Re: Update GCC/LLVM for RISC-V

[Matt Godbolt]

Hi there Christoph!

Our whole project is open source, including all the builders etc. We'd love help! I've tried to build a more up to date GCC for RISC-V but hit troubles with ng-crosstool.

Some background: We use github for development, and there's a number of tracking issues : https://github.com/compiler-explorer/compiler-explorer/issues?q=is%3Aissue+is%3Aopen++riscv

In particular https://github.com/compiler-explorer/compiler-explorer/issues/965 is the latest GCC issue.

Our GCC compilers are built with a docker image (referenced by https://github.com/compiler-explorer/compiler-explorer/issues/965#issuecomment-761582800) -- the source is at https://github.com/compiler-explorer/gcc-cross-builder/ and an example ng-crosstool is at https://github.com/compiler-explorer/gcc-cross-builder/blob/main/build/latest/riscv64-10.2.0.config - though that fails to compile.

Once we can build a RISC-V compiler using this docker image we can install it and configure it using the instructions at https://github.com/compiler-explorer/compiler-explorer/blob/master/docs/AddingACompiler.md

Any help appreciated!

--matt

On Tue, Feb 9, 2021 at 11:16 AM Christoph Muellner <cmue...@ventanamicro.com> wrote:

Hi Matt,

I'm Christoph from the RISC-V International Toolchain and Runtimes HSC.
Today I've pointed our community to godbolt.org and people were quite happy
with what it does (I've been a very happy user since several years).

I want to reach out to you and ask if it would be possible to update
the GCC on godbolt.org. Also, is there some way we can help you update it?

Thanks,
Christoph

--

Matt

(he/him)

[Christoph Muellner]

Hi Matt,

thanks for providing that information.
I'll distribute this in the community, so we might find somebody to
work on that issue.

Thanks,
Christoph

[Matt Godbolt]

Fantastic! Thanks so much! :)

--

Matt

(he/him)

[Christoph Muellner]

Hi Matt,

I've just successfully built the "riscv64-unknown-linux-gnu" configuration
of crosstools-ng (git HEAD) and it worked out of the box (GCC 10.2).
I admit that I am running Fedora here, but I would not expect this to matter.

I can make a PR for the config file in gcc-cross-builder, but before that
I'd like to ask if the folder "latest" refers to the crosstools-ng version.
I.e. can I assume you are running git HEAD of crosstools-ng?
If not, then what's the crosstools-ng version we need to get a working
configuration for?

Thanks,
Christoph

[Matt Godbolt]

Hi! The version in "latest" comes from https://github.com/compiler-explorer/gcc-cross-builder/blob/main/Dockerfile#L59 so tag fcf323336eab38aa8d0fffe75c11062d3e049caa.

We can absolutely change this; feel free to update the SHA as part of the PR, and we can deal with the older things!

Cheers, Matt

--

Matt

(he/him)

[Christoph Muellner]

Yes, I've seen this right after I sent the mail.
So what I did then was to get a fresh Ubuntu 18.04 instance,
execute the steps in the Dockerfile and build crosstools-ng (fcf3233).

Then I was able to successfully build the riscv64-10.2.0.config toolchain,
with having autoconf and automake turned off.

I will create a PR for that change in the config file and explain how I tested.
Could you then restart a build? And if the build fails provide a build log?

Thanks,
Christoph