[AArch64] Enable partial unrolling on cortex-a57 and 2 related improvement

Sun Mar 8 23:18:03 PDT 2015

Committed as r231630, r231631, r231632.

Thanks,
Kevin

2015-03-06 14:54 GMT+08:00 Hal Finkel <hfinkel at anl.gov>:

>
> ------------------------------
>
> *From: *"Kevin Qin" <kevinqindev at gmail.com>
> *To: *"Hal Finkel" <hfinkel at anl.gov>
> *Cc: *"llvm-commits" <llvm-commits at cs.uiuc.edu>
> *Sent: *Thursday, March 5, 2015 11:44:03 PM
> *Subject: *Re: [AArch64] Enable partial unrolling on cortex-a57 and 2
> related improvement
>
> Hi Hal,
>
> Here's the updated one. Please review again.
>
>
> Okay, LGTM. You need to add something to the LangRef about the metadata
> too.
>
> Thanks,
> Hal
>
>
> Thanks,
> Kevin
>
> 2015-03-06 0:13 GMT+08:00 Hal Finkel <hfinkel at anl.gov>:
>
>> ------------------------------
>>
>> > From: "Kevin Qin" <kevinqindev at gmail.com>
>> > To: "Hal Finkel" <hfinkel at anl.gov>
>> > Cc: "llvm-commits" <llvm-commits at cs.uiuc.edu>
>> > Sent: Thursday, March 5, 2015 12:48:09 AM
>> > Subject: Re: [AArch64] Enable partial unrolling on cortex-a57 and 2
>> related improvement
>> >
>> >
>> > Hi Hal,
>> >
>> >
>> > Thanks for your quick review again. I refactored the patch as your
>> > suggestion. It's a choice between duplicating the method to get
>> > whether or not to insert runtime checks, nor duplicating the data of
>> > recording that. And I agreed that the later one is better as it's
>> > easy to maintain. Here's the updated patch.
>>
>> Okay, but let's make this even easier to maintain: use only one boolean.
>> This way, if we add a new type of safety check, we need a new boolean, and
>> we need to add a new part to the if condition controlling the metadata.
>> Just use one variable: AddedSafetyChecks, set it to true if we add one of
>> any type, and then check that afterward.
>>
>> Thanks again,
>> Hal
>>
>> >
>> >
>> > Cheers,
>> > Kevin
>> >
>> >
>> > 2015-03-05 13:56 GMT+08:00 Hal Finkel < hfinkel at anl.gov > :
>> >
>> >
>> > ----- Original Message -----
>> > > From: "Kevin Qin" < kevinqindev at gmail.com >
>> > > To: "Hal Finkel" < hfinkel at anl.gov >
>> > > Cc: "llvm-commits" < llvm-commits at cs.uiuc.edu >
>> > > Sent: Wednesday, March 4, 2015 8:12:03 PM
>> > > Subject: Re: [AArch64] Enable partial unrolling on cortex-a57 and 2
>> > > related improvement
>> > >
>> > >
>> > > Hi Hal,
>> > >
>> > >
>> >
>> >
>> > > For the first patch, I've added comments to explain why we run LICM
>> > > pass after loop unrolling pass, and added a test to check if the
>> > > runtime unrolling prologue is promoted out by LICM at -O2. Can you
>> > > point me which part is not sufficient? For adding a run of
>> > > CorrelatedValuePropagation, it's because I found that LICM had
>> > > dependence on it. If I run LICM only after loop unrolling, llvm
>> > > will
>> > > crash with:
>> > >
>> > >
>> > > llvm/lib/Transforms/Scalar/LICM.cpp:196: virtual bool <anonymous
>> > > namespace>::LICM::runOnLoop(llvm::Loop *, llvm::LPPassManager &):
>> > > Assertion `InnerAST && "Where is my AST?"' failed.
>> > >
>> > >
>> > >
>> > > For the second patch becoming huge, it's caused by moving class.
>> > > The
>> > > problem is like,
>> > >
>> > >
>> > >
>> > > class B;
>> > >
>> > >
>> > > class A {
>> > > void doSomething(B * _b) { //This function is newly added by this
>> > > patch.
>> > > _b->add();
>> > > }
>> > > };
>> > >
>> > >
>> > > class B {
>> > >
>> > >
>> > > void add() {
>> > > ...
>> > > }
>> > >
>> > >
>> > > };
>> > >
>> > >
>> > > Above code can't be compiled with error: member access into
>> > > incomplete type 'B' . So I moved class B in front of A.
>> > >
>> > >
>> > > The meaningful changes comparing to last edition are,
>> > >
>> > >
>> > >
>> > > class InnerLoopVectorizer {
>> > >
>> > >
>> > > public:
>> > >
>> > > + // Whether runtime check about strides is added.
>> > > + bool IsCheckStrides() {
>> > > + return Legal->mustCheckStrides();
>> > > + }
>> > >
>> > > + // Whether runtime check about memory is added.
>> > > + bool IsCheckMemory() {
>> > > + return Legal->getLAI()->getRuntimePointerCheck()->Need;
>> > > + }
>> > > }
>> > >
>> > >
>> > >
>> > > + // Add metadata to disable runtime unrolling scalar loop when
>> > > there's no
>> > > + // runtime check about strides and memory. Because at this
>> > > situation,
>> > > + // scalar loop is rarely used and not worthy to be unrolled.
>> > > + if (!LB.IsCheckStrides() && !LB.IsCheckMemory())
>> > > + AddRuntimeUnrollDisableMetaData(L);
>> > >
>> > >
>> > > I'm sorry for generating such a huge patch and bring difficulty for
>> > > code review. Above information can help you to understand it a bit
>> > > easier.
>> >
>> > Okay, I think that it would be better not to repeat the logic for
>> > whether or not to insert runtime checks; it would be very each for
>> > these to get out of sync in the future. I think that it would be
>> > better to add some boolean to the InnerLoopVectorizer, and just
>> > record weather or not a check was added in
>> > InnerLoopVectorizer::createEmptyLoop so that we can query it later.
>> >
>> > -Hal
>> >
>> >
>> >
>> > >
>> > >
>> > > Thanks,
>> > > Kevin
>> > >
>> > >
>> > > 2015-03-05 0:43 GMT+08:00 Hal Finkel < hfinkel at anl.gov > :
>> > >
>> > >
>> > > Hi Kevin,
>> > >
>> > > Regarding the first patch, you did not comment on (nor add a test
>> > > for?) also adding a run of CorrelatedValuePropagation. Can you
>> > > please explain the rationale?
>> > >
>> > > The vectorizer/unrolling patch is now huge. What happened?
>> > >
>> > > Regarding the third, this LGTM.
>> > >
>> > > -Hal
>> > >
>> > > ----- Original Message -----
>> > > > From: "Kevin Qin" < kevinqindev at gmail.com >
>> > >
>> > >
>> > > > To: "Hal Finkel" < hfinkel at anl.gov >
>> > > > Cc: "llvm-commits" < llvm-commits at cs.uiuc.edu >
>> > > > Sent: Wednesday, March 4, 2015 3:09:51 AM
>> > > > Subject: Re: [AArch64] Enable partial unrolling on cortex-a57 and
>> > > > 2
>> > > > related improvement
>> > > >
>> > > >
>> > > > Hi Hal,
>> > > >
>> > > >
>> > > > Thanks a lot for your review. I totally agree with your review
>> > > > comments, and here are the updated patches.
>> > > >
>> > > >
>> > > > Regards,
>> > > > Kevin
>> > > >
>> > > >
>> > > > 2015-03-04 11:29 GMT+08:00 Hal Finkel < hfinkel at anl.gov > :
>> > > >
>> > > >
>> > > > ----- Original Message -----
>> > > > > From: "Kevin Qin" < kevinqindev at gmail.com >
>> > > > > To: "llvm-commits" < llvm-commits at cs.uiuc.edu >
>> > > > > Sent: Friday, February 27, 2015 11:55:05 PM
>> > > > > Subject: [AArch64] Enable partial unrolling on cortex-a57 and 2
>> > > > > related improvement
>> > > > >
>> > > > >
>> > > > >
>> > > > > Hi,
>> > > > >
>> > > > >
>> > > > > Previously, I made commit r219401 that try to enable partial &
>> > > > > runtime unrolling on cortex-a57, but I forgot to call base TTI
>> > > > > implementation in target specific hook, so those unrolling
>> > > > > methods
>> > > > > are not really enabled.
>> > > > >
>> > > > >
>> > > > > Here are the patch to get them enabled and 2 related patches to
>> > > > > improve it.
>> > > > >
>> > > > >
>> > > > > 0001 - Run LICM pass after loop unrolling pass. Runtime
>> > > > > unrollng
>> > > > > will
>> > > > > introduce a runtime check in loop prologue(you can treat it as
>> > > > > a
>> > > > > loop preheader). If the unrolled loop is a inner loop, then the
>> > > > > proglogue will be inside the outer loop. LICM pass can help to
>> > > > > promote the runtime check out if the checked value is loop
>> > > > > invariant.
>> > > >
>> > > > I think makes sense, at least for LICM, and is consistent with
>> > > > what
>> > > > James observed from the early run of the unroller. Please add a
>> > > > comment explaining why those passes are there. This file does not
>> > > > have many 'rationale' comments, and this is not a good thing. Why
>> > > > are you adding CVP? Can you please add some test cases (we
>> > > > normally
>> > > > don't add tests that runs the full pipeline, but for testing the
>> > > > pipeline, it is a good idea).
>> > > >
>> > > > >
>> > > > >
>> > > > > 0002 - Introduce runtime unrolling disable matadata and use it
>> > > > > to
>> > > > > mark the scalar loop from vectorization. Runtime unrolling is
>> > > > > an
>> > > > > expensive optimization which can bring benefit only if the loop
>> > > > > is
>> > > > > hot and iteration number is relatively large enough. For some
>> > > > > loops,
>> > > > > we know they are not worth to be runtime unrolled. The scalar
>> > > > > loop
>> > > > > from vectorization is one of the cases.
>> > > >
>> > > > I think this is a good idea. However, I think we might be
>> > > > overlooking
>> > > > something. If the purpose of the scalar loop is only to handle
>> > > > the
>> > > > 'left over' part of the iteration space that is not divisible by
>> > > > the
>> > > > vector length. However, if there are runtime safety checks, and
>> > > > those checks generally fail, then the loop could be hot. Can we
>> > > > exclude the case where we've emitted safety checks?
>> > > >
>> > > > >
>> > > > >
>> > > > > 0003 - Enable partial & runtime unrolling on cortex-a57, and
>> > > > > double
>> > > > > the unrolling threshold if the loop depth > 1. For inner one of
>> > > > > nested loops, it is more likely to be a hot loop, and the
>> > > > > runtime
>> > > > > check can be promoted out from patch 0001, so the overhead is
>> > > > > less,
>> > > > > we can try a larger threshold to unroll more loops.
>> > > > >
>> > > >
>> > > >
>> > > > + if (L->getLoopDepth() > 1)
>> > > > + UP.PartialThreshold *= 2;
>> > > >
>> > > > Please add a comment here.
>> > > >
>> > > > -Hal
>> > > >
>> > > > >
>> > > > >
>> > > > >
>> > > > > Combined above changes together, we can get below performance
>> > > > > and
>> > > > > code size changes.
>> > > > >
>> > > > >
>> > > > > Benchmark Execution time code bloat
>> > > > >
>> > > > >
>> > > > > spec.cpu2000.179_art -16.567% 8.805%
>> > > > > spec.cpu2000.177_mesa -2.771% 1.912%
>> > > > > spec.cpu2006.483_xalancbmk -2.555% 0.076%
>> > > > > spec.cpu2000.256_bzip2 -1.648% 2.414%
>> > > > > spec.cpu2006.433_milc -1.228% 1.353%
>> > > > > spec.cpu2006.456_hmmer -1.079% 2.413%
>> > > > >
>> > > > > spec.cpu2006.462_libquantum 2.492% 1.482%
>> > > > > spec.cpu2000.253_perlbmk 1.563% 0.464%
>> > > > > spec.cpu2006.450_soplex 1.379% 1.925%
>> > > > > spec.cpu2000.186_crafty 1.242% 0.005%
>> > > > >
>> > > > > spec.geomean -0.546% 0.952%
>> > > > >
>> > > > >
>> > > > > Please review. Thanks.
>> > > > >
>> > > > >
>> > > > > --
>> > > > >
>> > > > >
>> > > > > Best Regards,
>> > > > >
>> > > > >
>> > > > > Kevin Qin
>> > > > > _______________________________________________
>> > > > > llvm-commits mailing list
>> > > > > llvm-commits at cs.uiuc.edu
>> > > > > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>> > > > >
>> > > >
>> > > > --
>> > > > Hal Finkel
>> > > > Assistant Computational Scientist
>> > > > Leadership Computing Facility
>> > > > Argonne National Laboratory
>> > > >
>> > > >
>> > > >
>> > > >
>> > > > --
>> > > >
>> > > >
>> > > > Best Regards,
>> > > >
>> > > >
>> > > > Kevin Qin
>> > >
>> > > --
>> > > Hal Finkel
>> > > Assistant Computational Scientist
>> > > Leadership Computing Facility
>> > > Argonne National Laboratory
>> > >
>> > >
>> > >
>> > >
>> > > --
>> > >
>> > >
>> > > Best Regards,
>> > >
>> > >
>> > > Kevin Qin
>> >
>> > --
>> > Hal Finkel
>> > Assistant Computational Scientist
>> > Leadership Computing Facility
>> > Argonne National Laboratory
>> >
>> >
>> >
>> >
>> > --
>> >
>> >
>> > Best Regards,
>> >
>> >
>> > Kevin Qin
>>
>> --
>> Hal Finkel
>> Assistant Computational Scientist
>> Leadership Computing Facility
>> Argonne National Laboratory
>>
>
>
>
> --
> Best Regards,
>
> Kevin Qin
>
>
>
>
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
>


-- 
Best Regards,

Kevin Qin
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