llvm/lib/MC/MCSubtargetInfo.cpp

   1 //===- MCSubtargetInfo.cpp - Subtarget Information ------------------------===//
   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 #include "llvm/MC/MCSubtargetInfo.h"
  10 #include "llvm/ADT/ArrayRef.h"
  11 #include "llvm/ADT/StringRef.h"
  12 #include "llvm/MC/MCInstrItineraries.h"
  13 #include "llvm/MC/MCSchedule.h"
  14 #include "llvm/MC/SubtargetFeature.h"
  15 #include "llvm/Support/Format.h"
  16 #include "llvm/Support/raw_ostream.h"
  17 #include <algorithm>
  18 #include <cassert>
  19 #include <cstring>
  20
  21 using namespace llvm;
  22
  23 /// Find KV in array using binary search.
  24 template <typename T>
  25 static const T *Find(StringRef S, ArrayRef<T> A) {
  26   // Binary search the array
  27   auto F = llvm::lower_bound(A, S);
  28   // If not found then return NULL
  29   if (F == A.end() || StringRef(F->Key) != S) return nullptr;
  30   // Return the found array item
  31   return F;
  32 }
  33
  34 /// For each feature that is (transitively) implied by this feature, set it.
  35 static
  36 void SetImpliedBits(FeatureBitset &Bits, const FeatureBitset &Implies,
  37                     ArrayRef<SubtargetFeatureKV> FeatureTable) {
  38   // OR the Implies bits in outside the loop. This allows the Implies for CPUs
  39   // which might imply features not in FeatureTable to use this.
  40   Bits |= Implies;
  41   for (const SubtargetFeatureKV &FE : FeatureTable)
  42     if (Implies.test(FE.Value))
  43       SetImpliedBits(Bits, FE.Implies.getAsBitset(), FeatureTable);
  44 }
  45
  46 /// For each feature that (transitively) implies this feature, clear it.
  47 static
  48 void ClearImpliedBits(FeatureBitset &Bits, unsigned Value,
  49                       ArrayRef<SubtargetFeatureKV> FeatureTable) {
  50   for (const SubtargetFeatureKV &FE : FeatureTable) {
  51     if (FE.Implies.getAsBitset().test(Value)) {
  52       Bits.reset(FE.Value);
  53       ClearImpliedBits(Bits, FE.Value, FeatureTable);
  54     }
  55   }
  56 }
  57
  58 static void ApplyFeatureFlag(FeatureBitset &Bits, StringRef Feature,
  59                              ArrayRef<SubtargetFeatureKV> FeatureTable) {
  60   assert(SubtargetFeatures::hasFlag(Feature) &&
  61          "Feature flags should start with '+' or '-'");
  62
  63   // Find feature in table.
  64   const SubtargetFeatureKV *FeatureEntry =
  65       Find(SubtargetFeatures::StripFlag(Feature), FeatureTable);
  66   // If there is a match
  67   if (FeatureEntry) {
  68     // Enable/disable feature in bits
  69     if (SubtargetFeatures::isEnabled(Feature)) {
  70       Bits.set(FeatureEntry->Value);
  71
  72       // For each feature that this implies, set it.
  73       SetImpliedBits(Bits, FeatureEntry->Implies.getAsBitset(), FeatureTable);
  74     } else {
  75       Bits.reset(FeatureEntry->Value);
  76
  77       // For each feature that implies this, clear it.
  78       ClearImpliedBits(Bits, FeatureEntry->Value, FeatureTable);
  79     }
  80   } else {
  81     errs() << "'" << Feature << "' is not a recognized feature for this target"
  82            << " (ignoring feature)\n";
  83   }
  84 }
  85
  86 /// Return the length of the longest entry in the table.
  87 template <typename T>
  88 static size_t getLongestEntryLength(ArrayRef<T> Table) {
  89   size_t MaxLen = 0;
  90   for (auto &I : Table)
  91     MaxLen = std::max(MaxLen, std::strlen(I.Key));
  92   return MaxLen;
  93 }
  94
  95 /// Display help for feature and mcpu choices.
  96 static void Help(ArrayRef<SubtargetSubTypeKV> CPUTable,
  97                  ArrayRef<SubtargetFeatureKV> FeatTable) {
  98   // the static variable ensures that the help information only gets
  99   // printed once even though a target machine creates multiple subtargets
 100   static bool PrintOnce = false;
 101   if (PrintOnce) {
 102     return;
 103   }
 104
 105   // Determine the length of the longest CPU and Feature entries.
 106   unsigned MaxCPULen  = getLongestEntryLength(CPUTable);
 107   unsigned MaxFeatLen = getLongestEntryLength(FeatTable);
 108
 109   // Print the CPU table.
 110   errs() << "Available CPUs for this target:\n\n";
 111   for (auto &CPU : CPUTable)
 112     errs() << format("  %-*s - Select the %s processor.\n", MaxCPULen, CPU.Key,
 113                      CPU.Key);
 114   errs() << '\n';
 115
 116   // Print the Feature table.
 117   errs() << "Available features for this target:\n\n";
 118   for (auto &Feature : FeatTable)
 119     errs() << format("  %-*s - %s.\n", MaxFeatLen, Feature.Key, Feature.Desc);
 120   errs() << '\n';
 121
 122   errs() << "Use +feature to enable a feature, or -feature to disable it.\n"
 123             "For example, llc -mcpu=mycpu -mattr=+feature1,-feature2\n";
 124
 125   PrintOnce = true;
 126 }
 127
 128 /// Display help for mcpu choices only
 129 static void cpuHelp(ArrayRef<SubtargetSubTypeKV> CPUTable) {
 130   // the static variable ensures that the help information only gets
 131   // printed once even though a target machine creates multiple subtargets
 132   static bool PrintOnce = false;
 133   if (PrintOnce) {
 134     return;
 135   }
 136
 137   // Print the CPU table.
 138   errs() << "Available CPUs for this target:\n\n";
 139   for (auto &CPU : CPUTable)
 140     errs() << "\t" << CPU.Key << "\n";
 141   errs() << '\n';
 142
 143   errs() << "Use -mcpu or -mtune to specify the target's processor.\n"
 144             "For example, clang --target=aarch64-unknown-linux-gui "
 145             "-mcpu=cortex-a35\n";
 146
 147   PrintOnce = true;
 148 }
 149
 150 static FeatureBitset getFeatures(StringRef CPU, StringRef TuneCPU, StringRef FS,
 151                                  ArrayRef<SubtargetSubTypeKV> ProcDesc,
 152                                  ArrayRef<SubtargetFeatureKV> ProcFeatures) {
 153   SubtargetFeatures Features(FS);
 154
 155   if (ProcDesc.empty() || ProcFeatures.empty())
 156     return FeatureBitset();
 157
 158   assert(llvm::is_sorted(ProcDesc) && "CPU table is not sorted");
 159   assert(llvm::is_sorted(ProcFeatures) && "CPU features table is not sorted");
 160   // Resulting bits
 161   FeatureBitset Bits;
 162
 163   // Check if help is needed
 164   if (CPU == "help")
 165     Help(ProcDesc, ProcFeatures);
 166
 167   // Find CPU entry if CPU name is specified.
 168   else if (!CPU.empty()) {
 169     const SubtargetSubTypeKV *CPUEntry = Find(CPU, ProcDesc);
 170
 171     // If there is a match
 172     if (CPUEntry) {
 173       // Set the features implied by this CPU feature, if any.
 174       SetImpliedBits(Bits, CPUEntry->Implies.getAsBitset(), ProcFeatures);
 175     } else {
 176       errs() << "'" << CPU << "' is not a recognized processor for this target"
 177              << " (ignoring processor)\n";
 178     }
 179   }
 180
 181   if (!TuneCPU.empty()) {
 182     const SubtargetSubTypeKV *CPUEntry = Find(TuneCPU, ProcDesc);
 183
 184     // If there is a match
 185     if (CPUEntry) {
 186       // Set the features implied by this CPU feature, if any.
 187       SetImpliedBits(Bits, CPUEntry->TuneImplies.getAsBitset(), ProcFeatures);
 188     } else if (TuneCPU != CPU) {
 189       errs() << "'" << TuneCPU << "' is not a recognized processor for this "
 190              << "target (ignoring processor)\n";
 191     }
 192   }
 193
 194   // Iterate through each feature
 195   for (const std::string &Feature : Features.getFeatures()) {
 196     // Check for help
 197     if (Feature == "+help")
 198       Help(ProcDesc, ProcFeatures);
 199     else if (Feature == "+cpuhelp")
 200       cpuHelp(ProcDesc);
 201     else
 202       ApplyFeatureFlag(Bits, Feature, ProcFeatures);
 203   }
 204
 205   return Bits;
 206 }
 207
 208 void MCSubtargetInfo::InitMCProcessorInfo(StringRef CPU, StringRef TuneCPU,
 209                                           StringRef FS) {
 210   FeatureBits = getFeatures(CPU, TuneCPU, FS, ProcDesc, ProcFeatures);
 211   FeatureString = std::string(FS);
 212
 213   if (!TuneCPU.empty())
 214     CPUSchedModel = &getSchedModelForCPU(TuneCPU);
 215   else
 216     CPUSchedModel = &MCSchedModel::GetDefaultSchedModel();
 217 }
 218
 219 void MCSubtargetInfo::setDefaultFeatures(StringRef CPU, StringRef TuneCPU,
 220                                          StringRef FS) {
 221   FeatureBits = getFeatures(CPU, TuneCPU, FS, ProcDesc, ProcFeatures);
 222   FeatureString = std::string(FS);
 223 }
 224
 225 MCSubtargetInfo::MCSubtargetInfo(const Triple &TT, StringRef C, StringRef TC,
 226                                  StringRef FS, ArrayRef<SubtargetFeatureKV> PF,
 227                                  ArrayRef<SubtargetSubTypeKV> PD,
 228                                  const MCWriteProcResEntry *WPR,
 229                                  const MCWriteLatencyEntry *WL,
 230                                  const MCReadAdvanceEntry *RA,
 231                                  const InstrStage *IS, const unsigned *OC,
 232                                  const unsigned *FP)
 233     : TargetTriple(TT), CPU(std::string(C)), TuneCPU(std::string(TC)),
 234       ProcFeatures(PF), ProcDesc(PD), WriteProcResTable(WPR),
 235       WriteLatencyTable(WL), ReadAdvanceTable(RA), Stages(IS),
 236       OperandCycles(OC), ForwardingPaths(FP) {
 237   InitMCProcessorInfo(CPU, TuneCPU, FS);
 238 }
 239
 240 FeatureBitset MCSubtargetInfo::ToggleFeature(uint64_t FB) {
 241   FeatureBits.flip(FB);
 242   return FeatureBits;
 243 }
 244
 245 FeatureBitset MCSubtargetInfo::ToggleFeature(const FeatureBitset &FB) {
 246   FeatureBits ^= FB;
 247   return FeatureBits;
 248 }
 249
 250 FeatureBitset MCSubtargetInfo::SetFeatureBitsTransitively(
 251   const FeatureBitset &FB) {
 252   SetImpliedBits(FeatureBits, FB, ProcFeatures);
 253   return FeatureBits;
 254 }
 255
 256 FeatureBitset MCSubtargetInfo::ClearFeatureBitsTransitively(
 257   const FeatureBitset &FB) {
 258   for (unsigned I = 0, E = FB.size(); I < E; I++) {
 259     if (FB[I]) {
 260       FeatureBits.reset(I);
 261       ClearImpliedBits(FeatureBits, I, ProcFeatures);
 262     }
 263   }
 264   return FeatureBits;
 265 }
 266
 267 FeatureBitset MCSubtargetInfo::ToggleFeature(StringRef Feature) {
 268   // Find feature in table.
 269   const SubtargetFeatureKV *FeatureEntry =
 270       Find(SubtargetFeatures::StripFlag(Feature), ProcFeatures);
 271   // If there is a match
 272   if (FeatureEntry) {
 273     if (FeatureBits.test(FeatureEntry->Value)) {
 274       FeatureBits.reset(FeatureEntry->Value);
 275       // For each feature that implies this, clear it.
 276       ClearImpliedBits(FeatureBits, FeatureEntry->Value, ProcFeatures);
 277     } else {
 278       FeatureBits.set(FeatureEntry->Value);
 279
 280       // For each feature that this implies, set it.
 281       SetImpliedBits(FeatureBits, FeatureEntry->Implies.getAsBitset(),
 282                      ProcFeatures);
 283     }
 284   } else {
 285     errs() << "'" << Feature << "' is not a recognized feature for this target"
 286            << " (ignoring feature)\n";
 287   }
 288
 289   return FeatureBits;
 290 }
 291
 292 FeatureBitset MCSubtargetInfo::ApplyFeatureFlag(StringRef FS) {
 293   ::ApplyFeatureFlag(FeatureBits, FS, ProcFeatures);
 294   return FeatureBits;
 295 }
 296
 297 bool MCSubtargetInfo::checkFeatures(StringRef FS) const {
 298   SubtargetFeatures T(FS);
 299   FeatureBitset Set, All;
 300   for (std::string F : T.getFeatures()) {
 301     ::ApplyFeatureFlag(Set, F, ProcFeatures);
 302     if (F[0] == '-')
 303       F[0] = '+';
 304     ::ApplyFeatureFlag(All, F, ProcFeatures);
 305   }
 306   return (FeatureBits & All) == Set;
 307 }
 308
 309 const MCSchedModel &MCSubtargetInfo::getSchedModelForCPU(StringRef CPU) const {
 310   assert(llvm::is_sorted(ProcDesc) &&
 311          "Processor machine model table is not sorted");
 312
 313   // Find entry
 314   const SubtargetSubTypeKV *CPUEntry = Find(CPU, ProcDesc);
 315
 316   if (!CPUEntry) {
 317     if (CPU != "help") // Don't error if the user asked for help.
 318       errs() << "'" << CPU
 319              << "' is not a recognized processor for this target"
 320              << " (ignoring processor)\n";
 321     return MCSchedModel::GetDefaultSchedModel();
 322   }
 323   assert(CPUEntry->SchedModel && "Missing processor SchedModel value");
 324   return *CPUEntry->SchedModel;
 325 }
 326
 327 InstrItineraryData
 328 MCSubtargetInfo::getInstrItineraryForCPU(StringRef CPU) const {
 329   const MCSchedModel &SchedModel = getSchedModelForCPU(CPU);
 330   return InstrItineraryData(SchedModel, Stages, OperandCycles, ForwardingPaths);
 331 }
 332
 333 void MCSubtargetInfo::initInstrItins(InstrItineraryData &InstrItins) const {
 334   InstrItins = InstrItineraryData(getSchedModel(), Stages, OperandCycles,
 335                                   ForwardingPaths);
 336 }
 337
 338 Optional<unsigned> MCSubtargetInfo::getCacheSize(unsigned Level) const {
 339   return Optional<unsigned>();
 340 }
 341
 342 Optional<unsigned>
 343 MCSubtargetInfo::getCacheAssociativity(unsigned Level) const {
 344   return Optional<unsigned>();
 345 }
 346
 347 Optional<unsigned> MCSubtargetInfo::getCacheLineSize(unsigned Level) const {
 348   return Optional<unsigned>();
 349 }
 350
 351 unsigned MCSubtargetInfo::getPrefetchDistance() const {
 352   return 0;
 353 }
 354
 355 unsigned MCSubtargetInfo::getMaxPrefetchIterationsAhead() const {
 356   return UINT_MAX;
 357 }
 358
 359 bool MCSubtargetInfo::enableWritePrefetching() const {
 360   return false;
 361 }
 362
 363 unsigned MCSubtargetInfo::getMinPrefetchStride(unsigned NumMemAccesses,
 364                                                unsigned NumStridedMemAccesses,
 365                                                unsigned NumPrefetches,
 366                                                bool HasCall) const {
 367   return 1;
 368 }