[Bug middle-end/89501] Odd lack of warning about missing initialization

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89501

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jeffrey A. Law from comment #3)
> Yup.  It's the same as 18501.  We meet UNDEFINED and [0,0] resulting in
> [0,0] and nothing ever causes reevaluation of the PHI.  Things are working
> as "expected".    

And this meeting helps us avoid bogus warnings for cases where GCC has
difficulties proving dead code paths are actually dead ...  In fact
to preserve uninit warnings we avoid doing the same things for copies,
thus when meeting [i, i] with UNDEFINED which in fact causes some
false positives to appear...  (and with my
GCC-is-an-optimizing-compiler-not-a-static-analysis-tool hat on I'd wanted to
change that more than once,
but testsuite regressions prevented me from doing that)

Uninit warnings are hard ;)