src/jit/bc.lua

   1 ----------------------------------------------------------------------------
   2 -- LuaJIT bytecode listing module.
   3 --
   4 -- Copyright (C) 2005-2023 Mike Pall. All rights reserved.
   5 -- Released under the MIT license. See Copyright Notice in luajit.h
   6 ----------------------------------------------------------------------------
   7 --
   8 -- This module lists the bytecode of a Lua function. If it's loaded by -jbc
   9 -- it hooks into the parser and lists all functions of a chunk as they
  10 -- are parsed.
  11 --
  12 -- Example usage:
  13 --
  14 --   luajit -jbc -e 'local x=0; for i=1,1e6 do x=x+i end; print(x)'
  15 --   luajit -jbc=- foo.lua
  16 --   luajit -jbc=foo.list foo.lua
  17 --
  18 -- Default output is to stderr. To redirect the output to a file, pass a
  19 -- filename as an argument (use '-' for stdout) or set the environment
  20 -- variable LUAJIT_LISTFILE. The file is overwritten every time the module
  21 -- is started.
  22 --
  23 -- This module can also be used programmatically:
  24 --
  25 --   local bc = require("jit.bc")
  26 --
  27 --   local function foo() print("hello") end
  28 --
  29 --   bc.dump(foo)           --> -- BYTECODE -- [...]
  30 --   print(bc.line(foo, 2)) --> 0002    KSTR     1   1      ; "hello"
  31 --
  32 --   local out = {
  33 --     -- Do something with each line:
  34 --     write = function(t, ...) io.write(...) end,
  35 --     close = function(t) end,
  36 --     flush = function(t) end,
  37 --   }
  38 --   bc.dump(foo, out)
  39 --
  40 ------------------------------------------------------------------------------
  41
  42 -- Cache some library functions and objects.
  43 local jit = require("jit")
  44 local jutil = require("jit.util")
  45 local vmdef = require("jit.vmdef")
  46 local bit = require("bit")
  47 local sub, gsub, format = string.sub, string.gsub, string.format
  48 local byte, band, shr = string.byte, bit.band, bit.rshift
  49 local funcinfo, funcbc, funck = jutil.funcinfo, jutil.funcbc, jutil.funck
  50 local funcuvname = jutil.funcuvname
  51 local bcnames = vmdef.bcnames
  52 local stdout, stderr = io.stdout, io.stderr
  53
  54 ------------------------------------------------------------------------------
  55
  56 local function ctlsub(c)
  57   if c == "\n" then return "\\n"
  58   elseif c == "\r" then return "\\r"
  59   elseif c == "\t" then return "\\t"
  60   else return format("\\%03d", byte(c))
  61   end
  62 end
  63
  64 -- Return one bytecode line.
  65 local function bcline(func, pc, prefix)
  66   local ins, m = funcbc(func, pc)
  67   if not ins then return end
  68   local ma, mb, mc = band(m, 7), band(m, 15*8), band(m, 15*128)
  69   local a = band(shr(ins, 8), 0xff)
  70   local oidx = 6*band(ins, 0xff)
  71   local op = sub(bcnames, oidx+1, oidx+6)
  72   local s = format("%04d %s %-6s %3s ",
  73     pc, prefix or "  ", op, ma == 0 and "" or a)
  74   local d = shr(ins, 16)
  75   if mc == 13*128 then -- BCMjump
  76     return format("%s=> %04d\n", s, pc+d-0x7fff)
  77   end
  78   if mb ~= 0 then
  79     d = band(d, 0xff)
  80   elseif mc == 0 then
  81     return s.."\n"
  82   end
  83   local kc
  84   if mc == 10*128 then -- BCMstr
  85     kc = funck(func, -d-1)
  86     kc = format(#kc > 40 and '"%.40s"~' or '"%s"', gsub(kc, "%c", ctlsub))
  87   elseif mc == 9*128 then -- BCMnum
  88     kc = funck(func, d)
  89     if op == "TSETM " then kc = kc - 2^52 end
  90   elseif mc == 12*128 then -- BCMfunc
  91     local fi = funcinfo(funck(func, -d-1))
  92     if fi.ffid then
  93       kc = vmdef.ffnames[fi.ffid]
  94     else
  95       kc = fi.loc
  96     end
  97   elseif mc == 5*128 then -- BCMuv
  98     kc = funcuvname(func, d)
  99   end
 100   if ma == 5 then -- BCMuv
 101     local ka = funcuvname(func, a)
 102     if kc then kc = ka.." ; "..kc else kc = ka end
 103   end
 104   if mb ~= 0 then
 105     local b = shr(ins, 24)
 106     if kc then return format("%s%3d %3d  ; %s\n", s, b, d, kc) end
 107     return format("%s%3d %3d\n", s, b, d)
 108   end
 109   if kc then return format("%s%3d      ; %s\n", s, d, kc) end
 110   if mc == 7*128 and d > 32767 then d = d - 65536 end -- BCMlits
 111   return format("%s%3d\n", s, d)
 112 end
 113
 114 -- Collect branch targets of a function.
 115 local function bctargets(func)
 116   local target = {}
 117   for pc=1,1000000000 do
 118     local ins, m = funcbc(func, pc)
 119     if not ins then break end
 120     if band(m, 15*128) == 13*128 then target[pc+shr(ins, 16)-0x7fff] = true end
 121   end
 122   return target
 123 end
 124
 125 -- Dump bytecode instructions of a function.
 126 local function bcdump(func, out, all)
 127   if not out then out = stdout end
 128   local fi = funcinfo(func)
 129   if all and fi.children then
 130     for n=-1,-1000000000,-1 do
 131       local k = funck(func, n)
 132       if not k then break end
 133       if type(k) == "proto" then bcdump(k, out, true) end
 134     end
 135   end
 136   out:write(format("-- BYTECODE -- %s-%d\n", fi.loc, fi.lastlinedefined))
 137   local target = bctargets(func)
 138   for pc=1,1000000000 do
 139     local s = bcline(func, pc, target[pc] and "=>")
 140     if not s then break end
 141     out:write(s)
 142   end
 143   out:write("\n")
 144   out:flush()
 145 end
 146
 147 ------------------------------------------------------------------------------
 148
 149 -- Active flag and output file handle.
 150 local active, out
 151
 152 -- List handler.
 153 local function h_list(func)
 154   return bcdump(func, out)
 155 end
 156
 157 -- Detach list handler.
 158 local function bclistoff()
 159   if active then
 160     active = false
 161     jit.attach(h_list)
 162     if out and out ~= stdout and out ~= stderr then out:close() end
 163     out = nil
 164   end
 165 end
 166
 167 -- Open the output file and attach list handler.
 168 local function bcliston(outfile)
 169   if active then bclistoff() end
 170   if not outfile then outfile = os.getenv("LUAJIT_LISTFILE") end
 171   if outfile then
 172     out = outfile == "-" and stdout or assert(io.open(outfile, "w"))
 173   else
 174     out = stderr
 175   end
 176   jit.attach(h_list, "bc")
 177   active = true
 178 end
 179
 180 -- Public module functions.
 181 return {
 182   line = bcline,
 183   dump = bcdump,
 184   targets = bctargets,
 185   on = bcliston,
 186   off = bclistoff,
 187   start = bcliston -- For -j command line option.
 188 }
 189