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Next: <a href="Checking-for-a-poly_005fint-marker-value.html#Checking-for-a-poly_005fint-marker-value" accesskey="n" rel="next">Checking for a <code>poly_int</code> marker value</a>, Previous: <a href="Comparing-potentially_002dunordered-poly_005fints.html#Comparing-potentially_002dunordered-poly_005fints" accesskey="p" rel="prev">Comparing potentially-unordered <code>poly_int</code>s</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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<a name="Comparing-ordered-poly_005fints-1"></a>
<h4 class="subsection">10.3.4 Comparing ordered <code>poly_int</code>s</h4>
<p>In cases where there is a definite link between two <code>poly_int</code>s,
such as the outer and inner sizes of subregs, we usually require the sizes
to be ordered by the <code>known_le</code> partial order. <code>poly_int</code> provides
the following utility functions for ordered values:
</p>
<dl compact="compact">
<dt>‘<samp>ordered_p (<var>a</var>, <var>b</var>)</samp>’</dt>
<dd><p>Return true if <var>a</var> and <var>b</var> are ordered by the <code>known_le</code>
partial order.
</p>
</dd>
<dt>‘<samp>ordered_min (<var>a</var>, <var>b</var>)</samp>’</dt>
<dd><p>Assert that <var>a</var> and <var>b</var> are ordered by <code>known_le</code> and return the
minimum of the two. When using this function, please add a comment explaining
why the values are known to be ordered.
</p>
</dd>
<dt>‘<samp>ordered_max (<var>a</var>, <var>b</var>)</samp>’</dt>
<dd><p>Assert that <var>a</var> and <var>b</var> are ordered by <code>known_le</code> and return the
maximum of the two. When using this function, please add a comment explaining
why the values are known to be ordered.
</p></dd>
</dl>
<p>For example, if a subreg has an outer mode of size <var>outer</var> and an
inner mode of size <var>inner</var>:
</p>
<ul>
<li> the subreg is complete if known_eq (<var>inner</var>, <var>outer</var>)
</li><li> otherwise, the subreg is paradoxical if known_le (<var>inner</var>, <var>outer</var>)
</li><li> otherwise, the subreg is partial if known_le (<var>outer</var>, <var>inner</var>)
</li><li> otherwise, the subreg is ill-formed
</li></ul>
<p>Thus the subreg is only valid if
‘<samp>ordered_p (<var>outer</var>, <var>inner</var>)</samp>’ is true. If this condition
is already known to be true then:
</p>
<ul>
<li> the subreg is complete if known_eq (<var>inner</var>, <var>outer</var>)
</li><li> the subreg is paradoxical if maybe_lt (<var>inner</var>, <var>outer</var>)
</li><li> the subreg is partial if maybe_lt (<var>outer</var>, <var>inner</var>)
</li></ul>
<p>with the three conditions being mutually exclusive.
</p>
<p>Code that checks whether a subreg is valid would therefore generally
check whether <code>ordered_p</code> holds (in addition to whatever other
checks are required for subreg validity). Code that is dealing
with existing subregs can assert that <code>ordered_p</code> holds
and use either of the classifications above.
</p>
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Next: <a href="Checking-for-a-poly_005fint-marker-value.html#Checking-for-a-poly_005fint-marker-value" accesskey="n" rel="next">Checking for a <code>poly_int</code> marker value</a>, Previous: <a href="Comparing-potentially_002dunordered-poly_005fints.html#Comparing-potentially_002dunordered-poly_005fints" accesskey="p" rel="prev">Comparing potentially-unordered <code>poly_int</code>s</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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