[LLVMdev] Contributing the Apple ARM64 compiler backend

Manjunath N
Tue, 24 Jun 2014 09:45:16 -0000

Eric Christopher <echristo <at> gmail.com> writes:

>
> > The big pain issues I see merging from ARM64 to AArch64 are:
> > 1.      Apple have created a fairly complete scheduling model already
for
> > ARM64, and we'd have to merge the partial? model in AArch64 and
theirs.
We
> > risk regressing performance on Apple's targets here, and we
can't
determine
> > ourselves whether we have or not. This is not ideal.
> > 2.      Porting over the DAG-to-DAG optimizations and any other
> > optimizations that rely on the tablegen layout will be very tricky.
> > 3.      The conditional compare pass is fairly comprehensive -
we'd have
to
> > port that over or rewrite it and that would be a lot of work.
> > 4.      A very quick analysis last night indicated that ARM64 has
> > implemented just under half of the optimizations we discovered
opportunities
> > for in SPEC and EEMBC. That's a fairly comprehensive number of
> > optimizations, and they won't all be easy to port.
Eric,
You mention that there a quite a few  optimization opportunities in SPEC
2000/ EEMBC.
I am looking to optimize the Aarch64 backend. Could you please let me know
the big optimizations possible?