https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83403
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2017-12-13
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot
gnu.org
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
LIM has difficulties in disambiguating the 10 C[] refs against each other,
restrict doesn't help here. LIM uses its own dependence code, not relying on
the data-dependence framework.
An issue might be that we can't expand (long unsigned int) (_286 + 1) further
in affine combination speak but we do expand (long unsigned int) (_286).
This results in
/* The expansion of addresses may be a bit expensive, thus we only do
the check at -O2 and higher optimization levels. */
if (optimize < 2)
return true;
get_inner_reference_aff (mem1->mem.ref, &off1, &size1);
get_inner_reference_aff (mem2->mem.ref, &off2, &size2);
aff_combination_expand (&off1, ttae_cache);
aff_combination_expand (&off2, ttae_cache);
aff_combination_scale (&off1, -1);
aff_combination_add (&off2, &off1);
if (aff_comb_cannot_overlap_p (&off2, size1, size2))
return false;
ending up with
1603 if (aff_comb_cannot_overlap_p (&off2, size1, size2))
(gdb) p debug_aff (&off2)
{
type = sizetype
offset = 0
elements = {
[0] = (long unsigned int) (_286 + 1) * 8,
[1] = (long unsigned int) (l_n_70 * 10) *
0xfffffffffffffffffffffffffffffffffffffffffffffff8
}
}
where _286 is the definition of l_n_70 * 10.
Note that also SCEV / data-ref analysis doesn't see the consecutive accesses,
likely because of the similar issue of the addresses being of the form
*(&C + (long unsigned int)((l_n_70 * 10) + l_m) * 8)
where there is possible wrapping in the l_n_70 * 10 + l_m computation in
unsigned int type. loop bounds of course make it obvious this isn't the
case.
Let me see if I can cook up sth with a patch I have lying around providing
sth like get_range_info () for GENERIC exprs. That way we could enhance
chrec_convert (and also affine_comb_expand).
