PPCDisassembler.cpp

//===------ PPCDisassembler.cpp - Disassembler for PowerPC ------*- 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
//
//===----------------------------------------------------------------------===//

#include "MCTargetDesc/PPCMCTargetDesc.h"
#include "TargetInfo/PowerPCTargetInfo.h"
#include "llvm/MC/MCDecoderOps.h"
#include "llvm/MC/MCDisassembler/MCDisassembler.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Support/Endian.h"

using namespace llvm;

DEFINE_PPC_REGCLASSES

#define DEBUG_TYPE "ppc-disassembler"

typedef MCDisassembler::DecodeStatus DecodeStatus;

namespace {
class PPCDisassembler : public MCDisassembler {
  bool IsLittleEndian;

public:
  PPCDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx,
                  bool IsLittleEndian)
      : MCDisassembler(STI, Ctx), IsLittleEndian(IsLittleEndian) {}

  DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size,
                              ArrayRef<uint8_t> Bytes, uint64_t Address,
                              raw_ostream &CStream) const override;
};
} // end anonymous namespace

static MCDisassembler *createPPCDisassembler(const Target &T,
                                             const MCSubtargetInfo &STI,
                                             MCContext &Ctx) {
  return new PPCDisassembler(STI, Ctx, /*IsLittleEndian=*/false);
}

static MCDisassembler *createPPCLEDisassembler(const Target &T,
                                               const MCSubtargetInfo &STI,
                                               MCContext &Ctx) {
  return new PPCDisassembler(STI, Ctx, /*IsLittleEndian=*/true);
}

extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializePowerPCDisassembler() {
  // Register the disassembler for each target.
  TargetRegistry::RegisterMCDisassembler(getThePPC32Target(),
                                         createPPCDisassembler);
  TargetRegistry::RegisterMCDisassembler(getThePPC32LETarget(),
                                         createPPCLEDisassembler);
  TargetRegistry::RegisterMCDisassembler(getThePPC64Target(),
                                         createPPCDisassembler);
  TargetRegistry::RegisterMCDisassembler(getThePPC64LETarget(),
                                         createPPCLEDisassembler);
}

static DecodeStatus decodeCondBrTarget(MCInst &Inst, unsigned Imm,
                                       uint64_t /*Address*/,
                                       const MCDisassembler * /*Decoder*/) {
  Inst.addOperand(MCOperand::createImm(SignExtend32<14>(Imm)));
  return MCDisassembler::Success;
}

static DecodeStatus decodeDirectBrTarget(MCInst &Inst, unsigned Imm,
                                         uint64_t /*Address*/,
                                         const MCDisassembler * /*Decoder*/) {
  int32_t Offset = SignExtend32<24>(Imm);
  Inst.addOperand(MCOperand::createImm(Offset));
  return MCDisassembler::Success;
}

// FIXME: These can be generated by TableGen from the existing register
// encoding values!

template <std::size_t N>
static DecodeStatus decodeRegisterClass(MCInst &Inst, uint64_t RegNo,
                                        const MCPhysReg (&Regs)[N]) {
  if (RegNo >= N)
    return MCDisassembler::Fail;
  Inst.addOperand(MCOperand::createReg(Regs[RegNo]));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeCRRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, CRRegs);
}

static DecodeStatus DecodeCRBITRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                               uint64_t Address,
                                               const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, CRBITRegs);
}

static DecodeStatus DecodeF4RCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, FRegs);
}

static DecodeStatus DecodeF8RCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, FRegs);
}

static DecodeStatus DecodeFpRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  if (RegNo > 30 || (RegNo & 1))
    return MCDisassembler::Fail;
  return decodeRegisterClass(Inst, RegNo >> 1, FpRegs);
}

static DecodeStatus DecodeVFRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, VFRegs);
}

static DecodeStatus DecodeVRRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, VRegs);
}

static DecodeStatus DecodeVSRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, VSRegs);
}

static DecodeStatus DecodeVSFRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                             uint64_t Address,
                                             const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, VSFRegs);
}

static DecodeStatus DecodeVSSRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                             uint64_t Address,
                                             const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, VSSRegs);
}

static DecodeStatus DecodeGPRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, RRegs);
}

static DecodeStatus
DecodeGPRC_NOR0RegisterClass(MCInst &Inst, uint64_t RegNo, uint64_t Address,
                             const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, RRegsNoR0);
}

static DecodeStatus DecodeG8RCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, XRegs);
}

static DecodeStatus DecodeG8pRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                             uint64_t Address,
                                             const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, XRegs);
}

static DecodeStatus
DecodeG8RC_NOX0RegisterClass(MCInst &Inst, uint64_t RegNo, uint64_t Address,
                             const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, XRegsNoX0);
}

#define DecodePointerLikeRegClass0 DecodeGPRCRegisterClass
#define DecodePointerLikeRegClass1 DecodeGPRC_NOR0RegisterClass

static DecodeStatus DecodeSPERCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                             uint64_t Address,
                                             const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, SPERegs);
}

static DecodeStatus DecodeACCRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                             uint64_t Address,
                                             const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, ACCRegs);
}

static DecodeStatus DecodeWACCRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                              uint64_t Address,
                                              const void *Decoder) {
  return decodeRegisterClass(Inst, RegNo, WACCRegs);
}

static DecodeStatus DecodeWACC_HIRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                                 uint64_t Address,
                                                 const void *Decoder) {
  return decodeRegisterClass(Inst, RegNo, WACC_HIRegs);
}

// TODO: Make this function static when the register class is used by a new
//       instruction.
DecodeStatus DecodeDMRROWRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                         uint64_t Address,
                                         const void *Decoder) {
  return decodeRegisterClass(Inst, RegNo, DMRROWRegs);
}

static DecodeStatus DecodeDMRROWpRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                                 uint64_t Address,
                                                 const void *Decoder) {
  return decodeRegisterClass(Inst, RegNo, DMRROWpRegs);
}

static DecodeStatus DecodeDMRRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                             uint64_t Address,
                                             const void *Decoder) {
  return decodeRegisterClass(Inst, RegNo, DMRRegs);
}

// TODO: Make this function static when the register class is used by a new
//       instruction.
DecodeStatus DecodeDMRpRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                       uint64_t Address, const void *Decoder) {
  return decodeRegisterClass(Inst, RegNo, DMRpRegs);
}

static DecodeStatus DecodeVSRpRCRegisterClass(MCInst &Inst, uint64_t RegNo,
                                              uint64_t Address,
                                              const MCDisassembler *Decoder) {
  return decodeRegisterClass(Inst, RegNo, VSRpRegs);
}

#define DecodeQSRCRegisterClass DecodeQFRCRegisterClass
#define DecodeQBRCRegisterClass DecodeQFRCRegisterClass

template <unsigned N>
static DecodeStatus decodeUImmOperand(MCInst &Inst, uint64_t Imm,
                                      int64_t Address,
                                      const MCDisassembler *Decoder) {
  if (!isUInt<N>(Imm))
    return MCDisassembler::Fail;
  Inst.addOperand(MCOperand::createImm(Imm));
  return MCDisassembler::Success;
}

template <unsigned N>
static DecodeStatus decodeSImmOperand(MCInst &Inst, uint64_t Imm,
                                      int64_t Address,
                                      const MCDisassembler *Decoder) {
  if (!isUInt<N>(Imm))
    return MCDisassembler::Fail;
  Inst.addOperand(MCOperand::createImm(SignExtend64<N>(Imm)));
  return MCDisassembler::Success;
}

static DecodeStatus decodeImmZeroOperand(MCInst &Inst, uint64_t Imm,
                                         int64_t Address,
                                         const MCDisassembler *Decoder) {
  if (Imm != 0)
    return MCDisassembler::Fail;
  Inst.addOperand(MCOperand::createImm(Imm));
  return MCDisassembler::Success;
}

static DecodeStatus decodeVSRpEvenOperands(MCInst &Inst, uint64_t RegNo,
                                           uint64_t Address,
                                           const MCDisassembler *Decoder) {
  if (RegNo & 1)
    return MCDisassembler::Fail;
  Inst.addOperand(MCOperand::createReg(VSRpRegs[RegNo >> 1]));
  return MCDisassembler::Success;
}

static DecodeStatus decodeDispRIXOperand(MCInst &Inst, uint64_t Imm,
                                         int64_t Address,
                                         const MCDisassembler *Decoder) {
  // The rix displacement is an immediate shifted by 2
  Inst.addOperand(MCOperand::createImm(SignExtend64<16>(Imm << 2)));
  return MCDisassembler::Success;
}

static DecodeStatus decodeDispRIHashOperand(MCInst &Inst, uint64_t Imm,
                                            int64_t Address,
                                            const MCDisassembler *Decoder) {
  // Decode the disp field for a hash store or hash check operation.
  // The field is composed of an immediate value that is 6 bits
  // and covers the range -8 to -512. The immediate is always negative and 2s
  // complement which is why we sign extend a 7 bit value.
  const int64_t Disp = SignExtend64<7>((Imm & 0x3F) + 64) * 8;

  Inst.addOperand(MCOperand::createImm(Disp));
  return MCDisassembler::Success;
}

static DecodeStatus decodeDispRIX16Operand(MCInst &Inst, uint64_t Imm,
                                           int64_t Address,
                                           const MCDisassembler *Decoder) {
  // The rix16 displacement has 12-bits which are shifted by 4.
  Inst.addOperand(MCOperand::createImm(SignExtend64<16>(Imm << 4)));
  return MCDisassembler::Success;
}

static DecodeStatus decodeDispSPE8Operand(MCInst &Inst, uint64_t Imm,
                                          int64_t Address,
                                          const MCDisassembler *Decoder) {
  // Decode the dispSPE8 field, which has 5-bits, 8-byte aligned.

  uint64_t Disp = Imm & 0x1F;

  Inst.addOperand(MCOperand::createImm(Disp << 3));
  return MCDisassembler::Success;
}

static DecodeStatus decodeDispSPE4Operand(MCInst &Inst, uint64_t Imm,
                                          int64_t Address,
                                          const MCDisassembler *Decoder) {
  // Decode the dispSPE8 field, which has 5-bits, 4-byte aligned.

  uint64_t Disp = Imm & 0x1F;

  Inst.addOperand(MCOperand::createImm(Disp << 2));
  return MCDisassembler::Success;
}

static DecodeStatus decodeDispSPE2Operand(MCInst &Inst, uint64_t Imm,
                                          int64_t Address,
                                          const MCDisassembler *Decoder) {
  // Decode the dispSPE8 field, which has 5-bits, 2-byte aligned.

  uint64_t Disp = Imm & 0x1F;
  Inst.addOperand(MCOperand::createImm(Disp << 1));
  return MCDisassembler::Success;
}

static DecodeStatus decodeCRBitMOperand(MCInst &Inst, uint64_t Imm,
                                        int64_t Address,
                                        const MCDisassembler *Decoder) {
  // The cr bit encoding is 0x80 >> cr_reg_num.

  unsigned Zeros = llvm::countr_zero(Imm);
  if (Zeros >= 8)
    return MCDisassembler::Fail;

  Inst.addOperand(MCOperand::createReg(CRRegs[7 - Zeros]));
  return MCDisassembler::Success;
}

#include "PPCGenDisassemblerTables.inc"

DecodeStatus PPCDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
                                             ArrayRef<uint8_t> Bytes,
                                             uint64_t Address,
                                             raw_ostream &CS) const {
  auto *ReadFunc = IsLittleEndian ? support::endian::read32le
                                  : support::endian::read32be;

  // If this is an 8-byte prefixed instruction, handle it here.
  // Note: prefixed instructions aren't technically 8-byte entities - the prefix
  //       appears in memory at an address 4 bytes prior to that of the base
  //       instruction regardless of endianness. So we read the two pieces and
  //       rebuild the 8-byte instruction.
  // TODO: In this function we call decodeInstruction several times with
  //       different decoder tables. It may be possible to only call once by
  //       looking at the top 6 bits of the instruction.
  if (STI.hasFeature(PPC::FeaturePrefixInstrs) && Bytes.size() >= 8) {
    uint32_t Prefix = ReadFunc(Bytes.data());
    uint32_t BaseInst = ReadFunc(Bytes.data() + 4);
    uint64_t Inst = BaseInst | (uint64_t)Prefix << 32;
    DecodeStatus result = decodeInstruction(DecoderTable64, MI, Inst, Address,
                                            this, STI);
    if (result != MCDisassembler::Fail) {
      Size = 8;
      return result;
    }
  }

  // Get the four bytes of the instruction.
  Size = 4;
  if (Bytes.size() < 4) {
    Size = 0;
    return MCDisassembler::Fail;
  }

  // Read the instruction in the proper endianness.
  uint64_t Inst = ReadFunc(Bytes.data());

  if (STI.hasFeature(PPC::FeatureSPE)) {
    DecodeStatus result =
        decodeInstruction(DecoderTableSPE32, MI, Inst, Address, this, STI);
    if (result != MCDisassembler::Fail)
      return result;
  }

  return decodeInstruction(DecoderTable32, MI, Inst, Address, this, STI);
}