ARMUtils.h

//===-- ARMUtils.h ----------------------------------------------*- 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
//
//===----------------------------------------------------------------------===//

#ifndef LLDB_SOURCE_PLUGINS_PROCESS_UTILITY_ARMUTILS_H
#define LLDB_SOURCE_PLUGINS_PROCESS_UTILITY_ARMUTILS_H

#include "ARMDefines.h"
#include "InstructionUtils.h"
#include "llvm/ADT/bit.h"
#include "llvm/Support/MathExtras.h"

// Common utilities for the ARM/Thumb Instruction Set Architecture.

namespace lldb_private {

static inline uint32_t Align(uint32_t val, uint32_t alignment) {
  return alignment * (val / alignment);
}

static inline uint32_t DecodeImmShift(const uint32_t type, const uint32_t imm5,
                                      ARM_ShifterType &shift_t) {
  switch (type) {
  default:
    assert(0 && "Invalid shift type");
    break;
  case 0:
    shift_t = SRType_LSL;
    return imm5;
  case 1:
    shift_t = SRType_LSR;
    return (imm5 == 0 ? 32 : imm5);
  case 2:
    shift_t = SRType_ASR;
    return (imm5 == 0 ? 32 : imm5);
  case 3:
    if (imm5 == 0) {
      shift_t = SRType_RRX;
      return 1;
    } else {
      shift_t = SRType_ROR;
      return imm5;
    }
  }
  shift_t = SRType_Invalid;
  return UINT32_MAX;
}

// A8.6.35 CMP (register) -- Encoding T3
// Convenience function.
static inline uint32_t DecodeImmShiftThumb(const uint32_t opcode,
                                           ARM_ShifterType &shift_t) {
  return DecodeImmShift(Bits32(opcode, 5, 4),
                        Bits32(opcode, 14, 12) << 2 | Bits32(opcode, 7, 6),
                        shift_t);
}

// A8.6.35 CMP (register) -- Encoding A1
// Convenience function.
static inline uint32_t DecodeImmShiftARM(const uint32_t opcode,
                                         ARM_ShifterType &shift_t) {
  return DecodeImmShift(Bits32(opcode, 6, 5), Bits32(opcode, 11, 7), shift_t);
}

static inline uint32_t DecodeImmShift(const ARM_ShifterType shift_t,
                                      const uint32_t imm5) {
  ARM_ShifterType dont_care;
  return DecodeImmShift(shift_t, imm5, dont_care);
}

static inline ARM_ShifterType DecodeRegShift(const uint32_t type) {
  switch (type) {
  default:
    // assert(0 && "Invalid shift type");
    return SRType_Invalid;
  case 0:
    return SRType_LSL;
  case 1:
    return SRType_LSR;
  case 2:
    return SRType_ASR;
  case 3:
    return SRType_ROR;
  }
}

static inline uint32_t LSL_C(const uint32_t value, const uint32_t amount,
                             uint32_t &carry_out, bool *success) {
  if (amount == 0) {
    *success = false;
    return 0;
  }
  *success = true;
  carry_out = amount <= 32 ? Bit32(value, 32 - amount) : 0;
  return value << amount;
}

static inline uint32_t LSL(const uint32_t value, const uint32_t amount,
                           bool *success) {
  *success = true;
  if (amount == 0)
    return value;
  uint32_t dont_care;
  uint32_t result = LSL_C(value, amount, dont_care, success);
  if (*success)
    return result;
  else
    return 0;
}

static inline uint32_t LSR_C(const uint32_t value, const uint32_t amount,
                             uint32_t &carry_out, bool *success) {
  if (amount == 0) {
    *success = false;
    return 0;
  }
  *success = true;
  carry_out = amount <= 32 ? Bit32(value, amount - 1) : 0;
  return value >> amount;
}

static inline uint32_t LSR(const uint32_t value, const uint32_t amount,
                           bool *success) {
  *success = true;
  if (amount == 0)
    return value;
  uint32_t dont_care;
  uint32_t result = LSR_C(value, amount, dont_care, success);
  if (*success)
    return result;
  else
    return 0;
}

static inline uint32_t ASR_C(const uint32_t value, const uint32_t amount,
                             uint32_t &carry_out, bool *success) {
  if (amount == 0 || amount > 32) {
    *success = false;
    return 0;
  }
  *success = true;
  bool negative = BitIsSet(value, 31);
  if (amount <= 32) {
    carry_out = Bit32(value, amount - 1);
    int64_t extended = llvm::SignExtend64<32>(value);
    return UnsignedBits(extended, amount + 31, amount);
  } else {
    carry_out = (negative ? 1 : 0);
    return (negative ? 0xffffffff : 0);
  }
}

static inline uint32_t ASR(const uint32_t value, const uint32_t amount,
                           bool *success) {
  *success = true;
  if (amount == 0)
    return value;
  uint32_t dont_care;
  uint32_t result = ASR_C(value, amount, dont_care, success);
  if (*success)
    return result;
  else
    return 0;
}

static inline uint32_t ROR_C(const uint32_t value, const uint32_t amount,
                             uint32_t &carry_out, bool *success) {
  if (amount == 0) {
    *success = false;
    return 0;
  }
  *success = true;
  uint32_t result = llvm::rotr<uint32_t>(value, amount);
  carry_out = Bit32(value, 31);
  return result;
}

static inline uint32_t ROR(const uint32_t value, const uint32_t amount,
                           bool *success) {
  *success = true;
  if (amount == 0)
    return value;
  uint32_t dont_care;
  uint32_t result = ROR_C(value, amount, dont_care, success);
  if (*success)
    return result;
  else
    return 0;
}

static inline uint32_t RRX_C(const uint32_t value, const uint32_t carry_in,
                             uint32_t &carry_out, bool *success) {
  *success = true;
  carry_out = Bit32(value, 0);
  return Bit32(carry_in, 0) << 31 | Bits32(value, 31, 1);
}

static inline uint32_t RRX(const uint32_t value, const uint32_t carry_in,
                           bool *success) {
  *success = true;
  uint32_t dont_care;
  uint32_t result = RRX_C(value, carry_in, dont_care, success);
  if (*success)
    return result;
  else
    return 0;
}

static inline uint32_t Shift_C(const uint32_t value, ARM_ShifterType type,
                               const uint32_t amount, const uint32_t carry_in,
                               uint32_t &carry_out, bool *success) {
  if (type == SRType_RRX && amount != 1) {
    *success = false;
    return 0;
  }
  *success = true;

  if (amount == 0) {
    carry_out = carry_in;
    return value;
  }
  uint32_t result;
  switch (type) {
  case SRType_LSL:
    result = LSL_C(value, amount, carry_out, success);
    break;
  case SRType_LSR:
    result = LSR_C(value, amount, carry_out, success);
    break;
  case SRType_ASR:
    result = ASR_C(value, amount, carry_out, success);
    break;
  case SRType_ROR:
    result = ROR_C(value, amount, carry_out, success);
    break;
  case SRType_RRX:
    result = RRX_C(value, carry_in, carry_out, success);
    break;
  default:
    *success = false;
    break;
  }
  if (*success)
    return result;
  else
    return 0;
}

static inline uint32_t Shift(const uint32_t value, ARM_ShifterType type,
                             const uint32_t amount, const uint32_t carry_in,
                             bool *success) {
  // Don't care about carry out in this case.
  uint32_t dont_care;
  uint32_t result = Shift_C(value, type, amount, carry_in, dont_care, success);
  if (*success)
    return result;
  else
    return 0;
}

static inline uint32_t bits(const uint32_t val, const uint32_t msbit,
                            const uint32_t lsbit) {
  return Bits32(val, msbit, lsbit);
}

static inline uint32_t bit(const uint32_t val, const uint32_t msbit) {
  return bits(val, msbit, msbit);
}

static uint32_t ror(uint32_t val, uint32_t N, uint32_t shift) {
  uint32_t m = shift % N;
  return (val >> m) | (val << (N - m));
}

// (imm32, carry_out) = ARMExpandImm_C(imm12, carry_in)
static inline uint32_t ARMExpandImm_C(uint32_t opcode, uint32_t carry_in,
                                      uint32_t &carry_out) {
  uint32_t imm32;                         // the expanded result
  uint32_t imm = bits(opcode, 7, 0);      // immediate value
  uint32_t amt = 2 * bits(opcode, 11, 8); // rotate amount
  if (amt == 0) {
    imm32 = imm;
    carry_out = carry_in;
  } else {
    imm32 = ror(imm, 32, amt);
    carry_out = Bit32(imm32, 31);
  }
  return imm32;
}

static inline uint32_t ARMExpandImm(uint32_t opcode) {
  // 'carry_in' argument to following function call does not affect the imm32
  // result.
  uint32_t carry_in = 0;
  uint32_t carry_out;
  return ARMExpandImm_C(opcode, carry_in, carry_out);
}

// (imm32, carry_out) = ThumbExpandImm_C(imm12, carry_in)
static inline uint32_t ThumbExpandImm_C(uint32_t opcode, uint32_t carry_in,
                                        uint32_t &carry_out) {
  uint32_t imm32 = 0; // the expanded result
  const uint32_t i = bit(opcode, 26);
  const uint32_t imm3 = bits(opcode, 14, 12);
  const uint32_t abcdefgh = bits(opcode, 7, 0);
  const uint32_t imm12 = i << 11 | imm3 << 8 | abcdefgh;

  if (bits(imm12, 11, 10) == 0) {
    switch (bits(imm12, 9, 8)) {
    default: // Keep static analyzer happy with a default case
      break;

    case 0:
      imm32 = abcdefgh;
      break;

    case 1:
      imm32 = abcdefgh << 16 | abcdefgh;
      break;

    case 2:
      imm32 = abcdefgh << 24 | abcdefgh << 8;
      break;

    case 3:
      imm32 = abcdefgh << 24 | abcdefgh << 16 | abcdefgh << 8 | abcdefgh;
      break;
    }
    carry_out = carry_in;
  } else {
    const uint32_t unrotated_value = 0x80 | bits(imm12, 6, 0);
    imm32 = ror(unrotated_value, 32, bits(imm12, 11, 7));
    carry_out = Bit32(imm32, 31);
  }
  return imm32;
}

static inline uint32_t ThumbExpandImm(uint32_t opcode) {
  // 'carry_in' argument to following function call does not affect the imm32
  // result.
  uint32_t carry_in = 0;
  uint32_t carry_out;
  return ThumbExpandImm_C(opcode, carry_in, carry_out);
}

// imm32 = ZeroExtend(i:imm3:imm8, 32)
static inline uint32_t ThumbImm12(uint32_t opcode) {
  const uint32_t i = bit(opcode, 26);
  const uint32_t imm3 = bits(opcode, 14, 12);
  const uint32_t imm8 = bits(opcode, 7, 0);
  const uint32_t imm12 = i << 11 | imm3 << 8 | imm8;
  return imm12;
}

// imm32 = ZeroExtend(imm7:'00', 32)
static inline uint32_t ThumbImm7Scaled(uint32_t opcode) {
  const uint32_t imm7 = bits(opcode, 6, 0);
  return imm7 * 4;
}

// imm32 = ZeroExtend(imm8:'00', 32)
static inline uint32_t ThumbImm8Scaled(uint32_t opcode) {
  const uint32_t imm8 = bits(opcode, 7, 0);
  return imm8 * 4;
}

// This function performs the check for the register numbers 13 and 15 that are
// not permitted for many Thumb register specifiers.
static inline bool BadReg(uint32_t n) { return n == 13 || n == 15; }

} // namespace lldb_private

#endif // LLDB_SOURCE_PLUGINS_PROCESS_UTILITY_ARMUTILS_H