Experimental parser: merge to r19637

src/a64/disasm-a64.cc

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <string.h>
+
+#include "v8.h"
+
+#if V8_TARGET_ARCH_A64
+
+#include "disasm.h"
+#include "a64/decoder-a64-inl.h"
+#include "a64/disasm-a64.h"
+#include "macro-assembler.h"
+#include "platform.h"
+
+namespace v8 {
+namespace internal {
+
+
+Disassembler::Disassembler() {
+  buffer_size_ = 256;
+  buffer_ = reinterpret_cast<char*>(malloc(buffer_size_));
+  buffer_pos_ = 0;
+  own_buffer_ = true;
+}
+
+
+Disassembler::Disassembler(char* text_buffer, int buffer_size) {
+  buffer_size_ = buffer_size;
+  buffer_ = text_buffer;
+  buffer_pos_ = 0;
+  own_buffer_ = false;
+}
+
+
+Disassembler::~Disassembler() {
+  if (own_buffer_) {
+    free(buffer_);
+  }
+}
+
+
+char* Disassembler::GetOutput() {
+  return buffer_;
+}
+
+
+void Disassembler::VisitAddSubImmediate(Instruction* instr) {
+  bool rd_is_zr = RdIsZROrSP(instr);
+  bool stack_op = (rd_is_zr || RnIsZROrSP(instr)) &&
+                  (instr->ImmAddSub() == 0) ? true : false;
+  const char *mnemonic = "";
+  const char *form = "'Rds, 'Rns, 'IAddSub";
+  const char *form_cmp = "'Rns, 'IAddSub";
+  const char *form_mov = "'Rds, 'Rns";
+
+  switch (instr->Mask(AddSubImmediateMask)) {
+    case ADD_w_imm:
+    case ADD_x_imm: {
+      mnemonic = "add";
+      if (stack_op) {
+        mnemonic = "mov";
+        form = form_mov;
+      }
+      break;
+    }
+    case ADDS_w_imm:
+    case ADDS_x_imm: {
+      mnemonic = "adds";
+      if (rd_is_zr) {
+        mnemonic = "cmn";
+        form = form_cmp;
+      }
+      break;
+    }
+    case SUB_w_imm:
+    case SUB_x_imm: mnemonic = "sub"; break;
+    case SUBS_w_imm:
+    case SUBS_x_imm: {
+      mnemonic = "subs";
+      if (rd_is_zr) {
+        mnemonic = "cmp";
+        form = form_cmp;
+      }
+      break;
+    }
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitAddSubShifted(Instruction* instr) {
+  bool rd_is_zr = RdIsZROrSP(instr);
+  bool rn_is_zr = RnIsZROrSP(instr);
+  const char *mnemonic = "";
+  const char *form = "'Rd, 'Rn, 'Rm'HDP";
+  const char *form_cmp = "'Rn, 'Rm'HDP";
+  const char *form_neg = "'Rd, 'Rm'HDP";
+
+  switch (instr->Mask(AddSubShiftedMask)) {
+    case ADD_w_shift:
+    case ADD_x_shift: mnemonic = "add"; break;
+    case ADDS_w_shift:
+    case ADDS_x_shift: {
+      mnemonic = "adds";
+      if (rd_is_zr) {
+        mnemonic = "cmn";
+        form = form_cmp;
+      }
+      break;
+    }
+    case SUB_w_shift:
+    case SUB_x_shift: {
+      mnemonic = "sub";
+      if (rn_is_zr) {
+        mnemonic = "neg";
+        form = form_neg;
+      }
+      break;
+    }
+    case SUBS_w_shift:
+    case SUBS_x_shift: {
+      mnemonic = "subs";
+      if (rd_is_zr) {
+        mnemonic = "cmp";
+        form = form_cmp;
+      } else if (rn_is_zr) {
+        mnemonic = "negs";
+        form = form_neg;
+      }
+      break;
+    }
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitAddSubExtended(Instruction* instr) {
+  bool rd_is_zr = RdIsZROrSP(instr);
+  const char *mnemonic = "";
+  Extend mode = static_cast<Extend>(instr->ExtendMode());
+  const char *form = ((mode == UXTX) || (mode == SXTX)) ?
+                     "'Rds, 'Rns, 'Xm'Ext" : "'Rds, 'Rns, 'Wm'Ext";
+  const char *form_cmp = ((mode == UXTX) || (mode == SXTX)) ?
+                         "'Rns, 'Xm'Ext" : "'Rns, 'Wm'Ext";
+
+  switch (instr->Mask(AddSubExtendedMask)) {
+    case ADD_w_ext:
+    case ADD_x_ext: mnemonic = "add"; break;
+    case ADDS_w_ext:
+    case ADDS_x_ext: {
+      mnemonic = "adds";
+      if (rd_is_zr) {
+        mnemonic = "cmn";
+        form = form_cmp;
+      }
+      break;
+    }
+    case SUB_w_ext:
+    case SUB_x_ext: mnemonic = "sub"; break;
+    case SUBS_w_ext:
+    case SUBS_x_ext: {
+      mnemonic = "subs";
+      if (rd_is_zr) {
+        mnemonic = "cmp";
+        form = form_cmp;
+      }
+      break;
+    }
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitAddSubWithCarry(Instruction* instr) {
+  bool rn_is_zr = RnIsZROrSP(instr);
+  const char *mnemonic = "";
+  const char *form = "'Rd, 'Rn, 'Rm";
+  const char *form_neg = "'Rd, 'Rm";
+
+  switch (instr->Mask(AddSubWithCarryMask)) {
+    case ADC_w:
+    case ADC_x: mnemonic = "adc"; break;
+    case ADCS_w:
+    case ADCS_x: mnemonic = "adcs"; break;
+    case SBC_w:
+    case SBC_x: {
+      mnemonic = "sbc";
+      if (rn_is_zr) {
+        mnemonic = "ngc";
+        form = form_neg;
+      }
+      break;
+    }
+    case SBCS_w:
+    case SBCS_x: {
+      mnemonic = "sbcs";
+      if (rn_is_zr) {
+        mnemonic = "ngcs";
+        form = form_neg;
+      }
+      break;
+    }
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitLogicalImmediate(Instruction* instr) {
+  bool rd_is_zr = RdIsZROrSP(instr);
+  bool rn_is_zr = RnIsZROrSP(instr);
+  const char *mnemonic = "";
+  const char *form = "'Rds, 'Rn, 'ITri";
+
+  if (instr->ImmLogical() == 0) {
+    // The immediate encoded in the instruction is not in the expected format.
+    Format(instr, "unallocated", "(LogicalImmediate)");
+    return;
+  }
+
+  switch (instr->Mask(LogicalImmediateMask)) {
+    case AND_w_imm:
+    case AND_x_imm: mnemonic = "and"; break;
+    case ORR_w_imm:
+    case ORR_x_imm: {
+      mnemonic = "orr";
+      unsigned reg_size = (instr->SixtyFourBits() == 1) ? kXRegSize
+                                                        : kWRegSize;
+      if (rn_is_zr && !IsMovzMovnImm(reg_size, instr->ImmLogical())) {
+        mnemonic = "mov";
+        form = "'Rds, 'ITri";
+      }
+      break;
+    }
+    case EOR_w_imm:
+    case EOR_x_imm: mnemonic = "eor"; break;
+    case ANDS_w_imm:
+    case ANDS_x_imm: {
+      mnemonic = "ands";
+      if (rd_is_zr) {
+        mnemonic = "tst";
+        form = "'Rn, 'ITri";
+      }
+      break;
+    }
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+bool Disassembler::IsMovzMovnImm(unsigned reg_size, uint64_t value) {
+  ASSERT((reg_size == kXRegSize) ||
+         ((reg_size == kWRegSize) && (value <= 0xffffffff)));
+
+  // Test for movz: 16-bits set at positions 0, 16, 32 or 48.
+  if (((value & 0xffffffffffff0000UL) == 0UL) ||
+      ((value & 0xffffffff0000ffffUL) == 0UL) ||
+      ((value & 0xffff0000ffffffffUL) == 0UL) ||
+      ((value & 0x0000ffffffffffffUL) == 0UL)) {
+    return true;
+  }
+
+  // Test for movn: NOT(16-bits set at positions 0, 16, 32 or 48).
+  if ((reg_size == kXRegSize) &&
+      (((value & 0xffffffffffff0000UL) == 0xffffffffffff0000UL) ||
+       ((value & 0xffffffff0000ffffUL) == 0xffffffff0000ffffUL) ||
+       ((value & 0xffff0000ffffffffUL) == 0xffff0000ffffffffUL) ||
+       ((value & 0x0000ffffffffffffUL) == 0x0000ffffffffffffUL))) {
+    return true;
+  }
+  if ((reg_size == kWRegSize) &&
+      (((value & 0xffff0000) == 0xffff0000) ||
+       ((value & 0x0000ffff) == 0x0000ffff))) {
+    return true;
+  }
+  return false;
+}
+
+
+void Disassembler::VisitLogicalShifted(Instruction* instr) {
+  bool rd_is_zr = RdIsZROrSP(instr);
+  bool rn_is_zr = RnIsZROrSP(instr);
+  const char *mnemonic = "";
+  const char *form = "'Rd, 'Rn, 'Rm'HLo";
+
+  switch (instr->Mask(LogicalShiftedMask)) {
+    case AND_w:
+    case AND_x: mnemonic = "and"; break;
+    case BIC_w:
+    case BIC_x: mnemonic = "bic"; break;
+    case EOR_w:
+    case EOR_x: mnemonic = "eor"; break;
+    case EON_w:
+    case EON_x: mnemonic = "eon"; break;
+    case BICS_w:
+    case BICS_x: mnemonic = "bics"; break;
+    case ANDS_w:
+    case ANDS_x: {
+      mnemonic = "ands";
+      if (rd_is_zr) {
+        mnemonic = "tst";
+        form = "'Rn, 'Rm'HLo";
+      }
+      break;
+    }
+    case ORR_w:
+    case ORR_x: {
+      mnemonic = "orr";
+      if (rn_is_zr && (instr->ImmDPShift() == 0) && (instr->ShiftDP() == LSL)) {
+        mnemonic = "mov";
+        form = "'Rd, 'Rm";
+      }
+      break;
+    }
+    case ORN_w:
+    case ORN_x: {
+      mnemonic = "orn";
+      if (rn_is_zr) {
+        mnemonic = "mvn";
+        form = "'Rd, 'Rm'HLo";
+      }
+      break;
+    }
+    default: UNREACHABLE();
+  }
+
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitConditionalCompareRegister(Instruction* instr) {
+  const char *mnemonic = "";
+  const char *form = "'Rn, 'Rm, 'INzcv, 'Cond";
+
+  switch (instr->Mask(ConditionalCompareRegisterMask)) {
+    case CCMN_w:
+    case CCMN_x: mnemonic = "ccmn"; break;
+    case CCMP_w:
+    case CCMP_x: mnemonic = "ccmp"; break;
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitConditionalCompareImmediate(Instruction* instr) {
+  const char *mnemonic = "";
+  const char *form = "'Rn, 'IP, 'INzcv, 'Cond";
+
+  switch (instr->Mask(ConditionalCompareImmediateMask)) {
+    case CCMN_w_imm:
+    case CCMN_x_imm: mnemonic = "ccmn"; break;
+    case CCMP_w_imm:
+    case CCMP_x_imm: mnemonic = "ccmp"; break;
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitConditionalSelect(Instruction* instr) {
+  bool rnm_is_zr = (RnIsZROrSP(instr) && RmIsZROrSP(instr));
+  bool rn_is_rm = (instr->Rn() == instr->Rm());
+  const char *mnemonic = "";
+  const char *form = "'Rd, 'Rn, 'Rm, 'Cond";
+  const char *form_test = "'Rd, 'CInv";
+  const char *form_update = "'Rd, 'Rn, 'CInv";
+
+  Condition cond = static_cast<Condition>(instr->Condition());
+  bool invertible_cond = (cond != al) && (cond != nv);
+
+  switch (instr->Mask(ConditionalSelectMask)) {
+    case CSEL_w:
+    case CSEL_x: mnemonic = "csel"; break;
+    case CSINC_w:
+    case CSINC_x: {
+      mnemonic = "csinc";
+      if (rnm_is_zr && invertible_cond) {
+        mnemonic = "cset";
+        form = form_test;
+      } else if (rn_is_rm && invertible_cond) {
+        mnemonic = "cinc";
+        form = form_update;
+      }
+      break;
+    }
+    case CSINV_w:
+    case CSINV_x: {
+      mnemonic = "csinv";
+      if (rnm_is_zr && invertible_cond) {
+        mnemonic = "csetm";
+        form = form_test;
+      } else if (rn_is_rm && invertible_cond) {
+        mnemonic = "cinv";
+        form = form_update;
+      }
+      break;
+    }
+    case CSNEG_w:
+    case CSNEG_x: {
+      mnemonic = "csneg";
+      if (rn_is_rm && invertible_cond) {
+        mnemonic = "cneg";
+        form = form_update;
+      }
+      break;
+    }
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitBitfield(Instruction* instr) {
+  unsigned s = instr->ImmS();
+  unsigned r = instr->ImmR();
+  unsigned rd_size_minus_1 =
+    ((instr->SixtyFourBits() == 1) ? kXRegSize : kWRegSize) - 1;
+  const char *mnemonic = "";
+  const char *form = "";
+  const char *form_shift_right = "'Rd, 'Rn, 'IBr";
+  const char *form_extend = "'Rd, 'Wn";
+  const char *form_bfiz = "'Rd, 'Rn, 'IBZ-r, 'IBs+1";
+  const char *form_bfx = "'Rd, 'Rn, 'IBr, 'IBs-r+1";
+  const char *form_lsl = "'Rd, 'Rn, 'IBZ-r";
+
+  switch (instr->Mask(BitfieldMask)) {
+    case SBFM_w:
+    case SBFM_x: {
+      mnemonic = "sbfx";
+      form = form_bfx;
+      if (r == 0) {
+        form = form_extend;
+        if (s == 7) {
+          mnemonic = "sxtb";
+        } else if (s == 15) {
+          mnemonic = "sxth";
+        } else if ((s == 31) && (instr->SixtyFourBits() == 1)) {
+          mnemonic = "sxtw";
+        } else {
+          form = form_bfx;
+        }
+      } else if (s == rd_size_minus_1) {
+        mnemonic = "asr";
+        form = form_shift_right;
+      } else if (s < r) {
+        mnemonic = "sbfiz";
+        form = form_bfiz;
+      }
+      break;
+    }
+    case UBFM_w:
+    case UBFM_x: {
+      mnemonic = "ubfx";
+      form = form_bfx;
+      if (r == 0) {
+        form = form_extend;
+        if (s == 7) {
+          mnemonic = "uxtb";
+        } else if (s == 15) {
+          mnemonic = "uxth";
+        } else {
+          form = form_bfx;
+        }
+      }
+      if (s == rd_size_minus_1) {
+        mnemonic = "lsr";
+        form = form_shift_right;
+      } else if (r == s + 1) {
+        mnemonic = "lsl";
+        form = form_lsl;
+      } else if (s < r) {
+        mnemonic = "ubfiz";
+        form = form_bfiz;
+      }
+      break;
+    }
+    case BFM_w:
+    case BFM_x: {
+      mnemonic = "bfxil";
+      form = form_bfx;
+      if (s < r) {
+        mnemonic = "bfi";
+        form = form_bfiz;
+      }
+    }
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitExtract(Instruction* instr) {
+  const char *mnemonic = "";
+  const char *form = "'Rd, 'Rn, 'Rm, 'IExtract";
+
+  switch (instr->Mask(ExtractMask)) {
+    case EXTR_w:
+    case EXTR_x: {
+      if (instr->Rn() == instr->Rm()) {
+        mnemonic = "ror";
+        form = "'Rd, 'Rn, 'IExtract";
+      } else {
+        mnemonic = "extr";
+      }
+      break;
+    }
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitPCRelAddressing(Instruction* instr) {
+  switch (instr->Mask(PCRelAddressingMask)) {
+    case ADR: Format(instr, "adr", "'Xd, 'AddrPCRelByte"); break;
+    // ADRP is not implemented.
+    default: Format(instr, "unimplemented", "(PCRelAddressing)");
+  }
+}
+
+
+void Disassembler::VisitConditionalBranch(Instruction* instr) {
+  switch (instr->Mask(ConditionalBranchMask)) {
+    case B_cond: Format(instr, "b.'CBrn", "'BImmCond"); break;
+    default: UNREACHABLE();
+  }
+}
+
+
+void Disassembler::VisitUnconditionalBranchToRegister(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "'Xn";
+
+  switch (instr->Mask(UnconditionalBranchToRegisterMask)) {
+    case BR: mnemonic = "br"; break;
+    case BLR: mnemonic = "blr"; break;
+    case RET: {
+      mnemonic = "ret";
+      if (instr->Rn() == kLinkRegCode) {
+        form = NULL;
+      }
+      break;
+    }
+    default: form = "(UnconditionalBranchToRegister)";
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitUnconditionalBranch(Instruction* instr) {
+  const char *mnemonic = "";
+  const char *form = "'BImmUncn";
+
+  switch (instr->Mask(UnconditionalBranchMask)) {
+    case B: mnemonic = "b"; break;
+    case BL: mnemonic = "bl"; break;
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitDataProcessing1Source(Instruction* instr) {
+  const char *mnemonic = "";
+  const char *form = "'Rd, 'Rn";
+
+  switch (instr->Mask(DataProcessing1SourceMask)) {
+    #define FORMAT(A, B)  \
+    case A##_w:           \
+    case A##_x: mnemonic = B; break;
+    FORMAT(RBIT, "rbit");
+    FORMAT(REV16, "rev16");
+    FORMAT(REV, "rev");
+    FORMAT(CLZ, "clz");
+    FORMAT(CLS, "cls");
+    #undef FORMAT
+    case REV32_x: mnemonic = "rev32"; break;
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitDataProcessing2Source(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "'Rd, 'Rn, 'Rm";
+
+  switch (instr->Mask(DataProcessing2SourceMask)) {
+    #define FORMAT(A, B)  \
+    case A##_w:           \
+    case A##_x: mnemonic = B; break;
+    FORMAT(UDIV, "udiv");
+    FORMAT(SDIV, "sdiv");
+    FORMAT(LSLV, "lsl");
+    FORMAT(LSRV, "lsr");
+    FORMAT(ASRV, "asr");
+    FORMAT(RORV, "ror");
+    #undef FORMAT
+    default: form = "(DataProcessing2Source)";
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitDataProcessing3Source(Instruction* instr) {
+  bool ra_is_zr = RaIsZROrSP(instr);
+  const char *mnemonic = "";
+  const char *form = "'Xd, 'Wn, 'Wm, 'Xa";
+  const char *form_rrr = "'Rd, 'Rn, 'Rm";
+  const char *form_rrrr = "'Rd, 'Rn, 'Rm, 'Ra";
+  const char *form_xww = "'Xd, 'Wn, 'Wm";
+  const char *form_xxx = "'Xd, 'Xn, 'Xm";
+
+  switch (instr->Mask(DataProcessing3SourceMask)) {
+    case MADD_w:
+    case MADD_x: {
+      mnemonic = "madd";
+      form = form_rrrr;
+      if (ra_is_zr) {
+        mnemonic = "mul";
+        form = form_rrr;
+      }
+      break;
+    }
+    case MSUB_w:
+    case MSUB_x: {
+      mnemonic = "msub";
+      form = form_rrrr;
+      if (ra_is_zr) {
+        mnemonic = "mneg";
+        form = form_rrr;
+      }
+      break;
+    }
+    case SMADDL_x: {
+      mnemonic = "smaddl";
+      if (ra_is_zr) {
+        mnemonic = "smull";
+        form = form_xww;
+      }
+      break;
+    }
+    case SMSUBL_x: {
+      mnemonic = "smsubl";
+      if (ra_is_zr) {
+        mnemonic = "smnegl";
+        form = form_xww;
+      }
+      break;
+    }
+    case UMADDL_x: {
+      mnemonic = "umaddl";
+      if (ra_is_zr) {
+        mnemonic = "umull";
+        form = form_xww;
+      }
+      break;
+    }
+    case UMSUBL_x: {
+      mnemonic = "umsubl";
+      if (ra_is_zr) {
+        mnemonic = "umnegl";
+        form = form_xww;
+      }
+      break;
+    }
+    case SMULH_x: {
+      mnemonic = "smulh";
+      form = form_xxx;
+      break;
+    }
+    case UMULH_x: {
+      mnemonic = "umulh";
+      form = form_xxx;
+      break;
+    }
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitCompareBranch(Instruction* instr) {
+  const char *mnemonic = "";
+  const char *form = "'Rt, 'BImmCmpa";
+
+  switch (instr->Mask(CompareBranchMask)) {
+    case CBZ_w:
+    case CBZ_x: mnemonic = "cbz"; break;
+    case CBNZ_w:
+    case CBNZ_x: mnemonic = "cbnz"; break;
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitTestBranch(Instruction* instr) {
+  const char *mnemonic = "";
+  // If the top bit of the immediate is clear, the tested register is
+  // disassembled as Wt, otherwise Xt. As the top bit of the immediate is
+  // encoded in bit 31 of the instruction, we can reuse the Rt form, which
+  // uses bit 31 (normally "sf") to choose the register size.
+  const char *form = "'Rt, 'IS, 'BImmTest";
+
+  switch (instr->Mask(TestBranchMask)) {
+    case TBZ: mnemonic = "tbz"; break;
+    case TBNZ: mnemonic = "tbnz"; break;
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitMoveWideImmediate(Instruction* instr) {
+  const char *mnemonic = "";
+  const char *form = "'Rd, 'IMoveImm";
+
+  // Print the shift separately for movk, to make it clear which half word will
+  // be overwritten. Movn and movz print the computed immediate, which includes
+  // shift calculation.
+  switch (instr->Mask(MoveWideImmediateMask)) {
+    case MOVN_w:
+    case MOVN_x: mnemonic = "movn"; break;
+    case MOVZ_w:
+    case MOVZ_x: mnemonic = "movz"; break;
+    case MOVK_w:
+    case MOVK_x: mnemonic = "movk"; form = "'Rd, 'IMoveLSL"; break;
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+#define LOAD_STORE_LIST(V)    \
+  V(STRB_w, "strb", "'Wt")    \
+  V(STRH_w, "strh", "'Wt")    \
+  V(STR_w, "str", "'Wt")      \
+  V(STR_x, "str", "'Xt")      \
+  V(LDRB_w, "ldrb", "'Wt")    \
+  V(LDRH_w, "ldrh", "'Wt")    \
+  V(LDR_w, "ldr", "'Wt")      \
+  V(LDR_x, "ldr", "'Xt")      \
+  V(LDRSB_x, "ldrsb", "'Xt")  \
+  V(LDRSH_x, "ldrsh", "'Xt")  \
+  V(LDRSW_x, "ldrsw", "'Xt")  \
+  V(LDRSB_w, "ldrsb", "'Wt")  \
+  V(LDRSH_w, "ldrsh", "'Wt")  \
+  V(STR_s, "str", "'St")      \
+  V(STR_d, "str", "'Dt")      \
+  V(LDR_s, "ldr", "'St")      \
+  V(LDR_d, "ldr", "'Dt")
+
+void Disassembler::VisitLoadStorePreIndex(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "(LoadStorePreIndex)";
+
+  switch (instr->Mask(LoadStorePreIndexMask)) {
+    #define LS_PREINDEX(A, B, C) \
+    case A##_pre: mnemonic = B; form = C ", ['Xns'ILS]!"; break;
+    LOAD_STORE_LIST(LS_PREINDEX)
+    #undef LS_PREINDEX
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitLoadStorePostIndex(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "(LoadStorePostIndex)";
+
+  switch (instr->Mask(LoadStorePostIndexMask)) {
+    #define LS_POSTINDEX(A, B, C) \
+    case A##_post: mnemonic = B; form = C ", ['Xns]'ILS"; break;
+    LOAD_STORE_LIST(LS_POSTINDEX)
+    #undef LS_POSTINDEX
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitLoadStoreUnsignedOffset(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "(LoadStoreUnsignedOffset)";
+
+  switch (instr->Mask(LoadStoreUnsignedOffsetMask)) {
+    #define LS_UNSIGNEDOFFSET(A, B, C) \
+    case A##_unsigned: mnemonic = B; form = C ", ['Xns'ILU]"; break;
+    LOAD_STORE_LIST(LS_UNSIGNEDOFFSET)
+    #undef LS_UNSIGNEDOFFSET
+    case PRFM_unsigned: mnemonic = "prfm"; form = "'PrefOp, ['Xn'ILU]";
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitLoadStoreRegisterOffset(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "(LoadStoreRegisterOffset)";
+
+  switch (instr->Mask(LoadStoreRegisterOffsetMask)) {
+    #define LS_REGISTEROFFSET(A, B, C) \
+    case A##_reg: mnemonic = B; form = C ", ['Xns, 'Offsetreg]"; break;
+    LOAD_STORE_LIST(LS_REGISTEROFFSET)
+    #undef LS_REGISTEROFFSET
+    case PRFM_reg: mnemonic = "prfm"; form = "'PrefOp, ['Xns, 'Offsetreg]";
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitLoadStoreUnscaledOffset(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "'Wt, ['Xns'ILS]";
+  const char *form_x = "'Xt, ['Xns'ILS]";
+  const char *form_s = "'St, ['Xns'ILS]";
+  const char *form_d = "'Dt, ['Xns'ILS]";
+
+  switch (instr->Mask(LoadStoreUnscaledOffsetMask)) {
+    case STURB_w:  mnemonic = "sturb"; break;
+    case STURH_w:  mnemonic = "sturh"; break;
+    case STUR_w:   mnemonic = "stur"; break;
+    case STUR_x:   mnemonic = "stur"; form = form_x; break;
+    case STUR_s:   mnemonic = "stur"; form = form_s; break;
+    case STUR_d:   mnemonic = "stur"; form = form_d; break;
+    case LDURB_w:  mnemonic = "ldurb"; break;
+    case LDURH_w:  mnemonic = "ldurh"; break;
+    case LDUR_w:   mnemonic = "ldur"; break;
+    case LDUR_x:   mnemonic = "ldur"; form = form_x; break;
+    case LDUR_s:   mnemonic = "ldur"; form = form_s; break;
+    case LDUR_d:   mnemonic = "ldur"; form = form_d; break;
+    case LDURSB_x: form = form_x;  // Fall through.
+    case LDURSB_w: mnemonic = "ldursb"; break;
+    case LDURSH_x: form = form_x;  // Fall through.
+    case LDURSH_w: mnemonic = "ldursh"; break;
+    case LDURSW_x: mnemonic = "ldursw"; form = form_x; break;
+    default: form = "(LoadStoreUnscaledOffset)";
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitLoadLiteral(Instruction* instr) {
+  const char *mnemonic = "ldr";
+  const char *form = "(LoadLiteral)";
+
+  switch (instr->Mask(LoadLiteralMask)) {
+    case LDR_w_lit: form = "'Wt, 'ILLiteral 'LValue"; break;
+    case LDR_x_lit: form = "'Xt, 'ILLiteral 'LValue"; break;
+    case LDR_s_lit: form = "'St, 'ILLiteral 'LValue"; break;
+    case LDR_d_lit: form = "'Dt, 'ILLiteral 'LValue"; break;
+    default: mnemonic = "unimplemented";
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+#define LOAD_STORE_PAIR_LIST(V)         \
+  V(STP_w, "stp", "'Wt, 'Wt2", "4")     \
+  V(LDP_w, "ldp", "'Wt, 'Wt2", "4")     \
+  V(LDPSW_x, "ldpsw", "'Xt, 'Xt2", "4") \
+  V(STP_x, "stp", "'Xt, 'Xt2", "8")     \
+  V(LDP_x, "ldp", "'Xt, 'Xt2", "8")     \
+  V(STP_s, "stp", "'St, 'St2", "4")     \
+  V(LDP_s, "ldp", "'St, 'St2", "4")     \
+  V(STP_d, "stp", "'Dt, 'Dt2", "8")     \
+  V(LDP_d, "ldp", "'Dt, 'Dt2", "8")
+
+void Disassembler::VisitLoadStorePairPostIndex(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "(LoadStorePairPostIndex)";
+
+  switch (instr->Mask(LoadStorePairPostIndexMask)) {
+    #define LSP_POSTINDEX(A, B, C, D) \
+    case A##_post: mnemonic = B; form = C ", ['Xns]'ILP" D; break;
+    LOAD_STORE_PAIR_LIST(LSP_POSTINDEX)
+    #undef LSP_POSTINDEX
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitLoadStorePairPreIndex(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "(LoadStorePairPreIndex)";
+
+  switch (instr->Mask(LoadStorePairPreIndexMask)) {
+    #define LSP_PREINDEX(A, B, C, D) \
+    case A##_pre: mnemonic = B; form = C ", ['Xns'ILP" D "]!"; break;
+    LOAD_STORE_PAIR_LIST(LSP_PREINDEX)
+    #undef LSP_PREINDEX
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitLoadStorePairOffset(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "(LoadStorePairOffset)";
+
+  switch (instr->Mask(LoadStorePairOffsetMask)) {
+    #define LSP_OFFSET(A, B, C, D) \
+    case A##_off: mnemonic = B; form = C ", ['Xns'ILP" D "]"; break;
+    LOAD_STORE_PAIR_LIST(LSP_OFFSET)
+    #undef LSP_OFFSET
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitLoadStorePairNonTemporal(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form;
+
+  switch (instr->Mask(LoadStorePairNonTemporalMask)) {
+    case STNP_w: mnemonic = "stnp"; form = "'Wt, 'Wt2, ['Xns'ILP4]"; break;
+    case LDNP_w: mnemonic = "ldnp"; form = "'Wt, 'Wt2, ['Xns'ILP4]"; break;
+    case STNP_x: mnemonic = "stnp"; form = "'Xt, 'Xt2, ['Xns'ILP8]"; break;
+    case LDNP_x: mnemonic = "ldnp"; form = "'Xt, 'Xt2, ['Xns'ILP8]"; break;
+    case STNP_s: mnemonic = "stnp"; form = "'St, 'St2, ['Xns'ILP4]"; break;
+    case LDNP_s: mnemonic = "ldnp"; form = "'St, 'St2, ['Xns'ILP4]"; break;
+    case STNP_d: mnemonic = "stnp"; form = "'Dt, 'Dt2, ['Xns'ILP8]"; break;
+    case LDNP_d: mnemonic = "ldnp"; form = "'Dt, 'Dt2, ['Xns'ILP8]"; break;
+    default: form = "(LoadStorePairNonTemporal)";
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitFPCompare(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "'Fn, 'Fm";
+  const char *form_zero = "'Fn, #0.0";
+
+  switch (instr->Mask(FPCompareMask)) {
+    case FCMP_s_zero:
+    case FCMP_d_zero: form = form_zero;  // Fall through.
+    case FCMP_s:
+    case FCMP_d: mnemonic = "fcmp"; break;
+    default: form = "(FPCompare)";
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitFPConditionalCompare(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "'Fn, 'Fm, 'INzcv, 'Cond";
+
+  switch (instr->Mask(FPConditionalCompareMask)) {
+    case FCCMP_s:
+    case FCCMP_d: mnemonic = "fccmp"; break;
+    case FCCMPE_s:
+    case FCCMPE_d: mnemonic = "fccmpe"; break;
+    default: form = "(FPConditionalCompare)";
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitFPConditionalSelect(Instruction* instr) {
+  const char *mnemonic = "";
+  const char *form = "'Fd, 'Fn, 'Fm, 'Cond";
+
+  switch (instr->Mask(FPConditionalSelectMask)) {
+    case FCSEL_s:
+    case FCSEL_d: mnemonic = "fcsel"; break;
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitFPDataProcessing1Source(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "'Fd, 'Fn";
+
+  switch (instr->Mask(FPDataProcessing1SourceMask)) {
+    #define FORMAT(A, B)  \
+    case A##_s:           \
+    case A##_d: mnemonic = B; break;
+    FORMAT(FMOV, "fmov");
+    FORMAT(FABS, "fabs");
+    FORMAT(FNEG, "fneg");
+    FORMAT(FSQRT, "fsqrt");
+    FORMAT(FRINTN, "frintn");
+    FORMAT(FRINTP, "frintp");
+    FORMAT(FRINTM, "frintm");
+    FORMAT(FRINTZ, "frintz");
+    FORMAT(FRINTA, "frinta");
+    FORMAT(FRINTX, "frintx");
+    FORMAT(FRINTI, "frinti");
+    #undef FORMAT
+    case FCVT_ds: mnemonic = "fcvt"; form = "'Dd, 'Sn"; break;
+    case FCVT_sd: mnemonic = "fcvt"; form = "'Sd, 'Dn"; break;
+    default: form = "(FPDataProcessing1Source)";
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitFPDataProcessing2Source(Instruction* instr) {
+  const char *mnemonic = "";
+  const char *form = "'Fd, 'Fn, 'Fm";
+
+  switch (instr->Mask(FPDataProcessing2SourceMask)) {
+    #define FORMAT(A, B)  \
+    case A##_s:           \
+    case A##_d: mnemonic = B; break;
+    FORMAT(FMUL, "fmul");
+    FORMAT(FDIV, "fdiv");
+    FORMAT(FADD, "fadd");
+    FORMAT(FSUB, "fsub");
+    FORMAT(FMAX, "fmax");
+    FORMAT(FMIN, "fmin");
+    FORMAT(FMAXNM, "fmaxnm");
+    FORMAT(FMINNM, "fminnm");
+    FORMAT(FNMUL, "fnmul");
+    #undef FORMAT
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitFPDataProcessing3Source(Instruction* instr) {
+  const char *mnemonic = "";
+  const char *form = "'Fd, 'Fn, 'Fm, 'Fa";
+
+  switch (instr->Mask(FPDataProcessing3SourceMask)) {
+    #define FORMAT(A, B)  \
+    case A##_s:           \
+    case A##_d: mnemonic = B; break;
+    FORMAT(FMADD, "fmadd");
+    FORMAT(FMSUB, "fmsub");
+    FORMAT(FNMADD, "fnmadd");
+    FORMAT(FNMSUB, "fnmsub");
+    #undef FORMAT
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitFPImmediate(Instruction* instr) {
+  const char *mnemonic = "";
+  const char *form = "(FPImmediate)";
+
+  switch (instr->Mask(FPImmediateMask)) {
+    case FMOV_s_imm: mnemonic = "fmov"; form = "'Sd, 'IFPSingle"; break;
+    case FMOV_d_imm: mnemonic = "fmov"; form = "'Dd, 'IFPDouble"; break;
+    default: UNREACHABLE();
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitFPIntegerConvert(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "(FPIntegerConvert)";
+  const char *form_rf = "'Rd, 'Fn";
+  const char *form_fr = "'Fd, 'Rn";
+
+  switch (instr->Mask(FPIntegerConvertMask)) {
+    case FMOV_ws:
+    case FMOV_xd: mnemonic = "fmov"; form = form_rf; break;
+    case FMOV_sw:
+    case FMOV_dx: mnemonic = "fmov"; form = form_fr; break;
+    case FCVTAS_ws:
+    case FCVTAS_xs:
+    case FCVTAS_wd:
+    case FCVTAS_xd: mnemonic = "fcvtas"; form = form_rf; break;
+    case FCVTAU_ws:
+    case FCVTAU_xs:
+    case FCVTAU_wd:
+    case FCVTAU_xd: mnemonic = "fcvtau"; form = form_rf; break;
+    case FCVTMS_ws:
+    case FCVTMS_xs:
+    case FCVTMS_wd:
+    case FCVTMS_xd: mnemonic = "fcvtms"; form = form_rf; break;
+    case FCVTMU_ws:
+    case FCVTMU_xs:
+    case FCVTMU_wd:
+    case FCVTMU_xd: mnemonic = "fcvtmu"; form = form_rf; break;
+    case FCVTNS_ws:
+    case FCVTNS_xs:
+    case FCVTNS_wd:
+    case FCVTNS_xd: mnemonic = "fcvtns"; form = form_rf; break;
+    case FCVTNU_ws:
+    case FCVTNU_xs:
+    case FCVTNU_wd:
+    case FCVTNU_xd: mnemonic = "fcvtnu"; form = form_rf; break;
+    case FCVTZU_xd:
+    case FCVTZU_ws:
+    case FCVTZU_wd:
+    case FCVTZU_xs: mnemonic = "fcvtzu"; form = form_rf; break;
+    case FCVTZS_xd:
+    case FCVTZS_wd:
+    case FCVTZS_xs:
+    case FCVTZS_ws: mnemonic = "fcvtzs"; form = form_rf; break;
+    case SCVTF_sw:
+    case SCVTF_sx:
+    case SCVTF_dw:
+    case SCVTF_dx: mnemonic = "scvtf"; form = form_fr; break;
+    case UCVTF_sw:
+    case UCVTF_sx:
+    case UCVTF_dw:
+    case UCVTF_dx: mnemonic = "ucvtf"; form = form_fr; break;
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitFPFixedPointConvert(Instruction* instr) {
+  const char *mnemonic = "";
+  const char *form = "'Rd, 'Fn, 'IFPFBits";
+  const char *form_fr = "'Fd, 'Rn, 'IFPFBits";
+
+  switch (instr->Mask(FPFixedPointConvertMask)) {
+    case FCVTZS_ws_fixed:
+    case FCVTZS_xs_fixed:
+    case FCVTZS_wd_fixed:
+    case FCVTZS_xd_fixed: mnemonic = "fcvtzs"; break;
+    case FCVTZU_ws_fixed:
+    case FCVTZU_xs_fixed:
+    case FCVTZU_wd_fixed:
+    case FCVTZU_xd_fixed: mnemonic = "fcvtzu"; break;
+    case SCVTF_sw_fixed:
+    case SCVTF_sx_fixed:
+    case SCVTF_dw_fixed:
+    case SCVTF_dx_fixed: mnemonic = "scvtf"; form = form_fr; break;
+    case UCVTF_sw_fixed:
+    case UCVTF_sx_fixed:
+    case UCVTF_dw_fixed:
+    case UCVTF_dx_fixed: mnemonic = "ucvtf"; form = form_fr; break;
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitSystem(Instruction* instr) {
+  // Some system instructions hijack their Op and Cp fields to represent a
+  // range of immediates instead of indicating a different instruction. This
+  // makes the decoding tricky.
+  const char *mnemonic = "unimplemented";
+  const char *form = "(System)";
+
+  if (instr->Mask(SystemSysRegFMask) == SystemSysRegFixed) {
+    switch (instr->Mask(SystemSysRegMask)) {
+      case MRS: {
+        mnemonic = "mrs";
+        switch (instr->ImmSystemRegister()) {
+          case NZCV: form = "'Xt, nzcv"; break;
+          case FPCR: form = "'Xt, fpcr"; break;
+          default: form = "'Xt, (unknown)"; break;
+        }
+        break;
+      }
+      case MSR: {
+        mnemonic = "msr";
+        switch (instr->ImmSystemRegister()) {
+          case NZCV: form = "nzcv, 'Xt"; break;
+          case FPCR: form = "fpcr, 'Xt"; break;
+          default: form = "(unknown), 'Xt"; break;
+        }
+        break;
+      }
+    }
+  } else if (instr->Mask(SystemHintFMask) == SystemHintFixed) {
+    ASSERT(instr->Mask(SystemHintMask) == HINT);
+    switch (instr->ImmHint()) {
+      case NOP: {
+        mnemonic = "nop";
+        form = NULL;
+        break;
+      }
+    }
+  } else if (instr->Mask(MemBarrierFMask) == MemBarrierFixed) {
+    switch (instr->Mask(MemBarrierMask)) {
+      case DMB: {
+        mnemonic = "dmb";
+        form = "'M";
+        break;
+      }
+      case DSB: {
+        mnemonic = "dsb";
+        form = "'M";
+        break;
+      }
+      case ISB: {
+        mnemonic = "isb";
+        form = NULL;
+        break;
+      }
+    }
+  }
+
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitException(Instruction* instr) {
+  const char *mnemonic = "unimplemented";
+  const char *form = "'IDebug";
+
+  switch (instr->Mask(ExceptionMask)) {
+    case HLT: mnemonic = "hlt"; break;
+    case BRK: mnemonic = "brk"; break;
+    case SVC: mnemonic = "svc"; break;
+    case HVC: mnemonic = "hvc"; break;
+    case SMC: mnemonic = "smc"; break;
+    case DCPS1: mnemonic = "dcps1"; form = "{'IDebug}"; break;
+    case DCPS2: mnemonic = "dcps2"; form = "{'IDebug}"; break;
+    case DCPS3: mnemonic = "dcps3"; form = "{'IDebug}"; break;
+    default: form = "(Exception)";
+  }
+  Format(instr, mnemonic, form);
+}
+
+
+void Disassembler::VisitUnimplemented(Instruction* instr) {
+  Format(instr, "unimplemented", "(Unimplemented)");
+}
+
+
+void Disassembler::VisitUnallocated(Instruction* instr) {
+  Format(instr, "unallocated", "(Unallocated)");
+}
+
+
+void Disassembler::ProcessOutput(Instruction* /*instr*/) {
+  // The base disasm does nothing more than disassembling into a buffer.
+}
+
+
+void Disassembler::Format(Instruction* instr, const char* mnemonic,
+                          const char* format) {
+  // TODO(mcapewel) don't think I can use the instr address here - there needs
+  //                to be a base address too
+  ASSERT(mnemonic != NULL);
+  ResetOutput();
+  Substitute(instr, mnemonic);
+  if (format != NULL) {
+    buffer_[buffer_pos_++] = ' ';
+    Substitute(instr, format);
+  }
+  buffer_[buffer_pos_] = 0;
+  ProcessOutput(instr);
+}
+
+
+void Disassembler::Substitute(Instruction* instr, const char* string) {
+  char chr = *string++;
+  while (chr != '\0') {
+    if (chr == '\'') {
+      string += SubstituteField(instr, string);
+    } else {
+      buffer_[buffer_pos_++] = chr;
+    }
+    chr = *string++;
+  }
+}
+
+
+int Disassembler::SubstituteField(Instruction* instr, const char* format) {
+  switch (format[0]) {
+    case 'R':  // Register. X or W, selected by sf bit.
+    case 'F':  // FP Register. S or D, selected by type field.
+    case 'W':
+    case 'X':
+    case 'S':
+    case 'D': return SubstituteRegisterField(instr, format);
+    case 'I': return SubstituteImmediateField(instr, format);
+    case 'L': return SubstituteLiteralField(instr, format);
+    case 'H': return SubstituteShiftField(instr, format);
+    case 'P': return SubstitutePrefetchField(instr, format);
+    case 'C': return SubstituteConditionField(instr, format);
+    case 'E': return SubstituteExtendField(instr, format);
+    case 'A': return SubstitutePCRelAddressField(instr, format);
+    case 'B': return SubstituteBranchTargetField(instr, format);
+    case 'O': return SubstituteLSRegOffsetField(instr, format);
+    case 'M': return SubstituteBarrierField(instr, format);
+    default: {
+      UNREACHABLE();
+      return 1;
+    }
+  }
+}
+
+
+int Disassembler::SubstituteRegisterField(Instruction* instr,
+                                          const char* format) {
+  unsigned reg_num = 0;
+  unsigned field_len = 2;
+  switch (format[1]) {
+    case 'd': reg_num = instr->Rd(); break;
+    case 'n': reg_num = instr->Rn(); break;
+    case 'm': reg_num = instr->Rm(); break;
+    case 'a': reg_num = instr->Ra(); break;
+    case 't': {
+      if (format[2] == '2') {
+        reg_num = instr->Rt2();
+        field_len = 3;
+      } else {
+        reg_num = instr->Rt();
+      }
+      break;
+    }
+    default: UNREACHABLE();
+  }
+
+  // Increase field length for registers tagged as stack.
+  if (format[2] == 's') {
+    field_len = 3;
+  }
+
+  char reg_type;
+  if (format[0] == 'R') {
+    // Register type is R: use sf bit to choose X and W.
+    reg_type = instr->SixtyFourBits() ? 'x' : 'w';
+  } else if (format[0] == 'F') {
+    // Floating-point register: use type field to choose S or D.
+    reg_type = ((instr->FPType() & 1) == 0) ? 's' : 'd';
+  } else {
+    // Register type is specified. Make it lower case.
+    reg_type = format[0] + 0x20;
+  }
+
+  if ((reg_num != kZeroRegCode) || (reg_type == 's') || (reg_type == 'd')) {
+    // A normal register: w0 - w30, x0 - x30, s0 - s31, d0 - d31.
+
+    // Filter special registers
+    if ((reg_type == 'x') && (reg_num == 27)) {
+      AppendToOutput("cp");
+    } else if ((reg_type == 'x') && (reg_num == 28)) {
+      AppendToOutput("jssp");
+    } else if ((reg_type == 'x') && (reg_num == 29)) {
+      AppendToOutput("fp");
+    } else if ((reg_type == 'x') && (reg_num == 30)) {
+      AppendToOutput("lr");
+    } else {
+      AppendToOutput("%c%d", reg_type, reg_num);
+    }
+  } else if (format[2] == 's') {
+    // Disassemble w31/x31 as stack pointer wcsp/csp.
+    AppendToOutput("%s", (reg_type == 'w') ? "wcsp" : "csp");
+  } else {
+    // Disassemble w31/x31 as zero register wzr/xzr.
+    AppendToOutput("%czr", reg_type);
+  }
+
+  return field_len;
+}
+
+
+int Disassembler::SubstituteImmediateField(Instruction* instr,
+                                           const char* format) {
+  ASSERT(format[0] == 'I');
+
+  switch (format[1]) {
+    case 'M': {  // IMoveImm or IMoveLSL.
+      if (format[5] == 'I') {
+        uint64_t imm = instr->ImmMoveWide() << (16 * instr->ShiftMoveWide());
+        AppendToOutput("#0x%" PRIx64, imm);
+      } else {
+        ASSERT(format[5] == 'L');
+        AppendToOutput("#0x%" PRIx64, instr->ImmMoveWide());
+        if (instr->ShiftMoveWide() > 0) {
+          AppendToOutput(", lsl #%d", 16 * instr->ShiftMoveWide());
+        }
+      }
+      return 8;
+    }
+    case 'L': {
+      switch (format[2]) {
+        case 'L': {  // ILLiteral - Immediate Load Literal.
+          AppendToOutput("pc%+" PRId64,
+                         instr->ImmLLiteral() << kLiteralEntrySizeLog2);
+          return 9;
+        }
+        case 'S': {  // ILS - Immediate Load/Store.
+          if (instr->ImmLS() != 0) {
+            AppendToOutput(", #%" PRId64, instr->ImmLS());
+          }
+          return 3;
+        }
+        case 'P': {  // ILPx - Immediate Load/Store Pair, x = access size.
+          if (instr->ImmLSPair() != 0) {
+            // format[3] is the scale value. Convert to a number.
+            int scale = format[3] - 0x30;
+            AppendToOutput(", #%" PRId64, instr->ImmLSPair() * scale);
+          }
+          return 4;
+        }
+        case 'U': {  // ILU - Immediate Load/Store Unsigned.
+          if (instr->ImmLSUnsigned() != 0) {
+            AppendToOutput(", #%" PRIu64,
+                           instr->ImmLSUnsigned() << instr->SizeLS());
+          }
+          return 3;
+        }
+      }
+    }
+    case 'C': {  // ICondB - Immediate Conditional Branch.
+      int64_t offset = instr->ImmCondBranch() << 2;
+      char sign = (offset >= 0) ? '+' : '-';
+      AppendToOutput("#%c0x%" PRIx64, sign, offset);
+      return 6;
+    }
+    case 'A': {  // IAddSub.
+      ASSERT(instr->ShiftAddSub() <= 1);
+      int64_t imm = instr->ImmAddSub() << (12 * instr->ShiftAddSub());
+      AppendToOutput("#0x%" PRIx64 " (%" PRId64 ")", imm, imm);
+      return 7;
+    }
+    case 'F': {  // IFPSingle, IFPDouble or IFPFBits.
+      if (format[3] == 'F') {  // IFPFBits.
+        AppendToOutput("#%d", 64 - instr->FPScale());
+        return 8;
+      } else {
+        AppendToOutput("#0x%" PRIx64 " (%.4f)", instr->ImmFP(),
+                       format[3] == 'S' ? instr->ImmFP32() : instr->ImmFP64());
+        return 9;
+      }
+    }
+    case 'T': {  // ITri - Immediate Triangular Encoded.
+      AppendToOutput("#0x%" PRIx64, instr->ImmLogical());
+      return 4;
+    }
+    case 'N': {  // INzcv.
+      int nzcv = (instr->Nzcv() << Flags_offset);
+      AppendToOutput("#%c%c%c%c", ((nzcv & NFlag) == 0) ? 'n' : 'N',
+                                  ((nzcv & ZFlag) == 0) ? 'z' : 'Z',
+                                  ((nzcv & CFlag) == 0) ? 'c' : 'C',
+                                  ((nzcv & VFlag) == 0) ? 'v' : 'V');
+      return 5;
+    }
+    case 'P': {  // IP - Conditional compare.
+      AppendToOutput("#%d", instr->ImmCondCmp());
+      return 2;
+    }
+    case 'B': {  // Bitfields.
+      return SubstituteBitfieldImmediateField(instr, format);
+    }
+    case 'E': {  // IExtract.
+      AppendToOutput("#%d", instr->ImmS());
+      return 8;
+    }
+    case 'S': {  // IS - Test and branch bit.
+      AppendToOutput("#%d", (instr->ImmTestBranchBit5() << 5) |
+                            instr->ImmTestBranchBit40());
+      return 2;
+    }
+    case 'D': {  // IDebug - HLT and BRK instructions.
+      AppendToOutput("#0x%x", instr->ImmException());
+      return 6;
+    }
+    default: {
+      UNIMPLEMENTED();
+      return 0;
+    }
+  }
+}
+
+
+int Disassembler::SubstituteBitfieldImmediateField(Instruction* instr,
+                                                   const char* format) {
+  ASSERT((format[0] == 'I') && (format[1] == 'B'));
+  unsigned r = instr->ImmR();
+  unsigned s = instr->ImmS();
+
+  switch (format[2]) {
+    case 'r': {  // IBr.
+      AppendToOutput("#%d", r);
+      return 3;
+    }
+    case 's': {  // IBs+1 or IBs-r+1.
+      if (format[3] == '+') {
+        AppendToOutput("#%d", s + 1);
+        return 5;
+      } else {
+        ASSERT(format[3] == '-');
+        AppendToOutput("#%d", s - r + 1);
+        return 7;
+      }
+    }
+    case 'Z': {  // IBZ-r.
+      ASSERT((format[3] == '-') && (format[4] == 'r'));
+      unsigned reg_size = (instr->SixtyFourBits() == 1) ? kXRegSize : kWRegSize;
+      AppendToOutput("#%d", reg_size - r);
+      return 5;
+    }
+    default: {
+      UNREACHABLE();
+      return 0;
+    }
+  }
+}
+
+
+int Disassembler::SubstituteLiteralField(Instruction* instr,
+                                         const char* format) {
+  ASSERT(strncmp(format, "LValue", 6) == 0);
+  USE(format);
+
+  switch (instr->Mask(LoadLiteralMask)) {
+    case LDR_w_lit:
+    case LDR_x_lit:
+    case LDR_s_lit:
+    case LDR_d_lit: AppendToOutput("(addr %p)", instr->LiteralAddress()); break;
+    default: UNREACHABLE();
+  }
+
+  return 6;
+}
+
+
+int Disassembler::SubstituteShiftField(Instruction* instr, const char* format) {
+  ASSERT(format[0] == 'H');
+  ASSERT(instr->ShiftDP() <= 0x3);
+
+  switch (format[1]) {
+    case 'D': {  // HDP.
+      ASSERT(instr->ShiftDP() != ROR);
+    }  // Fall through.
+    case 'L': {  // HLo.
+      if (instr->ImmDPShift() != 0) {
+        const char* shift_type[] = {"lsl", "lsr", "asr", "ror"};
+        AppendToOutput(", %s #%" PRId64, shift_type[instr->ShiftDP()],
+                       instr->ImmDPShift());
+      }
+      return 3;
+    }
+    default:
+      UNIMPLEMENTED();
+      return 0;
+  }
+}
+
+
+int Disassembler::SubstituteConditionField(Instruction* instr,
+                                           const char* format) {
+  ASSERT(format[0] == 'C');
+  const char* condition_code[] = { "eq", "ne", "hs", "lo",
+                                   "mi", "pl", "vs", "vc",
+                                   "hi", "ls", "ge", "lt",
+                                   "gt", "le", "al", "nv" };
+  int cond;
+  switch (format[1]) {
+    case 'B': cond = instr->ConditionBranch(); break;
+    case 'I': {
+      cond = InvertCondition(static_cast<Condition>(instr->Condition()));
+      break;
+    }
+    default: cond = instr->Condition();
+  }
+  AppendToOutput("%s", condition_code[cond]);
+  return 4;
+}
+
+
+int Disassembler::SubstitutePCRelAddressField(Instruction* instr,
+                                              const char* format) {
+  USE(format);
+  ASSERT(strncmp(format, "AddrPCRel", 9) == 0);
+
+  int offset = instr->ImmPCRel();
+
+  // Only ADR (AddrPCRelByte) is supported.
+  ASSERT(strcmp(format, "AddrPCRelByte") == 0);
+
+  char sign = '+';
+  if (offset < 0) {
+    offset = -offset;
+    sign = '-';
+  }
+  // TODO(jbramley): Can we print the target address here?
+  AppendToOutput("#%c0x%x", sign, offset);
+  return 13;
+}
+
+
+int Disassembler::SubstituteBranchTargetField(Instruction* instr,
+                                              const char* format) {
+  ASSERT(strncmp(format, "BImm", 4) == 0);
+
+  int64_t offset = 0;
+  switch (format[5]) {
+    // BImmUncn - unconditional branch immediate.
+    case 'n': offset = instr->ImmUncondBranch(); break;
+    // BImmCond - conditional branch immediate.
+    case 'o': offset = instr->ImmCondBranch(); break;
+    // BImmCmpa - compare and branch immediate.
+    case 'm': offset = instr->ImmCmpBranch(); break;
+    // BImmTest - test and branch immediate.
+    case 'e': offset = instr->ImmTestBranch(); break;
+    default: UNIMPLEMENTED();
+  }
+  offset <<= kInstructionSizeLog2;
+  char sign = '+';
+  if (offset < 0) {
+    offset = -offset;
+    sign = '-';
+  }
+  // TODO(mcapewel): look up pc + offset in label table.
+  AppendToOutput("#%c0x%" PRIx64, sign, offset);
+  return 8;
+}
+
+
+int Disassembler::SubstituteExtendField(Instruction* instr,
+                                        const char* format) {
+  ASSERT(strncmp(format, "Ext", 3) == 0);
+  ASSERT(instr->ExtendMode() <= 7);
+  USE(format);
+
+  const char* extend_mode[] = { "uxtb", "uxth", "uxtw", "uxtx",
+                                "sxtb", "sxth", "sxtw", "sxtx" };
+
+  // If rd or rn is SP, uxtw on 32-bit registers and uxtx on 64-bit
+  // registers becomes lsl.
+  if (((instr->Rd() == kZeroRegCode) || (instr->Rn() == kZeroRegCode)) &&
+      (((instr->ExtendMode() == UXTW) && (instr->SixtyFourBits() == 0)) ||
+       (instr->ExtendMode() == UXTX))) {
+    if (instr->ImmExtendShift() > 0) {
+      AppendToOutput(", lsl #%d", instr->ImmExtendShift());
+    }
+  } else {
+    AppendToOutput(", %s", extend_mode[instr->ExtendMode()]);
+    if (instr->ImmExtendShift() > 0) {
+      AppendToOutput(" #%d", instr->ImmExtendShift());
+    }
+  }
+  return 3;
+}
+
+
+int Disassembler::SubstituteLSRegOffsetField(Instruction* instr,
+                                             const char* format) {
+  ASSERT(strncmp(format, "Offsetreg", 9) == 0);
+  const char* extend_mode[] = { "undefined", "undefined", "uxtw", "lsl",
+                                "undefined", "undefined", "sxtw", "sxtx" };
+  USE(format);
+
+  unsigned shift = instr->ImmShiftLS();
+  Extend ext = static_cast<Extend>(instr->ExtendMode());
+  char reg_type = ((ext == UXTW) || (ext == SXTW)) ? 'w' : 'x';
+
+  unsigned rm = instr->Rm();
+  if (rm == kZeroRegCode) {
+    AppendToOutput("%czr", reg_type);
+  } else {
+    AppendToOutput("%c%d", reg_type, rm);
+  }
+
+  // Extend mode UXTX is an alias for shift mode LSL here.
+  if (!((ext == UXTX) && (shift == 0))) {
+    AppendToOutput(", %s", extend_mode[ext]);
+    if (shift != 0) {
+      AppendToOutput(" #%d", instr->SizeLS());
+    }
+  }
+  return 9;
+}
+
+
+int Disassembler::SubstitutePrefetchField(Instruction* instr,
+                                          const char* format) {
+  ASSERT(format[0] == 'P');
+  USE(format);
+
+  int prefetch_mode = instr->PrefetchMode();
+
+  const char* ls = (prefetch_mode & 0x10) ? "st" : "ld";
+  int level = (prefetch_mode >> 1) + 1;
+  const char* ks = (prefetch_mode & 1) ? "strm" : "keep";
+
+  AppendToOutput("p%sl%d%s", ls, level, ks);
+  return 6;
+}
+
+int Disassembler::SubstituteBarrierField(Instruction* instr,
+                                         const char* format) {
+  ASSERT(format[0] == 'M');
+  USE(format);
+
+  static const char* options[4][4] = {
+    { "sy (0b0000)", "oshld", "oshst", "osh" },
+    { "sy (0b0100)", "nshld", "nshst", "nsh" },
+    { "sy (0b1000)", "ishld", "ishst", "ish" },
+    { "sy (0b1100)", "ld", "st", "sy" }
+  };
+  int domain = instr->ImmBarrierDomain();
+  int type = instr->ImmBarrierType();
+
+  AppendToOutput("%s", options[domain][type]);
+  return 1;
+}
+
+
+void Disassembler::ResetOutput() {
+  buffer_pos_ = 0;
+  buffer_[buffer_pos_] = 0;
+}
+
+
+void Disassembler::AppendToOutput(const char* format, ...) {
+  va_list args;
+  va_start(args, format);
+  buffer_pos_ += vsnprintf(&buffer_[buffer_pos_], buffer_size_, format, args);
+  va_end(args);
+}
+
+
+void PrintDisassembler::ProcessOutput(Instruction* instr) {
+  fprintf(stream_, "0x%016" PRIx64 "  %08" PRIx32 "\t\t%s\n",
+          reinterpret_cast<uint64_t>(instr), instr->InstructionBits(),
+          GetOutput());
+}
+
+} }  // namespace v8::internal
+
+
+namespace disasm {
+
+
+const char* NameConverter::NameOfAddress(byte* addr) const {
+  v8::internal::OS::SNPrintF(tmp_buffer_, "%p", addr);
+  return tmp_buffer_.start();
+}
+
+
+const char* NameConverter::NameOfConstant(byte* addr) const {
+  return NameOfAddress(addr);
+}
+
+
+const char* NameConverter::NameOfCPURegister(int reg) const {
+  unsigned ureg = reg;  // Avoid warnings about signed/unsigned comparisons.
+  if (ureg >= v8::internal::kNumberOfRegisters) {
+    return "noreg";
+  }
+  if (ureg == v8::internal::kZeroRegCode) {
+    return "xzr";
+  }
+  v8::internal::OS::SNPrintF(tmp_buffer_, "x%u", ureg);
+  return tmp_buffer_.start();
+}
+
+
+const char* NameConverter::NameOfByteCPURegister(int reg) const {
+  UNREACHABLE();  // A64 does not have the concept of a byte register
+  return "nobytereg";
+}
+
+
+const char* NameConverter::NameOfXMMRegister(int reg) const {
+  UNREACHABLE();  // A64 does not have any XMM registers
+  return "noxmmreg";
+}
+
+
+const char* NameConverter::NameInCode(byte* addr) const {
+  // The default name converter is called for unknown code, so we will not try
+  // to access any memory.
+  return "";
+}
+
+
+//------------------------------------------------------------------------------
+
+class BufferDisassembler : public v8::internal::Disassembler {
+ public:
+  explicit BufferDisassembler(v8::internal::Vector<char> out_buffer)
+      : out_buffer_(out_buffer) { }
+
+  ~BufferDisassembler() { }
+
+  virtual void ProcessOutput(v8::internal::Instruction* instr) {
+    v8::internal::OS::SNPrintF(out_buffer_, "%s", GetOutput());
+  }
+
+ private:
+  v8::internal::Vector<char> out_buffer_;
+};
+
+Disassembler::Disassembler(const NameConverter& converter)
+    : converter_(converter) {}
+
+
+Disassembler::~Disassembler() {}
+
+
+int Disassembler::InstructionDecode(v8::internal::Vector<char> buffer,
+                                    byte* instr) {
+  v8::internal::Decoder<v8::internal::DispatchingDecoderVisitor> decoder;
+  BufferDisassembler disasm(buffer);
+  decoder.AppendVisitor(&disasm);
+
+  decoder.Decode(reinterpret_cast<v8::internal::Instruction*>(instr));
+  return v8::internal::kInstructionSize;
+}
+
+
+int Disassembler::ConstantPoolSizeAt(byte* instr) {
+  return v8::internal::Assembler::ConstantPoolSizeAt(
+      reinterpret_cast<v8::internal::Instruction*>(instr));
+}
+
+
+void Disassembler::Disassemble(FILE* file, byte* start, byte* end) {
+  v8::internal::Decoder<v8::internal::DispatchingDecoderVisitor> decoder;
+  v8::internal::PrintDisassembler disasm(file);
+  decoder.AppendVisitor(&disasm);
+
+  for (byte* pc = start; pc < end; pc += v8::internal::kInstructionSize) {
+    decoder.Decode(reinterpret_cast<v8::internal::Instruction*>(pc));
+  }
+}
+
+}  // namespace disasm
+
+#endif  // V8_TARGET_ARCH_A64