[PATCH] D17652: [CGP] Duplicate addressing computation in cold paths if required to sink addressing mode

[Xinliang David Li via llvm-commits]

On Wed, Mar 2, 2016 at 4:12 PM, Philip Reames <listmail at philipreames.com>
wrote:

> reames added a comment.
>
> In http://reviews.llvm.org/D17652#364797, @davidxl wrote:
>
> > A general problem I see in address sinking optimization is the lack of
> global cost analysis -- the analysis should consider
> >
> > 1. the cost of the folded instruction (if the address can be folded in)
> > 2. whether the original address instruction can be eliminated (for
> instance, only sunk into some of the uses)
> > 3. if the address can not be folded, what is the additional cost
> > 4. what is the estimated register pressure reduction with the address
> sinking
>
>
> I'm confused by your comment.  Are you talking about my changes, or the
> existing code?  The existing code does most of this (except 1) and my
> extension preserves all of that except when duplicating into a cold call.
>


Mostly the existing code, but you new code introduces a new dimension to
it. IIUC, the new code introduces the case where address computation may
not be folded away so there is also potential size increase? Perhaps guard
this change with 'not built for Os or Oz' ?


>
> > The above should be all weighted with the block frequency information.
>
>
> While I agree, that's a separate change - particularly since CFG does not
> currently use profiling info at all.
>

Perhaps add a comment there to future cleanup ?

thanks,

David

>
>
> http://reviews.llvm.org/D17652
>
>
>
>
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