BPFMCInstLower.cpp

//=-- BPFMCInstLower.cpp - Convert BPF MachineInstr to an MCInst ------------=//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file contains code to lower BPF MachineInstrs to their corresponding
// MCInst records.
//
//===----------------------------------------------------------------------===//

#include "BPFMCInstLower.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;

MCSymbol *
BPFMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const {
  return Printer.getSymbol(MO.getGlobal());
}

MCSymbol *
BPFMCInstLower::GetExternalSymbolSymbol(const MachineOperand &MO) const {
  return Printer.GetExternalSymbolSymbol(MO.getSymbolName());
}

MCOperand BPFMCInstLower::LowerSymbolOperand(const MachineOperand &MO,
                                             MCSymbol *Sym) const {

  const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Ctx);

  if (!MO.isJTI() && MO.getOffset())
    llvm_unreachable("unknown symbol op");

  return MCOperand::createExpr(Expr);
}

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

  for (const MachineOperand &MO : MI->operands()) {
    MCOperand MCOp;
    switch (MO.getType()) {
    default:
      MI->print(errs());
      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_RegisterMask:
      continue;
    case MachineOperand::MO_ExternalSymbol:
      MCOp = LowerSymbolOperand(MO, GetExternalSymbolSymbol(MO));
      break;
    case MachineOperand::MO_GlobalAddress:
      MCOp = LowerSymbolOperand(MO, GetGlobalAddressSymbol(MO));
      break;
    case MachineOperand::MO_ConstantPoolIndex:
      MCOp = LowerSymbolOperand(MO, Printer.GetCPISymbol(MO.getIndex()));
      break;
    }

    OutMI.addOperand(MCOp);
  }
}