[Bug rtl-optimization/54300] [4.7, 4.8, 4.9 Regression] regcprop incorrectly looks through parallel register swap operation

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54300

--- Comment #12 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> Hmm, interesting.  Perhaps single_set should not do this if the dead set
> clobbers an input.

Yes, that seems to be a sensible proposal, but single_set is an old thing.