Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -8696,6 +8696,10 @@
 
     // Let the tool chain choose which runtime library to link.
     getMachOToolChain().AddLinkRuntimeLibArgs(Args, CmdArgs);
+
+    // No need to do anything for pthreads. Claim argument to avoid warning.
+    Args.ClaimAllArgs(options::OPT_pthread);
+    Args.ClaimAllArgs(options::OPT_pthreads);
   }
 
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles)) {
Index: test/Driver/darwin-ld-pthread.c
===================================================================
--- /dev/null
+++ test/Driver/darwin-ld-pthread.c
@@ -0,0 +1,4 @@
+// RUN: %clang -Wunused-command-line-argument -pthread -target x86_64-apple-darwin -### /dev/null -o %t.bin 2>&1 | FileCheck %s
+
+// There is nothing to do at link time to get pthread support. But do not warn.
+// CHECK-NOT: argument unused during compilation: '-pthread'