Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -152,6 +152,9 @@
 def driver_mode : Joined<["--"], "driver-mode=">, Group<internal_driver_Group>,
   Flags<[CoreOption, DriverOption, HelpHidden]>,
   HelpText<"Set the driver mode to either 'gcc', 'g++', 'cpp', or 'cl'">;
+def rsp_quoting : Joined<["--"], "rsp-quoting=">, Group<internal_driver_Group>,
+  Flags<[CoreOption, DriverOption, HelpHidden]>,
+  HelpText<"Set the rsp quoting to either 'posix', or 'windows'">;
 def ccc_gcc_name : Separate<["-"], "ccc-gcc-name">, InternalDriverOpt,
   HelpText<"Name for native GCC compiler">,
   MetaVarName<"<gcc-path>">;
Index: lib/Driver/Driver.cpp
===================================================================
--- lib/Driver/Driver.cpp
+++ lib/Driver/Driver.cpp
@@ -1813,8 +1813,9 @@
   // Claim -### here.
   (void)C.getArgs().hasArg(options::OPT__HASH_HASH_HASH);
 
-  // Claim --driver-mode, it was handled earlier.
+  // Claim --driver-mode, --rsp-quoting, it was handled earlier.
   (void)C.getArgs().hasArg(options::OPT_driver_mode);
+  (void)C.getArgs().hasArg(options::OPT_rsp_quoting);
 
   for (Arg *A : C.getArgs()) {
     // FIXME: It would be nice to be able to send the argument to the
Index: test/Driver/at_file.c
===================================================================
--- test/Driver/at_file.c
+++ test/Driver/at_file.c
@@ -14,9 +14,9 @@
 // CHECK-NEXT: foo9'bar9'zed9
 // CHECK-NEXT: foo10"bar10"zed10
 // CHECK: bar
-// CHECK: zed12
+// CHECK: zed1
 // CHECK: one\two
-// CHECK: c:\foo\bar.c
+// CHECK: c:foobar.c
 
 foo1
 foo2
Index: test/Driver/at_file.c.args
===================================================================
--- test/Driver/at_file.c.args
+++ test/Driver/at_file.c.args
@@ -8,6 +8,7 @@
 -Dfoo9=foo9\'bar9\'zed9
 -Dfoo10=foo10\"bar10\"zed10
 -D foo11
--Dfoo12=zed12\
+-Dfoo12=zed1\
+2
 -Dfoo13='one\\two'
 -Dfoo14='c:\foo\bar.c'
Index: test/Driver/at_file_win.c
===================================================================
--- test/Driver/at_file_win.c
+++ test/Driver/at_file_win.c
@@ -0,0 +1,34 @@
+// RUN: %clang --rsp-quoting=windows -E %s @%s.args -o %t.log
+// RUN: FileCheck --input-file=%t.log %s
+
+// CHECK: bar1
+// CHECK-NEXT: bar2 zed2
+// CHECK-NEXT: bar3 zed3
+// CHECK-NEXT: bar4 zed4
+// CHECK-NEXT: bar5 zed5
+// CHECK-NEXT: 'bar6 zed6'
+// CHECK-NEXT: 'bar7 zed7'
+// CHECK-NEXT: foo8bar8zed8
+// CHECK-NEXT: foo9\'bar9\'zed9
+// CHECK-NEXT: foo10"bar10"zed10
+// CHECK: bar
+// CHECK: zed12
+// CHECK: one\two
+// CHECK: c:\foo\bar.c
+
+foo1
+foo2
+foo3
+foo4
+foo5
+foo6
+foo7
+foo8
+foo9
+foo10
+#ifdef foo11
+bar
+#endif
+foo12
+foo13
+foo14
Index: test/Driver/at_file_win.c.args
===================================================================
--- test/Driver/at_file_win.c.args
+++ test/Driver/at_file_win.c.args
@@ -0,0 +1,13 @@
+-Dfoo1=bar1 -Dfoo2="bar2 zed2"
+-Dfoo3="bar3 zed3"
+"-Dfoo4=bar4 zed4"
+"-Dfoo5=bar5 zed5"
+-Dfoo6="'bar6 zed6'"
+-Dfoo7='"bar7 zed7"'
+-Dfoo8=foo8"bar8"zed8
+-Dfoo9=foo9\'bar9\'zed9
+-Dfoo10=foo10\"bar10\"zed10
+-D foo11
+-Dfoo12=zed12
+-Dfoo13=one\two
+-Dfoo14=c:\foo\bar.c
Index: tools/driver/driver.cpp
===================================================================
--- tools/driver/driver.cpp
+++ tools/driver/driver.cpp
@@ -345,17 +345,24 @@
       }) != argv.end()) {
     ClangCLMode = true;
   }
+  enum { Default, POSIX, Windows } RSPQuoting = Default;
+  for (const char *F : argv) {
+    if (strcmp(F, "--rsp-quoting=posix") == 0)
+      RSPQuoting = POSIX;
+    else if (strcmp(F, "--rsp-quoting=windows") == 0)
+      RSPQuoting = Windows;
+  }
 
   // Determines whether we want nullptr markers in argv to indicate response
   // files end-of-lines. We only use this for the /LINK driver argument with
   // clang-cl.exe on Windows.
-  bool MarkEOLs = false;
+  bool MarkEOLs = ClangCLMode;
 
-  llvm::cl::TokenizerCallback Tokenizer = &llvm::cl::TokenizeGNUCommandLine;
-  if (ClangCLMode) {
+  llvm::cl::TokenizerCallback Tokenizer;
+  if (RSPQuoting == Windows || (RSPQuoting == Default && ClangCLMode))
     Tokenizer = &llvm::cl::TokenizeWindowsCommandLine;
-    MarkEOLs = true;
-  }
+  else
+    Tokenizer = &llvm::cl::TokenizeGNUCommandLine;
 
   if (MarkEOLs && argv.size() > 1 && StringRef(argv[1]).startswith("-cc1"))
     MarkEOLs = false;