https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57193
Bernd Schmidt <bernds at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |bernds at gcc dot gnu.org
--- Comment #9 from Bernd Schmidt <bernds at gcc dot gnu.org> ---
It looks like the situation is as follows (X is the LRA-created reload reg)
X = a
op on X
b = X
where a and b are different registers already allocated by IRA, hence we can
avoid one copy at most. I'm not very familiar with LRA yet, but I see no code
to rethink such register allocation choices.
-frename-registers gets rid of one unnecessary copy, it was enhanced to detect
such situations for gcc-6. Maybe we should finally enable that for -O2 and
higher?
