Revert "[Driver] Support libc++ in MSVC"

This reverts commit 9625d61eb6 since
libc++ currently has issues with disabled exceptions which breaks
the runtimes build.

clang/include/clang/Driver/Options.td

@@ -3641,12 +3641,12 @@ def noprofilelib : Flag<["-"], "noprofilelib">;
 def noseglinkedit : Flag<["-"], "noseglinkedit">;
 def nostartfiles : Flag<["-"], "nostartfiles">, Group<Link_Group>;
 def nostdinc : Flag<["-"], "nostdinc">, Flags<[CoreOption]>;
-def nostdlibinc : Flag<["-"], "nostdlibinc">, Flags<[CoreOption]>;
-def nostdincxx : Flag<["-"], "nostdinc++">, Flags<[CC1Option, CoreOption]>,
+def nostdlibinc : Flag<["-"], "nostdlibinc">;
+def nostdincxx : Flag<["-"], "nostdinc++">, Flags<[CC1Option]>,
   HelpText<"Disable standard #include directories for the C++ standard library">,
   MarshallingInfoNegativeFlag<HeaderSearchOpts<"UseStandardCXXIncludes">>;
 def nostdlib : Flag<["-"], "nostdlib">, Group<Link_Group>;
-def nostdlibxx : Flag<["-"], "nostdlib++">, Group<Link_Group>;
+def nostdlibxx : Flag<["-"], "nostdlib++">;
 def object : Flag<["-"], "object">;
 def o : JoinedOrSeparate<["-"], "o">, Flags<[NoXarchOption, RenderAsInput,
   CC1Option, CC1AsOption, FC1Option, FlangOption]>,

clang/lib/Driver/ToolChains/MSVC.cpp

@@ -435,11 +435,6 @@ void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   if (!C.getDriver().IsCLMode() && Args.hasArg(options::OPT_L))
     for (const auto &LibPath : Args.getAllArgValues(options::OPT_L))
       CmdArgs.push_back(Args.MakeArgString("-libpath:" + LibPath));
-  // Add library directories for standard library shipped with the toolchain.
-  for (const auto &LibPath : TC.getFilePaths()) {
-    if (TC.getVFS().exists(LibPath))
-      CmdArgs.push_back(Args.MakeArgString("-libpath:" + LibPath));
-  }
 
   CmdArgs.push_back("-nologo");
 
@@ -1328,36 +1323,7 @@ void MSVCToolChain::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
 
 void MSVCToolChain::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
                                                  ArgStringList &CC1Args) const {
-  if (DriverArgs.hasArg(options::OPT_nostdlibinc) ||
-      DriverArgs.hasArg(options::OPT_nostdincxx))
-    return;
-
-  switch (GetCXXStdlibType(DriverArgs)) {
-  case ToolChain::CST_Libcxx: {
-    SmallString<128> P(getDriver().Dir);
-    llvm::sys::path::append(P, "..", "include");
-
-    std::string Version = detectLibcxxVersion(P);
-    if (Version.empty())
-      return;
-
-    // First add the per-target include path if it exists.
-    SmallString<128> TargetDir(P);
-    llvm::sys::path::append(TargetDir, getTripleString(), "c++", Version);
-    if (getVFS().exists(TargetDir))
-      addSystemInclude(DriverArgs, CC1Args, TargetDir);
-
-    // Second add the generic one.
-    SmallString<128> Dir(P);
-    llvm::sys::path::append(Dir, "c++", Version);
-    addSystemInclude(DriverArgs, CC1Args, Dir);
-    break;
-  }
-
-  default:
-    // TODO: Shall we report an error for other C++ standard libraries?
-    break;
-  }
+  // FIXME: There should probably be logic here to find libc++ on Windows.
 }
 
 VersionTuple MSVCToolChain::computeMSVCVersion(const Driver *D,

clang/test/Driver/msvc-libcxx.cpp

@@ -1,7 +0,0 @@
-// RUN: %clangxx -### %s 2>&1 -stdlib=libc++ -fuse-ld=lld \
-// RUN:   --target=x86_64-pc-windows-msvc \
-// RUN:   -ccc-install-dir %S/Inputs/msvc_libcxx_tree/usr/bin \
-// RUN:   | FileCheck %s -check-prefix MSVC-LIBCXX
-// MSVC-LIBCXX: "-internal-isystem" "{{.*[/\\]}}include{{/|\\\\}}x86_64-pc-windows-msvc{{/|\\\\}}c++{{/|\\\\}}v1"
-// MSVC-LIBCXX: "-internal-isystem" "{{.*[/\\]}}include{{/|\\\\}}c++{{/|\\\\}}v1"
-// MSVC-LIBCXX: "-libpath:{{.*}}{{/|\\\\}}..{{/|\\\\}}lib{{/|\\\\}}x86_64-pc-windows-msvc"