[Mlir-commits] [lldb] [llvm] [mlir] [DebugInfo] Add symbolic branches to DIExpression (PR #210850)

[Jeremy Morse]

jmorse wrote:

I tend to agree with @felipepiovezan -- it's not that there's anything wrong with this code, instead it's not clear how we should consider it's composition with other features because nothing generates symbolic-branches yet, and we can't consider the use-cases. This manifests as uncertainty and hedging at later dates.

A prime example is implicit pointers: you consider them in this patch and add carve-outs, however to the best of my knowledge nothing produces implicit-pointers today, and won't until #187642 lands (which may or may not have stalled).   But we can at least know that because there's an overall plan/direction.

I think @snowy1803 has hit the nail on the head with composition with DIArgList: could this lead to two incompatible flavours of DIExpressions? Conceivably this is a legitimate direction because different applications (GPUs etc) have different characteristics, but it's worth considering from the top level down rather than implementation-upwards. Ensuring that "dead" or "invalid" #dbg_values are still retained to kill invalidated variable assignments is a consideration too.

https://github.com/llvm/llvm-project/pull/210850