Index: include/llvm/MC/SubtargetFeature.h
===================================================================
--- include/llvm/MC/SubtargetFeature.h
+++ include/llvm/MC/SubtargetFeature.h
@@ -98,14 +98,13 @@
   /// Adding Features.
   void AddFeature(StringRef String, bool Enable = true);
 
-  /// ToggleFeature - Toggle a feature and returns the newly updated feature
-  /// bits.
-  FeatureBitset ToggleFeature(FeatureBitset Bits, StringRef String,
-                         ArrayRef<SubtargetFeatureKV> FeatureTable);
-
-  /// Apply the feature flag and return the newly updated feature bits.
-  FeatureBitset ApplyFeatureFlag(FeatureBitset Bits, StringRef Feature,
-                                 ArrayRef<SubtargetFeatureKV> FeatureTable);
+  /// ToggleFeature - Toggle a feature and update the feature bits.
+  static void ToggleFeature(FeatureBitset &Bits, StringRef String,
+                            ArrayRef<SubtargetFeatureKV> FeatureTable);
+
+  /// Apply the feature flag and update the feature bits.
+  static void ApplyFeatureFlag(FeatureBitset &Bits, StringRef Feature,
+                               ArrayRef<SubtargetFeatureKV> FeatureTable);
 
   /// Get feature bits of a CPU.
   FeatureBitset getFeatureBits(StringRef CPU,
Index: lib/MC/MCSubtargetInfo.cpp
===================================================================
--- lib/MC/MCSubtargetInfo.cpp
+++ lib/MC/MCSubtargetInfo.cpp
@@ -63,14 +63,12 @@
 /// ToggleFeature - Toggle a feature and returns the re-computed feature
 /// bits. This version will also change all implied bits.
 FeatureBitset MCSubtargetInfo::ToggleFeature(StringRef FS) {
-  SubtargetFeatures Features;
-  FeatureBits = Features.ToggleFeature(FeatureBits, FS, ProcFeatures);
+  SubtargetFeatures::ToggleFeature(FeatureBits, FS, ProcFeatures);
   return FeatureBits;
 }
 
 FeatureBitset MCSubtargetInfo::ApplyFeatureFlag(StringRef FS) {
-  SubtargetFeatures Features;
-  FeatureBits = Features.ApplyFeatureFlag(FeatureBits, FS, ProcFeatures);
+  SubtargetFeatures::ApplyFeatureFlag(FeatureBits, FS, ProcFeatures);
   return FeatureBits;
 }
 
Index: lib/MC/SubtargetFeature.cpp
===================================================================
--- lib/MC/SubtargetFeature.cpp
+++ lib/MC/SubtargetFeature.cpp
@@ -162,8 +162,8 @@
 
 /// ToggleFeature - Toggle a feature and returns the newly updated feature
 /// bits.
-FeatureBitset
-SubtargetFeatures::ToggleFeature(FeatureBitset Bits, StringRef Feature,
+void
+SubtargetFeatures::ToggleFeature(FeatureBitset &Bits, StringRef Feature,
                                  ArrayRef<SubtargetFeatureKV> FeatureTable) {
 
   // Find feature in table.
@@ -186,12 +186,9 @@
            << "' is not a recognized feature for this target"
            << " (ignoring feature)\n";
   }
-
-  return Bits;
 }
 
-FeatureBitset
-SubtargetFeatures::ApplyFeatureFlag(FeatureBitset Bits, StringRef Feature,
+void SubtargetFeatures::ApplyFeatureFlag(FeatureBitset &Bits, StringRef Feature,
                                     ArrayRef<SubtargetFeatureKV> FeatureTable) {
 
   assert(hasFlag(Feature));
@@ -203,7 +200,7 @@
   if (FeatureEntry) {
     // Enable/disable feature in bits
     if (isEnabled(Feature)) {
-      Bits |=  FeatureEntry->Value;
+      Bits |= FeatureEntry->Value;
 
       // For each feature that this implies, set it.
       SetImpliedBits(Bits, FeatureEntry, FeatureTable);
@@ -218,8 +215,6 @@
            << "' is not a recognized feature for this target"
            << " (ignoring feature)\n";
   }
-
-  return Bits;
 }
 
 
@@ -271,13 +266,28 @@
     }
   }
 
+  // Cancel out the disabled features which are explicitly re-enabled later on.
+  FeatureBitset ExplicitlyEnabled;
+  for (auto Feature  = Features.rbegin();
+            Feature != Features.rend();
+          ++Feature) {
+    const SubtargetFeatureKV *FeatureEntry =
+        Find(StripFlag(*Feature), FeatureTable);
+    if (FeatureEntry) {
+      if ((ExplicitlyEnabled & FeatureEntry->Value).any())
+        Features.erase(std::next(Feature).base());
+      else if (isEnabled(*Feature))
+        ExplicitlyEnabled |= FeatureEntry->Value;
+    }
+  }
+
   // Iterate through each feature
   for (auto &Feature : Features) {
     // Check for help
     if (Feature == "+help")
       Help(CPUTable, FeatureTable);
 
-    Bits = ApplyFeatureFlag(Bits, Feature, FeatureTable);
+    ApplyFeatureFlag(Bits, Feature, FeatureTable);
   }
 
   return Bits;
Index: test/MC/ARM/fullfp16-neon.s
===================================================================
--- test/MC/ARM/fullfp16-neon.s
+++ test/MC/ARM/fullfp16-neon.s
@@ -1,4 +1,4 @@
-@ RUN: llvm-mc -triple armv8a-none-eabi -mattr=+fullfp16,+neon -show-encoding < %s | FileCheck %s --check-prefix=ARM
+@ RUN: llvm-mc -triple armv8a-none-eabi -mattr=+fullfp16,-fp-armv8,+fp-armv8,+neon -show-encoding < %s | FileCheck %s --check-prefix=ARM
 @ RUN: llvm-mc -triple thumbv8a-none-eabi -mattr=+fullfp16,+neon -show-encoding < %s | FileCheck %s --check-prefix=THUMB
 
   vadd.f16 d0, d1, d2