Re: [RFC] ifcvt: Account for parallelism when costing noce sequences

Hi Kyrill

> You first need to check that targetm.sched.issue_rate is non-null.
> I wonder if the schedule issue_rate is too coarse. The midend also uses 
> reassociation width as an estimate of CPU parallelism. On aarch64 at least we
> describe different widths for int, fp, and vector reassociation.
> Have you considered using that hook instead?

Thanks for the suggestion.  I have updated the draft to use
targetm.sched.reassociation_width for integer, floating-point, and
vector operations separately.

I retained issue_rate, with a null check, only as a global per-level
limit, since reassociation width may exceed the actual issue width due
to latency hiding.

Regards,
Wang Jue