D39119: [llvm-dwarfdump] - Teach tool about few GNU call_sites constants.

[George Rimar via llvm-commits]

>> @JDevlieghere: could you perhaps help @grimar to figure out what is missing here?
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>The verifier currently doesn't consider DWARF expressions. I think this should be fairly easy to extend: just iterate over its iterations (as >the print function does) and check `DWARFExpression::Operation::isError()`.
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>Repository:
>  rL LLVM
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>https://reviews.llvm.org/D39119

Yeah, that what I meant. That is another issue of verifier (that it does not check any expressions at all), 
but it generally unrelative with DW_*_GNU_call_site things.

I think I can probably try extend it tomorrow though.

George.