[PATCH] D100446: [Transforms][Debugify] Fix "Missing line" false alarm on PHI nodes

Thu Apr 22 13:57:16 PDT 2021

vsk resigned from this revision.
vsk edited reviewers, added: aprantl, djtodoro, probinson; removed: vsk.
vsk added a comment.

Context: In D59417 <https://reviews.llvm.org/D59417> (see also llvm.org/PR37964), there was some debate about whether it's worthwhile to assign a line 0 location to a phi instruction which would otherwise not have a location. The consensus seemed to be: no, it's not worth it. So D75242 <https://reviews.llvm.org/D75242> was spun off to suppress the false positive in debugify. It looks like D75242 <https://reviews.llvm.org/D75242> had the unexpected/unfortunate side-effect of introducing a new FP: any unique, preserved DebugLoc attached to a phi instruction because "missing".

My two cents is that a total ban on attaching debug location/intrinsic info to phi instructions isn't the best way to fix this. That would lead to a loss in test coverage (we do see cases where passes copy debug locations from phi instructions, or where debug intrinsics refer to phi instructions). I think the current version of this patch (skip the warning on phi instructions) does the right thing. That said I'm no longer very active in debug info reviews so I'll defer to other reviewers.

Repository:
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https://reviews.llvm.org/D100446