Re: [PATCH v1 0/2] RISC-V: enable rust

From: Conor Dooley <conor@kernel.org>
To: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: "Conor Dooley" <conor.dooley@microchip.com>,
	linux-riscv@lists.infradead.org,
	"Miguel Ojeda" <ojeda@kernel.org>,
	"Alex Gaynor" <alex.gaynor@gmail.com>,
	"Wedson Almeida Filho" <wedsonaf@gmail.com>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Nathan Chancellor" <nathan@kernel.org>,
	"Nick Desaulniers" <ndesaulniers@google.com>,
	"Tom Rix" <trix@redhat.com>,
	rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH v1 0/2] RISC-V: enable rust
Date: Thu, 18 Jan 2024 15:49:21 +0000	[thread overview]
Message-ID: <20240118-implode-delirium-eefdd86e170e@spud> (raw)
In-Reply-To: <CANiq72mVKCOAuK4Qe+8AHmpkFwyJsVfx8AqB7ccGi3DYpSSWcw@mail.gmail.com>

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On Wed, Jan 17, 2024 at 07:23:17PM +0100, Miguel Ojeda wrote:
> On Wed, Jan 17, 2024 at 12:31 PM Conor Dooley <conor@kernel.org> wrote:
> >
> > 6.6 came and went, and I have been busy dealing with the other
> > responsibilities I mentioned and have not had a chance to look here.
> > I rebased this today and things still work as they did when I submitted
> > this version, but things have gotten muddier on the LLVM side of things,
> > as more recent versions have added yet more extension support.
> 
> Sounds fun :)
> 
> > My inclination at this point is to engage in a bit of LARPing as an
> > ostrich, and sorta ignore these concerns initially. Specifically, I'd
> > like to drop the idea of having the gcc support, and restrict to LLVM=1.
> 
> Yeah, if `LLVM=1` works, then I would suggest going ahead with that.
> 
> (Now that `rustc_codegen_gcc` is here, we will move to that and forget
> about mixed compiler builds, but we still have to handle `bindgen`
> flags until we have an alternative for that)

The bit that worries me most is bindgen, and in particular detecting the
version of libclang used. I mentioned to Nathan or Nick about needing a
buildtime test for the version of LIBCLANG being used.
I'm less worried about this for LLVM=1 builds, since while I think it is
possible to provide a LIBCLANG path to the build system, I suspect that
for LLVM=1 builds it's almost always going to match the LLVM toolchain
in use.

> > When it comes to asymmetrical extension support between the C and Rust
> > toolchains, I'm think we deal with that as we do for the C toolchains,
> > sort issues out as-and-when they arrive rather than punt this again.
> 
> Sounds good, thanks a lot!

I'll do another rebase and resend after the merge window closes I
suppose :)

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