[LLVMdev] How to make Polly ignore some non-affine memory accesses

[Marcello Maggioni]

2011/11/14 Tobias Grosser <tobias at grosser.es>:
> On 11/14/2011 02:45 PM, Marcello Maggioni wrote:
>>
>> 2011/11/14 Tobias Grosser<tobias at grosser.es>:
>>>
>>> On 11/14/2011 01:24 AM, Marcello Maggioni wrote:
>>>>
>>>> Hi Tobias.
>>>>
>>>> I worked on enabling Polly accepting non affine memory accesses and I
>>>> produced a patch.
>>>
>>> Great.
>>>
>>>> I saw that there were a lot of updates in Polly recently, so I had to
>>>> redo a lot of the work I did and that slowed me quite a bit.
>>>
>>> Ups, sorry! However, I believe without these changes detecting non-affine
>>> memory access functions would have been a lot more complicated.
>>
>> Indeed! The patch almost shrinked to half the code it was before those
>> changes! Great work.
>
> Thanks. (You motivated me to fix this, when you asked about non-affine
> access functions)
>
>>> this should be
>>>    } else {
>>>
>>>> +    Type = MayWrite;
>>>
>>> You are right, we should use may-accesses here. But why always setting
>>> the
>>> type to may-write? A read should remain a read (as there is no difference
>>> between read and may-read).
>>
>> You are right, in the patch for the old version that was handled
>> correctly, I don't know how this reverted back to this way in the
>> patch for the new version , I'll get it fixed.
>
> Wonderful. Very cool that you realized I added MayWrite exactly for this
> case.
>
>>>> +         Functions.push_back(std::make_pair(IRAccess(Type,
>>>> +
>>>>  BasePointer->getValue(),
>>>> +                                                  AccessFunction, Size,
>>>> false),
>>>> +&Inst));
>>>> +      }
>>>> +    }
>>>>    }
>>>>
>>>>    if (Functions.empty())
>>
>> Yeah, there are quite a few stylistic problems actually, my bad!! I'll
>> get all the style problems fixed as fast as possible! Sorry for that.
>
> Alright. I failed on this myself, which is why Polly is not everywhere
> perfect. Still, we should try to follow the LLVM style guide.
>
> BTW, if you find any problems in patches I commit or in Polly itself or if
> your find anything that you don't understand, please go ahead and let me
> know. Even if it is correct and you just did not get it, I think this is a
> documentation bug and should be fixed.
>
>>> Besides the comments above, the patch looks great. It is a nice
>>> improvement
>>> to Polly. Can you repost it after the comments are addressed? Also could
>>> you
>>> include a minimal test case in the patch, that verifies this features is
>>> working correctly.
>>
>> Thank you, for your time Tobias explaining all the issues with the
>> patch so throughly and in a clear manner .
>
> You did a good job working on the patch. It is great if people go ahead,
> work for themselves and send in a patch that works. Even better if the right
> approach was taken and just some smaller remarks are necessary.
>
>> Should I make a specific subdirectory for the test case?
>
> No. I think you can put one test case in test/ScopInfo that runs
> -polly-scops -analyze and one in test/CodeGeneration that ensures that the
> correct code is generated.
>
>> >> Thanks
>>>
>>> Tobi
>>>
>>> P.S.: Please post patches to the mailing lists.
>
>> What do you mean with post patches to the mailing lists? Do you mean
>> in llvm-dev or llvm-commit?
>> The previous patch has been posted on llvm-dev, was that wrong?
>
> Normally patches should either be posted on llvm-commit or
> polly-dev at googlegroups.com.
>
> In this case it seems you sent two separate emails, one to me and another to
> Sebastian and llvmdev. I just saw the one to me and did not see that another
> one was sent to llvmdev. Just send next time one email with all of us
> copied.
>
> Cheers
> Tobi
>

Hi, I implemented the changes you required, I hope this I solved all
the stylistic issues now and I also added the flag you required.

I added a test case to the patch , but I'm not very expert with the
llvm testing framework and I had difficulties testing running the
test. I tried running the polly test suite compiling polly with CMAKE,
but I have linking problems with CMAKE while linking the
LLVMPolly.dylib library and can't figure out why (lots of linker
errors). The autotools build works perfectly but polly-tests doesn't
work with autotools.
I tried running directly the tests with lit , but it gives me

lit.py: lit.cfg:74: fatal: No site specific configuration available!

Do you know how can I run the tests manually to check if they are
correct? I tried searching around , but couldn't find a reliable way
to check if the test works.

The preliminary patch is attached to the mail.

Marcello
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