1 //===- LowerTypeTests.cpp - type metadata lowering pass -------------------===// 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 pass lowers type metadata and calls to the llvm.type.test intrinsic. 10 // It also ensures that globals are properly laid out for the 11 // llvm.icall.branch.funnel intrinsic. 12 // See http://llvm.org/docs/TypeMetadata.html for more information. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #include "llvm/Transforms/IPO/LowerTypeTests.h" 17 #include "llvm/ADT/APInt.h" 18 #include "llvm/ADT/ArrayRef.h" 19 #include "llvm/ADT/DenseMap.h" 20 #include "llvm/ADT/EquivalenceClasses.h" 21 #include "llvm/ADT/PointerUnion.h" 22 #include "llvm/ADT/SetVector.h" 23 #include "llvm/ADT/SmallVector.h" 24 #include "llvm/ADT/Statistic.h" 25 #include "llvm/ADT/StringRef.h" 26 #include "llvm/ADT/TinyPtrVector.h" 27 #include "llvm/ADT/Triple.h" 28 #include "llvm/Analysis/TypeMetadataUtils.h" 29 #include "llvm/Analysis/ValueTracking.h" 30 #include "llvm/IR/Attributes.h" 31 #include "llvm/IR/BasicBlock.h" 32 #include "llvm/IR/Constant.h" 33 #include "llvm/IR/Constants.h" 34 #include "llvm/IR/DataLayout.h" 35 #include "llvm/IR/DerivedTypes.h" 36 #include "llvm/IR/Function.h" 37 #include "llvm/IR/GlobalAlias.h" 38 #include "llvm/IR/GlobalObject.h" 39 #include "llvm/IR/GlobalValue.h" 40 #include "llvm/IR/GlobalVariable.h" 41 #include "llvm/IR/IRBuilder.h" 42 #include "llvm/IR/InlineAsm.h" 43 #include "llvm/IR/Instruction.h" 44 #include "llvm/IR/Instructions.h" 45 #include "llvm/IR/IntrinsicInst.h" 46 #include "llvm/IR/Intrinsics.h" 47 #include "llvm/IR/LLVMContext.h" 48 #include "llvm/IR/Metadata.h" 49 #include "llvm/IR/Module.h" 50 #include "llvm/IR/ModuleSummaryIndex.h" 51 #include "llvm/IR/ModuleSummaryIndexYAML.h" 52 #include "llvm/IR/Operator.h" 53 #include "llvm/IR/PassManager.h" 54 #include "llvm/IR/Type.h" 55 #include "llvm/IR/Use.h" 56 #include "llvm/IR/User.h" 57 #include "llvm/IR/Value.h" 58 #include "llvm/InitializePasses.h" 59 #include "llvm/Pass.h" 60 #include "llvm/Support/Allocator.h" 61 #include "llvm/Support/Casting.h" 62 #include "llvm/Support/CommandLine.h" 63 #include "llvm/Support/Debug.h" 64 #include "llvm/Support/Error.h" 65 #include "llvm/Support/ErrorHandling.h" 66 #include "llvm/Support/FileSystem.h" 67 #include "llvm/Support/MathExtras.h" 68 #include "llvm/Support/MemoryBuffer.h" 69 #include "llvm/Support/TrailingObjects.h" 70 #include "llvm/Support/YAMLTraits.h" 71 #include "llvm/Support/raw_ostream.h" 72 #include "llvm/Transforms/IPO.h" 73 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 74 #include "llvm/Transforms/Utils/ModuleUtils.h" 75 #include <algorithm> 76 #include <cassert> 77 #include <cstdint> 78 #include <memory> 79 #include <set> 80 #include <string> 81 #include <system_error> 82 #include <utility> 83 #include <vector> 84 85 using namespace llvm; 86 using namespace lowertypetests; 87 88 #define DEBUG_TYPE "lowertypetests" 89 90 STATISTIC(ByteArraySizeBits, "Byte array size in bits"); 91 STATISTIC(ByteArraySizeBytes, "Byte array size in bytes"); 92 STATISTIC(NumByteArraysCreated, "Number of byte arrays created"); 93 STATISTIC(NumTypeTestCallsLowered, "Number of type test calls lowered"); 94 STATISTIC(NumTypeIdDisjointSets, "Number of disjoint sets of type identifiers"); 95 96 static cl::opt<bool> AvoidReuse( 97 "lowertypetests-avoid-reuse", 98 cl::desc("Try to avoid reuse of byte array addresses using aliases"), 99 cl::Hidden, cl::init(true)); 100 101 static cl::opt<PassSummaryAction> ClSummaryAction( 102 "lowertypetests-summary-action", 103 cl::desc("What to do with the summary when running this pass"), 104 cl::values(clEnumValN(PassSummaryAction::None, "none", "Do nothing"), 105 clEnumValN(PassSummaryAction::Import, "import", 106 "Import typeid resolutions from summary and globals"), 107 clEnumValN(PassSummaryAction::Export, "export", 108 "Export typeid resolutions to summary and globals")), 109 cl::Hidden); 110 111 static cl::opt<std::string> ClReadSummary( 112 "lowertypetests-read-summary", 113 cl::desc("Read summary from given YAML file before running pass"), 114 cl::Hidden); 115 116 static cl::opt<std::string> ClWriteSummary( 117 "lowertypetests-write-summary", 118 cl::desc("Write summary to given YAML file after running pass"), 119 cl::Hidden); 120 121 static cl::opt<bool> 122 ClDropTypeTests("lowertypetests-drop-type-tests", 123 cl::desc("Simply drop type test assume sequences"), 124 cl::Hidden, cl::init(false)); 125 126 bool BitSetInfo::containsGlobalOffset(uint64_t Offset) const { 127 if (Offset < ByteOffset) 128 return false; 129 130 if ((Offset - ByteOffset) % (uint64_t(1) << AlignLog2) != 0) 131 return false; 132 133 uint64_t BitOffset = (Offset - ByteOffset) >> AlignLog2; 134 if (BitOffset >= BitSize) 135 return false; 136 137 return Bits.count(BitOffset); 138 } 139 140 void BitSetInfo::print(raw_ostream &OS) const { 141 OS << "offset " << ByteOffset << " size " << BitSize << " align " 142 << (1 << AlignLog2); 143 144 if (isAllOnes()) { 145 OS << " all-ones\n"; 146 return; 147 } 148 149 OS << " { "; 150 for (uint64_t B : Bits) 151 OS << B << ' '; 152 OS << "}\n"; 153 } 154 155 BitSetInfo BitSetBuilder::build() { 156 if (Min > Max) 157 Min = 0; 158 159 // Normalize each offset against the minimum observed offset, and compute 160 // the bitwise OR of each of the offsets. The number of trailing zeros 161 // in the mask gives us the log2 of the alignment of all offsets, which 162 // allows us to compress the bitset by only storing one bit per aligned 163 // address. 164 uint64_t Mask = 0; 165 for (uint64_t &Offset : Offsets) { 166 Offset -= Min; 167 Mask |= Offset; 168 } 169 170 BitSetInfo BSI; 171 BSI.ByteOffset = Min; 172 173 BSI.AlignLog2 = 0; 174 if (Mask != 0) 175 BSI.AlignLog2 = countTrailingZeros(Mask, ZB_Undefined); 176 177 // Build the compressed bitset while normalizing the offsets against the 178 // computed alignment. 179 BSI.BitSize = ((Max - Min) >> BSI.AlignLog2) + 1; 180 for (uint64_t Offset : Offsets) { 181 Offset >>= BSI.AlignLog2; 182 BSI.Bits.insert(Offset); 183 } 184 185 return BSI; 186 } 187 188 void GlobalLayoutBuilder::addFragment(const std::set<uint64_t> &F) { 189 // Create a new fragment to hold the layout for F. 190 Fragments.emplace_back(); 191 std::vector<uint64_t> &Fragment = Fragments.back(); 192 uint64_t FragmentIndex = Fragments.size() - 1; 193 194 for (auto ObjIndex : F) { 195 uint64_t OldFragmentIndex = FragmentMap[ObjIndex]; 196 if (OldFragmentIndex == 0) { 197 // We haven't seen this object index before, so just add it to the current 198 // fragment. 199 Fragment.push_back(ObjIndex); 200 } else { 201 // This index belongs to an existing fragment. Copy the elements of the 202 // old fragment into this one and clear the old fragment. We don't update 203 // the fragment map just yet, this ensures that any further references to 204 // indices from the old fragment in this fragment do not insert any more 205 // indices. 206 std::vector<uint64_t> &OldFragment = Fragments[OldFragmentIndex]; 207 llvm::append_range(Fragment, OldFragment); 208 OldFragment.clear(); 209 } 210 } 211 212 // Update the fragment map to point our object indices to this fragment. 213 for (uint64_t ObjIndex : Fragment) 214 FragmentMap[ObjIndex] = FragmentIndex; 215 } 216 217 void ByteArrayBuilder::allocate(const std::set<uint64_t> &Bits, 218 uint64_t BitSize, uint64_t &AllocByteOffset, 219 uint8_t &AllocMask) { 220 // Find the smallest current allocation. 221 unsigned Bit = 0; 222 for (unsigned I = 1; I != BitsPerByte; ++I) 223 if (BitAllocs[I] < BitAllocs[Bit]) 224 Bit = I; 225 226 AllocByteOffset = BitAllocs[Bit]; 227 228 // Add our size to it. 229 unsigned ReqSize = AllocByteOffset + BitSize; 230 BitAllocs[Bit] = ReqSize; 231 if (Bytes.size() < ReqSize) 232 Bytes.resize(ReqSize); 233 234 // Set our bits. 235 AllocMask = 1 << Bit; 236 for (uint64_t B : Bits) 237 Bytes[AllocByteOffset + B] |= AllocMask; 238 } 239 240 bool lowertypetests::isJumpTableCanonical(Function *F) { 241 if (F->isDeclarationForLinker()) 242 return false; 243 auto *CI = mdconst::extract_or_null<ConstantInt>( 244 F->getParent()->getModuleFlag("CFI Canonical Jump Tables")); 245 if (!CI || CI->getZExtValue() != 0) 246 return true; 247 return F->hasFnAttribute("cfi-canonical-jump-table"); 248 } 249 250 namespace { 251 252 struct ByteArrayInfo { 253 std::set<uint64_t> Bits; 254 uint64_t BitSize; 255 GlobalVariable *ByteArray; 256 GlobalVariable *MaskGlobal; 257 uint8_t *MaskPtr = nullptr; 258 }; 259 260 /// A POD-like structure that we use to store a global reference together with 261 /// its metadata types. In this pass we frequently need to query the set of 262 /// metadata types referenced by a global, which at the IR level is an expensive 263 /// operation involving a map lookup; this data structure helps to reduce the 264 /// number of times we need to do this lookup. 265 class GlobalTypeMember final : TrailingObjects<GlobalTypeMember, MDNode *> { 266 friend TrailingObjects; 267 268 GlobalObject *GO; 269 size_t NTypes; 270 271 // For functions: true if the jump table is canonical. This essentially means 272 // whether the canonical address (i.e. the symbol table entry) of the function 273 // is provided by the local jump table. This is normally the same as whether 274 // the function is defined locally, but if canonical jump tables are disabled 275 // by the user then the jump table never provides a canonical definition. 276 bool IsJumpTableCanonical; 277 278 // For functions: true if this function is either defined or used in a thinlto 279 // module and its jumptable entry needs to be exported to thinlto backends. 280 bool IsExported; 281 282 size_t numTrailingObjects(OverloadToken<MDNode *>) const { return NTypes; } 283 284 public: 285 static GlobalTypeMember *create(BumpPtrAllocator &Alloc, GlobalObject *GO, 286 bool IsJumpTableCanonical, bool IsExported, 287 ArrayRef<MDNode *> Types) { 288 auto *GTM = static_cast<GlobalTypeMember *>(Alloc.Allocate( 289 totalSizeToAlloc<MDNode *>(Types.size()), alignof(GlobalTypeMember))); 290 GTM->GO = GO; 291 GTM->NTypes = Types.size(); 292 GTM->IsJumpTableCanonical = IsJumpTableCanonical; 293 GTM->IsExported = IsExported; 294 std::uninitialized_copy(Types.begin(), Types.end(), 295 GTM->getTrailingObjects<MDNode *>()); 296 return GTM; 297 } 298 299 GlobalObject *getGlobal() const { 300 return GO; 301 } 302 303 bool isJumpTableCanonical() const { 304 return IsJumpTableCanonical; 305 } 306 307 bool isExported() const { 308 return IsExported; 309 } 310 311 ArrayRef<MDNode *> types() const { 312 return makeArrayRef(getTrailingObjects<MDNode *>(), NTypes); 313 } 314 }; 315 316 struct ICallBranchFunnel final 317 : TrailingObjects<ICallBranchFunnel, GlobalTypeMember *> { 318 static ICallBranchFunnel *create(BumpPtrAllocator &Alloc, CallInst *CI, 319 ArrayRef<GlobalTypeMember *> Targets, 320 unsigned UniqueId) { 321 auto *Call = static_cast<ICallBranchFunnel *>( 322 Alloc.Allocate(totalSizeToAlloc<GlobalTypeMember *>(Targets.size()), 323 alignof(ICallBranchFunnel))); 324 Call->CI = CI; 325 Call->UniqueId = UniqueId; 326 Call->NTargets = Targets.size(); 327 std::uninitialized_copy(Targets.begin(), Targets.end(), 328 Call->getTrailingObjects<GlobalTypeMember *>()); 329 return Call; 330 } 331 332 CallInst *CI; 333 ArrayRef<GlobalTypeMember *> targets() const { 334 return makeArrayRef(getTrailingObjects<GlobalTypeMember *>(), NTargets); 335 } 336 337 unsigned UniqueId; 338 339 private: 340 size_t NTargets; 341 }; 342 343 struct ScopedSaveAliaseesAndUsed { 344 Module &M; 345 SmallVector<GlobalValue *, 4> Used, CompilerUsed; 346 std::vector<std::pair<GlobalAlias *, Function *>> FunctionAliases; 347 std::vector<std::pair<GlobalIFunc *, Function *>> ResolverIFuncs; 348 349 ScopedSaveAliaseesAndUsed(Module &M) : M(M) { 350 // The users of this class want to replace all function references except 351 // for aliases and llvm.used/llvm.compiler.used with references to a jump 352 // table. We avoid replacing aliases in order to avoid introducing a double 353 // indirection (or an alias pointing to a declaration in ThinLTO mode), and 354 // we avoid replacing llvm.used/llvm.compiler.used because these global 355 // variables describe properties of the global, not the jump table (besides, 356 // offseted references to the jump table in llvm.used are invalid). 357 // Unfortunately, LLVM doesn't have a "RAUW except for these (possibly 358 // indirect) users", so what we do is save the list of globals referenced by 359 // llvm.used/llvm.compiler.used and aliases, erase the used lists, let RAUW 360 // replace the aliasees and then set them back to their original values at 361 // the end. 362 if (GlobalVariable *GV = collectUsedGlobalVariables(M, Used, false)) 363 GV->eraseFromParent(); 364 if (GlobalVariable *GV = collectUsedGlobalVariables(M, CompilerUsed, true)) 365 GV->eraseFromParent(); 366 367 for (auto &GA : M.aliases()) { 368 // FIXME: This should look past all aliases not just interposable ones, 369 // see discussion on D65118. 370 if (auto *F = dyn_cast<Function>(GA.getAliasee()->stripPointerCasts())) 371 FunctionAliases.push_back({&GA, F}); 372 } 373 374 for (auto &GI : M.ifuncs()) 375 if (auto *F = dyn_cast<Function>(GI.getResolver()->stripPointerCasts())) 376 ResolverIFuncs.push_back({&GI, F}); 377 } 378 379 ~ScopedSaveAliaseesAndUsed() { 380 appendToUsed(M, Used); 381 appendToCompilerUsed(M, CompilerUsed); 382 383 for (auto P : FunctionAliases) 384 P.first->setAliasee( 385 ConstantExpr::getBitCast(P.second, P.first->getType())); 386 387 for (auto P : ResolverIFuncs) { 388 // This does not preserve pointer casts that may have been stripped by the 389 // constructor, but the resolver's type is different from that of the 390 // ifunc anyway. 391 P.first->setResolver(P.second); 392 } 393 } 394 }; 395 396 class LowerTypeTestsModule { 397 Module &M; 398 399 ModuleSummaryIndex *ExportSummary; 400 const ModuleSummaryIndex *ImportSummary; 401 // Set when the client has invoked this to simply drop all type test assume 402 // sequences. 403 bool DropTypeTests; 404 405 Triple::ArchType Arch; 406 Triple::OSType OS; 407 Triple::ObjectFormatType ObjectFormat; 408 409 IntegerType *Int1Ty = Type::getInt1Ty(M.getContext()); 410 IntegerType *Int8Ty = Type::getInt8Ty(M.getContext()); 411 PointerType *Int8PtrTy = Type::getInt8PtrTy(M.getContext()); 412 ArrayType *Int8Arr0Ty = ArrayType::get(Type::getInt8Ty(M.getContext()), 0); 413 IntegerType *Int32Ty = Type::getInt32Ty(M.getContext()); 414 PointerType *Int32PtrTy = PointerType::getUnqual(Int32Ty); 415 IntegerType *Int64Ty = Type::getInt64Ty(M.getContext()); 416 IntegerType *IntPtrTy = M.getDataLayout().getIntPtrType(M.getContext(), 0); 417 418 // Indirect function call index assignment counter for WebAssembly 419 uint64_t IndirectIndex = 1; 420 421 // Mapping from type identifiers to the call sites that test them, as well as 422 // whether the type identifier needs to be exported to ThinLTO backends as 423 // part of the regular LTO phase of the ThinLTO pipeline (see exportTypeId). 424 struct TypeIdUserInfo { 425 std::vector<CallInst *> CallSites; 426 bool IsExported = false; 427 }; 428 DenseMap<Metadata *, TypeIdUserInfo> TypeIdUsers; 429 430 /// This structure describes how to lower type tests for a particular type 431 /// identifier. It is either built directly from the global analysis (during 432 /// regular LTO or the regular LTO phase of ThinLTO), or indirectly using type 433 /// identifier summaries and external symbol references (in ThinLTO backends). 434 struct TypeIdLowering { 435 TypeTestResolution::Kind TheKind = TypeTestResolution::Unsat; 436 437 /// All except Unsat: the start address within the combined global. 438 Constant *OffsetedGlobal; 439 440 /// ByteArray, Inline, AllOnes: log2 of the required global alignment 441 /// relative to the start address. 442 Constant *AlignLog2; 443 444 /// ByteArray, Inline, AllOnes: one less than the size of the memory region 445 /// covering members of this type identifier as a multiple of 2^AlignLog2. 446 Constant *SizeM1; 447 448 /// ByteArray: the byte array to test the address against. 449 Constant *TheByteArray; 450 451 /// ByteArray: the bit mask to apply to bytes loaded from the byte array. 452 Constant *BitMask; 453 454 /// Inline: the bit mask to test the address against. 455 Constant *InlineBits; 456 }; 457 458 std::vector<ByteArrayInfo> ByteArrayInfos; 459 460 Function *WeakInitializerFn = nullptr; 461 462 bool shouldExportConstantsAsAbsoluteSymbols(); 463 uint8_t *exportTypeId(StringRef TypeId, const TypeIdLowering &TIL); 464 TypeIdLowering importTypeId(StringRef TypeId); 465 void importTypeTest(CallInst *CI); 466 void importFunction(Function *F, bool isJumpTableCanonical, 467 std::vector<GlobalAlias *> &AliasesToErase); 468 469 BitSetInfo 470 buildBitSet(Metadata *TypeId, 471 const DenseMap<GlobalTypeMember *, uint64_t> &GlobalLayout); 472 ByteArrayInfo *createByteArray(BitSetInfo &BSI); 473 void allocateByteArrays(); 474 Value *createBitSetTest(IRBuilder<> &B, const TypeIdLowering &TIL, 475 Value *BitOffset); 476 void lowerTypeTestCalls( 477 ArrayRef<Metadata *> TypeIds, Constant *CombinedGlobalAddr, 478 const DenseMap<GlobalTypeMember *, uint64_t> &GlobalLayout); 479 Value *lowerTypeTestCall(Metadata *TypeId, CallInst *CI, 480 const TypeIdLowering &TIL); 481 482 void buildBitSetsFromGlobalVariables(ArrayRef<Metadata *> TypeIds, 483 ArrayRef<GlobalTypeMember *> Globals); 484 unsigned getJumpTableEntrySize(); 485 Type *getJumpTableEntryType(); 486 void createJumpTableEntry(raw_ostream &AsmOS, raw_ostream &ConstraintOS, 487 Triple::ArchType JumpTableArch, 488 SmallVectorImpl<Value *> &AsmArgs, Function *Dest); 489 void verifyTypeMDNode(GlobalObject *GO, MDNode *Type); 490 void buildBitSetsFromFunctions(ArrayRef<Metadata *> TypeIds, 491 ArrayRef<GlobalTypeMember *> Functions); 492 void buildBitSetsFromFunctionsNative(ArrayRef<Metadata *> TypeIds, 493 ArrayRef<GlobalTypeMember *> Functions); 494 void buildBitSetsFromFunctionsWASM(ArrayRef<Metadata *> TypeIds, 495 ArrayRef<GlobalTypeMember *> Functions); 496 void 497 buildBitSetsFromDisjointSet(ArrayRef<Metadata *> TypeIds, 498 ArrayRef<GlobalTypeMember *> Globals, 499 ArrayRef<ICallBranchFunnel *> ICallBranchFunnels); 500 501 void replaceWeakDeclarationWithJumpTablePtr(Function *F, Constant *JT, 502 bool IsJumpTableCanonical); 503 void moveInitializerToModuleConstructor(GlobalVariable *GV); 504 void findGlobalVariableUsersOf(Constant *C, 505 SmallSetVector<GlobalVariable *, 8> &Out); 506 507 void createJumpTable(Function *F, ArrayRef<GlobalTypeMember *> Functions); 508 509 /// replaceCfiUses - Go through the uses list for this definition 510 /// and make each use point to "V" instead of "this" when the use is outside 511 /// the block. 'This's use list is expected to have at least one element. 512 /// Unlike replaceAllUsesWith this function skips blockaddr and direct call 513 /// uses. 514 void replaceCfiUses(Function *Old, Value *New, bool IsJumpTableCanonical); 515 516 /// replaceDirectCalls - Go through the uses list for this definition and 517 /// replace each use, which is a direct function call. 518 void replaceDirectCalls(Value *Old, Value *New); 519 520 public: 521 LowerTypeTestsModule(Module &M, ModuleSummaryIndex *ExportSummary, 522 const ModuleSummaryIndex *ImportSummary, 523 bool DropTypeTests); 524 525 bool lower(); 526 527 // Lower the module using the action and summary passed as command line 528 // arguments. For testing purposes only. 529 static bool runForTesting(Module &M); 530 }; 531 } // end anonymous namespace 532 533 /// Build a bit set for TypeId using the object layouts in 534 /// GlobalLayout. 535 BitSetInfo LowerTypeTestsModule::buildBitSet( 536 Metadata *TypeId, 537 const DenseMap<GlobalTypeMember *, uint64_t> &GlobalLayout) { 538 BitSetBuilder BSB; 539 540 // Compute the byte offset of each address associated with this type 541 // identifier. 542 for (auto &GlobalAndOffset : GlobalLayout) { 543 for (MDNode *Type : GlobalAndOffset.first->types()) { 544 if (Type->getOperand(1) != TypeId) 545 continue; 546 uint64_t Offset = 547 cast<ConstantInt>( 548 cast<ConstantAsMetadata>(Type->getOperand(0))->getValue()) 549 ->getZExtValue(); 550 BSB.addOffset(GlobalAndOffset.second + Offset); 551 } 552 } 553 554 return BSB.build(); 555 } 556 557 /// Build a test that bit BitOffset mod sizeof(Bits)*8 is set in 558 /// Bits. This pattern matches to the bt instruction on x86. 559 static Value *createMaskedBitTest(IRBuilder<> &B, Value *Bits, 560 Value *BitOffset) { 561 auto BitsType = cast<IntegerType>(Bits->getType()); 562 unsigned BitWidth = BitsType->getBitWidth(); 563 564 BitOffset = B.CreateZExtOrTrunc(BitOffset, BitsType); 565 Value *BitIndex = 566 B.CreateAnd(BitOffset, ConstantInt::get(BitsType, BitWidth - 1)); 567 Value *BitMask = B.CreateShl(ConstantInt::get(BitsType, 1), BitIndex); 568 Value *MaskedBits = B.CreateAnd(Bits, BitMask); 569 return B.CreateICmpNE(MaskedBits, ConstantInt::get(BitsType, 0)); 570 } 571 572 ByteArrayInfo *LowerTypeTestsModule::createByteArray(BitSetInfo &BSI) { 573 // Create globals to stand in for byte arrays and masks. These never actually 574 // get initialized, we RAUW and erase them later in allocateByteArrays() once 575 // we know the offset and mask to use. 576 auto ByteArrayGlobal = new GlobalVariable( 577 M, Int8Ty, /*isConstant=*/true, GlobalValue::PrivateLinkage, nullptr); 578 auto MaskGlobal = new GlobalVariable(M, Int8Ty, /*isConstant=*/true, 579 GlobalValue::PrivateLinkage, nullptr); 580 581 ByteArrayInfos.emplace_back(); 582 ByteArrayInfo *BAI = &ByteArrayInfos.back(); 583 584 BAI->Bits = BSI.Bits; 585 BAI->BitSize = BSI.BitSize; 586 BAI->ByteArray = ByteArrayGlobal; 587 BAI->MaskGlobal = MaskGlobal; 588 return BAI; 589 } 590 591 void LowerTypeTestsModule::allocateByteArrays() { 592 llvm::stable_sort(ByteArrayInfos, 593 [](const ByteArrayInfo &BAI1, const ByteArrayInfo &BAI2) { 594 return BAI1.BitSize > BAI2.BitSize; 595 }); 596 597 std::vector<uint64_t> ByteArrayOffsets(ByteArrayInfos.size()); 598 599 ByteArrayBuilder BAB; 600 for (unsigned I = 0; I != ByteArrayInfos.size(); ++I) { 601 ByteArrayInfo *BAI = &ByteArrayInfos[I]; 602 603 uint8_t Mask; 604 BAB.allocate(BAI->Bits, BAI->BitSize, ByteArrayOffsets[I], Mask); 605 606 BAI->MaskGlobal->replaceAllUsesWith( 607 ConstantExpr::getIntToPtr(ConstantInt::get(Int8Ty, Mask), Int8PtrTy)); 608 BAI->MaskGlobal->eraseFromParent(); 609 if (BAI->MaskPtr) 610 *BAI->MaskPtr = Mask; 611 } 612 613 Constant *ByteArrayConst = ConstantDataArray::get(M.getContext(), BAB.Bytes); 614 auto ByteArray = 615 new GlobalVariable(M, ByteArrayConst->getType(), /*isConstant=*/true, 616 GlobalValue::PrivateLinkage, ByteArrayConst); 617 618 for (unsigned I = 0; I != ByteArrayInfos.size(); ++I) { 619 ByteArrayInfo *BAI = &ByteArrayInfos[I]; 620 621 Constant *Idxs[] = {ConstantInt::get(IntPtrTy, 0), 622 ConstantInt::get(IntPtrTy, ByteArrayOffsets[I])}; 623 Constant *GEP = ConstantExpr::getInBoundsGetElementPtr( 624 ByteArrayConst->getType(), ByteArray, Idxs); 625 626 // Create an alias instead of RAUW'ing the gep directly. On x86 this ensures 627 // that the pc-relative displacement is folded into the lea instead of the 628 // test instruction getting another displacement. 629 GlobalAlias *Alias = GlobalAlias::create( 630 Int8Ty, 0, GlobalValue::PrivateLinkage, "bits", GEP, &M); 631 BAI->ByteArray->replaceAllUsesWith(Alias); 632 BAI->ByteArray->eraseFromParent(); 633 } 634 635 ByteArraySizeBits = BAB.BitAllocs[0] + BAB.BitAllocs[1] + BAB.BitAllocs[2] + 636 BAB.BitAllocs[3] + BAB.BitAllocs[4] + BAB.BitAllocs[5] + 637 BAB.BitAllocs[6] + BAB.BitAllocs[7]; 638 ByteArraySizeBytes = BAB.Bytes.size(); 639 } 640 641 /// Build a test that bit BitOffset is set in the type identifier that was 642 /// lowered to TIL, which must be either an Inline or a ByteArray. 643 Value *LowerTypeTestsModule::createBitSetTest(IRBuilder<> &B, 644 const TypeIdLowering &TIL, 645 Value *BitOffset) { 646 if (TIL.TheKind == TypeTestResolution::Inline) { 647 // If the bit set is sufficiently small, we can avoid a load by bit testing 648 // a constant. 649 return createMaskedBitTest(B, TIL.InlineBits, BitOffset); 650 } else { 651 Constant *ByteArray = TIL.TheByteArray; 652 if (AvoidReuse && !ImportSummary) { 653 // Each use of the byte array uses a different alias. This makes the 654 // backend less likely to reuse previously computed byte array addresses, 655 // improving the security of the CFI mechanism based on this pass. 656 // This won't work when importing because TheByteArray is external. 657 ByteArray = GlobalAlias::create(Int8Ty, 0, GlobalValue::PrivateLinkage, 658 "bits_use", ByteArray, &M); 659 } 660 661 Value *ByteAddr = B.CreateGEP(Int8Ty, ByteArray, BitOffset); 662 Value *Byte = B.CreateLoad(Int8Ty, ByteAddr); 663 664 Value *ByteAndMask = 665 B.CreateAnd(Byte, ConstantExpr::getPtrToInt(TIL.BitMask, Int8Ty)); 666 return B.CreateICmpNE(ByteAndMask, ConstantInt::get(Int8Ty, 0)); 667 } 668 } 669 670 static bool isKnownTypeIdMember(Metadata *TypeId, const DataLayout &DL, 671 Value *V, uint64_t COffset) { 672 if (auto GV = dyn_cast<GlobalObject>(V)) { 673 SmallVector<MDNode *, 2> Types; 674 GV->getMetadata(LLVMContext::MD_type, Types); 675 for (MDNode *Type : Types) { 676 if (Type->getOperand(1) != TypeId) 677 continue; 678 uint64_t Offset = 679 cast<ConstantInt>( 680 cast<ConstantAsMetadata>(Type->getOperand(0))->getValue()) 681 ->getZExtValue(); 682 if (COffset == Offset) 683 return true; 684 } 685 return false; 686 } 687 688 if (auto GEP = dyn_cast<GEPOperator>(V)) { 689 APInt APOffset(DL.getPointerSizeInBits(0), 0); 690 bool Result = GEP->accumulateConstantOffset(DL, APOffset); 691 if (!Result) 692 return false; 693 COffset += APOffset.getZExtValue(); 694 return isKnownTypeIdMember(TypeId, DL, GEP->getPointerOperand(), COffset); 695 } 696 697 if (auto Op = dyn_cast<Operator>(V)) { 698 if (Op->getOpcode() == Instruction::BitCast) 699 return isKnownTypeIdMember(TypeId, DL, Op->getOperand(0), COffset); 700 701 if (Op->getOpcode() == Instruction::Select) 702 return isKnownTypeIdMember(TypeId, DL, Op->getOperand(1), COffset) && 703 isKnownTypeIdMember(TypeId, DL, Op->getOperand(2), COffset); 704 } 705 706 return false; 707 } 708 709 /// Lower a llvm.type.test call to its implementation. Returns the value to 710 /// replace the call with. 711 Value *LowerTypeTestsModule::lowerTypeTestCall(Metadata *TypeId, CallInst *CI, 712 const TypeIdLowering &TIL) { 713 // Delay lowering if the resolution is currently unknown. 714 if (TIL.TheKind == TypeTestResolution::Unknown) 715 return nullptr; 716 if (TIL.TheKind == TypeTestResolution::Unsat) 717 return ConstantInt::getFalse(M.getContext()); 718 719 Value *Ptr = CI->getArgOperand(0); 720 const DataLayout &DL = M.getDataLayout(); 721 if (isKnownTypeIdMember(TypeId, DL, Ptr, 0)) 722 return ConstantInt::getTrue(M.getContext()); 723 724 BasicBlock *InitialBB = CI->getParent(); 725 726 IRBuilder<> B(CI); 727 728 Value *PtrAsInt = B.CreatePtrToInt(Ptr, IntPtrTy); 729 730 Constant *OffsetedGlobalAsInt = 731 ConstantExpr::getPtrToInt(TIL.OffsetedGlobal, IntPtrTy); 732 if (TIL.TheKind == TypeTestResolution::Single) 733 return B.CreateICmpEQ(PtrAsInt, OffsetedGlobalAsInt); 734 735 Value *PtrOffset = B.CreateSub(PtrAsInt, OffsetedGlobalAsInt); 736 737 // We need to check that the offset both falls within our range and is 738 // suitably aligned. We can check both properties at the same time by 739 // performing a right rotate by log2(alignment) followed by an integer 740 // comparison against the bitset size. The rotate will move the lower 741 // order bits that need to be zero into the higher order bits of the 742 // result, causing the comparison to fail if they are nonzero. The rotate 743 // also conveniently gives us a bit offset to use during the load from 744 // the bitset. 745 Value *OffsetSHR = 746 B.CreateLShr(PtrOffset, ConstantExpr::getZExt(TIL.AlignLog2, IntPtrTy)); 747 Value *OffsetSHL = B.CreateShl( 748 PtrOffset, ConstantExpr::getZExt( 749 ConstantExpr::getSub( 750 ConstantInt::get(Int8Ty, DL.getPointerSizeInBits(0)), 751 TIL.AlignLog2), 752 IntPtrTy)); 753 Value *BitOffset = B.CreateOr(OffsetSHR, OffsetSHL); 754 755 Value *OffsetInRange = B.CreateICmpULE(BitOffset, TIL.SizeM1); 756 757 // If the bit set is all ones, testing against it is unnecessary. 758 if (TIL.TheKind == TypeTestResolution::AllOnes) 759 return OffsetInRange; 760 761 // See if the intrinsic is used in the following common pattern: 762 // br(llvm.type.test(...), thenbb, elsebb) 763 // where nothing happens between the type test and the br. 764 // If so, create slightly simpler IR. 765 if (CI->hasOneUse()) 766 if (auto *Br = dyn_cast<BranchInst>(*CI->user_begin())) 767 if (CI->getNextNode() == Br) { 768 BasicBlock *Then = InitialBB->splitBasicBlock(CI->getIterator()); 769 BasicBlock *Else = Br->getSuccessor(1); 770 BranchInst *NewBr = BranchInst::Create(Then, Else, OffsetInRange); 771 NewBr->setMetadata(LLVMContext::MD_prof, 772 Br->getMetadata(LLVMContext::MD_prof)); 773 ReplaceInstWithInst(InitialBB->getTerminator(), NewBr); 774 775 // Update phis in Else resulting from InitialBB being split 776 for (auto &Phi : Else->phis()) 777 Phi.addIncoming(Phi.getIncomingValueForBlock(Then), InitialBB); 778 779 IRBuilder<> ThenB(CI); 780 return createBitSetTest(ThenB, TIL, BitOffset); 781 } 782 783 IRBuilder<> ThenB(SplitBlockAndInsertIfThen(OffsetInRange, CI, false)); 784 785 // Now that we know that the offset is in range and aligned, load the 786 // appropriate bit from the bitset. 787 Value *Bit = createBitSetTest(ThenB, TIL, BitOffset); 788 789 // The value we want is 0 if we came directly from the initial block 790 // (having failed the range or alignment checks), or the loaded bit if 791 // we came from the block in which we loaded it. 792 B.SetInsertPoint(CI); 793 PHINode *P = B.CreatePHI(Int1Ty, 2); 794 P->addIncoming(ConstantInt::get(Int1Ty, 0), InitialBB); 795 P->addIncoming(Bit, ThenB.GetInsertBlock()); 796 return P; 797 } 798 799 /// Given a disjoint set of type identifiers and globals, lay out the globals, 800 /// build the bit sets and lower the llvm.type.test calls. 801 void LowerTypeTestsModule::buildBitSetsFromGlobalVariables( 802 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Globals) { 803 // Build a new global with the combined contents of the referenced globals. 804 // This global is a struct whose even-indexed elements contain the original 805 // contents of the referenced globals and whose odd-indexed elements contain 806 // any padding required to align the next element to the next power of 2 plus 807 // any additional padding required to meet its alignment requirements. 808 std::vector<Constant *> GlobalInits; 809 const DataLayout &DL = M.getDataLayout(); 810 DenseMap<GlobalTypeMember *, uint64_t> GlobalLayout; 811 Align MaxAlign; 812 uint64_t CurOffset = 0; 813 uint64_t DesiredPadding = 0; 814 for (GlobalTypeMember *G : Globals) { 815 auto *GV = cast<GlobalVariable>(G->getGlobal()); 816 Align Alignment = 817 DL.getValueOrABITypeAlignment(GV->getAlign(), GV->getValueType()); 818 MaxAlign = std::max(MaxAlign, Alignment); 819 uint64_t GVOffset = alignTo(CurOffset + DesiredPadding, Alignment); 820 GlobalLayout[G] = GVOffset; 821 if (GVOffset != 0) { 822 uint64_t Padding = GVOffset - CurOffset; 823 GlobalInits.push_back( 824 ConstantAggregateZero::get(ArrayType::get(Int8Ty, Padding))); 825 } 826 827 GlobalInits.push_back(GV->getInitializer()); 828 uint64_t InitSize = DL.getTypeAllocSize(GV->getValueType()); 829 CurOffset = GVOffset + InitSize; 830 831 // Compute the amount of padding that we'd like for the next element. 832 DesiredPadding = NextPowerOf2(InitSize - 1) - InitSize; 833 834 // Experiments of different caps with Chromium on both x64 and ARM64 835 // have shown that the 32-byte cap generates the smallest binary on 836 // both platforms while different caps yield similar performance. 837 // (see https://lists.llvm.org/pipermail/llvm-dev/2018-July/124694.html) 838 if (DesiredPadding > 32) 839 DesiredPadding = alignTo(InitSize, 32) - InitSize; 840 } 841 842 Constant *NewInit = ConstantStruct::getAnon(M.getContext(), GlobalInits); 843 auto *CombinedGlobal = 844 new GlobalVariable(M, NewInit->getType(), /*isConstant=*/true, 845 GlobalValue::PrivateLinkage, NewInit); 846 CombinedGlobal->setAlignment(MaxAlign); 847 848 StructType *NewTy = cast<StructType>(NewInit->getType()); 849 lowerTypeTestCalls(TypeIds, CombinedGlobal, GlobalLayout); 850 851 // Build aliases pointing to offsets into the combined global for each 852 // global from which we built the combined global, and replace references 853 // to the original globals with references to the aliases. 854 for (unsigned I = 0; I != Globals.size(); ++I) { 855 GlobalVariable *GV = cast<GlobalVariable>(Globals[I]->getGlobal()); 856 857 // Multiply by 2 to account for padding elements. 858 Constant *CombinedGlobalIdxs[] = {ConstantInt::get(Int32Ty, 0), 859 ConstantInt::get(Int32Ty, I * 2)}; 860 Constant *CombinedGlobalElemPtr = ConstantExpr::getGetElementPtr( 861 NewInit->getType(), CombinedGlobal, CombinedGlobalIdxs); 862 assert(GV->getType()->getAddressSpace() == 0); 863 GlobalAlias *GAlias = 864 GlobalAlias::create(NewTy->getElementType(I * 2), 0, GV->getLinkage(), 865 "", CombinedGlobalElemPtr, &M); 866 GAlias->setVisibility(GV->getVisibility()); 867 GAlias->takeName(GV); 868 GV->replaceAllUsesWith(GAlias); 869 GV->eraseFromParent(); 870 } 871 } 872 873 bool LowerTypeTestsModule::shouldExportConstantsAsAbsoluteSymbols() { 874 return (Arch == Triple::x86 || Arch == Triple::x86_64) && 875 ObjectFormat == Triple::ELF; 876 } 877 878 /// Export the given type identifier so that ThinLTO backends may import it. 879 /// Type identifiers are exported by adding coarse-grained information about how 880 /// to test the type identifier to the summary, and creating symbols in the 881 /// object file (aliases and absolute symbols) containing fine-grained 882 /// information about the type identifier. 883 /// 884 /// Returns a pointer to the location in which to store the bitmask, if 885 /// applicable. 886 uint8_t *LowerTypeTestsModule::exportTypeId(StringRef TypeId, 887 const TypeIdLowering &TIL) { 888 TypeTestResolution &TTRes = 889 ExportSummary->getOrInsertTypeIdSummary(TypeId).TTRes; 890 TTRes.TheKind = TIL.TheKind; 891 892 auto ExportGlobal = [&](StringRef Name, Constant *C) { 893 GlobalAlias *GA = 894 GlobalAlias::create(Int8Ty, 0, GlobalValue::ExternalLinkage, 895 "__typeid_" + TypeId + "_" + Name, C, &M); 896 GA->setVisibility(GlobalValue::HiddenVisibility); 897 }; 898 899 auto ExportConstant = [&](StringRef Name, uint64_t &Storage, Constant *C) { 900 if (shouldExportConstantsAsAbsoluteSymbols()) 901 ExportGlobal(Name, ConstantExpr::getIntToPtr(C, Int8PtrTy)); 902 else 903 Storage = cast<ConstantInt>(C)->getZExtValue(); 904 }; 905 906 if (TIL.TheKind != TypeTestResolution::Unsat) 907 ExportGlobal("global_addr", TIL.OffsetedGlobal); 908 909 if (TIL.TheKind == TypeTestResolution::ByteArray || 910 TIL.TheKind == TypeTestResolution::Inline || 911 TIL.TheKind == TypeTestResolution::AllOnes) { 912 ExportConstant("align", TTRes.AlignLog2, TIL.AlignLog2); 913 ExportConstant("size_m1", TTRes.SizeM1, TIL.SizeM1); 914 915 uint64_t BitSize = cast<ConstantInt>(TIL.SizeM1)->getZExtValue() + 1; 916 if (TIL.TheKind == TypeTestResolution::Inline) 917 TTRes.SizeM1BitWidth = (BitSize <= 32) ? 5 : 6; 918 else 919 TTRes.SizeM1BitWidth = (BitSize <= 128) ? 7 : 32; 920 } 921 922 if (TIL.TheKind == TypeTestResolution::ByteArray) { 923 ExportGlobal("byte_array", TIL.TheByteArray); 924 if (shouldExportConstantsAsAbsoluteSymbols()) 925 ExportGlobal("bit_mask", TIL.BitMask); 926 else 927 return &TTRes.BitMask; 928 } 929 930 if (TIL.TheKind == TypeTestResolution::Inline) 931 ExportConstant("inline_bits", TTRes.InlineBits, TIL.InlineBits); 932 933 return nullptr; 934 } 935 936 LowerTypeTestsModule::TypeIdLowering 937 LowerTypeTestsModule::importTypeId(StringRef TypeId) { 938 const TypeIdSummary *TidSummary = ImportSummary->getTypeIdSummary(TypeId); 939 if (!TidSummary) 940 return {}; // Unsat: no globals match this type id. 941 const TypeTestResolution &TTRes = TidSummary->TTRes; 942 943 TypeIdLowering TIL; 944 TIL.TheKind = TTRes.TheKind; 945 946 auto ImportGlobal = [&](StringRef Name) { 947 // Give the global a type of length 0 so that it is not assumed not to alias 948 // with any other global. 949 Constant *C = M.getOrInsertGlobal(("__typeid_" + TypeId + "_" + Name).str(), 950 Int8Arr0Ty); 951 if (auto *GV = dyn_cast<GlobalVariable>(C)) 952 GV->setVisibility(GlobalValue::HiddenVisibility); 953 C = ConstantExpr::getBitCast(C, Int8PtrTy); 954 return C; 955 }; 956 957 auto ImportConstant = [&](StringRef Name, uint64_t Const, unsigned AbsWidth, 958 Type *Ty) { 959 if (!shouldExportConstantsAsAbsoluteSymbols()) { 960 Constant *C = 961 ConstantInt::get(isa<IntegerType>(Ty) ? Ty : Int64Ty, Const); 962 if (!isa<IntegerType>(Ty)) 963 C = ConstantExpr::getIntToPtr(C, Ty); 964 return C; 965 } 966 967 Constant *C = ImportGlobal(Name); 968 auto *GV = cast<GlobalVariable>(C->stripPointerCasts()); 969 if (isa<IntegerType>(Ty)) 970 C = ConstantExpr::getPtrToInt(C, Ty); 971 if (GV->getMetadata(LLVMContext::MD_absolute_symbol)) 972 return C; 973 974 auto SetAbsRange = [&](uint64_t Min, uint64_t Max) { 975 auto *MinC = ConstantAsMetadata::get(ConstantInt::get(IntPtrTy, Min)); 976 auto *MaxC = ConstantAsMetadata::get(ConstantInt::get(IntPtrTy, Max)); 977 GV->setMetadata(LLVMContext::MD_absolute_symbol, 978 MDNode::get(M.getContext(), {MinC, MaxC})); 979 }; 980 if (AbsWidth == IntPtrTy->getBitWidth()) 981 SetAbsRange(~0ull, ~0ull); // Full set. 982 else 983 SetAbsRange(0, 1ull << AbsWidth); 984 return C; 985 }; 986 987 if (TIL.TheKind != TypeTestResolution::Unsat) 988 TIL.OffsetedGlobal = ImportGlobal("global_addr"); 989 990 if (TIL.TheKind == TypeTestResolution::ByteArray || 991 TIL.TheKind == TypeTestResolution::Inline || 992 TIL.TheKind == TypeTestResolution::AllOnes) { 993 TIL.AlignLog2 = ImportConstant("align", TTRes.AlignLog2, 8, Int8Ty); 994 TIL.SizeM1 = 995 ImportConstant("size_m1", TTRes.SizeM1, TTRes.SizeM1BitWidth, IntPtrTy); 996 } 997 998 if (TIL.TheKind == TypeTestResolution::ByteArray) { 999 TIL.TheByteArray = ImportGlobal("byte_array"); 1000 TIL.BitMask = ImportConstant("bit_mask", TTRes.BitMask, 8, Int8PtrTy); 1001 } 1002 1003 if (TIL.TheKind == TypeTestResolution::Inline) 1004 TIL.InlineBits = ImportConstant( 1005 "inline_bits", TTRes.InlineBits, 1 << TTRes.SizeM1BitWidth, 1006 TTRes.SizeM1BitWidth <= 5 ? Int32Ty : Int64Ty); 1007 1008 return TIL; 1009 } 1010 1011 void LowerTypeTestsModule::importTypeTest(CallInst *CI) { 1012 auto TypeIdMDVal = dyn_cast<MetadataAsValue>(CI->getArgOperand(1)); 1013 if (!TypeIdMDVal) 1014 report_fatal_error("Second argument of llvm.type.test must be metadata"); 1015 1016 auto TypeIdStr = dyn_cast<MDString>(TypeIdMDVal->getMetadata()); 1017 // If this is a local unpromoted type, which doesn't have a metadata string, 1018 // treat as Unknown and delay lowering, so that we can still utilize it for 1019 // later optimizations. 1020 if (!TypeIdStr) 1021 return; 1022 1023 TypeIdLowering TIL = importTypeId(TypeIdStr->getString()); 1024 Value *Lowered = lowerTypeTestCall(TypeIdStr, CI, TIL); 1025 if (Lowered) { 1026 CI->replaceAllUsesWith(Lowered); 1027 CI->eraseFromParent(); 1028 } 1029 } 1030 1031 // ThinLTO backend: the function F has a jump table entry; update this module 1032 // accordingly. isJumpTableCanonical describes the type of the jump table entry. 1033 void LowerTypeTestsModule::importFunction( 1034 Function *F, bool isJumpTableCanonical, 1035 std::vector<GlobalAlias *> &AliasesToErase) { 1036 assert(F->getType()->getAddressSpace() == 0); 1037 1038 GlobalValue::VisibilityTypes Visibility = F->getVisibility(); 1039 std::string Name = std::string(F->getName()); 1040 1041 if (F->isDeclarationForLinker() && isJumpTableCanonical) { 1042 // Non-dso_local functions may be overriden at run time, 1043 // don't short curcuit them 1044 if (F->isDSOLocal()) { 1045 Function *RealF = Function::Create(F->getFunctionType(), 1046 GlobalValue::ExternalLinkage, 1047 F->getAddressSpace(), 1048 Name + ".cfi", &M); 1049 RealF->setVisibility(GlobalVariable::HiddenVisibility); 1050 replaceDirectCalls(F, RealF); 1051 } 1052 return; 1053 } 1054 1055 Function *FDecl; 1056 if (!isJumpTableCanonical) { 1057 // Either a declaration of an external function or a reference to a locally 1058 // defined jump table. 1059 FDecl = Function::Create(F->getFunctionType(), GlobalValue::ExternalLinkage, 1060 F->getAddressSpace(), Name + ".cfi_jt", &M); 1061 FDecl->setVisibility(GlobalValue::HiddenVisibility); 1062 } else { 1063 F->setName(Name + ".cfi"); 1064 F->setLinkage(GlobalValue::ExternalLinkage); 1065 FDecl = Function::Create(F->getFunctionType(), GlobalValue::ExternalLinkage, 1066 F->getAddressSpace(), Name, &M); 1067 FDecl->setVisibility(Visibility); 1068 Visibility = GlobalValue::HiddenVisibility; 1069 1070 // Delete aliases pointing to this function, they'll be re-created in the 1071 // merged output. Don't do it yet though because ScopedSaveAliaseesAndUsed 1072 // will want to reset the aliasees first. 1073 for (auto &U : F->uses()) { 1074 if (auto *A = dyn_cast<GlobalAlias>(U.getUser())) { 1075 Function *AliasDecl = Function::Create( 1076 F->getFunctionType(), GlobalValue::ExternalLinkage, 1077 F->getAddressSpace(), "", &M); 1078 AliasDecl->takeName(A); 1079 A->replaceAllUsesWith(AliasDecl); 1080 AliasesToErase.push_back(A); 1081 } 1082 } 1083 } 1084 1085 if (F->hasExternalWeakLinkage()) 1086 replaceWeakDeclarationWithJumpTablePtr(F, FDecl, isJumpTableCanonical); 1087 else 1088 replaceCfiUses(F, FDecl, isJumpTableCanonical); 1089 1090 // Set visibility late because it's used in replaceCfiUses() to determine 1091 // whether uses need to to be replaced. 1092 F->setVisibility(Visibility); 1093 } 1094 1095 void LowerTypeTestsModule::lowerTypeTestCalls( 1096 ArrayRef<Metadata *> TypeIds, Constant *CombinedGlobalAddr, 1097 const DenseMap<GlobalTypeMember *, uint64_t> &GlobalLayout) { 1098 CombinedGlobalAddr = ConstantExpr::getBitCast(CombinedGlobalAddr, Int8PtrTy); 1099 1100 // For each type identifier in this disjoint set... 1101 for (Metadata *TypeId : TypeIds) { 1102 // Build the bitset. 1103 BitSetInfo BSI = buildBitSet(TypeId, GlobalLayout); 1104 LLVM_DEBUG({ 1105 if (auto MDS = dyn_cast<MDString>(TypeId)) 1106 dbgs() << MDS->getString() << ": "; 1107 else 1108 dbgs() << "<unnamed>: "; 1109 BSI.print(dbgs()); 1110 }); 1111 1112 ByteArrayInfo *BAI = nullptr; 1113 TypeIdLowering TIL; 1114 TIL.OffsetedGlobal = ConstantExpr::getGetElementPtr( 1115 Int8Ty, CombinedGlobalAddr, ConstantInt::get(IntPtrTy, BSI.ByteOffset)), 1116 TIL.AlignLog2 = ConstantInt::get(Int8Ty, BSI.AlignLog2); 1117 TIL.SizeM1 = ConstantInt::get(IntPtrTy, BSI.BitSize - 1); 1118 if (BSI.isAllOnes()) { 1119 TIL.TheKind = (BSI.BitSize == 1) ? TypeTestResolution::Single 1120 : TypeTestResolution::AllOnes; 1121 } else if (BSI.BitSize <= 64) { 1122 TIL.TheKind = TypeTestResolution::Inline; 1123 uint64_t InlineBits = 0; 1124 for (auto Bit : BSI.Bits) 1125 InlineBits |= uint64_t(1) << Bit; 1126 if (InlineBits == 0) 1127 TIL.TheKind = TypeTestResolution::Unsat; 1128 else 1129 TIL.InlineBits = ConstantInt::get( 1130 (BSI.BitSize <= 32) ? Int32Ty : Int64Ty, InlineBits); 1131 } else { 1132 TIL.TheKind = TypeTestResolution::ByteArray; 1133 ++NumByteArraysCreated; 1134 BAI = createByteArray(BSI); 1135 TIL.TheByteArray = BAI->ByteArray; 1136 TIL.BitMask = BAI->MaskGlobal; 1137 } 1138 1139 TypeIdUserInfo &TIUI = TypeIdUsers[TypeId]; 1140 1141 if (TIUI.IsExported) { 1142 uint8_t *MaskPtr = exportTypeId(cast<MDString>(TypeId)->getString(), TIL); 1143 if (BAI) 1144 BAI->MaskPtr = MaskPtr; 1145 } 1146 1147 // Lower each call to llvm.type.test for this type identifier. 1148 for (CallInst *CI : TIUI.CallSites) { 1149 ++NumTypeTestCallsLowered; 1150 Value *Lowered = lowerTypeTestCall(TypeId, CI, TIL); 1151 if (Lowered) { 1152 CI->replaceAllUsesWith(Lowered); 1153 CI->eraseFromParent(); 1154 } 1155 } 1156 } 1157 } 1158 1159 void LowerTypeTestsModule::verifyTypeMDNode(GlobalObject *GO, MDNode *Type) { 1160 if (Type->getNumOperands() != 2) 1161 report_fatal_error("All operands of type metadata must have 2 elements"); 1162 1163 if (GO->isThreadLocal()) 1164 report_fatal_error("Bit set element may not be thread-local"); 1165 if (isa<GlobalVariable>(GO) && GO->hasSection()) 1166 report_fatal_error( 1167 "A member of a type identifier may not have an explicit section"); 1168 1169 // FIXME: We previously checked that global var member of a type identifier 1170 // must be a definition, but the IR linker may leave type metadata on 1171 // declarations. We should restore this check after fixing PR31759. 1172 1173 auto OffsetConstMD = dyn_cast<ConstantAsMetadata>(Type->getOperand(0)); 1174 if (!OffsetConstMD) 1175 report_fatal_error("Type offset must be a constant"); 1176 auto OffsetInt = dyn_cast<ConstantInt>(OffsetConstMD->getValue()); 1177 if (!OffsetInt) 1178 report_fatal_error("Type offset must be an integer constant"); 1179 } 1180 1181 static const unsigned kX86JumpTableEntrySize = 8; 1182 static const unsigned kARMJumpTableEntrySize = 4; 1183 static const unsigned kARMBTIJumpTableEntrySize = 8; 1184 static const unsigned kRISCVJumpTableEntrySize = 8; 1185 1186 unsigned LowerTypeTestsModule::getJumpTableEntrySize() { 1187 switch (Arch) { 1188 case Triple::x86: 1189 case Triple::x86_64: 1190 return kX86JumpTableEntrySize; 1191 case Triple::arm: 1192 case Triple::thumb: 1193 return kARMJumpTableEntrySize; 1194 case Triple::aarch64: 1195 if (const auto *BTE = mdconst::extract_or_null<ConstantInt>( 1196 M.getModuleFlag("branch-target-enforcement"))) 1197 if (BTE->getZExtValue()) 1198 return kARMBTIJumpTableEntrySize; 1199 return kARMJumpTableEntrySize; 1200 case Triple::riscv32: 1201 case Triple::riscv64: 1202 return kRISCVJumpTableEntrySize; 1203 default: 1204 report_fatal_error("Unsupported architecture for jump tables"); 1205 } 1206 } 1207 1208 // Create a jump table entry for the target. This consists of an instruction 1209 // sequence containing a relative branch to Dest. Appends inline asm text, 1210 // constraints and arguments to AsmOS, ConstraintOS and AsmArgs. 1211 void LowerTypeTestsModule::createJumpTableEntry( 1212 raw_ostream &AsmOS, raw_ostream &ConstraintOS, 1213 Triple::ArchType JumpTableArch, SmallVectorImpl<Value *> &AsmArgs, 1214 Function *Dest) { 1215 unsigned ArgIndex = AsmArgs.size(); 1216 1217 if (JumpTableArch == Triple::x86 || JumpTableArch == Triple::x86_64) { 1218 AsmOS << "jmp ${" << ArgIndex << ":c}@plt\n"; 1219 AsmOS << "int3\nint3\nint3\n"; 1220 } else if (JumpTableArch == Triple::arm) { 1221 AsmOS << "b $" << ArgIndex << "\n"; 1222 } else if (JumpTableArch == Triple::aarch64) { 1223 if (const auto *BTE = mdconst::extract_or_null<ConstantInt>( 1224 Dest->getParent()->getModuleFlag("branch-target-enforcement"))) 1225 if (BTE->getZExtValue()) 1226 AsmOS << "bti c\n"; 1227 AsmOS << "b $" << ArgIndex << "\n"; 1228 } else if (JumpTableArch == Triple::thumb) { 1229 AsmOS << "b.w $" << ArgIndex << "\n"; 1230 } else if (JumpTableArch == Triple::riscv32 || 1231 JumpTableArch == Triple::riscv64) { 1232 AsmOS << "tail $" << ArgIndex << "@plt\n"; 1233 } else { 1234 report_fatal_error("Unsupported architecture for jump tables"); 1235 } 1236 1237 ConstraintOS << (ArgIndex > 0 ? ",s" : "s"); 1238 AsmArgs.push_back(Dest); 1239 } 1240 1241 Type *LowerTypeTestsModule::getJumpTableEntryType() { 1242 return ArrayType::get(Int8Ty, getJumpTableEntrySize()); 1243 } 1244 1245 /// Given a disjoint set of type identifiers and functions, build the bit sets 1246 /// and lower the llvm.type.test calls, architecture dependently. 1247 void LowerTypeTestsModule::buildBitSetsFromFunctions( 1248 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Functions) { 1249 if (Arch == Triple::x86 || Arch == Triple::x86_64 || Arch == Triple::arm || 1250 Arch == Triple::thumb || Arch == Triple::aarch64 || 1251 Arch == Triple::riscv32 || Arch == Triple::riscv64) 1252 buildBitSetsFromFunctionsNative(TypeIds, Functions); 1253 else if (Arch == Triple::wasm32 || Arch == Triple::wasm64) 1254 buildBitSetsFromFunctionsWASM(TypeIds, Functions); 1255 else 1256 report_fatal_error("Unsupported architecture for jump tables"); 1257 } 1258 1259 void LowerTypeTestsModule::moveInitializerToModuleConstructor( 1260 GlobalVariable *GV) { 1261 if (WeakInitializerFn == nullptr) { 1262 WeakInitializerFn = Function::Create( 1263 FunctionType::get(Type::getVoidTy(M.getContext()), 1264 /* IsVarArg */ false), 1265 GlobalValue::InternalLinkage, 1266 M.getDataLayout().getProgramAddressSpace(), 1267 "__cfi_global_var_init", &M); 1268 BasicBlock *BB = 1269 BasicBlock::Create(M.getContext(), "entry", WeakInitializerFn); 1270 ReturnInst::Create(M.getContext(), BB); 1271 WeakInitializerFn->setSection( 1272 ObjectFormat == Triple::MachO 1273 ? "__TEXT,__StaticInit,regular,pure_instructions" 1274 : ".text.startup"); 1275 // This code is equivalent to relocation application, and should run at the 1276 // earliest possible time (i.e. with the highest priority). 1277 appendToGlobalCtors(M, WeakInitializerFn, /* Priority */ 0); 1278 } 1279 1280 IRBuilder<> IRB(WeakInitializerFn->getEntryBlock().getTerminator()); 1281 GV->setConstant(false); 1282 IRB.CreateAlignedStore(GV->getInitializer(), GV, GV->getAlign()); 1283 GV->setInitializer(Constant::getNullValue(GV->getValueType())); 1284 } 1285 1286 void LowerTypeTestsModule::findGlobalVariableUsersOf( 1287 Constant *C, SmallSetVector<GlobalVariable *, 8> &Out) { 1288 for (auto *U : C->users()){ 1289 if (auto *GV = dyn_cast<GlobalVariable>(U)) 1290 Out.insert(GV); 1291 else if (auto *C2 = dyn_cast<Constant>(U)) 1292 findGlobalVariableUsersOf(C2, Out); 1293 } 1294 } 1295 1296 // Replace all uses of F with (F ? JT : 0). 1297 void LowerTypeTestsModule::replaceWeakDeclarationWithJumpTablePtr( 1298 Function *F, Constant *JT, bool IsJumpTableCanonical) { 1299 // The target expression can not appear in a constant initializer on most 1300 // (all?) targets. Switch to a runtime initializer. 1301 SmallSetVector<GlobalVariable *, 8> GlobalVarUsers; 1302 findGlobalVariableUsersOf(F, GlobalVarUsers); 1303 for (auto GV : GlobalVarUsers) 1304 moveInitializerToModuleConstructor(GV); 1305 1306 // Can not RAUW F with an expression that uses F. Replace with a temporary 1307 // placeholder first. 1308 Function *PlaceholderFn = 1309 Function::Create(cast<FunctionType>(F->getValueType()), 1310 GlobalValue::ExternalWeakLinkage, 1311 F->getAddressSpace(), "", &M); 1312 replaceCfiUses(F, PlaceholderFn, IsJumpTableCanonical); 1313 1314 Constant *Target = ConstantExpr::getSelect( 1315 ConstantExpr::getICmp(CmpInst::ICMP_NE, F, 1316 Constant::getNullValue(F->getType())), 1317 JT, Constant::getNullValue(F->getType())); 1318 PlaceholderFn->replaceAllUsesWith(Target); 1319 PlaceholderFn->eraseFromParent(); 1320 } 1321 1322 static bool isThumbFunction(Function *F, Triple::ArchType ModuleArch) { 1323 Attribute TFAttr = F->getFnAttribute("target-features"); 1324 if (TFAttr.isValid()) { 1325 SmallVector<StringRef, 6> Features; 1326 TFAttr.getValueAsString().split(Features, ','); 1327 for (StringRef Feature : Features) { 1328 if (Feature == "-thumb-mode") 1329 return false; 1330 else if (Feature == "+thumb-mode") 1331 return true; 1332 } 1333 } 1334 1335 return ModuleArch == Triple::thumb; 1336 } 1337 1338 // Each jump table must be either ARM or Thumb as a whole for the bit-test math 1339 // to work. Pick one that matches the majority of members to minimize interop 1340 // veneers inserted by the linker. 1341 static Triple::ArchType 1342 selectJumpTableArmEncoding(ArrayRef<GlobalTypeMember *> Functions, 1343 Triple::ArchType ModuleArch) { 1344 if (ModuleArch != Triple::arm && ModuleArch != Triple::thumb) 1345 return ModuleArch; 1346 1347 unsigned ArmCount = 0, ThumbCount = 0; 1348 for (const auto GTM : Functions) { 1349 if (!GTM->isJumpTableCanonical()) { 1350 // PLT stubs are always ARM. 1351 // FIXME: This is the wrong heuristic for non-canonical jump tables. 1352 ++ArmCount; 1353 continue; 1354 } 1355 1356 Function *F = cast<Function>(GTM->getGlobal()); 1357 ++(isThumbFunction(F, ModuleArch) ? ThumbCount : ArmCount); 1358 } 1359 1360 return ArmCount > ThumbCount ? Triple::arm : Triple::thumb; 1361 } 1362 1363 void LowerTypeTestsModule::createJumpTable( 1364 Function *F, ArrayRef<GlobalTypeMember *> Functions) { 1365 std::string AsmStr, ConstraintStr; 1366 raw_string_ostream AsmOS(AsmStr), ConstraintOS(ConstraintStr); 1367 SmallVector<Value *, 16> AsmArgs; 1368 AsmArgs.reserve(Functions.size() * 2); 1369 1370 Triple::ArchType JumpTableArch = selectJumpTableArmEncoding(Functions, Arch); 1371 1372 for (unsigned I = 0; I != Functions.size(); ++I) 1373 createJumpTableEntry(AsmOS, ConstraintOS, JumpTableArch, AsmArgs, 1374 cast<Function>(Functions[I]->getGlobal())); 1375 1376 // Align the whole table by entry size. 1377 F->setAlignment(Align(getJumpTableEntrySize())); 1378 // Skip prologue. 1379 // Disabled on win32 due to https://llvm.org/bugs/show_bug.cgi?id=28641#c3. 1380 // Luckily, this function does not get any prologue even without the 1381 // attribute. 1382 if (OS != Triple::Win32) 1383 F->addFnAttr(Attribute::Naked); 1384 if (JumpTableArch == Triple::arm) 1385 F->addFnAttr("target-features", "-thumb-mode"); 1386 if (JumpTableArch == Triple::thumb) { 1387 F->addFnAttr("target-features", "+thumb-mode"); 1388 // Thumb jump table assembly needs Thumb2. The following attribute is added 1389 // by Clang for -march=armv7. 1390 F->addFnAttr("target-cpu", "cortex-a8"); 1391 } 1392 if (JumpTableArch == Triple::aarch64) { 1393 F->addFnAttr("branch-target-enforcement", "false"); 1394 F->addFnAttr("sign-return-address", "none"); 1395 } 1396 if (JumpTableArch == Triple::riscv32 || JumpTableArch == Triple::riscv64) { 1397 // Make sure the jump table assembly is not modified by the assembler or 1398 // the linker. 1399 F->addFnAttr("target-features", "-c,-relax"); 1400 } 1401 // Make sure we don't emit .eh_frame for this function. 1402 F->addFnAttr(Attribute::NoUnwind); 1403 1404 BasicBlock *BB = BasicBlock::Create(M.getContext(), "entry", F); 1405 IRBuilder<> IRB(BB); 1406 1407 SmallVector<Type *, 16> ArgTypes; 1408 ArgTypes.reserve(AsmArgs.size()); 1409 for (const auto &Arg : AsmArgs) 1410 ArgTypes.push_back(Arg->getType()); 1411 InlineAsm *JumpTableAsm = 1412 InlineAsm::get(FunctionType::get(IRB.getVoidTy(), ArgTypes, false), 1413 AsmOS.str(), ConstraintOS.str(), 1414 /*hasSideEffects=*/true); 1415 1416 IRB.CreateCall(JumpTableAsm, AsmArgs); 1417 IRB.CreateUnreachable(); 1418 } 1419 1420 /// Given a disjoint set of type identifiers and functions, build a jump table 1421 /// for the functions, build the bit sets and lower the llvm.type.test calls. 1422 void LowerTypeTestsModule::buildBitSetsFromFunctionsNative( 1423 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Functions) { 1424 // Unlike the global bitset builder, the function bitset builder cannot 1425 // re-arrange functions in a particular order and base its calculations on the 1426 // layout of the functions' entry points, as we have no idea how large a 1427 // particular function will end up being (the size could even depend on what 1428 // this pass does!) Instead, we build a jump table, which is a block of code 1429 // consisting of one branch instruction for each of the functions in the bit 1430 // set that branches to the target function, and redirect any taken function 1431 // addresses to the corresponding jump table entry. In the object file's 1432 // symbol table, the symbols for the target functions also refer to the jump 1433 // table entries, so that addresses taken outside the module will pass any 1434 // verification done inside the module. 1435 // 1436 // In more concrete terms, suppose we have three functions f, g, h which are 1437 // of the same type, and a function foo that returns their addresses: 1438 // 1439 // f: 1440 // mov 0, %eax 1441 // ret 1442 // 1443 // g: 1444 // mov 1, %eax 1445 // ret 1446 // 1447 // h: 1448 // mov 2, %eax 1449 // ret 1450 // 1451 // foo: 1452 // mov f, %eax 1453 // mov g, %edx 1454 // mov h, %ecx 1455 // ret 1456 // 1457 // We output the jump table as module-level inline asm string. The end result 1458 // will (conceptually) look like this: 1459 // 1460 // f = .cfi.jumptable 1461 // g = .cfi.jumptable + 4 1462 // h = .cfi.jumptable + 8 1463 // .cfi.jumptable: 1464 // jmp f.cfi ; 5 bytes 1465 // int3 ; 1 byte 1466 // int3 ; 1 byte 1467 // int3 ; 1 byte 1468 // jmp g.cfi ; 5 bytes 1469 // int3 ; 1 byte 1470 // int3 ; 1 byte 1471 // int3 ; 1 byte 1472 // jmp h.cfi ; 5 bytes 1473 // int3 ; 1 byte 1474 // int3 ; 1 byte 1475 // int3 ; 1 byte 1476 // 1477 // f.cfi: 1478 // mov 0, %eax 1479 // ret 1480 // 1481 // g.cfi: 1482 // mov 1, %eax 1483 // ret 1484 // 1485 // h.cfi: 1486 // mov 2, %eax 1487 // ret 1488 // 1489 // foo: 1490 // mov f, %eax 1491 // mov g, %edx 1492 // mov h, %ecx 1493 // ret 1494 // 1495 // Because the addresses of f, g, h are evenly spaced at a power of 2, in the 1496 // normal case the check can be carried out using the same kind of simple 1497 // arithmetic that we normally use for globals. 1498 1499 // FIXME: find a better way to represent the jumptable in the IR. 1500 assert(!Functions.empty()); 1501 1502 // Build a simple layout based on the regular layout of jump tables. 1503 DenseMap<GlobalTypeMember *, uint64_t> GlobalLayout; 1504 unsigned EntrySize = getJumpTableEntrySize(); 1505 for (unsigned I = 0; I != Functions.size(); ++I) 1506 GlobalLayout[Functions[I]] = I * EntrySize; 1507 1508 Function *JumpTableFn = 1509 Function::Create(FunctionType::get(Type::getVoidTy(M.getContext()), 1510 /* IsVarArg */ false), 1511 GlobalValue::PrivateLinkage, 1512 M.getDataLayout().getProgramAddressSpace(), 1513 ".cfi.jumptable", &M); 1514 ArrayType *JumpTableType = 1515 ArrayType::get(getJumpTableEntryType(), Functions.size()); 1516 auto JumpTable = 1517 ConstantExpr::getPointerCast(JumpTableFn, JumpTableType->getPointerTo(0)); 1518 1519 lowerTypeTestCalls(TypeIds, JumpTable, GlobalLayout); 1520 1521 { 1522 ScopedSaveAliaseesAndUsed S(M); 1523 1524 // Build aliases pointing to offsets into the jump table, and replace 1525 // references to the original functions with references to the aliases. 1526 for (unsigned I = 0; I != Functions.size(); ++I) { 1527 Function *F = cast<Function>(Functions[I]->getGlobal()); 1528 bool IsJumpTableCanonical = Functions[I]->isJumpTableCanonical(); 1529 1530 Constant *CombinedGlobalElemPtr = ConstantExpr::getBitCast( 1531 ConstantExpr::getInBoundsGetElementPtr( 1532 JumpTableType, JumpTable, 1533 ArrayRef<Constant *>{ConstantInt::get(IntPtrTy, 0), 1534 ConstantInt::get(IntPtrTy, I)}), 1535 F->getType()); 1536 1537 const bool IsExported = Functions[I]->isExported(); 1538 if (!IsJumpTableCanonical) { 1539 GlobalValue::LinkageTypes LT = IsExported 1540 ? GlobalValue::ExternalLinkage 1541 : GlobalValue::InternalLinkage; 1542 GlobalAlias *JtAlias = GlobalAlias::create(F->getValueType(), 0, LT, 1543 F->getName() + ".cfi_jt", 1544 CombinedGlobalElemPtr, &M); 1545 if (IsExported) 1546 JtAlias->setVisibility(GlobalValue::HiddenVisibility); 1547 else 1548 appendToUsed(M, {JtAlias}); 1549 } 1550 1551 if (IsExported) { 1552 if (IsJumpTableCanonical) 1553 ExportSummary->cfiFunctionDefs().insert(std::string(F->getName())); 1554 else 1555 ExportSummary->cfiFunctionDecls().insert(std::string(F->getName())); 1556 } 1557 1558 if (!IsJumpTableCanonical) { 1559 if (F->hasExternalWeakLinkage()) 1560 replaceWeakDeclarationWithJumpTablePtr(F, CombinedGlobalElemPtr, 1561 IsJumpTableCanonical); 1562 else 1563 replaceCfiUses(F, CombinedGlobalElemPtr, IsJumpTableCanonical); 1564 } else { 1565 assert(F->getType()->getAddressSpace() == 0); 1566 1567 GlobalAlias *FAlias = 1568 GlobalAlias::create(F->getValueType(), 0, F->getLinkage(), "", 1569 CombinedGlobalElemPtr, &M); 1570 FAlias->setVisibility(F->getVisibility()); 1571 FAlias->takeName(F); 1572 if (FAlias->hasName()) 1573 F->setName(FAlias->getName() + ".cfi"); 1574 replaceCfiUses(F, FAlias, IsJumpTableCanonical); 1575 if (!F->hasLocalLinkage()) 1576 F->setVisibility(GlobalVariable::HiddenVisibility); 1577 } 1578 } 1579 } 1580 1581 createJumpTable(JumpTableFn, Functions); 1582 } 1583 1584 /// Assign a dummy layout using an incrementing counter, tag each function 1585 /// with its index represented as metadata, and lower each type test to an 1586 /// integer range comparison. During generation of the indirect function call 1587 /// table in the backend, it will assign the given indexes. 1588 /// Note: Dynamic linking is not supported, as the WebAssembly ABI has not yet 1589 /// been finalized. 1590 void LowerTypeTestsModule::buildBitSetsFromFunctionsWASM( 1591 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Functions) { 1592 assert(!Functions.empty()); 1593 1594 // Build consecutive monotonic integer ranges for each call target set 1595 DenseMap<GlobalTypeMember *, uint64_t> GlobalLayout; 1596 1597 for (GlobalTypeMember *GTM : Functions) { 1598 Function *F = cast<Function>(GTM->getGlobal()); 1599 1600 // Skip functions that are not address taken, to avoid bloating the table 1601 if (!F->hasAddressTaken()) 1602 continue; 1603 1604 // Store metadata with the index for each function 1605 MDNode *MD = MDNode::get(F->getContext(), 1606 ArrayRef<Metadata *>(ConstantAsMetadata::get( 1607 ConstantInt::get(Int64Ty, IndirectIndex)))); 1608 F->setMetadata("wasm.index", MD); 1609 1610 // Assign the counter value 1611 GlobalLayout[GTM] = IndirectIndex++; 1612 } 1613 1614 // The indirect function table index space starts at zero, so pass a NULL 1615 // pointer as the subtracted "jump table" offset. 1616 lowerTypeTestCalls(TypeIds, ConstantPointerNull::get(Int32PtrTy), 1617 GlobalLayout); 1618 } 1619 1620 void LowerTypeTestsModule::buildBitSetsFromDisjointSet( 1621 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Globals, 1622 ArrayRef<ICallBranchFunnel *> ICallBranchFunnels) { 1623 DenseMap<Metadata *, uint64_t> TypeIdIndices; 1624 for (unsigned I = 0; I != TypeIds.size(); ++I) 1625 TypeIdIndices[TypeIds[I]] = I; 1626 1627 // For each type identifier, build a set of indices that refer to members of 1628 // the type identifier. 1629 std::vector<std::set<uint64_t>> TypeMembers(TypeIds.size()); 1630 unsigned GlobalIndex = 0; 1631 DenseMap<GlobalTypeMember *, uint64_t> GlobalIndices; 1632 for (GlobalTypeMember *GTM : Globals) { 1633 for (MDNode *Type : GTM->types()) { 1634 // Type = { offset, type identifier } 1635 auto I = TypeIdIndices.find(Type->getOperand(1)); 1636 if (I != TypeIdIndices.end()) 1637 TypeMembers[I->second].insert(GlobalIndex); 1638 } 1639 GlobalIndices[GTM] = GlobalIndex; 1640 GlobalIndex++; 1641 } 1642 1643 for (ICallBranchFunnel *JT : ICallBranchFunnels) { 1644 TypeMembers.emplace_back(); 1645 std::set<uint64_t> &TMSet = TypeMembers.back(); 1646 for (GlobalTypeMember *T : JT->targets()) 1647 TMSet.insert(GlobalIndices[T]); 1648 } 1649 1650 // Order the sets of indices by size. The GlobalLayoutBuilder works best 1651 // when given small index sets first. 1652 llvm::stable_sort(TypeMembers, [](const std::set<uint64_t> &O1, 1653 const std::set<uint64_t> &O2) { 1654 return O1.size() < O2.size(); 1655 }); 1656 1657 // Create a GlobalLayoutBuilder and provide it with index sets as layout 1658 // fragments. The GlobalLayoutBuilder tries to lay out members of fragments as 1659 // close together as possible. 1660 GlobalLayoutBuilder GLB(Globals.size()); 1661 for (auto &&MemSet : TypeMembers) 1662 GLB.addFragment(MemSet); 1663 1664 // Build a vector of globals with the computed layout. 1665 bool IsGlobalSet = 1666 Globals.empty() || isa<GlobalVariable>(Globals[0]->getGlobal()); 1667 std::vector<GlobalTypeMember *> OrderedGTMs(Globals.size()); 1668 auto OGTMI = OrderedGTMs.begin(); 1669 for (auto &&F : GLB.Fragments) { 1670 for (auto &&Offset : F) { 1671 if (IsGlobalSet != isa<GlobalVariable>(Globals[Offset]->getGlobal())) 1672 report_fatal_error("Type identifier may not contain both global " 1673 "variables and functions"); 1674 *OGTMI++ = Globals[Offset]; 1675 } 1676 } 1677 1678 // Build the bitsets from this disjoint set. 1679 if (IsGlobalSet) 1680 buildBitSetsFromGlobalVariables(TypeIds, OrderedGTMs); 1681 else 1682 buildBitSetsFromFunctions(TypeIds, OrderedGTMs); 1683 } 1684 1685 /// Lower all type tests in this module. 1686 LowerTypeTestsModule::LowerTypeTestsModule( 1687 Module &M, ModuleSummaryIndex *ExportSummary, 1688 const ModuleSummaryIndex *ImportSummary, bool DropTypeTests) 1689 : M(M), ExportSummary(ExportSummary), ImportSummary(ImportSummary), 1690 DropTypeTests(DropTypeTests || ClDropTypeTests) { 1691 assert(!(ExportSummary && ImportSummary)); 1692 Triple TargetTriple(M.getTargetTriple()); 1693 Arch = TargetTriple.getArch(); 1694 OS = TargetTriple.getOS(); 1695 ObjectFormat = TargetTriple.getObjectFormat(); 1696 } 1697 1698 bool LowerTypeTestsModule::runForTesting(Module &M) { 1699 ModuleSummaryIndex Summary(/*HaveGVs=*/false); 1700 1701 // Handle the command-line summary arguments. This code is for testing 1702 // purposes only, so we handle errors directly. 1703 if (!ClReadSummary.empty()) { 1704 ExitOnError ExitOnErr("-lowertypetests-read-summary: " + ClReadSummary + 1705 ": "); 1706 auto ReadSummaryFile = 1707 ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(ClReadSummary))); 1708 1709 yaml::Input In(ReadSummaryFile->getBuffer()); 1710 In >> Summary; 1711 ExitOnErr(errorCodeToError(In.error())); 1712 } 1713 1714 bool Changed = 1715 LowerTypeTestsModule( 1716 M, ClSummaryAction == PassSummaryAction::Export ? &Summary : nullptr, 1717 ClSummaryAction == PassSummaryAction::Import ? &Summary : nullptr, 1718 /*DropTypeTests*/ false) 1719 .lower(); 1720 1721 if (!ClWriteSummary.empty()) { 1722 ExitOnError ExitOnErr("-lowertypetests-write-summary: " + ClWriteSummary + 1723 ": "); 1724 std::error_code EC; 1725 raw_fd_ostream OS(ClWriteSummary, EC, sys::fs::OF_TextWithCRLF); 1726 ExitOnErr(errorCodeToError(EC)); 1727 1728 yaml::Output Out(OS); 1729 Out << Summary; 1730 } 1731 1732 return Changed; 1733 } 1734 1735 static bool isDirectCall(Use& U) { 1736 auto *Usr = dyn_cast<CallInst>(U.getUser()); 1737 if (Usr) { 1738 auto *CB = dyn_cast<CallBase>(Usr); 1739 if (CB && CB->isCallee(&U)) 1740 return true; 1741 } 1742 return false; 1743 } 1744 1745 void LowerTypeTestsModule::replaceCfiUses(Function *Old, Value *New, 1746 bool IsJumpTableCanonical) { 1747 SmallSetVector<Constant *, 4> Constants; 1748 for (Use &U : llvm::make_early_inc_range(Old->uses())) { 1749 // Skip block addresses and no_cfi values, which refer to the function 1750 // body instead of the jump table. 1751 if (isa<BlockAddress, NoCFIValue>(U.getUser())) 1752 continue; 1753 1754 // Skip direct calls to externally defined or non-dso_local functions 1755 if (isDirectCall(U) && (Old->isDSOLocal() || !IsJumpTableCanonical)) 1756 continue; 1757 1758 // Must handle Constants specially, we cannot call replaceUsesOfWith on a 1759 // constant because they are uniqued. 1760 if (auto *C = dyn_cast<Constant>(U.getUser())) { 1761 if (!isa<GlobalValue>(C)) { 1762 // Save unique users to avoid processing operand replacement 1763 // more than once. 1764 Constants.insert(C); 1765 continue; 1766 } 1767 } 1768 1769 U.set(New); 1770 } 1771 1772 // Process operand replacement of saved constants. 1773 for (auto *C : Constants) 1774 C->handleOperandChange(Old, New); 1775 } 1776 1777 void LowerTypeTestsModule::replaceDirectCalls(Value *Old, Value *New) { 1778 Old->replaceUsesWithIf(New, isDirectCall); 1779 } 1780 1781 static void dropTypeTests(Module &M, Function &TypeTestFunc) { 1782 for (Use &U : llvm::make_early_inc_range(TypeTestFunc.uses())) { 1783 auto *CI = cast<CallInst>(U.getUser()); 1784 // Find and erase llvm.assume intrinsics for this llvm.type.test call. 1785 for (Use &CIU : llvm::make_early_inc_range(CI->uses())) 1786 if (auto *Assume = dyn_cast<AssumeInst>(CIU.getUser())) 1787 Assume->eraseFromParent(); 1788 // If the assume was merged with another assume, we might have a use on a 1789 // phi (which will feed the assume). Simply replace the use on the phi 1790 // with "true" and leave the merged assume. 1791 if (!CI->use_empty()) { 1792 assert( 1793 all_of(CI->users(), [](User *U) -> bool { return isa<PHINode>(U); })); 1794 CI->replaceAllUsesWith(ConstantInt::getTrue(M.getContext())); 1795 } 1796 CI->eraseFromParent(); 1797 } 1798 } 1799 1800 bool LowerTypeTestsModule::lower() { 1801 Function *TypeTestFunc = 1802 M.getFunction(Intrinsic::getName(Intrinsic::type_test)); 1803 1804 if (DropTypeTests) { 1805 if (TypeTestFunc) 1806 dropTypeTests(M, *TypeTestFunc); 1807 // Normally we'd have already removed all @llvm.public.type.test calls, 1808 // except for in the case where we originally were performing ThinLTO but 1809 // decided not to in the backend. 1810 Function *PublicTypeTestFunc = 1811 M.getFunction(Intrinsic::getName(Intrinsic::public_type_test)); 1812 if (PublicTypeTestFunc) 1813 dropTypeTests(M, *PublicTypeTestFunc); 1814 if (TypeTestFunc || PublicTypeTestFunc) { 1815 // We have deleted the type intrinsics, so we no longer have enough 1816 // information to reason about the liveness of virtual function pointers 1817 // in GlobalDCE. 1818 for (GlobalVariable &GV : M.globals()) 1819 GV.eraseMetadata(LLVMContext::MD_vcall_visibility); 1820 return true; 1821 } 1822 return false; 1823 } 1824 1825 // If only some of the modules were split, we cannot correctly perform 1826 // this transformation. We already checked for the presense of type tests 1827 // with partially split modules during the thin link, and would have emitted 1828 // an error if any were found, so here we can simply return. 1829 if ((ExportSummary && ExportSummary->partiallySplitLTOUnits()) || 1830 (ImportSummary && ImportSummary->partiallySplitLTOUnits())) 1831 return false; 1832 1833 Function *ICallBranchFunnelFunc = 1834 M.getFunction(Intrinsic::getName(Intrinsic::icall_branch_funnel)); 1835 if ((!TypeTestFunc || TypeTestFunc->use_empty()) && 1836 (!ICallBranchFunnelFunc || ICallBranchFunnelFunc->use_empty()) && 1837 !ExportSummary && !ImportSummary) 1838 return false; 1839 1840 if (ImportSummary) { 1841 if (TypeTestFunc) 1842 for (Use &U : llvm::make_early_inc_range(TypeTestFunc->uses())) 1843 importTypeTest(cast<CallInst>(U.getUser())); 1844 1845 if (ICallBranchFunnelFunc && !ICallBranchFunnelFunc->use_empty()) 1846 report_fatal_error( 1847 "unexpected call to llvm.icall.branch.funnel during import phase"); 1848 1849 SmallVector<Function *, 8> Defs; 1850 SmallVector<Function *, 8> Decls; 1851 for (auto &F : M) { 1852 // CFI functions are either external, or promoted. A local function may 1853 // have the same name, but it's not the one we are looking for. 1854 if (F.hasLocalLinkage()) 1855 continue; 1856 if (ImportSummary->cfiFunctionDefs().count(std::string(F.getName()))) 1857 Defs.push_back(&F); 1858 else if (ImportSummary->cfiFunctionDecls().count( 1859 std::string(F.getName()))) 1860 Decls.push_back(&F); 1861 } 1862 1863 std::vector<GlobalAlias *> AliasesToErase; 1864 { 1865 ScopedSaveAliaseesAndUsed S(M); 1866 for (auto F : Defs) 1867 importFunction(F, /*isJumpTableCanonical*/ true, AliasesToErase); 1868 for (auto F : Decls) 1869 importFunction(F, /*isJumpTableCanonical*/ false, AliasesToErase); 1870 } 1871 for (GlobalAlias *GA : AliasesToErase) 1872 GA->eraseFromParent(); 1873 1874 return true; 1875 } 1876 1877 // Equivalence class set containing type identifiers and the globals that 1878 // reference them. This is used to partition the set of type identifiers in 1879 // the module into disjoint sets. 1880 using GlobalClassesTy = EquivalenceClasses< 1881 PointerUnion<GlobalTypeMember *, Metadata *, ICallBranchFunnel *>>; 1882 GlobalClassesTy GlobalClasses; 1883 1884 // Verify the type metadata and build a few data structures to let us 1885 // efficiently enumerate the type identifiers associated with a global: 1886 // a list of GlobalTypeMembers (a GlobalObject stored alongside a vector 1887 // of associated type metadata) and a mapping from type identifiers to their 1888 // list of GlobalTypeMembers and last observed index in the list of globals. 1889 // The indices will be used later to deterministically order the list of type 1890 // identifiers. 1891 BumpPtrAllocator Alloc; 1892 struct TIInfo { 1893 unsigned UniqueId; 1894 std::vector<GlobalTypeMember *> RefGlobals; 1895 }; 1896 DenseMap<Metadata *, TIInfo> TypeIdInfo; 1897 unsigned CurUniqueId = 0; 1898 SmallVector<MDNode *, 2> Types; 1899 1900 // Cross-DSO CFI emits jumptable entries for exported functions as well as 1901 // address taken functions in case they are address taken in other modules. 1902 const bool CrossDsoCfi = M.getModuleFlag("Cross-DSO CFI") != nullptr; 1903 1904 struct ExportedFunctionInfo { 1905 CfiFunctionLinkage Linkage; 1906 MDNode *FuncMD; // {name, linkage, type[, type...]} 1907 }; 1908 DenseMap<StringRef, ExportedFunctionInfo> ExportedFunctions; 1909 if (ExportSummary) { 1910 // A set of all functions that are address taken by a live global object. 1911 DenseSet<GlobalValue::GUID> AddressTaken; 1912 for (auto &I : *ExportSummary) 1913 for (auto &GVS : I.second.SummaryList) 1914 if (GVS->isLive()) 1915 for (auto &Ref : GVS->refs()) 1916 AddressTaken.insert(Ref.getGUID()); 1917 1918 NamedMDNode *CfiFunctionsMD = M.getNamedMetadata("cfi.functions"); 1919 if (CfiFunctionsMD) { 1920 for (auto FuncMD : CfiFunctionsMD->operands()) { 1921 assert(FuncMD->getNumOperands() >= 2); 1922 StringRef FunctionName = 1923 cast<MDString>(FuncMD->getOperand(0))->getString(); 1924 CfiFunctionLinkage Linkage = static_cast<CfiFunctionLinkage>( 1925 cast<ConstantAsMetadata>(FuncMD->getOperand(1)) 1926 ->getValue() 1927 ->getUniqueInteger() 1928 .getZExtValue()); 1929 const GlobalValue::GUID GUID = GlobalValue::getGUID( 1930 GlobalValue::dropLLVMManglingEscape(FunctionName)); 1931 // Do not emit jumptable entries for functions that are not-live and 1932 // have no live references (and are not exported with cross-DSO CFI.) 1933 if (!ExportSummary->isGUIDLive(GUID)) 1934 continue; 1935 if (!AddressTaken.count(GUID)) { 1936 if (!CrossDsoCfi || Linkage != CFL_Definition) 1937 continue; 1938 1939 bool Exported = false; 1940 if (auto VI = ExportSummary->getValueInfo(GUID)) 1941 for (auto &GVS : VI.getSummaryList()) 1942 if (GVS->isLive() && !GlobalValue::isLocalLinkage(GVS->linkage())) 1943 Exported = true; 1944 1945 if (!Exported) 1946 continue; 1947 } 1948 auto P = ExportedFunctions.insert({FunctionName, {Linkage, FuncMD}}); 1949 if (!P.second && P.first->second.Linkage != CFL_Definition) 1950 P.first->second = {Linkage, FuncMD}; 1951 } 1952 1953 for (const auto &P : ExportedFunctions) { 1954 StringRef FunctionName = P.first; 1955 CfiFunctionLinkage Linkage = P.second.Linkage; 1956 MDNode *FuncMD = P.second.FuncMD; 1957 Function *F = M.getFunction(FunctionName); 1958 if (F && F->hasLocalLinkage()) { 1959 // Locally defined function that happens to have the same name as a 1960 // function defined in a ThinLTO module. Rename it to move it out of 1961 // the way of the external reference that we're about to create. 1962 // Note that setName will find a unique name for the function, so even 1963 // if there is an existing function with the suffix there won't be a 1964 // name collision. 1965 F->setName(F->getName() + ".1"); 1966 F = nullptr; 1967 } 1968 1969 if (!F) 1970 F = Function::Create( 1971 FunctionType::get(Type::getVoidTy(M.getContext()), false), 1972 GlobalVariable::ExternalLinkage, 1973 M.getDataLayout().getProgramAddressSpace(), FunctionName, &M); 1974 1975 // If the function is available_externally, remove its definition so 1976 // that it is handled the same way as a declaration. Later we will try 1977 // to create an alias using this function's linkage, which will fail if 1978 // the linkage is available_externally. This will also result in us 1979 // following the code path below to replace the type metadata. 1980 if (F->hasAvailableExternallyLinkage()) { 1981 F->setLinkage(GlobalValue::ExternalLinkage); 1982 F->deleteBody(); 1983 F->setComdat(nullptr); 1984 F->clearMetadata(); 1985 } 1986 1987 // Update the linkage for extern_weak declarations when a definition 1988 // exists. 1989 if (Linkage == CFL_Definition && F->hasExternalWeakLinkage()) 1990 F->setLinkage(GlobalValue::ExternalLinkage); 1991 1992 // If the function in the full LTO module is a declaration, replace its 1993 // type metadata with the type metadata we found in cfi.functions. That 1994 // metadata is presumed to be more accurate than the metadata attached 1995 // to the declaration. 1996 if (F->isDeclaration()) { 1997 if (Linkage == CFL_WeakDeclaration) 1998 F->setLinkage(GlobalValue::ExternalWeakLinkage); 1999 2000 F->eraseMetadata(LLVMContext::MD_type); 2001 for (unsigned I = 2; I < FuncMD->getNumOperands(); ++I) 2002 F->addMetadata(LLVMContext::MD_type, 2003 *cast<MDNode>(FuncMD->getOperand(I).get())); 2004 } 2005 } 2006 } 2007 } 2008 2009 DenseMap<GlobalObject *, GlobalTypeMember *> GlobalTypeMembers; 2010 for (GlobalObject &GO : M.global_objects()) { 2011 if (isa<GlobalVariable>(GO) && GO.isDeclarationForLinker()) 2012 continue; 2013 2014 Types.clear(); 2015 GO.getMetadata(LLVMContext::MD_type, Types); 2016 2017 bool IsJumpTableCanonical = false; 2018 bool IsExported = false; 2019 if (Function *F = dyn_cast<Function>(&GO)) { 2020 IsJumpTableCanonical = isJumpTableCanonical(F); 2021 if (ExportedFunctions.count(F->getName())) { 2022 IsJumpTableCanonical |= 2023 ExportedFunctions[F->getName()].Linkage == CFL_Definition; 2024 IsExported = true; 2025 // TODO: The logic here checks only that the function is address taken, 2026 // not that the address takers are live. This can be updated to check 2027 // their liveness and emit fewer jumptable entries once monolithic LTO 2028 // builds also emit summaries. 2029 } else if (!F->hasAddressTaken()) { 2030 if (!CrossDsoCfi || !IsJumpTableCanonical || F->hasLocalLinkage()) 2031 continue; 2032 } 2033 } 2034 2035 auto *GTM = GlobalTypeMember::create(Alloc, &GO, IsJumpTableCanonical, 2036 IsExported, Types); 2037 GlobalTypeMembers[&GO] = GTM; 2038 for (MDNode *Type : Types) { 2039 verifyTypeMDNode(&GO, Type); 2040 auto &Info = TypeIdInfo[Type->getOperand(1)]; 2041 Info.UniqueId = ++CurUniqueId; 2042 Info.RefGlobals.push_back(GTM); 2043 } 2044 } 2045 2046 auto AddTypeIdUse = [&](Metadata *TypeId) -> TypeIdUserInfo & { 2047 // Add the call site to the list of call sites for this type identifier. We 2048 // also use TypeIdUsers to keep track of whether we have seen this type 2049 // identifier before. If we have, we don't need to re-add the referenced 2050 // globals to the equivalence class. 2051 auto Ins = TypeIdUsers.insert({TypeId, {}}); 2052 if (Ins.second) { 2053 // Add the type identifier to the equivalence class. 2054 GlobalClassesTy::iterator GCI = GlobalClasses.insert(TypeId); 2055 GlobalClassesTy::member_iterator CurSet = GlobalClasses.findLeader(GCI); 2056 2057 // Add the referenced globals to the type identifier's equivalence class. 2058 for (GlobalTypeMember *GTM : TypeIdInfo[TypeId].RefGlobals) 2059 CurSet = GlobalClasses.unionSets( 2060 CurSet, GlobalClasses.findLeader(GlobalClasses.insert(GTM))); 2061 } 2062 2063 return Ins.first->second; 2064 }; 2065 2066 if (TypeTestFunc) { 2067 for (const Use &U : TypeTestFunc->uses()) { 2068 auto CI = cast<CallInst>(U.getUser()); 2069 // If this type test is only used by llvm.assume instructions, it 2070 // was used for whole program devirtualization, and is being kept 2071 // for use by other optimization passes. We do not need or want to 2072 // lower it here. We also don't want to rewrite any associated globals 2073 // unnecessarily. These will be removed by a subsequent LTT invocation 2074 // with the DropTypeTests flag set. 2075 bool OnlyAssumeUses = !CI->use_empty(); 2076 for (const Use &CIU : CI->uses()) { 2077 if (isa<AssumeInst>(CIU.getUser())) 2078 continue; 2079 OnlyAssumeUses = false; 2080 break; 2081 } 2082 if (OnlyAssumeUses) 2083 continue; 2084 2085 auto TypeIdMDVal = dyn_cast<MetadataAsValue>(CI->getArgOperand(1)); 2086 if (!TypeIdMDVal) 2087 report_fatal_error("Second argument of llvm.type.test must be metadata"); 2088 auto TypeId = TypeIdMDVal->getMetadata(); 2089 AddTypeIdUse(TypeId).CallSites.push_back(CI); 2090 } 2091 } 2092 2093 if (ICallBranchFunnelFunc) { 2094 for (const Use &U : ICallBranchFunnelFunc->uses()) { 2095 if (Arch != Triple::x86_64) 2096 report_fatal_error( 2097 "llvm.icall.branch.funnel not supported on this target"); 2098 2099 auto CI = cast<CallInst>(U.getUser()); 2100 2101 std::vector<GlobalTypeMember *> Targets; 2102 if (CI->arg_size() % 2 != 1) 2103 report_fatal_error("number of arguments should be odd"); 2104 2105 GlobalClassesTy::member_iterator CurSet; 2106 for (unsigned I = 1; I != CI->arg_size(); I += 2) { 2107 int64_t Offset; 2108 auto *Base = dyn_cast<GlobalObject>(GetPointerBaseWithConstantOffset( 2109 CI->getOperand(I), Offset, M.getDataLayout())); 2110 if (!Base) 2111 report_fatal_error( 2112 "Expected branch funnel operand to be global value"); 2113 2114 GlobalTypeMember *GTM = GlobalTypeMembers[Base]; 2115 Targets.push_back(GTM); 2116 GlobalClassesTy::member_iterator NewSet = 2117 GlobalClasses.findLeader(GlobalClasses.insert(GTM)); 2118 if (I == 1) 2119 CurSet = NewSet; 2120 else 2121 CurSet = GlobalClasses.unionSets(CurSet, NewSet); 2122 } 2123 2124 GlobalClasses.unionSets( 2125 CurSet, GlobalClasses.findLeader( 2126 GlobalClasses.insert(ICallBranchFunnel::create( 2127 Alloc, CI, Targets, ++CurUniqueId)))); 2128 } 2129 } 2130 2131 if (ExportSummary) { 2132 DenseMap<GlobalValue::GUID, TinyPtrVector<Metadata *>> MetadataByGUID; 2133 for (auto &P : TypeIdInfo) { 2134 if (auto *TypeId = dyn_cast<MDString>(P.first)) 2135 MetadataByGUID[GlobalValue::getGUID(TypeId->getString())].push_back( 2136 TypeId); 2137 } 2138 2139 for (auto &P : *ExportSummary) { 2140 for (auto &S : P.second.SummaryList) { 2141 if (!ExportSummary->isGlobalValueLive(S.get())) 2142 continue; 2143 if (auto *FS = dyn_cast<FunctionSummary>(S->getBaseObject())) 2144 for (GlobalValue::GUID G : FS->type_tests()) 2145 for (Metadata *MD : MetadataByGUID[G]) 2146 AddTypeIdUse(MD).IsExported = true; 2147 } 2148 } 2149 } 2150 2151 if (GlobalClasses.empty()) 2152 return false; 2153 2154 // Build a list of disjoint sets ordered by their maximum global index for 2155 // determinism. 2156 std::vector<std::pair<GlobalClassesTy::iterator, unsigned>> Sets; 2157 for (GlobalClassesTy::iterator I = GlobalClasses.begin(), 2158 E = GlobalClasses.end(); 2159 I != E; ++I) { 2160 if (!I->isLeader()) 2161 continue; 2162 ++NumTypeIdDisjointSets; 2163 2164 unsigned MaxUniqueId = 0; 2165 for (GlobalClassesTy::member_iterator MI = GlobalClasses.member_begin(I); 2166 MI != GlobalClasses.member_end(); ++MI) { 2167 if (auto *MD = MI->dyn_cast<Metadata *>()) 2168 MaxUniqueId = std::max(MaxUniqueId, TypeIdInfo[MD].UniqueId); 2169 else if (auto *BF = MI->dyn_cast<ICallBranchFunnel *>()) 2170 MaxUniqueId = std::max(MaxUniqueId, BF->UniqueId); 2171 } 2172 Sets.emplace_back(I, MaxUniqueId); 2173 } 2174 llvm::sort(Sets, llvm::less_second()); 2175 2176 // For each disjoint set we found... 2177 for (const auto &S : Sets) { 2178 // Build the list of type identifiers in this disjoint set. 2179 std::vector<Metadata *> TypeIds; 2180 std::vector<GlobalTypeMember *> Globals; 2181 std::vector<ICallBranchFunnel *> ICallBranchFunnels; 2182 for (GlobalClassesTy::member_iterator MI = 2183 GlobalClasses.member_begin(S.first); 2184 MI != GlobalClasses.member_end(); ++MI) { 2185 if (MI->is<Metadata *>()) 2186 TypeIds.push_back(MI->get<Metadata *>()); 2187 else if (MI->is<GlobalTypeMember *>()) 2188 Globals.push_back(MI->get<GlobalTypeMember *>()); 2189 else 2190 ICallBranchFunnels.push_back(MI->get<ICallBranchFunnel *>()); 2191 } 2192 2193 // Order type identifiers by unique ID for determinism. This ordering is 2194 // stable as there is a one-to-one mapping between metadata and unique IDs. 2195 llvm::sort(TypeIds, [&](Metadata *M1, Metadata *M2) { 2196 return TypeIdInfo[M1].UniqueId < TypeIdInfo[M2].UniqueId; 2197 }); 2198 2199 // Same for the branch funnels. 2200 llvm::sort(ICallBranchFunnels, 2201 [&](ICallBranchFunnel *F1, ICallBranchFunnel *F2) { 2202 return F1->UniqueId < F2->UniqueId; 2203 }); 2204 2205 // Build bitsets for this disjoint set. 2206 buildBitSetsFromDisjointSet(TypeIds, Globals, ICallBranchFunnels); 2207 } 2208 2209 allocateByteArrays(); 2210 2211 // Parse alias data to replace stand-in function declarations for aliases 2212 // with an alias to the intended target. 2213 if (ExportSummary) { 2214 if (NamedMDNode *AliasesMD = M.getNamedMetadata("aliases")) { 2215 for (auto AliasMD : AliasesMD->operands()) { 2216 assert(AliasMD->getNumOperands() >= 4); 2217 StringRef AliasName = 2218 cast<MDString>(AliasMD->getOperand(0))->getString(); 2219 StringRef Aliasee = cast<MDString>(AliasMD->getOperand(1))->getString(); 2220 2221 if (!ExportedFunctions.count(Aliasee) || 2222 ExportedFunctions[Aliasee].Linkage != CFL_Definition || 2223 !M.getNamedAlias(Aliasee)) 2224 continue; 2225 2226 GlobalValue::VisibilityTypes Visibility = 2227 static_cast<GlobalValue::VisibilityTypes>( 2228 cast<ConstantAsMetadata>(AliasMD->getOperand(2)) 2229 ->getValue() 2230 ->getUniqueInteger() 2231 .getZExtValue()); 2232 bool Weak = 2233 static_cast<bool>(cast<ConstantAsMetadata>(AliasMD->getOperand(3)) 2234 ->getValue() 2235 ->getUniqueInteger() 2236 .getZExtValue()); 2237 2238 auto *Alias = GlobalAlias::create("", M.getNamedAlias(Aliasee)); 2239 Alias->setVisibility(Visibility); 2240 if (Weak) 2241 Alias->setLinkage(GlobalValue::WeakAnyLinkage); 2242 2243 if (auto *F = M.getFunction(AliasName)) { 2244 Alias->takeName(F); 2245 F->replaceAllUsesWith(Alias); 2246 F->eraseFromParent(); 2247 } else { 2248 Alias->setName(AliasName); 2249 } 2250 } 2251 } 2252 } 2253 2254 // Emit .symver directives for exported functions, if they exist. 2255 if (ExportSummary) { 2256 if (NamedMDNode *SymversMD = M.getNamedMetadata("symvers")) { 2257 for (auto Symver : SymversMD->operands()) { 2258 assert(Symver->getNumOperands() >= 2); 2259 StringRef SymbolName = 2260 cast<MDString>(Symver->getOperand(0))->getString(); 2261 StringRef Alias = cast<MDString>(Symver->getOperand(1))->getString(); 2262 2263 if (!ExportedFunctions.count(SymbolName)) 2264 continue; 2265 2266 M.appendModuleInlineAsm( 2267 (llvm::Twine(".symver ") + SymbolName + ", " + Alias).str()); 2268 } 2269 } 2270 } 2271 2272 return true; 2273 } 2274 2275 PreservedAnalyses LowerTypeTestsPass::run(Module &M, 2276 ModuleAnalysisManager &AM) { 2277 bool Changed; 2278 if (UseCommandLine) 2279 Changed = LowerTypeTestsModule::runForTesting(M); 2280 else 2281 Changed = 2282 LowerTypeTestsModule(M, ExportSummary, ImportSummary, DropTypeTests) 2283 .lower(); 2284 if (!Changed) 2285 return PreservedAnalyses::all(); 2286 return PreservedAnalyses::none(); 2287 } 2288