same group as that node.
  60     std::vector<unsigned> GroupNodes;
  61
  62     /// For each register, the index of the GroupNode
  63     /// currently representing the group that the register belongs to.
  64     /// Register 0 is always represented by the 0 group, a group
  65     /// composed of registers that are not eligible for anti-aliasing.
  66     std::vector<unsigned> GroupNodeIndices;
  67
  68     /// Map registers to all their references within a live range.
  69     std::multimap<unsigned, RegisterReference> RegRefs;
  70
  71     /// The index of the most recent kill (proceeding bottom-up),
  72     /// or ~0u if the register is not live.
  73     std::vector<unsigned> KillIndices;
  74
  75     /// The index of the most recent complete def (proceeding bottom
  76     /// up), or ~0u if the register is live.
  77     std::vector<unsigned> DefIndices;
  78
  79   public:
  80     AggressiveAntiDepState(const unsigned TargetRegs, MachineBasicBlock *BB);
  81
  82     /// Return the kill indices.
  83     std::vector<unsigned> &GetKillIndices() { return KillIndices; }
  84
  85     /// Return the define indices.
  86     std::vector<unsigned> &GetDefIndices() { return DefIndices; }
  87
  88     /// Return the RegRefs map.
  89     std::multimap<unsigned, RegisterReference>& GetRegRefs() { return RegRefs; }
  90
  91     // Get the group for a register. The returned value is
  92     // the index of the GroupNode representing the group.
  93     unsigned GetGroup(unsigned Reg);
  94
  95     // Return a vector of the registers belonging to a group.
  96     // If RegRefs is non-NULL then only included referenced registers.
  97     void GetGroupRegs(
  98        unsigned Group,
  99        std::vector<unsigned> &Regs,
 100        std::multimap<unsigned,
 101          AggressiveAntiDepState::RegisterReference> *RegRefs);
 102
 103     // Union Reg1's and Reg2's groups to form a new group.
 104     // Return the index of the GroupNode representing the group.
 105     unsigned UnionGroups(unsigned Reg1, unsigned Reg2);
 106
 107     // Remove a register from its current group and place
 108     // it alone in its own group. Return the index of the GroupNode
 109     // representing the registers new group.
 110     unsigned LeaveGroup(unsigned Reg);
 111
 112     /// Return true if Reg is live.
 113     bool IsLive(unsigned Reg);
 114   };
 115
 116   class LLVM_LIBRARY_VISIBILITY AggressiveAntiDepBreaker
 117       : public AntiDepBreaker {
 118     MachineFunction &MF;
 119     MachineRegisterInfo &MRI;
 120     const TargetInstrInfo *TII;
 121     const TargetRegisterInfo *TRI;
 122     const RegisterClassInfo &RegClassInfo;
 123
 124     /// The set of registers that should only be
 125     /// renamed if they are on the critical path.
 126     BitVector CriticalPathSet;
 127
 128     /// The state used to identify and rename anti-dependence registers.
 129     AggressiveAntiDepState *State = nullptr;
 130
 131   public:
 132     AggressiveAntiDepBreaker(MachineFunction &MFi,
 133                           const RegisterClassInfo &RCI,
 134                           TargetSubtargetInfo::RegClassVector& CriticalPathRCs);
 135     ~AggressiveAntiDepBreaker() override;
 136
 137     /// Initialize anti-dep breaking for a new basic block.
 138     void StartBlock(MachineBasicBlock *BB) override;
 139
 140     /// Identifiy anti-dependencies along the critical path
 141     /// of the ScheduleDAG and break them by renaming registers.
 142     unsigned BreakAntiDependencies(const std::vector<SUnit> &SUnits,
 143                                    MachineBasicBlock::iterator Begin,
 144                                    MachineBasicBlock::iterator End,
 145                                    unsigned InsertPosIndex,
 146                                    DbgValueVector &DbgValues) override;
 147
 148     /// Update liveness information to account for the current
 149     /// instruction, which will not be scheduled.
 150     void Observe(MachineInstr &MI, unsigned Count,
 151                  unsigned InsertPosIndex) override;
 152
 153     /// Finish anti-dep breaking for a basic block.
 154     void FinishBlock() override;
 155
 156   private:
 157     /// Keep track of a position in the allocation order for each regclass.
 158     using RenameOrderType = std::map<const TargetRegisterClass *, unsigned>;
 159
 160     /// Return true if MO represents a register
 161     /// that is both implicitly used and defined in MI
 162     bool IsImplicitDefUse(MachineInstr &MI, MachineOperand &MO);
 163
 164     /// If MI implicitly def/uses a register, then
 165     /// return that register and all subregisters.
 166     void GetPassthruRegs(MachineInstr &MI, std::set<unsigned> &PassthruRegs);
 167
 168     void HandleLastUse(unsigned Reg, unsigned KillIdx, const char *tag,
 169                        const char *header = nullptr,
 170                        const char *footer = nullptr);
 171
 172     void PrescanInstruction(MachineInstr &MI, unsigned Count,
 173                             std::set<unsigned> &PassthruRegs);
 174     void ScanInstruction(MachineInstr &MI, unsigned Count);
 175     BitVector GetRenameRegisters(unsigned Reg);
 176     bool FindSuitableFreeRegisters(unsigned AntiDepGroupIndex,
 177                                    RenameOrderType& RenameOrder,
 178                                    std::map<unsigned, unsigned> &RenameMap);
 179   };
 180
 181 } // end namespace llvm
 182
 183 #endif // LLVM_LIB_CODEGEN_AGGRESSIVEANTIDEPBREAKER_H