[Bug tree-optimization/63445] [5 Regression] request: make -Wstrict-overflow avoid a class of false positives

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63445

--- Comment #7 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> The range of n_7 is suboptimal and the test on _6 can be eliminated.

The previous enhancement was apparently:

2010-04-06  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/43627
        * tree-vrp.c (extract_range_from_unary_expr): Widenings
        of [1, +INF(OVF)] go to [1, +INF(OVF)] of the wider type,
        not varying.

but it didn't go far enough for this case.