Index: MinGW/Driver.cpp
===================================================================
--- MinGW/Driver.cpp
+++ MinGW/Driver.cpp
@@ -146,6 +146,8 @@
 
   if (auto *A = Args.getLastArg(OPT_subs))
     Add("-subsystem:" + StringRef(A->getValue()));
+  if (Args.hasFlag(OPT_allow_multiple_definition, OPT_no_allow_multiple_definition, false))
+    Add("-force:multiple");
   if (auto *A = Args.getLastArg(OPT_out_implib))
     Add("-implib:" + StringRef(A->getValue()));
   if (auto *A = Args.getLastArg(OPT_stack))
Index: MinGW/Options.td
===================================================================
--- MinGW/Options.td
+++ MinGW/Options.td
@@ -4,8 +4,18 @@
 class J<string name>: Joined<["--", "-"], name>;
 class S<string name>: Separate<["--", "-"], name>;
 
+multiclass B<string name, string help1, string help2> {
+  def NAME: Flag<["--", "-"], name>, HelpText<help1>;
+  def no_ # NAME: Flag<["--", "-"], "no-" # name>, HelpText<help2>;
+}
+
 def L: JoinedOrSeparate<["-"], "L">, MetaVarName<"<dir>">,
   HelpText<"Add a directory to the library search path">;
+
+defm allow_multiple_definition: B<"allow-multiple-definition",
+    "Allow multiple definitions",
+    "Do not allow multiple definitions (default)">;
+
 def dynamicbase: F<"dynamicbase">, HelpText<"Enable ASLR">;
 def entry: S<"entry">, MetaVarName<"<entry>">,
   HelpText<"Name of entry point symbol">;
Index: test/MinGW/driver.test
===================================================================
--- test/MinGW/driver.test
+++ test/MinGW/driver.test
@@ -37,6 +37,14 @@
 RUN: ld.lld -### foo.o -m i386pep -o bar.exe | FileCheck -check-prefix=OUT %s
 OUT: -out:bar.exe
 
+RUN: ld.lld -### foo.o -m i386pep --allow-multiple-definitions | FileCheck -check-prefix=FORCE_MULTIPLE %s
+RUN: ld.lld -### foo.o -m i386pep --no-allow-multiple-definitions --allow-multiple-definitions | FileCheck -check-prefix=FORCE_MULTIPLE %s
+FORCE_MULTIPLE: -force:multiple
+
+RUN: ld.lld -### foo.o -m i386pep --no-allow-multiple-definitions | FileCheck -check-prefix=NO_FORCE_MULTIPLE %s
+RUN: ld.lld -### foo.o -m i386pep --allow-multiple-definitions --no-allow-multiple-definitions | FileCheck -check-prefix=NO_FORCE_MULTIPLE %s
+NO_FORCE_MULTIPLE-NOT: -force:multiple
+
 RUN: ld.lld -### foo.o -m i386pep --out-implib bar | FileCheck -check-prefix=IMPLIB %s
 RUN: ld.lld -### foo.o -m i386pep --out-implib=bar | FileCheck -check-prefix=IMPLIB %s
 IMPLIB: -implib:bar