[Bug target/79964] Cortex A53 codegen still not optimal

["wilco at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79964

--- Comment #3 from wilco at gcc dot gnu.org ---
(In reply to PeteVine from comment #2)
> I can confirm the first part of the issue gets fixed with this patch:
> 
> https://gcc.gnu.org/ml/gcc-patches/2017-04/msg01415.html

There are a few more division patches on the way, eg.
https://gcc.gnu.org/ml/gcc-patches/2017-04/msg01312.html is one of them,
another should remove the redundant shift.

> but there's a regression in gcc8 concerning the second part. (or rather the
> workarounds don't work any more) 
> 
> http://openbenchmarking.org/result/1704298-RI-CRAYREGRE13
> 
> ("basic flags" didn't deactivate -mfix-cortex-a53-843419, hence the
> difference)

I'm not sure what you're trying to measure here - it's very confusing with
multiple overlapping options (O3/Ofast/tree-vectorize), -mcpu/-march. Is it
related to -fipa-pta or is that not relevant?