https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64164
--- Comment #24 from Jeffrey A. Law <law at redhat dot com> --- Integrating uncprop and out-of-ssa certainly crossed my mind when I wrote that comment :-) Or at least arranging to build the life info/conflict stuff once and have it shared. A poor man's version is to note the path for the equivalence and see if any of the blocks on that path define the other PHI arguments. That ought to be fast and simple enough to possibly include in gcc5.
