[PATCH] D80391: [Driver] Don't make -gsplit-dwarf imply -g2

[David Blaikie via Phabricator via cfe-commits]

dblaikie added a comment.

In D80391#2497018 <https://reviews.llvm.org/D80391#2497018>, @inglorion wrote:

> For Chrome on Chrome OS, this is https://crbug.com/1158215
>
> Here, we saw our links fail with "output file too large". Investigation revealed that debug info was being included in the binary, instead of in .dwo files as expected. That turned out to be caused by this change.
>
> It seems that there are cases where -gsplit-dwarf is passed, but it does not take effect because there isn't also a -g (or -g<level>) option:
>
>   clang -c -fthinlto-index=foo.o.thinlto.bc -gsplit-dwarf foo.o -o foo.bin.o
>
> Shows no .dwo file and debug info in foo.bin.o, whereas
>
>   clang -c -fthinlto-index=foo.o.thinlto.bc -gsplit-dwarf -g foo.o -o foo.bin.o
>
> shows a .dwo file which is referenced from foo.bin.o
>
> The only thing that is different here is that the latter command has "-g" whereas the former doesn't.
>
> In other words, the new implementation still doesn't make -g and -gsplit-dwarf fully orthogonal; instead of -gsplit-dwarf always turning on debug fission, it *only* turns it on when there is also a -g or -g<level> option - at least in distributed ThinLTO code generation.
>
> It seems that orthogonality was the motivation for this change, and that -gsplit-dwarf without -g is supposed to work in the linker (per MaskRay's comment about -g being ignored by the linker).
>
> Can we make it so that -gsplit-dwarf turns on debug fission and we then use that even if no -g options were passed?

Ah, sorry - I assumed you were using implicit thinlto rather than explicit thinlto.

Yes, I think you've demonstrated a bug here - hopefully @Maskray can look into/fix this so that only -gN is required when the IR is generated and only -gsplit-dwarf is required when real object files are generated - without needing both files even when only one of those operations (IR generation or object generation) is being performed.


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