[PATCH][LoopVectorizer] Restrict the unroll factor of reductions in loops

[James Molloy]

Hi All,

Thanks, committed as r21614[01].

Gerolf, I didn’t do specific checking of compile time for this change because it is just adding a bailout condition – I can’t see how that could significantly alter compile time.

Cheers, and sorry for the high latency on this one,

James

From: Gerolf Hoflehner <ghoflehner at apple.com<mailto:ghoflehner at apple.com>>
Date: Wednesday, 13 August 2014 21:25
To: Arnold Schwaighofer <aschwaighofer at apple.com<mailto:aschwaighofer at apple.com>>, Admin <james.molloy at arm.com<mailto:james.molloy at arm.com>>
Cc: James Molloy <james at jamesmolloy.co.uk<mailto:james at jamesmolloy.co.uk>>, Hal Finkel <hfinkel at anl.gov<mailto:hfinkel at anl.gov>>, Admin <james.molloy at arm.com<mailto:james.molloy at arm.com>>, "llvm-commits at cs.uiuc.edu<mailto:llvm-commits at cs.uiuc.edu>" <llvm-commits at cs.uiuc.edu<mailto:llvm-commits at cs.uiuc.edu>>
Subject: Re: [PATCH][LoopVectorizer] Restrict the unroll factor of reductions in loops

There are a number of regression (lowercase -40%, link pack ~-5%) and gains (puzzle? >30%, sgefa > 13%). I’ll do some analysis in the next couple of days and follow up with bug filings as necessary. So go for the gains for now and trust that we’ll recover the losses.

I haven’t done any compile-time measurements for the patch. Did you cover it with high confidence?

Thanks
Gerolf



On Aug 12, 2014, at 10:19 AM, Arnold Schwaighofer <aschwaighofer at apple.com<mailto:aschwaighofer at apple.com>> wrote:

LGTM.

I did see some regressions running the whole test-suite on the two patches (+ "ST->isCyclone()") we (on our end) might want to look into - I’ll send my results to Gerolf.


Thanks,
Arnold


On Aug 11, 2014, at 9:17 AM, James Molloy <james at jamesmolloy.co.uk<mailto:james at jamesmolloy.co.uk>> wrote:

Hi Arnold, Gerolf, Hal,

Good idea about a tuning option. Attached is a patch that implements that tuning option. Is it OK to commit?

Gerolf, did you want me to add "|| isCyclone()" to AArch64TargetTransformInfo?

Cheers,

James



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