IREE LLVM Integration Procedure

procedure.md

Notes on integrating LLVM from the OSS side

Strategy 1: Sync everything to a Google/TensorFlow commit

cd ~/src
git clone git clone https://github.com/tensorflow/tensorflow.git
git clone https://github.com/tensorflow/mlir-hlo.git

Get MHLO's published version:

We use this one because it is the easiest to get at and most of the activity is LLVM integrates.

cat mlir-hlo/build_tools/llvm_version.txt

Or git log to find a commit like:

commit f9f696890acbe198b6164a7ca43523e2bddd630a (HEAD -> master, origin/master, origin/HEAD)
Author: Stephan Herhut <herhut@google.com>
Date:   Wed Jan 12 08:00:24 2022 -0800

    Integrate LLVM at llvm/llvm-project@c490f8feb71e

    Updates LLVM usage to match
    [c490f8feb71e](https://github.com/llvm/llvm-project/commit/c490f8feb71e)

    PiperOrigin-RevId: 421298939

You can correlate this with a tensorflow commit by searching TensorFlow commits for the PiperOrigin-RevId, which is shared between them. While not strictly necessary to keep all of this in sync, if doing so, it will yield fewer surprises.

An example of a corresponding commit in the tensorflow repo:

commit a20bfc24dfbc34ef4de644e6bf46b41e6e57b878
Author: Stephan Herhut <herhut@google.com>
Date:   Wed Jan 12 08:00:24 2022 -0800

    Integrate LLVM at llvm/llvm-project@c490f8feb71e

    Updates LLVM usage to match
    [c490f8feb71e](https://github.com/llvm/llvm-project/commit/c490f8feb71e)

    PiperOrigin-RevId: 421298939
    Change-Id: I7e6c1c25d42f6936f626550930957f5ee522b645

From this example:

LLVM_COMMIT="c490f8feb71e"
MHLO_COMMIT="f9f696890acbe198b6164a7ca43523e2bddd630a"
TF_COMMIT="a20bfc24dfbc34ef4de644e6bf46b41e6e57b878"

Apply:

cd ~/src/iree
git fetch
(cd third_party/llvm-project && git checkout $LLVM_COMMIT)
(cd third_party/mlir-hlo && git checkout $MHLO_COMMIT)
sed -i "s/^TENSORFLOW_COMMIT = .*$/TENSORFLOW_COMMIT = \"$TF_COMMIT\"/" integrations/tensorflow/WORKSPACE

# git status should show:
#        modified:   integrations/tensorflow/WORKSPACE
#        modified:   third_party/llvm-project (new commits)
#        modified:   third_party/mlir-hlo (new commits)

(NOTE: until we can disable it, the SUBMODULE_VERSIONS.txt file must be updated in tandem since the CI will internally change to the versions listed there)

Make a patch:

git add -A
git commit
# Message like:
#    Integrate llvm-project and bump dependencies.
#
#    * llvm-project: c490f8feb71e
#    * mlir-hlo: f9f696890acbe198b6164a7ca43523e2bddd630a
#    * tensorflow: a20bfc24dfbc34ef4de644e6bf46b41e6e57b878

Either Yolo and send a PR to have the CI run it or do a local build. I will typically only build integrations/tensorflow if the CI indicates there is an issue.

# Push to the main repo so that we can better collaboratively apply fixes.
git push origin HEAD:llvm-bump

Either fix any issues or get people to do so and land patches until the PR is green.