[llvm] r270478 - [LoopUnroll] Enable advanced unrolling analysis by default.

[Mikhail Zolotukhin via llvm-commits]

> On May 23, 2016, at 4:50 PM, Hans Wennborg <hans at chromium.org> wrote:
> 
> On Mon, May 23, 2016 at 12:10 PM, Michael Zolotukhin via llvm-commits
> <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> wrote:
>> Author: mzolotukhin
>> Date: Mon May 23 14:10:19 2016
>> New Revision: 270478
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=270478&view=rev
>> Log:
>> [LoopUnroll] Enable advanced unrolling analysis by default.
>> 
>> Summary:
>> This patch turns on LoopUnrollAnalyzer by default. To mitigate compile
>> time regressions, I chose very conservative thresholds for now. Later we
>> can make them more aggressive, but it might require being smarter in
>> which loops we're optimizing. E.g. currently the biggest issue is that
>> with more agressive thresholds we unroll many cold loops, which
>> increases compile time for no performance benefit (performance of those
>> loops is improved, but it doesn't matter since they are cold).
> [..]
>> Differential Revision: http://reviews.llvm.org/D20482 <http://reviews.llvm.org/D20482>
> 
> I've reverted this in r270512, as it caused PR27847.
Thanks, I'm looking into it!

Michael

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