llvm/utils/TableGen/DFAPacketizerEmitter.cpp

   1 //===- DFAPacketizerEmitter.cpp - Packetization DFA for a VLIW machine ----===//
   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 class parses the Schedule.td file and produces an API that can be used
  10 // to reason about whether an instruction can be added to a packet on a VLIW
  11 // architecture. The class internally generates a deterministic finite
  12 // automaton (DFA) that models all possible mappings of machine instructions
  13 // to functional units as instructions are added to a packet.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "Common/CodeGenSchedule.h"
  18 #include "Common/CodeGenTarget.h"
  19 #include "DFAEmitter.h"
  20 #include "llvm/ADT/SmallVector.h"
  21 #include "llvm/Support/Debug.h"
  22 #include "llvm/Support/raw_ostream.h"
  23 #include "llvm/TableGen/Record.h"
  24 #include "llvm/TableGen/TableGenBackend.h"
  25 #include <cassert>
  26 #include <cstdint>
  27 #include <deque>
  28 #include <map>
  29 #include <set>
  30 #include <string>
  31 #include <unordered_map>
  32 #include <vector>
  33
  34 #define DEBUG_TYPE "dfa-emitter"
  35
  36 using namespace llvm;
  37
  38 // We use a uint64_t to represent a resource bitmask.
  39 #define DFA_MAX_RESOURCES 64
  40
  41 namespace {
  42 using ResourceVector = SmallVector<uint64_t, 4>;
  43
  44 struct ScheduleClass {
  45   /// The parent itinerary index (processor model ID).
  46   unsigned ItineraryID;
  47
  48   /// Index within this itinerary of the schedule class.
  49   unsigned Idx;
  50
  51   /// The index within the uniqued set of required resources of Resources.
  52   unsigned ResourcesIdx;
  53
  54   /// Conjunctive list of resource requirements:
  55   ///   {a|b, b|c} => (a OR b) AND (b or c).
  56   /// Resources are unique across all itineraries.
  57   ResourceVector Resources;
  58 };
  59
  60 // Generates and prints out the DFA for resource tracking.
  61 class DFAPacketizerEmitter {
  62 private:
  63   std::string TargetName;
  64   const RecordKeeper &Records;
  65
  66   UniqueVector<ResourceVector> UniqueResources;
  67   std::vector<ScheduleClass> ScheduleClasses;
  68   std::map<std::string, uint64_t> FUNameToBitsMap;
  69   std::map<unsigned, uint64_t> ComboBitToBitsMap;
  70
  71 public:
  72   DFAPacketizerEmitter(const RecordKeeper &R);
  73
  74   // Construct a map of function unit names to bits.
  75   int collectAllFuncUnits(ArrayRef<const CodeGenProcModel *> ProcModels);
  76
  77   // Construct a map from a combo function unit bit to the bits of all included
  78   // functional units.
  79   int collectAllComboFuncs(ArrayRef<const Record *> ComboFuncList);
  80
  81   ResourceVector getResourcesForItinerary(const Record *Itinerary);
  82   void createScheduleClasses(unsigned ItineraryIdx,
  83                              ArrayRef<const Record *> Itineraries);
  84
  85   // Emit code for a subset of itineraries.
  86   void emitForItineraries(raw_ostream &OS,
  87                           std::vector<const CodeGenProcModel *> &ProcItinList,
  88                           std::string DFAName);
  89
  90   void run(raw_ostream &OS);
  91 };
  92 } // end anonymous namespace
  93
  94 DFAPacketizerEmitter::DFAPacketizerEmitter(const RecordKeeper &R)
  95     : TargetName(std::string(CodeGenTarget(R).getName())), Records(R) {}
  96
  97 int DFAPacketizerEmitter::collectAllFuncUnits(
  98     ArrayRef<const CodeGenProcModel *> ProcModels) {
  99   LLVM_DEBUG(dbgs() << "-------------------------------------------------------"
 100                        "----------------------\n");
 101   LLVM_DEBUG(dbgs() << "collectAllFuncUnits");
 102   LLVM_DEBUG(dbgs() << " (" << ProcModels.size() << " itineraries)\n");
 103
 104   std::set<const Record *> ProcItinList;
 105   for (const CodeGenProcModel *Model : ProcModels)
 106     ProcItinList.insert(Model->ItinsDef);
 107
 108   int TotalFUs = 0;
 109   // Parse functional units for all the itineraries.
 110   for (const Record *Proc : ProcItinList) {
 111     std::vector<const Record *> FUs = Proc->getValueAsListOfDefs("FU");
 112
 113     LLVM_DEBUG(dbgs() << "    FU:"
 114                       << " (" << FUs.size() << " FUs) " << Proc->getName());
 115
 116     // Convert macros to bits for each stage.
 117     unsigned numFUs = FUs.size();
 118     for (unsigned j = 0; j < numFUs; ++j) {
 119       assert((j < DFA_MAX_RESOURCES) &&
 120              "Exceeded maximum number of representable resources");
 121       uint64_t FuncResources = 1ULL << j;
 122       FUNameToBitsMap[std::string(FUs[j]->getName())] = FuncResources;
 123       LLVM_DEBUG(dbgs() << " " << FUs[j]->getName() << ":0x"
 124                         << Twine::utohexstr(FuncResources));
 125     }
 126     TotalFUs += numFUs;
 127     LLVM_DEBUG(dbgs() << "\n");
 128   }
 129   return TotalFUs;
 130 }
 131
 132 int DFAPacketizerEmitter::collectAllComboFuncs(
 133     ArrayRef<const Record *> ComboFuncList) {
 134   LLVM_DEBUG(dbgs() << "-------------------------------------------------------"
 135                        "----------------------\n");
 136   LLVM_DEBUG(dbgs() << "collectAllComboFuncs");
 137   LLVM_DEBUG(dbgs() << " (" << ComboFuncList.size() << " sets)\n");
 138
 139   int NumCombos = 0;
 140   for (unsigned I = 0, N = ComboFuncList.size(); I < N; ++I) {
 141     const Record *Func = ComboFuncList[I];
 142     std::vector<const Record *> FUs = Func->getValueAsListOfDefs("CFD");
 143
 144     LLVM_DEBUG(dbgs() << "    CFD:" << I << " (" << FUs.size() << " combo FUs) "
 145                       << Func->getName() << "\n");
 146
 147     // Convert macros to bits for each stage.
 148     for (unsigned J = 0, N = FUs.size(); J < N; ++J) {
 149       assert((J < DFA_MAX_RESOURCES) &&
 150              "Exceeded maximum number of DFA resources");
 151       const Record *FuncData = FUs[J];
 152       const Record *ComboFunc = FuncData->getValueAsDef("TheComboFunc");
 153       const std::vector<const Record *> FuncList =
 154           FuncData->getValueAsListOfDefs("FuncList");
 155       const std::string &ComboFuncName = std::string(ComboFunc->getName());
 156       uint64_t ComboBit = FUNameToBitsMap[ComboFuncName];
 157       uint64_t ComboResources = ComboBit;
 158       LLVM_DEBUG(dbgs() << "      combo: " << ComboFuncName << ":0x"
 159                         << Twine::utohexstr(ComboResources) << "\n");
 160       for (const Record *K : FuncList) {
 161         std::string FuncName = std::string(K->getName());
 162         uint64_t FuncResources = FUNameToBitsMap[FuncName];
 163         LLVM_DEBUG(dbgs() << "        " << FuncName << ":0x"
 164                           << Twine::utohexstr(FuncResources) << "\n");
 165         ComboResources |= FuncResources;
 166       }
 167       ComboBitToBitsMap[ComboBit] = ComboResources;
 168       NumCombos++;
 169       LLVM_DEBUG(dbgs() << "          => combo bits: " << ComboFuncName << ":0x"
 170                         << Twine::utohexstr(ComboBit) << " = 0x"
 171                         << Twine::utohexstr(ComboResources) << "\n");
 172     }
 173   }
 174   return NumCombos;
 175 }
 176
 177 ResourceVector
 178 DFAPacketizerEmitter::getResourcesForItinerary(const Record *Itinerary) {
 179   ResourceVector Resources;
 180   assert(Itinerary);
 181   for (const Record *StageDef : Itinerary->getValueAsListOfDefs("Stages")) {
 182     uint64_t StageResources = 0;
 183     for (const Record *Unit : StageDef->getValueAsListOfDefs("Units")) {
 184       StageResources |= FUNameToBitsMap[std::string(Unit->getName())];
 185     }
 186     if (StageResources != 0)
 187       Resources.push_back(StageResources);
 188   }
 189   return Resources;
 190 }
 191
 192 void DFAPacketizerEmitter::createScheduleClasses(
 193     unsigned ItineraryIdx, ArrayRef<const Record *> Itineraries) {
 194   unsigned Idx = 0;
 195   for (const Record *Itinerary : Itineraries) {
 196     if (!Itinerary) {
 197       ScheduleClasses.push_back({ItineraryIdx, Idx++, 0, ResourceVector{}});
 198       continue;
 199     }
 200     ResourceVector Resources = getResourcesForItinerary(Itinerary);
 201     ScheduleClasses.push_back(
 202         {ItineraryIdx, Idx++, UniqueResources.insert(Resources), Resources});
 203   }
 204 }
 205
 206 //
 207 // Run the worklist algorithm to generate the DFA.
 208 //
 209 void DFAPacketizerEmitter::run(raw_ostream &OS) {
 210   emitSourceFileHeader("Target DFA Packetizer Tables", OS);
 211   OS << "\n"
 212      << "#include \"llvm/CodeGen/DFAPacketizer.h\"\n";
 213   OS << "namespace llvm {\n";
 214
 215   CodeGenTarget CGT(Records);
 216   CodeGenSchedModels CGS(Records, CGT);
 217
 218   std::unordered_map<std::string, std::vector<const CodeGenProcModel *>>
 219       ItinsByNamespace;
 220   for (const CodeGenProcModel &ProcModel : CGS.procModels()) {
 221     if (ProcModel.hasItineraries()) {
 222       auto NS = ProcModel.ItinsDef->getValueAsString("PacketizerNamespace");
 223       ItinsByNamespace[std::string(NS)].push_back(&ProcModel);
 224     }
 225   }
 226
 227   for (auto &KV : ItinsByNamespace)
 228     emitForItineraries(OS, KV.second, KV.first);
 229   OS << "} // end namespace llvm\n";
 230 }
 231
 232 void DFAPacketizerEmitter::emitForItineraries(
 233     raw_ostream &OS, std::vector<const CodeGenProcModel *> &ProcModels,
 234     std::string DFAName) {
 235   OS << "} // end namespace llvm\n\n";
 236   OS << "namespace {\n";
 237   collectAllFuncUnits(ProcModels);
 238   collectAllComboFuncs(Records.getAllDerivedDefinitions("ComboFuncUnits"));
 239
 240   // Collect the itineraries.
 241   DenseMap<const CodeGenProcModel *, unsigned> ProcModelStartIdx;
 242   for (const CodeGenProcModel *Model : ProcModels) {
 243     assert(Model->hasItineraries());
 244     ProcModelStartIdx[Model] = ScheduleClasses.size();
 245     createScheduleClasses(Model->Index, Model->ItinDefList);
 246   }
 247
 248   // Output the mapping from ScheduleClass to ResourcesIdx.
 249   unsigned Idx = 0;
 250   OS << "constexpr unsigned " << TargetName << DFAName
 251      << "ResourceIndices[] = {";
 252   for (const ScheduleClass &SC : ScheduleClasses) {
 253     if (Idx++ % 32 == 0)
 254       OS << "\n  ";
 255     OS << SC.ResourcesIdx << ", ";
 256   }
 257   OS << "\n};\n\n";
 258
 259   // And the mapping from Itinerary index into the previous table.
 260   OS << "constexpr unsigned " << TargetName << DFAName
 261      << "ProcResourceIndexStart[] = {\n";
 262   OS << "  0, // NoSchedModel\n";
 263   for (const CodeGenProcModel *Model : ProcModels) {
 264     OS << "  " << ProcModelStartIdx[Model] << ", // " << Model->ModelName
 265        << "\n";
 266   }
 267   OS << "  " << ScheduleClasses.size() << "\n};\n\n";
 268
 269   // The type of a state in the nondeterministic automaton we're defining.
 270   using NfaStateTy = uint64_t;
 271
 272   // Given a resource state, return all resource states by applying
 273   // InsnClass.
 274   auto ApplyInsnClass = [&](const ResourceVector &InsnClass,
 275                             NfaStateTy State) -> std::deque<NfaStateTy> {
 276     std::deque<NfaStateTy> V(1, State);
 277     // Apply every stage in the class individually.
 278     for (NfaStateTy Stage : InsnClass) {
 279       // Apply this stage to every existing member of V in turn.
 280       size_t Sz = V.size();
 281       for (unsigned I = 0; I < Sz; ++I) {
 282         NfaStateTy S = V.front();
 283         V.pop_front();
 284
 285         // For this stage, state combination, try all possible resources.
 286         for (unsigned J = 0; J < DFA_MAX_RESOURCES; ++J) {
 287           NfaStateTy ResourceMask = 1ULL << J;
 288           if ((ResourceMask & Stage) == 0)
 289             // This resource isn't required by this stage.
 290             continue;
 291           NfaStateTy Combo = ComboBitToBitsMap[ResourceMask];
 292           if (Combo && ((~S & Combo) != Combo))
 293             // This combo units bits are not available.
 294             continue;
 295           NfaStateTy ResultingResourceState = S | ResourceMask | Combo;
 296           if (ResultingResourceState == S)
 297             continue;
 298           V.push_back(ResultingResourceState);
 299         }
 300       }
 301     }
 302     return V;
 303   };
 304
 305   // Given a resource state, return a quick (conservative) guess as to whether
 306   // InsnClass can be applied. This is a filter for the more heavyweight
 307   // ApplyInsnClass.
 308   auto canApplyInsnClass = [](const ResourceVector &InsnClass,
 309                               NfaStateTy State) -> bool {
 310     for (NfaStateTy Resources : InsnClass) {
 311       if ((State | Resources) == State)
 312         return false;
 313     }
 314     return true;
 315   };
 316
 317   DfaEmitter Emitter;
 318   std::deque<NfaStateTy> Worklist(1, 0);
 319   std::set<NfaStateTy> SeenStates;
 320   SeenStates.insert(Worklist.front());
 321   while (!Worklist.empty()) {
 322     NfaStateTy State = Worklist.front();
 323     Worklist.pop_front();
 324     for (const ResourceVector &Resources : UniqueResources) {
 325       if (!canApplyInsnClass(Resources, State))
 326         continue;
 327       unsigned ResourcesID = UniqueResources.idFor(Resources);
 328       for (uint64_t NewState : ApplyInsnClass(Resources, State)) {
 329         if (SeenStates.emplace(NewState).second)
 330           Worklist.emplace_back(NewState);
 331         Emitter.addTransition(State, NewState, ResourcesID);
 332       }
 333     }
 334   }
 335
 336   std::string TargetAndDFAName = TargetName + DFAName;
 337   Emitter.emit(TargetAndDFAName, OS);
 338   OS << "} // end anonymous namespace\n\n";
 339
 340   std::string SubTargetClassName = TargetName + "GenSubtargetInfo";
 341   OS << "namespace llvm {\n";
 342   OS << "DFAPacketizer *" << SubTargetClassName << "::"
 343      << "create" << DFAName
 344      << "DFAPacketizer(const InstrItineraryData *IID) const {\n"
 345      << "  static Automaton<uint64_t> A(ArrayRef<" << TargetAndDFAName
 346      << "Transition>(" << TargetAndDFAName << "Transitions), "
 347      << TargetAndDFAName << "TransitionInfo);\n"
 348      << "  unsigned ProcResIdxStart = " << TargetAndDFAName
 349      << "ProcResourceIndexStart[IID->SchedModel.ProcID];\n"
 350      << "  unsigned ProcResIdxNum = " << TargetAndDFAName
 351      << "ProcResourceIndexStart[IID->SchedModel.ProcID + 1] - "
 352         "ProcResIdxStart;\n"
 353      << "  return new DFAPacketizer(IID, A, {&" << TargetAndDFAName
 354      << "ResourceIndices[ProcResIdxStart], ProcResIdxNum});\n"
 355      << "\n}\n\n";
 356 }
 357
 358 static TableGen::Emitter::OptClass<DFAPacketizerEmitter>
 359     X("gen-dfa-packetizer", "Generate DFA Packetizer for VLIW targets");