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

[Mikhail Zolotukhin via llvm-commits]

> On May 24, 2016, at 9:18 AM, Hans Wennborg <hans at chromium.org> wrote:
> 
> On Mon, May 23, 2016 at 5:58 PM, Mikhail Zolotukhin
> <mzolotukhin at apple.com <mailto:mzolotukhin at apple.com>> wrote:
>> 
>> 
>> On May 23, 2016, at 4:52 PM, Mikhail Zolotukhin via llvm-commits
>> <llvm-commits at lists.llvm.org> wrote:
>> 
>> 
>> 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> 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
>> 
>> 
>> I've reverted this in r270512, as it caused PR27847.
>> 
>> It should be fixed in r270517. I'm going to reapply r270478 - please let me
>> know if you see any failures after it.
> 
> Yes, I'm still seeing the same assert and have uploaded a new
> reproducer to the bug.
> 
> I've reverted the enabling of the analysis in r270577
Hi Hans,

I've made one more attempt in r270629 and r270630. Hopefully this time I actually fixed the issue. As usual, please let me know if I break anything:)

Thanks,
Michael
> 
> Thanks,
> Hans

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