IPO: Const correctness for summaries passed into passes.

[pcc]

Summary

Pass const qualified summaries into importers and unqualified summaries into
exporters. This lets us const-qualify the summary argument to thinBackend.

Depends on D31226

[mehdi_amini]

LGTM

llvm/include/llvm/LTO/LTOBackend.h

 /// Runs a regular LTO backend. The regular LTO backend can also act as the
 /// regular LTO phase of ThinLTO, which may need to access the combined index.
 Error backend(Config &C, AddStreamFn AddStream,
               unsigned ParallelCodeGenParallelismLevel,
               std::unique_ptr<Module> M, ModuleSummaryIndex &CombinedIndex);
 
 /// Runs a ThinLTO backend.
 Error thinBackend(Config &C, unsigned Task, AddStreamFn AddStream, Module &M,
-                  ModuleSummaryIndex &CombinedIndex,
+                  const ModuleSummaryIndex &CombinedIndex,
                   const FunctionImporter::ImportMapTy &ImportList,
                   const GVSummaryMapTy &DefinedGlobals,
                   MapVector<StringRef, BitcodeModule> &ModuleMap);
 }
 }
 
 #endif

llvm/include/llvm/Transforms/IPO.h

 enum class PassSummaryAction {
   None,   ///< Do nothing.
   Import, ///< Import information from summary.
   Export, ///< Export information to summary.
 };
 
 /// \brief This pass lowers type metadata and the llvm.type.test intrinsic to
 /// bitsets.
-/// \param Action What to do with the summary passed as Index.
-/// \param Index The summary to use for importing or exporting, this can be null
-///              when Action is None.
-ModulePass *createLowerTypeTestsPass(PassSummaryAction Action,
-                                     ModuleSummaryIndex *Index);
+///
+/// The behavior depends on the summary arguments:
+/// - If ExportSummary is non-null, this pass will export type identifiers to
+///   the given summary.
+/// - Otherwise, if ImportSummary is non-null, this pass will import type
+///   identifiers from the given summary.
+/// - Otherwise it does neither.
+/// It is invalid for both ExportSummary and ImportSummary to be non-null.
+ModulePass *createLowerTypeTestsPass(ModuleSummaryIndex *ExportSummary,
+                                     const ModuleSummaryIndex *ImportSummary);
 
 /// \brief This pass export CFI checks for use by external modules.
 ModulePass *createCrossDSOCFIPass();
 
 /// \brief This pass implements whole-program devirtualization using type
 /// metadata.
-ModulePass *createWholeProgramDevirtPass(PassSummaryAction Action,
-                                         ModuleSummaryIndex *Index);
+///
+/// The behavior depends on the summary arguments:
+/// - If ExportSummary is non-null, this pass will export type identifiers to
+///   the given summary.
+/// - Otherwise, if ImportSummary is non-null, this pass will import type
+///   identifiers from the given summary.
+/// - Otherwise it does neither.
+/// It is invalid for both ExportSummary and ImportSummary to be non-null.
+ModulePass *
+createWholeProgramDevirtPass(ModuleSummaryIndex *ExportSummary,
+                             const ModuleSummaryIndex *ImportSummary);
 
 /// This pass splits globals into pieces for the benefit of whole-program
 /// devirtualization and control-flow integrity.
 ModulePass *createGlobalSplitPass();
 
 //===----------------------------------------------------------------------===//
 // SampleProfilePass - Loads sample profile data from disk and generates
 // IR metadata to reflect the profile.

llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h

public:
   /// optimizer.  If this is non-null, it is added to both the function and
   /// per-module pass pipeline.
   TargetLibraryInfoImpl *LibraryInfo;
 
   /// Inliner - Specifies the inliner to use.  If this is non-null, it is
   /// added to the per-module passes.
   Pass *Inliner;
 
-  /// The module summary index to use for passing information between the
-  /// regular LTO phase and the thin LTO backends, for example the CFI and
-  /// devirtualization type tests.
-  ModuleSummaryIndex *Summary = nullptr;
+  /// The module summary index to use for exporting information from the
+  /// regular LTO phase, for example for the CFI and devirtualization type
+  /// tests.
+  ModuleSummaryIndex *ExportSummary = nullptr;
+
+  /// The module summary index to use for importing information to the
+  /// thin LTO backends, for example for the CFI and devirtualization type
+  /// tests.
+  const ModuleSummaryIndex *ImportSummary = nullptr;
 
   bool DisableTailCalls;
   bool DisableUnitAtATime;
   bool DisableUnrollLoops;
   bool BBVectorize;
   bool SLPVectorize;
   bool LoopVectorize;
   bool RerollLoops;

llvm/lib/LTO/LTOBackend.cpp

report_fatal_error("unable to parse pass pipeline description: " +
                        PipelineDesc);
 
   if (!DisableVerify)
     MPM.addPass(VerifierPass());
   MPM.run(Mod, MAM);
 }
 
 static void runOldPMPasses(Config &Conf, Module &Mod, TargetMachine *TM,
-                           bool IsThinLTO, ModuleSummaryIndex &CombinedIndex) {
+                           bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
+                           const ModuleSummaryIndex *ImportSummary) {
   legacy::PassManager passes;
   passes.add(createTargetTransformInfoWrapperPass(TM->getTargetIRAnalysis()));
 
   PassManagerBuilder PMB;
   PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM->getTargetTriple()));
   PMB.Inliner = createFunctionInliningPass();
-  PMB.Summary = &CombinedIndex;
+  PMB.ExportSummary = ExportSummary;
+  PMB.ImportSummary = ImportSummary;
   // Unconditionally verify input since it is not verified before this
   // point and has unknown origin.
   PMB.VerifyInput = true;
   PMB.VerifyOutput = !Conf.DisableVerify;
   PMB.LoopVectorize = true;
   PMB.SLPVectorize = true;
   PMB.OptLevel = Conf.OptLevel;
   PMB.PGOSampleUse = Conf.SampleProfile;
   if (IsThinLTO)
     PMB.populateThinLTOPassManager(passes);
   else
     PMB.populateLTOPassManager(passes);
   passes.run(Mod);
 }
 
 bool opt(Config &Conf, TargetMachine *TM, unsigned Task, Module &Mod,
-         bool IsThinLTO, ModuleSummaryIndex &CombinedIndex) {
+         bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
+         const ModuleSummaryIndex *ImportSummary) {
   // There's still no ThinLTO pipeline hooked up in the new pass manager,
   // once there is one, we can just remove this.
   if (LTOUseNewPM && IsThinLTO)
     report_fatal_error("ThinLTO not supported with the new PM yet!");
 
   // FIXME: Plumb the combined index into the new pass manager.
   if (!Conf.OptPipeline.empty())
     runNewPMCustomPasses(Mod, TM, Conf.OptPipeline, Conf.AAPipeline,
                          Conf.DisableVerify);
   else if (LTOUseNewPM)
     runNewPMPasses(Mod, TM, Conf.OptLevel);
   else
-    runOldPMPasses(Conf, Mod, TM, IsThinLTO, CombinedIndex);
+    runOldPMPasses(Conf, Mod, TM, IsThinLTO, ExportSummary, ImportSummary);
   return !Conf.PostOptModuleHook || Conf.PostOptModuleHook(Task, Mod);
 }
 
 void codegen(Config &Conf, TargetMachine *TM, AddStreamFn AddStream,
              unsigned Task, Module &Mod) {
   if (Conf.PreCodeGenModuleHook && !Conf.PreCodeGenModuleHook(Task, Mod))
     return;
 
Error lto::backend(Config &C, AddStreamFn AddStream,
   // Setup optimization remarks.
   auto DiagFileOrErr = lto::setupOptimizationRemarks(
       Mod->getContext(), C.RemarksFilename, C.RemarksWithHotness);
   if (!DiagFileOrErr)
     return DiagFileOrErr.takeError();
   auto DiagnosticOutputFile = std::move(*DiagFileOrErr);
 
   if (!C.CodeGenOnly) {
-    if (!opt(C, TM.get(), 0, *Mod, /*IsThinLTO=*/false, CombinedIndex)) {
+    if (!opt(C, TM.get(), 0, *Mod, /*IsThinLTO=*/false,
+             /*ExportSummary=*/&CombinedIndex, /*ImportSummary=*/nullptr)) {
       finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
       return Error::success();
     }
   }
 
   if (ParallelCodeGenParallelismLevel == 1) {
     codegen(C, TM.get(), AddStream, 0, *Mod);
   } else {
     splitCodeGen(C, TM.get(), AddStream, ParallelCodeGenParallelismLevel,
                  std::move(Mod));
   }
   finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
   return Error::success();
 }
 
 Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream,
-                       Module &Mod, ModuleSummaryIndex &CombinedIndex,
+                       Module &Mod, const ModuleSummaryIndex &CombinedIndex,
                        const FunctionImporter::ImportMapTy &ImportList,
                        const GVSummaryMapTy &DefinedGlobals,
                        MapVector<StringRef, BitcodeModule> &ModuleMap) {
   Expected<const Target *> TOrErr = initAndLookupTarget(Conf, Mod);
   if (!TOrErr)
     return TOrErr.takeError();
 
   std::unique_ptr<TargetMachine> TM =
Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream,
 
   FunctionImporter Importer(CombinedIndex, ModuleLoader);
   if (Error Err = Importer.importFunctions(Mod, ImportList).takeError())
     return Err;
 
   if (Conf.PostImportModuleHook && !Conf.PostImportModuleHook(Task, Mod))
     return Error::success();
 
-  if (!opt(Conf, TM.get(), Task, Mod, /*IsThinLTO=*/true, CombinedIndex))
+  if (!opt(Conf, TM.get(), Task, Mod, /*IsThinLTO=*/true,
+           /*ExportSummary=*/nullptr, /*ImportSummary=*/&CombinedIndex))
     return Error::success();
 
   codegen(Conf, TM.get(), AddStream, Task, Mod);
   return Error::success();
 }

llvm/lib/Transforms/IPO/LowerTypeTests.cpp

public:
   ArrayRef<MDNode *> types() const {
     return makeArrayRef(getTrailingObjects<MDNode *>(), NTypes);
   }
 };
 
 class LowerTypeTestsModule {
   Module &M;
 
-  PassSummaryAction Action;
-  ModuleSummaryIndex *Summary;
+  ModuleSummaryIndex *ExportSummary;
+  const ModuleSummaryIndex *ImportSummary;
 
   bool LinkerSubsectionsViaSymbols;
   Triple::ArchType Arch;
   Triple::OSType OS;
   Triple::ObjectFormatType ObjectFormat;
 
   IntegerType *Int1Ty = Type::getInt1Ty(M.getContext());
   IntegerType *Int8Ty = Type::getInt8Ty(M.getContext());
class LowerTypeTestsModule {
   void replaceWeakDeclarationWithJumpTablePtr(Function *F, Constant *JT);
   void moveInitializerToModuleConstructor(GlobalVariable *GV);
   void findGlobalVariableUsersOf(Constant *C,
                                  SmallSetVector<GlobalVariable *, 8> &Out);
 
   void createJumpTable(Function *F, ArrayRef<GlobalTypeMember *> Functions);
 
 public:
-  LowerTypeTestsModule(Module &M, PassSummaryAction Action,
-                       ModuleSummaryIndex *Summary);
+  LowerTypeTestsModule(Module &M, ModuleSummaryIndex *ExportSummary,
+                       const ModuleSummaryIndex *ImportSummary);
   bool lower();
 
   // Lower the module using the action and summary passed as command line
   // arguments. For testing purposes only.
   static bool runForTesting(Module &M);
 };
 
 struct LowerTypeTests : public ModulePass {
   static char ID;
 
   bool UseCommandLine = false;
 
-  PassSummaryAction Action;
-  ModuleSummaryIndex *Summary;
+  ModuleSummaryIndex *ExportSummary;
+  const ModuleSummaryIndex *ImportSummary;
 
   LowerTypeTests() : ModulePass(ID), UseCommandLine(true) {
     initializeLowerTypeTestsPass(*PassRegistry::getPassRegistry());
   }
 
-  LowerTypeTests(PassSummaryAction Action, ModuleSummaryIndex *Summary)
-      : ModulePass(ID), Action(Action), Summary(Summary) {
+  LowerTypeTests(ModuleSummaryIndex *ExportSummary,
+                 const ModuleSummaryIndex *ImportSummary)
+      : ModulePass(ID), ExportSummary(ExportSummary),
+        ImportSummary(ImportSummary) {
     initializeLowerTypeTestsPass(*PassRegistry::getPassRegistry());
   }
 
   bool runOnModule(Module &M) override {
     if (skipModule(M))
       return false;
     if (UseCommandLine)
       return LowerTypeTestsModule::runForTesting(M);
-    return LowerTypeTestsModule(M, Action, Summary).lower();
+    return LowerTypeTestsModule(M, ExportSummary, ImportSummary).lower();
   }
 };
 
 } // anonymous namespace
 
 INITIALIZE_PASS(LowerTypeTests, "lowertypetests", "Lower type metadata", false,
                 false)
 char LowerTypeTests::ID = 0;
 
-ModulePass *llvm::createLowerTypeTestsPass(PassSummaryAction Action,
-                                           ModuleSummaryIndex *Summary) {
-  return new LowerTypeTests(Action, Summary);
+ModulePass *
+llvm::createLowerTypeTestsPass(ModuleSummaryIndex *ExportSummary,
+                               const ModuleSummaryIndex *ImportSummary) {
+  return new LowerTypeTests(ExportSummary, ImportSummary);
 }
 
 /// Build a bit set for TypeId using the object layouts in
 /// GlobalLayout.
 BitSetInfo LowerTypeTestsModule::buildBitSet(
     Metadata *TypeId,
     const DenseMap<GlobalTypeMember *, uint64_t> &GlobalLayout) {
   BitSetBuilder BSB;
Value *LowerTypeTestsModule::createBitSetTest(IRBuilder<> &B,
                                               const TypeIdLowering &TIL,
                                               Value *BitOffset) {
   if (TIL.TheKind == TypeTestResolution::Inline) {
     // If the bit set is sufficiently small, we can avoid a load by bit testing
     // a constant.
     return createMaskedBitTest(B, TIL.InlineBits, BitOffset);
   } else {
     Constant *ByteArray = TIL.TheByteArray;
-    if (!LinkerSubsectionsViaSymbols && AvoidReuse &&
-        Action != PassSummaryAction::Import) {
+    if (!LinkerSubsectionsViaSymbols && AvoidReuse && !ImportSummary) {
       // Each use of the byte array uses a different alias. This makes the
       // backend less likely to reuse previously computed byte array addresses,
       // improving the security of the CFI mechanism based on this pass.
       // This won't work when importing because TheByteArray is external.
       ByteArray = GlobalAlias::create(Int8Ty, 0, GlobalValue::PrivateLinkage,
                                       "bits_use", ByteArray, &M);
     }
 

 
 /// Export the given type identifier so that ThinLTO backends may import it.
 /// Type identifiers are exported by adding coarse-grained information about how
 /// to test the type identifier to the summary, and creating symbols in the
 /// object file (aliases and absolute symbols) containing fine-grained
 /// information about the type identifier.
 void LowerTypeTestsModule::exportTypeId(StringRef TypeId,
                                         const TypeIdLowering &TIL) {
-  TypeTestResolution &TTRes = Summary->getOrInsertTypeIdSummary(TypeId).TTRes;
+  TypeTestResolution &TTRes =
+      ExportSummary->getOrInsertTypeIdSummary(TypeId).TTRes;
   TTRes.TheKind = TIL.TheKind;
 
   auto ExportGlobal = [&](StringRef Name, Constant *C) {
     GlobalAlias *GA =
         GlobalAlias::create(Int8Ty, 0, GlobalValue::ExternalLinkage,
                             "__typeid_" + TypeId + "_" + Name, C, &M);
     GA->setVisibility(GlobalValue::HiddenVisibility);
   };
void LowerTypeTestsModule::exportTypeId(StringRef TypeId,
 
   if (TIL.TheKind == TypeTestResolution::Inline)
     ExportGlobal("inline_bits",
                  ConstantExpr::getIntToPtr(TIL.InlineBits, Int8PtrTy));
 }
 
 LowerTypeTestsModule::TypeIdLowering
 LowerTypeTestsModule::importTypeId(StringRef TypeId) {
-  const TypeIdSummary *TidSummary = Summary->getTypeIdSummary(TypeId);
+  const TypeIdSummary *TidSummary = ImportSummary->getTypeIdSummary(TypeId);
   if (!TidSummary)
     return {}; // Unsat: no globals match this type id.
   const TypeTestResolution &TTRes = TidSummary->TTRes;
 
   TypeIdLowering TIL;
   TIL.TheKind = TTRes.TheKind;
 
   auto ImportGlobal = [&](StringRef Name, unsigned AbsWidth) {
for (auto &&F : GLB.Fragments) {
       }
     }
 
     buildBitSetsFromFunctions(TypeIds, OrderedFns);
   }
 }
 
 /// Lower all type tests in this module.
-LowerTypeTestsModule::LowerTypeTestsModule(Module &M, PassSummaryAction Action,
-                                           ModuleSummaryIndex *Summary)
-    : M(M), Action(Action), Summary(Summary) {
+LowerTypeTestsModule::LowerTypeTestsModule(
+    Module &M, ModuleSummaryIndex *ExportSummary,
+    const ModuleSummaryIndex *ImportSummary)
+    : M(M), ExportSummary(ExportSummary), ImportSummary(ImportSummary) {
+  assert(!(ExportSummary && ImportSummary));
   Triple TargetTriple(M.getTargetTriple());
   LinkerSubsectionsViaSymbols = TargetTriple.isMacOSX();
   Arch = TargetTriple.getArch();
   OS = TargetTriple.getOS();
   ObjectFormat = TargetTriple.getObjectFormat();
 }
 
 bool LowerTypeTestsModule::runForTesting(Module &M) {
   ModuleSummaryIndex Summary;
 
   // Handle the command-line summary arguments. This code is for testing
   // purposes only, so we handle errors directly.
   if (!ClReadSummary.empty()) {
     ExitOnError ExitOnErr("-lowertypetests-read-summary: " + ClReadSummary +
                           ": ");
     auto ReadSummaryFile =
         ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(ClReadSummary)));
 
     yaml::Input In(ReadSummaryFile->getBuffer());
     In >> Summary;
     ExitOnErr(errorCodeToError(In.error()));
   }
 
-  bool Changed = LowerTypeTestsModule(M, ClSummaryAction, &Summary).lower();
+  bool Changed =
+      LowerTypeTestsModule(
+          M, ClSummaryAction == PassSummaryAction::Export ? &Summary : nullptr,
+          ClSummaryAction == PassSummaryAction::Import ? &Summary : nullptr)
+          .lower();
 
   if (!ClWriteSummary.empty()) {
     ExitOnError ExitOnErr("-lowertypetests-write-summary: " + ClWriteSummary +
                           ": ");
     std::error_code EC;
     raw_fd_ostream OS(ClWriteSummary, EC, sys::fs::F_Text);
     ExitOnErr(errorCodeToError(EC));
 
     yaml::Output Out(OS);
     Out << Summary;
   }
 
   return Changed;
 }
 
 bool LowerTypeTestsModule::lower() {
   Function *TypeTestFunc =
       M.getFunction(Intrinsic::getName(Intrinsic::type_test));
-  if ((!TypeTestFunc || TypeTestFunc->use_empty()) &&
-      Action != PassSummaryAction::Export)
+  if ((!TypeTestFunc || TypeTestFunc->use_empty()) && !ExportSummary)
     return false;
 
-  if (Action == PassSummaryAction::Import) {
+  if (ImportSummary) {
     for (auto UI = TypeTestFunc->use_begin(), UE = TypeTestFunc->use_end();
          UI != UE;) {
       auto *CI = cast<CallInst>((*UI++).getUser());
       importTypeTest(CI);
     }
     return true;
   }
 
for (const Use &U : TypeTestFunc->uses()) {
       auto TypeIdMDVal = dyn_cast<MetadataAsValue>(CI->getArgOperand(1));
       if (!TypeIdMDVal)
         report_fatal_error("Second argument of llvm.type.test must be metadata");
       auto TypeId = TypeIdMDVal->getMetadata();
       AddTypeIdUse(TypeId).CallSites.push_back(CI);
     }
   }
 
-  if (Action == PassSummaryAction::Export) {
+  if (ExportSummary) {
     DenseMap<GlobalValue::GUID, TinyPtrVector<Metadata *>> MetadataByGUID;
     for (auto &P : TypeIdInfo) {
       if (auto *TypeId = dyn_cast<MDString>(P.first))
         MetadataByGUID[GlobalValue::getGUID(TypeId->getString())].push_back(
             TypeId);
     }
 
-    for (auto &P : *Summary) {
+    for (auto &P : *ExportSummary) {
       for (auto &S : P.second) {
         auto *FS = dyn_cast<FunctionSummary>(S.get());
         if (!FS)
           continue;
         // FIXME: Only add live functions.
         for (GlobalValue::GUID G : FS->type_tests())
           for (Metadata *MD : MetadataByGUID[G])
             AddTypeIdUse(MD).IsExported = true;
bool LowerTypeTestsModule::lower() {
 
   allocateByteArrays();
 
   return true;
 }
 
 PreservedAnalyses LowerTypeTestsPass::run(Module &M,
                                           ModuleAnalysisManager &AM) {
-  bool Changed =
-      LowerTypeTestsModule(M, PassSummaryAction::None, /*Summary=*/nullptr)
+  bool Changed = LowerTypeTestsModule(M, /*ExportSummary=*/nullptr,
+                                      /*ImportSummary=*/nullptr)
                      .lower();
   if (!Changed)
     return PreservedAnalyses::all();
   return PreservedAnalyses::none();
 }

llvm/lib/Transforms/IPO/PassManagerBuilder.cpp

void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) {
   PM.add(createReversePostOrderFunctionAttrsPass());
 
   // Split globals using inrange annotations on GEP indices. This can help
   // improve the quality of generated code when virtual constant propagation or
   // control flow integrity are enabled.
   PM.add(createGlobalSplitPass());
 
   // Apply whole-program devirtualization and virtual constant propagation.
-  PM.add(createWholeProgramDevirtPass(
-      Summary ? PassSummaryAction::Export : PassSummaryAction::None, Summary));
+  PM.add(createWholeProgramDevirtPass(ExportSummary, nullptr));
 
   // That's all we need at opt level 1.
   if (OptLevel == 1)
     return;
 
   // Now that we internalized some globals, see if we can hack on them!
   PM.add(createGlobalOptimizerPass());
   // Promote any localized global vars.

 
 void PassManagerBuilder::populateThinLTOPassManager(
     legacy::PassManagerBase &PM) {
   PerformThinLTO = true;
 
   if (VerifyInput)
     PM.add(createVerifierPass());
 
-  if (Summary) {
+  if (ImportSummary) {
     // These passes import type identifier resolutions for whole-program
     // devirtualization and CFI. They must run early because other passes may
     // disturb the specific instruction patterns that these passes look for,
     // creating dependencies on resolutions that may not appear in the summary.
     //
     // For example, GVN may transform the pattern assume(type.test) appearing in
     // two basic blocks into assume(phi(type.test, type.test)), which would
     // transform a dependency on a WPD resolution into a dependency on a type
     // identifier resolution for CFI.
     //
     // Also, WPD has access to more precise information than ICP and can
     // devirtualize more effectively, so it should operate on the IR first.
-    PM.add(createWholeProgramDevirtPass(PassSummaryAction::Import, Summary));
-    PM.add(createLowerTypeTestsPass(PassSummaryAction::Import, Summary));
+    PM.add(createWholeProgramDevirtPass(nullptr, ImportSummary));
+    PM.add(createLowerTypeTestsPass(nullptr, ImportSummary));
   }
 
   populateModulePassManager(PM);
 
   if (VerifyOutput)
     PM.add(createVerifierPass());
   PerformThinLTO = false;
 }
void PassManagerBuilder::populateLTOPassManager(legacy::PassManagerBase &PM) {
 
   // Create a function that performs CFI checks for cross-DSO calls with targets
   // in the current module.
   PM.add(createCrossDSOCFIPass());
 
   // Lower type metadata and the type.test intrinsic. This pass supports Clang's
   // control flow integrity mechanisms (-fsanitize=cfi*) and needs to run at
   // link time if CFI is enabled. The pass does nothing if CFI is disabled.
-  PM.add(createLowerTypeTestsPass(
-      Summary ? PassSummaryAction::Export : PassSummaryAction::None, Summary));
+  PM.add(createLowerTypeTestsPass(ExportSummary, nullptr));
 
   if (OptLevel != 0)
     addLateLTOOptimizationPasses(PM);
 
   if (VerifyOutput)
     PM.add(createVerifierPass());
 }
 

llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp

void VTableSlotInfo::addCallSite(Value *VTable, CallSite CS,
                                  unsigned *NumUnsafeUses) {
   findCallSiteInfo(CS).CallSites.push_back({VTable, CS, NumUnsafeUses});
 }
 
 struct DevirtModule {
   Module &M;
   function_ref<AAResults &(Function &)> AARGetter;
 
-  PassSummaryAction Action;
-  ModuleSummaryIndex *Summary;
+  ModuleSummaryIndex *ExportSummary;
+  const ModuleSummaryIndex *ImportSummary;
 
   IntegerType *Int8Ty;
   PointerType *Int8PtrTy;
   IntegerType *Int32Ty;
   IntegerType *Int64Ty;
   IntegerType *IntPtrTy;
 
   bool RemarksEnabled;
 
   MapVector<VTableSlot, VTableSlotInfo> CallSlots;
 
   // This map keeps track of the number of "unsafe" uses of a loaded function
   // pointer. The key is the associated llvm.type.test intrinsic call generated
   // by this pass. An unsafe use is one that calls the loaded function pointer
   // directly. Every time we eliminate an unsafe use (for example, by
   // devirtualizing it or by applying virtual constant propagation), we
   // decrement the value stored in this map. If a value reaches zero, we can
   // eliminate the type check by RAUWing the associated llvm.type.test call with
   // true.
   std::map<CallInst *, unsigned> NumUnsafeUsesForTypeTest;
 
   DevirtModule(Module &M, function_ref<AAResults &(Function &)> AARGetter,
-               PassSummaryAction Action, ModuleSummaryIndex *Summary)
-      : M(M), AARGetter(AARGetter), Action(Action), Summary(Summary),
-        Int8Ty(Type::getInt8Ty(M.getContext())),
+               ModuleSummaryIndex *ExportSummary,
+               const ModuleSummaryIndex *ImportSummary)
+      : M(M), AARGetter(AARGetter), ExportSummary(ExportSummary),
+        ImportSummary(ImportSummary), Int8Ty(Type::getInt8Ty(M.getContext())),
         Int8PtrTy(Type::getInt8PtrTy(M.getContext())),
         Int32Ty(Type::getInt32Ty(M.getContext())),
         Int64Ty(Type::getInt64Ty(M.getContext())),
         IntPtrTy(M.getDataLayout().getIntPtrType(M.getContext(), 0)),
-        RemarksEnabled(areRemarksEnabled()) {}
+        RemarksEnabled(areRemarksEnabled()) {
+    assert(!(ExportSummary && ImportSummary));
+  }
 
   bool areRemarksEnabled();
 
   void scanTypeTestUsers(Function *TypeTestFunc, Function *AssumeFunc);
   void scanTypeCheckedLoadUsers(Function *TypeCheckedLoadFunc);
 
   void buildTypeIdentifierMap(
       std::vector<VTableBits> &Bits,
static bool runForTesting(Module &M,
                             function_ref<AAResults &(Function &)> AARGetter);
 };
 
 struct WholeProgramDevirt : public ModulePass {
   static char ID;
 
   bool UseCommandLine = false;
 
-  PassSummaryAction Action;
-  ModuleSummaryIndex *Summary;
+  ModuleSummaryIndex *ExportSummary;
+  const ModuleSummaryIndex *ImportSummary;
 
   WholeProgramDevirt() : ModulePass(ID), UseCommandLine(true) {
     initializeWholeProgramDevirtPass(*PassRegistry::getPassRegistry());
   }
 
-  WholeProgramDevirt(PassSummaryAction Action, ModuleSummaryIndex *Summary)
-      : ModulePass(ID), Action(Action), Summary(Summary) {
+  WholeProgramDevirt(ModuleSummaryIndex *ExportSummary,
+                     const ModuleSummaryIndex *ImportSummary)
+      : ModulePass(ID), ExportSummary(ExportSummary),
+        ImportSummary(ImportSummary) {
     initializeWholeProgramDevirtPass(*PassRegistry::getPassRegistry());
   }
 
   bool runOnModule(Module &M) override {
     if (skipModule(M))
       return false;
     if (UseCommandLine)
       return DevirtModule::runForTesting(M, LegacyAARGetter(*this));
-    return DevirtModule(M, LegacyAARGetter(*this), Action, Summary).run();
+    return DevirtModule(M, LegacyAARGetter(*this), ExportSummary, ImportSummary)
+        .run();
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<AssumptionCacheTracker>();
     AU.addRequired<TargetLibraryInfoWrapperPass>();
   }
 };
 
 } // end anonymous namespace
 
 INITIALIZE_PASS_BEGIN(WholeProgramDevirt, "wholeprogramdevirt",
                       "Whole program devirtualization", false, false)
 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
 INITIALIZE_PASS_END(WholeProgramDevirt, "wholeprogramdevirt",
                     "Whole program devirtualization", false, false)
 char WholeProgramDevirt::ID = 0;
 
-ModulePass *llvm::createWholeProgramDevirtPass(PassSummaryAction Action,
-                                               ModuleSummaryIndex *Summary) {
-  return new WholeProgramDevirt(Action, Summary);
+ModulePass *
+llvm::createWholeProgramDevirtPass(ModuleSummaryIndex *ExportSummary,
+                                   const ModuleSummaryIndex *ImportSummary) {
+  return new WholeProgramDevirt(ExportSummary, ImportSummary);
 }
 
 PreservedAnalyses WholeProgramDevirtPass::run(Module &M,
                                               ModuleAnalysisManager &AM) {
   auto &FAM = AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
   auto AARGetter = [&](Function &F) -> AAResults & {
     return FAM.getResult<AAManager>(F);
   };
-  if (!DevirtModule(M, AARGetter, PassSummaryAction::None, nullptr).run())
+  if (!DevirtModule(M, AARGetter, nullptr, nullptr).run())
     return PreservedAnalyses::all();
   return PreservedAnalyses::none();
 }
 
 bool DevirtModule::runForTesting(
     Module &M, function_ref<AAResults &(Function &)> AARGetter) {
   ModuleSummaryIndex Summary;
 
   // Handle the command-line summary arguments. This code is for testing
   // purposes only, so we handle errors directly.
   if (!ClReadSummary.empty()) {
     ExitOnError ExitOnErr("-wholeprogramdevirt-read-summary: " + ClReadSummary +
                           ": ");
     auto ReadSummaryFile =
         ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(ClReadSummary)));
 
     yaml::Input In(ReadSummaryFile->getBuffer());
     In >> Summary;
     ExitOnErr(errorCodeToError(In.error()));
   }
 
-  bool Changed = DevirtModule(M, AARGetter, ClSummaryAction, &Summary).run();
+  bool Changed =
+      DevirtModule(
+          M, AARGetter,
+          ClSummaryAction == PassSummaryAction::Export ? &Summary : nullptr,
+          ClSummaryAction == PassSummaryAction::Import ? &Summary : nullptr)
+          .run();
 
   if (!ClWriteSummary.empty()) {
     ExitOnError ExitOnErr(
         "-wholeprogramdevirt-write-summary: " + ClWriteSummary + ": ");
     std::error_code EC;
     raw_fd_ostream OS(ClWriteSummary, EC, sys::fs::F_Text);
     ExitOnErr(errorCodeToError(EC));
 
for (auto I = TypeCheckedLoadFunc->use_begin(),
     }
 
     CI->eraseFromParent();
   }
 }
 
 void DevirtModule::importResolution(VTableSlot Slot, VTableSlotInfo &SlotInfo) {
   const TypeIdSummary *TidSummary =
-      Summary->getTypeIdSummary(cast<MDString>(Slot.TypeID)->getString());
+      ImportSummary->getTypeIdSummary(cast<MDString>(Slot.TypeID)->getString());
   if (!TidSummary)
     return;
   auto ResI = TidSummary->WPDRes.find(Slot.ByteOffset);
   if (ResI == TidSummary->WPDRes.end())
     return;
   const WholeProgramDevirtResolution &Res = ResI->second;
 
   if (Res.TheKind == WholeProgramDevirtResolution::SingleImpl) {
Function *TypeTestFunc =
       M.getFunction(Intrinsic::getName(Intrinsic::type_test));
   Function *TypeCheckedLoadFunc =
       M.getFunction(Intrinsic::getName(Intrinsic::type_checked_load));
   Function *AssumeFunc = M.getFunction(Intrinsic::getName(Intrinsic::assume));
 
   // Normally if there are no users of the devirtualization intrinsics in the
   // module, this pass has nothing to do. But if we are exporting, we also need
   // to handle any users that appear only in the function summaries.
-  if (Action != PassSummaryAction::Export &&
+  if (!ExportSummary &&
       (!TypeTestFunc || TypeTestFunc->use_empty() || !AssumeFunc ||
        AssumeFunc->use_empty()) &&
       (!TypeCheckedLoadFunc || TypeCheckedLoadFunc->use_empty()))
     return false;
 
   if (TypeTestFunc && AssumeFunc)
     scanTypeTestUsers(TypeTestFunc, AssumeFunc);
 
   if (TypeCheckedLoadFunc)
     scanTypeCheckedLoadUsers(TypeCheckedLoadFunc);
 
-  if (Action == PassSummaryAction::Import) {
+  if (ImportSummary) {
     for (auto &S : CallSlots)
       importResolution(S.first, S.second);
 
     removeRedundantTypeTests();
 
     // The rest of the code is only necessary when exporting or during regular
     // LTO, so we are done.
     return true;
   }
 
   // Rebuild type metadata into a map for easy lookup.
   std::vector<VTableBits> Bits;
   DenseMap<Metadata *, std::set<TypeMemberInfo>> TypeIdMap;
   buildTypeIdentifierMap(Bits, TypeIdMap);
   if (TypeIdMap.empty())
     return true;
 
   // Collect information from summary about which calls to try to devirtualize.
-  if (Action == PassSummaryAction::Export) {
+  if (ExportSummary) {
     DenseMap<GlobalValue::GUID, TinyPtrVector<Metadata *>> MetadataByGUID;
     for (auto &P : TypeIdMap) {
       if (auto *TypeId = dyn_cast<MDString>(P.first))
         MetadataByGUID[GlobalValue::getGUID(TypeId->getString())].push_back(
             TypeId);
     }
 
-    for (auto &P : *Summary) {
+    for (auto &P : *ExportSummary) {
       for (auto &S : P.second) {
         auto *FS = dyn_cast<FunctionSummary>(S.get());
         if (!FS)
           continue;
         // FIXME: Only add live functions.
         for (FunctionSummary::VFuncId VF : FS->type_test_assume_vcalls()) {
           for (Metadata *MD : MetadataByGUID[VF.GUID]) {
             CallSlots[{MD, VF.Offset}].CSInfo.SummaryHasTypeTestAssumeUsers =
bool DevirtModule::run() {
   for (auto &S : CallSlots) {
     // Search each of the members of the type identifier for the virtual
     // function implementation at offset S.first.ByteOffset, and add to
     // TargetsForSlot.
     std::vector<VirtualCallTarget> TargetsForSlot;
     if (tryFindVirtualCallTargets(TargetsForSlot, TypeIdMap[S.first.TypeID],
                                   S.first.ByteOffset)) {
       WholeProgramDevirtResolution *Res = nullptr;
-      if (Action == PassSummaryAction::Export && isa<MDString>(S.first.TypeID))
-        Res = &Summary
+      if (ExportSummary && isa<MDString>(S.first.TypeID))
+        Res = &ExportSummary
                    ->getOrInsertTypeIdSummary(
                        cast<MDString>(S.first.TypeID)->getString())
                    .WPDRes[S.first.ByteOffset];
 
       if (!trySingleImplDevirt(TargetsForSlot, S.second, Res) &&
           tryVirtualConstProp(TargetsForSlot, S.second, Res, S.first))
         DidVirtualConstProp = true;
 
       // Collect functions devirtualized at least for one call site for stats.
       if (RemarksEnabled)
         for (const auto &T : TargetsForSlot)
           if (T.WasDevirt)
             DevirtTargets[T.Fn->getName()] = T.Fn;
     }
 
     // CFI-specific: if we are exporting and any llvm.type.checked.load
     // intrinsics were *not* devirtualized, we need to add the resulting
     // llvm.type.test intrinsics to the function summaries so that the
     // LowerTypeTests pass will export them.
-    if (Action == PassSummaryAction::Export && isa<MDString>(S.first.TypeID)) {
+    if (ExportSummary && isa<MDString>(S.first.TypeID)) {
       auto GUID =
           GlobalValue::getGUID(cast<MDString>(S.first.TypeID)->getString());
       for (auto FS : S.second.CSInfo.SummaryTypeCheckedLoadUsers)
         FS->addTypeTest(GUID);
       for (auto &CCS : S.second.ConstCSInfo)
         for (auto FS : CCS.second.SummaryTypeCheckedLoadUsers)
           FS->addTypeTest(GUID);
     }