Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -1950,6 +1950,8 @@
   HelpText<"Force linking the clang builtins runtime library">;
 def flto_EQ : Joined<["-"], "flto=">, Flags<[CoreOption, CC1Option]>, Group<f_Group>,
   HelpText<"Set LTO mode to either 'full' or 'thin'">, Values<"thin,full">;
+def flto_EQ_jobserver : Flag<["-"], "flto=jobserver">, Group<f_Group>;
+def flto_EQ_auto : Flag<["-"], "flto=auto">, Group<f_Group>;
 def flto : Flag<["-"], "flto">, Flags<[CoreOption, CC1Option]>, Group<f_Group>,
   HelpText<"Enable LTO in 'full' mode">;
 def fno_lto : Flag<["-"], "fno-lto">, Flags<[CoreOption, CC1Option]>, Group<f_Group>,
@@ -4244,8 +4246,6 @@
 defm branch_count_reg : BooleanFFlag<"branch-count-reg">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm default_inline : BooleanFFlag<"default-inline">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm fat_lto_objects : BooleanFFlag<"fat-lto-objects">, Group<clang_ignored_gcc_optimization_f_Group>;
-def : Flag<["-"], "flto=auto">, Group<clang_ignored_gcc_optimization_f_Group>;
-def : Flag<["-"], "flto=jobserver">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm float_store : BooleanFFlag<"float-store">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm friend_injection : BooleanFFlag<"friend-injection">, Group<clang_ignored_f_Group>;
 defm function_attribute_list : BooleanFFlag<"function-attribute-list">, Group<clang_ignored_f_Group>;
Index: clang/lib/Driver/Driver.cpp
===================================================================
--- clang/lib/Driver/Driver.cpp
+++ clang/lib/Driver/Driver.cpp
@@ -598,7 +598,9 @@
 void Driver::setLTOMode(const llvm::opt::ArgList &Args) {
   LTOMode = LTOK_None;
   if (!Args.hasFlag(options::OPT_flto, options::OPT_flto_EQ,
-                    options::OPT_fno_lto, false))
+                    options::OPT_fno_lto, false) &&
+      !Args.hasArg(options::OPT_flto_EQ_auto) &&
+      !Args.hasArg(options::OPT_flto_EQ_jobserver))
     return;
 
   StringRef LTOName("full");
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -4454,7 +4454,14 @@
                                    JA.isDeviceOffloading(Action::OFK_Host));
 
     if (D.isUsingLTO() && !isDeviceOffloadAction) {
-      Args.AddLastArg(CmdArgs, options::OPT_flto, options::OPT_flto_EQ);
+      if (Args.hasArg(options::OPT_flto))
+        CmdArgs.push_back("-flto");
+      else {
+        if (D.getLTOMode() == LTOK_Thin)
+          CmdArgs.push_back("-flto=thin");
+        else
+          CmdArgs.push_back("-flto=full");
+      }
       CmdArgs.push_back("-flto-unit");
     }
   }
Index: clang/test/Driver/lto.c
===================================================================
--- clang/test/Driver/lto.c
+++ clang/test/Driver/lto.c
@@ -77,3 +77,11 @@
 //
 // CHECK-TUNING-LLDB:   "-plugin-opt=-debugger-tune=lldb"
 // CHECK-NO-TUNING-NOT: "-plugin-opt=-debugger-tune
+//
+// -flto=auto and -flto=jobserver pass along -flto=full
+// RUN: %clang -target x86_64-unknown-linux -### %s -flto=auto 2>&1 | FileCheck --check-prefix=FLTO-AUTO %s
+// RUN: %clang -target x86_64-unknown-linux -### %s -flto=jobserver 2>&1 | FileCheck --check-prefix=FLTO-JOBSERVER %s
+//
+// FLTO-AUTO: -flto=full
+// FLTO-JOBSERVER: -flto=full
+//