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Re: GCC extension proposal (loop unswitching)
- From: Andi Kleen <andi at firstfloor dot org>
- To: Nils Pipenbrinck <n dot pipenbrinck at cubic dot org>
- Cc: gcc at gcc dot gnu dot org
- Date: 30 Mar 2008 19:12:14 +0200
- Subject: Re: GCC extension proposal (loop unswitching)
- References: <47EFA37B.email@example.com>
Nils Pipenbrinck <firstname.lastname@example.org> writes:
> Most of the stuff I write is performance critical, and I always find
> myself in the same situation: I spend counter less hours to unswitch
> loops by hand because the built-in loop unswitcher is not always smart
> when multiple variables can be unswitched.
I'm sure the developers would appreciate simple test cases in bugzilla
demonstrating the problem. That would not help you immediately
(because it would only be fixed in some future gcc version), but long term.
> Also you can not
> enable/disable loop unswitching on a per-function basis.
I often wished for a way to enable/disable loop unrolling on a per
loop basis. Some way to annotate loops similar to what OpenMP
does would be quite nice.