[PATCH] Fix write-back value propagation for pre-indexed addressing modes

[Silviu Baranga]

Great! I'll commit the patch by the end of today.

Thanks,
Silviu

> -----Original Message-----
> From: Hal Finkel [mailto:hfinkel at anl.gov]
> Sent: 26 April 2013 13:36
> To: Silviu Baranga
> Cc: llvm-commits at cs.uiuc.edu; Dmitry Antipov
> Subject: Re: [PATCH] Fix write-back value propagation for pre-indexed
> addressing modes
> 
> ----- Original Message -----
> > From: "Silviu Baranga" <Silviu.Baranga at arm.com>
> > To: "Hal Finkel" <hfinkel at anl.gov>
> > Cc: llvm-commits at cs.uiuc.edu, "Dmitry Antipov"
> <antipov at dev.rtsoft.ru>
> > Sent: Friday, April 26, 2013 5:21:35 AM
> > Subject: RE: [PATCH] Fix write-back value propagation for pre-indexed
> addressing modes
> >
> > > -----Original Message-----
> > > From: Hal Finkel [mailto:hfinkel at anl.gov]
> > > Sent: 25 April 2013 20:58
> > > To: Silviu Baranga
> > > Cc: llvm-commits at cs.uiuc.edu; Dmitry Antipov
> > > Subject: Re: [PATCH] Fix write-back value propagation for
> > > pre-indexed
> > > addressing modes
> >
> >
> > > I understand; we're kind of talking past each other at this point.
> > > In
> > > any case, looking at the ARM implementation, I disagree with
> > > Dmitry's
> > > interpretation of the problem. As I wrote the code in question,
> > > please
> > > feel free to commit your fix.
> >
> > Sorry about that. The problem is reasonably complex and we both seem
> > to
> > have strong divergent views about it.
> 
> It is not your fault, and we're on the same page. I had been trying to
> construct an explanation based on Dimitry's diagnosis of the problem,
> which essentially included the possibility that PRE_DEC on ARM was
> essentially a PRE_INC with a negative offset. But looking at the code
> myself, I think that he was misinterpreting things.
> 
> >
> > > I would really like, however, if we had a test case for this. If
> > > you
> > > had code that the current implementation miscompiled, can you place
> > > an
> > > assert that triggers in the bad case (pre_dec + swap), and use
> > > bugpoint
> > > to reduce the test case?
> >
> > I've only seen the pre_dec + swap failure in a user of the LLVM
> > libraries,
> > and I cannot reproduce the failure with llc (I've really tried).
> > Also, the
> > failure goes away with even small modifications of the test case.
> >
> > I would actually like to include Dmitry's test case if he's OK with
> > that
> > so at least the patch does gets a test case.
> 
> Okay. FWIW, Dmitry did not respond to my last e-mail from last week, so
> if he does not respond promptly, I'm in favor of committing the fix and
> then the test case later.
> 
>  -Hal
> 
> >
> > Thanks,
> > Silviu
> >
> >
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