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Re: [PATCH] Fix PR40062, exponential behavior in SCEV
- From: Sebastian Pop <sebpop at gmail dot com>
- To: Richard Guenther <rguenther at suse dot de>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Fri, 8 May 2009 07:16:43 -0500
- Subject: Re: [PATCH] Fix PR40062, exponential behavior in SCEV
- References: <alpine.LNX.email@example.com>
On Fri, May 8, 2009 at 05:09, Richard Guenther <firstname.lastname@example.org> wrote:
> This fixes PR40062, a case where SCEV at -O3 uses up all memory
> in my machine (no idea what it would take if it would finish).
> The issue is that while we limit recursion depth in walking
> PHI nodes somewhat we do not effectively limit breath of the search
> for a path through the loop. ÂThis effectively makes the
> complexity exponential if you have, like in the testcase, several
> non-loop PHI nodes with a large number of arguments.
> The fix is to take this into account like for example with the following.
> Bootstrap / regtest in progress. ÂSebastian - are you ok with that?
Yes, thank you for fixing this.
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