[llvm-dev] FC : A MLIR+LLVM based Fortran front end

James Y Knight via llvm-dev llvm-dev at lists.llvm.org
Mon Jan 13 09:02:23 PST 2020

Neat, another fortran compiler option.

Does anyone have a list/comparison of all the LLVM fortran compilers? I'm
not really tracking this, since Fortran isn't really my area of expertise,
but I've seen the following. Perhaps there are even more?

"Flang". The original of the name, I think? Abandoned.
"Fort" -- fork of the above flang, renamed. Seems active.

"Flag". Different from the other "flang". Active, but deprecated in favor
of f18.
"f18". Rewrite-from-scratch (?) of adjacent "flang". Active, but not
fully-functional yet (I think?).

"FC". Newly-developed, independent of the other compilers. Active. (But
this source-code dates from the previous announcement, not yet updated with
latest developments):

I don't know how any of these compare with each other, nor why we have so
many. I have no opinion on which or whether any of these should be
"blessed", nor do I really want to become educated enough on this topic to
gain such an opinion personally.

But, given that there appear to be at least 3 fortran compilers under
active development by different people, I would love to be reassured that
such a comparison has been done, and that we are selecting one of them for
good reasons. It'd be great if someone (or multiple someones) could post a
summary/comparison of what these things all are, and why one is the right
path forward vs another.

On Mon, Jan 13, 2020 at 2:46 AM Prashanth N R via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hi Chris-
> We are mostly cleaning up the code for open sourcing. Early code drop will
> happen in a day or two and will continue through this week. We would love
> to work with the rest of the community on this.
> thanks,
> -Prashanth
> On Mon, Jan 13, 2020 at 11:17 AM Chris Lattner <clattner at nondot.org>
> wrote:
>> Agreed!  Is the code already available?  What are your plans for it, and
>> are you interested in collaboration with the rest of the LLVM community?
>> -Chris
>> On Jan 11, 2020, at 11:58 AM, Finkel, Hal J. via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>> Hi, Prashanth,
>> That's great news! It sounds like you've made a lot of progress, and I
>> certainly hope that you can make your source available under the LLVM
>> license and that we can all work together going forward.
>>  -Hal
>> On 1/11/20 12:52 PM, Prashanth N R via llvm-dev wrote:
>> Hi-
>> In August we made an announcement  of "FC: A new fortran front end"  [1].
>> At that time to get an end-to-end solution, we made FC to emit LLVM IR
>> directly.  At present, we have upgraded FC to emit MLIR. Currently the
>> language supported is close to Fortran-95. Apart from 400+ unit test cases,
>> out framework passes two SPEC-2017 benchmarks successfully.  Currently we
>> are cleaning up the code and plan to open source the same in a week or so.
>> Apart from the front end changes, we have defined a new high level
>> dialect in MLIR for representing Fortran. We have defined a new Loop Nest
>> Optimization framework along with one Loop Nest Optimization in it for the
>> time being. Also we have supported 4 OpenMP constructs and way to express
>> the same in MLIR framework.
>> Entire code is in the spirit of LLVM. If the community is interested, we
>> would like to work with the community and move forward.
>> thanks,
>> -Prashanth
>> PS: We did try to use F18 for a while and hit the issues raised in [2],
>> [3].
>> 1. http://lists.llvm.org/pipermail/llvm-dev/2019-August/134620.html
>> 2. http://lists.llvm.org/pipermail/llvm-dev/2020-January/138069.html
>> 3.
>> http://lists.llvm.org/pipermail/flang-dev/attachments/20191202/6e7c1e51/attachment-0001.pdf
>> OR http://lists.llvm.org/pipermail/flang-dev/2019-December/000089.html
>> _______________________________________________
>> LLVM Developers mailing listllvm-dev at lists.llvm.orghttps://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>> --
>> Hal Finkel
>> Lead, Compiler Technology and Programming Languages
>> Leadership Computing Facility
>> Argonne National Laboratory
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
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