lib/Analysis/ModuleSummaryAnalysis.cpp

   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/TypeMetadataUtils.h"
  29 #include "llvm/IR/Attributes.h"
  30 #include "llvm/IR/BasicBlock.h"
  31 #include "llvm/IR/CallSite.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/Object/ModuleSymbolTable.h"
  48 #include "llvm/Object/SymbolicFile.h"
  49 #include "llvm/Pass.h"
  50 #include "llvm/Support/Casting.h"
  51 #include "llvm/Support/CommandLine.h"
  52 #include <algorithm>
  53 #include <cassert>
  54 #include <cstdint>
  55 #include <vector>
  56
  57 using namespace llvm;
  58
  59 #define DEBUG_TYPE "module-summary-analysis"
  60
  61 // Option to force edges cold which will block importing when the
  62 // -import-cold-multiplier is set to 0. Useful for debugging.
  63 FunctionSummary::ForceSummaryHotnessType ForceSummaryEdgesCold =
  64     FunctionSummary::FSHT_None;
  65 cl::opt<FunctionSummary::ForceSummaryHotnessType, true> FSEC(
  66     "force-summary-edges-cold", cl::Hidden, cl::location(ForceSummaryEdgesCold),
  67     cl::desc("Force all edges in the function summary to cold"),
  68     cl::values(clEnumValN(FunctionSummary::FSHT_None, "none", "None."),
  69                clEnumValN(FunctionSummary::FSHT_AllNonCritical,
  70                           "all-non-critical", "All non-critical edges."),
  71                clEnumValN(FunctionSummary::FSHT_All, "all", "All edges.")));
  72
  73 cl::opt<std::string> ModuleSummaryDotFile(
  74     "module-summary-dot-file", cl::init(""), cl::Hidden,
  75     cl::value_desc("filename"),
  76     cl::desc("File to emit dot graph of new summary into."));
  77
  78 // Walk through the operands of a given User via worklist iteration and populate
  79 // the set of GlobalValue references encountered. Invoked either on an
  80 // Instruction or a GlobalVariable (which walks its initializer).
  81 // Return true if any of the operands contains blockaddress. This is important
  82 // to know when computing summary for global var, because if global variable
  83 // references basic block address we can't import it separately from function
  84 // containing that basic block. For simplicity we currently don't import such
  85 // global vars at all. When importing function we aren't interested if any
  86 // instruction in it takes an address of any basic block, because instruction
  87 // can only take an address of basic block located in the same function.
  88 static bool findRefEdges(ModuleSummaryIndex &Index, const User *CurUser,
  89                          SetVector<ValueInfo> &RefEdges,
  90                          SmallPtrSet<const User *, 8> &Visited) {
  91   bool HasBlockAddress = false;
  92   SmallVector<const User *, 32> Worklist;
  93   Worklist.push_back(CurUser);
  94
  95   while (!Worklist.empty()) {
  96     const User *U = Worklist.pop_back_val();
  97
  98     if (!Visited.insert(U).second)
  99       continue;
 100
 101     ImmutableCallSite CS(U);
 102
 103     for (const auto &OI : U->operands()) {
 104       const User *Operand = dyn_cast<User>(OI);
 105       if (!Operand)
 106         continue;
 107       if (isa<BlockAddress>(Operand)) {
 108         HasBlockAddress = true;
 109         continue;
 110       }
 111       if (auto *GV = dyn_cast<GlobalValue>(Operand)) {
 112         // We have a reference to a global value. This should be added to
 113         // the reference set unless it is a callee. Callees are handled
 114         // specially by WriteFunction and are added to a separate list.
 115         if (!(CS && CS.isCallee(&OI)))
 116           RefEdges.insert(Index.getOrInsertValueInfo(GV));
 117         continue;
 118       }
 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 : make_range(Call.CS.arg_begin() + 1, Call.CS.arg_end())) {
 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       auto *AssumeCI = dyn_cast<CallInst>(CIU.getUser());
 181       if (!AssumeCI)
 182         return true;
 183       Function *F = AssumeCI->getCalledFunction();
 184       return !F || F->getIntrinsicID() != Intrinsic::assume;
 185     });
 186     if (HasNonAssumeUses)
 187       TypeTests.insert(Guid);
 188
 189     SmallVector<DevirtCallSite, 4> DevirtCalls;
 190     SmallVector<CallInst *, 4> Assumes;
 191     findDevirtualizableCallsForTypeTest(DevirtCalls, Assumes, CI, DT);
 192     for (auto &Call : DevirtCalls)
 193       addVCallToSet(Call, Guid, TypeTestAssumeVCalls,
 194                     TypeTestAssumeConstVCalls);
 195
 196     break;
 197   }
 198
 199   case Intrinsic::type_checked_load: {
 200     auto *TypeMDVal = cast<MetadataAsValue>(CI->getArgOperand(2));
 201     auto *TypeId = dyn_cast<MDString>(TypeMDVal->getMetadata());
 202     if (!TypeId)
 203       break;
 204     GlobalValue::GUID Guid = GlobalValue::getGUID(TypeId->getString());
 205
 206     SmallVector<DevirtCallSite, 4> DevirtCalls;
 207     SmallVector<Instruction *, 4> LoadedPtrs;
 208     SmallVector<Instruction *, 4> Preds;
 209     bool HasNonCallUses = false;
 210     findDevirtualizableCallsForTypeCheckedLoad(DevirtCalls, LoadedPtrs, Preds,
 211                                                HasNonCallUses, CI, DT);
 212     // Any non-call uses of the result of llvm.type.checked.load will
 213     // prevent us from optimizing away the llvm.type.test.
 214     if (HasNonCallUses)
 215       TypeTests.insert(Guid);
 216     for (auto &Call : DevirtCalls)
 217       addVCallToSet(Call, Guid, TypeCheckedLoadVCalls,
 218                     TypeCheckedLoadConstVCalls);
 219
 220     break;
 221   }
 222   default:
 223     break;
 224   }
 225 }
 226
 227 static bool isNonVolatileLoad(const Instruction *I) {
 228   if (const auto *LI = dyn_cast<LoadInst>(I))
 229     return !LI->isVolatile();
 230
 231   return false;
 232 }
 233
 234 static void computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
 235                                    const Function &F, BlockFrequencyInfo *BFI,
 236                                    ProfileSummaryInfo *PSI, DominatorTree &DT,
 237                                    bool HasLocalsInUsedOrAsm,
 238                                    DenseSet<GlobalValue::GUID> &CantBePromoted,
 239                                    bool IsThinLTO) {
 240   // Summary not currently supported for anonymous functions, they should
 241   // have been named.
 242   assert(F.hasName());
 243
 244   unsigned NumInsts = 0;
 245   // Map from callee ValueId to profile count. Used to accumulate profile
 246   // counts for all static calls to a given callee.
 247   MapVector<ValueInfo, CalleeInfo> CallGraphEdges;
 248   SetVector<ValueInfo> RefEdges;
 249   SetVector<GlobalValue::GUID> TypeTests;
 250   SetVector<FunctionSummary::VFuncId> TypeTestAssumeVCalls,
 251       TypeCheckedLoadVCalls;
 252   SetVector<FunctionSummary::ConstVCall> TypeTestAssumeConstVCalls,
 253       TypeCheckedLoadConstVCalls;
 254   ICallPromotionAnalysis ICallAnalysis;
 255   SmallPtrSet<const User *, 8> Visited;
 256
 257   // Add personality function, prefix data and prologue data to function's ref
 258   // list.
 259   findRefEdges(Index, &F, RefEdges, Visited);
 260   std::vector<const Instruction *> NonVolatileLoads;
 261
 262   bool HasInlineAsmMaybeReferencingInternal = false;
 263   for (const BasicBlock &BB : F)
 264     for (const Instruction &I : BB) {
 265       if (isa<DbgInfoIntrinsic>(I))
 266         continue;
 267       ++NumInsts;
 268       if (isNonVolatileLoad(&I)) {
 269         // Postpone processing of non-volatile load instructions
 270         // See comments below
 271         Visited.insert(&I);
 272         NonVolatileLoads.push_back(&I);
 273         continue;
 274       }
 275       findRefEdges(Index, &I, RefEdges, Visited);
 276       auto CS = ImmutableCallSite(&I);
 277       if (!CS)
 278         continue;
 279
 280       const auto *CI = dyn_cast<CallInst>(&I);
 281       // Since we don't know exactly which local values are referenced in inline
 282       // assembly, conservatively mark the function as possibly referencing
 283       // a local value from inline assembly to ensure we don't export a
 284       // reference (which would require renaming and promotion of the
 285       // referenced value).
 286       if (HasLocalsInUsedOrAsm && CI && CI->isInlineAsm())
 287         HasInlineAsmMaybeReferencingInternal = true;
 288
 289       auto *CalledValue = CS.getCalledValue();
 290       auto *CalledFunction = CS.getCalledFunction();
 291       if (CalledValue && !CalledFunction) {
 292         CalledValue = CalledValue->stripPointerCastsNoFollowAliases();
 293         // Stripping pointer casts can reveal a called function.
 294         CalledFunction = dyn_cast<Function>(CalledValue);
 295       }
 296       // Check if this is an alias to a function. If so, get the
 297       // called aliasee for the checks below.
 298       if (auto *GA = dyn_cast<GlobalAlias>(CalledValue)) {
 299         assert(!CalledFunction && "Expected null called function in callsite for alias");
 300         CalledFunction = dyn_cast<Function>(GA->getBaseObject());
 301       }
 302       // Check if this is a direct call to a known function or a known
 303       // intrinsic, or an indirect call with profile data.
 304       if (CalledFunction) {
 305         if (CI && CalledFunction->isIntrinsic()) {
 306           addIntrinsicToSummary(
 307               CI, TypeTests, TypeTestAssumeVCalls, TypeCheckedLoadVCalls,
 308               TypeTestAssumeConstVCalls, TypeCheckedLoadConstVCalls, DT);
 309           continue;
 310         }
 311         // We should have named any anonymous globals
 312         assert(CalledFunction->hasName());
 313         auto ScaledCount = PSI->getProfileCount(&I, BFI);
 314         auto Hotness = ScaledCount ? getHotness(ScaledCount.getValue(), PSI)
 315                                    : CalleeInfo::HotnessType::Unknown;
 316         if (ForceSummaryEdgesCold != FunctionSummary::FSHT_None)
 317           Hotness = CalleeInfo::HotnessType::Cold;
 318
 319         // Use the original CalledValue, in case it was an alias. We want
 320         // to record the call edge to the alias in that case. Eventually
 321         // an alias summary will be created to associate the alias and
 322         // aliasee.
 323         auto &ValueInfo = CallGraphEdges[Index.getOrInsertValueInfo(
 324             cast<GlobalValue>(CalledValue))];
 325         ValueInfo.updateHotness(Hotness);
 326         // Add the relative block frequency to CalleeInfo if there is no profile
 327         // information.
 328         if (BFI != nullptr && Hotness == CalleeInfo::HotnessType::Unknown) {
 329           uint64_t BBFreq = BFI->getBlockFreq(&BB).getFrequency();
 330           uint64_t EntryFreq = BFI->getEntryFreq();
 331           ValueInfo.updateRelBlockFreq(BBFreq, EntryFreq);
 332         }
 333       } else {
 334         // Skip inline assembly calls.
 335         if (CI && CI->isInlineAsm())
 336           continue;
 337         // Skip direct calls.
 338         if (!CalledValue || isa<Constant>(CalledValue))
 339           continue;
 340
 341         // Check if the instruction has a callees metadata. If so, add callees
 342         // to CallGraphEdges to reflect the references from the metadata, and
 343         // to enable importing for subsequent indirect call promotion and
 344         // inlining.
 345         if (auto *MD = I.getMetadata(LLVMContext::MD_callees)) {
 346           for (auto &Op : MD->operands()) {
 347             Function *Callee = mdconst::extract_or_null<Function>(Op);
 348             if (Callee)
 349               CallGraphEdges[Index.getOrInsertValueInfo(Callee)];
 350           }
 351         }
 352
 353         uint32_t NumVals, NumCandidates;
 354         uint64_t TotalCount;
 355         auto CandidateProfileData =
 356             ICallAnalysis.getPromotionCandidatesForInstruction(
 357                 &I, NumVals, TotalCount, NumCandidates);
 358         for (auto &Candidate : CandidateProfileData)
 359           CallGraphEdges[Index.getOrInsertValueInfo(Candidate.Value)]
 360               .updateHotness(getHotness(Candidate.Count, PSI));
 361       }
 362     }
 363
 364   // By now we processed all instructions in a function, except
 365   // non-volatile loads. All new refs we add in a loop below
 366   // are obviously constant. All constant refs are grouped in the
 367   // end of RefEdges vector, so we can use a single integer value
 368   // to identify them.
 369   unsigned RefCnt = RefEdges.size();
 370   for (const Instruction *I : NonVolatileLoads) {
 371     Visited.erase(I);
 372     findRefEdges(Index, I, RefEdges, Visited);
 373   }
 374   std::vector<ValueInfo> Refs = RefEdges.takeVector();
 375   // Regular LTO module doesn't participate in ThinLTO import,
 376   // so no reference from it can be readonly, since this would
 377   // require importing variable as local copy
 378   if (IsThinLTO)
 379     for (; RefCnt < Refs.size(); ++RefCnt)
 380       Refs[RefCnt].setReadOnly();
 381
 382   // Explicit add hot edges to enforce importing for designated GUIDs for
 383   // sample PGO, to enable the same inlines as the profiled optimized binary.
 384   for (auto &I : F.getImportGUIDs())
 385     CallGraphEdges[Index.getOrInsertValueInfo(I)].updateHotness(
 386         ForceSummaryEdgesCold == FunctionSummary::FSHT_All
 387             ? CalleeInfo::HotnessType::Cold
 388             : CalleeInfo::HotnessType::Critical);
 389
 390   bool NonRenamableLocal = isNonRenamableLocal(F);
 391   bool NotEligibleForImport =
 392       NonRenamableLocal || HasInlineAsmMaybeReferencingInternal;
 393   GlobalValueSummary::GVFlags Flags(F.getLinkage(), NotEligibleForImport,
 394                                     /* Live = */ false, F.isDSOLocal());
 395   FunctionSummary::FFlags FunFlags{
 396       F.hasFnAttribute(Attribute::ReadNone),
 397       F.hasFnAttribute(Attribute::ReadOnly),
 398       F.hasFnAttribute(Attribute::NoRecurse), F.returnDoesNotAlias(),
 399       // FIXME: refactor this to use the same code that inliner is using.
 400       // Don't try to import functions with noinline attribute.
 401       F.getAttributes().hasFnAttribute(Attribute::NoInline)};
 402   auto FuncSummary = llvm::make_unique<FunctionSummary>(
 403       Flags, NumInsts, FunFlags, /*EntryCount=*/0, std::move(Refs),
 404       CallGraphEdges.takeVector(), TypeTests.takeVector(),
 405       TypeTestAssumeVCalls.takeVector(), TypeCheckedLoadVCalls.takeVector(),
 406       TypeTestAssumeConstVCalls.takeVector(),
 407       TypeCheckedLoadConstVCalls.takeVector());
 408   if (NonRenamableLocal)
 409     CantBePromoted.insert(F.getGUID());
 410   Index.addGlobalValueSummary(F, std::move(FuncSummary));
 411 }
 412
 413 static void
 414 computeVariableSummary(ModuleSummaryIndex &Index, const GlobalVariable &V,
 415                        DenseSet<GlobalValue::GUID> &CantBePromoted) {
 416   SetVector<ValueInfo> RefEdges;
 417   SmallPtrSet<const User *, 8> Visited;
 418   bool HasBlockAddress = findRefEdges(Index, &V, RefEdges, Visited);
 419   bool NonRenamableLocal = isNonRenamableLocal(V);
 420   GlobalValueSummary::GVFlags Flags(V.getLinkage(), NonRenamableLocal,
 421                                     /* Live = */ false, V.isDSOLocal());
 422
 423   // Don't mark variables we won't be able to internalize as read-only.
 424   GlobalVarSummary::GVarFlags VarFlags(
 425       !V.hasComdat() && !V.hasAppendingLinkage() && !V.isInterposable() &&
 426       !V.hasAvailableExternallyLinkage() && !V.hasDLLExportStorageClass());
 427   auto GVarSummary = llvm::make_unique<GlobalVarSummary>(Flags, VarFlags,
 428                                                          RefEdges.takeVector());
 429   if (NonRenamableLocal)
 430     CantBePromoted.insert(V.getGUID());
 431   if (HasBlockAddress)
 432     GVarSummary->setNotEligibleToImport();
 433   Index.addGlobalValueSummary(V, std::move(GVarSummary));
 434 }
 435
 436 static void
 437 computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A,
 438                     DenseSet<GlobalValue::GUID> &CantBePromoted) {
 439   bool NonRenamableLocal = isNonRenamableLocal(A);
 440   GlobalValueSummary::GVFlags Flags(A.getLinkage(), NonRenamableLocal,
 441                                     /* Live = */ false, A.isDSOLocal());
 442   auto AS = llvm::make_unique<AliasSummary>(Flags);
 443   auto *Aliasee = A.getBaseObject();
 444   auto *AliaseeSummary = Index.getGlobalValueSummary(*Aliasee);
 445   assert(AliaseeSummary && "Alias expects aliasee summary to be parsed");
 446   AS->setAliasee(AliaseeSummary);
 447   if (NonRenamableLocal)
 448     CantBePromoted.insert(A.getGUID());
 449   Index.addGlobalValueSummary(A, std::move(AS));
 450 }
 451
 452 // Set LiveRoot flag on entries matching the given value name.
 453 static void setLiveRoot(ModuleSummaryIndex &Index, StringRef Name) {
 454   if (ValueInfo VI = Index.getValueInfo(GlobalValue::getGUID(Name)))
 455     for (auto &Summary : VI.getSummaryList())
 456       Summary->setLive(true);
 457 }
 458
 459 ModuleSummaryIndex llvm::buildModuleSummaryIndex(
 460     const Module &M,
 461     std::function<BlockFrequencyInfo *(const Function &F)> GetBFICallback,
 462     ProfileSummaryInfo *PSI) {
 463   assert(PSI);
 464   bool EnableSplitLTOUnit = false;
 465   if (auto *MD = mdconst::extract_or_null<ConstantInt>(
 466           M.getModuleFlag("EnableSplitLTOUnit")))
 467     EnableSplitLTOUnit = MD->getZExtValue();
 468   ModuleSummaryIndex Index(/*HaveGVs=*/true, EnableSplitLTOUnit);
 469
 470   // Identify the local values in the llvm.used and llvm.compiler.used sets,
 471   // which should not be exported as they would then require renaming and
 472   // promotion, but we may have opaque uses e.g. in inline asm. We collect them
 473   // here because we use this information to mark functions containing inline
 474   // assembly calls as not importable.
 475   SmallPtrSet<GlobalValue *, 8> LocalsUsed;
 476   SmallPtrSet<GlobalValue *, 8> Used;
 477   // First collect those in the llvm.used set.
 478   collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);
 479   // Next collect those in the llvm.compiler.used set.
 480   collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ true);
 481   DenseSet<GlobalValue::GUID> CantBePromoted;
 482   for (auto *V : Used) {
 483     if (V->hasLocalLinkage()) {
 484       LocalsUsed.insert(V);
 485       CantBePromoted.insert(V->getGUID());
 486     }
 487   }
 488
 489   bool HasLocalInlineAsmSymbol = false;
 490   if (!M.getModuleInlineAsm().empty()) {
 491     // Collect the local values defined by module level asm, and set up
 492     // summaries for these symbols so that they can be marked as NoRename,
 493     // to prevent export of any use of them in regular IR that would require
 494     // renaming within the module level asm. Note we don't need to create a
 495     // summary for weak or global defs, as they don't need to be flagged as
 496     // NoRename, and defs in module level asm can't be imported anyway.
 497     // Also, any values used but not defined within module level asm should
 498     // be listed on the llvm.used or llvm.compiler.used global and marked as
 499     // referenced from there.
 500     ModuleSymbolTable::CollectAsmSymbols(
 501         M, [&](StringRef Name, object::BasicSymbolRef::Flags Flags) {
 502           // Symbols not marked as Weak or Global are local definitions.
 503           if (Flags & (object::BasicSymbolRef::SF_Weak |
 504                        object::BasicSymbolRef::SF_Global))
 505             return;
 506           HasLocalInlineAsmSymbol = true;
 507           GlobalValue *GV = M.getNamedValue(Name);
 508           if (!GV)
 509             return;
 510           assert(GV->isDeclaration() && "Def in module asm already has definition");
 511           GlobalValueSummary::GVFlags GVFlags(GlobalValue::InternalLinkage,
 512                                               /* NotEligibleToImport = */ true,
 513                                               /* Live = */ true,
 514                                               /* Local */ GV->isDSOLocal());
 515           CantBePromoted.insert(GV->getGUID());
 516           // Create the appropriate summary type.
 517           if (Function *F = dyn_cast<Function>(GV)) {
 518             std::unique_ptr<FunctionSummary> Summary =
 519                 llvm::make_unique<FunctionSummary>(
 520                     GVFlags, /*InstCount=*/0,
 521                     FunctionSummary::FFlags{
 522                         F->hasFnAttribute(Attribute::ReadNone),
 523                         F->hasFnAttribute(Attribute::ReadOnly),
 524                         F->hasFnAttribute(Attribute::NoRecurse),
 525                         F->returnDoesNotAlias(),
 526                         /* NoInline = */ false},
 527                     /*EntryCount=*/0, ArrayRef<ValueInfo>{},
 528                     ArrayRef<FunctionSummary::EdgeTy>{},
 529                     ArrayRef<GlobalValue::GUID>{},
 530                     ArrayRef<FunctionSummary::VFuncId>{},
 531                     ArrayRef<FunctionSummary::VFuncId>{},
 532                     ArrayRef<FunctionSummary::ConstVCall>{},
 533                     ArrayRef<FunctionSummary::ConstVCall>{});
 534             Index.addGlobalValueSummary(*GV, std::move(Summary));
 535           } else {
 536             std::unique_ptr<GlobalVarSummary> Summary =
 537                 llvm::make_unique<GlobalVarSummary>(
 538                     GVFlags, GlobalVarSummary::GVarFlags(),
 539                     ArrayRef<ValueInfo>{});
 540             Index.addGlobalValueSummary(*GV, std::move(Summary));
 541           }
 542         });
 543   }
 544
 545   bool IsThinLTO = true;
 546   if (auto *MD =
 547           mdconst::extract_or_null<ConstantInt>(M.getModuleFlag("ThinLTO")))
 548     IsThinLTO = MD->getZExtValue();
 549
 550   // Compute summaries for all functions defined in module, and save in the
 551   // index.
 552   for (auto &F : M) {
 553     if (F.isDeclaration())
 554       continue;
 555
 556     DominatorTree DT(const_cast<Function &>(F));
 557     BlockFrequencyInfo *BFI = nullptr;
 558     std::unique_ptr<BlockFrequencyInfo> BFIPtr;
 559     if (GetBFICallback)
 560       BFI = GetBFICallback(F);
 561     else if (F.hasProfileData()) {
 562       LoopInfo LI{DT};
 563       BranchProbabilityInfo BPI{F, LI};
 564       BFIPtr = llvm::make_unique<BlockFrequencyInfo>(F, BPI, LI);
 565       BFI = BFIPtr.get();
 566     }
 567
 568     computeFunctionSummary(Index, M, F, BFI, PSI, DT,
 569                            !LocalsUsed.empty() || HasLocalInlineAsmSymbol,
 570                            CantBePromoted, IsThinLTO);
 571   }
 572
 573   // Compute summaries for all variables defined in module, and save in the
 574   // index.
 575   for (const GlobalVariable &G : M.globals()) {
 576     if (G.isDeclaration())
 577       continue;
 578     computeVariableSummary(Index, G, CantBePromoted);
 579   }
 580
 581   // Compute summaries for all aliases defined in module, and save in the
 582   // index.
 583   for (const GlobalAlias &A : M.aliases())
 584     computeAliasSummary(Index, A, CantBePromoted);
 585
 586   for (auto *V : LocalsUsed) {
 587     auto *Summary = Index.getGlobalValueSummary(*V);
 588     assert(Summary && "Missing summary for global value");
 589     Summary->setNotEligibleToImport();
 590   }
 591
 592   // The linker doesn't know about these LLVM produced values, so we need
 593   // to flag them as live in the index to ensure index-based dead value
 594   // analysis treats them as live roots of the analysis.
 595   setLiveRoot(Index, "llvm.used");
 596   setLiveRoot(Index, "llvm.compiler.used");
 597   setLiveRoot(Index, "llvm.global_ctors");
 598   setLiveRoot(Index, "llvm.global_dtors");
 599   setLiveRoot(Index, "llvm.global.annotations");
 600
 601   for (auto &GlobalList : Index) {
 602     // Ignore entries for references that are undefined in the current module.
 603     if (GlobalList.second.SummaryList.empty())
 604       continue;
 605
 606     assert(GlobalList.second.SummaryList.size() == 1 &&
 607            "Expected module's index to have one summary per GUID");
 608     auto &Summary = GlobalList.second.SummaryList[0];
 609     if (!IsThinLTO) {
 610       Summary->setNotEligibleToImport();
 611       continue;
 612     }
 613
 614     bool AllRefsCanBeExternallyReferenced =
 615         llvm::all_of(Summary->refs(), [&](const ValueInfo &VI) {
 616           return !CantBePromoted.count(VI.getGUID());
 617         });
 618     if (!AllRefsCanBeExternallyReferenced) {
 619       Summary->setNotEligibleToImport();
 620       continue;
 621     }
 622
 623     if (auto *FuncSummary = dyn_cast<FunctionSummary>(Summary.get())) {
 624       bool AllCallsCanBeExternallyReferenced = llvm::all_of(
 625           FuncSummary->calls(), [&](const FunctionSummary::EdgeTy &Edge) {
 626             return !CantBePromoted.count(Edge.first.getGUID());
 627           });
 628       if (!AllCallsCanBeExternallyReferenced)
 629         Summary->setNotEligibleToImport();
 630     }
 631   }
 632
 633   if (!ModuleSummaryDotFile.empty()) {
 634     std::error_code EC;
 635     raw_fd_ostream OSDot(ModuleSummaryDotFile, EC, sys::fs::OpenFlags::F_None);
 636     if (EC)
 637       report_fatal_error(Twine("Failed to open dot file ") +
 638                          ModuleSummaryDotFile + ": " + EC.message() + "\n");
 639     Index.exportToDot(OSDot);
 640   }
 641
 642   return Index;
 643 }
 644
 645 AnalysisKey ModuleSummaryIndexAnalysis::Key;
 646
 647 ModuleSummaryIndex
 648 ModuleSummaryIndexAnalysis::run(Module &M, ModuleAnalysisManager &AM) {
 649   ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M);
 650   auto &FAM = AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
 651   return buildModuleSummaryIndex(
 652       M,
 653       [&FAM](const Function &F) {
 654         return &FAM.getResult<BlockFrequencyAnalysis>(
 655             *const_cast<Function *>(&F));
 656       },
 657       &PSI);
 658 }
 659
 660 char ModuleSummaryIndexWrapperPass::ID = 0;
 661
 662 INITIALIZE_PASS_BEGIN(ModuleSummaryIndexWrapperPass, "module-summary-analysis",
 663                       "Module Summary Analysis", false, true)
 664 INITIALIZE_PASS_DEPENDENCY(BlockFrequencyInfoWrapperPass)
 665 INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
 666 INITIALIZE_PASS_END(ModuleSummaryIndexWrapperPass, "module-summary-analysis",
 667                     "Module Summary Analysis", false, true)
 668
 669 ModulePass *llvm::createModuleSummaryIndexWrapperPass() {
 670   return new ModuleSummaryIndexWrapperPass();
 671 }
 672
 673 ModuleSummaryIndexWrapperPass::ModuleSummaryIndexWrapperPass()
 674     : ModulePass(ID) {
 675   initializeModuleSummaryIndexWrapperPassPass(*PassRegistry::getPassRegistry());
 676 }
 677
 678 bool ModuleSummaryIndexWrapperPass::runOnModule(Module &M) {
 679   auto *PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
 680   Index.emplace(buildModuleSummaryIndex(
 681       M,
 682       [this](const Function &F) {
 683         return &(this->getAnalysis<BlockFrequencyInfoWrapperPass>(
 684                          *const_cast<Function *>(&F))
 685                      .getBFI());
 686       },
 687       PSI));
 688   return false;
 689 }
 690
 691 bool ModuleSummaryIndexWrapperPass::doFinalization(Module &M) {
 692   Index.reset();
 693   return false;
 694 }
 695
 696 void ModuleSummaryIndexWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
 697   AU.setPreservesAll();
 698   AU.addRequired<BlockFrequencyInfoWrapperPass>();
 699   AU.addRequired<ProfileSummaryInfoWrapperPass>();
 700 }