https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68911
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
This goes wrong during vrp1.
Analyzing # of iterations of loop 2
exit condition [e_6, + , 1] <= 93
bounds on difference of bases: -4294967202 ... 93
result:
zero if e_6 > 94
# of iterations 94 - e_6, bounded by 94
looks wrong to me, e_6 as well as the additions and comparison are performed in
unsigned type, therefore 94 - e_6 is I believe not bounded by 94. The value
ranges for e_6 clearly allow (and in the testcase are) some very large unsigned
numbers, so 94 - e_6. If assuming the value of f is arbitrary (it is not),
then the possible values of e before entering the
while (e < 94)
e++;
loop are either 2, 94, 0xffffffffU or 0xfffffffeU (of course f is not arbitrary
and as b and d are both 0, it will be actually 0xffffffffU each time.
But from those 4 numbers the number of iterations would be bound by 96.
