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Re: [PATCH 21/25] GCN Back-end (part 2/2).

From: Segher Boessenkool <segher at kernel dot crashing dot org>
To: Andrew Stubbs <ams at codesourcery dot com>
Cc: Jeff Law <law at redhat dot com>, gcc-patches at gcc dot gnu dot org
Date: Mon, 12 Nov 2018 12:33:37 -0600
Subject: Re: [PATCH 21/25] GCN Back-end (part 2/2).
References: <cover.1536144068.git.ams@codesourcery.com> <4c633833-1954-4b62-1a96-4f1c2cf541fd@codesourcery.com> <a8084ecb-c638-8e46-8734-3446079e002a@redhat.com> <4fe09f84-10d6-d30c-e458-27a4a3220eef@codesourcery.com> <20181112171958.GM23873@gate.crashing.org> <30cf3b4d-14f8-3659-cee9-ebac2ee4c652@codesourcery.com>

On Mon, Nov 12, 2018 at 05:52:25PM +0000, Andrew Stubbs wrote:
> On 12/11/2018 17:20, Segher Boessenkool wrote:
> >If you don't want useless USEs deleted, use UNSPEC_VOLATILE instead?
> >Or actually use the register, i.e. as input to an actually needed
> >instruction.
> 
> They're not useless.

> >If combine is changing an X and a USE to just that X if it can, combine
> >is doing a great job!

Actually, it is incorrect to delete a USE.

Please open a PR.  Thanks.


Segher

References:
- Re: [PATCH 21/25] GCN Back-end (part 2/2).
  - From: Jeff Law
- Re: [PATCH 21/25] GCN Back-end (part 2/2).
  - From: Andrew Stubbs
- Re: [PATCH 21/25] GCN Back-end (part 2/2).
  - From: Segher Boessenkool
- Re: [PATCH 21/25] GCN Back-end (part 2/2).
  - From: Andrew Stubbs

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