[PATCH][AArch64] Improve SHA1 scheduling

[Wilco Dijkstra]

Wilco Dijkstra wrote:
> James Greenhalgh wrote:
>
> > I haven't seen a follow-up to Andrew's point regarding other
> > read-modify-write operations.
> > 
> > Did youi investigate the cost of these?
>
> I looked at whether there are other similar cases, but it appears SHA1
> is unique due to the odd dataflow, the mismatch in latencies and the high
> repetition.  So it seems best to handle it as a special case.
>
> What does seem useful is teaching GCC to prefer using the same
> register for accumulators.  That is a general issue that would improve
> performance in many cases. 

Any further comments?

Wilco