Index: lib/Driver/ToolChains/Darwin.cpp
===================================================================
--- lib/Driver/ToolChains/Darwin.cpp
+++ lib/Driver/ToolChains/Darwin.cpp
@@ -1472,10 +1472,16 @@
 std::string getOSVersion(llvm::Triple::OSType OS, const llvm::Triple &Triple,
                          const Driver &TheDriver) {
   unsigned Major, Minor, Micro;
+  llvm::Triple SystemTriple(llvm::sys::getProcessTriple());
   switch (OS) {
   case llvm::Triple::Darwin:
   case llvm::Triple::MacOSX:
-    if (!Triple.getMacOSXVersion(Major, Minor, Micro))
+    // If there is no version specified on triple, and both host and target are
+    // macos, use the host triple to infer OS version.
+    if (Triple.isMacOSX() && SystemTriple.isMacOSX() &&
+        !Triple.getOSMajorVersion())
+      SystemTriple.getMacOSXVersion(Major, Minor, Micro);
+    else if (!Triple.getMacOSXVersion(Major, Minor, Micro))
       TheDriver.Diag(diag::err_drv_invalid_darwin_version)
           << Triple.getOSName();
     break;
Index: test/Driver/clang-g-opts.c
===================================================================
--- test/Driver/clang-g-opts.c
+++ test/Driver/clang-g-opts.c
@@ -3,7 +3,7 @@
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G %s
 
 // Assert that the toolchains which should default to a lower Dwarf version do so.
-// RUN: %clang -### -S %s -g -target x86_64-apple-darwin 2>&1 \
+// RUN: %clang -### -S %s -g -target x86_64-apple-darwin8 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF2 %s
 // RUN: %clang -### -S %s -g -target i686-pc-openbsd 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF2 %s
@@ -21,7 +21,7 @@
 //
 // RUN: %clang -### -S %s -g0 -g -target x86_64-linux-gnu 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G %s
-// RUN: %clang -### -S %s -g0 -g -target x86_64-apple-darwin 2>&1 \
+// RUN: %clang -### -S %s -g0 -g -target x86_64-apple-darwin8 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G-STANDALONE %s
 // RUN: %clang -### -S %s -g0 -g -target i686-pc-openbsd 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF2 %s
Index: test/Driver/target-triple-deployment.c
===================================================================
--- test/Driver/target-triple-deployment.c
+++ test/Driver/target-triple-deployment.c
@@ -1,5 +1,5 @@
 // RUN: touch %t.o
-// RUN: %clang -target x86_64-apple-macosx -### %t.o 2> %t.log
+// RUN: %clang -target x86_64-apple-macosx10.4 -### %t.o 2> %t.log
 // RUN: %clang -target x86_64-apple-darwin9 -### %t.o 2>> %t.log
 // RUN: %clang -target x86_64-apple-macosx10.7 -### %t.o 2>> %t.log
 //