diff third_party/luajit/src/jit/dump.lua @ 186:8cf4ec5e2191 hg-web

Fixed merge conflict.
author MrJuneJune <me@mrjunejune.com>
date Fri, 23 Jan 2026 22:38:59 -0800
parents 94705b5986b3
children
line wrap: on
line diff
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/luajit/src/jit/dump.lua	Fri Jan 23 22:38:59 2026 -0800
@@ -0,0 +1,725 @@
+----------------------------------------------------------------------------
+-- LuaJIT compiler dump module.
+--
+-- Copyright (C) 2005-2023 Mike Pall. All rights reserved.
+-- Released under the MIT license. See Copyright Notice in luajit.h
+----------------------------------------------------------------------------
+--
+-- This module can be used to debug the JIT compiler itself. It dumps the
+-- code representations and structures used in various compiler stages.
+--
+-- Example usage:
+--
+--   luajit -jdump -e "local x=0; for i=1,1e6 do x=x+i end; print(x)"
+--   luajit -jdump=im -e "for i=1,1000 do for j=1,1000 do end end" | less -R
+--   luajit -jdump=is myapp.lua | less -R
+--   luajit -jdump=-b myapp.lua
+--   luajit -jdump=+aH,myapp.html myapp.lua
+--   luajit -jdump=ixT,myapp.dump myapp.lua
+--
+-- The first argument specifies the dump mode. The second argument gives
+-- the output file name. Default output is to stdout, unless the environment
+-- variable LUAJIT_DUMPFILE is set. The file is overwritten every time the
+-- module is started.
+--
+-- Different features can be turned on or off with the dump mode. If the
+-- mode starts with a '+', the following features are added to the default
+-- set of features; a '-' removes them. Otherwise the features are replaced.
+--
+-- The following dump features are available (* marks the default):
+--
+--  * t  Print a line for each started, ended or aborted trace (see also -jv).
+--  * b  Dump the traced bytecode.
+--  * i  Dump the IR (intermediate representation).
+--    r  Augment the IR with register/stack slots.
+--    s  Dump the snapshot map.
+--  * m  Dump the generated machine code.
+--    x  Print each taken trace exit.
+--    X  Print each taken trace exit and the contents of all registers.
+--    a  Print the IR of aborted traces, too.
+--
+-- The output format can be set with the following characters:
+--
+--    T  Plain text output.
+--    A  ANSI-colored text output
+--    H  Colorized HTML + CSS output.
+--
+-- The default output format is plain text. It's set to ANSI-colored text
+-- if the COLORTERM variable is set. Note: this is independent of any output
+-- redirection, which is actually considered a feature.
+--
+-- You probably want to use less -R to enjoy viewing ANSI-colored text from
+-- a pipe or a file. Add this to your ~/.bashrc: export LESS="-R"
+--
+------------------------------------------------------------------------------
+
+-- Cache some library functions and objects.
+local jit = require("jit")
+local jutil = require("jit.util")
+local vmdef = require("jit.vmdef")
+local funcinfo, funcbc = jutil.funcinfo, jutil.funcbc
+local traceinfo, traceir, tracek = jutil.traceinfo, jutil.traceir, jutil.tracek
+local tracemc, tracesnap = jutil.tracemc, jutil.tracesnap
+local traceexitstub, ircalladdr = jutil.traceexitstub, jutil.ircalladdr
+local bit = require("bit")
+local band, shr, tohex = bit.band, bit.rshift, bit.tohex
+local sub, gsub, format = string.sub, string.gsub, string.format
+local byte, rep = string.byte, string.rep
+local type, tostring = type, tostring
+local stdout, stderr = io.stdout, io.stderr
+
+-- Load other modules on-demand.
+local bcline, disass
+
+-- Active flag, output file handle and dump mode.
+local active, out, dumpmode
+
+------------------------------------------------------------------------------
+
+local symtabmt = { __index = false }
+local symtab = {}
+local nexitsym = 0
+
+-- Fill nested symbol table with per-trace exit stub addresses.
+local function fillsymtab_tr(tr, nexit)
+  local t = {}
+  symtabmt.__index = t
+  if jit.arch:sub(1, 4) == "mips" then
+    t[traceexitstub(tr, 0)] = "exit"
+    return
+  end
+  for i=0,nexit-1 do
+    local addr = traceexitstub(tr, i)
+    if addr < 0 then addr = addr + 2^32 end
+    t[addr] = tostring(i)
+  end
+  local addr = traceexitstub(tr, nexit)
+  if addr then t[addr] = "stack_check" end
+end
+
+-- Fill symbol table with trace exit stub addresses.
+local function fillsymtab(tr, nexit)
+  local t = symtab
+  if nexitsym == 0 then
+    local maskaddr = jit.arch == "arm" and -2
+    local ircall = vmdef.ircall
+    for i=0,#ircall do
+      local addr = ircalladdr(i)
+      if addr ~= 0 then
+	if maskaddr then addr = band(addr, maskaddr) end
+	if addr < 0 then addr = addr + 2^32 end
+	t[addr] = ircall[i]
+      end
+    end
+  end
+  if nexitsym == 1000000 then -- Per-trace exit stubs.
+    fillsymtab_tr(tr, nexit)
+  elseif nexit > nexitsym then -- Shared exit stubs.
+    for i=nexitsym,nexit-1 do
+      local addr = traceexitstub(i)
+      if addr == nil then -- Fall back to per-trace exit stubs.
+	fillsymtab_tr(tr, nexit)
+	setmetatable(symtab, symtabmt)
+	nexit = 1000000
+	break
+      end
+      if addr < 0 then addr = addr + 2^32 end
+      t[addr] = tostring(i)
+    end
+    nexitsym = nexit
+  end
+  return t
+end
+
+local function dumpwrite(s)
+  out:write(s)
+end
+
+-- Disassemble machine code.
+local function dump_mcode(tr)
+  local info = traceinfo(tr)
+  if not info then return end
+  local mcode, addr, loop = tracemc(tr)
+  if not mcode then return end
+  if not disass then disass = require("jit.dis_"..jit.arch) end
+  if addr < 0 then addr = addr + 2^32 end
+  out:write("---- TRACE ", tr, " mcode ", #mcode, "\n")
+  local ctx = disass.create(mcode, addr, dumpwrite)
+  ctx.hexdump = 0
+  ctx.symtab = fillsymtab(tr, info.nexit)
+  if loop ~= 0 then
+    symtab[addr+loop] = "LOOP"
+    ctx:disass(0, loop)
+    out:write("->LOOP:\n")
+    ctx:disass(loop, #mcode-loop)
+    symtab[addr+loop] = nil
+  else
+    ctx:disass(0, #mcode)
+  end
+end
+
+------------------------------------------------------------------------------
+
+local irtype_text = {
+  [0] = "nil",
+  "fal",
+  "tru",
+  "lud",
+  "str",
+  "p32",
+  "thr",
+  "pro",
+  "fun",
+  "p64",
+  "cdt",
+  "tab",
+  "udt",
+  "flt",
+  "num",
+  "i8 ",
+  "u8 ",
+  "i16",
+  "u16",
+  "int",
+  "u32",
+  "i64",
+  "u64",
+  "sfp",
+}
+
+local colortype_ansi = {
+  [0] = "%s",
+  "%s",
+  "%s",
+  "\027[36m%s\027[m",
+  "\027[32m%s\027[m",
+  "%s",
+  "\027[1m%s\027[m",
+  "%s",
+  "\027[1m%s\027[m",
+  "%s",
+  "\027[33m%s\027[m",
+  "\027[31m%s\027[m",
+  "\027[36m%s\027[m",
+  "\027[34m%s\027[m",
+  "\027[34m%s\027[m",
+  "\027[35m%s\027[m",
+  "\027[35m%s\027[m",
+  "\027[35m%s\027[m",
+  "\027[35m%s\027[m",
+  "\027[35m%s\027[m",
+  "\027[35m%s\027[m",
+  "\027[35m%s\027[m",
+  "\027[35m%s\027[m",
+  "\027[35m%s\027[m",
+}
+
+local function colorize_text(s)
+  return s
+end
+
+local function colorize_ansi(s, t, extra)
+  local out = format(colortype_ansi[t], s)
+  if extra then out = "\027[3m"..out end
+  return out
+end
+
+local irtype_ansi = setmetatable({},
+  { __index = function(tab, t)
+      local s = colorize_ansi(irtype_text[t], t); tab[t] = s; return s; end })
+
+local html_escape = { ["<"] = "&lt;", [">"] = "&gt;", ["&"] = "&amp;", }
+
+local function colorize_html(s, t, extra)
+  s = gsub(s, "[<>&]", html_escape)
+  return format('<span class="irt_%s%s">%s</span>',
+		irtype_text[t], extra and " irt_extra" or "", s)
+end
+
+local irtype_html = setmetatable({},
+  { __index = function(tab, t)
+      local s = colorize_html(irtype_text[t], t); tab[t] = s; return s; end })
+
+local header_html = [[
+<style type="text/css">
+background { background: #ffffff; color: #000000; }
+pre.ljdump {
+font-size: 10pt;
+background: #f0f4ff;
+color: #000000;
+border: 1px solid #bfcfff;
+padding: 0.5em;
+margin-left: 2em;
+margin-right: 2em;
+}
+span.irt_str { color: #00a000; }
+span.irt_thr, span.irt_fun { color: #404040; font-weight: bold; }
+span.irt_tab { color: #c00000; }
+span.irt_udt, span.irt_lud { color: #00c0c0; }
+span.irt_num { color: #4040c0; }
+span.irt_int, span.irt_i8, span.irt_u8, span.irt_i16, span.irt_u16 { color: #b040b0; }
+span.irt_extra { font-style: italic; }
+</style>
+]]
+
+local colorize, irtype
+
+-- Lookup tables to convert some literals into names.
+local litname = {
+  ["SLOAD "] = setmetatable({}, { __index = function(t, mode)
+    local s = ""
+    if band(mode, 1) ~= 0 then s = s.."P" end
+    if band(mode, 2) ~= 0 then s = s.."F" end
+    if band(mode, 4) ~= 0 then s = s.."T" end
+    if band(mode, 8) ~= 0 then s = s.."C" end
+    if band(mode, 16) ~= 0 then s = s.."R" end
+    if band(mode, 32) ~= 0 then s = s.."I" end
+    if band(mode, 64) ~= 0 then s = s.."K" end
+    t[mode] = s
+    return s
+  end}),
+  ["XLOAD "] = { [0] = "", "R", "V", "RV", "U", "RU", "VU", "RVU", },
+  ["CONV  "] = setmetatable({}, { __index = function(t, mode)
+    local s = irtype[band(mode, 31)]
+    s = irtype[band(shr(mode, 5), 31)].."."..s
+    if band(mode, 0x800) ~= 0 then s = s.." sext" end
+    local c = shr(mode, 12)
+    if c == 1 then s = s.." none"
+    elseif c == 2 then s = s.." index"
+    elseif c == 3 then s = s.." check" end
+    t[mode] = s
+    return s
+  end}),
+  ["FLOAD "] = vmdef.irfield,
+  ["FREF  "] = vmdef.irfield,
+  ["FPMATH"] = vmdef.irfpm,
+  ["TMPREF"] = { [0] = "", "IN", "OUT", "INOUT", "", "", "OUT2", "INOUT2" },
+  ["BUFHDR"] = { [0] = "RESET", "APPEND", "WRITE" },
+  ["TOSTR "] = { [0] = "INT", "NUM", "CHAR" },
+}
+
+local function ctlsub(c)
+  if c == "\n" then return "\\n"
+  elseif c == "\r" then return "\\r"
+  elseif c == "\t" then return "\\t"
+  else return format("\\%03d", byte(c))
+  end
+end
+
+local function fmtfunc(func, pc)
+  local fi = funcinfo(func, pc)
+  if fi.loc then
+    return fi.loc
+  elseif fi.ffid then
+    return vmdef.ffnames[fi.ffid]
+  elseif fi.addr then
+    return format("C:%x", fi.addr)
+  else
+    return "(?)"
+  end
+end
+
+local function formatk(tr, idx, sn)
+  local k, t, slot = tracek(tr, idx)
+  local tn = type(k)
+  local s
+  if tn == "number" then
+    if t < 12 then
+      s = k == 0 and "NULL" or format("[0x%08x]", k)
+    elseif band(sn or 0, 0x30000) ~= 0 then
+      s = band(sn, 0x20000) ~= 0 and "contpc" or "ftsz"
+    elseif k == 2^52+2^51 then
+      s = "bias"
+    else
+      s = format(0 < k and k < 0x1p-1026 and "%+a" or "%+.14g", k)
+    end
+  elseif tn == "string" then
+    s = format(#k > 20 and '"%.20s"~' or '"%s"', gsub(k, "%c", ctlsub))
+  elseif tn == "function" then
+    s = fmtfunc(k)
+  elseif tn == "table" then
+    s = format("{%p}", k)
+  elseif tn == "userdata" then
+    if t == 12 then
+      s = format("userdata:%p", k)
+    else
+      s = format("[%p]", k)
+      if s == "[NULL]" then s = "NULL" end
+    end
+  elseif t == 21 then -- int64_t
+    s = sub(tostring(k), 1, -3)
+    if sub(s, 1, 1) ~= "-" then s = "+"..s end
+  elseif sn == 0x1057fff then -- SNAP(1, SNAP_FRAME | SNAP_NORESTORE, REF_NIL)
+    return "----" -- Special case for LJ_FR2 slot 1.
+  else
+    s = tostring(k) -- For primitives.
+  end
+  s = colorize(format("%-4s", s), t, band(sn or 0, 0x100000) ~= 0)
+  if slot then
+    s = format("%s @%d", s, slot)
+  end
+  return s
+end
+
+local function printsnap(tr, snap)
+  local n = 2
+  for s=0,snap[1]-1 do
+    local sn = snap[n]
+    if shr(sn, 24) == s then
+      n = n + 1
+      local ref = band(sn, 0xffff) - 0x8000 -- REF_BIAS
+      if ref < 0 then
+	out:write(formatk(tr, ref, sn))
+      elseif band(sn, 0x80000) ~= 0 then -- SNAP_SOFTFPNUM
+	out:write(colorize(format("%04d/%04d", ref, ref+1), 14))
+      else
+	local m, ot, op1, op2 = traceir(tr, ref)
+	out:write(colorize(format("%04d", ref), band(ot, 31), band(sn, 0x100000) ~= 0))
+      end
+      out:write(band(sn, 0x10000) == 0 and " " or "|") -- SNAP_FRAME
+    else
+      out:write("---- ")
+    end
+  end
+  out:write("]\n")
+end
+
+-- Dump snapshots (not interleaved with IR).
+local function dump_snap(tr)
+  out:write("---- TRACE ", tr, " snapshots\n")
+  for i=0,1000000000 do
+    local snap = tracesnap(tr, i)
+    if not snap then break end
+    out:write(format("#%-3d %04d [ ", i, snap[0]))
+    printsnap(tr, snap)
+  end
+end
+
+-- Return a register name or stack slot for a rid/sp location.
+local function ridsp_name(ridsp, ins)
+  if not disass then disass = require("jit.dis_"..jit.arch) end
+  local rid, slot = band(ridsp, 0xff), shr(ridsp, 8)
+  if rid == 253 or rid == 254 then
+    return (slot == 0 or slot == 255) and " {sink" or format(" {%04d", ins-slot)
+  end
+  if ridsp > 255 then return format("[%x]", slot*4) end
+  if rid < 128 then return disass.regname(rid) end
+  return ""
+end
+
+-- Dump CALL* function ref and return optional ctype.
+local function dumpcallfunc(tr, ins)
+  local ctype
+  if ins > 0 then
+    local m, ot, op1, op2 = traceir(tr, ins)
+    if band(ot, 31) == 0 then -- nil type means CARG(func, ctype).
+      ins = op1
+      ctype = formatk(tr, op2)
+    end
+  end
+  if ins < 0 then
+    out:write(format("[0x%x](", tonumber((tracek(tr, ins)))))
+  else
+    out:write(format("%04d (", ins))
+  end
+  return ctype
+end
+
+-- Recursively gather CALL* args and dump them.
+local function dumpcallargs(tr, ins)
+  if ins < 0 then
+    out:write(formatk(tr, ins))
+  else
+    local m, ot, op1, op2 = traceir(tr, ins)
+    local oidx = 6*shr(ot, 8)
+    local op = sub(vmdef.irnames, oidx+1, oidx+6)
+    if op == "CARG  " then
+      dumpcallargs(tr, op1)
+      if op2 < 0 then
+	out:write(" ", formatk(tr, op2))
+      else
+	out:write(" ", format("%04d", op2))
+      end
+    else
+      out:write(format("%04d", ins))
+    end
+  end
+end
+
+-- Dump IR and interleaved snapshots.
+local function dump_ir(tr, dumpsnap, dumpreg)
+  local info = traceinfo(tr)
+  if not info then return end
+  local nins = info.nins
+  out:write("---- TRACE ", tr, " IR\n")
+  local irnames = vmdef.irnames
+  local snapref = 65536
+  local snap, snapno
+  if dumpsnap then
+    snap = tracesnap(tr, 0)
+    snapref = snap[0]
+    snapno = 0
+  end
+  for ins=1,nins do
+    if ins >= snapref then
+      if dumpreg then
+	out:write(format("....              SNAP   #%-3d [ ", snapno))
+      else
+	out:write(format("....        SNAP   #%-3d [ ", snapno))
+      end
+      printsnap(tr, snap)
+      snapno = snapno + 1
+      snap = tracesnap(tr, snapno)
+      snapref = snap and snap[0] or 65536
+    end
+    local m, ot, op1, op2, ridsp = traceir(tr, ins)
+    local oidx, t = 6*shr(ot, 8), band(ot, 31)
+    local op = sub(irnames, oidx+1, oidx+6)
+    if op == "LOOP  " then
+      if dumpreg then
+	out:write(format("%04d ------------ LOOP ------------\n", ins))
+      else
+	out:write(format("%04d ------ LOOP ------------\n", ins))
+      end
+    elseif op ~= "NOP   " and op ~= "CARG  " and
+	   (dumpreg or op ~= "RENAME") then
+      local rid = band(ridsp, 255)
+      if dumpreg then
+	out:write(format("%04d %-6s", ins, ridsp_name(ridsp, ins)))
+      else
+	out:write(format("%04d ", ins))
+      end
+      out:write(format("%s%s %s %s ",
+		       (rid == 254 or rid == 253) and "}" or
+		       (band(ot, 128) == 0 and " " or ">"),
+		       band(ot, 64) == 0 and " " or "+",
+		       irtype[t], op))
+      local m1, m2 = band(m, 3), band(m, 3*4)
+      if sub(op, 1, 4) == "CALL" then
+	local ctype
+	if m2 == 1*4 then -- op2 == IRMlit
+	  out:write(format("%-10s  (", vmdef.ircall[op2]))
+	else
+	  ctype = dumpcallfunc(tr, op2)
+	end
+	if op1 ~= -1 then dumpcallargs(tr, op1) end
+	out:write(")")
+	if ctype then out:write(" ctype ", ctype) end
+      elseif op == "CNEW  " and op2 == -1 then
+	out:write(formatk(tr, op1))
+      elseif m1 ~= 3 then -- op1 != IRMnone
+	if op1 < 0 then
+	  out:write(formatk(tr, op1))
+	else
+	  out:write(format(m1 == 0 and "%04d" or "#%-3d", op1))
+	end
+	if m2 ~= 3*4 then -- op2 != IRMnone
+	  if m2 == 1*4 then -- op2 == IRMlit
+	    local litn = litname[op]
+	    if litn and litn[op2] then
+	      out:write("  ", litn[op2])
+	    elseif op == "UREFO " or op == "UREFC " then
+	      out:write(format("  #%-3d", shr(op2, 8)))
+	    else
+	      out:write(format("  #%-3d", op2))
+	    end
+	  elseif op2 < 0 then
+	    out:write("  ", formatk(tr, op2))
+	  else
+	    out:write(format("  %04d", op2))
+	  end
+	end
+      end
+      out:write("\n")
+    end
+  end
+  if snap then
+    if dumpreg then
+      out:write(format("....              SNAP   #%-3d [ ", snapno))
+    else
+      out:write(format("....        SNAP   #%-3d [ ", snapno))
+    end
+    printsnap(tr, snap)
+  end
+end
+
+------------------------------------------------------------------------------
+
+local recprefix = ""
+local recdepth = 0
+
+-- Format trace error message.
+local function fmterr(err, info)
+  if type(err) == "number" then
+    if type(info) == "function" then info = fmtfunc(info) end
+    err = format(vmdef.traceerr[err], info)
+  end
+  return err
+end
+
+-- Dump trace states.
+local function dump_trace(what, tr, func, pc, otr, oex)
+  if what == "stop" or (what == "abort" and dumpmode.a) then
+    if dumpmode.i then dump_ir(tr, dumpmode.s, dumpmode.r and what == "stop")
+    elseif dumpmode.s then dump_snap(tr) end
+    if dumpmode.m then dump_mcode(tr) end
+  end
+  if what == "start" then
+    if dumpmode.H then out:write('<pre class="ljdump">\n') end
+    out:write("---- TRACE ", tr, " ", what)
+    if otr then out:write(" ", otr, "/", oex == -1 and "stitch" or oex) end
+    out:write(" ", fmtfunc(func, pc), "\n")
+  elseif what == "stop" or what == "abort" then
+    out:write("---- TRACE ", tr, " ", what)
+    if what == "abort" then
+      out:write(" ", fmtfunc(func, pc), " -- ", fmterr(otr, oex), "\n")
+    else
+      local info = traceinfo(tr)
+      local link, ltype = info.link, info.linktype
+      if link == tr or link == 0 then
+	out:write(" -> ", ltype, "\n")
+      elseif ltype == "root" then
+	out:write(" -> ", link, "\n")
+      else
+	out:write(" -> ", link, " ", ltype, "\n")
+      end
+    end
+    if dumpmode.H then out:write("</pre>\n\n") else out:write("\n") end
+  else
+    if what == "flush" then symtab, nexitsym = {}, 0 end
+    out:write("---- TRACE ", what, "\n\n")
+  end
+  out:flush()
+end
+
+-- Dump recorded bytecode.
+local function dump_record(tr, func, pc, depth)
+  if depth ~= recdepth then
+    recdepth = depth
+    recprefix = rep(" .", depth)
+  end
+  local line
+  if pc >= 0 then
+    line = bcline(func, pc, recprefix)
+    if dumpmode.H then line = gsub(line, "[<>&]", html_escape) end
+  else
+    line = "0000 "..recprefix.." FUNCC      \n"
+  end
+  if pc <= 0 then
+    out:write(sub(line, 1, -2), "         ; ", fmtfunc(func), "\n")
+  else
+    out:write(line)
+  end
+  if pc >= 0 and band(funcbc(func, pc), 0xff) < 16 then -- ORDER BC
+    out:write(bcline(func, pc+1, recprefix)) -- Write JMP for cond.
+  end
+end
+
+------------------------------------------------------------------------------
+
+local gpr64 = jit.arch:match("64")
+local fprmips32 = jit.arch == "mips" or jit.arch == "mipsel"
+
+-- Dump taken trace exits.
+local function dump_texit(tr, ex, ngpr, nfpr, ...)
+  out:write("---- TRACE ", tr, " exit ", ex, "\n")
+  if dumpmode.X then
+    local regs = {...}
+    if gpr64 then
+      for i=1,ngpr do
+	out:write(format(" %016x", regs[i]))
+	if i % 4 == 0 then out:write("\n") end
+      end
+    else
+      for i=1,ngpr do
+	out:write(" ", tohex(regs[i]))
+	if i % 8 == 0 then out:write("\n") end
+      end
+    end
+    if fprmips32 then
+      for i=1,nfpr,2 do
+	out:write(format(" %+17.14g", regs[ngpr+i]))
+	if i % 8 == 7 then out:write("\n") end
+      end
+    else
+      for i=1,nfpr do
+	out:write(format(" %+17.14g", regs[ngpr+i]))
+	if i % 4 == 0 then out:write("\n") end
+      end
+    end
+  end
+end
+
+------------------------------------------------------------------------------
+
+-- Detach dump handlers.
+local function dumpoff()
+  if active then
+    active = false
+    jit.attach(dump_texit)
+    jit.attach(dump_record)
+    jit.attach(dump_trace)
+    if out and out ~= stdout and out ~= stderr then out:close() end
+    out = nil
+  end
+end
+
+-- Open the output file and attach dump handlers.
+local function dumpon(opt, outfile)
+  if active then dumpoff() end
+
+  local term = os.getenv("TERM")
+  local colormode = (term and term:match("color") or os.getenv("COLORTERM")) and "A" or "T"
+  if opt then
+    opt = gsub(opt, "[TAH]", function(mode) colormode = mode; return ""; end)
+  end
+
+  local m = { t=true, b=true, i=true, m=true, }
+  if opt and opt ~= "" then
+    local o = sub(opt, 1, 1)
+    if o ~= "+" and o ~= "-" then m = {} end
+    for i=1,#opt do m[sub(opt, i, i)] = (o ~= "-") end
+  end
+  dumpmode = m
+
+  if m.t or m.b or m.i or m.s or m.m then
+    jit.attach(dump_trace, "trace")
+  end
+  if m.b then
+    jit.attach(dump_record, "record")
+    if not bcline then bcline = require("jit.bc").line end
+  end
+  if m.x or m.X then
+    jit.attach(dump_texit, "texit")
+  end
+
+  if not outfile then outfile = os.getenv("LUAJIT_DUMPFILE") end
+  if outfile then
+    out = outfile == "-" and stdout or assert(io.open(outfile, "w"))
+  else
+    out = stdout
+  end
+
+  m[colormode] = true
+  if colormode == "A" then
+    colorize = colorize_ansi
+    irtype = irtype_ansi
+  elseif colormode == "H" then
+    colorize = colorize_html
+    irtype = irtype_html
+    out:write(header_html)
+  else
+    colorize = colorize_text
+    irtype = irtype_text
+  end
+
+  active = true
+end
+
+-- Public module functions.
+return {
+  on = dumpon,
+  off = dumpoff,
+  start = dumpon -- For -j command line option.
+}
+