dblaikie accepted this revision. dblaikie added a comment. In D94655#2498811 <https://reviews.llvm.org/D94655#2498811>, @MaskRay wrote:
> In D94655#2498669 <https://reviews.llvm.org/D94655#2498669>, @dblaikie wrote: > >> In D94655#2498548 <https://reviews.llvm.org/D94655#2498548>, @MaskRay wrote: >> >>> In D94655#2498504 <https://reviews.llvm.org/D94655#2498504>, @dblaikie >>> wrote: >>> >>>> Is there any way to condition this on the type of the output, rather than >>>> the input? (or, more specifically, on whether machine code is being >>>> generated) >>>> >>>> Or maybe we could always pass the split-dwarf-file down through LLVM and >>>> not need to conditionalize it at all? It'd be a no-op if there's no DWARF >>>> in the IR anyway? >>> >>> I tried replacing `if (IRInput || Args.hasArg(options::OPT_g_Group)) {` >>> with `if (1)`, -gsplit-dwarf may produce .dwo for regular non-g .c compile. >> >> Are you saying that if you make that change -gsplit-dwarf does cause .dwo >> files to be created for non-g .c compiles? Do the dwo files have anything in >> them? I had modified llvm to dynamically choose split or non-split based on >> whether there was enough data to be worth splitting into a .dwo file, but I >> guess that situation might still be producing an empty .dwo file which isn't >> ideal - I haven't tested that. > > > > % clang a.c -gsplit-dwarf -c > % readelf -WS a.dwo > There are 2 section headers, starting at offset 0x50: > > Section Headers: > [Nr] Name Type Address Off Size ES > Flg Lk Inf Al > [ 0] NULL 0000000000000000 000000 000000 00 > 0 0 0 > [ 1] .strtab STRTAB 0000000000000000 000040 000009 00 > 0 0 1 OK, thanks. Yeah, wouldn't mind if that got fixed at some point. It turns up in existing behavior/without patches with situations like `clang++ -gmlt -gsplit-dwarf x.cpp -c` if there's no inlining (that's the feature I mentioned/referenced in my previous comment) - since the split CU would be empty, LLVM avoids emitting a split CU at all - but does end up with that empty dwo situation you described. If that bug were fixed (lazily choosing not to create a dwo file at all, if no CUs were emitted into it) then we could pass the split dwarf request straight down unmodified all the time - making the architecture as orthogonal as the user-facing feature is intended to be. >>> Since we already have the >>> >>> // For -g0 or -gline-tables-only, drop -gsplit-dwarf. This gets a bit more >>> // complicated if you've disabled inline info in the skeleton CUs >>> // (SplitDWARFInlining) - then there's value in composing split-dwarf and >>> // line-tables-only, so let those compose naturally in that case. >>> >>> logic, I think altering `DwarfFission` in the driver is fine. If not, I'd >>> hope the backend to process `DwarfFission` ... >> >> Sorry, I'm not understanding this comment - could you describe/rephrase it >> in more detail? > > The driver already decides that DwarfFission should be disabled in -g0 and > -g1 cases. If the driver does not already do this, passing through > DwarfFission in the driver and letting CC1 handle it seems right to me. > > Since the driver already has some logic, I think adding more logic about IR > input types is fine. My concern is that we'll miss other cases where code generation/dwo file creation is done when handling special cases like this & the code would be more robust if we didn't have to special case things like this. But I guess it'll do for now. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D94655/new/ https://reviews.llvm.org/D94655 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
