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Subject: Re: [RFC] Speed-up -fprofile-update=atomic
To: Richard Biener <richard.guenther@gmail.com>
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Cc: Jakub Jelinek <jakub@redhat.com>, Andi Kleen <andi@firstfloor.org>, Jeff Law <law@redhat.com>, Nathan Sidwell <nathan@acm.org>, GCC Patches <gcc-patches@gcc.gnu.org>, "Hubicha, Jan" <jh@suse.cz>
From: =?UTF-8?Q?Martin_Li=c5=a1ka?= <mliska@suse.cz>
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On 10/24/2016 03:51 PM, Richard Biener wrote:

> It's quite ad-hoc :/  The IFN will also be a memory optimization
> barrier unless you add special support
> for it in the alias oracle - so the performance measurement needs to
> be taken with a grain of salt
> (same is true for all atomics of course... - I have some local patches
> to improve things here).

Good, thus please ping me with the patches you have and I'll integrate it.

> 
> The way you implement process_sm_for_coverage_counter is more like a
> final value replacement.
> You could maybe use create_iv for the loop counter or even wind up
> computing the final value
> (number of iterations) only after the loop, avoiding the IV completely
> (eventually SCEV cprop
> saves you here afterwards).

Or maybe we can basically assign loop->niter as the argument of UPDATE_COVERAGE_COUNTER
function?

Martin

> 
> Richard.