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//===-- X86InstrBuilder.h - Functions to aid building x86 insts -*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// 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.
#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 {
} BaseType;
union {
unsigned Reg;
int FrameIndex;
} Base;
unsigned Scale;
unsigned IndexReg;
int Disp;
const GlobalValue *GV;
unsigned GVOpFlags;
: 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::CreateReg(IndexReg, false, false, false, false,
false, false, 0, false));
if (GV)
MO.push_back(MachineOperand::CreateGA(GV, Disp, GVOpFlags));
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();
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 + 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)
else {
assert(AM.BaseType == X86AddressMode::FrameIndexBase);
if (AM.GV)
MIB.addGlobalAddress(AM.GV, AM.Disp, AM.GVOpFlags);
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)
/// 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