David Blaikie via llvm-dev
2018-Mar-29 14:59 UTC
[llvm-dev] [DWARFv5] Assembler syntax for new line-table features
+Eric Christopher <echristo at gmail.com> +Adrian Prantl <aprantl at apple.com> +Jonas Devlieghere <jdevlieghere at apple.com> (seems Jonas is doing a bunch of debug info work - guessing he's working with you, Adrian?) I'm guessing Eric's the most likely to have contacts over in GCC land to maybe bridge the gap when talking about assembly syntax across the two. Eric - any ideas how best to negotiate this pseudo-standard? (there's another feature or two I'd like to propose too - at least to standardize what the syntax /should/ be, even if gas doesn't support it immediately) Paul - perhaps a brief description of the proposed syntax would be helpful to get the ball rolling (even if it's just discussing it amongst ourselves before it ends up in a cross-project discussion). - Dave On Wed, Mar 28, 2018 at 11:16 AM via llvm-dev <llvm-dev at lists.llvm.org> wrote:> TL;DR: If I'm trying to define new assembler directive syntax to > support DWARF v5, it seems like a good idea for all the various > assemblers out there in the world to support the same syntax. > How would I go about negotiating that syntax with other assembler > providers? Is GNU as the only really relevant one? > > Long version: > > DWARF v5 introduces a couple of new features in the .debug_line section > that require assembler syntax, because the information relates to the > files read by the compiler and there's no other way to inform the > assembler. > > The two bits of information are: > (1) the MD5 checksum of each source file; and > (2) the primary source filename. > > The primary source filename is given in the .debug_info section. In > DWARF v5 this is repeated in the .debug_line section; prior to DWARF v5 > it is not. In both cases, file number 0 refers to this file. Because > the compiler emits the .debug_info section directly, the assembler is > not aware of the name of the primary source file without some new syntax > to provide that information. And, it needs the MD5 checksum as well, so > relying on the old-format '.file' directive is insufficient. > > I've added support in LLVM for both of these features, but somewhat > arbitrarily defined assembler syntax to support them. Obviously if > implementers of other assemblers also want to support DWARF v5, the same > information will have to be represented with assembler syntax somehow, > and of course it would be best if all assemblers supporting DWARF v5 > used the same syntax. But I don't know how to go about doing that. > > Any advice would be welcome. > Thanks, > --paulr > > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20180329/e1a2e43d/attachment.html>
via llvm-dev
2018-Apr-04 22:48 UTC
[llvm-dev] [DWARFv5] Assembler syntax for new line-table features
> > I'm guessing Eric's the most likely to have contacts over in GCC land to > maybe bridge the gap when talking about assembly syntax across the two. > Eric - any ideas how best to negotiate this pseudo-standard? (there's > another feature or two I'd like to propose too - at least to standardize > what the syntax /should/ be, even if gas doesn't support it immediately) > > Can we discuss this on the GCC mailing list? I guess if we both use the > same syntax it’s more likely others will follow.My inclination was the dwarf-discuss mailing list, which has members from the gcc community and others. But if people really prefer a gcc-specific list, after which we simply impose a decision on everyone else, let me know the address.> > > On Mar 29, 2018, at 6:22 PM, David Blaikie <dblaikie at gmail.com> wrote: > > > > Sorry, I meant specifically the choice for it to be quoted rather than a > bare hex literal. > > +1, I’m wondering the same.I assumed that LLVM's AsmParser could not accept a 128-bit hex literal, given that the CodeView equivalent used a quotes. That's the only reason. More digging turns up the .octa directive which demonstrates the quotes are not necessary. I'll take an action item to make the 'md5' option take a bare 128-bit number. --paulr
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