[PATCH] D83890: [DebugInfo] Process DBG_VALUE_LIST in LiveDebugValues

Wed Jan 27 09:55:00 PST 2021

StephenTozer added a comment.

In D83890#2525566 <https://reviews.llvm.org/D83890#2525566>, @vsk wrote:

> I do still have the bitcode handy, but wasn't able to apply D94631 <https://reviews.llvm.org/D94631> cleanly to my checkout. Happy to report results back, just let me know which hash of llvm-project to apply D94631 <https://reviews.llvm.org/D94631> onto.

The current version of the patch can be applied to 993c488ed <https://reviews.llvm.org/rG993c488ed2b347011d9d71990af38a82aaf5bdf5>, although I'll be updating it tomorrow onto the latest master, plus some bug fixes (also, D95463 <https://reviews.llvm.org/D95463> is necessary for some source files to prevent an immense excess of debug values). I'd be very interested to see the results with just what we have now, however.

Finally, assuming that the bitcode you have is already optimized, we won't see the full impact of this change with it: the major feature being added is the support for DBG_VALUEs that reference more than one machine location (DBG_VALUE_LISTs), which makes the LiveDebugValues analysis more complicated. These DBG_VALUE_LISTs can currently only be produced when salvaging debug values in `opt` passes; with pre-optimized bitcode, the resulting MIR won't have any DBG_VALUE_LISTs and so won't give an indication of how well we handle the new instruction. However, it would still be very valuable just to know what impact this change has on simple DBG_VALUEs - preventing a regression here is vital.

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https://reviews.llvm.org/D83890