[Lldb-commits] [PATCH] D73206: Pass `CompileUnit *` along `DWARFDIE` for DWZ

Pavel Labath via Phabricator via lldb-commits lldb-commits at lists.llvm.org
Wed Apr 1 04:58:19 PDT 2020

labath added a comment.

The internal representation of DebugNames and Apple indexes is fixed by the relevant (pseudo-)standards, so we can't really change it. The question is how to efficiently (and cleanly) convert from the internal representation to some common thing. The conversion from AppleIndex to DIERef is trivial (which is not surprising as it was the first and the overall design was optimized for that). With debug_names, the situation gets more tricky. The internal representation of debug_names uses CU-relative DIE offsets, but DIERef wants an absolute offset. That means the index has to do more work to produce the common representation. And it needs to do that for all results, even though a lot of the index users are really interested only in a single entry. With the switch to user_id_t, _all_ indexes would have to do some extra work to encode it, only for their users to have to immediately decode it back.  Having a iterator/callback based api would allow us to minimize the impact of that, as it would only need to happen for the entries that are really used. And /I think/ we could make it interface returns DWARFDies directly, and each index converts to that using the most direct approach available.

Another aspect is that is seems fundamentally wrong to use an representation which requires knowledge of multiple SymbolFiles when dealing with entities which are statically know to come from a single file (here, I mean SymbolFileDWARFDebugMap -- I'm glossing over SymbolFileDWARFDwos as those aren't really standalone files, and I hope that class will go away soon).

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