X86InstrBuilder.h

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//===-- X86InstrBuilder.h - Functions to aid building x86 insts -*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file exposes functions that may be used with BuildMI from the
// MachineInstrBuilder.h file to handle X86'isms in a clean way.
//
// The BuildMem function may be used with the BuildMI function to add entire
// memory references in a single, typed, function call.  X86 memory references
// can be very complex expressions (described in the README), so wrapping them
// up behind an easier to use interface makes sense.  Descriptions of the
// functions are included below.
//
// For reference, the order of operands for memory references is:
// (Operand), Base, Scale, Index, Displacement.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_TARGET_X86_X86INSTRBUILDER_H
#define LLVM_LIB_TARGET_X86_X86INSTRBUILDER_H

#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/MC/MCInstrDesc.h"
#include <cassert>

namespace llvm {

/// X86AddressMode - This struct holds a generalized full x86 address mode.
/// The base register can be a frame index, which will eventually be replaced
/// with BP or SP and Disp being offsetted accordingly.  The displacement may
/// also include the offset of a global value.
struct X86AddressMode {
  enum {
    RegBase,
    FrameIndexBase
  } BaseType;

  union {
    unsigned Reg;
    int FrameIndex;
  } Base;

  unsigned Scale;
  unsigned IndexReg;
  int Disp;
  const GlobalValue *GV;
  unsigned GVOpFlags;

  X86AddressMode()
    : BaseType(RegBase), Scale(1), IndexReg(0), Disp(0), GV(nullptr),
      GVOpFlags(0) {
    Base.Reg = 0;
  }

  void getFullAddress(SmallVectorImpl<MachineOperand> &MO) {
    assert(Scale == 1 || Scale == 2 || Scale == 4 || Scale == 8);

    if (BaseType == X86AddressMode::RegBase)
      MO.push_back(MachineOperand::CreateReg(Base.Reg, false, false, false,
                                             false, false, false, 0, false));
    else {
      assert(BaseType == X86AddressMode::FrameIndexBase);
      MO.push_back(MachineOperand::CreateFI(Base.FrameIndex));
    }

    MO.push_back(MachineOperand::CreateImm(Scale));
    MO.push_back(MachineOperand::CreateReg(IndexReg, false, false, false, false,
                                           false, false, 0, false));

    if (GV)
      MO.push_back(MachineOperand::CreateGA(GV, Disp, GVOpFlags));
    else
      MO.push_back(MachineOperand::CreateImm(Disp));

    MO.push_back(MachineOperand::CreateReg(0, false, false, false, false, false,
                                           false, 0, false));
  }
};

/// Compute the addressing mode from an machine instruction starting with the
/// given operand.
static inline X86AddressMode getAddressFromInstr(const MachineInstr *MI,
                                                 unsigned Operand) {
  X86AddressMode AM;
  const MachineOperand &Op0 = MI->getOperand(Operand);
  if (Op0.isReg()) {
    AM.BaseType = X86AddressMode::RegBase;
    AM.Base.Reg = Op0.getReg();
  } else {
    AM.BaseType = X86AddressMode::FrameIndexBase;
    AM.Base.FrameIndex = Op0.getIndex();
  }

  const MachineOperand &Op1 = MI->getOperand(Operand + 1);
  AM.Scale = Op1.getImm();

  const MachineOperand &Op2 = MI->getOperand(Operand + 2);
  AM.IndexReg = Op2.getReg();

  const MachineOperand &Op3 = MI->getOperand(Operand + 3);
  if (Op3.isGlobal())
    AM.GV = Op3.getGlobal();
  else
    AM.Disp = Op3.getImm();

  return AM;
}

/// addDirectMem - This function is used to add a direct memory reference to the
/// current instruction -- that is, a dereference of an address in a register,
/// with no scale, index or displacement. An example is: DWORD PTR [EAX].
///
static inline const MachineInstrBuilder &
addDirectMem(const MachineInstrBuilder &MIB, unsigned Reg) {
  // Because memory references are always represented with five
  // values, this adds: Reg, 1, NoReg, 0, NoReg to the instruction.
  return MIB.addReg(Reg).addImm(1).addReg(0).addImm(0).addReg(0);
}

/// Replace the address used in the instruction with the direct memory
/// reference.
static inline void setDirectAddressInInstr(MachineInstr *MI, unsigned Operand,
                                           unsigned Reg) {
  // Direct memory address is in a form of: Reg, 1 (Scale), NoReg, 0, NoReg.
  MI->getOperand(Operand).setReg(Reg);
  MI->getOperand(Operand + 1).setImm(1);
  MI->getOperand(Operand + 2).setReg(0);
  MI->getOperand(Operand + 3).setImm(0);
  MI->getOperand(Operand + 4).setReg(0);
}

static inline const MachineInstrBuilder &
addOffset(const MachineInstrBuilder &MIB, int Offset) {
  return MIB.addImm(1).addReg(0).addImm(Offset).addReg(0);
}

static inline const MachineInstrBuilder &
addOffset(const MachineInstrBuilder &MIB, const MachineOperand& Offset) {
  return MIB.addImm(1).addReg(0).add(Offset).addReg(0);
}

/// addRegOffset - This function is used to add a memory reference of the form
/// [Reg + Offset], i.e., one with no scale or index, but with a
/// displacement. An example is: DWORD PTR [EAX + 4].
///
static inline const MachineInstrBuilder &
addRegOffset(const MachineInstrBuilder &MIB,
             unsigned Reg, bool isKill, int Offset) {
  return addOffset(MIB.addReg(Reg, getKillRegState(isKill)), Offset);
}

/// addRegReg - This function is used to add a memory reference of the form:
/// [Reg + Reg].
static inline const MachineInstrBuilder &addRegReg(const MachineInstrBuilder &MIB,
                                            unsigned Reg1, bool isKill1,
                                            unsigned Reg2, bool isKill2) {
  return MIB.addReg(Reg1, getKillRegState(isKill1)).addImm(1)
    .addReg(Reg2, getKillRegState(isKill2)).addImm(0).addReg(0);
}

static inline const MachineInstrBuilder &
addFullAddress(const MachineInstrBuilder &MIB,
               const X86AddressMode &AM) {
  assert(AM.Scale == 1 || AM.Scale == 2 || AM.Scale == 4 || AM.Scale == 8);

  if (AM.BaseType == X86AddressMode::RegBase)
    MIB.addReg(AM.Base.Reg);
  else {
    assert(AM.BaseType == X86AddressMode::FrameIndexBase);
    MIB.addFrameIndex(AM.Base.FrameIndex);
  }

  MIB.addImm(AM.Scale).addReg(AM.IndexReg);
  if (AM.GV)
    MIB.addGlobalAddress(AM.GV, AM.Disp, AM.GVOpFlags);
  else
    MIB.addImm(AM.Disp);

  return MIB.addReg(0);
}

/// addFrameReference - This function is used to add a reference to the base of
/// an abstract object on the stack frame of the current function.  This
/// reference has base register as the FrameIndex offset until it is resolved.
/// This allows a constant offset to be specified as well...
///
static inline const MachineInstrBuilder &
addFrameReference(const MachineInstrBuilder &MIB, int FI, int Offset = 0) {
  MachineInstr *MI = MIB;
  MachineFunction &MF = *MI->getParent()->getParent();
  MachineFrameInfo &MFI = MF.getFrameInfo();
  const MCInstrDesc &MCID = MI->getDesc();
  auto Flags = MachineMemOperand::MONone;
  if (MCID.mayLoad())
    Flags |= MachineMemOperand::MOLoad;
  if (MCID.mayStore())
    Flags |= MachineMemOperand::MOStore;
  MachineMemOperand *MMO = MF.getMachineMemOperand(
      MachinePointerInfo::getFixedStack(MF, FI, Offset), Flags,
      MFI.getObjectSize(FI), MFI.getObjectAlignment(FI));
  return addOffset(MIB.addFrameIndex(FI), Offset)
            .addMemOperand(MMO);
}

/// addConstantPoolReference - This function is used to add a reference to the
/// base of a constant value spilled to the per-function constant pool.  The
/// reference uses the abstract ConstantPoolIndex which is retained until
/// either machine code emission or assembly output. In PIC mode on x86-32,
/// the GlobalBaseReg parameter can be used to make this a
/// GlobalBaseReg-relative reference.
///
static inline const MachineInstrBuilder &
addConstantPoolReference(const MachineInstrBuilder &MIB, unsigned CPI,
                         unsigned GlobalBaseReg, unsigned char OpFlags) {
  //FIXME: factor this
  return MIB.addReg(GlobalBaseReg).addImm(1).addReg(0)
    .addConstantPoolIndex(CPI, 0, OpFlags).addReg(0);
}

} // end namespace llvm

#endif // LLVM_LIB_TARGET_X86_X86INSTRBUILDER_H