1 //===- RegisterBankEmitter.cpp - Generate a Register Bank Desc. -*- C++ -*-===// 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 tablegen backend is responsible for emitting a description of a target 10 // register bank for a code generator. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/ADT/BitVector.h" 15 #include "llvm/Support/Debug.h" 16 #include "llvm/TableGen/Error.h" 17 #include "llvm/TableGen/Record.h" 18 #include "llvm/TableGen/TableGenBackend.h" 19 20 #include "CodeGenRegisters.h" 21 #include "CodeGenTarget.h" 22 23 #define DEBUG_TYPE "register-bank-emitter" 24 25 using namespace llvm; 26 27 namespace { 28 class RegisterBank { 29 30 /// A vector of register classes that are included in the register bank. 31 typedef std::vector<const CodeGenRegisterClass *> RegisterClassesTy; 32 33 private: 34 const Record &TheDef; 35 36 /// The register classes that are covered by the register bank. 37 RegisterClassesTy RCs; 38 39 /// The register class with the largest register size. 40 const CodeGenRegisterClass *RCWithLargestRegsSize; 41 42 public: 43 RegisterBank(const Record &TheDef) 44 : TheDef(TheDef), RCWithLargestRegsSize(nullptr) {} 45 46 /// Get the human-readable name for the bank. 47 StringRef getName() const { return TheDef.getValueAsString("Name"); } 48 /// Get the name of the enumerator in the ID enumeration. 49 std::string getEnumeratorName() const { return (TheDef.getName() + "ID").str(); } 50 51 /// Get the name of the array holding the register class coverage data; 52 std::string getCoverageArrayName() const { 53 return (TheDef.getName() + "CoverageData").str(); 54 } 55 56 /// Get the name of the global instance variable. 57 StringRef getInstanceVarName() const { return TheDef.getName(); } 58 59 const Record &getDef() const { return TheDef; } 60 61 /// Get the register classes listed in the RegisterBank.RegisterClasses field. 62 std::vector<const CodeGenRegisterClass *> 63 getExplicitlySpecifiedRegisterClasses( 64 const CodeGenRegBank &RegisterClassHierarchy) const { 65 std::vector<const CodeGenRegisterClass *> RCs; 66 for (const auto *RCDef : getDef().getValueAsListOfDefs("RegisterClasses")) 67 RCs.push_back(RegisterClassHierarchy.getRegClass(RCDef)); 68 return RCs; 69 } 70 71 /// Add a register class to the bank without duplicates. 72 void addRegisterClass(const CodeGenRegisterClass *RC) { 73 if (llvm::is_contained(RCs, RC)) 74 return; 75 76 // FIXME? We really want the register size rather than the spill size 77 // since the spill size may be bigger on some targets with 78 // limited load/store instructions. However, we don't store the 79 // register size anywhere (we could sum the sizes of the subregisters 80 // but there may be additional bits too) and we can't derive it from 81 // the VT's reliably due to Untyped. 82 if (RCWithLargestRegsSize == nullptr) 83 RCWithLargestRegsSize = RC; 84 else if (RCWithLargestRegsSize->RSI.get(DefaultMode).SpillSize < 85 RC->RSI.get(DefaultMode).SpillSize) 86 RCWithLargestRegsSize = RC; 87 assert(RCWithLargestRegsSize && "RC was nullptr?"); 88 89 RCs.emplace_back(RC); 90 } 91 92 const CodeGenRegisterClass *getRCWithLargestRegsSize() const { 93 return RCWithLargestRegsSize; 94 } 95 96 iterator_range<typename RegisterClassesTy::const_iterator> 97 register_classes() const { 98 return llvm::make_range(RCs.begin(), RCs.end()); 99 } 100 }; 101 102 class RegisterBankEmitter { 103 private: 104 CodeGenTarget Target; 105 RecordKeeper &Records; 106 107 void emitHeader(raw_ostream &OS, const StringRef TargetName, 108 const std::vector<RegisterBank> &Banks); 109 void emitBaseClassDefinition(raw_ostream &OS, const StringRef TargetName, 110 const std::vector<RegisterBank> &Banks); 111 void emitBaseClassImplementation(raw_ostream &OS, const StringRef TargetName, 112 std::vector<RegisterBank> &Banks); 113 114 public: 115 RegisterBankEmitter(RecordKeeper &R) : Target(R), Records(R) {} 116 117 void run(raw_ostream &OS); 118 }; 119 120 } // end anonymous namespace 121 122 /// Emit code to declare the ID enumeration and external global instance 123 /// variables. 124 void RegisterBankEmitter::emitHeader(raw_ostream &OS, 125 const StringRef TargetName, 126 const std::vector<RegisterBank> &Banks) { 127 // <Target>RegisterBankInfo.h 128 OS << "namespace llvm {\n" 129 << "namespace " << TargetName << " {\n" 130 << "enum : unsigned {\n"; 131 132 OS << " InvalidRegBankID = ~0u,\n"; 133 unsigned ID = 0; 134 for (const auto &Bank : Banks) 135 OS << " " << Bank.getEnumeratorName() << " = " << ID++ << ",\n"; 136 OS << " NumRegisterBanks,\n" 137 << "};\n" 138 << "} // end namespace " << TargetName << "\n" 139 << "} // end namespace llvm\n"; 140 } 141 142 /// Emit declarations of the <Target>GenRegisterBankInfo class. 143 void RegisterBankEmitter::emitBaseClassDefinition( 144 raw_ostream &OS, const StringRef TargetName, 145 const std::vector<RegisterBank> &Banks) { 146 OS << "private:\n" 147 << " static RegisterBank *RegBanks[];\n\n" 148 << "protected:\n" 149 << " " << TargetName << "GenRegisterBankInfo();\n" 150 << "\n"; 151 } 152 153 /// Visit each register class belonging to the given register bank. 154 /// 155 /// A class belongs to the bank iff any of these apply: 156 /// * It is explicitly specified 157 /// * It is a subclass of a class that is a member. 158 /// * It is a class containing subregisters of the registers of a class that 159 /// is a member. This is known as a subreg-class. 160 /// 161 /// This function must be called for each explicitly specified register class. 162 /// 163 /// \param RC The register class to search. 164 /// \param Kind A debug string containing the path the visitor took to reach RC. 165 /// \param VisitFn The action to take for each class visited. It may be called 166 /// multiple times for a given class if there are multiple paths 167 /// to the class. 168 static void visitRegisterBankClasses( 169 const CodeGenRegBank &RegisterClassHierarchy, 170 const CodeGenRegisterClass *RC, const Twine &Kind, 171 std::function<void(const CodeGenRegisterClass *, StringRef)> VisitFn, 172 SmallPtrSetImpl<const CodeGenRegisterClass *> &VisitedRCs) { 173 174 // Make sure we only visit each class once to avoid infinite loops. 175 if (VisitedRCs.count(RC)) 176 return; 177 VisitedRCs.insert(RC); 178 179 // Visit each explicitly named class. 180 VisitFn(RC, Kind.str()); 181 182 for (const auto &PossibleSubclass : RegisterClassHierarchy.getRegClasses()) { 183 std::string TmpKind = 184 (Kind + " (" + PossibleSubclass.getName() + ")").str(); 185 186 // Visit each subclass of an explicitly named class. 187 if (RC != &PossibleSubclass && RC->hasSubClass(&PossibleSubclass)) 188 visitRegisterBankClasses(RegisterClassHierarchy, &PossibleSubclass, 189 TmpKind + " " + RC->getName() + " subclass", 190 VisitFn, VisitedRCs); 191 192 // Visit each class that contains only subregisters of RC with a common 193 // subregister-index. 194 // 195 // More precisely, PossibleSubclass is a subreg-class iff Reg:SubIdx is in 196 // PossibleSubclass for all registers Reg from RC using any 197 // subregister-index SubReg 198 for (const auto &SubIdx : RegisterClassHierarchy.getSubRegIndices()) { 199 BitVector BV(RegisterClassHierarchy.getRegClasses().size()); 200 PossibleSubclass.getSuperRegClasses(&SubIdx, BV); 201 if (BV.test(RC->EnumValue)) { 202 std::string TmpKind2 = (Twine(TmpKind) + " " + RC->getName() + 203 " class-with-subregs: " + RC->getName()) 204 .str(); 205 VisitFn(&PossibleSubclass, TmpKind2); 206 } 207 } 208 } 209 } 210 211 void RegisterBankEmitter::emitBaseClassImplementation( 212 raw_ostream &OS, StringRef TargetName, 213 std::vector<RegisterBank> &Banks) { 214 const CodeGenRegBank &RegisterClassHierarchy = Target.getRegBank(); 215 216 OS << "namespace llvm {\n" 217 << "namespace " << TargetName << " {\n"; 218 for (const auto &Bank : Banks) { 219 std::vector<std::vector<const CodeGenRegisterClass *>> RCsGroupedByWord( 220 (RegisterClassHierarchy.getRegClasses().size() + 31) / 32); 221 222 for (const auto &RC : Bank.register_classes()) 223 RCsGroupedByWord[RC->EnumValue / 32].push_back(RC); 224 225 OS << "const uint32_t " << Bank.getCoverageArrayName() << "[] = {\n"; 226 unsigned LowestIdxInWord = 0; 227 for (const auto &RCs : RCsGroupedByWord) { 228 OS << " // " << LowestIdxInWord << "-" << (LowestIdxInWord + 31) << "\n"; 229 for (const auto &RC : RCs) { 230 std::string QualifiedRegClassID = 231 (Twine(RC->Namespace) + "::" + RC->getName() + "RegClassID").str(); 232 OS << " (1u << (" << QualifiedRegClassID << " - " 233 << LowestIdxInWord << ")) |\n"; 234 } 235 OS << " 0,\n"; 236 LowestIdxInWord += 32; 237 } 238 OS << "};\n"; 239 } 240 OS << "\n"; 241 242 for (const auto &Bank : Banks) { 243 std::string QualifiedBankID = 244 (TargetName + "::" + Bank.getEnumeratorName()).str(); 245 const CodeGenRegisterClass &RC = *Bank.getRCWithLargestRegsSize(); 246 unsigned Size = RC.RSI.get(DefaultMode).SpillSize; 247 OS << "RegisterBank " << Bank.getInstanceVarName() << "(/* ID */ " 248 << QualifiedBankID << ", /* Name */ \"" << Bank.getName() 249 << "\", /* Size */ " << Size << ", " 250 << "/* CoveredRegClasses */ " << Bank.getCoverageArrayName() 251 << ", /* NumRegClasses */ " 252 << RegisterClassHierarchy.getRegClasses().size() << ");\n"; 253 } 254 OS << "} // end namespace " << TargetName << "\n" 255 << "\n"; 256 257 OS << "RegisterBank *" << TargetName 258 << "GenRegisterBankInfo::RegBanks[] = {\n"; 259 for (const auto &Bank : Banks) 260 OS << " &" << TargetName << "::" << Bank.getInstanceVarName() << ",\n"; 261 OS << "};\n\n"; 262 263 OS << TargetName << "GenRegisterBankInfo::" << TargetName 264 << "GenRegisterBankInfo()\n" 265 << " : RegisterBankInfo(RegBanks, " << TargetName 266 << "::NumRegisterBanks) {\n" 267 << " // Assert that RegBank indices match their ID's\n" 268 << "#ifndef NDEBUG\n" 269 << " unsigned Index = 0;\n" 270 << " for (const auto &RB : RegBanks)\n" 271 << " assert(Index++ == RB->getID() && \"Index != ID\");\n" 272 << "#endif // NDEBUG\n" 273 << "}\n" 274 << "} // end namespace llvm\n"; 275 } 276 277 void RegisterBankEmitter::run(raw_ostream &OS) { 278 StringRef TargetName = Target.getName(); 279 const CodeGenRegBank &RegisterClassHierarchy = Target.getRegBank(); 280 281 Records.startTimer("Analyze records"); 282 std::vector<RegisterBank> Banks; 283 for (const auto &V : Records.getAllDerivedDefinitions("RegisterBank")) { 284 SmallPtrSet<const CodeGenRegisterClass *, 8> VisitedRCs; 285 RegisterBank Bank(*V); 286 287 for (const CodeGenRegisterClass *RC : 288 Bank.getExplicitlySpecifiedRegisterClasses(RegisterClassHierarchy)) { 289 visitRegisterBankClasses( 290 RegisterClassHierarchy, RC, "explicit", 291 [&Bank](const CodeGenRegisterClass *RC, StringRef Kind) { 292 LLVM_DEBUG(dbgs() 293 << "Added " << RC->getName() << "(" << Kind << ")\n"); 294 Bank.addRegisterClass(RC); 295 }, 296 VisitedRCs); 297 } 298 299 Banks.push_back(Bank); 300 } 301 302 // Warn about ambiguous MIR caused by register bank/class name clashes. 303 Records.startTimer("Warn ambiguous"); 304 for (const auto &Class : RegisterClassHierarchy.getRegClasses()) { 305 for (const auto &Bank : Banks) { 306 if (Bank.getName().lower() == StringRef(Class.getName()).lower()) { 307 PrintWarning(Bank.getDef().getLoc(), "Register bank names should be " 308 "distinct from register classes " 309 "to avoid ambiguous MIR"); 310 PrintNote(Bank.getDef().getLoc(), "RegisterBank was declared here"); 311 PrintNote(Class.getDef()->getLoc(), "RegisterClass was declared here"); 312 } 313 } 314 } 315 316 Records.startTimer("Emit output"); 317 emitSourceFileHeader("Register Bank Source Fragments", OS); 318 OS << "#ifdef GET_REGBANK_DECLARATIONS\n" 319 << "#undef GET_REGBANK_DECLARATIONS\n"; 320 emitHeader(OS, TargetName, Banks); 321 OS << "#endif // GET_REGBANK_DECLARATIONS\n\n" 322 << "#ifdef GET_TARGET_REGBANK_CLASS\n" 323 << "#undef GET_TARGET_REGBANK_CLASS\n"; 324 emitBaseClassDefinition(OS, TargetName, Banks); 325 OS << "#endif // GET_TARGET_REGBANK_CLASS\n\n" 326 << "#ifdef GET_TARGET_REGBANK_IMPL\n" 327 << "#undef GET_TARGET_REGBANK_IMPL\n"; 328 emitBaseClassImplementation(OS, TargetName, Banks); 329 OS << "#endif // GET_TARGET_REGBANK_IMPL\n"; 330 } 331 332 namespace llvm { 333 334 void EmitRegisterBank(RecordKeeper &RK, raw_ostream &OS) { 335 RegisterBankEmitter(RK).run(OS); 336 } 337 338 } // end namespace llvm 339