You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
180 lines
8.7 KiB
HTML
180 lines
8.7 KiB
HTML
4 years ago
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html>
|
||
|
|
<!-- Copyright (C) 1988-2018 Free Software Foundation, Inc.
|
||
|
|
|
||
|
|
Permission is granted to copy, distribute and/or modify this document
|
||
|
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
||
|
|
any later version published by the Free Software Foundation; with the
|
||
|
|
Invariant Sections being "Funding Free Software", the Front-Cover
|
||
|
|
Texts being (a) (see below), and with the Back-Cover Texts being (b)
|
||
|
|
(see below). A copy of the license is included in the section entitled
|
||
|
|
"GNU Free Documentation License".
|
||
|
|
|
||
|
|
(a) The FSF's Front-Cover Text is:
|
||
|
|
|
||
|
|
A GNU Manual
|
||
|
|
|
||
|
|
(b) The FSF's Back-Cover Text is:
|
||
|
|
|
||
|
|
You have freedom to copy and modify this GNU Manual, like GNU
|
||
|
|
software. Copies published by the Free Software Foundation raise
|
||
|
|
funds for GNU development. -->
|
||
|
|
<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<title>Alignment of poly_ints (GNU Compiler Collection (GCC) Internals)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="Alignment of poly_ints (GNU Compiler Collection (GCC) Internals)">
|
||
|
|
<meta name="keywords" content="Alignment of poly_ints (GNU Compiler Collection (GCC) Internals)">
|
||
|
|
<meta name="resource-type" content="document">
|
||
|
|
<meta name="distribution" content="global">
|
||
|
|
<meta name="Generator" content="makeinfo">
|
||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
||
|
|
<link href="index.html#Top" rel="start" title="Top">
|
||
|
|
<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
|
||
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
||
|
|
<link href="poly_005fint.html#poly_005fint" rel="up" title="poly_int">
|
||
|
|
<link href="Computing-bounds-on-poly_005fints.html#Computing-bounds-on-poly_005fints" rel="next" title="Computing bounds on poly_ints">
|
||
|
|
<link href="Other-poly_005fint-arithmetic.html#Other-poly_005fint-arithmetic" rel="prev" title="Other poly_int arithmetic">
|
||
|
|
<style type="text/css">
|
||
|
|
<!--
|
||
|
|
a.summary-letter {text-decoration: none}
|
||
|
|
blockquote.indentedblock {margin-right: 0em}
|
||
|
|
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
|
||
|
|
blockquote.smallquotation {font-size: smaller}
|
||
|
|
div.display {margin-left: 3.2em}
|
||
|
|
div.example {margin-left: 3.2em}
|
||
|
|
div.lisp {margin-left: 3.2em}
|
||
|
|
div.smalldisplay {margin-left: 3.2em}
|
||
|
|
div.smallexample {margin-left: 3.2em}
|
||
|
|
div.smalllisp {margin-left: 3.2em}
|
||
|
|
kbd {font-style: oblique}
|
||
|
|
pre.display {font-family: inherit}
|
||
|
|
pre.format {font-family: inherit}
|
||
|
|
pre.menu-comment {font-family: serif}
|
||
|
|
pre.menu-preformatted {font-family: serif}
|
||
|
|
pre.smalldisplay {font-family: inherit; font-size: smaller}
|
||
|
|
pre.smallexample {font-size: smaller}
|
||
|
|
pre.smallformat {font-family: inherit; font-size: smaller}
|
||
|
|
pre.smalllisp {font-size: smaller}
|
||
|
|
span.nolinebreak {white-space: nowrap}
|
||
|
|
span.roman {font-family: initial; font-weight: normal}
|
||
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
||
|
|
ul.no-bullet {list-style: none}
|
||
|
|
-->
|
||
|
|
</style>
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body lang="en">
|
||
|
|
<a name="Alignment-of-poly_005fints"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Computing-bounds-on-poly_005fints.html#Computing-bounds-on-poly_005fints" accesskey="n" rel="next">Computing bounds on <code>poly_int</code>s</a>, Previous: <a href="Arithmetic-on-poly_005fints.html#Arithmetic-on-poly_005fints" accesskey="p" rel="prev">Arithmetic on <code>poly_int</code>s</a>, Up: <a href="poly_005fint.html#poly_005fint" accesskey="u" rel="up">poly_int</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<a name="Alignment-of-poly_005fints-1"></a>
|
||
|
|
<h3 class="section">10.5 Alignment of <code>poly_int</code>s</h3>
|
||
|
|
|
||
|
|
<p><code>poly_int</code> provides various routines for aligning values and for querying
|
||
|
|
misalignments. In each case the alignment must be a power of 2.
|
||
|
|
</p>
|
||
|
|
<dl compact="compact">
|
||
|
|
<dt>‘<samp>can_align_p (<var>value</var>, <var>align</var>)</samp>’</dt>
|
||
|
|
<dd><p>Return true if we can align <var>value</var> up or down to the nearest multiple
|
||
|
|
of <var>align</var> at compile time. The answer is the same for both directions.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>can_align_down (<var>value</var>, <var>align</var>, &<var>aligned</var>)</samp>’</dt>
|
||
|
|
<dd><p>Return true if <code>can_align_p</code>; if so, set <var>aligned</var> to the greatest
|
||
|
|
aligned value that is less than or equal to <var>value</var>.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>can_align_up (<var>value</var>, <var>align</var>, &<var>aligned</var>)</samp>’</dt>
|
||
|
|
<dd><p>Return true if <code>can_align_p</code>; if so, set <var>aligned</var> to the lowest
|
||
|
|
aligned value that is greater than or equal to <var>value</var>.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>known_equal_after_align_down (<var>a</var>, <var>b</var>, <var>align</var>)</samp>’</dt>
|
||
|
|
<dd><p>Return true if we can align <var>a</var> and <var>b</var> down to the nearest
|
||
|
|
<var>align</var> boundary at compile time and if the two results are equal.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>known_equal_after_align_up (<var>a</var>, <var>b</var>, <var>align</var>)</samp>’</dt>
|
||
|
|
<dd><p>Return true if we can align <var>a</var> and <var>b</var> up to the nearest
|
||
|
|
<var>align</var> boundary at compile time and if the two results are equal.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>aligned_lower_bound (<var>value</var>, <var>align</var>)</samp>’</dt>
|
||
|
|
<dd><p>Return a result that is no greater than <var>value</var> and that is aligned
|
||
|
|
to <var>align</var>. The result will the closest aligned value for some
|
||
|
|
indeterminate values but not necessarily for all.
|
||
|
|
</p>
|
||
|
|
<p>For example, suppose we are allocating an object of <var>size</var> bytes
|
||
|
|
in a downward-growing stack whose current limit is given by <var>limit</var>.
|
||
|
|
If the object requires <var>align</var> bytes of alignment, the new stack
|
||
|
|
limit is given by:
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">aligned_lower_bound (<var>limit</var> - <var>size</var>, <var>align</var>)
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>aligned_upper_bound (<var>value</var>, <var>align</var>)</samp>’</dt>
|
||
|
|
<dd><p>Likewise return a result that is no less than <var>value</var> and that is
|
||
|
|
aligned to <var>align</var>. This is the routine that would be used for
|
||
|
|
upward-growing stacks in the scenario just described.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>known_misalignment (<var>value</var>, <var>align</var>, &<var>misalign</var>)</samp>’</dt>
|
||
|
|
<dd><p>Return true if we can calculate the misalignment of <var>value</var>
|
||
|
|
with respect to <var>align</var> at compile time, storing the result in
|
||
|
|
<var>misalign</var> if so.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>known_alignment (<var>value</var>)</samp>’</dt>
|
||
|
|
<dd><p>Return the minimum alignment that <var>value</var> is known to have
|
||
|
|
(in other words, the largest alignment that can be guaranteed
|
||
|
|
whatever the values of the indeterminates turn out to be).
|
||
|
|
Return 0 if <var>value</var> is known to be 0.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>force_align_down (<var>value</var>, <var>align</var>)</samp>’</dt>
|
||
|
|
<dd><p>Assert that <var>value</var> can be aligned down to <var>align</var> at compile
|
||
|
|
time and return the result. When using this routine, please add a
|
||
|
|
comment explaining why the assertion is known to hold.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>force_align_up (<var>value</var>, <var>align</var>)</samp>’</dt>
|
||
|
|
<dd><p>Likewise, but aligning up.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>force_align_down_and_div (<var>value</var>, <var>align</var>)</samp>’</dt>
|
||
|
|
<dd><p>Divide the result of <code>force_align_down</code> by <var>align</var>. Again,
|
||
|
|
please add a comment explaining why the assertion in <code>force_align_down</code>
|
||
|
|
is known to hold.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>force_align_up_and_div (<var>value</var>, <var>align</var>)</samp>’</dt>
|
||
|
|
<dd><p>Likewise for <code>force_align_up</code>.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>force_get_misalignment (<var>value</var>, <var>align</var>)</samp>’</dt>
|
||
|
|
<dd><p>Assert that we can calculate the misalignment of <var>value</var> with
|
||
|
|
respect to <var>align</var> at compile time and return the misalignment.
|
||
|
|
When using this function, please add a comment explaining why
|
||
|
|
the assertion is known to hold.
|
||
|
|
</p></dd>
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Computing-bounds-on-poly_005fints.html#Computing-bounds-on-poly_005fints" accesskey="n" rel="next">Computing bounds on <code>poly_int</code>s</a>, Previous: <a href="Arithmetic-on-poly_005fints.html#Arithmetic-on-poly_005fints" accesskey="p" rel="prev">Arithmetic on <code>poly_int</code>s</a>, Up: <a href="poly_005fint.html#poly_005fint" accesskey="u" rel="up">poly_int</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|