fix a layering problem by moving the x86 implementation

of AsmPrinter and InstLowering into libx86 and out of the
asmprinter subdirectory.  Now X86/AsmPrinter just depends on
MC stuff, not all of codegen and LLVM IR.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108782 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 632 insertions, 0 deletions

diff --git a/lib/Target/X86/X86MCInstLower.cpp b/lib/Target/X86/X86MCInstLower.cpp
new file mode 100644
index 0000000..e67fc06
--- /dev/null
+++ b/lib/Target/X86/X86MCInstLower.cpp
@@ -0,0 +1,632 @@
+//===-- X86MCInstLower.cpp - Convert X86 MachineInstr to an MCInst --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains code to lower X86 MachineInstrs to their corresponding
+// MCInst records.
+//
+//===----------------------------------------------------------------------===//
+
+#include "X86MCInstLower.h"
+#include "X86AsmPrinter.h"
+#include "X86COFFMachineModuleInfo.h"
+#include "X86MCAsmInfo.h"
+#include "llvm/Analysis/DebugInfo.h"
+#include "llvm/CodeGen/MachineModuleInfoImpls.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/Target/Mangler.h"
+#include "llvm/Support/FormattedStream.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/Type.h"
+using namespace llvm;
+
+
+const X86Subtarget &X86MCInstLower::getSubtarget() const {
+  return AsmPrinter.getSubtarget();
+}
+
+MachineModuleInfoMachO &X86MCInstLower::getMachOMMI() const {
+  assert(getSubtarget().isTargetDarwin() &&"Can only get MachO info on darwin");
+  return AsmPrinter.MMI->getObjFileInfo<MachineModuleInfoMachO>(); 
+}
+
+
+MCSymbol *X86MCInstLower::GetPICBaseSymbol() const {
+  const TargetLowering *TLI = AsmPrinter.TM.getTargetLowering();
+  return static_cast<const X86TargetLowering*>(TLI)->
+    getPICBaseSymbol(AsmPrinter.MF, Ctx);
+}
+
+/// GetSymbolFromOperand - Lower an MO_GlobalAddress or MO_ExternalSymbol
+/// operand to an MCSymbol.
+MCSymbol *X86MCInstLower::
+GetSymbolFromOperand(const MachineOperand &MO) const {
+  assert((MO.isGlobal() || MO.isSymbol()) && "Isn't a symbol reference");
+
+  SmallString<128> Name;
+  
+  if (!MO.isGlobal()) {
+    assert(MO.isSymbol());
+    Name += AsmPrinter.MAI->getGlobalPrefix();
+    Name += MO.getSymbolName();
+  } else {    
+    const GlobalValue *GV = MO.getGlobal();
+    bool isImplicitlyPrivate = false;
+    if (MO.getTargetFlags() == X86II::MO_DARWIN_STUB ||
+        MO.getTargetFlags() == X86II::MO_DARWIN_NONLAZY ||
+        MO.getTargetFlags() == X86II::MO_DARWIN_NONLAZY_PIC_BASE ||
+        MO.getTargetFlags() == X86II::MO_DARWIN_HIDDEN_NONLAZY_PIC_BASE)
+      isImplicitlyPrivate = true;
+    
+    Mang->getNameWithPrefix(Name, GV, isImplicitlyPrivate);
+  }
+
+  // If the target flags on the operand changes the name of the symbol, do that
+  // before we return the symbol.
+  switch (MO.getTargetFlags()) {
+  default: break;
+  case X86II::MO_DLLIMPORT: {
+    // Handle dllimport linkage.
+    const char *Prefix = "__imp_";
+    Name.insert(Name.begin(), Prefix, Prefix+strlen(Prefix));
+    break;
+  }
+  case X86II::MO_DARWIN_NONLAZY:
+  case X86II::MO_DARWIN_NONLAZY_PIC_BASE: {
+    Name += "$non_lazy_ptr";
+    MCSymbol *Sym = Ctx.GetOrCreateSymbol(Name.str());
+
+    MachineModuleInfoImpl::StubValueTy &StubSym =
+      getMachOMMI().getGVStubEntry(Sym);
+    if (StubSym.getPointer() == 0) {
+      assert(MO.isGlobal() && "Extern symbol not handled yet");
+      StubSym =
+        MachineModuleInfoImpl::
+        StubValueTy(AsmPrinter.Mang->getSymbol(MO.getGlobal()),
+                    !MO.getGlobal()->hasInternalLinkage());
+    }
+    return Sym;
+  }
+  case X86II::MO_DARWIN_HIDDEN_NONLAZY_PIC_BASE: {
+    Name += "$non_lazy_ptr";
+    MCSymbol *Sym = Ctx.GetOrCreateSymbol(Name.str());
+    MachineModuleInfoImpl::StubValueTy &StubSym =
+      getMachOMMI().getHiddenGVStubEntry(Sym);
+    if (StubSym.getPointer() == 0) {
+      assert(MO.isGlobal() && "Extern symbol not handled yet");
+      StubSym =
+        MachineModuleInfoImpl::
+        StubValueTy(AsmPrinter.Mang->getSymbol(MO.getGlobal()),
+                    !MO.getGlobal()->hasInternalLinkage());
+    }
+    return Sym;
+  }
+  case X86II::MO_DARWIN_STUB: {
+    Name += "$stub";
+    MCSymbol *Sym = Ctx.GetOrCreateSymbol(Name.str());
+    MachineModuleInfoImpl::StubValueTy &StubSym =
+      getMachOMMI().getFnStubEntry(Sym);
+    if (StubSym.getPointer())
+      return Sym;
+    
+    if (MO.isGlobal()) {
+      StubSym =
+        MachineModuleInfoImpl::
+        StubValueTy(AsmPrinter.Mang->getSymbol(MO.getGlobal()),
+                    !MO.getGlobal()->hasInternalLinkage());
+    } else {
+      Name.erase(Name.end()-5, Name.end());
+      StubSym =
+        MachineModuleInfoImpl::
+        StubValueTy(Ctx.GetOrCreateSymbol(Name.str()), false);
+    }
+    return Sym;
+  }
+  }
+
+  return Ctx.GetOrCreateSymbol(Name.str());
+}
+
+MCOperand X86MCInstLower::LowerSymbolOperand(const MachineOperand &MO,
+                                             MCSymbol *Sym) const {
+  // FIXME: We would like an efficient form for this, so we don't have to do a
+  // lot of extra uniquing.
+  const MCExpr *Expr = 0;
+  MCSymbolRefExpr::VariantKind RefKind = MCSymbolRefExpr::VK_None;
+  
+  switch (MO.getTargetFlags()) {
+  default: llvm_unreachable("Unknown target flag on GV operand");
+  case X86II::MO_NO_FLAG:    // No flag.
+  // These affect the name of the symbol, not any suffix.
+  case X86II::MO_DARWIN_NONLAZY:
+  case X86II::MO_DLLIMPORT:
+  case X86II::MO_DARWIN_STUB:
+    break;
+      
+  case X86II::MO_TLVP:      RefKind = MCSymbolRefExpr::VK_TLVP; break;
+  case X86II::MO_TLVP_PIC_BASE:
+    Expr = MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_TLVP, Ctx);
+    // Subtract the pic base.
+    Expr = MCBinaryExpr::CreateSub(Expr,
+                                   MCSymbolRefExpr::Create(GetPICBaseSymbol(),
+                                                           Ctx),
+                                   Ctx);
+    break;
+  case X86II::MO_TLSGD:     RefKind = MCSymbolRefExpr::VK_TLSGD; break;
+  case X86II::MO_GOTTPOFF:  RefKind = MCSymbolRefExpr::VK_GOTTPOFF; break;
+  case X86II::MO_INDNTPOFF: RefKind = MCSymbolRefExpr::VK_INDNTPOFF; break;
+  case X86II::MO_TPOFF:     RefKind = MCSymbolRefExpr::VK_TPOFF; break;
+  case X86II::MO_NTPOFF:    RefKind = MCSymbolRefExpr::VK_NTPOFF; break;
+  case X86II::MO_GOTPCREL:  RefKind = MCSymbolRefExpr::VK_GOTPCREL; break;
+  case X86II::MO_GOT:       RefKind = MCSymbolRefExpr::VK_GOT; break;
+  case X86II::MO_GOTOFF:    RefKind = MCSymbolRefExpr::VK_GOTOFF; break;
+  case X86II::MO_PLT:       RefKind = MCSymbolRefExpr::VK_PLT; break;
+  case X86II::MO_PIC_BASE_OFFSET:
+  case X86II::MO_DARWIN_NONLAZY_PIC_BASE:
+  case X86II::MO_DARWIN_HIDDEN_NONLAZY_PIC_BASE:
+    Expr = MCSymbolRefExpr::Create(Sym, Ctx);
+    // Subtract the pic base.
+    Expr = MCBinaryExpr::CreateSub(Expr, 
+                               MCSymbolRefExpr::Create(GetPICBaseSymbol(), Ctx),
+                                   Ctx);
+    if (MO.isJTI() && AsmPrinter.MAI->hasSetDirective()) {
+      // If .set directive is supported, use it to reduce the number of
+      // relocations the assembler will generate for differences between
+      // local labels. This is only safe when the symbols are in the same
+      // section so we are restricting it to jumptable references.
+      MCSymbol *Label = Ctx.CreateTempSymbol();
+      AsmPrinter.OutStreamer.EmitAssignment(Label, Expr);
+      Expr = MCSymbolRefExpr::Create(Label, Ctx);
+    }
+    break;
+  }
+  
+  if (Expr == 0)
+    Expr = MCSymbolRefExpr::Create(Sym, RefKind, Ctx);
+  
+  if (!MO.isJTI() && MO.getOffset())
+    Expr = MCBinaryExpr::CreateAdd(Expr,
+                                   MCConstantExpr::Create(MO.getOffset(), Ctx),
+                                   Ctx);
+  return MCOperand::CreateExpr(Expr);
+}
+
+
+
+static void lower_subreg32(MCInst *MI, unsigned OpNo) {
+  // Convert registers in the addr mode according to subreg32.
+  unsigned Reg = MI->getOperand(OpNo).getReg();
+  if (Reg != 0)
+    MI->getOperand(OpNo).setReg(getX86SubSuperRegister(Reg, MVT::i32));
+}
+
+static void lower_lea64_32mem(MCInst *MI, unsigned OpNo) {
+  // Convert registers in the addr mode according to subreg64.
+  for (unsigned i = 0; i != 4; ++i) {
+    if (!MI->getOperand(OpNo+i).isReg()) continue;
+    
+    unsigned Reg = MI->getOperand(OpNo+i).getReg();
+    if (Reg == 0) continue;
+    
+    MI->getOperand(OpNo+i).setReg(getX86SubSuperRegister(Reg, MVT::i64));
+  }
+}
+
+/// LowerSubReg32_Op0 - Things like MOVZX16rr8 -> MOVZX32rr8.
+static void LowerSubReg32_Op0(MCInst &OutMI, unsigned NewOpc) {
+  OutMI.setOpcode(NewOpc);
+  lower_subreg32(&OutMI, 0);
+}
+/// LowerUnaryToTwoAddr - R = setb   -> R = sbb R, R
+static void LowerUnaryToTwoAddr(MCInst &OutMI, unsigned NewOpc) {
+  OutMI.setOpcode(NewOpc);
+  OutMI.addOperand(OutMI.getOperand(0));
+  OutMI.addOperand(OutMI.getOperand(0));
+}
+
+/// \brief Simplify FOO $imm, %{al,ax,eax,rax} to FOO $imm, for instruction with
+/// a short fixed-register form.
+static void SimplifyShortImmForm(MCInst &Inst, unsigned Opcode) {
+  unsigned ImmOp = Inst.getNumOperands() - 1;
+  assert(Inst.getOperand(0).isReg() && Inst.getOperand(ImmOp).isImm() &&
+         ((Inst.getNumOperands() == 3 && Inst.getOperand(1).isReg() &&
+           Inst.getOperand(0).getReg() == Inst.getOperand(1).getReg()) ||
+          Inst.getNumOperands() == 2) && "Unexpected instruction!");
+
+  // Check whether the destination register can be fixed.
+  unsigned Reg = Inst.getOperand(0).getReg();
+  if (Reg != X86::AL && Reg != X86::AX && Reg != X86::EAX && Reg != X86::RAX)
+    return;
+
+  // If so, rewrite the instruction.
+  MCOperand Saved = Inst.getOperand(ImmOp);
+  Inst = MCInst();
+  Inst.setOpcode(Opcode);
+  Inst.addOperand(Saved);
+}
+
+/// \brief Simplify things like MOV32rm to MOV32o32a.
+static void SimplifyShortMoveForm(MCInst &Inst, unsigned Opcode) {
+  bool IsStore = Inst.getOperand(0).isReg() && Inst.getOperand(1).isReg();
+  unsigned AddrBase = IsStore;
+  unsigned RegOp = IsStore ? 0 : 5;
+  unsigned AddrOp = AddrBase + 3;
+  assert(Inst.getNumOperands() == 6 && Inst.getOperand(RegOp).isReg() &&
+         Inst.getOperand(AddrBase + 0).isReg() && // base
+         Inst.getOperand(AddrBase + 1).isImm() && // scale
+         Inst.getOperand(AddrBase + 2).isReg() && // index register
+         (Inst.getOperand(AddrOp).isExpr() ||     // address
+          Inst.getOperand(AddrOp).isImm())&&
+         Inst.getOperand(AddrBase + 4).isReg() && // segment
+         "Unexpected instruction!");
+
+  // Check whether the destination register can be fixed.
+  unsigned Reg = Inst.getOperand(RegOp).getReg();
+  if (Reg != X86::AL && Reg != X86::AX && Reg != X86::EAX && Reg != X86::RAX)
+    return;
+
+  // Check whether this is an absolute address.
+  // FIXME: We know TLVP symbol refs aren't, but there should be a better way 
+  // to do this here.
+  bool Absolute = true;
+  if (Inst.getOperand(AddrOp).isExpr()) {
+    const MCExpr *MCE = Inst.getOperand(AddrOp).getExpr();
+    if (const MCSymbolRefExpr *SRE = dyn_cast<MCSymbolRefExpr>(MCE))
+      if (SRE->getKind() == MCSymbolRefExpr::VK_TLVP)
+        Absolute = false;
+  }
+  
+  if (Absolute &&
+      (Inst.getOperand(AddrBase + 0).getReg() != 0 ||
+       Inst.getOperand(AddrBase + 2).getReg() != 0 ||
+       Inst.getOperand(AddrBase + 4).getReg() != 0 ||
+       Inst.getOperand(AddrBase + 1).getImm() != 1))
+    return;
+
+  // If so, rewrite the instruction.
+  MCOperand Saved = Inst.getOperand(AddrOp);
+  Inst = MCInst();
+  Inst.setOpcode(Opcode);
+  Inst.addOperand(Saved);
+}
+
+void X86MCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
+  OutMI.setOpcode(MI->getOpcode());
+  
+  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+    const MachineOperand &MO = MI->getOperand(i);
+    
+    MCOperand MCOp;
+    switch (MO.getType()) {
+    default:
+      MI->dump();
+      llvm_unreachable("unknown operand type");
+    case MachineOperand::MO_Register:
+      // Ignore all implicit register operands.
+      if (MO.isImplicit()) continue;
+      MCOp = MCOperand::CreateReg(MO.getReg());
+      break;
+    case MachineOperand::MO_Immediate:
+      MCOp = MCOperand::CreateImm(MO.getImm());
+      break;
+    case MachineOperand::MO_MachineBasicBlock:
+      MCOp = MCOperand::CreateExpr(MCSymbolRefExpr::Create(
+                       MO.getMBB()->getSymbol(), Ctx));
+      break;
+    case MachineOperand::MO_GlobalAddress:
+      MCOp = LowerSymbolOperand(MO, GetSymbolFromOperand(MO));
+      break;
+    case MachineOperand::MO_ExternalSymbol:
+      MCOp = LowerSymbolOperand(MO, GetSymbolFromOperand(MO));
+      break;
+    case MachineOperand::MO_JumpTableIndex:
+      MCOp = LowerSymbolOperand(MO, AsmPrinter.GetJTISymbol(MO.getIndex()));
+      break;
+    case MachineOperand::MO_ConstantPoolIndex:
+      MCOp = LowerSymbolOperand(MO, AsmPrinter.GetCPISymbol(MO.getIndex()));
+      break;
+    case MachineOperand::MO_BlockAddress:
+      MCOp = LowerSymbolOperand(MO,
+                        AsmPrinter.GetBlockAddressSymbol(MO.getBlockAddress()));
+      break;
+    }
+    
+    OutMI.addOperand(MCOp);
+  }
+  
+  // Handle a few special cases to eliminate operand modifiers.
+  switch (OutMI.getOpcode()) {
+  case X86::LEA64_32r: // Handle 'subreg rewriting' for the lea64_32mem operand.
+    lower_lea64_32mem(&OutMI, 1);
+    // FALL THROUGH.
+  case X86::LEA64r:
+  case X86::LEA16r:
+  case X86::LEA32r:
+    // LEA should have a segment register, but it must be empty.
+    assert(OutMI.getNumOperands() == 1+X86::AddrNumOperands &&
+           "Unexpected # of LEA operands");
+    assert(OutMI.getOperand(1+X86::AddrSegmentReg).getReg() == 0 &&
+           "LEA has segment specified!");
+    break;
+  case X86::MOVZX16rr8:   LowerSubReg32_Op0(OutMI, X86::MOVZX32rr8); break;
+  case X86::MOVZX16rm8:   LowerSubReg32_Op0(OutMI, X86::MOVZX32rm8); break;
+  case X86::MOVSX16rr8:   LowerSubReg32_Op0(OutMI, X86::MOVSX32rr8); break;
+  case X86::MOVSX16rm8:   LowerSubReg32_Op0(OutMI, X86::MOVSX32rm8); break;
+  case X86::MOVZX64rr32:  LowerSubReg32_Op0(OutMI, X86::MOV32rr); break;
+  case X86::MOVZX64rm32:  LowerSubReg32_Op0(OutMI, X86::MOV32rm); break;
+  case X86::MOV64ri64i32: LowerSubReg32_Op0(OutMI, X86::MOV32ri); break;
+  case X86::MOVZX64rr8:   LowerSubReg32_Op0(OutMI, X86::MOVZX32rr8); break;
+  case X86::MOVZX64rm8:   LowerSubReg32_Op0(OutMI, X86::MOVZX32rm8); break;
+  case X86::MOVZX64rr16:  LowerSubReg32_Op0(OutMI, X86::MOVZX32rr16); break;
+  case X86::MOVZX64rm16:  LowerSubReg32_Op0(OutMI, X86::MOVZX32rm16); break;
+  case X86::SETB_C8r:     LowerUnaryToTwoAddr(OutMI, X86::SBB8rr); break;
+  case X86::SETB_C16r:    LowerUnaryToTwoAddr(OutMI, X86::SBB16rr); break;
+  case X86::SETB_C32r:    LowerUnaryToTwoAddr(OutMI, X86::SBB32rr); break;
+  case X86::SETB_C64r:    LowerUnaryToTwoAddr(OutMI, X86::SBB64rr); break;
+  case X86::MOV8r0:       LowerUnaryToTwoAddr(OutMI, X86::XOR8rr); break;
+  case X86::MOV32r0:      LowerUnaryToTwoAddr(OutMI, X86::XOR32rr); break;
+  case X86::MMX_V_SET0:   LowerUnaryToTwoAddr(OutMI, X86::MMX_PXORrr); break;
+  case X86::MMX_V_SETALLONES:
+    LowerUnaryToTwoAddr(OutMI, X86::MMX_PCMPEQDrr); break;
+  case X86::FsFLD0SS:     LowerUnaryToTwoAddr(OutMI, X86::PXORrr); break;
+  case X86::FsFLD0SD:     LowerUnaryToTwoAddr(OutMI, X86::PXORrr); break;
+  case X86::V_SET0PS:     LowerUnaryToTwoAddr(OutMI, X86::XORPSrr); break;
+  case X86::V_SET0PD:     LowerUnaryToTwoAddr(OutMI, X86::XORPDrr); break;
+  case X86::V_SET0PI:     LowerUnaryToTwoAddr(OutMI, X86::PXORrr); break;
+  case X86::V_SETALLONES: LowerUnaryToTwoAddr(OutMI, X86::PCMPEQDrr); break;
+
+  case X86::MOV16r0:
+    LowerSubReg32_Op0(OutMI, X86::MOV32r0);   // MOV16r0 -> MOV32r0
+    LowerUnaryToTwoAddr(OutMI, X86::XOR32rr); // MOV32r0 -> XOR32rr
+    break;
+  case X86::MOV64r0:
+    LowerSubReg32_Op0(OutMI, X86::MOV32r0);   // MOV64r0 -> MOV32r0
+    LowerUnaryToTwoAddr(OutMI, X86::XOR32rr); // MOV32r0 -> XOR32rr
+    break;
+
+  // TAILJMPr64, CALL64r, CALL64pcrel32 - These instructions have
+  // register inputs modeled as normal uses instead of implicit uses.  As such,
+  // truncate off all but the first operand (the callee).  FIXME: Change isel.
+  case X86::TAILJMPr64:
+  case X86::CALL64r:
+  case X86::CALL64pcrel32: {
+    unsigned Opcode = OutMI.getOpcode();
+    MCOperand Saved = OutMI.getOperand(0);
+    OutMI = MCInst();
+    OutMI.setOpcode(Opcode);
+    OutMI.addOperand(Saved);
+    break;
+  }
+
+  // TAILJMPd, TAILJMPd64 - Lower to the correct jump instructions.
+  case X86::TAILJMPr:
+  case X86::TAILJMPd:
+  case X86::TAILJMPd64: {
+    unsigned Opcode;
+    switch (OutMI.getOpcode()) {
+    default: assert(0 && "Invalid opcode");
+    case X86::TAILJMPr: Opcode = X86::JMP32r; break;
+    case X86::TAILJMPd:
+    case X86::TAILJMPd64: Opcode = X86::JMP_1; break;
+    }
+    
+    MCOperand Saved = OutMI.getOperand(0);
+    OutMI = MCInst();
+    OutMI.setOpcode(Opcode);
+    OutMI.addOperand(Saved);
+    break;
+  }
+
+  // The assembler backend wants to see branches in their small form and relax
+  // them to their large form.  The JIT can only handle the large form because
+  // it does not do relaxation.  For now, translate the large form to the
+  // small one here.
+  case X86::JMP_4: OutMI.setOpcode(X86::JMP_1); break;
+  case X86::JO_4:  OutMI.setOpcode(X86::JO_1); break;
+  case X86::JNO_4: OutMI.setOpcode(X86::JNO_1); break;
+  case X86::JB_4:  OutMI.setOpcode(X86::JB_1); break;
+  case X86::JAE_4: OutMI.setOpcode(X86::JAE_1); break;
+  case X86::JE_4:  OutMI.setOpcode(X86::JE_1); break;
+  case X86::JNE_4: OutMI.setOpcode(X86::JNE_1); break;
+  case X86::JBE_4: OutMI.setOpcode(X86::JBE_1); break;
+  case X86::JA_4:  OutMI.setOpcode(X86::JA_1); break;
+  case X86::JS_4:  OutMI.setOpcode(X86::JS_1); break;
+  case X86::JNS_4: OutMI.setOpcode(X86::JNS_1); break;
+  case X86::JP_4:  OutMI.setOpcode(X86::JP_1); break;
+  case X86::JNP_4: OutMI.setOpcode(X86::JNP_1); break;
+  case X86::JL_4:  OutMI.setOpcode(X86::JL_1); break;
+  case X86::JGE_4: OutMI.setOpcode(X86::JGE_1); break;
+  case X86::JLE_4: OutMI.setOpcode(X86::JLE_1); break;
+  case X86::JG_4:  OutMI.setOpcode(X86::JG_1); break;
+
+  // We don't currently select the correct instruction form for instructions
+  // which have a short %eax, etc. form. Handle this by custom lowering, for
+  // now.
+  //
+  // Note, we are currently not handling the following instructions:
+  // MOV64ao8, MOV64o8a
+  // XCHG16ar, XCHG32ar, XCHG64ar
+  case X86::MOV8mr_NOREX:
+  case X86::MOV8mr:     SimplifyShortMoveForm(OutMI, X86::MOV8ao8); break;
+  case X86::MOV8rm_NOREX:
+  case X86::MOV8rm:     SimplifyShortMoveForm(OutMI, X86::MOV8o8a); break;
+  case X86::MOV16mr:    SimplifyShortMoveForm(OutMI, X86::MOV16ao16); break;
+  case X86::MOV16rm:    SimplifyShortMoveForm(OutMI, X86::MOV16o16a); break;
+  case X86::MOV32mr:    SimplifyShortMoveForm(OutMI, X86::MOV32ao32); break;
+  case X86::MOV32rm:    SimplifyShortMoveForm(OutMI, X86::MOV32o32a); break;
+  case X86::MOV64mr:    SimplifyShortMoveForm(OutMI, X86::MOV64ao64); break;
+  case X86::MOV64rm:    SimplifyShortMoveForm(OutMI, X86::MOV64o64a); break;
+
+  case X86::ADC8ri:     SimplifyShortImmForm(OutMI, X86::ADC8i8);    break;
+  case X86::ADC16ri:    SimplifyShortImmForm(OutMI, X86::ADC16i16);  break;
+  case X86::ADC32ri:    SimplifyShortImmForm(OutMI, X86::ADC32i32);  break;
+  case X86::ADC64ri32:  SimplifyShortImmForm(OutMI, X86::ADC64i32);  break;
+  case X86::ADD8ri:     SimplifyShortImmForm(OutMI, X86::ADD8i8);    break;
+  case X86::ADD16ri:    SimplifyShortImmForm(OutMI, X86::ADD16i16);  break;
+  case X86::ADD32ri:    SimplifyShortImmForm(OutMI, X86::ADD32i32);  break;
+  case X86::ADD64ri32:  SimplifyShortImmForm(OutMI, X86::ADD64i32);  break;
+  case X86::AND8ri:     SimplifyShortImmForm(OutMI, X86::AND8i8);    break;
+  case X86::AND16ri:    SimplifyShortImmForm(OutMI, X86::AND16i16);  break;
+  case X86::AND32ri:    SimplifyShortImmForm(OutMI, X86::AND32i32);  break;
+  case X86::AND64ri32:  SimplifyShortImmForm(OutMI, X86::AND64i32);  break;
+  case X86::CMP8ri:     SimplifyShortImmForm(OutMI, X86::CMP8i8);    break;
+  case X86::CMP16ri:    SimplifyShortImmForm(OutMI, X86::CMP16i16);  break;
+  case X86::CMP32ri:    SimplifyShortImmForm(OutMI, X86::CMP32i32);  break;
+  case X86::CMP64ri32:  SimplifyShortImmForm(OutMI, X86::CMP64i32);  break;
+  case X86::OR8ri:      SimplifyShortImmForm(OutMI, X86::OR8i8);     break;
+  case X86::OR16ri:     SimplifyShortImmForm(OutMI, X86::OR16i16);   break;
+  case X86::OR32ri:     SimplifyShortImmForm(OutMI, X86::OR32i32);   break;
+  case X86::OR64ri32:   SimplifyShortImmForm(OutMI, X86::OR64i32);   break;
+  case X86::SBB8ri:     SimplifyShortImmForm(OutMI, X86::SBB8i8);    break;
+  case X86::SBB16ri:    SimplifyShortImmForm(OutMI, X86::SBB16i16);  break;
+  case X86::SBB32ri:    SimplifyShortImmForm(OutMI, X86::SBB32i32);  break;
+  case X86::SBB64ri32:  SimplifyShortImmForm(OutMI, X86::SBB64i32);  break;
+  case X86::SUB8ri:     SimplifyShortImmForm(OutMI, X86::SUB8i8);    break;
+  case X86::SUB16ri:    SimplifyShortImmForm(OutMI, X86::SUB16i16);  break;
+  case X86::SUB32ri:    SimplifyShortImmForm(OutMI, X86::SUB32i32);  break;
+  case X86::SUB64ri32:  SimplifyShortImmForm(OutMI, X86::SUB64i32);  break;
+  case X86::TEST8ri:    SimplifyShortImmForm(OutMI, X86::TEST8i8);   break;
+  case X86::TEST16ri:   SimplifyShortImmForm(OutMI, X86::TEST16i16); break;
+  case X86::TEST32ri:   SimplifyShortImmForm(OutMI, X86::TEST32i32); break;
+  case X86::TEST64ri32: SimplifyShortImmForm(OutMI, X86::TEST64i32); break;
+  case X86::XOR8ri:     SimplifyShortImmForm(OutMI, X86::XOR8i8);    break;
+  case X86::XOR16ri:    SimplifyShortImmForm(OutMI, X86::XOR16i16);  break;
+  case X86::XOR32ri:    SimplifyShortImmForm(OutMI, X86::XOR32i32);  break;
+  case X86::XOR64ri32:  SimplifyShortImmForm(OutMI, X86::XOR64i32);  break;
+  }
+}
+
+void X86AsmPrinter::PrintDebugValueComment(const MachineInstr *MI,
+                                           raw_ostream &O) {
+  // Only the target-dependent form of DBG_VALUE should get here.
+  // Referencing the offset and metadata as NOps-2 and NOps-1 is
+  // probably portable to other targets; frame pointer location is not.
+  unsigned NOps = MI->getNumOperands();
+  assert(NOps==7);
+  O << '\t' << MAI->getCommentString() << "DEBUG_VALUE: ";
+  // cast away const; DIetc do not take const operands for some reason.
+  DIVariable V(const_cast<MDNode *>(MI->getOperand(NOps-1).getMetadata()));
+  if (V.getContext().isSubprogram())
+    O << DISubprogram(V.getContext()).getDisplayName() << ":";
+  O << V.getName();
+  O << " <- ";
+  // Frame address.  Currently handles register +- offset only.
+  O << '['; 
+  if (MI->getOperand(0).isReg() && MI->getOperand(0).getReg())
+    printOperand(MI, 0, O); 
+  else
+    O << "undef";
+  O << '+'; printOperand(MI, 3, O);
+  O << ']';
+  O << "+";
+  printOperand(MI, NOps-2, O);
+}
+
+MachineLocation 
+X86AsmPrinter::getDebugValueLocation(const MachineInstr *MI) const {
+  MachineLocation Location;
+  assert (MI->getNumOperands() == 7 && "Invalid no. of machine operands!");
+  // Frame address.  Currently handles register +- offset only.
+
+  if (MI->getOperand(0).isReg() && MI->getOperand(3).isImm())
+    Location.set(MI->getOperand(0).getReg(), MI->getOperand(3).getImm());
+  return Location;
+}
+
+
+void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
+  X86MCInstLower MCInstLowering(OutContext, Mang, *this);
+  switch (MI->getOpcode()) {
+  case TargetOpcode::DBG_VALUE:
+    if (isVerbose() && OutStreamer.hasRawTextSupport()) {
+      std::string TmpStr;
+      raw_string_ostream OS(TmpStr);
+      PrintDebugValueComment(MI, OS);
+      OutStreamer.EmitRawText(StringRef(OS.str()));
+    }
+    return;
+
+  case X86::TAILJMPr:
+  case X86::TAILJMPd:
+  case X86::TAILJMPd64:
+    // Lower these as normal, but add some comments.
+    OutStreamer.AddComment("TAILCALL");
+    break;
+      
+  case X86::MOVPC32r: {
+    MCInst TmpInst;
+    // This is a pseudo op for a two instruction sequence with a label, which
+    // looks like:
+    //     call "L1$pb"
+    // "L1$pb":
+    //     popl %esi
+    
+    // Emit the call.
+    MCSymbol *PICBase = MCInstLowering.GetPICBaseSymbol();
+    TmpInst.setOpcode(X86::CALLpcrel32);
+    // FIXME: We would like an efficient form for this, so we don't have to do a
+    // lot of extra uniquing.
+    TmpInst.addOperand(MCOperand::CreateExpr(MCSymbolRefExpr::Create(PICBase,
+                                                                 OutContext)));
+    OutStreamer.EmitInstruction(TmpInst);
+    
+    // Emit the label.
+    OutStreamer.EmitLabel(PICBase);
+    
+    // popl $reg
+    TmpInst.setOpcode(X86::POP32r);
+    TmpInst.getOperand(0) = MCOperand::CreateReg(MI->getOperand(0).getReg());
+    OutStreamer.EmitInstruction(TmpInst);
+    return;
+  }
+      
+  case X86::ADD32ri: {
+    // Lower the MO_GOT_ABSOLUTE_ADDRESS form of ADD32ri.
+    if (MI->getOperand(2).getTargetFlags() != X86II::MO_GOT_ABSOLUTE_ADDRESS)
+      break;
+    
+    // Okay, we have something like:
+    //  EAX = ADD32ri EAX, MO_GOT_ABSOLUTE_ADDRESS(@MYGLOBAL)
+    
+    // For this, we want to print something like:
+    //   MYGLOBAL + (. - PICBASE)
+    // However, we can't generate a ".", so just emit a new label here and refer
+    // to it.
+    MCSymbol *DotSym = OutContext.CreateTempSymbol();
+    OutStreamer.EmitLabel(DotSym);
+    
+    // Now that we have emitted the label, lower the complex operand expression.
+    MCSymbol *OpSym = MCInstLowering.GetSymbolFromOperand(MI->getOperand(2));
+    
+    const MCExpr *DotExpr = MCSymbolRefExpr::Create(DotSym, OutContext);
+    const MCExpr *PICBase =
+      MCSymbolRefExpr::Create(MCInstLowering.GetPICBaseSymbol(), OutContext);
+    DotExpr = MCBinaryExpr::CreateSub(DotExpr, PICBase, OutContext);
+    
+    DotExpr = MCBinaryExpr::CreateAdd(MCSymbolRefExpr::Create(OpSym,OutContext), 
+                                      DotExpr, OutContext);
+    
+    MCInst TmpInst;
+    TmpInst.setOpcode(X86::ADD32ri);
+    TmpInst.addOperand(MCOperand::CreateReg(MI->getOperand(0).getReg()));
+    TmpInst.addOperand(MCOperand::CreateReg(MI->getOperand(1).getReg()));
+    TmpInst.addOperand(MCOperand::CreateExpr(DotExpr));
+    OutStreamer.EmitInstruction(TmpInst);
+    return;
+  }
+  }
+  
+  MCInst TmpInst;
+  MCInstLowering.Lower(MI, TmpInst);
+  OutStreamer.EmitInstruction(TmpInst);
+}
+