[llvm] [DebugInfo] Clone dbg.values in SimplifyCFG like normal instructions (PR #72526)

[Orlando Cazalet-Hyams via llvm-commits]

https://github.com/OCHyams commented:

It's good to be removing weird behaviour. Hurray!

It looks like in `llvm/test/Transforms/SimplifyCFG/branch-fold-dbg.ll` some conditional assignments become unconditional, which seems bad/undesirable. But the existing behaviour of pushing the dbg.values to the end of the block doesn't solve that, so we might as well preserve the order (as you're doing here). Does that line up with your thoughts on this?

I wonder if there are compile time implications - I assume previously lots of block folding would result in a lot of redundant dbg.values (because of how they get clumped without this patch), which might've artificially been improving performance over the baseline correct behaviour. Not much we can do about it I guess.


https://github.com/llvm/llvm-project/pull/72526