Index: clang/lib/Driver/ToolChains/OpenBSD.h
===================================================================
--- clang/lib/Driver/ToolChains/OpenBSD.h
+++ clang/lib/Driver/ToolChains/OpenBSD.h
@@ -65,6 +65,12 @@
     return ToolChain::CST_Libcxx;
   }
 
+  void
+  AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
+                            llvm::opt::ArgStringList &CC1Args) const override;
+
+  bool HasNativeLLVMSupport() const override;
+
   void AddCXXStdlibLibArgs(const llvm::opt::ArgList &Args,
                            llvm::opt::ArgStringList &CmdArgs) const override;
 
Index: clang/lib/Driver/ToolChains/OpenBSD.cpp
===================================================================
--- clang/lib/Driver/ToolChains/OpenBSD.cpp
+++ clang/lib/Driver/ToolChains/OpenBSD.cpp
@@ -10,10 +10,12 @@
 #include "Arch/Mips.h"
 #include "Arch/Sparc.h"
 #include "CommonArgs.h"
+#include "clang/Config/config.h"
 #include "clang/Driver/Compilation.h"
 #include "clang/Driver/Options.h"
 #include "clang/Driver/SanitizerArgs.h"
 #include "llvm/Option/ArgList.h"
+#include "llvm/Support/Path.h"
 
 using namespace clang::driver;
 using namespace clang::driver::tools;
@@ -276,3 +278,37 @@
                           options::OPT_fno_use_init_array, false))
     CC1Args.push_back("-fno-use-init-array");
 }
+
+void OpenBSD::AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
+                                        llvm::opt::ArgStringList &CC1Args) const {
+  const Driver &D = getDriver();
+
+  if (DriverArgs.hasArg(clang::driver::options::OPT_nostdinc))
+    return;
+
+  if (!DriverArgs.hasArg(options::OPT_nobuiltininc)) {
+    SmallString<128> Dir(D.ResourceDir);
+    llvm::sys::path::append(Dir, "include");
+    addSystemInclude(DriverArgs, CC1Args, Dir.str());
+  }
+
+  if (DriverArgs.hasArg(options::OPT_nostdlibinc))
+    return;
+
+  // Check for configure-time C include directories.
+  StringRef CIncludeDirs(C_INCLUDE_DIRS);
+  if (CIncludeDirs != "") {
+    SmallVector<StringRef, 5> dirs;
+    CIncludeDirs.split(dirs, ":");
+    for (StringRef dir : dirs) {
+      StringRef Prefix =
+          llvm::sys::path::is_absolute(dir) ? StringRef(D.SysRoot) : "";
+      addExternCSystemInclude(DriverArgs, CC1Args, Prefix + dir);
+    }
+    return;
+  }
+
+  addExternCSystemInclude(DriverArgs, CC1Args, D.SysRoot + "/usr/include");
+}
+
+bool OpenBSD::HasNativeLLVMSupport() const { return true; }