include/llvm/CodeGen/ScoreboardHazardRecognizer.h

   1 //=- llvm/CodeGen/ScoreboardHazardRecognizer.h - Schedule 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 defines the ScoreboardHazardRecognizer class, which
  10 // encapsulates hazard-avoidance heuristics for scheduling, based on the
  11 // scheduling itineraries specified for the target.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #ifndef LLVM_CODEGEN_SCOREBOARDHAZARDRECOGNIZER_H
  16 #define LLVM_CODEGEN_SCOREBOARDHAZARDRECOGNIZER_H
  17
  18 #include "llvm/CodeGen/ScheduleHazardRecognizer.h"
  19 #include <cassert>
  20 #include <cstddef>
  21 #include <cstring>
  22
  23 namespace llvm {
  24
  25 class InstrItineraryData;
  26 class ScheduleDAG;
  27 class SUnit;
  28
  29 class ScoreboardHazardRecognizer : public ScheduleHazardRecognizer {
  30   // Scoreboard to track function unit usage. Scoreboard[0] is a
  31   // mask of the FUs in use in the cycle currently being
  32   // schedule. Scoreboard[1] is a mask for the next cycle. The
  33   // Scoreboard is used as a circular buffer with the current cycle
  34   // indicated by Head.
  35   //
  36   // Scoreboard always counts cycles in forward execution order. If used by a
  37   // bottom-up scheduler, then the scoreboard cycles are the inverse of the
  38   // scheduler's cycles.
  39   class Scoreboard {
  40     unsigned *Data = nullptr;
  41
  42     // The maximum number of cycles monitored by the Scoreboard. This
  43     // value is determined based on the target itineraries to ensure
  44     // that all hazards can be tracked.
  45     size_t Depth = 0;
  46
  47     // Indices into the Scoreboard that represent the current cycle.
  48     size_t Head = 0;
  49
  50   public:
  51     Scoreboard() = default;
  52
  53     ~Scoreboard() {
  54       delete[] Data;
  55     }
  56
  57     size_t getDepth() const { return Depth; }
  58
  59     unsigned& operator[](size_t idx) const {
  60       // Depth is expected to be a power-of-2.
  61       assert(Depth && !(Depth & (Depth - 1)) &&
  62              "Scoreboard was not initialized properly!");
  63
  64       return Data[(Head + idx) & (Depth-1)];
  65     }
  66
  67     void reset(size_t d = 1) {
  68       if (!Data) {
  69         Depth = d;
  70         Data = new unsigned[Depth];
  71       }
  72
  73       memset(Data, 0, Depth * sizeof(Data[0]));
  74       Head = 0;
  75     }
  76
  77     void advance() {
  78       Head = (Head + 1) & (Depth-1);
  79     }
  80
  81     void recede() {
  82       Head = (Head - 1) & (Depth-1);
  83     }
  84
  85     // Print the scoreboard.
  86     void dump() const;
  87   };
  88
  89   // Support for tracing ScoreboardHazardRecognizer as a component within
  90   // another module.
  91   const char *DebugType;
  92
  93   // Itinerary data for the target.
  94   const InstrItineraryData *ItinData;
  95
  96   const ScheduleDAG *DAG;
  97
  98   /// IssueWidth - Max issue per cycle. 0=Unknown.
  99   unsigned IssueWidth = 0;
 100
 101   /// IssueCount - Count instructions issued in this cycle.
 102   unsigned IssueCount = 0;
 103
 104   Scoreboard ReservedScoreboard;
 105   Scoreboard RequiredScoreboard;
 106
 107 public:
 108   ScoreboardHazardRecognizer(const InstrItineraryData *II,
 109                              const ScheduleDAG *DAG,
 110                              const char *ParentDebugType = "");
 111
 112   /// atIssueLimit - Return true if no more instructions may be issued in this
 113   /// cycle.
 114   bool atIssueLimit() const override;
 115
 116   // Stalls provides an cycle offset at which SU will be scheduled. It will be
 117   // negative for bottom-up scheduling.
 118   HazardType getHazardType(SUnit *SU, int Stalls) override;
 119   void Reset() override;
 120   void EmitInstruction(SUnit *SU) override;
 121   void AdvanceCycle() override;
 122   void RecedeCycle() override;
 123 };
 124
 125 } // end namespace llvm
 126
 127 #endif // LLVM_CODEGEN_SCOREBOARDHAZARDRECOGNIZER_H