[PATCH] [SimplifyCFG] Swap to using TargetTransformInfo for cost analysis.

[Hal Finkel]

----- Original Message -----
> From: "James Molloy" <james at jamesmolloy.co.uk>
> To: reviews+D7506+public+d608f0951474be02 at reviews.llvm.org, "james molloy" <james.molloy at arm.com>, hfinkel at anl.gov,
> "t p northover" <t.p.northover at gmail.com>, "Andrea DiBiagio" <Andrea_DiBiagio at sn.scee.net>
> Cc: llvm-commits at cs.uiuc.edu
> Sent: Tuesday, February 10, 2015 10:22:07 AM
> Subject: Re: [PATCH] [SimplifyCFG] Swap to using TargetTransformInfo for cost analysis.
> 
> 
> Hi Andrea,
> 
> Performance on AArch64 showed no major swings. However, it sounds to
> me like your TargetTransformInfo isn't behaving correctly. That's
> TTI's entire point, and the x86 one should surely return
> "TCC_Expensive" for such intrinsic calls.
> 
> I see that the default TTI does return TCC_Basic for almost all
> intrinsics, and that is arguable behaviour. But there's no reason
> you shouldn't override this. In fact, it seems the right thing to
> do.
> 

I agree, x86 should override these. I'll add that we're going to run into this more because we're starting to use the user-cost interface for more things. The target's user-cost implementations are not as well tuned as the cost interfaces used by the vectorizer.

 -Hal

> 
> Cheers,
> 
> 
> James
> 
> On Tue Feb 10 2015 at 2:53:52 PM Andrea Di Biagio <
> Andrea_DiBiagio at sn.scee.net > wrote:
> 
> 
> REPOSITORY
> rL LLVM
> 
> http://reviews.llvm.org/D7506
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory