Revert "[ThinLTO][Bitcode] Generate import type in bitcode (#87600)" (#94502)

This reverts commit 6262763, to prepare
for the revert of #92718.


#92718 causes LTO indexing OOM
in some applications.

Author: mingmingl-llvm

llvm/include/llvm/Bitcode/BitcodeWriter.h

@@ -102,8 +102,7 @@ class BitcodeWriter {
 
   void writeIndex(
       const ModuleSummaryIndex *Index,
-      const std::map<std::string, GVSummaryMapTy> *ModuleToSummariesForIndex,
-      const GVSummaryPtrSet *DecSummaries);
+      const std::map<std::string, GVSummaryMapTy> *ModuleToSummariesForIndex);
 };
 
 /// Write the specified module to the specified raw output stream.
@@ -148,12 +147,10 @@ void writeThinLinkBitcodeToFile(const Module &M, raw_ostream &Out,
 /// where it will be written in a new bitcode block. This is used when
 /// writing the combined index file for ThinLTO. When writing a subset of the
 /// index for a distributed backend, provide the \p ModuleToSummariesForIndex
-/// map. \p DecSummaries specifies the set of summaries for which the
-/// corresponding value should be imported as a declaration (prototype).
+/// map.
 void writeIndexToFile(const ModuleSummaryIndex &Index, raw_ostream &Out,
                       const std::map<std::string, GVSummaryMapTy>
-                          *ModuleToSummariesForIndex = nullptr,
-                      const GVSummaryPtrSet *DecSummaries = nullptr);
+                          *ModuleToSummariesForIndex = nullptr);
 
 /// If EmbedBitcode is set, save a copy of the llvm IR as data in the
 ///  __LLVM,__bitcode section (.llvmbc on non-MacOS).

llvm/include/llvm/LTO/legacy/ThinLTOCodeGenerator.h

@@ -271,13 +271,12 @@ class ThinLTOCodeGenerator {
                          const lto::InputFile &File);
 
   /**
-   * Compute the list of summaries and the subset of declaration summaries
-   * needed for importing into module.
+   * Compute the list of summaries needed for importing into module.
    */
   void gatherImportedSummariesForModule(
       Module &Module, ModuleSummaryIndex &Index,
       std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex,
-      GVSummaryPtrSet &DecSummaries, const lto::InputFile &File);
+      const lto::InputFile &File);
 
   /**
    * Perform internalization. Index is updated to reflect linkage changes.

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

@@ -212,15 +212,11 @@ bool convertToDeclaration(GlobalValue &GV);
 /// \p ModuleToSummariesForIndex will be populated with the needed summaries
 /// from each required module path. Use a std::map instead of StringMap to get
 /// stable order for bitcode emission.
-///
-/// \p DecSummaries will be popluated with the subset of of summary pointers
-/// that have 'declaration' import type among all summaries the module need.
 void gatherImportedSummariesForModule(
     StringRef ModulePath,
     const DenseMap<StringRef, GVSummaryMapTy> &ModuleToDefinedGVSummaries,
     const FunctionImporter::ImportMapTy &ImportList,
-    std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex,
-    GVSummaryPtrSet &DecSummaries);
+    std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex);
 
 /// Emit into \p OutputFilename the files module \p ModulePath will import from.
 std::error_code EmitImportsFiles(

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -424,11 +424,6 @@ class IndexBitcodeWriter : public BitcodeWriterBase {
   /// The combined index to write to bitcode.
   const ModuleSummaryIndex &Index;
 
-  /// When writing combined summaries, provides the set of global value
-  /// summaries for which the value (function, function alias, etc) should be
-  /// imported as a declaration.
-  const GVSummaryPtrSet *DecSummaries = nullptr;
-
   /// When writing a subset of the index for distributed backends, client
   /// provides a map of modules to the corresponding GUIDs/summaries to write.
   const std::map<std::string, GVSummaryMapTy> *ModuleToSummariesForIndex;
@@ -457,16 +452,11 @@ class IndexBitcodeWriter : public BitcodeWriterBase {
   /// Constructs a IndexBitcodeWriter object for the given combined index,
   /// writing to the provided \p Buffer. When writing a subset of the index
   /// for a distributed backend, provide a \p ModuleToSummariesForIndex map.
-  /// If provided, \p ModuleToDecSummaries specifies the set of summaries for
-  /// which the corresponding functions or aliased functions should be imported
-  /// as a declaration (but not definition) for each module.
   IndexBitcodeWriter(BitstreamWriter &Stream, StringTableBuilder &StrtabBuilder,
                      const ModuleSummaryIndex &Index,
-                     const GVSummaryPtrSet *DecSummaries = nullptr,
                      const std::map<std::string, GVSummaryMapTy>
                          *ModuleToSummariesForIndex = nullptr)
       : BitcodeWriterBase(Stream, StrtabBuilder), Index(Index),
-        DecSummaries(DecSummaries),
         ModuleToSummariesForIndex(ModuleToSummariesForIndex) {
 
     // See if the StackIdIndex was already added to the StackId map and
@@ -1221,8 +1211,7 @@ static uint64_t getEncodedFFlags(FunctionSummary::FFlags Flags) {
 
 // Decode the flags for GlobalValue in the summary. See getDecodedGVSummaryFlags
 // in BitcodeReader.cpp.
-static uint64_t getEncodedGVSummaryFlags(GlobalValueSummary::GVFlags Flags,
-                                         bool ImportAsDecl = false) {
+static uint64_t getEncodedGVSummaryFlags(GlobalValueSummary::GVFlags Flags) {
   uint64_t RawFlags = 0;
 
   RawFlags |= Flags.NotEligibleToImport; // bool
@@ -1237,8 +1226,7 @@ static uint64_t getEncodedGVSummaryFlags(GlobalValueSummary::GVFlags Flags,
 
   RawFlags |= (Flags.Visibility << 8); // 2 bits
 
-  unsigned ImportType = Flags.ImportType | ImportAsDecl;
-  RawFlags |= (ImportType << 10); // 1 bit
+  RawFlags |= (Flags.ImportType << 10); // 1 bit
 
   return RawFlags;
 }
@@ -4565,12 +4553,6 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
   unsigned AllocAbbrev = Stream.EmitAbbrev(std::move(Abbv));
 
-  auto shouldImportValueAsDecl = [&](GlobalValueSummary *GVS) -> bool {
-    if (DecSummaries == nullptr)
-      return false;
-    return DecSummaries->contains(GVS);
-  };
-
   // The aliases are emitted as a post-pass, and will point to the value
   // id of the aliasee. Save them in a vector for post-processing.
   SmallVector<AliasSummary *, 64> Aliases;
@@ -4681,8 +4663,7 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
     NameVals.push_back(*ValueId);
     assert(ModuleIdMap.count(FS->modulePath()));
     NameVals.push_back(ModuleIdMap[FS->modulePath()]);
-    NameVals.push_back(
-        getEncodedGVSummaryFlags(FS->flags(), shouldImportValueAsDecl(FS)));
+    NameVals.push_back(getEncodedGVSummaryFlags(FS->flags()));
     NameVals.push_back(FS->instCount());
     NameVals.push_back(getEncodedFFlags(FS->fflags()));
     NameVals.push_back(FS->entryCount());
@@ -4731,8 +4712,7 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
     NameVals.push_back(AliasValueId);
     assert(ModuleIdMap.count(AS->modulePath()));
     NameVals.push_back(ModuleIdMap[AS->modulePath()]);
-    NameVals.push_back(
-        getEncodedGVSummaryFlags(AS->flags(), shouldImportValueAsDecl(AS)));
+    NameVals.push_back(getEncodedGVSummaryFlags(AS->flags()));
     auto AliaseeValueId = SummaryToValueIdMap[&AS->getAliasee()];
     assert(AliaseeValueId);
     NameVals.push_back(AliaseeValueId);
@@ -5073,9 +5053,8 @@ void BitcodeWriter::writeModule(const Module &M,
 
 void BitcodeWriter::writeIndex(
     const ModuleSummaryIndex *Index,
-    const std::map<std::string, GVSummaryMapTy> *ModuleToSummariesForIndex,
-    const GVSummaryPtrSet *DecSummaries) {
-  IndexBitcodeWriter IndexWriter(*Stream, StrtabBuilder, *Index, DecSummaries,
+    const std::map<std::string, GVSummaryMapTy> *ModuleToSummariesForIndex) {
+  IndexBitcodeWriter IndexWriter(*Stream, StrtabBuilder, *Index,
                                  ModuleToSummariesForIndex);
   IndexWriter.write();
 }
@@ -5130,13 +5109,12 @@ void IndexBitcodeWriter::write() {
 // index for a distributed backend, provide a \p ModuleToSummariesForIndex map.
 void llvm::writeIndexToFile(
     const ModuleSummaryIndex &Index, raw_ostream &Out,
-    const std::map<std::string, GVSummaryMapTy> *ModuleToSummariesForIndex,
-    const GVSummaryPtrSet *DecSummaries) {
+    const std::map<std::string, GVSummaryMapTy> *ModuleToSummariesForIndex) {
   SmallVector<char, 0> Buffer;
   Buffer.reserve(256 * 1024);
 
   BitcodeWriter Writer(Buffer);
-  Writer.writeIndex(&Index, ModuleToSummariesForIndex, DecSummaries);
+  Writer.writeIndex(&Index, ModuleToSummariesForIndex);
   Writer.writeStrtab();
 
   Out.write((char *)&Buffer.front(), Buffer.size());

llvm/lib/LTO/LTO.cpp

@@ -1400,20 +1400,18 @@ class lto::ThinBackendProc {
                   llvm::StringRef ModulePath,
                   const std::string &NewModulePath) {
     std::map<std::string, GVSummaryMapTy> ModuleToSummariesForIndex;
-    GVSummaryPtrSet DeclarationSummaries;
 
     std::error_code EC;
     gatherImportedSummariesForModule(ModulePath, ModuleToDefinedGVSummaries,
-                                     ImportList, ModuleToSummariesForIndex,
-                                     DeclarationSummaries);
+                                     ImportList, ModuleToSummariesForIndex);
 
     raw_fd_ostream OS(NewModulePath + ".thinlto.bc", EC,
                       sys::fs::OpenFlags::OF_None);
     if (EC)
       return errorCodeToError(EC);
 
-    writeIndexToFile(CombinedIndex, OS, &ModuleToSummariesForIndex,
-                     &DeclarationSummaries);
+    // TODO: Serialize declaration bits to bitcode.
+    writeIndexToFile(CombinedIndex, OS, &ModuleToSummariesForIndex);
 
     if (ShouldEmitImportsFiles) {
       EC = EmitImportsFiles(ModulePath, NewModulePath + ".imports",

llvm/lib/LTO/ThinLTOCodeGenerator.cpp

@@ -766,7 +766,7 @@ void ThinLTOCodeGenerator::crossModuleImport(Module &TheModule,
 void ThinLTOCodeGenerator::gatherImportedSummariesForModule(
     Module &TheModule, ModuleSummaryIndex &Index,
     std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex,
-    GVSummaryPtrSet &DecSummaries, const lto::InputFile &File) {
+    const lto::InputFile &File) {
   auto ModuleCount = Index.modulePaths().size();
   auto ModuleIdentifier = TheModule.getModuleIdentifier();
 
@@ -796,7 +796,7 @@ void ThinLTOCodeGenerator::gatherImportedSummariesForModule(
 
   llvm::gatherImportedSummariesForModule(
       ModuleIdentifier, ModuleToDefinedGVSummaries,
-      ImportLists[ModuleIdentifier], ModuleToSummariesForIndex, DecSummaries);
+      ImportLists[ModuleIdentifier], ModuleToSummariesForIndex);
 }
 
 /**
@@ -832,14 +832,10 @@ void ThinLTOCodeGenerator::emitImports(Module &TheModule, StringRef OutputName,
                            IsPrevailing(PrevailingCopy), ImportLists,
                            ExportLists);
 
-  // 'EmitImportsFiles' emits the list of modules from which to import from, and
-  // the set of keys in `ModuleToSummariesForIndex` should be a superset of keys
-  // in `DecSummaries`, so no need to use `DecSummaries` in `EmitImportFiles`.
-  GVSummaryPtrSet DecSummaries;
   std::map<std::string, GVSummaryMapTy> ModuleToSummariesForIndex;
   llvm::gatherImportedSummariesForModule(
       ModuleIdentifier, ModuleToDefinedGVSummaries,
-      ImportLists[ModuleIdentifier], ModuleToSummariesForIndex, DecSummaries);
+      ImportLists[ModuleIdentifier], ModuleToSummariesForIndex);
 
   std::error_code EC;
   if ((EC = EmitImportsFiles(ModuleIdentifier, OutputName,

llvm/lib/Transforms/IPO/FunctionImport.cpp

@@ -1435,8 +1435,7 @@ void llvm::gatherImportedSummariesForModule(
     StringRef ModulePath,
     const DenseMap<StringRef, GVSummaryMapTy> &ModuleToDefinedGVSummaries,
     const FunctionImporter::ImportMapTy &ImportList,
-    std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex,
-    GVSummaryPtrSet &DecSummaries) {
+    std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex) {
   // Include all summaries from the importing module.
   ModuleToSummariesForIndex[std::string(ModulePath)] =
       ModuleToDefinedGVSummaries.lookup(ModulePath);
@@ -1451,7 +1450,7 @@ void llvm::gatherImportedSummariesForModule(
       assert(DS != DefinedGVSummaries.end() &&
              "Expected a defined summary for imported global value");
       if (Type == GlobalValueSummary::Declaration)
-        DecSummaries.insert(DS->second);
+        continue;
 
       SummariesForIndex[GUID] = DS->second;
     }