More refactoring.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135939 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1055 insertions, 0 deletions

diff --git a/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp b/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
new file mode 100644
index 0000000000..7a56e5c5a2
--- /dev/null
+++ b/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
@@ -0,0 +1,1055 @@
+//===-- X86/X86MCCodeEmitter.cpp - Convert X86 code to machine code -------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the X86MCCodeEmitter class.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "mccodeemitter"
+#include "MCTargetDesc/X86MCTargetDesc.h"
+#include "MCTargetDesc/X86BaseInfo.h"
+#include "MCTargetDesc/X86FixupKinds.h"
+#include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCInstrInfo.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+namespace {
+class X86MCCodeEmitter : public MCCodeEmitter {
+  X86MCCodeEmitter(const X86MCCodeEmitter &); // DO NOT IMPLEMENT
+  void operator=(const X86MCCodeEmitter &); // DO NOT IMPLEMENT
+  const MCInstrInfo &MCII;
+  const MCSubtargetInfo &STI;
+  MCContext &Ctx;
+public:
+  X86MCCodeEmitter(const MCInstrInfo &mcii, const MCSubtargetInfo &sti,
+                   MCContext &ctx)
+    : MCII(mcii), STI(sti), Ctx(ctx) {
+  }
+
+  ~X86MCCodeEmitter() {}
+
+  bool is64BitMode() const {
+    // FIXME: Can tablegen auto-generate this?
+    return (STI.getFeatureBits() & X86::Mode64Bit) != 0;
+  }
+
+  static unsigned GetX86RegNum(const MCOperand &MO) {
+    return X86_MC::getX86RegNum(MO.getReg());
+  }
+
+  // On regular x86, both XMM0-XMM7 and XMM8-XMM15 are encoded in the range
+  // 0-7 and the difference between the 2 groups is given by the REX prefix.
+  // In the VEX prefix, registers are seen sequencially from 0-15 and encoded
+  // in 1's complement form, example:
+  //
+  //  ModRM field => XMM9 => 1
+  //  VEX.VVVV    => XMM9 => ~9
+  //
+  // See table 4-35 of Intel AVX Programming Reference for details.
+  static unsigned char getVEXRegisterEncoding(const MCInst &MI,
+                                              unsigned OpNum) {
+    unsigned SrcReg = MI.getOperand(OpNum).getReg();
+    unsigned SrcRegNum = GetX86RegNum(MI.getOperand(OpNum));
+    if ((SrcReg >= X86::XMM8 && SrcReg <= X86::XMM15) ||
+        (SrcReg >= X86::YMM8 && SrcReg <= X86::YMM15))
+      SrcRegNum += 8;
+
+    // The registers represented through VEX_VVVV should
+    // be encoded in 1's complement form.
+    return (~SrcRegNum) & 0xf;
+  }
+
+  void EmitByte(unsigned char C, unsigned &CurByte, raw_ostream &OS) const {
+    OS << (char)C;
+    ++CurByte;
+  }
+
+  void EmitConstant(uint64_t Val, unsigned Size, unsigned &CurByte,
+                    raw_ostream &OS) const {
+    // Output the constant in little endian byte order.
+    for (unsigned i = 0; i != Size; ++i) {
+      EmitByte(Val & 255, CurByte, OS);
+      Val >>= 8;
+    }
+  }
+
+  void EmitImmediate(const MCOperand &Disp,
+                     unsigned ImmSize, MCFixupKind FixupKind,
+                     unsigned &CurByte, raw_ostream &OS,
+                     SmallVectorImpl<MCFixup> &Fixups,
+                     int ImmOffset = 0) const;
+
+  inline static unsigned char ModRMByte(unsigned Mod, unsigned RegOpcode,
+                                        unsigned RM) {
+    assert(Mod < 4 && RegOpcode < 8 && RM < 8 && "ModRM Fields out of range!");
+    return RM | (RegOpcode << 3) | (Mod << 6);
+  }
+
+  void EmitRegModRMByte(const MCOperand &ModRMReg, unsigned RegOpcodeFld,
+                        unsigned &CurByte, raw_ostream &OS) const {
+    EmitByte(ModRMByte(3, RegOpcodeFld, GetX86RegNum(ModRMReg)), CurByte, OS);
+  }
+
+  void EmitSIBByte(unsigned SS, unsigned Index, unsigned Base,
+                   unsigned &CurByte, raw_ostream &OS) const {
+    // SIB byte is in the same format as the ModRMByte.
+    EmitByte(ModRMByte(SS, Index, Base), CurByte, OS);
+  }
+
+
+  void EmitMemModRMByte(const MCInst &MI, unsigned Op,
+                        unsigned RegOpcodeField,
+                        uint64_t TSFlags, unsigned &CurByte, raw_ostream &OS,
+                        SmallVectorImpl<MCFixup> &Fixups) const;
+
+  void EncodeInstruction(const MCInst &MI, raw_ostream &OS,
+                         SmallVectorImpl<MCFixup> &Fixups) const;
+
+  void EmitVEXOpcodePrefix(uint64_t TSFlags, unsigned &CurByte, int MemOperand,
+                           const MCInst &MI, const MCInstrDesc &Desc,
+                           raw_ostream &OS) const;
+
+  void EmitSegmentOverridePrefix(uint64_t TSFlags, unsigned &CurByte,
+                                 int MemOperand, const MCInst &MI,
+                                 raw_ostream &OS) const;
+
+  void EmitOpcodePrefix(uint64_t TSFlags, unsigned &CurByte, int MemOperand,
+                        const MCInst &MI, const MCInstrDesc &Desc,
+                        raw_ostream &OS) const;
+};
+
+} // end anonymous namespace
+
+
+MCCodeEmitter *llvm::createX86MCCodeEmitter(const MCInstrInfo &MCII,
+                                            const MCSubtargetInfo &STI,
+                                            MCContext &Ctx) {
+  return new X86MCCodeEmitter(MCII, STI, Ctx);
+}
+
+/// isDisp8 - Return true if this signed displacement fits in a 8-bit
+/// sign-extended field.
+static bool isDisp8(int Value) {
+  return Value == (signed char)Value;
+}
+
+/// getImmFixupKind - Return the appropriate fixup kind to use for an immediate
+/// in an instruction with the specified TSFlags.
+static MCFixupKind getImmFixupKind(uint64_t TSFlags) {
+  unsigned Size = X86II::getSizeOfImm(TSFlags);
+  bool isPCRel = X86II::isImmPCRel(TSFlags);
+
+  return MCFixup::getKindForSize(Size, isPCRel);
+}
+
+namespace llvm {
+  // FIXME: TableGen this?
+  extern MCRegisterClass X86MCRegisterClasses[]; // In X86GenRegisterInfo.inc.
+}
+
+/// Is32BitMemOperand - Return true if the specified instruction with a memory
+/// operand should emit the 0x67 prefix byte in 64-bit mode due to a 32-bit
+/// memory operand.  Op specifies the operand # of the memoperand.
+static bool Is32BitMemOperand(const MCInst &MI, unsigned Op) {
+  const MCOperand &BaseReg  = MI.getOperand(Op+X86::AddrBaseReg);
+  const MCOperand &IndexReg = MI.getOperand(Op+X86::AddrIndexReg);
+  
+  if ((BaseReg.getReg() != 0 &&
+       X86MCRegisterClasses[X86::GR32RegClassID].contains(BaseReg.getReg())) ||
+      (IndexReg.getReg() != 0 &&
+       X86MCRegisterClasses[X86::GR32RegClassID].contains(IndexReg.getReg())))
+    return true;
+  return false;
+}
+
+/// StartsWithGlobalOffsetTable - Return true for the simple cases where this
+/// expression starts with _GLOBAL_OFFSET_TABLE_. This is a needed to support
+/// PIC on ELF i386 as that symbol is magic. We check only simple case that
+/// are know to be used: _GLOBAL_OFFSET_TABLE_ by itself or at the start
+/// of a binary expression.
+static bool StartsWithGlobalOffsetTable(const MCExpr *Expr) {
+  if (Expr->getKind() == MCExpr::Binary) {
+    const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(Expr);
+    Expr = BE->getLHS();
+  }
+
+  if (Expr->getKind() != MCExpr::SymbolRef)
+    return false;
+
+  const MCSymbolRefExpr *Ref = static_cast<const MCSymbolRefExpr*>(Expr);
+  const MCSymbol &S = Ref->getSymbol();
+  return S.getName() == "_GLOBAL_OFFSET_TABLE_";
+}
+
+void X86MCCodeEmitter::
+EmitImmediate(const MCOperand &DispOp, unsigned Size, MCFixupKind FixupKind,
+              unsigned &CurByte, raw_ostream &OS,
+              SmallVectorImpl<MCFixup> &Fixups, int ImmOffset) const {
+  const MCExpr *Expr = NULL;
+  if (DispOp.isImm()) {
+    // If this is a simple integer displacement that doesn't require a relocation,
+    // emit it now.
+    if (FixupKind != FK_PCRel_1 &&
+	FixupKind != FK_PCRel_2 &&
+	FixupKind != FK_PCRel_4) {
+      EmitConstant(DispOp.getImm()+ImmOffset, Size, CurByte, OS);
+      return;
+    }
+    Expr = MCConstantExpr::Create(DispOp.getImm(), Ctx);
+  } else {
+    Expr = DispOp.getExpr();
+  }
+
+  // If we have an immoffset, add it to the expression.
+  if ((FixupKind == FK_Data_4 ||
+       FixupKind == MCFixupKind(X86::reloc_signed_4byte)) &&
+      StartsWithGlobalOffsetTable(Expr)) {
+    assert(ImmOffset == 0);
+
+    FixupKind = MCFixupKind(X86::reloc_global_offset_table);
+    ImmOffset = CurByte;
+  }
+
+  // If the fixup is pc-relative, we need to bias the value to be relative to
+  // the start of the field, not the end of the field.
+  if (FixupKind == FK_PCRel_4 ||
+      FixupKind == MCFixupKind(X86::reloc_riprel_4byte) ||
+      FixupKind == MCFixupKind(X86::reloc_riprel_4byte_movq_load))
+    ImmOffset -= 4;
+  if (FixupKind == FK_PCRel_2)
+    ImmOffset -= 2;
+  if (FixupKind == FK_PCRel_1)
+    ImmOffset -= 1;
+
+  if (ImmOffset)
+    Expr = MCBinaryExpr::CreateAdd(Expr, MCConstantExpr::Create(ImmOffset, Ctx),
+                                   Ctx);
+
+  // Emit a symbolic constant as a fixup and 4 zeros.
+  Fixups.push_back(MCFixup::Create(CurByte, Expr, FixupKind));
+  EmitConstant(0, Size, CurByte, OS);
+}
+
+void X86MCCodeEmitter::EmitMemModRMByte(const MCInst &MI, unsigned Op,
+                                        unsigned RegOpcodeField,
+                                        uint64_t TSFlags, unsigned &CurByte,
+                                        raw_ostream &OS,
+                                        SmallVectorImpl<MCFixup> &Fixups) const{
+  const MCOperand &Disp     = MI.getOperand(Op+X86::AddrDisp);
+  const MCOperand &Base     = MI.getOperand(Op+X86::AddrBaseReg);
+  const MCOperand &Scale    = MI.getOperand(Op+X86::AddrScaleAmt);
+  const MCOperand &IndexReg = MI.getOperand(Op+X86::AddrIndexReg);
+  unsigned BaseReg = Base.getReg();
+
+  // Handle %rip relative addressing.
+  if (BaseReg == X86::RIP) {    // [disp32+RIP] in X86-64 mode
+    assert(is64BitMode() && "Rip-relative addressing requires 64-bit mode");
+    assert(IndexReg.getReg() == 0 && "Invalid rip-relative address");
+    EmitByte(ModRMByte(0, RegOpcodeField, 5), CurByte, OS);
+
+    unsigned FixupKind = X86::reloc_riprel_4byte;
+
+    // movq loads are handled with a special relocation form which allows the
+    // linker to eliminate some loads for GOT references which end up in the
+    // same linkage unit.
+    if (MI.getOpcode() == X86::MOV64rm)
+      FixupKind = X86::reloc_riprel_4byte_movq_load;
+
+    // rip-relative addressing is actually relative to the *next* instruction.
+    // Since an immediate can follow the mod/rm byte for an instruction, this
+    // means that we need to bias the immediate field of the instruction with
+    // the size of the immediate field.  If we have this case, add it into the
+    // expression to emit.
+    int ImmSize = X86II::hasImm(TSFlags) ? X86II::getSizeOfImm(TSFlags) : 0;
+
+    EmitImmediate(Disp, 4, MCFixupKind(FixupKind),
+                  CurByte, OS, Fixups, -ImmSize);
+    return;
+  }
+
+  unsigned BaseRegNo = BaseReg ? GetX86RegNum(Base) : -1U;
+
+  // Determine whether a SIB byte is needed.
+  // If no BaseReg, issue a RIP relative instruction only if the MCE can
+  // resolve addresses on-the-fly, otherwise use SIB (Intel Manual 2A, table
+  // 2-7) and absolute references.
+
+  if (// The SIB byte must be used if there is an index register.
+      IndexReg.getReg() == 0 &&
+      // The SIB byte must be used if the base is ESP/RSP/R12, all of which
+      // encode to an R/M value of 4, which indicates that a SIB byte is
+      // present.
+      BaseRegNo != N86::ESP &&
+      // If there is no base register and we're in 64-bit mode, we need a SIB
+      // byte to emit an addr that is just 'disp32' (the non-RIP relative form).
+      (!is64BitMode() || BaseReg != 0)) {
+
+    if (BaseReg == 0) {          // [disp32]     in X86-32 mode
+      EmitByte(ModRMByte(0, RegOpcodeField, 5), CurByte, OS);
+      EmitImmediate(Disp, 4, FK_Data_4, CurByte, OS, Fixups);
+      return;
+    }
+
+    // If the base is not EBP/ESP and there is no displacement, use simple
+    // indirect register encoding, this handles addresses like [EAX].  The
+    // encoding for [EBP] with no displacement means [disp32] so we handle it
+    // by emitting a displacement of 0 below.
+    if (Disp.isImm() && Disp.getImm() == 0 && BaseRegNo != N86::EBP) {
+      EmitByte(ModRMByte(0, RegOpcodeField, BaseRegNo), CurByte, OS);
+      return;
+    }
+
+    // Otherwise, if the displacement fits in a byte, encode as [REG+disp8].
+    if (Disp.isImm() && isDisp8(Disp.getImm())) {
+      EmitByte(ModRMByte(1, RegOpcodeField, BaseRegNo), CurByte, OS);
+      EmitImmediate(Disp, 1, FK_Data_1, CurByte, OS, Fixups);
+      return;
+    }
+
+    // Otherwise, emit the most general non-SIB encoding: [REG+disp32]
+    EmitByte(ModRMByte(2, RegOpcodeField, BaseRegNo), CurByte, OS);
+    EmitImmediate(Disp, 4, MCFixupKind(X86::reloc_signed_4byte), CurByte, OS,
+                  Fixups);
+    return;
+  }
+
+  // We need a SIB byte, so start by outputting the ModR/M byte first
+  assert(IndexReg.getReg() != X86::ESP &&
+         IndexReg.getReg() != X86::RSP && "Cannot use ESP as index reg!");
+
+  bool ForceDisp32 = false;
+  bool ForceDisp8  = false;
+  if (BaseReg == 0) {
+    // If there is no base register, we emit the special case SIB byte with
+    // MOD=0, BASE=5, to JUST get the index, scale, and displacement.
+    EmitByte(ModRMByte(0, RegOpcodeField, 4), CurByte, OS);
+    ForceDisp32 = true;
+  } else if (!Disp.isImm()) {
+    // Emit the normal disp32 encoding.
+    EmitByte(ModRMByte(2, RegOpcodeField, 4), CurByte, OS);
+    ForceDisp32 = true;
+  } else if (Disp.getImm() == 0 &&
+             // Base reg can't be anything that ends up with '5' as the base
+             // reg, it is the magic [*] nomenclature that indicates no base.
+             BaseRegNo != N86::EBP) {
+    // Emit no displacement ModR/M byte
+    EmitByte(ModRMByte(0, RegOpcodeField, 4), CurByte, OS);
+  } else if (isDisp8(Disp.getImm())) {
+    // Emit the disp8 encoding.
+    EmitByte(ModRMByte(1, RegOpcodeField, 4), CurByte, OS);
+    ForceDisp8 = true;           // Make sure to force 8 bit disp if Base=EBP
+  } else {
+    // Emit the normal disp32 encoding.
+    EmitByte(ModRMByte(2, RegOpcodeField, 4), CurByte, OS);
+  }
+
+  // Calculate what the SS field value should be...
+  static const unsigned SSTable[] = { ~0, 0, 1, ~0, 2, ~0, ~0, ~0, 3 };
+  unsigned SS = SSTable[Scale.getImm()];
+
+  if (BaseReg == 0) {
+    // Handle the SIB byte for the case where there is no base, see Intel
+    // Manual 2A, table 2-7. The displacement has already been output.
+    unsigned IndexRegNo;
+    if (IndexReg.getReg())
+      IndexRegNo = GetX86RegNum(IndexReg);
+    else // Examples: [ESP+1*<noreg>+4] or [scaled idx]+disp32 (MOD=0,BASE=5)
+      IndexRegNo = 4;
+    EmitSIBByte(SS, IndexRegNo, 5, CurByte, OS);
+  } else {
+    unsigned IndexRegNo;
+    if (IndexReg.getReg())
+      IndexRegNo = GetX86RegNum(IndexReg);
+    else
+      IndexRegNo = 4;   // For example [ESP+1*<noreg>+4]
+    EmitSIBByte(SS, IndexRegNo, GetX86RegNum(Base), CurByte, OS);
+  }
+
+  // Do we need to output a displacement?
+  if (ForceDisp8)
+    EmitImmediate(Disp, 1, FK_Data_1, CurByte, OS, Fixups);
+  else if (ForceDisp32 || Disp.getImm() != 0)
+    EmitImmediate(Disp, 4, MCFixupKind(X86::reloc_signed_4byte), CurByte, OS,
+                  Fixups);
+}
+
+/// EmitVEXOpcodePrefix - AVX instructions are encoded using a opcode prefix
+/// called VEX.
+void X86MCCodeEmitter::EmitVEXOpcodePrefix(uint64_t TSFlags, unsigned &CurByte,
+                                           int MemOperand, const MCInst &MI,
+                                           const MCInstrDesc &Desc,
+                                           raw_ostream &OS) const {
+  bool HasVEX_4V = false;
+  if ((TSFlags >> X86II::VEXShift) & X86II::VEX_4V)
+    HasVEX_4V = true;
+
+  // VEX_R: opcode externsion equivalent to REX.R in
+  // 1's complement (inverted) form
+  //
+  //  1: Same as REX_R=0 (must be 1 in 32-bit mode)
+  //  0: Same as REX_R=1 (64 bit mode only)
+  //
+  unsigned char VEX_R = 0x1;
+
+  // VEX_X: equivalent to REX.X, only used when a
+  // register is used for index in SIB Byte.
+  //
+  //  1: Same as REX.X=0 (must be 1 in 32-bit mode)
+  //  0: Same as REX.X=1 (64-bit mode only)
+  unsigned char VEX_X = 0x1;
+
+  // VEX_B:
+  //
+  //  1: Same as REX_B=0 (ignored in 32-bit mode)
+  //  0: Same as REX_B=1 (64 bit mode only)
+  //
+  unsigned char VEX_B = 0x1;
+
+  // VEX_W: opcode specific (use like REX.W, or used for
+  // opcode extension, or ignored, depending on the opcode byte)
+  unsigned char VEX_W = 0;
+
+  // VEX_5M (VEX m-mmmmm field):
+  //
+  //  0b00000: Reserved for future use
+  //  0b00001: implied 0F leading opcode
+  //  0b00010: implied 0F 38 leading opcode bytes
+  //  0b00011: implied 0F 3A leading opcode bytes
+  //  0b00100-0b11111: Reserved for future use
+  //
+  unsigned char VEX_5M = 0x1;
+
+  // VEX_4V (VEX vvvv field): a register specifier
+  // (in 1's complement form) or 1111 if unused.
+  unsigned char VEX_4V = 0xf;
+
+  // VEX_L (Vector Length):
+  //
+  //  0: scalar or 128-bit vector
+  //  1: 256-bit vector
+  //
+  unsigned char VEX_L = 0;
+
+  // VEX_PP: opcode extension providing equivalent
+  // functionality of a SIMD prefix
+  //
+  //  0b00: None
+  //  0b01: 66
+  //  0b10: F3
+  //  0b11: F2
+  //
+  unsigned char VEX_PP = 0;
+
+  // Encode the operand size opcode prefix as needed.
+  if (TSFlags & X86II::OpSize)
+    VEX_PP = 0x01;
+
+  if ((TSFlags >> X86II::VEXShift) & X86II::VEX_W)
+    VEX_W = 1;
+
+  if ((TSFlags >> X86II::VEXShift) & X86II::VEX_L)
+    VEX_L = 1;
+
+  switch (TSFlags & X86II::Op0Mask) {
+  default: assert(0 && "Invalid prefix!");
+  case X86II::T8:  // 0F 38
+    VEX_5M = 0x2;
+    break;
+  case X86II::TA:  // 0F 3A
+    VEX_5M = 0x3;
+    break;
+  case X86II::TF:  // F2 0F 38
+    VEX_PP = 0x3;
+    VEX_5M = 0x2;
+    break;
+  case X86II::XS:  // F3 0F
+    VEX_PP = 0x2;
+    break;
+  case X86II::XD:  // F2 0F
+    VEX_PP = 0x3;
+    break;
+  case X86II::A6:  // Bypass: Not used by VEX
+  case X86II::A7:  // Bypass: Not used by VEX
+  case X86II::TB:  // Bypass: Not used by VEX
+  case 0:
+    break;  // No prefix!
+  }
+
+  // Set the vector length to 256-bit if YMM0-YMM15 is used
+  for (unsigned i = 0; i != MI.getNumOperands(); ++i) {
+    if (!MI.getOperand(i).isReg())
+      continue;
+    unsigned SrcReg = MI.getOperand(i).getReg();
+    if (SrcReg >= X86::YMM0 && SrcReg <= X86::YMM15)
+      VEX_L = 1;
+  }
+
+  unsigned NumOps = MI.getNumOperands();
+  unsigned CurOp = 0;
+  bool IsDestMem = false;
+
+  switch (TSFlags & X86II::FormMask) {
+  case X86II::MRMInitReg: assert(0 && "FIXME: Remove this!");
+  case X86II::MRMDestMem:
+    IsDestMem = true;
+    // The important info for the VEX prefix is never beyond the address
+    // registers. Don't check beyond that.
+    NumOps = CurOp = X86::AddrNumOperands;
+  case X86II::MRM0m: case X86II::MRM1m:
+  case X86II::MRM2m: case X86II::MRM3m:
+  case X86II::MRM4m: case X86II::MRM5m:
+  case X86II::MRM6m: case X86II::MRM7m:
+  case X86II::MRMSrcMem:
+  case X86II::MRMSrcReg:
+    if (MI.getNumOperands() > CurOp && MI.getOperand(CurOp).isReg() &&
+        X86II::isX86_64ExtendedReg(MI.getOperand(CurOp).getReg()))
+      VEX_R = 0x0;
+    CurOp++;
+
+    if (HasVEX_4V) {
+      VEX_4V = getVEXRegisterEncoding(MI, IsDestMem ? CurOp-1 : CurOp);
+      CurOp++;
+    }
+
+    // To only check operands before the memory address ones, start
+    // the search from the beginning
+    if (IsDestMem)
+      CurOp = 0;
+
+    // If the last register should be encoded in the immediate field
+    // do not use any bit from VEX prefix to this register, ignore it
+    if ((TSFlags >> X86II::VEXShift) & X86II::VEX_I8IMM)
+      NumOps--;
+
+    for (; CurOp != NumOps; ++CurOp) {
+      const MCOperand &MO = MI.getOperand(CurOp);
+      if (MO.isReg() && X86II::isX86_64ExtendedReg(MO.getReg()))
+        VEX_B = 0x0;
+      if (!VEX_B && MO.isReg() &&
+          ((TSFlags & X86II::FormMask) == X86II::MRMSrcMem) &&
+          X86II::isX86_64ExtendedReg(MO.getReg()))
+        VEX_X = 0x0;
+    }
+    break;
+  default: // MRMDestReg, MRM0r-MRM7r, RawFrm
+    if (!MI.getNumOperands())
+      break;
+
+    if (MI.getOperand(CurOp).isReg() &&
+        X86II::isX86_64ExtendedReg(MI.getOperand(CurOp).getReg()))
+      VEX_B = 0;
+
+    if (HasVEX_4V)
+      VEX_4V = getVEXRegisterEncoding(MI, CurOp);
+
+    CurOp++;
+    for (; CurOp != NumOps; ++CurOp) {
+      const MCOperand &MO = MI.getOperand(CurOp);
+      if (MO.isReg() && !HasVEX_4V &&
+          X86II::isX86_64ExtendedReg(MO.getReg()))
+        VEX_R = 0x0;
+    }
+    break;
+  }
+
+  // Emit segment override opcode prefix as needed.
+  EmitSegmentOverridePrefix(TSFlags, CurByte, MemOperand, MI, OS);
+
+  // VEX opcode prefix can have 2 or 3 bytes
+  //
+  //  3 bytes:
+  //    +-----+ +--------------+ +-------------------+
+  //    | C4h | | RXB | m-mmmm | | W | vvvv | L | pp |
+  //    +-----+ +--------------+ +-------------------+
+  //  2 bytes:
+  //    +-----+ +-------------------+
+  //    | C5h | | R | vvvv | L | pp |
+  //    +-----+ +-------------------+
+  //
+  unsigned char LastByte = VEX_PP | (VEX_L << 2) | (VEX_4V << 3);
+
+  if (VEX_B && VEX_X && !VEX_W && (VEX_5M == 1)) { // 2 byte VEX prefix
+    EmitByte(0xC5, CurByte, OS);
+    EmitByte(LastByte | (VEX_R << 7), CurByte, OS);
+    return;
+  }
+
+  // 3 byte VEX prefix
+  EmitByte(0xC4, CurByte, OS);
+  EmitByte(VEX_R << 7 | VEX_X << 6 | VEX_B << 5 | VEX_5M, CurByte, OS);
+  EmitByte(LastByte | (VEX_W << 7), CurByte, OS);
+}
+
+/// DetermineREXPrefix - Determine if the MCInst has to be encoded with a X86-64
+/// REX prefix which specifies 1) 64-bit instructions, 2) non-default operand
+/// size, and 3) use of X86-64 extended registers.
+static unsigned DetermineREXPrefix(const MCInst &MI, uint64_t TSFlags,
+                                   const MCInstrDesc &Desc) {
+  unsigned REX = 0;
+  if (TSFlags & X86II::REX_W)
+    REX |= 1 << 3; // set REX.W
+
+  if (MI.getNumOperands() == 0) return REX;
+
+  unsigned NumOps = MI.getNumOperands();
+  // FIXME: MCInst should explicitize the two-addrness.
+  bool isTwoAddr = NumOps > 1 &&
+                      Desc.getOperandConstraint(1, MCOI::TIED_TO) != -1;
+
+  // If it accesses SPL, BPL, SIL, or DIL, then it requires a 0x40 REX prefix.
+  unsigned i = isTwoAddr ? 1 : 0;
+  for (; i != NumOps; ++i) {
+    const MCOperand &MO = MI.getOperand(i);
+    if (!MO.isReg()) continue;
+    unsigned Reg = MO.getReg();
+    if (!X86II::isX86_64NonExtLowByteReg(Reg)) continue;
+    // FIXME: The caller of DetermineREXPrefix slaps this prefix onto anything
+    // that returns non-zero.
+    REX |= 0x40; // REX fixed encoding prefix
+    break;
+  }
+
+  switch (TSFlags & X86II::FormMask) {
+  case X86II::MRMInitReg: assert(0 && "FIXME: Remove this!");
+  case X86II::MRMSrcReg:
+    if (MI.getOperand(0).isReg() &&
+        X86II::isX86_64ExtendedReg(MI.getOperand(0).getReg()))
+      REX |= 1 << 2; // set REX.R
+    i = isTwoAddr ? 2 : 1;
+    for (; i != NumOps; ++i) {
+      const MCOperand &MO = MI.getOperand(i);
+      if (MO.isReg() && X86II::isX86_64ExtendedReg(MO.getReg()))
+        REX |= 1 << 0; // set REX.B
+    }
+    break;
+  case X86II::MRMSrcMem: {
+    if (MI.getOperand(0).isReg() &&
+        X86II::isX86_64ExtendedReg(MI.getOperand(0).getReg()))
+      REX |= 1 << 2; // set REX.R
+    unsigned Bit = 0;
+    i = isTwoAddr ? 2 : 1;
+    for (; i != NumOps; ++i) {
+      const MCOperand &MO = MI.getOperand(i);
+      if (MO.isReg()) {
+        if (X86II::isX86_64ExtendedReg(MO.getReg()))
+          REX |= 1 << Bit; // set REX.B (Bit=0) and REX.X (Bit=1)
+        Bit++;
+      }
+    }
+    break;
+  }
+  case X86II::MRM0m: case X86II::MRM1m:
+  case X86II::MRM2m: case X86II::MRM3m:
+  case X86II::MRM4m: case X86II::MRM5m:
+  case X86II::MRM6m: case X86II::MRM7m:
+  case X86II::MRMDestMem: {
+    unsigned e = (isTwoAddr ? X86::AddrNumOperands+1 : X86::AddrNumOperands);
+    i = isTwoAddr ? 1 : 0;
+    if (NumOps > e && MI.getOperand(e).isReg() &&
+        X86II::isX86_64ExtendedReg(MI.getOperand(e).getReg()))
+      REX |= 1 << 2; // set REX.R
+    unsigned Bit = 0;
+    for (; i != e; ++i) {
+      const MCOperand &MO = MI.getOperand(i);
+      if (MO.isReg()) {
+        if (X86II::isX86_64ExtendedReg(MO.getReg()))
+          REX |= 1 << Bit; // REX.B (Bit=0) and REX.X (Bit=1)
+        Bit++;
+      }
+    }
+    break;
+  }
+  default:
+    if (MI.getOperand(0).isReg() &&
+        X86II::isX86_64ExtendedReg(MI.getOperand(0).getReg()))
+      REX |= 1 << 0; // set REX.B
+    i = isTwoAddr ? 2 : 1;
+    for (unsigned e = NumOps; i != e; ++i) {
+      const MCOperand &MO = MI.getOperand(i);
+      if (MO.isReg() && X86II::isX86_64ExtendedReg(MO.getReg()))
+        REX |= 1 << 2; // set REX.R
+    }
+    break;
+  }
+  return REX;
+}
+
+/// EmitSegmentOverridePrefix - Emit segment override opcode prefix as needed
+void X86MCCodeEmitter::EmitSegmentOverridePrefix(uint64_t TSFlags,
+                                        unsigned &CurByte, int MemOperand,
+                                        const MCInst &MI,
+                                        raw_ostream &OS) const {
+  switch (TSFlags & X86II::SegOvrMask) {
+  default: assert(0 && "Invalid segment!");
+  case 0:
+    // No segment override, check for explicit one on memory operand.
+    if (MemOperand != -1) {   // If the instruction has a memory operand.
+      switch (MI.getOperand(MemOperand+X86::AddrSegmentReg).getReg()) {
+      default: assert(0 && "Unknown segment register!");
+      case 0: break;
+      case X86::CS: EmitByte(0x2E, CurByte, OS); break;
+      case X86::SS: EmitByte(0x36, CurByte, OS); break;
+      case X86::DS: EmitByte(0x3E, CurByte, OS); break;
+      case X86::ES: EmitByte(0x26, CurByte, OS); break;
+      case X86::FS: EmitByte(0x64, CurByte, OS); break;
+      case X86::GS: EmitByte(0x65, CurByte, OS); break;
+      }
+    }
+    break;
+  case X86II::FS:
+    EmitByte(0x64, CurByte, OS);
+    break;
+  case X86II::GS:
+    EmitByte(0x65, CurByte, OS);
+    break;
+  }
+}
+
+/// EmitOpcodePrefix - Emit all instruction prefixes prior to the opcode.
+///
+/// MemOperand is the operand # of the start of a memory operand if present.  If
+/// Not present, it is -1.
+void X86MCCodeEmitter::EmitOpcodePrefix(uint64_t TSFlags, unsigned &CurByte,
+                                        int MemOperand, const MCInst &MI,
+                                        const MCInstrDesc &Desc,
+                                        raw_ostream &OS) const {
+
+  // Emit the lock opcode prefix as needed.
+  if (TSFlags & X86II::LOCK)
+    EmitByte(0xF0, CurByte, OS);
+
+  // Emit segment override opcode prefix as needed.
+  EmitSegmentOverridePrefix(TSFlags, CurByte, MemOperand, MI, OS);
+
+  // Emit the repeat opcode prefix as needed.
+  if ((TSFlags & X86II::Op0Mask) == X86II::REP)
+    EmitByte(0xF3, CurByte, OS);
+
+  // Emit the address size opcode prefix as needed.
+  if ((TSFlags & X86II::AdSize) ||
+      (MemOperand != -1 && is64BitMode() && Is32BitMemOperand(MI, MemOperand)))
+    EmitByte(0x67, CurByte, OS);
+  
+  // Emit the operand size opcode prefix as needed.
+  if (TSFlags & X86II::OpSize)
+    EmitByte(0x66, CurByte, OS);
+
+  bool Need0FPrefix = false;
+  switch (TSFlags & X86II::Op0Mask) {
+  default: assert(0 && "Invalid prefix!");
+  case 0: break;  // No prefix!
+  case X86II::REP: break; // already handled.
+  case X86II::TB:  // Two-byte opcode prefix
+  case X86II::T8:  // 0F 38
+  case X86II::TA:  // 0F 3A
+  case X86II::A6:  // 0F A6
+  case X86II::A7:  // 0F A7
+    Need0FPrefix = true;
+    break;
+  case X86II::TF: // F2 0F 38
+    EmitByte(0xF2, CurByte, OS);
+    Need0FPrefix = true;
+    break;
+  case X86II::XS:   // F3 0F
+    EmitByte(0xF3, CurByte, OS);
+    Need0FPrefix = true;
+    break;
+  case X86II::XD:   // F2 0F
+    EmitByte(0xF2, CurByte, OS);
+    Need0FPrefix = true;
+    break;
+  case X86II::D8: EmitByte(0xD8, CurByte, OS); break;
+  case X86II::D9: EmitByte(0xD9, CurByte, OS); break;
+  case X86II::DA: EmitByte(0xDA, CurByte, OS); break;
+  case X86II::DB: EmitByte(0xDB, CurByte, OS); break;
+  case X86II::DC: EmitByte(0xDC, CurByte, OS); break;
+  case X86II::DD: EmitByte(0xDD, CurByte, OS); break;
+  case X86II::DE: EmitByte(0xDE, CurByte, OS); break;
+  case X86II::DF: EmitByte(0xDF, CurByte, OS); break;
+  }
+
+  // Handle REX prefix.
+  // FIXME: Can this come before F2 etc to simplify emission?
+  if (is64BitMode()) {
+    if (unsigned REX = DetermineREXPrefix(MI, TSFlags, Desc))
+      EmitByte(0x40 | REX, CurByte, OS);
+  }
+
+  // 0x0F escape code must be emitted just before the opcode.
+  if (Need0FPrefix)
+    EmitByte(0x0F, CurByte, OS);
+
+  // FIXME: Pull this up into previous switch if REX can be moved earlier.
+  switch (TSFlags & X86II::Op0Mask) {
+  case X86II::TF:    // F2 0F 38
+  case X86II::T8:    // 0F 38
+    EmitByte(0x38, CurByte, OS);
+    break;
+  case X86II::TA:    // 0F 3A
+    EmitByte(0x3A, CurByte, OS);
+    break;
+  case X86II::A6:    // 0F A6
+    EmitByte(0xA6, CurByte, OS);
+    break;
+  case X86II::A7:    // 0F A7
+    EmitByte(0xA7, CurByte, OS);
+    break;
+  }
+}
+
+void X86MCCodeEmitter::
+EncodeInstruction(const MCInst &MI, raw_ostream &OS,
+                  SmallVectorImpl<MCFixup> &Fixups) const {
+  unsigned Opcode = MI.getOpcode();
+  const MCInstrDesc &Desc = MCII.get(Opcode);
+  uint64_t TSFlags = Desc.TSFlags;
+
+  // Pseudo instructions don't get encoded.
+  if ((TSFlags & X86II::FormMask) == X86II::Pseudo)
+    return;
+
+  // If this is a two-address instruction, skip one of the register operands.
+  // FIXME: This should be handled during MCInst lowering.
+  unsigned NumOps = Desc.getNumOperands();
+  unsigned CurOp = 0;
+  if (NumOps > 1 && Desc.getOperandConstraint(1, MCOI::TIED_TO) != -1)
+    ++CurOp;
+  else if (NumOps > 2 && Desc.getOperandConstraint(NumOps-1, MCOI::TIED_TO)== 0)
+    // Skip the last source operand that is tied_to the dest reg. e.g. LXADD32
+    --NumOps;
+
+  // Keep track of the current byte being emitted.
+  unsigned CurByte = 0;
+
+  // Is this instruction encoded using the AVX VEX prefix?
+  bool HasVEXPrefix = false;
+
+  // It uses the VEX.VVVV field?
+  bool HasVEX_4V = false;
+
+  if ((TSFlags >> X86II::VEXShift) & X86II::VEX)
+    HasVEXPrefix = true;
+  if ((TSFlags >> X86II::VEXShift) & X86II::VEX_4V)
+    HasVEX_4V = true;
+
+  
+  // Determine where the memory operand starts, if present.
+  int MemoryOperand = X86II::getMemoryOperandNo(TSFlags);
+  if (MemoryOperand != -1) MemoryOperand += CurOp;
+
+  if (!HasVEXPrefix)
+    EmitOpcodePrefix(TSFlags, CurByte, MemoryOperand, MI, Desc, OS);
+  else
+    EmitVEXOpcodePrefix(TSFlags, CurByte, MemoryOperand, MI, Desc, OS);
+
+  
+  unsigned char BaseOpcode = X86II::getBaseOpcodeFor(TSFlags);
+  
+  if ((TSFlags >> X86II::VEXShift) & X86II::Has3DNow0F0FOpcode)
+    BaseOpcode = 0x0F;   // Weird 3DNow! encoding.
+  
+  unsigned SrcRegNum = 0;
+  switch (TSFlags & X86II::FormMask) {
+  case X86II::MRMInitReg:
+    assert(0 && "FIXME: Remove this form when the JIT moves to MCCodeEmitter!");
+  default: errs() << "FORM: " << (TSFlags & X86II::FormMask) << "\n";
+    assert(0 && "Unknown FormMask value in X86MCCodeEmitter!");
+  case X86II::Pseudo:
+    assert(0 && "Pseudo instruction shouldn't be emitted");
+  case X86II::RawFrm:
+    EmitByte(BaseOpcode, CurByte, OS);
+    break;
+      
+  case X86II::RawFrmImm8:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitImmediate(MI.getOperand(CurOp++),
+                  X86II::getSizeOfImm(TSFlags), getImmFixupKind(TSFlags),
+                  CurByte, OS, Fixups);
+    EmitImmediate(MI.getOperand(CurOp++), 1, FK_Data_1, CurByte, OS, Fixups);
+    break;
+  case X86II::RawFrmImm16:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitImmediate(MI.getOperand(CurOp++),
+                  X86II::getSizeOfImm(TSFlags), getImmFixupKind(TSFlags),
+                  CurByte, OS, Fixups);
+    EmitImmediate(MI.getOperand(CurOp++), 2, FK_Data_2, CurByte, OS, Fixups);
+    break;
+
+  case X86II::AddRegFrm:
+    EmitByte(BaseOpcode + GetX86RegNum(MI.getOperand(CurOp++)), CurByte, OS);
+    break;
+
+  case X86II::MRMDestReg:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitRegModRMByte(MI.getOperand(CurOp),
+                     GetX86RegNum(MI.getOperand(CurOp+1)), CurByte, OS);
+    CurOp += 2;
+    break;
+
+  case X86II::MRMDestMem:
+    EmitByte(BaseOpcode, CurByte, OS);
+    SrcRegNum = CurOp + X86::AddrNumOperands;
+
+    if (HasVEX_4V) // Skip 1st src (which is encoded in VEX_VVVV)
+      SrcRegNum++;
+
+    EmitMemModRMByte(MI, CurOp,
+                     GetX86RegNum(MI.getOperand(SrcRegNum)),
+                     TSFlags, CurByte, OS, Fixups);
+    CurOp = SrcRegNum + 1;
+    break;
+
+  case X86II::MRMSrcReg:
+    EmitByte(BaseOpcode, CurByte, OS);
+    SrcRegNum = CurOp + 1;
+
+    if (HasVEX_4V) // Skip 1st src (which is encoded in VEX_VVVV)
+      SrcRegNum++;
+
+    EmitRegModRMByte(MI.getOperand(SrcRegNum),
+                     GetX86RegNum(MI.getOperand(CurOp)), CurByte, OS);
+    CurOp = SrcRegNum + 1;
+    break;
+
+  case X86II::MRMSrcMem: {
+    int AddrOperands = X86::AddrNumOperands;
+    unsigned FirstMemOp = CurOp+1;
+    if (HasVEX_4V) {
+      ++AddrOperands;
+      ++FirstMemOp;  // Skip the register source (which is encoded in VEX_VVVV).
+    }
+
+    EmitByte(BaseOpcode, CurByte, OS);
+
+    EmitMemModRMByte(MI, FirstMemOp, GetX86RegNum(MI.getOperand(CurOp)),
+                     TSFlags, CurByte, OS, Fixups);
+    CurOp += AddrOperands + 1;
+    break;
+  }
+
+  case X86II::MRM0r: case X86II::MRM1r:
+  case X86II::MRM2r: case X86II::MRM3r:
+  case X86II::MRM4r: case X86II::MRM5r:
+  case X86II::MRM6r: case X86II::MRM7r:
+    if (HasVEX_4V) // Skip the register dst (which is encoded in VEX_VVVV).
+      CurOp++;
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitRegModRMByte(MI.getOperand(CurOp++),
+                     (TSFlags & X86II::FormMask)-X86II::MRM0r,
+                     CurByte, OS);
+    break;
+  case X86II::MRM0m: case X86II::MRM1m:
+  case X86II::MRM2m: case X86II::MRM3m:
+  case X86II::MRM4m: case X86II::MRM5m:
+  case X86II::MRM6m: case X86II::MRM7m:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitMemModRMByte(MI, CurOp, (TSFlags & X86II::FormMask)-X86II::MRM0m,
+                     TSFlags, CurByte, OS, Fixups);
+    CurOp += X86::AddrNumOperands;
+    break;
+  case X86II::MRM_C1:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitByte(0xC1, CurByte, OS);
+    break;
+  case X86II::MRM_C2:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitByte(0xC2, CurByte, OS);
+    break;
+  case X86II::MRM_C3:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitByte(0xC3, CurByte, OS);
+    break;
+  case X86II::MRM_C4:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitByte(0xC4, CurByte, OS);
+    break;
+  case X86II::MRM_C8:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitByte(0xC8, CurByte, OS);
+    break;
+  case X86II::MRM_C9:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitByte(0xC9, CurByte, OS);
+    break;
+  case X86II::MRM_E8:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitByte(0xE8, CurByte, OS);
+    break;
+  case X86II::MRM_F0:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitByte(0xF0, CurByte, OS);
+    break;
+  case X86II::MRM_F8:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitByte(0xF8, CurByte, OS);
+    break;
+  case X86II::MRM_F9:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitByte(0xF9, CurByte, OS);
+    break;
+  case X86II::MRM_D0:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitByte(0xD0, CurByte, OS);
+    break;
+  case X86II::MRM_D1:
+    EmitByte(BaseOpcode, CurByte, OS);
+    EmitByte(0xD1, CurByte, OS);
+    break;
+  }
+
+  // If there is a remaining operand, it must be a trailing immediate.  Emit it
+  // according to the right size for the instruction.
+  if (CurOp != NumOps) {
+    // The last source register of a 4 operand instruction in AVX is encoded
+    // in bits[7:4] of a immediate byte, and bits[3:0] are ignored.
+    if ((TSFlags >> X86II::VEXShift) & X86II::VEX_I8IMM) {
+      const MCOperand &MO = MI.getOperand(CurOp++);
+      bool IsExtReg =
+        X86II::isX86_64ExtendedReg(MO.getReg());
+      unsigned RegNum = (IsExtReg ? (1 << 7) : 0);
+      RegNum |= GetX86RegNum(MO) << 4;
+      EmitImmediate(MCOperand::CreateImm(RegNum), 1, FK_Data_1, CurByte, OS,
+                    Fixups);
+    } else {
+      unsigned FixupKind;
+      // FIXME: Is there a better way to know that we need a signed relocation?
+      if (MI.getOpcode() == X86::ADD64ri32 ||
+          MI.getOpcode() == X86::MOV64ri32 ||
+          MI.getOpcode() == X86::MOV64mi32 ||
+          MI.getOpcode() == X86::PUSH64i32)
+        FixupKind = X86::reloc_signed_4byte;
+      else
+        FixupKind = getImmFixupKind(TSFlags);
+      EmitImmediate(MI.getOperand(CurOp++),
+                    X86II::getSizeOfImm(TSFlags), MCFixupKind(FixupKind),
+                    CurByte, OS, Fixups);
+    }
+  }
+
+  if ((TSFlags >> X86II::VEXShift) & X86II::Has3DNow0F0FOpcode)
+    EmitByte(X86II::getBaseOpcodeFor(TSFlags), CurByte, OS);
+  
+
+#ifndef NDEBUG
+  // FIXME: Verify.
+  if (/*!Desc.isVariadic() &&*/ CurOp != NumOps) {
+    errs() << "Cannot encode all operands of: ";
+    MI.dump();
+    errs() << '\n';
+    abort();
+  }
+#endif
+}