ARCMCInstLower.cpp

//===- ARCMCInstLower.cpp - ARC MachineInstr to MCInst ----------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file contains code to lower ARC MachineInstrs to their
/// corresponding MCInst records.
///
//===----------------------------------------------------------------------===//

#include "ARCMCInstLower.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"

using namespace llvm;

ARCMCInstLower::ARCMCInstLower(MCContext *C, AsmPrinter &AsmPrinter)
    : Ctx(C), Printer(AsmPrinter) {}

MCOperand ARCMCInstLower::LowerSymbolOperand(const MachineOperand &MO,
                                             MachineOperandType MOTy,
                                             unsigned Offset) const {
  MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None;
  const MCSymbol *Symbol;

  switch (MOTy) {
  case MachineOperand::MO_MachineBasicBlock:
    Symbol = MO.getMBB()->getSymbol();
    break;
  case MachineOperand::MO_GlobalAddress:
    Symbol = Printer.getSymbol(MO.getGlobal());
    Offset += MO.getOffset();
    break;
  case MachineOperand::MO_BlockAddress:
    Symbol = Printer.GetBlockAddressSymbol(MO.getBlockAddress());
    Offset += MO.getOffset();
    break;
  case MachineOperand::MO_ExternalSymbol:
    Symbol = Printer.GetExternalSymbolSymbol(MO.getSymbolName());
    Offset += MO.getOffset();
    break;
  case MachineOperand::MO_JumpTableIndex:
    Symbol = Printer.GetJTISymbol(MO.getIndex());
    break;
  case MachineOperand::MO_ConstantPoolIndex:
    Symbol = Printer.GetCPISymbol(MO.getIndex());
    Offset += MO.getOffset();
    break;
  default:
    llvm_unreachable("<unknown operand type>");
  }

  assert(Symbol && "Symbol creation failed.\n");
  const MCSymbolRefExpr *MCSym = MCSymbolRefExpr::create(Symbol, Kind, *Ctx);

  if (!Offset)
    return MCOperand::createExpr(MCSym);

  // Assume offset is never negative.
  assert(Offset > 0);

  const MCConstantExpr *OffsetExpr = MCConstantExpr::create(Offset, *Ctx);
  const MCBinaryExpr *Add = MCBinaryExpr::createAdd(MCSym, OffsetExpr, *Ctx);
  return MCOperand::createExpr(Add);
}

MCOperand ARCMCInstLower::LowerOperand(const MachineOperand &MO,
                                       unsigned Offset) const {
  MachineOperandType MOTy = MO.getType();

  switch (MOTy) {
  default:
    llvm_unreachable("unknown operand type");
  case MachineOperand::MO_Register:
    // Ignore all implicit register operands.
    if (MO.isImplicit())
      break;
    return MCOperand::createReg(MO.getReg());
  case MachineOperand::MO_Immediate:
    return MCOperand::createImm(MO.getImm() + Offset);
  case MachineOperand::MO_MachineBasicBlock:
  case MachineOperand::MO_GlobalAddress:
  case MachineOperand::MO_ExternalSymbol:
  case MachineOperand::MO_JumpTableIndex:
  case MachineOperand::MO_ConstantPoolIndex:
  case MachineOperand::MO_BlockAddress:
    return LowerSymbolOperand(MO, MOTy, Offset);
  case MachineOperand::MO_RegisterMask:
    break;
  }

  return {};
}

void ARCMCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
  OutMI.setOpcode(MI->getOpcode());

  for (const MachineOperand &MO : MI->operands()) {
    MCOperand MCOp = LowerOperand(MO);

    if (MCOp.isValid())
      OutMI.addOperand(MCOp);
  }
}