llvm/lib/Target/SystemZ/SystemZMachineScheduler.h

   1 //==- SystemZMachineScheduler.h - SystemZ Scheduler Interface ----*- 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 // -------------------------- Post RA scheduling ---------------------------- //
  10 // SystemZPostRASchedStrategy is a scheduling strategy which is plugged into
  11 // the MachineScheduler. It has a sorted Available set of SUs and a pickNode()
  12 // implementation that looks to optimize decoder grouping and balance the
  13 // usage of processor resources. Scheduler states are saved for the end
  14 // region of each MBB, so that a successor block can learn from it.
  15 //===----------------------------------------------------------------------===//
  16
  17 #ifndef LLVM_LIB_TARGET_SYSTEMZ_SYSTEMZMACHINESCHEDULER_H
  18 #define LLVM_LIB_TARGET_SYSTEMZ_SYSTEMZMACHINESCHEDULER_H
  19
  20 #include "SystemZHazardRecognizer.h"
  21 #include "llvm/CodeGen/MachineScheduler.h"
  22 #include "llvm/CodeGen/ScheduleDAG.h"
  23 #include <set>
  24
  25 namespace llvm {
  26
  27 /// A MachineSchedStrategy implementation for SystemZ post RA scheduling.
  28 class SystemZPostRASchedStrategy : public MachineSchedStrategy {
  29
  30   const MachineLoopInfo *MLI;
  31   const SystemZInstrInfo *TII;
  32
  33   // A SchedModel is needed before any DAG is built while advancing past
  34   // non-scheduled instructions, so it would not always be possible to call
  35   // DAG->getSchedClass(SU).
  36   TargetSchedModel SchedModel;
  37
  38   /// A candidate during instruction evaluation.
  39   struct Candidate {
  40     SUnit *SU = nullptr;
  41
  42     /// The decoding cost.
  43     int GroupingCost = 0;
  44
  45     /// The processor resources cost.
  46     int ResourcesCost = 0;
  47
  48     Candidate() = default;
  49     Candidate(SUnit *SU_, SystemZHazardRecognizer &HazardRec);
  50
  51     // Compare two candidates.
  52     bool operator<(const Candidate &other);
  53
  54     // Check if this node is free of cost ("as good as any").
  55     bool noCost() const {
  56       return (GroupingCost <= 0 && !ResourcesCost);
  57     }
  58
  59 #ifndef NDEBUG
  60     void dumpCosts() {
  61       if (GroupingCost != 0)
  62         dbgs() << "  Grouping cost:" << GroupingCost;
  63       if (ResourcesCost != 0)
  64         dbgs() << "  Resource cost:" << ResourcesCost;
  65     }
  66 #endif
  67   };
  68
  69   // A sorter for the Available set that makes sure that SUs are considered
  70   // in the best order.
  71   struct SUSorter {
  72     bool operator() (SUnit *lhs, SUnit *rhs) const {
  73       if (lhs->isScheduleHigh && !rhs->isScheduleHigh)
  74         return true;
  75       if (!lhs->isScheduleHigh && rhs->isScheduleHigh)
  76         return false;
  77
  78       if (lhs->getHeight() > rhs->getHeight())
  79         return true;
  80       else if (lhs->getHeight() < rhs->getHeight())
  81         return false;
  82
  83       return (lhs->NodeNum < rhs->NodeNum);
  84     }
  85   };
  86   // A set of SUs with a sorter and dump method.
  87   struct SUSet : std::set<SUnit*, SUSorter> {
  88     #ifndef NDEBUG
  89     void dump(SystemZHazardRecognizer &HazardRec) const;
  90     #endif
  91   };
  92
  93   /// The set of available SUs to schedule next.
  94   SUSet Available;
  95
  96   /// Current MBB
  97   MachineBasicBlock *MBB;
  98
  99   /// Maintain hazard recognizers for all blocks, so that the scheduler state
 100   /// can be maintained past BB boundaries when appropariate.
 101   typedef std::map<MachineBasicBlock*, SystemZHazardRecognizer*> MBB2HazRec;
 102   MBB2HazRec SchedStates;
 103
 104   /// Pointer to the HazardRecognizer that tracks the scheduler state for
 105   /// the current region.
 106   SystemZHazardRecognizer *HazardRec;
 107
 108   /// Update the scheduler state by emitting (non-scheduled) instructions
 109   /// up to, but not including, NextBegin.
 110   void advanceTo(MachineBasicBlock::iterator NextBegin);
 111
 112 public:
 113   SystemZPostRASchedStrategy(const MachineSchedContext *C);
 114   virtual ~SystemZPostRASchedStrategy();
 115
 116   /// Called for a region before scheduling.
 117   void initPolicy(MachineBasicBlock::iterator Begin,
 118                   MachineBasicBlock::iterator End,
 119                   unsigned NumRegionInstrs) override;
 120
 121   /// PostRA scheduling does not track pressure.
 122   bool shouldTrackPressure() const override { return false; }
 123
 124   // Process scheduling regions top-down so that scheduler states can be
 125   // transferrred over scheduling boundaries.
 126   bool doMBBSchedRegionsTopDown() const override { return true; }
 127
 128   void initialize(ScheduleDAGMI *dag) override;
 129
 130   /// Tell the strategy that MBB is about to be processed.
 131   void enterMBB(MachineBasicBlock *NextMBB) override;
 132
 133   /// Tell the strategy that current MBB is done.
 134   void leaveMBB() override;
 135
 136   /// Pick the next node to schedule, or return NULL.
 137   SUnit *pickNode(bool &IsTopNode) override;
 138
 139   /// ScheduleDAGMI has scheduled an instruction - tell HazardRec
 140   /// about it.
 141   void schedNode(SUnit *SU, bool IsTopNode) override;
 142
 143   /// SU has had all predecessor dependencies resolved. Put it into
 144   /// Available.
 145   void releaseTopNode(SUnit *SU) override;
 146
 147   /// Currently only scheduling top-down, so this method is empty.
 148   void releaseBottomNode(SUnit *SU) override {};
 149 };
 150
 151 } // end namespace llvm
 152
 153 #endif // LLVM_LIB_TARGET_SYSTEMZ_SYSTEMZMACHINESCHEDULER_H