Plumb through the -fsplit-stack option using the existing backend
support.

Caveat: Other than the existing segmented stacks support, no
claims are made of this working.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178744 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Driver/CC1Options.td b/include/clang/Driver/CC1Options.td
index 65326c6..ab2d5dc 100644
--- a/include/clang/Driver/CC1Options.td
+++ b/include/clang/Driver/CC1Options.td
@@ -184,6 +184,8 @@
   HelpText<"Limit float precision to the given value">;
 def mno_exec_stack : Flag<["-"], "mnoexecstack">,
   HelpText<"Mark the file as not needing an executable stack">;
+def split_stacks : Flag<["-"], "split-stacks">,
+  HelpText<"Try to use a split stack if possible.">;
 def mno_zero_initialized_in_bss : Flag<["-"], "mno-zero-initialized-in-bss">,
   HelpText<"Do not put zero initialized data in the BSS">;
 def backend_option : Separate<["-"], "backend-option">,
diff --git a/include/clang/Driver/Options.td b/include/clang/Driver/Options.td
index 6aea22f..dd5062c 100644
--- a/include/clang/Driver/Options.td
+++ b/include/clang/Driver/Options.td
@@ -675,6 +675,7 @@
 def fspell_checking : Flag<["-"], "fspell-checking">, Group<f_Group>;
 def fsigned_bitfields : Flag<["-"], "fsigned-bitfields">, Group<f_Group>;
 def fsigned_char : Flag<["-"], "fsigned-char">, Group<f_Group>;
+def fsplit_stack : Flag<["-"], "fsplit-stack">, Group<f_Group>;
 def fstack_protector_all : Flag<["-"], "fstack-protector-all">, Group<f_Group>;
 def fstack_protector : Flag<["-"], "fstack-protector">, Group<f_Group>;
 def fstrict_aliasing : Flag<["-"], "fstrict-aliasing">, Group<f_Group>;
diff --git a/include/clang/Frontend/CodeGenOptions.def b/include/clang/Frontend/CodeGenOptions.def
index 92df6bb..4b6754d 100644
--- a/include/clang/Frontend/CodeGenOptions.def
+++ b/include/clang/Frontend/CodeGenOptions.def
@@ -70,6 +70,7 @@
 CODEGENOPT(NoDwarfDirectoryAsm , 1, 0) ///< Set when -fno-dwarf-directory-asm is
                                        ///< enabled.
 CODEGENOPT(NoExecStack       , 1, 0) ///< Set when -Wa,--noexecstack is enabled.
+CODEGENOPT(EnableSegmentedStacks , 1, 0) ///< Set when -fsplit-stack is enabled.
 CODEGENOPT(NoGlobalMerge     , 1, 0) ///< Set when -mno-global-merge is enabled.
 CODEGENOPT(NoImplicitFloat   , 1, 0) ///< Set when -mno-implicit-float is enabled.
 CODEGENOPT(NoInfsFPMath      , 1, 0) ///< Assume FP arguments, results not +-Inf.