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| Next: <a href="Loop-manipulation.html#Loop-manipulation" accesskey="n" rel="next">Loop manipulation</a>, Previous: <a href="Loop-representation.html#Loop-representation" accesskey="p" rel="prev">Loop representation</a>, Up: <a href="Loop-Analysis-and-Representation.html#Loop-Analysis-and-Representation" accesskey="u" rel="up">Loop Analysis and Representation</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="Loop-querying-1"></a> |
| <h3 class="section">15.2 Loop querying</h3> |
| <a name="index-Loop-querying"></a> |
| |
| <p>The functions to query the information about loops are declared in |
| <samp>cfgloop.h</samp>. Some of the information can be taken directly from |
| the structures. <code>loop_father</code> field of each basic block contains |
| the innermost loop to that the block belongs. The most useful fields of |
| loop structure (that are kept up-to-date at all times) are: |
| </p> |
| <ul> |
| <li> <code>header</code>, <code>latch</code>: Header and latch basic blocks of the |
| loop. |
| </li><li> <code>num_nodes</code>: Number of basic blocks in the loop (including |
| the basic blocks of the sub-loops). |
| </li><li> <code>depth</code>: The depth of the loop in the loops tree, i.e., the |
| number of super-loops of the loop. |
| </li><li> <code>outer</code>, <code>inner</code>, <code>next</code>: The super-loop, the first |
| sub-loop, and the sibling of the loop in the loops tree. |
| </li></ul> |
| |
| <p>There are other fields in the loop structures, many of them used only by |
| some of the passes, or not updated during CFG changes; in general, they |
| should not be accessed directly. |
| </p> |
| <p>The most important functions to query loop structures are: |
| </p> |
| <ul> |
| <li> <code>flow_loops_dump</code>: Dumps the information about loops to a |
| file. |
| </li><li> <code>verify_loop_structure</code>: Checks consistency of the loop |
| structures. |
| </li><li> <code>loop_latch_edge</code>: Returns the latch edge of a loop. |
| </li><li> <code>loop_preheader_edge</code>: If loops have preheaders, returns |
| the preheader edge of a loop. |
| </li><li> <code>flow_loop_nested_p</code>: Tests whether loop is a sub-loop of |
| another loop. |
| </li><li> <code>flow_bb_inside_loop_p</code>: Tests whether a basic block belongs |
| to a loop (including its sub-loops). |
| </li><li> <code>find_common_loop</code>: Finds the common super-loop of two loops. |
| </li><li> <code>superloop_at_depth</code>: Returns the super-loop of a loop with |
| the given depth. |
| </li><li> <code>tree_num_loop_insns</code>, <code>num_loop_insns</code>: Estimates the |
| number of insns in the loop, on GIMPLE and on RTL. |
| </li><li> <code>loop_exit_edge_p</code>: Tests whether edge is an exit from a |
| loop. |
| </li><li> <code>mark_loop_exit_edges</code>: Marks all exit edges of all loops |
| with <code>EDGE_LOOP_EXIT</code> flag. |
| </li><li> <code>get_loop_body</code>, <code>get_loop_body_in_dom_order</code>, |
| <code>get_loop_body_in_bfs_order</code>: Enumerates the basic blocks in the |
| loop in depth-first search order in reversed CFG, ordered by dominance |
| relation, and breath-first search order, respectively. |
| </li><li> <code>single_exit</code>: Returns the single exit edge of the loop, or |
| <code>NULL</code> if the loop has more than one exit. You can only use this |
| function if LOOPS_HAVE_MARKED_SINGLE_EXITS property is used. |
| </li><li> <code>get_loop_exit_edges</code>: Enumerates the exit edges of a loop. |
| </li><li> <code>just_once_each_iteration_p</code>: Returns true if the basic block |
| is executed exactly once during each iteration of a loop (that is, it |
| does not belong to a sub-loop, and it dominates the latch of the loop). |
| </li></ul> |
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