Index: include/llvm/ADT/Triple.h
===================================================================
--- include/llvm/ADT/Triple.h
+++ include/llvm/ADT/Triple.h
@@ -176,7 +176,8 @@
     WatchOS,    // Apple watchOS
     Mesa3D,
     Contiki,
-    LastOSType = Contiki
+    Hurd,
+    LastOSType = Hurd
   };
   enum EnvironmentType {
     UnknownEnvironment,
Index: lib/Support/Triple.cpp
===================================================================
--- lib/Support/Triple.cpp
+++ lib/Support/Triple.cpp
@@ -201,6 +201,7 @@
   case WatchOS: return "watchos";
   case Mesa3D: return "mesa3d";
   case Contiki: return "contiki";
+  case Hurd: return "gnu";
   }
 
   llvm_unreachable("Invalid OSType");
@@ -481,6 +482,7 @@
     .StartsWith("watchos", Triple::WatchOS)
     .StartsWith("mesa3d", Triple::Mesa3D)
     .StartsWith("contiki", Triple::Contiki)
+    .StartsWith("gnu0", Triple::Hurd)
     .Default(Triple::UnknownOS);
 }
 
Index: unittests/ADT/TripleTest.cpp
===================================================================
--- unittests/ADT/TripleTest.cpp
+++ unittests/ADT/TripleTest.cpp
@@ -290,6 +290,12 @@
   EXPECT_EQ(Triple::Linux, T.getOS());
   EXPECT_EQ(Triple::GNUEABI, T.getEnvironment());
 
+  T = Triple("i686-unknown-gnu0.9");
+  EXPECT_EQ(Triple::x86, T.getArch());
+  EXPECT_EQ(Triple::UnknownVendor, T.getVendor());
+  EXPECT_EQ(Triple::Hurd, T.getOS());
+  EXPECT_EQ(Triple::UnknownEnvironment, T.getEnvironment());
+
   T = Triple("huh");
   EXPECT_EQ(Triple::UnknownArch, T.getArch());
 }
@@ -391,6 +397,12 @@
   for (int OS = FirstOSType; OS <= Triple::LastOSType; ++OS) {
     if (OS == Triple::Win32)
       continue;
+    // We skip the Hurd OS, as permutations of it (whose string is "gnu")
+    // might produce different results than expected -- it could be
+    // misrecognized as environment, when placed as last element in the
+    // permutation.
+    if (OS == Triple::Hurd)
+      continue;
     StringRef C[] = {InitialC[0], InitialC[1], InitialC[2], InitialC[3]};
     C[2] = Triple::getOSTypeName(Triple::OSType(OS));
     std::string E = Join(C[0], C[1], C[2]);