[PATCH] D113741: [RFC][DwarfDebug][AsmPrinter] Support emitting function-local declaration for a lexical block

Thu Dec 23 13:26:54 PST 2021

dblaikie added a comment.

In D113741#3208256 <https://reviews.llvm.org/D113741#3208256>, @krisb wrote:

> @dblaikie added another attempt to revert this as a review: D116225 <https://reviews.llvm.org/D116225>. Will commit once pre-commit tests + local lldb tests passed.
>
> About the issues.
> First of all, thank you for all the details! I was able to reproduce both issues.
> (1) The crash doesn't seem related to the patch and reverting it doesn't make things better. It seems there is an inconsistency between when/where an abstract origin gets emitted and when/where it's requested.

Hmm, bother - guess I failed to correctly reduce the issue. I'll try again.

> (2) The issue with wrong dwo attributes is indeed caused by the imported declaration that gets emitted where it shouldn't (at least comparing with the behavior before this patch). 
> Before this patch 'includeMinimalInlineScopes()' makes emission of imported entity skipped and the second CU assumed empty, so we did not emit dwo attributes for it.
> But I'm not sure I fully understand how DwarfDebug handles split dwarf. Why do we need the 'includeMinimalInlineScopes()' check for correctness here?

It gets a bit complicated because a DWO file can only contain a single CU, but the .o file can contain multiple CUs - so to preserve as much fidelity as possible, if "split dwarf inlining" is enabled (include inline stack frames in the CU in the .o file, so the program can be symbolized even without the dwo/dwp files) then the .o file will get multiple CUs with -g1-like debug info, and one of those CUs will also have the dwo attributes and be a skeleton for the .dwo CU (but the dwo file, instead of having multiple CUs to describe the cross-CU inlining, it'll degrade the debug info quality by moving the DIEs that should be in other CUs in the dwo into the single CU there).

Repository:
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https://reviews.llvm.org/D113741