diff --git a/lld/COFF/Driver.h b/lld/COFF/Driver.h
--- a/lld/COFF/Driver.h
+++ b/lld/COFF/Driver.h
@@ -41,6 +41,17 @@
   COFFOptTable();
 };
 
+// The result of parsing the .drective section. The /export: and /include:
+// options are handled separately because they reference symbols, and the number
+// of symbols can be quite large. The LLVM Option library will perform at least
+// one memory allocation per argument, and that is prohibitively slow for
+// parsing directives.
+struct ParsedDirectives {
+  std::vector<StringRef> exports;
+  std::vector<StringRef> includes;
+  llvm::opt::InputArgList args;
+};
+
 class ArgParser {
 public:
   // Parses command line options.
@@ -52,8 +63,7 @@
   // Tokenizes a given string and then parses as command line options in
   // .drectve section. /EXPORT options are returned in second element
   // to be processed in fastpath.
-  std::pair<llvm::opt::InputArgList, std::vector<StringRef>>
-  parseDirectives(StringRef s);
+  ParsedDirectives parseDirectives(StringRef s);
 
 private:
   // Concatenate LINK environment variable.
diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
--- a/lld/COFF/Driver.cpp
+++ b/lld/COFF/Driver.cpp
@@ -343,11 +343,9 @@
   ArgParser parser;
   // .drectve is always tokenized using Windows shell rules.
   // /EXPORT: option can appear too many times, processing in fastpath.
-  opt::InputArgList args;
-  std::vector<StringRef> exports;
-  std::tie(args, exports) = parser.parseDirectives(s);
+  ParsedDirectives directives = parser.parseDirectives(s);
 
-  for (StringRef e : exports) {
+  for (StringRef e : directives.exports) {
     // If a common header file contains dllexported function
     // declarations, many object files may end up with having the
     // same /EXPORT options. In order to save cost of parsing them,
@@ -366,7 +364,11 @@
     config->exports.push_back(exp);
   }
 
-  for (auto *arg : args) {
+  // Handle /include: in bulk.
+  for (StringRef inc : directives.includes)
+    addUndefined(inc);
+
+  for (auto *arg : directives.args) {
     switch (arg->getOption().getID()) {
     case OPT_aligncomm:
       parseAligncomm(arg->getValue());
diff --git a/lld/COFF/DriverUtils.cpp b/lld/COFF/DriverUtils.cpp
--- a/lld/COFF/DriverUtils.cpp
+++ b/lld/COFF/DriverUtils.cpp
@@ -862,14 +862,16 @@
 
 // Tokenizes and parses a given string as command line in .drective section.
 // /EXPORT options are processed in fastpath.
-std::pair<opt::InputArgList, std::vector<StringRef>>
-ArgParser::parseDirectives(StringRef s) {
-  std::vector<StringRef> exports;
+ParsedDirectives ArgParser::parseDirectives(StringRef s) {
+  ParsedDirectives result;
   SmallVector<const char *, 16> rest;
 
   for (StringRef tok : tokenize(s)) {
     if (tok.startswith_lower("/export:") || tok.startswith_lower("-export:"))
-      exports.push_back(tok.substr(strlen("/export:")));
+      result.exports.push_back(tok.substr(strlen("/export:")));
+    else if (tok.startswith_lower("/include:") ||
+             tok.startswith_lower("-include:"))
+      result.includes.push_back(tok.substr(strlen("/include:")));
     else
       rest.push_back(tok.data());
   }
@@ -878,13 +880,13 @@
   unsigned missingIndex;
   unsigned missingCount;
 
-  opt::InputArgList args = table.ParseArgs(rest, missingIndex, missingCount);
+  result.args = table.ParseArgs(rest, missingIndex, missingCount);
 
   if (missingCount)
-    fatal(Twine(args.getArgString(missingIndex)) + ": missing argument");
-  for (auto *arg : args.filtered(OPT_UNKNOWN))
-    warn("ignoring unknown argument: " + arg->getAsString(args));
-  return {std::move(args), std::move(exports)};
+    fatal(Twine(result.args.getArgString(missingIndex)) + ": missing argument");
+  for (auto *arg : result.args.filtered(OPT_UNKNOWN))
+    warn("ignoring unknown argument: " + arg->getAsString(result.args));
+  return result;
 }
 
 // link.exe has an interesting feature. If LINK or _LINK_ environment