1 //===- ModuleSummaryAnalysis.cpp - Module summary index builder -----------===// 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 builds a ModuleSummaryIndex object for the module, to be written 10 // to bitcode or LLVM assembly. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/Analysis/ModuleSummaryAnalysis.h" 15 #include "llvm/ADT/ArrayRef.h" 16 #include "llvm/ADT/DenseSet.h" 17 #include "llvm/ADT/MapVector.h" 18 #include "llvm/ADT/STLExtras.h" 19 #include "llvm/ADT/SetVector.h" 20 #include "llvm/ADT/SmallPtrSet.h" 21 #include "llvm/ADT/SmallVector.h" 22 #include "llvm/ADT/StringRef.h" 23 #include "llvm/Analysis/BlockFrequencyInfo.h" 24 #include "llvm/Analysis/BranchProbabilityInfo.h" 25 #include "llvm/Analysis/IndirectCallPromotionAnalysis.h" 26 #include "llvm/Analysis/LoopInfo.h" 27 #include "llvm/Analysis/ProfileSummaryInfo.h" 28 #include "llvm/Analysis/StackSafetyAnalysis.h" 29 #include "llvm/Analysis/TypeMetadataUtils.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/Dominators.h" 35 #include "llvm/IR/Function.h" 36 #include "llvm/IR/GlobalAlias.h" 37 #include "llvm/IR/GlobalValue.h" 38 #include "llvm/IR/GlobalVariable.h" 39 #include "llvm/IR/Instructions.h" 40 #include "llvm/IR/IntrinsicInst.h" 41 #include "llvm/IR/Intrinsics.h" 42 #include "llvm/IR/Metadata.h" 43 #include "llvm/IR/Module.h" 44 #include "llvm/IR/ModuleSummaryIndex.h" 45 #include "llvm/IR/Use.h" 46 #include "llvm/IR/User.h" 47 #include "llvm/InitializePasses.h" 48 #include "llvm/Object/ModuleSymbolTable.h" 49 #include "llvm/Object/SymbolicFile.h" 50 #include "llvm/Pass.h" 51 #include "llvm/Support/Casting.h" 52 #include "llvm/Support/CommandLine.h" 53 #include "llvm/Support/FileSystem.h" 54 #include <algorithm> 55 #include <cassert> 56 #include <cstdint> 57 #include <vector> 58 59 using namespace llvm; 60 61 #define DEBUG_TYPE "module-summary-analysis" 62 63 // Option to force edges cold which will block importing when the 64 // -import-cold-multiplier is set to 0. Useful for debugging. 65 FunctionSummary::ForceSummaryHotnessType ForceSummaryEdgesCold = 66 FunctionSummary::FSHT_None; 67 cl::opt<FunctionSummary::ForceSummaryHotnessType, true> FSEC( 68 "force-summary-edges-cold", cl::Hidden, cl::location(ForceSummaryEdgesCold), 69 cl::desc("Force all edges in the function summary to cold"), 70 cl::values(clEnumValN(FunctionSummary::FSHT_None, "none", "None."), 71 clEnumValN(FunctionSummary::FSHT_AllNonCritical, 72 "all-non-critical", "All non-critical edges."), 73 clEnumValN(FunctionSummary::FSHT_All, "all", "All edges."))); 74 75 cl::opt<std::string> ModuleSummaryDotFile( 76 "module-summary-dot-file", cl::init(""), cl::Hidden, 77 cl::value_desc("filename"), 78 cl::desc("File to emit dot graph of new summary into.")); 79 80 // Walk through the operands of a given User via worklist iteration and populate 81 // the set of GlobalValue references encountered. Invoked either on an 82 // Instruction or a GlobalVariable (which walks its initializer). 83 // Return true if any of the operands contains blockaddress. This is important 84 // to know when computing summary for global var, because if global variable 85 // references basic block address we can't import it separately from function 86 // containing that basic block. For simplicity we currently don't import such 87 // global vars at all. When importing function we aren't interested if any 88 // instruction in it takes an address of any basic block, because instruction 89 // can only take an address of basic block located in the same function. 90 static bool findRefEdges(ModuleSummaryIndex &Index, const User *CurUser, 91 SetVector<ValueInfo> &RefEdges, 92 SmallPtrSet<const User *, 8> &Visited) { 93 bool HasBlockAddress = false; 94 SmallVector<const User *, 32> Worklist; 95 if (Visited.insert(CurUser).second) 96 Worklist.push_back(CurUser); 97 98 while (!Worklist.empty()) { 99 const User *U = Worklist.pop_back_val(); 100 const auto *CB = dyn_cast<CallBase>(U); 101 102 for (const auto &OI : U->operands()) { 103 const User *Operand = dyn_cast<User>(OI); 104 if (!Operand) 105 continue; 106 if (isa<BlockAddress>(Operand)) { 107 HasBlockAddress = true; 108 continue; 109 } 110 if (auto *GV = dyn_cast<GlobalValue>(Operand)) { 111 // We have a reference to a global value. This should be added to 112 // the reference set unless it is a callee. Callees are handled 113 // specially by WriteFunction and are added to a separate list. 114 if (!(CB && CB->isCallee(&OI))) 115 RefEdges.insert(Index.getOrInsertValueInfo(GV)); 116 continue; 117 } 118 if (Visited.insert(Operand).second) 119 Worklist.push_back(Operand); 120 } 121 } 122 return HasBlockAddress; 123 } 124 125 static CalleeInfo::HotnessType getHotness(uint64_t ProfileCount, 126 ProfileSummaryInfo *PSI) { 127 if (!PSI) 128 return CalleeInfo::HotnessType::Unknown; 129 if (PSI->isHotCount(ProfileCount)) 130 return CalleeInfo::HotnessType::Hot; 131 if (PSI->isColdCount(ProfileCount)) 132 return CalleeInfo::HotnessType::Cold; 133 return CalleeInfo::HotnessType::None; 134 } 135 136 static bool isNonRenamableLocal(const GlobalValue &GV) { 137 return GV.hasSection() && GV.hasLocalLinkage(); 138 } 139 140 /// Determine whether this call has all constant integer arguments (excluding 141 /// "this") and summarize it to VCalls or ConstVCalls as appropriate. 142 static void addVCallToSet(DevirtCallSite Call, GlobalValue::GUID Guid, 143 SetVector<FunctionSummary::VFuncId> &VCalls, 144 SetVector<FunctionSummary::ConstVCall> &ConstVCalls) { 145 std::vector<uint64_t> Args; 146 // Start from the second argument to skip the "this" pointer. 147 for (auto &Arg : drop_begin(Call.CB.args())) { 148 auto *CI = dyn_cast<ConstantInt>(Arg); 149 if (!CI || CI->getBitWidth() > 64) { 150 VCalls.insert({Guid, Call.Offset}); 151 return; 152 } 153 Args.push_back(CI->getZExtValue()); 154 } 155 ConstVCalls.insert({{Guid, Call.Offset}, std::move(Args)}); 156 } 157 158 /// If this intrinsic call requires that we add information to the function 159 /// summary, do so via the non-constant reference arguments. 160 static void addIntrinsicToSummary( 161 const CallInst *CI, SetVector<GlobalValue::GUID> &TypeTests, 162 SetVector<FunctionSummary::VFuncId> &TypeTestAssumeVCalls, 163 SetVector<FunctionSummary::VFuncId> &TypeCheckedLoadVCalls, 164 SetVector<FunctionSummary::ConstVCall> &TypeTestAssumeConstVCalls, 165 SetVector<FunctionSummary::ConstVCall> &TypeCheckedLoadConstVCalls, 166 DominatorTree &DT) { 167 switch (CI->getCalledFunction()->getIntrinsicID()) { 168 case Intrinsic::type_test: { 169 auto *TypeMDVal = cast<MetadataAsValue>(CI->getArgOperand(1)); 170 auto *TypeId = dyn_cast<MDString>(TypeMDVal->getMetadata()); 171 if (!TypeId) 172 break; 173 GlobalValue::GUID Guid = GlobalValue::getGUID(TypeId->getString()); 174 175 // Produce a summary from type.test intrinsics. We only summarize type.test 176 // intrinsics that are used other than by an llvm.assume intrinsic. 177 // Intrinsics that are assumed are relevant only to the devirtualization 178 // pass, not the type test lowering pass. 179 bool HasNonAssumeUses = llvm::any_of(CI->uses(), [](const Use &CIU) { 180 return !isa<AssumeInst>(CIU.getUser()); 181 }); 182 if (HasNonAssumeUses) 183 TypeTests.insert(Guid); 184 185 SmallVector<DevirtCallSite, 4> DevirtCalls; 186 SmallVector<CallInst *, 4> Assumes; 187 findDevirtualizableCallsForTypeTest(DevirtCalls, Assumes, CI, DT); 188 for (auto &Call : DevirtCalls) 189 addVCallToSet(Call, Guid, TypeTestAssumeVCalls, 190 TypeTestAssumeConstVCalls); 191 192 break; 193 } 194 195 case Intrinsic::type_checked_load: { 196 auto *TypeMDVal = cast<MetadataAsValue>(CI->getArgOperand(2)); 197 auto *TypeId = dyn_cast<MDString>(TypeMDVal->getMetadata()); 198 if (!TypeId) 199 break; 200 GlobalValue::GUID Guid = GlobalValue::getGUID(TypeId->getString()); 201 202 SmallVector<DevirtCallSite, 4> DevirtCalls; 203 SmallVector<Instruction *, 4> LoadedPtrs; 204 SmallVector<Instruction *, 4> Preds; 205 bool HasNonCallUses = false; 206 findDevirtualizableCallsForTypeCheckedLoad(DevirtCalls, LoadedPtrs, Preds, 207 HasNonCallUses, CI, DT); 208 // Any non-call uses of the result of llvm.type.checked.load will 209 // prevent us from optimizing away the llvm.type.test. 210 if (HasNonCallUses) 211 TypeTests.insert(Guid); 212 for (auto &Call : DevirtCalls) 213 addVCallToSet(Call, Guid, TypeCheckedLoadVCalls, 214 TypeCheckedLoadConstVCalls); 215 216 break; 217 } 218 default: 219 break; 220 } 221 } 222 223 static bool isNonVolatileLoad(const Instruction *I) { 224 if (const auto *LI = dyn_cast<LoadInst>(I)) 225 return !LI->isVolatile(); 226 227 return false; 228 } 229 230 static bool isNonVolatileStore(const Instruction *I) { 231 if (const auto *SI = dyn_cast<StoreInst>(I)) 232 return !SI->isVolatile(); 233 234 return false; 235 } 236 237 static void computeFunctionSummary( 238 ModuleSummaryIndex &Index, const Module &M, const Function &F, 239 BlockFrequencyInfo *BFI, ProfileSummaryInfo *PSI, DominatorTree &DT, 240 bool HasLocalsInUsedOrAsm, DenseSet<GlobalValue::GUID> &CantBePromoted, 241 bool IsThinLTO, 242 std::function<const StackSafetyInfo *(const Function &F)> GetSSICallback) { 243 // Summary not currently supported for anonymous functions, they should 244 // have been named. 245 assert(F.hasName()); 246 247 unsigned NumInsts = 0; 248 // Map from callee ValueId to profile count. Used to accumulate profile 249 // counts for all static calls to a given callee. 250 MapVector<ValueInfo, CalleeInfo> CallGraphEdges; 251 SetVector<ValueInfo> RefEdges, LoadRefEdges, StoreRefEdges; 252 SetVector<GlobalValue::GUID> TypeTests; 253 SetVector<FunctionSummary::VFuncId> TypeTestAssumeVCalls, 254 TypeCheckedLoadVCalls; 255 SetVector<FunctionSummary::ConstVCall> TypeTestAssumeConstVCalls, 256 TypeCheckedLoadConstVCalls; 257 ICallPromotionAnalysis ICallAnalysis; 258 SmallPtrSet<const User *, 8> Visited; 259 260 // Add personality function, prefix data and prologue data to function's ref 261 // list. 262 findRefEdges(Index, &F, RefEdges, Visited); 263 std::vector<const Instruction *> NonVolatileLoads; 264 std::vector<const Instruction *> NonVolatileStores; 265 266 bool HasInlineAsmMaybeReferencingInternal = false; 267 bool HasIndirBranchToBlockAddress = false; 268 for (const BasicBlock &BB : F) { 269 // We don't allow inlining of function with indirect branch to blockaddress. 270 // If the blockaddress escapes the function, e.g., via a global variable, 271 // inlining may lead to an invalid cross-function reference. So we shouldn't 272 // import such function either. 273 if (BB.hasAddressTaken()) { 274 for (User *U : BlockAddress::get(const_cast<BasicBlock *>(&BB))->users()) 275 if (!isa<CallBrInst>(*U)) { 276 HasIndirBranchToBlockAddress = true; 277 break; 278 } 279 } 280 281 for (const Instruction &I : BB) { 282 if (isa<DbgInfoIntrinsic>(I)) 283 continue; 284 ++NumInsts; 285 // Regular LTO module doesn't participate in ThinLTO import, 286 // so no reference from it can be read/writeonly, since this 287 // would require importing variable as local copy 288 if (IsThinLTO) { 289 if (isNonVolatileLoad(&I)) { 290 // Postpone processing of non-volatile load instructions 291 // See comments below 292 Visited.insert(&I); 293 NonVolatileLoads.push_back(&I); 294 continue; 295 } else if (isNonVolatileStore(&I)) { 296 Visited.insert(&I); 297 NonVolatileStores.push_back(&I); 298 // All references from second operand of store (destination address) 299 // can be considered write-only if they're not referenced by any 300 // non-store instruction. References from first operand of store 301 // (stored value) can't be treated either as read- or as write-only 302 // so we add them to RefEdges as we do with all other instructions 303 // except non-volatile load. 304 Value *Stored = I.getOperand(0); 305 if (auto *GV = dyn_cast<GlobalValue>(Stored)) 306 // findRefEdges will try to examine GV operands, so instead 307 // of calling it we should add GV to RefEdges directly. 308 RefEdges.insert(Index.getOrInsertValueInfo(GV)); 309 else if (auto *U = dyn_cast<User>(Stored)) 310 findRefEdges(Index, U, RefEdges, Visited); 311 continue; 312 } 313 } 314 findRefEdges(Index, &I, RefEdges, Visited); 315 const auto *CB = dyn_cast<CallBase>(&I); 316 if (!CB) 317 continue; 318 319 const auto *CI = dyn_cast<CallInst>(&I); 320 // Since we don't know exactly which local values are referenced in inline 321 // assembly, conservatively mark the function as possibly referencing 322 // a local value from inline assembly to ensure we don't export a 323 // reference (which would require renaming and promotion of the 324 // referenced value). 325 if (HasLocalsInUsedOrAsm && CI && CI->isInlineAsm()) 326 HasInlineAsmMaybeReferencingInternal = true; 327 328 auto *CalledValue = CB->getCalledOperand(); 329 auto *CalledFunction = CB->getCalledFunction(); 330 if (CalledValue && !CalledFunction) { 331 CalledValue = CalledValue->stripPointerCasts(); 332 // Stripping pointer casts can reveal a called function. 333 CalledFunction = dyn_cast<Function>(CalledValue); 334 } 335 // Check if this is an alias to a function. If so, get the 336 // called aliasee for the checks below. 337 if (auto *GA = dyn_cast<GlobalAlias>(CalledValue)) { 338 assert(!CalledFunction && "Expected null called function in callsite for alias"); 339 CalledFunction = dyn_cast<Function>(GA->getBaseObject()); 340 } 341 // Check if this is a direct call to a known function or a known 342 // intrinsic, or an indirect call with profile data. 343 if (CalledFunction) { 344 if (CI && CalledFunction->isIntrinsic()) { 345 addIntrinsicToSummary( 346 CI, TypeTests, TypeTestAssumeVCalls, TypeCheckedLoadVCalls, 347 TypeTestAssumeConstVCalls, TypeCheckedLoadConstVCalls, DT); 348 continue; 349 } 350 // We should have named any anonymous globals 351 assert(CalledFunction->hasName()); 352 auto ScaledCount = PSI->getProfileCount(*CB, BFI); 353 auto Hotness = ScaledCount ? getHotness(ScaledCount.getValue(), PSI) 354 : CalleeInfo::HotnessType::Unknown; 355 if (ForceSummaryEdgesCold != FunctionSummary::FSHT_None) 356 Hotness = CalleeInfo::HotnessType::Cold; 357 358 // Use the original CalledValue, in case it was an alias. We want 359 // to record the call edge to the alias in that case. Eventually 360 // an alias summary will be created to associate the alias and 361 // aliasee. 362 auto &ValueInfo = CallGraphEdges[Index.getOrInsertValueInfo( 363 cast<GlobalValue>(CalledValue))]; 364 ValueInfo.updateHotness(Hotness); 365 // Add the relative block frequency to CalleeInfo if there is no profile 366 // information. 367 if (BFI != nullptr && Hotness == CalleeInfo::HotnessType::Unknown) { 368 uint64_t BBFreq = BFI->getBlockFreq(&BB).getFrequency(); 369 uint64_t EntryFreq = BFI->getEntryFreq(); 370 ValueInfo.updateRelBlockFreq(BBFreq, EntryFreq); 371 } 372 } else { 373 // Skip inline assembly calls. 374 if (CI && CI->isInlineAsm()) 375 continue; 376 // Skip direct calls. 377 if (!CalledValue || isa<Constant>(CalledValue)) 378 continue; 379 380 // Check if the instruction has a callees metadata. If so, add callees 381 // to CallGraphEdges to reflect the references from the metadata, and 382 // to enable importing for subsequent indirect call promotion and 383 // inlining. 384 if (auto *MD = I.getMetadata(LLVMContext::MD_callees)) { 385 for (auto &Op : MD->operands()) { 386 Function *Callee = mdconst::extract_or_null<Function>(Op); 387 if (Callee) 388 CallGraphEdges[Index.getOrInsertValueInfo(Callee)]; 389 } 390 } 391 392 uint32_t NumVals, NumCandidates; 393 uint64_t TotalCount; 394 auto CandidateProfileData = 395 ICallAnalysis.getPromotionCandidatesForInstruction( 396 &I, NumVals, TotalCount, NumCandidates); 397 for (auto &Candidate : CandidateProfileData) 398 CallGraphEdges[Index.getOrInsertValueInfo(Candidate.Value)] 399 .updateHotness(getHotness(Candidate.Count, PSI)); 400 } 401 } 402 } 403 Index.addBlockCount(F.size()); 404 405 std::vector<ValueInfo> Refs; 406 if (IsThinLTO) { 407 auto AddRefEdges = [&](const std::vector<const Instruction *> &Instrs, 408 SetVector<ValueInfo> &Edges, 409 SmallPtrSet<const User *, 8> &Cache) { 410 for (const auto *I : Instrs) { 411 Cache.erase(I); 412 findRefEdges(Index, I, Edges, Cache); 413 } 414 }; 415 416 // By now we processed all instructions in a function, except 417 // non-volatile loads and non-volatile value stores. Let's find 418 // ref edges for both of instruction sets 419 AddRefEdges(NonVolatileLoads, LoadRefEdges, Visited); 420 // We can add some values to the Visited set when processing load 421 // instructions which are also used by stores in NonVolatileStores. 422 // For example this can happen if we have following code: 423 // 424 // store %Derived* @foo, %Derived** bitcast (%Base** @bar to %Derived**) 425 // %42 = load %Derived*, %Derived** bitcast (%Base** @bar to %Derived**) 426 // 427 // After processing loads we'll add bitcast to the Visited set, and if 428 // we use the same set while processing stores, we'll never see store 429 // to @bar and @bar will be mistakenly treated as readonly. 430 SmallPtrSet<const llvm::User *, 8> StoreCache; 431 AddRefEdges(NonVolatileStores, StoreRefEdges, StoreCache); 432 433 // If both load and store instruction reference the same variable 434 // we won't be able to optimize it. Add all such reference edges 435 // to RefEdges set. 436 for (auto &VI : StoreRefEdges) 437 if (LoadRefEdges.remove(VI)) 438 RefEdges.insert(VI); 439 440 unsigned RefCnt = RefEdges.size(); 441 // All new reference edges inserted in two loops below are either 442 // read or write only. They will be grouped in the end of RefEdges 443 // vector, so we can use a single integer value to identify them. 444 for (auto &VI : LoadRefEdges) 445 RefEdges.insert(VI); 446 447 unsigned FirstWORef = RefEdges.size(); 448 for (auto &VI : StoreRefEdges) 449 RefEdges.insert(VI); 450 451 Refs = RefEdges.takeVector(); 452 for (; RefCnt < FirstWORef; ++RefCnt) 453 Refs[RefCnt].setReadOnly(); 454 455 for (; RefCnt < Refs.size(); ++RefCnt) 456 Refs[RefCnt].setWriteOnly(); 457 } else { 458 Refs = RefEdges.takeVector(); 459 } 460 // Explicit add hot edges to enforce importing for designated GUIDs for 461 // sample PGO, to enable the same inlines as the profiled optimized binary. 462 for (auto &I : F.getImportGUIDs()) 463 CallGraphEdges[Index.getOrInsertValueInfo(I)].updateHotness( 464 ForceSummaryEdgesCold == FunctionSummary::FSHT_All 465 ? CalleeInfo::HotnessType::Cold 466 : CalleeInfo::HotnessType::Critical); 467 468 bool NonRenamableLocal = isNonRenamableLocal(F); 469 bool NotEligibleForImport = NonRenamableLocal || 470 HasInlineAsmMaybeReferencingInternal || 471 HasIndirBranchToBlockAddress; 472 GlobalValueSummary::GVFlags Flags( 473 F.getLinkage(), F.getVisibility(), NotEligibleForImport, 474 /* Live = */ false, F.isDSOLocal(), 475 F.hasLinkOnceODRLinkage() && F.hasGlobalUnnamedAddr()); 476 FunctionSummary::FFlags FunFlags{ 477 F.hasFnAttribute(Attribute::ReadNone), 478 F.hasFnAttribute(Attribute::ReadOnly), 479 F.hasFnAttribute(Attribute::NoRecurse), F.returnDoesNotAlias(), 480 // FIXME: refactor this to use the same code that inliner is using. 481 // Don't try to import functions with noinline attribute. 482 F.getAttributes().hasFnAttribute(Attribute::NoInline), 483 F.hasFnAttribute(Attribute::AlwaysInline)}; 484 std::vector<FunctionSummary::ParamAccess> ParamAccesses; 485 if (auto *SSI = GetSSICallback(F)) 486 ParamAccesses = SSI->getParamAccesses(Index); 487 auto FuncSummary = std::make_unique<FunctionSummary>( 488 Flags, NumInsts, FunFlags, /*EntryCount=*/0, std::move(Refs), 489 CallGraphEdges.takeVector(), TypeTests.takeVector(), 490 TypeTestAssumeVCalls.takeVector(), TypeCheckedLoadVCalls.takeVector(), 491 TypeTestAssumeConstVCalls.takeVector(), 492 TypeCheckedLoadConstVCalls.takeVector(), std::move(ParamAccesses)); 493 if (NonRenamableLocal) 494 CantBePromoted.insert(F.getGUID()); 495 Index.addGlobalValueSummary(F, std::move(FuncSummary)); 496 } 497 498 /// Find function pointers referenced within the given vtable initializer 499 /// (or subset of an initializer) \p I. The starting offset of \p I within 500 /// the vtable initializer is \p StartingOffset. Any discovered function 501 /// pointers are added to \p VTableFuncs along with their cumulative offset 502 /// within the initializer. 503 static void findFuncPointers(const Constant *I, uint64_t StartingOffset, 504 const Module &M, ModuleSummaryIndex &Index, 505 VTableFuncList &VTableFuncs) { 506 // First check if this is a function pointer. 507 if (I->getType()->isPointerTy()) { 508 auto Fn = dyn_cast<Function>(I->stripPointerCasts()); 509 // We can disregard __cxa_pure_virtual as a possible call target, as 510 // calls to pure virtuals are UB. 511 if (Fn && Fn->getName() != "__cxa_pure_virtual") 512 VTableFuncs.push_back({Index.getOrInsertValueInfo(Fn), StartingOffset}); 513 return; 514 } 515 516 // Walk through the elements in the constant struct or array and recursively 517 // look for virtual function pointers. 518 const DataLayout &DL = M.getDataLayout(); 519 if (auto *C = dyn_cast<ConstantStruct>(I)) { 520 StructType *STy = dyn_cast<StructType>(C->getType()); 521 assert(STy); 522 const StructLayout *SL = DL.getStructLayout(C->getType()); 523 524 for (auto EI : llvm::enumerate(STy->elements())) { 525 auto Offset = SL->getElementOffset(EI.index()); 526 unsigned Op = SL->getElementContainingOffset(Offset); 527 findFuncPointers(cast<Constant>(I->getOperand(Op)), 528 StartingOffset + Offset, M, Index, VTableFuncs); 529 } 530 } else if (auto *C = dyn_cast<ConstantArray>(I)) { 531 ArrayType *ATy = C->getType(); 532 Type *EltTy = ATy->getElementType(); 533 uint64_t EltSize = DL.getTypeAllocSize(EltTy); 534 for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) { 535 findFuncPointers(cast<Constant>(I->getOperand(i)), 536 StartingOffset + i * EltSize, M, Index, VTableFuncs); 537 } 538 } 539 } 540 541 // Identify the function pointers referenced by vtable definition \p V. 542 static void computeVTableFuncs(ModuleSummaryIndex &Index, 543 const GlobalVariable &V, const Module &M, 544 VTableFuncList &VTableFuncs) { 545 if (!V.isConstant()) 546 return; 547 548 findFuncPointers(V.getInitializer(), /*StartingOffset=*/0, M, Index, 549 VTableFuncs); 550 551 #ifndef NDEBUG 552 // Validate that the VTableFuncs list is ordered by offset. 553 uint64_t PrevOffset = 0; 554 for (auto &P : VTableFuncs) { 555 // The findVFuncPointers traversal should have encountered the 556 // functions in offset order. We need to use ">=" since PrevOffset 557 // starts at 0. 558 assert(P.VTableOffset >= PrevOffset); 559 PrevOffset = P.VTableOffset; 560 } 561 #endif 562 } 563 564 /// Record vtable definition \p V for each type metadata it references. 565 static void 566 recordTypeIdCompatibleVtableReferences(ModuleSummaryIndex &Index, 567 const GlobalVariable &V, 568 SmallVectorImpl<MDNode *> &Types) { 569 for (MDNode *Type : Types) { 570 auto TypeID = Type->getOperand(1).get(); 571 572 uint64_t Offset = 573 cast<ConstantInt>( 574 cast<ConstantAsMetadata>(Type->getOperand(0))->getValue()) 575 ->getZExtValue(); 576 577 if (auto *TypeId = dyn_cast<MDString>(TypeID)) 578 Index.getOrInsertTypeIdCompatibleVtableSummary(TypeId->getString()) 579 .push_back({Offset, Index.getOrInsertValueInfo(&V)}); 580 } 581 } 582 583 static void computeVariableSummary(ModuleSummaryIndex &Index, 584 const GlobalVariable &V, 585 DenseSet<GlobalValue::GUID> &CantBePromoted, 586 const Module &M, 587 SmallVectorImpl<MDNode *> &Types) { 588 SetVector<ValueInfo> RefEdges; 589 SmallPtrSet<const User *, 8> Visited; 590 bool HasBlockAddress = findRefEdges(Index, &V, RefEdges, Visited); 591 bool NonRenamableLocal = isNonRenamableLocal(V); 592 GlobalValueSummary::GVFlags Flags( 593 V.getLinkage(), V.getVisibility(), NonRenamableLocal, 594 /* Live = */ false, V.isDSOLocal(), 595 V.hasLinkOnceODRLinkage() && V.hasGlobalUnnamedAddr()); 596 597 VTableFuncList VTableFuncs; 598 // If splitting is not enabled, then we compute the summary information 599 // necessary for index-based whole program devirtualization. 600 if (!Index.enableSplitLTOUnit()) { 601 Types.clear(); 602 V.getMetadata(LLVMContext::MD_type, Types); 603 if (!Types.empty()) { 604 // Identify the function pointers referenced by this vtable definition. 605 computeVTableFuncs(Index, V, M, VTableFuncs); 606 607 // Record this vtable definition for each type metadata it references. 608 recordTypeIdCompatibleVtableReferences(Index, V, Types); 609 } 610 } 611 612 // Don't mark variables we won't be able to internalize as read/write-only. 613 bool CanBeInternalized = 614 !V.hasComdat() && !V.hasAppendingLinkage() && !V.isInterposable() && 615 !V.hasAvailableExternallyLinkage() && !V.hasDLLExportStorageClass(); 616 bool Constant = V.isConstant(); 617 GlobalVarSummary::GVarFlags VarFlags(CanBeInternalized, 618 Constant ? false : CanBeInternalized, 619 Constant, V.getVCallVisibility()); 620 auto GVarSummary = std::make_unique<GlobalVarSummary>(Flags, VarFlags, 621 RefEdges.takeVector()); 622 if (NonRenamableLocal) 623 CantBePromoted.insert(V.getGUID()); 624 if (HasBlockAddress) 625 GVarSummary->setNotEligibleToImport(); 626 if (!VTableFuncs.empty()) 627 GVarSummary->setVTableFuncs(VTableFuncs); 628 Index.addGlobalValueSummary(V, std::move(GVarSummary)); 629 } 630 631 static void 632 computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A, 633 DenseSet<GlobalValue::GUID> &CantBePromoted) { 634 bool NonRenamableLocal = isNonRenamableLocal(A); 635 GlobalValueSummary::GVFlags Flags( 636 A.getLinkage(), A.getVisibility(), NonRenamableLocal, 637 /* Live = */ false, A.isDSOLocal(), 638 A.hasLinkOnceODRLinkage() && A.hasGlobalUnnamedAddr()); 639 auto AS = std::make_unique<AliasSummary>(Flags); 640 auto *Aliasee = A.getBaseObject(); 641 auto AliaseeVI = Index.getValueInfo(Aliasee->getGUID()); 642 assert(AliaseeVI && "Alias expects aliasee summary to be available"); 643 assert(AliaseeVI.getSummaryList().size() == 1 && 644 "Expected a single entry per aliasee in per-module index"); 645 AS->setAliasee(AliaseeVI, AliaseeVI.getSummaryList()[0].get()); 646 if (NonRenamableLocal) 647 CantBePromoted.insert(A.getGUID()); 648 Index.addGlobalValueSummary(A, std::move(AS)); 649 } 650 651 // Set LiveRoot flag on entries matching the given value name. 652 static void setLiveRoot(ModuleSummaryIndex &Index, StringRef Name) { 653 if (ValueInfo VI = Index.getValueInfo(GlobalValue::getGUID(Name))) 654 for (auto &Summary : VI.getSummaryList()) 655 Summary->setLive(true); 656 } 657 658 ModuleSummaryIndex llvm::buildModuleSummaryIndex( 659 const Module &M, 660 std::function<BlockFrequencyInfo *(const Function &F)> GetBFICallback, 661 ProfileSummaryInfo *PSI, 662 std::function<const StackSafetyInfo *(const Function &F)> GetSSICallback) { 663 assert(PSI); 664 bool EnableSplitLTOUnit = false; 665 if (auto *MD = mdconst::extract_or_null<ConstantInt>( 666 M.getModuleFlag("EnableSplitLTOUnit"))) 667 EnableSplitLTOUnit = MD->getZExtValue(); 668 ModuleSummaryIndex Index(/*HaveGVs=*/true, EnableSplitLTOUnit); 669 670 // Identify the local values in the llvm.used and llvm.compiler.used sets, 671 // which should not be exported as they would then require renaming and 672 // promotion, but we may have opaque uses e.g. in inline asm. We collect them 673 // here because we use this information to mark functions containing inline 674 // assembly calls as not importable. 675 SmallPtrSet<GlobalValue *, 4> LocalsUsed; 676 SmallVector<GlobalValue *, 4> Used; 677 // First collect those in the llvm.used set. 678 collectUsedGlobalVariables(M, Used, /*CompilerUsed=*/false); 679 // Next collect those in the llvm.compiler.used set. 680 collectUsedGlobalVariables(M, Used, /*CompilerUsed=*/true); 681 DenseSet<GlobalValue::GUID> CantBePromoted; 682 for (auto *V : Used) { 683 if (V->hasLocalLinkage()) { 684 LocalsUsed.insert(V); 685 CantBePromoted.insert(V->getGUID()); 686 } 687 } 688 689 bool HasLocalInlineAsmSymbol = false; 690 if (!M.getModuleInlineAsm().empty()) { 691 // Collect the local values defined by module level asm, and set up 692 // summaries for these symbols so that they can be marked as NoRename, 693 // to prevent export of any use of them in regular IR that would require 694 // renaming within the module level asm. Note we don't need to create a 695 // summary for weak or global defs, as they don't need to be flagged as 696 // NoRename, and defs in module level asm can't be imported anyway. 697 // Also, any values used but not defined within module level asm should 698 // be listed on the llvm.used or llvm.compiler.used global and marked as 699 // referenced from there. 700 ModuleSymbolTable::CollectAsmSymbols( 701 M, [&](StringRef Name, object::BasicSymbolRef::Flags Flags) { 702 // Symbols not marked as Weak or Global are local definitions. 703 if (Flags & (object::BasicSymbolRef::SF_Weak | 704 object::BasicSymbolRef::SF_Global)) 705 return; 706 HasLocalInlineAsmSymbol = true; 707 GlobalValue *GV = M.getNamedValue(Name); 708 if (!GV) 709 return; 710 assert(GV->isDeclaration() && "Def in module asm already has definition"); 711 GlobalValueSummary::GVFlags GVFlags( 712 GlobalValue::InternalLinkage, GlobalValue::DefaultVisibility, 713 /* NotEligibleToImport = */ true, 714 /* Live = */ true, 715 /* Local */ GV->isDSOLocal(), 716 GV->hasLinkOnceODRLinkage() && GV->hasGlobalUnnamedAddr()); 717 CantBePromoted.insert(GV->getGUID()); 718 // Create the appropriate summary type. 719 if (Function *F = dyn_cast<Function>(GV)) { 720 std::unique_ptr<FunctionSummary> Summary = 721 std::make_unique<FunctionSummary>( 722 GVFlags, /*InstCount=*/0, 723 FunctionSummary::FFlags{ 724 F->hasFnAttribute(Attribute::ReadNone), 725 F->hasFnAttribute(Attribute::ReadOnly), 726 F->hasFnAttribute(Attribute::NoRecurse), 727 F->returnDoesNotAlias(), 728 /* NoInline = */ false, 729 F->hasFnAttribute(Attribute::AlwaysInline)}, 730 /*EntryCount=*/0, ArrayRef<ValueInfo>{}, 731 ArrayRef<FunctionSummary::EdgeTy>{}, 732 ArrayRef<GlobalValue::GUID>{}, 733 ArrayRef<FunctionSummary::VFuncId>{}, 734 ArrayRef<FunctionSummary::VFuncId>{}, 735 ArrayRef<FunctionSummary::ConstVCall>{}, 736 ArrayRef<FunctionSummary::ConstVCall>{}, 737 ArrayRef<FunctionSummary::ParamAccess>{}); 738 Index.addGlobalValueSummary(*GV, std::move(Summary)); 739 } else { 740 std::unique_ptr<GlobalVarSummary> Summary = 741 std::make_unique<GlobalVarSummary>( 742 GVFlags, 743 GlobalVarSummary::GVarFlags( 744 false, false, cast<GlobalVariable>(GV)->isConstant(), 745 GlobalObject::VCallVisibilityPublic), 746 ArrayRef<ValueInfo>{}); 747 Index.addGlobalValueSummary(*GV, std::move(Summary)); 748 } 749 }); 750 } 751 752 bool IsThinLTO = true; 753 if (auto *MD = 754 mdconst::extract_or_null<ConstantInt>(M.getModuleFlag("ThinLTO"))) 755 IsThinLTO = MD->getZExtValue(); 756 757 // Compute summaries for all functions defined in module, and save in the 758 // index. 759 for (auto &F : M) { 760 if (F.isDeclaration()) 761 continue; 762 763 DominatorTree DT(const_cast<Function &>(F)); 764 BlockFrequencyInfo *BFI = nullptr; 765 std::unique_ptr<BlockFrequencyInfo> BFIPtr; 766 if (GetBFICallback) 767 BFI = GetBFICallback(F); 768 else if (F.hasProfileData()) { 769 LoopInfo LI{DT}; 770 BranchProbabilityInfo BPI{F, LI}; 771 BFIPtr = std::make_unique<BlockFrequencyInfo>(F, BPI, LI); 772 BFI = BFIPtr.get(); 773 } 774 775 computeFunctionSummary(Index, M, F, BFI, PSI, DT, 776 !LocalsUsed.empty() || HasLocalInlineAsmSymbol, 777 CantBePromoted, IsThinLTO, GetSSICallback); 778 } 779 780 // Compute summaries for all variables defined in module, and save in the 781 // index. 782 SmallVector<MDNode *, 2> Types; 783 for (const GlobalVariable &G : M.globals()) { 784 if (G.isDeclaration()) 785 continue; 786 computeVariableSummary(Index, G, CantBePromoted, M, Types); 787 } 788 789 // Compute summaries for all aliases defined in module, and save in the 790 // index. 791 for (const GlobalAlias &A : M.aliases()) 792 computeAliasSummary(Index, A, CantBePromoted); 793 794 for (auto *V : LocalsUsed) { 795 auto *Summary = Index.getGlobalValueSummary(*V); 796 assert(Summary && "Missing summary for global value"); 797 Summary->setNotEligibleToImport(); 798 } 799 800 // The linker doesn't know about these LLVM produced values, so we need 801 // to flag them as live in the index to ensure index-based dead value 802 // analysis treats them as live roots of the analysis. 803 setLiveRoot(Index, "llvm.used"); 804 setLiveRoot(Index, "llvm.compiler.used"); 805 setLiveRoot(Index, "llvm.global_ctors"); 806 setLiveRoot(Index, "llvm.global_dtors"); 807 setLiveRoot(Index, "llvm.global.annotations"); 808 809 for (auto &GlobalList : Index) { 810 // Ignore entries for references that are undefined in the current module. 811 if (GlobalList.second.SummaryList.empty()) 812 continue; 813 814 assert(GlobalList.second.SummaryList.size() == 1 && 815 "Expected module's index to have one summary per GUID"); 816 auto &Summary = GlobalList.second.SummaryList[0]; 817 if (!IsThinLTO) { 818 Summary->setNotEligibleToImport(); 819 continue; 820 } 821 822 bool AllRefsCanBeExternallyReferenced = 823 llvm::all_of(Summary->refs(), [&](const ValueInfo &VI) { 824 return !CantBePromoted.count(VI.getGUID()); 825 }); 826 if (!AllRefsCanBeExternallyReferenced) { 827 Summary->setNotEligibleToImport(); 828 continue; 829 } 830 831 if (auto *FuncSummary = dyn_cast<FunctionSummary>(Summary.get())) { 832 bool AllCallsCanBeExternallyReferenced = llvm::all_of( 833 FuncSummary->calls(), [&](const FunctionSummary::EdgeTy &Edge) { 834 return !CantBePromoted.count(Edge.first.getGUID()); 835 }); 836 if (!AllCallsCanBeExternallyReferenced) 837 Summary->setNotEligibleToImport(); 838 } 839 } 840 841 if (!ModuleSummaryDotFile.empty()) { 842 std::error_code EC; 843 raw_fd_ostream OSDot(ModuleSummaryDotFile, EC, sys::fs::OpenFlags::OF_None); 844 if (EC) 845 report_fatal_error(Twine("Failed to open dot file ") + 846 ModuleSummaryDotFile + ": " + EC.message() + "\n"); 847 Index.exportToDot(OSDot, {}); 848 } 849 850 return Index; 851 } 852 853 AnalysisKey ModuleSummaryIndexAnalysis::Key; 854 855 ModuleSummaryIndex 856 ModuleSummaryIndexAnalysis::run(Module &M, ModuleAnalysisManager &AM) { 857 ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M); 858 auto &FAM = AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager(); 859 bool NeedSSI = needsParamAccessSummary(M); 860 return buildModuleSummaryIndex( 861 M, 862 [&FAM](const Function &F) { 863 return &FAM.getResult<BlockFrequencyAnalysis>( 864 *const_cast<Function *>(&F)); 865 }, 866 &PSI, 867 [&FAM, NeedSSI](const Function &F) -> const StackSafetyInfo * { 868 return NeedSSI ? &FAM.getResult<StackSafetyAnalysis>( 869 const_cast<Function &>(F)) 870 : nullptr; 871 }); 872 } 873 874 char ModuleSummaryIndexWrapperPass::ID = 0; 875 876 INITIALIZE_PASS_BEGIN(ModuleSummaryIndexWrapperPass, "module-summary-analysis", 877 "Module Summary Analysis", false, true) 878 INITIALIZE_PASS_DEPENDENCY(BlockFrequencyInfoWrapperPass) 879 INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass) 880 INITIALIZE_PASS_DEPENDENCY(StackSafetyInfoWrapperPass) 881 INITIALIZE_PASS_END(ModuleSummaryIndexWrapperPass, "module-summary-analysis", 882 "Module Summary Analysis", false, true) 883 884 ModulePass *llvm::createModuleSummaryIndexWrapperPass() { 885 return new ModuleSummaryIndexWrapperPass(); 886 } 887 888 ModuleSummaryIndexWrapperPass::ModuleSummaryIndexWrapperPass() 889 : ModulePass(ID) { 890 initializeModuleSummaryIndexWrapperPassPass(*PassRegistry::getPassRegistry()); 891 } 892 893 bool ModuleSummaryIndexWrapperPass::runOnModule(Module &M) { 894 auto *PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI(); 895 bool NeedSSI = needsParamAccessSummary(M); 896 Index.emplace(buildModuleSummaryIndex( 897 M, 898 [this](const Function &F) { 899 return &(this->getAnalysis<BlockFrequencyInfoWrapperPass>( 900 *const_cast<Function *>(&F)) 901 .getBFI()); 902 }, 903 PSI, 904 [&](const Function &F) -> const StackSafetyInfo * { 905 return NeedSSI ? &getAnalysis<StackSafetyInfoWrapperPass>( 906 const_cast<Function &>(F)) 907 .getResult() 908 : nullptr; 909 })); 910 return false; 911 } 912 913 bool ModuleSummaryIndexWrapperPass::doFinalization(Module &M) { 914 Index.reset(); 915 return false; 916 } 917 918 void ModuleSummaryIndexWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const { 919 AU.setPreservesAll(); 920 AU.addRequired<BlockFrequencyInfoWrapperPass>(); 921 AU.addRequired<ProfileSummaryInfoWrapperPass>(); 922 AU.addRequired<StackSafetyInfoWrapperPass>(); 923 } 924 925 char ImmutableModuleSummaryIndexWrapperPass::ID = 0; 926 927 ImmutableModuleSummaryIndexWrapperPass::ImmutableModuleSummaryIndexWrapperPass( 928 const ModuleSummaryIndex *Index) 929 : ImmutablePass(ID), Index(Index) { 930 initializeImmutableModuleSummaryIndexWrapperPassPass( 931 *PassRegistry::getPassRegistry()); 932 } 933 934 void ImmutableModuleSummaryIndexWrapperPass::getAnalysisUsage( 935 AnalysisUsage &AU) const { 936 AU.setPreservesAll(); 937 } 938 939 ImmutablePass *llvm::createImmutableModuleSummaryIndexWrapperPass( 940 const ModuleSummaryIndex *Index) { 941 return new ImmutableModuleSummaryIndexWrapperPass(Index); 942 } 943 944 INITIALIZE_PASS(ImmutableModuleSummaryIndexWrapperPass, "module-summary-info", 945 "Module summary info", false, true) 946