diff --git a/include/clang/Driver/CC1Options.td b/include/clang/Driver/CC1Options.td
index fdc073b..6ac40f5 100644
--- a/include/clang/Driver/CC1Options.td
+++ b/include/clang/Driver/CC1Options.td
@@ -210,6 +210,8 @@
   HelpText<"Run the SLP vectorization passes">;
 def vectorize_slp_aggressive : Flag<["-"], "vectorize-slp-aggressive">,
   HelpText<"Run the BB vectorization passes">;
+def dependent_lib : Joined<["--"], "dependent-lib=">,
+  HelpText<"Add dependent library">;
 
 //===----------------------------------------------------------------------===//
 // Dependency Output Options
diff --git a/include/clang/Driver/CLCompatOptions.td b/include/clang/Driver/CLCompatOptions.td
index b29fc88..e98d8e8 100644
--- a/include/clang/Driver/CLCompatOptions.td
+++ b/include/clang/Driver/CLCompatOptions.td
@@ -86,6 +86,12 @@
 def _SLASH_Fo : CLJoined<"Fo">,
   HelpText<"Set output object file, or directory (ends in / or \\)">,
   MetaVarName<"<file or directory>">;
+def _SLASH_MD : CLFlag<"MD">,
+  HelpText<"Use DLL run-time">;
+def _SLASH_MDd : CLFlag<"MDd">,
+  HelpText<"Use DLL debug run-time">;
+def _SLASH_MT : CLFlag<"MT">, HelpText<"Use static run-time">;
+def _SLASH_MTd : CLFlag<"MTd">, HelpText<"Use static debug run-time">;
 def _SLASH_Tc : CLJoinedOrSeparate<"Tc">, HelpText<"Specify a C source file">,
   MetaVarName<"<filename>">;
 def _SLASH_TC : CLFlag<"TC">, HelpText<"Treat all source files as C">;
@@ -119,10 +125,6 @@
 def _SLASH_Gy : CLFlag<"Gy">;
 def _SLASH_Gy_ : CLFlag<"Gy-">;
 def _SLASH_GZ : CLFlag<"GZ">;
-def _SLASH_MD : CLFlag<"MD">;
-def _SLASH_MT : CLFlag<"MT">;
-def _SLASH_MDd : CLFlag<"MDd">;
-def _SLASH_MTd : CLFlag<"MTd">;
 def _SLASH_Oi : CLFlag<"Oi">;
 def _SLASH_RTC : CLJoined<"RTC">;
 def _SLASH_showIncludes : CLJoined<"showIncludes">;
diff --git a/include/clang/Frontend/CodeGenOptions.h b/include/clang/Frontend/CodeGenOptions.h
index 6717791..45d2bda 100644
--- a/include/clang/Frontend/CodeGenOptions.h
+++ b/include/clang/Frontend/CodeGenOptions.h
@@ -128,6 +128,9 @@
   /// A list of command-line options to forward to the LLVM backend.
   std::vector<std::string> BackendOptions;
 
+  /// A list of dependent libraries.
+  std::vector<std::string> DependentLibraries;
+
 public:
   // Define accessors/mutators for code generation options of enumeration type.
 #define CODEGENOPT(Name, Bits, Default)
diff --git a/lib/CodeGen/ModuleBuilder.cpp b/lib/CodeGen/ModuleBuilder.cpp
index 7e0e3aa..c6d4033 100644
--- a/lib/CodeGen/ModuleBuilder.cpp
+++ b/lib/CodeGen/ModuleBuilder.cpp
@@ -60,6 +60,9 @@
       TD.reset(new llvm::DataLayout(Ctx->getTargetInfo().getTargetDescription()));
       Builder.reset(new CodeGen::CodeGenModule(Context, CodeGenOpts, *M, *TD,
                                                Diags));
+
+      for (size_t i = 0, e = CodeGenOpts.DependentLibraries.size(); i < e; ++i)
+        HandleDependentLibrary(CodeGenOpts.DependentLibraries[i]);
     }
 
     virtual void HandleCXXStaticMemberVarInstantiation(VarDecl *VD) {
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 4a3ce42..e4acadb 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -2516,6 +2516,10 @@
     break;
   }
 
+  // Add clang-cl arguments.
+  if (getToolChain().getDriver().IsCLMode())
+    AddClangCLArgs(Args, CmdArgs);
+
   // Pass the linker version in use.
   if (Arg *A = Args.getLastArg(options::OPT_mlinker_version_EQ)) {
     CmdArgs.push_back("-target-linker-version");
@@ -3803,6 +3807,47 @@
   return runtime;
 }
 
+void Clang::AddClangCLArgs(const ArgList &Args, ArgStringList &CmdArgs) const {
+  unsigned RTOptionID = options::OPT__SLASH_MT;
+
+  if (Arg *A = Args.getLastArg(options::OPT__SLASH_MD,
+                               options::OPT__SLASH_MDd,
+                               options::OPT__SLASH_MT,
+                               options::OPT__SLASH_MTd)) {
+    RTOptionID = A->getOption().getID();
+  }
+
+  switch(RTOptionID) {
+    case options::OPT__SLASH_MD:
+      CmdArgs.push_back("-D_MT");
+      CmdArgs.push_back("-D_DLL");
+      CmdArgs.push_back("--dependent-lib=msvcrt");
+      break;
+    case options::OPT__SLASH_MDd:
+      CmdArgs.push_back("-D_DEBUG");
+      CmdArgs.push_back("-D_MT");
+      CmdArgs.push_back("-D_DLL");
+      CmdArgs.push_back("--dependent-lib=msvcrtd");
+      break;
+    case options::OPT__SLASH_MT:
+      CmdArgs.push_back("-D_MT");
+      CmdArgs.push_back("--dependent-lib=libcmt");
+      break;
+    case options::OPT__SLASH_MTd:
+      CmdArgs.push_back("-D_DEBUG");
+      CmdArgs.push_back("-D_MT");
+      CmdArgs.push_back("--dependent-lib=libcmtd");
+      break;
+    default:
+      llvm_unreachable("Unexpected option ID.");
+  }
+
+  // This provides POSIX compatibility (maps 'open' to '_open'), which most users
+  // want.  MSVC has a switch to turn off this autolinking, but it's not
+  // implemented in clang yet.
+  CmdArgs.push_back("--dependent-lib=oldnames");
+}
+
 void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,
                            const InputInfo &Output,
                            const InputInfoList &Inputs,
diff --git a/lib/Driver/Tools.h b/lib/Driver/Tools.h
index 9138ddf..8c1e695 100644
--- a/lib/Driver/Tools.h
+++ b/lib/Driver/Tools.h
@@ -74,6 +74,9 @@
                                    llvm::opt::ArgStringList &cmdArgs,
                                    RewriteKind rewrite) const;
 
+    void AddClangCLArgs(const llvm::opt::ArgList &Args,
+                        llvm::opt::ArgStringList &CmdArgs) const;
+
   public:
     Clang(const ToolChain &TC) : Tool("clang", "clang frontend", TC) {}
 
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 27ddd84..a4c93fa 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -502,6 +502,8 @@
     }
   }
 
+  Opts.DependentLibraries = Args.getAllArgValues(OPT_dependent_lib);
+
   return Success;
 }
 
diff --git a/test/CodeGen/dependent-lib.c b/test/CodeGen/dependent-lib.c
new file mode 100644
index 0000000..df4aaf0
--- /dev/null
+++ b/test/CodeGen/dependent-lib.c
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 %s --dependent-lib=msvcrt -triple i686-pc-win32 -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 %s --dependent-lib=msvcrt -triple x86_64-pc-win32 -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 %s --dependent-lib=msvcrt -triple i686-pc-linux -emit-llvm -o - | FileCheck -check-prefix LINUX %s
+
+// CHECK: !llvm.module.flags = !{!0}
+// CHECK: !0 = metadata !{i32 6, metadata !"Linker Options", metadata ![[link_opts:[0-9]+]]}
+// CHECK: ![[link_opts]] = metadata !{metadata ![[msvcrt:[0-9]+]]}
+// CHECK: ![[msvcrt]] = metadata !{metadata !"/DEFAULTLIB:msvcrt.lib"}
+
+// LINUX: !llvm.module.flags = !{!0}
+// LINUX: !0 = metadata !{i32 6, metadata !"Linker Options", metadata ![[link_opts:[0-9]+]]}
+// LINUX: ![[link_opts]] = metadata !{metadata ![[msvcrt:[0-9]+]]}
+// LINUX: ![[msvcrt]] = metadata !{metadata !"-lmsvcrt"}
+
+int f();
diff --git a/test/Driver/cl-options.c b/test/Driver/cl-options.c
index ba1c1f3..d37e88e 100644
--- a/test/Driver/cl-options.c
+++ b/test/Driver/cl-options.c
@@ -89,6 +89,6 @@
 // Unsupported but parsed options. Check that we don't error on them.
 // (/Zs is for syntax-only)
 // RUN: %clang_cl /Zs /EHsc /Fdfoo /fp:precise /Gd /GL /GL- -- %s 2>&1
-// RUN: %clang_cl /Zs /Gm /Gm- /GS /Gy /Gy- /GZ /MD /MT /MDd /MTd /Oi -- %s 2>&1
+// RUN: %clang_cl /Zs /Gm /Gm- /GS /Gy /Gy- /GZ /Oi -- %s 2>&1
 // RUN: %clang_cl /Zs /RTC1 /wfoo /Zc:wchar_t- -- %s 2>&1
 // RUN: %clang_cl /Zs /ZI /Zi /showIncludes -- %s 2>&1
diff --git a/test/Driver/cl-runtime-flags.c b/test/Driver/cl-runtime-flags.c
new file mode 100644
index 0000000..520093c
--- /dev/null
+++ b/test/Driver/cl-runtime-flags.c
@@ -0,0 +1,41 @@
+// Don't attempt slash switches on msys bash.
+// REQUIRES: shell-preserves-root
+
+// Note: %s must be preceded by --, otherwise it may be interpreted as a
+// command-line option, e.g. on Mac where %s is commonly under /Users.
+
+// First check that regular clang doesn't do any of this stuff.
+// RUN: %clang -### %s 2>&1 | FileCheck -check-prefix=CHECK-CLANG %s
+// CHECK-CLANG-NOT: "-D_DEBUG"
+// CHECK-CLANG-NOT: "-D_MT"
+// CHECK-CLANG-NOT: "-D_DLL"
+// CHECK-CLANG-NOT: --dependent-lib
+
+// RUN: %clang_cl -### -- %s 2>&1 | FileCheck -check-prefix=CHECK-MT %s
+// RUN: %clang_cl -### /MT -- %s 2>&1 | FileCheck -check-prefix=CHECK-MT %s
+// CHECK-MT-NOT: "-D_DEBUG"
+// CHECK-MT: "-D_MT"
+// CHECK-MT-NOT: "-D_DLL"
+// CHECK-MT: "--dependent-lib=libcmt"
+// CHECK-MT: "--dependent-lib=oldnames"
+
+// RUN: %clang_cl -### /MTd -- %s 2>&1 | FileCheck -check-prefix=CHECK-MTd %s
+// CHECK-MTd: "-D_DEBUG"
+// CHECK-MTd: "-D_MT"
+// CHECK-MTd-NOT: "-D_DLL"
+// CHECK-MTd: "--dependent-lib=libcmtd"
+// CHECK-MTd: "--dependent-lib=oldnames"
+
+// RUN: %clang_cl -### /MD -- %s 2>&1 | FileCheck -check-prefix=CHECK-MD %s
+// CHECK-MD-NOT: "-D_DEBUG"
+// CHECK-MD: "-D_MT"
+// CHECK-MD: "-D_DLL"
+// CHECK-MD: "--dependent-lib=msvcrt"
+// CHECK-MD: "--dependent-lib=oldnames"
+
+// RUN: %clang_cl -### /MDd -- %s 2>&1 | FileCheck -check-prefix=CHECK-MDd %s
+// CHECK-MDd: "-D_DEBUG"
+// CHECK-MDd: "-D_MT"
+// CHECK-MDd: "-D_DLL"
+// CHECK-MDd: "--dependent-lib=msvcrtd"
+// CHECK-MDd: "--dependent-lib=oldnames"