[LLVMdev] How to strip all unused debugging metadata?

[Renato Golin]

On 24 April 2012 16:04, Matt Pharr <matt.pharr at gmail.com> wrote:
> When I generate debug information for a source file that has a number of static functions that are unused, all of the debugging metadata that I generated for them during initial compilation remains even after the source function definitions have been stripped out of the IR.  (e.g. in the MD for DW_TAG_compile_unit's list of subprograms, each of those functions' info is still in the list, and so forth).  How can I remove that unused stuff?  (It continues on to generated object files, which is extra undesirable when there is a lot of this.)

In theory, every metadata that is not attached to a real value (or a
named metadata) is stripped out. I think even if they're not in gv/sp
arrays, but I'm not sure.

Are you sure there isn't any path to a real value from the dangling
metadata? Do you create named metadata?


> I would have expected that the strip-dead-debug-info pass would take care of this, but it doesn't make a difference--looking at its implementation, it just iterates over llvm.dbg.gv and llvm.dbg.sp and removes entries from there that are unused.  In my case, DIBuilder doesn't seem to be declaring llvm.dbg.sp in the first place--is the a symptom of a problem?

I'd assume that has nothing to do with it. Not sure it's a strict
requirement to produce the gv/sp arrays. Have you tried producing them
and linking all your metadata in it to see if the dangling ones get
removed?

-- 
cheers,
--renato

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