[Bug tree-optimization/63185] Improve DSE with branches

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63185

--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #1)
> Hm?  The PHI does post-dominate the memset.  I think you run into another
> check, namely we visited the call already (temp != NULL).

Oups... The original testcase was failing because a PHI didn't post-dominate,
and I wasn't very careful when reducing. Bah, the issue seems close enough...