[Bug middle-end/107709] IVOPTs is introducing a non-zero assumption

[amacleod at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107709

--- Comment #2 from Andrew Macleod <amacleod at redhat dot com> ---
(In reply to Richard Biener from comment #1)
> IVOPTs is usually quite careful with this and the infer of non-NULL from
> ptr + CST is new - that introduced a new undefinedness in GIMPLE.  The
> workaround would be to avoid the POINTER_PLUS_EXPR here and perform the
> increment in an unsigned type.
> 
> 
> Now, do we really want to introduce this new undefined behavior without
> seriously auditing the code base?

I think not. I will defer the inferred range code until next release to give us
a chance to sort this kind of thing out. I will attach the patch to PR 78655,
which when it is applied triggers the bug.  That way it is easy to at least
find this one..  I can probably even attach an executable test to this PR that,
when combined with that patch, will fail.  I think :-)