This patch extends verify_loop_structure by checking that header's
are really its own headers (this proved as useful in PR56181).
The bulk of the code is taken from flow_loops_find.
Bootstrapped on x86_64 linux. The only fallout now is (for C/C++):
FAIL: gcc.dg/torture/pr54458.c -O3 -fomit-frame-pointer (internal compiler
error)
FAIL: gcc.dg/torture/pr54458.c -O3 -fomit-frame-pointer (test for excess
errors)
FAIL: gcc.dg/torture/pr54458.c -O3 -fomit-frame-pointer -funroll-loops
(internal compiler error)
FAIL: gcc.dg/torture/pr54458.c -O3 -fomit-frame-pointer -funroll-loops (test
for excess errors)
FAIL: gcc.dg/torture/pr54458.c -O3 -fomit-frame-pointer -funroll-all-loops
-finline-functions (internal compiler error)
FAIL: gcc.dg/torture/pr54458.c -O3 -fomit-frame-pointer -funroll-all-loops
-finline-functions (test for excess errors)
FAIL: gcc.dg/torture/pr54458.c -O3 -g (internal compiler error)
FAIL: gcc.dg/torture/pr54458.c -O3 -g (test for excess errors)
which is only because -O3 means -funswitch-loops as well. What happens
here is quite interesting situation, we have three analogical loops
which look like below. BB7 is marked as IRREDUCIBLE_LOOP.
|
+---------------+ |
| | |
| +---+-+-+
| | 6 |
| +---+---+
| | ---|
| | -----/ |
| +-----/-+ |
| | 7 | |
| +-------+ |
| / \ |
| / \ |
| +------+ +------+ |
| | 9 | | 8 | |
| +--+---+ +---+--+ |
| | | |
| | +-------+
| +-------+
| | 10 |
| +---+---+
| |
+-------+
Thus, we basically have two headers in a loop.
So, shall I skip the BB_IRREDUCIBLE_LOOP blocks? (Although this leads to
another crash: we get into the same situation in another pass, just
the BB isn't marked as BB_IRREDUCIBLE_LOOP, so we don't skip it. Perhaps
this could be sorted out by just calling mark_irreducible_loops somewhere.)
Comments?
2013-02-06 Marek Polacek <pola...@redhat.com>
* cfgloop.c (verify_loop_structure): Check that header
BBs are really its own headers.
--- gcc/cfgloop.c.mp 2013-02-06 12:08:01.536918761 +0100
+++ gcc/cfgloop.c 2013-02-06 18:32:59.957027313 +0100
@@ -1316,6 +1316,41 @@ verify_loop_structure (void)
else
verify_dominators (CDI_DOMINATORS);
+ /* Check the loop headers. */
+ FOR_EACH_BB (bb)
+ {
+ edge_iterator ei;
+
+ /* If we have an abnormal predecessor, do not consider the
+ loop (not worth the problems). */
+ if (bb_has_abnormal_pred (bb))
+ continue;
+
+ if (bb->loop_father == current_loops->tree_root)
+ continue;
+
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ {
+ basic_block latch = e->src;
+
+ gcc_assert (!(e->flags & EDGE_ABNORMAL));
+
+ /* Look for back edges where a predecessor is dominated
+ by this block. A natural loop has a single entry
+ node (header) that dominates all the nodes in the
+ loop. It also has single back edge to the header
+ from a latch node. */
+ if (latch != ENTRY_BLOCK_PTR
+ && bb != latch
+ && dominated_by_p (CDI_DOMINATORS, latch, bb))
+ if (bb->loop_father->header != bb)
+ {
+ error ("header %d is not its own header", bb->index);
+ err = 1;
+ }
+ }
+ }
+
/* Check sizes. */
sizes = XCNEWVEC (unsigned, num);
sizes[0] = 2;
Marek
