Create symlink for llvm-link in libc docker image

[jinge90]

We are working on using llvm-link to build LLVM libc bitcode library for GPU targets. In standalone build environment which amd-gpu pre-ci uses, only clang-23, clang++-23, lld-23 and llvm-23-tools are installed and added to /usr/bin path. This PR creates symlink for llvm-link.

[llvmorg-github-actions]

@llvm/pr-subscribers-github-workflow

Author: jinge90

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/210929.diff

1 Files Affected:

• (modified) .github/workflows/containers/libc/Dockerfile (+4-2)

diff --git a/.github/workflows/containers/libc/Dockerfile b/.github/workflows/containers/libc/Dockerfile
index 1367b89fab104..1794ea3f3da8b 100644
--- a/.github/workflows/containers/libc/Dockerfile
+++ b/.github/workflows/containers/libc/Dockerfile
@@ -51,8 +51,10 @@ RUN wget https://apt.llvm.org/llvm.sh && \
 # testing CI for libc-based compiler-rt builtins. The package only symlinks
 # the tools into /usr/bin under versioned names (lit-23, FileCheck-23, ...),
 # so also symlink them under their canonical names.
-RUN apt-get install -y llvm-23-tools && \
-    ln -s -t /usr/bin $(dpkg -L llvm-23-tools | grep '^/usr/lib/llvm-23/bin/')
+# Also install LLVM tools to include llvm-link, we use it to build bitcode
+# for GPU targets.
+RUN apt-get install -y llvm-23-tools llvm-23 && \
+    ln -s -t /usr/bin $(dpkg -L llvm-23-tools llvm-23 | grep '^/usr/lib/llvm-23/bin/')
 
 
 # Install gmp and mpfr for cross compilation

[boomanaiden154]

There's no package more specific than general llvm-23 that would work here?

[jinge90]

There's no package more specific than general llvm-23 that would work here?

Hi, @boomanaiden154
I am afraid there is no more specific package which can work here. The docker image is ubuntu, I used apt search to list all llvm related packages and checked them all, only llvm-23 includes llvm-link. Other packages are:
llvm-23-dev: llvm libraries and headers
llvm-23-linker-tools: linker plugin libraries
llvm-23-tools (already included in the image): tools used in testing
llvm-23-runtime: lli

Thanks very much.

[boomanaiden154]

Can you collect numbers on how much this increases the container image size?

[jinge90]

Can you collect numbers on how much this increases the container image size?

Hi, @boomanaiden154
To my surprise, there is almost no image size increase at all. I created the docker image using previous Dockfile and find /usr/lib/llvm-23/bin/llvm-link does exist but the symbolic link "/usr/bin/llvm-link" is not created.
After applying the change to Dockfile, I create a new image and both llvm-23/bin/llvm-link and /usr/bin/llvm-link exists since we explicitly install llvm-23 and creates symbolic link in this PR.
The image size keeps 4.67 GB before and after applying this PR.
The llvm.sh 23 will install clang-23, so I manually run 'apt install clang-23' in my local ubuntu 24.04 and find all tools such as llvm-tool, llvm-readobj.... are installed into /usr/lib/llvm-23/bin, this aligns with my observation.
Although apt install -y llvm-23-tools llvm-23 seems to be redundant, I prefer to keeping them to make the dependency clear.
Thanks very much.

[boomanaiden154]

I created the docker image using previous Dockfile and find /usr/lib/llvm-23/bin/llvm-link

Then can we just create a symlink rather than installing additional packages?

[jinge90]

I created the docker image using previous Dockfile and find /usr/lib/llvm-23/bin/llvm-link

Then can we just create a symlink rather than installing additional packages?

Hi, @boomanaiden154
I expect it should work if we just create a symlink since these binaries (llvm-link, llvm-objdump, llvm-readelf...) have been already installed together with clang-23.
However, is it acceptable if we keep apt-get install llvm-23? I prefer it for 2 reasons:

1. it has no impact to image size
2. we already did the same thing for llvm-23-tools and aligning with llvm-23-tools makes the logic more clear and unified.

Thanks very much.

[boomanaiden154]

it has no impact to image size

This I'm a bit skeptical of, but if I guess llvm-23 is a metapackage where we already install all of its dependents, it makes sense.

we already did the same thing for llvm-23-tools and aligning with llvm-23-tools makes the logic more clear and unified.

This argument does not make any sense to me. Neither llvm-23-tools nor llvm-23 really seem to indicate that they have llvm-link in them. I think keeping llvm-23 makes the meaning less clear. If llvm-23 pulls in additional dependencies that we don't already have installed, this will also result in an image size regression.

[jinge90]

it has no impact to image size

This I'm a bit skeptical of, but if I guess llvm-23 is a metapackage where we already install all of its dependents, it makes sense.

we already did the same thing for llvm-23-tools and aligning with llvm-23-tools makes the logic more clear and unified.

This argument does not make any sense to me. Neither llvm-23-tools nor llvm-23 really seem to indicate that they have llvm-link in them. I think keeping llvm-23 makes the meaning less clear. If llvm-23 pulls in additional dependencies that we don't already have installed, this will also result in an image size regression.

Hi, @boomanaiden154
Got it, I will update the PR to directly create a symbolic link for llvm-link once I finished verification locally.
Thanks very much.

[jinge90]

I created the docker image using previous Dockfile and find /usr/lib/llvm-23/bin/llvm-link

Then can we just create a symlink rather than installing additional packages?

Hi, @boomanaiden154 I expect it should work if we just create a symlink since these binaries (llvm-link, llvm-objdump, llvm-readelf...) have been already installed together with clang-23. However, is it acceptable if we keep apt-get install llvm-23? I prefer it for 2 reasons:

1. it has no impact to image size
2. we already did the same thing for llvm-23-tools and aligning with llvm-23-tools makes the logic more clear and unified.

Thanks very much.

Hi, @boomanaiden154
I updated the PR to create symlink directly instead of installing llvm-23, could you help review again?
Thanks very much.

[boomanaiden154]

Can you collect numbers on how much this increases the container image size?

[boomanaiden154]

We can drop the if statement and only keep the ln -s command, and also fold this into the previous RUN line.

[jinge90]

Hi, @boomanaiden154
Done.
Thanks very much.

[jinge90]

Can you collect numbers on how much this increases the container image size?

Hi, @boomanaiden154
In my local machine, the image size increase 586 bytes after the change. The total image size is 4.67G.
Thanks very much.

[boomanaiden154]

LGTM