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

[Konrad Kleine via llvm-commits]

================
@@ -0,0 +1,136 @@
+# 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
+
+jobs:
+  test-suite:
+    name: Build and diff
+    runs-on: ubuntu-24.04
----------------
kwk wrote:

Looking at the timetable from [here](https://github.com/actions/runner-images/issues/13964#issuecomment-4360396351) it will take some time before the 26.04 images will be available:

| Milestone | Optimistic | Most likely | Pessimistic |
|---|---|---|---|
| **Beta available** (`ubuntu-26.04`) | May 10 | May 20–28 | June 15 |
| **GA on runners** | Aug 15 | Sep 15 – Oct 1 | Nov 15 |
| **`ubuntu-latest` flip starts** | Sep 15 | Oct 15 – Nov 15 | Jan 2027 |
| **`ubuntu-latest` flip complete** | Nov 2026 | Jan – Feb 2027 | Apr 2027 |
| **22.04 deprecation begins** | Oct 2026 | Dec 2026 – Feb 2027 | Apr 2027 |

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