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1 //=- llvm/CodeGen/ScoreboardHazardRecognizer.h - Schedule Support -*- C++ -*-=//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines the ScoreboardHazardRecognizer class, which
11 // encapsulates hazard-avoidance heuristics for scheduling, based on the
12 // scheduling itineraries specified for the target.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_CODEGEN_SCOREBOARDHAZARDRECOGNIZER_H
17 #define LLVM_CODEGEN_SCOREBOARDHAZARDRECOGNIZER_H
18 
19 #include "llvm/CodeGen/ScheduleHazardRecognizer.h"
20 #include "llvm/Support/DataTypes.h"
21 #include <cassert>
22 #include <cstring>
23 
24 namespace llvm {
25 
26 class InstrItineraryData;
27 class ScheduleDAG;
28 class SUnit;
29 
30 class ScoreboardHazardRecognizer : public ScheduleHazardRecognizer {
31   // Scoreboard to track function unit usage. Scoreboard[0] is a
32   // mask of the FUs in use in the cycle currently being
33   // schedule. Scoreboard[1] is a mask for the next cycle. The
34   // Scoreboard is used as a circular buffer with the current cycle
35   // indicated by Head.
36   //
37   // Scoreboard always counts cycles in forward execution order. If used by a
38   // bottom-up scheduler, then the scoreboard cycles are the inverse of the
39   // scheduler's cycles.
40   class Scoreboard {
41     unsigned *Data;
42 
43     // The maximum number of cycles monitored by the Scoreboard. This
44     // value is determined based on the target itineraries to ensure
45     // that all hazards can be tracked.
46     size_t Depth;
47     // Indices into the Scoreboard that represent the current cycle.
48     size_t Head;
49   public:
Scoreboard()50     Scoreboard():Data(nullptr), Depth(0), Head(0) { }
~Scoreboard()51     ~Scoreboard() {
52       delete[] Data;
53     }
54 
getDepth()55     size_t getDepth() const { return Depth; }
56     unsigned& operator[](size_t idx) const {
57       // Depth is expected to be a power-of-2.
58       assert(Depth && !(Depth & (Depth - 1)) &&
59              "Scoreboard was not initialized properly!");
60 
61       return Data[(Head + idx) & (Depth-1)];
62     }
63 
64     void reset(size_t d = 1) {
65       if (!Data) {
66         Depth = d;
67         Data = new unsigned[Depth];
68       }
69 
70       memset(Data, 0, Depth * sizeof(Data[0]));
71       Head = 0;
72     }
73 
advance()74     void advance() {
75       Head = (Head + 1) & (Depth-1);
76     }
77 
recede()78     void recede() {
79       Head = (Head - 1) & (Depth-1);
80     }
81 
82     // Print the scoreboard.
83     void dump() const;
84   };
85 
86   // Support for tracing ScoreboardHazardRecognizer as a component within
87   // another module.
88   const char *DebugType;
89 
90   // Itinerary data for the target.
91   const InstrItineraryData *ItinData;
92 
93   const ScheduleDAG *DAG;
94 
95   /// IssueWidth - Max issue per cycle. 0=Unknown.
96   unsigned IssueWidth;
97 
98   /// IssueCount - Count instructions issued in this cycle.
99   unsigned IssueCount;
100 
101   Scoreboard ReservedScoreboard;
102   Scoreboard RequiredScoreboard;
103 
104 public:
105   ScoreboardHazardRecognizer(const InstrItineraryData *ItinData,
106                              const ScheduleDAG *DAG,
107                              const char *ParentDebugType = "");
108 
109   /// atIssueLimit - Return true if no more instructions may be issued in this
110   /// cycle.
111   bool atIssueLimit() const override;
112 
113   // Stalls provides an cycle offset at which SU will be scheduled. It will be
114   // negative for bottom-up scheduling.
115   HazardType getHazardType(SUnit *SU, int Stalls) override;
116   void Reset() override;
117   void EmitInstruction(SUnit *SU) override;
118   void AdvanceCycle() override;
119   void RecedeCycle() override;
120 };
121 
122 }
123 
124 #endif //!LLVM_CODEGEN_SCOREBOARDHAZARDRECOGNIZER_H
125