https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63445
--- Comment #6 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> Found new range for j_9: [i_15 + 1, +INF]
>
> Visiting statement:
> _6 = j_9 - i_15;
> Found new range for _6: [1, +INF(OVF)]
>
> i_15 could be negative and thus j_9 - i_15 could well overflow the input
> range at the +INF side. (i_15 is [-INF, j_5(D) + -1])
Yes, the range is as expected here but...
> I believe we are just better in propagating the ranges here and 4.9
> computed _6 as VARYING (and thus not applying the optimization).
...we actually don't apply any optimization to the code:
Value ranges after VRP:
n_1: [1, +INF] EQUIVALENCES: { n_7 c_8 n_16 } (3 elements)
_2: [1, +INF] EQUIVALENCES: { n_7 n_16 } (2 elements)
pretmp_3: ~[0, 0]
i_4(D): VARYING
j_5(D): VARYING
_6: [1, +INF(OVF)]
n_7: [0, +INF]
[...]
<bb 2>:
if (i_4(D) < j_5(D))
goto <bb 3>;
else
goto <bb 7>;
<bb 3>:
_6 = j_5(D) - i_4(D);
n_7 = (unsigned int) _6;
if (_6 != 0)
goto <bb 4>;
else
goto <bb 7>;
The range of n_7 is suboptimal and the test on _6 can be eliminated.
