Index: lib/Driver/MSVCToolChain.cpp
===================================================================
--- lib/Driver/MSVCToolChain.cpp
+++ lib/Driver/MSVCToolChain.cpp
@@ -212,6 +212,73 @@
   return hasSDKDir && !path.empty();
 }
 
+// Gets the library path required to link against the Windows SDK.
+bool MSVCToolChain::getWindowsSDKLibraryPath(std::string &path) const {
+  std::string sdkPath;
+  int sdkMajor = 0;
+  int sdkMinor = 0;
+
+  path.clear();
+  if (!getWindowsSDKDir(sdkPath, sdkMajor, sdkMinor))
+    return false;
+
+  llvm::SmallString<128> libPath(sdkPath);
+  llvm::sys::path::append(libPath, "Lib");
+  if (sdkMajor <= 7) {
+    switch (getArch()) {
+    // In Windows SDK 7.x, x86 libraries are directly in the Lib folder.
+    case llvm::Triple::x86:
+      break;
+    case llvm::Triple::x86_64:
+      llvm::sys::path::append(libPath, "x64");
+      break;
+    case llvm::Triple::arm:
+      // It is not necessary to link against Windows SDK 7.x when targeting ARM.
+      libPath.clear();
+      return false;
+    default:
+      return false;
+    }
+  } else {
+    // Windows SDK 8.x installs libraries in an folder whose names depend on
+    // the version of the OS you're targeting.  By default choose the newest,
+    // which usually will correspond to the version of the OS you've installed
+    // the SDK on.
+    char *tests[] = {"winv6.3", "win8", "win7"};
+    bool found = false;
+    for (char *test : tests) {
+      llvm::SmallString<128> testPath(libPath);
+      llvm::sys::path::append(testPath, test);
+      if (llvm::sys::fs::exists(testPath.c_str())) {
+        libPath = testPath;
+        found = true;
+        break;
+      }
+    }
+
+    if (!found)
+      return false;
+
+    llvm::sys::path::append(libPath, "um");
+    switch (getArch()) {
+    case llvm::Triple::x86:
+      llvm::sys::path::append(libPath, "x86");
+      break;
+    case llvm::Triple::x86_64:
+      llvm::sys::path::append(libPath, "x64");
+      break;
+    case llvm::Triple::arm:
+      llvm::sys::path::append(libPath, "arm");
+      break;
+    default:
+      return false;
+    }
+  }
+
+  path = libPath.str();
+  return true;
+}
+
 // Get the location to use for Visual Studio binaries.  The location priority
 // is: %VCINSTALLDIR% > %PATH% > newest copy of Visual Studio installed on
 // system (as reported by the registry).
Index: lib/Driver/ToolChains.h
===================================================================
--- lib/Driver/ToolChains.h
+++ lib/Driver/ToolChains.h
@@ -746,6 +746,7 @@
                                llvm::opt::ArgStringList &CC1Args) const override;
 
   bool getWindowsSDKDir(std::string &path, int &major, int &minor) const;
+  bool getWindowsSDKLibraryPath(std::string &path) const;
   bool getVisualStudioInstallDir(std::string &path) const;
   bool getVisualStudioBinariesFolder(const char *clangProgramPath,
                                      std::string &path) const;
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -7854,6 +7854,39 @@
     CmdArgs.push_back("-defaultlib:libcmt");
   }
 
+  if (!llvm::sys::Process::GetEnv("LIB")) {
+    // If the VC environment hasn't been configured (perhaps because the user
+    // did not run vcvarsall), try to build a consistent link environment.  If
+    // the environment variable is set however, assume the user knows what he's
+    // doing.
+    std::string VisualStudioDir;
+    const auto &MSVC = static_cast<const toolchains::MSVCToolChain &>(getToolChain());
+    if (MSVC.getVisualStudioInstallDir(VisualStudioDir)) {
+      SmallString<128> LibDir(VisualStudioDir);
+      llvm::sys::path::append(LibDir, "VC", "lib");
+      switch (MSVC.getArch()) {
+      case llvm::Triple::x86:
+        // x86 just puts the libraries directly in lib
+        break;
+      case llvm::Triple::x86_64:
+        llvm::sys::path::append(LibDir, "amd64");
+        break;
+      case llvm::Triple::arm:
+        llvm::sys::path::append(LibDir, "arm");
+        break;
+      default:
+        break;
+      }
+      CmdArgs.push_back(
+          Args.MakeArgString(std::string("-libpath:") + LibDir.c_str()));
+    }
+
+    std::string WindowsSdkLibPath;
+    if (MSVC.getWindowsSDKLibraryPath(WindowsSdkLibPath))
+      CmdArgs.push_back(Args.MakeArgString(std::string("-libpath:") +
+                                           WindowsSdkLibPath.c_str()));
+  }
+
   CmdArgs.push_back("-nologo");
 
   if (Args.hasArg(options::OPT_g_Group)) {