llvm-project

9d48df7a - [UpdateTestChecks] Don't fail silently when conflicting CHECK lines means no checks are generated for some functions (#159321)

[UpdateTestChecks] Don't fail silently when conflicting CHECK lines means no checks are generated for some functions (#159321) There is a warning that triggers if you (for instance) run `update_llc_test_checks.py` on an input where _all_ functions have conflicting check lines and so no checks are generated. However, there are no warnings emitted at all for the case where some functions have non-conflicting check lines but others don't. This is a source of frustration because running update_llc_test_checks can result in all check lines being removed for certain functions when such a conflict exists with no warning, meaning we have to be extra vigilant inspecting the diff. I've also personally wasted time tracking down the source of the dropped lines assuming that update_test_checks would emit a warning in such cases. This change adds logic to emit warnings on a function-by-function basis for any RUN that has conflicting prefixes meaning no output is generated. This subsumes the previous warning for when _all_ functions conflict.