Question regarding "patch to remove temporary clobbers in LRA"

[Vladimir Makarov]

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.