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diff --git a/development/gcc.html b/development/gcc.html new file mode 100644 index 0000000..bf457aa --- /dev/null +++ b/development/gcc.html @@ -0,0 +1,269 @@ +<!DOCTYPE HTML> +<html lang="en" class="sidebar-visible no-js light"> + <head> + <!-- Book generated using mdBook --> + <meta charset="UTF-8"> + <title>gcc - Notes</title> + + + <meta content="text/html; charset=utf-8" http-equiv="Content-Type"> + <meta name="description" content=""> + <meta name="viewport" content="width=device-width, initial-scale=1"> + <meta name="theme-color" content="#ffffff" /> + + <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 href="https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,800italic,400,300,600,700,800" rel="stylesheet" type="text/css"> + <link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:500" rel="stylesheet" type="text/css"> + + <!-- Highlight.js Stylesheets --> + <link rel="stylesheet" href="../highlight.css"> + <link rel="stylesheet" href="../tomorrow-night.css"> + <link rel="stylesheet" href="../ayu-highlight.css"> + + <!-- Custom theme stylesheets --> + + + + </head> + <body> + <!-- Provide site root to javascript --> + <script type="text/javascript"> + var path_to_root = "../"; + var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? 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+ </script> + + <!-- Hide / unhide sidebar before it is displayed --> + <script type="text/javascript"> + var html = document.querySelector('html'); + var sidebar = 'hidden'; + if (document.body.clientWidth >= 1080) { + try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { } + sidebar = sidebar || 'visible'; + } + html.classList.remove('sidebar-visible'); + html.classList.add("sidebar-" + sidebar); + </script> + + <nav id="sidebar" class="sidebar" aria-label="Table of contents"> + <div id="sidebar-scrollbox" class="sidebar-scrollbox"> + <ol class="chapter"><li class="expanded "><a href="../misc/index.html"><strong aria-hidden="true">1.</strong> Misc</a></li><li><ol class="section"><li class="expanded "><a href="../misc/zsh.html"><strong aria-hidden="true">1.1.</strong> zsh</a></li><li class="expanded "><a href="../misc/bash.html"><strong aria-hidden="true">1.2.</strong> bash</a></li><li class="expanded "><a href="../misc/fish.html"><strong aria-hidden="true">1.3.</strong> fish</a></li><li class="expanded "><a href="../misc/tmux.html"><strong aria-hidden="true">1.4.</strong> tmux</a></li><li class="expanded "><a href="../misc/git.html"><strong aria-hidden="true">1.5.</strong> git</a></li><li class="expanded "><a href="../misc/awk.html"><strong aria-hidden="true">1.6.</strong> awk</a></li><li class="expanded "><a href="../misc/emacs.html"><strong aria-hidden="true">1.7.</strong> emacs</a></li><li class="expanded "><a href="../misc/gdb.html"><strong aria-hidden="true">1.8.</strong> gdb</a></li><li class="expanded "><a href="../misc/radare2.html"><strong aria-hidden="true">1.9.</strong> radare2</a></li></ol></li><li class="expanded "><a href="../monitor/index.html"><strong aria-hidden="true">2.</strong> Resource analysis & monitor</a></li><li><ol class="section"><li class="expanded "><a href="../monitor/lsof.html"><strong aria-hidden="true">2.1.</strong> lsof</a></li><li class="expanded "><a href="../monitor/pidstat.html"><strong aria-hidden="true">2.2.</strong> pidstat</a></li><li class="expanded "><a href="../monitor/pgrep.html"><strong aria-hidden="true">2.3.</strong> pgrep</a></li><li class="expanded "><a href="../monitor/pmap.html"><strong aria-hidden="true">2.4.</strong> pmap</a></li><li class="expanded "><a href="../monitor/pstack.html"><strong aria-hidden="true">2.5.</strong> pstack</a></li></ol></li><li class="expanded "><a href="../trace_profile/index.html"><strong aria-hidden="true">3.</strong> Trace and Profile</a></li><li><ol class="section"><li class="expanded "><a href="../trace_profile/strace.html"><strong aria-hidden="true">3.1.</strong> strace</a></li><li class="expanded "><a href="../trace_profile/ltrace.html"><strong aria-hidden="true">3.2.</strong> ltrace</a></li><li class="expanded "><a href="../trace_profile/perf.html"><strong aria-hidden="true">3.3.</strong> perf</a></li><li class="expanded "><a href="../trace_profile/oprofile.html"><strong aria-hidden="true">3.4.</strong> OProfile</a></li><li class="expanded "><a href="../trace_profile/time.html"><strong aria-hidden="true">3.5.</strong> time</a></li></ol></li><li class="expanded "><a href="../binary/index.html"><strong aria-hidden="true">4.</strong> Binary</a></li><li><ol class="section"><li class="expanded "><a href="../binary/od.html"><strong aria-hidden="true">4.1.</strong> od</a></li><li class="expanded "><a href="../binary/xxd.html"><strong aria-hidden="true">4.2.</strong> xxd</a></li><li class="expanded "><a href="../binary/readelf.html"><strong aria-hidden="true">4.3.</strong> readelf</a></li><li class="expanded "><a href="../binary/objdump.html"><strong aria-hidden="true">4.4.</strong> objdump</a></li><li class="expanded "><a href="../binary/nm.html"><strong aria-hidden="true">4.5.</strong> nm</a></li></ol></li><li class="expanded "><a href="../development/index.html"><strong aria-hidden="true">5.</strong> Development</a></li><li><ol class="section"><li class="expanded "><a href="../development/c++filt.html"><strong aria-hidden="true">5.1.</strong> c++filt</a></li><li class="expanded "><a href="../development/c++.html"><strong aria-hidden="true">5.2.</strong> c++</a></li><li class="expanded "><a href="../development/glibc.html"><strong aria-hidden="true">5.3.</strong> glibc</a></li><li class="expanded "><a href="../development/gcc.html" class="active"><strong aria-hidden="true">5.4.</strong> gcc</a></li><li class="expanded "><a href="../development/ld.so.html"><strong aria-hidden="true">5.5.</strong> ld.so</a></li></ol></li></ol> + </div> + <div id="sidebar-resize-handle" class="sidebar-resize-handle"></div> + </nav> + + <div id="page-wrapper" class="page-wrapper"> + + <div class="page"> + + <div id="menu-bar" class="menu-bar"> + <div id="menu-bar-sticky-container"> + <div class="left-buttons"> + <button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" 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(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">Notes</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> + + </div> + </div> + </div> + + + <div id="search-wrapper" class="hidden"> + <form id="searchbar-outer" class="searchbar-outer"> + <input type="search" name="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 type="text/javascript"> + 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><a class="header" href="#gcc1" id="gcc1">gcc(1)</a></h1> +<h2><a class="header" href="#cli" id="cli">CLI</a></h2> +<h3><a class="header" href="#preprocessing" id="preprocessing">Preprocessing</a></h3> +<p>While debugging can be helpful to just pre-process files.</p> +<pre><code class="language-bash">gcc -E [-dM] ... +</code></pre> +<ul> +<li><code>-E</code> run only preprocessor</li> +<li><code>-dM</code> list only <code>#define</code> statements</li> +</ul> +<h2><a class="header" href="#a-hrefhttpsgccgnuorgonlinedocsgccother-builtinshtmlbuiltinsa" id="a-hrefhttpsgccgnuorgonlinedocsgccother-builtinshtmlbuiltinsa"><a href="https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html">Builtins</a></a></h2> +<h3><a class="header" href="#__builtin_expectexpr-cond" id="__builtin_expectexpr-cond"><code>__builtin_expect(expr, cond)</code></a></h3> +<p>Give the compiler a hint which branch is hot, so it can lay out the code +accordingly to reduce number of jump instructions. +See on <a href="https://godbolt.org/z/MbTHAP">compiler explorer</a>.</p> +<pre><code class="language-bash">echo " +extern void foo(); +extern void bar(); +void run0(int x) { + if (__builtin_expect(x,0)) { foo(); } + else { bar(); } +} +void run1(int x) { + if (__builtin_expect(x,1)) { foo(); } + else { bar(); } +} +" | gcc -O2 -S -masm=intel -o /dev/stdout -xc - +</code></pre> +<p>Will generate something similar to the following.</p> +<ul> +<li><code>run0</code>: <code>bar</code> is on the path without branch</li> +<li><code>run1</code>: <code>foo</code> is on the path without branch</li> +</ul> +<pre><code class="language-c">run0: + test edi, edi + jne .L4 + xor eax, eax + jmp bar +.L4: + xor eax, eax + jmp foo +run1: + test edi, edi + je .L6 + xor eax, eax + jmp foo +.L6: + xor eax, eax + jmp bar +</code></pre> + + </main> + + <nav class="nav-wrapper" aria-label="Page navigation"> + <!-- Mobile navigation buttons --> + + <a rel="prev" href="../development/glibc.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" href="../development/ld.so.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 href="../development/glibc.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> + <i class="fa fa-angle-left"></i> + </a> + + + + <a href="../development/ld.so.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 type="text/javascript"> + window.playpen_copyable = true; + </script> + + + + + + <script src="../elasticlunr.min.js" type="text/javascript" charset="utf-8"></script> + <script src="../mark.min.js" type="text/javascript" charset="utf-8"></script> + <script src="../searcher.js" type="text/javascript" charset="utf-8"></script> + + + <script src="../clipboard.min.js" type="text/javascript" charset="utf-8"></script> + <script src="../highlight.js" type="text/javascript" charset="utf-8"></script> + <script src="../book.js" type="text/javascript" charset="utf-8"></script> + + <!-- Custom JS scripts --> + + + + + </body> +</html> |