Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -2033,9 +2033,14 @@
 def mfancy_math_387 : Flag<["-"], "mfancy-math-387">, Group<clang_ignored_m_Group>;
 def mlong_calls : Flag<["-"], "mlong-calls">, Group<m_Group>,
   HelpText<"Generate branches with extended addressability, usually via indirect jumps.">;
-def mlong_double_64 : Flag<["-"], "mlong-double-64">, Group<f_Group>, Flags<[CC1Option]>,
+def LongDouble_Group : OptionGroup<"<LongDouble group>">, Group<m_Group>,
+  DocName<"Long double flags">,
+  DocBrief<[{Selects the long double implementation}]>;
+def mlong_double_64 : Flag<["-"], "mlong-double-64">, Group<LongDouble_Group>, Flags<[CC1Option]>,
   HelpText<"Force long double to be 64 bits">;
-def mlong_double_128 : Flag<["-"], "mlong-double-128">, Group<f_Group>, Flags<[CC1Option]>,
+def mlong_double_80 : Flag<["-"], "mlong-double-80">, Group<LongDouble_Group>, Flags<[CC1Option]>,
+  HelpText<"Force long double to be 80 bits, padded to 128 bits for storage">;
+def mlong_double_128 : Flag<["-"], "mlong-double-128">, Group<LongDouble_Group>, Flags<[CC1Option]>,
   HelpText<"Force long double to be 128 bits">;
 def mno_long_calls : Flag<["-"], "mno-long-calls">, Group<m_Group>,
   HelpText<"Restore the default behaviour of not generating long calls">;
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -4046,8 +4046,7 @@
 
   RenderFloatingPointOptions(TC, D, OFastEnabled, Args, CmdArgs);
 
-  if (Arg *A = Args.getLastArg(options::OPT_mlong_double_64,
-                               options::OPT_mlong_double_128)) {
+  if (Arg *A = Args.getLastArg(options::OPT_LongDouble_Group)) {
     if (TC.getArch() == llvm::Triple::x86 ||
         TC.getArch() == llvm::Triple::x86_64 ||
         TC.getArch() == llvm::Triple::ppc || TC.getTriple().isPPC64())
Index: clang/test/CodeGen/x86-long-double.cpp
===================================================================
--- clang/test/CodeGen/x86-long-double.cpp
+++ clang/test/CodeGen/x86-long-double.cpp
@@ -16,6 +16,26 @@
 // RUN: %clang_cc1 %s -emit-llvm -o - -triple=x86_64-apple-darwin -mlong-double-64 | \
 // RUN:   FileCheck --check-prefixes=FP64,FP64-X64 %s
 
+// Check that the last option wins.
+// RUN: %clang_cc1 %s -emit-llvm -o - -triple=i686 -mlong-double-64 -mlong-double-80 | \
+// RUN:   FileCheck --check-prefixes=FP80,FP80-ELF32 %s
+// RUN: %clang_cc1 %s -emit-llvm -o - -triple=i686-apple-darwin -mlong-double-64 -mlong-double-80 | \
+// RUN:   FileCheck --check-prefixes=FP80,FP80-DARWIN %s
+// RUN: %clang_cc1 %s -emit-llvm -o - -triple=x86_64 -mlong-double-64 -mlong-double-80 | \
+// RUN:   FileCheck --check-prefixes=FP80,FP80-ELF64 %s
+// RUN: %clang_cc1 %s -emit-llvm -o - -triple=x86_64-apple-darwin -mlong-double-64 -mlong-double-80 | \
+// RUN:   FileCheck --check-prefixes=FP80,FP80-DARWIN %s
+
+// Check that the last option wins.
+// RUN: %clang_cc1 %s -emit-llvm -o - -triple=i686 -mlong-double-128 -mlong-double-80 | \
+// RUN:   FileCheck --check-prefixes=FP80,FP80-ELF32 %s
+// RUN: %clang_cc1 %s -emit-llvm -o - -triple=i686-apple-darwin -mlong-double-128 -mlong-double-80 | \
+// RUN:   FileCheck --check-prefixes=FP80,FP80-DARWIN %s
+// RUN: %clang_cc1 %s -emit-llvm -o - -triple=x86_64 -mlong-double-128 -mlong-double-80 | \
+// RUN:   FileCheck --check-prefixes=FP80,FP80-ELF64 %s
+// RUN: %clang_cc1 %s -emit-llvm -o - -triple=x86_64-apple-darwin -mlong-double-128 -mlong-double-80 | \
+// RUN:   FileCheck --check-prefixes=FP80,FP80-DARWIN %s
+
 // RUN: %clang_cc1 %s -emit-llvm -o - -triple=i686 -mlong-double-128 | \
 // RUN:   FileCheck --check-prefix=FP128 %s
 // RUN: %clang_cc1 %s -emit-llvm -o - -triple=i686-apple-darwin -mlong-double-128 | \