[LLVMdev] Contributing the Apple ARM64 compiler backend

Eric Christopher
Tue, 24 Jun 2014 14:23:03 -0000

On Tue, Jun 24, 2014 at 2:45 AM, Manjunath N <manjunath.dn at gmail.com>
wrote:
>
>
> 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?
>

Wasn't me here. I was just on the thread. Might have been Amara?

-eric