llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

//===-- X86AsmParser.cpp - Parse X86 assembly to MCInst instructions ------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/Target/TargetAsmParser.h"
#include "X86.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCParser/MCAsmLexer.h"
#include "llvm/MC/MCParser/MCAsmParser.h"
#include "llvm/MC/MCParser/MCParsedAsmOperand.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Target/TargetRegistry.h"
#include "llvm/Target/TargetAsmParser.h"
using namespace llvm;

namespace {
struct X86Operand;

class X86ATTAsmParser : public TargetAsmParser {
  MCAsmParser &Parser;

protected:
  unsigned Is64Bit : 1;

private:
  MCAsmParser &getParser() const { return Parser; }

  MCAsmLexer &getLexer() const { return Parser.getLexer(); }

  void Warning(SMLoc L, const Twine &Msg) { Parser.Warning(L, Msg); }

  bool Error(SMLoc L, const Twine &Msg) { return Parser.Error(L, Msg); }

  bool ParseRegister(unsigned &RegNo, SMLoc &StartLoc, SMLoc &EndLoc);

  X86Operand *ParseOperand();
  X86Operand *ParseMemOperand(unsigned SegReg, SMLoc StartLoc);

  bool ParseDirectiveWord(unsigned Size, SMLoc L);

  void InstructionCleanup(MCInst &Inst);

  /// @name Auto-generated Match Functions
  /// {

  bool MatchInstruction(const SmallVectorImpl<MCParsedAsmOperand*> &Operands,
                        MCInst &Inst);

  bool MatchInstructionImpl(
    const SmallVectorImpl<MCParsedAsmOperand*> &Operands, MCInst &Inst);

  /// }

public:
  X86ATTAsmParser(const Target &T, MCAsmParser &_Parser)
    : TargetAsmParser(T), Parser(_Parser) {}

  virtual bool ParseInstruction(const StringRef &Name, SMLoc NameLoc,
                                SmallVectorImpl<MCParsedAsmOperand*> &Operands);

  virtual bool ParseDirective(AsmToken DirectiveID);
};
 
class X86_32ATTAsmParser : public X86ATTAsmParser {
public:
  X86_32ATTAsmParser(const Target &T, MCAsmParser &_Parser)
    : X86ATTAsmParser(T, _Parser) {
    Is64Bit = false;
  }
};

class X86_64ATTAsmParser : public X86ATTAsmParser {
public:
  X86_64ATTAsmParser(const Target &T, MCAsmParser &_Parser)
    : X86ATTAsmParser(T, _Parser) {
    Is64Bit = true;
  }
};

} // end anonymous namespace

/// @name Auto-generated Match Functions
/// {  

static unsigned MatchRegisterName(StringRef Name);

/// }

namespace {

/// X86Operand - Instances of this class represent a parsed X86 machine
/// instruction.
struct X86Operand : public MCParsedAsmOperand {
  enum KindTy {
    Token,
    Register,
    Immediate,
    Memory
  } Kind;

  SMLoc StartLoc, EndLoc;
  
  union {
    struct {
      const char *Data;
      unsigned Length;
    } Tok;

    struct {
      unsigned RegNo;
    } Reg;

    struct {
      const MCExpr *Val;
    } Imm;

    struct {
      unsigned SegReg;
      const MCExpr *Disp;
      unsigned BaseReg;
      unsigned IndexReg;
      unsigned Scale;
    } Mem;
  };

  X86Operand(KindTy K, SMLoc Start, SMLoc End)
    : Kind(K), StartLoc(Start), EndLoc(End) {}

  /// getStartLoc - Get the location of the first token of this operand.
  SMLoc getStartLoc() const { return StartLoc; }
  /// getEndLoc - Get the location of the last token of this operand.
  SMLoc getEndLoc() const { return EndLoc; }

  StringRef getToken() const {
    assert(Kind == Token && "Invalid access!");
    return StringRef(Tok.Data, Tok.Length);
  }
  void setTokenValue(StringRef Value) {
    assert(Kind == Token && "Invalid access!");
    Tok.Data = Value.data();
    Tok.Length = Value.size();
  }

  unsigned getReg() const {
    assert(Kind == Register && "Invalid access!");
    return Reg.RegNo;
  }

  const MCExpr *getImm() const {
    assert(Kind == Immediate && "Invalid access!");
    return Imm.Val;
  }

  const MCExpr *getMemDisp() const {
    assert(Kind == Memory && "Invalid access!");
    return Mem.Disp;
  }
  unsigned getMemSegReg() const {
    assert(Kind == Memory && "Invalid access!");
    return Mem.SegReg;
  }
  unsigned getMemBaseReg() const {
    assert(Kind == Memory && "Invalid access!");
    return Mem.BaseReg;
  }
  unsigned getMemIndexReg() const {
    assert(Kind == Memory && "Invalid access!");
    return Mem.IndexReg;
  }
  unsigned getMemScale() const {
    assert(Kind == Memory && "Invalid access!");
    return Mem.Scale;
  }

  bool isToken() const {return Kind == Token; }

  bool isImm() const { return Kind == Immediate; }
  
  bool isImmSExti16i8() const {
    if (!isImm())
      return false;

    // If this isn't a constant expr, just assume it fits and let relaxation
    // handle it.
    const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
    if (!CE)
      return true;

    // Otherwise, check the value is in a range that makes sense for this
    // extension.
    uint64_t Value = CE->getValue();
    return ((                                  Value <= 0x000000000000007FULL)||
            (0x000000000000FF80ULL <= Value && Value <= 0x000000000000FFFFULL)||
            (0xFFFFFFFFFFFFFF80ULL <= Value && Value <= 0xFFFFFFFFFFFFFFFFULL));
  }
  bool isImmSExti32i8() const {
    if (!isImm())
      return false;

    // If this isn't a constant expr, just assume it fits and let relaxation
    // handle it.
    const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
    if (!CE)
      return true;

    // Otherwise, check the value is in a range that makes sense for this
    // extension.
    uint64_t Value = CE->getValue();
    return ((                                  Value <= 0x000000000000007FULL)||
            (0x00000000FFFFFF80ULL <= Value && Value <= 0x00000000FFFFFFFFULL)||
            (0xFFFFFFFFFFFFFF80ULL <= Value && Value <= 0xFFFFFFFFFFFFFFFFULL));
  }
  bool isImmSExti64i8() const {
    if (!isImm())
      return false;

    // If this isn't a constant expr, just assume it fits and let relaxation
    // handle it.
    const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
    if (!CE)
      return true;

    // Otherwise, check the value is in a range that makes sense for this
    // extension.
    uint64_t Value = CE->getValue();
    return ((                                  Value <= 0x000000000000007FULL)||
            (0xFFFFFFFFFFFFFF80ULL <= Value && Value <= 0xFFFFFFFFFFFFFFFFULL));
  }
  bool isImmSExti64i32() const {
    if (!isImm())
      return false;

    // If this isn't a constant expr, just assume it fits and let relaxation
    // handle it.
    const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
    if (!CE)
      return true;

    // Otherwise, check the value is in a range that makes sense for this
    // extension.
    uint64_t Value = CE->getValue();
    return ((                                  Value <= 0x000000007FFFFFFFULL)||
            (0xFFFFFFFF80000000ULL <= Value && Value <= 0xFFFFFFFFFFFFFFFFULL));
  }

  bool isMem() const { return Kind == Memory; }

  bool isAbsMem() const {
    return Kind == Memory && !getMemSegReg() && !getMemBaseReg() &&
      !getMemIndexReg() && getMemScale() == 1;
  }

  bool isNoSegMem() const {
    return Kind == Memory && !getMemSegReg();
  }

  bool isReg() const { return Kind == Register; }

  void addExpr(MCInst &Inst, const MCExpr *Expr) const {
    // Add as immediates when possible.
    if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(Expr))
      Inst.addOperand(MCOperand::CreateImm(CE->getValue()));
    else
      Inst.addOperand(MCOperand::CreateExpr(Expr));
  }

  void addRegOperands(MCInst &Inst, unsigned N) const {
    assert(N == 1 && "Invalid number of operands!");
    Inst.addOperand(MCOperand::CreateReg(getReg()));
  }

  void addImmOperands(MCInst &Inst, unsigned N) const {
    assert(N == 1 && "Invalid number of operands!");
    addExpr(Inst, getImm());
  }

  void addMemOperands(MCInst &Inst, unsigned N) const {
    assert((N == 5) && "Invalid number of operands!");
    Inst.addOperand(MCOperand::CreateReg(getMemBaseReg()));
    Inst.addOperand(MCOperand::CreateImm(getMemScale()));
    Inst.addOperand(MCOperand::CreateReg(getMemIndexReg()));
    addExpr(Inst, getMemDisp());
    Inst.addOperand(MCOperand::CreateReg(getMemSegReg()));
  }

  void addAbsMemOperands(MCInst &Inst, unsigned N) const {
    assert((N == 1) && "Invalid number of operands!");
    Inst.addOperand(MCOperand::CreateExpr(getMemDisp()));
  }

  void addNoSegMemOperands(MCInst &Inst, unsigned N) const {
    assert((N == 4) && "Invalid number of operands!");
    Inst.addOperand(MCOperand::CreateReg(getMemBaseReg()));
    Inst.addOperand(MCOperand::CreateImm(getMemScale()));
    Inst.addOperand(MCOperand::CreateReg(getMemIndexReg()));
    addExpr(Inst, getMemDisp());
  }

  static X86Operand *CreateToken(StringRef Str, SMLoc Loc) {
    X86Operand *Res = new X86Operand(Token, Loc, Loc);
    Res->Tok.Data = Str.data();
    Res->Tok.Length = Str.size();
    return Res;
  }

  static X86Operand *CreateReg(unsigned RegNo, SMLoc StartLoc, SMLoc EndLoc) {
    X86Operand *Res = new X86Operand(Register, StartLoc, EndLoc);
    Res->Reg.RegNo = RegNo;
    return Res;
  }

  static X86Operand *CreateImm(const MCExpr *Val, SMLoc StartLoc, SMLoc EndLoc){
    X86Operand *Res = new X86Operand(Immediate, StartLoc, EndLoc);
    Res->Imm.Val = Val;
    return Res;
  }

  /// Create an absolute memory operand.
  static X86Operand *CreateMem(const MCExpr *Disp, SMLoc StartLoc,
                               SMLoc EndLoc) {
    X86Operand *Res = new X86Operand(Memory, StartLoc, EndLoc);
    Res->Mem.SegReg   = 0;
    Res->Mem.Disp     = Disp;
    Res->Mem.BaseReg  = 0;
    Res->Mem.IndexReg = 0;
    Res->Mem.Scale    = 1;
    return Res;
  }

  /// Create a generalized memory operand.
  static X86Operand *CreateMem(unsigned SegReg, const MCExpr *Disp,
                               unsigned BaseReg, unsigned IndexReg,
                               unsigned Scale, SMLoc StartLoc, SMLoc EndLoc) {
    // We should never just have a displacement, that should be parsed as an
    // absolute memory operand.
    assert((SegReg || BaseReg || IndexReg) && "Invalid memory operand!");

    // The scale should always be one of {1,2,4,8}.
    assert(((Scale == 1 || Scale == 2 || Scale == 4 || Scale == 8)) &&
           "Invalid scale!");
    X86Operand *Res = new X86Operand(Memory, StartLoc, EndLoc);
    Res->Mem.SegReg   = SegReg;
    Res->Mem.Disp     = Disp;
    Res->Mem.BaseReg  = BaseReg;
    Res->Mem.IndexReg = IndexReg;
    Res->Mem.Scale    = Scale;
    return Res;
  }
};

} // end anonymous namespace.


bool X86ATTAsmParser::ParseRegister(unsigned &RegNo,
                                    SMLoc &StartLoc, SMLoc &EndLoc) {
  RegNo = 0;
  const AsmToken &TokPercent = Parser.getTok();
  assert(TokPercent.is(AsmToken::Percent) && "Invalid token kind!");
  StartLoc = TokPercent.getLoc();
  Parser.Lex(); // Eat percent token.

  const AsmToken &Tok = Parser.getTok();
  if (Tok.isNot(AsmToken::Identifier))
    return Error(Tok.getLoc(), "invalid register name");

  // FIXME: Validate register for the current architecture; we have to do
  // validation later, so maybe there is no need for this here.
  RegNo = MatchRegisterName(Tok.getString());
  
  // Parse %st(1) and "%st" as "%st(0)"
  if (RegNo == 0 && Tok.getString() == "st") {
    RegNo = X86::ST0;
    EndLoc = Tok.getLoc();
    Parser.Lex(); // Eat 'st'
    
    // Check to see if we have '(4)' after %st.
    if (getLexer().isNot(AsmToken::LParen))
      return false;
    // Lex the paren.
    getParser().Lex();

    const AsmToken &IntTok = Parser.getTok();
    if (IntTok.isNot(AsmToken::Integer))
      return Error(IntTok.getLoc(), "expected stack index");
    switch (IntTok.getIntVal()) {
    case 0: RegNo = X86::ST0; break;
    case 1: RegNo = X86::ST1; break;
    case 2: RegNo = X86::ST2; break;
    case 3: RegNo = X86::ST3; break;
    case 4: RegNo = X86::ST4; break;
    case 5: RegNo = X86::ST5; break;
    case 6: RegNo = X86::ST6; break;
    case 7: RegNo = X86::ST7; break;
    default: return Error(IntTok.getLoc(), "invalid stack index");
    }
    
    if (getParser().Lex().isNot(AsmToken::RParen))
      return Error(Parser.getTok().getLoc(), "expected ')'");
    
    EndLoc = Tok.getLoc();
    Parser.Lex(); // Eat ')'
    return false;
  }
  
  if (RegNo == 0)
    return Error(Tok.getLoc(), "invalid register name");

  EndLoc = Tok.getLoc();
  Parser.Lex(); // Eat identifier token.
  return false;
}

X86Operand *X86ATTAsmParser::ParseOperand() {
  switch (getLexer().getKind()) {
  default:
    // Parse a memory operand with no segment register.
    return ParseMemOperand(0, Parser.getTok().getLoc());
  case AsmToken::Percent: {
    // Read the register.
    unsigned RegNo;
    SMLoc Start, End;
    if (ParseRegister(RegNo, Start, End)) return 0;
    
    // If this is a segment register followed by a ':', then this is the start
    // of a memory reference, otherwise this is a normal register reference.
    if (getLexer().isNot(AsmToken::Colon))
      return X86Operand::CreateReg(RegNo, Start, End);
    
    
    getParser().Lex(); // Eat the colon.
    return ParseMemOperand(RegNo, Start);
  }
  case AsmToken::Dollar: {
    // $42 -> immediate.
    SMLoc Start = Parser.getTok().getLoc(), End;
    Parser.Lex();
    const MCExpr *Val;
    if (getParser().ParseExpression(Val, End))
      return 0;
    return X86Operand::CreateImm(Val, Start, End);
  }
  }
}

/// ParseMemOperand: segment: disp(basereg, indexreg, scale).  The '%ds:' prefix
/// has already been parsed if present.
X86Operand *X86ATTAsmParser::ParseMemOperand(unsigned SegReg, SMLoc MemStart) {
 
  // We have to disambiguate a parenthesized expression "(4+5)" from the start
  // of a memory operand with a missing displacement "(%ebx)" or "(,%eax)".  The
  // only way to do this without lookahead is to eat the '(' and see what is
  // after it.
  const MCExpr *Disp = MCConstantExpr::Create(0, getParser().getContext());
  if (getLexer().isNot(AsmToken::LParen)) {
    SMLoc ExprEnd;
    if (getParser().ParseExpression(Disp, ExprEnd)) return 0;
    
    // After parsing the base expression we could either have a parenthesized
    // memory address or not.  If not, return now.  If so, eat the (.
    if (getLexer().isNot(AsmToken::LParen)) {
      // Unless we have a segment register, treat this as an immediate.
      if (SegReg == 0)
        return X86Operand::CreateMem(Disp, MemStart, ExprEnd);
      return X86Operand::CreateMem(SegReg, Disp, 0, 0, 1, MemStart, ExprEnd);
    }
    
    // Eat the '('.
    Parser.Lex();
  } else {
    // Okay, we have a '('.  We don't know if this is an expression or not, but
    // so we have to eat the ( to see beyond it.
    SMLoc LParenLoc = Parser.getTok().getLoc();
    Parser.Lex(); // Eat the '('.
    
    if (getLexer().is(AsmToken::Percent) || getLexer().is(AsmToken::Comma)) {
      // Nothing to do here, fall into the code below with the '(' part of the
      // memory operand consumed.
    } else {
      SMLoc ExprEnd;
      
      // It must be an parenthesized expression, parse it now.
      if (getParser().ParseParenExpression(Disp, ExprEnd))
        return 0;
      
      // After parsing the base expression we could either have a parenthesized
      // memory address or not.  If not, return now.  If so, eat the (.
      if (getLexer().isNot(AsmToken::LParen)) {
        // Unless we have a segment register, treat this as an immediate.
        if (SegReg == 0)
          return X86Operand::CreateMem(Disp, LParenLoc, ExprEnd);
        return X86Operand::CreateMem(SegReg, Disp, 0, 0, 1, MemStart, ExprEnd);
      }
      
      // Eat the '('.
      Parser.Lex();
    }
  }
  
  // If we reached here, then we just ate the ( of the memory operand.  Process
  // the rest of the memory operand.
  unsigned BaseReg = 0, IndexReg = 0, Scale = 1;
  
  if (getLexer().is(AsmToken::Percent)) {
    SMLoc L;
    if (ParseRegister(BaseReg, L, L)) return 0;
  }
  
  if (getLexer().is(AsmToken::Comma)) {
    Parser.Lex(); // Eat the comma.

    // Following the comma we should have either an index register, or a scale
    // value. We don't support the later form, but we want to parse it
    // correctly.
    //
    // Not that even though it would be completely consistent to support syntax
    // like "1(%eax,,1)", the assembler doesn't.
    if (getLexer().is(AsmToken::Percent)) {
      SMLoc L;
      if (ParseRegister(IndexReg, L, L)) return 0;
    
      if (getLexer().isNot(AsmToken::RParen)) {
        // Parse the scale amount:
        //  ::= ',' [scale-expression]
        if (getLexer().isNot(AsmToken::Comma)) {
          Error(Parser.getTok().getLoc(),
                "expected comma in scale expression");
          return 0;
        }
        Parser.Lex(); // Eat the comma.

        if (getLexer().isNot(AsmToken::RParen)) {
          SMLoc Loc = Parser.getTok().getLoc();

          int64_t ScaleVal;
          if (getParser().ParseAbsoluteExpression(ScaleVal))
            return 0;
          
          // Validate the scale amount.
          if (ScaleVal != 1 && ScaleVal != 2 && ScaleVal != 4 && ScaleVal != 8){
            Error(Loc, "scale factor in address must be 1, 2, 4 or 8");
            return 0;
          }
          Scale = (unsigned)ScaleVal;
        }
      }
    } else if (getLexer().isNot(AsmToken::RParen)) {
      // Otherwise we have the unsupported form of a scale amount without an
      // index.
      SMLoc Loc = Parser.getTok().getLoc();

      int64_t Value;
      if (getParser().ParseAbsoluteExpression(Value))
        return 0;
      
      Error(Loc, "cannot have scale factor without index register");
      return 0;
    }
  }
  
  // Ok, we've eaten the memory operand, verify we have a ')' and eat it too.
  if (getLexer().isNot(AsmToken::RParen)) {
    Error(Parser.getTok().getLoc(), "unexpected token in memory operand");
    return 0;
  }
  SMLoc MemEnd = Parser.getTok().getLoc();
  Parser.Lex(); // Eat the ')'.
  
  return X86Operand::CreateMem(SegReg, Disp, BaseReg, IndexReg, Scale,
                               MemStart, MemEnd);
}

bool X86ATTAsmParser::
ParseInstruction(const StringRef &Name, SMLoc NameLoc,
                 SmallVectorImpl<MCParsedAsmOperand*> &Operands) {
  // The various flavors of pushf and popf use Requires<In32BitMode> and
  // Requires<In64BitMode>, but the assembler doesn't yet implement that.
  // For now, just do a manual check to prevent silent misencoding.
  if (Is64Bit) {
    if (Name == "popfl")
      return Error(NameLoc, "popfl cannot be encoded in 64-bit mode");
    else if (Name == "pushfl")
      return Error(NameLoc, "pushfl cannot be encoded in 64-bit mode");
  } else {
    if (Name == "popfq")
      return Error(NameLoc, "popfq cannot be encoded in 32-bit mode");
    else if (Name == "pushfq")
      return Error(NameLoc, "pushfq cannot be encoded in 32-bit mode");
  }

  // The "Jump if rCX Zero" form jcxz is not allowed in 64-bit mode and
  // the form jrcxz is not allowed in 32-bit mode.
  if (Is64Bit) {
    if (Name == "jcxz")
      return Error(NameLoc, "jcxz cannot be encoded in 64-bit mode");
  } else {
    if (Name == "jrcxz")
      return Error(NameLoc, "jrcxz cannot be encoded in 32-bit mode");
  }

  // FIXME: Hack to recognize "sal..." and "rep..." for now. We need a way to
  // represent alternative syntaxes in the .td file, without requiring
  // instruction duplication.
  StringRef PatchedName = StringSwitch<StringRef>(Name)
    .Case("sal", "shl")
    .Case("salb", "shlb")
    .Case("sall", "shll")
    .Case("salq", "shlq")
    .Case("salw", "shlw")
    .Case("repe", "rep")
    .Case("repz", "rep")
    .Case("repnz", "repne")
    .Case("pushf", Is64Bit ? "pushfq" : "pushfl")
    .Case("popf",  Is64Bit ? "popfq"  : "popfl")
    .Case("retl", Is64Bit ? "retl" : "ret")
    .Case("retq", Is64Bit ? "ret" : "retq")
    .Case("setz", "sete")
    .Case("setnz", "setne")
    .Case("jz", "je")
    .Case("jnz", "jne")
    .Case("jc", "jb")
    // FIXME: in 32-bit mode jcxz requires an AdSize prefix. In 64-bit mode
    // jecxz requires an AdSize prefix but jecxz does not have a prefix in
    // 32-bit mode.
    .Case("jecxz", "jcxz")
    .Case("jrcxz", "jcxz")
    .Case("jna", "jbe")
    .Case("jnae", "jb")
    .Case("jnb", "jae")
    .Case("jnbe", "ja")
    .Case("jnc", "jae")
    .Case("jng", "jle")
    .Case("jnge", "jl")
    .Case("jnl", "jge")
    .Case("jnle", "jg")
    .Case("jpe", "jp")
    .Case("jpo", "jnp")
    .Case("cmovcl", "cmovbl")
    .Case("cmovcl", "cmovbl")
    .Case("cmovnal", "cmovbel")
    .Case("cmovnbl", "cmovael")
    .Case("cmovnbel", "cmoval")
    .Case("cmovncl", "cmovael")
    .Case("cmovngl", "cmovlel")
    .Case("cmovnl", "cmovgel")
    .Case("cmovngl", "cmovlel")
    .Case("cmovngel", "cmovll")
    .Case("cmovnll", "cmovgel")
    .Case("cmovnlel", "cmovgl")
    .Case("cmovnzl", "cmovnel")
    .Case("cmovzl", "cmovel")
    .Case("fwait", "wait")
    .Case("movzx", "movzb")
    .Default(Name);

  // FIXME: Hack to recognize cmp<comparison code>{ss,sd,ps,pd}.
  const MCExpr *ExtraImmOp = 0;
  if ((PatchedName.startswith("cmp") || PatchedName.startswith("vcmp")) &&
      (PatchedName.endswith("ss") || PatchedName.endswith("sd") ||
       PatchedName.endswith("ps") || PatchedName.endswith("pd"))) {
    bool IsVCMP = PatchedName.startswith("vcmp");
    unsigned SSECCIdx = IsVCMP ? 4 : 3;
    unsigned SSEComparisonCode = StringSwitch<unsigned>(
      PatchedName.slice(SSECCIdx, PatchedName.size() - 2))
      .Case("eq", 0)
      .Case("lt", 1)
      .Case("le", 2)
      .Case("unord", 3)
      .Case("neq", 4)
      .Case("nlt", 5)
      .Case("nle", 6)
      .Case("ord", 7)
      .Default(~0U);
    if (SSEComparisonCode != ~0U) {
      ExtraImmOp = MCConstantExpr::Create(SSEComparisonCode,
                                          getParser().getContext());
      if (PatchedName.endswith("ss")) {
        PatchedName = IsVCMP ? "vcmpss" : "cmpss";
      } else if (PatchedName.endswith("sd")) {
        PatchedName = IsVCMP ? "vcmpsd" : "cmpsd";
      } else if (PatchedName.endswith("ps")) {
        PatchedName = IsVCMP ? "vcmpps" : "cmpps";
      } else {
        assert(PatchedName.endswith("pd") && "Unexpected mnemonic!");
        PatchedName = IsVCMP ? "vcmppd" : "cmppd";
      }
    }
  }
  Operands.push_back(X86Operand::CreateToken(PatchedName, NameLoc));

  if (ExtraImmOp)
    Operands.push_back(X86Operand::CreateImm(ExtraImmOp, NameLoc, NameLoc));

  if (getLexer().isNot(AsmToken::EndOfStatement)) {

    // Parse '*' modifier.
    if (getLexer().is(AsmToken::Star)) {
      SMLoc Loc = Parser.getTok().getLoc();
      Operands.push_back(X86Operand::CreateToken("*", Loc));
      Parser.Lex(); // Eat the star.
    }

    // Read the first operand.
    if (X86Operand *Op = ParseOperand())
      Operands.push_back(Op);
    else
      return true;

    while (getLexer().is(AsmToken::Comma)) {
      Parser.Lex();  // Eat the comma.

      // Parse and remember the operand.
      if (X86Operand *Op = ParseOperand())
        Operands.push_back(Op);
      else
        return true;
    }
  }

  // FIXME: Hack to handle recognizing s{hr,ar,hl}? $1.
  if ((Name.startswith("shr") || Name.startswith("sar") ||
       Name.startswith("shl")) &&
      Operands.size() == 3 &&
      static_cast<X86Operand*>(Operands[1])->isImm() &&
      isa<MCConstantExpr>(static_cast<X86Operand*>(Operands[1])->getImm()) &&
      cast<MCConstantExpr>(static_cast<X86Operand*>(Operands[1])->getImm())->getValue() == 1) {
    delete Operands[1];
    Operands.erase(Operands.begin() + 1);
  }

  // FIXME: Hack to handle "f{mul*,add*,sub*,div*} $op, st(0)" the same as
  // "f{mul*,add*,sub*,div*} $op"
  if ((Name.startswith("fmul") || Name.startswith("fadd") ||
       Name.startswith("fsub") || Name.startswith("fdiv")) &&
      Operands.size() == 3 &&
      static_cast<X86Operand*>(Operands[2])->isReg() &&
      static_cast<X86Operand*>(Operands[2])->getReg() == X86::ST0) {
    delete Operands[2];
    Operands.erase(Operands.begin() + 2);
  }

  return false;
}

bool X86ATTAsmParser::ParseDirective(AsmToken DirectiveID) {
  StringRef IDVal = DirectiveID.getIdentifier();
  if (IDVal == ".word")
    return ParseDirectiveWord(2, DirectiveID.getLoc());
  return true;
}

/// ParseDirectiveWord
///  ::= .word [ expression (, expression)* ]
bool X86ATTAsmParser::ParseDirectiveWord(unsigned Size, SMLoc L) {
  if (getLexer().isNot(AsmToken::EndOfStatement)) {
    for (;;) {
      const MCExpr *Value;
      if (getParser().ParseExpression(Value))
        return true;

      getParser().getStreamer().EmitValue(Value, Size, 0 /*addrspace*/);

      if (getLexer().is(AsmToken::EndOfStatement))
        break;
      
      // FIXME: Improve diagnostic.
      if (getLexer().isNot(AsmToken::Comma))
        return Error(L, "unexpected token in directive");
      Parser.Lex();
    }
  }

  Parser.Lex();
  return false;
}

/// LowerMOffset - Lower an 'moffset' form of an instruction, which just has a
/// imm operand, to having "rm" or "mr" operands with the offset in the disp
/// field.
static void LowerMOffset(MCInst &Inst, unsigned Opc, unsigned RegNo,
                         bool isMR) {
  MCOperand Disp = Inst.getOperand(0);

  // Start over with an empty instruction.
  Inst = MCInst();
  Inst.setOpcode(Opc);
  
  if (!isMR)
    Inst.addOperand(MCOperand::CreateReg(RegNo));
  
  // Add the mem operand.
  Inst.addOperand(MCOperand::CreateReg(0));  // Segment
  Inst.addOperand(MCOperand::CreateImm(1));  // Scale
  Inst.addOperand(MCOperand::CreateReg(0));  // IndexReg
  Inst.addOperand(Disp);                     // Displacement
  Inst.addOperand(MCOperand::CreateReg(0));  // BaseReg
 
  if (isMR)
    Inst.addOperand(MCOperand::CreateReg(RegNo));
}

// FIXME: Custom X86 cleanup function to implement a temporary hack to handle
// matching INCL/DECL correctly for x86_64. This needs to be replaced by a
// proper mechanism for supporting (ambiguous) feature dependent instructions.
void X86ATTAsmParser::InstructionCleanup(MCInst &Inst) {
  if (!Is64Bit) return;

  switch (Inst.getOpcode()) {
  case X86::DEC16r: Inst.setOpcode(X86::DEC64_16r); break;
  case X86::DEC16m: Inst.setOpcode(X86::DEC64_16m); break;
  case X86::DEC32r: Inst.setOpcode(X86::DEC64_32r); break;
  case X86::DEC32m: Inst.setOpcode(X86::DEC64_32m); break;
  case X86::INC16r: Inst.setOpcode(X86::INC64_16r); break;
  case X86::INC16m: Inst.setOpcode(X86::INC64_16m); break;
  case X86::INC32r: Inst.setOpcode(X86::INC64_32r); break;
  case X86::INC32m: Inst.setOpcode(X86::INC64_32m); break;
      
  // moffset instructions are x86-32 only.
  case X86::MOV8o8a:   LowerMOffset(Inst, X86::MOV8rm , X86::AL , false); break;
  case X86::MOV16o16a: LowerMOffset(Inst, X86::MOV16rm, X86::AX , false); break;
  case X86::MOV32o32a: LowerMOffset(Inst, X86::MOV32rm, X86::EAX, false); break;
  case X86::MOV8ao8:   LowerMOffset(Inst, X86::MOV8mr , X86::AL , true); break;
  case X86::MOV16ao16: LowerMOffset(Inst, X86::MOV16mr, X86::AX , true); break;
  case X86::MOV32ao32: LowerMOffset(Inst, X86::MOV32mr, X86::EAX, true); break;
  }
}

bool
X86ATTAsmParser::MatchInstruction(const SmallVectorImpl<MCParsedAsmOperand*>
                                    &Operands,
                                  MCInst &Inst) {
  // First, try a direct match.
  if (!MatchInstructionImpl(Operands, Inst))
    return false;

  // Ignore anything which is obviously not a suffix match.
  if (Operands.size() == 0)
    return true;
  X86Operand *Op = static_cast<X86Operand*>(Operands[0]);
  if (!Op->isToken() || Op->getToken().size() > 15)
    return true;

  // FIXME: Ideally, we would only attempt suffix matches for things which are
  // valid prefixes, and we could just infer the right unambiguous
  // type. However, that requires substantially more matcher support than the
  // following hack.

  // Change the operand to point to a temporary token.
  char Tmp[16];
  StringRef Base = Op->getToken();
  memcpy(Tmp, Base.data(), Base.size());
  Op->setTokenValue(StringRef(Tmp, Base.size() + 1));

  // Check for the various suffix matches.
  Tmp[Base.size()] = 'b';
  bool MatchB = MatchInstructionImpl(Operands, Inst);
  Tmp[Base.size()] = 'w';
  bool MatchW = MatchInstructionImpl(Operands, Inst);
  Tmp[Base.size()] = 'l';
  bool MatchL = MatchInstructionImpl(Operands, Inst);
  Tmp[Base.size()] = 'q';
  bool MatchQ = MatchInstructionImpl(Operands, Inst);

  // 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 (MatchB + MatchW + MatchL + MatchQ == 3)
    return false;

  // Otherwise, the match failed.
  return true;
}


extern "C" void LLVMInitializeX86AsmLexer();

// Force static initialization.
extern "C" void LLVMInitializeX86AsmParser() {
  RegisterAsmParser<X86_32ATTAsmParser> X(TheX86_32Target);
  RegisterAsmParser<X86_64ATTAsmParser> Y(TheX86_64Target);
  LLVMInitializeX86AsmLexer();
}

#include "X86GenAsmMatcher.inc"