linux-kernel - Re: Alpha: suspicious compiler warning in entry.S

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Message-ID: <5962.1256908619@redhat.com>
Date:	Fri, 30 Oct 2009 13:16:59 +0000
From:	David Howells <dhowells@...hat.com>
To:	Michael Cree <mcree@...on.net.nz>
Cc:	dhowells@...hat.com, linux-alpha@...r.kernel.org,
	linux-kernel@...r.kernel.org, rth@...ddle.net,
	ink@...assic.park.msu.ru
Subject: Re: Alpha: suspicious compiler warning in entry.S

Michael Cree <mcree@...on.net.nz> wrote:

> On the assumption that it is important to include the TIF_NOTIFY_RESUME bit
> one might be tempted to modify the code to:
> 
>    lda    $2, _TIF_WORK_MASK
>    and    $5, $2, $2
> 
> but this is time critical code.  I am wondering whether it might be better
> to rearrange the bits in the thread information flags so that _TIF_WORK_MASK
> has a value less than 255 and the single instruction to perform an and
> operation can be maintained.

Unless the LDA can be interleaved around some memory accesses, then yes,
compressing _TIF_WORK_MASK would be good.

David
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