diff --git a/include/llvm/MC/SubtargetFeature.h b/include/llvm/MC/SubtargetFeature.h
index bfecb8ba6ab..6f195d7be99 100644
--- a/include/llvm/MC/SubtargetFeature.h
+++ b/include/llvm/MC/SubtargetFeature.h
@@ -78,7 +78,7 @@ public:
   std::string getString() const;
 
   /// Adding Features.
-  void AddFeature(StringRef String);
+  void AddFeature(StringRef String, bool Enable = true);
 
   /// ToggleFeature - Toggle a feature and returns the newly updated feature
   /// bits.
diff --git a/lib/MC/SubtargetFeature.cpp b/lib/MC/SubtargetFeature.cpp
index fcb43d63cb9..3880d883389 100644
--- a/lib/MC/SubtargetFeature.cpp
+++ b/lib/MC/SubtargetFeature.cpp
@@ -81,11 +81,12 @@ static std::string Join(const std::vector<std::string> &V) {
 }
 
 /// Adding features.
-void SubtargetFeatures::AddFeature(StringRef String) {
+void SubtargetFeatures::AddFeature(StringRef String, bool Enable) {
   // Don't add empty features.
   if (!String.empty())
     // Convert to lowercase, prepend flag if we don't already have a flag.
-    Features.push_back(hasFlag(String) ? String.lower() : "+" + String.lower());
+    Features.push_back(hasFlag(String) ? String.lower()
+                                       : (Enable ? "+" : "-") + String.lower());
 }
 
 /// Find KV in array using binary search.
diff --git a/tools/llc/llc.cpp b/tools/llc/llc.cpp
index 000948c10a0..d46cbb3181b 100644
--- a/tools/llc/llc.cpp
+++ b/tools/llc/llc.cpp
@@ -212,12 +212,6 @@ static int compileModule(char **argv, LLVMContext &Context) {
   bool SkipModule = MCPU == "help" ||
                     (!MAttrs.empty() && MAttrs.front() == "help");
 
-  // If user asked for the 'native' CPU, autodetect here. If autodection fails,
-  // this will set the CPU to an empty string which tells the target to
-  // pick a basic default.
-  if (MCPU == "native")
-    MCPU = sys::getHostCPUName();
-
   // If user just wants to list available options, skip module loading
   if (!SkipModule) {
     M = parseIRFile(InputFilename, Err, Context);
@@ -256,13 +250,31 @@ static int compileModule(char **argv, LLVMContext &Context) {
 
   // Package up features to be passed to target/subtarget
   std::string FeaturesStr;
-  if (MAttrs.size()) {
+  if (!MAttrs.empty() || MCPU == "native") {
     SubtargetFeatures Features;
+
+    // If user asked for the 'native' CPU, we need to autodetect features.
+    // This is necessary for x86 where the CPU might not support all the
+    // features the autodetected CPU name lists in the target. For example,
+    // not all Sandybridge processors support AVX.
+    if (MCPU == "native") {
+      StringMap<bool> HostFeatures;
+      if (sys::getHostCPUFeatures(HostFeatures))
+        for (auto &F : HostFeatures)
+          Features.AddFeature(F.first(), F.second);
+    }
+
     for (unsigned i = 0; i != MAttrs.size(); ++i)
       Features.AddFeature(MAttrs[i]);
     FeaturesStr = Features.getString();
   }
 
+  // If user asked for the 'native' CPU, autodetect here. If autodection fails,
+  // this will set the CPU to an empty string which tells the target to
+  // pick a basic default.
+  if (MCPU == "native")
+    MCPU = sys::getHostCPUName();
+
   CodeGenOpt::Level OLvl = CodeGenOpt::Default;
   switch (OptLevel) {
   default: