[cfe-dev] [llvm-dev] [PATCH/DRAFT] Embed metadata into object file
Christian Dietrich via cfe-dev
cfe-dev at lists.llvm.org
Tue Apr 5 07:51:49 PDT 2016
Mehdi Amini <mehdi.amini at apple.com> writes:
> Worded like that, I can see a close analogy with "Debug Info".
Indeed, it is very similar, but there are some differences and
shortcoming, if a developer only wants to smuggle some metadata out in a
very specific format:
For the IR->ELF path, the debug information is encoded as Dwarf (or
something else) in the binary. The plugin developer has not much
control about the binary format of the data. !llvm.extra_sections
would give a quite fine-grained control.
For the AST->IR path, I don't see an easy way to annotate a few pieces
of information in the AST without spinning up the whole
debug-information generation process.
>>  This is a _seperate_ drawback of clang plugins at the moment: They
>> cannot define an LLVM IR transformation that should be applied when
>> the plugin is active.
> You can write clang plugin that are LLVM pass and insert them in the
I can? How? I have not seen any possibility to inject a LLVM pass into
the Clang CodeGen PassManager infrastructure from a clang plugin, which
is also FrontentAction like CodeGen.
>> I think it would be useful for many analyzes
>> to have access both to the AST and to the IR.
> This is more fuzzy to me, I don't know enough about clang but I'm not
> sure the design allow to keep a link from the IR to the clang AST? (If
> it is the case, I'd be curious to see how it works).
If you restrict the possible subjects to top-level functions, global
variables, and the compilation unit, this should be implementable quite
Christian Dietrich, M.Sc. (Wissenschaftlicher Mitarbeiter)
Lehrstuhl für Informatik 4 (Verteilte Systeme und Betriebssysteme)
Tel: (09131) 85-27280
Fax: (09131) 85-28732
eMail: christian.dietrich at fau.de
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