2 files changed, 28 insertions, 21 deletions

diff --git a/lld/lib/Core/Resolver.cpp b/lld/lib/Core/Resolver.cpp
index d139f8a4625..6ed35598d60 100644
--- a/lld/lib/Core/Resolver.cpp
+++ b/lld/lib/Core/Resolver.cpp
@@ -48,15 +48,12 @@ private:
 } // namespace
 
 void Resolver::handleFile(const File &file) {
-  bool isEmpty = file.defined().empty() && file.undefined().empty() &&
-                 file.sharedLibrary().empty() && file.absolute().empty();
-  if (isEmpty)
-    return;
-
+  bool undefAdded = false;
   for (const DefinedAtom *atom : file.defined())
     doDefinedAtom(*atom);
   for (const UndefinedAtom *atom : file.undefined())
-    doUndefinedAtom(*atom);
+    if (doUndefinedAtom(*atom))
+      undefAdded = true;
   for (const SharedLibraryAtom *atom : file.sharedLibrary())
     doSharedLibraryAtom(*atom);
   for (const AbsoluteAtom *atom : file.absolute())
@@ -65,7 +62,9 @@ void Resolver::handleFile(const File &file) {
   // Notify the input file manager of the fact that we have made some progress
   // on linking using the current input file. It may want to know the fact for
   // --start-group/--end-group.
-  _context.getInputGraph().notifyProgress();
+  if (undefAdded) {
+    _context.getInputGraph().notifyProgress();
+  }
 }
 
 void Resolver::forEachUndefines(bool searchForOverrides,
@@ -124,7 +123,7 @@ void Resolver::handleSharedLibrary(const File &file) {
   });
 }
 
-void Resolver::doUndefinedAtom(const UndefinedAtom &atom) {
+bool Resolver::doUndefinedAtom(const UndefinedAtom &atom) {
   DEBUG_WITH_TYPE("resolver", llvm::dbgs()
                     << "       UndefinedAtom: "
                     << llvm::format("0x%09lX", &atom)
@@ -134,7 +133,7 @@ void Resolver::doUndefinedAtom(const UndefinedAtom &atom) {
   _atoms.push_back(&atom);
 
   // tell symbol table
-  _symbolTable.add(atom);
+  bool newUndefAdded = _symbolTable.add(atom);
 
   // If the undefined symbol has an alternative name, try to resolve the
   // symbol with the name to give it a second chance. This feature is used
@@ -145,6 +144,7 @@ void Resolver::doUndefinedAtom(const UndefinedAtom &atom) {
       _symbolTable.addReplacement(&atom, fallbackAtom);
     }
   }
+  return newUndefAdded;
 }
 
 /// \brief Add the section group and the group-child reference members.
@@ -178,7 +178,8 @@ bool Resolver::maybeAddSectionGroupOrGnuLinkOnce(const DefinedAtom &atom) {
   return true;
 }
 
-// called on each atom when a file is added
+// Called on each atom when a file is added. Returns true if a given
+// atom is added to the symbol table.
 void Resolver::doDefinedAtom(const DefinedAtom &atom) {
   DEBUG_WITH_TYPE("resolver", llvm::dbgs()
                     << "         DefinedAtom: "
diff --git a/lld/lib/Core/SymbolTable.cpp b/lld/lib/Core/SymbolTable.cpp
index a6620753424..81ed9bb0b5e 100644
--- a/lld/lib/Core/SymbolTable.cpp
+++ b/lld/lib/Core/SymbolTable.cpp
@@ -32,26 +32,26 @@
 namespace lld {
 SymbolTable::SymbolTable(const LinkingContext &context) : _context(context) {}
 
-void SymbolTable::add(const UndefinedAtom &atom) { addByName(atom); }
+bool SymbolTable::add(const UndefinedAtom &atom) { return addByName(atom); }
 
-void SymbolTable::add(const SharedLibraryAtom &atom) { addByName(atom); }
+bool SymbolTable::add(const SharedLibraryAtom &atom) { return addByName(atom); }
 
-void SymbolTable::add(const AbsoluteAtom &atom) { addByName(atom); }
+bool SymbolTable::add(const AbsoluteAtom &atom) { return addByName(atom); }
 
-void SymbolTable::add(const DefinedAtom &atom) {
+bool SymbolTable::add(const DefinedAtom &atom) {
   if (!atom.name().empty() &&
       atom.scope() != DefinedAtom::scopeTranslationUnit) {
     // Named atoms cannot be merged by content.
     assert(atom.merge() != DefinedAtom::mergeByContent);
     // Track named atoms that are not scoped to file (static).
-    addByName(atom);
-    return;
+    return addByName(atom);
   }
   if (atom.merge() == DefinedAtom::mergeByContent) {
     // Named atoms cannot be merged by content.
     assert(atom.name().empty());
-    addByContent(atom);
+    return addByContent(atom);
   }
+  return false;
 }
 
 const Atom *SymbolTable::findGroup(StringRef sym) {
@@ -162,16 +162,20 @@ static uint64_t sectionSize(const DefinedAtom *atom) {
       + getSizeFollowReferences(atom, lld::Reference::kindLayoutAfter);
 }
 
-void SymbolTable::addByName(const Atom &newAtom) {
+bool SymbolTable::addByName(const Atom &newAtom) {
   StringRef name = newAtom.name();
   assert(!name.empty());
   const Atom *existing = findByName(name);
   if (existing == nullptr) {
     // Name is not in symbol table yet, add it associate with this atom.
     _nameTable[name] = &newAtom;
-    return;
+    return true;
   }
 
+  // Do nothing if the same object is added more than once.
+  if (existing == &newAtom)
+    return false;
+
   // Name is already in symbol table and associated with another atom.
   bool useNew = true;
   switch (collide(existing->definition(), newAtom.definition())) {
@@ -301,6 +305,7 @@ void SymbolTable::addByName(const Atom &newAtom) {
     // New atom is not being used.  Add it to replacement table.
     _replacedAtoms[&newAtom] = existing;
   }
+  return false;
 }
 
 unsigned SymbolTable::AtomMappingInfo::getHashValue(const DefinedAtom *atom) {
@@ -332,17 +337,18 @@ bool SymbolTable::AtomMappingInfo::isEqual(const DefinedAtom * const l,
   return memcmp(lc.data(), rc.data(), lc.size()) == 0;
 }
 
-void SymbolTable::addByContent(const DefinedAtom & newAtom) {
+bool SymbolTable::addByContent(const DefinedAtom &newAtom) {
   // Currently only read-only constants can be merged.
   assert(newAtom.permissions() == DefinedAtom::permR__);
   AtomContentSet::iterator pos = _contentTable.find(&newAtom);
   if (pos == _contentTable.end()) {
     _contentTable.insert(&newAtom);
-    return;
+    return true;
   }
   const Atom* existing = *pos;
   // New atom is not being used.  Add it to replacement table.
   _replacedAtoms[&newAtom] = existing;
+  return false;
 }
 
 const Atom *SymbolTable::findByName(StringRef sym) {