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9.3 Annotations

The optimizers need to associate attributes with statements and variables during the optimization process. For instance, we need to know what basic block a statement belongs to or whether a variable has aliases. All these attributes are stored in data structures called annotations which are then linked to the field ann in struct tree_common.

Presently, we define annotations for statements (stmt_ann_t), variables (var_ann_t) and SSA names (ssa_name_ann_t). Annotations are defined and documented in tree-flow.h.