http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54767
--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-01-15
10:47:36 UTC ---
Yeah, indeed. The bug seems to be in the second vrp pass on xxx function.
iaii_23: [_79, _79] EQUIVALENCES: { } (0 elements)
looks wrong (iaii_23 is only conditionally equal to _79 (in the first iteration
that sets iaii, i.e. ia = 2, second iteration), it can be the value from
previous cycle too (in the ia = 3, third iteration).
This then leads to
_35 = prephitmp_50 - iaii_23;
being
_35: [0, 0]
(again, wrong) and that is why we end up with 1 instead of 2 in the second row.
There is:
Visiting PHI node: iaii_23 = PHI <iaii_1(11), prephitmp_50(10)>
Argument #0 (11 -> 12 not executable)
Argument #1 (10 -> 12 executable)
prephitmp_50
Value: [_79, _79] EQUIVALENCES: { _79 } (1 elements)
Found new range for iaii_23: [_79, _79]
which is wrong, but not sure if this is the first spot in the dump. iaii_1
here is only conditionally UNDEFINED, it might be iaii value from previous
iteration too.
