Re: [2/5] C-SKY port: Backend implementation

[Sandra Loosemore <sandra@codesourcery.com>]

On 07/24/2018 09:45 AM, Jeff Law wrote:
> On 07/23/2018 10:21 PM, Sandra Loosemore wrote:
>> 2018-07-23  Jojo  <jijie_rong@c-sky.com>
>>              Huibin Wang  <huibin_wang@c-sky.com>
>>              Sandra Loosemore  <sandra@codesourcery.com>
>>              Chung-Lin Tang  <cltang@codesourcery.com>
>>
>>          C-SKY port: Backend implementation
>>
>>          gcc/
>>          * config/csky/*: New.
>>          * common/config/csky/*: New.
> 
> Let's avoid gratutious whitespace that attempts to line up conditionals.
>    As an example, look at the predicate csky_load_multiple_operation.  I
> think just doing a quick pass over the .c, .h and main .md files should
> be sufficient here.

OK, will do.

> I'm not a big fan of more awk code, but I'm not going to object to it :-)
> 
> Why does the port have its own little pass for condition code
> optimization (cse_cc)?  What is it doing that can't be done with our
> generic optimizers?

This pass was included in the initial patch set we got from C-SKY, and 
as it didn't seem to break anything I left it in.  Perhaps C-SKY can 
provide a testcase that demonstrates why it's still useful in the 
current version of GCC; otherwise we can remove this from the initial 
port submission and restore it later if some performance analysis shows 
it is still worthwhile.

> Any thoughts on using the newer function descriptor bits rather than old
> style stack trampolines?

Has that been committed?  I vaguely remembered discussion of a new way 
to handle nested functions without using the trampoline interface, but I 
couldn't find any documentation in the internals manual.

> I don't see anything terribly concerning in the core of the port.  The
> amount of support code for minipool is huge and I wonder if some sharing
> across the various ports would be possible, but I don't think that
> should be a blocking issue for this port.

Yes, that code was clearly copied almost verbatim from the ARM backend. 
I left it alone as much as possible to simplify any future attempts at 
genericizing it.

> Can you update the backends.html web page here appropriately for the
> c-sky target?

Sure, I can take care of updating that when the port is committed.  I 
believe the right entry is

"csky                          b   ia"

> I'd like to take a closer look, but those are the high level comment's
> I've got this morning :-)

Thanks.  I'll wait a bit for more comments to come in before preparing a 
revised patch.

-Sandra