[PATCH] D104394: [MachineCopyPropagation] Fix differences in code gen when compiling with -g

[Jeremy Morse via Phabricator via llvm-commits]

jmorse added subscribers: probinson, aprantl, dblaikie.
jmorse added a comment.

@predator5047 This patch is worth pursuing -- D98401 <https://reviews.llvm.org/D98401> involves codegen alterations and will necessarily take a long while to review; wheras this patch could land before llvm-13.

This patch is obviously effective at preventing codegen from being changed by debug-info; the downside is that the variable location is wrong afterwards (`DBG_VALUE $rcx` in the CHECK lines). I'm fairly confident we would prefer to have a false variable location over unstable code generation so it could land as-is; @aprantl @probinson @dblaikie would you agree?

To get the variable location right, you need to populate the `CopyDbgUsers` container, and re-write them when propagateDefs deletes the copy.


Repository:
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https://reviews.llvm.org/D104394