search for: isliveatsafepoint

...a very straigh forward and, due to implementation simplicity, expensive estimation based on simple reachability*. This suffices for correctness, but is not ideal from a performance perspective. (To put it mildly.) * For those curious, you can find the current implement by searching for "isLiveAtSafepoint" in https://github.com/AzulSystems/llvm-late-safepoint-placement/blob/master/lib/Transforms/Scalar/SafepointPlacementPass.cpp. It's a trivial reachability algorithm with special cases for inbound values into a phi and uses that are encountered along paths which contain the original def...