BPFAsmPrinter.cpp

//===-- BPFAsmPrinter.cpp - BPF LLVM assembly writer ----------------------===//
//
// 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 a printer that converts from our internal representation
// of machine-dependent LLVM code to the BPF assembly language.
//
//===----------------------------------------------------------------------===//

#include "BPF.h"
#include "BPFInstrInfo.h"
#include "BPFMCInstLower.h"
#include "BPFTargetMachine.h"
#include "BTFDebug.h"
#include "MCTargetDesc/BPFInstPrinter.h"
#include "TargetInfo/BPFTargetInfo.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;

#define DEBUG_TYPE "asm-printer"

namespace {
class BPFAsmPrinter : public AsmPrinter {
public:
  explicit BPFAsmPrinter(TargetMachine &TM,
                         std::unique_ptr<MCStreamer> Streamer)
      : AsmPrinter(TM, std::move(Streamer)), BTF(nullptr) {}

  StringRef getPassName() const override { return "BPF Assembly Printer"; }
  bool doInitialization(Module &M) override;
  void printOperand(const MachineInstr *MI, int OpNum, raw_ostream &O);
  bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
                       const char *ExtraCode, raw_ostream &O) override;
  bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNum,
                             const char *ExtraCode, raw_ostream &O) override;

  void emitInstruction(const MachineInstr *MI) override;

private:
  BTFDebug *BTF;
};
} // namespace

bool BPFAsmPrinter::doInitialization(Module &M) {
  AsmPrinter::doInitialization(M);

  // Only emit BTF when debuginfo available.
  if (MAI->doesSupportDebugInformation() && !M.debug_compile_units().empty()) {
    BTF = new BTFDebug(this);
    DebugHandlers.push_back(std::unique_ptr<BTFDebug>(BTF));
  }

  return false;
}

void BPFAsmPrinter::printOperand(const MachineInstr *MI, int OpNum,
                                 raw_ostream &O) {
  const MachineOperand &MO = MI->getOperand(OpNum);

  switch (MO.getType()) {
  case MachineOperand::MO_Register:
    O << BPFInstPrinter::getRegisterName(MO.getReg());
    break;

  case MachineOperand::MO_Immediate:
    O << MO.getImm();
    break;

  case MachineOperand::MO_MachineBasicBlock:
    O << *MO.getMBB()->getSymbol();
    break;

  case MachineOperand::MO_GlobalAddress:
    O << *getSymbol(MO.getGlobal());
    break;

  case MachineOperand::MO_BlockAddress: {
    MCSymbol *BA = GetBlockAddressSymbol(MO.getBlockAddress());
    O << BA->getName();
    break;
  }

  case MachineOperand::MO_ExternalSymbol:
    O << *GetExternalSymbolSymbol(MO.getSymbolName());
    break;

  case MachineOperand::MO_JumpTableIndex:
  case MachineOperand::MO_ConstantPoolIndex:
  default:
    llvm_unreachable("<unknown operand type>");
  }
}

bool BPFAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
                                    const char *ExtraCode, raw_ostream &O) {
  if (ExtraCode && ExtraCode[0])
    return AsmPrinter::PrintAsmOperand(MI, OpNo, ExtraCode, O);

  printOperand(MI, OpNo, O);
  return false;
}

bool BPFAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
                                          unsigned OpNum, const char *ExtraCode,
                                          raw_ostream &O) {
  assert(OpNum + 1 < MI->getNumOperands() && "Insufficient operands");
  const MachineOperand &BaseMO = MI->getOperand(OpNum);
  const MachineOperand &OffsetMO = MI->getOperand(OpNum + 1);
  assert(BaseMO.isReg() && "Unexpected base pointer for inline asm memory operand.");
  assert(OffsetMO.isImm() && "Unexpected offset for inline asm memory operand.");
  int Offset = OffsetMO.getImm();

  if (ExtraCode)
    return true; // Unknown modifier.

  if (Offset < 0)
    O << "(" << BPFInstPrinter::getRegisterName(BaseMO.getReg()) << " - " << -Offset << ")";
  else
    O << "(" << BPFInstPrinter::getRegisterName(BaseMO.getReg()) << " + " << Offset << ")";

  return false;
}

void BPFAsmPrinter::emitInstruction(const MachineInstr *MI) {
  BPF_MC::verifyInstructionPredicates(MI->getOpcode(),
                                      getSubtargetInfo().getFeatureBits());

  MCInst TmpInst;

  if (!BTF || !BTF->InstLower(MI, TmpInst)) {
    BPFMCInstLower MCInstLowering(OutContext, *this);
    MCInstLowering.Lower(MI, TmpInst);
  }
  EmitToStreamer(*OutStreamer, TmpInst);
}

// Force static initialization.
extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeBPFAsmPrinter() {
  RegisterAsmPrinter<BPFAsmPrinter> X(getTheBPFleTarget());
  RegisterAsmPrinter<BPFAsmPrinter> Y(getTheBPFbeTarget());
  RegisterAsmPrinter<BPFAsmPrinter> Z(getTheBPFTarget());
}