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Re: [PATCH] Fix overzealous DSE on sparc


From: Richard Guenther <richard.guenther@gmail.com>
Date: Thu, 3 May 2012 10:42:30 +0200

> On Thu, May 3, 2012 at 10:31 AM, Richard Sandiford
> <rdsandiford@googlemail.com> wrote:
>> David Miller <davem@davemloft.net> writes:
>>> From: Richard Sandiford <rdsandiford@googlemail.com>
>>> Date: Wed, 02 May 2012 20:37:58 +0100
>>>
>>>> I think the DSE assuption is fair though. ?If you reuse MEMs like
>>>> this, then they're no longer just serving the purpose described by
>>>> MEM_EXPR.
>>>
>>> The following seems to work, and matches what calls.c does when it
>>> passes a value by reference. ?Is this what you had in mind?
>>
>> Yeah, looks good to me.
> 
> I don't think that will work reliably (well, maybe now by luck, so better than
> nothing).  You'd at least need to adjust the ESCAPED points-to set of the
> function, too (yes, DSE does very very conservative use analysis right now).
> Why not simply clear MEM_EXPR for the MEM?

Then why does calls.c not have to do this?


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