Index: cfe/trunk/include/clang/Basic/DiagnosticDriverKinds.td
===================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticDriverKinds.td
+++ cfe/trunk/include/clang/Basic/DiagnosticDriverKinds.td
@@ -368,6 +368,9 @@
 def err_drv_ropi_incompatible_with_cxx : Error<
   "ROPI is not compatible with c++">;
 
+def err_stack_tagging_requires_hardware_feature : Error<
+  "'-fsanitize=memtag' requires hardware support (+memtag)">;
+
 def warn_target_unsupported_nan2008 : Warning<
   "ignoring '-mnan=2008' option because the '%0' architecture does not support it">,
   InGroup<UnsupportedNan>;
Index: cfe/trunk/lib/Driver/SanitizerArgs.cpp
===================================================================
--- cfe/trunk/lib/Driver/SanitizerArgs.cpp
+++ cfe/trunk/lib/Driver/SanitizerArgs.cpp
@@ -873,6 +873,18 @@
   CmdArgs.push_back(Args.MakeArgString(LinkerOptionFlag));
 }
 
+static bool hasTargetFeatureMTE(const llvm::opt::ArgStringList &CmdArgs) {
+  for (auto Start = CmdArgs.begin(), End = CmdArgs.end(); Start != End; ++Start) {
+    auto It = std::find(Start, End, StringRef("+mte"));
+    if (It == End)
+      break;
+    if (It > Start && *std::prev(It) == StringRef("-target-feature"))
+      return true;
+    Start = It;
+  }
+  return false;
+}
+
 void SanitizerArgs::addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
                             llvm::opt::ArgStringList &CmdArgs,
                             types::ID InputType) const {
@@ -1043,6 +1055,9 @@
                                Sanitizers.Mask & CFIClasses)
         << "-fvisibility=";
   }
+
+  if (Sanitizers.has(SanitizerKind::MemTag) && !hasTargetFeatureMTE(CmdArgs))
+    TC.getDriver().Diag(diag::err_stack_tagging_requires_hardware_feature);
 }
 
 SanitizerMask parseArgValues(const Driver &D, const llvm::opt::Arg *A,
Index: cfe/trunk/test/Driver/fsanitize.c
===================================================================
--- cfe/trunk/test/Driver/fsanitize.c
+++ cfe/trunk/test/Driver/fsanitize.c
@@ -191,6 +191,16 @@
 // RUN: %clang -target x86_64-linux-android -fsanitize=memtag -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANMT-BAD-ARCH
 // CHECK-SANMT-BAD-ARCH: unsupported option '-fsanitize=memtag' for target
 
+// RUN: %clang -target aarch64-linux -fsanitize=memtag -march=armv8-a+memtag %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANMT-MT
+// CHECK-SANMT-MT: "-target-feature" "+mte"
+// CHECK-SANMT-MT-SAME: "-fsanitize=memtag"
+
+// RUN: %clang -target aarch64-linux -fsanitize=memtag %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANMT-NOMT-0
+// CHECK-SANMT-NOMT-0: '-fsanitize=memtag' requires hardware support (+memtag)
+
+// RUN: %clang -target aarch64-linux -fsanitize=memtag -I +mte %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANMT-NOMT-1
+// CHECK-SANMT-NOMT-1: '-fsanitize=memtag' requires hardware support (+memtag)
+
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=address -fsanitize-address-use-after-scope %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-USE-AFTER-SCOPE
 // RUN: %clang_cl --target=x86_64-windows -fsanitize=address -fsanitize-address-use-after-scope -### -- %s 2>&1 | FileCheck %s --check-prefix=CHECK-USE-AFTER-SCOPE
 // CHECK-USE-AFTER-SCOPE: -cc1{{.*}}-fsanitize-address-use-after-scope