[clang] [Clang] [Driver] add a Cygwin ToolChain (PR #135691)

[Brad Smith via cfe-commits]

================
@@ -180,35 +170,14 @@ bool InitHeaderSearch::AddUnmappedPath(const Twine &Path, IncludeDirGroup Group,
   return false;
 }
 
-void InitHeaderSearch::AddMinGWCPlusPlusIncludePaths(StringRef Base,
-                                                     StringRef Arch,
-                                                     StringRef Version) {
-  AddPath(Base + "/" + Arch + "/" + Version + "/include/c++",
-          CXXSystem, false);
-  AddPath(Base + "/" + Arch + "/" + Version + "/include/c++/" + Arch,
-          CXXSystem, false);
-  AddPath(Base + "/" + Arch + "/" + Version + "/include/c++/backward",
-          CXXSystem, false);
-}
-
 void InitHeaderSearch::AddDefaultCIncludePaths(const llvm::Triple &triple,
                                             const HeaderSearchOptions &HSOpts) {
   if (!ShouldAddDefaultIncludePaths(triple))
     llvm_unreachable("Include management is handled in the driver.");
 
-  llvm::Triple::OSType os = triple.getOS();
-
   if (HSOpts.UseStandardSystemIncludes) {
-    switch (os) {
-    case llvm::Triple::Win32:
-      if (triple.getEnvironment() != llvm::Triple::Cygnus)
-        break;
-      [[fallthrough]];
-    default:
-      // FIXME: temporary hack: hard-coded paths.
-      AddPath("/usr/local/include", System, false);
-      break;
-    }
+    // FIXME: temporary hack: hard-coded paths.
----------------
brad0 wrote:

> Won't this change here cause win32-non-cygwin (e.g. mingw) to end up adding this path, where it wasn't added before?

No, adding Win32 to ShouldAddDefaultIncludePaths means not utilizing this code path.

> Then again, it looks like the removed switch below indicates that we never hit the win32 case here before, except for cygwin.

Correct.

https://github.com/llvm/llvm-project/pull/135691