[PATCH] D146595: [clang] Add "transparent_stepping" attribute

Mon Apr 3 16:23:48 PDT 2023

aprantl added a comment.

> Is there some place (bug, discourse thread, etc) where the broader direction is discussed? I want to checkin on the design decisions/alternatives without fragmenting this across multiple reviews/losing context/etc?

No, I believe that all the relevant discussion happened in this review. While there is a separate review for an LLDB implementation, there is no general direction discussion there, it's just implementing a DWARF feature.

> (specifically - this started out with the trampoline attribute, then switched to this transparent idea (perhaps based on my feedback? Also other feedback? I'd like to know more about how that change in direction happened, what the tradeoffs were, etc - I don't think my suggestion alone was probably enough to make this direction clearly the right one (nor clearly the wrong one)), etc)

It was partially based on your feedback, but also on @arphaman pointing out that the `DW_AT_trampoline("call_target")` implementation wouldn't be able to deal with the jump target being a virtual function call. So @augusto2112 
landed on implementing the "flag variant" of `DW_AT_trampiline` instead. This is also an existing DWARF feature, albeit not yet supported by LLVM.

> & there was some tangent about DWARF v COFF too, which I wouldn't mind weighing in on, but feel like it's all a bit fragmented, so not sure where all the discussions are/how to keep track of them.

That was also in this review; @aaron.ballman pointed out that it would be best if new Clang attributes weren't targeting only DWARF, though I believe this request may run into some hard limitations of what CodeView/PDB can support.

Repository:
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  https://reviews.llvm.org/D146595/new/

https://reviews.llvm.org/D146595