diff --git a/clang/lib/Driver/ToolChains/DragonFly.h b/clang/lib/Driver/ToolChains/DragonFly.h
--- a/clang/lib/Driver/ToolChains/DragonFly.h
+++ b/clang/lib/Driver/ToolChains/DragonFly.h
@@ -55,6 +55,13 @@
 
   bool IsMathErrnoDefault() const override { return false; }
 
+  void
+  AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
+                            llvm::opt::ArgStringList &CC1Args) const override;
+  void addLibStdCxxIncludePaths(
+      const llvm::opt::ArgList &DriverArgs,
+      llvm::opt::ArgStringList &CC1Args) const override;
+
 protected:
   Tool *buildAssembler() const override;
   Tool *buildLinker() const override;
diff --git a/clang/lib/Driver/ToolChains/DragonFly.cpp b/clang/lib/Driver/ToolChains/DragonFly.cpp
--- a/clang/lib/Driver/ToolChains/DragonFly.cpp
+++ b/clang/lib/Driver/ToolChains/DragonFly.cpp
@@ -8,10 +8,12 @@
 
 #include "DragonFly.h"
 #include "CommonArgs.h"
+#include "clang/Config/config.h"
 #include "clang/Driver/Compilation.h"
 #include "clang/Driver/Driver.h"
 #include "clang/Driver/Options.h"
 #include "llvm/Option/ArgList.h"
+#include "llvm/Support/Path.h"
 
 using namespace clang::driver;
 using namespace clang::driver::tools;
@@ -195,6 +197,46 @@
   getFilePaths().push_back("/usr/lib/gcc80");
 }
 
+void DragonFly::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,
+                          concat(D.SysRoot, "/usr/include"));
+}
+
+void DragonFly::addLibStdCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
+                                         llvm::opt::ArgStringList &CC1Args) const {
+  addLibStdCXXIncludePaths(concat(getDriver().SysRoot, "/usr/include/c++/8.0"), "", "",
+                           DriverArgs, CC1Args);
+}
+
 Tool *DragonFly::buildAssembler() const {
   return new tools::dragonfly::Assembler(*this);
 }
diff --git a/clang/lib/Lex/InitHeaderSearch.cpp b/clang/lib/Lex/InitHeaderSearch.cpp
--- a/clang/lib/Lex/InitHeaderSearch.cpp
+++ b/clang/lib/Lex/InitHeaderSearch.cpp
@@ -329,9 +329,6 @@
       break;
     }
     break;
-  case llvm::Triple::DragonFly:
-    AddPath("/usr/include/c++/5.0", CXXSystem, false);
-    break;
   case llvm::Triple::Minix:
     AddGnuCPlusPlusIncludePaths("/usr/gnu/include/c++/4.4.3",
                                 "", "", "", triple);
@@ -345,6 +342,7 @@
     const llvm::Triple &triple) {
   switch (triple.getOS()) {
   case llvm::Triple::AIX:
+  case llvm::Triple::DragonFly:
   case llvm::Triple::Emscripten:
   case llvm::Triple::FreeBSD:
   case llvm::Triple::NetBSD: