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<h3 class="section">12.1 Annotations</h3>
<p><a name="index-annotations-2507"></a>
The optimizers need to associate attributes with variables during the
optimization process. For instance, we need to know whether a
variable has aliases. All these attributes are stored in data
structures called annotations which are then linked to the field
<code>ann</code> in <code>struct tree_common</code>.
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