[llvm-dev] Flang landing in the monorepo - next Monday!

[Eric Christopher via llvm-dev]

Hi Gregory,

(As a note, you didn't reply to the thread so I didn't see this until now.)

As I said in my previous thread: "You don't use a single llvm header
anywhere" that's a pretty low bar for "looks like an llvm project" - and
nothing has changed in the 3 weeks since I sent my earlier message. "We
plan on" isn't a very compelling argument for "looks like llvm".

As far as the current use in the clang driver: Honestly I don't think you
should be using the clang driver and had I seen I probably wouldn't have
accepted those patches either. I think it would be better off to turn parts
of the driver you might need into a separable library rather than include
fortran support into a "c based languages" driver and will probably try to
dig up that patch set and comment.

To be clear: I support the idea of a fortran compiler in llvm and
appreciate that you want to do it right. I would like to see a plan of
attack before we talk about imminently putting things in as relying on the
community to adopt llvm development practices and libraries seems to put a
lot of weight in the community rather than on the project that wants to
move in.

Thanks.

-eric


On Wed, Jan 8, 2020 at 11:16 AM Gregory Rodgers via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hal, Eric, Johannes, David and Peter,
>
> I lead the development of OpenMP for AMD GPUs and work with others at AMD
> who support OpenMP on AMD CPUs. On behalf of our development teams, we
> greatly appreciate your efforts to move the development of flang into a
> subproject in the llvm-project repository and to integrate this development
> effort into the overall LLVM development community.
>
> Like most commercial companies, we have certain procedures (some legal) to
> participate in open source projects.  Since AMD has already engaged in LLVM
> development, adding flang as an LLVM subproject makes it much easier to
> participate in the development of flang.    I look forward to my team
> getting more involved in the development of flang now that it is part of
> LLVM.
>
> I would respectfully disagree with "There's nothing llvm about it".  Flang
> uses the clang offloading architecture used by cuda, hip, and
> openmp-target.  And the runtime will use both libomp and libomptarget
> runtimes found in the llvm project openmp.   While flang frontend may not
> immediately use clang -cc1 parsing and codegen, the upstream clang driver
> already supports a flang toolchain. See clang/lib/Driver/Types.cpp and
> clang/lib/Driver/ToolChains/Flang.cpp.
>
> I think it is better for flang to join LLVM sooner than later.  This will
> help flang developers better adopt llvm development practices.  For
> example, an earlier variant of flang written in c, generated LLVM-IR
> without using llvm::IRBuilder.  This is because the origin of that source
> was from a non-LLVM project. This architecture was rejected partly because
> it was not llvm enough.  This lead to the creation of the f18 C++ project
> which will use llvm::IRbuilder.  F18 is the flang that I expect and hope to
> land in monorepo next Monday.
>
> I am also AMD's representative to the OpenMP Architecture Review Board.
> Adding flang is an important step to completely cover the OpenMP
> specification for c, C++, and FORTRAN in LLVM.
>
> I agree, flang has a long way to go.  But I believe there is enough
> critical mass with flang to join the LLVM development now.
>
> Thank you
>
> Greg Rodgers
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> llvm-dev at lists.llvm.org
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>
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