[Chore] Install clang in CI Docker image for pre-built JIT IR support

[zhangxffff]

Chore Type

Dependency Update (Conan/Third-party)

Task Description

Install clang in the CI Docker image (bolt-ci) so that the pre-built JIT IR framework (#501) can compile kernel bitcode without a workaround.

Motivation / Benefit

PR #501 introduces pre-built JIT IR which requires clang -emit-llvm at build time. The current Docker image doesn't have clang, so #501 works around this by adding apt-get install clang to three workflow files (build-test.yml, build-main.yml, pre-commit-checks.yml). This adds ~10s to every CI run. Installing clang in the Docker image eliminates this overhead and the workaround

Related Files (Optional)

No response

Implementation Plan (Optional)

No response

Additional Context

No response

[zhangxffff]

Hi @ZacBlanco, could you help with this when you get a chance? The pre-built JIT IR feature (#501) needs clang in the CI Docker image. I've added a workaround in the workflows for now, but installing it in the image would be cleaner. I know how to update the Dockerfile, but I'm not sure how to rebuild and push a new Docker image to the registry.

[ZacBlanco]

If you can make an PR which only updates the dockerfile, I will build and push it to the registry after the PR is merged

[ZacBlanco]

Also, I'm wondering if we can somehow use the conan LLVM dependency instead to generate the IR during the build process? Does the conan dependency build any executable that is able to emit the LLVM IR?

One thing I am concerned about is that the LLVM used to to emit the IR in your change might need to be compatible with the LLVM used in bolt. I think It would be better to use binaries from the LLVM conan package, rather than the OS package manager since it will guarantee compatibility. I haven't looked into how compatible LLVM IR is between versions though

[zhangxffff]

Also, I'm wondering if we can somehow use the conan LLVM dependency instead to generate the IR during the build process? Does the conan dependency build any executable that is able to emit the LLVM IR?

One thing I am concerned about is that the LLVM used to to emit the IR in your change might need to be compatible with the LLVM used in bolt. I think It would be better to use binaries from the LLVM conan package, rather than the OS package manager since it will guarantee compatibility. I haven't looked into how compatible LLVM IR is between versions though

Thanks for the suggestion. The current llvm-core Conan recipe only builds the LLVM libraries and does not include Clang. The system-installed Clang may be a different version from the Conan LLVM dependency. I also tried installing Clang via [LLVM's official install script](https://apt.llvm.org/), but it only allows specifying the major version, which may still differ from the Conan LLVM version. So I'll try modifying the llvm-core Conan recipe to build Clang alongside LLVM, ensuring that Clang uses exactly the same version as LLVM.

[zhangxffff]

@ZacBlanco add clang support to llvm-core recipe in this PR: #513