[Bug middle-end/104986] [12 Regression] bogus writing 1 byte into a region of size 0 with -fwrapv and -O2 -fpeel-loops since r12-4698-gf6d012338bf87f42

[aldyh at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104986

--- Comment #6 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Aldy Hernandez from comment #4)
> (In reply to Richard Biener from comment #3)
> > This is peeling leaving us with unreachable code we warn on and somehow
> > while figuring prephitmp_30 + -6 is -1 we don't figure nb_58 is zero on
> > the path to bb9.
> > 
> > I think I've seen this backward-forward dependency issue with ranger before
> > in another missed optimization PR.
> 
> This is not ranger, but the legacy conditional folding in vr-values.  It's
> the test_for_singularity() code that turns x<=0 where x is [0,6] into x!=0.

Ooops, sorry I totally missed Richi's comment on prephitmp.  I see Andrew
answered though :).