[LinkingContext] Limit shared library undefined atoms to be added.

This adds functionality to limit shared library undefined atoms to be added
only once by the Resolver.

Dynamic libraries may be processed more than once if they exist within a
Group.

Also adds a test to verify the change.

llvm-svn: 195307

1 files changed, 16 insertions, 11 deletions

diff --git a/lld/lib/Core/Resolver.cpp b/lld/lib/Core/Resolver.cpp
index cdacc64a7eb..51325896ad7 100644
--- a/lld/lib/Core/Resolver.cpp
+++ b/lld/lib/Core/Resolver.cpp
@@ -75,22 +75,27 @@ void Resolver::doFile(const File &file) {}
 
 void Resolver::handleFile(const File &file) {
   uint32_t resolverState = Resolver::StateNoChange;
+  const SharedLibraryFile *sharedLibraryFile =
+      llvm::dyn_cast<SharedLibraryFile>(&file);
+
   doFile(file);
   for (const DefinedAtom *atom : file.defined()) {
     doDefinedAtom(*atom);
     resolverState |= StateNewDefinedAtoms;
   }
-  for (const UndefinedAtom *undefAtom : file.undefined()) {
-    doUndefinedAtom(*undefAtom);
-    resolverState |= StateNewUndefinedAtoms;
-
-    // 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 for
-    // COFF "weak external" symbol.
-    if (!_symbolTable.isDefined(undefAtom->name())) {
-      if (const UndefinedAtom *fallbackAtom = undefAtom->fallback()) {
-        doUndefinedAtom(*fallbackAtom);
-        _symbolTable.addReplacement(undefAtom, fallbackAtom);
+  if (!sharedLibraryFile ||
+      _context.addUndefinedAtomsFromSharedLibrary(sharedLibraryFile)) {
+    for (const UndefinedAtom *undefAtom : file.undefined()) {
+      doUndefinedAtom(*undefAtom);
+      resolverState |= StateNewUndefinedAtoms;
+      // 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
+      // for COFF "weak external" symbol.
+      if (!_symbolTable.isDefined(undefAtom->name())) {
+        if (const UndefinedAtom *fallbackAtom = undefAtom->fallback()) {
+          doUndefinedAtom(*fallbackAtom);
+          _symbolTable.addReplacement(undefAtom, fallbackAtom);
+        }
       }
     }
   }