[cfe-dev] [F18/AST] Using clang tooling with f18
Petr Penzin via cfe-dev
cfe-dev at lists.llvm.org
Thu Oct 18 19:32:11 PDT 2018
There was a different Flang project before Nvidia's involvement, which
successfully used and extended Clang ASTs. The code is still on Github
<https://github.com/llvm-flang/flang>, along with updated fork
<https://github.com/llvm-fortran/fort/> (which builds with trunk). It
implements a fair share of the Fortran features that you have mentioned
using (what is essentially) Clang's infrastructure.
IMO, it is possible to use Clang ASTs, but also there is a lot of other
code and patterns in Clang that would be useful for a Fortran frontend
- error handling, driver, testing, etc. It would make sense to take
those things from Clang rather than reinvent them in F18.
On 10/14/2018 09:21, David Greene via cfe-dev wrote:
> F18 currently lowers to LLVM IR, but that is too low-level for the kind of tooling we
> want to have. Clang's tooling works on the AST because it is high-level enough to
> express source language concepts and reason about them.
> For example, one can't easily write a source-level documentation tool that works
> with LLVM IR. The same goes for tools like code formatters, syntax highlighters
> and anything else that wants to analyze and/or modify source.
> From: Marcus Johnson<bumblebritches57 at gmail.com>
> Sent: Friday, October 12, 2018 7:20:51 PM
> To: David Greene
> Cc: Flang development; Clang development
> Subject: Re: [cfe-dev] [F18/AST] Using clang tooling with f18
> I know absolutely nothing about the AST, but why not just use LLVM's IR?
>> On Oct 12, 2018, at 1:58 PM, David Greene via cfe-dev<cfe-dev at lists.llvm.org> wrote:
>> [Reposted with the correct clang mailing list -- sorry about the
>> Hi all,
>> We've been having a bit of discussion over on flang-dev and wanted to
>> bring in clang people to comment/brainstorm. Here is the original post
>> that kicked this off on flang-dev:
>> I was hoping f18 would lower to something akin to clang's AST.
>> Obviously clang's AST doesn't directly apply to Fortran but perhaps
>> some kind of common interface could exist so that clang tools could
>> work with Fortran codes. It would be great to have things like the
>> clang static analyzer and clang-doc for Fortran.
>> Some tools will be language-specific of course but it seems like
>> Fortran and C-family languages share enough common concepts that some
>> tooling could work with both, given a common interface.
>> Language-specific tools would work with a more language-specific
>> My impression from the presentation is that there's a lot more that
>> could be shared with clang. The messaging system and command-line
>> options infrastructure should be shareable, for example. Maybe
>> there's already work being done in these areas to make f18 a
>> first-class LLVM project.
>> Folks raised some concerns/areas to explore:
>> - Can we represent various Fortran constructs with additions to the
>> clang AST? For example:
>> * Implied DO loops
>> * Array syntax
>> * I/O statements (FORMAT, READ, NAMELIST, etc.)
>> * Array declarations (DIMENSION, etc.)
>> * Array syntax
>> * ...
>> - Can clang's infrastructure handle various Fortran oddities like
>> non-reserved keyworks and the ability to redefine constants?
>> These may primarily be "dusty deck" issues and perhaps for tooling
>> purposes a 98% solution is ok. F18 still needs to fully handle them,
>> of course.
>> - Can we modify clang's AST and surrounding infrastructure to re-use
>> bits of clang tooling for f18 or should we create some kind of common
>> tooling interface for clang/f18 tooling that can also support
>> language-specific bits?
>> - Can this be forward-looking for tooling for other languages (Rust,
>> Chapel, Go, etc.)?
>> We pretty quickly came to a point where we needed input from clang
>> folks, so here we are. :)
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>> cfe-dev at lists.llvm.org
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