diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 977f351..61887e8 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -133,6 +133,8 @@
     Res.push_back("-fno-common");
   if (Opts.ForbidGuardVariables)
     Res.push_back("-fforbid-guard-variables");
+  if (Opts.UseRegisterSizedBitfieldAccess)
+    Res.push_back("-fuse-register-sized-bitfield-access");
   if (Opts.NoImplicitFloat)
     Res.push_back("-no-implicit-float");
   if (Opts.OmitLeafFramePointer)
@@ -956,6 +958,8 @@
   Opts.DisableLLVMOpts = Args.hasArg(OPT_disable_llvm_optzns);
   Opts.DisableRedZone = Args.hasArg(OPT_disable_red_zone);
   Opts.ForbidGuardVariables = Args.hasArg(OPT_fforbid_guard_variables);
+  Opts.UseRegisterSizedBitfieldAccess = Args.hasArg(
+    OPT_fuse_register_sized_bitfield_access);
   Opts.RelaxedAliasing = Args.hasArg(OPT_relaxed_aliasing);
   Opts.DwarfDebugFlags = Args.getLastArgValue(OPT_dwarf_debug_flags);
   Opts.MergeAllConstants = !Args.hasArg(OPT_fno_merge_all_constants);