diff --git a/clang/include/clang/Basic/LangOptions.h b/clang/include/clang/Basic/LangOptions.h
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -57,7 +57,7 @@
   using RoundingMode = llvm::RoundingMode;
 
   enum GCMode { NonGC, GCOnly, HybridGC };
-  enum StackProtectorMode { SSPOff, SSPOn, SSPStrong, SSPReq };
+  enum StackProtectorMode { SSPOff, SSPOn, SSPStrong, SSPReq, SSPUnspecified };
 
   // Automatic variables live on the stack, and when trivial they're usually
   // uninitialized because it's undefined behavior to use them without
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -309,7 +309,7 @@
         "apply global symbol visibility to external declarations without an explicit visibility")
 BENIGN_LANGOPT(SemanticInterposition        , 1, 0, "semantic interposition")
 BENIGN_LANGOPT(ExplicitNoSemanticInterposition, 1, 0, "explicitly no semantic interposition")
-ENUM_LANGOPT(StackProtector, StackProtectorMode, 2, SSPOff,
+ENUM_LANGOPT(StackProtector, StackProtectorMode, 3, SSPUnspecified,
              "stack protector mode")
 ENUM_LANGOPT(TrivialAutoVarInit, TrivialAutoVarInitKind, 2, TrivialAutoVarInitKind::Uninitialized,
              "trivial automatic variable initialization")
diff --git a/clang/include/clang/Driver/ToolChain.h b/clang/include/clang/Driver/ToolChain.h
--- a/clang/include/clang/Driver/ToolChain.h
+++ b/clang/include/clang/Driver/ToolChain.h
@@ -382,9 +382,10 @@
   virtual bool useRelaxRelocations() const;
 
   /// GetDefaultStackProtectorLevel - Get the default stack protector level for
-  /// this tool chain (0=off, 1=on, 2=strong, 3=all).
-  virtual unsigned GetDefaultStackProtectorLevel(bool KernelOrKext) const {
-    return 0;
+  /// this tool chain.
+  virtual LangOptions::StackProtectorMode
+  GetDefaultStackProtectorLevel(bool KernelOrKext) const {
+    return LangOptions::SSPUnspecified;
   }
 
   /// Get the default trivial automatic variable initialization.
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1594,7 +1594,8 @@
   if (!hasUnwindExceptions(LangOpts))
     B.addAttribute(llvm::Attribute::NoUnwind);
 
-  if (D && D->hasAttr<NoStackProtectorAttr>())
+  if (LangOpts.getStackProtector() == LangOptions::SSPOff ||
+      (D && D->hasAttr<NoStackProtectorAttr>()))
     B.addAttribute(llvm::Attribute::NoStackProtect);
   else if (LangOpts.getStackProtector() == LangOptions::SSPOn)
     B.addAttribute(llvm::Attribute::StackProtect);
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -2994,9 +2994,9 @@
   if (EffectiveTriple.isNVPTX())
     return;
 
-  // -stack-protector=0 is default.
-  unsigned StackProtectorLevel = 0;
-  unsigned DefaultStackProtectorLevel =
+  LangOptions::StackProtectorMode StackProtectorLevel =
+      LangOptions::SSPUnspecified;
+  LangOptions::StackProtectorMode DefaultStackProtectorLevel =
       TC.GetDefaultStackProtectorLevel(KernelOrKext);
 
   if (Arg *A = Args.getLastArg(options::OPT_fno_stack_protector,
@@ -3004,17 +3004,22 @@
                                options::OPT_fstack_protector_strong,
                                options::OPT_fstack_protector)) {
     if (A->getOption().matches(options::OPT_fstack_protector))
-      StackProtectorLevel =
-          std::max<unsigned>(LangOptions::SSPOn, DefaultStackProtectorLevel);
+      if (DefaultStackProtectorLevel == LangOptions::SSPUnspecified)
+        StackProtectorLevel = LangOptions::SSPOn;
+      else
+        StackProtectorLevel =
+            std::max<>(LangOptions::SSPOn, DefaultStackProtectorLevel);
     else if (A->getOption().matches(options::OPT_fstack_protector_strong))
       StackProtectorLevel = LangOptions::SSPStrong;
     else if (A->getOption().matches(options::OPT_fstack_protector_all))
       StackProtectorLevel = LangOptions::SSPReq;
+    else if (A->getOption().matches(options::OPT_fno_stack_protector))
+      StackProtectorLevel = LangOptions::SSPOff;
   } else {
     StackProtectorLevel = DefaultStackProtectorLevel;
   }
 
-  if (StackProtectorLevel) {
+  if (StackProtectorLevel != LangOptions::SSPUnspecified) {
     CmdArgs.push_back("-stack-protector");
     CmdArgs.push_back(Args.MakeArgString(Twine(StackProtectorLevel)));
   }
diff --git a/clang/lib/Driver/ToolChains/CrossWindows.h b/clang/lib/Driver/ToolChains/CrossWindows.h
--- a/clang/lib/Driver/ToolChains/CrossWindows.h
+++ b/clang/lib/Driver/ToolChains/CrossWindows.h
@@ -11,6 +11,7 @@
 
 #include "Cuda.h"
 #include "Gnu.h"
+#include "clang/Basic/LangOptions.h"
 #include "clang/Driver/Tool.h"
 #include "clang/Driver/ToolChain.h"
 
@@ -59,8 +60,9 @@
   bool isPIEDefault() const override;
   bool isPICDefaultForced() const override;
 
-  unsigned int GetDefaultStackProtectorLevel(bool KernelOrKext) const override {
-    return 0;
+  LangOptions::StackProtectorMode
+  GetDefaultStackProtectorLevel(bool KernelOrKext) const override {
+    return LangOptions::SSPUnspecified;
   }
 
   void
diff --git a/clang/lib/Driver/ToolChains/Darwin.h b/clang/lib/Driver/ToolChains/Darwin.h
--- a/clang/lib/Driver/ToolChains/Darwin.h
+++ b/clang/lib/Driver/ToolChains/Darwin.h
@@ -491,17 +491,18 @@
     return !(isTargetMacOS() && isMacosxVersionLT(10, 6));
   }
 
-  unsigned GetDefaultStackProtectorLevel(bool KernelOrKext) const override {
+  LangOptions::StackProtectorMode
+  GetDefaultStackProtectorLevel(bool KernelOrKext) const override {
     // Stack protectors default to on for user code on 10.5,
     // and for everything in 10.6 and beyond
     if (isTargetIOSBased() || isTargetWatchOSBased())
-      return 1;
+      return LangOptions::SSPOn;
     else if (isTargetMacOS() && !isMacosxVersionLT(10, 6))
-      return 1;
+      return LangOptions::SSPOn;
     else if (isTargetMacOS() && !isMacosxVersionLT(10, 5) && !KernelOrKext)
-      return 1;
+      return LangOptions::SSPOn;
 
-    return 0;
+    return LangOptions::SSPUnspecified;
   }
 
   void CheckObjCARC() const override;
diff --git a/clang/lib/Driver/ToolChains/Fuchsia.h b/clang/lib/Driver/ToolChains/Fuchsia.h
--- a/clang/lib/Driver/ToolChains/Fuchsia.h
+++ b/clang/lib/Driver/ToolChains/Fuchsia.h
@@ -10,6 +10,7 @@
 #define LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_FUCHSIA_H
 
 #include "Gnu.h"
+#include "clang/Basic/LangOptions.h"
 #include "clang/Driver/Tool.h"
 #include "clang/Driver/ToolChain.h"
 
@@ -59,8 +60,9 @@
     return llvm::DebuggerKind::GDB;
   }
 
-  unsigned GetDefaultStackProtectorLevel(bool KernelOrKext) const override {
-    return 2; // SSPStrong
+  LangOptions::StackProtectorMode
+  GetDefaultStackProtectorLevel(bool KernelOrKext) const override {
+    return LangOptions::SSPStrong;
   }
 
   std::string ComputeEffectiveClangTriple(const llvm::opt::ArgList &Args,
diff --git a/clang/lib/Driver/ToolChains/OpenBSD.h b/clang/lib/Driver/ToolChains/OpenBSD.h
--- a/clang/lib/Driver/ToolChains/OpenBSD.h
+++ b/clang/lib/Driver/ToolChains/OpenBSD.h
@@ -10,6 +10,7 @@
 #define LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_OPENBSD_H
 
 #include "Gnu.h"
+#include "clang/Basic/LangOptions.h"
 #include "clang/Driver/Tool.h"
 #include "clang/Driver/ToolChain.h"
 
@@ -79,8 +80,9 @@
   std::string getCompilerRT(const llvm::opt::ArgList &Args, StringRef Component,
                             FileType Type = ToolChain::FT_Static) const override;
 
-  unsigned GetDefaultStackProtectorLevel(bool KernelOrKext) const override {
-    return 2;
+  LangOptions::StackProtectorMode
+  GetDefaultStackProtectorLevel(bool KernelOrKext) const override {
+    return LangOptions::SSPStrong;
   }
   unsigned GetDefaultDwarfVersion() const override { return 2; }
 
diff --git a/clang/lib/Driver/ToolChains/PS4CPU.h b/clang/lib/Driver/ToolChains/PS4CPU.h
--- a/clang/lib/Driver/ToolChains/PS4CPU.h
+++ b/clang/lib/Driver/ToolChains/PS4CPU.h
@@ -10,6 +10,7 @@
 #define LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_PS4CPU_H
 
 #include "Gnu.h"
+#include "clang/Basic/LangOptions.h"
 #include "clang/Driver/Tool.h"
 #include "clang/Driver/ToolChain.h"
 
@@ -73,8 +74,9 @@
   bool HasNativeLLVMSupport() const override;
   bool isPICDefault() const override;
 
-  unsigned GetDefaultStackProtectorLevel(bool KernelOrKext) const override {
-    return 2; // SSPStrong
+  enum LangOptions::StackProtectorMode
+  GetDefaultStackProtectorLevel(bool KernelOrKext) const override {
+    return LangOptions::SSPStrong;
   }
 
   llvm::DebuggerKind getDefaultDebuggerTuning() const override {
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -3379,7 +3379,7 @@
   Opts.RetainCommentsFromSystemHeaders =
       Args.hasArg(OPT_fretain_comments_from_system_headers);
 
-  unsigned SSP = getLastArgIntValue(Args, OPT_stack_protector, 0, Diags);
+  unsigned SSP = getLastArgIntValue(Args, OPT_stack_protector, UINT_MAX, Diags);
   switch (SSP) {
   default:
     Diags.Report(diag::err_drv_invalid_value)
@@ -3389,6 +3389,9 @@
   case 1: Opts.setStackProtector(LangOptions::SSPOn);  break;
   case 2: Opts.setStackProtector(LangOptions::SSPStrong); break;
   case 3: Opts.setStackProtector(LangOptions::SSPReq); break;
+  case UINT_MAX:
+    Opts.setStackProtector(LangOptions::SSPUnspecified);
+    break;
   }
 
   if (Arg *A = Args.getLastArg(OPT_ftrivial_auto_var_init)) {
diff --git a/clang/test/CodeGen/stack-protector.c b/clang/test/CodeGen/stack-protector.c
--- a/clang/test/CodeGen/stack-protector.c
+++ b/clang/test/CodeGen/stack-protector.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -emit-llvm -o - %s -stack-protector 0 | FileCheck -check-prefix=DEF -check-prefix=NOSSP %s
+// RUN: %clang_cc1 -emit-llvm -o - %s -stack-protector 0 | FileCheck -check-prefix=DEF-NOSSP -check-prefix=NOSSP %s
 // RUN: %clang_cc1 -emit-llvm -o - %s -stack-protector 1 | FileCheck -check-prefix=DEF -check-prefix=SSP %s
 // RUN: %clang_cc1 -emit-llvm -o - %s -stack-protector 2 | FileCheck -check-prefix=DEF -check-prefix=SSPSTRONG %s
 // RUN: %clang_cc1 -emit-llvm -o - %s -stack-protector 3 | FileCheck -check-prefix=DEF -check-prefix=SSPREQ %s
@@ -16,6 +16,7 @@
 char *strcpy(char *s1, const char *s2);
 
 // DEF: define {{.*}}void @test1(i8* %msg) #[[A:.*]] {
+// DEF-NOSSP: define {{.*}}void @test1(i8* %msg) #[[B:.*]] {
 void test1(const char *msg) {
   char a[strlen(msg) + 1];
   strcpy(a, msg);
@@ -23,6 +24,7 @@
 }
 
 // DEF: define {{.*}}void @test2(i8* %msg) #[[B:.*]] {
+// DEF-NOSSP: define {{.*}}void @test2(i8* %msg) #[[B:.*]] {
 __attribute__((no_stack_protector))
 void test2(const char *msg) {
   char a[strlen(msg) + 1];
diff --git a/clang/test/Driver/stack-protector.c b/clang/test/Driver/stack-protector.c
--- a/clang/test/Driver/stack-protector.c
+++ b/clang/test/Driver/stack-protector.c
@@ -1,6 +1,6 @@
 // RUN: %clang -fno-stack-protector -### %s 2>&1 | FileCheck %s -check-prefix=NOSSP
-// NOSSP-NOT: "-stack-protector"
-// NOSSP-NOT: "-stack-protector-buffer-size" 
+// NOSSP: "-stack-protector" "0"
+// NOSSP-NOT: "-stack-protector-buffer-size"
 
 // RUN: %clang -target i386-unknown-linux -fstack-protector -### %s 2>&1 | FileCheck %s -check-prefix=SSP
 // SSP: "-stack-protector" "1"