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/Support/Format.h"
  15 #include "llvm/Support/raw_ostream.h"
  16 #include "llvm/TargetParser/SubtargetFeature.h"
  17 #include <algorithm>
  18 #include <cassert>
  19 #include <cstring>
  20 #include <optional>
  21
  22 using namespace llvm;
  23
  24 /// Find KV in array using binary search.
  25 template <typename T>
  26 static const T *Find(StringRef S, ArrayRef<T> A) {
  27   // Binary search the array
  28   auto F = llvm::lower_bound(A, S);
  29   // If not found then return NULL
  30   if (F == A.end() || StringRef(F->Key) != S) return nullptr;
  31   // Return the found array item
  32   return F;
  33 }
  34
  35 /// For each feature that is (transitively) implied by this feature, set it.
  36 static
  37 void SetImpliedBits(FeatureBitset &Bits, const FeatureBitset &Implies,
  38                     ArrayRef<SubtargetFeatureKV> FeatureTable) {
  39   // OR the Implies bits in outside the loop. This allows the Implies for CPUs
  40   // which might imply features not in FeatureTable to use this.
  41   Bits |= Implies;
  42   for (const SubtargetFeatureKV &FE : FeatureTable)
  43     if (Implies.test(FE.Value))
  44       SetImpliedBits(Bits, FE.Implies.getAsBitset(), FeatureTable);
  45 }
  46
  47 /// For each feature that (transitively) implies this feature, clear it.
  48 static
  49 void ClearImpliedBits(FeatureBitset &Bits, unsigned Value,
  50                       ArrayRef<SubtargetFeatureKV> FeatureTable) {
  51   for (const SubtargetFeatureKV &FE : FeatureTable) {
  52     if (FE.Implies.getAsBitset().test(Value)) {
  53       Bits.reset(FE.Value);
  54       ClearImpliedBits(Bits, FE.Value, FeatureTable);
  55     }
  56   }
  57 }
  58
  59 static void ApplyFeatureFlag(FeatureBitset &Bits, StringRef Feature,
  60                              ArrayRef<SubtargetFeatureKV> FeatureTable) {
  61   assert(SubtargetFeatures::hasFlag(Feature) &&
  62          "Feature flags should start with '+' or '-'");
  63
  64   // Find feature in table.
  65   const SubtargetFeatureKV *FeatureEntry =
  66       Find(SubtargetFeatures::StripFlag(Feature), FeatureTable);
  67   // If there is a match
  68   if (FeatureEntry) {
  69     // Enable/disable feature in bits
  70     if (SubtargetFeatures::isEnabled(Feature)) {
  71       Bits.set(FeatureEntry->Value);
  72
  73       // For each feature that this implies, set it.
  74       SetImpliedBits(Bits, FeatureEntry->Implies.getAsBitset(), FeatureTable);
  75     } else {
  76       Bits.reset(FeatureEntry->Value);
  77
  78       // For each feature that implies this, clear it.
  79       ClearImpliedBits(Bits, FeatureEntry->Value, FeatureTable);
  80     }
  81   } else {
  82     errs() << "'" << Feature << "' is not a recognized feature for this target"
  83            << " (ignoring feature)\n";
  84   }
  85 }
  86
  87 /// Return the length of the longest entry in the table.
  88 template <typename T>
  89 static size_t getLongestEntryLength(ArrayRef<T> Table) {
  90   size_t MaxLen = 0;
  91   for (auto &I : Table)
  92     MaxLen = std::max(MaxLen, std::strlen(I.Key));
  93   return MaxLen;
  94 }
  95
  96 /// Display help for feature and mcpu choices.
  97 static void Help(ArrayRef<SubtargetSubTypeKV> CPUTable,
  98                  ArrayRef<SubtargetFeatureKV> FeatTable) {
  99   // the static variable ensures that the help information only gets
 100   // printed once even though a target machine creates multiple subtargets
 101   static bool PrintOnce = false;
 102   if (PrintOnce) {
 103     return;
 104   }
 105
 106   // Determine the length of the longest CPU and Feature entries.
 107   unsigned MaxCPULen  = getLongestEntryLength(CPUTable);
 108   unsigned MaxFeatLen = getLongestEntryLength(FeatTable);
 109
 110   // Print the CPU table.
 111   errs() << "Available CPUs for this target:\n\n";
 112   for (auto &CPU : CPUTable)
 113     errs() << format("  %-*s - Select the %s processor.\n", MaxCPULen, CPU.Key,
 114                      CPU.Key);
 115   errs() << '\n';
 116
 117   // Print the Feature table.
 118   errs() << "Available features for this target:\n\n";
 119   for (auto &Feature : FeatTable)
 120     errs() << format("  %-*s - %s.\n", MaxFeatLen, Feature.Key, Feature.Desc);
 121   errs() << '\n';
 122
 123   errs() << "Use +feature to enable a feature, or -feature to disable it.\n"
 124             "For example, llc -mcpu=mycpu -mattr=+feature1,-feature2\n";
 125
 126   PrintOnce = true;
 127 }
 128
 129 /// Display help for mcpu choices only
 130 static void cpuHelp(ArrayRef<SubtargetSubTypeKV> CPUTable) {
 131   // the static variable ensures that the help information only gets
 132   // printed once even though a target machine creates multiple subtargets
 133   static bool PrintOnce = false;
 134   if (PrintOnce) {
 135     return;
 136   }
 137
 138   // Print the CPU table.
 139   errs() << "Available CPUs for this target:\n\n";
 140   for (auto &CPU : CPUTable)
 141     errs() << "\t" << CPU.Key << "\n";
 142   errs() << '\n';
 143
 144   errs() << "Use -mcpu or -mtune to specify the target's processor.\n"
 145             "For example, clang --target=aarch64-unknown-linux-gnu "
 146             "-mcpu=cortex-a35\n";
 147
 148   PrintOnce = true;
 149 }
 150
 151 static FeatureBitset getFeatures(StringRef CPU, StringRef TuneCPU, StringRef FS,
 152                                  ArrayRef<SubtargetSubTypeKV> ProcDesc,
 153                                  ArrayRef<SubtargetFeatureKV> ProcFeatures) {
 154   SubtargetFeatures Features(FS);
 155
 156   if (ProcDesc.empty() || ProcFeatures.empty())
 157     return FeatureBitset();
 158
 159   assert(llvm::is_sorted(ProcDesc) && "CPU table is not sorted");
 160   assert(llvm::is_sorted(ProcFeatures) && "CPU features table is not sorted");
 161   // Resulting bits
 162   FeatureBitset Bits;
 163
 164   // Check if help is needed
 165   if (CPU == "help")
 166     Help(ProcDesc, ProcFeatures);
 167
 168   // Find CPU entry if CPU name is specified.
 169   else if (!CPU.empty()) {
 170     const SubtargetSubTypeKV *CPUEntry = Find(CPU, ProcDesc);
 171
 172     // If there is a match
 173     if (CPUEntry) {
 174       // Set the features implied by this CPU feature, if any.
 175       SetImpliedBits(Bits, CPUEntry->Implies.getAsBitset(), ProcFeatures);
 176     } else {
 177       errs() << "'" << CPU << "' is not a recognized processor for this target"
 178              << " (ignoring processor)\n";
 179     }
 180   }
 181
 182   if (!TuneCPU.empty()) {
 183     const SubtargetSubTypeKV *CPUEntry = Find(TuneCPU, ProcDesc);
 184
 185     // If there is a match
 186     if (CPUEntry) {
 187       // Set the features implied by this CPU feature, if any.
 188       SetImpliedBits(Bits, CPUEntry->TuneImplies.getAsBitset(), ProcFeatures);
 189     } else if (TuneCPU != CPU) {
 190       errs() << "'" << TuneCPU << "' is not a recognized processor for this "
 191              << "target (ignoring processor)\n";
 192     }
 193   }
 194
 195   // Iterate through each feature
 196   for (const std::string &Feature : Features.getFeatures()) {
 197     // Check for help
 198     if (Feature == "+help")
 199       Help(ProcDesc, ProcFeatures);
 200     else if (Feature == "+cpuhelp")
 201       cpuHelp(ProcDesc);
 202     else
 203       ApplyFeatureFlag(Bits, Feature, ProcFeatures);
 204   }
 205
 206   return Bits;
 207 }
 208
 209 void MCSubtargetInfo::InitMCProcessorInfo(StringRef CPU, StringRef TuneCPU,
 210                                           StringRef FS) {
 211   FeatureBits = getFeatures(CPU, TuneCPU, FS, ProcDesc, ProcFeatures);
 212   FeatureString = std::string(FS);
 213
 214   if (!TuneCPU.empty())
 215     CPUSchedModel = &getSchedModelForCPU(TuneCPU);
 216   else
 217     CPUSchedModel = &MCSchedModel::Default;
 218 }
 219
 220 void MCSubtargetInfo::setDefaultFeatures(StringRef CPU, StringRef TuneCPU,
 221                                          StringRef FS) {
 222   FeatureBits = getFeatures(CPU, TuneCPU, FS, ProcDesc, ProcFeatures);
 223   FeatureString = std::string(FS);
 224 }
 225
 226 MCSubtargetInfo::MCSubtargetInfo(const Triple &TT, StringRef C, StringRef TC,
 227                                  StringRef FS, ArrayRef<SubtargetFeatureKV> PF,
 228                                  ArrayRef<SubtargetSubTypeKV> PD,
 229                                  const MCWriteProcResEntry *WPR,
 230                                  const MCWriteLatencyEntry *WL,
 231                                  const MCReadAdvanceEntry *RA,
 232                                  const InstrStage *IS, const unsigned *OC,
 233                                  const unsigned *FP)
 234     : TargetTriple(TT), CPU(std::string(C)), TuneCPU(std::string(TC)),
 235       ProcFeatures(PF), ProcDesc(PD), WriteProcResTable(WPR),
 236       WriteLatencyTable(WL), ReadAdvanceTable(RA), Stages(IS),
 237       OperandCycles(OC), ForwardingPaths(FP) {
 238   InitMCProcessorInfo(CPU, TuneCPU, FS);
 239 }
 240
 241 FeatureBitset MCSubtargetInfo::ToggleFeature(uint64_t FB) {
 242   FeatureBits.flip(FB);
 243   return FeatureBits;
 244 }
 245
 246 FeatureBitset MCSubtargetInfo::ToggleFeature(const FeatureBitset &FB) {
 247   FeatureBits ^= FB;
 248   return FeatureBits;
 249 }
 250
 251 FeatureBitset MCSubtargetInfo::SetFeatureBitsTransitively(
 252   const FeatureBitset &FB) {
 253   SetImpliedBits(FeatureBits, FB, ProcFeatures);
 254   return FeatureBits;
 255 }
 256
 257 FeatureBitset MCSubtargetInfo::ClearFeatureBitsTransitively(
 258   const FeatureBitset &FB) {
 259   for (unsigned I = 0, E = FB.size(); I < E; I++) {
 260     if (FB[I]) {
 261       FeatureBits.reset(I);
 262       ClearImpliedBits(FeatureBits, I, ProcFeatures);
 263     }
 264   }
 265   return FeatureBits;
 266 }
 267
 268 FeatureBitset MCSubtargetInfo::ToggleFeature(StringRef Feature) {
 269   // Find feature in table.
 270   const SubtargetFeatureKV *FeatureEntry =
 271       Find(SubtargetFeatures::StripFlag(Feature), ProcFeatures);
 272   // If there is a match
 273   if (FeatureEntry) {
 274     if (FeatureBits.test(FeatureEntry->Value)) {
 275       FeatureBits.reset(FeatureEntry->Value);
 276       // For each feature that implies this, clear it.
 277       ClearImpliedBits(FeatureBits, FeatureEntry->Value, ProcFeatures);
 278     } else {
 279       FeatureBits.set(FeatureEntry->Value);
 280
 281       // For each feature that this implies, set it.
 282       SetImpliedBits(FeatureBits, FeatureEntry->Implies.getAsBitset(),
 283                      ProcFeatures);
 284     }
 285   } else {
 286     errs() << "'" << Feature << "' is not a recognized feature for this target"
 287            << " (ignoring feature)\n";
 288   }
 289
 290   return FeatureBits;
 291 }
 292
 293 FeatureBitset MCSubtargetInfo::ApplyFeatureFlag(StringRef FS) {
 294   ::ApplyFeatureFlag(FeatureBits, FS, ProcFeatures);
 295   return FeatureBits;
 296 }
 297
 298 bool MCSubtargetInfo::checkFeatures(StringRef FS) const {
 299   SubtargetFeatures T(FS);
 300   FeatureBitset Set, All;
 301   for (std::string F : T.getFeatures()) {
 302     ::ApplyFeatureFlag(Set, F, ProcFeatures);
 303     if (F[0] == '-')
 304       F[0] = '+';
 305     ::ApplyFeatureFlag(All, F, ProcFeatures);
 306   }
 307   return (FeatureBits & All) == Set;
 308 }
 309
 310 const MCSchedModel &MCSubtargetInfo::getSchedModelForCPU(StringRef CPU) const {
 311   assert(llvm::is_sorted(ProcDesc) &&
 312          "Processor machine model table is not sorted");
 313
 314   // Find entry
 315   const SubtargetSubTypeKV *CPUEntry = Find(CPU, ProcDesc);
 316
 317   if (!CPUEntry) {
 318     if (CPU != "help") // Don't error if the user asked for help.
 319       errs() << "'" << CPU
 320              << "' is not a recognized processor for this target"
 321              << " (ignoring processor)\n";
 322     return MCSchedModel::Default;
 323   }
 324   assert(CPUEntry->SchedModel && "Missing processor SchedModel value");
 325   return *CPUEntry->SchedModel;
 326 }
 327
 328 InstrItineraryData
 329 MCSubtargetInfo::getInstrItineraryForCPU(StringRef CPU) const {
 330   const MCSchedModel &SchedModel = getSchedModelForCPU(CPU);
 331   return InstrItineraryData(SchedModel, Stages, OperandCycles, ForwardingPaths);
 332 }
 333
 334 void MCSubtargetInfo::initInstrItins(InstrItineraryData &InstrItins) const {
 335   InstrItins = InstrItineraryData(getSchedModel(), Stages, OperandCycles,
 336                                   ForwardingPaths);
 337 }
 338
 339 std::optional<unsigned> MCSubtargetInfo::getCacheSize(unsigned Level) const {
 340   return std::nullopt;
 341 }
 342
 343 std::optional<unsigned>
 344 MCSubtargetInfo::getCacheAssociativity(unsigned Level) const {
 345   return std::nullopt;
 346 }
 347
 348 std::optional<unsigned>
 349 MCSubtargetInfo::getCacheLineSize(unsigned Level) const {
 350   return std::nullopt;
 351 }
 352
 353 unsigned MCSubtargetInfo::getPrefetchDistance() const {
 354   return 0;
 355 }
 356
 357 unsigned MCSubtargetInfo::getMaxPrefetchIterationsAhead() const {
 358   return UINT_MAX;
 359 }
 360
 361 bool MCSubtargetInfo::enableWritePrefetching() const {
 362   return false;
 363 }
 364
 365 unsigned MCSubtargetInfo::getMinPrefetchStride(unsigned NumMemAccesses,
 366                                                unsigned NumStridedMemAccesses,
 367                                                unsigned NumPrefetches,
 368                                                bool HasCall) const {
 369   return 1;
 370 }
 371
 372 bool MCSubtargetInfo::shouldPrefetchAddressSpace(unsigned AS) const {
 373   return !AS;
 374 }