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<title>Comparing potentially-unordered poly_ints (GNU Compiler Collection (GCC) Internals)</title>

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<a name="Comparing-potentially_002dunordered-poly_005fints"></a>
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Next: <a href="Comparing-ordered-poly_005fints.html#Comparing-ordered-poly_005fints" accesskey="n" rel="next">Comparing ordered <code>poly_int</code>s</a>, Previous: <a href="Properties-of-the-poly_005fint-comparisons.html#Properties-of-the-poly_005fint-comparisons" accesskey="p" rel="prev">Properties of the <code>poly_int</code> comparisons</a>, Up: <a href="Comparisons-involving-poly_005fint.html#Comparisons-involving-poly_005fint" accesskey="u" rel="up">Comparisons involving <code>poly_int</code></a> &nbsp; [<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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<a name="Comparing-potentially_002dunordered-poly_005fints-1"></a>
<h4 class="subsection">10.3.3 Comparing potentially-unordered <code>poly_int</code>s</h4>

<p>In cases where there is no definite link between two <code>poly_int</code>s,
we can usually make a conservatively-correct assumption.  For example,
the conservative assumption for alias analysis is that two references
<em>might</em> alias.
</p>
<p>One way of checking whether [<var>begin1</var>, <var>end1</var>) might overlap
[<var>begin2</var>, <var>end2</var>) using the <code>poly_int</code> comparisons is:
</p>
<div class="smallexample">
<pre class="smallexample">maybe_gt (<var>end1</var>, <var>begin2</var>) &amp;&amp; maybe_gt (<var>end2</var>, <var>begin1</var>)
</pre></div>

<p>and another (equivalent) way is:
</p>
<div class="smallexample">
<pre class="smallexample">!(known_le (<var>end1</var>, <var>begin2</var>) || known_le (<var>end2</var>, <var>begin1</var>))
</pre></div>

<p>However, in this particular example, it is better to use the range helper
functions instead.  See <a href="Range-checks-on-poly_005fints.html#Range-checks-on-poly_005fints">Range checks on <code>poly_int</code>s</a>.
</p>


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