1 //===- lib/CodeGen/GlobalISel/LegalizerInfo.cpp - Legalizer ---------------===// 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 // Implement an interface to specify and query how an illegal operation on a 10 // given type should be expanded. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/CodeGen/GlobalISel/LegalizerInfo.h" 15 #include "llvm/ADT/SmallBitVector.h" 16 #include "llvm/CodeGen/LowLevelType.h" 17 #include "llvm/CodeGen/MachineInstr.h" 18 #include "llvm/CodeGen/MachineOperand.h" 19 #include "llvm/CodeGen/MachineRegisterInfo.h" 20 #include "llvm/CodeGen/TargetOpcodes.h" 21 #include "llvm/MC/MCInstrDesc.h" 22 #include "llvm/MC/MCInstrInfo.h" 23 #include "llvm/Support/Debug.h" 24 #include "llvm/Support/ErrorHandling.h" 25 #include <algorithm> 26 27 using namespace llvm; 28 using namespace LegalizeActions; 29 30 #define DEBUG_TYPE "legalizer-info" 31 32 cl::opt<bool> llvm::DisableGISelLegalityCheck( 33 "disable-gisel-legality-check", 34 cl::desc("Don't verify that MIR is fully legal between GlobalISel passes"), 35 cl::Hidden); 36 37 raw_ostream &llvm::operator<<(raw_ostream &OS, LegalizeAction Action) { 38 switch (Action) { 39 case Legal: 40 OS << "Legal"; 41 break; 42 case NarrowScalar: 43 OS << "NarrowScalar"; 44 break; 45 case WidenScalar: 46 OS << "WidenScalar"; 47 break; 48 case FewerElements: 49 OS << "FewerElements"; 50 break; 51 case MoreElements: 52 OS << "MoreElements"; 53 break; 54 case Bitcast: 55 OS << "Bitcast"; 56 break; 57 case Lower: 58 OS << "Lower"; 59 break; 60 case Libcall: 61 OS << "Libcall"; 62 break; 63 case Custom: 64 OS << "Custom"; 65 break; 66 case Unsupported: 67 OS << "Unsupported"; 68 break; 69 case NotFound: 70 OS << "NotFound"; 71 break; 72 case UseLegacyRules: 73 OS << "UseLegacyRules"; 74 break; 75 } 76 return OS; 77 } 78 79 raw_ostream &LegalityQuery::print(raw_ostream &OS) const { 80 OS << "Opcode=" << Opcode << ", Tys={"; 81 for (const auto &Type : Types) { 82 OS << Type << ", "; 83 } 84 OS << "}, MMOs={"; 85 for (const auto &MMODescr : MMODescrs) { 86 OS << MMODescr.MemoryTy << ", "; 87 } 88 OS << "}"; 89 90 return OS; 91 } 92 93 #ifndef NDEBUG 94 // Make sure the rule won't (trivially) loop forever. 95 static bool hasNoSimpleLoops(const LegalizeRule &Rule, const LegalityQuery &Q, 96 const std::pair<unsigned, LLT> &Mutation) { 97 switch (Rule.getAction()) { 98 case Legal: 99 case Custom: 100 case Lower: 101 case MoreElements: 102 case FewerElements: 103 case Libcall: 104 break; 105 default: 106 return Q.Types[Mutation.first] != Mutation.second; 107 } 108 return true; 109 } 110 111 // Make sure the returned mutation makes sense for the match type. 112 static bool mutationIsSane(const LegalizeRule &Rule, 113 const LegalityQuery &Q, 114 std::pair<unsigned, LLT> Mutation) { 115 // If the user wants a custom mutation, then we can't really say much about 116 // it. Return true, and trust that they're doing the right thing. 117 if (Rule.getAction() == Custom || Rule.getAction() == Legal) 118 return true; 119 120 // Skip null mutation. 121 if (!Mutation.second.isValid()) 122 return true; 123 124 const unsigned TypeIdx = Mutation.first; 125 const LLT OldTy = Q.Types[TypeIdx]; 126 const LLT NewTy = Mutation.second; 127 128 switch (Rule.getAction()) { 129 case FewerElements: 130 if (!OldTy.isVector()) 131 return false; 132 [[fallthrough]]; 133 case MoreElements: { 134 // MoreElements can go from scalar to vector. 135 const ElementCount OldElts = OldTy.isVector() ? 136 OldTy.getElementCount() : ElementCount::getFixed(1); 137 if (NewTy.isVector()) { 138 if (Rule.getAction() == FewerElements) { 139 // Make sure the element count really decreased. 140 if (ElementCount::isKnownGE(NewTy.getElementCount(), OldElts)) 141 return false; 142 } else { 143 // Make sure the element count really increased. 144 if (ElementCount::isKnownLE(NewTy.getElementCount(), OldElts)) 145 return false; 146 } 147 } else if (Rule.getAction() == MoreElements) 148 return false; 149 150 // Make sure the element type didn't change. 151 return NewTy.getScalarType() == OldTy.getScalarType(); 152 } 153 case NarrowScalar: 154 case WidenScalar: { 155 if (OldTy.isVector()) { 156 // Number of elements should not change. 157 if (!NewTy.isVector() || OldTy.getNumElements() != NewTy.getNumElements()) 158 return false; 159 } else { 160 // Both types must be vectors 161 if (NewTy.isVector()) 162 return false; 163 } 164 165 if (Rule.getAction() == NarrowScalar) { 166 // Make sure the size really decreased. 167 if (NewTy.getScalarSizeInBits() >= OldTy.getScalarSizeInBits()) 168 return false; 169 } else { 170 // Make sure the size really increased. 171 if (NewTy.getScalarSizeInBits() <= OldTy.getScalarSizeInBits()) 172 return false; 173 } 174 175 return true; 176 } 177 case Bitcast: { 178 return OldTy != NewTy && OldTy.getSizeInBits() == NewTy.getSizeInBits(); 179 } 180 default: 181 return true; 182 } 183 } 184 #endif 185 186 LegalizeActionStep LegalizeRuleSet::apply(const LegalityQuery &Query) const { 187 LLVM_DEBUG(dbgs() << "Applying legalizer ruleset to: "; Query.print(dbgs()); 188 dbgs() << "\n"); 189 if (Rules.empty()) { 190 LLVM_DEBUG(dbgs() << ".. fallback to legacy rules (no rules defined)\n"); 191 return {LegalizeAction::UseLegacyRules, 0, LLT{}}; 192 } 193 for (const LegalizeRule &Rule : Rules) { 194 if (Rule.match(Query)) { 195 LLVM_DEBUG(dbgs() << ".. match\n"); 196 std::pair<unsigned, LLT> Mutation = Rule.determineMutation(Query); 197 LLVM_DEBUG(dbgs() << ".. .. " << Rule.getAction() << ", " 198 << Mutation.first << ", " << Mutation.second << "\n"); 199 assert(mutationIsSane(Rule, Query, Mutation) && 200 "legality mutation invalid for match"); 201 assert(hasNoSimpleLoops(Rule, Query, Mutation) && "Simple loop detected"); 202 return {Rule.getAction(), Mutation.first, Mutation.second}; 203 } else 204 LLVM_DEBUG(dbgs() << ".. no match\n"); 205 } 206 LLVM_DEBUG(dbgs() << ".. unsupported\n"); 207 return {LegalizeAction::Unsupported, 0, LLT{}}; 208 } 209 210 bool LegalizeRuleSet::verifyTypeIdxsCoverage(unsigned NumTypeIdxs) const { 211 #ifndef NDEBUG 212 if (Rules.empty()) { 213 LLVM_DEBUG( 214 dbgs() << ".. type index coverage check SKIPPED: no rules defined\n"); 215 return true; 216 } 217 const int64_t FirstUncovered = TypeIdxsCovered.find_first_unset(); 218 if (FirstUncovered < 0) { 219 LLVM_DEBUG(dbgs() << ".. type index coverage check SKIPPED:" 220 " user-defined predicate detected\n"); 221 return true; 222 } 223 const bool AllCovered = (FirstUncovered >= NumTypeIdxs); 224 if (NumTypeIdxs > 0) 225 LLVM_DEBUG(dbgs() << ".. the first uncovered type index: " << FirstUncovered 226 << ", " << (AllCovered ? "OK" : "FAIL") << "\n"); 227 return AllCovered; 228 #else 229 return true; 230 #endif 231 } 232 233 bool LegalizeRuleSet::verifyImmIdxsCoverage(unsigned NumImmIdxs) const { 234 #ifndef NDEBUG 235 if (Rules.empty()) { 236 LLVM_DEBUG( 237 dbgs() << ".. imm index coverage check SKIPPED: no rules defined\n"); 238 return true; 239 } 240 const int64_t FirstUncovered = ImmIdxsCovered.find_first_unset(); 241 if (FirstUncovered < 0) { 242 LLVM_DEBUG(dbgs() << ".. imm index coverage check SKIPPED:" 243 " user-defined predicate detected\n"); 244 return true; 245 } 246 const bool AllCovered = (FirstUncovered >= NumImmIdxs); 247 LLVM_DEBUG(dbgs() << ".. the first uncovered imm index: " << FirstUncovered 248 << ", " << (AllCovered ? "OK" : "FAIL") << "\n"); 249 return AllCovered; 250 #else 251 return true; 252 #endif 253 } 254 255 /// Helper function to get LLT for the given type index. 256 static LLT getTypeFromTypeIdx(const MachineInstr &MI, 257 const MachineRegisterInfo &MRI, unsigned OpIdx, 258 unsigned TypeIdx) { 259 assert(TypeIdx < MI.getNumOperands() && "Unexpected TypeIdx"); 260 // G_UNMERGE_VALUES has variable number of operands, but there is only 261 // one source type and one destination type as all destinations must be the 262 // same type. So, get the last operand if TypeIdx == 1. 263 if (MI.getOpcode() == TargetOpcode::G_UNMERGE_VALUES && TypeIdx == 1) 264 return MRI.getType(MI.getOperand(MI.getNumOperands() - 1).getReg()); 265 return MRI.getType(MI.getOperand(OpIdx).getReg()); 266 } 267 268 unsigned LegalizerInfo::getOpcodeIdxForOpcode(unsigned Opcode) const { 269 assert(Opcode >= FirstOp && Opcode <= LastOp && "Unsupported opcode"); 270 return Opcode - FirstOp; 271 } 272 273 unsigned LegalizerInfo::getActionDefinitionsIdx(unsigned Opcode) const { 274 unsigned OpcodeIdx = getOpcodeIdxForOpcode(Opcode); 275 if (unsigned Alias = RulesForOpcode[OpcodeIdx].getAlias()) { 276 LLVM_DEBUG(dbgs() << ".. opcode " << Opcode << " is aliased to " << Alias 277 << "\n"); 278 OpcodeIdx = getOpcodeIdxForOpcode(Alias); 279 assert(RulesForOpcode[OpcodeIdx].getAlias() == 0 && "Cannot chain aliases"); 280 } 281 282 return OpcodeIdx; 283 } 284 285 const LegalizeRuleSet & 286 LegalizerInfo::getActionDefinitions(unsigned Opcode) const { 287 unsigned OpcodeIdx = getActionDefinitionsIdx(Opcode); 288 return RulesForOpcode[OpcodeIdx]; 289 } 290 291 LegalizeRuleSet &LegalizerInfo::getActionDefinitionsBuilder(unsigned Opcode) { 292 unsigned OpcodeIdx = getActionDefinitionsIdx(Opcode); 293 auto &Result = RulesForOpcode[OpcodeIdx]; 294 assert(!Result.isAliasedByAnother() && "Modifying this opcode will modify aliases"); 295 return Result; 296 } 297 298 LegalizeRuleSet &LegalizerInfo::getActionDefinitionsBuilder( 299 std::initializer_list<unsigned> Opcodes) { 300 unsigned Representative = *Opcodes.begin(); 301 302 assert(Opcodes.size() >= 2 && 303 "Initializer list must have at least two opcodes"); 304 305 for (unsigned Op : llvm::drop_begin(Opcodes)) 306 aliasActionDefinitions(Representative, Op); 307 308 auto &Return = getActionDefinitionsBuilder(Representative); 309 Return.setIsAliasedByAnother(); 310 return Return; 311 } 312 313 void LegalizerInfo::aliasActionDefinitions(unsigned OpcodeTo, 314 unsigned OpcodeFrom) { 315 assert(OpcodeTo != OpcodeFrom && "Cannot alias to self"); 316 assert(OpcodeTo >= FirstOp && OpcodeTo <= LastOp && "Unsupported opcode"); 317 const unsigned OpcodeFromIdx = getOpcodeIdxForOpcode(OpcodeFrom); 318 RulesForOpcode[OpcodeFromIdx].aliasTo(OpcodeTo); 319 } 320 321 LegalizeActionStep 322 LegalizerInfo::getAction(const LegalityQuery &Query) const { 323 LegalizeActionStep Step = getActionDefinitions(Query.Opcode).apply(Query); 324 if (Step.Action != LegalizeAction::UseLegacyRules) { 325 return Step; 326 } 327 328 return getLegacyLegalizerInfo().getAction(Query); 329 } 330 331 LegalizeActionStep 332 LegalizerInfo::getAction(const MachineInstr &MI, 333 const MachineRegisterInfo &MRI) const { 334 SmallVector<LLT, 8> Types; 335 SmallBitVector SeenTypes(8); 336 ArrayRef<MCOperandInfo> OpInfo = MI.getDesc().operands(); 337 // FIXME: probably we'll need to cache the results here somehow? 338 for (unsigned i = 0; i < MI.getDesc().getNumOperands(); ++i) { 339 if (!OpInfo[i].isGenericType()) 340 continue; 341 342 // We must only record actions once for each TypeIdx; otherwise we'd 343 // try to legalize operands multiple times down the line. 344 unsigned TypeIdx = OpInfo[i].getGenericTypeIndex(); 345 if (SeenTypes[TypeIdx]) 346 continue; 347 348 SeenTypes.set(TypeIdx); 349 350 LLT Ty = getTypeFromTypeIdx(MI, MRI, i, TypeIdx); 351 Types.push_back(Ty); 352 } 353 354 SmallVector<LegalityQuery::MemDesc, 2> MemDescrs; 355 for (const auto &MMO : MI.memoperands()) 356 MemDescrs.push_back({*MMO}); 357 358 return getAction({MI.getOpcode(), Types, MemDescrs}); 359 } 360 361 bool LegalizerInfo::isLegal(const MachineInstr &MI, 362 const MachineRegisterInfo &MRI) const { 363 return getAction(MI, MRI).Action == Legal; 364 } 365 366 bool LegalizerInfo::isLegalOrCustom(const MachineInstr &MI, 367 const MachineRegisterInfo &MRI) const { 368 auto Action = getAction(MI, MRI).Action; 369 // If the action is custom, it may not necessarily modify the instruction, 370 // so we have to assume it's legal. 371 return Action == Legal || Action == Custom; 372 } 373 374 unsigned LegalizerInfo::getExtOpcodeForWideningConstant(LLT SmallTy) const { 375 return SmallTy.isByteSized() ? TargetOpcode::G_SEXT : TargetOpcode::G_ZEXT; 376 } 377 378 /// \pre Type indices of every opcode form a dense set starting from 0. 379 void LegalizerInfo::verify(const MCInstrInfo &MII) const { 380 #ifndef NDEBUG 381 std::vector<unsigned> FailedOpcodes; 382 for (unsigned Opcode = FirstOp; Opcode <= LastOp; ++Opcode) { 383 const MCInstrDesc &MCID = MII.get(Opcode); 384 const unsigned NumTypeIdxs = std::accumulate( 385 MCID.operands().begin(), MCID.operands().end(), 0U, 386 [](unsigned Acc, const MCOperandInfo &OpInfo) { 387 return OpInfo.isGenericType() 388 ? std::max(OpInfo.getGenericTypeIndex() + 1U, Acc) 389 : Acc; 390 }); 391 const unsigned NumImmIdxs = std::accumulate( 392 MCID.operands().begin(), MCID.operands().end(), 0U, 393 [](unsigned Acc, const MCOperandInfo &OpInfo) { 394 return OpInfo.isGenericImm() 395 ? std::max(OpInfo.getGenericImmIndex() + 1U, Acc) 396 : Acc; 397 }); 398 LLVM_DEBUG(dbgs() << MII.getName(Opcode) << " (opcode " << Opcode 399 << "): " << NumTypeIdxs << " type ind" 400 << (NumTypeIdxs == 1 ? "ex" : "ices") << ", " 401 << NumImmIdxs << " imm ind" 402 << (NumImmIdxs == 1 ? "ex" : "ices") << "\n"); 403 const LegalizeRuleSet &RuleSet = getActionDefinitions(Opcode); 404 if (!RuleSet.verifyTypeIdxsCoverage(NumTypeIdxs)) 405 FailedOpcodes.push_back(Opcode); 406 else if (!RuleSet.verifyImmIdxsCoverage(NumImmIdxs)) 407 FailedOpcodes.push_back(Opcode); 408 } 409 if (!FailedOpcodes.empty()) { 410 errs() << "The following opcodes have ill-defined legalization rules:"; 411 for (unsigned Opcode : FailedOpcodes) 412 errs() << " " << MII.getName(Opcode); 413 errs() << "\n"; 414 415 report_fatal_error("ill-defined LegalizerInfo" 416 ", try -debug-only=legalizer-info for details"); 417 } 418 #endif 419 } 420 421 #ifndef NDEBUG 422 // FIXME: This should be in the MachineVerifier, but it can't use the 423 // LegalizerInfo as it's currently in the separate GlobalISel library. 424 // Note that RegBankSelected property already checked in the verifier 425 // has the same layering problem, but we only use inline methods so 426 // end up not needing to link against the GlobalISel library. 427 const MachineInstr *llvm::machineFunctionIsIllegal(const MachineFunction &MF) { 428 if (const LegalizerInfo *MLI = MF.getSubtarget().getLegalizerInfo()) { 429 const MachineRegisterInfo &MRI = MF.getRegInfo(); 430 for (const MachineBasicBlock &MBB : MF) 431 for (const MachineInstr &MI : MBB) 432 if (isPreISelGenericOpcode(MI.getOpcode()) && 433 !MLI->isLegalOrCustom(MI, MRI)) 434 return &MI; 435 } 436 return nullptr; 437 } 438 #endif 439