similar to: DWARF Fission + ThinLTO

On Wed, May 3, 2017 at 2:09 PM Adrian Prantl <aprantl at apple.com> wrote: > > > On May 3, 2017, at 2:00 PM, David Blaikie <dblaikie at gmail.com> wrote: > > > > So Dehao and I have been dealing with some of the nitty gritty details > of debug info with ThinLTO, specifically with Fission(Split DWARF). > > > > This applies to LTO as well, so I

> On May 3, 2017, at 7:43 PM, Adrian Prantl via llvm-dev <llvm-dev at lists.llvm.org> wrote: > >> >> On May 3, 2017, at 2:59 PM, David Blaikie <dblaikie at gmail.com <mailto:dblaikie at gmail.com>> wrote: >> >> >> >> On Wed, May 3, 2017 at 2:09 PM Adrian Prantl <aprantl at apple.com <mailto:aprantl at apple.com>> wrote:

Sorry, trying to catch up a bit late… It sounds like having more than one CU per .dwo is outside of the intention of the DWARF specification (though not explicitly forbidden), since there is an implied 1-1 relationship between skeleton CU and .dwo. There is an explicit 1-1 relationship between skeleton CU and split-full CU (not .dwo). This suggests to me that if you want a .dwo to have multiple

> On May 4, 2017, at 4:53 PM, David Blaikie <dblaikie at gmail.com> wrote: > > Alrighty, a little fuzzy on how best to implement this - Adrian, you've probably got the most context here as to how to wrangle this. > > My first attempt was in IRMover.cpp, IRLinker::linkFunctionBody - after metadata is copied over, create a new subprogram derived from Dst.getSubprogram,

Much like the recent efforts to provide a port of dsymutil in the LLVM project, I'm looking at providing an implementation of the Fission/Split DWARF DWP tool ( https://gcc.gnu.org/wiki/DebugFissionDWP ) in LLVM. While there's potentially some overlap between the two tools, I'm thinking of keeping them separate at least initially since much of the debug info doesn't need to be

On Thu, May 4, 2017 at 7:22 AM, Rafael Avila de Espindola via llvm-dev < llvm-dev at lists.llvm.org> wrote: > David Blaikie via llvm-dev <llvm-dev at lists.llvm.org> writes: > > > So Dehao and I have been dealing with some of the nitty gritty details of > > debug info with ThinLTO, specifically with Fission(Split DWARF). > > > > This applies to LTO as

On Tue, Nov 3, 2015 at 5:06 PM, Alexey Samsonov <vonosmas at gmail.com> wrote: > SGTM. This will bring us closer to the point when we can write tests, > where we strip out the .dwo files from executables, package them together > with llvm-dwp, and then verify that we still get all we need from > llvm-symbolizer. > Not quite following here - dwo sections are already stripped

So I've been looking at a particular performance problem with LLVM's symbolizer due to the use of ThinLTO, split DWARF, and split DWARF inlining info. This combination has a couple of problems: 1) it means multiple CUs in a single DWO, which isn't well defined/specified, and best avoided - so I'm working on fixing that here (won't fix split DWARF+Full LTO) because we already

Hi David, please find my comments inside: >>>Broad question: Do you have any specific motivation/users/etc in implementing this (if you can speak about it)? >>> - it might help motivate the work, understand what tradeoffs might be suitable for you/your users, etc. >>There are two general requirements: >> 1) Remove (or clean) invalid debug info. > >Perhaps a

Hi David, Excuse me for delayed answer. It took some time to prepare. Please, find the answers bellow... >Broad question: Do you have any specific motivation/users/etc in implementing this (if you can speak about it)? > - it might help motivate the work, understand what tradeoffs might be suitable for you/your users, etc. There are two general requirements: 1) Remove (or clean) invalid

It makes me sad that the linker (via a library or otherwise) has to be "DWARF-aware" to be able to effectively handle --gc-sections, COMDATs, --icf etc for debug info, without leaving large blocks of data kicking around. The patching to -1 (or equivalent) is probably a good lightweight solution (though I'd love it if it could be done based on section type in the future rather than

Bunch of initially unrelated context: * type units can be referenced in a variety of ways: * DW_FORM_ref_sig8 on any attribute needing to reference the type * DW_AT_signature on a declaration of the type * extra wrinkle: the declaration can be nested into the appropriate namespace and given a name, or not * LLVM always does the "most expressive"/expensive thing: a full

> -----Original Message----- > From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Pieb, > Wolfgang via llvm-dev > Sent: Wednesday, July 05, 2017 6:14 PM > To: llvm-dev at lists.llvm.org > Subject: Re: [llvm-dev] [DWARFv5] Reading the .debug_str_offsets section > > > -----Original Message----- > > From: llvm-dev [mailto:llvm-dev-bounces at

>On Mon, Jun 22, 2020 at 7:21 AM Alexey Lapshin ><alapshin at accesssoftek.com> wrote: >> >> >> >> >> >> This idea goes in another direction than fragmenting dwarf >> >> >> using elf sections&tricks. It seems to me that the cost of fragmenting is too high. >> >> >> >> >I tend to agree - but I'm

>> >> >Alexey> Probably we could try to make DWARF easy to parsing, trimming, rewriting so that full DWARF >> >> >Alexey> parsing solution would not take too much time? >> >> >Alexey> >> >> >Alexey> f.e. -debug-types-section solution uses COMDAT sections to split and deduplicate types. >> >> >Alexey> That

FWIW, I think it's probably best to at least initially frame the discussion around non-configurable value for the sake of reducing the scope/possible surface area of the feature/users/etc. I'd probably only encourage adding the user-configurable flag if/when someone has a use case for it. On Thu, Jun 4, 2020 at 2:31 PM Fangrui Song <maskray at google.com> wrote: > > > On

>> >> >> >> This idea goes in another direction than fragmenting dwarf >> >> >> >> using elf sections&tricks. It seems to me that the cost of fragmenting is too high. >> >> >> >> >> >> >I tend to agree - but I'm sort of leaning towards trying to use object >> >> >> >features as much

On Wed, Jun 3, 2020 at 6:34 AM Robinson, Paul <paul.robinson at sony.com> wrote: > > DWARF was designed in an era when COMDAT and ICF were not a thing, or at least not common, certainly not when talking about function code. The overhead of a unit occurred only once per translation unit, so that expense was reasonably amortized. > > > > Splitting functions into their own

Yep, Wolfgang picked up on the one thing I saw too. This is why I like having people review my stuff. I think it's a bit of a pity that str_offsets_base can point into the middle of a str_offsets contribution in some ways Actually I changed my mind after saying that in the review, and in this writeup I concluded that it cannot do that. str_offsets_base points to the element immediately

It looks like we only attach the GNU_ranges_base to skeleton CUs, and never use the attribute under non-fission. Is that right? It's not obvious to me why we'd want to only include this under fission, but I admittedly don't fully understand it anyway. - Dave