----------------------------------------------------------------------------
-- LuaJIT x86/x64 disassembler module.
--
-- Copyright (C) 2005-2023 Mike Pall. All rights reserved.
-- Released under the MIT license. See Copyright Notice in luajit.h
----------------------------------------------------------------------------
-- This is a helper module used by the LuaJIT machine code dumper module.
--
-- Sending small code snippets to an external disassembler and mixing the
-- output with our own stuff was too fragile. So I had to bite the bullet
-- and write yet another x86 disassembler. Oh well ...
--
-- The output format is very similar to what ndisasm generates. But it has
-- been developed independently by looking at the opcode tables from the
-- Intel and AMD manuals. The supported instruction set is quite extensive
-- and reflects what a current generation Intel or AMD CPU implements in
-- 32 bit and 64 bit mode. Yes, this includes MMX, SSE, SSE2, SSE3, SSSE3,
-- SSE4.1, SSE4.2, SSE4a, AVX, AVX2 and even privileged and hypervisor
-- (VMX/SVM) instructions.
--
-- Notes:
-- * The (useless) a16 prefix, 3DNow and pre-586 opcodes are unsupported.
-- * No attempt at optimization has been made -- it's fast enough for my needs.
------------------------------------------------------------------------------

local type = type
local sub, byte, format = string.sub, string.byte, string.format
local match, gmatch, gsub = string.match, string.gmatch, string.gsub
local lower, rep = string.lower, string.rep
local bit = require("bit")
local tohex = bit.tohex

-- Map for 1st opcode byte in 32 bit mode. Ugly? Well ... read on.
local map_opc1_32 = {
    --0x
    [0] = "addBmr",
    "addVmr",
    "addBrm",
    "addVrm",
    "addBai",
    "addVai",
    "push es",
    "pop es",
    "orBmr",
    "orVmr",
    "orBrm",
    "orVrm",
    "orBai",
    "orVai",
    "push cs",
    "opc2*",
    --1x
    "adcBmr",
    "adcVmr",
    "adcBrm",
    "adcVrm",
    "adcBai",
    "adcVai",
    "push ss",
    "pop ss",
    "sbbBmr",
    "sbbVmr",
    "sbbBrm",
    "sbbVrm",
    "sbbBai",
    "sbbVai",
    "push ds",
    "pop ds",
    --2x
    "andBmr",
    "andVmr",
    "andBrm",
    "andVrm",
    "andBai",
    "andVai",
    "es:seg",
    "daa",
    "subBmr",
    "subVmr",
    "subBrm",
    "subVrm",
    "subBai",
    "subVai",
    "cs:seg",
    "das",
    --3x
    "xorBmr",
    "xorVmr",
    "xorBrm",
    "xorVrm",
    "xorBai",
    "xorVai",
    "ss:seg",
    "aaa",
    "cmpBmr",
    "cmpVmr",
    "cmpBrm",
    "cmpVrm",
    "cmpBai",
    "cmpVai",
    "ds:seg",
    "aas",
    --4x
    "incVR",
    "incVR",
    "incVR",
    "incVR",
    "incVR",
    "incVR",
    "incVR",
    "incVR",
    "decVR",
    "decVR",
    "decVR",
    "decVR",
    "decVR",
    "decVR",
    "decVR",
    "decVR",
    --5x
    "pushUR",
    "pushUR",
    "pushUR",
    "pushUR",
    "pushUR",
    "pushUR",
    "pushUR",
    "pushUR",
    "popUR",
    "popUR",
    "popUR",
    "popUR",
    "popUR",
    "popUR",
    "popUR",
    "popUR",
    --6x
    "sz*pushaw,pusha",
    "sz*popaw,popa",
    "boundVrm",
    "arplWmr",
    "fs:seg",
    "gs:seg",
    "o16:",
    "a16",
    "pushUi",
    "imulVrmi",
    "pushBs",
    "imulVrms",
    "insb",
    "insVS",
    "outsb",
    "outsVS",
    --7x
    "joBj",
    "jnoBj",
    "jbBj",
    "jnbBj",
    "jzBj",
    "jnzBj",
    "jbeBj",
    "jaBj",
    "jsBj",
    "jnsBj",
    "jpeBj",
    "jpoBj",
    "jlBj",
    "jgeBj",
    "jleBj",
    "jgBj",
    --8x
    "arith!Bmi",
    "arith!Vmi",
    "arith!Bmi",
    "arith!Vms",
    "testBmr",
    "testVmr",
    "xchgBrm",
    "xchgVrm",
    "movBmr",
    "movVmr",
    "movBrm",
    "movVrm",
    "movVmg",
    "leaVrm",
    "movWgm",
    "popUm",
    --9x
    "nop*xchgVaR|pause|xchgWaR|repne nop",
    "xchgVaR",
    "xchgVaR",
    "xchgVaR",
    "xchgVaR",
    "xchgVaR",
    "xchgVaR",
    "xchgVaR",
    "sz*cbw,cwde,cdqe",
    "sz*cwd,cdq,cqo",
    "call farViw",
    "wait",
    "sz*pushfw,pushf",
    "sz*popfw,popf",
    "sahf",
    "lahf",
    --Ax
    "movBao",
    "movVao",
    "movBoa",
    "movVoa",
    "movsb",
    "movsVS",
    "cmpsb",
    "cmpsVS",
    "testBai",
    "testVai",
    "stosb",
    "stosVS",
    "lodsb",
    "lodsVS",
    "scasb",
    "scasVS",
    --Bx
    "movBRi",
    "movBRi",
    "movBRi",
    "movBRi",
    "movBRi",
    "movBRi",
    "movBRi",
    "movBRi",
    "movVRI",
    "movVRI",
    "movVRI",
    "movVRI",
    "movVRI",
    "movVRI",
    "movVRI",
    "movVRI",
    --Cx
    "shift!Bmu",
    "shift!Vmu",
    "retBw",
    "ret",
    "vex*3$lesVrm",
    "vex*2$ldsVrm",
    "movBmi",
    "movVmi",
    "enterBwu",
    "leave",
    "retfBw",
    "retf",
    "int3",
    "intBu",
    "into",
    "iretVS",
    --Dx
    "shift!Bm1",
    "shift!Vm1",
    "shift!Bmc",
    "shift!Vmc",
    "aamBu",
    "aadBu",
    "salc",
    "xlatb",
    "fp*0",
    "fp*1",
    "fp*2",
    "fp*3",
    "fp*4",
    "fp*5",
    "fp*6",
    "fp*7",
    --Ex
    "loopneBj",
    "loopeBj",
    "loopBj",
    "sz*jcxzBj,jecxzBj,jrcxzBj",
    "inBau",
    "inVau",
    "outBua",
    "outVua",
    "callVj",
    "jmpVj",
    "jmp farViw",
    "jmpBj",
    "inBad",
    "inVad",
    "outBda",
    "outVda",
    --Fx
    "lock:",
    "int1",
    "repne:rep",
    "rep:",
    "hlt",
    "cmc",
    "testb!Bm",
    "testv!Vm",
    "clc",
    "stc",
    "cli",
    "sti",
    "cld",
    "std",
    "incb!Bm",
    "incd!Vm",
}
assert(#map_opc1_32 == 255)

-- Map for 1st opcode byte in 64 bit mode (overrides only).
local map_opc1_64 = setmetatable({
    [0x06] = false,
    [0x07] = false,
    [0x0e] = false,
    [0x16] = false,
    [0x17] = false,
    [0x1e] = false,
    [0x1f] = false,
    [0x27] = false,
    [0x2f] = false,
    [0x37] = false,
    [0x3f] = false,
    [0x60] = false,
    [0x61] = false,
    [0x62] = false,
    [0x63] = "movsxdVrDmt",
    [0x67] = "a32:",
    [0x40] = "rex*",
    [0x41] = "rex*b",
    [0x42] = "rex*x",
    [0x43] = "rex*xb",
    [0x44] = "rex*r",
    [0x45] = "rex*rb",
    [0x46] = "rex*rx",
    [0x47] = "rex*rxb",
    [0x48] = "rex*w",
    [0x49] = "rex*wb",
    [0x4a] = "rex*wx",
    [0x4b] = "rex*wxb",
    [0x4c] = "rex*wr",
    [0x4d] = "rex*wrb",
    [0x4e] = "rex*wrx",
    [0x4f] = "rex*wrxb",
    [0x82] = false,
    [0x9a] = false,
    [0xc4] = "vex*3",
    [0xc5] = "vex*2",
    [0xce] = false,
    [0xd4] = false,
    [0xd5] = false,
    [0xd6] = false,
    [0xea] = false,
}, { __index = map_opc1_32 })

-- Map for 2nd opcode byte (0F xx). True CISC hell. Hey, I told you.
-- Prefix dependent MMX/SSE opcodes: (none)|rep|o16|repne, -|F3|66|F2
local map_opc2 = {
    --0x
    [0] = "sldt!Dmp",
    "sgdt!Ump",
    "larVrm",
    "lslVrm",
    nil,
    "syscall",
    "clts",
    "sysret",
    "invd",
    "wbinvd",
    nil,
    "ud1",
    nil,
    "$prefetch!Bm",
    "femms",
    "3dnowMrmu",
    --1x
    "movupsXrm|movssXrvm|movupdXrm|movsdXrvm",
    "movupsXmr|movssXmvr|movupdXmr|movsdXmvr",
    "movhlpsXrm$movlpsXrm|movsldupXrm|movlpdXrm|movddupXrm",
    "movlpsXmr||movlpdXmr",
    "unpcklpsXrvm||unpcklpdXrvm",
    "unpckhpsXrvm||unpckhpdXrvm",
    "movlhpsXrm$movhpsXrm|movshdupXrm|movhpdXrm",
    "movhpsXmr||movhpdXmr",
    "$prefetcht!Bm",
    "hintnopVm",
    "hintnopVm",
    "hintnopVm",
    "hintnopVm",
    "hintnopVm",
    "hintnopVm",
    "hintnopVm",
    --2x
    "movUmx$",
    "movUmy$",
    "movUxm$",
    "movUym$",
    "movUmz$",
    nil,
    "movUzm$",
    nil,
    "movapsXrm||movapdXrm",
    "movapsXmr||movapdXmr",
    "cvtpi2psXrMm|cvtsi2ssXrvVmt|cvtpi2pdXrMm|cvtsi2sdXrvVmt",
    "movntpsXmr|movntssXmr|movntpdXmr|movntsdXmr",
    "cvttps2piMrXm|cvttss2siVrXm|cvttpd2piMrXm|cvttsd2siVrXm",
    "cvtps2piMrXm|cvtss2siVrXm|cvtpd2piMrXm|cvtsd2siVrXm",
    "ucomissXrm||ucomisdXrm",
    "comissXrm||comisdXrm",
    --3x
    "wrmsr",
    "rdtsc",
    "rdmsr",
    "rdpmc",
    "sysenter",
    "sysexit",
    nil,
    "getsec",
    "opc3*38",
    nil,
    "opc3*3a",
    nil,
    nil,
    nil,
    nil,
    nil,
    --4x
    "cmovoVrm",
    "cmovnoVrm",
    "cmovbVrm",
    "cmovnbVrm",
    "cmovzVrm",
    "cmovnzVrm",
    "cmovbeVrm",
    "cmovaVrm",
    "cmovsVrm",
    "cmovnsVrm",
    "cmovpeVrm",
    "cmovpoVrm",
    "cmovlVrm",
    "cmovgeVrm",
    "cmovleVrm",
    "cmovgVrm",
    --5x
    "movmskpsVrXm$||movmskpdVrXm$",
    "sqrtpsXrm|sqrtssXrm|sqrtpdXrm|sqrtsdXrm",
    "rsqrtpsXrm|rsqrtssXrvm",
    "rcppsXrm|rcpssXrvm",
    "andpsXrvm||andpdXrvm",
    "andnpsXrvm||andnpdXrvm",
    "orpsXrvm||orpdXrvm",
    "xorpsXrvm||xorpdXrvm",
    "addpsXrvm|addssXrvm|addpdXrvm|addsdXrvm",
    "mulpsXrvm|mulssXrvm|mulpdXrvm|mulsdXrvm",
    "cvtps2pdXrm|cvtss2sdXrvm|cvtpd2psXrm|cvtsd2ssXrvm",
    "cvtdq2psXrm|cvttps2dqXrm|cvtps2dqXrm",
    "subpsXrvm|subssXrvm|subpdXrvm|subsdXrvm",
    "minpsXrvm|minssXrvm|minpdXrvm|minsdXrvm",
    "divpsXrvm|divssXrvm|divpdXrvm|divsdXrvm",
    "maxpsXrvm|maxssXrvm|maxpdXrvm|maxsdXrvm",
    --6x
    "punpcklbwPrvm",
    "punpcklwdPrvm",
    "punpckldqPrvm",
    "packsswbPrvm",
    "pcmpgtbPrvm",
    "pcmpgtwPrvm",
    "pcmpgtdPrvm",
    "packuswbPrvm",
    "punpckhbwPrvm",
    "punpckhwdPrvm",
    "punpckhdqPrvm",
    "packssdwPrvm",
    "||punpcklqdqXrvm",
    "||punpckhqdqXrvm",
    "movPrVSm",
    "movqMrm|movdquXrm|movdqaXrm",
    --7x
    "pshufwMrmu|pshufhwXrmu|pshufdXrmu|pshuflwXrmu",
    "pshiftw!Pvmu",
    "pshiftd!Pvmu",
    "pshiftq!Mvmu||pshiftdq!Xvmu",
    "pcmpeqbPrvm",
    "pcmpeqwPrvm",
    "pcmpeqdPrvm",
    "emms*|",
    "vmreadUmr||extrqXmuu$|insertqXrmuu$",
    "vmwriteUrm||extrqXrm$|insertqXrm$",
    nil,
    nil,
    "||haddpdXrvm|haddpsXrvm",
    "||hsubpdXrvm|hsubpsXrvm",
    "movVSmMr|movqXrm|movVSmXr",
    "movqMmr|movdquXmr|movdqaXmr",
    --8x
    "joVj",
    "jnoVj",
    "jbVj",
    "jnbVj",
    "jzVj",
    "jnzVj",
    "jbeVj",
    "jaVj",
    "jsVj",
    "jnsVj",
    "jpeVj",
    "jpoVj",
    "jlVj",
    "jgeVj",
    "jleVj",
    "jgVj",
    --9x
    "setoBm",
    "setnoBm",
    "setbBm",
    "setnbBm",
    "setzBm",
    "setnzBm",
    "setbeBm",
    "setaBm",
    "setsBm",
    "setnsBm",
    "setpeBm",
    "setpoBm",
    "setlBm",
    "setgeBm",
    "setleBm",
    "setgBm",
    --Ax
    "push fs",
    "pop fs",
    "cpuid",
    "btVmr",
    "shldVmru",
    "shldVmrc",
    nil,
    nil,
    "push gs",
    "pop gs",
    "rsm",
    "btsVmr",
    "shrdVmru",
    "shrdVmrc",
    "fxsave!Dmp",
    "imulVrm",
    --Bx
    "cmpxchgBmr",
    "cmpxchgVmr",
    "$lssVrm",
    "btrVmr",
    "$lfsVrm",
    "$lgsVrm",
    "movzxVrBmt",
    "movzxVrWmt",
    "|popcntVrm",
    "ud2Dp",
    "bt!Vmu",
    "btcVmr",
    "bsfVrm",
    "bsrVrm|lzcntVrm|bsrWrm",
    "movsxVrBmt",
    "movsxVrWmt",
    --Cx
    "xaddBmr",
    "xaddVmr",
    "cmppsXrvmu|cmpssXrvmu|cmppdXrvmu|cmpsdXrvmu",
    "$movntiVmr|",
    "pinsrwPrvWmu",
    "pextrwDrPmu",
    "shufpsXrvmu||shufpdXrvmu",
    "$cmpxchg!Qmp",
    "bswapVR",
    "bswapVR",
    "bswapVR",
    "bswapVR",
    "bswapVR",
    "bswapVR",
    "bswapVR",
    "bswapVR",
    --Dx
    "||addsubpdXrvm|addsubpsXrvm",
    "psrlwPrvm",
    "psrldPrvm",
    "psrlqPrvm",
    "paddqPrvm",
    "pmullwPrvm",
    "|movq2dqXrMm|movqXmr|movdq2qMrXm$",
    "pmovmskbVrMm||pmovmskbVrXm",
    "psubusbPrvm",
    "psubuswPrvm",
    "pminubPrvm",
    "pandPrvm",
    "paddusbPrvm",
    "padduswPrvm",
    "pmaxubPrvm",
    "pandnPrvm",
    --Ex
    "pavgbPrvm",
    "psrawPrvm",
    "psradPrvm",
    "pavgwPrvm",
    "pmulhuwPrvm",
    "pmulhwPrvm",
    "|cvtdq2pdXrm|cvttpd2dqXrm|cvtpd2dqXrm",
    "$movntqMmr||$movntdqXmr",
    "psubsbPrvm",
    "psubswPrvm",
    "pminswPrvm",
    "porPrvm",
    "paddsbPrvm",
    "paddswPrvm",
    "pmaxswPrvm",
    "pxorPrvm",
    --Fx
    "|||lddquXrm",
    "psllwPrvm",
    "pslldPrvm",
    "psllqPrvm",
    "pmuludqPrvm",
    "pmaddwdPrvm",
    "psadbwPrvm",
    "maskmovqMrm||maskmovdquXrm$",
    "psubbPrvm",
    "psubwPrvm",
    "psubdPrvm",
    "psubqPrvm",
    "paddbPrvm",
    "paddwPrvm",
    "padddPrvm",
    "ud",
}
assert(map_opc2[255] == "ud")

-- Map for three-byte opcodes. Can't wait for their next invention.
local map_opc3 = {
    ["38"] = { -- [66] 0f 38 xx
        --0x
        [0] = "pshufbPrvm", "phaddwPrvm", "phadddPrvm", "phaddswPrvm",
        "pmaddubswPrvm", "phsubwPrvm", "phsubdPrvm", "phsubswPrvm",
        "psignbPrvm", "psignwPrvm", "psigndPrvm", "pmulhrswPrvm",
        "||permilpsXrvm", "||permilpdXrvm", nil, nil,
        --1x
        "||pblendvbXrma", nil, nil, nil,
        "||blendvpsXrma", "||blendvpdXrma", "||permpsXrvm", "||ptestXrm",
        "||broadcastssXrm", "||broadcastsdXrm", "||broadcastf128XrlXm", nil,
        "pabsbPrm", "pabswPrm", "pabsdPrm", nil,
        --2x
        "||pmovsxbwXrm", "||pmovsxbdXrm", "||pmovsxbqXrm", "||pmovsxwdXrm",
        "||pmovsxwqXrm", "||pmovsxdqXrm", nil, nil,
        "||pmuldqXrvm", "||pcmpeqqXrvm", "||$movntdqaXrm", "||packusdwXrvm",
        "||maskmovpsXrvm", "||maskmovpdXrvm", "||maskmovpsXmvr", "||maskmovpdXmvr",
        --3x
        "||pmovzxbwXrm", "||pmovzxbdXrm", "||pmovzxbqXrm", "||pmovzxwdXrm",
        "||pmovzxwqXrm", "||pmovzxdqXrm", "||permdXrvm", "||pcmpgtqXrvm",
        "||pminsbXrvm", "||pminsdXrvm", "||pminuwXrvm", "||pminudXrvm",
        "||pmaxsbXrvm", "||pmaxsdXrvm", "||pmaxuwXrvm", "||pmaxudXrvm",
        --4x
        "||pmulddXrvm", "||phminposuwXrm", nil, nil,
        nil, "||psrlvVSXrvm", "||psravdXrvm", "||psllvVSXrvm",
        --5x
        [0x58] = "||pbroadcastdXrlXm", [0x59] = "||pbroadcastqXrlXm",
        [0x5a] = "||broadcasti128XrlXm",
        --7x
        [0x78] = "||pbroadcastbXrlXm", [0x79] = "||pbroadcastwXrlXm",
        --8x
        [0x8c] = "||pmaskmovXrvVSm",
        [0x8e] = "||pmaskmovVSmXvr",
        --9x
        [0x96] = "||fmaddsub132pHXrvm", [0x97] = "||fmsubadd132pHXrvm",
        [0x98] = "||fmadd132pHXrvm", [0x99] = "||fmadd132sHXrvm",
        [0x9a] = "||fmsub132pHXrvm", [0x9b] = "||fmsub132sHXrvm",
        [0x9c] = "||fnmadd132pHXrvm", [0x9d] = "||fnmadd132sHXrvm",
        [0x9e] = "||fnmsub132pHXrvm", [0x9f] = "||fnmsub132sHXrvm",
        --Ax
        [0xa6] = "||fmaddsub213pHXrvm", [0xa7] = "||fmsubadd213pHXrvm",
        [0xa8] = "||fmadd213pHXrvm", [0xa9] = "||fmadd213sHXrvm",
        [0xaa] = "||fmsub213pHXrvm", [0xab] = "||fmsub213sHXrvm",
        [0xac] = "||fnmadd213pHXrvm", [0xad] = "||fnmadd213sHXrvm",
        [0xae] = "||fnmsub213pHXrvm", [0xaf] = "||fnmsub213sHXrvm",
        --Bx
        [0xb6] = "||fmaddsub231pHXrvm", [0xb7] = "||fmsubadd231pHXrvm",
        [0xb8] = "||fmadd231pHXrvm", [0xb9] = "||fmadd231sHXrvm",
        [0xba] = "||fmsub231pHXrvm", [0xbb] = "||fmsub231sHXrvm",
        [0xbc] = "||fnmadd231pHXrvm", [0xbd] = "||fnmadd231sHXrvm",
        [0xbe] = "||fnmsub231pHXrvm", [0xbf] = "||fnmsub231sHXrvm",
        --Dx
        [0xdc] = "||aesencXrvm", [0xdd] = "||aesenclastXrvm",
        [0xde] = "||aesdecXrvm", [0xdf] = "||aesdeclastXrvm",
        --Fx
        [0xf0] = "|||crc32TrBmt", [0xf1] = "|||crc32TrVmt",
        [0xf7] = "| sarxVrmv| shlxVrmv| shrxVrmv",
    },

    ["3a"] = { -- [66] 0f 3a xx
        --0x
        [0x00] = "||permqXrmu", "||permpdXrmu", "||pblenddXrvmu", nil,
        "||permilpsXrmu", "||permilpdXrmu", "||perm2f128Xrvmu", nil,
        "||roundpsXrmu", "||roundpdXrmu", "||roundssXrvmu", "||roundsdXrvmu",
        "||blendpsXrvmu", "||blendpdXrvmu", "||pblendwXrvmu", "palignrPrvmu",
        --1x
        nil, nil, nil, nil,
        "||pextrbVmXru", "||pextrwVmXru", "||pextrVmSXru", "||extractpsVmXru",
        "||insertf128XrvlXmu", "||extractf128XlXmYru", nil, nil,
        nil, nil, nil, nil,
        --2x
        "||pinsrbXrvVmu", "||insertpsXrvmu", "||pinsrXrvVmuS", nil,
        --3x
        [0x38] = "||inserti128Xrvmu", [0x39] = "||extracti128XlXmYru",
        --4x
        [0x40] = "||dppsXrvmu",
        [0x41] = "||dppdXrvmu",
        [0x42] = "||mpsadbwXrvmu",
        [0x44] = "||pclmulqdqXrvmu",
        [0x46] = "||perm2i128Xrvmu",
        [0x4a] = "||blendvpsXrvmb", [0x4b] = "||blendvpdXrvmb",
        [0x4c] = "||pblendvbXrvmb",
        --6x
        [0x60] = "||pcmpestrmXrmu", [0x61] = "||pcmpestriXrmu",
        [0x62] = "||pcmpistrmXrmu", [0x63] = "||pcmpistriXrmu",
        [0xdf] = "||aeskeygenassistXrmu",
        --Fx
        [0xf0] = "||| rorxVrmu",
    },
}

-- Map for VMX/SVM opcodes 0F 01 C0-FF (sgdt group with register operands).
local map_opcvm = {
    [0xc1] = "vmcall",
    [0xc2] = "vmlaunch",
    [0xc3] = "vmresume",
    [0xc4] = "vmxoff",
    [0xc8] = "monitor",
    [0xc9] = "mwait",
    [0xd8] = "vmrun",
    [0xd9] = "vmmcall",
    [0xda] = "vmload",
    [0xdb] = "vmsave",
    [0xdc] = "stgi",
    [0xdd] = "clgi",
    [0xde] = "skinit",
    [0xdf] = "invlpga",
    [0xf8] = "swapgs",
    [0xf9] = "rdtscp",
}

-- Map for FP opcodes. And you thought stack machines are simple?
local map_opcfp = {
    -- D8-DF 00-BF: opcodes with a memory operand.
    -- D8
    [0] = "faddFm",
    "fmulFm",
    "fcomFm",
    "fcompFm",
    "fsubFm",
    "fsubrFm",
    "fdivFm",
    "fdivrFm",
    "fldFm",
    nil,
    "fstFm",
    "fstpFm",
    "fldenvVm",
    "fldcwWm",
    "fnstenvVm",
    "fnstcwWm",
    -- DA
    "fiaddDm",
    "fimulDm",
    "ficomDm",
    "ficompDm",
    "fisubDm",
    "fisubrDm",
    "fidivDm",
    "fidivrDm",
    -- DB
    "fildDm",
    "fisttpDm",
    "fistDm",
    "fistpDm",
    nil,
    "fld twordFmp",
    nil,
    "fstp twordFmp",
    -- DC
    "faddGm",
    "fmulGm",
    "fcomGm",
    "fcompGm",
    "fsubGm",
    "fsubrGm",
    "fdivGm",
    "fdivrGm",
    -- DD
    "fldGm",
    "fisttpQm",
    "fstGm",
    "fstpGm",
    "frstorDmp",
    nil,
    "fnsaveDmp",
    "fnstswWm",
    -- DE
    "fiaddWm",
    "fimulWm",
    "ficomWm",
    "ficompWm",
    "fisubWm",
    "fisubrWm",
    "fidivWm",
    "fidivrWm",
    -- DF
    "fildWm",
    "fisttpWm",
    "fistWm",
    "fistpWm",
    "fbld twordFmp",
    "fildQm",
    "fbstp twordFmp",
    "fistpQm",
    -- xx C0-FF: opcodes with a pseudo-register operand.
    -- D8
    "faddFf",
    "fmulFf",
    "fcomFf",
    "fcompFf",
    "fsubFf",
    "fsubrFf",
    "fdivFf",
    "fdivrFf",
    -- D9
    "fldFf",
    "fxchFf",
    { "fnop" },
    nil,
    { "fchs",  "fabs",    nil,      nil,       "ftst",    "fxam" },
    { "fld1",  "fldl2t",  "fldl2e", "fldpi",   "fldlg2",  "fldln2", "fldz" },
    { "f2xm1", "fyl2x",   "fptan",  "fpatan",  "fxtract", "fprem1", "fdecstp", "fincstp" },
    { "fprem", "fyl2xp1", "fsqrt",  "fsincos", "frndint", "fscale", "fsin",    "fcos" },
    -- DA
    "fcmovbFf",
    "fcmoveFf",
    "fcmovbeFf",
    "fcmovuFf",
    nil,
    { nil, "fucompp" },
    nil,
    nil,
    -- DB
    "fcmovnbFf",
    "fcmovneFf",
    "fcmovnbeFf",
    "fcmovnuFf",
    { nil, nil,      "fnclex", "fninit" },
    "fucomiFf",
    "fcomiFf",
    nil,
    -- DC
    "fadd toFf",
    "fmul toFf",
    nil,
    nil,
    "fsub toFf",
    "fsubr toFf",
    "fdivr toFf",
    "fdiv toFf",
    -- DD
    "ffreeFf",
    nil,
    "fstFf",
    "fstpFf",
    "fucomFf",
    "fucompFf",
    nil,
    nil,
    -- DE
    "faddpFf",
    "fmulpFf",
    nil,
    { nil,        "fcompp" },
    "fsubrpFf",
    "fsubpFf",
    "fdivrpFf",
    "fdivpFf",
    -- DF
    nil,
    nil,
    nil,
    nil,
    { "fnstsw ax" },
    "fucomipFf",
    "fcomipFf",
    nil,
}
assert(map_opcfp[126] == "fcomipFf")

-- Map for opcode groups. The subkey is sp from the ModRM byte.
local map_opcgroup = {
    arith = { "add", "or", "adc", "sbb", "and", "sub", "xor", "cmp" },
    shift = { "rol", "ror", "rcl", "rcr", "shl", "shr", "sal", "sar" },
    testb = { "testBmi", "testBmi", "not", "neg", "mul", "imul", "div", "idiv" },
    testv = { "testVmi", "testVmi", "not", "neg", "mul", "imul", "div", "idiv" },
    incb = { "inc", "dec" },
    incd = { "inc", "dec", "callUmp", "$call farDmp",
        "jmpUmp", "$jmp farDmp", "pushUm" },
    sldt = { "sldt", "str", "lldt", "ltr", "verr", "verw" },
    sgdt = { "vm*$sgdt", "vm*$sidt", "$lgdt", "vm*$lidt",
        "smsw", nil, "lmsw", "vm*$invlpg" },
    bt = { nil, nil, nil, nil, "bt", "bts", "btr", "btc" },
    cmpxchg = { nil, "sz*,cmpxchg8bQmp,cmpxchg16bXmp", nil, nil,
        nil, nil, "vmptrld|vmxon|vmclear", "vmptrst" },
    pshiftw = { nil, nil, "psrlw", nil, "psraw", nil, "psllw" },
    pshiftd = { nil, nil, "psrld", nil, "psrad", nil, "pslld" },
    pshiftq = { nil, nil, "psrlq", nil, nil, nil, "psllq" },
    pshiftdq = { nil, nil, "psrlq", "psrldq", nil, nil, "psllq", "pslldq" },
    fxsave = { "$fxsave", "$fxrstor", "$ldmxcsr", "$stmxcsr",
        nil, "lfenceDp$", "mfenceDp$", "sfenceDp$clflush" },
    prefetch = { "prefetch", "prefetchw" },
    prefetcht = { "prefetchnta", "prefetcht0", "prefetcht1", "prefetcht2" },
}

------------------------------------------------------------------------------

-- Maps for register names.
local map_regs = {
    B = { "al", "cl", "dl", "bl", "ah", "ch", "dh", "bh",
        "r8b", "r9b", "r10b", "r11b", "r12b", "r13b", "r14b", "r15b" },
    B64 = { "al", "cl", "dl", "bl", "spl", "bpl", "sil", "dil",
        "r8b", "r9b", "r10b", "r11b", "r12b", "r13b", "r14b", "r15b" },
    W = { "ax", "cx", "dx", "bx", "sp", "bp", "si", "di",
        "r8w", "r9w", "r10w", "r11w", "r12w", "r13w", "r14w", "r15w" },
    D = { "eax", "ecx", "edx", "ebx", "esp", "ebp", "esi", "edi",
        "r8d", "r9d", "r10d", "r11d", "r12d", "r13d", "r14d", "r15d" },
    Q = { "rax", "rcx", "rdx", "rbx", "rsp", "rbp", "rsi", "rdi",
        "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15" },
    M = { "mm0", "mm1", "mm2", "mm3", "mm4", "mm5", "mm6", "mm7",
        "mm0", "mm1", "mm2", "mm3", "mm4", "mm5", "mm6", "mm7" }, -- No x64 ext!
    X = { "xmm0", "xmm1", "xmm2", "xmm3", "xmm4", "xmm5", "xmm6", "xmm7",
        "xmm8", "xmm9", "xmm10", "xmm11", "xmm12", "xmm13", "xmm14", "xmm15" },
    Y = { "ymm0", "ymm1", "ymm2", "ymm3", "ymm4", "ymm5", "ymm6", "ymm7",
        "ymm8", "ymm9", "ymm10", "ymm11", "ymm12", "ymm13", "ymm14", "ymm15" },
}
local map_segregs = { "es", "cs", "ss", "ds", "fs", "gs", "segr6", "segr7" }

-- Maps for size names.
local map_sz2n = {
    B = 1, W = 2, D = 4, Q = 8, M = 8, X = 16, Y = 32,
}
local map_sz2prefix = {
    B = "byte",
    W = "word",
    D = "dword",
    Q = "qword",
    M = "qword",
    X = "xword",
    Y = "yword",
    F = "dword",
    G = "qword",            -- No need for sizes/register names for these two.
}

------------------------------------------------------------------------------

-- Output a nicely formatted line with an opcode and operands.
local function putop(ctx, text, operands)
    local code, pos, hex = ctx.code, ctx.pos, ""
    local hmax = ctx.hexdump
    if hmax > 0 then
        for i = ctx.start, pos - 1 do
            hex = hex .. format("%02X", byte(code, i, i))
        end
        if #hex > hmax then
            hex = sub(hex, 1, hmax) .. ". "
        else
            hex = hex .. rep(" ", hmax - #hex + 2)
        end
    end
    if operands then text = text .. " " .. operands end
    if ctx.o16 then
        text = "o16 " .. text; ctx.o16 = false
    end
    if ctx.a32 then
        text = "a32 " .. text; ctx.a32 = false
    end
    if ctx.rep then
        text = ctx.rep .. " " .. text; ctx.rep = false
    end
    if ctx.rex then
        local t = (ctx.rexw and "w" or "") .. (ctx.rexr and "r" or "") ..
            (ctx.rexx and "x" or "") .. (ctx.rexb and "b" or "") ..
            (ctx.vexl and "l" or "")
        if ctx.vexv and ctx.vexv ~= 0 then t = t .. "v" .. ctx.vexv end
        if t ~= "" then
            text = ctx.rex .. "." .. t .. " " .. gsub(text, "^ ", "")
        elseif ctx.rex == "vex" then
            text = gsub("v" .. text, "^v ", "")
        end
        ctx.rexw = false; ctx.rexr = false; ctx.rexx = false; ctx.rexb = false
        ctx.rex = false; ctx.vexl = false; ctx.vexv = false
    end
    if ctx.seg then
        local text2, n = gsub(text, "%[", "[" .. ctx.seg .. ":")
        if n == 0 then text = ctx.seg .. " " .. text else text = text2 end
        ctx.seg = false
    end
    if ctx.lock then
        text = "lock " .. text; ctx.lock = false
    end
    local imm = ctx.imm
    if imm then
        local sym = ctx.symtab[imm]
        if sym then text = text .. "\t->" .. sym end
    end
    ctx.out(format("%08x  %s%s\n", ctx.addr + ctx.start, hex, text))
    ctx.mrm = false
    ctx.vexv = false
    ctx.start = pos
    ctx.imm = nil
end

-- Clear all prefix flags.
local function clearprefixes(ctx)
    ctx.o16 = false; ctx.seg = false; ctx.lock = false; ctx.rep = false
    ctx.rexw = false; ctx.rexr = false; ctx.rexx = false; ctx.rexb = false
    ctx.rex = false; ctx.a32 = false; ctx.vexl = false
end

-- Fallback for incomplete opcodes at the end.
local function incomplete(ctx)
    ctx.pos = ctx.stop + 1
    clearprefixes(ctx)
    return putop(ctx, "(incomplete)")
end

-- Fallback for unknown opcodes.
local function unknown(ctx)
    clearprefixes(ctx)
    return putop(ctx, "(unknown)")
end

-- Return an immediate of the specified size.
local function getimm(ctx, pos, n)
    if pos + n - 1 > ctx.stop then return incomplete(ctx) end
    local code = ctx.code
    if n == 1 then
        local b1 = byte(code, pos, pos)
        return b1
    elseif n == 2 then
        local b1, b2 = byte(code, pos, pos + 1)
        return b1 + b2 * 256
    else
        local b1, b2, b3, b4 = byte(code, pos, pos + 3)
        local imm = b1 + b2 * 256 + b3 * 65536 + b4 * 16777216
        ctx.imm = imm
        return imm
    end
end

-- Process pattern string and generate the operands.
local function putpat(ctx, name, pat)
    local operands, regs, sz, mode, sp, rm, sc, rx, sdisp
    local code, pos, stop, vexl = ctx.code, ctx.pos, ctx.stop, ctx.vexl

    -- Chars used: 1DFGHIMPQRSTUVWXYabcdfgijlmoprstuvwxyz
    for p in gmatch(pat, ".") do
        local x = nil
        if p == "V" or p == "U" then
            if ctx.rexw then
                sz = "Q"; ctx.rexw = false
            elseif ctx.o16 then
                sz = "W"; ctx.o16 = false
            elseif p == "U" and ctx.x64 then
                sz = "Q"
            else
                sz = "D"
            end
            regs = map_regs[sz]
        elseif p == "T" then
            if ctx.rexw then
                sz = "Q"; ctx.rexw = false
            else sz = "D" end
            regs = map_regs[sz]
        elseif p == "B" then
            sz = "B"
            regs = ctx.rex and map_regs.B64 or map_regs.B
        elseif match(p, "[WDQMXYFG]") then
            sz = p
            if sz == "X" and vexl then
                sz = "Y"; ctx.vexl = false
            end
            regs = map_regs[sz]
        elseif p == "P" then
            sz = ctx.o16 and "X" or "M"; ctx.o16 = false
            if sz == "X" and vexl then
                sz = "Y"; ctx.vexl = false
            end
            regs = map_regs[sz]
        elseif p == "H" then
            name = name .. (ctx.rexw and "d" or "s")
            ctx.rexw = false
        elseif p == "S" then
            name = name .. lower(sz)
        elseif p == "s" then
            local imm = getimm(ctx, pos, 1); if not imm then return end
            x = imm <= 127 and format("+0x%02x", imm)
                or format("-0x%02x", 256 - imm)
            pos = pos + 1
        elseif p == "u" then
            local imm = getimm(ctx, pos, 1); if not imm then return end
            x = format("0x%02x", imm)
            pos = pos + 1
        elseif p == "b" then
            local imm = getimm(ctx, pos, 1); if not imm then return end
            x = regs[imm / 16 + 1]
            pos = pos + 1
        elseif p == "w" then
            local imm = getimm(ctx, pos, 2); if not imm then return end
            x = format("0x%x", imm)
            pos = pos + 2
        elseif p == "o" then -- [offset]
            if ctx.x64 then
                local imm1 = getimm(ctx, pos, 4); if not imm1 then return end
                local imm2 = getimm(ctx, pos + 4, 4); if not imm2 then return end
                x = format("[0x%08x%08x]", imm2, imm1)
                pos = pos + 8
            else
                local imm = getimm(ctx, pos, 4); if not imm then return end
                x = format("[0x%08x]", imm)
                pos = pos + 4
            end
        elseif p == "i" or p == "I" then
            local n = map_sz2n[sz]
            if n == 8 and ctx.x64 and p == "I" then
                local imm1 = getimm(ctx, pos, 4); if not imm1 then return end
                local imm2 = getimm(ctx, pos + 4, 4); if not imm2 then return end
                x = format("0x%08x%08x", imm2, imm1)
            else
                if n == 8 then n = 4 end
                local imm = getimm(ctx, pos, n); if not imm then return end
                if sz == "Q" and (imm < 0 or imm > 0x7fffffff) then
                    imm = (0xffffffff + 1) - imm
                    x = format(imm > 65535 and "-0x%08x" or "-0x%x", imm)
                else
                    x = format(imm > 65535 and "0x%08x" or "0x%x", imm)
                end
            end
            pos = pos + n
        elseif p == "j" then
            local n = map_sz2n[sz]
            if n == 8 then n = 4 end
            local imm = getimm(ctx, pos, n); if not imm then return end
            if sz == "B" and imm > 127 then
                imm = imm - 256
            elseif imm > 2147483647 then
                imm = imm - 4294967296
            end
            pos = pos + n
            imm = imm + pos + ctx.addr
            if imm > 4294967295 and not ctx.x64 then imm = imm - 4294967296 end
            ctx.imm = imm
            if sz == "W" then
                x = format("word 0x%04x", imm % 65536)
            elseif ctx.x64 then
                local lo = imm % 0x1000000
                x = format("0x%02x%06x", (imm - lo) / 0x1000000, lo)
            else
                x = "0x" .. tohex(imm)
            end
        elseif p == "R" then
            local r = byte(code, pos - 1, pos - 1) % 8
            if ctx.rexb then
                r = r + 8; ctx.rexb = false
            end
            x = regs[r + 1]
        elseif p == "a" then
            x = regs[1]
        elseif p == "c" then
            x = "cl"
        elseif p == "d" then
            x = "dx"
        elseif p == "1" then
            x = "1"
        else
            if not mode then
                mode = ctx.mrm
                if not mode then
                    if pos > stop then return incomplete(ctx) end
                    mode = byte(code, pos, pos)
                    pos = pos + 1
                end
                rm = mode % 8; mode = (mode - rm) / 8
                sp = mode % 8; mode = (mode - sp) / 8
                sdisp = ""
                if mode < 3 then
                    if rm == 4 then
                        if pos > stop then return incomplete(ctx) end
                        sc = byte(code, pos, pos)
                        pos = pos + 1
                        rm = sc % 8; sc = (sc - rm) / 8
                        rx = sc % 8; sc = (sc - rx) / 8
                        if ctx.rexx then
                            rx = rx + 8; ctx.rexx = false
                        end
                        if rx == 4 then rx = nil end
                    end
                    if mode > 0 or rm == 5 then
                        local dsz = mode
                        if dsz ~= 1 then dsz = 4 end
                        local disp = getimm(ctx, pos, dsz); if not disp then return end
                        if mode == 0 then rm = nil end
                        if rm or rx or (not sc and ctx.x64 and not ctx.a32) then
                            if dsz == 1 and disp > 127 then
                                sdisp = format("-0x%x", 256 - disp)
                            elseif disp >= 0 and disp <= 0x7fffffff then
                                sdisp = format("+0x%x", disp)
                            else
                                sdisp = format("-0x%x", (0xffffffff + 1) - disp)
                            end
                        else
                            sdisp = format(ctx.x64 and not ctx.a32 and
                                not (disp >= 0 and disp <= 0x7fffffff)
                                and "0xffffffff%08x" or "0x%08x", disp)
                        end
                        pos = pos + dsz
                    end
                end
                if rm and ctx.rexb then
                    rm = rm + 8; ctx.rexb = false
                end
                if ctx.rexr then
                    sp = sp + 8; ctx.rexr = false
                end
            end
            if p == "m" then
                if mode == 3 then
                    x = regs[rm + 1]
                else
                    local aregs = ctx.a32 and map_regs.D or ctx.aregs
                    local srm, srx = "", ""
                    if rm then
                        srm = aregs[rm + 1]
                    elseif not sc and ctx.x64 and not ctx.a32 then
                        srm = "rip"
                    end
                    ctx.a32 = false
                    if rx then
                        if rm then srm = srm .. "+" end
                        srx = aregs[rx + 1]
                        if sc > 0 then srx = srx .. "*" .. (2 ^ sc) end
                    end
                    x = format("[%s%s%s]", srm, srx, sdisp)
                end
                if mode < 3 and
                    (not match(pat, "[aRrgp]") or match(pat, "t")) then -- Yuck.
                    x = map_sz2prefix[sz] .. " " .. x
                end
            elseif p == "r" then
                x = regs[sp + 1]
            elseif p == "g" then
                x = map_segregs[sp + 1]
            elseif p == "p" then -- Suppress prefix.
            elseif p == "f" then
                x = "st" .. rm
            elseif p == "x" then
                if sp == 0 and ctx.lock and not ctx.x64 then
                    x = "CR8"; ctx.lock = false
                else
                    x = "CR" .. sp
                end
            elseif p == "v" then
                if ctx.vexv then
                    x = regs[ctx.vexv + 1]; ctx.vexv = false
                end
            elseif p == "y" then
                x = "DR" .. sp
            elseif p == "z" then
                x = "TR" .. sp
            elseif p == "l" then
                vexl = false
            elseif p == "t" then
            else
                error("bad pattern `" .. pat .. "'")
            end
        end
        if x then operands = operands and operands .. ", " .. x or x end
    end
    ctx.pos = pos
    return putop(ctx, name, operands)
end

-- Forward declaration.
local map_act

-- Fetch and cache MRM byte.
local function getmrm(ctx)
    local mrm = ctx.mrm
    if not mrm then
        local pos = ctx.pos
        if pos > ctx.stop then return nil end
        mrm = byte(ctx.code, pos, pos)
        ctx.pos = pos + 1
        ctx.mrm = mrm
    end
    return mrm
end

-- Dispatch to handler depending on pattern.
local function dispatch(ctx, opat, patgrp)
    if not opat then return unknown(ctx) end
    if match(opat, "%|") then -- MMX/SSE variants depending on prefix.
        local p
        if ctx.rep then
            p = ctx.rep == "rep" and "%|([^%|]*)" or "%|[^%|]*%|[^%|]*%|([^%|]*)"
            ctx.rep = false
        elseif ctx.o16 then
            p = "%|[^%|]*%|([^%|]*)"; ctx.o16 = false
        else
            p = "^[^%|]*"
        end
        opat = match(opat, p)
        if not opat then return unknown(ctx) end
        --    ctx.rep = false; ctx.o16 = false
        --XXX fails for 66 f2 0f 38 f1 06  crc32 eax,WORD PTR [esi]
        --XXX remove in branches?
    end
    if match(opat, "%$") then -- reg$mem variants.
        local mrm = getmrm(ctx); if not mrm then return incomplete(ctx) end
        opat = match(opat, mrm >= 192 and "^[^%$]*" or "%$(.*)")
        if opat == "" then return unknown(ctx) end
    end
    if opat == "" then return unknown(ctx) end
    local name, pat = match(opat, "^([a-z0-9 ]*)(.*)")
    if pat == "" and patgrp then pat = patgrp end
    return map_act[sub(pat, 1, 1)](ctx, name, pat)
end

-- Get a pattern from an opcode map and dispatch to handler.
local function dispatchmap(ctx, opcmap)
    local pos = ctx.pos
    local opat = opcmap[byte(ctx.code, pos, pos)]
    pos = pos + 1
    ctx.pos = pos
    return dispatch(ctx, opat)
end

-- Map for action codes. The key is the first char after the name.
map_act = {
    -- Simple opcodes without operands.
    [""] = function(ctx, name, pat)
        return putop(ctx, name)
    end,

    -- Operand size chars fall right through.
    B = putpat,
    W = putpat,
    D = putpat,
    Q = putpat,
    V = putpat,
    U = putpat,
    T = putpat,
    M = putpat,
    X = putpat,
    P = putpat,
    F = putpat,
    G = putpat,
    Y = putpat,
    H = putpat,

    -- Collect prefixes.
    [":"] = function(ctx, name, pat)
        ctx[pat == ":" and name or sub(pat, 2)] = name
        if ctx.pos - ctx.start > 5 then return unknown(ctx) end -- Limit #prefixes.
    end,

    -- Chain to special handler specified by name.
    ["*"] = function(ctx, name, pat)
        return map_act[name](ctx, name, sub(pat, 2))
    end,

    -- Use named subtable for opcode group.
    ["!"] = function(ctx, name, pat)
        local mrm = getmrm(ctx); if not mrm then return incomplete(ctx) end
        return dispatch(ctx, map_opcgroup[name][((mrm - (mrm % 8)) / 8) % 8 + 1], sub(pat, 2))
    end,

    -- o16,o32[,o64] variants.
    sz = function(ctx, name, pat)
        if ctx.o16 then
            ctx.o16 = false
        else
            pat = match(pat, ",(.*)")
            if ctx.rexw then
                local p = match(pat, ",(.*)")
                if p then
                    pat = p; ctx.rexw = false
                end
            end
        end
        pat = match(pat, "^[^,]*")
        return dispatch(ctx, pat)
    end,

    -- Two-byte opcode dispatch.
    opc2 = function(ctx, name, pat)
        return dispatchmap(ctx, map_opc2)
    end,

    -- Three-byte opcode dispatch.
    opc3 = function(ctx, name, pat)
        return dispatchmap(ctx, map_opc3[pat])
    end,

    -- VMX/SVM dispatch.
    vm = function(ctx, name, pat)
        return dispatch(ctx, map_opcvm[ctx.mrm])
    end,

    -- Floating point opcode dispatch.
    fp = function(ctx, name, pat)
        local mrm = getmrm(ctx); if not mrm then return incomplete(ctx) end
        local rm = mrm % 8
        local idx = pat * 8 + ((mrm - rm) / 8) % 8
        if mrm >= 192 then idx = idx + 64 end
        local opat = map_opcfp[idx]
        if type(opat) == "table" then opat = opat[rm + 1] end
        return dispatch(ctx, opat)
    end,

    -- REX prefix.
    rex = function(ctx, name, pat)
        if ctx.rex then return unknown(ctx) end -- Only 1 REX or VEX prefix allowed.
        for p in gmatch(pat, ".") do ctx["rex" .. p] = true end
        ctx.rex = "rex"
    end,

    -- VEX prefix.
    vex = function(ctx, name, pat)
        if ctx.rex then return unknown(ctx) end -- Only 1 REX or VEX prefix allowed.
        ctx.rex = "vex"
        local pos = ctx.pos
        if ctx.mrm then
            ctx.mrm = nil
            pos = pos - 1
        end
        local b = byte(ctx.code, pos, pos)
        if not b then return incomplete(ctx) end
        pos = pos + 1
        if b < 128 then ctx.rexr = true end
        local m = 1
        if pat == "3" then
            m = b % 32; b = (b - m) / 32
            local nb = b % 2; b = (b - nb) / 2
            if nb == 0 then ctx.rexb = true end
            local nx = b % 2
            if nx == 0 then ctx.rexx = true end
            b = byte(ctx.code, pos, pos)
            if not b then return incomplete(ctx) end
            pos = pos + 1
            if b >= 128 then ctx.rexw = true end
        end
        ctx.pos = pos
        local map
        if m == 1 then
            map = map_opc2
        elseif m == 2 then
            map = map_opc3["38"]
        elseif m == 3 then
            map = map_opc3["3a"]
        else
            return unknown(ctx)
        end
        local p = b % 4; b = (b - p) / 4
        if p == 1 then
            ctx.o16 = "o16"
        elseif p == 2 then
            ctx.rep = "rep"
        elseif p == 3 then
            ctx.rep = "repne"
        end
        local l = b % 2; b = (b - l) / 2
        if l ~= 0 then ctx.vexl = true end
        ctx.vexv = (-1 - b) % 16
        return dispatchmap(ctx, map)
    end,

    -- Special case for nop with REX prefix.
    nop = function(ctx, name, pat)
        return dispatch(ctx, ctx.rex and pat or "nop")
    end,

    -- Special case for 0F 77.
    emms = function(ctx, name, pat)
        if ctx.rex ~= "vex" then
            return putop(ctx, "emms")
        elseif ctx.vexl then
            ctx.vexl = false
            return putop(ctx, "zeroall")
        else
            return putop(ctx, "zeroupper")
        end
    end,
}

------------------------------------------------------------------------------

-- Disassemble a block of code.
local function disass_block(ctx, ofs, len)
    if not ofs then ofs = 0 end
    local stop = len and ofs + len or #ctx.code
    ofs = ofs + 1
    ctx.start = ofs
    ctx.pos = ofs
    ctx.stop = stop
    ctx.imm = nil
    ctx.mrm = false
    clearprefixes(ctx)
    while ctx.pos <= stop do dispatchmap(ctx, ctx.map1) end
    if ctx.pos ~= ctx.start then incomplete(ctx) end
end

-- Extended API: create a disassembler context. Then call ctx:disass(ofs, len).
local function create(code, addr, out)
    local ctx = {}
    ctx.code = code
    ctx.addr = (addr or 0) - 1
    ctx.out = out or io.write
    ctx.symtab = {}
    ctx.disass = disass_block
    ctx.hexdump = 16
    ctx.x64 = false
    ctx.map1 = map_opc1_32
    ctx.aregs = map_regs.D
    return ctx
end

local function create64(code, addr, out)
    local ctx = create(code, addr, out)
    ctx.x64 = true
    ctx.map1 = map_opc1_64
    ctx.aregs = map_regs.Q
    return ctx
end

-- Simple API: disassemble code (a string) at address and output via out.
local function disass(code, addr, out)
    create(code, addr, out):disass()
end

local function disass64(code, addr, out)
    create64(code, addr, out):disass()
end

-- Return register name for RID.
local function regname(r)
    if r < 8 then return map_regs.D[r + 1] end
    return map_regs.X[r - 7]
end

local function regname64(r)
    if r < 16 then return map_regs.Q[r + 1] end
    return map_regs.X[r - 15]
end

-- Public module functions.
return {
    create = create,
    create64 = create64,
    disass = disass,
    disass64 = disass64,
    regname = regname,
    regname64 = regname64
}
