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  35 <div id="site">
  36 <a href="http://luajit.org"><span>Lua<span id="logo">JIT</span></span></a>
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  39 <h1>Running LuaJIT</h1>
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  79 <p>
  80 LuaJIT has only a single stand-alone executable, called <tt>luajit</tt> on
  81 POSIX systems or <tt>luajit.exe</tt> on Windows. It can be used to run simple
  82 Lua statements or whole Lua applications from the command line. It has an
  83 interactive mode, too.
  84 </p>
  85 <p class="indent" style="color: #c00000;">
  86 Note: the beta test releases only install under the versioned name on
  87 POSIX systems (to avoid overwriting a previous version). You either need
  88 to type <tt>luajit-2.0.0-beta8</tt> to start it or create a symlink
  89 with a command like this:
  90 </p>
  91 <pre class="code" style="color: #c00000;">
  92 sudo ln -sf luajit-2.0.0-beta8&nbsp;/usr/local/bin/luajit
  93 </pre>
  94 <p>
  95 Unlike previous versions <b>optimization is turned on by default</b> in
  96 LuaJIT 2.0!<br>It's no longer necessary to use <tt>luajit&nbsp;-O</tt>.
  97 </p>
  98
  99 <h2 id="options">Command Line Options</h2>
 100 <p>
 101 The <tt>luajit</tt> stand-alone executable is just a slightly modified
 102 version of the regular <tt>lua</tt> stand-alone executable.
 103 It supports the same basic options, too. <tt>luajit&nbsp;-h</tt>
 104 prints a short list of the available options. Please have a look at the
 105 <a href="http://www.lua.org/manual/5.1/manual.html#6"><span class="ext">&raquo;</span>&nbsp;Lua manual</a>
 106 for details.
 107 </p>
 108 <p>
 109 LuaJIT has some additional options:
 110 </p>
 111
 112 <h3 id="opt_b"><tt>-b[options] input output</tt></h3>
 113 <p>
 114 This option saves or lists bytecode. The following additional options
 115 are accepted:
 116 </p>
 117 <ul>
 118 <li><tt>-l</tt> &mdash; Only list bytecode.</li>
 119 <li><tt>-s</tt> &mdash; Strip debug info (this is the default).</li>
 120 <li><tt>-g</tt> &mdash; Keep debug info.</li>
 121 <li><tt>-n name</tt> &mdash; Set module name (default: auto-detect from input name)</li>
 122 <li><tt>-t type</tt> &mdash; Set output file type (default: auto-detect from output name).</li>
 123 <li><tt>-a arch</tt> &mdash; Override architecture for object files (default: native).</li>
 124 <li><tt>-o os</tt> &mdash; Override OS for object files (default: native).</li>
 125 <li><tt>-e chunk</tt> &mdash; Use chunk string as input.</li>
 126 <li><tt>-</tt> (a single minus sign) &mdash; Use stdin as input and/or stdout as output.</li>
 127 </ul>
 128 <p>
 129 The output file type is auto-detected from the extension of the output
 130 file name:
 131 </p>
 132 <ul>
 133 <li><tt>c</tt> &mdash; C source file, exported bytecode data.</li>
 134 <li><tt>h</tt> &mdash; C header file, static bytecode data.</li>
 135 <li><tt>obj</tt> or <tt>o</tt> &mdash; Object file, exported bytecode data
 136 (OS- and architecture-specific).</li>
 137 <li><tt>raw</tt> or any other extension &mdash; Raw bytecode file (portable).
 138 </ul>
 139 <p>
 140 Notes:
 141 </p>
 142 <ul>
 143 <li>See also <a href="extensions.html#string_dump">string.dump()</a>
 144 for information on bytecode portability and compatibility.</li>
 145 <li>A file in raw bytecode format is auto-detected and can be loaded like
 146 any Lua source file. E.g. directly from the command line or with
 147 <tt>loadfile()</tt>, <tt>dofile()</tt> etc.</li>
 148 <li>To statically embed the bytecode of a module in your application,
 149 generate an object file and just link it with your application.</li>
 150 <li>On most ELF-based systems (e.g. Linux) you need to explicitly export the
 151 global symbols when linking your application, e.g. with: <tt>-Wl,-E</tt></li>
 152 <li><tt>require()</tt> tries to load embedded bytecode data from exported
 153 symbols (in <tt>*.exe</tt> or <tt>lua51.dll</tt> on Windows) and from
 154 shared libraries in <tt>package.cpath</tt>.</li>
 155 </ul>
 156 <p>
 157 Typical usage examples:
 158 </p>
 159 <pre class="code">
 160 luajit -b test.lua test.out                 # Save bytecode to test.out
 161 luajit -bg test.lua test.out                # Keep debug info
 162 luajit -be "print('hello world')" test.out  # Save cmdline script
 163
 164 luajit -bl test.lua                         # List to stdout
 165 luajit -bl test.lua test.txt                # List to test.txt
 166 luajit -ble "print('hello world')"          # List cmdline script
 167
 168 luajit -b test.lua test.obj                 # Generate object file
 169 # Link test.obj with your application and load it with require("test")
 170 </pre>
 171
 172 <h3 id="opt_j"><tt>-j cmd[=arg[,arg...]]</tt></h3>
 173 <p>
 174 This option performs a LuaJIT control command or activates one of the
 175 loadable extension modules. The command is first looked up in the
 176 <tt>jit.*</tt> library. If no matching function is found, a module
 177 named <tt>jit.&lt;cmd&gt;</tt> is loaded and the <tt>start()</tt>
 178 function of the module is called with the specified arguments (if
 179 any). The space between <tt>-j</tt> and <tt>cmd</tt> is optional.
 180 </p>
 181 <p>
 182 Here are the available LuaJIT control commands:
 183 </p>
 184 <ul>
 185 <li id="j_on"><tt>-jon</tt> &mdash; Turns the JIT compiler on (default).</li>
 186 <li id="j_off"><tt>-joff</tt> &mdash; Turns the JIT compiler off (only use the interpreter).</li>
 187 <li id="j_flush"><tt>-jflush</tt> &mdash; Flushes the whole cache of compiled code.</li>
 188 <li id="j_v"><tt>-jv</tt> &mdash; Shows verbose information about the progress of the JIT compiler.</li>
 189 <li id="j_dump"><tt>-jdump</tt> &mdash; Dumps the code and structures used in various compiler stages.</li>
 190 </ul>
 191 <p>
 192 The <tt>-jv</tt> and <tt>-jdump</tt> commands are extension modules
 193 written in Lua. They are mainly used for debugging the JIT compiler
 194 itself. For a description of their options and output format, please
 195 read the comment block at the start of their source.
 196 They can be found in the <tt>lib</tt> directory of the source
 197 distribution or installed under the <tt>jit</tt> directory. By default
 198 this is <tt>/usr/local/share/luajit-2.0.0-beta8/jit</tt> on POSIX
 199 systems.
 200 </p>
 201
 202 <h3 id="opt_O"><tt>-O[level]</tt><br>
 203 <tt>-O[+]flag</tt>&nbsp;&nbsp;&nbsp;<tt>-O-flag</tt><br>
 204 <tt>-Oparam=value</tt></h3>
 205 <p>
 206 This options allows fine-tuned control of the optimizations used by
 207 the JIT compiler. This is mainly intended for debugging LuaJIT itself.
 208 Please note that the JIT compiler is extremely fast (we are talking
 209 about the microsecond to millisecond range). Disabling optimizations
 210 doesn't have any visible impact on its overhead, but usually generates
 211 code that runs slower.
 212 </p>
 213 <p>
 214 The first form sets an optimization level &mdash; this enables a
 215 specific mix of optimization flags. <tt>-O0</tt> turns off all
 216 optimizations and higher numbers enable more optimizations. Omitting
 217 the level (i.e. just <tt>-O</tt>) sets the default optimization level,
 218 which is <tt>-O3</tt> in the current version.
 219 </p>
 220 <p>
 221 The second form adds or removes individual optimization flags.
 222 The third form sets a parameter for the VM or the JIT compiler
 223 to a specific value.
 224 </p>
 225 <p>
 226 You can either use this option multiple times (like <tt>-Ocse
 227 -O-dce -Ohotloop=10</tt>) or separate several settings with a comma
 228 (like <tt>-O+cse,-dce,hotloop=10</tt>). The settings are applied from
 229 left to right and later settings override earlier ones. You can freely
 230 mix the three forms, but note that setting an optimization level
 231 overrides all earlier flags.
 232 </p>
 233 <p>
 234 Here are the available flags and at what optimization levels they
 235 are enabled:
 236 </p>
 237 <table class="opt">
 238 <tr class="opthead">
 239 <td class="flag_name">Flag</td>
 240 <td class="flag_level">-O1</td>
 241 <td class="flag_level">-O2</td>
 242 <td class="flag_level">-O3</td>
 243 <td class="flag_desc">&nbsp;</td>
 244 </tr>
 245 <tr class="odd separate">
 246 <td class="flag_name">fold</td><td class="flag_level">&bull;</td><td class="flag_level">&bull;</td><td class="flag_level">&bull;</td><td class="flag_desc">Constant Folding, Simplifications and Reassociation</td></tr>
 247 <tr class="even">
 248 <td class="flag_name">cse</td><td class="flag_level">&bull;</td><td class="flag_level">&bull;</td><td class="flag_level">&bull;</td><td class="flag_desc">Common-Subexpression Elimination</td></tr>
 249 <tr class="odd">
 250 <td class="flag_name">dce</td><td class="flag_level">&bull;</td><td class="flag_level">&bull;</td><td class="flag_level">&bull;</td><td class="flag_desc">Dead-Code Elimination</td></tr>
 251 <tr class="even">
 252 <td class="flag_name">narrow</td><td class="flag_level">&nbsp;</td><td class="flag_level">&bull;</td><td class="flag_level">&bull;</td><td class="flag_desc">Narrowing of numbers to integers</td></tr>
 253 <tr class="odd">
 254 <td class="flag_name">loop</td><td class="flag_level">&nbsp;</td><td class="flag_level">&bull;</td><td class="flag_level">&bull;</td><td class="flag_desc">Loop Optimizations (code hoisting)</td></tr>
 255 <tr class="even">
 256 <td class="flag_name">fwd</td><td class="flag_level">&nbsp;</td><td class="flag_level">&nbsp;</td><td class="flag_level">&bull;</td><td class="flag_desc">Load Forwarding (L2L) and Store Forwarding (S2L)</td></tr>
 257 <tr class="odd">
 258 <td class="flag_name">dse</td><td class="flag_level">&nbsp;</td><td class="flag_level">&nbsp;</td><td class="flag_level">&bull;</td><td class="flag_desc">Dead-Store Elimination</td></tr>
 259 <tr class="even">
 260 <td class="flag_name">abc</td><td class="flag_level">&nbsp;</td><td class="flag_level">&nbsp;</td><td class="flag_level">&bull;</td><td class="flag_desc">Array Bounds Check Elimination</td></tr>
 261 <tr class="odd">
 262 <td class="flag_name">fuse</td><td class="flag_level">&nbsp;</td><td class="flag_level">&nbsp;</td><td class="flag_level">&bull;</td><td class="flag_desc">Fusion of operands into instructions</td></tr>
 263 </table>
 264 <p>
 265 Here are the parameters and their default settings:
 266 </p>
 267 <table class="opt">
 268 <tr class="opthead">
 269 <td class="param_name">Parameter</td>
 270 <td class="param_default">Default</td>
 271 <td class="param_desc">&nbsp;</td>
 272 </tr>
 273 <tr class="odd separate">
 274 <td class="param_name">maxtrace</td><td class="param_default">1000</td><td class="param_desc">Max. number of traces in the cache</td></tr>
 275 <tr class="even">
 276 <td class="param_name">maxrecord</td><td class="param_default">4000</td><td class="param_desc">Max. number of recorded IR instructions</td></tr>
 277 <tr class="odd">
 278 <td class="param_name">maxirconst</td><td class="param_default">500</td><td class="param_desc">Max. number of IR constants of a trace</td></tr>
 279 <tr class="even">
 280 <td class="param_name">maxside</td><td class="param_default">100</td><td class="param_desc">Max. number of side traces of a root trace</td></tr>
 281 <tr class="odd">
 282 <td class="param_name">maxsnap</td><td class="param_default">500</td><td class="param_desc">Max. number of snapshots for a trace</td></tr>
 283 <tr class="even separate">
 284 <td class="param_name">hotloop</td><td class="param_default">56</td><td class="param_desc">Number of iterations to detect a hot loop or hot call</td></tr>
 285 <tr class="odd">
 286 <td class="param_name">hotexit</td><td class="param_default">10</td><td class="param_desc">Number of taken exits to start a side trace</td></tr>
 287 <tr class="even">
 288 <td class="param_name">tryside</td><td class="param_default">4</td><td class="param_desc">Number of attempts to compile a side trace</td></tr>
 289 <tr class="odd separate">
 290 <td class="param_name">instunroll</td><td class="param_default">4</td><td class="param_desc">Max. unroll factor for instable loops</td></tr>
 291 <tr class="even">
 292 <td class="param_name">loopunroll</td><td class="param_default">15</td><td class="param_desc">Max. unroll factor for loop ops in side traces</td></tr>
 293 <tr class="odd">
 294 <td class="param_name">callunroll</td><td class="param_default">3</td><td class="param_desc">Max. unroll factor for pseudo-recursive calls</td></tr>
 295 <tr class="even">
 296 <td class="param_name">recunroll</td><td class="param_default">2</td><td class="param_desc">Min. unroll factor for true recursion</td></tr>
 297 <tr class="odd separate">
 298 <td class="param_name">sizemcode</td><td class="param_default">32</td><td class="param_desc">Size of each machine code area in KBytes (Windows: 64K)</td></tr>
 299 <tr class="even">
 300 <td class="param_name">maxmcode</td><td class="param_default">512</td><td class="param_desc">Max. total size of all machine code areas in KBytes</td></tr>
 301 </table>
 302 <br class="flush">
 303 </div>
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 305 <hr class="hide">
 306 Copyright &copy; 2005-2011 Mike Pall
 307 <span class="noprint">
 308 &middot;
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