Index: cfe/trunk/lib/Driver/MinGWToolChain.cpp
===================================================================
--- cfe/trunk/lib/Driver/MinGWToolChain.cpp
+++ cfe/trunk/lib/Driver/MinGWToolChain.cpp
@@ -47,7 +47,7 @@
   Archs.emplace_back(getTriple().getArchName());
   Archs[0] += "-w64-mingw32";
   Archs.emplace_back("mingw32");
-  Arch = "unknown";
+  Arch = Archs[0].str();
   // lib: Arch Linux, Ubuntu, Windows
   // lib64: openSUSE Linux
   for (StringRef CandidateLib : {"lib", "lib64"}) {
Index: cfe/trunk/test/Driver/mingw.cpp
===================================================================
--- cfe/trunk/test/Driver/mingw.cpp
+++ cfe/trunk/test/Driver/mingw.cpp
@@ -1,3 +1,8 @@
+// RUN: %clang -target i686-windows-gnu -c -### --sysroot=%S/Inputs/mingw_clang_tree/mingw32 %s 2>&1 | FileCheck -check-prefix=CHECK_MINGW_CLANG_TREE %s
+// CHECK_MINGW_CLANG_TREE: "{{.*}}/Inputs/mingw_clang_tree/mingw32{{/|\\\\}}i686-w64-mingw32{{/|\\\\}}include"
+// CHECK_MINGW_CLANG_TREE: "{{.*}}/Inputs/mingw_clang_tree/mingw32{{/|\\\\}}include"
+
+
 // RUN: %clang -target i686-pc-windows-gnu -stdlib=libstdc++ -c -### --sysroot=%S/Inputs/mingw_mingw_org_tree/mingw %s 2>&1 | FileCheck -check-prefix=CHECK_MINGW_ORG_TREE %s
 // CHECK_MINGW_ORG_TREE: "{{.*}}/Inputs/mingw_mingw_org_tree/mingw{{/|\\\\}}lib{{/|\\\\}}gcc{{/|\\\\}}mingw32{{/|\\\\}}4.8.1{{/|\\\\}}include{{/|\\\\}}c++"
 // CHECK_MINGW_ORG_TREE: "{{.*}}/Inputs/mingw_mingw_org_tree/mingw{{/|\\\\}}lib{{/|\\\\}}gcc{{/|\\\\}}mingw32{{/|\\\\}}4.8.1{{/|\\\\}}include{{/|\\\\}}c++{{/|\\\\}}mingw32"