319 lines
17 KiB
HTML
319 lines
17 KiB
HTML
<!DOCTYPE HTML>
|
|
<html lang="en" class="light sidebar-visible" dir="ltr">
|
|
<head>
|
|
<!-- Book generated using mdBook -->
|
|
<meta charset="UTF-8">
|
|
<title>Optimized build - Rust Compiler Development Guide</title>
|
|
|
|
|
|
<!-- Custom HTML head -->
|
|
|
|
<meta name="description" content="A guide to developing the Rust compiler (rustc)">
|
|
<meta name="viewport" content="width=device-width, initial-scale=1">
|
|
<meta name="theme-color" content="#ffffff">
|
|
|
|
<link rel="icon" href="../favicon.svg">
|
|
<link rel="shortcut icon" href="../favicon.png">
|
|
<link rel="stylesheet" href="../css/variables.css">
|
|
<link rel="stylesheet" href="../css/general.css">
|
|
<link rel="stylesheet" href="../css/chrome.css">
|
|
<link rel="stylesheet" href="../css/print.css" media="print">
|
|
|
|
<!-- Fonts -->
|
|
<link rel="stylesheet" href="../FontAwesome/css/font-awesome.css">
|
|
<link rel="stylesheet" href="../fonts/fonts.css">
|
|
|
|
<!-- Highlight.js Stylesheets -->
|
|
<link rel="stylesheet" id="highlight-css" href="../highlight.css">
|
|
<link rel="stylesheet" id="tomorrow-night-css" href="../tomorrow-night.css">
|
|
<link rel="stylesheet" id="ayu-highlight-css" href="../ayu-highlight.css">
|
|
|
|
<!-- Custom theme stylesheets -->
|
|
|
|
|
|
<!-- Provide site root and default themes to javascript -->
|
|
<script>
|
|
const path_to_root = "../";
|
|
const default_light_theme = "light";
|
|
const default_dark_theme = "navy";
|
|
</script>
|
|
<!-- Start loading toc.js asap -->
|
|
<script src="../toc.js"></script>
|
|
</head>
|
|
<body>
|
|
<div id="body-container">
|
|
<!-- Work around some values being stored in localStorage wrapped in quotes -->
|
|
<script>
|
|
try {
|
|
let theme = localStorage.getItem('mdbook-theme');
|
|
let sidebar = localStorage.getItem('mdbook-sidebar');
|
|
|
|
if (theme.startsWith('"') && theme.endsWith('"')) {
|
|
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
|
|
}
|
|
|
|
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
|
|
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
|
|
}
|
|
} catch (e) { }
|
|
</script>
|
|
|
|
<!-- Set the theme before any content is loaded, prevents flash -->
|
|
<script>
|
|
const default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? default_dark_theme : default_light_theme;
|
|
let theme;
|
|
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
|
|
if (theme === null || theme === undefined) { theme = default_theme; }
|
|
const html = document.documentElement;
|
|
html.classList.remove('light')
|
|
html.classList.add(theme);
|
|
html.classList.add("js");
|
|
</script>
|
|
|
|
<input type="checkbox" id="sidebar-toggle-anchor" class="hidden">
|
|
|
|
<!-- Hide / unhide sidebar before it is displayed -->
|
|
<script>
|
|
let sidebar = null;
|
|
const sidebar_toggle = document.getElementById("sidebar-toggle-anchor");
|
|
if (document.body.clientWidth >= 1080) {
|
|
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
|
|
sidebar = sidebar || 'visible';
|
|
} else {
|
|
sidebar = 'hidden';
|
|
}
|
|
sidebar_toggle.checked = sidebar === 'visible';
|
|
html.classList.remove('sidebar-visible');
|
|
html.classList.add("sidebar-" + sidebar);
|
|
</script>
|
|
|
|
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
|
<!-- populated by js -->
|
|
<mdbook-sidebar-scrollbox class="sidebar-scrollbox"></mdbook-sidebar-scrollbox>
|
|
<noscript>
|
|
<iframe class="sidebar-iframe-outer" src="../toc.html"></iframe>
|
|
</noscript>
|
|
<div id="sidebar-resize-handle" class="sidebar-resize-handle">
|
|
<div class="sidebar-resize-indicator"></div>
|
|
</div>
|
|
</nav>
|
|
|
|
<div id="page-wrapper" class="page-wrapper">
|
|
|
|
<div class="page">
|
|
<div id="menu-bar-hover-placeholder"></div>
|
|
<div id="menu-bar" class="menu-bar sticky">
|
|
<div class="left-buttons">
|
|
<label id="sidebar-toggle" class="icon-button" for="sidebar-toggle-anchor" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
|
|
<i class="fa fa-bars"></i>
|
|
</label>
|
|
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
|
|
<i class="fa fa-paint-brush"></i>
|
|
</button>
|
|
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
|
|
<li role="none"><button role="menuitem" class="theme" id="default_theme">Auto</button></li>
|
|
<li role="none"><button role="menuitem" class="theme" id="light">Light</button></li>
|
|
<li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
|
|
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
|
|
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
|
|
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
|
|
</ul>
|
|
<button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
|
|
<i class="fa fa-search"></i>
|
|
</button>
|
|
</div>
|
|
|
|
<h1 class="menu-title">Rust Compiler Development Guide</h1>
|
|
|
|
<div class="right-buttons">
|
|
<a href="../print.html" title="Print this book" aria-label="Print this book">
|
|
<i id="print-button" class="fa fa-print"></i>
|
|
</a>
|
|
<a href="https://github.com/rust-lang/rustc-dev-guide" title="Git repository" aria-label="Git repository">
|
|
<i id="git-repository-button" class="fa fa-github"></i>
|
|
</a>
|
|
<a href="https://github.com/rust-lang/rustc-dev-guide/edit/master/src/building/optimized-build.md" title="Suggest an edit" aria-label="Suggest an edit">
|
|
<i id="git-edit-button" class="fa fa-edit"></i>
|
|
</a>
|
|
|
|
</div>
|
|
</div>
|
|
|
|
<div id="search-wrapper" class="hidden">
|
|
<form id="searchbar-outer" class="searchbar-outer">
|
|
<input type="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
|
|
</form>
|
|
<div id="searchresults-outer" class="searchresults-outer hidden">
|
|
<div id="searchresults-header" class="searchresults-header"></div>
|
|
<ul id="searchresults">
|
|
</ul>
|
|
</div>
|
|
</div>
|
|
|
|
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
|
|
<script>
|
|
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
|
|
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
|
|
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
|
|
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
|
|
});
|
|
</script>
|
|
|
|
<div id="content" class="content">
|
|
<main>
|
|
<h1 id="optimized-build-of-the-compiler"><a class="header" href="#optimized-build-of-the-compiler">Optimized build of the compiler</a></h1>
|
|
<ul>
|
|
<li><a href="#link-time-optimization">Link-time optimization</a></li>
|
|
<li><a href="#memory-allocator">Memory allocator</a></li>
|
|
<li><a href="#codegen-units">Codegen units</a></li>
|
|
<li><a href="#instruction-set">Instruction set</a></li>
|
|
<li><a href="#profile-guided-optimization">Profile-guided optimization</a></li>
|
|
</ul>
|
|
<p>There are multiple additional build configuration options and techniques that can be used to compile a
|
|
build of <code>rustc</code> that is as optimized as possible (for example when building <code>rustc</code> for a Linux
|
|
distribution). The status of these configuration options for various Rust targets is tracked <a href="https://github.com/rust-lang/rust/issues/103595">here</a>.
|
|
This page describes how you can use these approaches when building <code>rustc</code> yourself.</p>
|
|
<h2 id="link-time-optimization"><a class="header" href="#link-time-optimization">Link-time optimization</a></h2>
|
|
<p>Link-time optimization is a powerful compiler technique that can increase program performance. To
|
|
enable (Thin-)LTO when building <code>rustc</code>, set the <code>rust.lto</code> config option to <code>"thin"</code>
|
|
in <code>bootstrap.toml</code>:</p>
|
|
<pre><code class="language-toml">[rust]
|
|
lto = "thin"
|
|
</code></pre>
|
|
<blockquote>
|
|
<p>Note that LTO for <code>rustc</code> is currently supported and tested only for
|
|
the <code>x86_64-unknown-linux-gnu</code> target. Other targets <em>may</em> work, but no guarantees are provided.
|
|
Notably, LTO-optimized <code>rustc</code> currently produces <a href="https://github.com/rust-lang/rust/issues/109114">miscompilations</a> on Windows.</p>
|
|
</blockquote>
|
|
<p>Enabling LTO on Linux has <a href="https://github.com/rust-lang/rust/pull/101403#issuecomment-1288190019">produced</a> speed-ups by up to 10%.</p>
|
|
<h2 id="memory-allocator"><a class="header" href="#memory-allocator">Memory allocator</a></h2>
|
|
<p>Using a different memory allocator for <code>rustc</code> can provide significant performance benefits. If you
|
|
want to enable the <code>jemalloc</code> allocator, you can set the <code>rust.jemalloc</code> option to <code>true</code>
|
|
in <code>bootstrap.toml</code>:</p>
|
|
<pre><code class="language-toml">[rust]
|
|
jemalloc = true
|
|
</code></pre>
|
|
<blockquote>
|
|
<p>Note that this option is currently only supported for Linux and macOS targets.</p>
|
|
</blockquote>
|
|
<h2 id="codegen-units"><a class="header" href="#codegen-units">Codegen units</a></h2>
|
|
<p>Reducing the amount of codegen units per <code>rustc</code> crate can produce a faster build of the compiler.
|
|
You can modify the number of codegen units for <code>rustc</code> and <code>libstd</code> in <code>bootstrap.toml</code> with the
|
|
following options:</p>
|
|
<pre><code class="language-toml">[rust]
|
|
codegen-units = 1
|
|
codegen-units-std = 1
|
|
</code></pre>
|
|
<h2 id="instruction-set"><a class="header" href="#instruction-set">Instruction set</a></h2>
|
|
<p>By default, <code>rustc</code> is compiled for a generic (and conservative) instruction set architecture
|
|
(depending on the selected target), to make it support as many CPUs as possible. If you want to
|
|
compile <code>rustc</code> for a specific instruction set architecture, you can set the <code>target_cpu</code> compiler
|
|
option in <code>RUSTFLAGS</code>:</p>
|
|
<pre><code class="language-bash">RUSTFLAGS="-C target_cpu=x86-64-v3" ./x build ...
|
|
</code></pre>
|
|
<p>If you also want to compile LLVM for a specific instruction set, you can set <code>llvm</code> flags
|
|
in <code>bootstrap.toml</code>:</p>
|
|
<pre><code class="language-toml">[llvm]
|
|
cxxflags = "-march=x86-64-v3"
|
|
cflags = "-march=x86-64-v3"
|
|
</code></pre>
|
|
<h2 id="profile-guided-optimization"><a class="header" href="#profile-guided-optimization">Profile-guided optimization</a></h2>
|
|
<p>Applying profile-guided optimizations (or more generally, feedback-directed optimizations) can
|
|
produce a large increase to <code>rustc</code> performance, by up to 15% (<a href="https://blog.rust-lang.org/inside-rust/2020/11/11/exploring-pgo-for-the-rust-compiler.html#final-numbers-and-a-benchmarking-plot-twist">1</a>, <a href="https://github.com/rust-lang/rust/pull/96978">2</a>). However, these techniques
|
|
are not simply enabled by a configuration option, but rather they require a complex build workflow
|
|
that compiles <code>rustc</code> multiple times and profiles it on selected benchmarks.</p>
|
|
<p>There is a tool called <code>opt-dist</code> that is used to optimize <code>rustc</code> with <a href="https://doc.rust-lang.org/rustc/profile-guided-optimization.html">PGO</a> (profile-guided
|
|
optimizations) and <a href="https://github.com/llvm/llvm-project/blob/main/bolt/README.md">BOLT</a> (a post-link binary optimizer) for builds distributed to end users. You
|
|
can examine the tool, which is located in <code>src/tools/opt-dist</code>, and build a custom PGO build
|
|
workflow based on it, or try to use it directly. Note that the tool is currently quite hardcoded to
|
|
the way we use it in Rust's continuous integration workflows, and it might require some custom
|
|
changes to make it work in a different environment.</p>
|
|
<p>To use the tool, you will need to provide some external dependencies:</p>
|
|
<ul>
|
|
<li>A Python3 interpreter (for executing <code>x.py</code>).</li>
|
|
<li>Compiled LLVM toolchain, with the <code>llvm-profdata</code> binary. Optionally, if you want to use BOLT,
|
|
the <code>llvm-bolt</code> and
|
|
<code>merge-fdata</code> binaries have to be available in the toolchain.</li>
|
|
</ul>
|
|
<p>These dependencies are provided to <code>opt-dist</code> by an implementation of the <a href="https://github.com/rust-lang/rust/blob/ee451f8faccf3050c76cdcd82543c917b40c7962/src/tools/opt-dist/src/environment.rs#L5"><code>Environment</code></a> struct.
|
|
It specifies directories where will the PGO/BOLT pipeline take place, and also external dependencies
|
|
like Python or LLVM.</p>
|
|
<p>Here is an example of how can <code>opt-dist</code> be used locally (outside of CI):</p>
|
|
<ol>
|
|
<li>Enable metrics in your <code>bootstrap.toml</code> file, because <code>opt-dist</code> expects it to be enabled:
|
|
<pre><code class="language-toml">[build]
|
|
metrics = true
|
|
</code></pre>
|
|
</li>
|
|
<li>Build the tool with the following command:
|
|
<pre><code class="language-bash">./x build tools/opt-dist
|
|
</code></pre>
|
|
</li>
|
|
<li>Run the tool with the <code>local</code> mode and provide necessary parameters:
|
|
<pre><code class="language-bash">./build/host/stage0-tools-bin/opt-dist local \
|
|
--target-triple <target> \ # select target, e.g. "x86_64-unknown-linux-gnu"
|
|
--checkout-dir <path> \ # path to rust checkout, e.g. "."
|
|
--llvm-dir <path> \ # path to built LLVM toolchain, e.g. "/foo/bar/llvm/install"
|
|
-- python3 x.py dist # pass the actual build command
|
|
</code></pre>
|
|
You can run <code>--help</code> to see further parameters that you can modify.</li>
|
|
</ol>
|
|
<blockquote>
|
|
<p>Note: if you want to run the actual CI pipeline, instead of running <code>opt-dist</code> locally,
|
|
you can execute <code>cargo run --manifest-path src/ci/citool/Cargo.toml run-local dist-x86_64-linux</code>.</p>
|
|
</blockquote>
|
|
|
|
</main>
|
|
|
|
<nav class="nav-wrapper" aria-label="Page navigation">
|
|
<!-- Mobile navigation buttons -->
|
|
<a rel="prev" href="../building/new-target.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
|
|
<i class="fa fa-angle-left"></i>
|
|
</a>
|
|
|
|
<a rel="next prefetch" href="../tests/intro.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
|
|
<i class="fa fa-angle-right"></i>
|
|
</a>
|
|
|
|
<div style="clear: both"></div>
|
|
</nav>
|
|
</div>
|
|
</div>
|
|
|
|
<nav class="nav-wide-wrapper" aria-label="Page navigation">
|
|
<a rel="prev" href="../building/new-target.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
|
|
<i class="fa fa-angle-left"></i>
|
|
</a>
|
|
|
|
<a rel="next prefetch" href="../tests/intro.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
|
|
<i class="fa fa-angle-right"></i>
|
|
</a>
|
|
</nav>
|
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<script>
|
|
window.playground_copyable = true;
|
|
</script>
|
|
|
|
|
|
<script src="../elasticlunr.min.js"></script>
|
|
<script src="../mark.min.js"></script>
|
|
<script src="../searcher.js"></script>
|
|
|
|
<script src="../clipboard.min.js"></script>
|
|
<script src="../highlight.js"></script>
|
|
<script src="../book.js"></script>
|
|
|
|
<!-- Custom JS scripts -->
|
|
<script src="../mermaid.min.js"></script>
|
|
<script src="../mermaid-init.js"></script>
|
|
|
|
|
|
</div>
|
|
</body>
|
|
</html>
|