[flang-dev] Notes from the Flang Roundtable

Damian Rouson via flang-dev flang-dev at lists.llvm.org
Thu Nov 18 14:32:09 PST 2021

I had to leave the call early so I don't know whether the topics below were
addressed.  Hopefully my comments below are useful.

On Thu, Nov 18, 2021 at 12:37 PM Perry-Holby, Alexis via flang-dev <
flang-dev at lists.llvm.org> wrote:

>    - Driver can make an executable now!
>       - Is now a good time to switch name from flang-new to flang?
> This it sounds like a good idea to me.  On a possibly related note, at
what point in the process does an end user have the experience of
installing flang and producing an executable file with something like
"flang hello_world.f90"?  And when will the end user be able to install
flang via common package managers?

>    - Two different ways to approach continued development: keep chasing
>    standards or make a high-quality F95 compiler with optimizations and such?
> The utility of a compiler only becomes non-zero once the compiler supports
the standards a code uses.  Every project I lead uses Fortran 2018.  Also,
any support for Fortran 2018 parallel features might improve  performance
more than optimizing Fortran 95 serial features.  For example, any time
spent on optimizing the Fortran 95 FOR ALL statement would be better spent
offloading DO CONCURRENT to GPUs -- especially given that the Fortran 2018
standard officially declares FOR ALL to be obsolescent. Fortran 2018 also
deletes some features so you probably don't want to optimize any of those.

Progressing through the standards chronologically also means missing some
attractive low-hanging fruit.  For example, supporting the Fortran 2018
collective subroutines is much easier than supporting Fortran 2008
coarrays. I've worked on several production applications for which the
collective subroutines provide all of the parallel communication needs even
with no coarrays anywhere in the codes.

If the decision is to focus on Fortran 2003 next, will patches for more
recent standards be accepted?

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