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<title>GNU Compiler Collection (GCC) Internals: Sequence iterators</title>

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<a name="Sequence-iterators"></a>
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<p>
Next: <a href="Adding-a-new-GIMPLE-statement-code.html#Adding-a-new-GIMPLE-statement-code" accesskey="n" rel="next">Adding a new GIMPLE statement code</a>, Previous: <a href="GIMPLE-sequences.html#GIMPLE-sequences" accesskey="p" rel="prev">GIMPLE sequences</a>, Up: <a href="GIMPLE.html#GIMPLE" accesskey="u" rel="up">GIMPLE</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>
</div>
<hr>
<a name="Sequence-iterators-1"></a>
<h3 class="section">11.10 Sequence iterators</h3>
<a name="index-Sequence-iterators"></a>

<p>Sequence iterators are convenience constructs for iterating
through statements in a sequence.  Given a sequence <code>SEQ</code>, here is
a typical use of gimple sequence iterators:
</p>
<div class="smallexample">
<pre class="smallexample">gimple_stmt_iterator gsi;

for (gsi = gsi_start (seq); !gsi_end_p (gsi); gsi_next (&amp;gsi))
  {
    gimple g = gsi_stmt (gsi);
    /* Do something with gimple statement <code>G</code>.  */
  }
</pre></div>

<p>Backward iterations are possible:
</p>
<div class="smallexample">
<pre class="smallexample">        for (gsi = gsi_last (seq); !gsi_end_p (gsi); gsi_prev (&amp;gsi))
</pre></div>

<p>Forward and backward iterations on basic blocks are possible with
<code>gsi_start_bb</code> and <code>gsi_last_bb</code>.
</p>
<p>In the documentation below we sometimes refer to enum
<code>gsi_iterator_update</code>.  The valid options for this enumeration are:
</p>
<ul>
<li> <code>GSI_NEW_STMT</code>
Only valid when a single statement is added.  Move the iterator to it.

</li><li> <code>GSI_SAME_STMT</code>
Leave the iterator at the same statement.

</li><li> <code>GSI_CONTINUE_LINKING</code>
Move iterator to whatever position is suitable for linking other
statements in the same direction.
</li></ul>

<p>Below is a list of the functions used to manipulate and use
statement iterators.
</p>
<dl>
<dt><a name="index-gsi_005fstart"></a>GIMPLE function: <em>gimple_stmt_iterator</em> <strong>gsi_start</strong> <em>(gimple_seq seq)</em></dt>
<dd><p>Return a new iterator pointing to the sequence <code>SEQ</code>&rsquo;s first
statement.  If <code>SEQ</code> is empty, the iterator&rsquo;s basic block is <code>NULL</code>.
Use <code>gsi_start_bb</code> instead when the iterator needs to always have
the correct basic block set.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fstart_005fbb"></a>GIMPLE function: <em>gimple_stmt_iterator</em> <strong>gsi_start_bb</strong> <em>(basic_block bb)</em></dt>
<dd><p>Return a new iterator pointing to the first statement in basic
block <code>BB</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005flast"></a>GIMPLE function: <em>gimple_stmt_iterator</em> <strong>gsi_last</strong> <em>(gimple_seq seq)</em></dt>
<dd><p>Return a new iterator initially pointing to the last statement of
sequence <code>SEQ</code>.  If <code>SEQ</code> is empty, the iterator&rsquo;s basic block is
<code>NULL</code>.  Use <code>gsi_last_bb</code> instead when the iterator needs to always
have the correct basic block set.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005flast_005fbb"></a>GIMPLE function: <em>gimple_stmt_iterator</em> <strong>gsi_last_bb</strong> <em>(basic_block bb)</em></dt>
<dd><p>Return a new iterator pointing to the last statement in basic
block <code>BB</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fend_005fp"></a>GIMPLE function: <em>bool</em> <strong>gsi_end_p</strong> <em>(gimple_stmt_iterator i)</em></dt>
<dd><p>Return <code>TRUE</code> if at the end of <code>I</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fone_005fbefore_005fend_005fp"></a>GIMPLE function: <em>bool</em> <strong>gsi_one_before_end_p</strong> <em>(gimple_stmt_iterator i)</em></dt>
<dd><p>Return <code>TRUE</code> if we&rsquo;re one statement before the end of <code>I</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fnext"></a>GIMPLE function: <em>void</em> <strong>gsi_next</strong> <em>(gimple_stmt_iterator *i)</em></dt>
<dd><p>Advance the iterator to the next gimple statement.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fprev"></a>GIMPLE function: <em>void</em> <strong>gsi_prev</strong> <em>(gimple_stmt_iterator *i)</em></dt>
<dd><p>Advance the iterator to the previous gimple statement.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fstmt"></a>GIMPLE function: <em>gimple</em> <strong>gsi_stmt</strong> <em>(gimple_stmt_iterator i)</em></dt>
<dd><p>Return the current stmt.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fafter_005flabels"></a>GIMPLE function: <em>gimple_stmt_iterator</em> <strong>gsi_after_labels</strong> <em>(basic_block bb)</em></dt>
<dd><p>Return a block statement iterator that points to the first
non-label statement in block <code>BB</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fstmt_005fptr"></a>GIMPLE function: <em>gimple *</em> <strong>gsi_stmt_ptr</strong> <em>(gimple_stmt_iterator *i)</em></dt>
<dd><p>Return a pointer to the current stmt.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fbb"></a>GIMPLE function: <em>basic_block</em> <strong>gsi_bb</strong> <em>(gimple_stmt_iterator i)</em></dt>
<dd><p>Return the basic block associated with this iterator.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fseq"></a>GIMPLE function: <em>gimple_seq</em> <strong>gsi_seq</strong> <em>(gimple_stmt_iterator i)</em></dt>
<dd><p>Return the sequence associated with this iterator.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fremove"></a>GIMPLE function: <em>void</em> <strong>gsi_remove</strong> <em>(gimple_stmt_iterator *i, bool remove_eh_info)</em></dt>
<dd><p>Remove the current stmt from the sequence.  The iterator is
updated to point to the next statement.  When <code>REMOVE_EH_INFO</code> is
true we remove the statement pointed to by iterator <code>I</code> from the <code>EH</code>
tables.  Otherwise we do not modify the <code>EH</code> tables.  Generally,
<code>REMOVE_EH_INFO</code> should be true when the statement is going to be
removed from the <code>IL</code> and not reinserted elsewhere.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005flink_005fseq_005fbefore"></a>GIMPLE function: <em>void</em> <strong>gsi_link_seq_before</strong> <em>(gimple_stmt_iterator *i, gimple_seq seq, enum gsi_iterator_update mode)</em></dt>
<dd><p>Links the sequence of statements <code>SEQ</code> before the statement pointed
by iterator <code>I</code>.  <code>MODE</code> indicates what to do with the iterator
after insertion (see <code>enum gsi_iterator_update</code> above).
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005flink_005fbefore"></a>GIMPLE function: <em>void</em> <strong>gsi_link_before</strong> <em>(gimple_stmt_iterator *i, gimple g, enum gsi_iterator_update mode)</em></dt>
<dd><p>Links statement <code>G</code> before the statement pointed-to by iterator <code>I</code>.
Updates iterator <code>I</code> according to <code>MODE</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005flink_005fseq_005fafter"></a>GIMPLE function: <em>void</em> <strong>gsi_link_seq_after</strong> <em>(gimple_stmt_iterator *i, gimple_seq seq, enum gsi_iterator_update mode)</em></dt>
<dd><p>Links sequence <code>SEQ</code> after the statement pointed-to by iterator <code>I</code>.
<code>MODE</code> is as in <code>gsi_insert_after</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005flink_005fafter"></a>GIMPLE function: <em>void</em> <strong>gsi_link_after</strong> <em>(gimple_stmt_iterator *i, gimple g, enum gsi_iterator_update mode)</em></dt>
<dd><p>Links statement <code>G</code> after the statement pointed-to by iterator <code>I</code>.
<code>MODE</code> is as in <code>gsi_insert_after</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fsplit_005fseq_005fafter"></a>GIMPLE function: <em>gimple_seq</em> <strong>gsi_split_seq_after</strong> <em>(gimple_stmt_iterator i)</em></dt>
<dd><p>Move all statements in the sequence after <code>I</code> to a new sequence.
Return this new sequence.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fsplit_005fseq_005fbefore"></a>GIMPLE function: <em>gimple_seq</em> <strong>gsi_split_seq_before</strong> <em>(gimple_stmt_iterator *i)</em></dt>
<dd><p>Move all statements in the sequence before <code>I</code> to a new sequence.
Return this new sequence.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005freplace"></a>GIMPLE function: <em>void</em> <strong>gsi_replace</strong> <em>(gimple_stmt_iterator *i, gimple stmt, bool update_eh_info)</em></dt>
<dd><p>Replace the statement pointed-to by <code>I</code> to <code>STMT</code>.  If <code>UPDATE_EH_INFO</code>
is true, the exception handling information of the original
statement is moved to the new statement.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005finsert_005fbefore"></a>GIMPLE function: <em>void</em> <strong>gsi_insert_before</strong> <em>(gimple_stmt_iterator *i, gimple stmt, enum gsi_iterator_update mode)</em></dt>
<dd><p>Insert statement <code>STMT</code> before the statement pointed-to by iterator
<code>I</code>, update <code>STMT</code>&rsquo;s basic block and scan it for new operands.  <code>MODE</code>
specifies how to update iterator <code>I</code> after insertion (see enum
<code>gsi_iterator_update</code>).
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005finsert_005fseq_005fbefore"></a>GIMPLE function: <em>void</em> <strong>gsi_insert_seq_before</strong> <em>(gimple_stmt_iterator *i, gimple_seq seq, enum gsi_iterator_update mode)</em></dt>
<dd><p>Like <code>gsi_insert_before</code>, but for all the statements in <code>SEQ</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005finsert_005fafter"></a>GIMPLE function: <em>void</em> <strong>gsi_insert_after</strong> <em>(gimple_stmt_iterator *i, gimple stmt, enum gsi_iterator_update mode)</em></dt>
<dd><p>Insert statement <code>STMT</code> after the statement pointed-to by iterator
<code>I</code>, update <code>STMT</code>&rsquo;s basic block and scan it for new operands.  <code>MODE</code>
specifies how to update iterator <code>I</code> after insertion (see enum
<code>gsi_iterator_update</code>).
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005finsert_005fseq_005fafter"></a>GIMPLE function: <em>void</em> <strong>gsi_insert_seq_after</strong> <em>(gimple_stmt_iterator *i, gimple_seq seq, enum gsi_iterator_update mode)</em></dt>
<dd><p>Like <code>gsi_insert_after</code>, but for all the statements in <code>SEQ</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005ffor_005fstmt"></a>GIMPLE function: <em>gimple_stmt_iterator</em> <strong>gsi_for_stmt</strong> <em>(gimple stmt)</em></dt>
<dd><p>Finds iterator for <code>STMT</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fmove_005fafter"></a>GIMPLE function: <em>void</em> <strong>gsi_move_after</strong> <em>(gimple_stmt_iterator *from, gimple_stmt_iterator *to)</em></dt>
<dd><p>Move the statement at <code>FROM</code> so it comes right after the statement
at <code>TO</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fmove_005fbefore"></a>GIMPLE function: <em>void</em> <strong>gsi_move_before</strong> <em>(gimple_stmt_iterator *from, gimple_stmt_iterator *to)</em></dt>
<dd><p>Move the statement at <code>FROM</code> so it comes right before the statement
at <code>TO</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fmove_005fto_005fbb_005fend"></a>GIMPLE function: <em>void</em> <strong>gsi_move_to_bb_end</strong> <em>(gimple_stmt_iterator *from, basic_block bb)</em></dt>
<dd><p>Move the statement at <code>FROM</code> to the end of basic block <code>BB</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005finsert_005fon_005fedge"></a>GIMPLE function: <em>void</em> <strong>gsi_insert_on_edge</strong> <em>(edge e, gimple stmt)</em></dt>
<dd><p>Add <code>STMT</code> to the pending list of edge <code>E</code>.  No actual insertion is
made until a call to <code>gsi_commit_edge_inserts</code>() is made.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005finsert_005fseq_005fon_005fedge"></a>GIMPLE function: <em>void</em> <strong>gsi_insert_seq_on_edge</strong> <em>(edge e, gimple_seq seq)</em></dt>
<dd><p>Add the sequence of statements in <code>SEQ</code> to the pending list of edge
<code>E</code>.  No actual insertion is made until a call to
<code>gsi_commit_edge_inserts</code>() is made.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005finsert_005fon_005fedge_005fimmediate"></a>GIMPLE function: <em>basic_block</em> <strong>gsi_insert_on_edge_immediate</strong> <em>(edge e, gimple stmt)</em></dt>
<dd><p>Similar to <code>gsi_insert_on_edge</code>+<code>gsi_commit_edge_inserts</code>.  If a new
block has to be created, it is returned.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fcommit_005fone_005fedge_005finsert"></a>GIMPLE function: <em>void</em> <strong>gsi_commit_one_edge_insert</strong> <em>(edge e, basic_block *new_bb)</em></dt>
<dd><p>Commit insertions pending at edge <code>E</code>.  If a new block is created,
set <code>NEW_BB</code> to this block, otherwise set it to <code>NULL</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsi_005fcommit_005fedge_005finserts"></a>GIMPLE function: <em>void</em> <strong>gsi_commit_edge_inserts</strong> <em>(void)</em></dt>
<dd><p>This routine will commit all pending edge insertions, creating
any new basic blocks which are necessary.
</p></dd></dl>


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Next: <a href="Adding-a-new-GIMPLE-statement-code.html#Adding-a-new-GIMPLE-statement-code" accesskey="n" rel="next">Adding a new GIMPLE statement code</a>, Previous: <a href="GIMPLE-sequences.html#GIMPLE-sequences" accesskey="p" rel="prev">GIMPLE sequences</a>, Up: <a href="GIMPLE.html#GIMPLE" accesskey="u" rel="up">GIMPLE</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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