[Bug target/83008] [performance] Is it better to avoid extra instructions in data passing between loops?

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83008

--- Comment #25 from rguenther at suse dot de <rguenther at suse dot de> ---
On Wed, 10 Jan 2018, sergey.shalnov at intel dot com wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83008
> 
> --- Comment #24 from sergey.shalnov at intel dot com ---
> Richard,
> The latest "SLP costing for constants/externs improvement" patch generates the
> same code as baseline for the test example.
> 
> Are you sure that "num_vects_to_check" should 1 if vector is not constant? I
> would expect "num_vects_to_check = ncopies_for_cost;" here:
> 
> 1863              else
> 1864                {
> 1865                  num_vects_to_check = 1;
> 1866                  nelt_limit = group_size;
> 1867                }

Yes, that's correct for variable length vectors (SVE)