1 files changed, 13 insertions, 1 deletions
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 5b96120df97..e5f2681f7b3 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -6712,7 +6712,19 @@ Command *visualstudio::Compile::GetCommand(Compilation &C, const JobAction &JA,
   // These are spelled the same way in clang and cl.exe,.
   Args.AddAllArgs(CmdArgs, options::OPT_D, options::OPT_U);
   Args.AddAllArgs(CmdArgs, options::OPT_I);
-  Args.AddLastArg(CmdArgs, options::OPT_O, options::OPT_O0);
+
+  // Optimization level.
+  if (Arg *A = Args.getLastArg(options::OPT_O, options::OPT_O0)) {
+    if (A->getOption().getID() == options::OPT_O0) {
+      CmdArgs.push_back("/Od");
+    } else {
+      StringRef OptLevel = A->getValue();
+      if (OptLevel == "1" || OptLevel == "2" || OptLevel == "s")
+        A->render(Args, CmdArgs);
+      else if (OptLevel == "3")
+        CmdArgs.push_back("/Ox");
+    }
+  }
 
   // Flags for which clang-cl have an alias.
   // FIXME: How can we ensure this stays in sync with relevant clang-cl options?