[Bug middle-end/59119] Segfault in -fisolate-erroneous-paths pass

[law at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59119

--- Comment #2 from Jeffrey A. Law <law at redhat dot com> ---
Ah nuts.

While pondering this a bit more, I realized we have the same problem in this
code that we do in DOM.   Namely that we can have references to SSA_NAMEs that
have been released to the name manager in blocks that become unreachable. 
That's fine except that we're also creating new SSA_NAMEs which is strictly
verboten if there are still references to released names in the IL.

I'm going to have to ponder this a bit more.