Revert "Reland "[ThinLTO] Populate declaration import status except for distributed ThinLTO under a default-off new option" (#92718) (#94503)

This reverts commit e33db24.

The change from *set to *map increases memory usage, and caused indexing
OOM in some applications. Need to profile offline to bring the memory
usage down.

Author: mingmingl-llvm

llvm/include/llvm/IR/ModuleSummaryIndex.h

@@ -587,10 +587,6 @@ class GlobalValueSummary {
 
   void setImportKind(ImportKind IK) { Flags.ImportType = IK; }
 
-  GlobalValueSummary::ImportKind importType() const {
-    return static_cast<ImportKind>(Flags.ImportType);
-  }
-
   GlobalValue::VisibilityTypes getVisibility() const {
     return (GlobalValue::VisibilityTypes)Flags.Visibility;
   }
@@ -1276,9 +1272,6 @@ using ModulePathStringTableTy = StringMap<ModuleHash>;
 /// a particular module, and provide efficient access to their summary.
 using GVSummaryMapTy = DenseMap<GlobalValue::GUID, GlobalValueSummary *>;
 
-/// A set of global value summary pointers.
-using GVSummaryPtrSet = SmallPtrSet<GlobalValueSummary *, 4>;
-
 /// Map of a type GUID to type id string and summary (multimap used
 /// in case of GUID conflicts).
 using TypeIdSummaryMapTy =

llvm/include/llvm/Transforms/IPO/FunctionImport.h

@@ -31,9 +31,9 @@ class Module;
 /// based on the provided summary informations.
 class FunctionImporter {
 public:
-  /// The functions to import from a source module and their import type.
-  using FunctionsToImportTy =
-      DenseMap<GlobalValue::GUID, GlobalValueSummary::ImportKind>;
+  /// Set of functions to import from a source module. Each entry is a set
+  /// containing all the GUIDs of all functions to import for a source module.
+  using FunctionsToImportTy = std::unordered_set<GlobalValue::GUID>;
 
   /// The different reasons selectCallee will chose not to import a
   /// candidate.
@@ -99,13 +99,8 @@ class FunctionImporter {
   /// index's module path string table).
   using ImportMapTy = DenseMap<StringRef, FunctionsToImportTy>;
 
-  /// The map contains an entry for every global value the module exports.
-  /// The key is ValueInfo, and the value indicates whether the definition
-  /// or declaration is visible to another module. If a function's definition is
-  /// visible to other modules, the global values this function referenced are
-  /// visible and shouldn't be internalized.
-  /// TODO: Rename to `ExportMapTy`.
-  using ExportSetTy = DenseMap<ValueInfo, GlobalValueSummary::ImportKind>;
+  /// The set contains an entry for every global value the module exports.
+  using ExportSetTy = DenseSet<ValueInfo>;
 
   /// A function of this type is used to load modules referenced by the index.
   using ModuleLoaderTy =

llvm/lib/LTO/LTO.cpp

@@ -121,9 +121,6 @@ void llvm::computeLTOCacheKey(
     support::endian::write64le(Data, I);
     Hasher.update(Data);
   };
-  auto AddUint8 = [&](const uint8_t I) {
-    Hasher.update(ArrayRef<uint8_t>((const uint8_t *)&I, 1));
-  };
   AddString(Conf.CPU);
   // FIXME: Hash more of Options. For now all clients initialize Options from
   // command-line flags (which is unsupported in production), but may set
@@ -159,18 +156,18 @@ void llvm::computeLTOCacheKey(
   auto ModHash = Index.getModuleHash(ModuleID);
   Hasher.update(ArrayRef<uint8_t>((uint8_t *)&ModHash[0], sizeof(ModHash)));
 
-  std::vector<std::pair<uint64_t, uint8_t>> ExportsGUID;
+  std::vector<uint64_t> ExportsGUID;
   ExportsGUID.reserve(ExportList.size());
-  for (const auto &[VI, ExportType] : ExportList)
-    ExportsGUID.push_back(
-        std::make_pair(VI.getGUID(), static_cast<uint8_t>(ExportType)));
+  for (const auto &VI : ExportList) {
+    auto GUID = VI.getGUID();
+    ExportsGUID.push_back(GUID);
+  }
 
   // Sort the export list elements GUIDs.
   llvm::sort(ExportsGUID);
-  for (auto [GUID, ExportType] : ExportsGUID) {
+  for (uint64_t GUID : ExportsGUID) {
     // The export list can impact the internalization, be conservative here
     Hasher.update(ArrayRef<uint8_t>((uint8_t *)&GUID, sizeof(GUID)));
-    AddUint8(ExportType);
   }
 
   // Include the hash for every module we import functions from. The set of
@@ -202,21 +199,19 @@ void llvm::computeLTOCacheKey(
              [](const ImportModule &Lhs, const ImportModule &Rhs) -> bool {
                return Lhs.getHash() < Rhs.getHash();
              });
-  std::vector<std::pair<uint64_t, uint8_t>> ImportedGUIDs;
+  std::vector<uint64_t> ImportedGUIDs;
   for (const ImportModule &Entry : ImportModulesVector) {
     auto ModHash = Entry.getHash();
     Hasher.update(ArrayRef<uint8_t>((uint8_t *)&ModHash[0], sizeof(ModHash)));
 
     AddUint64(Entry.getFunctions().size());
 
     ImportedGUIDs.clear();
-    for (auto &[Fn, ImportType] : Entry.getFunctions())
-      ImportedGUIDs.push_back(std::make_pair(Fn, ImportType));
+    for (auto &Fn : Entry.getFunctions())
+      ImportedGUIDs.push_back(Fn);
     llvm::sort(ImportedGUIDs);
-    for (auto &[GUID, Type] : ImportedGUIDs) {
+    for (auto &GUID : ImportedGUIDs)
       AddUint64(GUID);
-      AddUint8(Type);
-    }
   }
 
   // Include the hash for the resolved ODR.
@@ -286,9 +281,9 @@ void llvm::computeLTOCacheKey(
   // Imported functions may introduce new uses of type identifier resolutions,
   // so we need to collect their used resolutions as well.
   for (const ImportModule &ImpM : ImportModulesVector)
-    for (auto &[GUID, UnusedImportType] : ImpM.getFunctions()) {
+    for (auto &ImpF : ImpM.getFunctions()) {
       GlobalValueSummary *S =
-          Index.findSummaryInModule(GUID, ImpM.getIdentifier());
+          Index.findSummaryInModule(ImpF, ImpM.getIdentifier());
       AddUsedThings(S);
       // If this is an alias, we also care about any types/etc. that the aliasee
       // may reference.
@@ -1400,7 +1395,6 @@ class lto::ThinBackendProc {
                   llvm::StringRef ModulePath,
                   const std::string &NewModulePath) {
     std::map<std::string, GVSummaryMapTy> ModuleToSummariesForIndex;
-
     std::error_code EC;
     gatherImportedSummariesForModule(ModulePath, ModuleToDefinedGVSummaries,
                                      ImportList, ModuleToSummariesForIndex);
@@ -1409,8 +1403,6 @@ class lto::ThinBackendProc {
                       sys::fs::OpenFlags::OF_None);
     if (EC)
       return errorCodeToError(EC);
-
-    // TODO: Serialize declaration bits to bitcode.
     writeIndexToFile(CombinedIndex, OS, &ModuleToSummariesForIndex);
 
     if (ShouldEmitImportsFiles) {

llvm/lib/LTO/LTOBackend.cpp

@@ -720,14 +720,7 @@ bool lto::initImportList(const Module &M,
       if (Summary->modulePath() == M.getModuleIdentifier())
         continue;
       // Add an entry to provoke importing by thinBackend.
-      // Try emplace the entry first. If an entry with the same key already
-      // exists, set the value to 'std::min(existing-value, new-value)' to make
-      // sure a definition takes precedence over a declaration.
-      auto [Iter, Inserted] = ImportList[Summary->modulePath()].try_emplace(
-          GUID, Summary->importType());
-
-      if (!Inserted)
-        Iter->second = std::min(Iter->second, Summary->importType());
+      ImportList[Summary->modulePath()].insert(GUID);
     }
   }
   return true;