[LLVMdev] GSoC project questions.

Fri Apr 19 10:33:47 PDT 2013

Alex,

Please follow the guidelines listed at
https://google-melange.appspot.com/gsoc/org/google/gsoc2013/llvm

:)

On Fri, Apr 19, 2013 at 9:17 PM, Alex L <arphaman at gmail.com> wrote:
> Hi again,
>
> I was studying and building the lfort repository as I said I would do, but
> after a while I decided that I would like to work on flang instead.
> So, I forked flang and so far I've had pretty good success with it, here's
> what I've done:
> - Merged a pull request from a github user Michael Gottesman(He added
> support for latest llvm and cmake)
> - Fixed character literal continuation bug.
> - Implemented INCLUDE statement (Only searches for files in -I dirs now)
> - Implemented if-stmt(not the full if-construct yet).
> You can see my repository here: https://github.com/hyp/flang
>
> So far I've enjoyed working on flang, and I would like to apply to GSoC with
> it. I will start writing a proposal in the next couple of days. Should I
> send it to the mailing list first, or should I send it directly to GSoC?
>
> Thanks.
>
>
> 2013/4/13 Alex L <arphaman at gmail.com>
>>>
>>> No. I think that you might want to use Clang for inspiration on design,
>>> but you'd certainly not be bound to that. If you'd like to take a much more
>>> start-from-scratch approach, you can also look at the code that Bill put
>>> together: https://github.com/isanbard/flang - If you use that as a base, we
>>> can always merge it with the useful lfort pieces later.
>>
>> Ok, that's good to know. In the next couple of days I will study the lfort
>> repository more, and see if I can perhaps contribute a commit or two.
>> Thankfully I know git and github and so that would make lfort really
>> accessible for me.
>>
>>
>> 2013/4/13 Hal Finkel <hfinkel at anl.gov>
>>>
>>> ----- Original Message -----
>>> > From: "Alex L" <arphaman at gmail.com>
>>> > To: "Hal Finkel" <hfinkel at anl.gov>
>>> > Cc: "Anton Korobeynikov" <anton at korobeynikov.info>, "Bill Wendling"
>>> > <isanbard at gmail.com>, "LLVM Developers Mailing
>>> > List" <llvmdev at cs.uiuc.edu>
>>> > Sent: Saturday, April 13, 2013 11:34:43 AM
>>> > Subject: Re: [LLVMdev] GSoC project questions.
>>> >
>>> >
>>> > Thanks for your replies.
>>> > Working on the lfort compiler would certainly be an interesting
>>> > project for me for this GSoC.
>>>
>>> Great!
>>>
>>> > I have studied lfort repository and
>>> > commits, and I see that it has a lot of stuff for C/C++, am I
>>> > correct that this is a fork of Clang? If this is correct, I wonder
>>> > why this approach was chosen instead of starting out from scratch -
>>> > is it because Clang already has a lot of code which can be reused
>>> > for the Fortran compiler?
>>>
>>> Yes, lfort started out as a fork of Clang, but I don't think that is
>>> overly relevant at this point. There are a few things from Clang that the
>>> Fortran compiler could really reuse:
>>>
>>>  1. The driver/tools infrastructure (the code that finds the system
>>> libraries, knows how to call the assembler, linker, etc.)
>>>  2. The C preprocessor (in practice, a lot of Fortran code assumes the
>>> existence of an integrated C preprocessor).
>>>    2a. The lexical analysis framework, and to some extent, the classes
>>> for printing nice error messages
>>>  3. The directory layout and regression-testing setup
>>>
>>> At this point, I've pretty much finished taking advantage of all of those
>>> pieces in lfort, and the remainder of the core code from Clang needs to be
>>> replaced with Fortran-specific bits. Keeping the same general design
>>> probably makes sense, but I could certainly be convinced otherwise.
>>>
>>> > I'm also unfamiliar with Clang and I was a
>>> > bit overwhelmed when I saw the lfort repository at first because of
>>> > this. If I were to work on this project, would I be required to use
>>> > the Clang code?
>>>
>>> No. I think that you might want to use Clang for inspiration on design,
>>> but you'd certainly not be bound to that. If you'd like to take a much more
>>> start-from-scratch approach, you can also look at the code that Bill put
>>> together: https://github.com/isanbard/flang - If you use that as a base, we
>>> can always merge it with the useful lfort pieces later.
>>>
>>> Thanks again,
>>> Hal
>>>
>>> >
>>> >
>>> >
>>> > 2013/4/13 Hal Finkel < hfinkel at anl.gov >
>>> >
>>> >
>>> >
>>> > ----- Original Message -----
>>> > > From: "Anton Korobeynikov" < anton at korobeynikov.info >
>>> >
>>> > > To: "James Courtier-Dutton" < james.dutton at gmail.com >
>>> > > Cc: "Hal Finkel" < hfinkel at anl.gov >, "Bill Wendling" <
>>> > > isanbard at gmail.com >, "LLVM Developers Mailing List"
>>> > > < llvmdev at cs.uiuc.edu >
>>> >
>>> > > Sent: Saturday, April 13, 2013 9:12:39 AM
>>> > > Subject: Re: [LLVMdev] GSoC project questions.
>>> > >
>>> >
>>> > > > I agree that creating a complete Fortran compiler is a huge
>>> > > > effort.
>>> > > > But what about approaching it from a test driven development
>>> > > > perspective?
>>> > > > We start with a few small Fortran programs as "test cases".
>>> > > > The GSoC task then gives the task as getting test case 1 to work.
>>> > > > We could also apply this of "lfort". Determine a test case that
>>> > > > currently
>>> > > > fails on lfort, and ask the GSoC task to pass the test.
>>> > > All this make sense only if there is interested party in long-term
>>> > > development and maintenance. Otherwise the code will bitrot really
>>> > > quickly and thus will be waste of time and money. Is there such a
>>> > > party?
>>> >
>>> > I am certainly interested in long-term development and maintenance. I
>>> > think that the first step toward making a useful Fortran compiler is
>>> > this:
>>> >
>>> > 1. It should be able to compile BLAS: http://www.netlib.org/blas/
>>> > (these are Fortran 77, and have no I/O, so should be relatively
>>> > simple)
>>> >
>>> > 2. If that is complete, then move on to LAPACK:
>>> > http://www.netlib.org/lapack/index.html (these use some subset of
>>> > Fortran 90)
>>> >
>>> > As you can see from the test cases currently in lfort, most of the
>>> > driver functionality and lexical analysis (for both Fortran 77 and
>>> > 90) is done, and I've started on parsing (and semantic analysis and
>>> > codegen for) variable declarations and some simple statements. I
>>> > think that a motivated student could make a lot of headway, and
>>> > should be able to at least finish step 1. Thoughts?
>>> >
>>> > -Hal
>>> >
>>> >
>>> >
>>> > >
>>> > > --
>>> > > With best regards, Anton Korobeynikov
>>> > > Faculty of Mathematics and Mechanics, Saint Petersburg State
>>> > > University
>>> > >
>>> > _______________________________________________
>>> > LLVM Developers mailing list
>>> > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
>>> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>> >
>>> >
>>
>>
>


-- 
With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University