Index: clang/include/clang/Basic/DiagnosticCommonKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticCommonKinds.td
+++ clang/include/clang/Basic/DiagnosticCommonKinds.td
@@ -327,6 +327,8 @@
   "option '%0' cannot be specified on this target">;
 def err_invalid_feature_combination : Error<
   "invalid feature combination: %0">;
+def warn_invalid_feature_flags : Warning<
+  "feature flags '%0' should start with '+' or '-'">;
 
 // Source manager
 def err_cannot_open_file : Error<"cannot open file '%0': %1">, DefaultFatal;
Index: clang/lib/Basic/TargetInfo.cpp
===================================================================
--- clang/lib/Basic/TargetInfo.cpp
+++ clang/lib/Basic/TargetInfo.cpp
@@ -493,10 +493,14 @@
     llvm::StringMap<bool> &Features, DiagnosticsEngine &Diags, StringRef CPU,
     const std::vector<std::string> &FeatureVec) const {
   for (const auto &F : FeatureVec) {
+    if (F.empty())
+      continue;
     StringRef Name = F;
     // Apply the feature via the target.
-    bool Enabled = Name[0] == '+';
-    setFeatureEnabled(Features, Name.substr(1), Enabled);
+    if (Name[0] != '+' && Name[0] != '-')
+      Diags.Report(diag::warn_invalid_feature_flags) << Name;
+    else
+      setFeatureEnabled(Features, Name.substr(1), Name[0] == '+');
   }
   return true;
 }
Index: clang/test/Driver/invalid-target-feature.c
===================================================================
--- /dev/null
+++ clang/test/Driver/invalid-target-feature.c
@@ -0,0 +1,5 @@
+// RUN: %clang -c -target aarch64 -Xclang -target-feature -Xclang '' -Xclang -target-feature -Xclang m %s 2>&1 \
+// RUN:    | FileCheck --check-prefix=XCLANG %s
+
+// XCLANG: warning: feature flags 'm' should start with '+' or '-'
+//