Index: include/clang/Driver/CLCompatOptions.td
===================================================================
--- include/clang/Driver/CLCompatOptions.td
+++ include/clang/Driver/CLCompatOptions.td
@@ -62,6 +62,8 @@
 def _SLASH_GR_ : CLFlag<"GR-">, HelpText<"Disable emission of RTTI data">;
 def _SLASH_GF_ : CLFlag<"GF-">, HelpText<"Disable string pooling">,
   Alias<fwritable_strings>;
+def _SLASH_Gs : CLJoined<"Gs">, HelpText<"Set stack probe size">, 
+  Alias<mstack_probe_size>;
 def _SLASH_Gy : CLFlag<"Gy">, HelpText<"Put each function in its own section">,
   Alias<ffunction_sections>;
 def _SLASH_Gy_ : CLFlag<"Gy-">, HelpText<"Don't put each function in its own section">,
@@ -252,7 +254,6 @@
 def _SLASH_Gm_ : CLFlag<"Gm-">;
 def _SLASH_Gr : CLFlag<"Gr">;
 def _SLASH_GS : CLFlag<"GS">;
-def _SLASH_Gs : CLJoined<"Gs">;
 def _SLASH_GT : CLFlag<"GT">;
 def _SLASH_GX : CLFlag<"GX">;
 def _SLASH_Gv : CLFlag<"Gv">;
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -1105,6 +1105,8 @@
   HelpText<"Force realign the stack at entry to every function">;
 def mstack_alignment : Joined<["-"], "mstack-alignment=">, Group<m_Group>, Flags<[CC1Option]>,
   HelpText<"Set the stack alignment">;
+def mstack_probe_size : Joined<["-"], "mstack-probe-size=">, Group<m_Group>, Flags<[CC1Option]>,
+  HelpText<"Set the stack probe size">;
 def mthread_model : Separate<["-"], "mthread-model">, Group<m_Group>, Flags<[CC1Option]>,
   HelpText<"The thread model to use, e.g. posix, single (posix by default)">;
 
Index: include/clang/Frontend/CodeGenOptions.def
===================================================================
--- include/clang/Frontend/CodeGenOptions.def
+++ include/clang/Frontend/CodeGenOptions.def
@@ -138,6 +138,8 @@
                                      ///< .ctors.
 VALUE_CODEGENOPT(StackAlignment    , 32, 0) ///< Overrides default stack 
                                             ///< alignment, if not 0.
+VALUE_CODEGENOPT(StackProbeSize    , 32, 0) ///< Overrides default stack 
+                                            ///< probe size, if not 0.
 CODEGENOPT(DebugColumnInfo, 1, 0) ///< Whether or not to use column information
                                   ///< in debug info.
 
Index: lib/CodeGen/BackendUtil.cpp
===================================================================
--- lib/CodeGen/BackendUtil.cpp
+++ lib/CodeGen/BackendUtil.cpp
@@ -500,6 +500,7 @@
   Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
   Options.UseSoftFloat = CodeGenOpts.SoftFloat;
   Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
+  Options.StackProbeSizeOverride = CodeGenOpts.StackProbeSize;
   Options.DisableTailCalls = CodeGenOpts.DisableTailCalls;
   Options.TrapFuncName = CodeGenOpts.TrapFuncName;
   Options.PositionIndependentExecutable = LangOpts.PIELevel != 0;
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -3705,6 +3705,11 @@
     CmdArgs.push_back(Args.MakeArgString("-mstack-alignment=" + alignment));
   }
 
+  if (Args.hasArg(options::OPT_mstack_probe_size)) {
+    StringRef alignment = Args.getLastArgValue(options::OPT_mstack_probe_size);
+    CmdArgs.push_back(Args.MakeArgString("-mstack-probe-size=" + alignment));
+  }
+
   if (getToolChain().getTriple().getArch() == llvm::Triple::aarch64 ||
       getToolChain().getTriple().getArch() == llvm::Triple::aarch64_be)
     CmdArgs.push_back("-fallow-half-arguments-and-returns");
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -506,6 +506,13 @@
     Opts.StackAlignment = StackAlignment;
   }
 
+  if (Arg *A = Args.getLastArg(OPT_mstack_probe_size)) {
+    StringRef Val = A->getValue();
+    unsigned StackProbeSize = Opts.StackProbeSize;
+    Val.getAsInteger(0, StackProbeSize);
+    Opts.StackProbeSize = StackProbeSize;
+  }
+
   if (Arg *A = Args.getLastArg(OPT_fobjc_dispatch_method_EQ)) {
     StringRef Name = A->getValue();
     unsigned Method = llvm::StringSwitch<unsigned>(Name)