Hi,
In verify_loop_structure, we stop checking the latch once we find that
it's NULL.
This patch tries a bit harder:
- if !LOOPS_MAY_HAVE_MULTIPLE_LATCHES, we don't allow a NULL latch
- if LOOPS_MAY_HAVE_MULTIPLE_LATCHES, we check that indeed there's no
single loop latch.
As a consequence of adding this check, I needed to fix
expand_omp_for_generic, which missed an initialization of a loop latch.
Bootstrapped and reg-tested on x86_64.
OK for stage3 trunk?
Thanks,
- Tom
Check NULL loop->latch in verify_loop_structure
2015-11-22 Tom de Vries <t...@codesourcery.com>
* cfgloop.c (find_single_latch): New function, factored out of ...
(flow_loops_find): ... here.
(verify_loop_structure): Verify validity of a NULL loop->latch.
* cfgloop.h (find_single_latch): Declare.
* omp-low.c (expand_omp_for_generic): Initialize latch of orig_loop.
---
gcc/cfgloop.c | 65 +++++++++++++++++++++++++++++++++++++++++------------------
gcc/cfgloop.h | 1 +
gcc/omp-low.c | 1 +
3 files changed, 47 insertions(+), 20 deletions(-)
diff --git a/gcc/cfgloop.c b/gcc/cfgloop.c
index bf00e0e..b610860 100644
--- a/gcc/cfgloop.c
+++ b/gcc/cfgloop.c
@@ -388,6 +388,33 @@ bb_loop_header_p (basic_block header)
return false;
}
+/* Return the latch block for this header block, if it has just a single one.
+ Otherwise, return NULL. */
+
+basic_block
+find_single_latch (struct loop* loop)
+{
+ basic_block header = loop->header;
+ edge_iterator ei;
+ edge e;
+ basic_block latch = NULL;
+
+ FOR_EACH_EDGE (e, ei, header->preds)
+ {
+ basic_block cand = e->src;
+ if (!flow_bb_inside_loop_p (loop, cand))
+ continue;
+
+ if (latch != NULL)
+ /* More than one latch edge. */
+ return NULL;
+
+ latch = cand;
+ }
+
+ return latch;
+}
+
/* Find all the natural loops in the function and save in LOOPS structure and
recalculate loop_father information in basic block structures.
If LOOPS is non-NULL then the loop structures for already recorded loops
@@ -482,29 +509,10 @@ flow_loops_find (struct loops *loops)
{
struct loop *loop = larray[i];
basic_block header = loop->header;
- edge_iterator ei;
- edge e;
flow_loop_tree_node_add (header->loop_father, loop);
loop->num_nodes = flow_loop_nodes_find (loop->header, loop);
-
- /* Look for the latch for this header block, if it has just a
- single one. */
- FOR_EACH_EDGE (e, ei, header->preds)
- {
- basic_block latch = e->src;
-
- if (flow_bb_inside_loop_p (loop, latch))
- {
- if (loop->latch != NULL)
- {
- /* More than one latch edge. */
- loop->latch = NULL;
- break;
- }
- loop->latch = latch;
- }
- }
+ loop->latch = find_single_latch (loop);
}
return loops;
@@ -1440,6 +1448,23 @@ verify_loop_structure (void)
err = 1;
}
}
+ else
+ {
+ if (loops_state_satisfies_p (LOOPS_MAY_HAVE_MULTIPLE_LATCHES))
+ {
+ if (find_single_latch (loop) != NULL)
+ {
+ error ("loop %d%'s latch is missing", i);
+ err = 1;
+ }
+ }
+ else
+ {
+ error ("loop %d%'s latch is missing, and loops may not have"
+ " multiple latches", i);
+ err = 1;
+ }
+ }
if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES))
{
if (!single_succ_p (loop->latch))
diff --git a/gcc/cfgloop.h b/gcc/cfgloop.h
index ee73bf9..7faf591 100644
--- a/gcc/cfgloop.h
+++ b/gcc/cfgloop.h
@@ -270,6 +270,7 @@ bool mark_irreducible_loops (void);
void release_recorded_exits (function *);
void record_loop_exits (void);
void rescan_loop_exit (edge, bool, bool);
+basic_block find_single_latch (struct loop*);
/* Loop data structure manipulation/querying. */
extern void flow_loop_tree_node_add (struct loop *, struct loop *);
diff --git a/gcc/omp-low.c b/gcc/omp-low.c
index b47864e..00e314d6 100644
--- a/gcc/omp-low.c
+++ b/gcc/omp-low.c
@@ -8900,6 +8900,7 @@ expand_omp_for_generic (struct omp_region *region,
orig_loop->header = l1_bb;
/* The loop may have multiple latches. */
add_loop (orig_loop, new_loop);
+ orig_loop->latch = find_single_latch (orig_loop);
}
}
}
