[llvm] [Github][RFC] Add workflow to diff codegen on llvm-test-suite (PR #190010)

[Konrad Kleine via llvm-commits]

================
@@ -0,0 +1,149 @@
+# When /test-suite is commented on a PR, checks out the PR, builds clang and
+# then the test-suite in several configurations. It then checks out the base of
+# the PR, builds clang and the test-suite again, and then uploads the diff of
+# the codegen.
+
+name: Diff test-suite codegen
+
+on:
+  issue_comment:
+    types:
+      - created
+
+permissions:
+  contents: read
+
+jobs:
+  test-suite:
+    name: Build test-suite and diff
+    runs-on: ubuntu-24.04
+    container:
+      image: ghcr.io/llvm/ci-ubuntu-24.04:35e958d7f0b7
+    if: github.event.issue.pull_request && startswith(github.event.comment.body, '/test-suite')
+    steps:
+      - name: Check permissions
----------------
kwk wrote:

This is nitpicking but I suggest to give the user some feedback by reacting to the comment with an `EYES` reaction. We've something similar [here](https://github.com/fedora-llvm-team/llvm-snapshots/blob/d9a548ad3d4671da9bdcc5dd7b096b02beb7dc01/.github/workflows/retest-chroots-on-testing-farm.yml#L15-L34). And depending on the outcome you can remove the `EYES` and add a `THUMBS_UP` (see [here](https://github.com/fedora-llvm-team/llvm-snapshots/blob/d9a548ad3d4671da9bdcc5dd7b096b02beb7dc01/.github/workflows/retest-chroots-on-testing-farm.yml#L95-L131)).



```suggestion
      - name: Add reaction to trigger comment
        uses: actions/github-script at v9
        with:
          script: |
            const mutation = `mutation($comment_id: ID!, $reaction: ReactionContent!) {
              addReaction(input: {subjectId: $comment_id, content: $reaction}) {
                reaction {content}
                subject {id}
              }
            }`;
            const variables = {
              comment_id: '${{ github.event.comment.node_id }}',
              reaction: 'EYES'
            }
            const result = await github.graphql(mutation, variables)
            console.log(result)

      - name: Check permissions
```

https://github.com/llvm/llvm-project/pull/190010