Index: include/lld/Core/InputGraph.h
===================================================================
--- include/lld/Core/InputGraph.h
+++ include/lld/Core/InputGraph.h
@@ -80,6 +80,12 @@
   /// it with getReplacements() results.
   void normalize();
 
+  /// Start parsing the file containing a given symbol, so that when the
+  /// file is requested from the core linker we can respond to it quickly.
+  /// It does not change the meaining of the code. In particualr this
+  /// function should not have any observable side effect.
+  void preload(StringRef sym);
+
   range<InputElementIterT> inputElements() {
     return make_range(_inputArgs.begin(), _inputArgs.end());
   }
Index: lib/Core/Resolver.cpp
===================================================================
--- lib/Core/Resolver.cpp
+++ lib/Core/Resolver.cpp
@@ -117,6 +117,13 @@
   // tell symbol table
   bool newUndefAdded = _symbolTable.add(atom);
 
+  // If the undefined symbol is in an archive file, we want to start parsing the
+  // file in background to use more than one core. It's semantically no-op from
+  // the core linker's point of view because the speculative loading has no side
+  // effect.
+  if (newUndefAdded)
+    _context.getInputGraph().preload(atom.name());
+
   // 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.