llvm dev - May 2016 - [GSoC 2016] Introduction & Feedback - Better Alias Analysis

On 05/11/2016 05:16 PM, George Burgess IV via llvm-dev
wrote:
> > After applying the patch on r267335 and bootstrap LLVM/clang with 
> cfl-aa enabled on its own as well as behind basic-aa on an x86 
> machine, I ran test-suite with lit and saw no failed test cases
>
> Woohoo! This is great news. :D
Awesome!
>
> I'm not sure how closely everyone is reading the intro emails, so we 
> may get more help if we also send a slightly more targeted "Hey, CFLAA
> isn't obviously broken anymore. Please help us find any other 
> problems/please report performance numbers to us," email. Whether we 
> do that this very second, or when GSoC actually starts, is up to you.
Once this lands in tree, I'll do a run on our codebase to see if I see 
anything obvious.  I suspect others can do the same.

Philip
>
> On Wed, May 11, 2016 at 3:02 PM, Jia Chen via llvm-dev 
> <llvm-dev at lists.llvm.org <mailto:llvm-dev at
lists.llvm.org>> wrote:
>
>     Dear LLVM community,
>
>     I am a GSoC student this year working on the project of improving
>     alias analysis in LLVM.
>
>     The proposal initially came from a discussion I had with various
>     devs on the mailing list some time ago [1]. The general goal of
>     this project is to make alias analysis (in particular, cfl-aa)
>     "better", and to be more concrete here is a list of
objectives I
>     had in mind:
>
>     - Evaluating the current state of cfl-aa, and fix all known bugs.
>     - Improving the precision of cfl-aa. Although flow sensitivity may
>     not be very helpful for LLVM in its current form, field
>     sensitivity should be something important and I'll definitely try
>     to add it to cfl-aa. Given the complexity LLVM's memory model has,
>     my guess is that I may need to spend most of my summer on this task.
>     - Improving the performance of cfl-aa. (It is fairly efficient in
>     its current form, IMO. Further performance tuning may be needed if
>     more features such as field sensitivity were added.)
>     - Understanding how various clients interacts with cfl-aa, and
>     exploring various ways to minimize precision/performance losses
>     caused by the interaction.
>     - If time permits, maybe I can look at scev-aa and try to bring it
>     back to the compilation pipeline.
>
>     I know these objectives are not as clear cut as other GSoC
>     projects people used to have, and it is hard to come up with a
>     clear schedule as well as a success metric. Nevertheless even if
>     my contributions may seem fragmented and incremental, I felt that
>     as long as the work is useful to the community, it is going to be
>     the most valuable summer I've ever had as a student.
>
>     ** Current Status **
>
>     I've submitted a simple patch last week (D19776) to fix a subtle
>     bug in cfl-aa. After applying the patch on r267335 and bootstrap
>     LLVM/clang with cfl-aa enabled on its own as well as behind
>     basic-aa on an x86 machine, I ran test-suite with lit and saw no
>     failed test cases. I didn't time the tests in any rigorous way,
>     but it didn't look like cfl-aa add very noticable performance
>     overhead. It may be a good time, I think, to call for people's
>     help to test cfl-aa on their internal codebase. If everything goes
>     well, we should be able to safely turn on cfl-aa by default soon.
>
>     Let me conclude this introduction by saying thank you for
>     accepting my proposal, and in particular I want to thank my
>     mentors George and Hal for the providing me with so much support
>     and guidance. Please let me know if you have any comments or
>     suggestions.
>
>     [1] http://lists.llvm.org/pipermail/llvm-dev/2016-March/096851.html
>
>     -- 
>     Best Regards,
>
>     --
>     Jia Chen
>     Department of Computer Science
>     University of Texas at Austin
>     jchen at cs.utexas.edu <mailto:jchen at cs.utexas.edu>
>
>
>     _______________________________________________
>     LLVM Developers mailing list
>     llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
>     http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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Yep, same. What's the magic rune to enable cfl-aa?

James

On Thu, 12 May 2016 at 05:58 Philip Reames via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> On 05/11/2016 05:16 PM, George Burgess IV via llvm-dev wrote:
>
> > After applying the patch on r267335 and bootstrap LLVM/clang with
> cfl-aa enabled on its own as well as behind basic-aa on an x86 machine, I
> ran test-suite with lit and saw no failed test cases
>
> Woohoo! This is great news. :D
>
> Awesome!
>
>
> I'm not sure how closely everyone is reading the intro emails, so we
may
> get more help if we also send a slightly more targeted "Hey, CFLAA
isn't
> obviously broken anymore. Please help us find any other problems/please
> report performance numbers to us," email. Whether we do that this very
> second, or when GSoC actually starts, is up to you.
>
> Once this lands in tree, I'll do a run on our codebase to see if I see
> anything obvious.  I suspect others can do the same.
>
>
> Philip
>
>
> On Wed, May 11, 2016 at 3:02 PM, Jia Chen via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Dear LLVM community,
>>
>> I am a GSoC student this year working on the project of improving alias
>> analysis in LLVM.
>>
>> The proposal initially came from a discussion I had with various devs
on
>> the mailing list some time ago [1]. The general goal of this project is
to
>> make alias analysis (in particular, cfl-aa) "better", and to
be more
>> concrete here is a list of objectives I had in mind:
>>
>> - Evaluating the current state of cfl-aa, and fix all known bugs.
>> - Improving the precision of cfl-aa. Although flow sensitivity may not
be
>> very helpful for LLVM in its current form, field sensitivity should be
>> something important and I'll definitely try to add it to cfl-aa.
Given the
>> complexity LLVM's memory model has, my guess is that I may need to
spend
>> most of my summer on this task.
>> - Improving the performance of cfl-aa. (It is fairly efficient in its
>> current form, IMO. Further performance tuning may be needed if more
>> features such as field sensitivity were added.)
>> - Understanding how various clients interacts with cfl-aa, and
exploring
>> various ways to minimize precision/performance losses caused by the
>> interaction.
>> - If time permits, maybe I can look at scev-aa and try to bring it back
>> to the compilation pipeline.
>>
>> I know these objectives are not as clear cut as other GSoC projects
>> people used to have, and it is hard to come up with a clear schedule as
>> well as a success metric. Nevertheless even if my contributions may
seem
>> fragmented and incremental, I felt that as long as the work is useful
to
>> the community, it is going to be the most valuable summer I've ever
had as
>> a student.
>>
>> ** Current Status **
>>
>> I've submitted a simple patch last week (D19776) to fix a subtle
bug in
>> cfl-aa. After applying the patch on r267335 and bootstrap LLVM/clang
with
>> cfl-aa enabled on its own as well as behind basic-aa on an x86 machine,
I
>> ran test-suite with lit and saw no failed test cases. I didn't time
the
>> tests in any rigorous way, but it didn't look like cfl-aa add very
>> noticable performance overhead. It may be a good time, I think, to call
for
>> people's help to test cfl-aa on their internal codebase. If
everything goes
>> well, we should be able to safely turn on cfl-aa by default soon.
>>
>> Let me conclude this introduction by saying thank you for accepting my
>> proposal, and in particular I want to thank my mentors George and Hal
for
>> the providing me with so much support and guidance. Please let me know
if
>> you have any comments or suggestions.
>>
>> [1] http://lists.llvm.org/pipermail/llvm-dev/2016-March/096851.html
>>
>> --
>> Best Regards,
>>
>> --
>> Jia Chen
>> Department of Computer Science
>> University of Texas at Austinjchen at cs.utexas.edu
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>
>
> _______________________________________________
> LLVM Developers mailing listllvm-dev at
lists.llvm.orghttp://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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(Just to note: the other issue i remember with CFL-AA is that it currently
causes performance loss. This is quite common when you increase precision,
because things move/change things they couldn't before, and often do so
without the natural bounds imprecision provided before :P)


On Thu, May 12, 2016 at 12:29 AM, James Molloy via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Yep, same. What's the magic rune to enable cfl-aa?
>
> James
>
> On Thu, 12 May 2016 at 05:58 Philip Reames via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> On 05/11/2016 05:16 PM, George Burgess IV via llvm-dev wrote:
>>
>> > After applying the patch on r267335 and bootstrap LLVM/clang with
>> cfl-aa enabled on its own as well as behind basic-aa on an x86 machine,
I
>> ran test-suite with lit and saw no failed test cases
>>
>> Woohoo! This is great news. :D
>>
>> Awesome!
>>
>>
>> I'm not sure how closely everyone is reading the intro emails, so
we may
>> get more help if we also send a slightly more targeted "Hey, CFLAA
isn't
>> obviously broken anymore. Please help us find any other problems/please
>> report performance numbers to us," email. Whether we do that this
very
>> second, or when GSoC actually starts, is up to you.
>>
>> Once this lands in tree, I'll do a run on our codebase to see if I
see
>> anything obvious.  I suspect others can do the same.
>>
>>
>> Philip
>>
>>
>> On Wed, May 11, 2016 at 3:02 PM, Jia Chen via llvm-dev <
>> <llvm-dev at lists.llvm.org>llvm-dev at lists.llvm.org> wrote:
>>
>>> Dear LLVM community,
>>>
>>> I am a GSoC student this year working on the project of improving
alias
>>> analysis in LLVM.
>>>
>>> The proposal initially came from a discussion I had with various
devs on
>>> the mailing list some time ago [1]. The general goal of this
project is to
>>> make alias analysis (in particular, cfl-aa) "better", and
to be more
>>> concrete here is a list of objectives I had in mind:
>>>
>>> - Evaluating the current state of cfl-aa, and fix all known bugs.
>>> - Improving the precision of cfl-aa. Although flow sensitivity may
not
>>> be very helpful for LLVM in its current form, field sensitivity
should be
>>> something important and I'll definitely try to add it to
cfl-aa. Given the
>>> complexity LLVM's memory model has, my guess is that I may need
to spend
>>> most of my summer on this task.
>>> - Improving the performance of cfl-aa. (It is fairly efficient in
its
>>> current form, IMO. Further performance tuning may be needed if more
>>> features such as field sensitivity were added.)
>>> - Understanding how various clients interacts with cfl-aa, and
exploring
>>> various ways to minimize precision/performance losses caused by the
>>> interaction.
>>> - If time permits, maybe I can look at scev-aa and try to bring it
back
>>> to the compilation pipeline.
>>>
>>> I know these objectives are not as clear cut as other GSoC projects
>>> people used to have, and it is hard to come up with a clear
schedule as
>>> well as a success metric. Nevertheless even if my contributions may
seem
>>> fragmented and incremental, I felt that as long as the work is
useful to
>>> the community, it is going to be the most valuable summer I've
ever had as
>>> a student.
>>>
>>> ** Current Status **
>>>
>>> I've submitted a simple patch last week (D19776) to fix a
subtle bug in
>>> cfl-aa. After applying the patch on r267335 and bootstrap
LLVM/clang with
>>> cfl-aa enabled on its own as well as behind basic-aa on an x86
machine, I
>>> ran test-suite with lit and saw no failed test cases. I didn't
time the
>>> tests in any rigorous way, but it didn't look like cfl-aa add
very
>>> noticable performance overhead. It may be a good time, I think, to
call for
>>> people's help to test cfl-aa on their internal codebase. If
everything goes
>>> well, we should be able to safely turn on cfl-aa by default soon.
>>>
>>> Let me conclude this introduction by saying thank you for accepting
my
>>> proposal, and in particular I want to thank my mentors George and
Hal for
>>> the providing me with so much support and guidance. Please let me
know if
>>> you have any comments or suggestions.
>>>
>>> [1] http://lists.llvm.org/pipermail/llvm-dev/2016-March/096851.html
>>>
>>> --
>>> Best Regards,
>>>
>>> --
>>> Jia Chen
>>> Department of Computer Science
>>> University of Texas at Austinjchen at cs.utexas.edu
>>>
>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>>
>>
>>
>> _______________________________________________
>> LLVM Developers mailing listllvm-dev at
lists.llvm.orghttp://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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