src/disassembler_arm.cc

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "disassembler_arm.h"

#include <iostream>

#include "base/logging.h"
#include "base/stringprintf.h"
#include "thread.h"

namespace art {
namespace arm {

DisassemblerArm::DisassemblerArm() {
}

size_t DisassemblerArm::Dump(std::ostream& os, const uint8_t* begin) {
  if ((reinterpret_cast<intptr_t>(begin) & 1) == 0) {
    DumpArm(os, begin);
    return 4;
  } else {
    // remove thumb specifier bits
    begin = reinterpret_cast<const uint8_t*>(reinterpret_cast<uintptr_t>(begin) & ~1);
    return DumpThumb16(os, begin);
  }
}

void DisassemblerArm::Dump(std::ostream& os, const uint8_t* begin, const uint8_t* end) {
  if ((reinterpret_cast<intptr_t>(begin) & 1) == 0) {
    for (const uint8_t* cur = begin; cur < end; cur += 4) {
      DumpArm(os, cur);
    }
  } else {
    // remove thumb specifier bits
    begin = reinterpret_cast<const uint8_t*>(reinterpret_cast<uintptr_t>(begin) & ~1);
    end = reinterpret_cast<const uint8_t*>(reinterpret_cast<uintptr_t>(end) & ~1);
    for (const uint8_t* cur = begin; cur < end;) {
      cur += DumpThumb16(os, cur);
    }
  }
}

static const char* kConditionCodeNames[] = {
  "eq",  // 0000 - equal
  "ne",  // 0001 - not-equal
  "cs",  // 0010 - carry-set, greater than, equal or unordered
  "cc",  // 0011 - carry-clear, less than
  "mi",  // 0100 - minus, negative
  "pl",  // 0101 - plus, positive or zero
  "vs",  // 0110 - overflow
  "vc",  // 0111 - no overflow
  "hi",  // 1000 - unsigned higher
  "ls",  // 1001 - unsigned lower or same
  "ge",  // 1010 - signed greater than or equal
  "lt",  // 1011 - signed less than
  "gt",  // 1100 - signed greater than
  "le",  // 1101 - signed less than or equal
  "",    // 1110 - always
  "nv",  // 1111 - never (mostly obsolete, but might be a clue that we're mistranslating)
};

void DisassemblerArm::DumpCond(std::ostream& os, uint32_t cond) {
  if (cond < 15) {
    os << kConditionCodeNames[cond];
  } else {
    os << "Unexpected condition: " << cond;
  }
}

void DisassemblerArm::DumpBranchTarget(std::ostream& os, const uint8_t* instr_ptr, int32_t imm32) {
  os << StringPrintf("%+d (%p)", imm32, instr_ptr + imm32);
}

static uint32_t ReadU16(const uint8_t* ptr) {
  return ptr[0] | (ptr[1] << 8);
}

static uint32_t ReadU32(const uint8_t* ptr) {
  return ptr[0] | (ptr[1] << 8) | (ptr[2] << 16) | (ptr[3] << 24);
}

static const char* kDataProcessingOperations[] = {
  "and", "eor", "sub", "rsb", "add", "adc", "sbc", "rsc",
  "tst", "teq", "cmp", "cmn", "orr", "mov", "bic", "mvn",
};

static const char* kThumbDataProcessingOperations[] = {
  "and", "eor", "lsl", "lsr", "asr", "adc", "sbc", "ror",
  "tst", "rsb", "cmp", "cmn", "orr", "mul", "bic", "mvn",
};

struct ArmRegister {
  explicit ArmRegister(uint32_t r) : r(r) { CHECK_LE(r, 15U); }
  ArmRegister(uint32_t instruction, uint32_t at_bit) : r((instruction >> at_bit) & 0xf) { CHECK_LE(r, 15U); }
  uint32_t r;
};
std::ostream& operator<<(std::ostream& os, const ArmRegister& r) {
  if (r.r == 13) {
    os << "sp";
  } else if (r.r == 14) {
    os << "lr";
  } else if (r.r == 15) {
    os << "pc";
  } else {
    os << "r" << r.r;
  }
  return os;
}

struct ThumbRegister : ArmRegister {
  ThumbRegister(uint16_t instruction, uint16_t at_bit) : ArmRegister((instruction >> at_bit) & 0x7) {}
};

struct Rm {
  explicit Rm(uint32_t instruction) : shift((instruction >> 4) & 0xff), rm(instruction & 0xf) {}
  uint32_t shift;
  ArmRegister rm;
};
std::ostream& operator<<(std::ostream& os, const Rm& r) {
  os << r.rm;
  if (r.shift != 0) {
    os << "-shift-" << r.shift; // TODO
  }
  return os;
}

struct ShiftedImmediate {
  explicit ShiftedImmediate(uint32_t instruction) {
    uint32_t rotate = ((instruction >> 8) & 0xf);
    uint32_t imm = (instruction & 0xff);
    value = (imm >> (2 * rotate)) | (imm << (32 - (2 * rotate)));
  }
  uint32_t value;
};
std::ostream& operator<<(std::ostream& os, const ShiftedImmediate& rhs) {
  os << "#" << rhs.value;
  return os;
}

struct RegisterList {
  explicit RegisterList(uint32_t instruction) : register_list(instruction & 0xffff) {}
  uint32_t register_list;
};
std::ostream& operator<<(std::ostream& os, const RegisterList& rhs) {
  if (rhs.register_list == 0) {
    os << "<no register list?>";
    return os;
  }
  os << "{";
  bool first = true;
  for (size_t i = 0; i < 16; i++) {
    if ((rhs.register_list & (1 << i)) != 0) {
      if (first) {
        first = false;
      } else {
        os << ", ";
      }
      os << ArmRegister(i);
    }
  }
  os << "}";
  return os;
}

void DisassemblerArm::DumpArm(std::ostream& os, const uint8_t* instr_ptr) {
  uint32_t instruction = ReadU32(instr_ptr);
  uint32_t cond = (instruction >> 28) & 0xf;
  uint32_t op1 = (instruction >> 25) & 0x7;
  std::string opcode;
  std::string suffixes;
  std::ostringstream args;
  switch (op1) {
    case 0:
    case 1: // Data processing instructions.
      {
        if ((instruction & 0x0ff000f0) == 0x01200070) { // BKPT
          opcode = "bkpt";
          uint32_t imm12 = (instruction >> 8) & 0xfff;
          uint32_t imm4 = (instruction & 0xf);
          args << '#' << ((imm12 << 4) | imm4);
          break;
        }
        if ((instruction & 0x0fffffd0) == 0x012fff10) { // BX and BLX (register)
          opcode = (((instruction >> 5) & 1) ? "blx" : "bx");
          args << ArmRegister(instruction & 0xf);
          break;
        }
        bool i = (instruction & (1 << 25)) != 0;
        bool s = (instruction & (1 << 20)) != 0;
        uint32_t op = (instruction >> 21) & 0xf;
        opcode = kDataProcessingOperations[op];
        bool implicit_s = ((op & ~3) == 8); // TST, TEQ, CMP, and CMN.
        if (implicit_s) {
          // Rd is unused (and not shown), and we don't show the 's' suffix either.
        } else {
          if (s) {
            suffixes += 's';
          }
          args << ArmRegister(instruction, 12) << ", ";
        }
        if (i) {
          args << ArmRegister(instruction, 16) << ", " << ShiftedImmediate(instruction);
        } else {
          args << Rm(instruction);
        }
      }
      break;
    case 2: // Load/store word and unsigned byte.
      {
        bool p = (instruction & (1 << 24)) != 0;
        bool b = (instruction & (1 << 22)) != 0;
        bool w = (instruction & (1 << 21)) != 0;
        bool l = (instruction & (1 << 20)) != 0;
        opcode = StringPrintf("%s%s", (l ? "ldr" : "str"), (b ? "b" : ""));
        args << ArmRegister(instruction, 12) << ", ";
        ArmRegister rn(instruction, 16);
        if (rn.r == 0xf) {
          UNIMPLEMENTED(FATAL) << "literals";
        } else {
          bool wback = !p || w;
          uint32_t offset = (instruction & 0xfff);
          if (p && !wback) {
            args << "[" << rn << ", #" << offset << "]";
          } else if (p && wback) {
            args << "[" << rn << ", #" << offset << "]!";
          } else if (!p && wback) {
            args << "[" << rn << "], #" << offset;
          } else {
            LOG(FATAL) << p << " " << w;
          }
          if (rn.r == 9) {
            args << "  ; ";
            Thread::DumpThreadOffset(args, offset, 4);
          }
        }
      }
      break;
    case 4: // Load/store multiple.
      {
        bool p = (instruction & (1 << 24)) != 0;
        bool u = (instruction & (1 << 23)) != 0;
        bool w = (instruction & (1 << 21)) != 0;
        bool l = (instruction & (1 << 20)) != 0;
        opcode = StringPrintf("%s%c%c", (l ? "ldm" : "stm"), (u ? 'i' : 'd'), (p ? 'b' : 'a'));
        args << ArmRegister(instruction, 16) << (w ? "!" : "") << ", " << RegisterList(instruction);
      }
      break;
    case 5: // Branch/branch with link.
      {
        bool bl = (instruction & (1 << 24)) != 0;
        opcode = (bl ? "bl" : "b");
        int32_t imm26 = (instruction & 0xffffff) << 2;
        int32_t imm32 = (imm26 << 6) >> 6; // Sign extend.
        DumpBranchTarget(args, instr_ptr + 8, imm32);
      }
      break;
    default:
      opcode = "???";
      break;
    }
    opcode += kConditionCodeNames[cond];
    opcode += suffixes;
    // TODO: a more complete ARM disassembler could generate wider opcodes.
    os << StringPrintf("%p: %08x\t%-7s ", instr_ptr, instruction, opcode.c_str()) << args.str() << '\n';
}

size_t DisassemblerArm::DumpThumb32(std::ostream& os, const uint8_t* instr_ptr) {
  uint32_t instr = (ReadU16(instr_ptr) << 16) | ReadU16(instr_ptr + 2);
  // |111|1 1|1000000|0000|1111110000000000|
  // |5 3|2 1|0987654|3  0|5    0    5    0|
  // |---|---|-------|----|----------------|
  // |332|2 2|2222222|1111|1111110000000000|
  // |1 9|8 7|6543210|9  6|5    0    5    0|
  // |---|---|-------|----|----------------|
  // |111|op1| op2   |    |                |
  uint32_t op1 = (instr >> 27) & 3;
  if (op1 == 0) {
    return DumpThumb16(os, instr_ptr);
  }

  uint32_t op2 = (instr >> 20) & 0x7F;
  std::ostringstream opcode;
  std::ostringstream args;
  switch (op1) {
    case 0:
      break;
    case 1:
      if ((op2 & 0x64) == 0) {  // 00x x0xx
        // |111|11|10|00|0|00|0000|1111110000000000|
        // |5 3|21|09|87|6|54|3  0|5    0    5    0|
        // |---|--|--|--|-|--|----|----------------|
        // |332|22|22|22|2|22|1111|1111110000000000|
        // |1 9|87|65|43|2|10|9  6|5    0    5    0|
        // |---|--|--|--|-|--|----|----------------|
        // |111|01|00|op|0|WL| Rn |                |
        // |111|01| op2      |    |                |
        // STM - 111 01 00-01-0-W0 nnnn rrrrrrrrrrrrrrrr
        // LDM - 111 01 00-01-0-W1 nnnn rrrrrrrrrrrrrrrr
        // PUSH- 111 01 00-01-0-10 1101 0M0rrrrrrrrrrrrr
        // POP - 111 01 00-01-0-11 1101 PM0rrrrrrrrrrrrr
        uint32_t op = (instr >> 23) & 3;
        uint32_t W = (instr >> 21) & 1;
        uint32_t L = (instr >> 20) & 1;
        ArmRegister Rn(instr, 16);
        if (op == 1 || op == 2) {
          if (op == 1) {
            if (L == 0) {
              opcode << "stm";
              args << Rn << (W == 0 ? "" : "!") << ", ";
            } else {
              if (Rn.r != 13) {
                opcode << "ldm";
                args << Rn << (W == 0 ? "" : "!") << ", ";
              } else {
                opcode << "pop";
              }
            }
          } else {
            if (L == 0) {
              if (Rn.r != 13) {
                opcode << "stmdb";
                args << Rn << (W == 0 ? "" : "!") << ", ";
              } else {
                opcode << "push";
              }
            } else {
              opcode << "ldmdb";
              args << Rn << (W == 0 ? "" : "!") << ", ";
            }
          }
          args << RegisterList(instr);
        }
      } else if ((op2 & 0x64) == 4) { // 00x x1xx
        uint32_t op3 = (instr >> 23) & 3;
        uint32_t op4 = (instr >> 20) & 3;
        //uint32_t op5 = (instr >> 4) & 0xF;
        ArmRegister Rn(instr, 16);
        ArmRegister Rt(instr, 12);
        uint32_t imm8 = instr & 0xFF;
        if (op3 == 0 && op4 == 0) {  // STREX
          ArmRegister Rd(instr, 8);
          opcode << "strex";
          args << Rd << ", " << Rt << ", [" << Rn << ", #" << (imm8 << 2) << "]";
        } else if (op3 == 0 && op4 == 1) {  // LDREX
          opcode << "ldrex";
          args << Rt << ", [" << Rn << ", #" << (imm8 << 2) << "]";
        }
      } else if ((op2 & 0x60) == 0x20) {  // 01x xxxx
        // Data-processing (shifted register)
        // |111|1110|0000|0|0000|1111|1100|0000|0000|
        // |5 3|2109|8765|4|3  0|5   |10 8|7 5 |3  0|
        // |---|----|----|-|----|----|----|----|----|
        // |332|2222|2222|2|1111|1111|1100|0000|0000|
        // |1 9|8765|4321|0|9  6|5   |10 8|7 5 |3  0|
        // |---|----|----|-|----|----|----|----|----|
        // |111|0101| op3|S| Rn |    | Rd |    | Rm |
        uint32_t op3 = (instr >> 21) & 0xF;
        uint32_t S = (instr >> 20) & 1;
        uint32_t Rn = (instr >> 16) & 0xF;
        ArmRegister Rd(instr, 8);
        ArmRegister Rm(instr, 0);
        switch (op3) {
          case 0x0:
            if (Rn != 0xF) {
              opcode << "and";
            } else {
              opcode << "tst";
              S = 0;  // don't print 's'
            }
            break;
          case 0x1: opcode << "bic"; break;
          case 0x2:
            if (Rn != 0xF) {
              opcode << "orr";
            } else {
              opcode << "mov";
            }
            break;
          case 0x3:
            if (Rn != 0xF) {
              opcode << "orn";
            } else {
              opcode << "mvn";
            }
            break;
          case 0x4:
            if (Rn != 0xF) {
              opcode << "eor";
            } else {
              opcode << "teq";
              S = 0;  // don't print 's'
            }
            break;
          case 0x6: opcode << "pkh"; break;
          case 0x8:
            if (Rn != 0xF) {
              opcode << "add";
            } else {
              opcode << "cmn";
              S = 0;  // don't print 's'
            }
            break;
          case 0xA: opcode << "adc"; break;
          case 0xB: opcode << "sbc"; break;
        }

        if (S == 1) {
          opcode << "s";
        }
        opcode << ".w";
        args << Rd << ", " << Rm;
      } else if ((op2 & 0x40) == 0x40) {  // 1xx xxxx
        // Co-processor instructions
        // |111|1|11|000000|0000|1111|1100|000|0  |0000|
        // |5 3|2|10|987654|3  0|54 2|10 8|7 5|4  |   0|
        // |---|-|--|------|----|----|----|---|---|----|
        // |332|2|22|222222|1111|1111|1100|000|0  |0000|
        // |1 9|8|76|543210|9  6|54 2|10 8|7 5|4  |   0|
        // |---|-|--|------|----|----|----|---|---|----|
        // |111| |11| op3  | Rn |    |copr|   |op4|    |
        uint32_t op3 = (instr >> 20) & 0x3F;
        uint32_t coproc = (instr >> 8) & 0xF;
        uint32_t op4 = (instr >> 4) & 0x1;
        if ((op3 == 2 || op3 == 2 || op3 == 6 || op3 == 7) || // 00x1x
            (op3 >= 8 && op3 <= 15) || (op3 >= 16 && op3 <= 31)) { // 001xxx, 01xxxx
          // Extension register load/store instructions
          // |111|1|110|00000|0000|1111|110|000000000|
          // |5 3|2|109|87654|3  0|54 2|10 |87 54   0|
          // |---|-|---|-----|----|----|---|---------|
          // |332|2|222|22222|1111|1111|110|000000000|
          // |1 9|8|765|43210|9  6|54 2|10 |87 54   0|
          // |---|-|---|-----|----|----|---|---------|
          // |111|T|110| op3 | Rn |    |101|         |
          //  111 0 110 01001 0011 0000 101 000000011 - ec930a03
          if (op3 == 9 || op3 == 0xD) {  // VLDM
            //  1110 110 PUDW1 nnnn dddd 101S iiii iiii
            uint32_t P = (instr >> 24) & 1;
            uint32_t U = (instr >> 23) & 1;
            uint32_t D = (instr >> 22) & 1;
            uint32_t W = (instr >> 21) & 1;
            uint32_t S = (instr >> 8) & 1;
            ArmRegister Rn(instr, 16);
            uint32_t Vd = (instr >> 12) & 0xF;
            uint32_t imm8 = instr & 0xFF;
            uint32_t d = (S == 0 ? ((Vd << 1) | D) : (Vd | (D << 4)));
            if (P == 0 && U == 0 && W == 0) {
              // TODO: 64bit transfers between ARM core and extension registers.
            } else if (P == 0 && U == 1 && Rn.r == 13) { // VPOP
              opcode << "vpop" << (S == 0 ? ".f64" : ".f32");
              args << d << " .. " << (d + imm8);
            } else if (P == 1 && W == 0) {  // VLDR
              opcode << "vldr" << (S == 0 ? ".f64" : ".f32");
              args << d << ", [" << Rn << ", #" << imm8 << "]";
            } else { // VLDM
              opcode << "vldm" << (S == 0 ? ".f64" : ".f32");
              args << Rn << ", " << d << " .. " << (d + imm8);
            }
          }
        } else if ((op3 & 0x30) == 0x20 && op4 == 0) {  // 10 xxxx ... 0
          if ((coproc & 0xE) == 0xA) {
            // VFP data-processing instructions
            // |111|1|1100|0000|0000|1111|110|0|00  |0|0|0000|
            // |5 3|2|1098|7654|3  0|54 2|10 |8|76  |5|4|3  0|
            // |---|-|----|----|----|----|---|-|----|-|-|----|
            // |332|2|2222|2222|1111|1111|110|0|00  |0|0|0000|
            // |1 9|8|7654|3210|9  6|54 2|109|8|76  |5|4|3  0|
            // |---|-|----|----|----|----|---|-|----|-|-|----|
            // |111|T|1110|opc1|opc2|    |101| |opc3| | |    |
            //  111 0 1110|1111 0100 1110 101 0 01   1 0 1001 - eef4ea69
            uint32_t opc1 = (instr >> 20) & 0xF;
            uint32_t opc2 = (instr >> 16) & 0xF;
            uint32_t opc3 = (instr >> 6) & 0x3;
            if ((opc1 & 0xB) == 0xB) {  // 1x11
              // Other VFP data-processing instructions.
              uint32_t D  = (instr >> 22) & 0x1;
              uint32_t Vd = (instr >> 12) & 0xF;
              uint32_t sz = (instr >> 8) & 1;
              uint32_t M  = (instr >> 5) & 1;
              uint32_t Vm = instr & 0xF;
              bool dp_operation = sz == 1;
              switch (opc2) {
                case 0x1: // Vneg/Vsqrt
                  //  1110 11101 D 11 0001 dddd 101s o1M0 mmmm
                  opcode << (opc3 == 1 ? "vneg" : "vsqrt") << (dp_operation ? ".f64" : ".f32");
                  if (dp_operation) {
                    args << "f" << ((D << 4) | Vd) << ", " << "f" << ((M << 4) | Vm);
                  } else {
                    args << "f" << ((Vd << 1) | D) << ", " << "f" << ((Vm << 1) | M);
                  }
                  break;
                case 0x4: case 0x5:  { // Vector compare
                  // 1110 11101 D 11 0100 dddd 101 sE1M0 mmmm
                  opcode << (opc3 == 1 ? "vcmp" : "vcmpe") << (dp_operation ? ".f64" : ".f32");
                  if (dp_operation) {
                    args << "f" << ((D << 4) | Vd) << ", " << "f" << ((M << 4) | Vm);
                  } else {
                    args << "f" << ((Vd << 1) | D) << ", " << "f" << ((Vm << 1) | M);
                  }
                  break;
                }
              }
            }
          }
        } else if ((op3 & 0x30) == 0x30) {  // 11 xxxx
          // Advanced SIMD
          if ((instr & 0xFFBF0ED0) == 0xeeb10ac0) {  // Vsqrt
            //  1110 11101 D 11 0001 dddd 101S 11M0 mmmm
            //  1110 11101 0 11 0001 1101 1011 1100 1000 - eeb1dbc8
            uint32_t D = (instr >> 22) & 1;
            uint32_t Vd = (instr >> 12) & 0xF;
            uint32_t sz = (instr >> 8) & 1;
            uint32_t M = (instr >> 5) & 1;
            uint32_t Vm = instr & 0xF;
            bool dp_operation = sz == 1;
            opcode << "vsqrt" << (dp_operation ? ".f64" : ".f32");
            if (dp_operation) {
              args << "f" << ((D << 4) | Vd) << ", " << "f" << ((M << 4) | Vm);
            } else {
              args << "f" << ((Vd << 1) | D) << ", " << "f" << ((Vm << 1) | M);
            }
          }
        }
      }
      break;
    case 2:
      if ((instr & 0x8000) == 0 && (op2 & 0x20) == 0) {
        // Data-processing (modified immediate)
        // |111|11|10|0000|0|0000|1|111|1100|00000000|
        // |5 3|21|09|8765|4|3  0|5|4 2|10 8|7 5    0|
        // |---|--|--|----|-|----|-|---|----|--------|
        // |332|22|22|2222|2|1111|1|111|1100|00000000|
        // |1 9|87|65|4321|0|9  6|5|4 2|10 8|7 5    0|
        // |---|--|--|----|-|----|-|---|----|--------|
        // |111|10|i0| op3|S| Rn |0|iii| Rd |iiiiiiii|
        //  111 10 x0 xxxx x xxxx opxxx xxxx xxxxxxxx
        uint32_t i = (instr >> 26) & 1;
        uint32_t op3 = (instr >> 21) & 0xF;
        uint32_t S = (instr >> 20) & 1;
        ArmRegister Rn(instr, 16);
        uint32_t imm3 = (instr >> 12) & 7;
        ArmRegister Rd(instr, 8);
        uint32_t imm8 = instr & 0xFF;
        int32_t imm32 = (i << 11) | (imm3 << 8) | imm8;
        if (Rn.r == 0xF && (op3 == 0x2 || op3 == 0x3)) {
          if (op3 == 0x2) {
            opcode << "mov";
            if (S == 1) {
              opcode << "s";
            }
            opcode << ".w";
          } else {
            opcode << "mvn";
            if (S == 1) {
              opcode << "s";
            }
          }
          args << Rd << ", ThumbExpand(" << imm32 << ")";
        } else if (Rd.r == 0xF && S == 1 &&
                   (op3 == 0x0 || op3 == 0x4 || op3 == 0x8 || op3 == 0xD)) {
          if (op3 == 0x0) {
            opcode << "tst";
          } else if (op3 == 0x4) {
            opcode << "teq";
          } else if (op3 == 0x8) {
            opcode << "cmw";
          } else {
            opcode << "cmp.w";
          }
          args << Rn << ", ThumbExpand(" << imm32 << ")";
        } else {
          switch (op3) {
            case 0x0: opcode << "and"; break;
            case 0x1: opcode << "bic"; break;
            case 0x2: opcode << "orr"; break;
            case 0x3: opcode << "orn"; break;
            case 0x4: opcode << "eor"; break;
            case 0x8: opcode << "add"; break;
            case 0xA: opcode << "adc"; break;
            case 0xB: opcode << "sbc"; break;
            case 0xD: opcode << "sub"; break;
            case 0xE: opcode << "rsb"; break;
            default: opcode << "UNKNOWN DPMI-" << op3; break;
          }
          if (S == 1) {
            opcode << "s";
          }
          args << Rd << ", " << Rn << ", ThumbExpand(" << imm32 << ")";
        }
      } else if ((instr & 0x8000) == 0 && (op2 & 0x20) != 0) {
        // Data-processing (plain binary immediate)
        // |111|11|10|00000|0000|1|111110000000000|
        // |5 3|21|09|87654|3  0|5|4   0    5    0|
        // |---|--|--|-----|----|-|---------------|
        // |332|22|22|22222|1111|1|111110000000000|
        // |1 9|87|65|43210|9  6|5|4   0    5    0|
        // |---|--|--|-----|----|-|---------------|
        // |111|10|x1| op3 | Rn |0|xxxxxxxxxxxxxxx|
        uint32_t op3 = (instr >> 20) & 0x1F;
        switch (op3) {
          case 0x00: {
            ArmRegister Rd(instr, 8);
            ArmRegister Rn(instr, 16);
            uint32_t i = (instr >> 26) & 1;
            uint32_t imm3 = (instr >> 12) & 0x7;
            uint32_t imm8 = instr & 0xFF;
            uint32_t imm12 = (i << 11) | (imm3 << 8) | imm8;
            if (Rn.r != 0xF) {
              opcode << "addw";
              args << Rd << ", " << Rn << ", #" << imm12;
            } else {
              opcode << "adr";
              args << Rd << ", ";
              DumpBranchTarget(args, instr_ptr + 4, imm12);
            }
            break;
          }
          case 0x04: {
            // MOVW Rd, #imm16     - 111 10 i0 0010 0 iiii 0 iii dddd iiiiiiii
            ArmRegister Rd(instr, 8);
            uint32_t i = (instr >> 26) & 1;
            uint32_t imm3 = (instr >> 12) & 0x7;
            uint32_t imm8 = instr & 0xFF;
            uint32_t Rn = (instr >> 16) & 0xF;
            uint32_t imm16 = (Rn << 12) | (i << 11) | (imm3 << 8) | imm8;
            opcode << "movw";
            args << Rd << ", #" << imm16;
            break;
          }
          case 0x0A: {
            // SUB.W Rd, Rn #imm12 - 111 10 i1 0101 0 nnnn 0 iii dddd iiiiiiii
            ArmRegister Rd(instr, 8);
            ArmRegister Rn(instr, 16);
            uint32_t i = (instr >> 26) & 1;
            uint32_t imm3 = (instr >> 12) & 0x7;
            uint32_t imm8 = instr & 0xFF;
            uint32_t imm12 = (i << 11) | (imm3 << 8) | imm8;
            opcode << "sub.w";
            args << Rd << ", " << Rn << ", #" << imm12;
            break;
          }
          case 0x16: {
            // BFI Rd, Rn, #lsb, #width - 111 10 0 11 011 0 nnnn 0 iii dddd ii 0 iiiii
            ArmRegister Rd(instr, 8);
            ArmRegister Rn(instr, 16);
            uint32_t msb = instr & 0x1F;
            uint32_t imm2 = (instr >> 6) & 0x3;
            uint32_t imm3 = (instr >> 12) & 0x7;
            uint32_t lsb = (imm3 << 2) | imm2;
            uint32_t width = msb - lsb + 1;
            if (Rn.r != 0xF) {
              opcode << "bfi";
              args << Rd << ", " << Rn << ", #" << lsb << ", #" << width;
            } else {
              opcode << "bfc";
              args << Rd << ", #" << lsb << ", #" << width;
            }
            break;
          }
          default:
            break;
        }
      } else {
        // Branches and miscellaneous control
        // |111|11|1000000|0000|1|111|1100|00000000|
        // |5 3|21|0987654|3  0|5|4 2|10 8|7 5    0|
        // |---|--|-------|----|-|---|----|--------|
        // |332|22|2222222|1111|1|111|1100|00000000|
        // |1 9|87|6543210|9  6|5|4 2|10 8|7 5    0|
        // |---|--|-------|----|-|---|----|--------|
        // |111|10| op2   |    |1|op3|op4 |        |

        uint32_t op3 = (instr >> 12) & 7;
        //uint32_t op4 = (instr >> 8) & 0xF;
        switch (op3) {
          case 0:
            if ((op2 & 0x38) != 0x38) {
              // Conditional branch
              // |111|11|1|0000|000000|1|1|1 |1|1 |10000000000|
              // |5 3|21|0|9876|543  0|5|4|3 |2|1 |0    5    0|
              // |---|--|-|----|------|-|-|--|-|--|-----------|
              // |332|22|2|2222|221111|1|1|1 |1|1 |10000000000|
              // |1 9|87|6|5432|109  6|5|4|3 |2|1 |0    5    0|
              // |---|--|-|----|------|-|-|--|-|--|-----------|
              // |111|10|S|cond| imm6 |1|0|J1|0|J2| imm11     |
              uint32_t S = (instr >> 26) & 1;
              uint32_t J2 = (instr >> 11) & 1;
              uint32_t J1 = (instr >> 13) & 1;
              uint32_t imm6 = (instr >> 16) & 0x3F;
              uint32_t imm11 = instr & 0x7FF;
              uint32_t cond = (instr >> 22) & 0xF;
              int32_t imm32 = (S << 20) |  (J2 << 19) | (J1 << 18) | (imm6 << 12) | (imm11 << 1);
              imm32 = (imm32 << 11) >> 11;  // sign extend 21bit immediate
              opcode << "b";
              DumpCond(opcode, cond);
              opcode << ".w";
              DumpBranchTarget(args, instr_ptr + 4, imm32);
            } else if (op2 == 0x3B) {
              // Miscellaneous control instructions
              uint32_t op5 = (instr >> 4) & 0xF;
              switch (op5) {
                case 4: opcode << "dsb"; break;
                case 5: opcode << "dmb"; break;
                case 6: opcode << "isb"; break;
              }
            }
            break;
          case 2:
          case 1: case 3:
            break;
          case 4: case 6: case 5: case 7: {
            // BL, BLX (immediate)
            // |111|11|1|0000000000|11|1 |1|1 |10000000000|
            // |5 3|21|0|9876543  0|54|3 |2|1 |0    5    0|
            // |---|--|-|----------|--|--|-|--|-----------|
            // |332|22|2|2222221111|11|1 |1|1 |10000000000|
            // |1 9|87|6|5    0   6|54|3 |2|1 |0    5    0|
            // |---|--|-|----------|--|--|-|--|-----------|
            // |111|10|S| imm10    |11|J1|L|J2| imm11     |
            uint32_t S = (instr >> 26) & 1;
            uint32_t J2 = (instr >> 11) & 1;
            uint32_t L = (instr >> 12) & 1;
            uint32_t J1 = (instr >> 13) & 1;
            uint32_t imm10 = (instr >> 16) & 0x3FF;
            uint32_t imm11 = instr & 0x7FF;
            if (L == 0) {
              opcode << "bx";
            } else {
              opcode << "blx";
            }
            uint32_t I1 = ~(J1 ^ S);
            uint32_t I2 = ~(J2 ^ S);
            int32_t imm32 = (S << 24) | (I1 << 23) | (I2 << 22) | (imm10 << 12) | (imm11 << 1);
            imm32 = (imm32 << 8) >> 8;  // sign extend 24 bit immediate.
            DumpBranchTarget(args, instr_ptr + 4, imm32);
            break;
          }
        }
      }
      break;
    case 3:
      switch (op2) {
        case 0x00: case 0x02: case 0x04: case 0x06:  // 000xxx0
        case 0x08: case 0x0A: case 0x0C: case 0x0E: {
          // Store single data item
          // |111|11|100|000|0|0000|1111|110000|000000|
          // |5 3|21|098|765|4|3  0|5  2|10   6|5    0|
          // |---|--|---|---|-|----|----|------|------|
          // |332|22|222|222|2|1111|1111|110000|000000|
          // |1 9|87|654|321|0|9  6|5  2|10   6|5    0|
          // |---|--|---|---|-|----|----|------|------|
          // |111|11|000|op3|0|    |    |  op4 |      |
          uint32_t op3 = (instr >> 21) & 7;
          //uint32_t op4 = (instr >> 6) & 0x3F;
          switch (op3) {
            case 0x0: case 0x4: {
              // STRB Rt,[Rn,#+/-imm8]     - 111 11 00 0 0 00 0 nnnn tttt 1 PUWii ii iiii
              // STRB Rt,[Rn,Rm,lsl #imm2] - 111 11 00 0 0 00 0 nnnn tttt 0 00000 ii mmmm
              ArmRegister Rn(instr, 16);
              ArmRegister Rt(instr, 12);
              opcode << "strb";
              if ((instr & 0x800) != 0) {
                uint32_t imm8 = instr & 0xFF;
                args << Rt << ", [" << Rn << ",#" << imm8 << "]";
              } else {
                uint32_t imm2 = (instr >> 4) & 3;
                ArmRegister Rm(instr, 0);
                args << Rt << ", [" << Rn << ", " << Rm;
                if (imm2 != 0) {
                  args << ", " << "lsl #" << imm2;
                }
                args << "]";
              }
              break;
            }
            case 0x2: case 0x6: {
              ArmRegister Rn(instr, 16);
              ArmRegister Rt(instr, 12);
              if (op3 == 2) {
                if ((instr & 0x800) != 0) {
                  // STR Rt, [Rn, #imm8] - 111 11 000 010 0 nnnn tttt 1PUWiiiiiiii
                  uint32_t P = (instr >> 10) & 1;
                  uint32_t U = (instr >> 9) & 1;
                  uint32_t W = (instr >> 8) & 1;
                  uint32_t imm8 = instr & 0xFF;
                  int32_t imm32 = (imm8 << 24) >> 24;  // sign-extend imm8
                  if (Rn.r == 13 && P == 1 && U == 0 && W == 1 && imm32 == 4) {
                    opcode << "push";
                    args << Rt;
                  } else if (Rn.r == 15 || (P == 0 && W == 0)) {
                    opcode << "UNDEFINED";
                  } else {
                    if (P == 1 && U == 1 && W == 0) {
                      opcode << "strt";
                    } else {
                      opcode << "str";
                    }
                    args << Rt << ", [" << Rn;
                    if (P == 0 && W == 1) {
                      args << "], #" << imm32;
                    } else {
                      args << ", #" << imm32 << "]";
                      if (W == 1) {
                        args << "!";
                      }
                    }
                  }
                } else {
                  // STR Rt, [Rn, Rm, LSL #imm2] - 111 11 000 010 0 nnnn tttt 000000iimmmm
                  ArmRegister Rn(instr, 16);
                  ArmRegister Rt(instr, 12);
                  ArmRegister Rm(instr, 0);
                  uint32_t imm2 = (instr >> 4) & 3;
                  opcode << "str.w";
                  args << Rt << ", [" << Rn << ", " << Rm;
                  if (imm2 != 0) {
                    args << ", lsl #" << imm2;
                  }
                  args << "]";
                }
              } else if (op3 == 6) {
                // STR.W Rt, [Rn, #imm12] - 111 11 000 110 0 nnnn tttt iiiiiiiiiiii
                uint32_t imm12 = instr & 0xFFF;
                opcode << "str.w";
                args << Rt << ", [" << Rn << ", #" << imm12 << "]";
              }
              break;
            }
          }

          break;
        }
        case 0x03: case 0x0B: case 0x13: case 0x1B: { // 00xx011
          // Load halfword
          // |111|11|10|0 0|00|0|0000|1111|110000|000000|
          // |5 3|21|09|8 7|65|4|3  0|5  2|10   6|5    0|
          // |---|--|--|---|--|-|----|----|------|------|
          // |332|22|22|2 2|22|2|1111|1111|110000|000000|
          // |1 9|87|65|4 3|21|0|9  6|5  2|10   6|5    0|
          // |---|--|--|---|--|-|----|----|------|------|
          // |111|11|00|op3|01|1| Rn | Rt | op4  |      |
          // |111|11| op2       |    |    | imm12       |
          uint32_t op3 = (instr >> 23) & 3;
          ArmRegister Rn(instr, 16);
          ArmRegister Rt(instr, 12);
          if (Rt.r != 15) {
            if (op3 == 1) {
              // LDRH.W Rt, [Rn, #imm12]       - 111 11 00 01 011 nnnn tttt iiiiiiiiiiii
              uint32_t imm12 = instr & 0xFFF;
              opcode << "ldrh.w";
              args << Rt << ", [" << Rn << ", #" << imm12 << "]";
              if (Rn.r == 9) {
                args << "  ; ";
                Thread::DumpThreadOffset(args, imm12, 4);
              } else if (Rn.r == 15) {
                intptr_t lit_adr = reinterpret_cast<intptr_t>(instr_ptr);
                lit_adr = RoundDown(lit_adr, 4) + 4 + imm12;
                args << "  ; " << reinterpret_cast<void*>(*reinterpret_cast<int32_t*>(lit_adr));
              }
            } else if (op3 == 3) {
              // LDRSH.W Rt, [Rn, #imm12]      - 111 11 00 11 011 nnnn tttt iiiiiiiiiiii
              uint32_t imm12 = instr & 0xFFF;
              opcode << "ldrsh.w";
              args << Rt << ", [" << Rn << ", #" << imm12 << "]";
              if (Rn.r == 9) {
                args << "  ; ";
                Thread::DumpThreadOffset(args, imm12, 4);
              } else if (Rn.r == 15) {
                intptr_t lit_adr = reinterpret_cast<intptr_t>(instr_ptr);
                lit_adr = RoundDown(lit_adr, 4) + 4 + imm12;
                args << "  ; " << reinterpret_cast<void*>(*reinterpret_cast<int32_t*>(lit_adr));
              }
            }
          }
          break;
        }
        case 0x05: case 0x0D: case 0x15: case 0x1D: { // 00xx101
          // Load word
          // |111|11|10|0 0|00|0|0000|1111|110000|000000|
          // |5 3|21|09|8 7|65|4|3  0|5  2|10   6|5    0|
          // |---|--|--|---|--|-|----|----|------|------|
          // |332|22|22|2 2|22|2|1111|1111|110000|000000|
          // |1 9|87|65|4 3|21|0|9  6|5  2|10   6|5    0|
          // |---|--|--|---|--|-|----|----|------|------|
          // |111|11|00|op3|10|1| Rn | Rt | op4  |      |
          // |111|11| op2       |    |    | imm12       |
          uint32_t op3 = (instr >> 23) & 3;
          uint32_t op4 = (instr >> 6) & 0x3F;
          ArmRegister Rn(instr, 16);
          ArmRegister Rt(instr, 12);
          if (op3 == 1 || Rn.r == 15) {
            // LDR.W Rt, [Rn, #imm12]          - 111 11 00 00 101 nnnn tttt iiiiiiiiiiii
            // LDR.W Rt, [PC, #imm12]          - 111 11 00 0x 101 1111 tttt iiiiiiiiiiii
            uint32_t imm12 = instr & 0xFFF;
            opcode << "ldr.w";
            args << Rt << ", [" << Rn << ", #" << imm12 << "]";
            if (Rn.r == 9) {
              args << "  ; ";
              Thread::DumpThreadOffset(args, imm12, 4);
            } else if (Rn.r == 15) {
              intptr_t lit_adr = reinterpret_cast<intptr_t>(instr_ptr);
              lit_adr = RoundDown(lit_adr, 4) + 4 + imm12;
              args << "  ; " << reinterpret_cast<void*>(*reinterpret_cast<int32_t*>(lit_adr));
            }
          } else if (op4 == 0) {
            // LDR.W Rt, [Rn, Rm{, LSL #imm2}] - 111 11 00 00 101 nnnn tttt 000000iimmmm
            uint32_t imm2 = (instr >> 4) & 0xF;
            ArmRegister rm(instr, 0);
            opcode << "ldr.w";
            args << Rt << ", [" << Rn << ", " << rm;
            if (imm2 != 0) {
              args << ", lsl #" << imm2;
            }
            args << "]";
          } else {
            // LDRT Rt, [Rn, #imm8]            - 111 11 00 00 101 nnnn tttt 1110iiiiiiii
            uint32_t imm8 = instr & 0xFF;
            opcode << "ldrt";
            args << Rt << ", [" << Rn << ", #" << imm8 << "]";
          }
          break;
        }
      }
    default:
      break;
  }

  // Apply any IT-block conditions to the opcode if necessary.
  if (!it_conditions_.empty()) {
    opcode << it_conditions_.back();
    it_conditions_.pop_back();
  }

  os << StringPrintf("%p: %08x\t%-7s ", instr_ptr, instr, opcode.str().c_str()) << args.str() << '\n';
  return 4;
}

size_t DisassemblerArm::DumpThumb16(std::ostream& os, const uint8_t* instr_ptr) {
  uint16_t instr = ReadU16(instr_ptr);
  bool is_32bit = ((instr & 0xF000) == 0xF000) || ((instr & 0xF800) == 0xE800);
  if (is_32bit) {
    return DumpThumb32(os, instr_ptr);
  } else {
    std::ostringstream opcode;
    std::ostringstream args;
    uint16_t opcode1 = instr >> 10;
    if (opcode1 < 0x10) {
      // shift (immediate), add, subtract, move, and compare
      uint16_t opcode2 = instr >> 9;
      switch (opcode2) {
        case 0x0: case 0x1: case 0x2: case 0x3: case 0x4: case 0x5: case 0x6: case 0x7:
        case 0x8: case 0x9: case 0xA: case 0xB: {
          // Logical shift left     - 00 000xx xxxxxxxxx
          // Logical shift right    - 00 001xx xxxxxxxxx
          // Arithmetic shift right - 00 010xx xxxxxxxxx
          uint16_t imm5 = (instr >> 6) & 0x1F;
          ThumbRegister rm(instr, 3);
          ThumbRegister Rd(instr, 7);
          if (opcode2 <= 3) {
            opcode << "lsls";
          } else if (opcode2 <= 7) {
            opcode << "lsrs";
          } else {
            opcode << "asrs";
          }
          args << Rd << ", " << rm << ", #" << imm5;
          break;
        }
        case 0xC: case 0xD: case 0xE: case 0xF: {
          // Add register        - 00 01100 mmm nnn ddd
          // Sub register        - 00 01101 mmm nnn ddd
          // Add 3-bit immediate - 00 01110 iii nnn ddd
          // Sub 3-bit immediate - 00 01111 iii nnn ddd
          uint16_t imm3_or_Rm = (instr >> 6) & 7;
          ThumbRegister Rn(instr, 3);
          ThumbRegister Rd(instr, 0);
          if ((opcode2 & 2) != 0 && imm3_or_Rm == 0) {
            opcode << "mov";
          } else {
            if ((opcode2 & 1) == 0) {
              opcode << "adds";
            } else {
              opcode << "subs";
            }
          }
          args << Rd << ", " << Rn;
          if ((opcode2 & 2) == 0) {
            ArmRegister Rm(imm3_or_Rm);
            args << ", " << Rm;
          } else if (imm3_or_Rm != 0) {
            args << ", #" << imm3_or_Rm;
          }
          break;
        }
        case 0x10: case 0x11: case 0x12: case 0x13:
        case 0x14: case 0x15: case 0x16: case 0x17:
        case 0x18: case 0x19: case 0x1A: case 0x1B:
        case 0x1C: case 0x1D: case 0x1E: case 0x1F: {
          // MOVS Rd, #imm8 - 00100 ddd iiiiiiii
          // CMP  Rn, #imm8 - 00101 nnn iiiiiiii
          // ADDS Rn, #imm8 - 00110 nnn iiiiiiii
          // SUBS Rn, #imm8 - 00111 nnn iiiiiiii
          ThumbRegister Rn(instr, 8);
          uint16_t imm8 = instr & 0xFF;
          switch (opcode2 >> 2) {
            case 4: opcode << "movs"; break;
            case 5: opcode << "cmp"; break;
            case 6: opcode << "adds"; break;
            case 7: opcode << "subs"; break;
          }
          args << Rn << ", #" << imm8;
          break;
        }
        default:
          break;
      }
    } else if (opcode1 == 0x10) {
      // Data-processing
      uint16_t opcode2 = (instr >> 6) & 0xF;
      ThumbRegister rm(instr, 3);
      ThumbRegister rdn(instr, 0);
      opcode << kThumbDataProcessingOperations[opcode2];
      args << rdn << ", " << rm;
    } else if (opcode1 == 0x11) {
      // Special data instructions and branch and exchange
      uint16_t opcode2 = (instr >> 6) & 0x0F;
      switch (opcode2) {
        case 0x0: case 0x1: case 0x2: case 0x3: {
          // Add low registers  - 010001 0000 xxxxxx
          // Add high registers - 010001 0001/001x xxxxxx
          uint16_t DN = (instr >> 7) & 1;
          ArmRegister rm(instr, 3);
          uint16_t Rdn = instr & 7;
          ArmRegister DN_Rdn((DN << 3) | Rdn);
          opcode << "add";
          args << DN_Rdn << ", " << rm;
          break;
        }
        case 0x8: case 0x9: case 0xA: case 0xB: {
          // Move low registers  - 010001 1000 xxxxxx
          // Move high registers - 010001 1001/101x xxxxxx
          uint16_t DN = (instr >> 7) & 1;
          ArmRegister rm(instr, 3);
          uint16_t Rdn = instr & 7;
          ArmRegister DN_Rdn((DN << 3) | Rdn);
          opcode << "mov";
          args << DN_Rdn << ", " << rm;
          break;
        }
        case 0x5: case 0x6: case 0x7: {
          // Compare high registers - 010001 0101/011x xxxxxx
          uint16_t N = (instr >> 7) & 1;
          ArmRegister rm(instr, 3);
          uint16_t Rn = instr & 7;
          ArmRegister N_Rn((N << 3) | Rn);
          opcode << "cmp";
          args << N_Rn << ", " << rm;
          break;
        }
        case 0xC: case 0xD: case 0xE: case 0xF: {
          // Branch and exchange           - 010001 110x xxxxxx
          // Branch with link and exchange - 010001 111x xxxxxx
          ArmRegister rm(instr, 3);
          opcode << ((opcode2 & 0x2) == 0 ? "bx" : "blx");
          args << rm;
          break;
        }
        default:
          break;
      }
    } else if (opcode1 == 0x12 || opcode1 == 0x13) {  // 01001x
      ThumbRegister Rt(instr, 8);
      uint16_t imm8 = instr & 0xFF;
      opcode << "ldr";
      args << Rt << ", [pc, #" << (imm8 << 2) << "]";
    } else if ((opcode1 >= 0x14 && opcode1 <= 0x17) ||  // 0101xx
               (opcode1 >= 0x18 && opcode1 <= 0x1f) ||  // 011xxx
               (opcode1 >= 0x20 && opcode1 <= 0x27)) {  // 100xxx
      // Load/store single data item
      uint16_t opA = (instr >> 12) & 0xF;
      if (opA == 0x5) {
        uint16_t opB = (instr >> 9) & 0x7;
        ThumbRegister Rm(instr, 6);
        ThumbRegister Rn(instr, 3);
        ThumbRegister Rt(instr, 0);
        switch(opB) {
          case 0: opcode << "str"; break;
          case 1: opcode << "strh"; break;
          case 2: opcode << "strb"; break;
          case 3: opcode << "ldrsb"; break;
          case 4: opcode << "ldr"; break;
          case 5: opcode << "ldrh"; break;
          case 6: opcode << "ldrb"; break;
          case 7: opcode << "ldrsh"; break;
        }
        args << Rt << ", [" << Rn << ", " << Rm << "]";
      } else if (opA == 9) {
        uint16_t opB = (instr >> 11) & 1;
        ThumbRegister Rt(instr, 8);
        uint16_t imm8 = instr & 0xFF;
        opcode << (opB == 0 ? "str" : "ldr");
        args << Rt << ", [sp, #" << (imm8 << 2) << "]";
      } else {
        uint16_t imm5 = (instr >> 6) & 0x1F;
        uint16_t opB = (instr >> 11) & 1;
        ThumbRegister Rn(instr, 3);
        ThumbRegister Rt(instr, 0);
        switch(opA) {
          case 6:
            imm5 <<= 2;
            opcode << (opB == 0 ? "str" : "ldr");
            break;
          case 7:
            imm5 <<= 0;
            opcode << (opB == 0 ? "strb" : "ldrb");
            break;
          case 8:
            imm5 <<= 1;
            opcode << (opB == 0 ? "strh" : "ldrh");
            break;
        }
        args << Rt << ", [" << Rn << ", #" << imm5 << "]";
      }
    } else if (opcode1 >= 0x34 && opcode1 <= 0x37) {  // 1101xx
      uint32_t imm8 = instr & 0xFF;
      uint32_t cond = (instr >> 8) & 0xF;
      opcode << "b";
      DumpCond(opcode, cond);
      DumpBranchTarget(args, instr_ptr + 4, (imm8 << 1));
    } else if ((instr & 0xF800) == 0xA800) {
      // Generate SP-relative address
      ThumbRegister rd(instr, 8);
      int imm8 = instr & 0xFF;
      opcode << "add";
      args << rd << ", sp, #" << (imm8 << 2);
    } else if ((instr & 0xF000) == 0xB000) {
      // Miscellaneous 16-bit instructions
      uint16_t opcode2 = (instr >> 5) & 0x7F;
      switch (opcode2) {
        case 0x00: case 0x01: case 0x02: case 0x03: case 0x04: case 0x05: case 0x06: case 0x07: {
          // Add immediate to SP        - 1011 00000 ii iiiii
          // Subtract immediate from SP - 1011 00001 ii iiiii
          int imm7 = instr & 0x7F;
          opcode << ((opcode2 & 4) == 0 ? "add" : "sub");
          args << "sp, sp, #" << (imm7 << 2);
          break;
        }
        case 0x08: case 0x09: case 0x0A: case 0x0B:  // 0001xxx
        case 0x0C: case 0x0D: case 0x0E: case 0x0F:
        case 0x48: case 0x49: case 0x4A: case 0x4B:  // 1001xxx
        case 0x4C: case 0x4D: case 0x4E: case 0x4F: {
          // CBNZ, CBZ
          uint16_t op = (instr >> 11) & 1;
          uint16_t i = (instr >> 9) & 1;
          uint16_t imm5 = (instr >> 3) & 0x1F;
          ThumbRegister Rn(instr, 0);
          opcode << (op != 0 ? "cbnz" : "cbz");
          uint32_t imm32 = (i << 7) | (imm5 << 1);
          args << Rn << ", ";
          DumpBranchTarget(args, instr_ptr + 4, imm32);
          break;
        }
        case 0x78: case 0x79: case 0x7A: case 0x7B:  // 1111xxx
        case 0x7C: case 0x7D: case 0x7E: case 0x7F: {
          // If-Then, and hints
          uint16_t opA = (instr >> 4) & 0xF;
          uint16_t opB = instr & 0xF;
          if (opB == 0) {
            switch (opA) {
              case 0: opcode << "nop"; break;
              case 1: opcode << "yield"; break;
              case 2: opcode << "wfe";  break;
              case 3: opcode << "sev"; break;
              default: break;
            }
          } else {
            uint32_t first_cond = opA;
            uint32_t mask = opB;
            opcode << "it";

            // Flesh out the base "it" opcode with the specific collection of 't's and 'e's,
            // and store up the actual condition codes we'll want to add to the next few opcodes.
            size_t count = 3 - CTZ(mask);
            it_conditions_.resize(count + 2); // Plus the implicit 't', plus the "" for the IT itself.
            for (size_t i = 0; i < count; ++i) {
              bool positive_cond = ((first_cond & 1) != 0);
              bool positive_mask = ((mask & (1 << (3 - i))) != 0);
              if (positive_mask == positive_cond) {
                opcode << 't';
                it_conditions_[i] = kConditionCodeNames[first_cond];
              } else {
                opcode << 'e';
                it_conditions_[i] = kConditionCodeNames[first_cond ^ 1];
              }
            }
            it_conditions_[count] = kConditionCodeNames[first_cond]; // The implicit 't'.

            it_conditions_[count + 1] = ""; // No condition code for the IT itself...
            DumpCond(args, first_cond); // ...because it's considered an argument.
          }
          break;
        }
        default:
          break;
      }
    } else if (((instr & 0xF000) == 0x5000) || ((instr & 0xE000) == 0x6000) ||
        ((instr & 0xE000) == 0x8000)) {
      // Load/store single data item
      uint16_t opA = instr >> 12;
      //uint16_t opB = (instr >> 9) & 7;
      switch (opA) {
        case 0x6: {
          // STR Rt, [Rn, #imm] - 01100 iiiii nnn ttt
          // LDR Rt, [Rn, #imm] - 01101 iiiii nnn ttt
          uint16_t imm5 = (instr >> 6) & 0x1F;
          ThumbRegister Rn(instr, 3);
          ThumbRegister Rt(instr, 0);
          opcode << ((instr & 0x800) == 0 ? "str" : "ldr");
          args << Rt << ", [" << Rn << ", #" << (imm5 << 2) << "]";
          break;
        }
        case 0x9: {
          // STR Rt, [SP, #imm] - 01100 ttt iiiiiiii
          // LDR Rt, [SP, #imm] - 01101 ttt iiiiiiii
          uint16_t imm8 = instr & 0xFF;
          ThumbRegister Rt(instr, 8);
          opcode << ((instr & 0x800) == 0 ? "str" : "ldr");
          args << Rt << ", [sp, #" << (imm8 << 2) << "]";
          break;
        }
        default:
          break;
      }
    } else if (opcode1 == 0x38 || opcode1 == 0x39) {
      uint16_t imm11 = instr & 0x7FFF;
      int32_t imm32 = imm11 << 1;
      imm32 = (imm32 << 20) >> 20;  // sign extend 12 bit immediate
      opcode << "b";
      DumpBranchTarget(args, instr_ptr + 4, imm32);
    }

    // Apply any IT-block conditions to the opcode if necessary.
    if (!it_conditions_.empty()) {
      opcode << it_conditions_.back();
      it_conditions_.pop_back();
    }

    os << StringPrintf("%p: %04x    \t%-7s ", instr_ptr, instr, opcode.str().c_str()) << args.str() << '\n';
  }
  return 2;
}

}  // namespace arm
}  // namespace art