Index: llvm/lib/MC/MCSubtargetInfo.cpp
===================================================================
--- llvm/lib/MC/MCSubtargetInfo.cpp
+++ llvm/lib/MC/MCSubtargetInfo.cpp
@@ -147,6 +147,20 @@
   PrintOnce = true;
 }
 
+/// Display help for feature and mcpu choices.
+static void PrintFullFeatureList(const FeatureBitset &FeatBits,
+                                 ArrayRef<SubtargetFeatureKV> FeatTable,
+                                 bool EnabledOnly) {
+  errs() << "Current full feature list:\n";
+  for (const SubtargetFeatureKV &Feat : FeatTable) {
+    bool IsSet = FeatBits.test(Feat.Value);
+    if (EnabledOnly && !IsSet)
+      continue;
+    errs() << "\t" << (IsSet ? '+' : '-') << Feat.Key << ":\t" << Feat.Desc
+           << '\n';
+  }
+}
+
 static FeatureBitset getFeatures(StringRef CPU, StringRef TuneCPU, StringRef FS,
                                  ArrayRef<SubtargetSubTypeKV> ProcDesc,
                                  ArrayRef<SubtargetFeatureKV> ProcFeatures) {
@@ -198,6 +212,10 @@
       Help(ProcDesc, ProcFeatures);
     else if (Feature == "+cpuhelp")
       cpuHelp(ProcDesc);
+    else if (Feature == "+dump-all")
+      PrintFullFeatureList(Bits, ProcFeatures, /*EnabledOnly=*/false);
+    else if (Feature == "+dump-enabled")
+      PrintFullFeatureList(Bits, ProcFeatures, /*EnabledOnly=*/true);
     else
       ApplyFeatureFlag(Bits, Feature, ProcFeatures);
   }