<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="API documentation for the Rust `arch` mod in crate `core`."><meta name="keywords" content="rust, rustlang, rust-lang, arch"><title>core::arch - Rust</title><link rel="stylesheet" type="text/css" href="../../normalize1.35.0.css"><link rel="stylesheet" type="text/css" href="../../rustdoc1.35.0.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../dark1.35.0.css"><link rel="stylesheet" type="text/css" href="../../light1.35.0.css" id="themeStyle"><script src="../../storage1.35.0.js"></script><noscript><link rel="stylesheet" href="../../noscript1.35.0.css"></noscript><link rel="shortcut icon" href="../../favicon1.35.0.ico"><style type="text/css">#crate-search{background-image:url("../../down-arrow1.35.0.svg");}</style></head><body class="rustdoc mod"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../core/index.html'><img src='../../rust-logo1.35.0.png' alt='logo' width='100'></a><p class='location'>Module arch</p><div class="sidebar-elems"><div class="block items"><ul><li><a href="#modules">Modules</a></li></ul></div><p class='location'><a href='../index.html'>core</a></p><script>window.sidebarCurrent = {name: 'arch', ty: 'mod', relpath: '../'};</script><script defer src="../sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../brush1.35.0.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../theme1.35.0.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><a id="settings-menu" href="../../settings.html"><img src="../../wheel1.35.0.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='out-of-band'><span class='since' title='Stable since Rust version 1.27.0'>1.27.0</span><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>−</span>]</a></span><a class='srclink' href='../../src/core/up/stdsimd/crates/core_arch/src/mod.rs.html#17-123' title='goto source code'>[src]</a></span><span class='in-band'>Module <a href='../index.html'>core</a>::<wbr><a class="mod" href=''>arch</a></span></h1><div class='docblock'><p>SIMD and vendor intrinsics module.</p>
<p>This module is intended to be the gateway to architecture-specific
intrinsic functions, typically related to SIMD (but not always!). Each
architecture that Rust compiles to may contain a submodule here, which
means that this is not a portable module! If you're writing a portable
library take care when using these APIs!</p>
<p>Under this module you'll find an architecture-named module, such as
<code>x86_64</code>. Each <code>#[cfg(target_arch)]</code> that Rust can compile to may have a
module entry here, only present on that particular target. For example the
<code>i686-pc-windows-msvc</code> target will have an <code>x86</code> module here, whereas
<code>x86_64-pc-windows-msvc</code> has <code>x86_64</code>.</p>
<h1 id="overview" class="section-header"><a href="#overview">Overview</a></h1>
<p>This module exposes vendor-specific intrinsics that typically correspond to
a single machine instruction. These intrinsics are not portable: their
availability is architecture-dependent, and not all machines of that
architecture might provide the intrinsic.</p>
<p>The <code>arch</code> module is intended to be a low-level implementation detail for
higher-level APIs. Using it correctly can be quite tricky as you need to
ensure at least a few guarantees are upheld:</p>
<ul>
<li>The correct architecture's module is used. For example the <code>arm</code> module
isn't available on the <code>x86_64-unknown-linux-gnu</code> target. This is
typically done by ensuring that <code>#[cfg]</code> is used appropriately when using
this module.</li>
<li>The CPU the program is currently running on supports the function being
called. For example it is unsafe to call an AVX2 function on a CPU that
doesn't actually support AVX2.</li>
</ul>
<p>As a result of the latter of these guarantees all intrinsics in this module
are <code>unsafe</code> and extra care needs to be taken when calling them!</p>
<h1 id="cpu-feature-detection" class="section-header"><a href="#cpu-feature-detection">CPU Feature Detection</a></h1>
<p>In order to call these APIs in a safe fashion there's a number of
mechanisms available to ensure that the correct CPU feature is available
to call an intrinsic. Let's consider, for example, the <code>_mm256_add_epi64</code>
intrinsics on the <code>x86</code> and <code>x86_64</code> architectures. This function requires
the AVX2 feature as <a href="https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_mm256_add_epi64&expand=100">documented by Intel</a> so to correctly call
this function we need to (a) guarantee we only call it on <code>x86</code>/<code>x86_64</code>
and (b) ensure that the CPU feature is available</p>
<h2 id="static-cpu-feature-detection" class="section-header"><a href="#static-cpu-feature-detection">Static CPU Feature Detection</a></h2>
<p>The first option available to us is to conditionally compile code via the
<code>#[cfg]</code> attribute. CPU features correspond to the <code>target_feature</code> cfg
available, and can be used like so:</p>
<div class='information'><div class='tooltip ignore'>ⓘ<span class='tooltiptext'>This example is not tested</span></div></div><div class="example-wrap"><pre class="rust rust-example-rendered ignore">
<span class="attribute">#[<span class="ident">cfg</span>(
<span class="ident">all</span>(
<span class="ident">any</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>, <span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>),
<span class="ident">target_feature</span> <span class="op">=</span> <span class="string">"avx2"</span>
)
)]</span>
<span class="kw">fn</span> <span class="ident">foo</span>() {
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>)]</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">arch</span>::<span class="ident">x86</span>::<span class="ident">_mm256_add_epi64</span>;
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>)]</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">arch</span>::<span class="ident">x86_64</span>::<span class="ident">_mm256_add_epi64</span>;
<span class="kw">unsafe</span> {
<span class="ident">_mm256_add_epi64</span>(...);
}
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0A%23%5Bcfg(%0A%20%20%20%20all(%0A%20%20%20%20%20%20%20%20any(target_arch%20%3D%20%22x86%22%2C%20target_arch%20%3D%20%22x86_64%22)%2C%0A%20%20%20%20%20%20%20%20target_feature%20%3D%20%22avx2%22%0A%20%20%20%20)%0A)%5D%0Afn%20foo()%20%7B%0A%20%20%20%20%23%5Bcfg(target_arch%20%3D%20%22x86%22)%5D%0A%20%20%20%20use%20std%3A%3Aarch%3A%3Ax86%3A%3A_mm256_add_epi64%3B%0A%20%20%20%20%23%5Bcfg(target_arch%20%3D%20%22x86_64%22)%5D%0A%20%20%20%20use%20std%3A%3Aarch%3A%3Ax86_64%3A%3A_mm256_add_epi64%3B%0A%0A%20%20%20%20unsafe%20%7B%0A%20%20%20%20%20%20%20%20_mm256_add_epi64(...)%3B%0A%20%20%20%20%7D%0A%7D%0A%7D">Run</a></pre></div>
<p>Here we're using <code>#[cfg(target_feature = "avx2")]</code> to conditionally compile
this function into our module. This means that if the <code>avx2</code> feature is
<em>enabled statically</em> then we'll use the <code>_mm256_add_epi64</code> function at
runtime. The <code>unsafe</code> block here can be justified through the usage of
<code>#[cfg]</code> to only compile the code in situations where the safety guarantees
are upheld.</p>
<p>Statically enabling a feature is typically done with the <code>-C target-feature</code> or <code>-C target-cpu</code> flags to the compiler. For example if
your local CPU supports AVX2 then you can compile the above function with:</p>
<pre><code class="language-sh">$ RUSTFLAGS='-C target-cpu=native' cargo build
</code></pre>
<p>Or otherwise you can specifically enable just the AVX2 feature:</p>
<pre><code class="language-sh">$ RUSTFLAGS='-C target-feature=+avx2' cargo build
</code></pre>
<p>Note that when you compile a binary with a particular feature enabled it's
important to ensure that you only run the binary on systems which satisfy
the required feature set.</p>
<h2 id="dynamic-cpu-feature-detection" class="section-header"><a href="#dynamic-cpu-feature-detection">Dynamic CPU Feature Detection</a></h2>
<p>Sometimes statically dispatching isn't quite what you want. Instead you
might want to build a portable binary that runs across a variety of CPUs,
but at runtime it selects the most optimized implementation available. This
allows you to build a "least common denominator" binary which has certain
sections more optimized for different CPUs.</p>
<p>Taking our previous example from before, we're going to compile our binary
<em>without</em> AVX2 support, but we'd like to enable it for just one function.
We can do that in a manner like:</p>
<div class='information'><div class='tooltip ignore'>ⓘ<span class='tooltiptext'>This example is not tested</span></div></div><div class="example-wrap"><pre class="rust rust-example-rendered ignore">
<span class="kw">fn</span> <span class="ident">foo</span>() {
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>, <span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>))]</span>
{
<span class="kw">if</span> <span class="macro">is_x86_feature_detected</span><span class="macro">!</span>(<span class="string">"avx2"</span>) {
<span class="kw">return</span> <span class="kw">unsafe</span> { <span class="ident">foo_avx2</span>() };
}
}
<span class="comment">// fallback implementation without using AVX2</span>
}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>, <span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>))]</span>
<span class="attribute">#[<span class="ident">target_feature</span>(<span class="ident">enable</span> <span class="op">=</span> <span class="string">"avx2"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">foo_avx2</span>() {
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>)]</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">arch</span>::<span class="ident">x86</span>::<span class="ident">_mm256_add_epi64</span>;
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>)]</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">arch</span>::<span class="ident">x86_64</span>::<span class="ident">_mm256_add_epi64</span>;
<span class="ident">_mm256_add_epi64</span>(...);
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Afn%20foo()%20%7B%0A%20%20%20%20%23%5Bcfg(any(target_arch%20%3D%20%22x86%22%2C%20target_arch%20%3D%20%22x86_64%22))%5D%0A%20%20%20%20%7B%0A%20%20%20%20%20%20%20%20if%20is_x86_feature_detected!(%22avx2%22)%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20return%20unsafe%20%7B%20foo_avx2()%20%7D%3B%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%7D%0A%0A%20%20%20%20%2F%2F%20fallback%20implementation%20without%20using%20AVX2%0A%7D%0A%0A%23%5Bcfg(any(target_arch%20%3D%20%22x86%22%2C%20target_arch%20%3D%20%22x86_64%22))%5D%0A%23%5Btarget_feature(enable%20%3D%20%22avx2%22)%5D%0Aunsafe%20fn%20foo_avx2()%20%7B%0A%20%20%20%20%23%5Bcfg(target_arch%20%3D%20%22x86%22)%5D%0A%20%20%20%20use%20std%3A%3Aarch%3A%3Ax86%3A%3A_mm256_add_epi64%3B%0A%20%20%20%20%23%5Bcfg(target_arch%20%3D%20%22x86_64%22)%5D%0A%20%20%20%20use%20std%3A%3Aarch%3A%3Ax86_64%3A%3A_mm256_add_epi64%3B%0A%0A%20%20%20%20_mm256_add_epi64(...)%3B%0A%7D%0A%7D">Run</a></pre></div>
<p>There's a couple of components in play here, so let's go through them in
detail!</p>
<ul>
<li>
<p>First up we notice the <code>is_x86_feature_detected!</code> macro. Provided by
the standard library, this macro will perform necessary runtime detection
to determine whether the CPU the program is running on supports the
specified feature. In this case the macro will expand to a boolean
expression evaluating to whether the local CPU has the AVX2 feature or
not.</p>
<p>Note that this macro, like the <code>arch</code> module, is platform-specific. For
example calling <code>is_x86_feature_detected!("avx2")</code> on ARM will be a
compile time error. To ensure we don't hit this error a statement level
<code>#[cfg]</code> is used to only compile usage of the macro on <code>x86</code>/<code>x86_64</code>.</p>
</li>
<li>
<p>Next up we see our AVX2-enabled function, <code>foo_avx2</code>. This function is
decorated with the <code>#[target_feature]</code> attribute which enables a CPU
feature for just this one function. Using a compiler flag like <code>-C target-feature=+avx2</code> will enable AVX2 for the entire program, but using
an attribute will only enable it for the one function. Usage of the
<code>#[target_feature]</code> attribute currently requires the function to also be
<code>unsafe</code>, as we see here. This is because the function can only be
correctly called on systems which have the AVX2 (like the intrinsics
themselves).</p>
</li>
</ul>
<p>And with all that we should have a working program! This program will run
across all machines and it'll use the optimized AVX2 implementation on
machines where support is detected.</p>
<h1 id="ergonomics" class="section-header"><a href="#ergonomics">Ergonomics</a></h1>
<p>It's important to note that using the <code>arch</code> module is not the easiest
thing in the world, so if you're curious to try it out you may want to
brace yourself for some wordiness!</p>
<p>The primary purpose of this module is to enable stable crates on crates.io
to build up much more ergonomic abstractions which end up using SIMD under
the hood. Over time these abstractions may also move into the standard
library itself, but for now this module is tasked with providing the bare
minimum necessary to use vendor intrinsics on stable Rust.</p>
<h1 id="other-architectures" class="section-header"><a href="#other-architectures">Other architectures</a></h1>
<p>This documentation is only for one particular architecture, you can find
others at:</p>
<ul>
<li><a href="x86/index.html"><code>x86</code></a></li>
<li><a href="x86_64/index.html"><code>x86_64</code></a></li>
<li><a href="arm/index.html"><code>arm</code></a></li>
<li><a href="aarch64/index.html"><code>aarch64</code></a></li>
<li><a href="mips/index.html"><code>mips</code></a></li>
<li><a href="mips64/index.html"><code>mips64</code></a></li>
<li><a href="powerpc/index.html"><code>powerpc</code></a></li>
<li><a href="powerpc64/index.html"><code>powerpc64</code></a></li>
<li><a href="nvptx/index.html"><code>nvptx</code></a></li>
<li><a href="wasm32/index.html"><code>wasm32</code></a></li>
</ul>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<p>First let's take a look at not actually using any intrinsics but instead
using LLVM's auto-vectorization to produce optimized vectorized code for
AVX2 and also for the default platform.</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">fn</span> <span class="ident">main</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dst</span> <span class="op">=</span> [<span class="number">0</span>];
<span class="ident">add_quickly</span>(<span class="kw-2">&</span>[<span class="number">1</span>], <span class="kw-2">&</span>[<span class="number">2</span>], <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">dst</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">dst</span>[<span class="number">0</span>], <span class="number">3</span>);
}
<span class="kw">fn</span> <span class="ident">add_quickly</span>(<span class="ident">a</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">b</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">c</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">u8</span>]) {
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>, <span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>))]</span>
{
<span class="comment">// Note that this `unsafe` block is safe because we're testing</span>
<span class="comment">// that the `avx2` feature is indeed available on our CPU.</span>
<span class="kw">if</span> <span class="macro">is_x86_feature_detected</span><span class="macro">!</span>(<span class="string">"avx2"</span>) {
<span class="kw">return</span> <span class="kw">unsafe</span> { <span class="ident">add_quickly_avx2</span>(<span class="ident">a</span>, <span class="ident">b</span>, <span class="ident">c</span>) };
}
}
<span class="ident">add_quickly_fallback</span>(<span class="ident">a</span>, <span class="ident">b</span>, <span class="ident">c</span>)
}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>, <span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>))]</span>
<span class="attribute">#[<span class="ident">target_feature</span>(<span class="ident">enable</span> <span class="op">=</span> <span class="string">"avx2"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">add_quickly_avx2</span>(<span class="ident">a</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">b</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">c</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">u8</span>]) {
<span class="ident">add_quickly_fallback</span>(<span class="ident">a</span>, <span class="ident">b</span>, <span class="ident">c</span>) <span class="comment">// the function below is inlined here</span>
}
<span class="kw">fn</span> <span class="ident">add_quickly_fallback</span>(<span class="ident">a</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">b</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">c</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">u8</span>]) {
<span class="kw">for</span> ((<span class="ident">a</span>, <span class="ident">b</span>), <span class="ident">c</span>) <span class="kw">in</span> <span class="ident">a</span>.<span class="ident">iter</span>().<span class="ident">zip</span>(<span class="ident">b</span>).<span class="ident">zip</span>(<span class="ident">c</span>) {
<span class="kw-2">*</span><span class="ident">c</span> <span class="op">=</span> <span class="kw-2">*</span><span class="ident">a</span> <span class="op">+</span> <span class="kw-2">*</span><span class="ident">b</span>;
}
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0A%23!%5Bcfg_attr(not(dox)%2Cfeature(stdsimd))%5D%0A%23%5Bcfg(not(dox))%5D%0A%23%5Bmacro_use(is_x86_feature_detected)%5D%0Aextern%20crate%20std_detect%3B%0A%0Afn%20main()%20%7B%0A%20%20%20%20let%20mut%20dst%20%3D%20%5B0%5D%3B%0A%20%20%20%20add_quickly(%26%5B1%5D%2C%20%26%5B2%5D%2C%20%26mut%20dst)%3B%0A%20%20%20%20assert_eq!(dst%5B0%5D%2C%203)%3B%0A%7D%0A%0Afn%20add_quickly(a%3A%20%26%5Bu8%5D%2C%20b%3A%20%26%5Bu8%5D%2C%20c%3A%20%26mut%20%5Bu8%5D)%20%7B%0A%20%20%20%20%23%5Bcfg(any(target_arch%20%3D%20%22x86%22%2C%20target_arch%20%3D%20%22x86_64%22))%5D%0A%20%20%20%20%7B%0A%20%20%20%20%20%20%20%20%2F%2F%20Note%20that%20this%20%60unsafe%60%20block%20is%20safe%20because%20we're%20testing%0A%20%20%20%20%20%20%20%20%2F%2F%20that%20the%20%60avx2%60%20feature%20is%20indeed%20available%20on%20our%20CPU.%0A%20%20%20%20%20%20%20%20if%20is_x86_feature_detected!(%22avx2%22)%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20return%20unsafe%20%7B%20add_quickly_avx2(a%2C%20b%2C%20c)%20%7D%3B%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%7D%0A%0A%20%20%20%20add_quickly_fallback(a%2C%20b%2C%20c)%0A%7D%0A%0A%23%5Bcfg(any(target_arch%20%3D%20%22x86%22%2C%20target_arch%20%3D%20%22x86_64%22))%5D%0A%23%5Btarget_feature(enable%20%3D%20%22avx2%22)%5D%0Aunsafe%20fn%20add_quickly_avx2(a%3A%20%26%5Bu8%5D%2C%20b%3A%20%26%5Bu8%5D%2C%20c%3A%20%26mut%20%5Bu8%5D)%20%7B%0A%20%20%20%20add_quickly_fallback(a%2C%20b%2C%20c)%20%2F%2F%20the%20function%20below%20is%20inlined%20here%0A%7D%0A%0Afn%20add_quickly_fallback(a%3A%20%26%5Bu8%5D%2C%20b%3A%20%26%5Bu8%5D%2C%20c%3A%20%26mut%20%5Bu8%5D)%20%7B%0A%20%20%20%20for%20((a%2C%20b)%2C%20c)%20in%20a.iter().zip(b).zip(c)%20%7B%0A%20%20%20%20%20%20%20%20*c%20%3D%20*a%20%2B%20*b%3B%0A%20%20%20%20%7D%0A%7D">Run</a></pre></div>
<p>Next up let's take a look at an example of manually using intrinsics. Here
we'll be using SSE4.1 features to implement hex encoding.</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">fn</span> <span class="ident">main</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dst</span> <span class="op">=</span> [<span class="number">0</span>; <span class="number">32</span>];
<span class="ident">hex_encode</span>(<span class="string">b"\x01\x02\x03"</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">dst</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&</span><span class="ident">dst</span>[..<span class="number">6</span>], <span class="string">b"010203"</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">src</span> <span class="op">=</span> [<span class="number">0</span>; <span class="number">16</span>];
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="number">16</span> {
<span class="ident">src</span>[<span class="ident">i</span>] <span class="op">=</span> (<span class="ident">i</span> <span class="op">+</span> <span class="number">1</span>) <span class="kw">as</span> <span class="ident">u8</span>;
}
<span class="ident">hex_encode</span>(<span class="kw-2">&</span><span class="ident">src</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">dst</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&</span><span class="ident">dst</span>, <span class="string">b"0102030405060708090a0b0c0d0e0f10"</span>);
}
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">hex_encode</span>(<span class="ident">src</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">dst</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">u8</span>]) {
<span class="kw">let</span> <span class="ident">len</span> <span class="op">=</span> <span class="ident">src</span>.<span class="ident">len</span>().<span class="ident">checked_mul</span>(<span class="number">2</span>).<span class="ident">unwrap</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">dst</span>.<span class="ident">len</span>() <span class="op">>=</span> <span class="ident">len</span>);
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>, <span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>))]</span>
{
<span class="kw">if</span> <span class="macro">is_x86_feature_detected</span><span class="macro">!</span>(<span class="string">"sse4.1"</span>) {
<span class="kw">return</span> <span class="kw">unsafe</span> { <span class="ident">hex_encode_sse41</span>(<span class="ident">src</span>, <span class="ident">dst</span>) };
}
}
<span class="ident">hex_encode_fallback</span>(<span class="ident">src</span>, <span class="ident">dst</span>)
}
<span class="comment">// translated from</span>
<span class="comment">// https://github.com/Matherunner/bin2hex-sse/blob/master/base16_sse4.cpp</span>
<span class="attribute">#[<span class="ident">target_feature</span>(<span class="ident">enable</span> <span class="op">=</span> <span class="string">"sse4.1"</span>)]</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>, <span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>))]</span>
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">hex_encode_sse41</span>(<span class="kw-2">mut</span> <span class="ident">src</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">dst</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">u8</span>]) {
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>)]</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">arch</span>::<span class="ident">x86</span>::<span class="kw-2">*</span>;
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>)]</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">arch</span>::<span class="ident">x86_64</span>::<span class="kw-2">*</span>;
<span class="kw">let</span> <span class="ident">ascii_zero</span> <span class="op">=</span> <span class="ident">_mm_set1_epi8</span>(<span class="string">b'0'</span> <span class="kw">as</span> <span class="ident">i8</span>);
<span class="kw">let</span> <span class="ident">nines</span> <span class="op">=</span> <span class="ident">_mm_set1_epi8</span>(<span class="number">9</span>);
<span class="kw">let</span> <span class="ident">ascii_a</span> <span class="op">=</span> <span class="ident">_mm_set1_epi8</span>((<span class="string">b'a'</span> <span class="op">-</span> <span class="number">9</span> <span class="op">-</span> <span class="number">1</span>) <span class="kw">as</span> <span class="ident">i8</span>);
<span class="kw">let</span> <span class="ident">and4bits</span> <span class="op">=</span> <span class="ident">_mm_set1_epi8</span>(<span class="number">0xf</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">i</span> <span class="op">=</span> <span class="number">0_isize</span>;
<span class="kw">while</span> <span class="ident">src</span>.<span class="ident">len</span>() <span class="op">>=</span> <span class="number">16</span> {
<span class="kw">let</span> <span class="ident">invec</span> <span class="op">=</span> <span class="ident">_mm_loadu_si128</span>(<span class="ident">src</span>.<span class="ident">as_ptr</span>() <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="kw">_</span>);
<span class="kw">let</span> <span class="ident">masked1</span> <span class="op">=</span> <span class="ident">_mm_and_si128</span>(<span class="ident">invec</span>, <span class="ident">and4bits</span>);
<span class="kw">let</span> <span class="ident">masked2</span> <span class="op">=</span> <span class="ident">_mm_and_si128</span>(<span class="ident">_mm_srli_epi64</span>(<span class="ident">invec</span>, <span class="number">4</span>), <span class="ident">and4bits</span>);
<span class="comment">// return 0xff corresponding to the elements > 9, or 0x00 otherwise</span>
<span class="kw">let</span> <span class="ident">cmpmask1</span> <span class="op">=</span> <span class="ident">_mm_cmpgt_epi8</span>(<span class="ident">masked1</span>, <span class="ident">nines</span>);
<span class="kw">let</span> <span class="ident">cmpmask2</span> <span class="op">=</span> <span class="ident">_mm_cmpgt_epi8</span>(<span class="ident">masked2</span>, <span class="ident">nines</span>);
<span class="comment">// add '0' or the offset depending on the masks</span>
<span class="kw">let</span> <span class="ident">masked1</span> <span class="op">=</span> <span class="ident">_mm_add_epi8</span>(
<span class="ident">masked1</span>,
<span class="ident">_mm_blendv_epi8</span>(<span class="ident">ascii_zero</span>, <span class="ident">ascii_a</span>, <span class="ident">cmpmask1</span>),
);
<span class="kw">let</span> <span class="ident">masked2</span> <span class="op">=</span> <span class="ident">_mm_add_epi8</span>(
<span class="ident">masked2</span>,
<span class="ident">_mm_blendv_epi8</span>(<span class="ident">ascii_zero</span>, <span class="ident">ascii_a</span>, <span class="ident">cmpmask2</span>),
);
<span class="comment">// interleave masked1 and masked2 bytes</span>
<span class="kw">let</span> <span class="ident">res1</span> <span class="op">=</span> <span class="ident">_mm_unpacklo_epi8</span>(<span class="ident">masked2</span>, <span class="ident">masked1</span>);
<span class="kw">let</span> <span class="ident">res2</span> <span class="op">=</span> <span class="ident">_mm_unpackhi_epi8</span>(<span class="ident">masked2</span>, <span class="ident">masked1</span>);
<span class="ident">_mm_storeu_si128</span>(<span class="ident">dst</span>.<span class="ident">as_mut_ptr</span>().<span class="ident">offset</span>(<span class="ident">i</span> <span class="op">*</span> <span class="number">2</span>) <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="kw">_</span>, <span class="ident">res1</span>);
<span class="ident">_mm_storeu_si128</span>(
<span class="ident">dst</span>.<span class="ident">as_mut_ptr</span>().<span class="ident">offset</span>(<span class="ident">i</span> <span class="op">*</span> <span class="number">2</span> <span class="op">+</span> <span class="number">16</span>) <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="kw">_</span>,
<span class="ident">res2</span>,
);
<span class="ident">src</span> <span class="op">=</span> <span class="kw-2">&</span><span class="ident">src</span>[<span class="number">16</span>..];
<span class="ident">i</span> <span class="op">+=</span> <span class="number">16</span>;
}
<span class="kw">let</span> <span class="ident">i</span> <span class="op">=</span> <span class="ident">i</span> <span class="kw">as</span> <span class="ident">usize</span>;
<span class="ident">hex_encode_fallback</span>(<span class="ident">src</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">dst</span>[<span class="ident">i</span> <span class="op">*</span> <span class="number">2</span>..]);
}
<span class="kw">fn</span> <span class="ident">hex_encode_fallback</span>(<span class="ident">src</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">dst</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">u8</span>]) {
<span class="kw">fn</span> <span class="ident">hex</span>(<span class="ident">byte</span>: <span class="ident">u8</span>) <span class="op">-></span> <span class="ident">u8</span> {
<span class="kw">static</span> <span class="ident">TABLE</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>] <span class="op">=</span> <span class="string">b"0123456789abcdef"</span>;
<span class="ident">TABLE</span>[<span class="ident">byte</span> <span class="kw">as</span> <span class="ident">usize</span>]
}
<span class="kw">for</span> (<span class="ident">byte</span>, <span class="ident">slots</span>) <span class="kw">in</span> <span class="ident">src</span>.<span class="ident">iter</span>().<span class="ident">zip</span>(<span class="ident">dst</span>.<span class="ident">chunks_mut</span>(<span class="number">2</span>)) {
<span class="ident">slots</span>[<span class="number">0</span>] <span class="op">=</span> <span class="ident">hex</span>((<span class="kw-2">*</span><span class="ident">byte</span> <span class="op">>></span> <span class="number">4</span>) <span class="op">&</span> <span class="number">0xf</span>);
<span class="ident">slots</span>[<span class="number">1</span>] <span class="op">=</span> <span class="ident">hex</span>(<span class="kw-2">*</span><span class="ident">byte</span> <span class="op">&</span> <span class="number">0xf</span>);
}
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0A%20%20%20%20let%20mut%20dst%20%3D%20%5B0%3B%2032%5D%3B%0A%20%20%20%20hex_encode(b%22%5Cx01%5Cx02%5Cx03%22%2C%20%26mut%20dst)%3B%0A%20%20%20%20assert_eq!(%26dst%5B..6%5D%2C%20b%22010203%22)%3B%0A%0A%20%20%20%20let%20mut%20src%20%3D%20%5B0%3B%2016%5D%3B%0A%20%20%20%20for%20i%20in%200..16%20%7B%0A%20%20%20%20%20%20%20%20src%5Bi%5D%20%3D%20(i%20%2B%201)%20as%20u8%3B%0A%20%20%20%20%7D%0A%20%20%20%20hex_encode(%26src%2C%20%26mut%20dst)%3B%0A%20%20%20%20assert_eq!(%26dst%2C%20b%220102030405060708090a0b0c0d0e0f10%22)%3B%0A%7D%0A%0Apub%20fn%20hex_encode(src%3A%20%26%5Bu8%5D%2C%20dst%3A%20%26mut%20%5Bu8%5D)%20%7B%0A%20%20%20%20let%20len%20%3D%20src.len().checked_mul(2).unwrap()%3B%0A%20%20%20%20assert!(dst.len()%20%3E%3D%20len)%3B%0A%0A%20%20%20%20%23%5Bcfg(any(target_arch%20%3D%20%22x86%22%2C%20target_arch%20%3D%20%22x86_64%22))%5D%0A%20%20%20%20%7B%0A%20%20%20%20%20%20%20%20if%20is_x86_feature_detected!(%22sse4.1%22)%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20return%20unsafe%20%7B%20hex_encode_sse41(src%2C%20dst)%20%7D%3B%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%7D%0A%0A%20%20%20%20hex_encode_fallback(src%2C%20dst)%0A%7D%0A%0A%2F%2F%20translated%20from%0A%2F%2F%20https%3A%2F%2Fgithub.com%2FMatherunner%2Fbin2hex-sse%2Fblob%2Fmaster%2Fbase16_sse4.cpp%0A%23%5Btarget_feature(enable%20%3D%20%22sse4.1%22)%5D%0A%23%5Bcfg(any(target_arch%20%3D%20%22x86%22%2C%20target_arch%20%3D%20%22x86_64%22))%5D%0Aunsafe%20fn%20hex_encode_sse41(mut%20src%3A%20%26%5Bu8%5D%2C%20dst%3A%20%26mut%20%5Bu8%5D)%20%7B%0A%20%20%20%20%23%5Bcfg(target_arch%20%3D%20%22x86%22)%5D%0A%20%20%20%20use%20std%3A%3Aarch%3A%3Ax86%3A%3A*%3B%0A%20%20%20%20%23%5Bcfg(target_arch%20%3D%20%22x86_64%22)%5D%0A%20%20%20%20use%20std%3A%3Aarch%3A%3Ax86_64%3A%3A*%3B%0A%0A%20%20%20%20let%20ascii_zero%20%3D%20_mm_set1_epi8(b'0'%20as%20i8)%3B%0A%20%20%20%20let%20nines%20%3D%20_mm_set1_epi8(9)%3B%0A%20%20%20%20let%20ascii_a%20%3D%20_mm_set1_epi8((b'a'%20-%209%20-%201)%20as%20i8)%3B%0A%20%20%20%20let%20and4bits%20%3D%20_mm_set1_epi8(0xf)%3B%0A%0A%20%20%20%20let%20mut%20i%20%3D%200_isize%3B%0A%20%20%20%20while%20src.len()%20%3E%3D%2016%20%7B%0A%20%20%20%20%20%20%20%20let%20invec%20%3D%20_mm_loadu_si128(src.as_ptr()%20as%20*const%20_)%3B%0A%0A%20%20%20%20%20%20%20%20let%20masked1%20%3D%20_mm_and_si128(invec%2C%20and4bits)%3B%0A%20%20%20%20%20%20%20%20let%20masked2%20%3D%20_mm_and_si128(_mm_srli_epi64(invec%2C%204)%2C%20and4bits)%3B%0A%0A%20%20%20%20%20%20%20%20%2F%2F%20return%200xff%20corresponding%20to%20the%20elements%20%3E%209%2C%20or%200x00%20otherwise%0A%20%20%20%20%20%20%20%20let%20cmpmask1%20%3D%20_mm_cmpgt_epi8(masked1%2C%20nines)%3B%0A%20%20%20%20%20%20%20%20let%20cmpmask2%20%3D%20_mm_cmpgt_epi8(masked2%2C%20nines)%3B%0A%0A%20%20%20%20%20%20%20%20%2F%2F%20add%20'0'%20or%20the%20offset%20depending%20on%20the%20masks%0A%20%20%20%20%20%20%20%20let%20masked1%20%3D%20_mm_add_epi8(%0A%20%20%20%20%20%20%20%20%20%20%20%20masked1%2C%0A%20%20%20%20%20%20%20%20%20%20%20%20_mm_blendv_epi8(ascii_zero%2C%20ascii_a%2C%20cmpmask1)%2C%0A%20%20%20%20%20%20%20%20)%3B%0A%20%20%20%20%20%20%20%20let%20masked2%20%3D%20_mm_add_epi8(%0A%20%20%20%20%20%20%20%20%20%20%20%20masked2%2C%0A%20%20%20%20%20%20%20%20%20%20%20%20_mm_blendv_epi8(ascii_zero%2C%20ascii_a%2C%20cmpmask2)%2C%0A%20%20%20%20%20%20%20%20)%3B%0A%0A%20%20%20%20%20%20%20%20%2F%2F%20interleave%20masked1%20and%20masked2%20bytes%0A%20%20%20%20%20%20%20%20let%20res1%20%3D%20_mm_unpacklo_epi8(masked2%2C%20masked1)%3B%0A%20%20%20%20%20%20%20%20let%20res2%20%3D%20_mm_unpackhi_epi8(masked2%2C%20masked1)%3B%0A%0A%20%20%20%20%20%20%20%20_mm_storeu_si128(dst.as_mut_ptr().offset(i%20*%202)%20as%20*mut%20_%2C%20res1)%3B%0A%20%20%20%20%20%20%20%20_mm_storeu_si128(%0A%20%20%20%20%20%20%20%20%20%20%20%20dst.as_mut_ptr().offset(i%20*%202%20%2B%2016)%20as%20*mut%20_%2C%0A%20%20%20%20%20%20%20%20%20%20%20%20res2%2C%0A%20%20%20%20%20%20%20%20)%3B%0A%20%20%20%20%20%20%20%20src%20%3D%20%26src%5B16..%5D%3B%0A%20%20%20%20%20%20%20%20i%20%2B%3D%2016%3B%0A%20%20%20%20%7D%0A%0A%20%20%20%20let%20i%20%3D%20i%20as%20usize%3B%0A%20%20%20%20hex_encode_fallback(src%2C%20%26mut%20dst%5Bi%20*%202..%5D)%3B%0A%7D%0A%0Afn%20hex_encode_fallback(src%3A%20%26%5Bu8%5D%2C%20dst%3A%20%26mut%20%5Bu8%5D)%20%7B%0A%20%20%20%20fn%20hex(byte%3A%20u8)%20-%3E%20u8%20%7B%0A%20%20%20%20%20%20%20%20static%20TABLE%3A%20%26%5Bu8%5D%20%3D%20b%220123456789abcdef%22%3B%0A%20%20%20%20%20%20%20%20TABLE%5Bbyte%20as%20usize%5D%0A%20%20%20%20%7D%0A%0A%20%20%20%20for%20(byte%2C%20slots)%20in%20src.iter().zip(dst.chunks_mut(2))%20%7B%0A%20%20%20%20%20%20%20%20slots%5B0%5D%20%3D%20hex((*byte%20%3E%3E%204)%20%26%200xf)%3B%0A%20%20%20%20%20%20%20%20slots%5B1%5D%20%3D%20hex(*byte%20%26%200xf)%3B%0A%20%20%20%20%7D%0A%7D">Run</a></pre></div>
</div><h2 id='modules' class='section-header'><a href="#modules">Modules</a></h2>
<table><tr class='module-item'><td><a class="mod" href="wasm32/index.html" title='core::arch::wasm32 mod'>wasm32</a></td><td class='docblock-short'><span class="stab portability">WebAssembly</span><p>Platform-specific intrinsics for the <code>wasm32</code> platform.</p>
</td></tr><tr class='module-item'><td><a class="mod" href="x86/index.html" title='core::arch::x86 mod'>x86</a></td><td class='docblock-short'><span class="stab portability">x86</span><p>Platform-specific intrinsics for the <code>x86</code> platform.</p>
</td></tr><tr class='module-item'><td><a class="mod" href="x86_64/index.html" title='core::arch::x86_64 mod'>x86_64</a></td><td class='docblock-short'><span class="stab portability">x86-64</span><p>Platform-specific intrinsics for the <code>x86_64</code> platform.</p>
</td></tr><tr class='unstable module-item'><td><a class="mod" href="aarch64/index.html" title='core::arch::aarch64 mod'>aarch64</a></td><td class='docblock-short'><span class="stab unstable">Experimental</span><span class="stab portability">AArch64</span><p>Platform-specific intrinsics for the <code>aarch64</code> platform.</p>
</td></tr><tr class='unstable module-item'><td><a class="mod" href="arm/index.html" title='core::arch::arm mod'>arm</a></td><td class='docblock-short'><span class="stab unstable">Experimental</span><span class="stab portability">ARM</span><p>Platform-specific intrinsics for the <code>arm</code> platform.</p>
</td></tr><tr class='unstable module-item'><td><a class="mod" href="mips/index.html" title='core::arch::mips mod'>mips</a></td><td class='docblock-short'><span class="stab unstable">Experimental</span><span class="stab portability">MIPS</span><p>Platform-specific intrinsics for the <code>mips</code> platform.</p>
</td></tr><tr class='unstable module-item'><td><a class="mod" href="mips64/index.html" title='core::arch::mips64 mod'>mips64</a></td><td class='docblock-short'><span class="stab unstable">Experimental</span><span class="stab portability">MIPS-64</span><p>Platform-specific intrinsics for the <code>mips64</code> platform.</p>
</td></tr><tr class='unstable module-item'><td><a class="mod" href="nvptx/index.html" title='core::arch::nvptx mod'>nvptx</a></td><td class='docblock-short'><span class="stab unstable">Experimental</span><span class="stab portability"><code>target_arch="nvptx"</code> or <code>target_arch="nvptx64"</code></span><p>Platform-specific intrinsics for the <code>NVPTX</code> platform.</p>
</td></tr><tr class='unstable module-item'><td><a class="mod" href="powerpc/index.html" title='core::arch::powerpc mod'>powerpc</a></td><td class='docblock-short'><span class="stab unstable">Experimental</span><span class="stab portability">PowerPC</span><p>Platform-specific intrinsics for the <code>PowerPC</code> platform.</p>
</td></tr><tr class='unstable module-item'><td><a class="mod" href="powerpc64/index.html" title='core::arch::powerpc64 mod'>powerpc64</a></td><td class='docblock-short'><span class="stab unstable">Experimental</span><span class="stab portability">PowerPC-64</span><p>Platform-specific intrinsics for the <code>PowerPC64</code> platform.</p>
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