Index: cfe/trunk/lib/Driver/ToolChains.cpp
===================================================================
--- cfe/trunk/lib/Driver/ToolChains.cpp
+++ cfe/trunk/lib/Driver/ToolChains.cpp
@@ -494,16 +494,28 @@
     if (char *env = ::getenv("IPHONEOS_DEPLOYMENT_TARGET"))
       iOSTarget = env;
 
-    // If no '-miphoneos-version-min' specified on the command line and
-    // IPHONEOS_DEPLOYMENT_TARGET is not defined, see if we can set the default
-    // based on -isysroot.
-    if (iOSTarget.empty()) {
+    // If there is no command-line argument to specify the Target version and
+    // no environment variable defined, see if we can set the default based
+    // on -isysroot.
+    if (iOSTarget.empty() && OSXTarget.empty() &&
+        Args.hasArg(options::OPT_isysroot)) {
       if (const Arg *A = Args.getLastArg(options::OPT_isysroot)) {
-        StringRef first, second;
         StringRef isysroot = A->getValue();
-        std::tie(first, second) = isysroot.split(StringRef("SDKs/iPhoneOS"));
-        if (second != "")
-          iOSTarget = second.substr(0,3);
+        // Assume SDK has path: SOME_PATH/SDKs/PlatformXX.YY.sdk
+        size_t BeginSDK = isysroot.rfind("SDKs/");
+        size_t EndSDK = isysroot.rfind(".sdk");
+        if (BeginSDK != StringRef::npos && EndSDK != StringRef::npos) {
+          StringRef SDK = isysroot.slice(BeginSDK + 5, EndSDK);
+          size_t StartVer = SDK.find_first_of("123456789");
+          if (StartVer != StringRef::npos) {
+            StringRef Version = SDK.substr(StartVer);
+            if (SDK.startswith("iPhoneOS") ||
+                SDK.startswith("iPhoneSimulator"))
+              iOSTarget = Version;
+            else if (SDK.startswith("MacOSX"))
+              OSXTarget = Version;
+          }
+        }
       }
     }
 
Index: cfe/trunk/test/Driver/darwin-sdkroot.c
===================================================================
--- cfe/trunk/test/Driver/darwin-sdkroot.c
+++ cfe/trunk/test/Driver/darwin-sdkroot.c
@@ -40,3 +40,38 @@
 //   env SDKROOT=/ cmd //c echo %SDKROOT%
 //
 // This test passes using env.exe from GnuWin32.
+
+// Check if clang set the correct deployment target from -sysroot
+//
+// RUN: rm -rf %t/SDKs/iPhoneOS8.0.0.sdk
+// RUN: mkdir -p %t/SDKs/iPhoneOS8.0.0.sdk
+// RUN: env SDKROOT=%t/SDKs/iPhoneOS8.0.0.sdk %clang -target arm64-apple-darwin %s -### 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-IPHONE %s
+//
+// CHECK-IPHONE: clang
+// CHECK-IPHONE: "-cc1"
+// CHECK-IPHONE: "-triple" "arm64-apple-ios8.0.0"
+// CHECK-IPHONE: ld
+// CHECK-IPHONE: "-iphoneos_version_min" "8.0.0"
+//
+// RUN: rm -rf %t/SDKs/iPhoneSimulator8.0.0.sdk
+// RUN: mkdir -p %t/SDKs/iPhoneSimulator8.0.0.sdk
+// RUN: env SDKROOT=%t/SDKs/iPhoneSimulator8.0.0.sdk %clang -target x86_64-apple-darwin %s -### 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-SIMULATOR %s
+//
+// CHECK-SIMULATOR: clang
+// CHECK-SIMULATOR: "-cc1"
+// CHECK-SIMULATOR: "-triple" "x86_64-apple-ios8.0.0"
+// CHECK-SIMULATOR: ld
+// CHECK-SIMULATOR: "-ios_simulator_version_min" "8.0.0"
+//
+// RUN: rm -rf %t/SDKs/MacOSX10.10.0.sdk
+// RUN: mkdir -p %t/SDKs/MacOSX10.10.0.sdk
+// RUN: env SDKROOT=%t/SDKs/MacOSX10.10.0.sdk %clang -target x86_64-apple-darwin %s -### 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MACOSX %s
+//
+// CHECK-MACOSX: clang
+// CHECK-MACOSX: "-cc1"
+// CHECK-MACOSX: "-triple" "x86_64-apple-macosx10.10.0"
+// CHECK-MACOSX: ld
+// CHECK-MACOSX: "-macosx_version_min" "10.10.0"