Use bitset for assembler predicates

[rampitec]

Summary

AMDGPU target run out of Subtarget feature flags hitting the limit of 64.
AssemblerPredicates uses at most uint64_t for their representation.
At the same time CodeGen has exhausted this a long time ago and switched
to a FeatureBitset with the current limit of 192 bits.

This patch completes transition to the bitset for feature bits extending
it to asm matcher and MC code emitter.

[rampitec]

Reduced tables size by creating a unique set of FeatureBitsets and referencing them from the tables.
That solves the problem with gcc hanging while compiling generated asm matcher if used with sanitizers.

[craig.topper]

include/llvm/MC/MCParser/MCTargetAsmParser.h

258

return a reference

363–368

Should this return a "const FeatureBitset&"?

364

Should probably take "const FeatureBitset&"

lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

4169–4170

Probably should pass the bits by const reference?

lib/Target/AArch64/MCTargetDesc/AArch64MCCodeEmitter.cpp

190–193

const FeatureBitset&

lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCCodeEmitter.h

67–70

const FeatureBitset&

lib/Target/ARM/AsmParser/ARMAsmParser.cpp

6071

const FeatureBitset&

10484

Can be a const reference?

10592–10593

This invokes the std::initializer_list constructor in FeatureBitset that can't be evaluated at compile time. Thus this is calling a static global constructor.

I just recently fixed this issue in the *GenSubtargetInfo.inc files

[rampitec]

Switched to const references to FeatureBitset where possible.

lib/Target/ARM/AsmParser/ARMAsmParser.cpp

10592–10593

I understand the concern, but use of FeatureBitArray makes it very dangerous for manual initialization since it does not provide any symbolic names for the initializers. If an individual bit will move to another dword it will start silently malfunction.

So far I have moved the array inside the consuming function in a hope that a smart compiler can postpone actual initialization until the first use, which may never happen. I suppose a best solution would be to change it when the above FIXME is resolved, so that this array will be auto generated by tablegen.

[craig.topper]

lib/Target/ARM/AsmParser/ARMAsmParser.cpp

10486

This seems to be making the assumption that ARM feature bits fit in a unisgned long long?

utils/TableGen/AsmMatcherEmitter.cpp

2834

Can we bound this to less than a full unsigned?

3366

How many entries end up in this table on different targets? Since we're tablegening this, can we use hex contants and use FeatureBitArray instead of invoking the std::initializer_list constructor? That probably depends on how many entries end up in the table.

3392

Surely we can bound this to less than a full unsigned? X86 uses almost no features in the assembler which means we can probably use a uint8_t and MatchEntry is used about 28000 times. So that's going to save like 3 * 28000 bytes just from X86.

[rampitec]

Reduced type size.

lib/Target/ARM/AsmParser/ARMAsmParser.cpp

10486

Yes, if exceptions enabled it would raise an exception. The set cannot be constructed from a FeatureBitset since it does not have comparison operators.
I would add an assert, but unfortunately cannot enumerate all features. The solution can be to use a SmallVector, but as long as it fits 64 bit this seems to be an overkill.

utils/TableGen/AsmMatcherEmitter.cpp

2834

Yes, 8 bit is enough.

3366

Asm matcher:

MSP430:0
AArch64:32
ARM:88
WebAssembly:7
Hexagon:11
BPF:0
Sparc:5
AMDGPU:55
Mips:137
PowerPC:10
SystemZ:28
Lanai:0
X86:5

MCCodeEmitter:

MSP430:0
AArch64:28
ARM:81
WebAssembly:8
Hexagon:11
BPF:0
Sparc:5
AMDGPU:68
AMDGPU:0
Mips:149
PowerPC:0
SystemZ:29
Lanai:0

Do you think we need FeatureBitArray here? It has a cost as well, every time one calls getAsBitset().

[rampitec]

Added FeatureBitset::operator < () so that ARM can use set of it.

[rampitec]

lib/Target/ARM/AsmParser/ARMAsmParser.cpp

10486

I have just added comparison operator to be on a safe side.

utils/TableGen/AsmMatcherEmitter.cpp

3392

BTW, table is now smaller. It used to be full 64 bit before per record. OperandMatchEntry can also be rearranged to save on padding now.

[craig.topper]

LGTM

utils/TableGen/AsmMatcherEmitter.cpp

3392

It wasn't a full 64 bit before, getMinimalTypeForEnumBitfield was making it uint8_t for X86.

[rampitec]

utils/TableGen/AsmMatcherEmitter.cpp

3392

Oh, I see. It was for us AMDGPU. Also a pretty big table.

[rampitec]

Use getMinimalTypeForRange() for FeatureBitset types. In case it will grow.
Resorted operand match table fields to decrease table size.

[craig.topper]

LGTM

include/llvm/MC/MCParser/MCTargetAsmParser.h

 
 #include "llvm/ADT/StringRef.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInstrInfo.h"
 #include "llvm/MC/MCParser/MCAsmLexer.h"
 #include "llvm/MC/MCParser/MCParsedAsmOperand.h"
 #include "llvm/MC/MCParser/MCAsmParserExtension.h"
 #include "llvm/MC/MCTargetOptions.h"
+#include "llvm/MC/SubtargetFeature.h"
 #include "llvm/Support/SMLoc.h"
 #include <cstdint>
 #include <memory>
 
 namespace llvm {
 
 class MCInst;
 class MCParsedAsmOperand;
public:
 
   // The encoding is valid for the parsed assembly string. This is only used
   // internally to the table-generated assembly matcher.
   static NearMissInfo getSuccess() { return NearMissInfo(); }
 
   // The instruction encoding is not valid because it requires some target
   // features that are not currently enabled. MissingFeatures has a bit set for
   // each feature that the encoding needs but which is not enabled.
-  static NearMissInfo getMissedFeature(uint64_t MissingFeatures) {
+  static NearMissInfo getMissedFeature(const FeatureBitset &MissingFeatures) {
     NearMissInfo Result;
     Result.Kind = NearMissFeature;
     Result.Features = MissingFeatures;
     return Result;
   }
 
   // The instruction encoding is not valid because the target-specific
   // predicate function returned an error code. FailureCode is the
public:
   }
 
   operator bool() const { return Kind != NoNearMiss; }
 
   NearMissKind getKind() const { return Kind; }
 
   // Feature flags required by the instruction, that the current target does
   // not have.
-  uint64_t getFeatures() const {
+  const FeatureBitset& getFeatures() const {
     assert(Kind == NearMissFeature);
     return Features;
   }
   // Error code returned by the target predicate when validating this
   // instruction encoding.
   unsigned getPredicateError() const {
     assert(Kind == NearMissPredicate);
     return PredicateError;
private:
   };
 
   struct TooFewOperandsInfo {
     unsigned Class;
     unsigned Opcode;
   };
 
   union {
-    uint64_t Features;
+    FeatureBitset Features;
     unsigned PredicateError;
     MissedOpInfo MissedOperand;
     TooFewOperandsInfo TooFewOperands;
   };
 
   NearMissInfo() : Kind(NoNearMiss) {}
 };
 

 protected: // Can only create subclasses.
   MCTargetAsmParser(MCTargetOptions const &, const MCSubtargetInfo &STI,
                     const MCInstrInfo &MII);
 
   /// Create a copy of STI and return a non-const reference to it.
   MCSubtargetInfo &copySTI();
 
   /// AvailableFeatures - The current set of available features.
-  uint64_t AvailableFeatures = 0;
+  FeatureBitset AvailableFeatures;
 
   /// ParsingInlineAsm - Are we parsing ms-style inline assembly?
   bool ParsingInlineAsm = false;
 
   /// SemaCallback - The Sema callback implementation.  Must be set when parsing
   /// ms-style inline assembly.
   MCAsmParserSemaCallback *SemaCallback;
 
   /// Set of options which affects instrumentation of inline assembly.
   MCTargetOptions MCOptions;
 
   /// Current STI.
   const MCSubtargetInfo *STI;
 
   const MCInstrInfo &MII;
 
 public:
   MCTargetAsmParser(const MCTargetAsmParser &) = delete;
   MCTargetAsmParser &operator=(const MCTargetAsmParser &) = delete;
 
   ~MCTargetAsmParser() override;
 
   const MCSubtargetInfo &getSTI() const;
 
-  uint64_t getAvailableFeatures() const { return AvailableFeatures; }
-  void setAvailableFeatures(uint64_t Value) { AvailableFeatures = Value; }
+  const FeatureBitset& getAvailableFeatures() const {
+    return AvailableFeatures;
+  }
+  void setAvailableFeatures(const FeatureBitset& Value) {
+    AvailableFeatures = Value;
+  }
 
   bool isParsingInlineAsm () { return ParsingInlineAsm; }
   void setParsingInlineAsm (bool Value) { ParsingInlineAsm = Value; }
 
   MCTargetOptions getTargetOptions() const { return MCOptions; }
 
   void setSemaCallback(MCAsmParserSemaCallback *Callback) {
     SemaCallback = Callback;

lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

case AArch64::SUBXri: {
     }
     return false;
   }
   default:
     return false;
   }
 }
 
-static std::string AArch64MnemonicSpellCheck(StringRef S, uint64_t FBS,
+static std::string AArch64MnemonicSpellCheck(StringRef S,
+                                             const FeatureBitset &FBS,
                                              unsigned VariantID = 0);
 
 bool AArch64AsmParser::showMatchError(SMLoc Loc, unsigned ErrCode,
                                       uint64_t ErrorInfo,
                                       OperandVector &Operands) {
   switch (ErrCode) {
   case Match_InvalidTiedOperand: {
     RegConstraintEqualityTy EqTy =
if (Op.isScalarReg() &&
         Operands[1] = AArch64Operand::CreateReg(Reg, RegKind::Scalar,
                                                 Op.getStartLoc(),
                                                 Op.getEndLoc(), getContext());
       }
     }
   }
 
   MCInst Inst;
+  FeatureBitset MissingFeatures;
   // First try to match against the secondary set of tables containing the
   // short-form NEON instructions (e.g. "fadd.2s v0, v1, v2").
   unsigned MatchResult =
-      MatchInstructionImpl(Operands, Inst, ErrorInfo, MatchingInlineAsm, 1);
+      MatchInstructionImpl(Operands, Inst, ErrorInfo, MissingFeatures,
+                           MatchingInlineAsm, 1);
 
   // If that fails, try against the alternate table containing long-form NEON:
   // "fadd v0.2s, v1.2s, v2.2s"
   if (MatchResult != Match_Success) {
     // But first, save the short-form match result: we can use it in case the
     // long-form match also fails.
     auto ShortFormNEONErrorInfo = ErrorInfo;
     auto ShortFormNEONMatchResult = MatchResult;
+    auto ShortFormNEONMissingFeatures = MissingFeatures;
 
     MatchResult =
-        MatchInstructionImpl(Operands, Inst, ErrorInfo, MatchingInlineAsm, 0);
+        MatchInstructionImpl(Operands, Inst, ErrorInfo, MissingFeatures,
+                             MatchingInlineAsm, 0);
 
     // Now, both matches failed, and the long-form match failed on the mnemonic
     // suffix token operand.  The short-form match failure is probably more
     // relevant: use it instead.
     if (MatchResult == Match_InvalidOperand && ErrorInfo == 1 &&
         Operands.size() > 1 && ((AArch64Operand &)*Operands[1]).isToken() &&
         ((AArch64Operand &)*Operands[1]).isTokenSuffix()) {
       MatchResult = ShortFormNEONMatchResult;
       ErrorInfo = ShortFormNEONErrorInfo;
+      MissingFeatures = ShortFormNEONMissingFeatures;
     }
   }
 
   switch (MatchResult) {
   case Match_Success: {
     // Perform range checking and other semantic validations
     SmallVector<SMLoc, 8> OperandLocs;
     NumOperands = Operands.size();
     for (unsigned i = 1; i < NumOperands; ++i)
       OperandLocs.push_back(Operands[i]->getStartLoc());
     if (validateInstruction(Inst, IDLoc, OperandLocs))
       return true;
 
     Inst.setLoc(IDLoc);
     Out.EmitInstruction(Inst, getSTI());
     return false;
   }
   case Match_MissingFeature: {
-    assert(ErrorInfo && "Unknown missing feature!");
+    assert(MissingFeatures.any() && "Unknown missing feature!");
     // Special case the error message for the very common case where only
     // a single subtarget feature is missing (neon, e.g.).
     std::string Msg = "instruction requires:";
-    uint64_t Mask = 1;
-    for (unsigned i = 0; i < (sizeof(ErrorInfo)*8-1); ++i) {
-      if (ErrorInfo & Mask) {
+    for (unsigned i = 0, e = MissingFeatures.size(); i != e; ++i) {
+      if (MissingFeatures[i]) {
         Msg += " ";
-        Msg += getSubtargetFeatureName(ErrorInfo & Mask);
+        Msg += getSubtargetFeatureName(i);
       }
-      Mask <<= 1;
     }
     return Error(IDLoc, Msg);
   }
   case Match_MnemonicFail:
     return showMatchError(IDLoc, MatchResult, ErrorInfo, Operands);
   case Match_InvalidOperand: {
     SMLoc ErrorLoc = IDLoc;
 
for (const auto &Extension : ExtensionMap) {
         continue;
 
       if (Extension.Features.none())
         report_fatal_error("unsupported architectural extension: " + Name);
 
       FeatureBitset ToggleFeatures = EnableFeature
                                          ? (~Features & Extension.Features)
                                          : ( Features & Extension.Features);
-      uint64_t Features =
+      FeatureBitset Features =
           ComputeAvailableFeatures(STI.ToggleFeature(ToggleFeatures));
       setAvailableFeatures(Features);
       break;
     }
   }
   return false;
 }
 
if (Extension.Name != Name)
       continue;
 
     if (Extension.Features.none())
       return Error(ExtLoc, "unsupported architectural extension: " + Name);
 
     FeatureBitset ToggleFeatures = EnableFeature
                                        ? (~Features & Extension.Features)
                                        : (Features & Extension.Features);
-    uint64_t Features =
+    FeatureBitset Features =
         ComputeAvailableFeatures(STI.ToggleFeature(ToggleFeatures));
     setAvailableFeatures(Features);
     return false;
   }
 
   return Error(ExtLoc, "unknown architectural extension: " + Name);
 }
 
for (const auto &Extension : ExtensionMap) {
         continue;
 
       if (Extension.Features.none())
         report_fatal_error("unsupported architectural extension: " + Name);
 
       FeatureBitset ToggleFeatures = EnableFeature
                                          ? (~Features & Extension.Features)
                                          : ( Features & Extension.Features);
-      uint64_t Features =
+      FeatureBitset Features =
           ComputeAvailableFeatures(STI.ToggleFeature(ToggleFeatures));
       setAvailableFeatures(Features);
       FoundExtension = true;
 
       break;
     }
 
     if (!FoundExtension)

lib/Target/AArch64/MCTargetDesc/AArch64MCCodeEmitter.cpp

public:
   template<int hasRs, int hasRt2> unsigned
   fixLoadStoreExclusive(const MCInst &MI, unsigned EncodedValue,
                         const MCSubtargetInfo &STI) const;
 
   unsigned fixOneOperandFPComparison(const MCInst &MI, unsigned EncodedValue,
                                      const MCSubtargetInfo &STI) const;
 
 private:
-  uint64_t computeAvailableFeatures(const FeatureBitset &FB) const;
-  void verifyInstructionPredicates(const MCInst &MI,
-                                   uint64_t AvailableFeatures) const;
+  FeatureBitset computeAvailableFeatures(const FeatureBitset &FB) const;
+  void
+  verifyInstructionPredicates(const MCInst &MI,
+                              const FeatureBitset &AvailableFeatures) const;
 };
 
 } // end anonymous namespace
 
 /// getMachineOpValue - Return binary encoding of operand. If the machine
 /// operand requires relocation, record the relocation and return zero.
 unsigned
 AArch64MCCodeEmitter::getMachineOpValue(const MCInst &MI, const MCOperand &MO,

lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp

if (!validateMIMGGatherDMask(Inst)) {
     Error(IDLoc,
       "invalid image_gather dmask: only one bit must be set");
     return false;
   }
 
   return true;
 }
 
-static std::string AMDGPUMnemonicSpellCheck(StringRef S, uint64_t FBS,
+static std::string AMDGPUMnemonicSpellCheck(StringRef S,
+                                            const FeatureBitset &FBS,
                                             unsigned VariantID = 0);
 
 bool AMDGPUAsmParser::MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
                                               OperandVector &Operands,
                                               MCStreamer &Out,
                                               uint64_t &ErrorInfo,
                                               bool MatchingInlineAsm) {
   MCInst Inst;
case Match_Success:
     Inst.setLoc(IDLoc);
     Out.EmitInstruction(Inst, getSTI());
     return false;
 
   case Match_MissingFeature:
     return Error(IDLoc, "instruction not supported on this GPU");
 
   case Match_MnemonicFail: {
-    uint64_t FBS = ComputeAvailableFeatures(getSTI().getFeatureBits());
+    FeatureBitset FBS = ComputeAvailableFeatures(getSTI().getFeatureBits());
     std::string Suggestion = AMDGPUMnemonicSpellCheck(
         ((AMDGPUOperand &)*Operands[0]).getToken(), FBS);
     return Error(IDLoc, "invalid instruction" + Suggestion,
                  ((AMDGPUOperand &)*Operands[0]).getLocRange());
   }
 
   case Match_InvalidOperand: {
     SMLoc ErrorLoc = IDLoc;

lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCCodeEmitter.h

public:
 
   virtual unsigned getSDWAVopcDstEncoding(const MCInst &MI, unsigned OpNo,
                                           SmallVectorImpl<MCFixup> &Fixups,
                                           const MCSubtargetInfo &STI) const {
     return 0;
   }
 
 protected:
-  uint64_t computeAvailableFeatures(const FeatureBitset &FB) const;
-  void verifyInstructionPredicates(const MCInst &MI,
-                                   uint64_t AvailableFeatures) const;
+  FeatureBitset computeAvailableFeatures(const FeatureBitset &FB) const;
+  void
+  verifyInstructionPredicates(const MCInst &MI,
+                              const FeatureBitset &AvailableFeatures) const;
 };
 
 } // End namespace llvm
 
 #endif

lib/Target/AMDGPU/MCTargetDesc/R600MCCodeEmitter.cpp

private:
   void Emit(uint32_t value, raw_ostream &OS) const;
   void Emit(uint64_t value, raw_ostream &OS) const;
 
   unsigned getHWReg(unsigned regNo) const;
 
   uint64_t getBinaryCodeForInstr(const MCInst &MI,
                                  SmallVectorImpl<MCFixup> &Fixups,
                                  const MCSubtargetInfo &STI) const;
-  uint64_t computeAvailableFeatures(const FeatureBitset &FB) const;
-  void verifyInstructionPredicates(const MCInst &MI,
-                                   uint64_t AvailableFeatures) const;
+  FeatureBitset computeAvailableFeatures(const FeatureBitset &FB) const;
+  void
+  verifyInstructionPredicates(const MCInst &MI,
+                              const FeatureBitset &AvailableFeatures) const;
 
 };
 
 } // end anonymous namespace
 
 enum RegElement {
   ELEMENT_X = 0,
   ELEMENT_Y,

lib/Target/ARM/AsmParser/ARMAsmParser.cpp

class ARMAsmParser : public MCTargetAsmParser {
   }
 
   bool hasRAS() const {
     return getSTI().getFeatureBits()[ARM::FeatureRAS];
   }
 
   void SwitchMode() {
     MCSubtargetInfo &STI = copySTI();
-    uint64_t FB = ComputeAvailableFeatures(STI.ToggleFeature(ARM::ModeThumb));
+    auto FB = ComputeAvailableFeatures(STI.ToggleFeature(ARM::ModeThumb));
     setAvailableFeatures(FB);
   }
 
   void FixModeAfterArchChange(bool WasThumb, SMLoc Loc);
 
   bool isMClass() const {
     return getSTI().getFeatureBits()[ARM::FeatureMClass];
   }

 
 // FIXME: This bit should probably be handled via an explicit match class
 // in the .td files that matches the suffix instead of having it be
 // a literal string token the way it is now.
 static bool doesIgnoreDataTypeSuffix(StringRef Mnemonic, StringRef DT) {
   return Mnemonic.startswith("vldm") || Mnemonic.startswith("vstm");
 }
 
-static void applyMnemonicAliases(StringRef &Mnemonic, uint64_t Features,
+static void applyMnemonicAliases(StringRef &Mnemonic,
+                                 const FeatureBitset &Features,
                                  unsigned VariantID);
 
 // The GNU assembler has aliases of ldrd and strd with the second register
 // omitted. We don't have a way to do that in tablegen, so fix it up here.
 //
 // We have to be careful to not emit an invalid Rt2 here, because the rest of
 // the assmebly parser could then generate confusing diagnostics refering to
 // it. If we do find anything that prevents us from doing the transformation we
bool ARMAsmParser::ParseInstruction(ParseInstructionInfo &Info, StringRef Name,
                                     SMLoc NameLoc, OperandVector &Operands) {
   MCAsmParser &Parser = getParser();
 
   // Apply mnemonic aliases before doing anything else, as the destination
   // mnemonic may include suffices and we want to handle them normally.
   // The generic tblgen'erated code does this later, at the start of
   // MatchInstructionImpl(), but that's too late for aliases that include
   // any sort of suffix.
-  uint64_t AvailableFeatures = getAvailableFeatures();
+  const FeatureBitset &AvailableFeatures = getAvailableFeatures();
   unsigned AssemblerDialect = getParser().getAssemblerDialect();
   applyMnemonicAliases(Name, AvailableFeatures, AssemblerDialect);
 
   // First check for the ARM-specific .req directive.
   if (Parser.getTok().is(AsmToken::Identifier) &&
       Parser.getTok().getIdentifier() == ".req") {
     parseDirectiveReq(Name, NameLoc);
     // We always return 'error' for this, as we're done with this
unsigned ARMAsmParser::MatchInstruction(OperandVector &Operands, MCInst &Inst,
   discardImplicitITBlock();
 
   // If none of these succeed, return the error we got when trying to match
   // outside any IT blocks.
   EmitInITBlock = false;
   return PlainMatchResult;
 }
 
-static std::string ARMMnemonicSpellCheck(StringRef S, uint64_t FBS,
+static std::string ARMMnemonicSpellCheck(StringRef S, const FeatureBitset &FBS,
                                          unsigned VariantID = 0);
 
 static const char *getSubtargetFeatureName(uint64_t Val);
 bool ARMAsmParser::MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
                                            OperandVector &Operands,
                                            MCStreamer &Out, uint64_t &ErrorInfo,
                                            bool MatchingInlineAsm) {
   MCInst Inst;
case Match_Success:
     } else {
       Out.EmitInstruction(Inst, getSTI());
     }
     return false;
   case Match_NearMisses:
     ReportNearMisses(NearMisses, IDLoc, Operands);
     return true;
   case Match_MnemonicFail: {
-    uint64_t FBS = ComputeAvailableFeatures(getSTI().getFeatureBits());
+    FeatureBitset FBS = ComputeAvailableFeatures(getSTI().getFeatureBits());
     std::string Suggestion = ARMMnemonicSpellCheck(
       ((ARMOperand &)*Operands[0]).getToken(), FBS);
     return Error(IDLoc, "invalid instruction" + Suggestion,
                  ((ARMOperand &)*Operands[0]).getLocRange());
   }
   }
 
   llvm_unreachable("Implement any new match types added!");
ARMAsmParser::FilterNearMisses(SmallVectorImpl<NearMissInfo> &NearMissesIn,
   // MCK_RegShiftedImm), we don't have any way to represent that currently.
   // TODO: This is not all ARM-specific, can some of it be factored out?
 
   // Record some information about near-misses that we have already seen, so
   // that we can avoid reporting redundant ones. For example, if there are
   // variants of an instruction that take 8- and 16-bit immediates, we want
   // to only report the widest one.
   std::multimap<unsigned, unsigned> OperandMissesSeen;
+  // NB: This assumes there are less than 64 subtarget features, so it fit
+  //     uint64_t!
   SmallSet<uint64_t, 4> FeatureMissesSeen;
   bool ReportedTooFewOperands = false;
 
   // Process the near-misses in reverse order, so that we see more general ones
   // first, and so can avoid emitting more specific ones.
   for (NearMissInfo &I : reverse(NearMissesIn)) {
     switch (I.getKind()) {
     case NearMissInfo::NearMissOperand: {
case NearMissInfo::NearMissOperand: {
                    << getMatchClassName((MatchClassKind)I.getOperandClass())
                    << I.getOperandClass() << ", error " << I.getOperandError()
                    << ", opcode " << MII.getName(I.getOpcode()) << "\n");
       }
       NearMissesOut.emplace_back(Message);
       break;
     }
     case NearMissInfo::NearMissFeature: {
-      uint64_t MissingFeatures = I.getFeatures();
+      const FeatureBitset &MissingFeatures = I.getFeatures();
       // Don't report the same set of features twice.
-      if (FeatureMissesSeen.count(MissingFeatures))
+      if (FeatureMissesSeen.count(MissingFeatures.to_ullong()))
         break;
-      FeatureMissesSeen.insert(MissingFeatures);
+      FeatureMissesSeen.insert(MissingFeatures.to_ullong());
 
       // Special case: don't report a feature set which includes arm-mode for
       // targets that don't have ARM mode.
-      if ((MissingFeatures & Feature_IsARM) && !hasARM())
+      if (MissingFeatures.test(Feature_IsARMBit) && !hasARM())
         break;
       // Don't report any near-misses that both require switching instruction
       // set, and adding other subtarget features.
-      if (isThumb() && (MissingFeatures & Feature_IsARM) &&
-          (MissingFeatures & ~Feature_IsARM))
+      if (isThumb() && MissingFeatures.test(Feature_IsARMBit) &&
+          MissingFeatures.count() > 1)
         break;
-      if (!isThumb() && (MissingFeatures & Feature_IsThumb) &&
-          (MissingFeatures & ~Feature_IsThumb))
+      if (!isThumb() && MissingFeatures.test(Feature_IsThumbBit) &&
+          MissingFeatures.count() > 1)
         break;
-      if (!isThumb() && (MissingFeatures & Feature_IsThumb2) &&
-          (MissingFeatures & ~(Feature_IsThumb2 | Feature_IsThumb)))
+      if (!isThumb() && MissingFeatures.test(Feature_IsThumb2Bit) &&
+          (MissingFeatures & ~FeatureBitset({Feature_IsThumb2Bit,
+                                             Feature_IsThumbBit})).any())
         break;
-      if (isMClass() && (MissingFeatures & Feature_HasNEON))
+      if (isMClass() && MissingFeatures.test(Feature_HasNEONBit))
         break;
 
       NearMissMessage Message;
       Message.Loc = IDLoc;
       raw_svector_ostream OS(Message.Message);
 
       OS << "instruction requires:";
-      uint64_t Mask = 1;
-      for (unsigned MaskPos = 0; MaskPos < (sizeof(MissingFeatures) * 8 - 1);
-           ++MaskPos) {
-        if (MissingFeatures & Mask) {
-          OS << " " << getSubtargetFeatureName(MissingFeatures & Mask);
-        }
-        Mask <<= 1;
-      }
+      for (unsigned i = 0, e = MissingFeatures.size(); i != e; ++i)
+        if (MissingFeatures.test(i))
+          OS << ' ' << getSubtargetFeatureName(i);
+
       NearMissesOut.emplace_back(Message);
 
       break;
     }
     case NearMissInfo::NearMissPredicate: {
       NearMissMessage Message;
       Message.Loc = IDLoc;
       switch (I.getPredicateError()) {
if (Messages.size() == 0) {
     // More than one near miss, so report a generic "invalid instruction"
     // error, followed by notes for each of the near-misses.
     Error(IDLoc, "invalid instruction, any one of the following would fix this:");
     for (auto &M : Messages) {
       Note(M.Loc, M.Message);
     }
   }
 }
 
+/// parseDirectiveArchExtension
+///   ::= .arch_extension [no]feature
+bool ARMAsmParser::parseDirectiveArchExtension(SMLoc L) {
   // FIXME: This structure should be moved inside ARMTargetParser
   // when we start to table-generate them, and we can use the ARM
   // flags below, that were generated by table-gen.
   static const struct {
     const unsigned Kind;
-  const uint64_t ArchCheck;
+    const FeatureBitset ArchCheck;
     const FeatureBitset Features;
   } Extensions[] = {
-  { ARM::AEK_CRC, Feature_HasV8, {ARM::FeatureCRC} },
-  { ARM::AEK_CRYPTO,  Feature_HasV8,
+    { ARM::AEK_CRC, {Feature_HasV8Bit}, {ARM::FeatureCRC} },
+    { ARM::AEK_CRYPTO,  {Feature_HasV8Bit},
       {ARM::FeatureCrypto, ARM::FeatureNEON, ARM::FeatureFPARMv8} },
-  { ARM::AEK_FP, Feature_HasV8, {ARM::FeatureFPARMv8} },
-  { (ARM::AEK_HWDIVTHUMB | ARM::AEK_HWDIVARM), Feature_HasV7 | Feature_IsNotMClass,
+    { ARM::AEK_FP, {Feature_HasV8Bit}, {ARM::FeatureFPARMv8} },
+    { (ARM::AEK_HWDIVTHUMB | ARM::AEK_HWDIVARM),
+      {Feature_HasV7Bit, Feature_IsNotMClassBit},
       {ARM::FeatureHWDivThumb, ARM::FeatureHWDivARM} },
-  { ARM::AEK_MP, Feature_HasV7 | Feature_IsNotMClass, {ARM::FeatureMP} },
-  { ARM::AEK_SIMD, Feature_HasV8, {ARM::FeatureNEON, ARM::FeatureFPARMv8} },
-  { ARM::AEK_SEC, Feature_HasV6K, {ARM::FeatureTrustZone} },
+    { ARM::AEK_MP, {Feature_HasV7Bit, Feature_IsNotMClassBit},
+      {ARM::FeatureMP} },
+    { ARM::AEK_SIMD, {Feature_HasV8Bit},
+      {ARM::FeatureNEON, ARM::FeatureFPARMv8} },
+    { ARM::AEK_SEC, {Feature_HasV6KBit}, {ARM::FeatureTrustZone} },
     // FIXME: Only available in A-class, isel not predicated
-  { ARM::AEK_VIRT, Feature_HasV7, {ARM::FeatureVirtualization} },
-  { ARM::AEK_FP16, Feature_HasV8_2a, {ARM::FeatureFPARMv8, ARM::FeatureFullFP16} },
-  { ARM::AEK_RAS, Feature_HasV8, {ARM::FeatureRAS} },
+    { ARM::AEK_VIRT, {Feature_HasV7Bit}, {ARM::FeatureVirtualization} },
+    { ARM::AEK_FP16, {Feature_HasV8_2aBit},
+      {ARM::FeatureFPARMv8, ARM::FeatureFullFP16} },
+    { ARM::AEK_RAS, {Feature_HasV8Bit}, {ARM::FeatureRAS} },
     // FIXME: Unsupported extensions.
-  { ARM::AEK_OS, Feature_None, {} },
-  { ARM::AEK_IWMMXT, Feature_None, {} },
-  { ARM::AEK_IWMMXT2, Feature_None, {} },
-  { ARM::AEK_MAVERICK, Feature_None, {} },
-  { ARM::AEK_XSCALE, Feature_None, {} },
+    { ARM::AEK_OS, {}, {} },
+    { ARM::AEK_IWMMXT, {}, {} },
+    { ARM::AEK_IWMMXT2, {}, {} },
+    { ARM::AEK_MAVERICK, {}, {} },
+    { ARM::AEK_XSCALE, {}, {} },
   };
 
-/// parseDirectiveArchExtension
-///   ::= .arch_extension [no]feature
-bool ARMAsmParser::parseDirectiveArchExtension(SMLoc L) {
   MCAsmParser &Parser = getParser();
 
   if (getLexer().isNot(AsmToken::Identifier))
     return Error(getLexer().getLoc(), "expected architecture extension name");
 
   StringRef Name = Parser.getTok().getString();
   SMLoc ExtLoc = Parser.getTok().getLoc();
   Lex();
if ((getAvailableFeatures() & Extension.ArchCheck) != Extension.ArchCheck)
                                "' is not "
                                "allowed for the current base architecture");
 
     MCSubtargetInfo &STI = copySTI();
     FeatureBitset ToggleFeatures = EnableFeature
       ? (~STI.getFeatureBits() & Extension.Features)
       : ( STI.getFeatureBits() & Extension.Features);
 
-    uint64_t Features =
+    FeatureBitset Features =
         ComputeAvailableFeatures(STI.ToggleFeature(ToggleFeatures));
     setAvailableFeatures(Features);
     return false;
   }
 
   return Error(ExtLoc, "unknown architectural extension: " + Name);
 }
 

lib/Target/BPF/MCTargetDesc/BPFMCCodeEmitter.cpp

uint64_t getMemoryOpValue(const MCInst &MI, unsigned Op,
                             SmallVectorImpl<MCFixup> &Fixups,
                             const MCSubtargetInfo &STI) const;
 
   void encodeInstruction(const MCInst &MI, raw_ostream &OS,
                          SmallVectorImpl<MCFixup> &Fixups,
                          const MCSubtargetInfo &STI) const override;
 
 private:
-  uint64_t computeAvailableFeatures(const FeatureBitset &FB) const;
-  void verifyInstructionPredicates(const MCInst &MI,
-                                   uint64_t AvailableFeatures) const;
+  FeatureBitset computeAvailableFeatures(const FeatureBitset &FB) const;
+  void
+  verifyInstructionPredicates(const MCInst &MI,
+                              const FeatureBitset &AvailableFeatures) const;
 };
 
 } // end anonymous namespace
 
 MCCodeEmitter *llvm::createBPFMCCodeEmitter(const MCInstrInfo &MCII,
                                             const MCRegisterInfo &MRI,
                                             MCContext &Ctx) {
   return new BPFMCCodeEmitter(MCII, MRI, true);

lib/Target/Hexagon/MCTargetDesc/HexagonMCCodeEmitter.h

private:
 
   Hexagon::Fixups getFixupNoBits(MCInstrInfo const &MCII, const MCInst &MI,
                                  const MCOperand &MO,
                                  const MCSymbolRefExpr::VariantKind Kind) const;
 
   // Return parse bits for instruction `MCI' inside bundle `MCB'
   uint32_t parseBits(size_t Last, MCInst const &MCB, MCInst const &MCI) const;
 
-  uint64_t computeAvailableFeatures(const FeatureBitset &FB) const;
-  void verifyInstructionPredicates(const MCInst &MI,
-                                   uint64_t AvailableFeatures) const;
+  FeatureBitset computeAvailableFeatures(const FeatureBitset &FB) const;
+  void
+  verifyInstructionPredicates(const MCInst &MI,
+                              const FeatureBitset &AvailableFeatures) const;
 };
 
 } // end namespace llvm
 
 #endif // LLVM_LIB_TARGET_HEXAGON_MCTARGETDESC_HEXAGONMCCODEEMITTER_H

lib/Target/Hexagon/MCTargetDesc/HexagonMCCodeEmitter.cpp

void HexagonMCCodeEmitter::encodeInstruction(const MCInst &MI, raw_ostream &OS,
 
   assert(HexagonMCInstrInfo::isBundle(HMB));
   LLVM_DEBUG(dbgs() << "Encoding bundle\n";);
   State.Addend = 0;
   State.Extended = false;
   State.Bundle = &MI;
   State.Index = 0;
   size_t Last = HexagonMCInstrInfo::bundleSize(HMB) - 1;
-  uint64_t Features = computeAvailableFeatures(STI.getFeatureBits());
+  FeatureBitset Features = computeAvailableFeatures(STI.getFeatureBits());
 
   for (auto &I : HexagonMCInstrInfo::bundleInstructions(HMB)) {
     MCInst &HMI = const_cast<MCInst &>(*I.getInst());
     verifyInstructionPredicates(HMI, Features);
 
     EncodeSingleInstruction(HMI, OS, Fixups, STI, parseBits(Last, HMB, HMI));
     State.Extended = HexagonMCInstrInfo::isImmext(HMI);
     State.Addend += HEXAGON_INSTR_SIZE;

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

if (getLexer().is(AsmToken::LBrac)) {
     }
     Operands.push_back(
         MipsOperand::CreateToken("]", getLexer().getLoc(), *this));
     Parser.Lex();
   }
   return false;
 }
 
-static std::string MipsMnemonicSpellCheck(StringRef S, uint64_t FBS,
+static std::string MipsMnemonicSpellCheck(StringRef S, const FeatureBitset &FBS,
                                           unsigned VariantID = 0);
 
 bool MipsAsmParser::ParseInstruction(ParseInstructionInfo &Info, StringRef Name,
                                      SMLoc NameLoc, OperandVector &Operands) {
   MCAsmParser &Parser = getParser();
   LLVM_DEBUG(dbgs() << "ParseInstruction\n");
 
   // We have reached first instruction, module directive are now forbidden.
   getTargetStreamer().forbidModuleDirective();
 
   // Check if we have valid mnemonic
   if (!mnemonicIsValid(Name, 0)) {
-    uint64_t FBS = ComputeAvailableFeatures(getSTI().getFeatureBits());
+    FeatureBitset FBS = ComputeAvailableFeatures(getSTI().getFeatureBits());
     std::string Suggestion = MipsMnemonicSpellCheck(Name, FBS);
     return Error(NameLoc, "unknown instruction" + Suggestion);
   }
   // First operand in MCInst is instruction mnemonic.
   Operands.push_back(MipsOperand::CreateToken(Name, NameLoc, *this));
 
   // Read the remaining operands.
   if (getLexer().isNot(AsmToken::EndOfStatement)) {

lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp

case PPC::CP_PASTE_LAST: {
     TmpInst.addOperand(MCOperand::createImm(Opcode == PPC::CP_PASTEx ? 0 : 1));
 
     Inst = TmpInst;
     break;
   }
   }
 }
 
-static std::string PPCMnemonicSpellCheck(StringRef S, uint64_t FBS,
+static std::string PPCMnemonicSpellCheck(StringRef S, const FeatureBitset &FBS,
                                          unsigned VariantID = 0);
 
 bool PPCAsmParser::MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
                                            OperandVector &Operands,
                                            MCStreamer &Out, uint64_t &ErrorInfo,
                                            bool MatchingInlineAsm) {
   MCInst Inst;
 
   switch (MatchInstructionImpl(Operands, Inst, ErrorInfo, MatchingInlineAsm)) {
   case Match_Success:
     // Post-process instructions (typically extended mnemonics)
     ProcessInstruction(Inst, Operands);
     Inst.setLoc(IDLoc);
     Out.EmitInstruction(Inst, getSTI());
     return false;
   case Match_MissingFeature:
     return Error(IDLoc, "instruction use requires an option to be enabled");
   case Match_MnemonicFail: {
-    uint64_t FBS = ComputeAvailableFeatures(getSTI().getFeatureBits());
+    FeatureBitset FBS = ComputeAvailableFeatures(getSTI().getFeatureBits());
     std::string Suggestion = PPCMnemonicSpellCheck(
         ((PPCOperand &)*Operands[0]).getToken(), FBS);
     return Error(IDLoc, "invalid instruction" + Suggestion,
                  ((PPCOperand &)*Operands[0]).getLocRange());
   }
   case Match_InvalidOperand: {
     SMLoc ErrorLoc = IDLoc;
     if (ErrorInfo != ~0ULL) {

lib/Target/PowerPC/MCTargetDesc/PPCMCCodeEmitter.h

public:
   void encodeInstruction(const MCInst &MI, raw_ostream &OS,
                          SmallVectorImpl<MCFixup> &Fixups,
                          const MCSubtargetInfo &STI) const override;
 
   // Get the number of bytes used to encode the given MCInst.
   unsigned getInstSizeInBytes(const MCInst &MI) const;
 
 private:
-  uint64_t computeAvailableFeatures(const FeatureBitset &FB) const;
-  void verifyInstructionPredicates(const MCInst &MI,
-                                   uint64_t AvailableFeatures) const;
+  FeatureBitset computeAvailableFeatures(const FeatureBitset &FB) const;
+  void
+  verifyInstructionPredicates(const MCInst &MI,
+                              const FeatureBitset &AvailableFeatures) const;
 };
 
 } // namespace llvm
 
 #endif // LLVM_LIB_TARGET_PPC_MCCODEEMITTER_PPCCODEEMITTER_H

lib/Target/Sparc/AsmParser/SparcAsmParser.cpp

bool SparcAsmParser::ParseRegister(unsigned &RegNo, SMLoc &StartLoc,
   if (matchRegisterName(Tok, RegNo, regKind)) {
     Parser.Lex();
     return false;
   }
 
   return Error(StartLoc, "invalid register name");
 }
 
-static void applyMnemonicAliases(StringRef &Mnemonic, uint64_t Features,
+static void applyMnemonicAliases(StringRef &Mnemonic,
+                                 const FeatureBitset &Features,
                                  unsigned VariantID);
 
 bool SparcAsmParser::ParseInstruction(ParseInstructionInfo &Info,
                                       StringRef Name, SMLoc NameLoc,
                                       OperandVector &Operands) {
 
   // First operand in MCInst is instruction mnemonic.
   Operands.push_back(SparcOperand::CreateToken(Name, NameLoc));

lib/Target/Sparc/MCTargetDesc/SparcMCCodeEmitter.cpp

public:
   unsigned getBranchPredTargetOpValue(const MCInst &MI, unsigned OpNo,
                                       SmallVectorImpl<MCFixup> &Fixups,
                                       const MCSubtargetInfo &STI) const;
   unsigned getBranchOnRegTargetOpValue(const MCInst &MI, unsigned OpNo,
                                        SmallVectorImpl<MCFixup> &Fixups,
                                        const MCSubtargetInfo &STI) const;
 
 private:
-  uint64_t computeAvailableFeatures(const FeatureBitset &FB) const;
-  void verifyInstructionPredicates(const MCInst &MI,
-                                   uint64_t AvailableFeatures) const;
+  FeatureBitset computeAvailableFeatures(const FeatureBitset &FB) const;
+  void
+  verifyInstructionPredicates(const MCInst &MI,
+                              const FeatureBitset &AvailableFeatures) const;
 };
 
 } // end anonymous namespace
 
 void SparcMCCodeEmitter::encodeInstruction(const MCInst &MI, raw_ostream &OS,
                                            SmallVectorImpl<MCFixup> &Fixups,
                                            const MCSubtargetInfo &STI) const {
   verifyInstructionPredicates(MI,

lib/Target/SystemZ/AsmParser/SystemZAsmParser.cpp

 
 bool SystemZAsmParser::parseOperand(OperandVector &Operands,
                                     StringRef Mnemonic) {
   // Check if the current operand has a custom associated parser, if so, try to
   // custom parse the operand, or fallback to the general approach.  Force all
   // features to be available during the operand check, or else we will fail to
   // find the custom parser, and then we will later get an InvalidOperand error
   // instead of a MissingFeature errror.
-  uint64_t AvailableFeatures = getAvailableFeatures();
-  setAvailableFeatures(~(uint64_t)0);
+  FeatureBitset AvailableFeatures = getAvailableFeatures();
+  FeatureBitset All;
+  All.set();
+  setAvailableFeatures(All);
   OperandMatchResultTy ResTy = MatchOperandParserImpl(Operands, Mnemonic);
   setAvailableFeatures(AvailableFeatures);
   if (ResTy == MatchOperand_Success)
     return false;
 
   // If there wasn't a custom match, try the generic matcher below. Otherwise,
   // there was a match, but an error occurred, in which case, just return that
   // the operand parsing failed.
SMLoc EndLoc =
     SMLoc::getFromPointer(Parser.getTok().getLoc().getPointer() - 1);
   if (HaveReg1 || HaveReg2 || Length)
     Operands.push_back(SystemZOperand::createInvalid(StartLoc, EndLoc));
   else
     Operands.push_back(SystemZOperand::createImm(Expr, StartLoc, EndLoc));
   return false;
 }
 
-static std::string SystemZMnemonicSpellCheck(StringRef S, uint64_t FBS,
+static std::string SystemZMnemonicSpellCheck(StringRef S,
+                                             const FeatureBitset &FBS,
                                              unsigned VariantID = 0);
 
 bool SystemZAsmParser::MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
                                                OperandVector &Operands,
                                                MCStreamer &Out,
                                                uint64_t &ErrorInfo,
                                                bool MatchingInlineAsm) {
   MCInst Inst;
   unsigned MatchResult;
 
+  FeatureBitset MissingFeatures;
   MatchResult = MatchInstructionImpl(Operands, Inst, ErrorInfo,
-                                     MatchingInlineAsm);
+                                     MissingFeatures, MatchingInlineAsm);
   switch (MatchResult) {
   case Match_Success:
     Inst.setLoc(IDLoc);
     Out.EmitInstruction(Inst, getSTI());
     return false;
 
   case Match_MissingFeature: {
-    assert(ErrorInfo && "Unknown missing feature!");
+    assert(MissingFeatures.any() && "Unknown missing feature!");
     // Special case the error message for the very common case where only
     // a single subtarget feature is missing
     std::string Msg = "instruction requires:";
-    uint64_t Mask = 1;
-    for (unsigned I = 0; I < sizeof(ErrorInfo) * 8 - 1; ++I) {
-      if (ErrorInfo & Mask) {
+    for (unsigned I = 0, E = MissingFeatures.size(); I != E; ++I) {
+      if (MissingFeatures[I]) {
         Msg += " ";
-        Msg += getSubtargetFeatureName(ErrorInfo & Mask);
+        Msg += getSubtargetFeatureName(I);
       }
-      Mask <<= 1;
     }
     return Error(IDLoc, Msg);
   }
 
   case Match_InvalidOperand: {
     SMLoc ErrorLoc = IDLoc;
     if (ErrorInfo != ~0ULL) {
       if (ErrorInfo >= Operands.size())
         return Error(IDLoc, "too few operands for instruction");
 
       ErrorLoc = ((SystemZOperand &)*Operands[ErrorInfo]).getStartLoc();
       if (ErrorLoc == SMLoc())
         ErrorLoc = IDLoc;
     }
     return Error(ErrorLoc, "invalid operand for instruction");
   }
 
   case Match_MnemonicFail: {
-    uint64_t FBS = ComputeAvailableFeatures(getSTI().getFeatureBits());
+    FeatureBitset FBS = ComputeAvailableFeatures(getSTI().getFeatureBits());
     std::string Suggestion = SystemZMnemonicSpellCheck(
       ((SystemZOperand &)*Operands[0]).getToken(), FBS);
     return Error(IDLoc, "invalid instruction" + Suggestion,
                  ((SystemZOperand &)*Operands[0]).getLocRange());
   }
   }
 
   llvm_unreachable("Unexpected match type");

lib/Target/SystemZ/MCTargetDesc/SystemZMCCodeEmitter.cpp

private:
   uint64_t getPC24DBLBPPEncoding(const MCInst &MI, unsigned OpNum,
                                  SmallVectorImpl<MCFixup> &Fixups,
                                  const MCSubtargetInfo &STI) const {
     return getPCRelEncoding(MI, OpNum, Fixups,
                             SystemZ::FK_390_PC24DBL, 3, false);
   }
 
 private:
-  uint64_t computeAvailableFeatures(const FeatureBitset &FB) const;
-  void verifyInstructionPredicates(const MCInst &MI,
-                                   uint64_t AvailableFeatures) const;
+  FeatureBitset computeAvailableFeatures(const FeatureBitset &FB) const;
+  void
+  verifyInstructionPredicates(const MCInst &MI,
+                              const FeatureBitset &AvailableFeatures) const;
 };
 
 } // end anonymous namespace
 
 void SystemZMCCodeEmitter::
 encodeInstruction(const MCInst &MI, raw_ostream &OS,
                   SmallVectorImpl<MCFixup> &Fixups,
                   const MCSubtargetInfo &STI) const {

lib/Target/X86/AsmParser/X86AsmParser.cpp

private:
   X86TargetStreamer &getTargetStreamer() {
     assert(getParser().getStreamer().getTargetStreamer() &&
            "do not have a target streamer");
     MCTargetStreamer &TS = *getParser().getStreamer().getTargetStreamer();
     return static_cast<X86TargetStreamer &>(TS);
   }
 
   unsigned MatchInstruction(const OperandVector &Operands, MCInst &Inst,
-                            uint64_t &ErrorInfo, bool matchingInlineAsm,
-                            unsigned VariantID = 0) {
+                            uint64_t &ErrorInfo, FeatureBitset &MissingFeatures,
+                            bool matchingInlineAsm, unsigned VariantID = 0) {
     // In Code16GCC mode, match as 32-bit.
     if (Code16GCC)
       SwitchMode(X86::Mode32Bit);
     unsigned rv = MatchInstructionImpl(Operands, Inst, ErrorInfo,
-                                       matchingInlineAsm, VariantID);
+                                       MissingFeatures, matchingInlineAsm,
+                                       VariantID);
     if (Code16GCC)
       SwitchMode(X86::Mode16Bit);
     return rv;
   }
 
   enum InfixCalculatorTok {
     IC_OR = 0,
     IC_XOR,
private:
   bool MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
                                OperandVector &Operands, MCStreamer &Out,
                                uint64_t &ErrorInfo,
                                bool MatchingInlineAsm) override;
 
   void MatchFPUWaitAlias(SMLoc IDLoc, X86Operand &Op, OperandVector &Operands,
                          MCStreamer &Out, bool MatchingInlineAsm);
 
-  bool ErrorMissingFeature(SMLoc IDLoc, uint64_t ErrorInfo,
+  bool ErrorMissingFeature(SMLoc IDLoc, const FeatureBitset &MissingFeatures,
                            bool MatchingInlineAsm);
 
   bool MatchAndEmitATTInstruction(SMLoc IDLoc, unsigned &Opcode,
                                   OperandVector &Operands, MCStreamer &Out,
                                   uint64_t &ErrorInfo,
                                   bool MatchingInlineAsm);
 
   bool MatchAndEmitIntelInstruction(SMLoc IDLoc, unsigned &Opcode,
private:
   bool is16BitMode() const {
     // FIXME: Can tablegen auto-generate this?
     return getSTI().getFeatureBits()[X86::Mode16Bit];
   }
   void SwitchMode(unsigned mode) {
     MCSubtargetInfo &STI = copySTI();
     FeatureBitset AllModes({X86::Mode64Bit, X86::Mode32Bit, X86::Mode16Bit});
     FeatureBitset OldMode = STI.getFeatureBits() & AllModes;
-    uint64_t FB = ComputeAvailableFeatures(
+    FeatureBitset FB = ComputeAvailableFeatures(
       STI.ToggleFeature(OldMode.flip(mode)));
     setAvailableFeatures(FB);
 
     assert(FeatureBitset({mode}) == (STI.getFeatureBits() & AllModes));
   }
 
   unsigned getPointerWidth() {
     if (is16BitMode()) return 16;
if (Repl) {
     Inst.setOpcode(X86::WAIT);
     Inst.setLoc(IDLoc);
     if (!MatchingInlineAsm)
       EmitInstruction(Inst, Operands, Out);
     Operands[0] = X86Operand::CreateToken(Repl, IDLoc);
   }
 }
 
-bool X86AsmParser::ErrorMissingFeature(SMLoc IDLoc, uint64_t ErrorInfo,
+bool X86AsmParser::ErrorMissingFeature(SMLoc IDLoc,
+                                       const FeatureBitset &MissingFeatures,
                                        bool MatchingInlineAsm) {
-  assert(ErrorInfo && "Unknown missing feature!");
+  assert(MissingFeatures.any() && "Unknown missing feature!");
   SmallString<126> Msg;
   raw_svector_ostream OS(Msg);
   OS << "instruction requires:";
-  uint64_t Mask = 1;
-  for (unsigned i = 0; i < (sizeof(ErrorInfo)*8-1); ++i) {
-    if (ErrorInfo & Mask)
-      OS << ' ' << getSubtargetFeatureName(ErrorInfo & Mask);
-    Mask <<= 1;
+  for (unsigned i = 0, e = MissingFeatures.size(); i != e; ++i) {
+    if (MissingFeatures[i])
+      OS << ' ' << getSubtargetFeatureName(i);
   }
   return Error(IDLoc, OS.str(), SMRange(), MatchingInlineAsm);
 }
 
 static unsigned getPrefixes(OperandVector &Operands) {
   unsigned Result = 0;
   X86Operand &Prefix = static_cast<X86Operand &>(*Operands.back());
   if (Prefix.isPrefix()) {
bool X86AsmParser::MatchAndEmitATTInstruction(SMLoc IDLoc, unsigned &Opcode,
   unsigned Prefixes = getPrefixes(Operands);
 
   MCInst Inst;
 
   if (Prefixes)
     Inst.setFlags(Prefixes);
 
   // First, try a direct match.
-  switch (MatchInstruction(Operands, Inst, ErrorInfo, MatchingInlineAsm,
-                           isParsingIntelSyntax())) {
+  FeatureBitset MissingFeatures;
+  switch (MatchInstruction(Operands, Inst, ErrorInfo, MissingFeatures,
+                           MatchingInlineAsm, isParsingIntelSyntax())) {
   default: llvm_unreachable("Unexpected match result!");
   case Match_Success:
     if (!MatchingInlineAsm && validateInstruction(Inst, Operands))
       return true;
     // Some instructions need post-processing to, for example, tweak which
     // encoding is selected. Loop on it while changes happen so the
     // individual transformations can chain off each other.
     if (!MatchingInlineAsm)
       while (processInstruction(Inst, Operands))
         ;
 
     Inst.setLoc(IDLoc);
     if (!MatchingInlineAsm)
       EmitInstruction(Inst, Operands, Out);
     Opcode = Inst.getOpcode();
     return false;
   case Match_MissingFeature:
-    return ErrorMissingFeature(IDLoc, ErrorInfo, MatchingInlineAsm);
+    return ErrorMissingFeature(IDLoc, MissingFeatures, MatchingInlineAsm);
   case Match_InvalidOperand:
     WasOriginallyInvalidOperand = true;
     break;
   case Match_MnemonicFail:
     break;
   }
 
   // FIXME: Ideally, we would only attempt suffix matches for things which are
bool X86AsmParser::MatchAndEmitATTInstruction(SMLoc IDLoc, unsigned &Opcode,
   // 80-bit floating point, which use the suffixes s,l,t respectively.
   //
   // Otherwise, we assume that this may be an integer instruction, which comes
   // in 8/16/32/64-bit forms using the b,w,l,q suffixes respectively.
   const char *Suffixes = Base[0] != 'f' ? "bwlq" : "slt\0";
 
   // Check for the various suffix matches.
   uint64_t ErrorInfoIgnore;
-  uint64_t ErrorInfoMissingFeature = 0; // Init suppresses compiler warnings.
+  FeatureBitset ErrorInfoMissingFeatures; // Init suppresses compiler warnings.
   unsigned Match[4];
 
   for (unsigned I = 0, E = array_lengthof(Match); I != E; ++I) {
     Tmp.back() = Suffixes[I];
     Match[I] = MatchInstruction(Operands, Inst, ErrorInfoIgnore,
-                                MatchingInlineAsm, isParsingIntelSyntax());
+                                MissingFeatures, MatchingInlineAsm,
+                                isParsingIntelSyntax());
     // If this returned as a missing feature failure, remember that.
     if (Match[I] == Match_MissingFeature)
-      ErrorInfoMissingFeature = ErrorInfoIgnore;
+      ErrorInfoMissingFeatures = MissingFeatures;
   }
 
   // Restore the old token.
   Op.setTokenValue(Base);
 
   // If exactly one matched, then we treat that as a successful match (and the
   // instruction will already have been filled in correctly, since the failing
   // matches won't have modified it).
if (std::count(std::begin(Match), std::end(Match), Match_MnemonicFail) == 4) {
     return Error(IDLoc, "invalid operand for instruction", EmptyRange,
                  MatchingInlineAsm);
   }
 
   // If one instruction matched with a missing feature, report this as a
   // missing feature.
   if (std::count(std::begin(Match), std::end(Match),
                  Match_MissingFeature) == 1) {
-    ErrorInfo = ErrorInfoMissingFeature;
-    return ErrorMissingFeature(IDLoc, ErrorInfoMissingFeature,
+    ErrorInfo = Match_MissingFeature;
+    return ErrorMissingFeature(IDLoc, ErrorInfoMissingFeatures,
                                MatchingInlineAsm);
   }
 
   // If one instruction matched with an invalid operand, report this as an
   // operand failure.
   if (std::count(std::begin(Match), std::end(Match),
                  Match_InvalidOperand) == 1) {
     return Error(IDLoc, "invalid operand for instruction", EmptyRange,
for (const char *Instr : PtrSizedInstrs) {
       if (Mnemonic == Instr) {
         UnsizedMemOp->Mem.Size = getPointerWidth();
         break;
       }
     }
   }
 
   SmallVector<unsigned, 8> Match;
-  uint64_t ErrorInfoMissingFeature = 0;
+  FeatureBitset ErrorInfoMissingFeatures;
+  FeatureBitset MissingFeatures;
 
   // If unsized push has immediate operand we should default the default pointer
   // size for the size.
   if (Mnemonic == "push" && Operands.size() == 2) {
     auto *X86Op = static_cast<X86Operand *>(Operands[1].get());
     if (X86Op->isImm()) {
       // If it's not a constant fall through and let remainder take care of it.
       const auto *CE = dyn_cast<MCConstantExpr>(X86Op->getImm());
       unsigned Size = getPointerWidth();
       if (CE &&
           (isIntN(Size, CE->getValue()) || isUIntN(Size, CE->getValue()))) {
         SmallString<16> Tmp;
         Tmp += Base;
         Tmp += (is64BitMode())
                    ? "q"
                    : (is32BitMode()) ? "l" : (is16BitMode()) ? "w" : " ";
         Op.setTokenValue(Tmp);
         // Do match in ATT mode to allow explicit suffix usage.
         Match.push_back(MatchInstruction(Operands, Inst, ErrorInfo,
-                                         MatchingInlineAsm,
+                                         MissingFeatures, MatchingInlineAsm,
                                          false /*isParsingIntelSyntax()*/));
         Op.setTokenValue(Base);
       }
     }
   }
 
   // If an unsized memory operand is present, try to match with each memory
   // operand size.  In Intel assembly, the size is not part of the instruction
   // mnemonic.
   if (UnsizedMemOp && UnsizedMemOp->isMemUnsized()) {
     static const unsigned MopSizes[] = {8, 16, 32, 64, 80, 128, 256, 512};
     for (unsigned Size : MopSizes) {
       UnsizedMemOp->Mem.Size = Size;
       uint64_t ErrorInfoIgnore;
       unsigned LastOpcode = Inst.getOpcode();
       unsigned M = MatchInstruction(Operands, Inst, ErrorInfoIgnore,
-                                    MatchingInlineAsm, isParsingIntelSyntax());
+                                    MissingFeatures, MatchingInlineAsm,
+                                    isParsingIntelSyntax());
       if (Match.empty() || LastOpcode != Inst.getOpcode())
         Match.push_back(M);
 
       // If this returned as a missing feature failure, remember that.
       if (Match.back() == Match_MissingFeature)
-        ErrorInfoMissingFeature = ErrorInfoIgnore;
+        ErrorInfoMissingFeatures = MissingFeatures;
     }
 
     // Restore the size of the unsized memory operand if we modified it.
     UnsizedMemOp->Mem.Size = 0;
   }
 
   // If we haven't matched anything yet, this is not a basic integer or FPU
   // operation.  There shouldn't be any ambiguity in our mnemonic table, so try
   // matching with the unsized operand.
   if (Match.empty()) {
     Match.push_back(MatchInstruction(
-        Operands, Inst, ErrorInfo, MatchingInlineAsm, isParsingIntelSyntax()));
+        Operands, Inst, ErrorInfo, MissingFeatures, MatchingInlineAsm,
+        isParsingIntelSyntax()));
     // If this returned as a missing feature failure, remember that.
     if (Match.back() == Match_MissingFeature)
-      ErrorInfoMissingFeature = ErrorInfo;
+      ErrorInfoMissingFeatures = MissingFeatures;
   }
 
   // Restore the size of the unsized memory operand if we modified it.
   if (UnsizedMemOp)
     UnsizedMemOp->Mem.Size = 0;
 
   // If it's a bad mnemonic, all results will be the same.
   if (Match.back() == Match_MnemonicFail) {
     return Error(IDLoc, "invalid instruction mnemonic '" + Mnemonic + "'",
                  Op.getLocRange(), MatchingInlineAsm);
   }
 
   unsigned NumSuccessfulMatches =
       std::count(std::begin(Match), std::end(Match), Match_Success);
 
   // If matching was ambiguous and we had size information from the frontend,
   // try again with that. This handles cases like "movxz eax, m8/m16".
   if (UnsizedMemOp && NumSuccessfulMatches > 1 &&
       UnsizedMemOp->getMemFrontendSize()) {
     UnsizedMemOp->Mem.Size = UnsizedMemOp->getMemFrontendSize();
     unsigned M = MatchInstruction(
-        Operands, Inst, ErrorInfo, MatchingInlineAsm, isParsingIntelSyntax());
+        Operands, Inst, ErrorInfo, MissingFeatures, MatchingInlineAsm,
+        isParsingIntelSyntax());
     if (M == Match_Success)
       NumSuccessfulMatches = 1;
 
     // Add a rewrite that encodes the size information we used from the
     // frontend.
     InstInfo->AsmRewrites->emplace_back(
         AOK_SizeDirective, UnsizedMemOp->getStartLoc(),
         /*Len=*/0, UnsizedMemOp->getMemFrontendSize());
return Error(UnsizedMemOp->getStartLoc(),
                  "ambiguous operand size for instruction '" + Mnemonic + "\'",
                  UnsizedMemOp->getLocRange());
   }
 
   // If one instruction matched with a missing feature, report this as a
   // missing feature.
   if (std::count(std::begin(Match), std::end(Match),
                  Match_MissingFeature) == 1) {
-    ErrorInfo = ErrorInfoMissingFeature;
-    return ErrorMissingFeature(IDLoc, ErrorInfoMissingFeature,
+    ErrorInfo = Match_MissingFeature;
+    return ErrorMissingFeature(IDLoc, ErrorInfoMissingFeatures,
                                MatchingInlineAsm);
   }
 
   // If one instruction matched with an invalid operand, report this as an
   // operand failure.
   if (std::count(std::begin(Match), std::end(Match),
                  Match_InvalidOperand) == 1) {
     return Error(IDLoc, "invalid operand for instruction", EmptyRange,

utils/TableGen/AsmMatcherEmitter.cpp

void AsmMatcherInfo::buildInfo() {
   const std::vector<std::pair<Record *, SubtargetFeatureInfo>>
       &SubtargetFeaturePairs = SubtargetFeatureInfo::getAll(Records);
   SubtargetFeatures.insert(SubtargetFeaturePairs.begin(),
                            SubtargetFeaturePairs.end());
 #ifndef NDEBUG
   for (const auto &Pair : SubtargetFeatures)
     LLVM_DEBUG(Pair.second.dump());
 #endif // NDEBUG
-  assert(SubtargetFeatures.size() <= 64 && "Too many subtarget features!");
 
   bool HasMnemonicFirst = AsmParser->getValueAsBit("HasMnemonicFirst");
   bool ReportMultipleNearMisses =
       AsmParser->getValueAsBit("ReportMultipleNearMisses");
 
   // Parse the instructions; we need to do this first so that we can gather the
   // singleton register classes.
   SmallPtrSet<Record*, 16> SingletonRegisters;
static void emitGetSubtargetFeatureName(AsmMatcherInfo &Info, raw_ostream &OS) {
   OS << "// User-level names for subtarget features that participate in\n"
      << "// instruction matching.\n"
      << "static const char *getSubtargetFeatureName(uint64_t Val) {\n";
   if (!Info.SubtargetFeatures.empty()) {
     OS << "  switch(Val) {\n";
     for (const auto &SF : Info.SubtargetFeatures) {
       const SubtargetFeatureInfo &SFI = SF.second;
       // FIXME: Totally just a placeholder name to get the algorithm working.
-      OS << "  case " << SFI.getEnumName() << ": return \""
+      OS << "  case " << SFI.getEnumBitName() << ": return \""
          << SFI.TheDef->getValueAsString("PredicateName") << "\";\n";
     }
     OS << "  default: return \"(unknown)\";\n";
     OS << "  }\n";
   } else {
     // Nothing to emit, so skip the switch
     OS << "  return \"(unknown)\";\n";
   }
   OS << "}\n\n";
 }
 
 static std::string GetAliasRequiredFeatures(Record *R,
                                             const AsmMatcherInfo &Info) {
   std::vector<Record*> ReqFeatures = R->getValueAsListOfDefs("Predicates");
   std::string Result;
-  unsigned NumFeatures = 0;
+
+  if (ReqFeatures.empty())
+    return Result;
+
   for (unsigned i = 0, e = ReqFeatures.size(); i != e; ++i) {
     const SubtargetFeatureInfo *F = Info.getSubtargetFeature(ReqFeatures[i]);
 
     if (!F)
       PrintFatalError(R->getLoc(), "Predicate '" + ReqFeatures[i]->getName() +
                     "' is not marked as an AssemblerPredicate!");
 
-    if (NumFeatures)
-      Result += '|';
+    if (i)
+      Result += " && ";
 
-    Result += F->getEnumName();
-    ++NumFeatures;
+    Result += "Features.test(" + F->getEnumBitName() + ')';
   }
 
-  if (NumFeatures > 1)
-    Result = '(' + Result + ')';
   return Result;
 }
 
 static void emitMnemonicAliasVariant(raw_ostream &OS,const AsmMatcherInfo &Info,
                                      std::vector<Record*> &Aliases,
                                      unsigned Indent = 0,
                                   StringRef AsmParserVariantName = StringRef()){
   // Keep track of all the aliases from a mnemonic.  Use an std::map so that the
for (unsigned i = 0, e = ToVec.size(); i != e; ++i) {
         AliasWithNoPredicate = i;
         continue;
       }
       if (R->getValueAsString("ToMnemonic") == AliasEntry.first)
         PrintFatalError(R->getLoc(), "MnemonicAlias to the same string");
 
       if (!MatchCode.empty())
         MatchCode += "else ";
-      MatchCode += "if ((Features & " + FeatureMask + ") == "+FeatureMask+")\n";
+      MatchCode += "if (" + FeatureMask + ")\n";
       MatchCode += "  Mnemonic = \"";
       MatchCode += R->getValueAsString("ToMnemonic");
       MatchCode += "\";\n";
     }
 
     if (AliasWithNoPredicate != -1) {
       Record *R = ToVec[AliasWithNoPredicate];
       if (!MatchCode.empty())
static bool emitMnemonicAliases(raw_ostream &OS, const AsmMatcherInfo &Info,
   if (!MatchPrefix.empty())
     return false;
 
   std::vector<Record*> Aliases =
     Info.getRecords().getAllDerivedDefinitions("MnemonicAlias");
   if (Aliases.empty()) return false;
 
   OS << "static void applyMnemonicAliases(StringRef &Mnemonic, "
-    "uint64_t Features, unsigned VariantID) {\n";
+    "const FeatureBitset &Features, unsigned VariantID) {\n";
   OS << "  switch (VariantID) {\n";
   unsigned VariantCount = Target.getAsmParserVariantCount();
   for (unsigned VC = 0; VC != VariantCount; ++VC) {
     Record *AsmVariant = Target.getAsmParserVariant(VC);
     int AsmParserVariantNo = AsmVariant->getValueAsInt("Variant");
     StringRef AsmParserVariantName = AsmVariant->getValueAsString("Name");
     OS << "    case " << AsmParserVariantNo << ":\n";
     emitMnemonicAliasVariant(OS, Info, Aliases, /*Indent=*/2,
static void emitCustomOperandParsing(raw_ostream &OS, CodeGenTarget &Target,
   unsigned MaxMask = 0;
   for (const OperandMatchEntry &OMI : Info.OperandMatchInfo) {
     MaxMask |= OMI.OperandMask;
   }
 
   // Emit the static custom operand parsing table;
   OS << "namespace {\n";
   OS << "  struct OperandMatchEntry {\n";
-  OS << "    " << getMinimalTypeForEnumBitfield(Info.SubtargetFeatures.size())
-               << " RequiredFeatures;\n";
+  OS << "    " << "uint8_t RequiredFeaturesIdx;\n";
   OS << "    " << getMinimalTypeForRange(MaxMnemonicIndex)
                << " Mnemonic;\n";
   OS << "    " << getMinimalTypeForRange(std::distance(
                       Info.Classes.begin(), Info.Classes.end())) << " Class;\n";
   OS << "    " << getMinimalTypeForRange(MaxMask)
                << " OperandMask;\n\n";
   OS << "    StringRef getMnemonic() const {\n";
   OS << "      return StringRef(MnemonicTable + Mnemonic + 1,\n";
static void emitCustomOperandParsing(raw_ostream &OS, CodeGenTarget &Target,
 
   OS << "  /* Operand List Mask, Mnemonic, Operand Class, Features */\n";
   for (const OperandMatchEntry &OMI : Info.OperandMatchInfo) {
     const MatchableInfo &II = *OMI.MI;
 
     OS << "  { ";
 
     // Write the required features mask.
-    if (!II.RequiredFeatures.empty()) {
-      for (unsigned i = 0, e = II.RequiredFeatures.size(); i != e; ++i) {
-        if (i) OS << "|";
-        OS << II.RequiredFeatures[i]->getEnumName();
-      }
-    } else
-      OS << "0";
+    OS << "AMFBS";
+    if (II.RequiredFeatures.empty())
+      OS << "_None";
+    else
+      for (unsigned i = 0, e = II.RequiredFeatures.size(); i != e; ++i)
+        OS << '_' << II.RequiredFeatures[i]->TheDef->getName();
 
     // Store a pascal-style length byte in the mnemonic.
     std::string LenMnemonic = char(II.Mnemonic.size()) + II.Mnemonic.str();
     OS << ", " << StringTable.GetOrAddStringOffset(LenMnemonic, false)
        << " /* " << II.Mnemonic << " */, ";
 
     OS << OMI.CI->Name;
 
static void emitCustomOperandParsing(raw_ostream &OS, CodeGenTarget &Target,
   // a better error handling.
   OS << "OperandMatchResultTy " << Target.getName() << ClassName << "::\n"
      << "MatchOperandParserImpl(OperandVector"
      << " &Operands,\n                       StringRef Mnemonic,\n"
      << "                       bool ParseForAllFeatures) {\n";
 
   // Emit code to get the available features.
   OS << "  // Get the current feature set.\n";
-  OS << "  uint64_t AvailableFeatures = getAvailableFeatures();\n\n";
+  OS << "  const FeatureBitset &AvailableFeatures = getAvailableFeatures();\n\n";
 
   OS << "  // Get the next operand index.\n";
   OS << "  unsigned NextOpNum = Operands.size()"
      << (HasMnemonicFirst ? " - 1" : "") << ";\n";
 
   // Emit code to search the table.
   OS << "  // Search the table.\n";
   if (HasMnemonicFirst) {
static void emitCustomOperandParsing(raw_ostream &OS, CodeGenTarget &Target,
   OS << "  for (const OperandMatchEntry *it = MnemonicRange.first,\n"
      << "       *ie = MnemonicRange.second; it != ie; ++it) {\n";
 
   OS << "    // equal_range guarantees that instruction mnemonic matches.\n";
   OS << "    assert(Mnemonic == it->getMnemonic());\n\n";
 
   // Emit check that the required features are available.
   OS << "    // check if the available features match\n";
+  OS << "    const FeatureBitset &RequiredFeatures = "
+        "FeatureBitsets[it->RequiredFeaturesIdx];\n";
   OS << "    if (!ParseForAllFeatures && (AvailableFeatures & "
-        "it->RequiredFeatures) != it->RequiredFeatures)\n";
+        "RequiredFeatures) != RequiredFeatures)\n";
   OS << "        continue;\n\n";
 
   // Emit check to ensure the operand number matches.
   OS << "    // check if the operand in question has a custom parser.\n";
   OS << "    if (!(it->OperandMask & (1 << NextOpNum)))\n";
   OS << "      continue;\n\n";
 
   // Emit call to the custom parser method
static void emitAsmTiedOperandConstraints(CodeGenTarget &Target,
   OS << "  }\n";
   OS << "  return true;\n";
   OS << "}\n\n";
 }
 
 static void emitMnemonicSpellChecker(raw_ostream &OS, CodeGenTarget &Target,
                                      unsigned VariantCount) {
   OS << "static std::string " << Target.getName()
-     << "MnemonicSpellCheck(StringRef S, uint64_t FBS, unsigned VariantID) {\n";
+     << "MnemonicSpellCheck(StringRef S, const FeatureBitset &FBS,"
+     << " unsigned VariantID) {\n";
   if (!VariantCount)
     OS <<  "  return \"\";";
   else {
     OS << "  const unsigned MaxEditDist = 2;\n";
     OS << "  std::vector<StringRef> Candidates;\n";
     OS << "  StringRef Prev = \"\";\n\n";
 
     OS << "  // Find the appropriate table for this asm variant.\n";
     OS << "  const MatchEntry *Start, *End;\n";
     OS << "  switch (VariantID) {\n";
     OS << "  default: llvm_unreachable(\"invalid variant!\");\n";
     for (unsigned VC = 0; VC != VariantCount; ++VC) {
       Record *AsmVariant = Target.getAsmParserVariant(VC);
       int AsmVariantNo = AsmVariant->getValueAsInt("Variant");
       OS << "  case " << AsmVariantNo << ": Start = std::begin(MatchTable" << VC
          << "); End = std::end(MatchTable" << VC << "); break;\n";
     }
     OS << "  }\n\n";
     OS << "  for (auto I = Start; I < End; I++) {\n";
     OS << "    // Ignore unsupported instructions.\n";
-    OS << "    if ((FBS & I->RequiredFeatures) != I->RequiredFeatures)\n";
+    OS << "    const FeatureBitset &RequiredFeatures = "
+          "FeatureBitsets[I->RequiredFeaturesIdx];\n";
+    OS << "    if ((FBS & RequiredFeatures) != RequiredFeatures)\n";
     OS << "      continue;\n";
     OS << "\n";
     OS << "    StringRef T = I->getMnemonic();\n";
     OS << "    // Avoid recomputing the edit distance for the same string.\n";
     OS << "    if (T.equals(Prev))\n";
     OS << "      continue;\n";
     OS << "\n";
     OS << "    Prev = T;\n";
static void emitMatchClassKindNames(std::forward_list<ClassInfo> &Infos,
   OS << "  case NumMatchClassKinds: return \"NumMatchClassKinds\";\n";
 
   OS << "  }\n";
   OS << "  llvm_unreachable(\"unhandled MatchClassKind!\");\n";
   OS << "}\n\n";
   OS << "#endif // NDEBUG\n";
 }
 
+static std::string
+getNameForFeatureBitset(const std::vector<Record *> &FeatureBitset) {
+  std::string Name = "AMFBS";
+  for (const auto &Feature : FeatureBitset)
+    Name += ("_" + Feature->getName()).str();
+  return Name;
+}
+
 void AsmMatcherEmitter::run(raw_ostream &OS) {
   CodeGenTarget Target(Records);
   Record *AsmParser = Target.getAsmParser();
   StringRef ClassName = AsmParser->getValueAsString("AsmParserClassName");
 
   // Compute the information on the instructions to match.
   AsmMatcherInfo Info(AsmParser, Target, Records);
   Info.buildInfo();
#endif
 
   // Write the output.
 
   // Information for the class declaration.
   OS << "\n#ifdef GET_ASSEMBLER_HEADER\n";
   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 << "  FeatureBitset ComputeAvailableFeatures(const FeatureBitset& FB) const;\n";
   if (HasOptionalOperands) {
     OS << "  void convertToMCInst(unsigned Kind, MCInst &Inst, "
        << "unsigned Opcode,\n"
        << "                       const OperandVector &Operands,\n"
        << "                       const SmallBitVector &OptionalOperandsMask);\n";
   } else {
     OS << "  void convertToMCInst(unsigned Kind, MCInst &Inst, "
        << "unsigned Opcode,\n"
        << "                       const OperandVector &Operands);\n";
   }
   OS << "  void convertToMapAndConstraints(unsigned Kind,\n                ";
   OS << "           const OperandVector &Operands) override;\n";
   OS << "  unsigned MatchInstructionImpl(const OperandVector &Operands,\n"
      << "                                MCInst &Inst,\n";
   if (ReportMultipleNearMisses)
     OS << "                                SmallVectorImpl<NearMissInfo> *NearMisses,\n";
   else
-    OS << "                                uint64_t &ErrorInfo,\n";
+    OS << "                                uint64_t &ErrorInfo,\n"
+       << "                                FeatureBitset &MissingFeatures,\n";
   OS << "                                bool matchingInlineAsm,\n"
      << "                                unsigned VariantID = 0);\n";
+  if (!ReportMultipleNearMisses)
+    OS << "  unsigned MatchInstructionImpl(const OperandVector &Operands,\n"
+       << "                                MCInst &Inst,\n"
+       << "                                uint64_t &ErrorInfo,\n"
+       << "                                bool matchingInlineAsm,\n"
+       << "                                unsigned VariantID = 0) {\n"
+       << "    FeatureBitset MissingFeatures;\n"
+       << "    return MatchInstructionImpl(Operands, Inst, ErrorInfo, MissingFeatures,\n"
+       << "                                matchingInlineAsm, VariantID);\n"
+       << "  }\n\n";
+
 
   if (!Info.OperandMatchInfo.empty()) {
     OS << "  OperandMatchResultTy MatchOperandParserImpl(\n";
     OS << "    OperandVector &Operands,\n";
     OS << "    StringRef Mnemonic,\n";
     OS << "    bool ParseForAllFeatures = false);\n";
 
     OS << "  OperandMatchResultTy tryCustomParseOperand(\n";
     OS << "    OperandVector &Operands,\n";
     OS << "    unsigned MCK);\n\n";
   }
 
   OS << "#endif // GET_ASSEMBLER_HEADER_INFO\n\n";
 
   // Emit the operand match diagnostic enum names.
   OS << "\n#ifdef GET_OPERAND_DIAGNOSTIC_TYPES\n";
   OS << "#undef GET_OPERAND_DIAGNOSTIC_TYPES\n\n";
   emitOperandDiagnosticTypes(Info, OS);
   OS << "#endif // GET_OPERAND_DIAGNOSTIC_TYPES\n\n";
 
   OS << "\n#ifdef GET_REGISTER_MATCHER\n";
   OS << "#undef GET_REGISTER_MATCHER\n\n";
 
   // Emit the subtarget feature enumeration.
-  SubtargetFeatureInfo::emitSubtargetFeatureFlagEnumeration(
+  SubtargetFeatureInfo::emitSubtargetFeatureBitEnumeration(
       Info.SubtargetFeatures, OS);
 
   // Emit the function to match a register name to number.
   // This should be omitted for Mips target
   if (AsmParser->getValueAsBit("ShouldEmitMatchRegisterName"))
     emitMatchRegisterName(Target, AsmParser, OS);
 
   if (AsmParser->getValueAsBit("ShouldEmitMatchRegisterAltName"))
for (const auto &MI : Info.Matchables) {
     MaxMnemonicIndex = std::max(MaxMnemonicIndex,
                         StringTable.GetOrAddStringOffset(LenMnemonic, false));
   }
 
   OS << "static const char *const MnemonicTable =\n";
   StringTable.EmitString(OS);
   OS << ";\n\n";
 
+  std::vector<std::vector<Record *>> FeatureBitsets;
+  for (const auto &MI : Info.Matchables) {
+    if (MI->RequiredFeatures.empty())
+      continue;
+    FeatureBitsets.emplace_back();
+    for (unsigned I = 0, E = MI->RequiredFeatures.size(); I != E; ++I)
+      FeatureBitsets.back().push_back(MI->RequiredFeatures[I]->TheDef);
+  }
+
+  llvm::sort(FeatureBitsets, [&](const std::vector<Record *> &A,
+                                 const std::vector<Record *> &B) {
+    if (A.size() < B.size())
+      return true;
+    if (A.size() > B.size())
+      return false;
+    for (const auto &Pair : zip(A, B)) {
+      if (std::get<0>(Pair)->getName() < std::get<1>(Pair)->getName())
+        return true;
+      if (std::get<0>(Pair)->getName() > std::get<1>(Pair)->getName())
+        return false;
+    }
+    return false;
+  });
+  FeatureBitsets.erase(
+      std::unique(FeatureBitsets.begin(), FeatureBitsets.end()),
+      FeatureBitsets.end());
+  OS << "// Feature bitsets.\n"
+     << "enum : uint8_t {\n"
+     << "  AMFBS_None,\n";
+  for (const auto &FeatureBitset : FeatureBitsets) {
+    if (FeatureBitset.empty())
+      continue;
+    OS << "  " << getNameForFeatureBitset(FeatureBitset) << ",\n";
+  }
+  OS << "};\n\n"
+     << "const static FeatureBitset FeatureBitsets[] {\n"
+     << "  {}, // AMFBS_None\n";
+  for (const auto &FeatureBitset : FeatureBitsets) {
+    if (FeatureBitset.empty())
+      continue;
+    OS << "  {";
+    for (const auto &Feature : FeatureBitset) {
+      const auto &I = Info.SubtargetFeatures.find(Feature);
+      assert(I != Info.SubtargetFeatures.end() && "Didn't import predicate?");
+      OS << I->second.getEnumBitName() << ", ";
+    }
+    OS << "},\n";
+  }
+  OS << "};\n\n";
+
   // Emit the static match table; unused classes get initialized to 0 which is
   // guaranteed to be InvalidMatchClass.
   //
   // FIXME: We can reduce the size of this table very easily. First, we change
   // it so that store the kinds in separate bit-fields for each index, which
   // only needs to be the max width used for classes at that index (we also need
   // to reject based on this during classification). If we then make sure to
   // order the match kinds appropriately (putting mnemonics last), then we
   // should only end up using a few bits for each class, especially the ones
   // following the mnemonic.
   OS << "namespace {\n";
   OS << "  struct MatchEntry {\n";
   OS << "    " << getMinimalTypeForRange(MaxMnemonicIndex)
                << " Mnemonic;\n";
   OS << "    uint16_t Opcode;\n";
   OS << "    " << getMinimalTypeForRange(Info.Matchables.size())
                << " ConvertFn;\n";
-  OS << "    " << getMinimalTypeForEnumBitfield(Info.SubtargetFeatures.size())
-               << " RequiredFeatures;\n";
+  OS << "    " << "uint8_t RequiredFeaturesIdx;\n";
   OS << "    " << getMinimalTypeForRange(
                       std::distance(Info.Classes.begin(), Info.Classes.end()))
      << " Classes[" << MaxNumOperands << "];\n";
   OS << "    StringRef getMnemonic() const {\n";
   OS << "      return StringRef(MnemonicTable + Mnemonic + 1,\n";
   OS << "                       MnemonicTable[Mnemonic]);\n";
   OS << "    }\n";
   OS << "  };\n\n";
for (const auto &MI : Info.Matchables) {
       std::string LenMnemonic = char(MI->Mnemonic.size()) + MI->Mnemonic.str();
       OS << "  { " << StringTable.GetOrAddStringOffset(LenMnemonic, false)
          << " /* " << MI->Mnemonic << " */, "
          << Target.getInstNamespace() << "::"
          << MI->getResultInst()->TheDef->getName() << ", "
          << MI->ConversionFnKind << ", ";
 
       // Write the required features mask.
-      if (!MI->RequiredFeatures.empty()) {
-        for (unsigned i = 0, e = MI->RequiredFeatures.size(); i != e; ++i) {
-          if (i) OS << "|";
-          OS << MI->RequiredFeatures[i]->getEnumName();
-        }
-      } else
-        OS << "0";
+      OS << "AMFBS";
+      if (MI->RequiredFeatures.empty())
+        OS << "_None";
+      else
+        for (unsigned i = 0, e = MI->RequiredFeatures.size(); i != e; ++i)
+          OS << '_' << MI->RequiredFeatures[i]->TheDef->getName();
 
       OS << ", { ";
       for (unsigned i = 0, e = MI->AsmOperands.size(); i != e; ++i) {
         const MatchableInfo::AsmOperand &Op = MI->AsmOperands[i];
 
         if (i) OS << ", ";
         OS << Op.Class->Name;
       }
       OS << " }, },\n";
     }
 
     OS << "};\n\n";
   }
 
   OS << "#include \"llvm/Support/Debug.h\"\n";
   OS << "#include \"llvm/Support/Format.h\"\n\n";
 
   // Finally, build the match function.
   OS << "unsigned " << Target.getName() << ClassName << "::\n"
      << "MatchInstructionImpl(const OperandVector &Operands,\n";
   OS << "                     MCInst &Inst,\n";
   if (ReportMultipleNearMisses)
     OS << "                     SmallVectorImpl<NearMissInfo> *NearMisses,\n";
   else
-    OS << "                     uint64_t &ErrorInfo,\n";
+    OS << "                     uint64_t &ErrorInfo,\n"
+       << "                     FeatureBitset &MissingFeatures,\n";
   OS << "                     bool matchingInlineAsm, unsigned VariantID) {\n";
 
   if (!ReportMultipleNearMisses) {
     OS << "  // Eliminate obvious mismatches.\n";
     OS << "  if (Operands.size() > "
        << (MaxNumOperands + HasMnemonicFirst) << ") {\n";
     OS << "    ErrorInfo = "
        << (MaxNumOperands + HasMnemonicFirst) << ";\n";
     OS << "    return Match_InvalidOperand;\n";
     OS << "  }\n\n";
   }
 
   // Emit code to get the available features.
   OS << "  // Get the current feature set.\n";
-  OS << "  uint64_t AvailableFeatures = getAvailableFeatures();\n\n";
+  OS << "  const FeatureBitset &AvailableFeatures = getAvailableFeatures();\n\n";
 
   OS << "  // Get the instruction mnemonic, which is the first token.\n";
   if (HasMnemonicFirst) {
     OS << "  StringRef Mnemonic = ((" << Target.getName()
        << "Operand&)*Operands[0]).getToken();\n\n";
   } else {
     OS << "  StringRef Mnemonic;\n";
     OS << "  if (Operands[0]->isToken())\n";
     OS << "    Mnemonic = ((" << Target.getName()
        << "Operand&)*Operands[0]).getToken();\n\n";
   }
 
   if (HasMnemonicAliases) {
     OS << "  // Process all MnemonicAliases to remap the mnemonic.\n";
     OS << "  applyMnemonicAliases(Mnemonic, AvailableFeatures, VariantID);\n\n";
   }
 
   // Emit code to compute the class list for this operand vector.
   if (!ReportMultipleNearMisses) {
     OS << "  // Some state to try to produce better error messages.\n";
     OS << "  bool HadMatchOtherThanFeatures = false;\n";
     OS << "  bool HadMatchOtherThanPredicate = false;\n";
     OS << "  unsigned RetCode = Match_InvalidOperand;\n";
-    OS << "  uint64_t MissingFeatures = ~0ULL;\n";
+    OS << "  MissingFeatures.set();\n";
     OS << "  // Set ErrorInfo to the operand that mismatches if it is\n";
     OS << "  // wrong for all instances of the instruction.\n";
     OS << "  ErrorInfo = ~0ULL;\n";
   }
 
   if (HasOptionalOperands) {
     OS << "  SmallBitVector OptionalOperandsMask(" << MaxNumOperands << ");\n";
   }
#endif
 
   OS << "  // Return a more specific error code if no mnemonics match.\n";
   OS << "  if (MnemonicRange.first == MnemonicRange.second)\n";
   OS << "    return Match_MnemonicFail;\n\n";
 
   OS << "  for (const MatchEntry *it = MnemonicRange.first, "
      << "*ie = MnemonicRange.second;\n";
   OS << "       it != ie; ++it) {\n";
+  OS << "    const FeatureBitset &RequiredFeatures = "
+        "FeatureBitsets[it->RequiredFeaturesIdx];\n";
   OS << "    bool HasRequiredFeatures =\n";
-  OS << "      (AvailableFeatures & it->RequiredFeatures) == "
-        "it->RequiredFeatures;\n";
+  OS << "      (AvailableFeatures & RequiredFeatures) == RequiredFeatures;\n";
   OS << "    DEBUG_WITH_TYPE(\"asm-matcher\", dbgs() << \"Trying to match opcode \"\n";
   OS << "                                          << MII.getName(it->Opcode) << \"\\n\");\n";
 
   if (ReportMultipleNearMisses) {
     OS << "    // Some state to record ways in which this instruction did not match.\n";
     OS << "    NearMissInfo OperandNearMiss = NearMissInfo::getSuccess();\n";
     OS << "    NearMissInfo FeaturesNearMiss = NearMissInfo::getSuccess();\n";
     OS << "    NearMissInfo EarlyPredicateNearMiss = NearMissInfo::getSuccess();\n";
#endif
   OS << "                                               \"this opcode\\n\");\n";
   OS << "      continue;\n";
   OS << "    }\n";
 
   // Emit check that the required features are available.
   OS << "    if (!HasRequiredFeatures) {\n";
   if (!ReportMultipleNearMisses)
     OS << "      HadMatchOtherThanFeatures = true;\n";
-  OS << "      uint64_t NewMissingFeatures = it->RequiredFeatures & "
+  OS << "      FeatureBitset NewMissingFeatures = RequiredFeatures & "
         "~AvailableFeatures;\n";
-  OS << "      DEBUG_WITH_TYPE(\"asm-matcher\", dbgs() << \"Missing target features: \"\n";
-  OS << "                                            << format_hex(NewMissingFeatures, 18)\n";
-  OS << "                                            << \"\\n\");\n";
+  OS << "      DEBUG_WITH_TYPE(\"asm-matcher\", dbgs() << \"Missing target features:\";\n";
+  OS << "                       for (unsigned I = 0, E = NewMissingFeatures.size(); I != E; ++I)\n";
+  OS << "                         if (NewMissingFeatures[I])\n";
+  OS << "                           dbgs() << ' ' << I;\n";
+  OS << "                       dbgs() << \"\\n\");\n";
   if (ReportMultipleNearMisses) {
     OS << "      FeaturesNearMiss = NearMissInfo::getMissedFeature(NewMissingFeatures);\n";
   } else {
-    OS << "      if (countPopulation(NewMissingFeatures) <=\n"
-          "          countPopulation(MissingFeatures))\n";
+    OS << "      if (NewMissingFeatures.count() <=\n"
+          "          MissingFeatures.count())\n";
     OS << "        MissingFeatures = NewMissingFeatures;\n";
     OS << "      continue;\n";
   }
   OS << "    }\n";
   OS << "\n";
   OS << "    Inst.clear();\n\n";
   OS << "    Inst.setOpcode(it->Opcode);\n";
   // Verify the instruction with the target-specific match predicate function.
#endif
 
   if (ReportMultipleNearMisses) {
     OS << "  // No instruction variants matched exactly.\n";
     OS << "  return Match_NearMisses;\n";
   } else {
     OS << "  // Okay, we had no match.  Try to return a useful error code.\n";
     OS << "  if (HadMatchOtherThanPredicate || !HadMatchOtherThanFeatures)\n";
     OS << "    return RetCode;\n\n";
-    OS << "  // Missing feature matches return which features were missing\n";
-    OS << "  ErrorInfo = MissingFeatures;\n";
+    OS << "  ErrorInfo = 0;\n";
     OS << "  return Match_MissingFeature;\n";
   }
   OS << "}\n\n";
 
   if (!Info.OperandMatchInfo.empty())
     emitCustomOperandParsing(OS, Target, Info, ClassName, StringTable,
                              MaxMnemonicIndex, HasMnemonicFirst);
 

utils/TableGen/CodeEmitterGen.cpp

if (!PostEmitter.empty()) {
     Case += "(MI, Value";
     Case += ", STI";
     Case += ");\n";
   }
   
   return Case;
 }
 
+static std::string
+getNameForFeatureBitset(const std::vector<Record *> &FeatureBitset) {
+  std::string Name = "CEFBS";
+  for (const auto &Feature : FeatureBitset)
+    Name += ("_" + Feature->getName()).str();
+  return Name;
+}
+
 void CodeEmitterGen::run(raw_ostream &o) {
   CodeGenTarget Target(Records);
   std::vector<Record*> Insts = Records.getAllDerivedDefinitions("Instruction");
 
   // For little-endian instruction bit encodings, reverse the bit order
   Target.reverseBitsForLittleEndianEncoding();
 
   ArrayRef<const CodeGenInstruction*> NumberedInstructions =
void CodeEmitterGen::run(raw_ostream &o) {
   std::map<Record *, SubtargetFeatureInfo, LessRecordByID> SubtargetFeatures;
   SubtargetFeatures.insert(All.begin(), All.end());
 
   o << "#ifdef ENABLE_INSTR_PREDICATE_VERIFIER\n"
     << "#undef ENABLE_INSTR_PREDICATE_VERIFIER\n"
     << "#include <sstream>\n\n";
 
   // Emit the subtarget feature enumeration.
-  SubtargetFeatureInfo::emitSubtargetFeatureFlagEnumeration(SubtargetFeatures,
-                                                            o);
+  SubtargetFeatureInfo::emitSubtargetFeatureBitEnumeration(SubtargetFeatures,
 
   // Emit the name table for error messages.
   o << "#ifndef NDEBUG\n";
   SubtargetFeatureInfo::emitNameTable(SubtargetFeatures, o);
   o << "#endif // NDEBUG\n";
 
   // Emit the available features compute function.
   SubtargetFeatureInfo::emitComputeAssemblerAvailableFeatures(
       Target.getName(), "MCCodeEmitter", "computeAvailableFeatures",
       SubtargetFeatures, o);
 
+  std::vector<std::vector<Record *>> FeatureBitsets;
+  for (const CodeGenInstruction *Inst : Target.getInstructionsByEnumValue()) {
+    FeatureBitsets.emplace_back();
+    for (Record *Predicate : Inst->TheDef->getValueAsListOfDefs("Predicates")) {
+      const auto &I = SubtargetFeatures.find(Predicate);
+      if (I != SubtargetFeatures.end())
+        FeatureBitsets.back().push_back(I->second.TheDef);
+    }
+  }
+
+  llvm::sort(FeatureBitsets, [&](const std::vector<Record *> &A,
+                                 const std::vector<Record *> &B) {
+    if (A.size() < B.size())
+      return true;
+    if (A.size() > B.size())
+      return false;
+    for (const auto &Pair : zip(A, B)) {
+      if (std::get<0>(Pair)->getName() < std::get<1>(Pair)->getName())
+        return true;
+      if (std::get<0>(Pair)->getName() > std::get<1>(Pair)->getName())
+        return false;
+    }
+    return false;
+  });
+  FeatureBitsets.erase(
+      std::unique(FeatureBitsets.begin(), FeatureBitsets.end()),
+      FeatureBitsets.end());
+  o << "#ifndef NDEBUG\n"
+    << "// Feature bitsets.\n"
+    << "enum : uint8_t {\n"
+    << "  CEFBS_None,\n";
+  for (const auto &FeatureBitset : FeatureBitsets) {
+    if (FeatureBitset.empty())
+      continue;
+    o << "  " << getNameForFeatureBitset(FeatureBitset) << ",\n";
+  }
+  o << "};\n\n"
+     << "const static FeatureBitset FeatureBitsets[] {\n"
+     << "  {}, // CEFBS_None\n";
+  for (const auto &FeatureBitset : FeatureBitsets) {
+    if (FeatureBitset.empty())
+      continue;
+    o << "  {";
+    for (const auto &Feature : FeatureBitset) {
+      const auto &I = SubtargetFeatures.find(Feature);
+      assert(I != SubtargetFeatures.end() && "Didn't import predicate?");
+      o << I->second.getEnumBitName() << ", ";
+    }
+    o << "},\n";
+  }
+  o << "};\n"
+    << "#endif // NDEBUG\n\n";
+
+
   // Emit the predicate verifier.
   o << "void " << Target.getName()
     << "MCCodeEmitter::verifyInstructionPredicates(\n"
-    << "    const MCInst &Inst, uint64_t AvailableFeatures) const {\n"
+    << "    const MCInst &Inst, const FeatureBitset &AvailableFeatures) const {\n"
     << "#ifndef NDEBUG\n"
-    << "  static uint64_t RequiredFeatures[] = {\n";
+    << "  static uint8_t RequiredFeaturesRefs[] = {\n";
   unsigned InstIdx = 0;
   for (const CodeGenInstruction *Inst : Target.getInstructionsByEnumValue()) {
-    o << "    ";
+    o << "    CEFBS";
+    unsigned NumPredicates = 0;
     for (Record *Predicate : Inst->TheDef->getValueAsListOfDefs("Predicates")) {
       const auto &I = SubtargetFeatures.find(Predicate);
-      if (I != SubtargetFeatures.end())
-        o << I->second.getEnumName() << " | ";
+      if (I != SubtargetFeatures.end()) {
+        o << '_' << I->second.TheDef->getName();
+        NumPredicates++;
+      }
     }
-    o << "0, // " << Inst->TheDef->getName() << " = " << InstIdx << "\n";
+    if (!NumPredicates)
+      o << "_None";
+    o << ", // " << Inst->TheDef->getName() << " = " << InstIdx << "\n";
     InstIdx++;
   }
   o << "  };\n\n";
   o << "  assert(Inst.getOpcode() < " << InstIdx << ");\n";
-  o << "  uint64_t MissingFeatures =\n"
-    << "      (AvailableFeatures & RequiredFeatures[Inst.getOpcode()]) ^\n"
-    << "      RequiredFeatures[Inst.getOpcode()];\n"
-    << "  if (MissingFeatures) {\n"
+  o << "  const FeatureBitset &RequiredFeatures = "
+       "FeatureBitsets[RequiredFeaturesRefs[Inst.getOpcode()]];\n";
+  o << "  FeatureBitset MissingFeatures =\n"
+    << "      (AvailableFeatures & RequiredFeatures) ^\n"
+    << "      RequiredFeatures;\n"
+    << "  if (MissingFeatures.any()) {\n"
     << "    std::ostringstream Msg;\n"
     << "    Msg << \"Attempting to emit \" << "
        "MCII.getName(Inst.getOpcode()).str()\n"
     << "        << \" instruction but the \";\n"
-    << "    for (unsigned i = 0; i < 8 * sizeof(MissingFeatures); ++i)\n"
-    << "      if (MissingFeatures & (1ULL << i))\n"
+    << "    for (unsigned i = 0, e = MissingFeatures.size(); i != e; ++i)\n"
+    << "      if (MissingFeatures.test(i))\n"
     << "        Msg << SubtargetFeatureNames[i] << \" \";\n"
     << "    Msg << \"predicate(s) are not met\";\n"
     << "    report_fatal_error(Msg.str());\n"
     << "  }\n"
     << "#else\n"
     << "// Silence unused variable warning on targets that don't use MCII for "
        "other purposes (e.g. BPF).\n"
     << "(void)MCII;\n"

utils/TableGen/SubtargetFeatureInfo.h

struct SubtargetFeatureInfo {
   }
 
   void dump() const;
   static std::vector<std::pair<Record *, SubtargetFeatureInfo>>
   getAll(const RecordKeeper &Records);
 
   /// Emit the subtarget feature flag definitions.
   ///
-  /// This version emits the bit value for the feature and is therefore limited
-  /// to 64 feature bits.
-  static void emitSubtargetFeatureFlagEnumeration(
-      SubtargetFeatureInfoMap &SubtargetFeatures, raw_ostream &OS);
-
-  /// Emit the subtarget feature flag definitions.
-  ///
   /// This version emits the bit index for the feature and can therefore support
   /// more than 64 feature bits.
   static void
   emitSubtargetFeatureBitEnumeration(SubtargetFeatureInfoMap &SubtargetFeatures,
                                      raw_ostream &OS);
 
   static void emitNameTable(SubtargetFeatureInfoMap &SubtargetFeatures,
                             raw_ostream &OS);

utils/TableGen/SubtargetFeatureInfo.cpp

if (Pred->getName().empty())
       PrintFatalError(Pred->getLoc(), "Predicate has no name!");
 
     SubtargetFeatures.emplace_back(
         Pred, SubtargetFeatureInfo(Pred, SubtargetFeatures.size()));
   }
   return SubtargetFeatures;
 }
 
-void SubtargetFeatureInfo::emitSubtargetFeatureFlagEnumeration(
-    SubtargetFeatureInfoMap &SubtargetFeatures, raw_ostream &OS) {
-  OS << "// Flags for subtarget features that participate in "
-     << "instruction matching.\n";
-  OS << "enum SubtargetFeatureFlag : "
-     << getMinimalTypeForEnumBitfield(SubtargetFeatures.size()) << " {\n";
-  for (const auto &SF : SubtargetFeatures) {
-    const SubtargetFeatureInfo &SFI = SF.second;
-    OS << "  " << SFI.getEnumName() << " = (1ULL << " << SFI.Index << "),\n";
-  }
-  OS << "  Feature_None = 0\n";
-  OS << "};\n\n";
-}
-
 void SubtargetFeatureInfo::emitSubtargetFeatureBitEnumeration(
     SubtargetFeatureInfoMap &SubtargetFeatures, raw_ostream &OS) {
   OS << "// Bits for subtarget features that participate in "
      << "instruction matching.\n";
   OS << "enum SubtargetFeatureBits : "
      << getMinimalTypeForRange(SubtargetFeatures.size()) << " {\n";
   for (const auto &SF : SubtargetFeatures) {
     const SubtargetFeatureInfo &SFI = SF.second;
void SubtargetFeatureInfo::emitComputeAvailableFeatures(
   }
   OS << "  return Features;\n";
   OS << "}\n\n";
 }
 
 void SubtargetFeatureInfo::emitComputeAssemblerAvailableFeatures(
     StringRef TargetName, StringRef ClassName, StringRef FuncName,
     SubtargetFeatureInfoMap &SubtargetFeatures, raw_ostream &OS) {
-  OS << "uint64_t " << TargetName << ClassName << "::\n"
+  OS << "FeatureBitset " << TargetName << ClassName << "::\n"
      << FuncName << "(const FeatureBitset& FB) const {\n";
-  OS << "  uint64_t Features = 0;\n";
+  OS << "  FeatureBitset Features;\n";
   for (const auto &SF : SubtargetFeatures) {
     const SubtargetFeatureInfo &SFI = SF.second;
 
     OS << "  if (";
     std::string CondStorage =
         SFI.TheDef->getValueAsString("AssemblerCondString");
     StringRef Conds = CondStorage;
     std::pair<StringRef, StringRef> Comma = Conds.split(',');
do {
       if (Comma.second.empty())
         break;
 
       First = false;
       Comma = Comma.second.split(',');
     } while (true);
 
     OS << ")\n";
-    OS << "    Features |= " << SFI.getEnumName() << ";\n";
+    OS << "    Features[" << SFI.getEnumBitName() << "] = 1;\n";
   }
   OS << "  return Features;\n";
   OS << "}\n\n";
 }