resolve review comments

Author: mingmingl-llvm

lld/ELF/InputFiles.cpp

@@ -1745,7 +1745,7 @@ createBitcodeSymbol(Symbol *&sym, const std::vector<bool> &keptComdats,
   uint8_t visibility = mapVisibility(objSym.getVisibility());
 
   if (!sym)
-    sym = symtab.insert(saver().save(objSym.getName()));
+    sym = symtab.insert(unique_saver().save(objSym.getName()));
 
   int c = objSym.getComdatIndex();
   if (objSym.isUndefined() || (c != -1 && !keptComdats[c])) {
@@ -1797,9 +1797,14 @@ void BitcodeFile::parseLazy() {
   symbols = std::make_unique<Symbol *[]>(numSymbols);
   for (auto [i, irSym] : llvm::enumerate(obj->symbols()))
     if (!irSym.isUndefined()) {
-      auto *sym = symtab.insert(saver().save(irSym.getName()));
+      auto *sym = symtab.insert(unique_saver().save(irSym.getName()));
       sym->resolve(LazySymbol{*this});
       symbols[i] = sym;
+    } else {
+      // Keep copies of per-module undefined symbols for LTO::GlobalResolutions
+      // usage.
+      [[maybe_unused]] StringRef SymbolRef =
+          unique_saver().save(irSym.getName());
     }
 }
 

lld/include/lld/Common/CommonLinkerContext.h

@@ -38,6 +38,7 @@ class CommonLinkerContext {
 
   llvm::BumpPtrAllocator bAlloc;
   llvm::StringSaver saver{bAlloc};
+  llvm::UniqueStringSaver unique_saver{bAlloc};
   llvm::DenseMap<void *, SpecificAllocBase *> instances;
 
   ErrorHandler e;
@@ -55,6 +56,9 @@ template <typename T = CommonLinkerContext> T &context() {
 bool hasContext();
 
 inline llvm::StringSaver &saver() { return context().saver; }
+inline llvm::UniqueStringSaver &unique_saver() {
+  return context().unique_saver;
+}
 inline llvm::BumpPtrAllocator &bAlloc() { return context().bAlloc; }
 } // namespace lld
 

llvm/include/llvm/LTO/LTO.h

@@ -420,6 +420,8 @@ class LTO {
   std::unique_ptr<llvm::DenseMap<StringRef, GlobalResolution>>
       GlobalResolutions;
 
+  void releaseGlobalResolutionsMemory();
+
   void addModuleToGlobalRes(ArrayRef<InputFile::Symbol> Syms,
                             ArrayRef<SymbolResolution> Res, unsigned Partition,
                             bool InSummary);

llvm/lib/LTO/LTO.cpp

@@ -695,6 +695,14 @@ void LTO::addModuleToGlobalRes(ArrayRef<InputFile::Symbol> Syms,
   }
 }
 
+void LTO::releaseGlobalResolutionsMemory() {
+  // Release GlobalResolutions dense-map itself.
+  GlobalResolutions.reset();
+  // Release the string saver memory.
+  GlobalResolutionSymbolSaver.reset();
+  Alloc.reset();
+}
+
 static void writeToResolutionFile(raw_ostream &OS, InputFile *Input,
                                   ArrayRef<SymbolResolution> Res) {
   StringRef Path = Input->getName();
@@ -1811,10 +1819,7 @@ Error LTO::runThinLTO(AddStreamFn AddStream, FileCache Cache,
   // are no further accesses. We specifically want to do this before computing
   // cross module importing, which adds to peak memory via the computed import
   // and export lists.
-  GlobalResolutions.reset();
-  // Release the string saver memory.
-  GlobalResolutionSymbolSaver.reset();
-  Alloc.reset();
+  releaseGlobalResolutionsMemory();
 
   if (Conf.OptLevel > 0)
     ComputeCrossModuleImport(ThinLTO.CombinedIndex, ModuleToDefinedGVSummaries,