1 //===- lib/CodeGen/GlobalISel/LegacyLegalizerInfo.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 // Issues to be resolved: 13 // + Make it fast. 14 // + Support weird types like i3, <7 x i3>, ... 15 // + Operations with more than one type (ICMP, CMPXCHG, intrinsics, ...) 16 // 17 //===----------------------------------------------------------------------===// 18 19 #include "llvm/CodeGen/GlobalISel/LegacyLegalizerInfo.h" 20 #include "llvm/CodeGen/GlobalISel/LegalizerInfo.h" 21 #include <map> 22 23 using namespace llvm; 24 using namespace LegacyLegalizeActions; 25 26 #define DEBUG_TYPE "legalizer-info" 27 28 raw_ostream &llvm::operator<<(raw_ostream &OS, LegacyLegalizeAction Action) { 29 switch (Action) { 30 case Legal: 31 OS << "Legal"; 32 break; 33 case NarrowScalar: 34 OS << "NarrowScalar"; 35 break; 36 case WidenScalar: 37 OS << "WidenScalar"; 38 break; 39 case FewerElements: 40 OS << "FewerElements"; 41 break; 42 case MoreElements: 43 OS << "MoreElements"; 44 break; 45 case Bitcast: 46 OS << "Bitcast"; 47 break; 48 case Lower: 49 OS << "Lower"; 50 break; 51 case Libcall: 52 OS << "Libcall"; 53 break; 54 case Custom: 55 OS << "Custom"; 56 break; 57 case Unsupported: 58 OS << "Unsupported"; 59 break; 60 case NotFound: 61 OS << "NotFound"; 62 break; 63 } 64 return OS; 65 } 66 67 LegacyLegalizerInfo::LegacyLegalizerInfo() { 68 // Set defaults. 69 // FIXME: these two (G_ANYEXT and G_TRUNC?) can be legalized to the 70 // fundamental load/store Jakob proposed. Once loads & stores are supported. 71 setScalarAction(TargetOpcode::G_ANYEXT, 1, {{1, Legal}}); 72 setScalarAction(TargetOpcode::G_ZEXT, 1, {{1, Legal}}); 73 setScalarAction(TargetOpcode::G_SEXT, 1, {{1, Legal}}); 74 setScalarAction(TargetOpcode::G_TRUNC, 0, {{1, Legal}}); 75 setScalarAction(TargetOpcode::G_TRUNC, 1, {{1, Legal}}); 76 77 setScalarAction(TargetOpcode::G_INTRINSIC, 0, {{1, Legal}}); 78 setScalarAction(TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS, 0, {{1, Legal}}); 79 80 setLegalizeScalarToDifferentSizeStrategy( 81 TargetOpcode::G_IMPLICIT_DEF, 0, narrowToSmallerAndUnsupportedIfTooSmall); 82 setLegalizeScalarToDifferentSizeStrategy( 83 TargetOpcode::G_ADD, 0, widenToLargerTypesAndNarrowToLargest); 84 setLegalizeScalarToDifferentSizeStrategy( 85 TargetOpcode::G_OR, 0, widenToLargerTypesAndNarrowToLargest); 86 setLegalizeScalarToDifferentSizeStrategy( 87 TargetOpcode::G_LOAD, 0, narrowToSmallerAndUnsupportedIfTooSmall); 88 setLegalizeScalarToDifferentSizeStrategy( 89 TargetOpcode::G_STORE, 0, narrowToSmallerAndUnsupportedIfTooSmall); 90 91 setLegalizeScalarToDifferentSizeStrategy( 92 TargetOpcode::G_BRCOND, 0, widenToLargerTypesUnsupportedOtherwise); 93 setLegalizeScalarToDifferentSizeStrategy( 94 TargetOpcode::G_INSERT, 0, narrowToSmallerAndUnsupportedIfTooSmall); 95 setLegalizeScalarToDifferentSizeStrategy( 96 TargetOpcode::G_EXTRACT, 0, narrowToSmallerAndUnsupportedIfTooSmall); 97 setLegalizeScalarToDifferentSizeStrategy( 98 TargetOpcode::G_EXTRACT, 1, narrowToSmallerAndUnsupportedIfTooSmall); 99 setScalarAction(TargetOpcode::G_FNEG, 0, {{1, Lower}}); 100 } 101 102 void LegacyLegalizerInfo::computeTables() { 103 assert(TablesInitialized == false); 104 105 for (unsigned OpcodeIdx = 0; OpcodeIdx <= LastOp - FirstOp; ++OpcodeIdx) { 106 const unsigned Opcode = FirstOp + OpcodeIdx; 107 for (unsigned TypeIdx = 0; TypeIdx != SpecifiedActions[OpcodeIdx].size(); 108 ++TypeIdx) { 109 // 0. Collect information specified through the setAction API, i.e. 110 // for specific bit sizes. 111 // For scalar types: 112 SizeAndActionsVec ScalarSpecifiedActions; 113 // For pointer types: 114 std::map<uint16_t, SizeAndActionsVec> AddressSpace2SpecifiedActions; 115 // For vector types: 116 std::map<uint16_t, SizeAndActionsVec> ElemSize2SpecifiedActions; 117 for (auto LLT2Action : SpecifiedActions[OpcodeIdx][TypeIdx]) { 118 const LLT Type = LLT2Action.first; 119 const LegacyLegalizeAction Action = LLT2Action.second; 120 121 auto SizeAction = std::make_pair(Type.getSizeInBits(), Action); 122 if (Type.isPointer()) 123 AddressSpace2SpecifiedActions[Type.getAddressSpace()].push_back( 124 SizeAction); 125 else if (Type.isVector()) 126 ElemSize2SpecifiedActions[Type.getElementType().getSizeInBits()] 127 .push_back(SizeAction); 128 else 129 ScalarSpecifiedActions.push_back(SizeAction); 130 } 131 132 // 1. Handle scalar types 133 { 134 // Decide how to handle bit sizes for which no explicit specification 135 // was given. 136 SizeChangeStrategy S = &unsupportedForDifferentSizes; 137 if (TypeIdx < ScalarSizeChangeStrategies[OpcodeIdx].size() && 138 ScalarSizeChangeStrategies[OpcodeIdx][TypeIdx] != nullptr) 139 S = ScalarSizeChangeStrategies[OpcodeIdx][TypeIdx]; 140 llvm::sort(ScalarSpecifiedActions); 141 checkPartialSizeAndActionsVector(ScalarSpecifiedActions); 142 setScalarAction(Opcode, TypeIdx, S(ScalarSpecifiedActions)); 143 } 144 145 // 2. Handle pointer types 146 for (auto PointerSpecifiedActions : AddressSpace2SpecifiedActions) { 147 llvm::sort(PointerSpecifiedActions.second); 148 checkPartialSizeAndActionsVector(PointerSpecifiedActions.second); 149 // For pointer types, we assume that there isn't a meaningfull way 150 // to change the number of bits used in the pointer. 151 setPointerAction( 152 Opcode, TypeIdx, PointerSpecifiedActions.first, 153 unsupportedForDifferentSizes(PointerSpecifiedActions.second)); 154 } 155 156 // 3. Handle vector types 157 SizeAndActionsVec ElementSizesSeen; 158 for (auto VectorSpecifiedActions : ElemSize2SpecifiedActions) { 159 llvm::sort(VectorSpecifiedActions.second); 160 const uint16_t ElementSize = VectorSpecifiedActions.first; 161 ElementSizesSeen.push_back({ElementSize, Legal}); 162 checkPartialSizeAndActionsVector(VectorSpecifiedActions.second); 163 // For vector types, we assume that the best way to adapt the number 164 // of elements is to the next larger number of elements type for which 165 // the vector type is legal, unless there is no such type. In that case, 166 // legalize towards a vector type with a smaller number of elements. 167 SizeAndActionsVec NumElementsActions; 168 for (SizeAndAction BitsizeAndAction : VectorSpecifiedActions.second) { 169 assert(BitsizeAndAction.first % ElementSize == 0); 170 const uint16_t NumElements = BitsizeAndAction.first / ElementSize; 171 NumElementsActions.push_back({NumElements, BitsizeAndAction.second}); 172 } 173 setVectorNumElementAction( 174 Opcode, TypeIdx, ElementSize, 175 moreToWiderTypesAndLessToWidest(NumElementsActions)); 176 } 177 llvm::sort(ElementSizesSeen); 178 SizeChangeStrategy VectorElementSizeChangeStrategy = 179 &unsupportedForDifferentSizes; 180 if (TypeIdx < VectorElementSizeChangeStrategies[OpcodeIdx].size() && 181 VectorElementSizeChangeStrategies[OpcodeIdx][TypeIdx] != nullptr) 182 VectorElementSizeChangeStrategy = 183 VectorElementSizeChangeStrategies[OpcodeIdx][TypeIdx]; 184 setScalarInVectorAction( 185 Opcode, TypeIdx, VectorElementSizeChangeStrategy(ElementSizesSeen)); 186 } 187 } 188 189 TablesInitialized = true; 190 } 191 192 // FIXME: inefficient implementation for now. Without ComputeValueVTs we're 193 // probably going to need specialized lookup structures for various types before 194 // we have any hope of doing well with something like <13 x i3>. Even the common 195 // cases should do better than what we have now. 196 std::pair<LegacyLegalizeAction, LLT> 197 LegacyLegalizerInfo::getAspectAction(const InstrAspect &Aspect) const { 198 assert(TablesInitialized && "backend forgot to call computeTables"); 199 // These *have* to be implemented for now, they're the fundamental basis of 200 // how everything else is transformed. 201 if (Aspect.Type.isScalar() || Aspect.Type.isPointer()) 202 return findScalarLegalAction(Aspect); 203 assert(Aspect.Type.isVector()); 204 return findVectorLegalAction(Aspect); 205 } 206 207 LegacyLegalizerInfo::SizeAndActionsVec 208 LegacyLegalizerInfo::increaseToLargerTypesAndDecreaseToLargest( 209 const SizeAndActionsVec &v, LegacyLegalizeAction IncreaseAction, 210 LegacyLegalizeAction DecreaseAction) { 211 SizeAndActionsVec result; 212 unsigned LargestSizeSoFar = 0; 213 if (v.size() >= 1 && v[0].first != 1) 214 result.push_back({1, IncreaseAction}); 215 for (size_t i = 0; i < v.size(); ++i) { 216 result.push_back(v[i]); 217 LargestSizeSoFar = v[i].first; 218 if (i + 1 < v.size() && v[i + 1].first != v[i].first + 1) { 219 result.push_back({LargestSizeSoFar + 1, IncreaseAction}); 220 LargestSizeSoFar = v[i].first + 1; 221 } 222 } 223 result.push_back({LargestSizeSoFar + 1, DecreaseAction}); 224 return result; 225 } 226 227 LegacyLegalizerInfo::SizeAndActionsVec 228 LegacyLegalizerInfo::decreaseToSmallerTypesAndIncreaseToSmallest( 229 const SizeAndActionsVec &v, LegacyLegalizeAction DecreaseAction, 230 LegacyLegalizeAction IncreaseAction) { 231 SizeAndActionsVec result; 232 if (v.size() == 0 || v[0].first != 1) 233 result.push_back({1, IncreaseAction}); 234 for (size_t i = 0; i < v.size(); ++i) { 235 result.push_back(v[i]); 236 if (i + 1 == v.size() || v[i + 1].first != v[i].first + 1) { 237 result.push_back({v[i].first + 1, DecreaseAction}); 238 } 239 } 240 return result; 241 } 242 243 LegacyLegalizerInfo::SizeAndAction 244 LegacyLegalizerInfo::findAction(const SizeAndActionsVec &Vec, const uint32_t Size) { 245 assert(Size >= 1); 246 // Find the last element in Vec that has a bitsize equal to or smaller than 247 // the requested bit size. 248 // That is the element just before the first element that is bigger than Size. 249 auto It = partition_point( 250 Vec, [=](const SizeAndAction &A) { return A.first <= Size; }); 251 assert(It != Vec.begin() && "Does Vec not start with size 1?"); 252 int VecIdx = It - Vec.begin() - 1; 253 254 LegacyLegalizeAction Action = Vec[VecIdx].second; 255 switch (Action) { 256 case Legal: 257 case Bitcast: 258 case Lower: 259 case Libcall: 260 case Custom: 261 return {Size, Action}; 262 case FewerElements: 263 // FIXME: is this special case still needed and correct? 264 // Special case for scalarization: 265 if (Vec == SizeAndActionsVec({{1, FewerElements}})) 266 return {1, FewerElements}; 267 [[fallthrough]]; 268 case NarrowScalar: { 269 // The following needs to be a loop, as for now, we do allow needing to 270 // go over "Unsupported" bit sizes before finding a legalizable bit size. 271 // e.g. (s8, WidenScalar), (s9, Unsupported), (s32, Legal). if Size==8, 272 // we need to iterate over s9, and then to s32 to return (s32, Legal). 273 // If we want to get rid of the below loop, we should have stronger asserts 274 // when building the SizeAndActionsVecs, probably not allowing 275 // "Unsupported" unless at the ends of the vector. 276 for (int i = VecIdx - 1; i >= 0; --i) 277 if (!needsLegalizingToDifferentSize(Vec[i].second) && 278 Vec[i].second != Unsupported) 279 return {Vec[i].first, Action}; 280 llvm_unreachable(""); 281 } 282 case WidenScalar: 283 case MoreElements: { 284 // See above, the following needs to be a loop, at least for now. 285 for (std::size_t i = VecIdx + 1; i < Vec.size(); ++i) 286 if (!needsLegalizingToDifferentSize(Vec[i].second) && 287 Vec[i].second != Unsupported) 288 return {Vec[i].first, Action}; 289 llvm_unreachable(""); 290 } 291 case Unsupported: 292 return {Size, Unsupported}; 293 case NotFound: 294 llvm_unreachable("NotFound"); 295 } 296 llvm_unreachable("Action has an unknown enum value"); 297 } 298 299 std::pair<LegacyLegalizeAction, LLT> 300 LegacyLegalizerInfo::findScalarLegalAction(const InstrAspect &Aspect) const { 301 assert(Aspect.Type.isScalar() || Aspect.Type.isPointer()); 302 if (Aspect.Opcode < FirstOp || Aspect.Opcode > LastOp) 303 return {NotFound, LLT()}; 304 const unsigned OpcodeIdx = getOpcodeIdxForOpcode(Aspect.Opcode); 305 if (Aspect.Type.isPointer() && 306 AddrSpace2PointerActions[OpcodeIdx].find(Aspect.Type.getAddressSpace()) == 307 AddrSpace2PointerActions[OpcodeIdx].end()) { 308 return {NotFound, LLT()}; 309 } 310 const SmallVector<SizeAndActionsVec, 1> &Actions = 311 Aspect.Type.isPointer() 312 ? AddrSpace2PointerActions[OpcodeIdx] 313 .find(Aspect.Type.getAddressSpace()) 314 ->second 315 : ScalarActions[OpcodeIdx]; 316 if (Aspect.Idx >= Actions.size()) 317 return {NotFound, LLT()}; 318 const SizeAndActionsVec &Vec = Actions[Aspect.Idx]; 319 // FIXME: speed up this search, e.g. by using a results cache for repeated 320 // queries? 321 auto SizeAndAction = findAction(Vec, Aspect.Type.getSizeInBits()); 322 return {SizeAndAction.second, 323 Aspect.Type.isScalar() ? LLT::scalar(SizeAndAction.first) 324 : LLT::pointer(Aspect.Type.getAddressSpace(), 325 SizeAndAction.first)}; 326 } 327 328 std::pair<LegacyLegalizeAction, LLT> 329 LegacyLegalizerInfo::findVectorLegalAction(const InstrAspect &Aspect) const { 330 assert(Aspect.Type.isVector()); 331 // First legalize the vector element size, then legalize the number of 332 // lanes in the vector. 333 if (Aspect.Opcode < FirstOp || Aspect.Opcode > LastOp) 334 return {NotFound, Aspect.Type}; 335 const unsigned OpcodeIdx = getOpcodeIdxForOpcode(Aspect.Opcode); 336 const unsigned TypeIdx = Aspect.Idx; 337 if (TypeIdx >= ScalarInVectorActions[OpcodeIdx].size()) 338 return {NotFound, Aspect.Type}; 339 const SizeAndActionsVec &ElemSizeVec = 340 ScalarInVectorActions[OpcodeIdx][TypeIdx]; 341 342 LLT IntermediateType; 343 auto ElementSizeAndAction = 344 findAction(ElemSizeVec, Aspect.Type.getScalarSizeInBits()); 345 IntermediateType = LLT::fixed_vector(Aspect.Type.getNumElements(), 346 ElementSizeAndAction.first); 347 if (ElementSizeAndAction.second != Legal) 348 return {ElementSizeAndAction.second, IntermediateType}; 349 350 auto i = NumElements2Actions[OpcodeIdx].find( 351 IntermediateType.getScalarSizeInBits()); 352 if (i == NumElements2Actions[OpcodeIdx].end()) { 353 return {NotFound, IntermediateType}; 354 } 355 const SizeAndActionsVec &NumElementsVec = (*i).second[TypeIdx]; 356 auto NumElementsAndAction = 357 findAction(NumElementsVec, IntermediateType.getNumElements()); 358 return {NumElementsAndAction.second, 359 LLT::fixed_vector(NumElementsAndAction.first, 360 IntermediateType.getScalarSizeInBits())}; 361 } 362 363 unsigned LegacyLegalizerInfo::getOpcodeIdxForOpcode(unsigned Opcode) const { 364 assert(Opcode >= FirstOp && Opcode <= LastOp && "Unsupported opcode"); 365 return Opcode - FirstOp; 366 } 367 368 369 LegacyLegalizeActionStep 370 LegacyLegalizerInfo::getAction(const LegalityQuery &Query) const { 371 for (unsigned i = 0; i < Query.Types.size(); ++i) { 372 auto Action = getAspectAction({Query.Opcode, i, Query.Types[i]}); 373 if (Action.first != Legal) { 374 LLVM_DEBUG(dbgs() << ".. (legacy) Type " << i << " Action=" 375 << Action.first << ", " << Action.second << "\n"); 376 return {Action.first, i, Action.second}; 377 } else 378 LLVM_DEBUG(dbgs() << ".. (legacy) Type " << i << " Legal\n"); 379 } 380 LLVM_DEBUG(dbgs() << ".. (legacy) Legal\n"); 381 return {Legal, 0, LLT{}}; 382 } 383 384