[clang-cl] Implement /X

[thakis]

Summary

/X makes cl stop looking in %INCLUDE%. Implement this for clang-cl.

As it turns out, the return in ToolChains/MSVC.cpp, AddClangSystemIncludeArgs() for -nostdlibinc is already in the right place (but -nostdlibinc isn't exposed by clang-cl), so just alias /X to that.

[hans]

lgtm

Nicely tested too :-)

[thakis]

r326357, thanks!

include/clang/Driver/CLCompatOptions.td

 def _SLASH_wd4100 : CLFlag<"wd4100">, Alias<W_Joined>,
   AliasArgs<["no-unused-parameter"]>;
 def _SLASH_wd4910 : CLFlag<"wd4910">, Alias<W_Joined>,
   AliasArgs<["no-dllexport-explicit-instantiation-decl"]>;
 def _SLASH_wd4996 : CLFlag<"wd4996">, Alias<W_Joined>,
   AliasArgs<["no-deprecated-declarations"]>;
 def _SLASH_vd : CLJoined<"vd">, HelpText<"Control vtordisp placement">,
   Alias<vtordisp_mode_EQ>;
+def _SLASH_X : CLFlag<"X">,
+  HelpText<"Don't add %INCLUDE% to the include search path">,
+  Alias<nostdlibinc>;
 def _SLASH_Zc_sizedDealloc : CLFlag<"Zc:sizedDealloc">,
   HelpText<"Enable C++14 sized global deallocation functions">,
   Alias<fsized_deallocation>;
 def _SLASH_Zc_sizedDealloc_ : CLFlag<"Zc:sizedDealloc-">,
   HelpText<"Disable C++14 sized global deallocation functions">,
   Alias<fno_sized_deallocation>;
 def _SLASH_Zc_strictStrings : CLFlag<"Zc:strictStrings">,
   HelpText<"Treat string literals as const">, Alias<W_Joined>,

 def _SLASH_QIfist : CLFlag<"QIfist">;
 def _SLASH_Qimprecise_fwaits : CLFlag<"Qimprecise_fwaits">;
 def _SLASH_Qpar : CLFlag<"Qpar">;
 def _SLASH_Qvec_report : CLJoined<"Qvec-report">;
 def _SLASH_u : CLFlag<"u">;
 def _SLASH_V : CLFlag<"V">;
 def _SLASH_WL : CLFlag<"WL">;
 def _SLASH_Wp64 : CLFlag<"Wp64">;
-def _SLASH_X : CLFlag<"X">;
 def _SLASH_Yd : CLFlag<"Yd">;
 def _SLASH_Yl : CLJoined<"Yl">;
 def _SLASH_Za : CLFlag<"Za">;
 def _SLASH_Zc : CLJoined<"Zc:">;
 def _SLASH_Ze : CLFlag<"Ze">;
 def _SLASH_Zg : CLFlag<"Zg">;
 def _SLASH_ZI : CLFlag<"ZI">;
 def _SLASH_ZW : CLJoined<"ZW">;

test/Driver/cl-include.c

 // 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.
 
 // RUN: %clang_cl -### -- %s 2>&1 | FileCheck %s --check-prefix=BUILTIN
 // BUILTIN: "-internal-isystem" "{{.*lib.*clang.*include}}"
 
 // RUN: %clang_cl -nobuiltininc -### -- %s 2>&1 | FileCheck %s --check-prefix=NOBUILTIN
 // NOBUILTIN-NOT: "-internal-isystem" "{{.*lib.*clang.*include}}"
 
 // RUN: env INCLUDE=/my/system/inc %clang_cl -### -- %s 2>&1 | FileCheck %s --check-prefix=STDINC
 // STDINC: "-internal-isystem" "/my/system/inc"
 
-// RUN: env INCLUDE=/my/system/inc %clang_cl -nostdinc -### -- %s 2>&1 | FileCheck %s --check-prefix=NOSTDINC
+// -nostdinc suppresses all of %INCLUDE%, clang resource dirs, and -imsvc dirs.
+// RUN: env INCLUDE=/my/system/inc %clang_cl -nostdinc -imsvc /my/other/inc -### -- %s 2>&1 | FileCheck %s --check-prefix=NOSTDINC
+// NOSTDINC: argument unused{{.*}}-imsvc
 // NOSTDINC-NOT: "-internal-isystem" "/my/system/inc"
+// NOSTDINC-NOT: "-internal-isystem" "{{.*}}/lib/clang/{{.*}}/include"
+// NOSTDINC-NOT: "-internal-isystem" "/my/other/inc"
+
+// /X suppresses %INCLUDE% but not clang resource dirs or -imsvc dirs.
+// RUN: env INCLUDE=/my/system/inc %clang_cl /X -imsvc /my/other/inc -### -- %s 2>&1 | FileCheck %s --check-prefix=SLASHX
+// SLASHX-NOT: "argument unused{{.*}}-imsvc"
+// SLASHX-NOT: "-internal-isystem" "/my/system/inc"
+// SLASHX: "-internal-isystem" "{{.*}}/lib/clang/{{.*}}/include"
+// SLASHX: "-internal-isystem" "/my/other/inc"