[lldb-dev] Adding DWARF5 accelerator table support to llvm

Pavel Labath via lldb-dev lldb-dev at lists.llvm.org
Wed Jan 17 08:13:36 PST 2018

Hello all,

In <https://reviews.llvm.org/D41986#977215> it was brought up that
there are at least two parties interested in having DWARF5 accelerator
tables implemented, so I'm writing this email to see if there's anyone
else interested in this topic, and to try to synchronize our efforts.

Our interest for this stems from a desire to make dwarf parsing fast
on non-apple targets (specifically android). As you may know, apple
targets already use a non-standard accelerator table format, which was
a precursor to the dwarf5 one. Due to other differences in debug info
deployment model, the apple tables are not directly applicable to
other targets, so instead of trying to make them fit, we chose to go
with the standard approach.

I personally will have some time to work on this this quarter or two,
and my plan is roughly the following:
1. add .debug_names support to llvm-dwarfdump via the DebugInfo
library (to enable testing of the table generation)
2. add .debug_names generation support (not enabled by default)
3. add .debug_names support to lldb
4. validate all three things work together
5. hook up .debug_names to clang's -glldb flag.
6. add .debug_names support to lld (accelerator table merging)

Right now I have (1) roughly implemented, and I think I'll be able to
put it up for review in a couple of days (although I expect the review
will go through several revisions before being accepted). I also have
a very basic implementation of (2), but this is still quite far from
being upstreamable.

So, my question is whether anyone is planning to work, or maybe
working already on dwarf5 accelerator tables? Help with reviewing
patches would also be greatly appreciated. If you have any questions
or concerns, let me know.


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