From: Michael Kuperstein <michael.m.kuperstein@intel.com>
Date: Tue, 24 Mar 2015 12:56:59 +0000 (+0000)
Subject: Revert "Use std::bitset for SubtargetFeatures"
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=765aab84d619c67a9a44d97b78c696d3d9bd4fb9;p=oota-llvm.git

Revert "Use std::bitset for SubtargetFeatures"

This reverts commit r233055.

It still causes buildbot failures (gcc running out of memory on several platforms, and a self-host failure on arm), although less than the previous time.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233068 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/llvm/MC/MCInstPrinter.h b/include/llvm/MC/MCInstPrinter.h
index 028d24ed72b..dce3a0690b3 100644
--- a/include/llvm/MC/MCInstPrinter.h
+++ b/include/llvm/MC/MCInstPrinter.h
@@ -10,7 +10,6 @@
 #ifndef LLVM_MC_MCINSTPRINTER_H
 #define LLVM_MC_MCINSTPRINTER_H
 
-#include "llvm/MC/SubtargetFeature.h"
 #include "llvm/Support/DataTypes.h"
 #include "llvm/Support/Format.h"
 
@@ -42,7 +41,7 @@ protected:
   const MCRegisterInfo &MRI;
 
   /// The current set of available features.
-  FeatureBitset AvailableFeatures;
+  uint64_t AvailableFeatures;
 
   /// True if we are printing marked up assembly.
   bool UseMarkup;
@@ -59,7 +58,7 @@ public:
   MCInstPrinter(const MCAsmInfo &mai, const MCInstrInfo &mii,
                 const MCRegisterInfo &mri)
     : CommentStream(nullptr), MAI(mai), MII(mii), MRI(mri),
-      AvailableFeatures(), UseMarkup(0), PrintImmHex(0),
+      AvailableFeatures(0), UseMarkup(0), PrintImmHex(0),
       PrintHexStyle(HexStyle::C) {}
 
   virtual ~MCInstPrinter();
@@ -79,8 +78,8 @@ public:
   /// printRegName - Print the assembler register name.
   virtual void printRegName(raw_ostream &OS, unsigned RegNo) const;
 
-  const FeatureBitset& getAvailableFeatures() const { return AvailableFeatures; }
-  void setAvailableFeatures(const FeatureBitset& Value) { AvailableFeatures = Value; }
+  uint64_t getAvailableFeatures() const { return AvailableFeatures; }
+  void setAvailableFeatures(uint64_t Value) { AvailableFeatures = Value; }
 
   bool getUseMarkup() const { return UseMarkup; }
   void setUseMarkup(bool Value) { UseMarkup = Value; }
diff --git a/include/llvm/MC/MCInstrDesc.h b/include/llvm/MC/MCInstrDesc.h
index 459efadb21f..360989305d3 100644
--- a/include/llvm/MC/MCInstrDesc.h
+++ b/include/llvm/MC/MCInstrDesc.h
@@ -150,7 +150,7 @@ public:
   const uint16_t *ImplicitUses;  // Registers implicitly read by this instr
   const uint16_t *ImplicitDefs;  // Registers implicitly defined by this instr
   const MCOperandInfo *OpInfo;   // 'NumOperands' entries about operands
-  FeatureBitset   DeprecatedFeatureMask; // Feature bits that this is deprecated on, if any
+  uint64_t DeprecatedFeatureMask;// Feature bits that this is deprecated on, if any
   // A complex method to determine is a certain is deprecated or not, and return
   // the reason for deprecation.
   bool (*ComplexDeprecationInfo)(MCInst &, MCSubtargetInfo &, std::string &);
@@ -173,7 +173,7 @@ public:
                          std::string &Info) const {
     if (ComplexDeprecationInfo)
       return ComplexDeprecationInfo(MI, STI, Info);
-    if ((STI.getFeatureBits() & DeprecatedFeatureMask).any()) {
+    if ((DeprecatedFeatureMask & STI.getFeatureBits()) != 0) {
       // FIXME: it would be nice to include the subtarget feature here.
       Info = "deprecated";
       return true;
diff --git a/include/llvm/MC/MCSubtargetInfo.h b/include/llvm/MC/MCSubtargetInfo.h
index 1778a6d13fb..3984a1fb21b 100644
--- a/include/llvm/MC/MCSubtargetInfo.h
+++ b/include/llvm/MC/MCSubtargetInfo.h
@@ -42,7 +42,7 @@ class MCSubtargetInfo {
   const InstrStage *Stages;            // Instruction itinerary stages
   const unsigned *OperandCycles;       // Itinerary operand cycles
   const unsigned *ForwardingPaths;     // Forwarding paths
-  FeatureBitset FeatureBits;           // Feature bits for current CPU + FS
+  uint64_t FeatureBits;                // Feature bits for current CPU + FS
 
 public:
   void InitMCSubtargetInfo(StringRef TT, StringRef CPU, StringRef FS,
@@ -67,13 +67,13 @@ public:
 
   /// getFeatureBits - Return the feature bits.
   ///
-  const FeatureBitset& getFeatureBits() const {
+  uint64_t getFeatureBits() const {
     return FeatureBits;
   }
 
   /// setFeatureBits - Set the feature bits.
   ///
-  void setFeatureBits(FeatureBitset& FeatureBits_) { FeatureBits = FeatureBits_; }
+  void setFeatureBits(uint64_t FeatureBits_) { FeatureBits = FeatureBits_; }
 
   /// InitMCProcessorInfo - Set or change the CPU (optionally supplemented with
   /// feature string). Recompute feature bits and scheduling model.
@@ -84,15 +84,11 @@ public:
 
   /// ToggleFeature - Toggle a feature and returns the re-computed feature
   /// bits. This version does not change the implied bits.
-  FeatureBitset ToggleFeature(uint64_t FB);
+  uint64_t ToggleFeature(uint64_t FB);
 
   /// ToggleFeature - Toggle a feature and returns the re-computed feature
-  /// bits. This version does not change the implied bits.
-  FeatureBitset ToggleFeature(const FeatureBitset& FB);
-
-  /// ToggleFeature - Toggle a set of features and returns the re-computed
-  /// feature bits. This version will also change all implied bits.
-  FeatureBitset ToggleFeature(StringRef FS);
+  /// bits. This version will also change all implied bits.
+  uint64_t ToggleFeature(StringRef FS);
 
   /// getSchedModelForCPU - Get the machine model of a CPU.
   ///
diff --git a/include/llvm/MC/SubtargetFeature.h b/include/llvm/MC/SubtargetFeature.h
index fd096382686..bfecb8ba6ab 100644
--- a/include/llvm/MC/SubtargetFeature.h
+++ b/include/llvm/MC/SubtargetFeature.h
@@ -21,29 +21,11 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Support/DataTypes.h"
-#include <bitset>
 
 namespace llvm {
   class raw_ostream;
   class StringRef;
 
-// A container class for subtarget features.
-// This is convenient because std::bitset does not have a constructor
-// with an initializer list of set bits.
-const unsigned MAX_SUBTARGET_FEATURES = 64;
-class FeatureBitset : public std::bitset<MAX_SUBTARGET_FEATURES> {
-public:
-  // Cannot inherit constructors because it's not supported by VC++..
-  FeatureBitset() : bitset() {}
-
-  FeatureBitset(const bitset<MAX_SUBTARGET_FEATURES>& B) : bitset(B) {}
-
-  FeatureBitset(std::initializer_list<unsigned> Init) : bitset() {
-    for (auto I = Init.begin() , E = Init.end(); I != E; ++I)
-      set(*I);
-  }
-};
-
 //===----------------------------------------------------------------------===//
 ///
 /// SubtargetFeatureKV - Used to provide key value pairs for feature and
@@ -52,8 +34,8 @@ public:
 struct SubtargetFeatureKV {
   const char *Key;                      // K-V key string
   const char *Desc;                     // Help descriptor
-  FeatureBitset Value;                  // K-V integer value
-  FeatureBitset Implies;                // K-V bit mask
+  uint64_t Value;                       // K-V integer value
+  uint64_t Implies;                     // K-V bit mask
 
   // Compare routine for std::lower_bound
   bool operator<(StringRef S) const {
@@ -100,11 +82,11 @@ public:
 
   /// ToggleFeature - Toggle a feature and returns the newly updated feature
   /// bits.
-  FeatureBitset ToggleFeature(FeatureBitset Bits, StringRef String,
+  uint64_t ToggleFeature(uint64_t Bits, StringRef String,
                          ArrayRef<SubtargetFeatureKV> FeatureTable);
 
   /// Get feature bits of a CPU.
-  FeatureBitset getFeatureBits(StringRef CPU,
+  uint64_t getFeatureBits(StringRef CPU,
                           ArrayRef<SubtargetFeatureKV> CPUTable,
                           ArrayRef<SubtargetFeatureKV> FeatureTable);
 
diff --git a/lib/MC/MCSubtargetInfo.cpp b/lib/MC/MCSubtargetInfo.cpp
index aed91c5cadf..ca3894b29d3 100644
--- a/lib/MC/MCSubtargetInfo.cpp
+++ b/lib/MC/MCSubtargetInfo.cpp
@@ -63,19 +63,14 @@ MCSubtargetInfo::InitMCSubtargetInfo(StringRef TT, StringRef C, StringRef FS,
 
 /// ToggleFeature - Toggle a feature and returns the re-computed feature
 /// bits. This version does not change the implied bits.
-FeatureBitset MCSubtargetInfo::ToggleFeature(uint64_t FB) {
-  FeatureBits.flip(FB);
-  return FeatureBits;
-}
-
-FeatureBitset MCSubtargetInfo::ToggleFeature(const FeatureBitset &FB) {
+uint64_t MCSubtargetInfo::ToggleFeature(uint64_t FB) {
   FeatureBits ^= FB;
   return FeatureBits;
 }
 
 /// ToggleFeature - Toggle a feature and returns the re-computed feature
 /// bits. This version will also change all implied bits.
-FeatureBitset MCSubtargetInfo::ToggleFeature(StringRef FS) {
+uint64_t MCSubtargetInfo::ToggleFeature(StringRef FS) {
   SubtargetFeatures Features;
   FeatureBits = Features.ToggleFeature(FeatureBits, FS, ProcFeatures);
   return FeatureBits;
diff --git a/lib/MC/SubtargetFeature.cpp b/lib/MC/SubtargetFeature.cpp
index 2740839cd99..587be5427aa 100644
--- a/lib/MC/SubtargetFeature.cpp
+++ b/lib/MC/SubtargetFeature.cpp
@@ -150,12 +150,12 @@ std::string SubtargetFeatures::getString() const {
 /// feature, set it.
 ///
 static
-void SetImpliedBits(FeatureBitset &Bits, const SubtargetFeatureKV *FeatureEntry,
+void SetImpliedBits(uint64_t &Bits, const SubtargetFeatureKV *FeatureEntry,
                     ArrayRef<SubtargetFeatureKV> FeatureTable) {
   for (auto &FE : FeatureTable) {
     if (FeatureEntry->Value == FE.Value) continue;
 
-    if ((FeatureEntry->Implies & FE.Value).any()) {
+    if (FeatureEntry->Implies & FE.Value) {
       Bits |= FE.Value;
       SetImpliedBits(Bits, &FE, FeatureTable);
     }
@@ -166,13 +166,12 @@ void SetImpliedBits(FeatureBitset &Bits, const SubtargetFeatureKV *FeatureEntry,
 /// feature, clear it.
 ///
 static
-void ClearImpliedBits(FeatureBitset &Bits, 
-                      const SubtargetFeatureKV *FeatureEntry,
+void ClearImpliedBits(uint64_t &Bits, const SubtargetFeatureKV *FeatureEntry,
                       ArrayRef<SubtargetFeatureKV> FeatureTable) {
   for (auto &FE : FeatureTable) {
     if (FeatureEntry->Value == FE.Value) continue;
 
-    if ((FE.Implies & FeatureEntry->Value).any()) {
+    if (FE.Implies & FeatureEntry->Value) {
       Bits &= ~FE.Value;
       ClearImpliedBits(Bits, &FE, FeatureTable);
     }
@@ -181,8 +180,8 @@ void ClearImpliedBits(FeatureBitset &Bits,
 
 /// ToggleFeature - Toggle a feature and returns the newly updated feature
 /// bits.
-FeatureBitset
-SubtargetFeatures::ToggleFeature(FeatureBitset Bits, StringRef Feature,
+uint64_t
+SubtargetFeatures::ToggleFeature(uint64_t Bits, StringRef Feature,
                                  ArrayRef<SubtargetFeatureKV> FeatureTable) {
 
   // Find feature in table.
@@ -192,6 +191,7 @@ SubtargetFeatures::ToggleFeature(FeatureBitset Bits, StringRef Feature,
   if (FeatureEntry) {
     if ((Bits & FeatureEntry->Value) == FeatureEntry->Value) {
       Bits &= ~FeatureEntry->Value;
+
       // For each feature that implies this, clear it.
       ClearImpliedBits(Bits, FeatureEntry, FeatureTable);
     } else {
@@ -212,13 +212,13 @@ SubtargetFeatures::ToggleFeature(FeatureBitset Bits, StringRef Feature,
 
 /// getFeatureBits - Get feature bits a CPU.
 ///
-FeatureBitset
+uint64_t
 SubtargetFeatures::getFeatureBits(StringRef CPU,
                                   ArrayRef<SubtargetFeatureKV> CPUTable,
                                   ArrayRef<SubtargetFeatureKV> FeatureTable) {
 
   if (CPUTable.empty() || FeatureTable.empty())
-    return FeatureBitset();
+    return 0;
 
 #ifndef NDEBUG
   for (size_t i = 1, e = CPUTable.size(); i != e; ++i) {
@@ -230,8 +230,7 @@ SubtargetFeatures::getFeatureBits(StringRef CPU,
           "CPU features table is not sorted");
   }
 #endif
-  // Resulting bits
-  FeatureBitset Bits;
+  uint64_t Bits = 0;                    // Resulting bits
 
   // Check if help is needed
   if (CPU == "help")
@@ -248,7 +247,7 @@ SubtargetFeatures::getFeatureBits(StringRef CPU,
 
       // Set the feature implied by this CPU feature, if any.
       for (auto &FE : FeatureTable) {
-        if ((CPUEntry->Value & FE.Value).any())
+        if (CPUEntry->Value & FE.Value)
           SetImpliedBits(Bits, &FE, FeatureTable);
       }
     } else {
diff --git a/lib/Target/AArch64/Utils/AArch64BaseInfo.cpp b/lib/Target/AArch64/Utils/AArch64BaseInfo.cpp
index d127773283f..bc6c7a96f85 100644
--- a/lib/Target/AArch64/Utils/AArch64BaseInfo.cpp
+++ b/lib/Target/AArch64/Utils/AArch64BaseInfo.cpp
@@ -14,7 +14,6 @@
 #include "llvm/ADT/APFloat.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
-#include "llvm/MC/SubtargetFeature.h"
 #include "llvm/Support/Regex.h"
 
 using namespace llvm;
@@ -246,7 +245,7 @@ const AArch64NamedImmMapper::Mapping AArch64SysReg::MRSMapper::MRSPairs[] = {
   {"ich_elsr_el2", ICH_ELSR_EL2}
 };
 
-AArch64SysReg::MRSMapper::MRSMapper(const FeatureBitset &FeatureBits)
+AArch64SysReg::MRSMapper::MRSMapper(uint64_t FeatureBits)
   : SysRegMapper(FeatureBits) {
     InstPairs = &MRSPairs[0];
     NumInstPairs = llvm::array_lengthof(MRSPairs);
@@ -270,7 +269,7 @@ const AArch64NamedImmMapper::Mapping AArch64SysReg::MSRMapper::MSRPairs[] = {
   {"icc_sgi0r_el1", ICC_SGI0R_EL1}
 };
 
-AArch64SysReg::MSRMapper::MSRMapper(const FeatureBitset &FeatureBits)
+AArch64SysReg::MSRMapper::MSRMapper(uint64_t FeatureBits)
   : SysRegMapper(FeatureBits) {
     InstPairs = &MSRPairs[0];
     NumInstPairs = llvm::array_lengthof(MSRPairs);
@@ -774,7 +773,7 @@ AArch64SysReg::SysRegMapper::fromString(StringRef Name, bool &Valid) const {
   }
 
   // Next search for target specific registers
-  if (FeatureBits[AArch64::ProcCyclone]) {
+  if (FeatureBits & AArch64::ProcCyclone) {
     for (unsigned i = 0; i < array_lengthof(CycloneSysRegPairs); ++i) {
       if (CycloneSysRegPairs[i].Name == NameLower) {
         Valid = true;
@@ -824,7 +823,7 @@ AArch64SysReg::SysRegMapper::toString(uint32_t Bits) const {
   }
 
   // Next search for target specific registers
-  if (FeatureBits[AArch64::ProcCyclone]) {
+  if (FeatureBits & AArch64::ProcCyclone) {
     for (unsigned i = 0; i < array_lengthof(CycloneSysRegPairs); ++i) {
       if (CycloneSysRegPairs[i].Value == Bits) {
         return CycloneSysRegPairs[i].Name;
diff --git a/lib/Target/AArch64/Utils/AArch64BaseInfo.h b/lib/Target/AArch64/Utils/AArch64BaseInfo.h
index 4e80a79d293..6d0337ce15e 100644
--- a/lib/Target/AArch64/Utils/AArch64BaseInfo.h
+++ b/lib/Target/AArch64/Utils/AArch64BaseInfo.h
@@ -26,8 +26,6 @@
 
 namespace llvm {
 
-class FeatureBitset;
-
 inline static unsigned getWRegFromXReg(unsigned Reg) {
   switch (Reg) {
   case AArch64::X0: return AArch64::W0;
@@ -1141,21 +1139,21 @@ namespace AArch64SysReg {
 
     const AArch64NamedImmMapper::Mapping *InstPairs;
     size_t NumInstPairs;
-    const FeatureBitset &FeatureBits;
+    uint64_t FeatureBits;
 
-    SysRegMapper(const FeatureBitset &FeatureBits) : FeatureBits(FeatureBits) { }
+    SysRegMapper(uint64_t FeatureBits) : FeatureBits(FeatureBits) { }
     uint32_t fromString(StringRef Name, bool &Valid) const;
     std::string toString(uint32_t Bits) const;
   };
 
   struct MSRMapper : SysRegMapper {
     static const AArch64NamedImmMapper::Mapping MSRPairs[];
-    MSRMapper(const FeatureBitset &FeatureBits);
+    MSRMapper(uint64_t FeatureBits);
   };
 
   struct MRSMapper : SysRegMapper {
     static const AArch64NamedImmMapper::Mapping MRSPairs[];
-    MRSMapper(const FeatureBitset &FeatureBits);
+    MRSMapper(uint64_t FeatureBits);
   };
 
   uint32_t ParseGenericRegister(StringRef Name, bool &Valid);
diff --git a/lib/Target/ARM/ARMAsmPrinter.cpp b/lib/Target/ARM/ARMAsmPrinter.cpp
index e21135c7cd3..971e10df8b9 100644
--- a/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -420,7 +420,7 @@ bool ARMAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
 }
 
 static bool isThumb(const MCSubtargetInfo& STI) {
-  return STI.getFeatureBits()[ARM::ModeThumb];
+  return (STI.getFeatureBits() & ARM::ModeThumb) != 0;
 }
 
 void ARMAsmPrinter::emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
diff --git a/lib/Target/ARM/ARMBaseInstrInfo.cpp b/lib/Target/ARM/ARMBaseInstrInfo.cpp
index 1dfc6194406..7ee3cb0a3d1 100644
--- a/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -4513,7 +4513,7 @@ breakPartialRegDependency(MachineBasicBlock::iterator MI,
 }
 
 bool ARMBaseInstrInfo::hasNOP() const {
-  return Subtarget.getFeatureBits()[ARM::HasV6KOps];
+  return (Subtarget.getFeatureBits() & ARM::HasV6KOps) != 0;
 }
 
 bool ARMBaseInstrInfo::isSwiftFastImmShift(const MachineInstr *MI) const {
diff --git a/lib/Target/ARM/ARMSubtarget.cpp b/lib/Target/ARM/ARMSubtarget.cpp
index a994869267e..3b0d787528d 100644
--- a/lib/Target/ARM/ARMSubtarget.cpp
+++ b/lib/Target/ARM/ARMSubtarget.cpp
@@ -263,8 +263,8 @@ void ARMSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
   }
 
   // NEON f32 ops are non-IEEE 754 compliant. Darwin is ok with it by default.
-  const FeatureBitset &Bits = getFeatureBits();
-  if ((Bits[ARM::ProcA5] || Bits[ARM::ProcA8]) && // Where this matters
+  uint64_t Bits = getFeatureBits();
+  if ((Bits & ARM::ProcA5 || Bits & ARM::ProcA8) && // Where this matters
       (Options.UnsafeFPMath || isTargetDarwin()))
     UseNEONForSinglePrecisionFP = true;
 }
diff --git a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 61dde57015c..f7d397b7f02 100644
--- a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -244,37 +244,37 @@ class ARMAsmParser : public MCTargetAsmParser {
 
   bool isThumb() const {
     // FIXME: Can tablegen auto-generate this?
-    return STI.getFeatureBits()[ARM::ModeThumb];
+    return (STI.getFeatureBits() & ARM::ModeThumb) != 0;
   }
   bool isThumbOne() const {
-    return isThumb() && !STI.getFeatureBits()[ARM::FeatureThumb2];
+    return isThumb() && (STI.getFeatureBits() & ARM::FeatureThumb2) == 0;
   }
   bool isThumbTwo() const {
-    return isThumb() && STI.getFeatureBits()[ARM::FeatureThumb2];
+    return isThumb() && (STI.getFeatureBits() & ARM::FeatureThumb2);
   }
   bool hasThumb() const {
-    return STI.getFeatureBits()[ARM::HasV4TOps];
+    return STI.getFeatureBits() & ARM::HasV4TOps;
   }
   bool hasV6Ops() const {
-    return STI.getFeatureBits()[ARM::HasV6Ops];
+    return STI.getFeatureBits() & ARM::HasV6Ops;
   }
   bool hasV6MOps() const {
-    return STI.getFeatureBits()[ARM::HasV6MOps];
+    return STI.getFeatureBits() & ARM::HasV6MOps;
   }
   bool hasV7Ops() const {
-    return STI.getFeatureBits()[ARM::HasV7Ops];
+    return STI.getFeatureBits() & ARM::HasV7Ops;
   }
   bool hasV8Ops() const {
-    return STI.getFeatureBits()[ARM::HasV8Ops];
+    return STI.getFeatureBits() & ARM::HasV8Ops;
   }
   bool hasARM() const {
-    return !STI.getFeatureBits()[ARM::FeatureNoARM];
+    return !(STI.getFeatureBits() & ARM::FeatureNoARM);
   }
   bool hasThumb2DSP() const {
-    return STI.getFeatureBits()[ARM::FeatureDSPThumb2];
+    return STI.getFeatureBits() & ARM::FeatureDSPThumb2;
   }
   bool hasD16() const {
-    return STI.getFeatureBits()[ARM::FeatureD16];
+    return STI.getFeatureBits() & ARM::FeatureD16;
   }
 
   void SwitchMode() {
@@ -282,7 +282,7 @@ class ARMAsmParser : public MCTargetAsmParser {
     setAvailableFeatures(FB);
   }
   bool isMClass() const {
-    return STI.getFeatureBits()[ARM::FeatureMClass];
+    return STI.getFeatureBits() & ARM::FeatureMClass;
   }
 
   /// @name Auto-generated Match Functions
@@ -9186,53 +9186,52 @@ bool ARMAsmParser::parseDirectiveCPU(SMLoc L) {
 // tools/clang/lib/Driver/Tools.cpp
 static const struct {
   const unsigned ID;
-  const FeatureBitset Enabled;
-  const FeatureBitset Disabled;
+  const uint64_t Enabled;
+  const uint64_t Disabled;
 } FPUs[] = {
-      {/* ID */ ARM::VFP, 
-       /* Enabled */ {ARM::FeatureVFP2}, 
-       /* Disabled */ {ARM::FeatureNEON}},
-      {/* ID */ ARM::VFPV2, 
-       /* Enabled */ {ARM::FeatureVFP2}, 
-       /* Disabled */ {ARM::FeatureNEON}},
-      {/* ID */ ARM::VFPV3, 
-       /* Enabled */ {ARM::FeatureVFP2, ARM::FeatureVFP3},  
-       /* Disabled */ {ARM::FeatureNEON, ARM::FeatureD16}},
-      {/* ID */ ARM::VFPV3_D16, 
-       /* Enabled */ {ARM::FeatureVFP2, ARM::FeatureVFP3, ARM::FeatureD16},
-       /* Disabled */ {ARM::FeatureNEON}},
-      {/* ID */ ARM::VFPV4, 
-       /* Enabled */ {ARM::FeatureVFP2, ARM::FeatureVFP3, ARM::FeatureVFP4},
-       /* Disabled */ {ARM::FeatureNEON, ARM::FeatureD16}},
-      {/* ID */ ARM::VFPV4_D16, 
-       /* Enabled */ {ARM::FeatureVFP2, ARM::FeatureVFP3, ARM::FeatureVFP4,
-                      ARM::FeatureD16},
-       /* Disabled */ {ARM::FeatureNEON}},
-      {/* ID */ ARM::FPV5_D16, 
-       /* Enabled */ {ARM::FeatureVFP2, ARM::FeatureVFP3, ARM::FeatureVFP4,
-                      ARM::FeatureFPARMv8, ARM::FeatureD16},
-       /* Disabled */ {ARM::FeatureNEON, ARM::FeatureCrypto}},
-      {/* ID */ ARM::FP_ARMV8, 
-       /* Enabled */ {ARM::FeatureVFP2, ARM::FeatureVFP3, ARM::FeatureVFP4,
-                      ARM::FeatureFPARMv8},
-       /* Disabled */ {ARM::FeatureNEON, ARM::FeatureCrypto, ARM::FeatureD16}},
-      {/* ID */ ARM::NEON, 
-       /* Enabled */ {ARM::FeatureVFP2, ARM::FeatureVFP3, ARM::FeatureNEON}, 
-       /* Disabled */ {ARM::FeatureD16}},
-      {/* ID */ ARM::NEON_VFPV4, 
-       /* Enabled */ {ARM::FeatureVFP2, ARM::FeatureVFP3, ARM::FeatureVFP4,
-                      ARM::FeatureNEON}, 
-       /* Disabled */ {ARM::FeatureD16}},
-      {/* ID */ ARM::NEON_FP_ARMV8, 
-       /* Enabled */ {ARM::FeatureVFP2, ARM::FeatureVFP3, ARM::FeatureVFP4,
-                      ARM::FeatureFPARMv8, ARM::FeatureNEON},
-       /* Disabled */ {ARM::FeatureCrypto, ARM::FeatureD16}},
-      {/* ID */ ARM::CRYPTO_NEON_FP_ARMV8,
-       /* Enabled */ {ARM::FeatureVFP2, ARM::FeatureVFP3, ARM::FeatureVFP4,
-                      ARM::FeatureFPARMv8, ARM::FeatureNEON, 
-                      ARM::FeatureCrypto},
-       /* Disabled */ {ARM::FeatureD16}},
-      {ARM::SOFTVFP, {}, {}},
+    {/* ID */ ARM::VFP,
+     /* Enabled */ ARM::FeatureVFP2,
+     /* Disabled */ ARM::FeatureNEON},
+    {/* ID */ ARM::VFPV2,
+     /* Enabled */ ARM::FeatureVFP2,
+     /* Disabled */ ARM::FeatureNEON},
+    {/* ID */ ARM::VFPV3,
+     /* Enabled */ ARM::FeatureVFP2 | ARM::FeatureVFP3,
+     /* Disabled */ ARM::FeatureNEON | ARM::FeatureD16},
+    {/* ID */ ARM::VFPV3_D16,
+     /* Enable */ ARM::FeatureVFP2 | ARM::FeatureVFP3 | ARM::FeatureD16,
+     /* Disabled */ ARM::FeatureNEON},
+    {/* ID */ ARM::VFPV4,
+     /* Enabled */ ARM::FeatureVFP2 | ARM::FeatureVFP3 | ARM::FeatureVFP4,
+     /* Disabled */ ARM::FeatureNEON | ARM::FeatureD16},
+    {/* ID */ ARM::VFPV4_D16,
+     /* Enabled */ ARM::FeatureVFP2 | ARM::FeatureVFP3 | ARM::FeatureVFP4 |
+         ARM::FeatureD16,
+     /* Disabled */ ARM::FeatureNEON},
+    {/* ID */ ARM::FPV5_D16,
+     /* Enabled */ ARM::FeatureVFP2 | ARM::FeatureVFP3 | ARM::FeatureVFP4 |
+         ARM::FeatureFPARMv8 | ARM::FeatureD16,
+     /* Disabled */ ARM::FeatureNEON | ARM::FeatureCrypto},
+    {/* ID */ ARM::FP_ARMV8,
+     /* Enabled */ ARM::FeatureVFP2 | ARM::FeatureVFP3 | ARM::FeatureVFP4 |
+         ARM::FeatureFPARMv8,
+     /* Disabled */ ARM::FeatureNEON | ARM::FeatureCrypto | ARM::FeatureD16},
+    {/* ID */ ARM::NEON,
+     /* Enabled */ ARM::FeatureVFP2 | ARM::FeatureVFP3 | ARM::FeatureNEON,
+     /* Disabled */ ARM::FeatureD16},
+    {/* ID */ ARM::NEON_VFPV4,
+     /* Enabled */ ARM::FeatureVFP2 | ARM::FeatureVFP3 | ARM::FeatureVFP4 |
+         ARM::FeatureNEON,
+     /* Disabled */ ARM::FeatureD16},
+    {/* ID */ ARM::NEON_FP_ARMV8,
+     /* Enabled */ ARM::FeatureVFP2 | ARM::FeatureVFP3 | ARM::FeatureVFP4 |
+         ARM::FeatureFPARMv8 | ARM::FeatureNEON,
+     /* Disabled */ ARM::FeatureCrypto | ARM::FeatureD16},
+    {/* ID */ ARM::CRYPTO_NEON_FP_ARMV8,
+     /* Enabled */ ARM::FeatureVFP2 | ARM::FeatureVFP3 | ARM::FeatureVFP4 |
+         ARM::FeatureFPARMv8 | ARM::FeatureNEON | ARM::FeatureCrypto,
+     /* Disabled */ ARM::FeatureD16},
+    {ARM::SOFTVFP, 0, 0},
 };
 
 /// parseDirectiveFPU
@@ -9257,8 +9256,8 @@ bool ARMAsmParser::parseDirectiveFPU(SMLoc L) {
 
     // Need to toggle features that should be on but are off and that
     // should off but are on.
-    FeatureBitset Toggle = (Entry.Enabled & ~STI.getFeatureBits()) |
-                           (Entry.Disabled & STI.getFeatureBits());
+    uint64_t Toggle = (Entry.Enabled & ~STI.getFeatureBits()) |
+                      (Entry.Disabled & STI.getFeatureBits());
     setAvailableFeatures(ComputeAvailableFeatures(STI.ToggleFeature(Toggle)));
     break;
   }
@@ -9995,30 +9994,30 @@ extern "C" void LLVMInitializeARMAsmParser() {
 static const struct {
   const char *Name;
   const unsigned ArchCheck;
-  const FeatureBitset Features;
+  const uint64_t Features;
 } Extensions[] = {
-  { "crc", Feature_HasV8, {ARM::FeatureCRC} },
+  { "crc", Feature_HasV8, ARM::FeatureCRC },
   { "crypto",  Feature_HasV8,
-    {ARM::FeatureCrypto, ARM::FeatureNEON, ARM::FeatureFPARMv8} },
-  { "fp", Feature_HasV8, {ARM::FeatureFPARMv8} },
+    ARM::FeatureCrypto | ARM::FeatureNEON | ARM::FeatureFPARMv8 },
+  { "fp", Feature_HasV8, ARM::FeatureFPARMv8 },
   { "idiv", Feature_HasV7 | Feature_IsNotMClass,
-    {ARM::FeatureHWDiv, ARM::FeatureHWDivARM} },
+    ARM::FeatureHWDiv | ARM::FeatureHWDivARM },
   // FIXME: iWMMXT not supported
-  { "iwmmxt", Feature_None, {} },
+  { "iwmmxt", Feature_None, 0 },
   // FIXME: iWMMXT2 not supported
-  { "iwmmxt2", Feature_None, {} },
+  { "iwmmxt2", Feature_None, 0 },
   // FIXME: Maverick not supported
-  { "maverick", Feature_None, {} },
-  { "mp", Feature_HasV7 | Feature_IsNotMClass, {ARM::FeatureMP} },
+  { "maverick", Feature_None, 0 },
+  { "mp", Feature_HasV7 | Feature_IsNotMClass, ARM::FeatureMP },
   // FIXME: ARMv6-m OS Extensions feature not checked
-  { "os", Feature_None, {} },
+  { "os", Feature_None, 0 },
   // FIXME: Also available in ARMv6-K
-  { "sec", Feature_HasV7, {ARM::FeatureTrustZone} },
-  { "simd", Feature_HasV8, {ARM::FeatureNEON, ARM::FeatureFPARMv8} },
+  { "sec", Feature_HasV7, ARM::FeatureTrustZone },
+  { "simd", Feature_HasV8, ARM::FeatureNEON | ARM::FeatureFPARMv8 },
   // FIXME: Only available in A-class, isel not predicated
-  { "virt", Feature_HasV7, {ARM::FeatureVirtualization} },
+  { "virt", Feature_HasV7, ARM::FeatureVirtualization },
   // FIXME: xscale not supported
-  { "xscale", Feature_None, {} },
+  { "xscale", Feature_None, 0 },
 };
 
 /// parseDirectiveArchExtension
@@ -10046,7 +10045,7 @@ bool ARMAsmParser::parseDirectiveArchExtension(SMLoc L) {
     if (Extension.Name != Name)
       continue;
 
-    if (Extension.Features.none())
+    if (!Extension.Features)
       report_fatal_error("unsupported architectural extension: " + Name);
 
     if ((getAvailableFeatures() & Extension.ArchCheck) != Extension.ArchCheck) {
@@ -10055,10 +10054,9 @@ bool ARMAsmParser::parseDirectiveArchExtension(SMLoc L) {
       return false;
     }
 
-    FeatureBitset ToggleFeatures = EnableFeature
-      ? (~STI.getFeatureBits() & Extension.Features)
-      : ( STI.getFeatureBits() & Extension.Features);
-
+    uint64_t ToggleFeatures = EnableFeature
+                                  ? (~STI.getFeatureBits() & Extension.Features)
+                                  : ( STI.getFeatureBits() & Extension.Features);
     uint64_t Features =
         ComputeAvailableFeatures(STI.ToggleFeature(ToggleFeatures));
     setAvailableFeatures(Features);
diff --git a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index bd04422f67f..4d5122a7620 100644
--- a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -431,7 +431,7 @@ DecodeStatus ARMDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
                                              raw_ostream &CS) const {
   CommentStream = &CS;
 
-  assert(!STI.getFeatureBits()[ARM::ModeThumb] &&
+  assert(!(STI.getFeatureBits() & ARM::ModeThumb) &&
          "Asked to disassemble an ARM instruction but Subtarget is in Thumb "
          "mode!");
 
@@ -696,7 +696,7 @@ DecodeStatus ThumbDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
                                                raw_ostream &CS) const {
   CommentStream = &CS;
 
-  assert(STI.getFeatureBits()[ARM::ModeThumb] &&
+  assert((STI.getFeatureBits() & ARM::ModeThumb) &&
          "Asked to disassemble in Thumb mode but Subtarget is in ARM mode!");
 
   // We want to read exactly 2 bytes of data.
@@ -1022,10 +1022,9 @@ static const uint16_t DPRDecoderTable[] = {
 
 static DecodeStatus DecodeDPRRegisterClass(MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder) {
-  const FeatureBitset &featureBits =
-    ((const MCDisassembler*)Decoder)->getSubtargetInfo().getFeatureBits();
-
-  bool hasD16 = featureBits[ARM::FeatureD16];
+  uint64_t featureBits = ((const MCDisassembler*)Decoder)->getSubtargetInfo()
+                                                          .getFeatureBits();
+  bool hasD16 = featureBits & ARM::FeatureD16;
 
   if (RegNo > 31 || (hasD16 && RegNo > 15))
     return MCDisassembler::Fail;
@@ -1370,9 +1369,9 @@ static DecodeStatus DecodeCopMemInstruction(MCInst &Inst, unsigned Insn,
       break;
   }
 
-  const FeatureBitset &featureBits =
-    ((const MCDisassembler*)Decoder)->getSubtargetInfo().getFeatureBits();
-  if (featureBits[ARM::HasV8Ops] && (coproc != 14))
+  uint64_t featureBits = ((const MCDisassembler*)Decoder)->getSubtargetInfo()
+                                                          .getFeatureBits();
+  if ((featureBits & ARM::HasV8Ops) && (coproc != 14))
     return MCDisassembler::Fail;
 
   Inst.addOperand(MCOperand::CreateImm(coproc));
@@ -3268,11 +3267,10 @@ static DecodeStatus DecodeT2LoadShift(MCInst &Inst, unsigned Insn,
   unsigned Rt = fieldFromInstruction(Insn, 12, 4);
   unsigned Rn = fieldFromInstruction(Insn, 16, 4);
 
-  const FeatureBitset &featureBits =
-    ((const MCDisassembler*)Decoder)->getSubtargetInfo().getFeatureBits();
-
-  bool hasMP = featureBits[ARM::FeatureMP];
-  bool hasV7Ops = featureBits[ARM::HasV7Ops];
+  uint64_t featureBits = ((const MCDisassembler*)Decoder)->getSubtargetInfo()
+                                                          .getFeatureBits();
+  bool hasMP = featureBits & ARM::FeatureMP;
+  bool hasV7Ops = featureBits & ARM::HasV7Ops;
 
   if (Rn == 15) {
     switch (Inst.getOpcode()) {
@@ -3355,11 +3353,10 @@ static DecodeStatus DecodeT2LoadImm8(MCInst &Inst, unsigned Insn,
   imm |= (Rn << 9);
   unsigned add = fieldFromInstruction(Insn, 9, 1);
 
-  const FeatureBitset &featureBits =
-    ((const MCDisassembler*)Decoder)->getSubtargetInfo().getFeatureBits();
-
-  bool hasMP = featureBits[ARM::FeatureMP];
-  bool hasV7Ops = featureBits[ARM::HasV7Ops];
+  uint64_t featureBits = ((const MCDisassembler*)Decoder)->getSubtargetInfo()
+                                                          .getFeatureBits();
+  bool hasMP = featureBits & ARM::FeatureMP;
+  bool hasV7Ops = featureBits & ARM::HasV7Ops;
 
   if (Rn == 15) {
     switch (Inst.getOpcode()) {
@@ -3436,11 +3433,10 @@ static DecodeStatus DecodeT2LoadImm12(MCInst &Inst, unsigned Insn,
   unsigned imm = fieldFromInstruction(Insn, 0, 12);
   imm |= (Rn << 13);
 
-  const FeatureBitset &featureBits =
-    ((const MCDisassembler*)Decoder)->getSubtargetInfo().getFeatureBits();
-
-  bool hasMP = featureBits[ARM::FeatureMP];
-  bool hasV7Ops = featureBits[ARM::HasV7Ops];
+  uint64_t featureBits = ((const MCDisassembler*)Decoder)->getSubtargetInfo()
+                                                          .getFeatureBits();
+  bool hasMP = (featureBits & ARM::FeatureMP);
+  bool hasV7Ops = (featureBits & ARM::HasV7Ops);
 
   if (Rn == 15) {
     switch (Inst.getOpcode()) {
@@ -3554,10 +3550,9 @@ static DecodeStatus DecodeT2LoadLabel(MCInst &Inst, unsigned Insn,
   unsigned U = fieldFromInstruction(Insn, 23, 1);
   int imm = fieldFromInstruction(Insn, 0, 12);
 
-  const FeatureBitset &featureBits =
-    ((const MCDisassembler*)Decoder)->getSubtargetInfo().getFeatureBits();
-
-  bool hasV7Ops = featureBits[ARM::HasV7Ops];
+  uint64_t featureBits = ((const MCDisassembler*)Decoder)->getSubtargetInfo()
+                                                          .getFeatureBits();
+  bool hasV7Ops = (featureBits & ARM::HasV7Ops);
 
   if (Rt == 15) {
     switch (Inst.getOpcode()) {
@@ -3878,10 +3873,9 @@ static DecodeStatus DecodeCoprocessor(MCInst &Inst, unsigned Val,
   if (Val == 0xA || Val == 0xB)
     return MCDisassembler::Fail;
 
-  const FeatureBitset &featureBits =
-    ((const MCDisassembler*)Decoder)->getSubtargetInfo().getFeatureBits();
-
-  if (featureBits[ARM::HasV8Ops] && !(Val == 14 || Val == 15))
+  uint64_t featureBits = ((const MCDisassembler*)Decoder)->getSubtargetInfo()
+                                                          .getFeatureBits();
+  if ((featureBits & ARM::HasV8Ops) && !(Val == 14 || Val == 15))
     return MCDisassembler::Fail;
 
   Inst.addOperand(MCOperand::CreateImm(Val));
@@ -4031,10 +4025,9 @@ static DecodeStatus DecodeInstSyncBarrierOption(MCInst &Inst, unsigned Val,
 static DecodeStatus DecodeMSRMask(MCInst &Inst, unsigned Val,
                           uint64_t Address, const void *Decoder) {
   DecodeStatus S = MCDisassembler::Success;
-  const FeatureBitset &FeatureBits =
-    ((const MCDisassembler*)Decoder)->getSubtargetInfo().getFeatureBits();
-
-  if (FeatureBits[ARM::FeatureMClass]) {
+  uint64_t FeatureBits = ((const MCDisassembler*)Decoder)->getSubtargetInfo()
+                                                          .getFeatureBits();
+  if (FeatureBits & ARM::FeatureMClass) {
     unsigned ValLow = Val & 0xff;
 
     // Validate the SYSm value first.
@@ -4054,7 +4047,7 @@ static DecodeStatus DecodeMSRMask(MCInst &Inst, unsigned Val,
     case 17: // basepri
     case 18: // basepri_max
     case 19: // faultmask
-      if (!(FeatureBits[ARM::HasV7Ops]))
+      if (!(FeatureBits & ARM::HasV7Ops))
         // Values basepri, basepri_max and faultmask are only valid for v7m.
         return MCDisassembler::Fail;
       break;
@@ -4064,7 +4057,7 @@ static DecodeStatus DecodeMSRMask(MCInst &Inst, unsigned Val,
 
     if (Inst.getOpcode() == ARM::t2MSR_M) {
       unsigned Mask = fieldFromInstruction(Val, 10, 2);
-      if (!(FeatureBits[ARM::HasV7Ops])) {
+      if (!(FeatureBits & ARM::HasV7Ops)) {
         // The ARMv6-M MSR bits {11-10} can be only 0b10, other values are
         // unpredictable.
         if (Mask != 2)
@@ -4078,7 +4071,7 @@ static DecodeStatus DecodeMSRMask(MCInst &Inst, unsigned Val,
         // indicates the move for the GE{3:0} bits, the mask{0} bit can be set
         // only if the processor includes the DSP extension.
         if (Mask == 0 || (Mask != 2 && ValLow > 3) ||
-            (!(FeatureBits[ARM::FeatureDSPThumb2]) && (Mask & 1)))
+            (!(FeatureBits & ARM::FeatureDSPThumb2) && (Mask & 1)))
           S = MCDisassembler::SoftFail;
       }
     }
diff --git a/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp b/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
index 41287df8276..16eea335261 100644
--- a/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
+++ b/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
@@ -90,7 +90,7 @@ void ARMInstPrinter::printInst(const MCInst *MI, raw_ostream &O,
     case 3: O << "\twfi"; break;
     case 4: O << "\tsev"; break;
     case 5:
-      if (getAvailableFeatures()[ARM::HasV8Ops]) {
+      if ((getAvailableFeatures() & ARM::HasV8Ops)) {
         O << "\tsevl";
         break;
       } // Fallthrough for non-v8
@@ -299,7 +299,7 @@ void ARMInstPrinter::printInst(const MCInst *MI, raw_ostream &O,
     if (MI->getNumOperands() == 3 &&
         MI->getOperand(0).isImm() &&
         MI->getOperand(0).getImm() == 0 &&
-        getAvailableFeatures()[ARM::FeatureVirtualization]) {
+        (getAvailableFeatures() & ARM::FeatureVirtualization)) {
       O << "\teret";
       printPredicateOperand(MI, 1, O);
       printAnnotation(O, Annot);
@@ -698,7 +698,7 @@ void ARMInstPrinter::printBitfieldInvMaskImmOperand(const MCInst *MI,
 void ARMInstPrinter::printMemBOption(const MCInst *MI, unsigned OpNum,
                                      raw_ostream &O) {
   unsigned val = MI->getOperand(OpNum).getImm();
-  O << ARM_MB::MemBOptToString(val, getAvailableFeatures()[ARM::HasV8Ops]);
+  O << ARM_MB::MemBOptToString(val, (getAvailableFeatures() & ARM::HasV8Ops));
 }
 
 void ARMInstPrinter::printInstSyncBOption(const MCInst *MI, unsigned OpNum,
@@ -796,14 +796,14 @@ void ARMInstPrinter::printMSRMaskOperand(const MCInst *MI, unsigned OpNum,
   const MCOperand &Op = MI->getOperand(OpNum);
   unsigned SpecRegRBit = Op.getImm() >> 4;
   unsigned Mask = Op.getImm() & 0xf;
-  const FeatureBitset &FeatureBits = getAvailableFeatures();
+  uint64_t FeatureBits = getAvailableFeatures();
 
-  if (FeatureBits[ARM::FeatureMClass]) {
+  if (FeatureBits & ARM::FeatureMClass) {
     unsigned SYSm = Op.getImm();
     unsigned Opcode = MI->getOpcode();
 
     // For writes, handle extended mask bits if the DSP extension is present.
-    if (Opcode == ARM::t2MSR_M && FeatureBits[ARM::FeatureDSPThumb2]) {
+    if (Opcode == ARM::t2MSR_M && (FeatureBits & ARM::FeatureDSPThumb2)) {
       switch (SYSm) {
       case 0x400: O << "apsr_g"; return;
       case 0xc00: O << "apsr_nzcvqg"; return;
@@ -819,7 +819,7 @@ void ARMInstPrinter::printMSRMaskOperand(const MCInst *MI, unsigned OpNum,
     // Handle the basic 8-bit mask.
     SYSm &= 0xff;
 
-    if (Opcode == ARM::t2MSR_M && FeatureBits [ARM::HasV7Ops]) {
+    if (Opcode == ARM::t2MSR_M && (FeatureBits & ARM::HasV7Ops)) {
       // ARMv7-M deprecates using MSR APSR without a _<bits> qualifier as an
       // alias for MSR APSR_nzcvq.
       switch (SYSm) {
diff --git a/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.h b/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.h
index 1246cc46a60..f4f10821037 100644
--- a/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.h
+++ b/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.h
@@ -33,7 +33,7 @@ public:
     return ARM::NumTargetFixupKinds;
   }
 
-  bool hasNOP() const { return STI->getFeatureBits()[ARM::HasV6T2Ops]; }
+  bool hasNOP() const { return (STI->getFeatureBits() & ARM::HasV6T2Ops) != 0; }
 
   const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
 
diff --git a/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp b/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
index 4d1bec33401..e48cabbf7ee 100644
--- a/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
+++ b/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
@@ -51,10 +51,10 @@ public:
   ~ARMMCCodeEmitter() {}
 
   bool isThumb(const MCSubtargetInfo &STI) const {
-    return STI.getFeatureBits()[ARM::ModeThumb];
+    return (STI.getFeatureBits() & ARM::ModeThumb) != 0;
   }
   bool isThumb2(const MCSubtargetInfo &STI) const {
-    return isThumb(STI) && STI.getFeatureBits()[ARM::FeatureThumb2];
+    return isThumb(STI) && (STI.getFeatureBits() & ARM::FeatureThumb2) != 0;
   }
   bool isTargetMachO(const MCSubtargetInfo &STI) const {
     Triple TT(STI.getTargetTriple());
diff --git a/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp b/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
index 3ecd559348a..82dac5c4357 100644
--- a/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
+++ b/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
@@ -33,7 +33,7 @@ using namespace llvm;
 
 static bool getMCRDeprecationInfo(MCInst &MI, MCSubtargetInfo &STI,
                                   std::string &Info) {
-  if (STI.getFeatureBits()[llvm::ARM::HasV7Ops] &&
+  if (STI.getFeatureBits() & llvm::ARM::HasV7Ops &&
       (MI.getOperand(0).isImm() && MI.getOperand(0).getImm() == 15) &&
       (MI.getOperand(1).isImm() && MI.getOperand(1).getImm() == 0) &&
       // Checks for the deprecated CP15ISB encoding:
@@ -65,7 +65,7 @@ static bool getMCRDeprecationInfo(MCInst &MI, MCSubtargetInfo &STI,
 
 static bool getITDeprecationInfo(MCInst &MI, MCSubtargetInfo &STI,
                                  std::string &Info) {
-  if (STI.getFeatureBits()[llvm::ARM::HasV8Ops] && MI.getOperand(1).isImm() &&
+  if (STI.getFeatureBits() & llvm::ARM::HasV8Ops && MI.getOperand(1).isImm() &&
       MI.getOperand(1).getImm() != 8) {
     Info = "applying IT instruction to more than one subsequent instruction is "
            "deprecated";
@@ -77,7 +77,7 @@ static bool getITDeprecationInfo(MCInst &MI, MCSubtargetInfo &STI,
 
 static bool getARMStoreDeprecationInfo(MCInst &MI, MCSubtargetInfo &STI,
                                        std::string &Info) {
-  assert(!STI.getFeatureBits()[llvm::ARM::ModeThumb] &&
+  assert((~STI.getFeatureBits() & llvm::ARM::ModeThumb) &&
          "cannot predicate thumb instructions");
 
   assert(MI.getNumOperands() >= 4 && "expected >= 4 arguments");
@@ -94,7 +94,7 @@ static bool getARMStoreDeprecationInfo(MCInst &MI, MCSubtargetInfo &STI,
 
 static bool getARMLoadDeprecationInfo(MCInst &MI, MCSubtargetInfo &STI,
                                       std::string &Info) {
-  assert(!STI.getFeatureBits()[llvm::ARM::ModeThumb] &&
+  assert((~STI.getFeatureBits() & llvm::ARM::ModeThumb) &&
          "cannot predicate thumb instructions");
 
   assert(MI.getNumOperands() >= 4 && "expected >= 4 arguments");
diff --git a/lib/Target/Mips/AsmParser/MipsAsmParser.cpp b/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
index 7f3858a22ad..a502466338b 100644
--- a/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ b/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -72,7 +72,15 @@ public:
   // The full table can be found in MipsGenSubtargetInfo.inc (MipsFeatureKV[]).
   // The reason we need this mask is explained in the selectArch function.
   // FIXME: Ideally we would like TableGen to generate this information.
-  static const FeatureBitset AllArchRelatedMask;
+  static const uint64_t AllArchRelatedMask =
+      Mips::FeatureMips1 | Mips::FeatureMips2 | Mips::FeatureMips3 |
+      Mips::FeatureMips3_32 | Mips::FeatureMips3_32r2 | Mips::FeatureMips4 |
+      Mips::FeatureMips4_32 | Mips::FeatureMips4_32r2 | Mips::FeatureMips5 |
+      Mips::FeatureMips5_32r2 | Mips::FeatureMips32 | Mips::FeatureMips32r2 |
+      Mips::FeatureMips32r3 | Mips::FeatureMips32r5 | Mips::FeatureMips32r6 |
+      Mips::FeatureMips64 | Mips::FeatureMips64r2 | Mips::FeatureMips64r3 |
+      Mips::FeatureMips64r5 | Mips::FeatureMips64r6 | Mips::FeatureCnMips |
+      Mips::FeatureFP64Bit | Mips::FeatureGP64Bit | Mips::FeatureNaN2008;
 
 private:
   unsigned ATReg;
@@ -82,17 +90,6 @@ private:
 };
 }
 
-const FeatureBitset MipsAssemblerOptions::AllArchRelatedMask = {
-    Mips::FeatureMips1, Mips::FeatureMips2, Mips::FeatureMips3,
-    Mips::FeatureMips3_32, Mips::FeatureMips3_32r2, Mips::FeatureMips4,
-    Mips::FeatureMips4_32, Mips::FeatureMips4_32r2, Mips::FeatureMips5,
-    Mips::FeatureMips5_32r2, Mips::FeatureMips32, Mips::FeatureMips32r2,
-    Mips::FeatureMips32r3, Mips::FeatureMips32r5, Mips::FeatureMips32r6,
-    Mips::FeatureMips64, Mips::FeatureMips64r2, Mips::FeatureMips64r3,
-    Mips::FeatureMips64r5, Mips::FeatureMips64r6, Mips::FeatureCnMips,
-    Mips::FeatureFP64Bit, Mips::FeatureGP64Bit, Mips::FeatureNaN2008
-};
-
 namespace {
 class MipsAsmParser : public MCTargetAsmParser {
   MipsTargetStreamer &getTargetStreamer() {
@@ -302,7 +299,7 @@ class MipsAsmParser : public MCTargetAsmParser {
   // FeatureMipsGP64 | FeatureMips1)
   // Clearing Mips3 is equivalent to clear (FeatureMips3 | FeatureMips4).
   void selectArch(StringRef ArchFeature) {
-    FeatureBitset FeatureBits = STI.getFeatureBits();
+    uint64_t FeatureBits = STI.getFeatureBits();
     FeatureBits &= ~MipsAssemblerOptions::AllArchRelatedMask;
     STI.setFeatureBits(FeatureBits);
     setAvailableFeatures(
@@ -311,7 +308,7 @@ class MipsAsmParser : public MCTargetAsmParser {
   }
 
   void setFeatureBits(uint64_t Feature, StringRef FeatureString) {
-    if (!(STI.getFeatureBits()[Feature])) {
+    if (!(STI.getFeatureBits() & Feature)) {
       setAvailableFeatures(
           ComputeAvailableFeatures(STI.ToggleFeature(FeatureString)));
     }
@@ -319,7 +316,7 @@ class MipsAsmParser : public MCTargetAsmParser {
   }
 
   void clearFeatureBits(uint64_t Feature, StringRef FeatureString) {
-    if (STI.getFeatureBits()[Feature]) {
+    if (STI.getFeatureBits() & Feature) {
       setAvailableFeatures(
           ComputeAvailableFeatures(STI.ToggleFeature(FeatureString)));
     }
@@ -364,66 +361,65 @@ public:
   /// True if all of $fcc0 - $fcc7 exist for the current ISA.
   bool hasEightFccRegisters() const { return hasMips4() || hasMips32(); }
 
-  bool isGP64bit() const { return STI.getFeatureBits()[Mips::FeatureGP64Bit]; }
-  bool isFP64bit() const { return STI.getFeatureBits()[Mips::FeatureFP64Bit]; }
+  bool isGP64bit() const { return STI.getFeatureBits() & Mips::FeatureGP64Bit; }
+  bool isFP64bit() const { return STI.getFeatureBits() & Mips::FeatureFP64Bit; }
   const MipsABIInfo &getABI() const { return ABI; }
   bool isABI_N32() const { return ABI.IsN32(); }
   bool isABI_N64() const { return ABI.IsN64(); }
   bool isABI_O32() const { return ABI.IsO32(); }
-  bool isABI_FPXX() const { return STI.getFeatureBits()[Mips::FeatureFPXX]; }
+  bool isABI_FPXX() const { return STI.getFeatureBits() & Mips::FeatureFPXX; }
 
   bool useOddSPReg() const {
-    return !(STI.getFeatureBits()[Mips::FeatureNoOddSPReg]);
+    return !(STI.getFeatureBits() & Mips::FeatureNoOddSPReg);
   }
 
   bool inMicroMipsMode() const {
-    return STI.getFeatureBits()[Mips::FeatureMicroMips];
+    return STI.getFeatureBits() & Mips::FeatureMicroMips;
   }
-  bool hasMips1() const { return STI.getFeatureBits()[Mips::FeatureMips1]; }
-  bool hasMips2() const { return STI.getFeatureBits()[Mips::FeatureMips2]; }
-  bool hasMips3() const { return STI.getFeatureBits()[Mips::FeatureMips3]; }
-  bool hasMips4() const { return STI.getFeatureBits()[Mips::FeatureMips4]; }
-  bool hasMips5() const { return STI.getFeatureBits()[Mips::FeatureMips5]; }
+  bool hasMips1() const { return STI.getFeatureBits() & Mips::FeatureMips1; }
+  bool hasMips2() const { return STI.getFeatureBits() & Mips::FeatureMips2; }
+  bool hasMips3() const { return STI.getFeatureBits() & Mips::FeatureMips3; }
+  bool hasMips4() const { return STI.getFeatureBits() & Mips::FeatureMips4; }
+  bool hasMips5() const { return STI.getFeatureBits() & Mips::FeatureMips5; }
   bool hasMips32() const {
-    return STI.getFeatureBits()[Mips::FeatureMips32];
+    return (STI.getFeatureBits() & Mips::FeatureMips32);
   }
   bool hasMips64() const {
-    return STI.getFeatureBits()[Mips::FeatureMips64];
+    return (STI.getFeatureBits() & Mips::FeatureMips64);
   }
   bool hasMips32r2() const {
-    return STI.getFeatureBits()[Mips::FeatureMips32r2];
+    return (STI.getFeatureBits() & Mips::FeatureMips32r2);
   }
   bool hasMips64r2() const {
-    return STI.getFeatureBits()[Mips::FeatureMips64r2];
+    return (STI.getFeatureBits() & Mips::FeatureMips64r2);
   }
   bool hasMips32r3() const {
-    return (STI.getFeatureBits()[Mips::FeatureMips32r3]);
+    return (STI.getFeatureBits() & Mips::FeatureMips32r3);
   }
   bool hasMips64r3() const {
-    return (STI.getFeatureBits()[Mips::FeatureMips64r3]);
+    return (STI.getFeatureBits() & Mips::FeatureMips64r3);
   }
   bool hasMips32r5() const {
-    return (STI.getFeatureBits()[Mips::FeatureMips32r5]);
+    return (STI.getFeatureBits() & Mips::FeatureMips32r5);
   }
   bool hasMips64r5() const {
-    return (STI.getFeatureBits()[Mips::FeatureMips64r5]);
+    return (STI.getFeatureBits() & Mips::FeatureMips64r5);
   }
   bool hasMips32r6() const {
-    return STI.getFeatureBits()[Mips::FeatureMips32r6];
+    return (STI.getFeatureBits() & Mips::FeatureMips32r6);
   }
   bool hasMips64r6() const {
-    return STI.getFeatureBits()[Mips::FeatureMips64r6];
+    return (STI.getFeatureBits() & Mips::FeatureMips64r6);
   }
-
-  bool hasDSP() const { return STI.getFeatureBits()[Mips::FeatureDSP]; }
-  bool hasDSPR2() const { return STI.getFeatureBits()[Mips::FeatureDSPR2]; }
-  bool hasMSA() const { return STI.getFeatureBits()[Mips::FeatureMSA]; }
   bool hasCnMips() const {
-    return (STI.getFeatureBits()[Mips::FeatureCnMips]);
+    return (STI.getFeatureBits() & Mips::FeatureCnMips);
   }
+  bool hasDSP() const { return (STI.getFeatureBits() & Mips::FeatureDSP); }
+  bool hasDSPR2() const { return (STI.getFeatureBits() & Mips::FeatureDSPR2); }
+  bool hasMSA() const { return (STI.getFeatureBits() & Mips::FeatureMSA); }
 
   bool inMips16Mode() const {
-    return STI.getFeatureBits()[Mips::FeatureMips16];
+    return STI.getFeatureBits() & Mips::FeatureMips16;
   }
   // TODO: see how can we get this info.
   bool abiUsesSoftFloat() const { return false; }
diff --git a/lib/Target/Mips/Disassembler/MipsDisassembler.cpp b/lib/Target/Mips/Disassembler/MipsDisassembler.cpp
index c69a60b5d21..8849366e837 100644
--- a/lib/Target/Mips/Disassembler/MipsDisassembler.cpp
+++ b/lib/Target/Mips/Disassembler/MipsDisassembler.cpp
@@ -36,16 +36,16 @@ class MipsDisassembler : public MCDisassembler {
 public:
   MipsDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx, bool IsBigEndian)
       : MCDisassembler(STI, Ctx),
-        IsMicroMips(STI.getFeatureBits()[Mips::FeatureMicroMips]),
+        IsMicroMips(STI.getFeatureBits() & Mips::FeatureMicroMips),
         IsBigEndian(IsBigEndian) {}
 
-  bool hasMips3() const { return STI.getFeatureBits()[Mips::FeatureMips3]; }
-  bool hasMips32() const { return STI.getFeatureBits()[Mips::FeatureMips32]; }
+  bool hasMips3() const { return STI.getFeatureBits() & Mips::FeatureMips3; }
+  bool hasMips32() const { return STI.getFeatureBits() & Mips::FeatureMips32; }
   bool hasMips32r6() const {
-    return STI.getFeatureBits()[Mips::FeatureMips32r6];
+    return STI.getFeatureBits() & Mips::FeatureMips32r6;
   }
 
-  bool isGP64() const { return STI.getFeatureBits()[Mips::FeatureGP64Bit]; }
+  bool isGP64() const { return STI.getFeatureBits() & Mips::FeatureGP64Bit; }
 
   bool hasCOP3() const {
     // Only present in MIPS-I and MIPS-II
diff --git a/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp b/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
index 152399a0d68..1c2f2da6c96 100644
--- a/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
+++ b/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
@@ -112,7 +112,7 @@ static void LowerDextDins(MCInst& InstIn) {
 }
 
 bool MipsMCCodeEmitter::isMicroMips(const MCSubtargetInfo &STI) const {
-  return STI.getFeatureBits()[Mips::FeatureMicroMips];
+  return STI.getFeatureBits() & Mips::FeatureMicroMips;
 }
 
 void MipsMCCodeEmitter::EmitByte(unsigned char C, raw_ostream &OS) const {
@@ -175,7 +175,7 @@ EncodeInstruction(const MCInst &MI, raw_ostream &OS,
       (Opcode != Mips::SLL_MM) && !Binary)
     llvm_unreachable("unimplemented opcode in EncodeInstruction()");
 
-  if (STI.getFeatureBits()[Mips::FeatureMicroMips]) {
+  if (STI.getFeatureBits() & Mips::FeatureMicroMips) {
     int NewOpcode = Mips::Std2MicroMips (Opcode, Mips::Arch_micromips);
     if (NewOpcode != -1) {
       if (Fixups.size() > N)
diff --git a/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp b/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
index 43b4c2c287b..5790a5c649a 100644
--- a/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
+++ b/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
@@ -380,7 +380,7 @@ MipsTargetELFStreamer::MipsTargetELFStreamer(MCStreamer &S,
   MCAssembler &MCA = getStreamer().getAssembler();
   Pic = MCA.getContext().getObjectFileInfo()->getRelocM() == Reloc::PIC_;
 
-  const FeatureBitset &Features = STI.getFeatureBits();
+  uint64_t Features = STI.getFeatureBits();
 
   // Set the header flags that we can in the constructor.
   // FIXME: This is a fairly terrible hack. We set the rest
@@ -396,35 +396,35 @@ MipsTargetELFStreamer::MipsTargetELFStreamer(MCStreamer &S,
   unsigned EFlags = MCA.getELFHeaderEFlags();
 
   // Architecture
-  if (Features[Mips::FeatureMips64r6])
+  if (Features & Mips::FeatureMips64r6)
     EFlags |= ELF::EF_MIPS_ARCH_64R6;
-  else if (Features[Mips::FeatureMips64r2] ||
-           Features[Mips::FeatureMips64r3] ||
-           Features[Mips::FeatureMips64r5])
+  else if (Features & Mips::FeatureMips64r2 ||
+           Features & Mips::FeatureMips64r3 ||
+           Features & Mips::FeatureMips64r5)
     EFlags |= ELF::EF_MIPS_ARCH_64R2;
-  else if (Features[Mips::FeatureMips64])
+  else if (Features & Mips::FeatureMips64)
     EFlags |= ELF::EF_MIPS_ARCH_64;
-  else if (Features[Mips::FeatureMips5])
+  else if (Features & Mips::FeatureMips5)
     EFlags |= ELF::EF_MIPS_ARCH_5;
-  else if (Features[Mips::FeatureMips4])
+  else if (Features & Mips::FeatureMips4)
     EFlags |= ELF::EF_MIPS_ARCH_4;
-  else if (Features[Mips::FeatureMips3])
+  else if (Features & Mips::FeatureMips3)
     EFlags |= ELF::EF_MIPS_ARCH_3;
-  else if (Features[Mips::FeatureMips32r6])
+  else if (Features & Mips::FeatureMips32r6)
     EFlags |= ELF::EF_MIPS_ARCH_32R6;
-  else if (Features[Mips::FeatureMips32r2] ||
-           Features[Mips::FeatureMips32r3] ||
-           Features[Mips::FeatureMips32r5])
+  else if (Features & Mips::FeatureMips32r2 ||
+           Features & Mips::FeatureMips32r3 ||
+           Features & Mips::FeatureMips32r5)
     EFlags |= ELF::EF_MIPS_ARCH_32R2;
-  else if (Features[Mips::FeatureMips32])
+  else if (Features & Mips::FeatureMips32)
     EFlags |= ELF::EF_MIPS_ARCH_32;
-  else if (Features[Mips::FeatureMips2])
+  else if (Features & Mips::FeatureMips2)
     EFlags |= ELF::EF_MIPS_ARCH_2;
   else
     EFlags |= ELF::EF_MIPS_ARCH_1;
 
   // Other options.
-  if (Features[Mips::FeatureNaN2008])
+  if (Features & Mips::FeatureNaN2008)
     EFlags |= ELF::EF_MIPS_NAN2008;
 
   // -mabicalls and -mplt are not implemented but we should act as if they were
@@ -464,7 +464,7 @@ void MipsTargetELFStreamer::finish() {
   DataSectionData.setAlignment(std::max(16u, DataSectionData.getAlignment()));
   BSSSectionData.setAlignment(std::max(16u, BSSSectionData.getAlignment()));
 
-  const FeatureBitset &Features = STI.getFeatureBits();
+  uint64_t Features = STI.getFeatureBits();
 
   // Update e_header flags. See the FIXME and comment above in
   // the constructor for a full rundown on this.
@@ -477,10 +477,10 @@ void MipsTargetELFStreamer::finish() {
   else if (getABI().IsN32())
     EFlags |= ELF::EF_MIPS_ABI2;
 
-  if (Features[Mips::FeatureGP64Bit]) {
+  if (Features & Mips::FeatureGP64Bit) {
     if (getABI().IsO32())
       EFlags |= ELF::EF_MIPS_32BITMODE; /* Compatibility Mode */
-  } else if (Features[Mips::FeatureMips64r2] || Features[Mips::FeatureMips64])
+  } else if (Features & Mips::FeatureMips64r2 || Features & Mips::FeatureMips64)
     EFlags |= ELF::EF_MIPS_32BITMODE;
 
   // If we've set the cpic eflag and we're n64, go ahead and set the pic
diff --git a/lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp b/lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp
index 605e74bf642..0ed07239327 100644
--- a/lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp
+++ b/lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp
@@ -355,7 +355,7 @@ DecodeStatus PPCDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
   uint32_t Inst =
       (Bytes[0] << 24) | (Bytes[1] << 16) | (Bytes[2] << 8) | (Bytes[3] << 0);
 
-  if (STI.getFeatureBits()[PPC::FeatureQPX]) {
+  if ((STI.getFeatureBits() & PPC::FeatureQPX) != 0) {
     DecodeStatus result =
       decodeInstruction(DecoderTableQPX32, MI, Inst, Address, this, STI);
     if (result != MCDisassembler::Fail)
diff --git a/lib/Target/R600/MCTargetDesc/R600MCCodeEmitter.cpp b/lib/Target/R600/MCTargetDesc/R600MCCodeEmitter.cpp
index 404663416f5..fa25f590f23 100644
--- a/lib/Target/R600/MCTargetDesc/R600MCCodeEmitter.cpp
+++ b/lib/Target/R600/MCTargetDesc/R600MCCodeEmitter.cpp
@@ -99,7 +99,7 @@ void R600MCCodeEmitter::EncodeInstruction(const MCInst &MI, raw_ostream &OS,
   } else if (IS_VTX(Desc)) {
     uint64_t InstWord01 = getBinaryCodeForInstr(MI, Fixups, STI);
     uint32_t InstWord2 = MI.getOperand(2).getImm(); // Offset
-    if (!(STI.getFeatureBits()[AMDGPU::FeatureCaymanISA])) {
+    if (!(STI.getFeatureBits() & AMDGPU::FeatureCaymanISA)) {
       InstWord2 |= 1 << 19; // Mega-Fetch bit
     }
 
@@ -132,7 +132,7 @@ void R600MCCodeEmitter::EncodeInstruction(const MCInst &MI, raw_ostream &OS,
       Emit((uint32_t) 0, OS);
   } else {
     uint64_t Inst = getBinaryCodeForInstr(MI, Fixups, STI);
-    if ((STI.getFeatureBits()[AMDGPU::FeatureR600ALUInst]) &&
+    if ((STI.getFeatureBits() & AMDGPU::FeatureR600ALUInst) &&
        ((Desc.TSFlags & R600_InstFlag::OP1) ||
          Desc.TSFlags & R600_InstFlag::OP2)) {
       uint64_t ISAOpCode = Inst & (0x3FFULL << 39);
diff --git a/lib/Target/Sparc/InstPrinter/SparcInstPrinter.cpp b/lib/Target/Sparc/InstPrinter/SparcInstPrinter.cpp
index dc9fb1ac51f..5975a517994 100644
--- a/lib/Target/Sparc/InstPrinter/SparcInstPrinter.cpp
+++ b/lib/Target/Sparc/InstPrinter/SparcInstPrinter.cpp
@@ -35,7 +35,7 @@ namespace Sparc {
 #include "SparcGenAsmWriter.inc"
 
 bool SparcInstPrinter::isV9() const {
-  return (STI.getFeatureBits()[Sparc::FeatureV9]) != 0;
+  return (STI.getFeatureBits() & Sparc::FeatureV9) != 0;
 }
 
 void SparcInstPrinter::printRegName(raw_ostream &OS, unsigned RegNo) const
diff --git a/lib/Target/X86/AsmParser/X86AsmInstrumentation.cpp b/lib/Target/X86/AsmParser/X86AsmInstrumentation.cpp
index ed31a58d7ff..543af8e4e77 100644
--- a/lib/Target/X86/AsmParser/X86AsmInstrumentation.cpp
+++ b/lib/Target/X86/AsmParser/X86AsmInstrumentation.cpp
@@ -262,13 +262,13 @@ protected:
                                               MCContext &Ctx, int64_t *Residue);
 
   bool is64BitMode() const {
-    return STI.getFeatureBits()[X86::Mode64Bit];
+    return (STI.getFeatureBits() & X86::Mode64Bit) != 0;
   }
   bool is32BitMode() const {
-    return STI.getFeatureBits()[X86::Mode32Bit];
+    return (STI.getFeatureBits() & X86::Mode32Bit) != 0;
   }
   bool is16BitMode() const {
-    return STI.getFeatureBits()[X86::Mode16Bit];
+    return (STI.getFeatureBits() & X86::Mode16Bit) != 0;
   }
 
   unsigned getPointerWidth() {
@@ -1073,9 +1073,9 @@ CreateX86AsmInstrumentation(const MCTargetOptions &MCOptions,
   const bool hasCompilerRTSupport = T.isOSLinux();
   if (ClAsanInstrumentAssembly && hasCompilerRTSupport &&
       MCOptions.SanitizeAddress) {
-    if (STI.getFeatureBits()[X86::Mode32Bit] != 0)
+    if ((STI.getFeatureBits() & X86::Mode32Bit) != 0)
       return new X86AddressSanitizer32(STI);
-    if (STI.getFeatureBits()[X86::Mode64Bit] != 0)
+    if ((STI.getFeatureBits() & X86::Mode64Bit) != 0)
       return new X86AddressSanitizer64(STI);
   }
   return new X86AsmInstrumentation(STI);
diff --git a/lib/Target/X86/AsmParser/X86AsmParser.cpp b/lib/Target/X86/AsmParser/X86AsmParser.cpp
index 59d0c1a89bb..c24805a6543 100644
--- a/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ b/lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -729,24 +729,23 @@ private:
 
   bool is64BitMode() const {
     // FIXME: Can tablegen auto-generate this?
-    return STI.getFeatureBits()[X86::Mode64Bit];
+    return (STI.getFeatureBits() & X86::Mode64Bit) != 0;
   }
   bool is32BitMode() const {
     // FIXME: Can tablegen auto-generate this?
-    return STI.getFeatureBits()[X86::Mode32Bit];
+    return (STI.getFeatureBits() & X86::Mode32Bit) != 0;
   }
   bool is16BitMode() const {
     // FIXME: Can tablegen auto-generate this?
-    return STI.getFeatureBits()[X86::Mode16Bit];
+    return (STI.getFeatureBits() & X86::Mode16Bit) != 0;
   }
-  void SwitchMode(unsigned mode) {
-    FeatureBitset AllModes({X86::Mode64Bit, X86::Mode32Bit, X86::Mode16Bit});
-    FeatureBitset OldMode = STI.getFeatureBits() & AllModes;
-    unsigned FB = ComputeAvailableFeatures(
-      STI.ToggleFeature(OldMode.flip(mode)));
+  void SwitchMode(uint64_t mode) {
+    uint64_t oldMode = STI.getFeatureBits() &
+        (X86::Mode64Bit | X86::Mode32Bit | X86::Mode16Bit);
+    unsigned FB = ComputeAvailableFeatures(STI.ToggleFeature(oldMode | mode));
     setAvailableFeatures(FB);
-    
-    assert(FeatureBitset({mode}) == (STI.getFeatureBits() & AllModes));
+    assert(mode == (STI.getFeatureBits() &
+                    (X86::Mode64Bit | X86::Mode32Bit | X86::Mode16Bit)));
   }
 
   unsigned getPointerWidth() {
@@ -1689,7 +1688,7 @@ std::unique_ptr<X86Operand> X86AsmParser::ParseIntelOperand() {
   }
 
   // rounding mode token
-  if (STI.getFeatureBits()[X86::FeatureAVX512] &&
+  if (STI.getFeatureBits() & X86::FeatureAVX512 &&
       getLexer().is(AsmToken::LCurly))
     return ParseRoundingModeOp(Start, End);
 
@@ -1747,7 +1746,7 @@ std::unique_ptr<X86Operand> X86AsmParser::ParseATTOperand() {
   }
   case AsmToken::LCurly:{
     SMLoc Start = Parser.getTok().getLoc(), End;
-    if (STI.getFeatureBits()[X86::FeatureAVX512])
+    if (STI.getFeatureBits() & X86::FeatureAVX512)
       return ParseRoundingModeOp(Start, End);
     return ErrorOperand(Start, "unknown token in expression");
   }
@@ -1757,7 +1756,7 @@ std::unique_ptr<X86Operand> X86AsmParser::ParseATTOperand() {
 bool X86AsmParser::HandleAVX512Operand(OperandVector &Operands,
                                        const MCParsedAsmOperand &Op) {
   MCAsmParser &Parser = getParser();
-  if(STI.getFeatureBits()[X86::FeatureAVX512]) {
+  if(STI.getFeatureBits() & X86::FeatureAVX512) {
     if (getLexer().is(AsmToken::LCurly)) {
       // Eat "{" and mark the current place.
       const SMLoc consumedToken = consumeToken();
diff --git a/lib/Target/X86/Disassembler/X86Disassembler.cpp b/lib/Target/X86/Disassembler/X86Disassembler.cpp
index 46a6b3c8b2e..e8c547517b0 100644
--- a/lib/Target/X86/Disassembler/X86Disassembler.cpp
+++ b/lib/Target/X86/Disassembler/X86Disassembler.cpp
@@ -80,19 +80,20 @@ X86GenericDisassembler::X86GenericDisassembler(
                                          MCContext &Ctx,
                                          std::unique_ptr<const MCInstrInfo> MII)
   : MCDisassembler(STI, Ctx), MII(std::move(MII)) {
-  const FeatureBitset &FB = STI.getFeatureBits();
-  if (FB[X86::Mode16Bit]) {
+  switch (STI.getFeatureBits() &
+          (X86::Mode16Bit | X86::Mode32Bit | X86::Mode64Bit)) {
+  case X86::Mode16Bit:
     fMode = MODE_16BIT;
-    return;
-  } else if (FB[X86::Mode32Bit]) {
+    break;
+  case X86::Mode32Bit:
     fMode = MODE_32BIT;
-    return;
-  } else if (FB[X86::Mode64Bit]) {
+    break;
+  case X86::Mode64Bit:
     fMode = MODE_64BIT;
-    return;
+    break;
+  default:
+    llvm_unreachable("Invalid CPU mode");
   }
-
-  llvm_unreachable("Invalid CPU mode");
 }
 
 struct Region {
diff --git a/lib/Target/X86/InstPrinter/X86ATTInstPrinter.cpp b/lib/Target/X86/InstPrinter/X86ATTInstPrinter.cpp
index ec2dc87398d..65461af5b7b 100644
--- a/lib/Target/X86/InstPrinter/X86ATTInstPrinter.cpp
+++ b/lib/Target/X86/InstPrinter/X86ATTInstPrinter.cpp
@@ -60,7 +60,7 @@ void X86ATTInstPrinter::printInst(const MCInst *MI, raw_ostream &OS,
   // InstrInfo.td as soon as Requires clause is supported properly
   // for InstAlias.
   if (MI->getOpcode() == X86::CALLpcrel32 &&
-      getAvailableFeatures()[X86::Mode64Bit]) {
+      (getAvailableFeatures() & X86::Mode64Bit) != 0) {
     OS << "\tcallq\t";
     printPCRelImm(MI, 0, OS);
   }
diff --git a/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp b/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
index 7124501f979..9b98a3e40d4 100644
--- a/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
+++ b/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
@@ -42,15 +42,15 @@ public:
   ~X86MCCodeEmitter() {}
 
   bool is64BitMode(const MCSubtargetInfo &STI) const {
-    return STI.getFeatureBits()[X86::Mode64Bit];
+    return (STI.getFeatureBits() & X86::Mode64Bit) != 0;
   }
 
   bool is32BitMode(const MCSubtargetInfo &STI) const {
-    return STI.getFeatureBits()[X86::Mode32Bit];
+    return (STI.getFeatureBits() & X86::Mode32Bit) != 0;
   }
 
   bool is16BitMode(const MCSubtargetInfo &STI) const {
-    return STI.getFeatureBits()[X86::Mode16Bit];
+    return (STI.getFeatureBits() & X86::Mode16Bit) != 0;
   }
 
   /// Is16BitMemOperand - Return true if the specified instruction has
diff --git a/utils/TableGen/AsmMatcherEmitter.cpp b/utils/TableGen/AsmMatcherEmitter.cpp
index 65d930ad858..159bc23fbff 100644
--- a/utils/TableGen/AsmMatcherEmitter.cpp
+++ b/utils/TableGen/AsmMatcherEmitter.cpp
@@ -2248,7 +2248,7 @@ static void emitComputeAvailableFeatures(AsmMatcherInfo &Info,
     Info.AsmParser->getValueAsString("AsmParserClassName");
 
   OS << "uint64_t " << Info.Target.getName() << ClassName << "::\n"
-     << "ComputeAvailableFeatures(const FeatureBitset& FB) const {\n";
+     << "ComputeAvailableFeatures(uint64_t FB) const {\n";
   OS << "  uint64_t Features = 0;\n";
   for (const auto &SF : Info.SubtargetFeatures) {
     const SubtargetFeatureInfo &SFI = SF.second;
@@ -2270,10 +2270,12 @@ static void emitComputeAvailableFeatures(AsmMatcherInfo &Info,
         Cond = Cond.substr(1);
       }
 
-      OS << "(";
+      OS << "((FB & " << Info.Target.getName() << "::" << Cond << ")";
       if (Neg)
-        OS << "!";
-      OS << "FB[" << Info.Target.getName() << "::" << Cond << "])";
+        OS << " == 0";
+      else
+        OS << " != 0";
+      OS << ")";
 
       if (Comma.second.empty())
         break;
@@ -2643,7 +2645,7 @@ void AsmMatcherEmitter::run(raw_ostream &OS) {
   OS << "#undef GET_ASSEMBLER_HEADER\n";
   OS << "  // This should be included into the middle of the declaration of\n";
   OS << "  // your subclasses implementation of MCTargetAsmParser.\n";
-  OS << "  uint64_t ComputeAvailableFeatures(const FeatureBitset& FB) const;\n";
+  OS << "  uint64_t ComputeAvailableFeatures(uint64_t FeatureBits) const;\n";
   OS << "  void convertToMCInst(unsigned Kind, MCInst &Inst, "
      << "unsigned Opcode,\n"
      << "                       const OperandVector "
diff --git a/utils/TableGen/FixedLenDecoderEmitter.cpp b/utils/TableGen/FixedLenDecoderEmitter.cpp
index 30812fb9548..c69b89b9bc0 100644
--- a/utils/TableGen/FixedLenDecoderEmitter.cpp
+++ b/utils/TableGen/FixedLenDecoderEmitter.cpp
@@ -848,7 +848,7 @@ emitPredicateFunction(formatted_raw_ostream &OS, PredicateSet &Predicates,
   // The predicate function is just a big switch statement based on the
   // input predicate index.
   OS.indent(Indentation) << "static bool checkDecoderPredicate(unsigned Idx, "
-    << "const FeatureBitset& Bits) {\n";
+    << "uint64_t Bits) {\n";
   Indentation += 2;
   if (!Predicates.empty()) {
     OS.indent(Indentation) << "switch (Idx) {\n";
@@ -1102,10 +1102,10 @@ unsigned FilterChooser::getDecoderIndex(DecoderSet &Decoders,
 static void emitSinglePredicateMatch(raw_ostream &o, StringRef str,
                                      const std::string &PredicateNamespace) {
   if (str[0] == '!')
-    o << "!Bits[" << PredicateNamespace << "::"
-      << str.slice(1,str.size()) << "]";
+    o << "!(Bits & " << PredicateNamespace << "::"
+      << str.slice(1,str.size()) << ")";
   else
-    o << "Bits[" << PredicateNamespace << "::" << str << "]";
+    o << "(Bits & " << PredicateNamespace << "::" << str << ")";
 }
 
 bool FilterChooser::emitPredicateMatch(raw_ostream &o, unsigned &Indentation,
@@ -2010,7 +2010,7 @@ static void emitDecodeInstruction(formatted_raw_ostream &OS) {
      << "                                      InsnType insn, uint64_t Address,\n"
      << "                                      const void *DisAsm,\n"
      << "                                      const MCSubtargetInfo &STI) {\n"
-     << "  const FeatureBitset& Bits = STI.getFeatureBits();\n"
+     << "  uint64_t Bits = STI.getFeatureBits();\n"
      << "\n"
      << "  const uint8_t *Ptr = DecodeTable;\n"
      << "  uint32_t CurFieldValue = 0;\n"
diff --git a/utils/TableGen/InstrInfoEmitter.cpp b/utils/TableGen/InstrInfoEmitter.cpp
index 798c407e900..f999326bc97 100644
--- a/utils/TableGen/InstrInfoEmitter.cpp
+++ b/utils/TableGen/InstrInfoEmitter.cpp
@@ -549,15 +549,15 @@ void InstrInfoEmitter::emitRecord(const CodeGenInstruction &Inst, unsigned Num,
   CodeGenTarget &Target = CDP.getTargetInfo();
   if (Inst.HasComplexDeprecationPredicate)
     // Emit a function pointer to the complex predicate method.
-    OS << ", { } "
+    OS << ",0"
        << ",&get" << Inst.DeprecatedReason << "DeprecationInfo";
   else if (!Inst.DeprecatedReason.empty())
     // Emit the Subtarget feature.
-    OS << ", { " << Target.getInstNamespace() << "::" << Inst.DeprecatedReason
-       << "} ,nullptr";
+    OS << "," << Target.getInstNamespace() << "::" << Inst.DeprecatedReason
+       << ",nullptr";
   else
     // Instruction isn't deprecated.
-    OS << ", { } ,nullptr";
+    OS << ",0,nullptr";
 
   OS << " },  // Inst #" << Num << " = " << Inst.TheDef->getName() << "\n";
 }
diff --git a/utils/TableGen/SubtargetEmitter.cpp b/utils/TableGen/SubtargetEmitter.cpp
index 831a7732ee4..e5c62fa1375 100644
--- a/utils/TableGen/SubtargetEmitter.cpp
+++ b/utils/TableGen/SubtargetEmitter.cpp
@@ -16,7 +16,6 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/MC/MCInstrItineraries.h"
-#include "llvm/MC/SubtargetFeature.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Format.h"
 #include "llvm/TableGen/Error.h"
@@ -63,7 +62,7 @@ class SubtargetEmitter {
   CodeGenSchedModels &SchedModels;
   std::string Target;
 
-  void Enumeration(raw_ostream &OS, const char *ClassName);
+  void Enumeration(raw_ostream &OS, const char *ClassName, bool isBits);
   unsigned FeatureKeyValues(raw_ostream &OS);
   unsigned CPUKeyValues(raw_ostream &OS);
   void FormItineraryStageString(const std::string &Names,
@@ -113,7 +112,8 @@ public:
 // Enumeration - Emit the specified class as an enumeration.
 //
 void SubtargetEmitter::Enumeration(raw_ostream &OS,
-                                   const char *ClassName) {
+                                   const char *ClassName,
+                                   bool isBits) {
   // Get all records of class and sort
   std::vector<Record*> DefList = Records.getAllDerivedDefinitions(ClassName);
   std::sort(DefList.begin(), DefList.end(), LessRecord());
@@ -121,8 +121,8 @@ void SubtargetEmitter::Enumeration(raw_ostream &OS,
   unsigned N = DefList.size();
   if (N == 0)
     return;
-  if (N > MAX_SUBTARGET_FEATURES) {
-    errs() << "Too many subtarget features! Bump MAX_SUBTARGET_FEATURES.";
+  if (N > 64) {
+    errs() << "Too many (> 64) subtarget features!\n";
     exit(1);
   }
 
@@ -137,14 +137,21 @@ void SubtargetEmitter::Enumeration(raw_ostream &OS,
     Record *Def = DefList[i];
 
     // Get and emit name
-    OS << "  " << Def->getName() << " = " << i;
+    OS << "  " << Def->getName();
+
+    // If bit flags then emit expression (1 << i)
+    if (isBits)  OS << " = " << " 1ULL << " << i;
+
+    // Depending on 'if more in the list' emit comma
     if (++i < N) OS << ",";
 
     OS << "\n";
   }
 
-  // Close enumeration and namespace
-  OS << "};\n}\n";
+  // Close enumeration
+  OS << "};\n";
+
+  OS << "}\n";
 }
 
 //
@@ -178,24 +185,22 @@ unsigned SubtargetEmitter::FeatureKeyValues(raw_ostream &OS) {
 
     if (CommandLineName.empty()) continue;
 
-    // Emit as { "feature", "description", { featureEnum }, { i1 , i2 , ... , in } }
+    // Emit as { "feature", "description", featureEnum, i1 | i2 | ... | in }
     OS << "  { "
        << "\"" << CommandLineName << "\", "
        << "\"" << Desc << "\", "
-       << "{ " << Target << "::" << Name << " }, ";
+       << Target << "::" << Name << ", ";
 
     const std::vector<Record*> &ImpliesList =
       Feature->getValueAsListOfDefs("Implies");
 
     if (ImpliesList.empty()) {
-      OS << "{ }";
+      OS << "0ULL";
     } else {
-      OS << "{ ";
       for (unsigned j = 0, M = ImpliesList.size(); j < M;) {
         OS << Target << "::" << ImpliesList[j]->getName();
-        if (++j < M) OS << ", ";
+        if (++j < M) OS << " | ";
       }
-      OS << " }";
     }
 
     OS << " }";
@@ -237,24 +242,22 @@ unsigned SubtargetEmitter::CPUKeyValues(raw_ostream &OS) {
     const std::vector<Record*> &FeatureList =
       Processor->getValueAsListOfDefs("Features");
 
-    // Emit as { "cpu", "description", { f1 , f2 , ... fn } },
+    // Emit as { "cpu", "description", f1 | f2 | ... fn },
     OS << "  { "
        << "\"" << Name << "\", "
        << "\"Select the " << Name << " processor\", ";
 
     if (FeatureList.empty()) {
-      OS << "{ }";
+      OS << "0ULL";
     } else {
-      OS << "{ ";
       for (unsigned j = 0, M = FeatureList.size(); j < M;) {
         OS << Target << "::" << FeatureList[j]->getName();
-        if (++j < M) OS << ", ";
+        if (++j < M) OS << " | ";
       }
-      OS << " }";
     }
 
-    // The { } is for the "implies" section of this data structure.
-    OS << ", { } }";
+    // The "0" is for the "implies" section of this data structure.
+    OS << ", 0ULL }";
 
     // Depending on 'if more in the list' emit comma
     if (++i < N) OS << ",";
@@ -1382,7 +1385,7 @@ void SubtargetEmitter::ParseFeaturesFunction(raw_ostream &OS,
   }
 
   OS << "  InitMCProcessorInfo(CPU, FS);\n"
-     << "  const FeatureBitset& Bits = getFeatureBits();\n";
+     << "  uint64_t Bits = getFeatureBits();\n";
 
   for (unsigned i = 0; i < Features.size(); i++) {
     // Next record
@@ -1392,12 +1395,12 @@ void SubtargetEmitter::ParseFeaturesFunction(raw_ostream &OS,
     const std::string &Attribute = R->getValueAsString("Attribute");
 
     if (Value=="true" || Value=="false")
-      OS << "  if (Bits[" << Target << "::"
-         << Instance << "]) "
+      OS << "  if ((Bits & " << Target << "::"
+         << Instance << ") != 0) "
          << Attribute << " = " << Value << ";\n";
     else
-      OS << "  if (Bits[" << Target << "::"
-         << Instance << "] && "
+      OS << "  if ((Bits & " << Target << "::"
+         << Instance << ") != 0 && "
          << Attribute << " < " << Value << ") "
          << Attribute << " = " << Value << ";\n";
   }
@@ -1415,7 +1418,7 @@ void SubtargetEmitter::run(raw_ostream &OS) {
   OS << "#undef GET_SUBTARGETINFO_ENUM\n";
 
   OS << "namespace llvm {\n";
-  Enumeration(OS, "SubtargetFeature");
+  Enumeration(OS, "SubtargetFeature", true);
   OS << "} // End llvm namespace \n";
   OS << "#endif // GET_SUBTARGETINFO_ENUM\n\n";