2009-12-08 18:46:35 +00:00
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<title>API Extensions</title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<meta name="Author" content="Mike Pall">
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2010-01-09 13:28:11 +00:00
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<meta name="Copyright" content="Copyright (C) 2005-2010, Mike Pall">
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2009-12-08 18:46:35 +00:00
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<meta name="Language" content="en">
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<link rel="stylesheet" type="text/css" href="bluequad.css" media="screen">
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<link rel="stylesheet" type="text/css" href="bluequad-print.css" media="print">
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</head>
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<body>
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<div id="site">
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<a href="http://luajit.org"><span>Lua<span id="logo">JIT</span></span></a>
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</div>
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<div id="head">
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<h1>API Extensions</h1>
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</div>
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<div id="nav">
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<ul><li>
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<a href="luajit.html">LuaJIT</a>
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<ul><li>
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<a href="install.html">Installation</a>
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</li><li>
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<a href="running.html">Running</a>
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</li><li>
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<a class="current" href="api.html">API Extensions</a>
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</li></ul>
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</li><li>
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<a href="status.html">Status</a>
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<ul><li>
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<a href="changes.html">Changes</a>
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</li><li>
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<a href="faq.html">FAQ</a>
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</li><li>
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2010-03-19 20:01:14 +00:00
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<a href="http://luajit.org/performance.html">Performance <span class="ext">»</span></a>
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</li><li>
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2009-12-08 18:46:35 +00:00
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<a href="http://luajit.org/download.html">Download <span class="ext">»</span></a>
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</li></ul>
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</div>
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<div id="main">
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<p>
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LuaJIT is fully upwards-compatible with Lua 5.1. It supports all
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<a href="http://www.lua.org/manual/5.1/manual.html#5"><span class="ext">»</span> standard Lua
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library functions</a> and the full set of
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<a href="http://www.lua.org/manual/5.1/manual.html#3"><span class="ext">»</span> Lua/C API
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functions</a>.
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</p>
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<p>
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LuaJIT is also fully ABI-compatible to Lua 5.1 at the linker/dynamic
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loader level. This means you can compile a C module against the
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standard Lua headers and load the same shared library from either Lua
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or LuaJIT.
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</p>
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<h2 id="bit"><tt>bit.*</tt> — Bitwise Operations</h2>
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<p>
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LuaJIT supports all bitwise operations as defined by
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<a href="http://bitop.luajit.org"><span class="ext">»</span> Lua BitOp</a>:
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</p>
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<pre class="code">
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bit.tobit bit.tohex bit.bnot bit.band bit.bor bit.bxor
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bit.lshift bit.rshift bit.arshift bit.rol bit.ror bit.bswap
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</pre>
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<p>
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This module is a LuaJIT built-in — you don't need to download or
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install Lua BitOp. The Lua BitOp site has full documentation for all
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<a href="http://bitop.luajit.org/api.html"><span class="ext">»</span> Lua BitOp API functions</a>.
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</p>
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<p>
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Please make sure to <tt>require</tt> the module before using any of
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its functions:
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</p>
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<pre class="code">
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local bit = require("bit")
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</pre>
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<p>
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An already installed Lua BitOp module is ignored by LuaJIT.
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This way you can use bit operations from both Lua and LuaJIT on a
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shared installation.
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</p>
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<h2 id="jit"><tt>jit.*</tt> — JIT compiler control</h2>
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<p>
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The functions in this built-in module control the behavior
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of the JIT compiler engine.
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</p>
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<h3 id="jit_onoff"><tt>jit.on()<br>
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jit.off()</tt></h3>
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<p>
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Turns the whole JIT compiler on (default) or off.
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</p>
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<p>
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These functions are typically used with the command line options
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<tt>-j on</tt> or <tt>-j off</tt>.
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</p>
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<h3 id="jit_flush"><tt>jit.flush()</tt></h3>
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<p>
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Flushes the whole cache of compiled code.
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</p>
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<h3 id="jit_onoff_func"><tt>jit.on(func|true [,true|false])<br>
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jit.off(func|true [,true|false])<br>
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jit.flush(func|true [,true|false])</tt></h3>
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<p>
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<tt>jit.on</tt> enables JIT compilation for a Lua function (this is
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the default).
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</p>
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<p>
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<tt>jit.off</tt> disables JIT compilation for a Lua function and
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flushes any already compiled code from the code cache.
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</p>
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<p>
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<tt>jit.flush</tt> flushes the code, but doesn't affect the
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enable/disable status.
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</p>
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<p>
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The current function, i.e. the Lua function calling this library
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function, can also be specified by passing <tt>true</tt> as the first
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argument.
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</p>
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<p>
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If the second argument is <tt>true</tt>, JIT compilation is also
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2010-03-07 16:12:21 +00:00
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enabled, disabled or flushed recursively for all sub-functions of a
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function. With <tt>false</tt> only the sub-functions are affected.
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2009-12-08 18:46:35 +00:00
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</p>
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<p>
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The <tt>jit.on</tt> and <tt>jit.off</tt> functions only set a flag
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which is checked when the function is about to be compiled. They do
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not trigger immediate compilation.
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</p>
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<p>
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Typical usage is <tt>jit.off(true, true)</tt> in the main chunk
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of a module to turn off JIT compilation for the whole module for
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debugging purposes.
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</p>
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2010-04-25 01:32:29 +00:00
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<h3 id="jit_flush_tr"><tt>jit.flush(tr)</tt></h3>
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2009-12-08 18:49:20 +00:00
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<p>
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2010-04-25 01:32:29 +00:00
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Flushes the specified root trace and all of its side traces from the cache.
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The code for the trace will be retained as long as there are any other
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traces which link to it.
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2009-12-08 18:49:20 +00:00
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</p>
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2010-03-04 19:46:07 +00:00
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<h3 id="jit_status"><tt>status, ... = jit.status()</tt></h3>
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<p>
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Returns the current status of the JIT compiler. The first result is
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either <tt>true</tt> or <tt>false</tt> if the JIT compiler is turned
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on or off. The remaining results are strings for CPU-specific features
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and enabled optimizations.
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</p>
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2009-12-08 18:46:35 +00:00
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<h3 id="jit_version"><tt>jit.version</tt></h3>
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<p>
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Contains the LuaJIT version string.
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</p>
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<h3 id="jit_version_num"><tt>jit.version_num</tt></h3>
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<p>
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Contains the version number of the LuaJIT core. Version xx.yy.zz
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is represented by the decimal number xxyyzz.
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</p>
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<h3 id="jit_arch"><tt>jit.arch</tt></h3>
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<p>
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Contains the target architecture name (CPU and optional ABI).
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</p>
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<h2 id="jit_opt"><tt>jit.opt.*</tt> — JIT compiler optimization control</h2>
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<p>
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This module provides the backend for the <tt>-O</tt> command line
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option.
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</p>
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<p>
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You can also use it programmatically, e.g.:
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</p>
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<pre class="code">
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jit.opt.start(2) -- same as -O2
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jit.opt.start("-dce")
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jit.opt.start("hotloop=10", "hotexit=2")
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</pre>
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<p>
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Unlike in LuaJIT 1.x, the module is built-in and
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<b>optimization is turned on by default!</b>
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It's no longer necessary to run <tt>require("jit.opt").start()</tt>,
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which was one of the ways to enable optimization.
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</p>
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<h2 id="jit_util"><tt>jit.util.*</tt> — JIT compiler introspection</h2>
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<p>
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This module holds functions to introspect the bytecode, generated
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traces, the IR and the generated machine code. The functionality
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provided by this module is still in flux and therefore undocumented.
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</p>
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<p>
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The debug modules <tt>-jbc</tt>, <tt>-jv</tt> and <tt>-jdump</tt> make
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extensive use of these functions. Please check out their source code,
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if you want to know more.
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</p>
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2009-12-08 18:49:20 +00:00
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<h2 id="c_api">C API extensions</h2>
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<p>
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LuaJIT adds some extensions to the Lua/C API. The LuaJIT include
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directory must be in the compiler search path (<tt>-I<i>path</i></tt>)
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to be able to include the required header for C code:
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</p>
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<pre class="code">
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#include "luajit.h"
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</pre>
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<p>
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Or for C++ code:
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</p>
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<pre class="code">
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#include "lua.hpp"
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</pre>
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<h2 id="luaJIT_setmode"><tt>luaJIT_setmode(L, idx, mode)</tt>
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— Control VM</h2>
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<p>
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This is a C API extension to allow control of the VM from C code. The
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full prototype of <tt>LuaJIT_setmode</tt> is:
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</p>
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<pre class="code">
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LUA_API int luaJIT_setmode(lua_State *L, int idx, int mode);
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</pre>
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<p>
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The returned status is either success (<tt>1</tt>) or failure (<tt>0</tt>).
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The second argument is either <tt>0</tt> or a stack index (similar to the
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other Lua/C API functions).
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</p>
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<p>
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The third argument specifies the mode, which is 'or'ed with a flag.
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The flag can be <tt>LUAJIT_MODE_OFF</tt> to turn a feature on,
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<tt>LUAJIT_MODE_ON</tt> to turn a feature off, or
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<tt>LUAJIT_MODE_FLUSH</tt> to flush cached code.
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</p>
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<p>
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The following modes are defined:
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</p>
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<h3 id="mode_engine"><tt>luaJIT_setmode(L, 0, LUAJIT_MODE_ENGINE|flag)</tt></h3>
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<p>
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Turn the whole JIT compiler on or off or flush the whole cache of compiled code.
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</p>
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<h3 id="mode_func"><tt>luaJIT_setmode(L, idx, LUAJIT_MODE_FUNC|flag)</tt><br>
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<tt>luaJIT_setmode(L, idx, LUAJIT_MODE_ALLFUNC|flag)</tt><br>
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<tt>luaJIT_setmode(L, idx, LUAJIT_MODE_ALLSUBFUNC|flag)</tt></h3>
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<p>
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This sets the mode for the function at the stack index <tt>idx</tt> or
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the parent of the calling function (<tt>idx = 0</tt>). It either
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enables JIT compilation for a function, disables it and flushes any
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already compiled code or only flushes already compiled code. This
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2010-03-07 16:12:21 +00:00
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applies recursively to all sub-functions of the function with
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<tt>LUAJIT_MODE_ALLFUNC</tt> or only to the sub-functions with
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2009-12-08 18:49:20 +00:00
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<tt>LUAJIT_MODE_ALLSUBFUNC</tt>.
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</p>
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2010-11-01 16:49:31 +00:00
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<h3 id="mode_trace"><tt>luaJIT_setmode(L, trace,<br>
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2009-12-08 18:49:20 +00:00
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LUAJIT_MODE_TRACE|LUAJIT_MODE_FLUSH)</tt></h3>
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<p>
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2010-04-25 01:32:29 +00:00
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Flushes the specified root trace and all of its side traces from the cache.
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The code for the trace will be retained as long as there are any other
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traces which link to it.
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2009-12-08 18:49:20 +00:00
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</p>
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2010-11-01 16:49:31 +00:00
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<h3 id="mode_wrapcfunc"><tt>luaJIT_setmode(L, idx, LUAJIT_MODE_WRAPCFUNC|flag)</tt></h3>
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2009-12-08 18:49:20 +00:00
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<p>
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2010-02-13 03:51:56 +00:00
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This mode defines a wrapper function for calls to C functions. If
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called with <tt>LUAJIT_MODE_ON</tt>, the stack index at <tt>idx</tt>
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must be a <tt>lightuserdata</tt> object holding a pointer to the wrapper
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function. From now on all C functions are called through the wrapper
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function. If called with <tt>LUAJIT_MODE_OFF</tt> this mode is turned
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off and all C functions are directly called.
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2009-12-08 18:49:20 +00:00
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</p>
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<p>
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The wrapper function can be used for debugging purposes or to catch
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and convert foreign exceptions. Recommended usage can be seen in this
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C++ code excerpt:
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</p>
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<pre class="code">
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#include <exception>
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#include "lua.hpp"
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// Catch C++ exceptions and convert them to Lua error messages.
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// Customize as needed for your own exception classes.
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static int wrap_exceptions(lua_State *L, lua_CFunction f)
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{
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try {
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return f(L); // Call wrapped function and return result.
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} catch (const char *s) { // Catch and convert exceptions.
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lua_pushstring(L, s);
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} catch (std::exception& e) {
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lua_pushstring(L, e.what());
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} catch (...) {
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lua_pushliteral(L, "caught (...)");
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}
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return lua_error(L); // Rethrow as a Lua error.
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}
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2010-02-13 03:51:56 +00:00
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static int myinit(lua_State *L)
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2009-12-08 18:49:20 +00:00
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{
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...
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// Define wrapper function and enable it.
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lua_pushlightuserdata(L, (void *)wrap_exceptions);
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luaJIT_setmode(L, -1, LUAJIT_MODE_WRAPCFUNC|LUAJIT_MODE_ON);
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lua_pop(L, 1);
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...
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}
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</pre>
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<p>
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Note that you can only define <b>a single global wrapper function</b>,
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so be careful when using this mechanism from multiple C++ modules.
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2010-02-13 03:51:56 +00:00
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Also note that this mechanism is not without overhead.
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2009-12-08 18:49:20 +00:00
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</p>
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<p>
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2010-02-13 03:51:56 +00:00
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LuaJIT already intercepts exception handling for systems using DWARF2
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stack unwinding (e.g. Linux or OSX) and for Windows/x64 (but <b>not</b>
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for Windows/x86). This is a zero-cost mechanism and always enabled.
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You don't need to use any wrapper functions, except when you want to get
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a more specific error message than <tt>"C++ exception"</tt>.
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2009-12-08 18:49:20 +00:00
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</p>
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2009-12-08 18:46:35 +00:00
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<br class="flush">
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</div>
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<div id="foot">
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<hr class="hide">
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2010-01-09 13:28:11 +00:00
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Copyright © 2005-2010 Mike Pall
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2009-12-08 18:46:35 +00:00
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<span class="noprint">
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·
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