Index: clang/include/clang/Basic/DiagnosticDriverKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -347,6 +347,8 @@
   "invalid branch protection option '%0' in '%1'">;
 def err_invalid_sls_hardening : Error<
   "invalid sls hardening option '%0' in '%1'">;
+def err_sls_hardening_arm_not_supported : Error<
+  "-mharden-sls is only supported on armv7-a or later">;
 
 def note_drv_command_failed_diag_msg : Note<
   "diagnostic msg: %0">;
Index: clang/lib/Driver/ToolChains/Arch/ARM.h
===================================================================
--- clang/lib/Driver/ToolChains/Arch/ARM.h
+++ clang/lib/Driver/ToolChains/Arch/ARM.h
@@ -63,6 +63,7 @@
                           std::vector<llvm::StringRef> &Features, bool ForAS);
 int getARMSubArchVersionNumber(const llvm::Triple &Triple);
 bool isARMMProfile(const llvm::Triple &Triple);
+bool isARMAProfile(const llvm::Triple &Triple);
 
 } // end namespace arm
 } // end namespace tools
Index: clang/lib/Driver/ToolChains/Arch/ARM.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Arch/ARM.cpp
+++ clang/lib/Driver/ToolChains/Arch/ARM.cpp
@@ -32,6 +32,12 @@
   return llvm::ARM::parseArchProfile(Arch) == llvm::ARM::ProfileKind::M;
 }
 
+// True if A-profile.
+bool arm::isARMAProfile(const llvm::Triple &Triple) {
+  llvm::StringRef Arch = Triple.getArchName();
+  return llvm::ARM::parseArchProfile(Arch) == llvm::ARM::ProfileKind::A;
+}
+
 // Get Arch/CPU from args.
 void arm::getARMArchCPUFromArgs(const ArgList &Args, llvm::StringRef &Arch,
                                 llvm::StringRef &CPU, bool FromAs) {
@@ -606,6 +612,45 @@
 
   if (Args.hasArg(options::OPT_mno_neg_immediates))
     Features.push_back("+no-neg-immediates");
+
+  // Enable/disable straight line speculation hardening.
+  if (Arg *A = Args.getLastArg(options::OPT_mharden_sls_EQ)) {
+    StringRef Scope = A->getValue();
+    bool EnableRetBr = false;
+    bool EnableBlr = false;
+    if (Scope != "none" && Scope != "all") {
+      SmallVector<StringRef, 4> Opts;
+      Scope.split(Opts, ",");
+      for (auto Opt : Opts) {
+        Opt = Opt.trim();
+        if (Opt == "retbr") {
+          EnableRetBr = true;
+          continue;
+        }
+        if (Opt == "blr") {
+          EnableBlr = true;
+          continue;
+        }
+        D.Diag(diag::err_invalid_sls_hardening)
+            << Scope << A->getAsString(Args);
+        break;
+      }
+    } else if (Scope == "all") {
+      EnableRetBr = true;
+      EnableBlr = true;
+    }
+
+    if (EnableRetBr || EnableBlr)
+      if (!(isARMAProfile(Triple) && getARMSubArchVersionNumber(Triple) >= 7))
+        D.Diag(diag::err_sls_hardening_arm_not_supported)
+            << Scope << A->getAsString(Args);
+
+    if (EnableRetBr)
+      Features.push_back("+harden-sls-retbr");
+    if (EnableBlr)
+      Features.push_back("+harden-sls-blr");
+  }
+
 }
 
 const std::string arm::getARMArch(StringRef Arch, const llvm::Triple &Triple) {
Index: clang/test/Driver/aarch64-sls-hardening-options.c
===================================================================
--- clang/test/Driver/aarch64-sls-hardening-options.c
+++ /dev/null
@@ -1,45 +0,0 @@
-// Check the -mharden-sls= option, which has a required argument to select
-// scope.
-// RUN: %clang -target aarch64--none-eabi -c %s -### 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=none 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-OFF
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=blr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-ON
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=blr -mharden-sls=none 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=blr -mharden-sls=retbr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-OFF
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr,blr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=all 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr,blr,retbr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr,blr,r 2>&1 | \
-// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=none,blr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=all,-blr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
-
-// RETBR-OFF-NOT: "harden-sls-retbr"
-// RETBR-ON:  "+harden-sls-retbr"
-
-// BLR-OFF-NOT: "harden-sls-blr"
-// BLR-ON:  "+harden-sls-blr"
-
-// BAD-SLS-SPEC: invalid sls hardening option '{{[^']+}}' in '-mharden-sls=
Index: clang/test/Driver/sls-hardening-options.c
===================================================================
--- /dev/null
+++ clang/test/Driver/sls-hardening-options.c
@@ -0,0 +1,97 @@
+// Check the -mharden-sls= option, which has a required argument to select
+// scope.
+// RUN: %clang -target aarch64--none-eabi -c %s -### 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
+// RUN: %clang -target armv7a--none-eabi -c %s -### 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=none 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=none 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-OFF
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-OFF
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-ON
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-ON
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=blr -mharden-sls=none 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=blr -mharden-sls=none 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=blr -mharden-sls=retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-OFF
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=blr -mharden-sls=retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-OFF
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr,blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=retbr,blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr,blr,retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=retbr,blr,retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr,blr,r 2>&1 | \
+// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=retbr,blr,r 2>&1 | \
+// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=none,blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=none,blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=all,-blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=all,-blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
+
+// RETBR-OFF-NOT: "harden-sls-retbr"
+// RETBR-ON:  "+harden-sls-retbr"
+
+// BLR-OFF-NOT: "harden-sls-blr"
+// BLR-ON:  "+harden-sls-blr"
+
+// BAD-SLS-SPEC: invalid sls hardening option '{{[^']+}}' in '-mharden-sls=
+
+// RUN: %clang -target armv6a--none-eabi -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-NOT-SUPPORTED
+
+// RUN: %clang -target armv6a--none-eabi -c %s -### -mharden-sls=retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-NOT-SUPPORTED
+
+// RUN: %clang -target armv6a--none-eabi -c %s -### -mharden-sls=blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-NOT-SUPPORTED
+
+// RUN: %clang -target armv7r--none-eabi -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-NOT-SUPPORTED
+
+// RUN: %clang -target armv7m--none-eabi -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-NOT-SUPPORTED
+
+// RUN: %clang -target armv6a--none-eabi -c %s -### -mharden-sls=none 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-SUPPORTED
+
+// RUN: %clang -target armv7a-linux-gnueabihf -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-SUPPORTED
+
+// RUN: %clang -target armv8a-linux-gnueabihf -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-SUPPORTED
+
+// SLS-NOT-SUPPORTED: -mharden-sls is only supported on armv7-a or later
+// SLS-SUPPORTED-NOT: mharden-sls
+