Index: include/clang/Driver/CLCompatOptions.td
===================================================================
--- include/clang/Driver/CLCompatOptions.td
+++ include/clang/Driver/CLCompatOptions.td
@@ -140,6 +140,8 @@
 
 def _SLASH_M_Group : OptionGroup<"</M group>">, Group<cl_compile_Group>;
 
+def _SLASH_EP : CLFlag<"EP">,
+  HelpText<"Disable linemarker output and preprocess to stdout">;
 def _SLASH_FA : CLFlag<"FA">,
   HelpText<"Output assembly code file during compilation">;
 def _SLASH_Fa : CLJoined<"Fa">,
@@ -205,7 +207,6 @@
 def _SLASH_d2Zi_PLUS : CLFlag<"d2Zi+">;
 def _SLASH_doc : CLJoined<"doc">;
 def _SLASH_EH : CLJoined<"EH">;
-def _SLASH_EP : CLFlag<"EP">;
 def _SLASH_FA_joined : CLJoined<"FA">;
 def _SLASH_favor : CLJoined<"favor">;
 def _SLASH_FC : CLFlag<"FC">;
Index: lib/Driver/Driver.cpp
===================================================================
--- lib/Driver/Driver.cpp
+++ lib/Driver/Driver.cpp
@@ -152,9 +152,10 @@
   Arg *PhaseArg = nullptr;
   phases::ID FinalPhase;
 
-  // -{E,M,MM} and /P only run the preprocessor.
+  // -{E,EP,P,M,MM} only run the preprocessor.
   if (CCCIsCPP() ||
       (PhaseArg = DAL.getLastArg(options::OPT_E)) ||
+      (PhaseArg = DAL.getLastArg(options::OPT__SLASH_EP)) ||
       (PhaseArg = DAL.getLastArg(options::OPT_M, options::OPT_MM)) ||
       (PhaseArg = DAL.getLastArg(options::OPT__SLASH_P))) {
     FinalPhase = phases::Preprocess;
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -4359,6 +4359,12 @@
   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);
Index: test/Driver/cl-options.c
===================================================================
--- test/Driver/cl-options.c
+++ test/Driver/cl-options.c
@@ -25,6 +25,11 @@
 // E: "-E"
 // E: "-o" "-"
 
+// RUN: %clang_cl /EP -### -- %s 2>&1 | FileCheck -check-prefix=EP %s
+// EP: "-E"
+// EP: "-P"
+// EP: "-o" "-"
+
 // RTTI is on by default; just check that we don't error.
 // RUN: %clang_cl /Zs /GR -- %s 2>&1
 
@@ -196,7 +201,6 @@
 // RUN:     /docname \
 // RUN:     /d2Zi+ \
 // RUN:     /EHsc \
-// RUN:     /EP \
 // RUN:     /F \
 // RUN:     /FA \
 // RUN:     /FAc \