https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106182
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot
gnu.org
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
This is a case where inner unswitched loops make one exit unconditional and one
never taken which means due to block loop ownership changes the outer loop
LC SSA is broken. I don't see how this is prevented for the non-virtual
operand case or how just including the set of blocks with changed loop depth
can properly
compute LC SSA in CFG cleanup repair_loop_structures.
Specifically gimple_merge_blocks propagation of virtual PHIs "breaks" things
here but there's no other way (also inserting an assignment will still have
broken LC SSA for regular defs there, and meanwhile the a->loop_father !=
b->loop_father test works on not up-to-date loop info).
The following fixes the ICE.
diff --git a/gcc/tree-cfgcleanup.cc b/gcc/tree-cfgcleanup.cc
index a6d0bf2c40a..b3aa6f92440 100644
--- a/gcc/tree-cfgcleanup.cc
+++ b/gcc/tree-cfgcleanup.cc
@@ -1169,25 +1169,18 @@ cleanup_tree_cfg_noloop (unsigned ssa_update_flags)
static void
repair_loop_structures (void)
{
- bitmap changed_bbs;
- unsigned n_new_loops;
-
calculate_dominance_info (CDI_DOMINATORS);
timevar_push (TV_REPAIR_LOOPS);
- changed_bbs = BITMAP_ALLOC (NULL);
- n_new_loops = fix_loop_structure (changed_bbs);
+ fix_loop_structure (NULL);
/* This usually does nothing. But sometimes parts of cfg that originally
were inside a loop get out of it due to edge removal (since they
become unreachable by back edges from latch). Also a former
- irreducible loop can become reducible - in this case force a full
- rewrite into loop-closed SSA form. */
+ irreducible loop can become reducible - in any case it's difficult
+ to restrict the rewrite to a set of affected blocks. */
if (loops_state_satisfies_p (LOOP_CLOSED_SSA))
- rewrite_into_loop_closed_ssa (n_new_loops ? NULL : changed_bbs,
- TODO_update_ssa);
-
- BITMAP_FREE (changed_bbs);
+ rewrite_into_loop_closed_ssa (NULL, 0);
checking_verify_loop_structure ();
scev_reset ();
