On 13-02-14 5:00 PM, Steven Bosscher wrote:
Hello Vlad,
Back in October, you added a patch to remove extra clobbers introduced by LRA:
http://gcc.gnu.org/ml/gcc-patches/2012-10/msg02531.html
This also disables some -frename-registers opportunities (a few 100 on
x86-64 for my collection of cc1-i files).
Do you think it's be possible (and worth the effort) to implement
something that keeps clobbers for registers that are live above the
clobber after removing the clobber?
I think # of missed opportunities you mentioned is enough reason to do
this. Although I don't know what final improvement/ compilation speed
will be at the end, In any case we can provide an option for this or
make it by default for -O3 and above. I might be wrong but I guess it
is mostly for 32-bit x86 with fp regs for now. It is hard for me to say
is it worth to spend your time for this dying architecture. Although it
can be useful for other architectures too. It is up to you. I believe
we could add this code to GCC anyway.
