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Re: [PATCH][RFC] Fix PR56113 more
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Richard Biener <rguenther at suse dot de>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Fri, 1 Feb 2013 10:49:22 +0100
- Subject: Re: [PATCH][RFC] Fix PR56113 more
- References: <alpine.LNX.2.00.1302010951500.6889@zhemvz.fhfr.qr>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Fri, Feb 01, 2013 at 10:00:00AM +0100, Richard Biener wrote:
>
> This reduces compile-time of the testcase in PR56113 (with n = 40000)
> from 575s to 353s. It does so by reducing the quadratic algorithm
> to impose an order on visiting dominator sons during a domwalk.
>
> Steven raises the issue that there exist domwalk users that modify
> the CFG during the walk and thus the new scheme does not work
> (at least optimally, as the current quadratic scheme does). As
> we are using a fixed-size sbitmap to track visited blocks existing
> domwalks cannot add new blocks to the CFG so the worst thing that
> can happen is that the order of dominator sons is no longer
> optimal (I suppose with the "right" CFG manipulations even the
> domwalk itself does not work - so I'd be hesitant to try to support
> such domwalk users) - back to the state before any ordering
> was imposed on the dom children visits (see rev 159100).
I think it would be desirable to first analyze the failures Steven saw, if
any. As you said, asan doesn't use domwalk, so it is a mystery to me.
Jakub