lib/CodeGen/SimpleHazardRecognizer.h

   1 //=- llvm/CodeGen/SimpleHazardRecognizer.h - Scheduling 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 implements the SimpleHazardRecognizer class, which
  11 // implements hazard-avoidance heuristics for scheduling, based on the
  12 // scheduling itineraries specified for the target.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #ifndef LLVM_CODEGEN_SIMPLEHAZARDRECOGNIZER_H
  17 #define LLVM_CODEGEN_SIMPLEHAZARDRECOGNIZER_H
  18
  19 #include "llvm/CodeGen/ScheduleHazardRecognizer.h"
  20 #include "llvm/CodeGen/ScheduleDAG.h"
  21 #include "llvm/Target/TargetMachine.h"
  22 #include "llvm/Target/TargetInstrInfo.h"
  23
  24 namespace llvm {
  25   /// SimpleHazardRecognizer - A *very* simple hazard recognizer. It uses
  26   /// a coarse classification and attempts to avoid that instructions of
  27   /// a given class aren't grouped too densely together.
  28   class SimpleHazardRecognizer : public ScheduleHazardRecognizer {
  29     /// Class - A simple classification for SUnits.
  30     enum Class {
  31       Other, Load, Store
  32     };
  33
  34     /// Window - The Class values of the most recently issued
  35     /// instructions.
  36     Class Window[8];
  37
  38     /// getClass - Classify the given SUnit.
  39     Class getClass(const SUnit *SU) {
  40       const MachineInstr *MI = SU->getInstr();
  41       const TargetInstrDesc &TID = MI->getDesc();
  42       if (TID.mayLoad())
  43         return Load;
  44       if (TID.mayStore())
  45         return Store;
  46       return Other;
  47     }
  48
  49     /// Step - Rotate the existing entries in Window and insert the
  50     /// given class value in position as the most recent.
  51     void Step(Class C) {
  52       std::copy(Window+1, array_endof(Window), Window);
  53       Window[array_lengthof(Window)-1] = C;
  54     }
  55
  56   public:
  57     SimpleHazardRecognizer() : Window() {
  58       Reset();
  59     }
  60
  61     virtual HazardType getHazardType(SUnit *SU) {
  62       Class C = getClass(SU);
  63       if (C == Other)
  64         return NoHazard;
  65       unsigned Score = 0;
  66       for (unsigned i = 0; i != array_lengthof(Window); ++i)
  67         if (Window[i] == C)
  68           Score += i + 1;
  69       if (Score > array_lengthof(Window) * 2)
  70         return Hazard;
  71       return NoHazard;
  72     }
  73
  74     virtual void Reset() {
  75       for (unsigned i = 0; i != array_lengthof(Window); ++i)
  76         Window[i] = Other;
  77     }
  78
  79     virtual void EmitInstruction(SUnit *SU) {
  80       Step(getClass(SU));
  81     }
  82
  83     virtual void AdvanceCycle() {
  84       Step(Other);
  85     }
  86   };
  87 }
  88
  89 #endif