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154 lines
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HTML
154 lines
8.0 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<!-- Copyright (C) 1988-2018 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Range checks on poly_ints (GNU Compiler Collection (GCC) Internals)</title>
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<meta name="description" content="Range checks on poly_ints (GNU Compiler Collection (GCC) Internals)">
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<meta name="keywords" content="Range checks on poly_ints (GNU Compiler Collection (GCC) Internals)">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Comparisons-involving-poly_005fint.html#Comparisons-involving-poly_005fint" rel="up" title="Comparisons involving poly_int">
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<link href="Sorting-poly_005fints.html#Sorting-poly_005fints" rel="next" title="Sorting poly_ints">
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<link href="Checking-for-a-poly_005fint-marker-value.html#Checking-for-a-poly_005fint-marker-value" rel="prev" title="Checking for a poly_int marker value">
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</head>
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<body lang="en">
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<a name="Range-checks-on-poly_005fints"></a>
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<div class="header">
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<p>
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Next: <a href="Sorting-poly_005fints.html#Sorting-poly_005fints" accesskey="n" rel="next">Sorting <code>poly_int</code>s</a>, Previous: <a href="Checking-for-a-poly_005fint-marker-value.html#Checking-for-a-poly_005fint-marker-value" accesskey="p" rel="prev">Checking for a <code>poly_int</code> marker value</a>, Up: <a href="Comparisons-involving-poly_005fint.html#Comparisons-involving-poly_005fint" accesskey="u" rel="up">Comparisons involving <code>poly_int</code></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>
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</div>
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<hr>
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<a name="Range-checks-on-poly_005fints-1"></a>
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<h4 class="subsection">10.3.6 Range checks on <code>poly_int</code>s</h4>
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<p>As well as the core comparisons
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(see <a href="Comparison-functions-for-poly_005fint.html#Comparison-functions-for-poly_005fint">Comparison functions for <code>poly_int</code></a>), <code>poly_int</code> provides
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utilities for various kinds of range check. In each case the range
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is represented by a start position and a size rather than a start
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position and an end position; this is because the former is used
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much more often than the latter in GCC. Also, the sizes can be
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-1 (or all ones for unsigned sizes) to indicate a range with a known
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start position but an unknown size. All other sizes must be nonnegative.
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A range of size 0 does not contain anything or overlap anything.
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</p>
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<dl compact="compact">
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<dt>‘<samp>known_size_p (<var>size</var>)</samp>’</dt>
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<dd><p>Return true if <var>size</var> represents a known range size, false if it
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is -1 or all ones (for signed and unsigned types respectively).
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</p>
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</dd>
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<dt>‘<samp>ranges_maybe_overlap_p (<var>pos1</var>, <var>size1</var>, <var>pos2</var>, <var>size2</var>)</samp>’</dt>
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<dd><p>Return true if the range described by <var>pos1</var> and <var>size1</var> <em>might</em>
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overlap the range described by <var>pos2</var> and <var>size2</var> (in other words,
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return true if we cannot prove that the ranges are disjoint).
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</p>
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</dd>
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<dt>‘<samp>ranges_known_overlap_p (<var>pos1</var>, <var>size1</var>, <var>pos2</var>, <var>size2</var>)</samp>’</dt>
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<dd><p>Return true if the range described by <var>pos1</var> and <var>size1</var> is known to
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overlap the range described by <var>pos2</var> and <var>size2</var>.
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</p>
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</dd>
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<dt>‘<samp>known_subrange_p (<var>pos1</var>, <var>size1</var>, <var>pos2</var>, <var>size2</var>)</samp>’</dt>
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<dd><p>Return true if the range described by <var>pos1</var> and <var>size1</var> is known to
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be contained in the range described by <var>pos2</var> and <var>size2</var>.
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</p>
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</dd>
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<dt>‘<samp>maybe_in_range_p (<var>value</var>, <var>pos</var>, <var>size</var>)</samp>’</dt>
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<dd><p>Return true if <var>value</var> <em>might</em> be in the range described by
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<var>pos</var> and <var>size</var> (in other words, return true if we cannot
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prove that <var>value</var> is outside that range).
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</p>
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</dd>
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<dt>‘<samp>known_in_range_p (<var>value</var>, <var>pos</var>, <var>size</var>)</samp>’</dt>
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<dd><p>Return true if <var>value</var> is known to be in the range described
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by <var>pos</var> and <var>size</var>.
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</p>
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</dd>
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<dt>‘<samp>endpoint_representable_p (<var>pos</var>, <var>size</var>)</samp>’</dt>
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<dd><p>Return true if the range described by <var>pos</var> and <var>size</var> is
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open-ended or if the endpoint (<var>pos</var> + <var>size</var>) is representable
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in the same type as <var>pos</var> and <var>size</var>. The function returns false
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if adding <var>size</var> to <var>pos</var> makes conceptual sense but could overflow.
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</p></dd>
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</dl>
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<p>There is also a <code>poly_int</code> version of the <code>IN_RANGE_P</code> macro:
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</p>
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<dl compact="compact">
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<dt>‘<samp>coeffs_in_range_p (<var>x</var>, <var>lower</var>, <var>upper</var>)</samp>’</dt>
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<dd><p>Return true if every coefficient of <var>x</var> is in the inclusive range
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[<var>lower</var>, <var>upper</var>]. This function can be useful when testing
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whether an operation would cause the values of coefficients to
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overflow.
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</p>
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<p>Note that the function does not indicate whether <var>x</var> itself is in the
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given range. <var>x</var> can be either a constant or a <code>poly_int</code>.
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</p></dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Sorting-poly_005fints.html#Sorting-poly_005fints" accesskey="n" rel="next">Sorting <code>poly_int</code>s</a>, Previous: <a href="Checking-for-a-poly_005fint-marker-value.html#Checking-for-a-poly_005fint-marker-value" accesskey="p" rel="prev">Checking for a <code>poly_int</code> marker value</a>, Up: <a href="Comparisons-involving-poly_005fint.html#Comparisons-involving-poly_005fint" accesskey="u" rel="up">Comparisons involving <code>poly_int</code></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>
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</div>
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</body>
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</html>
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