ext_jit.html (5903B)
1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> 2 <html> 3 <head> 4 <title>jit.* Library</title> 5 <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> 6 <meta name="Author" content="Mike Pall"> 7 <meta name="Copyright" content="Copyright (C) 2005-2016, Mike Pall"> 8 <meta name="Language" content="en"> 9 <link rel="stylesheet" type="text/css" href="bluequad.css" media="screen"> 10 <link rel="stylesheet" type="text/css" href="bluequad-print.css" media="print"> 11 </head> 12 <body> 13 <div id="site"> 14 <a href="http://luajit.org"><span>Lua<span id="logo">JIT</span></span></a> 15 </div> 16 <div id="head"> 17 <h1><tt>jit.*</tt> Library</h1> 18 </div> 19 <div id="nav"> 20 <ul><li> 21 <a href="luajit.html">LuaJIT</a> 22 <ul><li> 23 <a href="http://luajit.org/download.html">Download <span class="ext">»</span></a> 24 </li><li> 25 <a href="install.html">Installation</a> 26 </li><li> 27 <a href="running.html">Running</a> 28 </li></ul> 29 </li><li> 30 <a href="extensions.html">Extensions</a> 31 <ul><li> 32 <a href="ext_ffi.html">FFI Library</a> 33 <ul><li> 34 <a href="ext_ffi_tutorial.html">FFI Tutorial</a> 35 </li><li> 36 <a href="ext_ffi_api.html">ffi.* API</a> 37 </li><li> 38 <a href="ext_ffi_semantics.html">FFI Semantics</a> 39 </li></ul> 40 </li><li> 41 <a class="current" href="ext_jit.html">jit.* Library</a> 42 </li><li> 43 <a href="ext_c_api.html">Lua/C API</a> 44 </li><li> 45 <a href="ext_profiler.html">Profiler</a> 46 </li></ul> 47 </li><li> 48 <a href="status.html">Status</a> 49 <ul><li> 50 <a href="changes.html">Changes</a> 51 </li></ul> 52 </li><li> 53 <a href="faq.html">FAQ</a> 54 </li><li> 55 <a href="http://luajit.org/performance.html">Performance <span class="ext">»</span></a> 56 </li><li> 57 <a href="http://wiki.luajit.org/">Wiki <span class="ext">»</span></a> 58 </li><li> 59 <a href="http://luajit.org/list.html">Mailing List <span class="ext">»</span></a> 60 </li></ul> 61 </div> 62 <div id="main"> 63 <p> 64 The functions in this built-in module control the behavior of the JIT 65 compiler engine. Note that JIT-compilation is fully automatic — 66 you probably won't need to use any of the following functions unless 67 you have special needs. 68 </p> 69 70 <h3 id="jit_onoff"><tt>jit.on()<br> 71 jit.off()</tt></h3> 72 <p> 73 Turns the whole JIT compiler on (default) or off. 74 </p> 75 <p> 76 These functions are typically used with the command line options 77 <tt>-j on</tt> or <tt>-j off</tt>. 78 </p> 79 80 <h3 id="jit_flush"><tt>jit.flush()</tt></h3> 81 <p> 82 Flushes the whole cache of compiled code. 83 </p> 84 85 <h3 id="jit_onoff_func"><tt>jit.on(func|true [,true|false])<br> 86 jit.off(func|true [,true|false])<br> 87 jit.flush(func|true [,true|false])</tt></h3> 88 <p> 89 <tt>jit.on</tt> enables JIT compilation for a Lua function (this is 90 the default). 91 </p> 92 <p> 93 <tt>jit.off</tt> disables JIT compilation for a Lua function and 94 flushes any already compiled code from the code cache. 95 </p> 96 <p> 97 <tt>jit.flush</tt> flushes the code, but doesn't affect the 98 enable/disable status. 99 </p> 100 <p> 101 The current function, i.e. the Lua function calling this library 102 function, can also be specified by passing <tt>true</tt> as the first 103 argument. 104 </p> 105 <p> 106 If the second argument is <tt>true</tt>, JIT compilation is also 107 enabled, disabled or flushed recursively for all sub-functions of a 108 function. With <tt>false</tt> only the sub-functions are affected. 109 </p> 110 <p> 111 The <tt>jit.on</tt> and <tt>jit.off</tt> functions only set a flag 112 which is checked when the function is about to be compiled. They do 113 not trigger immediate compilation. 114 </p> 115 <p> 116 Typical usage is <tt>jit.off(true, true)</tt> in the main chunk 117 of a module to turn off JIT compilation for the whole module for 118 debugging purposes. 119 </p> 120 121 <h3 id="jit_flush_tr"><tt>jit.flush(tr)</tt></h3> 122 <p> 123 Flushes the root trace, specified by its number, and all of its side 124 traces from the cache. The code for the trace will be retained as long 125 as there are any other traces which link to it. 126 </p> 127 128 <h3 id="jit_status"><tt>status, ... = jit.status()</tt></h3> 129 <p> 130 Returns the current status of the JIT compiler. The first result is 131 either <tt>true</tt> or <tt>false</tt> if the JIT compiler is turned 132 on or off. The remaining results are strings for CPU-specific features 133 and enabled optimizations. 134 </p> 135 136 <h3 id="jit_version"><tt>jit.version</tt></h3> 137 <p> 138 Contains the LuaJIT version string. 139 </p> 140 141 <h3 id="jit_version_num"><tt>jit.version_num</tt></h3> 142 <p> 143 Contains the version number of the LuaJIT core. Version xx.yy.zz 144 is represented by the decimal number xxyyzz. 145 </p> 146 147 <h3 id="jit_os"><tt>jit.os</tt></h3> 148 <p> 149 Contains the target OS name: 150 "Windows", "Linux", "OSX", "BSD", "POSIX" or "Other". 151 </p> 152 153 <h3 id="jit_arch"><tt>jit.arch</tt></h3> 154 <p> 155 Contains the target architecture name: 156 "x86", "x64", "arm", "arm64", "ppc", "mips" or "mips64". 157 </p> 158 159 <h2 id="jit_opt"><tt>jit.opt.*</tt> — JIT compiler optimization control</h2> 160 <p> 161 This sub-module provides the backend for the <tt>-O</tt> command line 162 option. 163 </p> 164 <p> 165 You can also use it programmatically, e.g.: 166 </p> 167 <pre class="code"> 168 jit.opt.start(2) -- same as -O2 169 jit.opt.start("-dce") 170 jit.opt.start("hotloop=10", "hotexit=2") 171 </pre> 172 <p> 173 Unlike in LuaJIT 1.x, the module is built-in and 174 <b>optimization is turned on by default!</b> 175 It's no longer necessary to run <tt>require("jit.opt").start()</tt>, 176 which was one of the ways to enable optimization. 177 </p> 178 179 <h2 id="jit_util"><tt>jit.util.*</tt> — JIT compiler introspection</h2> 180 <p> 181 This sub-module holds functions to introspect the bytecode, generated 182 traces, the IR and the generated machine code. The functionality 183 provided by this module is still in flux and therefore undocumented. 184 </p> 185 <p> 186 The debug modules <tt>-jbc</tt>, <tt>-jv</tt> and <tt>-jdump</tt> make 187 extensive use of these functions. Please check out their source code, 188 if you want to know more. 189 </p> 190 <br class="flush"> 191 </div> 192 <div id="foot"> 193 <hr class="hide"> 194 Copyright © 2005-2016 Mike Pall 195 <span class="noprint"> 196 · 197 <a href="contact.html">Contact</a> 198 </span> 199 </div> 200 </body> 201 </html>