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<h3 class="section">11.10 Sequence iterators</h3>
<p><a name="index-Sequence-iterators-2465"></a>
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:
<pre class="smallexample"> gimple_stmt_iterator gsi;
for (gsi = gsi_start (seq); !gsi_end_p (gsi); gsi_next (&gsi))
{
gimple g = gsi_stmt (gsi);
/* Do something with gimple statement <code>G</code>. */
}
</pre>
<p>Backward iterations are possible:
<pre class="smallexample"> for (gsi = gsi_last (seq); !gsi_end_p (gsi); gsi_prev (&gsi))
</pre>
<p>Forward and backward iterations on basic blocks are possible with
<code>gsi_start_bb</code> and <code>gsi_last_bb</code>.
<p>In the documentation below we sometimes refer to enum
<code>gsi_iterator_update</code>. The valid options for this enumeration are:
<ul>
<li><code>GSI_NEW_STMT</code>
Only valid when a single statement is added. Move the iterator to it.
<li><code>GSI_SAME_STMT</code>
Leave the iterator at the same statement.
<li><code>GSI_CONTINUE_LINKING</code>
Move iterator to whatever position is suitable for linking other
statements in the same direction.
</ul>
<p>Below is a list of the functions used to manipulate and use
statement iterators.
<div class="defun">
— GIMPLE function: gimple_stmt_iterator <b>gsi_start</b> (<var>gimple_seq seq</var>)<var><a name="index-gsi_005fstart-2466"></a></var><br>
<blockquote><p>Return a new iterator pointing to the sequence <code>SEQ</code>'s first
statement. If <code>SEQ</code> is empty, the iterator'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></blockquote></div>
<div class="defun">
— GIMPLE function: gimple_stmt_iterator <b>gsi_start_bb</b> (<var>basic_block bb</var>)<var><a name="index-gsi_005fstart_005fbb-2467"></a></var><br>
<blockquote><p>Return a new iterator pointing to the first statement in basic
block <code>BB</code>.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: gimple_stmt_iterator <b>gsi_last</b> (<var>gimple_seq seq</var>)<var><a name="index-gsi_005flast-2468"></a></var><br>
<blockquote><p>Return a new iterator initially pointing to the last statement of
sequence <code>SEQ</code>. If <code>SEQ</code> is empty, the iterator'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></blockquote></div>
<div class="defun">
— GIMPLE function: gimple_stmt_iterator <b>gsi_last_bb</b> (<var>basic_block bb</var>)<var><a name="index-gsi_005flast_005fbb-2469"></a></var><br>
<blockquote><p>Return a new iterator pointing to the last statement in basic
block <code>BB</code>.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: bool <b>gsi_end_p</b> (<var>gimple_stmt_iterator i</var>)<var><a name="index-gsi_005fend_005fp-2470"></a></var><br>
<blockquote><p>Return <code>TRUE</code> if at the end of <code>I</code>.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: bool <b>gsi_one_before_end_p</b> (<var>gimple_stmt_iterator i</var>)<var><a name="index-gsi_005fone_005fbefore_005fend_005fp-2471"></a></var><br>
<blockquote><p>Return <code>TRUE</code> if we're one statement before the end of <code>I</code>.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_next</b> (<var>gimple_stmt_iterator *i</var>)<var><a name="index-gsi_005fnext-2472"></a></var><br>
<blockquote><p>Advance the iterator to the next gimple statement.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_prev</b> (<var>gimple_stmt_iterator *i</var>)<var><a name="index-gsi_005fprev-2473"></a></var><br>
<blockquote><p>Advance the iterator to the previous gimple statement.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: gimple <b>gsi_stmt</b> (<var>gimple_stmt_iterator i</var>)<var><a name="index-gsi_005fstmt-2474"></a></var><br>
<blockquote><p>Return the current stmt.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: gimple_stmt_iterator <b>gsi_after_labels</b> (<var>basic_block bb</var>)<var><a name="index-gsi_005fafter_005flabels-2475"></a></var><br>
<blockquote><p>Return a block statement iterator that points to the first
non-label statement in block <code>BB</code>.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: gimple * <b>gsi_stmt_ptr</b> (<var>gimple_stmt_iterator *i</var>)<var><a name="index-gsi_005fstmt_005fptr-2476"></a></var><br>
<blockquote><p>Return a pointer to the current stmt.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: basic_block <b>gsi_bb</b> (<var>gimple_stmt_iterator i</var>)<var><a name="index-gsi_005fbb-2477"></a></var><br>
<blockquote><p>Return the basic block associated with this iterator.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: gimple_seq <b>gsi_seq</b> (<var>gimple_stmt_iterator i</var>)<var><a name="index-gsi_005fseq-2478"></a></var><br>
<blockquote><p>Return the sequence associated with this iterator.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_remove</b> (<var>gimple_stmt_iterator *i, bool remove_eh_info</var>)<var><a name="index-gsi_005fremove-2479"></a></var><br>
<blockquote><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></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_link_seq_before</b> (<var>gimple_stmt_iterator *i, gimple_seq seq, enum gsi_iterator_update mode</var>)<var><a name="index-gsi_005flink_005fseq_005fbefore-2480"></a></var><br>
<blockquote><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></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_link_before</b> (<var>gimple_stmt_iterator *i, gimple g, enum gsi_iterator_update mode</var>)<var><a name="index-gsi_005flink_005fbefore-2481"></a></var><br>
<blockquote><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></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_link_seq_after</b> (<var>gimple_stmt_iterator *i, gimple_seq seq, enum gsi_iterator_update mode</var>)<var><a name="index-gsi_005flink_005fseq_005fafter-2482"></a></var><br>
<blockquote><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></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_link_after</b> (<var>gimple_stmt_iterator *i, gimple g, enum gsi_iterator_update mode</var>)<var><a name="index-gsi_005flink_005fafter-2483"></a></var><br>
<blockquote><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></blockquote></div>
<div class="defun">
— GIMPLE function: gimple_seq <b>gsi_split_seq_after</b> (<var>gimple_stmt_iterator i</var>)<var><a name="index-gsi_005fsplit_005fseq_005fafter-2484"></a></var><br>
<blockquote><p>Move all statements in the sequence after <code>I</code> to a new sequence.
Return this new sequence.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: gimple_seq <b>gsi_split_seq_before</b> (<var>gimple_stmt_iterator *i</var>)<var><a name="index-gsi_005fsplit_005fseq_005fbefore-2485"></a></var><br>
<blockquote><p>Move all statements in the sequence before <code>I</code> to a new sequence.
Return this new sequence.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_replace</b> (<var>gimple_stmt_iterator *i, gimple stmt, bool update_eh_info</var>)<var><a name="index-gsi_005freplace-2486"></a></var><br>
<blockquote><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></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_insert_before</b> (<var>gimple_stmt_iterator *i, gimple stmt, enum gsi_iterator_update mode</var>)<var><a name="index-gsi_005finsert_005fbefore-2487"></a></var><br>
<blockquote><p>Insert statement <code>STMT</code> before the statement pointed-to by iterator
<code>I</code>, update <code>STMT</code>'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></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_insert_seq_before</b> (<var>gimple_stmt_iterator *i, gimple_seq seq, enum gsi_iterator_update mode</var>)<var><a name="index-gsi_005finsert_005fseq_005fbefore-2488"></a></var><br>
<blockquote><p>Like <code>gsi_insert_before</code>, but for all the statements in <code>SEQ</code>.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_insert_after</b> (<var>gimple_stmt_iterator *i, gimple stmt, enum gsi_iterator_update mode</var>)<var><a name="index-gsi_005finsert_005fafter-2489"></a></var><br>
<blockquote><p>Insert statement <code>STMT</code> after the statement pointed-to by iterator
<code>I</code>, update <code>STMT</code>'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></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_insert_seq_after</b> (<var>gimple_stmt_iterator *i, gimple_seq seq, enum gsi_iterator_update mode</var>)<var><a name="index-gsi_005finsert_005fseq_005fafter-2490"></a></var><br>
<blockquote><p>Like <code>gsi_insert_after</code>, but for all the statements in <code>SEQ</code>.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: gimple_stmt_iterator <b>gsi_for_stmt</b> (<var>gimple stmt</var>)<var><a name="index-gsi_005ffor_005fstmt-2491"></a></var><br>
<blockquote><p>Finds iterator for <code>STMT</code>.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_move_after</b> (<var>gimple_stmt_iterator *from, gimple_stmt_iterator *to</var>)<var><a name="index-gsi_005fmove_005fafter-2492"></a></var><br>
<blockquote><p>Move the statement at <code>FROM</code> so it comes right after the statement
at <code>TO</code>.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_move_before</b> (<var>gimple_stmt_iterator *from, gimple_stmt_iterator *to</var>)<var><a name="index-gsi_005fmove_005fbefore-2493"></a></var><br>
<blockquote><p>Move the statement at <code>FROM</code> so it comes right before the statement
at <code>TO</code>.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_move_to_bb_end</b> (<var>gimple_stmt_iterator *from, basic_block bb</var>)<var><a name="index-gsi_005fmove_005fto_005fbb_005fend-2494"></a></var><br>
<blockquote><p>Move the statement at <code>FROM</code> to the end of basic block <code>BB</code>.
</p></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_insert_on_edge</b> (<var>edge e, gimple stmt</var>)<var><a name="index-gsi_005finsert_005fon_005fedge-2495"></a></var><br>
<blockquote><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></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_insert_seq_on_edge</b> (<var>edge e, gimple_seq seq</var>)<var><a name="index-gsi_005finsert_005fseq_005fon_005fedge-2496"></a></var><br>
<blockquote><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></blockquote></div>
<div class="defun">
— GIMPLE function: basic_block <b>gsi_insert_on_edge_immediate</b> (<var>edge e, gimple stmt</var>)<var><a name="index-gsi_005finsert_005fon_005fedge_005fimmediate-2497"></a></var><br>
<blockquote><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></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_commit_one_edge_insert</b> (<var>edge e, basic_block *new_bb</var>)<var><a name="index-gsi_005fcommit_005fone_005fedge_005finsert-2498"></a></var><br>
<blockquote><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></blockquote></div>
<div class="defun">
— GIMPLE function: void <b>gsi_commit_edge_inserts</b> (<var>void</var>)<var><a name="index-gsi_005fcommit_005fedge_005finserts-2499"></a></var><br>
<blockquote><p>This routine will commit all pending edge insertions, creating
any new basic blocks which are necessary.
</p></blockquote></div>
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