Re: [PATCH] predcom: Adjust some unnecessary update_ssa calls

[Martin Sebor <msebor@gmail.com>]

On 6/8/21 3:30 AM, Kewen.Lin wrote:
> on 2021/6/7 下午10:46, Richard Biener wrote:
>> On Wed, Jun 2, 2021 at 11:29 AM Kewen.Lin <linkw@linux.ibm.com> wrote:
>>>
>>> Hi,
>>>
>>> As Richi suggested in PR100794, this patch is to remove
>>> some unnecessary update_ssa calls with flag
>>> TODO_update_ssa_only_virtuals, also do some refactoring.
>>>
>>> Bootstrapped/regtested on powerpc64le-linux-gnu P9,
>>> x86_64-redhat-linux and aarch64-linux-gnu, built well
>>> on Power9 ppc64le with --with-build-config=bootstrap-O3,
>>> and passed both P8 and P9 SPEC2017 full build with
>>> {-O3, -Ofast} + {,-funroll-loops}.
>>>
>>> Is it ok for trunk?
>>
>> LGTM, minor comment on the fancy C++:
>>
>> +  auto cleanup = [&]() {
>> +    release_chains (chains);
>> +    free_data_refs (datarefs);
>> +    BITMAP_FREE (looparound_phis);
>> +    free_affine_expand_cache (&name_expansions);
>> +  };
>>
>> +      cleanup ();
>> +      return 0;
>>
>> so that could have been
>>
>>    class cleanup {
>>       ~cleanup()
>>          {
>>            release_chains (chains);
>>            free_data_refs (datarefs);
>>            BITMAP_FREE (looparound_phis);
>>            free_affine_expand_cache (&name_expansions);
>>          }
>>    } cleanup;
>>
>> ?  Or some other means of adding registering a RAII-style cleanup?
>> I mean, we can't wrap it all in
>>
>>    try {...}
>>    finally {...}
>>
>> because C++ doesn't have finally.
>>
>> OK with this tiny part of the C++ refactoring delayed, but we can also simply
>> discuss best options.  At least for looparound_phis a good cleanup would
>> be to pass the bitmap around and use auto_bitmap local to
>> tree_predictive_commoning_loop ...
>>
> 
> Thanks Richi!  One draft (not ready for review) is attached for the further
> discussion.  It follows the idea of RAII-style cleanup.  I noticed that
> Martin suggested stepping forward to make tree_predictive_commoning_loop
> and its callees into one class (Thanks Martin), since there are not many
> this kind of C++-style work functions, I want to double confirm which option
> do you guys prefer?

I meant that not necessarily as something to include in this patch
but as a suggestion for a future improvement.  If you'd like to
tackle it at any point that would be great of course :)  In any
event, thanks for double-checking!

The attached patch looks good to me as well (more for the sake of
style than anything else, declaring the class copy ctor and copy 
assignment = delete would make it clear it's not meant to be
copied, although in this case it's unlikely to make a practical
difference).

> 
> One point you might have seen is that to make tree_predictive_commoning_loop
> and its callees as member functions of one class can avoid to pass bitmap
> looparound_phis all around what's in the draft.  :)

Yes, that would simplify the interfaces of all the functions that
the info members are passed to as arguments.

Martin

> 
> BR,
> Kewen
>