----------------------------------------------------------------------------
-- LuaJIT compiler tracing module.
--
-- Copyright (C) 2005-2010 Mike Pall. All rights reserved.
-- Released under the MIT/X license. See luajit.h for full copyright notice.
----------------------------------------------------------------------------
-- Activate this module to trace the progress of the JIT compiler.
--
-- Try: luajit -j trace -e 'print "foo"'
--      luajit -j trace=foo.trace foo.lua
--
-- Default output is to stderr. To redirect output to a file,
-- pass a filename as an argument or set the environment variable
-- "LUAJIT_TRACEFILE".
-- Note: the file is overwritten each time you run luajit.
------------------------------------------------------------------------------

-- Priority for compiler pipeline. Must run after backend (negative)
-- and should be odd to catch compiler errors, too.
local PRIORITY = -99

-- Cache some library functions and objects.
local jit = require("jit")
assert(jit.version_num == 10106, "LuaJIT core/library version mismatch")
local jutil = require("jit.util")
local type, tostring, sub, format = type, tostring, string.sub, string.format
local getinfo, justats = debug.getinfo, jutil.stats
local stdout, stderr = io.stdout, io.stderr

-- Turn compilation off for the whole module. LuaJIT would do that anyway.
jit.off(true, true)

-- Active flag and output file handle.
local active, out

-- Generate range string from table: pc[-pc] [,...]
local function rangestring(t)
  local s = ""
  for i,range in ipairs(t) do
    if i ~= 1 then s = s.."," end
    local pc = range % 65536
    range = (range - pc) / 65536
    s = s..pc
    if range ~= 0 then s = s..(-(pc+range)) end
  end
  return s
end

-- Trace handler for compiler pipeline.
local function h_trace(st, status)
  local o = out or stderr
  local func = st.func
  if type(func) ~= "function" then return end
  local info = getinfo(func, "S")
  local src, line = info.source, info.linedefined or 0
  if src then
    if sub(src, 1, 1) == "@" or sub(src, 1, 2) == "=(" then
      src = sub(src, 2)
    else
      src = "**"..string.gsub(sub(src, 1, 40), "%c", " ").."**"
    end
  else
    src = "?"
  end
  local aux = st.deopt and "  DEOPT="..rangestring(st.deopt) or ""
  if status == nil then
    local stats = justats(func)
    if not stats then return end
    o:write(format("[LuaJIT: OK %4d %6d  %s:%d%s]\n",
		   stats.bytecodes, stats.mcodesize or -1, src, line, aux))
    return
  else
    local stname = jit.util.status[status] or status
    local pc, err = st.dasm_pc, st.dasm_err
    if type(pc) == "number" and type(err) == "number" then
      local op = jutil.bytecode(func, pc) or "END"
      o:write(format("[LuaJIT: %s  %s@%d %08x  %s:%d%s]\n",
		     stname, op, pc, err, src, line, aux))
    else
      o:write(format("[LuaJIT: %s  %s:%d%s]\n", stname, src, line, aux))
    end
  end
end

-- Detach trace handler from compiler pipeline.
local function traceoff()
  if active then
    active = false
    jit.attach(h_trace)
    if out and out ~= stdout then out:close() end
    out = nil
  end
end

-- Open the output file and attach trace handler to compiler pipeline.
local function traceon(filename)
  if active then traceoff() end
  local outfile = filename or os.getenv("LUAJIT_TRACEFILE")
  out = outfile and (outfile == "-" and stdout or assert(io.open(outfile, "w")))
  jit.attach(h_trace, PRIORITY)
  active = true
end


-- Public module functions.
module(...)

on = traceon
off = traceoff
start = traceon -- For -j command line option.

