https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112282
avieira at gcc dot gnu.org changed:
What |Removed |Added
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CC| |avieira at gcc dot gnu.org
--- Comment #9 from avieira at gcc dot gnu.org ---
So I had a look at this and this is as far as I got.
It seems to get stuck in the 'for (u = -22; u < 2; ++u)' loop. It looks like
the loop IV never gets updated and it keeps looping.
Looking at the codegen it seems that cunroll decides to remove A LOT of code
and there is now:
bb 4:
..
# ivtmp_1055 = PHI <ivtmp_1056(24), 24(2)>
..
bb 24:
...
ivtmp_1056 = ivtmp_1055 - 1;
goto <bb 4>; [100.00%]
I've not yet been able to figure out why this happens, the dumps weren't very
helpful. So I tried -fdisable-tree-cunroll, it was still failing. So I looked
at the dumps to try and see what was turning this loop into an infinite loop
and vrp2 shows me:
Global Exported: _19 = [irange] int [-21, 0]
Folding predicate _19 != 2 to 1
and in the dump before vrp2 we see:
<bb 4> [local count: 7354175]:
# u.13_485 = PHI <_19(105), -22(3)>
# u_lsm.72_510 = PHI <_19(105), _497(D)(3)>
# u_lsm_flag.73_235 = PHI <1(105), 0(3)>
...
<bb 27> [local count: 6634488]:
al ={v} {CLOBBER(eol)};
_19 = u.13_485 + 1;
if (_19 != 2)
goto <bb 105>; [96.34%]
else
goto <bb 28>; [3.66%]
<bb 105> [local count: 6391666]:
goto <bb 4>; [100.00%]
Something to point out here, that u_lsm.72_510 seems odd. It is used to set
global 'u', but its initialized with _497(D) which is undefined... So that
itself seems wrong to me too... I'll try and find out what's causing that
codegen next. Maybe that can explain why the irange for _19 is so wrong here.
