https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68963
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 #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
static bool
idx_infer_loop_bounds (tree base, tree *idx, void *dta)
{
...
/* If access is not executed on every iteration, we must ensure that overlow
may
not make the access valid later. */
if (!dominated_by_p (CDI_DOMINATORS, loop->latch, gimple_bb (data->stmt))
&& scev_probably_wraps_p (initial_condition_in_loop_num (ev, loop->num),
step, data->stmt, loop, true))
reliable = false;
record_nonwrapping_iv (loop, init, step, data->stmt, low, high, reliable,
upper);
return true;
I think we simply cannot make a bound from a not always executing array ref
reliable, even if the IV doesn't wrap. And of course the above fails to reset
'upper'.
Testing
Index: gcc/tree-ssa-loop-niter.c
===================================================================
--- gcc/tree-ssa-loop-niter.c (revision 233598)
+++ gcc/tree-ssa-loop-niter.c (working copy)
@@ -3183,14 +3183,18 @@ idx_infer_loop_bounds (tree base, tree *
&& tree_int_cst_compare (next, high) <= 0)
return true;
- /* If access is not executed on every iteration, we must ensure that overlow
may
- not make the access valid later. */
- if (!dominated_by_p (CDI_DOMINATORS, loop->latch, gimple_bb (data->stmt))
- && scev_probably_wraps_p (initial_condition_in_loop_num (ev, loop->num),
- step, data->stmt, loop, true))
+ /* If access is not executed on every iteration we cannot derive any
+ upper bound. */
+ if (!dominated_by_p (CDI_DOMINATORS, loop->latch, gimple_bb (data->stmt)))
+ upper = false;
+ /* If the IV of the access may wrap then the array size is not good for
+ an estimate either. */
+ if (scev_probably_wraps_p (initial_condition_in_loop_num (ev, loop->num),
+ step, data->stmt, loop, true))
reliable = false;
- record_nonwrapping_iv (loop, init, step, data->stmt, low, high, reliable,
upper);
+ record_nonwrapping_iv (loop, init, step, data->stmt, low, high,
+ reliable, upper);
return true;
}
