<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Nov 3, 2015 at 5:06 PM, Alexey Samsonov <span dir="ltr"><<a href="mailto:vonosmas@gmail.com" target="_blank">vonosmas@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">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.</div></blockquote><div><br></div><div>Not quite following here - dwo sections are already stripped from .o files and should never appear in executables.<br><br>llvm-symbolizer is tested against .o files that contain no dwo contents, right? Or is the dwo/dwp information optionally used in some way?</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>I didn't fully understand the part about walking DIEs to patch references from .debug_info.dwo to .debug_loc.dwo: shouldn't their values stay the same, as they will be treated relative to the value of DW_SECT_LOC offset?<br></div></div></blockquote><div><br></div><div>Ah, right you are - hadn't spotted that bit. I guess this'll all become more clear to me as I implement dumping support for the indexes and can start to look at some examples of the behavior of the existing dwp tool. (thanks muchly for the pointer there)<br><br>- Dave</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div></div></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Tue, Nov 3, 2015 at 1:52 PM, David Blaikie via llvm-dev <span dir="ltr"><<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><div dir="ltr">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 ( <a href="https://gcc.gnu.org/wiki/DebugFissionDWP" target="_blank">https://gcc.gnu.org/wiki/DebugFissionDWP</a> ) in LLVM.<br><br>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 touched by a DWP tool, unlike dsymutil.<br><br>Basically all the tool needs to do is concatenate (or deduplicate, in the case of type units) the sections and apply a few domain-specific relocations, but that doesn't include having to read the DIE tree in debug_info.dwo (only the headers). The other thing is to build a couple of indexing data structures to allow fast lookup of CUs and TUs.<br><br>Likely I'll start with:<br><br>* adding llvm-dwarfdump support for the DWP indexes<br>* basic prototype of llvm-dwp just concatenating sections<br>* handle each of the domain specific relocations in turn<br> * abbr_offset<br> * debug_str_offsets.dwo entries<br> * type_unit's DW_AT_stmt_list<br> * references to debug_loc.dwo from debug_info.dwo<div> * this one, at first blush, makes me particularly sad, as it'll involve actually walking all the DIEs in any CUs (stmt_list isn't great either, but at least that'd only be the header - same for accessing the signature for the CU, it's always in the root DIE)<br>* deduplicate type units<br>* add CU/TU indexes<div>* DWP merging (being able to read existing indexes and merge those into larger indexes)<br>* possibly support the thin DWP mode</div></div><div><br></div><div>Does this all seem feasible/plausible/reasonable to do in LLVM? Any particular points of contention/interest/clarification?</div><div><br></div><div>It's possible at some point in the future it might be nice to share the type merging logic of dsymutil (type units make sense when you don't have a debug aware linker - but they do have unfortunate overhead which would be nice to avoid, if possible), in which case there might be some code sharing opportunity. But the two tools are still going to be fairly different in their purpose/handling (dsymutil has to get the address mappings and update all of that, DWP won't have to deal with code addresses, etc).<br><br>- Dave</div></div>
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<br></blockquote></div><span class="HOEnZb"><font color="#888888"><br><br clear="all"><div><br></div>-- <br><div><div dir="ltr">Alexey Samsonov<br><a href="mailto:vonosmas@gmail.com" target="_blank">vonosmas@gmail.com</a></div></div>
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