JS/wasm CI

We should setup CI for the upcoming JS and wasm backends.

For the JS backend the following packages are needed from the CI environment (docker images):

• emscripten version 3.14 or better
• llvm 15
• (@TerrorJack: does the wasm backend need something else?)

Build instructions for the JS backend can be found on https://gitlab.haskell.org/ghc/ghc/-/wikis/javascript-backend

Note that for now the testsuite doesn't fully pass. We expect it to pass before the merge (be it by disabling the most problematic tests when the JS backend is used).

changed milestone to %9.6.1

added CI needs triage labels

assigned to @bgamari and @chreekat

added Phigh Ttask javascript wasm labels and removed needs triage label

Apologies for the rather late reply; for wasm backend CI, we download and extract linux binaries from GitHub actions artifacts. For us, the only missing thing in the ci images is unzip.

mentioned in commit ci-images@6eff020c

mentioned in commit ci-images@bf53ee47

mentioned in merge request ci-images!97 (closed)

@hsyl20, @TerrorJack, I have added emscripten support to the Debian images in ci-images!97 (closed).

Unfortunately, most of the relevant bindists for LLVM 15.0.0 are not yet available. Supposedly they will be uploaded soon but if this is time-critical then we could in principle build LLVM ourselves in the meantime.

@bgamari, note there's https://apt.llvm.org/. LLVM 15.0.0 is already available there and I'm using it.

Ahh great, thanks @TerrorJack .

mentioned in commit ci-images@4c9b1b71

Ah sorry @bgamari, I only meant "LLVM 15 in apt repo is stable enough", for wasm work, our LLVM build happens elsewhere on github, we simply download and extract tarballs on each CI run. I think it's better to leave it that way for the time being, installation is fast anyway, and there's little added value in adding those to the CI images.

I have added a commit to ci-images!97 (closed) to bump LLVM to 15 using the apt repo. In the short term I am okay with installing another LLVM during the job but in the medium term we should plan on handling this in the image. Afterall, LLVM bindists tend to be around a gigabyte; downloading a gigabyte at ~20MByte/s would add over a minute to the overall build time (as well as unnecessarily liberate nearly 100 grams-CO_2eq, by some estimates). For this reason, eliminating such a large repeated download is IMHO very worthwhile.

Before committing that LLVM bump in ci-images, we also need to sort out #21936 (closed)

mentioned in issue #21078 (closed)

@bgamari @chreekat Given the issues with LLVM 15 and the LLVM backend (#21936 (closed)), could the JS CI job use a dedicated ci-image?

Hey @hsyl20 , sorry for not having the full context - what would the dedicated image have differently from the other ones?

The image for the JS backend would contain LLVM 15:

• LLVM 15 required for the JS backend (cf https://gitlab.haskell.org/ghc/ghc/-/wikis/javascript-backend#js-backend-fails-during-stage1-with-error-symbol-memset-missing-functype)
• the LLVM backend requires LLVM < 15 (cf #21936 (closed))

Thanks, makes sense.

I'm gonna leave this up to @bgamari for now since he was already working on it. :)

mentioned in merge request !9133 (merged)

I've added some support for a configure wrapper in !9133 (merged).

unassigned @chreekat

I've modified the ci script in !9133 (merged) to download emscripten when needed for now.

The JS backend is merged but it still lacks a full testsuite run on CI. We should fix Hadrian so that it supports running the testsuite for a cross-compiler when run with --test-compiler=... (as done by ci.sh).

mentioned in merge request ci-images!106 (merged)

mentioned in merge request !9661 (merged)

closed with merge request !9661 (merged)