SLP/Loop vectorizer pass ordering
james at jamesmolloy.co.uk
Thu Sep 4 03:27:07 PDT 2014
Hal, I'm happy. Are you happy enough with the state of MDNoAlias that we
can flip both switches?
On 3 September 2014 18:46, Chandler Carruth <chandlerc at google.com> wrote:
> I've run our benchmarks and a sizable test suite. I see no regressions and
> some small improvements. Please feel free to enable both features provided
> everyone else is happy.
> On Sun, Aug 31, 2014 at 9:50 PM, Hal Finkel <hfinkel at anl.gov> wrote:
>> ----- Original Message -----
>> > From: "Chandler Carruth" <chandlerc at google.com>
>> > To: "James Molloy" <james at jamesmolloy.co.uk>
>> > Cc: "Chad Rosier" <mcrosier at codeaurora.org>, "Hal Finkel" <
>> hfinkel at anl.gov>, "LLVM Commits"
>> > <llvm-commits at cs.uiuc.edu>, "Tobias Grosser" <tobias at grosser.es>
>> > Sent: Wednesday, August 27, 2014 4:38:06 AM
>> > Subject: Re: SLP/Loop vectorizer pass ordering
>> > On Wed, Aug 27, 2014 at 2:29 AM, James Molloy <
>> > james at jamesmolloy.co.uk > wrote:
>> > Hi Chandler,
>> > This is waiting on you reporting numbers, I think. Did you get a
>> > chance to run your benchmarks?
>> > Sorry, I should have followed up here as well as on IRC with Hal.
>> > I tried to get numbers. However, enabling Hal's feature caused a
>> > large number of my benchmarks to fail... over 50% of them. So I
>> > didn't get much useful data. What I got looked fine, but I'd really
>> > rather some higher confidence in the scoped-aa stuff first.
>> Please try again after r216863 (which at least gives me a clean
>> test-suite and self-host on Linux/x86_64). The noalias parameter attribute
>> -> metadata conversion logic, as it turns out, was pretty broken -- it is
>> certainly better now.
>> In case you're curious where all your noalias parameters are coming from,
>> aside from the obvious places where you have __restrict__, it is also that
>> Clang adds noalias to every sret parameter (for aggregate return values).
>> As a result, we actually get reasonable testing coverage from self-hosting
>> on the noalias -> metadata conversion (or so I currently believe).
>> > I'm not sure what to do next though. I mean, I can spend a bunch of
>> > time trying to reduce a test case, but it will take me a huge amount
>> > of time.
>> > Note that all the code failing is compiled with no TBAA and there is
>> > very little C code involved... so I feel lik ethere must be
>> > something pretty basic that is going wrong with this new mode.
>> Yes, there certainly was.
>> Thanks again,
>> Hal Finkel
>> Assistant Computational Scientist
>> Leadership Computing Facility
>> Argonne National Laboratory
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