| <!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="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/memchr-2.5.0/src/memchr/x86/mod.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>mod.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../../normalize.css"><link rel="stylesheet" href="../../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../../ayu.css" disabled><link rel="stylesheet" href="../../../../dark.css" disabled><link rel="stylesheet" href="../../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../../storage.js"></script><script defer src="../../../../source-script.js"></script><script defer src="../../../../source-files.js"></script><script defer src="../../../../main.js"></script><noscript><link rel="stylesheet" href="../../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../../memchr/index.html"><div class="logo-container"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../../memchr/index.html"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="kw">use </span><span class="kw">super</span>::fallback; |
| |
| <span class="comment">// We only use AVX when we can detect at runtime whether it's available, which |
| // requires std. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">mod </span>avx; |
| <span class="kw">mod </span>sse2; |
| |
| <span class="doccomment">/// This macro employs a gcc-like "ifunc" trick where by upon first calling |
| /// `memchr` (for example), CPU feature detection will be performed at runtime |
| /// to determine the best implementation to use. After CPU feature detection |
| /// is done, we replace `memchr`'s function pointer with the selection. Upon |
| /// subsequent invocations, the CPU-specific routine is invoked directly, which |
| /// skips the CPU feature detection and subsequent branch that's required. |
| /// |
| /// While this typically doesn't matter for rare occurrences or when used on |
| /// larger haystacks, `memchr` can be called in tight loops where the overhead |
| /// of this branch can actually add up *and is measurable*. This trick was |
| /// necessary to bring this implementation up to glibc's speeds for the 'tiny' |
| /// benchmarks, for example. |
| /// |
| /// At some point, I expect the Rust ecosystem will get a nice macro for doing |
| /// exactly this, at which point, we can replace our hand-jammed version of it. |
| /// |
| /// N.B. The ifunc strategy does prevent function inlining of course, but |
| /// on modern CPUs, you'll probably end up with the AVX2 implementation, |
| /// which probably can't be inlined anyway---unless you've compiled your |
| /// entire program with AVX2 enabled. However, even then, the various memchr |
| /// implementations aren't exactly small, so inlining might not help anyway! |
| /// |
| /// # Safety |
| /// |
| /// Callers must ensure that fnty is function pointer type. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="macro">macro_rules! </span>unsafe_ifunc { |
| (<span class="macro-nonterminal">$fnty</span>:ty, <span class="macro-nonterminal">$name</span>:ident, <span class="macro-nonterminal">$haystack</span>:ident, $(<span class="macro-nonterminal">$needle</span>:ident),+) => {{ |
| <span class="kw">use </span>std::{mem, sync::atomic::{AtomicPtr, Ordering}}; |
| |
| <span class="kw">type </span>FnRaw = <span class="kw-2">*mut </span>(); |
| |
| <span class="kw">static </span>FN: AtomicPtr<()> = AtomicPtr::new(detect <span class="kw">as </span>FnRaw); |
| |
| <span class="kw">fn </span>detect($(<span class="macro-nonterminal">$needle</span>: u8),+, haystack: <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize> { |
| <span class="kw">let </span>fun = |
| <span class="kw">if </span><span class="macro">cfg!</span>(memchr_runtime_avx) && <span class="macro">is_x86_feature_detected!</span>(<span class="string">"avx2"</span>) { |
| avx::<span class="macro-nonterminal">$name </span><span class="kw">as </span>FnRaw |
| } <span class="kw">else if </span><span class="macro">cfg!</span>(memchr_runtime_sse2) { |
| sse2::<span class="macro-nonterminal">$name </span><span class="kw">as </span>FnRaw |
| } <span class="kw">else </span>{ |
| fallback::<span class="macro-nonterminal">$name </span><span class="kw">as </span>FnRaw |
| }; |
| FN.store(fun <span class="kw">as </span>FnRaw, Ordering::Relaxed); |
| <span class="comment">// SAFETY: By virtue of the caller contract, $fnty is a function |
| // pointer, which is always safe to transmute with a *mut (). |
| // Also, if 'fun is the AVX routine, then it is guaranteed to be |
| // supported since we checked the avx2 feature. |
| </span><span class="kw">unsafe </span>{ |
| mem::transmute::<FnRaw, <span class="macro-nonterminal">$fnty</span>>(fun)($(<span class="macro-nonterminal">$needle</span>),+, haystack) |
| } |
| } |
| |
| <span class="comment">// SAFETY: By virtue of the caller contract, $fnty is a function |
| // pointer, which is always safe to transmute with a *mut (). Also, if |
| // 'fun is the AVX routine, then it is guaranteed to be supported since |
| // we checked the avx2 feature. |
| </span><span class="kw">unsafe </span>{ |
| <span class="kw">let </span>fun = FN.load(Ordering::Relaxed); |
| mem::transmute::<FnRaw, <span class="macro-nonterminal">$fnty</span>>(fun)($(<span class="macro-nonterminal">$needle</span>),+, <span class="macro-nonterminal">$haystack</span>) |
| } |
| }} |
| } |
| |
| <span class="doccomment">/// When std isn't available to provide runtime CPU feature detection, or if |
| /// runtime CPU feature detection has been explicitly disabled, then just |
| /// call our optimized SSE2 routine directly. SSE2 is avalbale on all x86_64 |
| /// targets, so no CPU feature detection is necessary. |
| /// |
| /// # Safety |
| /// |
| /// There are no safety requirements for this definition of the macro. It is |
| /// safe for all inputs since it is restricted to either the fallback routine |
| /// or the SSE routine, which is always safe to call on x86_64. |
| </span><span class="attribute">#[cfg(not(feature = <span class="string">"std"</span>))] |
| </span><span class="macro">macro_rules! </span>unsafe_ifunc { |
| (<span class="macro-nonterminal">$fnty</span>:ty, <span class="macro-nonterminal">$name</span>:ident, <span class="macro-nonterminal">$haystack</span>:ident, $(<span class="macro-nonterminal">$needle</span>:ident),+) => {{ |
| <span class="kw">if </span><span class="macro">cfg!</span>(memchr_runtime_sse2) { |
| <span class="kw">unsafe </span>{ sse2::<span class="macro-nonterminal">$name</span>($(<span class="macro-nonterminal">$needle</span>),+, <span class="macro-nonterminal">$haystack</span>) } |
| } <span class="kw">else </span>{ |
| fallback::<span class="macro-nonterminal">$name</span>($(<span class="macro-nonterminal">$needle</span>),+, <span class="macro-nonterminal">$haystack</span>) |
| } |
| }} |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">pub fn </span>memchr(n1: u8, haystack: <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize> { |
| <span class="macro">unsafe_ifunc!</span>(<span class="kw">fn</span>(u8, <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize>, memchr, haystack, n1) |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">pub fn </span>memchr2(n1: u8, n2: u8, haystack: <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize> { |
| <span class="macro">unsafe_ifunc!</span>( |
| <span class="kw">fn</span>(u8, u8, <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize>, |
| memchr2, |
| haystack, |
| n1, |
| n2 |
| ) |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">pub fn </span>memchr3(n1: u8, n2: u8, n3: u8, haystack: <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize> { |
| <span class="macro">unsafe_ifunc!</span>( |
| <span class="kw">fn</span>(u8, u8, u8, <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize>, |
| memchr3, |
| haystack, |
| n1, |
| n2, |
| n3 |
| ) |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">pub fn </span>memrchr(n1: u8, haystack: <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize> { |
| <span class="macro">unsafe_ifunc!</span>(<span class="kw">fn</span>(u8, <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize>, memrchr, haystack, n1) |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">pub fn </span>memrchr2(n1: u8, n2: u8, haystack: <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize> { |
| <span class="macro">unsafe_ifunc!</span>( |
| <span class="kw">fn</span>(u8, u8, <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize>, |
| memrchr2, |
| haystack, |
| n1, |
| n2 |
| ) |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">pub fn </span>memrchr3(n1: u8, n2: u8, n3: u8, haystack: <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize> { |
| <span class="macro">unsafe_ifunc!</span>( |
| <span class="kw">fn</span>(u8, u8, u8, <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><usize>, |
| memrchr3, |
| haystack, |
| n1, |
| n2, |
| n3 |
| ) |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../../" data-current-crate="memchr" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
