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Re: [RFC] Fix PR rtl-optimization/33732


On Thu, Nov 08, 2007 at 02:23:19PM -0500, Kenneth Zadeck wrote:
> Rask,
> 
> I want to reiterate that none of the dataflow maintainers want to pursue
> this particular path to fix this bug. 
> 
> All of us who worked on the dataflow branch spent a lot of time looking
> at the bugs that came up and the performance tradeoffs and we made an
> informed and deliberate decision to do what we did.  Lazyness or
> stupidity were not the issues.

   If I thought DF maintainers were lazy or stupid, I would have rolled my
own loop over the insns to update the REG_DEAD notes rather than using DF.
Posting a patch touching subsystem xyz does not imply lazyness or
stupidity on the part of the subsystem xyz maintainers.

> The current stack of ra/reload passes have a fragile ordering in which
> they build and update their internal datastructures.  Choosing a place
> where you arbitrarily update the dataflow is going to disturb that flow
> of information.  We have been there. 

   I did not arbitrarily choose a place for a dataflow update. I
deliberately picked a place where the REG_DEAD notes have just been
corrupted to the point where they cause a P1 wrong-code regression. I also
deliberately picked a place early in reload for the reason you mention.
Lazyness or stupidity were not the issues.
 
> I am not saying that it cannot be done, but given that we are late into
> stage 3 AND a great deal of this code is due to be replaced in 4.4,
> major surgery is not the correct solution. 

   I'm not aware of any replacement of reload for 4.4. Until it arrives,
we'll have to live with reload. And reload relies on REG_DEAD notes. I also
don't know about major surgery, "late into stage 3" might just mean "great
time for working on stage 1 stuff", etc.

-- 
Rask Ingemann Lambertsen
Danish law requires addresses in e-mail to be logged and stored for a year


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