MaskRay added a comment.
In D94647#2497170 <https://reviews.llvm.org/D94647#2497170>, @dblaikie wrote:
> In implicit thinlto this seemed to work for me without any changes:
>
> $ clang++-tot -flto=thin test.cpp -g -c
> $ clang++-tot -flto=thin -fuse-ld=lld -gsplit-dwarf test.o &&
> llvm-dwarfdump-tot a.out
> a.out: file format elf64-x86-64
>
> .debug_info contents:
> 0x00000000: Compile Unit: length = 0x0000002c, format = DWARF32, version =
> 0x0004, abbr_offset = 0x0000, addr_size = 0x08 (next unit at 0x00000030)
>
> 0x0000000b: DW_TAG_compile_unit
> DW_AT_stmt_list (0x00000000)
> DW_AT_comp_dir
> ("/usr/local/google/home/blaikie/dev/scratch")
> DW_AT_GNU_dwo_name ("a.out_dwo/1.dwo")
> DW_AT_GNU_dwo_id (0xf29563d7c812deae)
> DW_AT_low_pc (0x0000000000201730)
> DW_AT_high_pc (0x0000000000201738)
> DW_AT_GNU_addr_base (0x00000000)
>
> Any idea why that worked without the need for a special case/changes? Might
> be nice if both these use cases (implicit and explicit thinlto) somehow
> managed to use more common code generation options. But I guess that's too
> different - probably some generic "take all the clang flags and pass them
> through to the linker to pass back to the compiler", which isn't really
> relevant to this... well, maybe (if they're being passed back to the compiler
> in implicit thin lto, how does implicit thin lto work correctly without the
> -g flag?)
Interesting. D44788 <https://reviews.llvm.org/D44788> let Clang driver pass
`-plugin-opt=dwo_dir=` to the linker. LTOBackend.cpp emits
`$dwo_dir/[1234].dwo`.
There are .dwo files but the file names are a bit less ideal. For distributed
ThinLTO, I think specifying the dwo filename explicitly is better.
Repository:
rG LLVM Github Monorepo
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https://reviews.llvm.org/D94647/new/
https://reviews.llvm.org/D94647
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