On Tue, Jun 14, 2011 at 12:13:47PM +0200, Richard Guenther wrote:
> On Tue, Jun 14, 2011 at 1:59 AM, Fang, Changpeng <changpeng.f...@amd.com>
> wrote:
> > The patch ( http://gcc.gnu.org/ml/gcc-patches/2011-02/txt00059.txt ) which
> > introduces splitting avx256 unaligned loads.
> > However, we found that it causes significant regressions for cpu2006 (
> > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49089 ).
> >
> > In this work, we introduce a tune option that sets splitting unaligned
> > loads default only for such CPUs that such splitting
> > is beneficial.
> >
> > The patch passed bootstrapping and regression tests on
> > x86_64-unknown-linux-gnu system.
> >
> > Is it OK to commit?
>
> It probably should go to the 4.6 branch as well. Note that I find the
> X86_TUNE_AVX256_SPLIT_UNALIGNED_LOAD_OPTIMAL odd,
> why not call it simply X86_TUNE_AVX256_SPLIT_UNALIGNED_LOAD?
I also wonder what we should do for -mtune=generic. Should we split or not?
How big improvement is it on Intel chips, how big degradation does it
cause on AMD chips (I assume no other chip maker currently supports AVX)?
Jakub
