Hi everyone,
I am very interested in contributing to LLVM project in this year’s GSoC. I am new with LLVM, but this is used in the compiler course in my university. So, I am thinking to involve in LLVM development to have a better knowledge of the system. Currently, I am preparing the proposal.
One of the project that caught my eyes is “New Transformations and Analysis”. Several code transformations and analyses have been introduced in the compiler course that I am currently taking. That’s why I am thinking to involve in writing some new transformations and code analyses. But the list of transformations in the LLVM Open Projects web page seems too brief for me and I need more details on those stuffs.
Loop Dependence Analysis Infrastructure. I have looked in the source codes repo and I saw that there is a file named “DependenceAnalysis.cpp”. So, does that mean this analysis has been implemented?
Value range propagation pass. There was a discussion about this topic (https://groups.google.com/forum/#!topic/llvm-dev/XXqfemtDX74/discussion). Someone already proposed to do this pass for several years ago GSoC. But I can’t find the progress of the work. If no progress, then does it mean that the VRP based on Patterson’s paper need to be implemented although range analysis has been implemented?
Predictive Commoning. The presentation side by Arie Tal seems provide quite clear explanation and examples of the algorithm. I guess the implementation should be straightforward, isn’t it?
Type Inference (aka. Devirtualization) and Value assertions.
Can I get more details of these topics? Does the type inference mean the translation of auto keyword or something else? For value assertions, “unreachable” intrinsic seems has been implemented cause I can find the usage in some of the testcases.
Finally, for this project, must I propose to do all of these analyses and transformations in my GSoC proposal or can I just propose some of them? In addition, I am also looking for a mentor for guidance?
Looking forward for your comments and feedbacks.
Thank you.
Best regards,
Aries Thio.
Hi everyone,
I am very interested in contributing to LLVM project in this year’s GSoC. I am new with LLVM, but this is used in the compiler course in my university. So, I am thinking to involve in LLVM development to have a better knowledge of the system. Currently, I am preparing the proposal.
One of the project that caught my eyes is “New Transformations and Analysis”. Several code transformations and analyses have been introduced in the compiler course that I am currently taking. That’s why I am thinking to involve in writing some new transformations and code analyses. But the list of transformations in the LLVM Open Projects web page seems too brief for me and I need more details on those stuffs.
Loop Dependence Analysis Infrastructure. I have looked in the source codes repo and I saw that there is a file named “DependenceAnalysis.cpp”. So, does that mean this analysis has been implemented?
Value range propagation pass. There was a discussion about this topic (https://groups.google.com/forum/#!topic/llvm-dev/XXqfemtDX74/discussion). Someone already proposed to do this pass for several years ago GSoC. But I can’t find the progress of the work. If no progress, then does it mean that the VRP based on Patterson’s paper need to be implemented although range analysis has been implemented?
Predictive Commoning. The presentation side by Arie Tal seems provide quite clear explanation and examples of the algorithm. I guess the implementation should be straightforward, isn’t it?
Type Inference (aka. Devirtualization) and Value assertions.
Can I get more details of these topics? Does the type inference mean the translation of auto keyword or something else? For value assertions, “unreachable” intrinsic seems has been implemented cause I can find the usage in some of the testcases.
Finally, for this project, must I propose to do all of these analyses and transformations in my GSoC proposal or can I just propose some of them? In addition, I am also looking for a mentor for guidance?
Looking forward for your comments and feedbacks.
Thank you.
Best regards,
Aries Thio.
_______________________________________________ LLVM Developers mailing list llvm...@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
On Mar 22, 2016, at 5:13 PM, Philip Reames <list...@philipreames.com> wrote:
On 03/20/2016 05:38 AM, Aries Gunawan via llvm-dev wrote:Hi everyone,I am very interested in contributing to LLVM project in this year’s GSoC. I am new with LLVM, but this is used in the compiler course in my university. So, I am thinking to involve in LLVM development to have a better knowledge of the system. Currently, I am preparing the proposal.One of the project that caught my eyes is “New Transformations and Analysis”. Several code transformations and analyses have been introduced in the compiler course that I am currently taking. That’s why I am thinking to involve in writing some new transformations and code analyses. But the list of transformations in the LLVM Open Projects web page seems too brief for me and I need more details on those stuffs.Loop Dependence Analysis Infrastructure. I have looked in the source codes repo and I saw that there is a file named “DependenceAnalysis.cpp”. So, does that mean this analysis has been implemented?
I believe major progress has been made it, but haven't been following it closely. I'd suggest talking to committers active in this file in the recent past to determine what useful work might be left of appropriate scope. \
This is largely stalled. The key problem is that between LazyValueInfo (constant ranges) and SCEV (symbolic ranges in loops), there's fairly little profit to be had and range analysis is relatively expensive. I'd strongly discourage you from implementing a traditional range analysis for LLVM without deeply understanding the history here.Value range propagation pass. There was a discussion about this topic (https://groups.google.com/forum/#!topic/llvm-dev/XXqfemtDX74/discussion). Someone already proposed to do this pass for several years ago GSoC. But I can’t find the progress of the work. If no progress, then does it mean that the VRP based on Patterson’s paper need to be implemented although range analysis has been implemented?The closest I know of to this in tree is LoadLoadElimination.cpp and (in some cases) the PRE code inside GVN.cpp. Building something like this on top of SCEV could be quite interesting. You should definitely talk to Adam Nemet (CC'd) about thisPredictive Commoning. The presentation side by Arie Tal seems provide quite clear explanation and examples of the algorithm. I guess the implementation should be straightforward, isn’t it?
On 23/03/16 01:13, Philip Reames via llvm-dev wrote:
>
>
> On 03/20/2016 05:38 AM, Aries Gunawan via llvm-dev wrote:
>>
>> Hi everyone,
>>
>> I am very interested in contributing to LLVM project in this year’s
>> GSoC. I am new with LLVM, but this is used in the compiler course in
>> my university. So, I am thinking to involve in LLVM development to
>> have a better knowledge of the system. Currently, I am preparing the
>> proposal.
>>
>> One of the project that caught my eyes is “New Transformations and
>> Analysis”. Several code transformations and analyses have been
>> introduced in the compiler course that I am currently taking. That’s
>> why I am thinking to involve in writing some new transformations and
>> code analyses. But the list of transformations in the LLVM Open
>> Projects web page seems too brief for me and I need more details on
>> those stuffs.
>>
>> *Loop Dependence Analysis Infrastructure. *I have looked in the source
>> codes repo and I saw that there is a file named
>> “DependenceAnalysis.cpp”. So, does that mean this analysis has been
>> implemented?
>>
> I believe major progress has been made it, but haven't been following it
> closely. I'd suggest talking to committers active in this file in the
> recent past to determine what useful work might be left of appropriate
> scope.
>>
>> **
>>
>> *Value range propagation pass. *There was a discussion about this
>> topic
>> (https://groups.google.com/forum/#!topic/llvm-dev/XXqfemtDX74/discussion
>> <https://groups.google.com/forum/#%21topic/llvm-dev/XXqfemtDX74/discussion>).
>> Someone already proposed to do this pass for several years ago GSoC.
>> But I can’t find the progress of the work. If no progress, then does
>> it mean that the VRP based on Patterson’s paper need to be implemented
>> although range analysis has been implemented?
>>
> This is largely stalled. The key problem is that between LazyValueInfo
> (constant ranges) and SCEV (symbolic ranges in loops), there's fairly
> little profit to be had and range analysis is relatively expensive. I'd
> strongly discourage you from implementing a traditional range analysis
> for LLVM without deeply understanding the history here.
>>
>> **
>>
>> *Predictive Commoning. *The presentation side by Arie Tal seems
>> provide quite clear explanation and examples of the algorithm. I guess
>> the implementation should be straightforward, isn’t it?
>>
> The closest I know of to this in tree is LoadLoadElimination.cpp and (in
> some cases) the PRE code inside GVN.cpp. Building something like this
> on top of SCEV could be quite interesting. You should definitely talk
> to Adam Nemet (CC'd) about this.
>>
>> **
>>
>> *Type Inference (aka. Devirtualization) and Value assertions. *
>>
>> Can I get more details of these topics? Does the type inference mean
>> the translation of _auto_ keyword or something else? For value
>> assertions, “unreachable” intrinsic seems has been implemented cause I
>> can find the usage in some of the testcases.
>>
> I believe the "value assertions" link may be stale. If I'm reading
> that correctly, it looks like the motivation for @llvm.assume.
This indeed sounds a lot like the @llvm.assume work. I did notice
though that these assumptions aren't yet always used when available.
For example, the following code will still contain a fallback loop when
compiled even though it is can be removed according to the provided
assumptions:
int foo(int *A, int n) {
int sum = 0;
__builtin_assume(n>7 && n%8==0);
for(int i=0; i < n; ++i)
sum += A[i] + c;
return sum;
}
Which was compiled with "clang -S -O3 test.c"
I guess that there are more similar cases where we're not using these
assumptions yet. Maybe that's a nice project as well.
Cheers,
Roel
On Mar 22, 2016, at 5:13 PM, Philip Reames <list...@philipreames.com> wrote:On 03/20/2016 05:38 AM, Aries Gunawan via llvm-dev wrote:I believe major progress has been made it, but haven't been following it closely. I'd suggest talking to committers active in this file in the recent past to determine what useful work might be left of appropriate scope. \Loop Dependence Analysis Infrastructure. I have looked in the source codes repo and I saw that there is a file named “DependenceAnalysis.cpp”. So, does that mean this analysis has been implemented?We actually have two DA frameworks at the moment. The file you mention is only used currently by the LoopInterchange pass that is off by default. There is also the other framework that I’ve been working on called LoopAccessAnalysis that’s currently used by the LoopVectorizer, LoopLoadElimination, LoopDistribution and LICMLoopVersioning (the latter two are off by default).
On Mar 28, 2016, at 7:12 AM, Hongbin Zheng <ethe...@gmail.com> wrote:Hi Adam,On Wed, Mar 23, 2016 at 1:50 PM, Adam Nemet via llvm-dev <llvm...@lists.llvm.org> wrote:On Mar 22, 2016, at 5:13 PM, Philip Reames <list...@philipreames.com> wrote:On 03/20/2016 05:38 AM, Aries Gunawan via llvm-dev wrote:I believe major progress has been made it, but haven't been following it closely. I'd suggest talking to committers active in this file in the recent past to determine what useful work might be left of appropriate scope. \Loop Dependence Analysis Infrastructure. I have looked in the source codes repo and I saw that there is a file named “DependenceAnalysis.cpp”. So, does that mean this analysis has been implemented?We actually have two DA frameworks at the moment. The file you mention is only used currently by the LoopInterchange pass that is off by default. There is also the other framework that I’ve been working on called LoopAccessAnalysis that’s currently used by the LoopVectorizer, LoopLoadElimination, LoopDistribution and LICMLoopVersioning (the latter two are off by default).Do you think it is reasonable and feasible to provide a common interface for different loop dependence analyses like alias analysis, such that passes like LoopVectorizer/LoopLoadElimination/LoopDistribution etc. can query loop dependency information from different implementations for precision/compile-time trade off?