lib/MC/SubtargetFeature.cpp

   1 //===- SubtargetFeature.cpp - CPU characteristics Implementation ----------===//
   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 /// \file Implements the SubtargetFeature interface.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/MC/SubtargetFeature.h"
  14 #include "llvm/ADT/ArrayRef.h"
  15 #include "llvm/ADT/SmallVector.h"
  16 #include "llvm/ADT/StringExtras.h"
  17 #include "llvm/ADT/StringRef.h"
  18 #include "llvm/ADT/Triple.h"
  19 #include "llvm/Config/llvm-config.h"
  20 #include "llvm/Support/Compiler.h"
  21 #include "llvm/Support/Debug.h"
  22 #include "llvm/Support/Format.h"
  23 #include "llvm/Support/raw_ostream.h"
  24 #include <algorithm>
  25 #include <cassert>
  26 #include <cstddef>
  27 #include <cstring>
  28 #include <iterator>
  29 #include <string>
  30 #include <vector>
  31
  32 using namespace llvm;
  33
  34 /// Determine if a feature has a flag; '+' or '-'
  35 static inline bool hasFlag(StringRef Feature) {
  36   assert(!Feature.empty() && "Empty string");
  37   // Get first character
  38   char Ch = Feature[0];
  39   // Check if first character is '+' or '-' flag
  40   return Ch == '+' || Ch =='-';
  41 }
  42
  43 /// Return string stripped of flag.
  44 static inline std::string StripFlag(StringRef Feature) {
  45   return hasFlag(Feature) ? Feature.substr(1) : Feature;
  46 }
  47
  48 /// Return true if enable flag; '+'.
  49 static inline bool isEnabled(StringRef Feature) {
  50   assert(!Feature.empty() && "Empty string");
  51   // Get first character
  52   char Ch = Feature[0];
  53   // Check if first character is '+' for enabled
  54   return Ch == '+';
  55 }
  56
  57 /// Splits a string of comma separated items in to a vector of strings.
  58 static void Split(std::vector<std::string> &V, StringRef S) {
  59   SmallVector<StringRef, 3> Tmp;
  60   S.split(Tmp, ',', -1, false /* KeepEmpty */);
  61   V.assign(Tmp.begin(), Tmp.end());
  62 }
  63
  64 void SubtargetFeatures::AddFeature(StringRef String, bool Enable) {
  65   // Don't add empty features.
  66   if (!String.empty())
  67     // Convert to lowercase, prepend flag if we don't already have a flag.
  68     Features.push_back(hasFlag(String) ? String.lower()
  69                                        : (Enable ? "+" : "-") + String.lower());
  70 }
  71
  72 /// Find KV in array using binary search.
  73 static const SubtargetFeatureKV *Find(StringRef S,
  74                                       ArrayRef<SubtargetFeatureKV> A) {
  75   // Binary search the array
  76   auto F = std::lower_bound(A.begin(), A.end(), S);
  77   // If not found then return NULL
  78   if (F == A.end() || StringRef(F->Key) != S) return nullptr;
  79   // Return the found array item
  80   return F;
  81 }
  82
  83 /// Return the length of the longest entry in the table.
  84 static size_t getLongestEntryLength(ArrayRef<SubtargetFeatureKV> Table) {
  85   size_t MaxLen = 0;
  86   for (auto &I : Table)
  87     MaxLen = std::max(MaxLen, std::strlen(I.Key));
  88   return MaxLen;
  89 }
  90
  91 /// Display help for feature choices.
  92 static void Help(ArrayRef<SubtargetFeatureKV> CPUTable,
  93                  ArrayRef<SubtargetFeatureKV> FeatTable) {
  94   // Determine the length of the longest CPU and Feature entries.
  95   unsigned MaxCPULen  = getLongestEntryLength(CPUTable);
  96   unsigned MaxFeatLen = getLongestEntryLength(FeatTable);
  97
  98   // Print the CPU table.
  99   errs() << "Available CPUs for this target:\n\n";
 100   for (auto &CPU : CPUTable)
 101     errs() << format("  %-*s - %s.\n", MaxCPULen, CPU.Key, CPU.Desc);
 102   errs() << '\n';
 103
 104   // Print the Feature table.
 105   errs() << "Available features for this target:\n\n";
 106   for (auto &Feature : FeatTable)
 107     errs() << format("  %-*s - %s.\n", MaxFeatLen, Feature.Key, Feature.Desc);
 108   errs() << '\n';
 109
 110   errs() << "Use +feature to enable a feature, or -feature to disable it.\n"
 111             "For example, llc -mcpu=mycpu -mattr=+feature1,-feature2\n";
 112 }
 113
 114 SubtargetFeatures::SubtargetFeatures(StringRef Initial) {
 115   // Break up string into separate features
 116   Split(Features, Initial);
 117 }
 118
 119 std::string SubtargetFeatures::getString() const {
 120   return join(Features.begin(), Features.end(), ",");
 121 }
 122
 123 /// For each feature that is (transitively) implied by this feature, set it.
 124 static
 125 void SetImpliedBits(FeatureBitset &Bits, const SubtargetFeatureKV &FeatureEntry,
 126                     ArrayRef<SubtargetFeatureKV> FeatureTable) {
 127   for (const SubtargetFeatureKV &FE : FeatureTable) {
 128     if (FeatureEntry.Value == FE.Value) continue;
 129
 130     if (FeatureEntry.Implies.test(FE.Value)) {
 131       Bits.set(FE.Value);
 132       SetImpliedBits(Bits, FE, FeatureTable);
 133     }
 134   }
 135 }
 136
 137 /// For each feature that (transitively) implies this feature, clear it.
 138 static
 139 void ClearImpliedBits(FeatureBitset &Bits,
 140                       const SubtargetFeatureKV &FeatureEntry,
 141                       ArrayRef<SubtargetFeatureKV> FeatureTable) {
 142   for (const SubtargetFeatureKV &FE : FeatureTable) {
 143     if (FeatureEntry.Value == FE.Value) continue;
 144
 145     if (FE.Implies.test(FeatureEntry.Value)) {
 146       Bits.reset(FE.Value);
 147       ClearImpliedBits(Bits, FE, FeatureTable);
 148     }
 149   }
 150 }
 151
 152 void
 153 SubtargetFeatures::ToggleFeature(FeatureBitset &Bits, StringRef Feature,
 154                                  ArrayRef<SubtargetFeatureKV> FeatureTable) {
 155   // Find feature in table.
 156   const SubtargetFeatureKV *FeatureEntry =
 157       Find(StripFlag(Feature), FeatureTable);
 158   // If there is a match
 159   if (FeatureEntry) {
 160     if (Bits.test(FeatureEntry->Value)) {
 161       Bits.reset(FeatureEntry->Value);
 162       // For each feature that implies this, clear it.
 163       ClearImpliedBits(Bits, *FeatureEntry, FeatureTable);
 164     } else {
 165       Bits.set(FeatureEntry->Value);
 166
 167       // For each feature that this implies, set it.
 168       SetImpliedBits(Bits, *FeatureEntry, FeatureTable);
 169     }
 170   } else {
 171     errs() << "'" << Feature << "' is not a recognized feature for this target"
 172            << " (ignoring feature)\n";
 173   }
 174 }
 175
 176 void SubtargetFeatures::ApplyFeatureFlag(FeatureBitset &Bits, StringRef Feature,
 177                                     ArrayRef<SubtargetFeatureKV> FeatureTable) {
 178   assert(hasFlag(Feature));
 179
 180   // Find feature in table.
 181   const SubtargetFeatureKV *FeatureEntry =
 182       Find(StripFlag(Feature), FeatureTable);
 183   // If there is a match
 184   if (FeatureEntry) {
 185     // Enable/disable feature in bits
 186     if (isEnabled(Feature)) {
 187       Bits.set(FeatureEntry->Value);
 188
 189       // For each feature that this implies, set it.
 190       SetImpliedBits(Bits, *FeatureEntry, FeatureTable);
 191     } else {
 192       Bits.reset(FeatureEntry->Value);
 193
 194       // For each feature that implies this, clear it.
 195       ClearImpliedBits(Bits, *FeatureEntry, FeatureTable);
 196     }
 197   } else {
 198     errs() << "'" << Feature << "' is not a recognized feature for this target"
 199            << " (ignoring feature)\n";
 200   }
 201 }
 202
 203 FeatureBitset
 204 SubtargetFeatures::getFeatureBits(StringRef CPU,
 205                                   ArrayRef<SubtargetFeatureKV> CPUTable,
 206                                   ArrayRef<SubtargetFeatureKV> FeatureTable) {
 207   if (CPUTable.empty() || FeatureTable.empty())
 208     return FeatureBitset();
 209
 210   assert(std::is_sorted(std::begin(CPUTable), std::end(CPUTable)) &&
 211          "CPU table is not sorted");
 212   assert(std::is_sorted(std::begin(FeatureTable), std::end(FeatureTable)) &&
 213          "CPU features table is not sorted");
 214   // Resulting bits
 215   FeatureBitset Bits;
 216
 217   // Check if help is needed
 218   if (CPU == "help")
 219     Help(CPUTable, FeatureTable);
 220
 221   // Find CPU entry if CPU name is specified.
 222   else if (!CPU.empty()) {
 223     const SubtargetFeatureKV *CPUEntry = Find(CPU, CPUTable);
 224
 225     // If there is a match
 226     if (CPUEntry) {
 227       // Set base feature bits
 228       Bits = CPUEntry->Implies;
 229
 230       // Set the feature implied by this CPU feature, if any.
 231       for (auto &FE : FeatureTable) {
 232         if (CPUEntry->Implies.test(FE.Value))
 233           SetImpliedBits(Bits, FE, FeatureTable);
 234       }
 235     } else {
 236       errs() << "'" << CPU << "' is not a recognized processor for this target"
 237              << " (ignoring processor)\n";
 238     }
 239   }
 240
 241   // Iterate through each feature
 242   for (const std::string &Feature : Features) {
 243     // Check for help
 244     if (Feature == "+help")
 245       Help(CPUTable, FeatureTable);
 246
 247     ApplyFeatureFlag(Bits, Feature, FeatureTable);
 248   }
 249
 250   return Bits;
 251 }
 252
 253 void SubtargetFeatures::print(raw_ostream &OS) const {
 254   for (auto &F : Features)
 255     OS << F << " ";
 256   OS << "\n";
 257 }
 258
 259 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 260 LLVM_DUMP_METHOD void SubtargetFeatures::dump() const {
 261   print(dbgs());
 262 }
 263 #endif
 264
 265 void SubtargetFeatures::getDefaultSubtargetFeatures(const Triple& Triple) {
 266   // FIXME: This is an inelegant way of specifying the features of a
 267   // subtarget. It would be better if we could encode this information
 268   // into the IR. See <rdar://5972456>.
 269   if (Triple.getVendor() == Triple::Apple) {
 270     if (Triple.getArch() == Triple::ppc) {
 271       // powerpc-apple-*
 272       AddFeature("altivec");
 273     } else if (Triple.getArch() == Triple::ppc64) {
 274       // powerpc64-apple-*
 275       AddFeature("64bit");
 276       AddFeature("altivec");
 277     }
 278   }
 279 }