https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85455
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2018-04-19
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot
gnu.org
Target Milestone|--- |8.0
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
So we end up in
bool
cleanup_cfg (int mode)
{
...
with mode == 41 and
/* ??? We probably do this way too often. */
if (current_loops
&& (changed
|| (mode & CLEANUP_CFG_CHANGED)))
{
timevar_push (TV_REPAIR_LOOPS);
/* The above doesn't preserve dominance info if available. */
gcc_assert (!dom_info_available_p (CDI_DOMINATORS));
calculate_dominance_info (CDI_DOMINATORS);
fix_loop_structure (NULL);
free_dominance_info (CDI_DOMINATORS);
timevar_pop (TV_REPAIR_LOOPS);
}
here changed is false and mode doesn't include CLEANUP_CFG_CHANGED.
while (try_optimize_cfg (mode))
{
returns false here so changed isn't set but the call wrecks loop info.
That is because of
if (mode & (CLEANUP_CROSSJUMP | CLEANUP_THREADING))
clear_bb_flags ();
and
/* Bit mask for all basic block flags that must be preserved. These are
the bit masks that are *not* cleared by clear_bb_flags. */
#define BB_FLAGS_TO_PRESERVE \
(BB_DISABLE_SCHEDULE | BB_RTL | BB_NON_LOCAL_GOTO_TARGET \
| BB_HOT_PARTITION | BB_COLD_PARTITION)
which doesn't include loop related flags. This is a latent issue, certainly
not a regression in general(?), a fix could be
Index: gcc/cfg.c
===================================================================
--- gcc/cfg.c (revision 259486)
+++ gcc/cfg.c (working copy)
@@ -386,9 +386,13 @@ void
clear_bb_flags (void)
{
basic_block bb;
+ int flags_to_preserve = BB_FLAGS_TO_PRESERVE;
+ if (current_loops
+ && loops_state_satisfies_p (cfun,
LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS))
+ flags_to_preserve |= BB_IRREDUCIBLE_LOOP;
FOR_ALL_BB_FN (bb, cfun)
- bb->flags &= BB_FLAGS_TO_PRESERVE;
+ bb->flags &= flags_to_preserve;
}
/* Check the consistency of profile information. We can't do that
