202 lines
5.8 KiB
HTML
202 lines
5.8 KiB
HTML
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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>jit.* Library</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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<meta name="Copyright" content="Copyright (C) 2005-2017, Mike Pall">
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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><tt>jit.*</tt> Library</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="http://luajit.org/download.html">Download <span class="ext">»</span></a>
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</li><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></ul>
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</li><li>
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<a href="extensions.html">Extensions</a>
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<ul><li>
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<a href="ext_ffi.html">FFI Library</a>
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<ul><li>
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<a href="ext_ffi_tutorial.html">FFI Tutorial</a>
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</li><li>
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<a href="ext_ffi_api.html">ffi.* API</a>
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</li><li>
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<a href="ext_ffi_semantics.html">FFI Semantics</a>
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</li></ul>
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</li><li>
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<a class="current" href="ext_jit.html">jit.* Library</a>
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</li><li>
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<a href="ext_c_api.html">Lua/C API</a>
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</li><li>
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<a href="ext_profiler.html">Profiler</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></ul>
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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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<a href="http://luajit.org/performance.html">Performance <span class="ext">»</span></a>
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</li><li>
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<a href="http://wiki.luajit.org/">Wiki <span class="ext">»</span></a>
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</li><li>
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<a href="http://luajit.org/list.html">Mailing List <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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The functions in this built-in module control the behavior of the JIT
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compiler engine. Note that JIT-compilation is fully automatic —
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you probably won't need to use any of the following functions unless
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you have special needs.
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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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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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</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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<h3 id="jit_flush_tr"><tt>jit.flush(tr)</tt></h3>
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<p>
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Flushes the root trace, specified by its number, and all of its side
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traces from the cache. The code for the trace will be retained as long
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as there are any other traces which link to it.
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</p>
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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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<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_os"><tt>jit.os</tt></h3>
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<p>
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Contains the target OS name:
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"Windows", "Linux", "OSX", "BSD", "POSIX" or "Other".
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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:
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"x86", "x64", "arm", "arm64", "ppc", "mips" or "mips64".
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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 sub-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 sub-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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<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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Copyright © 2005-2017 Mike Pall
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<span class="noprint">
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·
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<a href="contact.html">Contact</a>
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</span>
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</div>
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</body>
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</html>
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