Add support for the /EP argument to clang-cl

This maps the /EP argument to both -E and -P.

Patch by Ehsan Akhgari!

Differential Reviion: http://reviews.llvm.org/D4133

llvm-svn: 210935
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 0df398b..e49267a 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -4363,6 +4363,12 @@
   if (!Args.hasArg(options::OPT_frtti, options::OPT_fno_rtti))
     CmdArgs.push_back("-fno-rtti");
 
+  // /EP should expand to -E -P.
+  if (Args.hasArg(options::OPT__SLASH_EP)) {
+    CmdArgs.push_back("-E");
+    CmdArgs.push_back("-P");
+  }
+
   const Driver &D = getToolChain().getDriver();
   Arg *MostGeneralArg = Args.getLastArg(options::OPT__SLASH_vmg);
   Arg *BestCaseArg = Args.getLastArg(options::OPT__SLASH_vmb);