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); 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 ArrayRef(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 ArrayRef(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 (const 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 kX86IBTJumpTableEntrySize = 16; 1183 static const unsigned kARMJumpTableEntrySize = 4; 1184 static const unsigned kARMBTIJumpTableEntrySize = 8; 1185 static const unsigned kRISCVJumpTableEntrySize = 8; 1186 1187 unsigned LowerTypeTestsModule::getJumpTableEntrySize() { 1188 switch (Arch) { 1189 case Triple::x86: 1190 case Triple::x86_64: 1191 if (const auto *MD = mdconst::extract_or_null<ConstantInt>( 1192 M.getModuleFlag("cf-protection-branch"))) 1193 if (MD->getZExtValue()) 1194 return kX86IBTJumpTableEntrySize; 1195 return kX86JumpTableEntrySize; 1196 case Triple::arm: 1197 case Triple::thumb: 1198 return kARMJumpTableEntrySize; 1199 case Triple::aarch64: 1200 if (const auto *BTE = mdconst::extract_or_null<ConstantInt>( 1201 M.getModuleFlag("branch-target-enforcement"))) 1202 if (BTE->getZExtValue()) 1203 return kARMBTIJumpTableEntrySize; 1204 return kARMJumpTableEntrySize; 1205 case Triple::riscv32: 1206 case Triple::riscv64: 1207 return kRISCVJumpTableEntrySize; 1208 default: 1209 report_fatal_error("Unsupported architecture for jump tables"); 1210 } 1211 } 1212 1213 // Create a jump table entry for the target. This consists of an instruction 1214 // sequence containing a relative branch to Dest. Appends inline asm text, 1215 // constraints and arguments to AsmOS, ConstraintOS and AsmArgs. 1216 void LowerTypeTestsModule::createJumpTableEntry( 1217 raw_ostream &AsmOS, raw_ostream &ConstraintOS, 1218 Triple::ArchType JumpTableArch, SmallVectorImpl<Value *> &AsmArgs, 1219 Function *Dest) { 1220 unsigned ArgIndex = AsmArgs.size(); 1221 1222 if (JumpTableArch == Triple::x86 || JumpTableArch == Triple::x86_64) { 1223 bool Endbr = false; 1224 if (const auto *MD = mdconst::extract_or_null<ConstantInt>( 1225 Dest->getParent()->getModuleFlag("cf-protection-branch"))) 1226 Endbr = MD->getZExtValue() != 0; 1227 if (Endbr) 1228 AsmOS << (JumpTableArch == Triple::x86 ? "endbr32\n" : "endbr64\n"); 1229 AsmOS << "jmp ${" << ArgIndex << ":c}@plt\n"; 1230 if (Endbr) 1231 AsmOS << ".balign 16, 0xcc\n"; 1232 else 1233 AsmOS << "int3\nint3\nint3\n"; 1234 } else if (JumpTableArch == Triple::arm) { 1235 AsmOS << "b $" << ArgIndex << "\n"; 1236 } else if (JumpTableArch == Triple::aarch64) { 1237 if (const auto *BTE = mdconst::extract_or_null<ConstantInt>( 1238 Dest->getParent()->getModuleFlag("branch-target-enforcement"))) 1239 if (BTE->getZExtValue()) 1240 AsmOS << "bti c\n"; 1241 AsmOS << "b $" << ArgIndex << "\n"; 1242 } else if (JumpTableArch == Triple::thumb) { 1243 AsmOS << "b.w $" << ArgIndex << "\n"; 1244 } else if (JumpTableArch == Triple::riscv32 || 1245 JumpTableArch == Triple::riscv64) { 1246 AsmOS << "tail $" << ArgIndex << "@plt\n"; 1247 } else { 1248 report_fatal_error("Unsupported architecture for jump tables"); 1249 } 1250 1251 ConstraintOS << (ArgIndex > 0 ? ",s" : "s"); 1252 AsmArgs.push_back(Dest); 1253 } 1254 1255 Type *LowerTypeTestsModule::getJumpTableEntryType() { 1256 return ArrayType::get(Int8Ty, getJumpTableEntrySize()); 1257 } 1258 1259 /// Given a disjoint set of type identifiers and functions, build the bit sets 1260 /// and lower the llvm.type.test calls, architecture dependently. 1261 void LowerTypeTestsModule::buildBitSetsFromFunctions( 1262 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Functions) { 1263 if (Arch == Triple::x86 || Arch == Triple::x86_64 || Arch == Triple::arm || 1264 Arch == Triple::thumb || Arch == Triple::aarch64 || 1265 Arch == Triple::riscv32 || Arch == Triple::riscv64) 1266 buildBitSetsFromFunctionsNative(TypeIds, Functions); 1267 else if (Arch == Triple::wasm32 || Arch == Triple::wasm64) 1268 buildBitSetsFromFunctionsWASM(TypeIds, Functions); 1269 else 1270 report_fatal_error("Unsupported architecture for jump tables"); 1271 } 1272 1273 void LowerTypeTestsModule::moveInitializerToModuleConstructor( 1274 GlobalVariable *GV) { 1275 if (WeakInitializerFn == nullptr) { 1276 WeakInitializerFn = Function::Create( 1277 FunctionType::get(Type::getVoidTy(M.getContext()), 1278 /* IsVarArg */ false), 1279 GlobalValue::InternalLinkage, 1280 M.getDataLayout().getProgramAddressSpace(), 1281 "__cfi_global_var_init", &M); 1282 BasicBlock *BB = 1283 BasicBlock::Create(M.getContext(), "entry", WeakInitializerFn); 1284 ReturnInst::Create(M.getContext(), BB); 1285 WeakInitializerFn->setSection( 1286 ObjectFormat == Triple::MachO 1287 ? "__TEXT,__StaticInit,regular,pure_instructions" 1288 : ".text.startup"); 1289 // This code is equivalent to relocation application, and should run at the 1290 // earliest possible time (i.e. with the highest priority). 1291 appendToGlobalCtors(M, WeakInitializerFn, /* Priority */ 0); 1292 } 1293 1294 IRBuilder<> IRB(WeakInitializerFn->getEntryBlock().getTerminator()); 1295 GV->setConstant(false); 1296 IRB.CreateAlignedStore(GV->getInitializer(), GV, GV->getAlign()); 1297 GV->setInitializer(Constant::getNullValue(GV->getValueType())); 1298 } 1299 1300 void LowerTypeTestsModule::findGlobalVariableUsersOf( 1301 Constant *C, SmallSetVector<GlobalVariable *, 8> &Out) { 1302 for (auto *U : C->users()){ 1303 if (auto *GV = dyn_cast<GlobalVariable>(U)) 1304 Out.insert(GV); 1305 else if (auto *C2 = dyn_cast<Constant>(U)) 1306 findGlobalVariableUsersOf(C2, Out); 1307 } 1308 } 1309 1310 // Replace all uses of F with (F ? JT : 0). 1311 void LowerTypeTestsModule::replaceWeakDeclarationWithJumpTablePtr( 1312 Function *F, Constant *JT, bool IsJumpTableCanonical) { 1313 // The target expression can not appear in a constant initializer on most 1314 // (all?) targets. Switch to a runtime initializer. 1315 SmallSetVector<GlobalVariable *, 8> GlobalVarUsers; 1316 findGlobalVariableUsersOf(F, GlobalVarUsers); 1317 for (auto *GV : GlobalVarUsers) 1318 moveInitializerToModuleConstructor(GV); 1319 1320 // Can not RAUW F with an expression that uses F. Replace with a temporary 1321 // placeholder first. 1322 Function *PlaceholderFn = 1323 Function::Create(cast<FunctionType>(F->getValueType()), 1324 GlobalValue::ExternalWeakLinkage, 1325 F->getAddressSpace(), "", &M); 1326 replaceCfiUses(F, PlaceholderFn, IsJumpTableCanonical); 1327 1328 Constant *Target = ConstantExpr::getSelect( 1329 ConstantExpr::getICmp(CmpInst::ICMP_NE, F, 1330 Constant::getNullValue(F->getType())), 1331 JT, Constant::getNullValue(F->getType())); 1332 PlaceholderFn->replaceAllUsesWith(Target); 1333 PlaceholderFn->eraseFromParent(); 1334 } 1335 1336 static bool isThumbFunction(Function *F, Triple::ArchType ModuleArch) { 1337 Attribute TFAttr = F->getFnAttribute("target-features"); 1338 if (TFAttr.isValid()) { 1339 SmallVector<StringRef, 6> Features; 1340 TFAttr.getValueAsString().split(Features, ','); 1341 for (StringRef Feature : Features) { 1342 if (Feature == "-thumb-mode") 1343 return false; 1344 else if (Feature == "+thumb-mode") 1345 return true; 1346 } 1347 } 1348 1349 return ModuleArch == Triple::thumb; 1350 } 1351 1352 // Each jump table must be either ARM or Thumb as a whole for the bit-test math 1353 // to work. Pick one that matches the majority of members to minimize interop 1354 // veneers inserted by the linker. 1355 static Triple::ArchType 1356 selectJumpTableArmEncoding(ArrayRef<GlobalTypeMember *> Functions, 1357 Triple::ArchType ModuleArch) { 1358 if (ModuleArch != Triple::arm && ModuleArch != Triple::thumb) 1359 return ModuleArch; 1360 1361 unsigned ArmCount = 0, ThumbCount = 0; 1362 for (const auto GTM : Functions) { 1363 if (!GTM->isJumpTableCanonical()) { 1364 // PLT stubs are always ARM. 1365 // FIXME: This is the wrong heuristic for non-canonical jump tables. 1366 ++ArmCount; 1367 continue; 1368 } 1369 1370 Function *F = cast<Function>(GTM->getGlobal()); 1371 ++(isThumbFunction(F, ModuleArch) ? ThumbCount : ArmCount); 1372 } 1373 1374 return ArmCount > ThumbCount ? Triple::arm : Triple::thumb; 1375 } 1376 1377 void LowerTypeTestsModule::createJumpTable( 1378 Function *F, ArrayRef<GlobalTypeMember *> Functions) { 1379 std::string AsmStr, ConstraintStr; 1380 raw_string_ostream AsmOS(AsmStr), ConstraintOS(ConstraintStr); 1381 SmallVector<Value *, 16> AsmArgs; 1382 AsmArgs.reserve(Functions.size() * 2); 1383 1384 Triple::ArchType JumpTableArch = selectJumpTableArmEncoding(Functions, Arch); 1385 1386 for (GlobalTypeMember *GTM : Functions) 1387 createJumpTableEntry(AsmOS, ConstraintOS, JumpTableArch, AsmArgs, 1388 cast<Function>(GTM->getGlobal())); 1389 1390 // Align the whole table by entry size. 1391 F->setAlignment(Align(getJumpTableEntrySize())); 1392 // Skip prologue. 1393 // Disabled on win32 due to https://llvm.org/bugs/show_bug.cgi?id=28641#c3. 1394 // Luckily, this function does not get any prologue even without the 1395 // attribute. 1396 if (OS != Triple::Win32) 1397 F->addFnAttr(Attribute::Naked); 1398 if (JumpTableArch == Triple::arm) 1399 F->addFnAttr("target-features", "-thumb-mode"); 1400 if (JumpTableArch == Triple::thumb) { 1401 F->addFnAttr("target-features", "+thumb-mode"); 1402 // Thumb jump table assembly needs Thumb2. The following attribute is added 1403 // by Clang for -march=armv7. 1404 F->addFnAttr("target-cpu", "cortex-a8"); 1405 } 1406 // When -mbranch-protection= is used, the inline asm adds a BTI. Suppress BTI 1407 // for the function to avoid double BTI. This is a no-op without 1408 // -mbranch-protection=. 1409 if (JumpTableArch == Triple::aarch64) { 1410 F->addFnAttr("branch-target-enforcement", "false"); 1411 F->addFnAttr("sign-return-address", "none"); 1412 } 1413 if (JumpTableArch == Triple::riscv32 || JumpTableArch == Triple::riscv64) { 1414 // Make sure the jump table assembly is not modified by the assembler or 1415 // the linker. 1416 F->addFnAttr("target-features", "-c,-relax"); 1417 } 1418 // When -fcf-protection= is used, the inline asm adds an ENDBR. Suppress ENDBR 1419 // for the function to avoid double ENDBR. This is a no-op without 1420 // -fcf-protection=. 1421 if (JumpTableArch == Triple::x86 || JumpTableArch == Triple::x86_64) 1422 F->addFnAttr(Attribute::NoCfCheck); 1423 // Make sure we don't emit .eh_frame for this function. 1424 F->addFnAttr(Attribute::NoUnwind); 1425 1426 BasicBlock *BB = BasicBlock::Create(M.getContext(), "entry", F); 1427 IRBuilder<> IRB(BB); 1428 1429 SmallVector<Type *, 16> ArgTypes; 1430 ArgTypes.reserve(AsmArgs.size()); 1431 for (const auto &Arg : AsmArgs) 1432 ArgTypes.push_back(Arg->getType()); 1433 InlineAsm *JumpTableAsm = 1434 InlineAsm::get(FunctionType::get(IRB.getVoidTy(), ArgTypes, false), 1435 AsmOS.str(), ConstraintOS.str(), 1436 /*hasSideEffects=*/true); 1437 1438 IRB.CreateCall(JumpTableAsm, AsmArgs); 1439 IRB.CreateUnreachable(); 1440 } 1441 1442 /// Given a disjoint set of type identifiers and functions, build a jump table 1443 /// for the functions, build the bit sets and lower the llvm.type.test calls. 1444 void LowerTypeTestsModule::buildBitSetsFromFunctionsNative( 1445 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Functions) { 1446 // Unlike the global bitset builder, the function bitset builder cannot 1447 // re-arrange functions in a particular order and base its calculations on the 1448 // layout of the functions' entry points, as we have no idea how large a 1449 // particular function will end up being (the size could even depend on what 1450 // this pass does!) Instead, we build a jump table, which is a block of code 1451 // consisting of one branch instruction for each of the functions in the bit 1452 // set that branches to the target function, and redirect any taken function 1453 // addresses to the corresponding jump table entry. In the object file's 1454 // symbol table, the symbols for the target functions also refer to the jump 1455 // table entries, so that addresses taken outside the module will pass any 1456 // verification done inside the module. 1457 // 1458 // In more concrete terms, suppose we have three functions f, g, h which are 1459 // of the same type, and a function foo that returns their addresses: 1460 // 1461 // f: 1462 // mov 0, %eax 1463 // ret 1464 // 1465 // g: 1466 // mov 1, %eax 1467 // ret 1468 // 1469 // h: 1470 // mov 2, %eax 1471 // ret 1472 // 1473 // foo: 1474 // mov f, %eax 1475 // mov g, %edx 1476 // mov h, %ecx 1477 // ret 1478 // 1479 // We output the jump table as module-level inline asm string. The end result 1480 // will (conceptually) look like this: 1481 // 1482 // f = .cfi.jumptable 1483 // g = .cfi.jumptable + 4 1484 // h = .cfi.jumptable + 8 1485 // .cfi.jumptable: 1486 // jmp f.cfi ; 5 bytes 1487 // int3 ; 1 byte 1488 // int3 ; 1 byte 1489 // int3 ; 1 byte 1490 // jmp g.cfi ; 5 bytes 1491 // int3 ; 1 byte 1492 // int3 ; 1 byte 1493 // int3 ; 1 byte 1494 // jmp h.cfi ; 5 bytes 1495 // int3 ; 1 byte 1496 // int3 ; 1 byte 1497 // int3 ; 1 byte 1498 // 1499 // f.cfi: 1500 // mov 0, %eax 1501 // ret 1502 // 1503 // g.cfi: 1504 // mov 1, %eax 1505 // ret 1506 // 1507 // h.cfi: 1508 // mov 2, %eax 1509 // ret 1510 // 1511 // foo: 1512 // mov f, %eax 1513 // mov g, %edx 1514 // mov h, %ecx 1515 // ret 1516 // 1517 // Because the addresses of f, g, h are evenly spaced at a power of 2, in the 1518 // normal case the check can be carried out using the same kind of simple 1519 // arithmetic that we normally use for globals. 1520 1521 // FIXME: find a better way to represent the jumptable in the IR. 1522 assert(!Functions.empty()); 1523 1524 // Build a simple layout based on the regular layout of jump tables. 1525 DenseMap<GlobalTypeMember *, uint64_t> GlobalLayout; 1526 unsigned EntrySize = getJumpTableEntrySize(); 1527 for (unsigned I = 0; I != Functions.size(); ++I) 1528 GlobalLayout[Functions[I]] = I * EntrySize; 1529 1530 Function *JumpTableFn = 1531 Function::Create(FunctionType::get(Type::getVoidTy(M.getContext()), 1532 /* IsVarArg */ false), 1533 GlobalValue::PrivateLinkage, 1534 M.getDataLayout().getProgramAddressSpace(), 1535 ".cfi.jumptable", &M); 1536 ArrayType *JumpTableType = 1537 ArrayType::get(getJumpTableEntryType(), Functions.size()); 1538 auto JumpTable = 1539 ConstantExpr::getPointerCast(JumpTableFn, JumpTableType->getPointerTo(0)); 1540 1541 lowerTypeTestCalls(TypeIds, JumpTable, GlobalLayout); 1542 1543 { 1544 ScopedSaveAliaseesAndUsed S(M); 1545 1546 // Build aliases pointing to offsets into the jump table, and replace 1547 // references to the original functions with references to the aliases. 1548 for (unsigned I = 0; I != Functions.size(); ++I) { 1549 Function *F = cast<Function>(Functions[I]->getGlobal()); 1550 bool IsJumpTableCanonical = Functions[I]->isJumpTableCanonical(); 1551 1552 Constant *CombinedGlobalElemPtr = ConstantExpr::getBitCast( 1553 ConstantExpr::getInBoundsGetElementPtr( 1554 JumpTableType, JumpTable, 1555 ArrayRef<Constant *>{ConstantInt::get(IntPtrTy, 0), 1556 ConstantInt::get(IntPtrTy, I)}), 1557 F->getType()); 1558 1559 const bool IsExported = Functions[I]->isExported(); 1560 if (!IsJumpTableCanonical) { 1561 GlobalValue::LinkageTypes LT = IsExported 1562 ? GlobalValue::ExternalLinkage 1563 : GlobalValue::InternalLinkage; 1564 GlobalAlias *JtAlias = GlobalAlias::create(F->getValueType(), 0, LT, 1565 F->getName() + ".cfi_jt", 1566 CombinedGlobalElemPtr, &M); 1567 if (IsExported) 1568 JtAlias->setVisibility(GlobalValue::HiddenVisibility); 1569 else 1570 appendToUsed(M, {JtAlias}); 1571 } 1572 1573 if (IsExported) { 1574 if (IsJumpTableCanonical) 1575 ExportSummary->cfiFunctionDefs().insert(std::string(F->getName())); 1576 else 1577 ExportSummary->cfiFunctionDecls().insert(std::string(F->getName())); 1578 } 1579 1580 if (!IsJumpTableCanonical) { 1581 if (F->hasExternalWeakLinkage()) 1582 replaceWeakDeclarationWithJumpTablePtr(F, CombinedGlobalElemPtr, 1583 IsJumpTableCanonical); 1584 else 1585 replaceCfiUses(F, CombinedGlobalElemPtr, IsJumpTableCanonical); 1586 } else { 1587 assert(F->getType()->getAddressSpace() == 0); 1588 1589 GlobalAlias *FAlias = 1590 GlobalAlias::create(F->getValueType(), 0, F->getLinkage(), "", 1591 CombinedGlobalElemPtr, &M); 1592 FAlias->setVisibility(F->getVisibility()); 1593 FAlias->takeName(F); 1594 if (FAlias->hasName()) 1595 F->setName(FAlias->getName() + ".cfi"); 1596 replaceCfiUses(F, FAlias, IsJumpTableCanonical); 1597 if (!F->hasLocalLinkage()) 1598 F->setVisibility(GlobalVariable::HiddenVisibility); 1599 } 1600 } 1601 } 1602 1603 createJumpTable(JumpTableFn, Functions); 1604 } 1605 1606 /// Assign a dummy layout using an incrementing counter, tag each function 1607 /// with its index represented as metadata, and lower each type test to an 1608 /// integer range comparison. During generation of the indirect function call 1609 /// table in the backend, it will assign the given indexes. 1610 /// Note: Dynamic linking is not supported, as the WebAssembly ABI has not yet 1611 /// been finalized. 1612 void LowerTypeTestsModule::buildBitSetsFromFunctionsWASM( 1613 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Functions) { 1614 assert(!Functions.empty()); 1615 1616 // Build consecutive monotonic integer ranges for each call target set 1617 DenseMap<GlobalTypeMember *, uint64_t> GlobalLayout; 1618 1619 for (GlobalTypeMember *GTM : Functions) { 1620 Function *F = cast<Function>(GTM->getGlobal()); 1621 1622 // Skip functions that are not address taken, to avoid bloating the table 1623 if (!F->hasAddressTaken()) 1624 continue; 1625 1626 // Store metadata with the index for each function 1627 MDNode *MD = MDNode::get(F->getContext(), 1628 ArrayRef<Metadata *>(ConstantAsMetadata::get( 1629 ConstantInt::get(Int64Ty, IndirectIndex)))); 1630 F->setMetadata("wasm.index", MD); 1631 1632 // Assign the counter value 1633 GlobalLayout[GTM] = IndirectIndex++; 1634 } 1635 1636 // The indirect function table index space starts at zero, so pass a NULL 1637 // pointer as the subtracted "jump table" offset. 1638 lowerTypeTestCalls(TypeIds, ConstantPointerNull::get(Int32PtrTy), 1639 GlobalLayout); 1640 } 1641 1642 void LowerTypeTestsModule::buildBitSetsFromDisjointSet( 1643 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Globals, 1644 ArrayRef<ICallBranchFunnel *> ICallBranchFunnels) { 1645 DenseMap<Metadata *, uint64_t> TypeIdIndices; 1646 for (unsigned I = 0; I != TypeIds.size(); ++I) 1647 TypeIdIndices[TypeIds[I]] = I; 1648 1649 // For each type identifier, build a set of indices that refer to members of 1650 // the type identifier. 1651 std::vector<std::set<uint64_t>> TypeMembers(TypeIds.size()); 1652 unsigned GlobalIndex = 0; 1653 DenseMap<GlobalTypeMember *, uint64_t> GlobalIndices; 1654 for (GlobalTypeMember *GTM : Globals) { 1655 for (MDNode *Type : GTM->types()) { 1656 // Type = { offset, type identifier } 1657 auto I = TypeIdIndices.find(Type->getOperand(1)); 1658 if (I != TypeIdIndices.end()) 1659 TypeMembers[I->second].insert(GlobalIndex); 1660 } 1661 GlobalIndices[GTM] = GlobalIndex; 1662 GlobalIndex++; 1663 } 1664 1665 for (ICallBranchFunnel *JT : ICallBranchFunnels) { 1666 TypeMembers.emplace_back(); 1667 std::set<uint64_t> &TMSet = TypeMembers.back(); 1668 for (GlobalTypeMember *T : JT->targets()) 1669 TMSet.insert(GlobalIndices[T]); 1670 } 1671 1672 // Order the sets of indices by size. The GlobalLayoutBuilder works best 1673 // when given small index sets first. 1674 llvm::stable_sort(TypeMembers, [](const std::set<uint64_t> &O1, 1675 const std::set<uint64_t> &O2) { 1676 return O1.size() < O2.size(); 1677 }); 1678 1679 // Create a GlobalLayoutBuilder and provide it with index sets as layout 1680 // fragments. The GlobalLayoutBuilder tries to lay out members of fragments as 1681 // close together as possible. 1682 GlobalLayoutBuilder GLB(Globals.size()); 1683 for (auto &&MemSet : TypeMembers) 1684 GLB.addFragment(MemSet); 1685 1686 // Build a vector of globals with the computed layout. 1687 bool IsGlobalSet = 1688 Globals.empty() || isa<GlobalVariable>(Globals[0]->getGlobal()); 1689 std::vector<GlobalTypeMember *> OrderedGTMs(Globals.size()); 1690 auto OGTMI = OrderedGTMs.begin(); 1691 for (auto &&F : GLB.Fragments) { 1692 for (auto &&Offset : F) { 1693 if (IsGlobalSet != isa<GlobalVariable>(Globals[Offset]->getGlobal())) 1694 report_fatal_error("Type identifier may not contain both global " 1695 "variables and functions"); 1696 *OGTMI++ = Globals[Offset]; 1697 } 1698 } 1699 1700 // Build the bitsets from this disjoint set. 1701 if (IsGlobalSet) 1702 buildBitSetsFromGlobalVariables(TypeIds, OrderedGTMs); 1703 else 1704 buildBitSetsFromFunctions(TypeIds, OrderedGTMs); 1705 } 1706 1707 /// Lower all type tests in this module. 1708 LowerTypeTestsModule::LowerTypeTestsModule( 1709 Module &M, ModuleSummaryIndex *ExportSummary, 1710 const ModuleSummaryIndex *ImportSummary, bool DropTypeTests) 1711 : M(M), ExportSummary(ExportSummary), ImportSummary(ImportSummary), 1712 DropTypeTests(DropTypeTests || ClDropTypeTests) { 1713 assert(!(ExportSummary && ImportSummary)); 1714 Triple TargetTriple(M.getTargetTriple()); 1715 Arch = TargetTriple.getArch(); 1716 OS = TargetTriple.getOS(); 1717 ObjectFormat = TargetTriple.getObjectFormat(); 1718 } 1719 1720 bool LowerTypeTestsModule::runForTesting(Module &M) { 1721 ModuleSummaryIndex Summary(/*HaveGVs=*/false); 1722 1723 // Handle the command-line summary arguments. This code is for testing 1724 // purposes only, so we handle errors directly. 1725 if (!ClReadSummary.empty()) { 1726 ExitOnError ExitOnErr("-lowertypetests-read-summary: " + ClReadSummary + 1727 ": "); 1728 auto ReadSummaryFile = 1729 ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(ClReadSummary))); 1730 1731 yaml::Input In(ReadSummaryFile->getBuffer()); 1732 In >> Summary; 1733 ExitOnErr(errorCodeToError(In.error())); 1734 } 1735 1736 bool Changed = 1737 LowerTypeTestsModule( 1738 M, ClSummaryAction == PassSummaryAction::Export ? &Summary : nullptr, 1739 ClSummaryAction == PassSummaryAction::Import ? &Summary : nullptr, 1740 /*DropTypeTests*/ false) 1741 .lower(); 1742 1743 if (!ClWriteSummary.empty()) { 1744 ExitOnError ExitOnErr("-lowertypetests-write-summary: " + ClWriteSummary + 1745 ": "); 1746 std::error_code EC; 1747 raw_fd_ostream OS(ClWriteSummary, EC, sys::fs::OF_TextWithCRLF); 1748 ExitOnErr(errorCodeToError(EC)); 1749 1750 yaml::Output Out(OS); 1751 Out << Summary; 1752 } 1753 1754 return Changed; 1755 } 1756 1757 static bool isDirectCall(Use& U) { 1758 auto *Usr = dyn_cast<CallInst>(U.getUser()); 1759 if (Usr) { 1760 auto *CB = dyn_cast<CallBase>(Usr); 1761 if (CB && CB->isCallee(&U)) 1762 return true; 1763 } 1764 return false; 1765 } 1766 1767 void LowerTypeTestsModule::replaceCfiUses(Function *Old, Value *New, 1768 bool IsJumpTableCanonical) { 1769 SmallSetVector<Constant *, 4> Constants; 1770 for (Use &U : llvm::make_early_inc_range(Old->uses())) { 1771 // Skip block addresses and no_cfi values, which refer to the function 1772 // body instead of the jump table. 1773 if (isa<BlockAddress, NoCFIValue>(U.getUser())) 1774 continue; 1775 1776 // Skip direct calls to externally defined or non-dso_local functions 1777 if (isDirectCall(U) && (Old->isDSOLocal() || !IsJumpTableCanonical)) 1778 continue; 1779 1780 // Must handle Constants specially, we cannot call replaceUsesOfWith on a 1781 // constant because they are uniqued. 1782 if (auto *C = dyn_cast<Constant>(U.getUser())) { 1783 if (!isa<GlobalValue>(C)) { 1784 // Save unique users to avoid processing operand replacement 1785 // more than once. 1786 Constants.insert(C); 1787 continue; 1788 } 1789 } 1790 1791 U.set(New); 1792 } 1793 1794 // Process operand replacement of saved constants. 1795 for (auto *C : Constants) 1796 C->handleOperandChange(Old, New); 1797 } 1798 1799 void LowerTypeTestsModule::replaceDirectCalls(Value *Old, Value *New) { 1800 Old->replaceUsesWithIf(New, isDirectCall); 1801 } 1802 1803 static void dropTypeTests(Module &M, Function &TypeTestFunc) { 1804 for (Use &U : llvm::make_early_inc_range(TypeTestFunc.uses())) { 1805 auto *CI = cast<CallInst>(U.getUser()); 1806 // Find and erase llvm.assume intrinsics for this llvm.type.test call. 1807 for (Use &CIU : llvm::make_early_inc_range(CI->uses())) 1808 if (auto *Assume = dyn_cast<AssumeInst>(CIU.getUser())) 1809 Assume->eraseFromParent(); 1810 // If the assume was merged with another assume, we might have a use on a 1811 // phi (which will feed the assume). Simply replace the use on the phi 1812 // with "true" and leave the merged assume. 1813 if (!CI->use_empty()) { 1814 assert( 1815 all_of(CI->users(), [](User *U) -> bool { return isa<PHINode>(U); })); 1816 CI->replaceAllUsesWith(ConstantInt::getTrue(M.getContext())); 1817 } 1818 CI->eraseFromParent(); 1819 } 1820 } 1821 1822 bool LowerTypeTestsModule::lower() { 1823 Function *TypeTestFunc = 1824 M.getFunction(Intrinsic::getName(Intrinsic::type_test)); 1825 1826 if (DropTypeTests) { 1827 if (TypeTestFunc) 1828 dropTypeTests(M, *TypeTestFunc); 1829 // Normally we'd have already removed all @llvm.public.type.test calls, 1830 // except for in the case where we originally were performing ThinLTO but 1831 // decided not to in the backend. 1832 Function *PublicTypeTestFunc = 1833 M.getFunction(Intrinsic::getName(Intrinsic::public_type_test)); 1834 if (PublicTypeTestFunc) 1835 dropTypeTests(M, *PublicTypeTestFunc); 1836 if (TypeTestFunc || PublicTypeTestFunc) { 1837 // We have deleted the type intrinsics, so we no longer have enough 1838 // information to reason about the liveness of virtual function pointers 1839 // in GlobalDCE. 1840 for (GlobalVariable &GV : M.globals()) 1841 GV.eraseMetadata(LLVMContext::MD_vcall_visibility); 1842 return true; 1843 } 1844 return false; 1845 } 1846 1847 // If only some of the modules were split, we cannot correctly perform 1848 // this transformation. We already checked for the presense of type tests 1849 // with partially split modules during the thin link, and would have emitted 1850 // an error if any were found, so here we can simply return. 1851 if ((ExportSummary && ExportSummary->partiallySplitLTOUnits()) || 1852 (ImportSummary && ImportSummary->partiallySplitLTOUnits())) 1853 return false; 1854 1855 Function *ICallBranchFunnelFunc = 1856 M.getFunction(Intrinsic::getName(Intrinsic::icall_branch_funnel)); 1857 if ((!TypeTestFunc || TypeTestFunc->use_empty()) && 1858 (!ICallBranchFunnelFunc || ICallBranchFunnelFunc->use_empty()) && 1859 !ExportSummary && !ImportSummary) 1860 return false; 1861 1862 if (ImportSummary) { 1863 if (TypeTestFunc) 1864 for (Use &U : llvm::make_early_inc_range(TypeTestFunc->uses())) 1865 importTypeTest(cast<CallInst>(U.getUser())); 1866 1867 if (ICallBranchFunnelFunc && !ICallBranchFunnelFunc->use_empty()) 1868 report_fatal_error( 1869 "unexpected call to llvm.icall.branch.funnel during import phase"); 1870 1871 SmallVector<Function *, 8> Defs; 1872 SmallVector<Function *, 8> Decls; 1873 for (auto &F : M) { 1874 // CFI functions are either external, or promoted. A local function may 1875 // have the same name, but it's not the one we are looking for. 1876 if (F.hasLocalLinkage()) 1877 continue; 1878 if (ImportSummary->cfiFunctionDefs().count(std::string(F.getName()))) 1879 Defs.push_back(&F); 1880 else if (ImportSummary->cfiFunctionDecls().count( 1881 std::string(F.getName()))) 1882 Decls.push_back(&F); 1883 } 1884 1885 std::vector<GlobalAlias *> AliasesToErase; 1886 { 1887 ScopedSaveAliaseesAndUsed S(M); 1888 for (auto *F : Defs) 1889 importFunction(F, /*isJumpTableCanonical*/ true, AliasesToErase); 1890 for (auto *F : Decls) 1891 importFunction(F, /*isJumpTableCanonical*/ false, AliasesToErase); 1892 } 1893 for (GlobalAlias *GA : AliasesToErase) 1894 GA->eraseFromParent(); 1895 1896 return true; 1897 } 1898 1899 // Equivalence class set containing type identifiers and the globals that 1900 // reference them. This is used to partition the set of type identifiers in 1901 // the module into disjoint sets. 1902 using GlobalClassesTy = EquivalenceClasses< 1903 PointerUnion<GlobalTypeMember *, Metadata *, ICallBranchFunnel *>>; 1904 GlobalClassesTy GlobalClasses; 1905 1906 // Verify the type metadata and build a few data structures to let us 1907 // efficiently enumerate the type identifiers associated with a global: 1908 // a list of GlobalTypeMembers (a GlobalObject stored alongside a vector 1909 // of associated type metadata) and a mapping from type identifiers to their 1910 // list of GlobalTypeMembers and last observed index in the list of globals. 1911 // The indices will be used later to deterministically order the list of type 1912 // identifiers. 1913 BumpPtrAllocator Alloc; 1914 struct TIInfo { 1915 unsigned UniqueId; 1916 std::vector<GlobalTypeMember *> RefGlobals; 1917 }; 1918 DenseMap<Metadata *, TIInfo> TypeIdInfo; 1919 unsigned CurUniqueId = 0; 1920 SmallVector<MDNode *, 2> Types; 1921 1922 // Cross-DSO CFI emits jumptable entries for exported functions as well as 1923 // address taken functions in case they are address taken in other modules. 1924 const bool CrossDsoCfi = M.getModuleFlag("Cross-DSO CFI") != nullptr; 1925 1926 struct ExportedFunctionInfo { 1927 CfiFunctionLinkage Linkage; 1928 MDNode *FuncMD; // {name, linkage, type[, type...]} 1929 }; 1930 DenseMap<StringRef, ExportedFunctionInfo> ExportedFunctions; 1931 if (ExportSummary) { 1932 // A set of all functions that are address taken by a live global object. 1933 DenseSet<GlobalValue::GUID> AddressTaken; 1934 for (auto &I : *ExportSummary) 1935 for (auto &GVS : I.second.SummaryList) 1936 if (GVS->isLive()) 1937 for (const auto &Ref : GVS->refs()) 1938 AddressTaken.insert(Ref.getGUID()); 1939 1940 NamedMDNode *CfiFunctionsMD = M.getNamedMetadata("cfi.functions"); 1941 if (CfiFunctionsMD) { 1942 for (auto *FuncMD : CfiFunctionsMD->operands()) { 1943 assert(FuncMD->getNumOperands() >= 2); 1944 StringRef FunctionName = 1945 cast<MDString>(FuncMD->getOperand(0))->getString(); 1946 CfiFunctionLinkage Linkage = static_cast<CfiFunctionLinkage>( 1947 cast<ConstantAsMetadata>(FuncMD->getOperand(1)) 1948 ->getValue() 1949 ->getUniqueInteger() 1950 .getZExtValue()); 1951 const GlobalValue::GUID GUID = GlobalValue::getGUID( 1952 GlobalValue::dropLLVMManglingEscape(FunctionName)); 1953 // Do not emit jumptable entries for functions that are not-live and 1954 // have no live references (and are not exported with cross-DSO CFI.) 1955 if (!ExportSummary->isGUIDLive(GUID)) 1956 continue; 1957 if (!AddressTaken.count(GUID)) { 1958 if (!CrossDsoCfi || Linkage != CFL_Definition) 1959 continue; 1960 1961 bool Exported = false; 1962 if (auto VI = ExportSummary->getValueInfo(GUID)) 1963 for (const auto &GVS : VI.getSummaryList()) 1964 if (GVS->isLive() && !GlobalValue::isLocalLinkage(GVS->linkage())) 1965 Exported = true; 1966 1967 if (!Exported) 1968 continue; 1969 } 1970 auto P = ExportedFunctions.insert({FunctionName, {Linkage, FuncMD}}); 1971 if (!P.second && P.first->second.Linkage != CFL_Definition) 1972 P.first->second = {Linkage, FuncMD}; 1973 } 1974 1975 for (const auto &P : ExportedFunctions) { 1976 StringRef FunctionName = P.first; 1977 CfiFunctionLinkage Linkage = P.second.Linkage; 1978 MDNode *FuncMD = P.second.FuncMD; 1979 Function *F = M.getFunction(FunctionName); 1980 if (F && F->hasLocalLinkage()) { 1981 // Locally defined function that happens to have the same name as a 1982 // function defined in a ThinLTO module. Rename it to move it out of 1983 // the way of the external reference that we're about to create. 1984 // Note that setName will find a unique name for the function, so even 1985 // if there is an existing function with the suffix there won't be a 1986 // name collision. 1987 F->setName(F->getName() + ".1"); 1988 F = nullptr; 1989 } 1990 1991 if (!F) 1992 F = Function::Create( 1993 FunctionType::get(Type::getVoidTy(M.getContext()), false), 1994 GlobalVariable::ExternalLinkage, 1995 M.getDataLayout().getProgramAddressSpace(), FunctionName, &M); 1996 1997 // If the function is available_externally, remove its definition so 1998 // that it is handled the same way as a declaration. Later we will try 1999 // to create an alias using this function's linkage, which will fail if 2000 // the linkage is available_externally. This will also result in us 2001 // following the code path below to replace the type metadata. 2002 if (F->hasAvailableExternallyLinkage()) { 2003 F->setLinkage(GlobalValue::ExternalLinkage); 2004 F->deleteBody(); 2005 F->setComdat(nullptr); 2006 F->clearMetadata(); 2007 } 2008 2009 // Update the linkage for extern_weak declarations when a definition 2010 // exists. 2011 if (Linkage == CFL_Definition && F->hasExternalWeakLinkage()) 2012 F->setLinkage(GlobalValue::ExternalLinkage); 2013 2014 // If the function in the full LTO module is a declaration, replace its 2015 // type metadata with the type metadata we found in cfi.functions. That 2016 // metadata is presumed to be more accurate than the metadata attached 2017 // to the declaration. 2018 if (F->isDeclaration()) { 2019 if (Linkage == CFL_WeakDeclaration) 2020 F->setLinkage(GlobalValue::ExternalWeakLinkage); 2021 2022 F->eraseMetadata(LLVMContext::MD_type); 2023 for (unsigned I = 2; I < FuncMD->getNumOperands(); ++I) 2024 F->addMetadata(LLVMContext::MD_type, 2025 *cast<MDNode>(FuncMD->getOperand(I).get())); 2026 } 2027 } 2028 } 2029 } 2030 2031 DenseMap<GlobalObject *, GlobalTypeMember *> GlobalTypeMembers; 2032 for (GlobalObject &GO : M.global_objects()) { 2033 if (isa<GlobalVariable>(GO) && GO.isDeclarationForLinker()) 2034 continue; 2035 2036 Types.clear(); 2037 GO.getMetadata(LLVMContext::MD_type, Types); 2038 2039 bool IsJumpTableCanonical = false; 2040 bool IsExported = false; 2041 if (Function *F = dyn_cast<Function>(&GO)) { 2042 IsJumpTableCanonical = isJumpTableCanonical(F); 2043 if (ExportedFunctions.count(F->getName())) { 2044 IsJumpTableCanonical |= 2045 ExportedFunctions[F->getName()].Linkage == CFL_Definition; 2046 IsExported = true; 2047 // TODO: The logic here checks only that the function is address taken, 2048 // not that the address takers are live. This can be updated to check 2049 // their liveness and emit fewer jumptable entries once monolithic LTO 2050 // builds also emit summaries. 2051 } else if (!F->hasAddressTaken()) { 2052 if (!CrossDsoCfi || !IsJumpTableCanonical || F->hasLocalLinkage()) 2053 continue; 2054 } 2055 } 2056 2057 auto *GTM = GlobalTypeMember::create(Alloc, &GO, IsJumpTableCanonical, 2058 IsExported, Types); 2059 GlobalTypeMembers[&GO] = GTM; 2060 for (MDNode *Type : Types) { 2061 verifyTypeMDNode(&GO, Type); 2062 auto &Info = TypeIdInfo[Type->getOperand(1)]; 2063 Info.UniqueId = ++CurUniqueId; 2064 Info.RefGlobals.push_back(GTM); 2065 } 2066 } 2067 2068 auto AddTypeIdUse = [&](Metadata *TypeId) -> TypeIdUserInfo & { 2069 // Add the call site to the list of call sites for this type identifier. We 2070 // also use TypeIdUsers to keep track of whether we have seen this type 2071 // identifier before. If we have, we don't need to re-add the referenced 2072 // globals to the equivalence class. 2073 auto Ins = TypeIdUsers.insert({TypeId, {}}); 2074 if (Ins.second) { 2075 // Add the type identifier to the equivalence class. 2076 GlobalClassesTy::iterator GCI = GlobalClasses.insert(TypeId); 2077 GlobalClassesTy::member_iterator CurSet = GlobalClasses.findLeader(GCI); 2078 2079 // Add the referenced globals to the type identifier's equivalence class. 2080 for (GlobalTypeMember *GTM : TypeIdInfo[TypeId].RefGlobals) 2081 CurSet = GlobalClasses.unionSets( 2082 CurSet, GlobalClasses.findLeader(GlobalClasses.insert(GTM))); 2083 } 2084 2085 return Ins.first->second; 2086 }; 2087 2088 if (TypeTestFunc) { 2089 for (const Use &U : TypeTestFunc->uses()) { 2090 auto CI = cast<CallInst>(U.getUser()); 2091 // If this type test is only used by llvm.assume instructions, it 2092 // was used for whole program devirtualization, and is being kept 2093 // for use by other optimization passes. We do not need or want to 2094 // lower it here. We also don't want to rewrite any associated globals 2095 // unnecessarily. These will be removed by a subsequent LTT invocation 2096 // with the DropTypeTests flag set. 2097 bool OnlyAssumeUses = !CI->use_empty(); 2098 for (const Use &CIU : CI->uses()) { 2099 if (isa<AssumeInst>(CIU.getUser())) 2100 continue; 2101 OnlyAssumeUses = false; 2102 break; 2103 } 2104 if (OnlyAssumeUses) 2105 continue; 2106 2107 auto TypeIdMDVal = dyn_cast<MetadataAsValue>(CI->getArgOperand(1)); 2108 if (!TypeIdMDVal) 2109 report_fatal_error("Second argument of llvm.type.test must be metadata"); 2110 auto TypeId = TypeIdMDVal->getMetadata(); 2111 AddTypeIdUse(TypeId).CallSites.push_back(CI); 2112 } 2113 } 2114 2115 if (ICallBranchFunnelFunc) { 2116 for (const Use &U : ICallBranchFunnelFunc->uses()) { 2117 if (Arch != Triple::x86_64) 2118 report_fatal_error( 2119 "llvm.icall.branch.funnel not supported on this target"); 2120 2121 auto CI = cast<CallInst>(U.getUser()); 2122 2123 std::vector<GlobalTypeMember *> Targets; 2124 if (CI->arg_size() % 2 != 1) 2125 report_fatal_error("number of arguments should be odd"); 2126 2127 GlobalClassesTy::member_iterator CurSet; 2128 for (unsigned I = 1; I != CI->arg_size(); I += 2) { 2129 int64_t Offset; 2130 auto *Base = dyn_cast<GlobalObject>(GetPointerBaseWithConstantOffset( 2131 CI->getOperand(I), Offset, M.getDataLayout())); 2132 if (!Base) 2133 report_fatal_error( 2134 "Expected branch funnel operand to be global value"); 2135 2136 GlobalTypeMember *GTM = GlobalTypeMembers[Base]; 2137 Targets.push_back(GTM); 2138 GlobalClassesTy::member_iterator NewSet = 2139 GlobalClasses.findLeader(GlobalClasses.insert(GTM)); 2140 if (I == 1) 2141 CurSet = NewSet; 2142 else 2143 CurSet = GlobalClasses.unionSets(CurSet, NewSet); 2144 } 2145 2146 GlobalClasses.unionSets( 2147 CurSet, GlobalClasses.findLeader( 2148 GlobalClasses.insert(ICallBranchFunnel::create( 2149 Alloc, CI, Targets, ++CurUniqueId)))); 2150 } 2151 } 2152 2153 if (ExportSummary) { 2154 DenseMap<GlobalValue::GUID, TinyPtrVector<Metadata *>> MetadataByGUID; 2155 for (auto &P : TypeIdInfo) { 2156 if (auto *TypeId = dyn_cast<MDString>(P.first)) 2157 MetadataByGUID[GlobalValue::getGUID(TypeId->getString())].push_back( 2158 TypeId); 2159 } 2160 2161 for (auto &P : *ExportSummary) { 2162 for (auto &S : P.second.SummaryList) { 2163 if (!ExportSummary->isGlobalValueLive(S.get())) 2164 continue; 2165 if (auto *FS = dyn_cast<FunctionSummary>(S->getBaseObject())) 2166 for (GlobalValue::GUID G : FS->type_tests()) 2167 for (Metadata *MD : MetadataByGUID[G]) 2168 AddTypeIdUse(MD).IsExported = true; 2169 } 2170 } 2171 } 2172 2173 if (GlobalClasses.empty()) 2174 return false; 2175 2176 // Build a list of disjoint sets ordered by their maximum global index for 2177 // determinism. 2178 std::vector<std::pair<GlobalClassesTy::iterator, unsigned>> Sets; 2179 for (GlobalClassesTy::iterator I = GlobalClasses.begin(), 2180 E = GlobalClasses.end(); 2181 I != E; ++I) { 2182 if (!I->isLeader()) 2183 continue; 2184 ++NumTypeIdDisjointSets; 2185 2186 unsigned MaxUniqueId = 0; 2187 for (GlobalClassesTy::member_iterator MI = GlobalClasses.member_begin(I); 2188 MI != GlobalClasses.member_end(); ++MI) { 2189 if (auto *MD = MI->dyn_cast<Metadata *>()) 2190 MaxUniqueId = std::max(MaxUniqueId, TypeIdInfo[MD].UniqueId); 2191 else if (auto *BF = MI->dyn_cast<ICallBranchFunnel *>()) 2192 MaxUniqueId = std::max(MaxUniqueId, BF->UniqueId); 2193 } 2194 Sets.emplace_back(I, MaxUniqueId); 2195 } 2196 llvm::sort(Sets, llvm::less_second()); 2197 2198 // For each disjoint set we found... 2199 for (const auto &S : Sets) { 2200 // Build the list of type identifiers in this disjoint set. 2201 std::vector<Metadata *> TypeIds; 2202 std::vector<GlobalTypeMember *> Globals; 2203 std::vector<ICallBranchFunnel *> ICallBranchFunnels; 2204 for (GlobalClassesTy::member_iterator MI = 2205 GlobalClasses.member_begin(S.first); 2206 MI != GlobalClasses.member_end(); ++MI) { 2207 if (MI->is<Metadata *>()) 2208 TypeIds.push_back(MI->get<Metadata *>()); 2209 else if (MI->is<GlobalTypeMember *>()) 2210 Globals.push_back(MI->get<GlobalTypeMember *>()); 2211 else 2212 ICallBranchFunnels.push_back(MI->get<ICallBranchFunnel *>()); 2213 } 2214 2215 // Order type identifiers by unique ID for determinism. This ordering is 2216 // stable as there is a one-to-one mapping between metadata and unique IDs. 2217 llvm::sort(TypeIds, [&](Metadata *M1, Metadata *M2) { 2218 return TypeIdInfo[M1].UniqueId < TypeIdInfo[M2].UniqueId; 2219 }); 2220 2221 // Same for the branch funnels. 2222 llvm::sort(ICallBranchFunnels, 2223 [&](ICallBranchFunnel *F1, ICallBranchFunnel *F2) { 2224 return F1->UniqueId < F2->UniqueId; 2225 }); 2226 2227 // Build bitsets for this disjoint set. 2228 buildBitSetsFromDisjointSet(TypeIds, Globals, ICallBranchFunnels); 2229 } 2230 2231 allocateByteArrays(); 2232 2233 // Parse alias data to replace stand-in function declarations for aliases 2234 // with an alias to the intended target. 2235 if (ExportSummary) { 2236 if (NamedMDNode *AliasesMD = M.getNamedMetadata("aliases")) { 2237 for (auto *AliasMD : AliasesMD->operands()) { 2238 assert(AliasMD->getNumOperands() >= 4); 2239 StringRef AliasName = 2240 cast<MDString>(AliasMD->getOperand(0))->getString(); 2241 StringRef Aliasee = cast<MDString>(AliasMD->getOperand(1))->getString(); 2242 2243 if (!ExportedFunctions.count(Aliasee) || 2244 ExportedFunctions[Aliasee].Linkage != CFL_Definition || 2245 !M.getNamedAlias(Aliasee)) 2246 continue; 2247 2248 GlobalValue::VisibilityTypes Visibility = 2249 static_cast<GlobalValue::VisibilityTypes>( 2250 cast<ConstantAsMetadata>(AliasMD->getOperand(2)) 2251 ->getValue() 2252 ->getUniqueInteger() 2253 .getZExtValue()); 2254 bool Weak = 2255 static_cast<bool>(cast<ConstantAsMetadata>(AliasMD->getOperand(3)) 2256 ->getValue() 2257 ->getUniqueInteger() 2258 .getZExtValue()); 2259 2260 auto *Alias = GlobalAlias::create("", M.getNamedAlias(Aliasee)); 2261 Alias->setVisibility(Visibility); 2262 if (Weak) 2263 Alias->setLinkage(GlobalValue::WeakAnyLinkage); 2264 2265 if (auto *F = M.getFunction(AliasName)) { 2266 Alias->takeName(F); 2267 F->replaceAllUsesWith(Alias); 2268 F->eraseFromParent(); 2269 } else { 2270 Alias->setName(AliasName); 2271 } 2272 } 2273 } 2274 } 2275 2276 // Emit .symver directives for exported functions, if they exist. 2277 if (ExportSummary) { 2278 if (NamedMDNode *SymversMD = M.getNamedMetadata("symvers")) { 2279 for (auto *Symver : SymversMD->operands()) { 2280 assert(Symver->getNumOperands() >= 2); 2281 StringRef SymbolName = 2282 cast<MDString>(Symver->getOperand(0))->getString(); 2283 StringRef Alias = cast<MDString>(Symver->getOperand(1))->getString(); 2284 2285 if (!ExportedFunctions.count(SymbolName)) 2286 continue; 2287 2288 M.appendModuleInlineAsm( 2289 (llvm::Twine(".symver ") + SymbolName + ", " + Alias).str()); 2290 } 2291 } 2292 } 2293 2294 return true; 2295 } 2296 2297 PreservedAnalyses LowerTypeTestsPass::run(Module &M, 2298 ModuleAnalysisManager &AM) { 2299 bool Changed; 2300 if (UseCommandLine) 2301 Changed = LowerTypeTestsModule::runForTesting(M); 2302 else 2303 Changed = 2304 LowerTypeTestsModule(M, ExportSummary, ImportSummary, DropTypeTests) 2305 .lower(); 2306 if (!Changed) 2307 return PreservedAnalyses::all(); 2308 return PreservedAnalyses::none(); 2309 } 2310