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Re: [PATCH][AArch64] Improve SHA1 scheduling
- From: James Greenhalgh <james dot greenhalgh at arm dot com>
- To: Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, nd <nd at arm dot com>
- Date: Tue, 6 Dec 2016 16:58:13 +0000
- Subject: Re: [PATCH][AArch64] Improve SHA1 scheduling
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On Tue, Dec 06, 2016 at 03:10:50PM +0000, Wilco Dijkstra wrote:
>
>
> ping
I haven't seen a follow-up to Andrew's point regarding other
read-modify-write operations.
Did youi investigate the cost of these?
James
>
>
> From: Wilco Dijkstra
> Sent: 25 October 2016 18:08
> To: GCC Patches
> Cc: nd
> Subject: [PATCH][AArch64] Improve SHA1 scheduling
>
> SHA1H instructions may be scheduled after a SHA1C instruction
> that uses the same input register. However SHA1C updates its input,
> so if SHA1H is scheduled after it, it requires an extra move.
> Increase the priority of SHA1H to ensure it gets scheduled
> earlier, avoiding the move.
>
> Is this something the generic scheduler could do automatically for
> instructions with RMW operands?
>
> Passes bootstrap & regress. OK for commit?
>
> ChangeLog:
> 2016-10-25 Wilco Dijkstra <wdijkstr@arm.com>
>
> * config/aarch64/aarch64.c (aarch64_sched_adjust_priority)
> New function.
> (TARGET_SCHED_ADJUST_PRIORITY): Define target hook.