<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Copyright (C) 1988-2020 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 6.5, http://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Converting poly_ints (GNU Compiler Collection (GCC) Internals)</title>
<meta name="description" content="Converting poly_ints (GNU Compiler Collection (GCC) Internals)">
<meta name="keywords" content="Converting poly_ints (GNU Compiler Collection (GCC) Internals)">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<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="Miscellaneous-poly_005fint-routines.html#Miscellaneous-poly_005fint-routines" rel="next" title="Miscellaneous poly_int routines">
<link href="Computing-bounds-on-poly_005fints.html#Computing-bounds-on-poly_005fints" rel="prev" title="Computing bounds on poly_ints">
<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="Converting-poly_005fints"></a>
<div class="header">
<p>
Next: <a href="Miscellaneous-poly_005fint-routines.html#Miscellaneous-poly_005fint-routines" accesskey="n" rel="next">Miscellaneous <code>poly_int</code> routines</a>, Previous: <a href="Computing-bounds-on-poly_005fints.html#Computing-bounds-on-poly_005fints" accesskey="p" rel="prev">Computing bounds 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="Converting-poly_005fints-1"></a>
<h3 class="section">10.7 Converting <code>poly_int</code>s</h3>
<p>A <code>poly_int<<var>n</var>, <var>T</var>></code> can be constructed from up to
<var>n</var> individual <var>T</var> coefficients, with the remaining coefficients
being implicitly zero. In particular, this means that every
<code>poly_int<<var>n</var>, <var>T</var>></code> can be constructed from a single
scalar <var>T</var>, or something compatible with <var>T</var>.
</p>
<p>Also, a <code>poly_int<<var>n</var>, <var>T</var>></code> can be constructed from
a <code>poly_int<<var>n</var>, <var>U</var>></code> if <var>T</var> can be constructed
from <var>U</var>.
</p>
<p>The following functions provide other forms of conversion,
or test whether such a conversion would succeed.
</p>
<dl compact="compact">
<dt>‘<samp><var>value</var>.is_constant ()</samp>’</dt>
<dd><p>Return true if <code>poly_int</code> <var>value</var> is a compile-time constant.
</p>
</dd>
<dt>‘<samp><var>value</var>.is_constant (&<var>c1</var>)</samp>’</dt>
<dd><p>Return true if <code>poly_int</code> <var>value</var> is a compile-time constant,
storing it in <var>c1</var> if so. <var>c1</var> must be able to hold all
constant values of <var>value</var> without loss of precision.
</p>
</dd>
<dt>‘<samp><var>value</var>.to_constant ()</samp>’</dt>
<dd><p>Assert that <var>value</var> is a compile-time constant and return its value.
When using this function, please add a comment explaining why the
condition is known to hold (for example, because an earlier phase
of analysis rejected non-constants).
</p>
</dd>
<dt>‘<samp><var>value</var>.to_shwi (&<var>p2</var>)</samp>’</dt>
<dd><p>Return true if ‘<samp>poly_int<<var>N</var>, <var>T</var>></samp>’ <var>value</var> can be
represented without loss of precision as a
‘<samp>poly_int<<var>N</var>, <code>HOST_WIDE_INT</code>></samp>’, storing it in that
form in <var>p2</var> if so.
</p>
</dd>
<dt>‘<samp><var>value</var>.to_uhwi (&<var>p2</var>)</samp>’</dt>
<dd><p>Return true if ‘<samp>poly_int<<var>N</var>, <var>T</var>></samp>’ <var>value</var> can be
represented without loss of precision as a
‘<samp>poly_int<<var>N</var>, <code>unsigned HOST_WIDE_INT</code>></samp>’, storing it in that
form in <var>p2</var> if so.
</p>
</dd>
<dt>‘<samp><var>value</var>.force_shwi ()</samp>’</dt>
<dd><p>Forcibly convert each coefficient of ‘<samp>poly_int<<var>N</var>, <var>T</var>></samp>’
<var>value</var> to <code>HOST_WIDE_INT</code>, truncating any that are out of range.
Return the result as a ‘<samp>poly_int<<var>N</var>, <code>HOST_WIDE_INT</code>></samp>’.
</p>
</dd>
<dt>‘<samp><var>value</var>.force_uhwi ()</samp>’</dt>
<dd><p>Forcibly convert each coefficient of ‘<samp>poly_int<<var>N</var>, <var>T</var>></samp>’
<var>value</var> to <code>unsigned HOST_WIDE_INT</code>, truncating any that are
out of range. Return the result as a
‘<samp>poly_int<<var>N</var>, <code>unsigned HOST_WIDE_INT</code>></samp>’.
</p>
</dd>
<dt>‘<samp>wi::shwi (<var>value</var>, <var>precision</var>)</samp>’</dt>
<dd><p>Return a <code>poly_int</code> with the same value as <var>value</var>, but with
the coefficients converted from <code>HOST_WIDE_INT</code> to <code>wide_int</code>.
<var>precision</var> specifies the precision of the <code>wide_int</code> cofficients;
if this is wider than a <code>HOST_WIDE_INT</code>, the coefficients of
<var>value</var> will be sign-extended to fit.
</p>
</dd>
<dt>‘<samp>wi::uhwi (<var>value</var>, <var>precision</var>)</samp>’</dt>
<dd><p>Like <code>wi::shwi</code>, except that <var>value</var> has coefficients of
type <code>unsigned HOST_WIDE_INT</code>. If <var>precision</var> is wider than
a <code>HOST_WIDE_INT</code>, the coefficients of <var>value</var> will be
zero-extended to fit.
</p>
</dd>
<dt>‘<samp>wi::sext (<var>value</var>, <var>precision</var>)</samp>’</dt>
<dd><p>Return a <code>poly_int</code> of the same type as <var>value</var>, sign-extending
every coefficient from the low <var>precision</var> bits. This in effect
applies <code>wi::sext</code> to each coefficient individually.
</p>
</dd>
<dt>‘<samp>wi::zext (<var>value</var>, <var>precision</var>)</samp>’</dt>
<dd><p>Like <code>wi::sext</code>, but for zero extension.
</p>
</dd>
<dt>‘<samp>poly_wide_int::from (<var>value</var>, <var>precision</var>, <var>sign</var>)</samp>’</dt>
<dd><p>Convert <var>value</var> to a <code>poly_wide_int</code> in which each coefficient
has <var>precision</var> bits. Extend the coefficients according to
<var>sign</var> if the coefficients have fewer bits.
</p>
</dd>
<dt>‘<samp>poly_offset_int::from (<var>value</var>, <var>sign</var>)</samp>’</dt>
<dd><p>Convert <var>value</var> to a <code>poly_offset_int</code>, extending its coefficients
according to <var>sign</var> if they have fewer bits than <code>offset_int</code>.
</p>
</dd>
<dt>‘<samp>poly_widest_int::from (<var>value</var>, <var>sign</var>)</samp>’</dt>
<dd><p>Convert <var>value</var> to a <code>poly_widest_int</code>, extending its coefficients
according to <var>sign</var> if they have fewer bits than <code>widest_int</code>.
</p></dd>
</dl>
<hr>
<div class="header">
<p>
Next: <a href="Miscellaneous-poly_005fint-routines.html#Miscellaneous-poly_005fint-routines" accesskey="n" rel="next">Miscellaneous <code>poly_int</code> routines</a>, Previous: <a href="Computing-bounds-on-poly_005fints.html#Computing-bounds-on-poly_005fints" accesskey="p" rel="prev">Computing bounds 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>