| <!DOCTYPE html> |
| <html lang="en"> |
| <head> |
| <meta charset="UTF-8"> |
| <!--[if IE]><meta http-equiv="X-UA-Compatible" content="IE=edge"><![endif]--> |
| <meta name="viewport" content="width=device-width, initial-scale=1.0"> |
| <meta name="generator" content="Asciidoctor 1.5.8"> |
| <title>optionalAttributeQualifiers(3)</title> |
| <style> |
| /*! normalize.css v2.1.2 | MIT License | git.io/normalize */ |
| /* ========================================================================== HTML5 display definitions ========================================================================== */ |
| /** Correct `block` display not defined in IE 8/9. */ |
| article, aside, details, figcaption, figure, footer, header, hgroup, main, nav, section, summary { display: block; } |
| |
| /** Correct `inline-block` display not defined in IE 8/9. */ |
| audio, canvas, video { display: inline-block; } |
| |
| /** Prevent modern browsers from displaying `audio` without controls. Remove excess height in iOS 5 devices. */ |
| audio:not([controls]) { display: none; height: 0; } |
| |
| /** Address `[hidden]` styling not present in IE 8/9. Hide the `template` element in IE, Safari, and Firefox < 22. */ |
| [hidden], template { display: none; } |
| |
| script { display: none !important; } |
| |
| /* ========================================================================== Base ========================================================================== */ |
| /** 1. Set default font family to sans-serif. 2. Prevent iOS text size adjust after orientation change, without disabling user zoom. */ |
| html { font-family: sans-serif; /* 1 */ -ms-text-size-adjust: 100%; /* 2 */ -webkit-text-size-adjust: 100%; /* 2 */ } |
| |
| /** Remove default margin. */ |
| body { margin: 0; } |
| |
| /* ========================================================================== Links ========================================================================== */ |
| /** Remove the gray background color from active links in IE 10. */ |
| a { background: transparent; } |
| |
| /** Address `outline` inconsistency between Chrome and other browsers. */ |
| a:focus { outline: thin dotted; } |
| |
| /** Improve readability when focused and also mouse hovered in all browsers. */ |
| a:active, a:hover { outline: 0; } |
| |
| /* ========================================================================== Typography ========================================================================== */ |
| /** Address variable `h1` font-size and margin within `section` and `article` contexts in Firefox 4+, Safari 5, and Chrome. */ |
| h1 { font-size: 2em; margin: 0.67em 0; } |
| |
| /** Address styling not present in IE 8/9, Safari 5, and Chrome. */ |
| abbr[title] { border-bottom: 1px dotted; } |
| |
| /** Address style set to `bolder` in Firefox 4+, Safari 5, and Chrome. */ |
| b, strong { font-weight: bold; } |
| |
| /** Address styling not present in Safari 5 and Chrome. */ |
| dfn { font-style: italic; } |
| |
| /** Address differences between Firefox and other browsers. */ |
| hr { -moz-box-sizing: content-box; box-sizing: content-box; height: 0; } |
| |
| /** Address styling not present in IE 8/9. */ |
| mark { background: #ff0; color: #000; } |
| |
| /** Correct font family set oddly in Safari 5 and Chrome. */ |
| code, kbd, pre, samp { font-family: monospace, serif; font-size: 1em; } |
| |
| /** Improve readability of pre-formatted text in all browsers. */ |
| pre { white-space: pre-wrap; } |
| |
| /** Set consistent quote types. */ |
| q { quotes: "\201C" "\201D" "\2018" "\2019"; } |
| |
| /** Address inconsistent and variable font size in all browsers. */ |
| small { font-size: 80%; } |
| |
| /** Prevent `sub` and `sup` affecting `line-height` in all browsers. */ |
| sub, sup { font-size: 75%; line-height: 0; position: relative; vertical-align: baseline; } |
| |
| sup { top: -0.5em; } |
| |
| sub { bottom: -0.25em; } |
| |
| /* ========================================================================== Embedded content ========================================================================== */ |
| /** Remove border when inside `a` element in IE 8/9. */ |
| img { border: 0; } |
| |
| /** Correct overflow displayed oddly in IE 9. */ |
| svg:not(:root) { overflow: hidden; } |
| |
| /* ========================================================================== Figures ========================================================================== */ |
| /** Address margin not present in IE 8/9 and Safari 5. */ |
| figure { margin: 0; } |
| |
| /* ========================================================================== Forms ========================================================================== */ |
| /** Define consistent border, margin, and padding. */ |
| fieldset { border: 1px solid #c0c0c0; margin: 0 2px; padding: 0.35em 0.625em 0.75em; } |
| |
| /** 1. Correct `color` not being inherited in IE 8/9. 2. Remove padding so people aren't caught out if they zero out fieldsets. */ |
| legend { border: 0; /* 1 */ padding: 0; /* 2 */ } |
| |
| /** 1. Correct font family not being inherited in all browsers. 2. Correct font size not being inherited in all browsers. 3. Address margins set differently in Firefox 4+, Safari 5, and Chrome. */ |
| button, input, select, textarea { font-family: inherit; /* 1 */ font-size: 100%; /* 2 */ margin: 0; /* 3 */ } |
| |
| /** Address Firefox 4+ setting `line-height` on `input` using `!important` in the UA stylesheet. */ |
| button, input { line-height: normal; } |
| |
| /** Address inconsistent `text-transform` inheritance for `button` and `select`. All other form control elements do not inherit `text-transform` values. Correct `button` style inheritance in Chrome, Safari 5+, and IE 8+. Correct `select` style inheritance in Firefox 4+ and Opera. */ |
| button, select { text-transform: none; } |
| |
| /** 1. Avoid the WebKit bug in Android 4.0.* where (2) destroys native `audio` and `video` controls. 2. Correct inability to style clickable `input` types in iOS. 3. Improve usability and consistency of cursor style between image-type `input` and others. */ |
| button, html input[type="button"], input[type="reset"], input[type="submit"] { -webkit-appearance: button; /* 2 */ cursor: pointer; /* 3 */ } |
| |
| /** Re-set default cursor for disabled elements. */ |
| button[disabled], html input[disabled] { cursor: default; } |
| |
| /** 1. Address box sizing set to `content-box` in IE 8/9. 2. Remove excess padding in IE 8/9. */ |
| input[type="checkbox"], input[type="radio"] { box-sizing: border-box; /* 1 */ padding: 0; /* 2 */ } |
| |
| /** 1. Address `appearance` set to `searchfield` in Safari 5 and Chrome. 2. Address `box-sizing` set to `border-box` in Safari 5 and Chrome (include `-moz` to future-proof). */ |
| input[type="search"] { -webkit-appearance: textfield; /* 1 */ -moz-box-sizing: content-box; -webkit-box-sizing: content-box; /* 2 */ box-sizing: content-box; } |
| |
| /** Remove inner padding and search cancel button in Safari 5 and Chrome on OS X. */ |
| input[type="search"]::-webkit-search-cancel-button, input[type="search"]::-webkit-search-decoration { -webkit-appearance: none; } |
| |
| /** Remove inner padding and border in Firefox 4+. */ |
| button::-moz-focus-inner, input::-moz-focus-inner { border: 0; padding: 0; } |
| |
| /** 1. Remove default vertical scrollbar in IE 8/9. 2. Improve readability and alignment in all browsers. */ |
| textarea { overflow: auto; /* 1 */ vertical-align: top; /* 2 */ } |
| |
| /* ========================================================================== Tables ========================================================================== */ |
| /** Remove most spacing between table cells. */ |
| table { border-collapse: collapse; border-spacing: 0; } |
| |
| meta.foundation-mq-small { font-family: "only screen and (min-width: 768px)"; width: 768px; } |
| |
| meta.foundation-mq-medium { font-family: "only screen and (min-width:1280px)"; width: 1280px; } |
| |
| meta.foundation-mq-large { font-family: "only screen and (min-width:1440px)"; width: 1440px; } |
| |
| *, *:before, *:after { -moz-box-sizing: border-box; -webkit-box-sizing: border-box; box-sizing: border-box; } |
| |
| html, body { font-size: 100%; } |
| |
| body { background: white; color: #222222; padding: 0; margin: 0; font-family: "Helvetica Neue", "Helvetica", Helvetica, Arial, sans-serif; font-weight: normal; font-style: normal; line-height: 1; position: relative; cursor: auto; } |
| |
| a:hover { cursor: pointer; } |
| |
| img, object, embed { max-width: 100%; height: auto; } |
| |
| object, embed { height: 100%; } |
| |
| img { -ms-interpolation-mode: bicubic; } |
| |
| #map_canvas img, #map_canvas embed, #map_canvas object, .map_canvas img, .map_canvas embed, .map_canvas object { max-width: none !important; } |
| |
| .left { float: left !important; } |
| |
| .right { float: right !important; } |
| |
| .text-left { text-align: left !important; } |
| |
| .text-right { text-align: right !important; } |
| |
| .text-center { text-align: center !important; } |
| |
| .text-justify { text-align: justify !important; } |
| |
| .hide { display: none; } |
| |
| .antialiased { -webkit-font-smoothing: antialiased; } |
| |
| img { display: inline-block; vertical-align: middle; } |
| |
| textarea { height: auto; min-height: 50px; } |
| |
| select { width: 100%; } |
| |
| object, svg { display: inline-block; vertical-align: middle; } |
| |
| .center { margin-left: auto; margin-right: auto; } |
| |
| .spread { width: 100%; } |
| |
| p.lead, .paragraph.lead > p, #preamble > .sectionbody > .paragraph:first-of-type p { font-size: 1.21875em; line-height: 1.6; } |
| |
| .subheader, .admonitionblock td.content > .title, .audioblock > .title, .exampleblock > .title, .imageblock > .title, .listingblock > .title, .literalblock > .title, .stemblock > .title, .openblock > .title, .paragraph > .title, .quoteblock > .title, table.tableblock > .title, .verseblock > .title, .videoblock > .title, .dlist > .title, .olist > .title, .ulist > .title, .qlist > .title, .hdlist > .title { line-height: 1.4; color: black; font-weight: 300; margin-top: 0.2em; margin-bottom: 0.5em; } |
| |
| /* Typography resets */ |
| div, dl, dt, dd, ul, ol, li, h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6, pre, form, p, blockquote, th, td { margin: 0; padding: 0; direction: ltr; } |
| |
| /* Default Link Styles */ |
| a { color: #0068b0; text-decoration: none; line-height: inherit; } |
| a:hover, a:focus { color: #333333; } |
| a img { border: none; } |
| |
| /* Default paragraph styles */ |
| p { font-family: Noto, sans-serif; font-weight: normal; font-size: 1em; line-height: 1.6; margin-bottom: 0.75em; text-rendering: optimizeLegibility; } |
| p aside { font-size: 0.875em; line-height: 1.35; font-style: italic; } |
| |
| /* Default header styles */ |
| h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6 { font-family: Noto, sans-serif; font-weight: normal; font-style: normal; color: black; text-rendering: optimizeLegibility; margin-top: 0.5em; margin-bottom: 0.5em; line-height: 1.2125em; } |
| h1 small, h2 small, h3 small, #toctitle small, .sidebarblock > .content > .title small, h4 small, h5 small, h6 small { font-size: 60%; color: #4d4d4d; line-height: 0; } |
| |
| h1 { font-size: 2.125em; } |
| |
| h2 { font-size: 1.6875em; } |
| |
| h3, #toctitle, .sidebarblock > .content > .title { font-size: 1.375em; } |
| |
| h4 { font-size: 1.125em; } |
| |
| h5 { font-size: 1.125em; } |
| |
| h6 { font-size: 1em; } |
| |
| hr { border: solid #dddddd; border-width: 1px 0 0; clear: both; margin: 1.25em 0 1.1875em; height: 0; } |
| |
| /* Helpful Typography Defaults */ |
| em, i { font-style: italic; line-height: inherit; } |
| |
| strong, b { font-weight: bold; line-height: inherit; } |
| |
| small { font-size: 60%; line-height: inherit; } |
| |
| code { font-family: Consolas, "Liberation Mono", Courier, monospace; font-weight: normal; color: #264357; } |
| |
| /* Lists */ |
| ul, ol, dl { font-size: 1em; line-height: 1.6; margin-bottom: 0.75em; list-style-position: outside; font-family: Noto, sans-serif; } |
| |
| ul, ol { margin-left: 1.5em; } |
| ul.no-bullet, ol.no-bullet { margin-left: 1.5em; } |
| |
| /* Unordered Lists */ |
| ul li ul, ul li ol { margin-left: 1.25em; margin-bottom: 0; font-size: 1em; /* Override nested font-size change */ } |
| ul.square li ul, ul.circle li ul, ul.disc li ul { list-style: inherit; } |
| ul.square { list-style-type: square; } |
| ul.circle { list-style-type: circle; } |
| ul.disc { list-style-type: disc; } |
| ul.no-bullet { list-style: none; } |
| |
| /* Ordered Lists */ |
| ol li ul, ol li ol { margin-left: 1.25em; margin-bottom: 0; } |
| |
| /* Definition Lists */ |
| dl dt { margin-bottom: 0.3em; font-weight: bold; } |
| dl dd { margin-bottom: 0.75em; } |
| |
| /* Abbreviations */ |
| abbr, acronym { text-transform: uppercase; font-size: 90%; color: black; border-bottom: 1px dotted #dddddd; cursor: help; } |
| |
| abbr { text-transform: none; } |
| |
| /* Blockquotes */ |
| blockquote { margin: 0 0 0.75em; padding: 0.5625em 1.25em 0 1.1875em; border-left: 1px solid #dddddd; } |
| blockquote cite { display: block; font-size: 0.8125em; color: #5e93b8; } |
| blockquote cite:before { content: "\2014 \0020"; } |
| blockquote cite a, blockquote cite a:visited { color: #5e93b8; } |
| |
| blockquote, blockquote p { line-height: 1.6; color: #333333; } |
| |
| /* Microformats */ |
| .vcard { display: inline-block; margin: 0 0 1.25em 0; border: 1px solid #dddddd; padding: 0.625em 0.75em; } |
| .vcard li { margin: 0; display: block; } |
| .vcard .fn { font-weight: bold; font-size: 0.9375em; } |
| |
| .vevent .summary { font-weight: bold; } |
| .vevent abbr { cursor: auto; text-decoration: none; font-weight: bold; border: none; padding: 0 0.0625em; } |
| |
| @media only screen and (min-width: 768px) { h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6 { line-height: 1.4; } |
| h1 { font-size: 2.75em; } |
| h2 { font-size: 2.3125em; } |
| h3, #toctitle, .sidebarblock > .content > .title { font-size: 1.6875em; } |
| h4 { font-size: 1.4375em; } } |
| /* Tables */ |
| table { background: white; margin-bottom: 1.25em; border: solid 1px #d8d8ce; } |
| table thead, table tfoot { background: -webkit-linear-gradient(top, #add386, #90b66a); font-weight: bold; } |
| table thead tr th, table thead tr td, table tfoot tr th, table tfoot tr td { padding: 0.5em 0.625em 0.625em; font-size: inherit; color: white; text-align: left; } |
| table tr th, table tr td { padding: 0.5625em 0.625em; font-size: inherit; color: #6d6e71; } |
| table tr.even, table tr.alt, table tr:nth-of-type(even) { background: #edf2f2; } |
| table thead tr th, table tfoot tr th, table tbody tr td, table tr td, table tfoot tr td { display: table-cell; line-height: 1.4; } |
| |
| body { -moz-osx-font-smoothing: grayscale; -webkit-font-smoothing: antialiased; tab-size: 4; } |
| |
| h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6 { line-height: 1.4; } |
| |
| a:hover, a:focus { text-decoration: underline; } |
| |
| .clearfix:before, .clearfix:after, .float-group:before, .float-group:after { content: " "; display: table; } |
| .clearfix:after, .float-group:after { clear: both; } |
| |
| *:not(pre) > code { font-size: inherit; font-style: normal !important; letter-spacing: 0; padding: 0; background-color: white; -webkit-border-radius: 0; border-radius: 0; line-height: inherit; word-wrap: break-word; } |
| *:not(pre) > code.nobreak { word-wrap: normal; } |
| *:not(pre) > code.nowrap { white-space: nowrap; } |
| |
| pre, pre > code { line-height: 1.6; color: #264357; font-family: Consolas, "Liberation Mono", Courier, monospace; font-weight: normal; } |
| |
| em em { font-style: normal; } |
| |
| strong strong { font-weight: normal; } |
| |
| .keyseq { color: #333333; } |
| |
| kbd { font-family: Consolas, "Liberation Mono", Courier, monospace; display: inline-block; color: black; font-size: 0.65em; line-height: 1.45; background-color: #f7f7f7; border: 1px solid #ccc; -webkit-border-radius: 3px; border-radius: 3px; -webkit-box-shadow: 0 1px 0 rgba(0, 0, 0, 0.2), 0 0 0 0.1em white inset; box-shadow: 0 1px 0 rgba(0, 0, 0, 0.2), 0 0 0 0.1em white inset; margin: 0 0.15em; padding: 0.2em 0.5em; vertical-align: middle; position: relative; top: -0.1em; white-space: nowrap; } |
| |
| .keyseq kbd:first-child { margin-left: 0; } |
| |
| .keyseq kbd:last-child { margin-right: 0; } |
| |
| .menuseq, .menuref { color: #000; } |
| |
| .menuseq b:not(.caret), .menuref { font-weight: inherit; } |
| |
| .menuseq { word-spacing: -0.02em; } |
| .menuseq b.caret { font-size: 1.25em; line-height: 0.8; } |
| .menuseq i.caret { font-weight: bold; text-align: center; width: 0.45em; } |
| |
| b.button:before, b.button:after { position: relative; top: -1px; font-weight: normal; } |
| |
| b.button:before { content: "["; padding: 0 3px 0 2px; } |
| |
| b.button:after { content: "]"; padding: 0 2px 0 3px; } |
| |
| #header, #content, #footnotes, #footer { width: 100%; margin-left: auto; margin-right: auto; margin-top: 0; margin-bottom: 0; max-width: 62.5em; *zoom: 1; position: relative; padding-left: 1.5em; padding-right: 1.5em; } |
| #header:before, #header:after, #content:before, #content:after, #footnotes:before, #footnotes:after, #footer:before, #footer:after { content: " "; display: table; } |
| #header:after, #content:after, #footnotes:after, #footer:after { clear: both; } |
| |
| #content { margin-top: 1.25em; } |
| |
| #content:before { content: none; } |
| |
| #header > h1:first-child { color: black; margin-top: 2.25rem; margin-bottom: 0; } |
| #header > h1:first-child + #toc { margin-top: 8px; border-top: 1px solid #dddddd; } |
| #header > h1:only-child, body.toc2 #header > h1:nth-last-child(2) { border-bottom: 1px solid #dddddd; padding-bottom: 8px; } |
| #header .details { border-bottom: 1px solid #dddddd; line-height: 1.45; padding-top: 0.25em; padding-bottom: 0.25em; padding-left: 0.25em; color: #5e93b8; display: -ms-flexbox; display: -webkit-flex; display: flex; -ms-flex-flow: row wrap; -webkit-flex-flow: row wrap; flex-flow: row wrap; } |
| #header .details span:first-child { margin-left: -0.125em; } |
| #header .details span.email a { color: #333333; } |
| #header .details br { display: none; } |
| #header .details br + span:before { content: "\00a0\2013\00a0"; } |
| #header .details br + span.author:before { content: "\00a0\22c5\00a0"; color: #333333; } |
| #header .details br + span#revremark:before { content: "\00a0|\00a0"; } |
| #header #revnumber { text-transform: capitalize; } |
| #header #revnumber:after { content: "\00a0"; } |
| |
| #content > h1:first-child:not([class]) { color: black; border-bottom: 1px solid #dddddd; padding-bottom: 8px; margin-top: 0; padding-top: 1rem; margin-bottom: 1.25rem; } |
| |
| #toc { border-bottom: 0 solid #dddddd; padding-bottom: 0.5em; } |
| #toc > ul { margin-left: 0.125em; } |
| #toc ul.sectlevel0 > li > a { font-style: italic; } |
| #toc ul.sectlevel0 ul.sectlevel1 { margin: 0.5em 0; } |
| #toc ul { font-family: Noto, sans-serif; list-style-type: none; } |
| #toc li { line-height: 1.3334; margin-top: 0.3334em; } |
| #toc a { text-decoration: none; } |
| #toc a:active { text-decoration: underline; } |
| |
| #toctitle { color: black; font-size: 1.2em; } |
| |
| @media only screen and (min-width: 768px) { #toctitle { font-size: 1.375em; } |
| body.toc2 { padding-left: 15em; padding-right: 0; } |
| #toc.toc2 { margin-top: 0 !important; background-color: white; position: fixed; width: 15em; left: 0; top: 0; border-right: 1px solid #dddddd; border-top-width: 0 !important; border-bottom-width: 0 !important; z-index: 1000; padding: 1.25em 1em; height: 100%; overflow: auto; } |
| #toc.toc2 #toctitle { margin-top: 0; margin-bottom: 0.8rem; font-size: 1.2em; } |
| #toc.toc2 > ul { font-size: 0.9em; margin-bottom: 0; } |
| #toc.toc2 ul ul { margin-left: 0; padding-left: 1em; } |
| #toc.toc2 ul.sectlevel0 ul.sectlevel1 { padding-left: 0; margin-top: 0.5em; margin-bottom: 0.5em; } |
| body.toc2.toc-right { padding-left: 0; padding-right: 15em; } |
| body.toc2.toc-right #toc.toc2 { border-right-width: 0; border-left: 1px solid #dddddd; left: auto; right: 0; } } |
| @media only screen and (min-width: 1280px) { body.toc2 { padding-left: 20em; padding-right: 0; } |
| #toc.toc2 { width: 20em; } |
| #toc.toc2 #toctitle { font-size: 1.375em; } |
| #toc.toc2 > ul { font-size: 0.95em; } |
| #toc.toc2 ul ul { padding-left: 1.25em; } |
| body.toc2.toc-right { padding-left: 0; padding-right: 20em; } } |
| #content #toc { border-style: solid; border-width: 1px; border-color: #e6e6e6; margin-bottom: 1.25em; padding: 1.25em; background: white; -webkit-border-radius: 0; border-radius: 0; } |
| #content #toc > :first-child { margin-top: 0; } |
| #content #toc > :last-child { margin-bottom: 0; } |
| |
| #footer { max-width: 100%; background-color: none; padding: 1.25em; } |
| |
| #footer-text { color: black; line-height: 1.44; } |
| |
| #content { margin-bottom: 0.625em; } |
| |
| .sect1 { padding-bottom: 0.625em; } |
| |
| @media only screen and (min-width: 768px) { #content { margin-bottom: 1.25em; } |
| .sect1 { padding-bottom: 1.25em; } } |
| .sect1:last-child { padding-bottom: 0; } |
| |
| .sect1 + .sect1 { border-top: 0 solid #dddddd; } |
| |
| #content h1 > a.anchor, h2 > a.anchor, h3 > a.anchor, #toctitle > a.anchor, .sidebarblock > .content > .title > a.anchor, h4 > a.anchor, h5 > a.anchor, h6 > a.anchor { position: absolute; z-index: 1001; width: 1.5ex; margin-left: -1.5ex; display: block; text-decoration: none !important; visibility: hidden; text-align: center; font-weight: normal; } |
| #content h1 > a.anchor:before, h2 > a.anchor:before, h3 > a.anchor:before, #toctitle > a.anchor:before, .sidebarblock > .content > .title > a.anchor:before, h4 > a.anchor:before, h5 > a.anchor:before, h6 > a.anchor:before { content: "\00A7"; font-size: 0.85em; display: block; padding-top: 0.1em; } |
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| <body class="manpage"> |
| <div id="header"> |
| <h1>optionalAttributeQualifiers(3) Manual Page</h1> |
| <h2 id="_name">Name</h2> |
| <div class="sectionbody"> |
| <p>optionalAttributeQualifiers - Optional Attribute Qualifiers</p> |
| </div> |
| </div> |
| <div id="content"> |
| <div class="sect1"> |
| <h2 id="_description">Description</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>The <code>__kernel</code> qualifier can be used with the keyword <em>attribute</em> to |
| declare additional information about the kernel function as described below.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The optional <code>__attribute__((vec_type_hint(<type>)))</code><sup>24</sup> is a hint to the |
| compiler and is intended to be a representation of the computational <em>width</em> |
| of the <code>__kernel</code>, and should serve as the basis for calculating processor |
| bandwidth utilization when the compiler is looking to autovectorize the |
| code. |
| In the <code>__attribute__((vec_type_hint(<type>)))</code> qualifier <type> is one of |
| the built-in vector types listed in <a href="https://www.khronos.org/registry/OpenCL/specs/2.2/html/OpenCL_C.html#table-builtin-vector-types" class="bare" target="_blank" rel="noopener">https://www.khronos.org/registry/OpenCL/specs/2.2/html/OpenCL_C.html#table-builtin-vector-types</a> or the |
| constituent scalar element types. |
| If <code>vec_type_hint (<type>)</code> is not specified, the kernel is assumed to have |
| the <code>__attribute__((vec_type_hint(int)))</code> qualifier.</p> |
| </div> |
| <div class="paragraph"> |
| <p>[24] Implicit in autovectorization is the assumption that any libraries |
| called from the <code>__kernel</code> must be recompilable at run time to handle |
| cases where the compiler decides to merge or separate workitems. |
| This probably means that such libraries can never be hard coded binaries or |
| that hard coded binaries must be accompanied either by source or some |
| retargetable intermediate representation. |
| This may be a code security question for some.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For example, where the developer specified a width of <code>float4</code>, the compiler |
| should assume that the computation usually uses up to 4 lanes of a <code>float</code> |
| vector, and would decide to merge work-items or possibly even separate one |
| work-item into many threads to better match the hardware capabilities. |
| A conforming implementation is not required to autovectorize code, but shall |
| support the hint. |
| A compiler may autovectorize, even if no hint is provided. |
| If an implementation merges N work-items into one thread, it is responsible |
| for correctly handling cases where the number of <code>global</code> or <code>local</code> |
| work-items in any dimension modulo N is not zero.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Examples:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlight"><code class="language-c" data-lang="c">// autovectorize assuming float4 as the |
| // basic computation width |
| __kernel __attribute__((vec_type_hint(float4))) |
| void foo( __global float4 *p ) { ... } |
| |
| // autovectorize assuming double as the |
| // basic computation width |
| __kernel __attribute__((vec_type_hint(double))) |
| void foo( __global float4 *p ) { ... } |
| |
| // autovectorize assuming int (default) |
| // as the basic computation width |
| __kernel |
| void foo( __global float4 *p ) { ... }</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>If for example, a <code>__kernel</code> function is declared with</p> |
| </div> |
| <div class="dlist"> |
| <dl> |
| <dt class="hdlist1"></dt> |
| <dd> |
| <p><code>__attribute__(( vec_type_hint (float4)))</code></p> |
| </dd> |
| </dl> |
| </div> |
| <div class="paragraph"> |
| <p>(meaning that most operations in the <code>__kernel</code> function are explicitly |
| vectorized using <code>float4</code>) and the kernel is running using Intel<sup>®</sup> |
| Advanced Vector Instructions (Intel<sup>®</sup> AVX) which implements a |
| 8-float-wide vector unit, the autovectorizer might choose to merge two |
| work-items to one thread, running a second work-item in the high half of the |
| 256-bit AVX register.</p> |
| </div> |
| <div class="paragraph"> |
| <p>As another example, a Power4 machine has two scalar double precision |
| floating-point units with an 6-cycle deep pipe. |
| An autovectorizer for the Power4 machine might choose to interleave six |
| kernels declared with the <code>__attribute__(( vec_type_hint (double2)))</code> |
| qualifier into one hardware thread, to ensure that there is always 12-way |
| parallelism available to saturate the FPUs. |
| It might also choose to merge 4 or 8 work-items (or some other number) if it |
| concludes that these are better choices, due to resource utilization |
| concerns or some preference for divisibility by 2.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The optional <code>__attribute__((work_group_size_hint(X, Y, Z)))</code> is a hint to |
| the compiler and is intended to specify the work-group size that may be used |
| i.e. value most likely to be specified by the <em>local_work_size</em> argument to |
| <strong>clEnqueueNDRangeKernel</strong>. |
| For example, the <code>__attribute__((work_group_size_hint(1, 1, 1)))</code> is a |
| hint to the compiler that the kernel will most likely be executed with a |
| work-group size of 1.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The optional <code>__attribute__((reqd_work_group_size(X, Y, Z)))</code> is the |
| work-group size that must be used as the <em>local_work_size</em> argument to |
| <strong>clEnqueueNDRangeKernel</strong>. |
| This allows the compiler to optimize the generated code appropriately for |
| this kernel.</p> |
| </div> |
| <div class="paragraph"> |
| <p>If <code>Z</code> is one, the <em>work_dim</em> argument to <strong>clEnqueueNDRangeKernel</strong> can be 2 |
| or 3. |
| If <code>Y</code> and <code>Z</code> are one, the <em>work_dim</em> argument to <strong>clEnqueueNDRangeKernel</strong> |
| can be 1, 2 or 3.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The optional <code>__attribute__((nosvm))</code> qualifier can be used with a pointer |
| variable to inform the compiler that the pointer does not refer to a shared |
| virtual memory region.</p> |
| </div> |
| <div class="admonitionblock note"> |
| <table> |
| <tr> |
| <td class="icon"> |
| <i class="fa icon-note" title="Note"></i> |
| </td> |
| <td class="content"> |
| <div class="paragraph"> |
| <p><code>__attribute__((nosvm))</code> is deprecated, and the compiler can ignore it.</p> |
| </div> |
| </td> |
| </tr> |
| </table> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_see_also">See Also</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p><a href="accessQualifiers.html">accessQualifiers</a>, <a href="kernel.html">kernel</a></p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_document_notes">Document Notes</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>For more information, see the <a href="https://www.khronos.org/registry/OpenCL/specs/2.2/html/OpenCL_C.html#optional-attribute-qualifiers" target="_blank" rel="noopener">OpenCL C Specification</a></p> |
| </div> |
| <div class="paragraph"> |
| <p>This page is extracted from the OpenCL C Specification. |
| Fixes and changes should be made to the Specification, not directly.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_copyright">Copyright</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>Copyright (c) 2014-2019 Khronos Group. This work is licensed under a |
| <a href="http://creativecommons.org/licenses/by/4.0/" target="_blank" rel="noopener">Creative Commons |
| Attribution 4.0 International License</a>.</p> |
| </div> |
| </div> |
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